text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
The phenomenon of electromigration has been known for over 100 years, having been discovered by the French scientist Gerardin. The topic first became of practical interest during the late 1960s when packaged ICs first appeared. The earliest commercially available ICs failed in a mere three weeks of use from runaway electromigration, which led to a major industry effort to correct this problem. The first observation of electromigration in thin films was made by I. Blech. Research in this field was pioneered by a number of investigators throughout the fledgling semiconductor industry. One of the most important engineering studies was performed by Jim Black of Motorola, after whom Black's equation is named. At the time, the metal interconnects in ICs were still about 10 micrometres wide. Currently interconnects are only hundreds to tens of nanometers in width, making research in electromigration increasingly important. | 0 | Theoretical and Fundamental Chemistry |
Day received awards from both the Royal Society (including the Bakerian Lecture in 1999) and the Royal Society of Chemistry; the latter named one of its awards in materials chemistry after him. He served many national and international agencies and institutions, both professional and governmental, and held numerous honorary degrees and fellowships.
Day was elected a Fellow of the Royal Society (FRS) in 1986, and held the post of Director of the Royal Institution from 1991 to 1998. Day was also director of the Royal Institution's Davy-Faraday Research Laboratory and the Fullerian Professor of Chemistry.
Day was made an honorary fellow of Wadham College, Oxford in 2003 and was a Fellow of the Institute of Physics. | 0 | Theoretical and Fundamental Chemistry |
Carbolithiation is the addition of an organolithium reagent across a carbon-carbon pi-bond. The organolithium reagents used in this transformation can be commercial (such as n-butyllithium) or can be generated through deprotonation or lithium-halogen exchange. Both inter- and intramolecular examples of carbolithiation exist and can be used in synthesis to generate complexity. Organolithiums are highly reactive chemicals and often the resulting organolithium reagent generated from the carbolithiation can continue to react with electrophiles or remaining starting material (resulting in polymerization). This reaction has been rendered enantioselective through the use of sparteine, which can chelate the lithium ion and induce chirality. Today, this is not a common strategy due to a shortage of natural sparteine. However, recent advances in the synthesis of sparteine surrogates and their effective application in carbolithiation have reactivated interest in this strategy.
Another demonstration of this reaction type is an alternative route to tamoxifen starting from diphenylacetylene and ethyllithium: The capturing electrophile here is triisopropyl borate forming the boronic acid R–B(OH). The second step completing tamoxifen is a Suzuki reaction.
As a consequence of the high reactivity of organolithiums as strong bases and strong nucleophiles, the substrate scope of the carbolithiation is generally limited to chemicals that do not contain acidic or electrophilic functional groups. | 0 | Theoretical and Fundamental Chemistry |
Many inorganic compounds are found in nature as minerals. Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum. Inorganic compounds are also found multitasking as biomolecules: as electrolytes (sodium chloride), in energy storage (ATP) or in construction (the polyphosphate backbone in DNA). | 0 | Theoretical and Fundamental Chemistry |
The Journal of Radiation Research is a bimonthly peer-reviewed scientific journal covering research on radiation and oncology. It was established in 1960 and is published by Oxford University Press. Its editor-in-chief is Kenshi Komatsu (University of Kyoto).
It is an affiliated journal of the Japan Radiation Research Society and the Japanese Society for Radiation Oncology. In 1998 the journal absorbed the Japanese Society for Radiation Oncologys former title, the Journal of JASTRO'. This extended the scope of the journal to include medical and oncology research. | 0 | Theoretical and Fundamental Chemistry |
Booth designed an electromechanical computer, the ARC (Automatic Relay Computer), in the late 1940s (1947-1948). Later on, they built an experimental electronic computer named SEC (Simple Electronic Computer, designed around 1948-1949) - and finally, the APE(X)C (All-Purpose Electronic Computer) series.
The computers were programmed by Kathleen. | 0 | Theoretical and Fundamental Chemistry |
Phosphatidic acids are anionic phospholipids important to cell signaling and direct activation of lipid-gated ion channels. Hydrolysis of phosphatidic acid gives rise to one molecule each of glycerol and phosphoric acid and two molecules of fatty acids. They constitute about 0.25% of phospholipids in the bilayer. | 1 | Applied and Interdisciplinary Chemistry |
In his last years, Walden focused on history of chemistry and collected a unique library of over 10,000 volumes. The library and his house were destroyed when the British bombed Rostock in 1942. Walden moved to Berlin and then to Frankfurt am Main, where he became a visiting professor of the history of chemistry at the local university. He met the end of World War II in the French Occupation Zone, cut off from Rostock University, located in the Soviet Zone, and thus left without any source of income.
Walden survived on a modest pension arranged by German chemists, giving occasional lectures in Tübingen and writing memoirs. In 1949, he published his best-known book, History of Chemistry. He died in Gammertingen in 1957, at the age of 93. His memoirs were published only in 1974. | 0 | Theoretical and Fundamental Chemistry |
A special case of this is the formation of small droplets when water is dripping from a faucet/tap. When a segment of water begins to separate from the faucet, a neck is formed and then stretched. If the diameter of the faucet is big enough, the neck does not get sucked back in, and it undergoes a Plateau–Rayleigh instability and collapses into a small droplet. | 1 | Applied and Interdisciplinary Chemistry |
Online non-intrusive ultrasonic thickness sensors are a popular choice for corrosion monitoring in various industries, including oil and gas, chemical processing, and power generation. These sensors can provide accurate and reliable thickness measurements of metal structures without requiring physical access or disruption to the equipment. The sensors can be installed permanently and remotely connected to a monitoring system, allowing for continuous data collection and analysis. With the ability to detect corrosion early on, online ultrasonic thickness sensors can help prevent equipment failure, reduce downtime, and improve overall safety and efficiency. | 1 | Applied and Interdisciplinary Chemistry |
The discovery of the photoacoustic effect dates back to 1880, when Alexander Graham Bell was experimenting with long-distance sound transmission. Through his invention, called "photophone", he transmitted vocal signals by reflecting sun-light from a moving mirror to a selenium solar cell receiver. As a byproduct of this investigation, he observed that sound waves were produced directly from a solid sample when exposed to beam of sunlight that was rapidly interrupted with a rotating slotted wheel. He noticed that the resulting acoustic signal was dependent on the type of the material and correctly reasoned that the effect was caused by the absorbed light energy, which subsequently heats the sample. Later Bell showed that materials exposed to the non-visible (ultra-violet and infra-red) portions of the solar spectrum can also produce sounds and invented a device, which he called "spectrophone", to apply this effect for spectral identification of materials. Bell himself and later John Tyndall and Wilhelm Röntgen extended these experiments, demonstrating the same effect in liquids and gases. However, the results were too crude, dependent on ear detection, and this technique was soon abandoned. The application of the photoacoustic effect had to wait until the development of sensitive sensors and intense light sources. In 1938 Mark Leonidovitch Veingerov revived the interest in the photoacoustic effect, being able to use it in order to measure very small carbon dioxide concentration in nitrogen gas (as low as 0.2% in volume). Since then research and applications grew faster and wider, acquiring several fold more detection sensitivity.
While the heating effect of the absorbed radiation was considered to be the prime cause of the photoacoustic effect, it was shown in 1978 that gas evolution resulting from a photochemical reaction can also cause a photoacoustic effect. Independently, considering the apparent anomalous behaviour of the photoacoustic signal from a plant leaf, which could not be explained solely by the heating effect of the exciting light, led to the cognition that photosynthetic oxygen evolution is normally a major contributor to the photoacoustic signal in this case. | 0 | Theoretical and Fundamental Chemistry |
Biotin PEG2 amine is used as a linker or cross linker. This allows to attach specific compounds to proteins or to antibodies.
A common use of biotin PEG2 amine is to use EDC and crosslink the amine in the biotin PEG2 amine to carboxyl groups on protein residues that are either aspartate or glutamate or the carboxy-terminus of proteins.
A particular example of use is labeling red cells, which in turn allows for the detection of these labeled cells in small samples using flow cytometry. | 1 | Applied and Interdisciplinary Chemistry |
The studies of rapamycin as immunosuppressive agent enabled us to understand its mechanism of action. It inhibits T-cell proliferation and proliferative responses induced by several cytokines, including interleukin 1 (IL-1), IL-2, IL-3, IL-4, IL-6, IGF, PDGF, and colony-stimulating factors (CSFs). Rapamycin inhibitors and rapalogs can target tumor growth both directly and indirectly. Direct impact of them on cancer cells depend on the concentration of the drug and certain cellular characteristics. The indirect way, is based on interaction with processes required for tumor angiogenesis. | 1 | Applied and Interdisciplinary Chemistry |
There are two major pathways of deficiency of CoQ in humans: reduced biosynthesis, and increased use by the body. Biosynthesis is the major source of CoQ. Biosynthesis requires at least 15 genes, and mutations in any of them can cause CoQ deficiency. CoQ levels also may be affected by other genetic defects (such as mutations of mitochondrial DNA, ETFDH, APTX, FXN, and BRAF, genes that are not directly related to the CoQ biosynthetic process). Some of these, such as mutations in COQ6, can lead to serious diseases such as steroid-resistant nephrotic syndrome with sensorineural deafness. | 1 | Applied and Interdisciplinary Chemistry |
In middle and late transition metal complexes, there is larger thermodynamic preference for β-H elimination over β-alkyl elimination, where the difference is usually >15 kcal/mol. Examples involved middle and late transition metal complexes are either absent of β-hydrogens or use ring strain relief and aromaticity as driving forces to favor β-alkyl elimination over β-hydride elimination. | 0 | Theoretical and Fundamental Chemistry |
The act of recycling plastic degrades its polymer chains, usually as a result of thermal damage similar to that seen during initial processing. In some cases, this is turned into an advantage by intentionally and completely depolymerising the plastic back into its starting monomers, which can then be used to generate fresh, un-degraded plastic. In theory, this chemical (or feedstock) recycling offers infinite recyclability, but it is also more expensive and can have a higher carbon footprint because of its energy costs. Mechanical recycling, where the plastic is simply remelted and reformed, is more common, although this usually results in a lower-quality product. Alternatively, plastic may simply be burnt as a fuel in a waste-to-energy process. | 0 | Theoretical and Fundamental Chemistry |
Like many ACE inhibitors, this prodrug is converted to the active metabolite spiraprilat following oral administration. Unlike other members of the group, it is eliminated both by renal and hepatic routes, which may allow for greater use in patients with renal impairment.
