text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2 values |
|---|---|---|
A highly ordered π-conjugation TP-COF, consisting of pyrene and triphenylene functionalities alternately linked in a mesoporous hexagonal skeleton, is highly luminescent, harvests a wide wavelength range of photons, and allows energy transfer and migration. Furthermore, TP-COF is electrically conductive and capable of repetitive on–off current switching at room temperature. | 0 | Theoretical and Fundamental Chemistry |
Myosins are a superfamily of actin motor proteins that convert chemical energy in the form of ATP to mechanical energy, thus generating force and movement. The first identified myosin, myosin II, is responsible for generating muscle contraction. Myosin II is an elongated protein that is formed from two heavy chains with motor heads and two light chains. Each myosin head contains actin and ATP binding site. The myosin heads bind and hydrolyze ATP, which provides the energy to walk toward the plus end of an actin filament. Myosin II are also vital in the process of cell division. For example, non-muscle myosin II bipolar thick filaments provide the force of contraction needed to divide the cell into two daughter cells during cytokinesis. In addition to myosin II, many other myosin types are responsible for variety of movement of non-muscle cells. For example, myosin is involved in intracellular organization and the protrusion of actin-rich structures at the cell surface. Myosin V is involved in vesicle and organelle transport. Myosin XI is involved in cytoplasmic streaming, wherein movement along microfilament networks in the cell allows organelles and cytoplasm to stream in a particular direction. Eighteen different classes of myosins are known.
Genomic representation of myosin motors:
* Fungi (yeast): 5
* Plants (Arabidopsis): 17
* Insects (Drosophila): 13
* Mammals (human): 40
* Chromadorea ( nematode C. elegans): 15 | 0 | Theoretical and Fundamental Chemistry |
A type III secretion system means that a molecular syringe is used through which a bacterium (e.g. certain types of Salmonella, Shigella, Yersinia) can inject nutrients into protist cells. One such mechanism was first discovered in Y. pestis and showed that toxins could be injected directly from the bacterial cytoplasm into the cytoplasm of its host's cells rather than be secreted into the extracellular medium. | 1 | Applied and Interdisciplinary Chemistry |
The Unruh temperature, sometimes called the Davies–Unruh temperature, was derived separately by Paul Davies and William Unruh and is the effective temperature experienced by a uniformly accelerating detector in a vacuum field. It is given by
where is the reduced Planck constant, is the proper uniform acceleration, is the speed of light, and is the Boltzmann constant. Thus, for example, a proper acceleration of corresponds approximately to a temperature of . Conversely, an acceleration of corresponds to a temperature of .
The Unruh temperature has the same form as the Hawking temperature with denoting the surface gravity of a black hole, which was derived by Stephen Hawking in 1974. In the light of the equivalence principle, it is, therefore, sometimes called the Hawking–Unruh temperature.
Solving the Unruh temperature for the uniform acceleration, it can be expressed as
where is Planck acceleration and is Planck temperature. | 0 | Theoretical and Fundamental Chemistry |
Aryl azo compounds are usually stable, crystalline species. Azobenzene is the prototypical aromatic azo compound. It exists mainly as the trans isomer, but upon illumination, converts to the cis isomer.
Aromatic azo compounds can be synthesized by azo coupling, which entails an electrophilic substitution reaction where an aryl diazonium cation is attacked by another aryl ring, especially those substituted with electron-donating groups:
Since diazonium salts are often unstable near room temperature, the azo coupling reactions are typically conducted near 0 °C. The oxidation of hydrazines () also gives azo compounds. Azo dyes are also prepared by the condensation of nitroaromatics with anilines followed by reduction of the resulting azoxy intermediate:
For textile dying, a typical nitro coupling partner would be disodium 4,4′-dinitrostilbene-2,2′-disulfonate. Typical aniline partners are shown below.
As a consequence of π-delocalization, aryl azo compounds have vivid colors, especially reds, oranges, and yellows. Therefore, they are used as dyes, and are commonly known as azo dyes, an example of which is Disperse Orange 1. Some azo compounds, e.g., methyl orange, are used as acid-base indicators due to the different colors of their acid and salt forms. Most DVD-R/+R and some CD-R discs use blue azo dye as the recording layer. The commercial success of azo dyes motivated the development of azo compounds in general. | 0 | Theoretical and Fundamental Chemistry |
The dynamic sessile drop is similar to the static sessile drop but requires the drop to be modified. A common type of dynamic sessile drop study determines the largest contact angle possible without increasing its solid–liquid interfacial area by adding volume dynamically. This maximum angle is the advancing angle. Volume is removed to produce the smallest possible angle, the receding angle. The difference between the advancing and receding angle is the contact angle hysteresis. | 0 | Theoretical and Fundamental Chemistry |
The idea of rigid unit modes was developed for crystalline materials to enable an understanding of the origin of displacive phase transitions in materials such as silicates, which can be described as infinite three-dimensional networks of corner-lined SiO and AlO tetrahedra. The idea was that rigid unit modes could act as the soft modes for displacive phase transitions.
The original work in silicates showed that many of the phase transitions in silicates could be understood in terms of soft modes that are RUMs.
After the original work on displacive phase transitions, the RUM model was also applied to understanding the nature of the disordered high-temperature phases of materials such as cristobalite, the dynamics and localised structural distortions in zeolites, and negative thermal expansion. | 0 | Theoretical and Fundamental Chemistry |
The theory of tides is the application of continuum mechanics to interpret and predict the tidal deformations of planetary and satellite bodies and their atmospheres and oceans (especially Earth's oceans) under the gravitational loading of another astronomical body or bodies (especially the Moon and Sun). | 1 | Applied and Interdisciplinary Chemistry |
The Falcon semi batch centrifugal concentrator is primarily used for the recovery of free (liberated) precious metals such as gold, silver and platinum. The machine generates forces up to 200 times the force of gravity (200 Gs) and makes use of a two-stage rotating bowl for mineral separation. The smooth-walled lower portion is for particle stratification and then a fluidized upper portion is used for the collection of the heavier particles. The machine is stopped periodically to rinse and collect the valuable concentrate from the bowl. The Falcon SB concentrator is used for gold recovery at many mines around the world, including Quadra FNX Minings Robinson mine in the United States, Newcrest's Telfer Gold Mine in Australia and the Sadiola Gold Mine (owned principally by AngloGold Ashanti and Iamgold) in Mali. | 1 | Applied and Interdisciplinary Chemistry |
It was given a Royal Charter in 1975. In 1977 it became the sixteenth constituent of the •Council of Engineering Institutions, which became the Engineering Council in 1981. | 1 | Applied and Interdisciplinary Chemistry |
Surface ocean waters generally have oxygen concentrations close to equilibrium with the Earth's atmosphere. In general, colder waters hold more oxygen than warmer waters. As water moves out of the mixed layer into the thermocline, it is exposed to a rain of organic matter from above. Aerobic bacteria feed on this organic matter; oxygen is used as part of the bacterial metabolic process, lowering its concentration within the water. Therefore, the concentration of oxygen in deep water is dependent on the amount of oxygen it had when it was at the surface, minus depletion by deep sea organisms.
