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During World War I, various forms of tear gas were used in combat and tear gas was the most common form of chemical weapon used. None of the belligerents believed that the use of irritant gases violated the Hague Convention of 1899 which prohibited the use of "poison or poisoned weapons" in warfare. Use of chemical weapons escalated during the war to lethal gases, after 1914 (during which only tear gas was used).
The US Chemical Warfare Service developed tear gas grenades for use in riot control in 1919.
Use of tear gas in interstate warfare, as with all other chemical weapons, was prohibited by the Geneva Protocol of 1925: it prohibited the use of "asphyxiating gas, or any other kind of gas, liquids, substances or similar materials", a treaty that most states have signed. Police and civilian self-defense use is not banned in the same manner.
Tear gas was used in combat by Italy in the Second Italo-Ethiopian War, by Japan in the Second Sino-Japanese War, by Spain in the Rif War and by the United States in the Vietnam War, and the Israel–Palestine conflict.
Tear gas exposure is an element of military training programs, typically as a means of improving trainees' tolerance to tear gas and encouraging confidence in the ability of their issued protective equipment to prevent chemical weapons exposure. | 1 | Applied and Interdisciplinary Chemistry |
Many PAFPs have been engineered from existing fluorescent proteins or identified from large-scale screens in the wake of Kaede's discovery. Many of these undergo green-to-red photoconversion, but other colors are available. Some proteins take part in irreversible photoconversion reactions while other reactions can be reversed using light of a specific wavelength. | 1 | Applied and Interdisciplinary Chemistry |
Cyclamin is used as an ingredient for a nasal spray to reduce the tension of the wall and induce secretion of mucous. Furthermore, due to its toxic effects on different (cancer) cell types, cyclamin might be considered for use as chemotherapeutic drug. However, more research first has to be done to reduce its toxicity on normal human cells. | 0 | Theoretical and Fundamental Chemistry |
Optical waveguide lightmode spectroscopy (OWLS) is a device that relies on a thin-film optical waveguide, enclosing a discrete number of guided electromagnetic waves. Guidance is achieved by means of a grating coupler. It is based on the measurements of effective refractive index of a thin-film layer above the waveguide. This technique works only on highly transparent surfaces.
Other methods widely used for measuring the amount of protein adsorbed on surfaces include radio-labelling, Lowry assay, scanning angle reflectometry, total internal reflection fluorescence, bicinchoninic acid assay etc. | 1 | Applied and Interdisciplinary Chemistry |
One advantage of spectrograph mode is the ability to acquire IPES spectra over a wide range of photon energies simultaneously. Additionally, the incident electron energy remains fixed which allows better focusing of the electron beam on the sample. Furthermore, by changing the incident electron energy the electronic structure can be studied in great detail. Although the grating spectrometer is very stable over time, the set-up can be very complex and its maintenance can be very expensive. The advantages of isochromat mode are its low cost, simple design and higher count rates. | 0 | Theoretical and Fundamental Chemistry |
Organism cloning (also called reproductive cloning) refers to the procedure of creating a new multicellular organism, genetically identical to another. In essence this form of cloning is an asexual method of reproduction, where fertilization or inter-gamete contact does not take place. Asexual reproduction is a naturally occurring phenomenon in many species, including most plants and some insects. Scientists have made some major achievements with cloning, including the asexual reproduction of sheep and cows. There is a lot of ethical debate over whether or not cloning should be used. However, cloning, or asexual propagation, has been common practice in the horticultural world for hundreds of years. | 1 | Applied and Interdisciplinary Chemistry |
Pulse electrolysis is an alternate electrolysis method that utilises a pulsed direct current to initiate non-spontaneous chemical reactions. Also known as pulsed direct current (PDC) electrolysis, the increased number of variables that it introduces to the electrolysis method can change the application of the current to the electrodes and the resulting outcome. This varies from direct current (DC) electrolysis, which only allows the variation of one value, the voltage applied. By utilising conventional pulse width modulation (PMW), multiple dependent variables can be altered, including the type of waveform, typically a rectangular pulse wave, the duty cycle, and the frequency.
Currently, there has been a focus on theoretical and experimental research into PDC electrolysis in terms of the electrolysis of water to produce hydrogen. Past research has demonstrated that there is a possibility it can result in a higher electrical efficiency in comparison to DC electrolysis. This would allow electrolysis procedures to produce greater volumes of hydrogen with a reduced electrical energy consumption. Although theoretical research has made large promise for the efficiencies and benefits of utilising pulse electrolysis, it has many contradictions including a common issue that it is difficult to replicate the successes of patents experimentally and produces its own negative effects on the electrolyser.
PDC electrolysis is not only confined to the electrolysis of water. Uses in industry such as electroplating and electrocrystallisation are also undergoing research due to the wider range of properties that can be achieved.
The various and alterable effects of using intermittent pulses in PDC electrolysis has resulted in an area of interest that could benefit industry. However, as it is still being researched and has produced conflicting results, a consistent and reliable answer to how dependent electrolysis efficiency is on the properties of an electrical pulse has not been determined, hence, other forms of electrolysis such as polymer electrolyte membrane and alkaline water electrolysis are being used in industry. | 0 | Theoretical and Fundamental Chemistry |
An organism is suitable for a GUS assay if it lacks naturally occurring β-glucuronidase activity or if the activity is very low (background activity). For this reason, the assay is not useful in most vertebrates and many molluscs. Since there is no detectable GUS activity in higher plants, mosses, algae, ferns, fungi and most bacteria, the assay is ideally suited for gene expression studies in these organisms, and considered the reporter gene of choice for in plant science. | 1 | Applied and Interdisciplinary Chemistry |
The exact differential for a differentiable scalar function defined in an open domain is equal to , where is the gradient of , represents the scalar product, and is the general differential displacement vector, if an orthogonal coordinate system is used. If is of differentiability class (continuously differentiable), then is a conservative vector field for the corresponding potential by the definition. For three dimensional spaces, expressions such as and can be made.
The gradient theorem states
that does not depend on which integral path between the given path endpoints and is chosen. So it is concluded that the integral of an exact differential is independent of the choice of an integral path between given path endpoints (path independence).
For three dimensional spaces, if defined on an open domain is of differentiability class (equivalently is of ), then this integral path independence can also be proved by using the vector calculus identity and the Stokes' theorem.
for a simply closed loop with the smooth oriented surface in it. If the open domain is simply connected open space (roughly speaking, a single piece open space without a hole within it), then any irrotational vector field (defined as a vector field which curl is zero, i.e., ) has the path independence by the Stokes theorem, so the following statement is made; In a simply connected open region, any vector field that has the path-independence property (so it is a conservative vector field.) must also be irrotational and vise versa.' The equality of the path independence and conservative vector fields is shown here. | 0 | Theoretical and Fundamental Chemistry |
As a strong base, lithium tert-butoxide is easily protonated.
Lithium tert-butoxide is used to prepare other tert-butoxide compounds such as copper(I) t-butoxide and hexa(tert-butoxy)dimolybdenum(III):
:2 MoCl(thf) + 6 LiOBu-t → Mo(OBu-t) + 6 LiCl + 6 thf | 0 | Theoretical and Fundamental Chemistry |
Here is a summary of the sequence of events that take place in synaptic transmission from a presynaptic neuron to a postsynaptic cell. Each step is explained in more detail below. Note that with the exception of the final step, the entire process may run only a few hundred microseconds, in the fastest synapses.
#The process begins with a wave of electrochemical excitation called an action potential traveling along the membrane of the presynaptic cell, until it reaches the synapse.
#The electrical depolarization of the membrane at the synapse causes channels to open that are permeable to calcium ions.
#Calcium ions flow through the presynaptic membrane, rapidly increasing the calcium concentration in the interior.
#The high calcium concentration activates a set of calcium-sensitive proteins attached to vesicles that contain a neurotransmitter chemical.
#These proteins change shape, causing the membranes of some "docked" vesicles to fuse with the membrane of the presynaptic cell, thereby opening the vesicles and dumping their neurotransmitter contents into the synaptic cleft, the narrow space between the membranes of the pre- and postsynaptic cells.
#The neurotransmitter diffuses within the cleft. Some of it escapes, but some of it binds to chemical receptor molecules located on the membrane of the postsynaptic cell.
#The binding of neurotransmitter causes the receptor molecule to be activated in some way. Several types of activation are possible, as described in more detail below. In any case, this is the key step by which the synaptic process affects the behavior of the postsynaptic cell.
#Due to thermal vibration, the motion of atoms, vibrating about their equilibrium positions in a crystalline solid, neurotransmitter molecules eventually break loose from the receptors and drift away.
#The neurotransmitter is either reabsorbed by the presynaptic cell, and then repackaged for future release, or else it is broken down metabolically. | 1 | Applied and Interdisciplinary Chemistry |
Polarity also has an effect on allylic strain. In terms of stereoselectivity, polar groups act like large, bulky groups. Even though two groups may have approximately the same A values the polar group will act as though it were much bulkier. This is due to the donor character of the polar group. Polar groups increase the HOMO energy of the σ-system in the transition state. This causes the transition state to be in a much more favorable position when the polar group is not interacting in a 1,3 allylic strain. | 0 | Theoretical and Fundamental Chemistry |
An air classifier is an industrial machine which separates materials by a combination of size, shape, and density.
It works by injecting the material stream to be sorted into a chamber which contains a column of rising air. Inside the separation chamber, air drag on the objects supplies an upward force which counteracts the force of gravity and lifts the material to be sorted up into the air. Due to the dependence of air drag on object size and shape, the objects in the moving air column are sorted vertically and can be separated in this manner.
Air classifiers are commonly employed in industrial processes where a large volume of mixed materials with differing physical characteristics need to be separated quickly and efficiently. Air classifier is helpful for cement, air pollution control, food processing, pigments, pharmaceutical, cosmetics or chemical industries. One such example is in municipal recycling centers, where various types of metal, paper, and plastics arrive mixed together and need to be sorted before further processing can take place.
Air classifiers can also be used as a step in the automotive recycling process. For example, after the crushing and shredding steps, steel is removed by electromagnets, and nonferrous metals are removed by eddy-current separators. Then an air classifier can be used to deal with the remaining dense materials (such as glass) as well as the remaining materials of various densities, most notably plastics, foams, and cloth. | 1 | Applied and Interdisciplinary Chemistry |
A related intensive system parameter is the particle number density, a quantity of kind volumetric number density obtained by dividing the particle number of a system by its volume. This parameter is often denoted by the lower-case letter n. | 0 | Theoretical and Fundamental Chemistry |
SIR2 is an NAD-dependent lysine deacetylase. It was the first-discovered member of the Sirtuin protein family and it is highly conserved, with homologs found in organisms ranging from humans to bacteria and archaea. It interacts with a variety of protein substrates, but does not exhibit strong affinity for DNA, chromatin, or other silencer-binding factors. Instead, it relies on other SIR proteins to find its appropriate silencing target.