However, data on its effect upon the renal function are conflicting. | 0 | Theoretical and Fundamental Chemistry |
The capillary length can also be found through the manipulation of many different physical phenomenon. One method is to focus on capillary action, which is the attraction of a liquids surface to a surrounding solid. | 1 | Applied and Interdisciplinary Chemistry |
In order for long-term potentiation (LTP) to occur, there must be stimulation of NMDA receptors, which causes AMPA receptors to be inserted postsynaptically. PI3K binds to AMPA receptors in a conserved region to orient the receptors in the membrane, specifically at the GluR subunit. PI3K activity increases in response to calcium ions and CaM. Additionally, AKT localizes PtdIns-3Ps in the post synapse, which recruits docking proteins such as tSNARE and Vam7. This directly leads to the docking of AMPA in the post synapse. mTOR activated p70S6K and inactivated 4EBP1 which changes gene expression to allow LTP to occur. Long-term fear conditioning training was affected in rats but there was no effect in short term conditioning. Specifically, amygdala fear conditioning was lost. This is a type of trace conditioning which is a form of learning that requires association of a conditioned stimulus with an unconditioned stimulus. This effect was lost in PI3K knockdowns and increased in PI3K overexpressions. | 1 | Applied and Interdisciplinary Chemistry |
For example, the selective capture of particles by an aligned, thin-walled circular nozzle is given by Belyaev and Levin as:
where is particle concentration, is speed, and the subscript 0 indicates conditions far upstream of the nozzle. The characteristic distance is the diameter of the nozzle. Here the Stokes number is calculated,
where is the particles settling velocity, is the sampling tubes inner diameter, and is the acceleration of gravity. | 1 | Applied and Interdisciplinary Chemistry |
On average, the total power of the thermal radiation emitted by Earth is equal to the power absorbed from sunlight. As CO levels rise, the emitted radiation can maintain this equilibrium only if the temperature increases, so that the total emitted radiation is unchanged (averaged over enough time, in the order of few years so that diurnal and annual periods are averaged upon).
According to Stefan–Boltzmann law, the total emitted power by Earth per unit area is:
where σ is Stefan–Boltzmann constant and ε is the emissivity in the relevant wavelengths. T is some average temperature representing the effective radiation temperature.
CO content changes the effective T, but instead one may treat T to be a typical ground or lower-atmosphere temperature (same as T or close to it) and consider CO content as changing the emissivity ε. We thus re-interpret ε in the above equation as an effective emissivity that includes the CO effect;, and take T=T. A change in CO content thus causes a change dε in this effective emissivity, so that is the radiative forcing, divided by the total energy flux radiated by Earth.
The relative change in the total radiated energy flux due to changes in emissivity and temperature is:
Thus, if the total emitted power is to remain unchanged, a radiative forcing relative to the total energy flux radiated by Earth, causes a 1/4-fold relative change in temperature.
Thus: | 1 | Applied and Interdisciplinary Chemistry |
This compound is originated from mevalonic acid pathway which produce dimethylallyl diphosphate (DMAPP) from acetyl-CoA. Three DMAPPs, or one DMAPP and two isopentenyl diphosphate (IPP), are made into a farnesyl diphosphate (FPP), which is the fundamental precursor of sesquiterpene, and then sesquiterpene cyclise enzymes cause it a cyclization. The synthesis up to here is well known, though process after the first cyclization was unclear.
Anislactone-type sesquiterpenes which merrilactone A belongs to has been thought to be biosynthesized from majucin since they have γ-lactone. However, this pathway has trouble to elucidate some configurations and other feature they have. The biosynthesis shown in the figure was newly proposed and solved these problems.
The point of this pathway is that seco-prezizaane, anislactone and tashironin group which are all found in Illicium are all derived from the same intermediate 6. This is expected to be able to give all characteristic sesquiterpenes in Illicium plants a reasonable explanation of biosynthesis. | 0 | Theoretical and Fundamental Chemistry |
Pre-emption prevents damage from happening. This is done either by converting reactive metabolites to less harmful ones, or by speeding up an insufficiently fast chemical reaction. The reactive metabolite can be either a side product, or a normal, but highly reactive intermediate.
For example, a side activity of Rubisco yields small amounts of xylulose-1,5-bisphosphate, which can inhibit Rubisco activity. The CbbY enzyme dephosphorylates xylulose-1,5-bisphosphate to the natural metabolite xylulose-5-phosphate, thereby preventing inhibition of Rubisco. | 1 | Applied and Interdisciplinary Chemistry |
Since the motions of the atoms in a molecule are determined by quantum mechanics, "motion" must be defined in a quantum mechanical way. The overall (external) quantum mechanical motions translation and rotation hardly change the geometry of the molecule. (To some extent rotation influences the geometry via Coriolis forces and centrifugal distortion, but this is negligible for the present discussion.) In addition to translation and rotation, a third type of motion is molecular vibration, which corresponds to internal motions of the atoms such as bond stretching and bond angle variation. The molecular vibrations are harmonic (at least to good approximation), and the atoms oscillate about their equilibrium positions, even at the absolute zero of temperature. At absolute zero all atoms are in their vibrational ground state and show zero point quantum mechanical motion, so that the wavefunction of a single vibrational mode is not a sharp peak, but approximately a Gaussian function (the wavefunction for n = 0 depicted in the article on the quantum harmonic oscillator). At higher temperatures the vibrational modes may be thermally excited (in a classical interpretation one expresses this by stating that "the molecules will vibrate faster"), but they oscillate still around the recognizable geometry of the molecule.
To get a feeling for the probability that the vibration of molecule may be thermally excited,
we inspect the Boltzmann factor , where ΔE is the excitation energy of the vibrational mode, k the Boltzmann constant and T the absolute temperature. At 298 K (25 °C), typical values for the Boltzmann factor β are:
* β = 0.089 for ΔE = 500 cm
* β = 0.008 for ΔE = 1000 cm
* β = 0.0007 for ΔE = 1500 cm.
(The reciprocal centimeter is an energy unit that is commonly used in infrared spectroscopy; 1 cm corresponds to ). When an excitation energy is 500 cm, then about 8.9 percent of the molecules are thermally excited at room temperature. To put this in perspective: the lowest excitation vibrational energy in water is the bending mode (about 1600 cm). Thus, at room temperature less than 0.07 percent of all the molecules of a given amount of water will vibrate faster than at absolute zero.
As stated above, rotation hardly influences the molecular geometry. But, as a quantum mechanical motion, it is thermally excited at relatively (as compared to vibration) low temperatures. From a classical point of view it can be stated that at higher temperatures more molecules will rotate faster,
which implies that they have higher angular velocity and angular momentum. In quantum mechanical language: more eigenstates of higher angular momentum become thermally populated with rising temperatures. Typical rotational excitation energies are on the order of a few cm. The results of many spectroscopic experiments are broadened because they involve an averaging over rotational states. It is often difficult to extract geometries from spectra at high temperatures, because the number of rotational states probed in the experimental averaging increases with increasing temperature. Thus, many spectroscopic observations can only be expected to yield reliable molecular geometries at temperatures close to absolute zero, because at higher temperatures too many higher rotational states are thermally populated. | 0 | Theoretical and Fundamental Chemistry |
For intense beams of light (e.g. laser) traveling in a medium or in a waveguide, such as an optical fiber, the variations in the electric field of the beam itself may induce acoustic vibrations in the medium via electrostriction or radiation pressure. The beam may display Brillouin scattering as a result of those vibrations, usually in the direction opposite the incoming beam, a phenomenon known as stimulated Brillouin scattering (SBS). For liquids and gases, the frequency shifts typically created are of the order of 1–10 GHz resulting in wavelength shifts of ~1–10 pm in the visible light. Stimulated Brillouin scattering is one effect by which optical phase conjugation can take place. | 0 | Theoretical and Fundamental Chemistry |
Efforts are reported in asymmetric synthesis of halo carbonyls through organocatalysis. In one study an acid chloride is converted into an α-halo ester with a strong base (sodium hydride), a bromine donor and an organocatalyst based on proline and quinine:
In the proposed reaction mechanism the base first converts the acid chloride to the ketene, the organocatalyst then introduces chirality through its quinonoid tertiary amine, forming a ketene adduct. | 0 | Theoretical and Fundamental Chemistry |
In the process of studying natural radioactivity - studying the radiation of radioactive elements and radioactive transformations, new natural radioactive elements were discovered, systematized in radioactive groups - uranium and thorium, which include the third, so-called actinium family - actinides (this name was proposed by S. A. Shchukarev). F.Soddy's discovery of the law of radioactive displacements made it possible to assume that the final stable decay products of elements of all three families are three isotopes of the same element - lead.
The Bohr model of the atom is based on the study of natural radioactivity, which showed the complexity of the structure of the atom, the decay of which produces atoms of other elements, which is accompanied by three types of radiation: α, β и γ.