The downward flux of organic matter decreases sharply with depth, with 80–90% being consumed in the top . The deep ocean thus has higher oxygen because rates of oxygen consumption are low compared with the supply of cold, oxygen-rich deep waters from polar regions. In the surface layers, oxygen is supplied by photosynthesis of phytoplankton. Depths in between, however, have higher rates of oxygen consumption and lower rates of advective supply of oxygen-rich waters. In much of the ocean, mixing processes enable the resupply of oxygen to these waters (see upwelling).
A distribution of the open-ocean oxygen minimum zones is controlled by the large-scale ocean circulation as well as local physical as well as biological processes. For example, wind blowing parallel to the coast causes Ekman transport that upwells nutrients from deep water. The increased nutrients support phytoplankton blooms, zooplankton grazing, and an overall productive food web at the surface. The byproducts of these blooms and the subsequent grazing sink in the form of particulate and dissolved nutrients (from phytodetritus, dead organisms, fecal pellets, excretions, shed shells, scales, and other parts). This "rain" of organic matter (see the biological pump) feeds the microbial loop and may lead to bacterial blooms in water below the euphotic zone due to the influx of nutrients. Since oxygen is not being produced as a byproduct of photosynthesis below the euphotic zone, these microbes use up what oxygen is in the water as they break down the falling organic matter thus creating the lower oxygen conditions.
Physical processes then constrain the mixing and isolate this low oxygen water from outside water. Vertical mixing is constrained due to the separation from the mixed layer by depth. Horizontal mixing is constrained by bathymetry and boundaries formed by interactions with sub-tropical gyres and other major current systems. Low oxygen water may spread (by advection) from under areas of high productivity up to these physical boundaries to create a stagnant pool of water with no direct connection to the ocean surface even though (as in the Eastern Tropical North Pacific) there may be relatively little organic matter falling from the surface. | 0 | Theoretical and Fundamental Chemistry |
Aluminium hydroxide is amphoteric. In acid, it acts as a Brønsted–Lowry base. It neutralizes the acid, yielding a salt:
In bases, it acts as a Lewis acid by binding hydroxide ions: | 0 | Theoretical and Fundamental Chemistry |
Professor Zagal is also a man of many talents: he sings and plays several instruments, including the guitar and the scottish bagpipes. He also writes poetry, paints and draws cartoons. He played Caiphas in the Opera Rock Jesus Christ Superstar in the early 70s. He has been a volunteer firemen with the 14th British and Commonwealth Fire & Rescue Company in Santiago since 1972 and is also the official piper of his company. Some of his caricatures have been published in the magazine “Interface” of the Electrochemical Society and in the Journal of the Serbian Chemical Society. He is a devoted train enthusiast. He has built large replicas or working steam locomotive and full size freight wagons. He also collects full size railway items including 12 wagons and 2 locomotives, one steam and an electric locomotive. With other enthusiasts he started in the 80s the "Chilean Association for the Preservation of the Railways". With two other enthusiasts he owns the "Puangue Station" which is one of the few preserved railway stations in rural areas. | 0 | Theoretical and Fundamental Chemistry |
The largest subunit of Pol II (Rpb1) has a domain at its C-terminus called the CTD (C-terminal domain). This is the target of kinases and phosphatases. The phosphorylation of the CTD is an important regulation mechanism, as this allows attraction and rejection of factors that have a function in the transcription process. The CTD can be considered as a platform for transcription factors.
The CTD consists of repetitions of an amino acid motif, YSPTSPS, of which Serines and Threonines can be phosphorylated. The number of these repeats varies; the mammalian protein contains 52, while the yeast protein contains 26. Site-directed-mutagenesis of the yeast protein has found at least 10 repeats are needed for viability. There are many different combinations of phosphorylations possible on these repeats and these can change rapidly during transcription. The regulation of these phosphorylations and the consequences for the association of transcription factors plays a major role in the regulation of transcription.
During the transcription cycle, the CTD of the large subunit of RNAP II is reversibly phosphorylated. RNAP II containing unphosphorylated CTD is recruited to the promoter, whereas the hyperphosphorylated CTD form is involved in active transcription. Phosphorylation occurs at two sites within the heptapeptide repeat, at Serine 5 and Serine 2. Serine 5 phosphorylation is confined to promoter regions and is necessary for the initiation of transcription, whereas Serine 2 phosphorylation is important for mRNA elongation and 3'-end processing. | 1 | Applied and Interdisciplinary Chemistry |
Chitin (CHON) ( ) is a long-chain polymer of N-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chitin are produced each year in the biosphere. It is a primary component of cell walls in fungi (especially filamentous and mushroom forming fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae, cephalopod beaks and gladii of molluscs and in some nematodes and diatoms.
It is also synthesised by at least some fish and lissamphibians. Commercially, chitin is extracted from the shells of crabs, shrimps, shellfish and lobsters, which are major by-products of the seafood industry. The structure of chitin is comparable to cellulose, forming crystalline nanofibrils or whiskers. It is functionally comparable to the protein keratin. Chitin has proved useful for several medicinal, industrial and biotechnological purposes. | 1 | Applied and Interdisciplinary Chemistry |
*“Fixed film ecology” has superseded systems based on hydroponics or a fluid medium. In fixed film systems the wetland cells are filled with a solid aggregate medium having extensive surface area for beneficial biofilm (treatment bacteria) growth. Fixed film ecology allows denser and more diverse micro-ecosystems to form than does a liquid medium. These ecosystems go well beyond bacteria to include a variety of organisms up to and including macro-vegetation.