In the SIR protein complex, SIR2 removes acetyl groups from the lysine on histone tails H3 and H4, priming the nucleosome for chromatin packaging by the SIR3 component of the complex. | 1 | Applied and Interdisciplinary Chemistry |
Although the concept of molecular-weight markers has been retained, techniques of development have varied throughout the years. New inventions of molecular-weight markers are distributed in kits specific to the marker's type.
An early problem in the development of markers was achieving high resolution throughout the entire length of the marker. Depending on the running conditions of gel electrophoresis, fragments may have been compressed, disrupting clarity. To address this issue, a kit for Southern Blot analysis was developed in 1990, providing the first marker to combine target DNA and probe DNA. This technique took advantage of logarithmic spacing, and could be used to identify target bands ranging over a length of 20,000 nucleotides. | 1 | Applied and Interdisciplinary Chemistry |
Diffusion is of fundamental importance in many disciplines of physics, chemistry, and biology. Some example applications of diffusion:
* Sintering to produce solid materials (powder metallurgy, production of ceramics)
* Chemical reactor design
* Catalyst design in chemical industry
* Steel can be diffused (e.g., with carbon or nitrogen) to modify its properties
* Doping during production of semiconductors. | 1 | Applied and Interdisciplinary Chemistry |
During physical exertion or moderate intensity exercise lactate released from working muscle and other tissue beds is the primary fuel source for the heart, exiting the muscles through monocarboxylate transport protein (MCT). This evidence is supported by an increased amount of MCT shuttle proteins in the heart and muscle in direct proportion to exertion as measured through muscular contraction.
Furthermore, both neurons and astrocytes have been shown to express MCT proteins, suggesting that the lactate shuttle may be involved in brain metabolism. Astrocytes express MCT4, a low affinity transporter for lactate (Km = 35mM), suggesting its function is to export lactate produced by glycolysis. Conversely, neurons express MCT2, a high affinity transporter for lactate (Km = 0.7mM). Thus, it is hypothesized that the astrocytes produce lactate which is then taken up by the adjacent neurons and oxidized for fuel. | 1 | Applied and Interdisciplinary Chemistry |
Whereas FCS is a point measurement providing diffusion time at a given observation volume, svFCS is a technique where the observation spot is varied in order to measure diffusion times at different spot sizes. The relationship between the diffusion time and the spot area is linear and could be plotted in order to decipher the major contribution of confinement. The resulting curve is called the diffusion law.
This technique is used in Biology to study the plasma membrane organization on living cells.
where is the y axis intercept. In case of Brownian diffusion, . In case of a confinement due to isolated domains, whereas in case of isolated domains, .
svFCS studies on living cells and simulation papers
Sampling-Volume-Controlled Fluorescence Correlation Spectroscopy (SVC-FCS):
z-scan FCS
FCS with Nano-apertures: breaking the diffraction barrier
STED-FCS: | 0 | Theoretical and Fundamental Chemistry |
The Armijska Ratna Komanda D-0, also known as the Ark, was a Cold War-era nuclear bunker and military command centre located near the town of Konjic in Bosnia and Herzegovina. Built to protect Yugoslav President Josip Broz Tito and up to 350 members of his inner circle in the event of an atomic exchange, the structure is made up of residential areas, conference rooms, offices, strategic planning rooms, and other areas. The bunker remained a state secret until after the breakup of Yugoslavia in the 1990s.
The facility is now under the authority of the Bosnian Ministry of Defense and is managed by the country's military, guarded by a five-soldier detachment, but is designated by KONS as National Monuments of Bosnia and Herzegovina and used as exhibition space for project such as Cultural Event of Europe with strong UNESCO support, and tourist attraction.
Another underground facility is Željava Air Base, situated on the border between Bosnia and Herzegovina and Croatia under the mountain, near the city of Bihać. It was the largest underground airport and military air base in the Socialist Federal Republic of Yugoslavia (SFRY), and one of the largest in Europe. The role of the facility was to establish, integrate and coordinate a nationwide early warning radar network in SFRY akin to NORAD in the US. The complex contained tunnels in total length of 3.5 km (2.2 mi), and the bunker with four entrances protected by 100-ton pressurized doors, three of which were customized for use by fixed-wing aircraft. capable in housing two full fighter squadrons, one reconnaissance squadron, and associated maintenance facilities. It was designed and built to sustain a direct hit from a 20-kiloton nuclear bomb, equivalent to that dropped on Nagasaki. The underground facility was lined with semicircular concrete shields, arranged every 10 km (6.2 mi), to cushion the impact of incoming strike. The complex included an underground water source, power generators, crew quarters, and other strategic military facilities. It also housed a mess hall that could feed 1,000 people simultaneously, along with stores of food, fuel and arms sufficient to last 30 days. Fuel was supplied by a 20 km (12 mi) underground pipe network connected to a military warehouse on Pokoj Hill near Bihać. Nowadays, they are popular for urban exploration. | 0 | Theoretical and Fundamental Chemistry |
The Barbier–Wieland degradation is a procedure for shortening the carbon chain of a carboxylic acid by one carbon. It only works when the carbon adjacent to the carboxyl is a simple methylene bridge (an aliphatic carbon with no substituents). The reaction sequence involves conversion of the carboxyl and alpha carbon into an alkene, which is then cleaved by oxidation to convert the former alpha position into a carboxyl itself. | 0 | Theoretical and Fundamental Chemistry |
Lanthanide probes displays unique fluorescence properties, including long lifetime of fluorescence, large Stokes shift and narrow emission peak. These properties is highly advantageous to develop analytical probes for receptor-ligand interactions. Many lanthanide-based fluorescence studies have been developed for GPCRs, including CXCR1, insulin-like family peptide receptor 2, protease-activated receptor 2, β2-adrenergic receptor and C3a receptor. | 1 | Applied and Interdisciplinary Chemistry |
Used as drugs, compounds with different configuration normally have different physiological activity, including the desired pharmacological effect, the toxicology and the metabolism. Enantiomeric ratios and purity is an important factor in clinical assessments. Racemic mixtures are those that contain equimolar amounts of both enantiomers of a compound. Racemate and single enantiomer actions differ in most cases. | 0 | Theoretical and Fundamental Chemistry |
Sulfidation (British spelling also sulphidation) is a process of installing sulfide ions in a material or molecule. The process is widely used to convert oxides to sulfides but is also related to corrosion and surface modification. | 0 | Theoretical and Fundamental Chemistry |
The preferred geometries of the benzene dimer have been modeled at a high level of theory with MP2-R12/A computations and very large counterpoise-corrected aug-cc-PVTZ basis sets. The two most stable conformations are the parallel displaced and T-shaped, which are essentially isoenergetic. In contrast, the sandwich configuration maximizes overlap of the pi system, which destabilizes the interaction. The sandwich configuration represents an energetic saddle point, which is consistent with the relative rarity of this configuration in x-ray crystal data.
The relative binding energies of these three geometric configurations of the benzene dimer can be explained by a balance of quadrupole/quadrupole and London dispersion forces. While benzene does not have a dipole moment, it has a strong quadrupole moment. The local C–H dipole means that there is positive charge on the atoms in the ring and a correspondingly negative charge representing an electron cloud above and below the ring. The quadrupole moment is reversed for hexafluorobenzene due to the electronegativity of fluorine. The benzene dimer in the sandwich configuration is stabilized by London dispersion forces but destabilized by repulsive quadrupole/quadrupole interactions. By offsetting one of the benzene rings, the parallel displaced configuration reduces these repulsive interactions and is stabilized. The large polarizability of aromatic rings lead to dispersive interactions as major contribution to stacking effects. These play a major role for interactions of nucleobases e.g. in DNA. The T-shaped configuration enjoys favorable quadrupole/quadrupole interactions, as the positive quadrupole of one benzene ring interacts with the negative quadrupole of the other. The benzene rings are furthest apart in this configuration, so the favorable quadrupole/quadrupole interactions evidently compensate for diminished dispersion forces. | 0 | Theoretical and Fundamental Chemistry |
Integration of SBUs into a covalent framework results in the synergistic emergence of conductivities much greater than the monomeric values. The nature of the SBUs can improve conductivity. Through the use of highly conjugated linkers throughout the COF scaffold, the material can be engineered to be fully conjugated, enabling high charge carrier density as well as through- and in-plane charge transport. For instance, Mirica and coworkers synthesized a COF material (NiPc-Pyr COF) from nickel phthalocyanine (NiPc) and pyrene organic linkers that had a conductivity of 2.51 x 10 S/m, which was several orders of magnitude larger than the undoped molecular NiPc, 10 S/m. A similar COF structure made by Jiang and coworkers, CoPc-Pyr COF, exhibited a conductivity of 3.69 x 10 S/m. In both previously mentioned COFs, the 2D lattice allows for full π-conjugation in the x and y directions as well as π-conduction along the z axis due to the fully conjugated, aromatic scaffold and π-π stacking, respectively. Emergent electrical conductivity in COF structures is especially important for applications such as catalysis and energy storage where quick and efficient charge transport is required for optimal performance. | 0 | Theoretical and Fundamental Chemistry |
Nucleotide pyrophosphatase/phosphodiesterase (NPP) is a class of dimeric enzymes that catalyze the hydrolysis of phosphate diester bonds. NPP belongs to the alkaline phosphatase (AP) superfamily of enzymes. Humans express seven known NPP isoforms, some of which prefer nucleotide substrates, some of which prefer phospholipid substrates, and others of which prefer substrates that have not yet been determined. In eukaryotes, most NPPs are located in the cell membrane and hydrolyze extracellular phosphate diesters to affect a wide variety of biological processes. Bacterial NPP is thought to localize to the periplasm. | 1 | Applied and Interdisciplinary Chemistry |
The form of the crucible has varied through time, with designs reflecting the process for which they are used, as well as regional variation. The earliest crucible forms derive from the sixth/fifth millennium B.C. in Eastern Europe and Iran. | 0 | Theoretical and Fundamental Chemistry |
Corrosion coupons are made in different shapes and sizes. These coupons are often made from same material of the pipe or tank/vessel which should be monitored for corrosion. The most common used coupons are as follows:
* strip coupon
* ladder strip coupon
* flush disc coupon
* multi-disc coupon
* scale coupon | 1 | Applied and Interdisciplinary Chemistry |
The long half-life of technetium-99 and its ability to form an anionic species make it (along with I) a major concern when considering long-term disposal of high-level radioactive waste. Many of the processes designed to remove fission products from medium-active process streams in reprocessing plants are designed to remove cationic species like caesium (e.g., Cs, Cs) and strontium (e.g., Sr). Hence the pertechnetate escapes through these treatment processes. Current disposal options favor burial in geologically stable rock. The primary danger with such a course is that the waste is likely to come into contact with water, which could leach radioactive contamination into the environment. The natural cation-exchange capacity of soils tends to immobilize plutonium, uranium, and caesium cations. However, the anion-exchange capacity is usually much smaller, so minerals are less likely to adsorb the pertechnetate and iodide anions, leaving them mobile in the soil. For this reason, the environmental chemistry of technetium is an active area of research. | 0 | Theoretical and Fundamental Chemistry |
RIP140 is part of the chain by which tumors can cause cachexia.