The neutron-proton theory of the structure of the atomic nucleus owes its origin to the discovery of new elementary particles that make up the nucleus: the neutron (n) and the proton (p), which became possible by the artificial splitting of the atom under the influence of α-particles (1919): N+He→O+H, accompanied by the release of a proton (soon experiments were carried out with a number of other light elements).
Further fundamental research in this area showed that in light elements the number of neutrons in the nucleus is equal to the number of protons; and as we move to heavy elements, neutrons begin to dominate over protons, and the nuclei become unstable - they become radioactive.
As part of the atomic project, he was a member of the technical council and was responsible for the activities of the radium institute. Through the efforts of V.G. Khlopin and the First Secretary of the Leningrad Regional Committee and City Committee of the All-Union Communist Party of Bolsheviks, Alexey Kuznetsov, the Radium Institute received additional premises. The decision to allocate space was made by the Special Committee in November 1945, carried out by the chairmen of the Operations Bureau of the Council of People's Commissars of the RSFSR A. N. Kosygin and the representative of the State Planning Committee in the Special Committee N. A. Borisov. | 0 | Theoretical and Fundamental Chemistry |
Foams can form naturally within a variety of living organisms. For example, wood, cork, and plant matter all can have foam components or structures. Fungi are generally composed of mycelium, which is made up of hollow filaments of chitin nanofibers bound to other components. Animal parts like cancellous bone, horseshoe crab shells, toucan beaks, sponge, coral, feathers, and antlers all contain foam-like structures which decrease overall weight at the expense of other material properties.
Structures like bone, antlers, and shells have strong materials housing weaker but lighter materials within. Bones tend to have compact, dense external regions, which protect the internal foam-like cancelous bone. The same principle applies to horseshoe crab shells, toucan beaks, and antlers. The barbs and shafts of feathers similarly contain closed-cell foam.
Protective foams can be formed externally by parent organisms or by eggs interacting with the environment: tunicate egg mix with sea water to create a liquid-based foam; tree frog eggs grow in protein foams above and on water (see Figure 1); certain freshwater fish lay eggs in surface foam from their mucus; deep sea fish produce eggs in swimbladders of dual layered foams; and some insects keep their larvae in foam. | 0 | Theoretical and Fundamental Chemistry |
This list is extremely abbreviated in terms of the enzymes mimicked and the primary investigators working on each enzyme mimic.
Richard Holm's work on mimics of nitrogenase and creation of iron sulfur clusters.
Stephen Lippard's work on MMO.
Thomas Rauchfusss, Marcetta Darensbourgs and Christopher Pickett's work on Hydrogenase mimics.
Harry Gray's work with porphyrins complexes.
Ronald Breslow and Larry E. Overman coined the term of "artificial enzyme". | 0 | Theoretical and Fundamental Chemistry |
A biosignature must be able to last for long enough so that a probe, telescope, or human can be able to detect it. A consequence of a biological organism's use of metabolic reactions for energy is the production of metabolic waste. In addition, the structure of an organism can be preserved as a fossil and we know that some fossils on Earth are as old as 3.5 billion years. These byproducts can make excellent biosignatures since they provide direct evidence for life. However, in order to be a viable biosignature, a byproduct must subsequently remain intact so that scientists may discover it. | 1 | Applied and Interdisciplinary Chemistry |
With the use of an epifluorescent microscope, microscopic flows can be analyzed. MicroPIV makes use of fluorescing particles that excite at a specific wavelength and emit at another wavelength. Laser light is reflected through a dichroic mirror, travels through an objective lens that focuses on the point of interest, and illuminates a regional volume. The emission from the particles, along with reflected laser light, shines back through the objective, the dichroic mirror and through an emission filter that blocks the laser light. Where PIV draws its 2-dimensional analysis properties from the planar nature of the laser sheet, microPIV utilizes the ability of the objective lens to focus on only one plane at a time, thus creating a 2-dimensional plane of viewable particles.
MicroPIV particles are on the order of several hundred nm in diameter, meaning they are extremely susceptible to Brownian motion. Thus, a special ensemble averaging analysis technique must be utilized for this technique. The cross-correlation of a series of basic PIV analyses are averaged together to determine the actual velocity field. Thus, only steady flows can be investigated. Special preprocessing techniques must also be utilized since the images tend to have a zero-displacement bias from background noise and low signal-noise ratios. Usually, high numerical aperture objectives are also used to capture the maximum emission light possible. Optic choice is also critical for the same reasons. | 1 | Applied and Interdisciplinary Chemistry |
An elementary charge transfer step can be described by the Butler–Volmer model proposed by John Alfred Valentine Butler and Max Volmer. The reaction rate is given by the Butler-Volmer equation:
In this equation is the net current density, is the exchange current density, is the charge transfer coefficient, is the number of electrons transferred in the reaction, is the Faraday constant, is the molar gas constant, is the absolute temperature, is the electrode overpotential, is the thermodynamic equilibrium reduction potential and is the observed value of this potential.
The equation yields a negative current density for a reduction reaction (negative overpotential) and a positive current density for an oxidation reaction (positive overpotential). The sign of the current density has no physical meaning and is defined by an international convention. | 0 | Theoretical and Fundamental Chemistry |
Pyridine is used as a polar, basic, low-reactive solvent, for example in Knoevenagel condensations. It is especially suitable for the dehalogenation, where it acts as the base for the elimination reaction. In esterifications and acylations, pyridine activates the carboxylic acid chlorides and anhydrides. Even more active in these reactions are the derivatives 4-dimethylaminopyridine (DMAP) and 4-(1-pyrrolidinyl) pyridine. Pyridine is also used as a base in some condensation reactions. | 0 | Theoretical and Fundamental Chemistry |
Transcription of the cloned gene is a necessary component of the vector when expression of the gene is required: one gene may be amplified through transcription to generate multiple copies of mRNAs, the template on which protein may be produced through translation. A larger number of mRNAs would express a greater amount of protein, and how many copies of mRNA are generated depends on the promoter used in the vector. The expression may be constitutive, meaning that the protein is produced constantly in the background, or it may be inducible whereby the protein is expressed only under certain condition, for example when a chemical inducer is added. These two different types of expression depend on the types of promoter and operator used.
Viral promoters are often used for constitutive expression in plasmids and in viral vectors because they normally force constant transcription in many cell lines and types reliably. Inducible expression depends on promoters that respond to the induction conditions: for example, the murine mammary tumor virus promoter only initiates transcription after dexamethasone application and the Drosophila heat shock promoter only initiates after high temperatures.
Some vectors are designed for transcription only, for example for in vitro mRNA production. These vectors are called transcription vectors. They may lack the sequences necessary for polyadenylation and termination, therefore may not be used for protein production. | 1 | Applied and Interdisciplinary Chemistry |
The thermohaline circulation plays an important role in supplying heat to the polar regions, and thus in regulating the amount of sea ice in these regions, although poleward heat transport outside the tropics is considerably larger in the atmosphere than in the ocean. Changes in the thermohaline circulation are thought to have significant impacts on the Earth's radiation budget.
Large influxes of low-density meltwater from Lake Agassiz and deglaciation in North America are thought to have led to a shifting of deep water formation and subsidence in the extreme North Atlantic and caused the climate period in Europe known as the Younger Dryas. | 0 | Theoretical and Fundamental Chemistry |
Natural ventilation harnesses naturally available forces to supply and remove air in an enclosed space. Poor ventilation in rooms is identified to significantly increase the localized moldy smell in specific places of the room including room corners. There are three types of natural ventilation occurring in buildings: wind-driven ventilation, pressure-driven flows, and stack ventilation. The pressures generated by the stack effect rely upon the buoyancy of heated or rising air. Wind-driven ventilation relies upon the force of the prevailing wind to pull and push air through the enclosed space as well as through breaches in the building's envelope.
Almost all historic buildings were ventilated naturally. The technique was generally abandoned in larger US buildings during the late 20th century as the use of air conditioning became more widespread. However, with the advent of advanced Building Performance Simulation (BPS) software, improved Building Automation Systems (BAS), Leadership in Energy and Environmental Design (LEED) design requirements, and improved window manufacturing techniques; natural ventilation has made a resurgence in commercial buildings both globally and throughout the US.
The benefits of natural ventilation include:
*Improved Indoor air quality (IAQ)
*Energy savings
*Reduction of greenhouse gas emissions
*Occupant control
*Reduction in occupant illness associated with Sick Building Syndrome
*Increased worker productivity
Techniques and architectural features used to ventilate buildings and structures naturally include, but are not limited to:
*Operable windows
*Night purge ventilation
*Clerestory windows and vented skylights
*Building orientation
*Wind capture façades | 1 | Applied and Interdisciplinary Chemistry |
Prelogs main interest was focused on alkaloids. He found an ideal topic in the elucidation of the structure of solanine; he continued his work on Cinchona alkaloids and started to investigate strychnine. He showed that Robert Robinsons formula for strychnine was not correct. Although the formula he proposed was also not the right one, the discovery increased his international prestige. Later he worked on elucidating the structures of aromatic Erythrina alkaloids with Derek Barton, Oskar Jeger and Robert Burns Woodward.
At mid-century, the instrumental revolution necessitated a new approach to structural elucidation. Purely chemical methods had become outdated and had lost some of their intellectual appeal. Recognizing the growing importance of microbial metabolites, Prelog started working on these compounds, which possess unusual structures and interesting biological properties. It led him into antibiotics, and he subsequently elucidated the structures of such compounds as nonactin, boromycin, and rifamycins. For Prelog, natural products represented more than a chemical challenge. He considered them a record of billions of years of evolution.