*Tidal cycles (filling and draining the wetland in accelerated tidal action, with 12 or more cycles per day) are used to passively bring oxygen into the wetland cells. This action mimics the type of biological action that occurs in natural tidal estuaries. Tidal flow wetlands replace the need to blow air into a liquid medium -- they use gravity to bring atmospheric oxygen into the cell when it is drained. | 1 | Applied and Interdisciplinary Chemistry |
The bendo-capillary length of a flexible sheet is defined as:
where
B is the bending modulus of an elastic material.
γ is the surface tension of a liquid.
This provides a comparison between bending stiffness (elasticity) and surface tension (capillarity). An elastic structure will be significantly deformed once its length is larger than the elasto-capillary length, which can be explained when gain of surface energy of a material is larger than stored elastic energy while bending. | 1 | Applied and Interdisciplinary Chemistry |
Articles in the engineering field of heat transfer, including the mechanisms of radiation, convection, conduction. | 1 | Applied and Interdisciplinary Chemistry |
The properties of a compound relating to human olfactory perception includes its odour quality, threshold and intensity as a function of its concentration.
The odour quality of a (odour-active) compound is assessed using odour descriptors in sensory descriptive analyses. It shows the sensory–chemical relationship in volatile compounds. The odour quality of a compound may change with its concentration.
The absolute threshold of a compound is the minimum concentration at which it can be detected. In a mixture of volatile compounds, only the proportion of compounds present at concentrations above their threshold contribute to the odour. This property can be represented by the odour threshold (OT), the minimum concentration at which the odour is perceived by 50% of a human panel without determining its quality, or the recognition threshold, the minimum concentration at which the odour is perceived and can be described by 50% of a human panel.
The intensity of perception of a compound is positively correlated with its concentration. It is represented by the unique psychometric or concentration-response function of the compound. A psychometric function with a log concentration–perceived intensity plot is characterised by its sigmoidal shape, with its initial baseline representing the compound at concentrations below its threshold, a slow rise in response around the inflection point representing the threshold, an exponential rise in response as the concentration exceeds the threshold, a deceleration of the response to a flat region as the zone of saturation or the point at which the change in intensity is no longer perceived is reached. On the other hand, a log concentration–log perceived intensity plot, using Steven's power law, forms a linear line with the exponent characterising the relationship between the two variables. | 0 | Theoretical and Fundamental Chemistry |
The advent of Wacker Process has spurred on many investigations into the utility and applicability of the reactions to more complex terminal olefins. The Tsuji-Wacker oxidation is the palladium(II)-catalyzed transformation of such olefins into carbonyl compounds. Clement and Selwitz were the first to find that using an aqueous DMF as solvent allowed for the oxidation of 1-dodecene to 2-dodecanone, which addressed the insolubility problem of higher order olefins in water. Fahey noted the use of 3-methylsulfolane in place of DMF as solvent increased the yield of oxidation of 3,3-Dimethylbut-1-ene. Two years after, Tsuji applied the Selwitz conditions for selective oxidations of terminal olefins with multiple functional groups, and demonstrated its utility in synthesis of complex substrates. Further development of the reaction has led to various catalytic systems to address selectivity of the reaction, as well as introduction of intermolecular and intramolecular oxidations with non-water nucleophiles. | 0 | Theoretical and Fundamental Chemistry |
Low-energy surfaces primarily interact with liquids through dispersive (van der Waals) forces. William Zisman produced several key findings:
Zisman observed that cos θ increases linearly as the surface tension (γ) of the liquid decreased. Thus, he was able to establish a linear function between cos θ and the surface tension (γ) for various organic liquids.
A surface is more wettable when γ and θ is low. Zisman termed the intercept of these lines when cos θ = 1 as the critical surface tension (γ) of that surface. This critical surface tension is an important parameter because it is a characteristic of only the solid.
Knowing the critical surface tension of a solid, it is possible to predict the wettability of the surface.
The wettability of a surface is determined by the outermost chemical groups of the solid.
Differences in wettability between surfaces that are similar in structure are due to differences in the packing of the atoms. For instance, if a surface has branched chains, it will have poorer packing than a surface with straight chains.
Lower critical surface tension means a less wettable material surface. | 0 | Theoretical and Fundamental Chemistry |
Estimating lake metabolism requires approximating processes that influence the production and consumption of organic carbon by organisms within the lake. Cyclical changes on a daily scale occur in most lakes on Earth because sunlight is available for photosynthesis and production of new carbon only for a portion of the day. Researchers can take advantage of this diel pattern to measure rates of change in carbon itself or changes in dissolved gases such as carbon dioxide or oxygen that occur on a daily scale. Although daily estimates of metabolism are most common, whole-lake metabolism can be integrated over longer time periods such as seasonal or annual rates by estimating a whole-lake carbon budget. The following sections highlight the most common ways to estimate lake metabolism across a variety of temporal and spatial scales and go over some of the assumptions of each of these methods. | 1 | Applied and Interdisciplinary Chemistry |
The "upper phase" is formed by the more hydrophobic polyethylene glycol (PEG), which is of lower density than the "lower phase," consisting of the more hydrophilic and denser dextran solution.
Although PEG is inherently denser than water, it occupies the upper layer. This is believed to be due to its solvent ordering properties, which excludes excess water, creating a low density water environment. The degree of polymerization of PEG also affects the phase separation and the partitioning of molecules during extraction. | 0 | Theoretical and Fundamental Chemistry |
Conduction in a gas requires charge carriers, which can be either electrons or ions. Charge carriers come from ionizing some of the gas molecules. In terms of current flow, glow discharge falls between dark discharge and arc discharge.
*In a dark discharge, the gas is ionized (the carriers are generated) by a radiation source such as ultraviolet light or Cosmic rays. At higher voltages across the anode and cathode, the freed carriers can gain enough energy so that additional carriers are freed during collisions; the process is a Townsend avalanche or multiplication.