Levels of RIP140 expression in various tissues varies during aging in mice, suggesting changes in metabolic function. RIP140 is implicated in certain human disease processes. In morbid obesity, RIP140 levels are down-regulated in visceral adipose tissue. In breast cancer, RIP140 is involved in regulation of E2F1, an oncogene which discriminates between luminal and basal types of tumours. RIP140 has an influence upon cancer phenotype and prognosis. In addition, RIP140 has a role in inflammation, since it acts as a coactivator for NFkappaB/RelA-dependent cytokine gene expression. Lack of RIP140 leads to an inhibition of proinflammatory pathways in macrophages. | 1 | Applied and Interdisciplinary Chemistry |
Several features make two-phase flow an interesting and challenging branch of fluid mechanics:
*Surface tension makes all dynamical problems nonlinear (see Weber number)
*In the case of air and water at standard temperature and pressure, the density of the two phases differs by a factor of about 1000. Similar differences are typical of water liquid/water vapor densities
*The sound speed changes dramatically for materials undergoing phase change, and can be orders of magnitude different. This introduces compressible effects into the problem
*The phase changes are not instantaneous, and the liquid vapor system will not necessarily be in phase equilibrium
*The change of phase means flow-induced pressure drops can cause further phase-change (e.g. water can evaporate through a valve) increasing the relative volume of the gaseous, compressible medium and increasing exit velocities, unlike single-phase incompressible flow where closing a valve would decrease exit velocities
*Can give rise to other counter-intuitive, negative resistance-type instabilities, like Ledinegg instability, geysering, chugging, relaxation instability, and flow maldistribution instabilities as examples of static instabilities, and other dynamic instabilities | 1 | Applied and Interdisciplinary Chemistry |
For cellular processes that are not directly related to pathogen resistance or defense, BIK1 does not utilize traditional defense-mediating hormones such as SA, JA, or ACC, but instead utilizes an herbicide, known as paraquat which produces ROIs. It is believed that SA, JA, and ACC have no effect on BIK1 induction because they are likely located downstream from the BIK1 gene, or it is possible that BIK1 operates completely independently. However, it is believed that BIK1 does play a vital role in the ET signaling pathway. Based on the signaling function of BIK1 in ET responses, it is believed that Botrytis-induced kinase1 accumulates response signals that it receives from upstream regulators and then integrates them into its own resistance mechanism.
BIK1 is a receptor-like cytoplasmic kinase (RLCK) that associates with a cell-surface receptor, FLS2, and a co-receptor kinase, BAK1 to transduce signals when a PAMP is detected. In order for BIK1 to be activated, site-specific phosphorylation must occur. | 1 | Applied and Interdisciplinary Chemistry |
Consider a planet orbiting its host star. The star emits radiation isotropically, and some fraction of this radiation reaches the planet. The amount of radiation arriving at the planet is referred to as the incident solar radiation, . The planet has an albedo that depends on the characteristics of its surface and atmosphere, and therefore only absorbs a fraction of radiation. The planet absorbs the radiation that isn't reflected by the albedo, and heats up. One may assume that the planet radiates energy like a blackbody at some temperature according to the Stefan–Boltzmann law. Thermal equilibrium exists when the power supplied by the star is equal to the power emitted by the planet. The temperature at which this balance occurs is the planetary equilibrium temperature. | 0 | Theoretical and Fundamental Chemistry |
Andersen began his independent research career at UC Berkeley in 1976. Initially his research focused on ligand substitution patterns in quadruply-bonded Mo complexes. He also studied actinide coordination complexes bearing the sterically bulky amido ligand –N(SiMe), including the uranium(III) compound U[N(SiMe)] which was later found to have pyramidal geometry. | 0 | Theoretical and Fundamental Chemistry |
Silicon shows a peculiar profile, in that its electrical resistance increases with temperature up to about 160 °C, then starts decreasing, and drops further when the melting point is reached. This can lead to thermal runaway phenomena within internal regions of the semiconductor junction; the resistance decreases in the regions which become heated above this threshold, allowing more current to flow through the overheated regions, in turn causing yet more heating in comparison with the surrounding regions, which leads to further temperature increase and resistance decrease. This leads to the phenomenon of current crowding and formation of current filaments (similar to current hogging, but within a single device), and is one of the underlying causes of many semiconductor junction failures. | 1 | Applied and Interdisciplinary Chemistry |
In cases where the diameter of a trapped particle is significantly greater than the wavelength of light, the trapping phenomenon can be explained using ray optics. As shown in the figure, individual rays of light emitted from the laser will be refracted as it enters and exits the dielectric bead. As a result, the ray will exit in a direction different from which it originated. Since light has a momentum associated with it, this change in direction indicates that its momentum has changed. Due to Newton's third law, there should be an equal and opposite momentum change on the particle.
Most optical traps operate with a Gaussian beam (TEM mode) profile intensity. In this case, if the particle is displaced from the center of the beam, as in the right part of the figure, the particle has a net force returning it to the center of the trap because more intense beams impart a larger momentum change towards the center of the trap than less intense beams, which impart a smaller momentum change away from the trap center. The net momentum change, or force, returns the particle to the trap center.
If the particle is located at the center of the beam, then individual rays of light are refracting through the particle symmetrically, resulting in no net lateral force. The net force in this case is along the axial direction of the trap, which cancels out the scattering force of the laser light. The cancellation of this axial gradient force with the scattering force is what causes the bead to be stably trapped slightly downstream of the beam waist.
The standard tweezers works with the trapping laser propagated in the
direction of gravity and the inverted tweezers works against gravity. | 1 | Applied and Interdisciplinary Chemistry |
Raman scattering is another phenomenon that involves inelastic scattering of light caused by the vibrational properties of matter. The detected range of frequency shifts and other effects are very different compared to Brillouin scattering. In Raman scattering, photons are scattered by the effect of vibrational and rotational transitions in the bonds between first-order neighboring atoms, while Brillouin scattering results from the scattering of photons caused by large scale, low-frequency phonons. The effects of the two phenomena provide very different information about the sample: Raman spectroscopy can be used to determine the transmitting mediums chemical composition and molecular structure, while Brillouin scattering can be used to measure the materials properties on a larger scale – such as its elastic behavior. The frequency shifts from Brillouin scattering, a technique known as Brillouin spectroscopy, are detected with an interferometer while Raman scattering uses either an interferometer or a dispersive (grating) spectrometer. | 0 | Theoretical and Fundamental Chemistry |
Animals also represent a source of bioactive natural products. In particular, venomous animals such as snakes, spiders, scorpions, caterpillars, bees, wasps, centipedes, ants, toads, and frogs have attracted much attention. This is because venom constituents (peptides, enzymes, nucleotides, lipids, biogenic amines etc.) often have very specific interactions with a macromolecular target in the body (e.g. α-bungarotoxin from cobras). As with plant feeding deterrents, this biological activity is attributed to natural selection, organisms capable of killing or paralyzing their prey and/or defending themselves against predators being more likely to survive and reproduce.
Because of these specific chemical-target interactions, venom constituents have proved important tools for studying receptors, ion channels, and enzymes. In some cases, they have also served as leads in the development of novel drugs. For example, teprotide, a peptide isolated from the venom of the Brazilian pit viper Bothrops jararaca, was a lead in the development of the antihypertensive agents cilazapril and captopril. Also, echistatin, a disintegrin from the venom of the saw-scaled viper Echis carinatus was a lead in the development of the antiplatelet drug tirofiban.
In addition to the terrestrial animals and amphibians described above, many marine animals have been examined for pharmacologically active natural products, with corals, sponges, tunicates, sea snails, and bryozoans yielding chemicals with interesting analgesic, antiviral, and anticancer activities. Two examples developed for clinical use include ω-conotoxin (from the marine snail Conus magus) and ecteinascidin 743 (from the tunicate Ecteinascidia turbinata). The former, ω-conotoxin, is used to relieve severe and chronic pain, while the latter, ecteinascidin 743 is used to treat metastatic soft tissue sarcoma. Other natural products derived from marine animals and under investigation as possible therapies include the antitumour agents discodermolide (from the sponge Discodermia dissoluta), eleutherobin (from the coral Erythropodium caribaeorum), and the bryostatins (from the bryozoan Bugula neritina). | 1 | Applied and Interdisciplinary Chemistry |
Within the Earth's atmosphere and surface, the liquid phase is the most common and is the form that is generally denoted by the word "water". The solid phase of water is known as ice and commonly takes the structure of hard, amalgamated crystals, such as ice cubes, or loosely accumulated granular crystals, like snow. Aside from common hexagonal crystalline ice, other crystalline and amorphous phases of ice are known. The gaseous phase of water is known as water vapor (or steam). Visible steam and clouds are formed from minute droplets of water suspended in the air.