In 1944 at the ETH, Prelog managed to separate enantiomers with "asymmetric" trivalent nitrogen by column chromatography at a time when this method was still in its infancy. His work on medium-sized alicyclic and heterocyclic rings established him as a pioneer in stereochemistry and conformational theory and brought an invitation to give the first Centenary Lecture of the Chemical Society in London in 1949. He synthesised medium-sized ring compounds with 8 to 12 members from dicarboxylic acid esters by acyloin condensation and explained their unusual chemical reactivity by a "nonclassical" strain because of energetically unfavorable conformations. He also contributed to the understanding of Bredt's rule by showing that a double bond may occur at the bridgehead if the ring is large enough.
In his research of asymmetric syntheses, Prelog studied enantioselective reactions and established rules for the relationship between configuration of educts and products. From Prelog's researches into the stereospecificity of microbiological reductions of alicyclic ketones and the enzymic oxidation of alcohols, he contributed not only to the knowledge of the mechanism of stereospecificity of enzymic reactions in general but also to the structure of the active site of the enzyme.
Specifying the growing number of stereoisomers of organic compounds became for Prelog one of his important aims. In 1954 he joined R. S. Cahn and Christopher Ingold in their efforts to build a system for specifying a particular stereoisomers by simple and unambiguous descriptors that could be easily assigned and deciphered: The CIP system (Cahn-Ingold-Prelog) was developed for defining absolute configuration using "sequence rules". Together they published two papers. After Cahn and Ingold died, Prelog published a third paper on the topic. In 1959, Prelog obtained Swiss citizenship. | 0 | Theoretical and Fundamental Chemistry |
The Boc group can be added to the amine under aqueous conditions using di-tert-butyl dicarbonate in the presence of a base such as sodium bicarbonate. Protection of the amine can also be accomplished in acetonitrile solution using 4-dimethylaminopyridine (DMAP) as the base.
Removal of the Boc in amino acids can be accomplished with strong acids such as trifluoroacetic acid neat or in dichloromethane or with HCl in methanol. A complication may be the tendency of the t-butyl cation intermediate to alkylate other nucleophiles; scavengers such as anisole or thioanisole may be used.
Selective cleavage of the N-Boc group in the presence of other protecting groups is possible when using AlCl.
Reaction with trimethylsilyl iodide in acetonitrile followed by methanol is a mild and versatile method of deprotecting Boc-protected amines.
The use of triethylsilane as a carbocation scavenger in the presence of trifluoroacetic acid in dichloromethane has been shown to lead to increased yields, decreased reaction times, simple work-up and improved selectivity for the deprotection of t-butyl ester and t-butoxycarbonyl sites in protected amino-acids and peptides in the presence of other acid-sensitive protecting groups such as the benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, O- and S-benzyl and t-butylthio groups. | 0 | Theoretical and Fundamental Chemistry |
For the reaction
the observed rate equation (or rate expression) is:
As for many reactions, the experimental rate equation does not simply reflect the stoichiometric coefficients in the overall reaction: It is third order overall: first order in H and second order in NO, even though the stoichiometric coefficients of both reactants are equal to 2.
In chemical kinetics, the overall reaction rate is often explained using a mechanism consisting of a number of elementary steps. Not all of these steps affect the rate of reaction; normally the slowest elementary step controls the reaction rate. For this example, a possible mechanism is:
Reactions 1 and 3 are very rapid compared to the second, so the slow reaction 2 is the rate-determining step. This is a bimolecular elementary reaction whose rate is given by the second-order equation:
where is the rate constant for the second step.
However NO is an unstable intermediate whose concentration is determined by the fact that the first step is in equilibrium, so that where is the equilibrium constant of the first step. Substitution of this equation in the previous equation leads to a rate equation expressed in terms of the original reactants
This agrees with the form of the observed rate equation if it is assumed that . In practice the rate equation is used to suggest possible mechanisms which predict a rate equation in agreement with experiment.
The second molecule of H does not appear in the rate equation because it reacts in the third step, which is a rapid step after the rate-determining step, so that it does not affect the overall reaction rate. | 0 | Theoretical and Fundamental Chemistry |
In combustion, heat release parameter (or gas expansion parameter) is a dimensionless parameter which measures the amount of heat released by the combustion process. It is defined as
where
* is the burnt gas temperature
* is the unburnt mixture temperature.
In typical combustion process, . For isobaric combustion, using ideal gas law, the parameter can be expressed in terms of density, i.e.,
The ratio of burnt gas to unburnt gas temperature is | 1 | Applied and Interdisciplinary Chemistry |
An ion beam is a type of charged particle beam consisting of ions. Ion beams have many uses in electronics manufacturing (principally ion implantation) and other industries. A variety of ion beam sources exists, some derived from the mercury vapor thrusters developed by NASA in the 1960s. The most common ion beams are of singly-charged ions. | 0 | Theoretical and Fundamental Chemistry |
It may be shown that, in orthogonal coordinates, the -th component of the convection term of the material derivative of a vector field is given by
where the are related to the metric tensors by
In the special case of a three-dimensional Cartesian coordinate system (x, y, z), and being a 1-tensor (a vector with three components), this is just:
where is a Jacobian matrix. | 1 | Applied and Interdisciplinary Chemistry |
Nitrification is a process of nitrogen compound oxidation (effectively, loss of electrons from the nitrogen atom to the oxygen atoms), and is catalyzed step-wise by a series of enzymes.
: (Nitrosomonas, Comammox)
: (Nitrobacter, Nitrospira, Comammox)
OR
In Nitrosomonas europaea, the first step of oxidation (ammonia to hydroxylamine) is carried out by the enzyme ammonia monooxygenase (AMO).
The second step (hydroxylamine to nitrite) is catalyzed by two enzymes. Hydroxylamine oxidoreductase (HAO), converts hydroxylamine to nitric oxide.
Another currently unknown enzyme converts nitric oxide to nitrite.
The third step (nitrite to nitrate) is completed in a distinct organism. | 1 | Applied and Interdisciplinary Chemistry |
Capnellene-8β,10α-diol and its acylated derivatives exhibit significant cytotoxicity in vitro against cervical epitheloid carcinoma (HeLa, oral epidermoid (KB), medulloblastoma (Daoy) and colon adenocarcinoma (WiDr) human tumor cell lines. The diol was also effective against human leukemia, renal leiomyoblastoma, colon and breast cancer cell lines. In the same study, capnellene-8β-ol demonstrated selective toxicity for the renal leiomyoblastoma and ovarian cancer cell lines, while 3β-acetoxycapnellene-8β,10α,14β-triol was active against leukemia cell lines. The antitumor properties of capnellene derivatives have yet to be explored in vivo. | 0 | Theoretical and Fundamental Chemistry |
Both hypoxic conditions and serum deprivation induced increased expression of SFRP1 in leiomyoma cells. However, the smooth muscle cells cultured from the myometrium showed no significant correlation between SFRP1 expression and oxygen concentration. This suggests that SFRP1 may protect the cells from the damage caused by these stresses. | 1 | Applied and Interdisciplinary Chemistry |
After John Macadam and her children's deaths his widow, Elizabeth Clark, later remarried. She married the Reverend John Dalziel Dickie, who was pastor at Colac for 32 years. They married on 26 February 1868 They had four daughters. Elizabeth Dickie died aged 82 in 1915, in Brighton, Victoria, as the widow of the Rev. Dickie. Dickie had died 25 December 1909. | 0 | Theoretical and Fundamental Chemistry |
Micellar solubilization (solubilization) is the process of incorporating the solubilizate (the component that undergoes solubilization) into or onto micelles. Solubilization may occur in a system consisting of a solvent, an association colloid (a colloid that forms micelles), and at least one other solubilizate. | 0 | Theoretical and Fundamental Chemistry |
The dynamic Wilhelmy method is a method for calculating average advancing and receding contact angles on solids of uniform geometry. Both sides of the solid must have the same properties. Wetting force on the solid is measured as the solid is immersed in or withdrawn from a liquid of known surface tension. Also in that case it is possible to measure the equilibrium contact angle by applying a very controlled vibration. That methodology, called VIECA, can be implemented in a quite simple way on every Wilhelmy balance. | 0 | Theoretical and Fundamental Chemistry |
Coal tar was formerly one of the products of gasworks. Tar made from coal or petroleum is considered toxic and carcinogenic because of its high benzene content, though coal tar in low concentrations is used as a topical medicine for conditions such as psoriasis. Coal and petroleum tar has a pungent odor.
Coal tar is listed at number 1999 in the United Nations list of dangerous goods. | 0 | Theoretical and Fundamental Chemistry |
Reciprocal silencing on the tissue level refers to the same pattern of silencing and expression of homeologous loci. However, in this case, the differences in silencing and expression occur between two types of tissue within the same individual, rather than in individuals of different populations. This is an example of neofunctionalization, a process where duplicated genes that were once at equivalent loci evolve to carry out two separate functions. Since different tissues require different genes to be expressed, reciprocal silencing can occur between tissues. Importantly, while the pattern of gene expression is the same as in the population case, the genetic means by which this pattern is achieved are very different. While silencing mutations are thought to be the main source of reciprocal silencing
at the population level, at the tissue level only epigenetic factors are in play, since expressible copies of both homeologous loci must exist in all cells in an individual if different tissues express different homeologs. | 1 | Applied and Interdisciplinary Chemistry |
Silver nanoparticles are used for catalyzing chemical reactions, Raman imaging, and antimicrobial sterilization. Along with its antimicrobial properties, its low mammalian cell toxicity makes these particles a common addition to consumer products. Washing textiles embedded with silver nanoparticles results in the oxidation and transformation of metallic Ag into AgCl.
Silver nanoparticles have different physicochemical characteristics from the free silver ion, Ag and possess increased optical, electromagnetic, and catalytic properties. Particles with one dimension of 100 nm or less can generate reactive oxygen species. Smaller particles less than 10 nm may pass through cellular membranes and accumulate within the cell. Silver nanoparticles were also found to attach to cellular membranes, eventually dissipating the proton motive force, leading to cell death.