*In a glow discharge, the carrier generation process reaches a point where the average electron leaving the cathode allows another electron to leave the cathode. For example, the average electron may cause dozens of ionizing collisions via the Townsend avalanche; the resulting positive ions head toward the cathode, and a fraction of those that cause collisions with the cathode will dislodge an electron by secondary emission.
*In an arc discharge, electrons leave the cathode by thermionic emission and field emission, and the gas is ionized by thermal means.
Below the breakdown voltage there is little to no glow and the electric field is uniform. When the electric field increases enough to cause ionization, the Townsend discharge starts. When a glow discharge develops, the electric field is considerably modified by the presence of positive ions; the field is concentrated near the cathode. The glow discharge starts as a normal glow. As the current is increased, more of the cathode surface is involved in the glow. When the current is increased above the level where the entire cathode surface is involved, the discharge is known as an abnormal glow. If the current is increased still further, other factors come into play and an arc discharge begins. | 0 | Theoretical and Fundamental Chemistry |
A range of different sources can be used:
* A nuclear reactor
* An actinoid such as californium which emits neutrons through spontaneous fission
* An alpha source such as radium or americium, mixed with beryllium; this generates neutrons by a (α,C+n) reaction
* A D-T fusion reaction in a gas discharge tube | 0 | Theoretical and Fundamental Chemistry |
GPCRs become desensitized when exposed to their ligand for a long period of time. There are two recognized forms of desensitization: 1) homologous desensitization, in which the activated GPCR is downregulated; and 2) heterologous desensitization, wherein the activated GPCR causes downregulation of a different GPCR. The key reaction of this downregulation is the phosphorylation of the intracellular (or cytoplasmic) receptor domain by protein kinases. | 1 | Applied and Interdisciplinary Chemistry |
In vertebrates, the majority of gene promoters contain a CpG island with numerous CpG sites. When many of a gene's promoter CpG sites are methylated the gene becomes silenced. Colorectal cancers typically have 3 to 6 driver mutations and 33 to 66 hitchhiker or passenger mutations. However, transcriptional silencing may be of more importance than mutation in causing progression to cancer. For example, in colorectal cancers about 600 to 800 genes are transcriptionally silenced by CpG island methylation (see regulation of transcription in cancer). Transcriptional repression in cancer can also occur by other epigenetic mechanisms, such as altered expression of microRNAs. In breast cancer, transcriptional repression of BRCA1 may occur more frequently by over-expressed microRNA-182 than by hypermethylation of the BRCA1 promoter (see Low expression of BRCA1 in breast and ovarian cancers). | 1 | Applied and Interdisciplinary Chemistry |
The successful operation and development of the demonstration copper ISASMELT, and the degree of interest shown in the new process by the global smelting community, gave MIM Holdings sufficient confidence to license the ISASMELT technology to external companies, so an agreement under which MIM could incorporate the Sirosmelt lance into ISASMELT technology was signed with the CSIRO in 1989. | 1 | Applied and Interdisciplinary Chemistry |
[Ru(bpy)] absorbs ultraviolet and visible light. Aqueous solutions of [Ru(bpy)]Cl are orange due to a strong MLCT absorption at 452 ± 3 nm (extinction coefficient of 14,600 Mcm). Further absorption bands are found at 285 nm corresponding to ligand centered π← π transitions and a weak transition around 350 nm (d-d transition). Light absorption results in formation of an excited state have a relatively long lifetime of 890 ns in acetonitrile and 650 ns in water. The excited state relaxes to the ground state by emission of a photon or non-radiative relaxation. The quantum yield is 2.8% in air-saturated water at 298 K and the emission maximum wavelength is 620 nm. The long lifetime of the excited state is attributed to the fact that it is triplet, whereas the ground state is a singlet state and in part due to the fact that the structure of the molecule allows for charge separation. Singlet-triplet transitions are forbidden and therefore often slow.
Like all molecular excited states, the triplet excited state of [Ru(bpy)] has both stronger oxidizing and reducing properties than its ground state. This situation arises because the excited state can be described as an Ru complex containing a bpy radical anion as a ligand. Thus, the photochemical properties of [Ru(bpy)] are reminiscent of the photosynthetic assembly, which also involves separation of an electron and a hole.
[Ru(bpy)] has been examined as a photosensitizer for both the oxidation and reduction of water. Upon absorbing a photon, [Ru(bpy)] converts to the aforementioned triplet state, denoted [Ru(bpy)]*. This species transfers an electron, located on one bpy ligand, to a sacrificial oxidant such as peroxodisulfate (SO). The resulting [Ru(bpy)] is a powerful oxidant and oxidizes water into O and protons via a catalyst. Alternatively, the reducing power of [Ru(bpy)]* can be harnessed to reduce methylviologen, a recyclable carrier of electrons, which in turn reduces protons at a platinum catalyst. For this process to be catalytic, a sacrificial reductant, such as EDTA or triethanolamine is provided to return the Ru(III) back to Ru(II).
Derivatives of [Ru(bpy)] are numerous. Such complexes are widely discussed for applications in biodiagnostics, photovoltaics and organic light-emitting diode, but no derivative has been commercialized. Application of [Ru(bpy)] and its derivatives to fabrication of optical chemical sensors is arguably one of the most successful areas so far. | 0 | Theoretical and Fundamental Chemistry |
The second step of fatty acid degradation is beta oxidation. Beta oxidation occurs in mitochondria. After formation in the cytosol, acyl-CoA is transported into the mitochondria, the locus of beta oxidation. Transport of acyl-CoA into the mitochondria requires carnitine palmitoyltransferase 1 (CPT1), which converts acyl-CoA into acylcarnitine, which gets transported into the mitochondrial matrix. Once in the matrix, acylcarnitine is converted back to acyl-CoA by CPT2. Beta oxidation may begin now that Acyl-CoA is in the mitochondria.
Beta oxidation of acyl-CoA occurs in four steps.
1. Acyl-CoA dehydrogenase catalyzes dehydrogenation of the acyl-CoA, creating a double bond between the alpha and beta carbons. FAD is the hydrogen acceptor, yielding FADH2.
2. Enoyl-CoA hydrase catalyzes the addition of water across the newly formed double bond to make an alcohol.
3. 3-hydroxyacyl-CoA dehydrogenase oxidizes the alcohol group to a ketone. NADH is produced from NAD+.