Water also forms a supercritical fluid. The critical temperature is 647 K and the critical pressure is 22.064 MPa. In nature, this only rarely occurs in extremely hostile conditions. A likely example of naturally occurring supercritical water is in the hottest parts of deep water hydrothermal vents, in which water is heated to the critical temperature by volcanic plumes and the critical pressure is caused by the weight of the ocean at the extreme depths where the vents are located. This pressure is reached at a depth of about 2200 meters: much less than the mean depth of the ocean (3800 meters). | 1 | Applied and Interdisciplinary Chemistry |
Redox reactions are also used for gated delivery systems. Within cells and the bloodstream there are several reducing agents that can be used to trigger drug release in gated systems. The most common reducing agent used in gated delivery system is glutathione (GSH) because it has been determined that GSH is the most abundant reducing agent in the body. GSH also has significantly different concentrations between the intracellular and extracellular environments making it easier to target either environment without getting triggered by the other. Furthermore, GSH is found in higher concentration within tumor cells. This provides another way to have sustained and local release of drug at tumor sites. There are generally 2 different mechanisms for this type of gated system. One method is to cleave disulfide bonds. Another method is to cleave bonds through the use of reactive oxygen species (ROS). Bonds that are able to be cleaved by ROS are generally thioketals, ketals, and diselenides. | 1 | Applied and Interdisciplinary Chemistry |
Viel is a co-author of the book Biology: How Life Works. It is published by Macmillan Education and is the first project to develop three pillars: the text, the visual program, and the assessment at the same time. | 1 | Applied and Interdisciplinary Chemistry |
There are a number of ASTM analytical test methods to determine amine value. A number of states in the United States have adopted their own test methods but they are based on ASTM methods. Although there are similarities with the method it is not the same as an acid value.
* ASTM D2073 - This is a potentiometric method.
* ASTM D2074-07
* ASTM D2896 - potentiometric method with perchloric acid.
* ASTM D6979-03 | 0 | Theoretical and Fundamental Chemistry |
Evans was a much-loved person, giving freely of his time and his immense knowledge (which was not confined to chemistry) to all who asked for help. He kept a range of exotic pets which he looked after well, e. g. a Cayman Islands alligator and a five-foot sand snake called George fed with live toads obtained from his local Chelsea pub. George escaped into the King’s Road and was after re-capture given by Evans to the London Zoo. He also kept locusts (some of these escaped too), bird-eating lizards and giant scorpions. He became a celebrated member of the Chelsea Arts Club. | 0 | Theoretical and Fundamental Chemistry |
Copper does not require complex ventilation measures. It is suitable for both unventilated warm and ventilated cold roof constructions. | 1 | Applied and Interdisciplinary Chemistry |
Fineman and Ross rearranged the copolymer equation into a linear form:
where and
Thus, a plot of versus yields a straight line with slope and intercept | 0 | Theoretical and Fundamental Chemistry |
In −1 frameshifting, the ribosome slips back one nucleotide and continues translation in the −1 frame. There are typically three elements that comprise a −1 frameshift signal: a slippery sequence, a spacer region, and an RNA secondary structure. The slippery sequence fits a X_XXY_YYH motif, where XXX is any three identical nucleotides (though some exceptions occur), YYY typically represents UUU or AAA, and H is A, C or U. Because the structure of this motif contains 2 adjacent 3-nucleotide repeats it is believed that −1 frameshifting is described by a tandem slippage model, in which the ribosomal P-site tRNA anticodon re-pairs from XXY to XXX and the A-site anticodon re-pairs from YYH to YYY simultaneously. These new pairings are identical to the 0-frame pairings except at their third positions. This difference does not significantly disfavor anticodon binding because the third nucleotide in a codon, known as the wobble position, has weaker tRNA anticodon binding specificity than the first and second nucleotides. In this model, the motif structure is explained by the fact that the first and second positions of the anticodons must be able to pair perfectly in both the 0 and −1 frames. Therefore, nucleotides 2 and 1 must be identical, and nucleotides 3 and 2 must also be identical, leading to a required sequence of 3 identical nucleotides for each tRNA that slips. | 1 | Applied and Interdisciplinary Chemistry |
At branch points, two or more separate reactions compete for the same reactant. This affects the isotopic composition of all products downstream of the branch point. To illustrate this, consider the network below:
Here, the flux of material into pool B (φ) is balanced by two fluxes, one into pool C and the other into pool D (φ and φ respectively). The mass balance for the heavier isotope in this system is represented by
Define f = φ / (φ + φ) = φ/φ as the fractional yield of C. Dividing through by φ gives
Applying the approximation introduced in the previous section, δ ≈ δ + ε. Further, δ ≈ δ + ε and δ ≈ δ + ε. Substituting these relations into the mass balance and solving for δ gives
The isotopic composition of pool B is clearly dependent on the fractional yield of C. Since there are no fluxes out of pools C or D, δ = δ, δ = δ. Thus, the isotopic compositions of these pools are offset from δ by ε and ε respectively. The figure at right summarizes these results. | 0 | Theoretical and Fundamental Chemistry |
From the table, poly(ethylene) has a solubility parameter of 7.9 cal cm. Good solvents are likely to be diethyl ether and hexane. (However, PE only dissolves at temperatures well above 100 °C.) Poly(styrene) has a solubility parameter of 9.1 cal cm, and thus ethyl acetate is likely to be a good solvent. Nylon 6,6 has a solubility parameter of 13.7 cal cm, and ethanol is likely to be the best solvent of those tabulated. However, the latter is polar, and thus we should be very cautions about using just the Hildebrand solubility parameter to make predictions. | 0 | Theoretical and Fundamental Chemistry |
Willauer attended Berry College in Georgia, graduating with a bachelor's degree in chemistry in 1996. In mid-1999 she participated in the 11th International Conference on Partitioning in Aqueous Two-Phase Systems, held in Gulf Shores, Alabama. In 2002, she earned a doctorate in analytical chemistry from the University of Alabama, writing her thesis on "Fundamentals of phase behavior and solute partitioning in ABS and applications to the paper industry," the "ABS" an abbreviation for "aqueous biphasic systems". She began working with the NRL as an associate, then in 2004 she advanced to the position of research chemist. | 0 | Theoretical and Fundamental Chemistry |
Cathleen M. Crudden is a Canadian chemist. She is a Canada Research Chair in Metal Organic Chemistry at Queen's University at Kingston. In February 2021, she took up the role of Editor-in-chief at ACS Catalysis. | 0 | Theoretical and Fundamental Chemistry |
Mesoporous silica nanoparticles (MSN) are considered to be one of the most widely used systems for drug delivery. MSNs have some of the characteristic features of gated systems such as being porous and having a high loading capacity, but they also exhibit some special features such as increased biocompatibility and chemical inertness. These delivery systems are composed of two parts: the inorganic scaffold and the molecular gates. In a study conducted by the Kong Lab at Deakin University in Australia, the researchers generated MSNs by adding tetraethyl orthosilicate to aqueous cetyltrimethylammonium bromide. The MSN's they created had a surface area of 363 m^2/g, an average pore size of 2.59 nm, and a pore volume of 0.33 cm^3/g. | 1 | Applied and Interdisciplinary Chemistry |
The IUPAC has designated the symbols for nucleotides. Apart from the five (A, G, C, T/U) bases, often degenerate bases are used especially for designing PCR primers. These nucleotide codes are listed here. Some primer sequences may also include the character "I", which codes for the non-standard nucleotide inosine. Inosine occurs in tRNAs and will pair with adenine, cytosine, or thymine. This character does not appear in the following table, however, because it does not represent a degeneracy. While inosine can serve a similar function as the degeneracy "D", it is an actual nucleotide, rather than a representation of a mix of nucleotides that covers each possible pairing needed. | 1 | Applied and Interdisciplinary Chemistry |
While juggling his career at a major corporate company, Kang continued to pursue his musical interests as the main vocalist and guitarist with PITTA, a rock band he had formed together with his friends as college students. They continued to play even after graduating and working. In 2016, they gained local celebrity status after winning the Busan Employees' Band Competition for amateur musicians. | 1 | Applied and Interdisciplinary Chemistry |
Pelletizing of animal feeds can result in pellets from (shrimp feeds), through to (poultry feeds) up to (stock feeds). The pelletizing of stock feed is done with the pellet mill machinery, which is done in a feed mill. | 1 | Applied and Interdisciplinary Chemistry |
The transcriptional regulation of the genome is controlled primarily at the preinitiation stage by binding of the core transcriptional machinery proteins (namely, RNA polymerase, transcription factors, and activators and repressors) to the core promoter sequence on the coding region of the DNA. However, DNA is tightly packaged in the nucleus with the help of packaging proteins, chiefly histone proteins to form repeating units of nucleosomes which further bundle together to form condensed chromatin structure. Such condensed structure occludes many DNA regulatory regions, not allowing them to interact with transcriptional machinery proteins and regulate gene expression. To overcome this issue and allow dynamic access to condensed DNA, a process known as chromatin remodeling alters nucleosome architecture to expose or hide regions of DNA for transcriptional regulation.
By definition, chromatin remodeling is the enzyme-assisted process to facilitate access of nucleosomal DNA by remodeling the structure, composition and positioning of nucleosomes. | 1 | Applied and Interdisciplinary Chemistry |
Sonogashira coupling has found widespread use in coupling aryl halides with alkynes. TONs upwards of 2,000,000 and low catalyst loadings of 0.005 mol % can be achieved with PNP-based catalysts. | 0 | Theoretical and Fundamental Chemistry |
In organometallic chemistry, a migratory insertion is a type of reaction wherein two ligands on a metal complex combine. It is a subset of reactions that very closely resembles the insertion reactions, and both are differentiated by the mechanism that leads to the resulting stereochemistry of the products. However, often the two are used interchangeably because the mechanism is sometimes unknown. Therefore, migratory insertion reactions or insertion reactions, for short, are defined not by the mechanism but by the overall regiochemistry wherein one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.: | 0 | Theoretical and Fundamental Chemistry |
Cocaine is a potent psycho-stimulant that boosts dopamine levels by inhibiting dopamine transporters. It has been often linked to enhanced libido and risk-taking behavior in humans.
Cocaine has been observed to increase sexual arousal or to trigger spontaneous erections and orgasms.
In contrast, other data has shown that persistent cocaine use impairs sexual desire and the capacity of both men and females to achieve orgasm. | 1 | Applied and Interdisciplinary Chemistry |
Microcins are all RiPPs produced by Enterobacteriaceae with a molecular weight <10 kDa. Many members of other RiPP families, such as microcin E492, microcin B17 (LAP) and microcin J25 (Lasso peptide) are also considered microcins. Instead of being classified based on posttranslational modifications or modifying enzymes, microcins are instead identified by molecular weight, native producer, and antibacterial activity. Microcins are either plasmid- or chromosome-encoded, but specifically have activity against Enerobacteriaceae. Because these organisms are also often producers of microcins, the gene cluster contains not only a precursor peptide and modification enzymes, but also a self-immunity gene to protect the producing strain, and genes encoding export of the natural product.