Silver nanoparticles that are larger than the openings of membrane channel proteins can easily clog channels, leading to the disruption of membrane permeability and transport. However, the antimicrobial effectiveness of silver nanoparticles has been shown to decrease when dissolved in liquid media.
The free silver ion are potentially toxic to bacteria and planktonic species in the water. The positively charged silver ion can also attach to the negatively charged cell walls of bacteria, leading to deactivation of cellular enzymes, disruption of membrane permeability, and eventually, cell lysis and death. However, its toxicity to microorganisms is not overtly observed since the free silver ion is found in low concentrations in wastewater treatment systems and the natural environment due to its complexation with ligands such as chloride, sulfide, and thiosulfate. | 1 | Applied and Interdisciplinary Chemistry |
The maximum density of a substance is the highest attainable density of the substance under given conditions. | 0 | Theoretical and Fundamental Chemistry |
Construction of a 15 t/h demonstration copper ISASMELT plant began in 1986. The design was based on MIM's 250 kg/h test work and operating experience with the lead ISASMELT pilot plant. It cost A$11 million and was commissioned in April 1987. The initial capital cost was recovered in the first 14 months of operation.
As with the lead ISASMELT pilot plant, the copper ISASMELT demonstration plant was integrated into copper smelter operations and justified by the 20% (30,000 t/y) increase in copper production that it provided. It quickly treated the entire backlog of converter slag concentrate, which could not be treated at high rates in the reverberatory furnaces without generating magnetite ("FeO") accretions that would necessitate shutting down the reverberatory furnaces for their removal.
The demonstration copper ISASMELT plant was used to further develop the copper process. Refractory life was initially shorter than expected and considerable effort was devoted to understanding the reasons and attempting to extend the life of the refractories. At the end of the life of the demonstration plant, the longest refractory life achieved was 90 weeks.
Lance life was also low initially. Inexperienced operators could destroy a lance in as little as 10 minutes. However, as a result of modifications to the lance design, the development of techniques to determine the position of the lance in the bath, and a rise in the operating experience, the typical lance life was extended to a week.
The demonstration plant was commissioned with high-pressure (700 kPag) air injected down the lance. Later, after extensive testing of low-pressure lance designs and trials using oxygen enrichment of the lance air, a 70 t/d oxygen plant and a 5 Nm3/s blower with a discharge pressure of 146 kPag were purchased. The new lance design was capable of operating at pressures below 100 kPag. Using enrichment of the oxygen in the lance air to 35%, the demonstration plant throughput was lifted to 48 t/h of concentrate, and the gross energy used during smelting was reduced from 25.6 GJ/t of contained copper to 4.1 GJ/t. | 1 | Applied and Interdisciplinary Chemistry |
Carbon dioxide binds to metals in only a few ways. The bonding mode depends on the electrophilicity and basicity of the metal centre. Most common is the η-CO coordination mode as illustrated by Aresta's complex, Ni(CO)(PCy), which was the first reported complex of CO This square-planar compound is a derivative of Ni(II) with a reduced CO ligand. In rare cases, CO binds to metals as a Lewis base through its oxygen centres, but such adducts are weak and mainly of theoretical interest. A variety of multinuclear complexes are also known often involving Lewis basic and Lewis acidic metals, e.g. metallacarboxylate salts (CH)Fe(CO)COK. In multinuclear cases (compounds containing more than one metal), more complicated and more varied coordination geometries are observed. One example is the unsymmetrical compound containing four rhenium centres, [(CO)ReCORe(CO)]. Carbon dioxide can also bind to ligands on a metal complex (vs just the metal), e.g. by converting hydroxy ligands to carbonato ligands. | 0 | Theoretical and Fundamental Chemistry |
Common inspection methods for steel castings are magnetic particle testing and liquid penetrant testing. Common inspection methods for aluminum castings are radiography, ultrasonic testing, and liquid penetrant testing. | 1 | Applied and Interdisciplinary Chemistry |
Pipe materials with higher molecular weights (MW), or densities, will have slower material flow rates when in the molten state during fusion. Despite the differences in flow rates, the final joint strength is generally consistent over a fairly wide range of pipe molecular weights. | 0 | Theoretical and Fundamental Chemistry |
5-Methylcytosine and 5-hydroxymethylcytosine both read as a C in bisulfite sequencing. Oxidative bisulfite sequencing is a method to discriminate between 5-methylcytosine and 5-hydroxymethylcytosine at single base resolution. The method employs a specific (Tet-assisted) chemical oxidation of 5-hydroxymethylcytosine to 5-formylcytosine, which subsequently converts to uracil during bisulfite treatment. The only base that then reads as a C is 5‑methylcytosine, giving a map of the true methylation status in the DNA sample. Levels of 5‑hydroxymethylcytosine can also be quantified by measuring the difference between bisulfite and oxidative bisulfite sequencing. | 1 | Applied and Interdisciplinary Chemistry |
Once the cellular population is stable, all the action potential are compared to physiological data related to the most relevant anatomical regions to appropriately filter the action potential, aiming to consider just the physiologically relevant ones.
At the atrial level, the clusterization occurs with data associated to:
* Right atrium
* Right atrial appendage
* Left atrium
* Left atrial appendage
* Atrioventricular rings
* Crista terminalis
* Right Bachmann's bundle
* Left Bachmann's bundle
* Pectinate muscles | 1 | Applied and Interdisciplinary Chemistry |
Volumetric flow rate is defined by the limit
that is, the flow of volume of fluid through a surface per unit time .
Since this is only the time derivative of volume, a scalar quantity, the volumetric flow rate is also a scalar quantity. The change in volume is the amount that flows after crossing the boundary for some time duration, not simply the initial amount of volume at the boundary minus the final amount at the boundary, since the change in volume flowing through the area would be zero for steady flow.
IUPAC prefers the notation and for volumetric flow and mass flow respectively, to distinguish from the notation for heat. | 1 | Applied and Interdisciplinary Chemistry |
Liñán diffusion flame theory is a theory developed by Amable Liñán in 1974 to explain the diffusion flame structure using activation energy asymptotics and Damköhler number asymptotics. Liñán used counterflowing jets of fuel and oxidizer to study the diffusion flame structure, analyzing for the entire range of Damköhler number. His theory predicted four different types of flame structure as follows,
* Nearly-frozen ignition regime, where deviations from the frozen flow conditions are small (no reaction sheet exist in this regime),
* Partial burning regime, where both fuel and oxidizer cross the reaction zone and enter into the frozen flow on other side,
* Premixed flame regime, where only one of the reactants cross the reaction zone, in which case, reaction zone separates a frozen flow region from a near-equilibrium region,
* Near-equilibrium diffusion-controlled regime, is a thin reaction zone, separating two near-equilibrium region. | 1 | Applied and Interdisciplinary Chemistry |
An ideal cycle is simple to analyze and consists of:
# TOP (A) and BOTTOM (C) of the loop: a pair of parallel isobaric processes
# RIGHT (B) and LEFT (D) of the loop: a pair of parallel isochoric processes
If the working substance is a perfect gas, is only a function of for a closed system since its internal pressure vanishes. Therefore, the internal energy changes of a perfect gas undergoing various processes connecting initial state to final state are always given by the formula
Assuming that is constant, for any process undergone by a perfect gas.
Under this set of assumptions, for processes A and C we have and , whereas for processes B and D we have and .
The total work done per cycle is , which is just the area of the rectangle. If the total heat flow per cycle is required, this is easily obtained. Since , we have .
Thus, the total heat flow per cycle is calculated without knowing the heat capacities and temperature changes for each step (although this information would be needed to assess the thermodynamic efficiency of the cycle). | 0 | Theoretical and Fundamental Chemistry |
The results of the investigations are internationally evaluated by the members in specialist committees and made available to practice and the responsible bodies at regional and state level, as well as to the European Uninion for legislative and approval procedures. | 1 | Applied and Interdisciplinary Chemistry |
In addition to Cori Cycle, the lactate shuttle hypothesis proposes complementary functions of lactate in multiple tissues. Contrary to the long-held belief that lactate is formed as a result of oxygen-limited metabolism, substantial evidence exists that suggests lactate is formed under both aerobic and anaerobic conditions, as a result of substrate supply and equilibrium dynamics. | 1 | Applied and Interdisciplinary Chemistry |
In optical physics, transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is the ratio of the transmitted to incident electric field.
Internal transmittance refers to energy loss by absorption, whereas (total) transmittance is that due to absorption, scattering, reflection, etc. | 0 | Theoretical and Fundamental Chemistry |
The Lagrangian and Eulerian specifications of the kinematics and dynamics of the flow field are related by the material derivative (also called the Lagrangian derivative, convective derivative, substantial derivative, or particle derivative).
Suppose we have a flow field u, and we are also given a generic field with Eulerian specification F(x, t). Now one might ask about the total rate of change of F experienced by a specific flow parcel. This can be computed as
where ∇ denotes the nabla operator with respect to x, and the operator u⋅∇ is to be applied to each component of F. This tells us that the total rate of change of the function F as the fluid parcels moves through a flow field described by its Eulerian specification u is equal to the sum of the local rate of change and the convective rate of change of F. This is a consequence of the chain rule since we are differentiating the function F(X(x, t), t) with respect to t.
Conservation laws for a unit mass have a Lagrangian form, which together with mass conservation produce Eulerian conservation; on the contrary, when fluid particles can exchange a quantity (like energy or momentum), only Eulerian conservation laws exist. | 1 | Applied and Interdisciplinary Chemistry |
Given the widespread use of pesticides, herbicides and insecticides in modern farming, dendrimers are also being used by companies to help improve the delivery of agrochemicals to enable healthier plant growth and to help fight plant diseases.