4. Thiolase cleaves between the alpha carbon and ketone to release one molecule of Acetyl-CoA and the Acyl-CoA which is now 2 carbons shorter.
This four step process repeats until acyl-CoA has removed all carbons from the chain, leaving only Acetyl-CoA. During one cycle of beta oxidation, Acyl-CoA creates one molecule of Acetyl-CoA, FADH2, and NADH. Acetyl-CoA is then used in the citric acid cycle while FADH2 and NADH are sent to the electron transport chain. These intermediates all end up providing energy for the body as they are ultimately converted to ATP.
Beta oxidation, as well as alpha-oxidation, also occurs in the peroxisome. The peroxisome handles beta oxidation of fatty acids that have more than 20 carbons in their chain because the peroxisome contains very-long-chain Acyl-CoA synthetases. These enzymes are better equipped to oxidize Acyl-CoA with long chains that the mitochondria cannot handle. | 1 | Applied and Interdisciplinary Chemistry |
In 1998 Kubista founded LightUp Technologies AB after his research finding of lightUp probes, a company that specializes in the development of real-time PCR tests for human infectious diseases. Three years later In 2001, Kubista's research led to the establishments of MultiD Analyses AB, which develops GenEx software for gene expression data analysis and TATAA Biocenter for qPCR and gene expression analysis. The company became known for its qPCR training services globally and its provision of qPCR services, particularly in Europe. TATAA Biocenter was the first laboratory in Europe to obtain flexible ISO 17025 accreditation and also was the first to provide COVID tests at the onset of the pandemic. In 2014 Kubista implementated non-invasive prenatal testing (NIPT) in Sweden and subsequently founded Life Genomics AB. In 2020, Kubista co-founded SimSen Diagnostics, a company focused on developing technology for liquid biopsy analyses. | 1 | Applied and Interdisciplinary Chemistry |
The COLUMBUS PROGRAMS are a computational chemistry software suite for calculating ab initio molecular electronic structures, designed as a collection of individual programs communicating through files. The programs focus on extended multi-reference calculations of atomic and molecular ground and excited states. In addition to standard classes of reference wave functions such as CAS and RAS, calculations can be performed with selected configurations. Some features employ the atomic orbital integrals and gradient routines from the Dalton as well as MOLCAS program suites. COLUMBUS is distributed open-source under the LGPL license.
The COLUMBUS PROGRAMS are frequently used for nonadiabatic problems because of its ability to calculate MRCI nonadiabatic coupling vector analytically. | 0 | Theoretical and Fundamental Chemistry |
In the process of sewage treatment, sewage is digested by enzymes secreted by bacteria. Solid organic matters are broken down into harmless, soluble substances and carbon dioxide. Liquids that result are disinfected to remove pathogens before being discharged into rivers or the sea or can be used as liquid fertilizers. Digested solids, known also as sludge, is dried and used as fertilizer. Gaseous byproducts such as methane can be utilized as biogas to fuel electrical generators. One advantage of bacterial digestion is that it reduces the bulk and odor of sewage, thus reducing space needed for dumping. The main disadvantage of bacterial digestion in sewage disposal is that it is a very slow process. | 1 | Applied and Interdisciplinary Chemistry |
The iminium form of anabaseine binds to most nicotinic acetylcholine receptors in both the peripheral nervous system and central nervous system. But, there is a higher binding affinity for receptors in the brain with a α7 subunit, as well as skeletal muscle receptors. Binding causes the depolarization of neurons, and induces the release of both dopamine and norepinephrine. | 1 | Applied and Interdisciplinary Chemistry |
Rust is a general name for a complex of oxides and hydroxides of iron, which occur when iron or some alloys that contain iron are exposed to oxygen and moisture for a long period of time. Over time, the oxygen combines with the metal, forming new compounds collectively called rust, in a process called rusting. Rusting is an oxidation reaction specifically occurring with iron. Other metals also corrode via similar oxidation, but such corrosion is not called rusting.
The main catalyst for the rusting process is water. Iron or steel structures might appear to be solid, but water molecules can penetrate the microscopic pits and cracks in any exposed metal. The hydrogen atoms present in water molecules can combine with other elements to form acids, which will eventually cause more metal to be exposed. If chloride ions are present, as is the case with saltwater, the corrosion is likely to occur more quickly. Meanwhile, the oxygen atoms combine with metallic atoms to form the destructive oxide compound. These iron compounds are brittle and crumbly and replace strong metallic iron, reducing the strength of the object. | 1 | Applied and Interdisciplinary Chemistry |
The DNA formed after reverse transcription (the provirus) is longer than the RNA genome because each of the terminals have the U3 - R - U5 sequences called long terminal repeat (LTR). Thus, 5' terminal has the extra U3 sequence, while the other terminal has the U5 sequence. LTRs are able to send signals for vital tasks to be carried out such as initiation of RNA production or management of the rate of transcription. This way, LTRs can control replication, hence, the entire progress of the viral cycle. Although located in the nucleus, the non-integrated retroviral cDNA is a very weak substrate for transcription. For this reason, an integrated provirus is a necessary for permanent and an effective expression of retroviral genes.
This DNA can be incorporated into host genome as a provirus that can be passed on to progeny cells. The retrovirus DNA is inserted at random into the host genome. Because of this, it can be inserted into oncogenes. In this way some retroviruses can convert normal cells into cancer cells. Some provirus remains latent in the cell for a long period of time before it is activated by the change in cell environment. | 1 | Applied and Interdisciplinary Chemistry |
In plumbing, an adapter is generally a fitting that interfaces two different parts. The term commonly refers to:
*any fitting that connects pipes of different materials, including:
**expansion adapters which have a flexible section to absorb expansion or contraction from two dissimilar pipe materials
**mechanical joint (MJ) adapters for joining polyethylene pipe to another material
**bell adapters which are like mechanical joint adapters but contain a stainless steel backup ring to maintain a positive seal against the mating flange
**flange adapters which attach to a polyethylene pipe with butt fusion to stiffen a junction and allow another flanged pipe or fitting to be bolted on
*a fitting that connects pipes of different diameters, genders, or threads
**adapter spools (also called crossover spools), used on oilfields and pressure control, have different diameters, pressure ratings or designs at each end
**adapters to convert NPT to BSP pipe threads are available
*a fitting that connects threaded and non-threaded pipe | 1 | Applied and Interdisciplinary Chemistry |
Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron, copper, silver, tin, lead and zinc. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal behind. The reducing agent is commonly a fossil fuel source of carbon, such as carbon monoxide from incomplete combustion of coke—or, in earlier times, of charcoal. The oxygen in the ore binds to carbon at high temperatures as the chemical potential energy of the bonds in carbon dioxide () is lower than that of the bonds in the ore.