Microcins have bioactivity against Gram-negative bacteria but usually display narrow-spectrum activity due to hijacking of specific receptors involved in the transport of essential nutrients. | 1 | Applied and Interdisciplinary Chemistry |
The chemical bond present in carbene radicals is surprising in that it possesses aspects of both Fischer and Schrock type carbenes. As a result, the cobalt carbene radical complexes have discrete radical-character at their carbon atom, thus giving rise to interesting catalytic radical-type reaction pathways.
The mechanism of formation of a carbene radical at cobalt(II) typically involves carbene generation at the metal with simultaneous intramolecular electron transfer from the metal into the metal-carbene π* anti-bonding molecular orbital constructed from the metal d-orbital and the carbene p-orbital. As such, carbene radicals are perhaps best described as one-electron reduced Fischer-type carbenes.
Discrete electron transfer from a sigma-type metal d-orbital (typically the d orbital) occurs, leads the typical radical character of the carbene carbon. This behaviour not only explains the carbon-centered radical-type reactivity of these complexes, but also their reduced electrophilicity (suppressing carbene-carbene dimerisation side reactions) as well as their enhanced reactivity to electron-deficient substrates. Furthermore, second coordination sphere hydrogen-bonding interactions give rise to faster reactions because H-bonds are stronger to the reduced carbene as compared to the precursor.
Such H-bonding interactions can also facilitate chirality transfer in enantioselective carbene-transfer reactions.
In order for the σ bond to be stabilized (typically with a bond order slightly less than 1), a back-bonding action from the π molecular orbital to the anti-bonding π* molecular orbital is necessary and the porphyrin ring serves as an electron π-symmetry "buffer" to ensure this interaction is obtained.
The back-donation to the π* orbital would result in unfavorable excess electron density on the carbene carbon but the presence of adjacent functional groups (carbonyl or sulfonyl groups have the desired electronegativity) relieve this electron build-up and yield the final radical electron, which occupies a single p atomic orbital state on the carbon. | 0 | Theoretical and Fundamental Chemistry |
The application set for MR fluids is vast, and it expands with each advance in the dynamics of the fluid. | 1 | Applied and Interdisciplinary Chemistry |
The properties of RNA make the idea of the RNA world hypothesis conceptually plausible, though its general acceptance as an explanation for the origin of life requires further evidence. RNA is known to form efficient catalysts and its similarity to DNA makes clear its ability to store information. Opinions differ, however, as to whether RNA constituted the first autonomous self-replicating system or was a derivative of a still-earlier system. One version of the hypothesis is that a different type of nucleic acid, termed pre-RNA, was the first one to emerge as a self-reproducing molecule, to be replaced by RNA only later. On the other hand, the discovery in 2009 that activated pyrimidine ribonucleotides can be synthesized under plausible prebiotic conditions suggests that it is premature to dismiss the RNA-first scenarios. Suggestions for simple pre-RNA nucleic acids have included peptide nucleic acid (PNA), threose nucleic acid (TNA) or glycol nucleic acid (GNA). Despite their structural simplicity and possession of properties comparable with RNA, the chemically plausible generation of "simpler" nucleic acids under prebiotic conditions has yet to be demonstrated. | 0 | Theoretical and Fundamental Chemistry |
There was originally a simple and widely accepted argument that the genetic code should be universal: namely, that any variation in the genetic code would be lethal to the organism (although Crick had stated that viruses were an exception). This is known as the "frozen accident" argument for the universality of the genetic code. However, in his seminal paper on the origins of the genetic code in 1968, Francis Crick still stated that the universality of the genetic code in all organisms was an unproven assumption, and was probably not true in some instances. He predicted that "The code is universal (the same in all organisms) or nearly so". The first variation was discovered in 1979, by researchers studying human mitochondrial genes. Many slight variants were discovered thereafter, including various alternative mitochondrial codes. These minor variants for example involve translation of the codon UGA as tryptophan in Mycoplasma species, and translation of CUG as a serine rather than leucine in yeasts of the "CTG clade" (such as Candida albicans). Because viruses must use the same genetic code as their hosts, modifications to the standard genetic code could interfere with viral protein synthesis or functioning. However, viruses such as totiviruses have adapted to the host's genetic code modification. In bacteria and archaea, GUG and UUG are common start codons. In rare cases, certain proteins may use alternative start codons.
Surprisingly, variations in the interpretation of the genetic code exist also in human nuclear-encoded genes: In 2016, researchers studying the translation of malate dehydrogenase found that in about 4% of the mRNAs encoding this enzyme the stop codon is naturally used to encode the amino acids tryptophan and arginine. This type of recoding is induced by a high-readthrough stop codon context and it is referred to as functional translational readthrough.
Despite these differences, all known naturally occurring codes are very similar. The coding mechanism is the same for all organisms: three-base codons, tRNA, ribosomes, single direction reading and translating single codons into single amino acids. The most extreme variations occur in certain ciliates where the meaning of stop codons depends on their position within mRNA. When close to the 3 end they act as terminators while in internal positions they either code for amino acids as in Condylostoma magnum or trigger ribosomal frameshifting as in Euplotes'.
The origins and variation of the genetic code, including the mechanisms behind the evolvability of the genetic code, have been widely studied, and some studies have been done experimentally evolving the genetic code of some organisms. | 1 | Applied and Interdisciplinary Chemistry |
The most established and well-known homoaromatic species are cationic homoaromatic compounds. As stated earlier, the homotropenylium cation is one of the most studied homoaromatic compounds. Many homoaromatic cationic compounds use as a basis a cyclopropenyl cation, a tropylium cation, or a cyclobutadiene dication as these compounds exhibit strong aromatic character.
In addition to the homotropylium cation, another well established cationic homoaromatic compound is the norbornen-7-yl cation, which has been shown to be strongly homoaromatic, proven both theoretically and experimentally.
An intriguing case of σ-bishomoaromaticity can be found in the dications of pagodanes. In these 4-center-2-electron systems the delocalization happens in the plane that is defined by the four carbon atoms (prototype for the phenomenon of σ-aromaticity is cyclopropane which gains about 11.3 kcal mol stability from the effect). The dications are accessible either via oxidation of pagodane or via oxidation of the corresponding bis-seco-dodecahedradiene:
Reduction of the corresponding six electrons dianions was not possible so far. | 0 | Theoretical and Fundamental Chemistry |
Telluride-mediated polymerization or TERP first appeared to mainly operate under a reversible chain transfer mechanism by homolytic substitution under thermal initiation. However, in a kinetic study it was found that TERP predominantly proceeds by degenerative transfer rather than dissociation combination.
Alkyl tellurides of the structure Z-X-R, were Z=methyl and R= a good free radical leaving group, give the better control for a wide range of monomers, phenyl tellurides (Z=phenyl) giving poor control. Polymerization of methyl methacrylates are only controlled by ditellurides. The importance of X to chain transfer increases in the series O<S<Se<Te, makes alkyl tellurides effective in mediating control under thermally initiated conditions and the alkyl selenides and sulfides effective only under photoinitiated polymerization. | 0 | Theoretical and Fundamental Chemistry |
For any 2-dimensional lattice, the unit cells are parallelograms, which in special cases may have orthogonal angles, equal lengths, or both. Four of the five two-dimensional Bravais lattices are represented using conventional primitive cells, as shown below.
The centered rectangular lattice also has a primitive cell in the shape of a rhombus, but in order to allow easy discrimination on the basis of symmetry, it is represented by a conventional cell which contains two lattice points. | 0 | Theoretical and Fundamental Chemistry |
The [https://cran.r-project.org/web/packages/caroline/index.html caroline CRAN R package] contains the only known implementation of an RA plot. However, the meta-transcriptomics [http://bioconductor.org/packages/devel/bioc/html/manta.html "manta" R package] provides a wrapper around this RA plot implementation and is used for assessing fold change in transcription of genes (the points) while simultaneously visualizing each gene's taxonomic distributions as individual pie chart points. | 1 | Applied and Interdisciplinary Chemistry |
According to a 2015 salary survey by the American Institute of Chemical Engineers, the median annual salary for a chemical engineer was approximately $127,000. The survey was repeated in 2017 and the median annual salary dropped slightly to $124,000. The decrease in median salary was unexpected. A factor contributing to the decline may be that 2017’s survey was conducted by a different research and analysis firm. Median salaries ranged from $70,450 for chemical engineers with fewer than three years of experience to $156,000 for those with more than 40 years in the workforce.
In the UK, the IChemE 2016 Salary Survey reported a median salary of approximately £57,000, with a starting salary for a graduate averaging £28,350. Chemical engineering in the USA is one of the engineering disciplines with the highest participation of women, with 35% of students compared with 20% in engineering. In the UK in 2014, students starting degrees were 25% female, compared with 15% in engineering. US graduates who responded to a 2015 salary survey were 18.8% female.
According to the latest 2023 figures, Bayes Business School graduates get an average of £51,921 within 5 years of graduation, which is the most among UK universities. This was followed by the University of Oxford at £49,086 and the University of Warwick at £47,446. | 1 | Applied and Interdisciplinary Chemistry |
Two nuclear weapons have been deployed in combat—both by the United States against Japan in World War II. The first event occurred on the morning of 6 August 1945, when the United States Army Air Forces dropped a uranium gun-type device, code-named "Little Boy", on the city of Hiroshima, killing 70,000 people, including 20,000 Japanese combatants and 20,000 Korean slave laborers. The second event occurred three days later when the United States Army Air Forces dropped a plutonium implosion-type device, code-named "Fat Man", on the city of Nagasaki. It killed 39,000 people, including 27,778 Japanese munitions employees, 2,000 Korean slave laborers, and 150 Japanese combatants. In total, around 109,000 people were killed in these bombings. Nuclear weapons are largely seen as a deterrent by most governments; the sheer scale of the destruction caused by nuclear weapons has discouraged their use in warfare. | 0 | Theoretical and Fundamental Chemistry |
Brachytherapy is delivered by placing radiation source(s) inside or next to the area requiring treatment. Brachytherapy is commonly used as an effective treatment for cervical, prostate, breast, and skin cancer and can also be used to treat tumors in many other body sites.
In brachytherapy, radiation sources are precisely placed directly at the site of the cancerous tumor. This means that the irradiation only affects a very localized area – exposure to radiation of healthy tissues further away from the sources is reduced. These characteristics of brachytherapy provide advantages over external beam radiation therapy – the tumor can be treated with very high doses of localized radiation, whilst reducing the probability of unnecessary damage to surrounding healthy tissues. A course of brachytherapy can often be completed in less time than other radiation therapy techniques. This can help reduce the chance of surviving cancer cells dividing and growing in the intervals between each radiation therapy dose.