Dendrimers are also being investigated for use as blood substitutes. Their steric bulk surrounding a heme-mimetic centre significantly slows degradation compared to free heme, and prevents the cytotoxicity exhibited by free heme.
Dendritic functional polymer polyamidoamine (PAMAM) is used to prepare core shell structure i.e. microcapsules and utilized in formulation of self-healing coatings of conventional and renewable origins.
Different generations of polyamidoamine dendrimers have recently been implemented as selective contacts in photovoltaic devices. | 0 | Theoretical and Fundamental Chemistry |
The resonance assisted hydrogen bond (commonly abbreviated as RAHB) is a strong type of hydrogen bond. It is characterized by the π-delocalization that involves the hydrogen and cannot be properly described by the electrostatic model alone. This description of the hydrogen bond has been proposed to describe unusually short distances generally observed between or . | 0 | Theoretical and Fundamental Chemistry |
There are several different techniques to detect regulatory genes, but of the many there are a certain few that are used more frequently than others. One of these select few is called ChIP-chip. ChIP-chip is an in vivo technique used to determine genomic binding sites for transcription factors in two component system response regulators. In vitro microarray based assay (DAP-chip) can be used to determine gene targets and functions of two component signal transduction systems. This assay takes advantage of the fact that response regulators can be phosphorylated and thus activated in vitro using small molecule donors like acetyl phosphate. | 1 | Applied and Interdisciplinary Chemistry |
It is listed on Schedule 3 of the Chemical Weapons Convention: All production sites manufacturing more than 30 tonnes per year must be declared to the OPCW. Although less toxic than many other chemical weapons such as sarin, phosgene is still regarded as a viable chemical warfare agent because of its simpler manufacturing requirements when compared to that of more technically advanced chemical weapons such as tabun, a first-generation nerve agent.
Phosgene was first deployed as a chemical weapon by the French in 1915 in World War I. It was also used in a mixture with an equal volume of chlorine, with the chlorine helping to spread the denser phosgene. Phosgene was more potent than chlorine, though some symptoms took 24 hours or more to manifest.
Following the extensive use of phosgene during World War I, it was stockpiled by various countries.
Phosgene was then only infrequently used by the Imperial Japanese Army against the Chinese during the Second Sino-Japanese War. Gas weapons, such as phosgene, were produced by the IJA's Unit 731. | 0 | Theoretical and Fundamental Chemistry |
DTIs inhibit thrombin by two ways; bivalent DTIs block simultaneously the active site and exosite 1 and act as competitive inhibitors of fibrin, while univalent DTIs block only the active site and can therefore both inhibit unbound and fibrin-bound thrombin. In contrast, heparin drugs bind in exosite 2 and form a bridge between thrombin and antithrombin, a natural anticoagulant substrate formed in the body, and strongly catalyzes its function. But heparin can also form a bridge between thrombin and fibrin which binds to exosite 1 which protects the thrombin from inhibiting function of heparin-antithrombin complex and increases thrombins affinity to fibrin. DTIs that bind to the anion-binding site have shown to inactivate thrombin without disconnecting thrombin from fibrin, which points to a separate binding site for fibrin. DTIs arent dependent to cofactors like antithrombin to inhibit thrombin so they can both inhibit free/soluble thrombin as well as fibrin bound thrombin unlike heparins. The inhibition is either irreversible or reversible. Reversible inhibition is often linked to lesser risk of bleeding. Due to this action of DTIs they can both be used for prophylaxis as well as treatment for embolisms/clots. | 1 | Applied and Interdisciplinary Chemistry |
Gasulla, Casano and Guéra, concluded that the longer the lichen are subjected to darkness, the quicker the chlororespiratory pathways can begin. This is due to the fast depletion of PTOX molecules which reduce the PQ pool. These events then stimulate chlororespiratory ETCs into an ongoing loop until the lichen are placed in a luminous environment.
They also derived LHC to be another indicator for chlororespiration. When LHC concentrations inside the chloroplast increased, PS II activity decreased due to loss in ETC activity. This reduction then stimulated chlororespiratory activity to compensate for chemical energy synthesis.<br /> | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, pi stacking (also called π–π stacking) refers to the presumptive attractive, noncovalent pi interactions (orbital overlap) between the pi bonds of aromatic rings. However this is a misleading description of the phenomena since direct stacking of aromatic rings (the "sandwich interaction") is electrostatically repulsive. What is more commonly observed (see figure to the right) is either a staggered stacking (parallel displaced) or pi-teeing (perpendicular T-shaped) interaction both of which are electrostatic attractive For example, the most commonly observed interactions between aromatic rings of amino acid residues in proteins is a staggered stacked followed by a perpendicular orientation. Sandwiched orientations are relatively rare.
Pi stacking is repulsive as it places carbon atoms with partial negative charges from one ring on top of other partial negatively charged carbon atoms from the second ring and hydrogen atoms with partial positive charges on top of other hydrogen atoms that likewise carry partial positive charges. In staggered stacking, one of the two aromatic rings is offset sideways so that the carbon atoms with partial negative charge in the first ring are placed above hydrogen atoms with partial positive charge in the second ring so that the electrostatic interactions become attractive. Likewise, pi-teeing interactions in which the two rings are oriented perpendicular to either other is electrostatically attractive as it places partial positively charged hydrogen atoms in close proximity to partially negatively charged carbon atoms. An alternative explanation for the preference for staggered stacking is due to the balance between van der Waals interactions (attractive dispersion plus Pauli repulsion).
These staggered stacking and π-teeing interactions between aromatic rings are important in nucleobase stacking within DNA and RNA molecules, protein folding, template-directed synthesis, materials science, and molecular recognition. Despite the wide use of term pi stacking in the scientific literature, there is no theoretical justification for its use. | 0 | Theoretical and Fundamental Chemistry |
The reaction of a strong acid with a strong base is essentially a quantitative reaction. For example,
In this reaction both the sodium and chloride ions are spectators as the neutralization reaction,
does not involve them. With weak bases addition of acid is not quantitative because a solution of a weak base is a buffer solution. A solution of a weak acid is also a buffer solution. When a weak acid reacts with a weak base an equilibrium mixture is produced. For example, adenine, written as AH, can react with a hydrogen phosphate ion, .
The equilibrium constant for this reaction can be derived from the acid dissociation constants of adenine and of the dihydrogen phosphate ion.
The notation [X] signifies "concentration of X". When these two equations are combined by eliminating the hydrogen ion concentration, an expression for the equilibrium constant, is obtained. | 0 | Theoretical and Fundamental Chemistry |
Because oxygen and argon leak through packaging material at different rates, comparing the ratios inside a package can determine if and how quickly air from outside has leaked in. | 0 | Theoretical and Fundamental Chemistry |
LSAT is primarily used in its single crystal form, typically as thin (≤1 mm) wafers. These wafers are used as a common substrate for epitaxial growth of thin films. LSAT substrates are popular for epitaxial oxides and their heterostructures, often in the study of electron correlation phenomena. Typical materials grown on LSAT substrates include strontium titanate (SrTiO), cuprate superconductors (such as YBCO), iron-based superconductors (iron-pnictides), rare-earth manganites, rare-earth nickelates and others. Semiconductors such as gallium nitride can also be grown on LSAT.
LSAT's usefulness as a substrate for the growth of such films stems from its high chemical and thermal stability, and very low electrical conductivity. The growth conditions for such epitaxial layers can cause some substrates to form high densities of defects that can alter their properties. One example is the tendency of strontium titanate to form oxygen vacancy defects under high temperatures in high vacuum. These defects result in considerable variations of its properties, including the increase of electrical conductivity and optical opacity. LSAT on the other hand, is stable in both oxidizing and fairly reducing environments in high temperatures, thus enabling a larger window for the processing and growth conditions. | 0 | Theoretical and Fundamental Chemistry |
Isotopic reference materials exist for non-traditional isotope systems (elements other than hydrogen, carbon, oxygen, nitrogen, and sulfur), including lithium, boron, magnesium, calcium, iron, and many others. Because the non-traditional systems were developed relatively recently, the reference materials for these systems are more straightforward and less numerous than for the traditional isotopic systems. The following table contains the material defining the δ=0 for each isotopic scale, the best measurement of the absolute isotopic fractions of an indicated material (which is often the same as the material defining the scale, but not always), the calculated absolute isotopic ratio, and links to lists of isotopic reference materials prepared by the Commission on Isotopic Abundances and Atomic Weight (part of the International Union of Pure and Applied Chemistry (IUPAC)). A summary list of non-traditional stable isotope systems is available [http://www.ciaaw.org/reference-materials.htm here], and much of this information is derived from Brand et al. (2014). In addition to the isotope systems listed in Table 8, ongoing research is focused on measuring the isotopic composition of barium (Allmen et al., 2010; Miyazaki et al., 2014; Nan et al., 2015) and vanadium (Nielson et al., 2011). Specpure Alfa Aesar is an isotopically well-characterized vanadium solution (Nielson et al., 2011). Furthermore, fractionation during chemical processing can be problematic for certain isotopic analyses, such as measuring heavy isotope ratios following column chromatography. In these cases reference materials can be calibrated for particular chemical procedures.