Sulfide ores such as those commonly used to obtain copper, zinc or lead, are roasted before smelting in order to convert the sulfides to oxides, which are more readily reduced to the metal. Roasting heats the ore in the presence of oxygen from air, oxidizing the ore and liberating the sulfur as sulfur dioxide gas.
Smelting most prominently takes place in a blast furnace to produce pig iron, which is converted into steel.
Plants for the electrolytic reduction of aluminium are referred to as aluminium smelters. | 1 | Applied and Interdisciplinary Chemistry |
Somewhere between 1 and 2 billion years ago,
a free-living cyanobacterium entered an early eukaryotic cell, either as food or as an internal parasite, but managed to escape the phagocytic vacuole it was contained in. The two innermost lipid-bilayer membranes that surround all chloroplasts correspond to the outer and inner membranes of the ancestral cyanobacterium's gram negative cell wall, and not the phagosomal membrane from the host, which was probably lost.
The new cellular resident quickly became an advantage, providing food for the eukaryotic host, which allowed it to live within it. Over time, the cyanobacterium was assimilated, and many of its genes were lost or transferred to the nucleus of the host. From genomes that probably originally contained over 3000 genes only about 130 genes remain in the chloroplasts of contemporary plants. Some of its proteins were then synthesized in the cytoplasm of the host cell, and imported back into the chloroplast (formerly the cyanobacterium). Separately, somewhere about 90–140 million years ago, it happened again and led to the amoeboid Paulinella chromatophora.
This event is called endosymbiosis, or "cell living inside another cell with a mutual benefit for both". The external cell is commonly referred to as the host while the internal cell is called the endosymbiont.
Chloroplasts are believed to have arisen after mitochondria, since all eukaryotes contain mitochondria, but not all have chloroplasts. This is called serial endosymbiosis—an early eukaryote engulfing the mitochondrion ancestor, and some descendants of it then engulfing the chloroplast ancestor, creating a cell with both chloroplasts and mitochondria.
Whether or not primary chloroplasts came from a single endosymbiotic event, or many independent engulfments across various eukaryotic lineages, has long been debated. It is now generally held that organisms with primary chloroplasts share a single ancestor that took in a cyanobacterium 600–2000 million years ago. It has been proposed this the closest living relative of this bacterium is Gloeomargarita lithophora. The exception is the amoeboid Paulinella chromatophora, which descends from an ancestor that took in a Prochlorococcus cyanobacterium 90–500 million years ago.
These chloroplasts, which can be traced back directly to a cyanobacterial ancestor, are known as primary plastids ("plastid" in this context means almost the same thing as chloroplast). All primary chloroplasts belong to one of four chloroplast lineages—the glaucophyte chloroplast lineage, the amoeboid Paulinella chromatophora lineage, the rhodophyte (red algal) chloroplast lineage, or the chloroplastidan (green) chloroplast lineage. The rhodophyte and chloroplastidan lineages are the largest, with chloroplastidan (green) being the one that contains the land plants. | 0 | Theoretical and Fundamental Chemistry |
A variety of bioaerosols may contribute to cloud condensation nuclei or cloud ice nuclei, possible bioaerosol components are living or dead cells, cell fragments, hyphae, pollen, or spores. Cloud formation and precipitation are key features of many hydrologic cycles to which ecosystems are tied. In addition, global cloud cover is a significant factor in the overall radiation budget and therefore, temperature of the Earth.
Bioaerosols make up a small fraction of the total cloud condensation nuclei in the atmosphere (between 0.001% and 0.01%) so their global impact (i.e. radiation budget) is questionable. However, there are specific cases where bioaerosols may form a significant fraction of the clouds in an area. These include:
* Areas where there is cloud formation at temperatures over -15 °C since some bacteria have developed proteins which allow them to nucleate ice at higher temperatures.
* Areas over vegetated regions or under remote conditions where the air is less impacted by anthropogenic activity.
* Near surface air in remote marine regions like the Southern Ocean where sea spray may be more prevalent than dust transported from continents.
The collection of bioaerosol particles on a surface is called deposition. The removal of these particles from the atmosphere affects human health in regard to air quality and respiratory systems. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, kinetic resolution is a means of differentiating two enantiomers in a racemic mixture. In kinetic resolution, two enantiomers react with different reaction rates in a chemical reaction with a chiral catalyst or reagent, resulting in an enantioenriched sample of the less reactive enantiomer. As opposed to chiral resolution, kinetic resolution does not rely on different physical properties of diastereomeric products, but rather on the different chemical properties of the racemic starting materials. The enantiomeric excess (ee) of the unreacted starting material continually rises as more product is formed, reaching 100% just before full completion of the reaction. Kinetic resolution relies upon differences in reactivity between enantiomers or enantiomeric complexes.
Kinetic resolution can be used for the preparation of chiral molecules in organic synthesis. Kinetic resolution reactions utilizing purely synthetic reagents and catalysts are much less common than the use of enzymatic kinetic resolution in application towards organic synthesis, although a number of useful synthetic techniques have been developed in the past 30 years. | 0 | Theoretical and Fundamental Chemistry |
The composition of the human body can be classified as follows:
*Water
*Proteins
*Fats (or lipids)
*Hydroxyapatite in bones
*Carbohydrates such as glycogen and glucose
*DNA and RNA
*Inorganic ions such as sodium, potassium, chloride, bicarbonate, phosphate
*Gases mainly being oxygen, carbon dioxide
*Many cofactors.