As one example of the localized nature of breast brachytherapy, the SAVI device delivers the radiation dose through multiple catheters, each of which can be individually controlled. This approach decreases the exposure of healthy tissue and resulting side effects, compared both to external beam radiation therapy and older methods of breast brachytherapy. | 0 | Theoretical and Fundamental Chemistry |
Emanuel Gil-Av was born 1916 in Pensa of Tzarist Russia. After the death of his father, a physician, the family moved first to Central Europe and in 1928 to Tel-Aviv, Israel, where Gil-Av attended High School. Gil-Av studied petroleum chemistry at the University of Strasbourg. In 1940 he escaped the German occupation to England where he worked at first in the chemical laboratory of Chaim Weizmann, followed by the Petrochemical Ltd. in Manchester. After World War II, he moved to Palestine and he joined the Daniel Sieff Institute in Rehovot which was later on to become the Weizmann Institute of Science. In 1951 he earned his PhD under the supervision of Ernst David Bergmann.
In his study of oil shale deposits, Gil-Av developed complex-forming stationary phases employing silver(I) ions for selective olefin separations by gas chromatography (GC). In co-operation with the centre of peptide chemistry at the Weizmann Institute of Science, he developed methods of the gas-chromatographic resolution of racemic α-amino acids. By coating a glass capillary column with the chiral stationary phase (CSP) N-trifluoroacetyl-L-isoleucine lauryl ester, Gil-Av et al. carried out in 1966 the first gas-chromatographic enantioseparation of racemic amino acids as N-trifluoroacetyl-O-alkyl derivatives. Many racemic compounds, amenable for enantioselective interaction via hydrogen bonding with the CSP, could be analytically enantioseparated by GC.
Further contributions of Gil-Av and associates are concerned with the use of chiral mobile phase additives (CMPAs) in liquid chromatography (LC), enantiomeric separation of helicenes by supramolecular LC, the temperature-dependent reversal of enantioselectivity by enthalpy-entropy compensation and non-linear effects leading to enantiomeric enrichment during chromatography on achiral stationary phases. | 0 | Theoretical and Fundamental Chemistry |
The therapeutic window is the amount of a medication between the amount that gives an effect (effective dose) and the amount that gives more adverse effects than desired effects. For instance, medication with a small pharmaceutical window must be administered with care and control, e.g. by frequently measuring blood concentration of the drug, since it easily loses effects or gives adverse effects. | 1 | Applied and Interdisciplinary Chemistry |
London dispersion forces are the weakest type of non-covalent interaction. In organic molecules, however, the multitude of contacts can lead to larger contributions, particularly in the presence of heteroatoms. They are also known as "induced dipole-induced dipole interactions" and present between all molecules, even those which inherently do not have permanent dipoles. Dispersive interactions increase with the polarizability of interacting groups, but are weakened by solvents of increased polarizability. They are caused by the temporary repulsion of electrons away from the electrons of a neighboring molecule, leading to a partially positive dipole on one molecule and a partially negative dipole on another molecule. Hexane is a good example of a molecule with no polarity or highly electronegative atoms, yet is a liquid at room temperature due mainly to London dispersion forces. In this example, when one hexane molecule approaches another, a temporary, weak partially negative dipole on the incoming hexane can polarize the electron cloud of another, causing a partially positive dipole on that hexane molecule. In absence of solvents hydrocarbons such as hexane form crystals due to dispersive forces ; the sublimation heat of crystals is a measure of the dispersive interaction. While these interactions are short-lived and very weak, they can be responsible for why certain non-polar molecules are liquids at room temperature. | 0 | Theoretical and Fundamental Chemistry |
The Cieplak model has been met with mixed reviews, and criticisms of both its basic logic and predictive ability have emerged. The stabilizing interaction of donating electron density into the transition state σ* orbital of a forming bond was immediately questioned, as this interaction has been widely invoked to explain exactly the opposite—the destabilization of bonds. Traditionally, forming bonds are stabilized when they donate electron density from their bonding HOMO into a neighboring antibonding LUMO, not by accepting electron density into their LUMO. To this end, David A. Evans said of Cieplaks proposal: "Structures are stabilized by stabilizing their highest energy filled states. This is one of the fundamental assumptions in frontier molecular orbital theory. The Cieplak hypothesis is nonsense." However, Hahn and le Noble refute this point by invoking the principle of microscopic reversibility, where the process of bond formation and cleavage are fundamentally equivalent in an equilibrium, and little value should be placed on the terms ‘bonding’ and ‘antibonding’, σ or σ*. In another criticism of the model, Houk questions Cieplaks fundamental assumption that C-H bonds are better electron-donors than C-C bonds. This point is still contested and represents another major dispute in the field.
To further refute the Cieplak effect, Houk puts forth a system in which Cieplak's model predicts the wrong product distribution trend. In the case of substituted trans-decalones, electron-withdrawing substituents equatorial at C4 should discourage equatorial attack and yield more axial product, since the ring C–C bonds are deactivated for donation into the forming C-Nuc bond. Experimental evidence, however, shows that axial electron-withdrawing C4 substituents are more directing towards axial attack than equatorial substituents. Since axial orbitals are not aligned for hyperconjugation in this system, Houk rationalized this trend by invoking electrostatic arguments, described below. | 0 | Theoretical and Fundamental Chemistry |
The standardized uptake value (SUV) is defined as tissue concentration (KBq/ml) divided by activity injected normalized for body weight. | 1 | Applied and Interdisciplinary Chemistry |
Gated drug delivery systems are an emerging concept that have drawn a lot of attention for their wide variety of potential applications in the medical field. The abnormal physiological conditions found within the tumor environment provide a breadth of options that could be used for externally stimulating these systems to release cargo. Gated systems in cancer therapy also have the added effect of reducing off target effects and decreasing leakage and delivery of drug to normal tissues. Another use for this technology could also be antibacterial regulation. These systems could be used to limit bacterial resistance as well as accumulation of antibiotics within the body. Antibacterial regulation potentially opens the door to using gated systems in theranostics, in which the system is able to detect an issue and then provide a therapeutic response.
There is also the potential for inhalable pulmonary drug delivery. With an increase in respiratory disease cases, the need for a drug delivery system that can be targeted to the lungs and provide sustained release is becoming more severe. This type of system would be applicable to patients experiencing asthma, pneumonia, obstructive pulmonary disease, and a number of other lung related diseases. | 1 | Applied and Interdisciplinary Chemistry |
Neurotrophin-4 (NT-4) is a neurotrophic factor that signals predominantly through the TrkB receptor tyrosine kinase. It is also known as NT4, NT5, NTF4, and NT-4/5. | 1 | Applied and Interdisciplinary Chemistry |
As large quantities of genomic sequence data began to accumulate in public databases, genetic algorithms became important to decipher the enormous collection of genomic data. They are commonly used to generate high-quality solutions to optimization and search problems by relying on bio-inspired operators such as mutation, crossover and selection. The followings are commonly used genetic algorithms:
* AntiSMASH (Antibiotics and Secondary Metabolite Analysis Shell) addresses secondary metabolite genome pipelines.
* PRISM (Prediction Informatics for Secondary Metabolites) is a combinatorial approach to chemical structure prediction for genetically encoded nonribosomal peptides and type I and II polyketides.
* SIM (Statistically based sequence similarity) method, such as FASTA or PSI-BLAST, infer orthologous homology.
*BLAST (Basic local alignment search tool) is an approach for rapid sequence comparison. | 1 | Applied and Interdisciplinary Chemistry |
The analytical pipeline for preparation of sample material for Zn isotope measurements is similar to that of Cu, consisting of digestion of host material or concentration from seawater, isolation and purification via anion-exchange chromatography, removal of ions of interfering mass (in particular, Ni) and isotope measurement via MC-ICP-MS (see Copper Isotope Measurement section for more details). | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the baroclinity (often called baroclinicity) of a stratified fluid is a measure of how misaligned the gradient of pressure is from the gradient of density in a fluid. In meteorology a baroclinic flow is one in which the density depends on both temperature and pressure (the fully general case). A simpler case, barotropic flow, allows for density dependence only on pressure, so that the curl of the pressure-gradient force vanishes.
Baroclinity is proportional to:
which is proportional to the sine of the angle between surfaces of constant pressure and surfaces of constant density. Thus, in a barotropic fluid (which is defined by zero baroclinity), these surfaces are parallel.
In Earths atmosphere, barotropic flow is a better approximation in the tropics, where density surfaces and pressure surfaces are both nearly level, whereas in higher latitudes the flow is more baroclinic. These midlatitude belts of high atmospheric baroclinity are characterized by the frequent formation of synoptic-scale cyclones, although these are not really dependent on the baroclinity term per se': for instance, they are commonly studied on pressure coordinate iso-surfaces where that term has no contribution to vorticity production. | 1 | Applied and Interdisciplinary Chemistry |
This is a list of reports made under Project 4.1. This list is not exhaustive.
*E.P. Cronkite, V.P. Bond, L.E. Browning, W.H. Chapman, S.H. Cohn, R.A. Conard, C.L. Dunham, R.S. Farr, W.S. Hall, R. Sharp, N.R. Shulman, Study of Response of Human Beings Accidentally Exposed to Significant Fallout Radiation, Operation CASTLE, Project 4.1, Naval Medical Research Institute, Naval Radiological Defense Laboratory, Defense Atomic Support Agency, Oak Ridge National Laboratory, Report #WT-923 (October 1954). Online at http://worf.eh.doe.gov/data/ihp2/2776_.pdf.
*S.H. Cohn, R.W. Rinehart, J.K. Gong, J.S. Robertson, W.L. Milne, W.H. Chapman, V.P. Bond, Nature and Extent of Internal Radioactive Contamination of Human Beings, Plants, and Animals Exposed to Fallout, Operation CASTLE, Project 4.1, Naval Radiological Defense Laboratory, Naval Medical Research Institute, Report #WT-936 (December 1955). Online at http://worf.eh.doe.gov/data/ihp1d/6205e.pdf.
*V.P. Bond, R.A. Conrad, J.S. Robertson, E.A. Weden, Medical Examination of Rongelap People Six Months After Exposure to Fallout, Operation CASTLE, Project 4.1 Addendum, Naval Medical Research Institute, Naval Radiological Defense Laboratory, Report #WT-937 (April 1955). Online at http://worf.eh.doe.gov/data/ihp2/2774_.pdf.