Table 8 gives the material and isotopic ratio defining the δ = 0 scale for each of the indicated elements. In addition, Table 8 lists the material with the best measurement as determined by Meija et al. (2016). "Material" gives chemical formula, "Type of ratio" is the isotopic ratio reported in "Isotope ratio", and "Citation" gives the article(s) reporting the isotopic abundances on which the isotope ratio is based. The isotopic ratios reflect the results from individual analyses of absolute mass fraction, reported in the cited studies, aggregated in Meija et al. (2016), and manipulated to reach the reported ratios. Error was calculated as the square root of the sum of the squares of fractional reported errors. | 0 | Theoretical and Fundamental Chemistry |
In addition to the factors affecting monosaccharide residues, conformational analysis of oligosaccharides and polysaccharides requires consideration additional factors. | 0 | Theoretical and Fundamental Chemistry |
Mission data are provided to the public by the NASA Goddard Earth Science Data and Information Services Center (GES DISC). The Level 1B data product is the least processed and contains records for all collected soundings (about 74,000 soundings per orbit). The Level 2 product contains estimates of the column-averaged dry-air mole fractions of carbon dioxide, among other parameters such as surface albedo and aerosol content. The Level 3 product consists of global maps of carbon dioxide concentrations developed by OCO-2 scientists. | 1 | Applied and Interdisciplinary Chemistry |
Push–pull technology involves use of behaviour-modifying stimuli to manipulate the distribution and abundance of stemborers and beneficial insects for management of stemborer pests. It is based on in-depth understanding of chemical ecology, agrobiodiversity, plant-plant and insect-plant interactions, and involves intercropping a cereal crop with a repellent intercrop such as Desmodium uncinatum (silverleaf) (push), with an attractive trap plant such as Napier grass (pull) planted as a border crop around this intercrop. Gravid stemborer females are repelled from the main crop and are simultaneously attracted to the trap crop. | 1 | Applied and Interdisciplinary Chemistry |
An active metabolite results when a drug is metabolized by the body into a modified form which produces effects in the body. Usually these effects are similar to those of the parent drug but weaker, although they can still be significant (see e.g. 11-hydroxy-THC, morphine-6-glucuronide). Certain drugs such as codeine and tramadol have metabolites (morphine and O-desmethyltramadol respectively) that are stronger than the parent drug and in these cases the metabolite may be responsible for much of the therapeutic action of the parent drug. Sometimes, however, metabolites may produce toxic effects and patients must be monitored carefully to ensure they do not build up in the body. This is an issue with some well-known drugs, such as pethidine (meperidine) and dextropropoxyphene. | 1 | Applied and Interdisciplinary Chemistry |
African swine fever virus (ASFV) is a large double-stranded DNA virus which replicates in the cytoplasm of infected cells and is the only member of the Asfarviridae family. The virus causes a lethal haemorraghic disease in domestic pigs. Some strains can cause death of animals within as little as a week after infection. In other species, the virus causes no obvious disease. ASFV is endemic to sub-Saharan Africa and exists in the wild through a cycle of infection between ticks and wild pigs, bushpigs and warthogs. | 1 | Applied and Interdisciplinary Chemistry |
Hot blast was the single most important advance in fuel efficiency of the blast furnace and was one of the most important technologies developed during the Industrial Revolution. Hot blast was patented by James Beaumont Neilson at Wilsontown Ironworks in Scotland in 1828. Within a few years of the introduction, hot blast was developed to the point where fuel consumption was cut by one-third using coke or two-thirds using coal, while furnace capacity was also significantly increased. Within a few decades, the practice was to have a "stove" as large as the furnace next to it into which the waste gas (containing CO) from the furnace was directed and burnt. The resultant heat was used to preheat the air blown into the furnace.
Hot blast enabled the use of raw anthracite coal, which was difficult to light, in the blast furnace. Anthracite was first tried successfully by George Crane at Ynyscedwyn Ironworks in south Wales in 1837. It was taken up in America by the Lehigh Crane Iron Company at Catasauqua, Pennsylvania, in 1839. Anthracite use declined when very high capacity blast furnaces requiring coke were built in the 1870s. | 1 | Applied and Interdisciplinary Chemistry |
Neutralizing a solution containing an salt such as indium nitrate () or a solution of indium trichloride () gives a white precipitate that on aging forms indium(III) hydroxide. A thermal decomposition of freshly prepared shows the first step is the conversion of to cubic indium(III) hydroxide. The precipitation of indium hydroxide was a step in the separation of indium from zincblende ore by Reich and Richter, the discoverers of indium.
Indium(III) hydroxide is amphoteric, like gallium(III) hydroxide () and aluminium hydroxide (), but is much less acidic than gallium hydroxide (), having a lower solubility in alkaline solutions than in acid solutions. It is for all intents and purposes a basic hydroxide.
Dissolving indium(III) hydroxide in strong alkali gives solutions that probably contain either four coordinate or .
Reaction with acetic acid or carboxylic acids is likely to give the basic acetate or carboxylate salt, e.g. .
At 10 MPa pressure and 250-400 °C, indium(III) hydroxide converts to indium oxide hydroxide (InO(OH)), which has a distorted rutile structure.
Rapid decompression of samples of indium(III) hydroxide compressed at 34 GPa causes decomposition, yielding some indium metal.
Laser ablation of indium(III) hydroxide gives indium(I) hydroxide (InOH), a bent molecule with an In-O-H angle of around 132° and an In-O bond length of 201.7 pm. | 0 | Theoretical and Fundamental Chemistry |
2D synchronous and asynchronous spectra are basically 3D-datasets and are generally represented by contour plots. X- and y-axes are identical to the x-axis of the original dataset, whereas the different contours represent the magnitude of correlation between the spectral intensities. The 2D synchronous spectrum is symmetric relative to the main diagonal. The main diagonal thus contains positive peaks. As the peaks at (x,y) in the 2D synchronous spectrum are a measure for the correlation between the intensity changes at x and y in the original data, these main diagonal peaks are also called autopeaks and the main diagonal signal is referred to as autocorrelation signal. The off-diagonal cross-peaks can be either positive or negative. On the other hand, the asynchronous spectrum is asymmetric and never has peaks on the main diagonal.
Generally contour plots of 2D spectra are oriented with rising axes from left to right and top to down. Other orientations are possible, but interpretation has to be adapted accordingly. | 0 | Theoretical and Fundamental Chemistry |
When , the decay is referred to as "forbidden". Nuclear selection rules require high values to be accompanied by changes in nuclear spin () and parity (). The selection rules for the th forbidden transitions are:
where corresponds to no parity change or parity change, respectively. The special case of a transition between isobaric analogue states, where the structure of the final state is very similar to the structure of the initial state, is referred to as "superallowed" for beta decay, and proceeds very quickly. The following table lists the Δ and Δ values for the first few values of : | 0 | Theoretical and Fundamental Chemistry |
Mesohabitat simulation model (MesoHABSIM), created by Dr. Piotr Parasiewicz, addresses the requirements of watershed-based management of running waters and is designed to predict an aquatic community's response to habitat modification. | 1 | Applied and Interdisciplinary Chemistry |
The explanation of the Fano line-shape first appeared in the context of inelastic electron scattering by helium and autoionization. The incident electron doubly excites the atom to the state, a sort of shape resonance. The doubly excited atom spontaneously decays by ejecting one of the excited electrons. Fano showed that interference between the amplitude to simply scatter the incident electron and the amplitude to scatter via autoionization creates an asymmetric scattering line-shape around the autoionization energy with a line-width very close to the inverse of the autoionization lifetime. | 0 | Theoretical and Fundamental Chemistry |
Corby became a steelmaking centre through the establishment of the Stewarts & Lloyds production site in the 1930s, and by 1960 had grown to become one of the most heavily industrialised areas in the Midlands. In 1981 however the plant had become unprofitable and owners British Steel Corporation closed the site. By then it was one of the largest steelmaking operations in Western Europe, covering , with four blast furnaces, two coke oven complexes and associated facilities. During its operation a huge quantity of industrial waste, including toxic waste, had been deposited there.
Between 1984 and 1999 Corby Borough Council undertook the demolition, excavation and redevelopment of the site as part of a program of urban regeneration. This involved transporting the waste through populated areas to a quarry north of the site, utilising up to 200 vehicle movements daily. The toxic waste was carried in open lorries, spilling sludge over the roads and releasing huge amounts of dust into the air.
Subsequently, in the late 1980s and 1990s, the rates of upper-limb defects in babies born in Corby were found to be almost three times higher than those of children born in the surrounding area and ten times higher than a town with a population of 60,000 should expect. In all cases initially referred to the court there were no previous family histories of limb defect. | 1 | Applied and Interdisciplinary Chemistry |
Spin diffusion describes a situation wherein the individual nuclear spins undergo continuous exchange of energy. This permits polarization differences within the sample to be reduced on a timescale much shorter than relaxation effects.
Spin diffusion is a process by which magnetization can be exchanged spontaneously between spins. The process is driven by dipolar coupling, and is therefore related to internuclear distances. Spin diffusion has been used to study many structural problems in the past, ranging from domain sizes in polymers and disorder in glassy materials to high-resolution crystal structure determination of small molecules and proteins.
In solid-state nuclear magnetic resonance, spin diffusion plays a major role in Cross Polarization (CP) experiments. As mentioned before, by transferring the magnetization (and thus the population) from nuclei with different values for the spin-lattice relaxation (T), the overall time for the experiment is reduced. Is a very common practice when the sample contains hydrogen. Another desirable effect is that the signal to noise ratio (S/N) is increased until a theoretical factor γ/γ, being γ the gyromagnetic ratio. | 0 | Theoretical and Fundamental Chemistry |
Sabih Taher Darwish al-Masri is a Jordanian-Palestinian businessman. He is the founder and chairman of Arab Supply and Trading Company (Astra Group). He is also the chairman of Zara Investment Holding, Astra Industries, Paltel Corporation and Arab Bank, and a founder of the Palestine Securities Exchange (PSE).
He is the cousin of Munib al-Masri.
Al-Masri has a degree in Chemical Engineering from the University of Texas.