The estimated contents of a typical 20-micrometre human cell is as follows: | 1 | Applied and Interdisciplinary Chemistry |
The MTBE controversy concerns Methyl tert-butyl ether (MTBE), a gasoline additive that replaced tetraethyllead. MTBE is an oxygenate and raises gasoline's octane number. Its use declined in the United States in response to environmental and health concerns. It has polluted groundwater due to MTBE-containing gasoline being spilled or leaked at gas stations. MTBE spreads more easily underground than other gasoline components due to its higher solubility in water. Cost estimates for removing MTBE from groundwater and contaminated soil range from $1 billion to $30 billion, including removing the compound from aquifers and municipal water supplies, and replacing leaky underground oil tanks. Who will pay for remediation is controversial. In one case, the cost to oil companies to clean up the MTBE in wells belonging to the city of Santa Monica, California is estimated to exceed $200 million.
Some U.S. states banned MTBE in gasoline. California and New York, which together accounted for 40% of U.S. MTBE consumption, banned usage of the chemical in gasoline, effective 2002 and 2004, respectively. As of 2007, 25 states had issued complete or partial bans on the use of MTBE.
The Energy Policy Act of 2005 prompted gasoline refiners to replace MTBE with ethanol. | 1 | Applied and Interdisciplinary Chemistry |
Diphenylamine is considered practically insoluble according to the 2014 MSDS. It exhibits very low persistence in direct water photolysis experiments in the laboratory and is moderately volatile. Indirect photooxidation in the atmosphere through reaction with hydroxyl radicals was estimated. Despite limited data, the information was sufficient for the EC to characterize the environmental risk as negligible, because the intended use of diphenylamine was indoors. | 0 | Theoretical and Fundamental Chemistry |
The following derivation of the extended Butler–Volmer equation is adapted from that of Bard and Faulkner and Newman and Thomas-Alyea. For a simple unimolecular, one-step reaction of the form:
:O+ne → R
The forward and backward reaction rates (v and v) and, from Faradays laws of electrolysis, the associated electrical current densities (j'), may be written as:
where k and k are the reaction rate constants, with units of frequency (1/time) and c and c are the surface concentrations (mol/area) of the oxidized and reduced molecules, respectively (written as c(0,t) and c(0,t) in the previous section). The net rate of reaction v and net current density j are then:
The figure above plots various Gibbs energy curves as a function of the reaction coordinate ξ. The reaction coordinate is roughly a measure of distance, with the body of the electrode being on the left, the bulk solution being on the right. The blue energy curve shows the increase in Gibbs energy for an oxidized molecule as it moves closer to the surface of the electrode when no potential is applied. The black energy curve shows the increase in Gibbs energy as a reduced molecule moves closer to the electrode. The two energy curves intersect at . Applying a potential E to the electrode will move the energy curve downward (to the red curve) by nFE and the intersection point will move to . and are the activation energies (energy barriers) to be overcome by the oxidized and reduced species respectively for a general E, while and are the activation energies for E=0.
Assume that the rate constants are well approximated by an Arrhenius equation,
where the A and A are constants such that A c = A c is the "correctly oriented" O-R collision frequency, and the exponential term (Boltzmann factor) is the fraction of those collisions with sufficient energy to overcome the barrier and react.
Assuming that the energy curves are practically linear in the transition region, they may be represented there by:
The charge transfer coefficient for this simple case is equivalent to the symmetry factor, and can be expressed in terms of the slopes of the energy curves:
It follows that:
For conciseness, define:
The rate constants can now be expressed as:
where the rate constants at zero potential are:
The current density j as a function of applied potential E may now be written: | 0 | Theoretical and Fundamental Chemistry |
Karl Schlögl (October 5, 1924 – May 4, 2007) was professor of organic chemistry at the University of Vienna and secretary as well as vice-president of the Austrian Academy of Sciences. | 0 | Theoretical and Fundamental Chemistry |
The peripheral attack model is based on predicting lowest energy conformations of an inherently complicated system, where nuanced perturbations can cause huge stereodifferentiating consequences. By modeling peripheral attack using the Curtin-Hammett scenario depicted above, the transition state is excluded from this conformation analysis by assuming that the barrier to each transition state from a given conformation is the same and thus that ground state conformations are the sole product determining factor. A significant criticism is the mapping of medium-sized ring conformations and influences onto larger ring systems. Macrocycles can possess varying degrees of rigidity in their structure, making a single peripheral attack model difficult to apply to all systems. Different classes of reactions might not fit the peripheral attack model, as reactions such as epoxidations, hydroxylations, alkylations, and reductions all proceed through different transition states. | 0 | Theoretical and Fundamental Chemistry |
Oxygen is one of the reagents consumed during cyanidation, accepting the electrons from the gold, and a deficiency in dissolved oxygen slows leaching rate. Air or pure oxygen gas can be purged through the pulp to maximize the dissolved oxygen concentration. Intimate oxygen-pulp contactors are used to increase the partial pressure of the oxygen in contact with the solution, thus raising the dissolved oxygen concentration much higher than the saturation level at atmospheric pressure. Oxygen can also be added by dosing the pulp with hydrogen peroxide solution. | 1 | Applied and Interdisciplinary Chemistry |
A trap crop is a plant that attracts agricultural pests, usually insects, away from nearby target crops. This form of companion planting can save a target crop from decimation by pests without the use of artificial pesticides. A trap crop is used for attracting the insect and pests away from a target crop field. Many trap crops have successfully diverted pests from focal crops in small scale greenhouse, garden and field experiments; a small portion of these plants have been shown to reduce pest damage at larger commercial scales. A common explanation for reported trap cropping failures, is that attractive trap plants only protect nearby plants if the insects do not move back into the target crop. In a review of 100 trap cropping examples in 2006, only 10 trap crops were classified as successful at a commercial scale, and in all successful cases, trap cropping was supplemented with management practices that specifically limited insect dispersal from the trap crop back into the target crop. | 1 | Applied and Interdisciplinary Chemistry |
After her postdoctoral research, she joined Indiana University, where she became an associate professor. She moved to the University of Maryland School of Pharmacy in 2016.
In her research, Jones focusses on structural proteomics, having developed fast photochemical oxidation of proteins (FPOP) which uses an excimer laser for photolysis, which generates hydroxyl radicals. Hydroxyl radicals go on to oxidise the side chains of amino acids and provide solvent accessibility of proteins within a cell. FPOP can provide information on the sites of ligand binding, protein interaction and protein conformational changes in vivo. More recently, her group has extended the platform with a no-flow platform for high-throughput in-cell measurements.