*R. Sharp, W.H. Chapman, Exposure of Marshall Islanders and American Military Personnel to Fallout, Operation CASTLE, Project 4.1 Addendum, Naval Medical Research Institute, Report #WT-938 EX (March 1957). Online at http://worf.eh.doe.gov/data/ihp2a/0283_a.pdf.
*C.A. Sondhaus, V.P. Bond, Physical Factors and Dosimetry in the Marshall Island Radiation Exposures, Operation CASTLE, Report on Addendum Report for Project 4.1 Naval Radiological Defense Laboratory Report #WT-939 (December 1955). Online at http://worf.eh.doe.gov/data/ihp1d/15187e.pdf. | 0 | Theoretical and Fundamental Chemistry |
Normal serum levels of ketone bodies are less than 0.5 mM. Hyperketonemia is conventionally defined as levels in excess of 1 mM. | 1 | Applied and Interdisciplinary Chemistry |
SOCl adopts a trigonal pyramidal molecular geometry with C molecular symmetry. This geometry is attributed to the effects of the lone pair on the central sulfur(IV) center.
In the solid state SOCl forms monoclinic crystals with the space group P2/c. | 0 | Theoretical and Fundamental Chemistry |
Consequences of loss of pRb function is dependent on cell type and cell cycle status, as pRb's tumor suppressive role changes depending on the state and current identity of the cell.
In G0 quiescent stem cells, pRb is proposed to maintain G0 arrest although the mechanism remains largely unknown. Loss of pRb leads to exit from quiescence and an increase in the number of cells without loss of cell renewal capacity. In cycling progenitor cells, pRb plays a role at the G1, S, and G2 checkpoints and promotes differentiation. In differentiated cells, which make up the majority of cells in the body and are assumed to be in irreversible G0, pRb maintains both arrest and differentiation.
Loss of pRb therefore exhibits multiple different responses within different cells that ultimately all could result in cancer phenotypes. For cancer initiation, loss of pRb may induce cell cycle re-entry in both quiescent and post-mitotic differentiated cells through dedifferentiation. In cancer progression, loss of pRb decreases the differentiating potential of cycling cells, increases chromosomal instability, prevents induction of cellular senescence, promotes angiogenesis, and increases metastatic potential.
Although most cancers rely on glycolysis for energy production (Warburg effect), cancers due to pRb loss tend to upregulate oxidative phosphorylation. The increased oxidative phosphorylation can increase stemness, metastasis, and (when enough oxygen is available) cellular energy for anabolism.
In vivo, it is still not entirely clear how and which cell types cancer initiation occurs with solely loss of pRb, but it is clear that the pRb pathway is altered in large number of human cancers.[110] In mice, loss of pRb is sufficient to initiate tumors of the pituitary and thyroid glands, and mechanisms of initiation for these hyperplasia are currently being investigated. | 1 | Applied and Interdisciplinary Chemistry |
There are two drivers for spalling of concrete: thermal strain caused by rapid heating and internal pressures due to the removal of water. Being able to predict the outcome of different heating rates on thermal stresses and internal pressure during water removal is particularly important to industry and other concrete structures.
Explosive spalling events of refractory concrete can result in serious problems. If an explosive spalling occurs, projectiles of reasonable mass (1–10 kg) can be thrust violently over many metres, which will have safety implications and render the refractory structure unfit for service. Repairs will then be required resulting in significant costs to industry. | 1 | Applied and Interdisciplinary Chemistry |
Chloromethane was first synthesized by the French chemists Jean-Baptiste Dumas and Eugene Peligot in 1835 by boiling a mixture of methanol, sulfuric acid, and sodium chloride. This method is the forerunner for that used today, which uses hydrogen chloride instead of sulfuric acid and sodium chloride.
Chloromethane is produced commercially by treating methanol with hydrochloric acid or hydrogen chloride, according to the chemical equation:
: CHOH + HCl → CHCl + HO
A smaller amount of chloromethane is produced by treating a mixture of methane with chlorine at elevated temperatures. This method, however, also produces more highly chlorinated compounds such as dichloromethane, chloroform, and carbon tetrachloride. For this reason, methane chlorination is usually only practiced when these other products are also desired. This chlorination method also cogenerates hydrogen chloride, which poses a disposal problem.
: <br>
: <br>
: <br> | 1 | Applied and Interdisciplinary Chemistry |
Thomas was born in New Brunswick. The full tenure of Thomas career was at Columbia University, where he received his bachelors degree in 1912, his A.M. in 1914, and his Ph.D. in 1915. Thomas was an instructor in food chemistry from 1912 to 1917, an assistant professor from 1919 to 1923, and an associate professor from 1923 to 1928. He became full professor of chemistry in 1928. He died in New York, N. Y. | 0 | Theoretical and Fundamental Chemistry |
The rate of a chemical reaction is influenced by many different factors, such as temperature, pH, reactant, and product concentrations and other effectors. The degree to which these factors change the reaction rate is described by the elasticity coefficient. This coefficient is defined as follows:
where denotes the reaction rate and denotes the substrate concentration. Be aware that the notation will use lowercase roman letters, such as to indicate concentrations.
The partial derivative in the definition indicates that the elasticity is measured with respect to changes in a factor S while keeping all other factors constant. The most common factors include substrates, products, enzyme, and effectors. The scaling of the coefficient ensures that it is dimensionless and independent of the units used to measure the reaction rate and magnitude of the factor. The elasticity coefficient is an integral part of metabolic control analysis and was introduced in the early 1970s and possibly earlier by Henrik Kacser and Burns in Edinburgh and Heinrich and Rapoport in Berlin.
The elasticity concept has also been described by other authors, most notably Savageau in Michigan and Clarke at Edmonton. In the late 1960s Michael Savageau developed an innovative approach called biochemical systems theory that uses power-law expansions to approximate the nonlinearities in biochemical kinetics. The theory is very similar to metabolic control analysis and has been very successfully and extensively used to study the properties of different feedback and other regulatory structures in cellular networks. The power-law expansions used in the analysis invoke coefficients called kinetic orders, which are equivalent to the elasticity coefficients.
Bruce Clarke in the early 1970s, developed a sophisticated theory on analyzing the dynamic stability in chemical networks. As part of his analysis, Clarke also introduced the notion of kinetic orders and a power-law approximation that was somewhat similar to Savageaus power-law expansions. Clarkes approach relied heavily on certain structural characteristics of networks, called extreme currents (also called elementary modes in biochemical systems). Clarke's kinetic orders are also equivalent to elasticities.
Elasticities can also be usefully interpreted as the means by which signals propagate up or down a given pathway.
The fact that different groups independently introduced the same concept implies that elasticities, or their equivalent, kinetic orders, are most likely a fundamental concept in the analysis of complex biochemical or chemical systems. | 0 | Theoretical and Fundamental Chemistry |
In allometric scaling, maximum potential life span (MPLS) is directly related to metabolic rate (MR), where MR is the recharge rate of a biomass made up of covalent bonds. That biomass (W) is subjected to deterioration over time from thermodynamic, entropic pressure. Metabolism is essentially understood as redox coupling, and has nothing to do with thermogenesis. Metabolic efficiency (ME) is then expressed as the efficiency of this coupling, a ratio of amperes captured and used by biomass, to the amperes available for that purpose. MR is measured in watts, W is measured in grams. These factors are combined in a power law, an elaboration on Kleiber's law relating MR to W and MPLS, that appears as MR = W^ (4ME-1)/4ME. When ME is 100%, MR = W^3/4; this is popularly known as quarter power scaling, a version of allometric scaling that is premised upon unrealistic estimates of biological efficiency.
The equation reveals that as ME drops below 20%, for W < one gram, MR/MPLS increases so dramatically as to endow W with virtual immortality by 16%. The smaller W is to begin with, the more dramatic is the increase in MR as ME diminishes. All of the cells of an organism fit into this range, i.e., less than one gram, and so this MR will be referred to as BMR.
But the equation reveals that as ME increases over 25%, BMR approaches zero. The equation also shows that for all W > one gram, where W is the organization of all of the BMRs of the organism's structure, but also includes the activity of the structure, as ME increases over 25%, MR/MPLS increases rather than decreases, as it does for BMR. An MR made up of an organization of BMRs will be referred to as an FMR. As ME decreases below 25%, FMR diminishes rather than increases as it does for BMR.
The antagonism between FMR and BMR is what marks the process of aging of biomass W in energetic terms. The ME for the organism is the same as that for the cells, such that the success of the organism's ability to find food (and lower its ME), is key to maintaining the BMR of the cells driven, otherwise, by starvation, to approaching zero; while at the same time a lower ME diminishes the FMR/MPLS of the organism. | 1 | Applied and Interdisciplinary Chemistry |
Steam-electric power plants use a surface condenser cooled by water circulating through tubes. The steam which was used to turn the turbine is exhausted into the condenser and is condensed as it comes in contact with the tubes full of cool circulating water. The condensed steam, commonly referred to as condensate.
is withdrawn from the bottom of the condenser. The adjacent image is a diagram of a typical surface condenser.
For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 °C where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of non-condensable air into the closed loop must be prevented. Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning. If a good source of cooling water is not available, cooling towers may be used to reject waste heat to the atmosphere. A large river or lake can also be used as a heat sink for cooling the condensers; temperature rises in naturally occurring waters may have undesirable ecological effects, but may also incidentally improve yields of fish in some circumstances. | 1 | Applied and Interdisciplinary Chemistry |
In humans, can be synthesized in the liver via the metabolism of fatty acids (e.g., butyrate), , and ketogenic amino acids through a series of reactions that metabolize these compounds into acetoacetate, which is the first ketone body that is produced in the fasting state. The biosynthesis of from acetoacetate is catalyzed by the β-hydroxybutyrate dehydrogenase enzyme.
Butyrate can also be metabolized into via a second metabolic pathway that does not involve acetoacetate as a metabolic intermediate. This metabolic pathway is as follows:
:butyrate→butyryl-CoA→crotonyl-CoA→β-hydroxybutyryl-CoA→poly-β-hydroxybutyrate→()→
The last reaction in this metabolic pathway, which involves the conversion of () into , is catalyzed by the hydroxybutyrate-dimer hydrolase enzyme.