Al-Masri co-founded Zara Investment Holding in 1994. | 1 | Applied and Interdisciplinary Chemistry |
PET imaging with oxygen-15 indirectly measures blood flow to the brain. In this method, increased radioactivity signal indicates increased blood flow which is assumed to correlate with increased brain activity. Because of its 2-minute half-life, oxygen-15 must be piped directly from a medical cyclotron for such uses, which is difficult.
PET imaging with FDG takes advantage of the fact that the brain is normally a rapid user of glucose. Standard FDG PET of the brain measures regional glucose use and can be used in neuropathological diagnosis.
Brain pathologies such as Alzheimers disease (AD) greatly decrease brain metabolism of both glucose and oxygen in tandem. Therefore FDG PET of the brain may also be used to successfully differentiate Alzheimers disease from other dementing processes, and also to make early diagnoses of Alzheimers disease. The advantage of FDG PET for these uses is its much wider availability. Some fluorine-18 based radioactive tracers used for Alzheimers include florbetapir, flutemetamol, Pittsburgh compound B (PiB) and florbetaben, which are all used to detect amyloid-beta plaques, a potential biomarker for Alzheimer's in the brain.
PET imaging with FDG can also be used for localization of "seizure focus". A seizure focus will appear as hypometabolic during an interictal scan. Several radiotracers (i.e. radioligands) have been developed for PET that are ligands for specific neuroreceptor subtypes such as [C]raclopride, [F]fallypride and [F]desmethoxyfallypride for dopamine D/D receptors; [C]McN5652 and [C]DASB for serotonin transporters; [F]mefway for serotonin 5HT receptors; and [F]Nifene for nicotinic acetylcholine receptors or enzyme substrates (e.g. 6-FDOPA for the AADC enzyme). These agents permit the visualization of neuroreceptor pools in the context of a plurality of neuropsychiatric and neurologic illnesses.
PET may also be used for the diagnosis of hippocampal sclerosis, which causes epilepsy. FDG, and the less common tracers flumazenil and MPPF have been explored for this purpose. If the sclerosis is unilateral (right hippocampus or left hippocampus), FDG uptake can be compared with the healthy side. Even if the diagnosis is difficult with MRI, it may be diagnosed with PET.
The development of a number of novel probes for non-invasive, in-vivo PET imaging of neuroaggregate in human brain has brought amyloid imaging close to clinical use. The earliest amyloid imaging probes included [F]FDDNP developed at the University of California, Los Angeles and Pittsburgh compound B (PiB)developed at the University of Pittsburgh. These probes permit the visualization of amyloid plaques in the brains of Alzheimer's patients and could assist clinicians in making a positive clinical diagnosis of AD pre-mortem and aid in the development of novel anti-amyloid therapies. [C]polymethylpentene (PMP) is a novel radiopharmaceutical used in PET imaging to determine the activity of the acetylcholinergic neurotransmitter system by acting as a substrate for acetylcholinesterase. Post-mortem examination of AD patients have shown decreased levels of acetylcholinesterase. [C]PMP is used to map the acetylcholinesterase activity in the brain, which could allow for premortem diagnoses of AD and help to monitor AD treatments. Avid Radiopharmaceuticals has developed and commercialized a compound called florbetapir that uses the longer-lasting radionuclide fluorine-18 to detect amyloid plaques using PET scans. | 1 | Applied and Interdisciplinary Chemistry |
The sweetening properties of Synsepalum dulcificum berries were first noted by des Marchais during expeditions to West Africa in the 18th century. The term miraculin derived from experiments to isolate and purify the active glycoprotein that gave the berries their sweetening effects, results that were published simultaneously by Japanese and Dutch scientists working independently in the 1960s (the Dutch team called the glycoprotein mieraculin). The word miraculin was in common use by the mid-1970s. | 1 | Applied and Interdisciplinary Chemistry |
Nucleic acids (including RNA and DNA) are nucleotide polymers synthesized by polymerase enzymes during either transcription or DNA replication. Following 5-3 synthesis of the backbone, individual nitrogenous bases are capable of interacting with one another via hydrogen bonding, thus allowing for the formation of higher-order structures. Nucleic acid denaturation occurs when hydrogen bonding between nucleotides is disrupted, and results in the separation of previously annealed strands. For example, denaturation of DNA due to high temperatures results in the disruption of base pairs and the separation of the double stranded helix into two single strands. Nucleic acid strands are capable of re-annealling when "normal" conditions are restored, but if restoration occurs too quickly, the nucleic acid strands may re-anneal imperfectly resulting in the improper pairing of bases. | 1 | Applied and Interdisciplinary Chemistry |
Many different designs of vortex breaker are available. Some use radial vanes or baffles around the liquid exit to stop some of the angular velocity of the liquid. The "floor grate" design uses a system of grating similar to the metal floor of a catwalk. Different authors give different rules of thumb for vortex breaker design. | 1 | Applied and Interdisciplinary Chemistry |
Nucleophilic/electrophilic cascades are
defined as the cascade sequences in which the key step constitutes a nucleophilic
or electrophilic attack.
An example of such a cascade is seen in the short enantioselective synthesis of the broad-spectrum antibiotic (–)-chloramphenicol, reported by Rao et al. (Scheme 1). Herein, the chiral epoxy-alcohol 1 was first treated with dichloroacetonitrile in the presence of NaH. The resulting intermediate 2 then underwent a BF·EtO-mediated cascade reaction. Intramolecular opening of the epoxide ring yielded intermediate 3, which, after an in situ hydrolysis facilitated by excess BF·EtO, afforded (–)-chloramphenicol (4) in 71% overall yield.
A nucleophilic cascade was also employed in the total synthesis of the natural product pentalenene (Scheme 2). In this procedure, squarate ester 5 was treated with (5-methylcyclopent-1-en-1-yl)lithium and propynyllithium. The two nucleophilic attacks occurred predominantly with trans addition to afford intermediate 6, which spontaneously underwent a 4π-conrotatory electrocyclic opening of the cyclobutene ring. The resulting conjugated species 7 equilibrated to conformer 8, which more readily underwent an 8π-conrotatory electrocyclization to the highly strained intermediate 9. The potential to release strain directed protonation of 9 such that species 10 was obtained selectively. The cascade was completed by an intramolecular aldol condensation that afforded product 11 in 76% overall yield. Further elaboration afforded the target (±)-pentalenene (12). | 0 | Theoretical and Fundamental Chemistry |
If lichens are exposed to air pollutants at all times, without any deciduous parts, they are unable to avoid the accumulation of pollutants. Also lacking stomata and a cuticle, lichens may absorb aerosols and gases over the entire thallus surface from which they may readily diffuse to the photobiont layer. Because lichens do not possess roots, their primary source of most elements is the air, and therefore elemental levels in lichens often reflect the accumulated composition of ambient air. The processes by which atmospheric deposition occurs include fog and dew, gaseous absorption, and dry deposition. Consequently, environmental studies with lichens emphasize their feasibility as effective biomonitors of atmospheric quality.
Not all lichens are equally sensitive to air pollutants, so different lichen species show different levels of sensitivity to specific atmospheric pollutants. The sensitivity of a lichen to air pollution is directly related to the energy needs of the mycobiont, so that the stronger the dependency of the mycobiont on the photobiont, the more sensitive the lichen is to air pollution. Upon exposure to air pollution, the photobiont may use metabolic energy for repair of its cellular structures that would otherwise be used for maintenance of its photosynthetic activity, therefore leaving less metabolic energy available for the mycobiont. The alteration of the balance between the photobiont and mycobiont can lead to the breakdown of the symbiotic association. Therefore, lichen decline may result not only from the accumulation of toxic substances, but also from altered nutrient supplies that favor one symbiont over the other.
This interaction between lichens and air pollution has been used as a means of monitoring air quality since 1859, with more systematic methods developed by William Nylander in 1866. | 1 | Applied and Interdisciplinary Chemistry |
As HIV uses reverse transcriptase to copy its genetic material and generate new viruses (part of a retrovirus proliferation circle), specific drugs have been designed to disrupt the process and thereby suppress its growth. Collectively, these drugs are known as reverse-transcriptase inhibitors and include the nucleoside and nucleotide analogues zidovudine (trade name Retrovir), lamivudine (Epivir) and tenofovir (Viread), as well as non-nucleoside inhibitors, such as nevirapine (Viramune). | 1 | Applied and Interdisciplinary Chemistry |
The "chemical space" of all possible organic chemicals is large and increases exponentially with the size of the molecule. Most chemical libraries do not typically have a fully represented chemical space mostly because of storage and cost concerns.
Because of the expense and effort involved in chemical synthesis, the chemicals must be correctly stored and banked away for later use to prevent early degradation. Each chemical has a particular shelf life and storage requirement and in a good-sized chemical library, there is a timetable by which library chemicals are disposed of and replaced on a regular basis. Some chemicals are fairly unstable, radioactive, volatile or flammable and must be stored under careful conditions in accordance with safety standards such as OSHA.
Most chemical libraries are managed with information technologies such as barcoding and relational databases. Additionally, robotics are necessary to fetch compounds in larger chemical libraries.
Because a chemical library's individual entries can easily reach up into the millions of compounds, the management of even modest-sized chemical libraries can be a full-time endeavor. Compound management is one such field that attempts to manage and upkeep these chemical libraries as well as maximizing safety and effectiveness in their management. | 1 | Applied and Interdisciplinary Chemistry |
Gallamine triethiodide is originally developed for preventing muscle contractions during surgical procedures. However, it is no longer marketed in the United States according to the FDA orange book. | 1 | Applied and Interdisciplinary Chemistry |
In geography, a confluence (also: conflux) occurs where two or more watercourses join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main stem); or where two streams meet to become the source of a river of a new name (such as the confluence of the Monongahela and Allegheny rivers at Pittsburgh, forming the Ohio); or where two separated channels of a river (forming a river island) rejoin at the downstream end. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.