The concentration of β-hydroxybutyrate in human blood plasma, as with other ketone bodies, increases through ketosis. This elevated β-hydroxybutyrate level is naturally expected, as β-hydroxybutyrate is formed from acetoacetate. The compound can be used as an energy source by the brain and skeletal muscle when blood glucose is low. Diabetic patients can have their ketone levels tested via urine or blood to indicate diabetic ketoacidosis. In alcoholic ketoacidosis, this ketone body is produced in greatest concentration. Ketogenesis occurs if oxaloacetate in the liver cells is depleted, a circumstance created by reduced carbohydrate intake (through diet or starvation); prolonged, excessive alcohol consumption; and/or insulin deficiency. Because oxaloacetate is crucial for entry of acetyl-CoA into the TCA cycle, the rapid production of acetyl-CoA from fatty acid oxidation in the absence of ample oxaloacetate overwhelms the decreased capacity of the TCA cycle, and the resultant excess of acetyl-CoA is shunted towards ketone body production. | 1 | Applied and Interdisciplinary Chemistry |
Goss specialises in the biosynthesis of natural products at the chemical and genetic level.
Goss joined the University of Cambridge in 2000 to study the chemistry and molecular biology of polyketide biosynthesis in the research group of Professors Jim Staunton (FRS) and Peter Leadlay (FRS). She held a one-year teaching fellowship at the School of Chemistry, University of Nottingham between 2002 and 2003 before obtaining a lectureship at the School of Biological and Chemical Science, University of Exeter in 2003. Between 2005 and 2010 Goss held a lectureship at the University of East Anglia before being promoted to senior lecturer in 2010 and then reader in organic chemistry in 2012. Goss moved to the University of St. Andrews in 2012 to become a reader in biomolecular and organic chemistry. In 2018 she became the first woman to be appointed professor of organic chemistry in St Andrews' 600-year history.
She was awarded the Royal Society of Chemistry Meldola prize for her work to understand the interface of organic chemistry and molecular biology. In 2013 she was awarded the Royal Society of Chemistry Natural Product Report Emerging Researcher Lectureship for her pioneering approach to Genochemetics, which combines synthetic biology and chemistry for medicinal purposes. In 2014 she was awarded an ERC consolidator grant.
Goss is on the advisory board for the peer-reviewed journals Chemical Communications and Natural Product Reports. | 0 | Theoretical and Fundamental Chemistry |
A selectable marker is a gene introduced into a cell, especially a bacterium or to cells in culture, that confers a trait suitable for artificial selection. They are a type of reporter gene used in laboratory microbiology, molecular biology, and genetic engineering to indicate the success of a transfection or other procedure meant to introduce foreign DNA into a cell. Selectable markers are often antibiotic resistance genes (An antibiotic resistance marker is a gene that produces a protein that provides cells expressing this protein with resistance to an antibiotic.). Bacteria that have been subjected to a procedure to introduce foreign DNA are grown on a medium containing an antibiotic, and those bacterial colonies that can grow have successfully taken up and expressed the introduced genetic material.
Normally the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E. coli. | 1 | Applied and Interdisciplinary Chemistry |
The feed is then transferred to the presentation mechanism which is the belt or the chute in the two main machine types respectively. This sub-process has the function to pass single particles of the material stream in a stable and predictable manner, thus in a unidirectional movement orthogonal to the detection line with uniform speed profile. | 0 | Theoretical and Fundamental Chemistry |
Nuclear fallout can occur due to a number of different sources. One of the most common potential sources of nuclear fallout is that of nuclear reactors. Because of this, steps must be taken to ensure the risk of nuclear fallout at nuclear reactors is controlled.
In the 1950s and 60s, the United States Atomic Energy Commission (AEC) began developing safety regulations against nuclear fallout for civilian nuclear reactors. Because the effects of nuclear fallout are more widespread and longer lasting than other forms of energy production accidents, the AEC desired a more proactive response towards potential accidents than ever before. One step to prevent nuclear reactor accidents was the Price-Anderson Act. Passed by Congress in 1957, the Price-Anderson Act ensured government assistance above the $60 million covered by private insurance companies in the case of a nuclear reactor accident. The main goal of the Price-Anderson Act was to protect the multi-billion-dollar companies overseeing the production of nuclear reactors. Without this protection, the nuclear reactor industry could potentially come to a halt, and the protective measures against nuclear fallout would be reduced. However, because of the limited experience in nuclear reactor technology, engineers had a difficult time calculating the potential risk of released radiation. Engineers were forced to imagine every unlikely accident, and the potential fallout associated with each accident. The AECs regulations against potential nuclear reactor fallout were centered on the ability of the power plant to the Maximum Credible Accident (MCA). The MCA involved a "large release of radioactive isotopes after a substantial meltdown of the reactor fuel when the reactor coolant system failed through a Loss-of-Coolant Accident". The prevention of the MCA enabled a number of new nuclear fallout preventive measures. Static safety systems, or systems without power sources or user input, were enabled to prevent potential human error. Containment buildings, for example, were reliably effective at containing a release of radiation and did not need to be powered or turned on to operate. Active protective systems, although far less dependable, can do many things that static systems cannot. For example, a system to replace the escaping steam of a cooling system with cooling water could prevent reactor fuel from melting. However, this system would need a sensor to detect the presence of releasing steam. Sensors can fail, and the results of a lack of preventive measures would result in a local nuclear fallout. The AEC had to choose, then, between active and static systems to protect the public from nuclear fallout. With a lack of set standards and probabilistic calculations, the AEC and the industry became divided on the best safety precautions to use.
This division gave rise to the Nuclear Regulatory Commission (NRC). The NRC was committed to regulations through research, which gave the regulatory committee a knowledge bank of research on which to draw their regulations. Much of the research done by the NRC sought to move safety systems from a deterministic viewpoint into a new probabilistic approach. The deterministic approach sought to foresee all problems before they arose. The probabilistic approach uses a more mathematical approach to weigh the risks of potential radiation leaks. Much of the probabilistic safety approach can be drawn from the radiative transfer theory in Physics, which describes how radiation travels in free space and through barriers. Today, the NRC is still the leading regulatory committee on nuclear reactor power plants. | 0 | Theoretical and Fundamental Chemistry |
The alkali–silica reaction (ASR) is a deleterious chemical reaction between the alkali ( and ), dissolved in concrete pore water as NaOH and KOH, with reactive amorphous (non-crystalline) siliceous aggregates in the presence of moisture. The simplest way to write the reaction in a stylized manner is the following (other representations also exist):
: (young N-S-H gel)
This reaction produces a gel-like substance of sodium silicate ( • n ), also noted • n , or N-S-H (sodium silicate hydrate). This hygroscopic gel swells inside the affected reactive aggregates which expand and crack. In its turn, it causes concrete expansion. If concrete is heavily reinforced, it can first cause some prestressing effect before cracking and damaging the structure. ASR affects the aggregates and is recognizable by cracked aggregates. It does not directly affect the hardened cement paste (HCP). | 1 | Applied and Interdisciplinary Chemistry |
Push–pull technology is an intercropping strategy for controlling agricultural pests by using repellent "push" plants and trap "pull" plants. For example, cereal crops like maize or sorghum are often infested by stem borers. Grasses planted around the perimeter of the crop attract and trap the pests, whereas other plants, like Desmodium, planted between the rows of maize, repel the pests and control the parasitic plant Striga. Push–pull technology was developed at the International Centre of Insect Physiology and Ecology (ICIPE) in Kenya in collaboration with Rothamsted Research, UK. and national partners. This technology has been taught to smallholder farmers through collaborations with universities, NGOs and national research organizations. | 1 | Applied and Interdisciplinary Chemistry |
There are many examples of every possible d electron configuration. What follows is a short description of common geometries and characteristics of each possible d electron count and representative examples.
:d
:Commonly tetrahedral; however it is possible for d complexes to accommodate many electron pairs (bonds/coordination number) since their d orbitals are empty and well away from the 18-electron ceiling. Often colorless due to the lack of d to d transitions.
:Examples: titanium tetrachloride, titanocene dichloride, Schwartz's reagent.
:d
:Examples: molybdenum(V) chloride, vanadyl acetylacetonate, vanadocene dichloride, vanadium tetrachloride.
:d
:Examples: titanocene dicarbonyl.
:d
:Examples: Reinecke's salt.
:d
:Octahedral high-spin: 4 unpaired electrons, paramagnetic, substitutionally labile.
:Octahedral low-spin: 2 unpaired electrons, paramagnetic, substitutionally inert.
:d
:Octahedral high-spin: 5 unpaired electrons, paramagnetic, substitutionally labile.
:Octahedral low-spin: 1 unpaired electron, paramagnetic, substitutionally inert.
:Examples: potassium ferrioxalate, vanadium carbonyl.
:d
:Commonly octahedral complexes in both high spin and low spin.
:Octahedral high-spin: 4 unpaired electrons, paramagnetic, substitutionally labile.
:Octahedral low-spin: no unpaired electrons, diamagnetic, substitutionally inert.
:Examples: hexamminecobalt(III) chloride, sodium cobaltinitrite, molybdenum hexacarbonyl, ferrocene, ferroin, chromium carbonyl.
:d
:Octahedral high spin: 3 unpaired electrons, paramagnetic, substitutionally labile.
:Octahedral low spin: 1 unpaired electron, paramagnetic, substitutionally labile.
:Examples: cobaltocene.
:d
:Complexes which are d high-spin are usually octahedral (or tetrahedral) while low-spin d complexes are generally 16-electron square planar complexes. For first row transition metal complexes such as Ni and Cu also form five-coordinate 18-electron species which vary from square pyramidal to trigonal bipyramidal.
:Octahedral high spin: 2 unpaired electrons, paramagnetic, substitutionally labile.
:Square planar low spin: no unpaired electrons, diamagnetic, substitutionally inert.
:Examples: cisplatin, nickelocene, dichlorobis(ethylenediamine)nickel(II), iron pentacarbonyl, Zeises salt, Vaskas complex, Wilkinson's catalyst.
:d
:Stable complexes with this electron count are more common for first row (period four) transition metals center than they are for complexes based around second or third row transition metals centers. These include both four-coordinate 17-electron species and five-coordinate 19-electron species.
:Examples: Schweizer's reagent.
:d
:Often tetrahedral complexes limited to form 4 additional bonds (8 additional electrons) by the 18-electron ceiling. Often colorless due to the lack of d to d transitions.
:Examples: tetrakis(triphenylphosphine)palladium(0), nickel carbonyl. | 0 | Theoretical and Fundamental Chemistry |
Regardless of the definition of the isotopic ratio, the isotopic composition of substrate and product are expressed as
where is a standard isotopic ration. Here, definition 3 of isotopic ratio has been used, however, any of the three definitions of isotopic ratio can equally be used. | 0 | Theoretical and Fundamental Chemistry |
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