In 2019, she received the Biophysical Society's Junior Faculty Award.
Jones also works on science outreach and improving representation in the sciences. She is a mentor in the UMD CURE Scholars Program and a member of the American Society for Mass Spectrometry Diversity and Outreach Working Group. Jones is also co-director of the Initiative to Maximize Student Development (IMSD) Meyerhoff Graduate Fellowship Program, a program for increasing representation of minority students in STEM.
In 2021, Jones was in the news for turning down a faculty position at the University of North Carolina Chapel Hill in protest of controversy regarding the tenure status of journalist Nikole Hannah-Jones. | 1 | Applied and Interdisciplinary Chemistry |
The DNA sense strand looks like the messenger RNA (mRNA) transcript, and can therefore be used to read the expected codon sequence that will ultimately be used during translation (protein synthesis) to build an amino acid sequence and then a protein. For example, the sequence "ATG" within a DNA sense strand corresponds to an "AUG" codon in the mRNA, which codes for the amino acid methionine. However, the DNA sense strand itself is not used as the template for the mRNA; it is the DNA antisense strand that serves as the source for the protein code, because, with bases complementary to the DNA sense strand, it is used as a template for the mRNA. Since transcription results in an RNA product complementary to the DNA template strand, the mRNA is complementary to the DNA antisense strand.
Hence, a base triplet 3′-TAC-5′ in the DNA antisense strand (complementary to the 5′-ATG-3′ of the DNA sense strand) is used as the template which results in a 5′-AUG-3′ base triplet in the mRNA. The DNA sense strand will have the triplet ATG, which looks similar to the mRNA triplet AUG but will not be used to make methionine because it will not be directly used to make mRNA. The DNA sense strand is called a "sense" strand not because it will be used to make protein (it won't be), but because it has a sequence that corresponds directly to the RNA codon sequence. By this logic, the RNA transcript itself is sometimes described as "sense". | 1 | Applied and Interdisciplinary Chemistry |
Deep-sea hydrothermal vents and their associated fauna were first discovered along the Galapagos Rift in the eastern Pacific in 1977. Vents are now known to occur along all active mid ocean ridges and back-arc spreading centres, from fast to ultra-slow spreading ridges. The interest in chemosynthetic environments was strengthened by the discovery of chemosynthetic-based fauna at cold seeps along the base of the Florida Escarpment in 1983. Cold seeps occur along active and passive continental margins. More recently, the study of chemosynthetic fauna has extended to the communities that develop in other reducing habitats such as whale falls, sunken wood and areas of oxygen minima when they intersect with the margin or seamounts.
Since the first discovery of hydrothermal vents, more than 600 species have been described from vents and seeps. This is equivalent of 1 new description every 2 weeks(!). As biologists, geochemists, and physicists combine research efforts in these systems, new species will certainly be discovered. Moreover, because of the extreme conditions of the vent and seep habitat, certain species may have specific physiological adaptations with interesting results for the biochemical and medical industry.
These globally distributed, ephemeral and insular habitats that support endemic faunas offer natural laboratories for studies on dispersal, isolation and evolution. Here, hydrographic and topographic controls on biodiversity and biogeography might be much more readily resolved than in systems where climate and human activity obscure their role. In addition, hydrothermal vents have been suggested to be the habitat of the origin of life. These hypotheses are being used by ChEss researchers in collaboration with NASA to develop programmes to search for life in planets or moons of the outer space. | 0 | Theoretical and Fundamental Chemistry |
The styrene-maleic acid (SMA) alternating copolymer displays amphiphilicity depending on pH, allowing it to change conformations in different environments. Some conformations that SMA can take are random coil formation, compact globular formation, micelles, and nanodiscs. SMA has been used as a dispersing agent for dyes and inks, as drug delivery vehicles, and for membrane solubilization. | 0 | Theoretical and Fundamental Chemistry |
An activated complex with high symmetry can decrease the accuracy of rate expressions. Error can arise from introducing symmetry numbers into the rotational partition functions for the reactants and activated complexes. To reduce errors, symmetry numbers can by omitted by multiplying the rate expression by a statistical factor:where the statistical factor is the number of equivalent activated complexes that can be formed, and the Q are the partition functions from the symmetry numbers that have been omitted.
The activated complex is a collection of molecules that forms and then explodes along a particular internal normal coordinate. Ordinary molecules have three translational degrees of freedom, and their properties are similar to activated complexes. However, activated complexed have an extra degree of translation associated with their approach to the energy barrier, crossing it, and then dissociating. | 0 | Theoretical and Fundamental Chemistry |
In solar power plants, heat transfer fluids are used in concentrators like linear Fresnel and parabolic trough systems for efficient energy generation and thermal storage. Molten salts and synthetic heat transfer fluids are utilized based on their ability to function at various temperature ranges, contributing to the generation of electricity and the manufacturing of polysilicon for photovoltaic cells. These fluids assist in the purification and cooling steps of polysilicon production, essential for creating high-purity silicon for solar and electronic applications. | 1 | Applied and Interdisciplinary Chemistry |
Sodium-22 and chlorine-36 are commonly used to study ion transporters. However, sodium-22 is hard to screen off and chlorine-36, with a half-life of 300,000 years, has low activity. | 0 | Theoretical and Fundamental Chemistry |
Global paleoclimate indicators are the proxies sensitive to global paleoclimatic environment changes. They are mostly derived from marine sediments. Paleoclimate indicators derived from terrestrial sediments, on the other hand, are commonly influenced by local tectonic movements and paleogeographic variations. Factors governing the Earths climate system include plate tectonics, which controls the configuration of continents, the interplay between the atmosphere and the ocean, and the Earths orbital characteristics (Milankovitch cycles). Global paleoclimate indicators are established based on the information extracted from the analyses of geologic materials, including biological, geochemical and mineralogical data preserved in marine sediments. Indicators are generally grouped into three categories; paleontological, geochemical and lithological. | 0 | Theoretical and Fundamental Chemistry |
The enzyme is important for carotenoid biosynthesis during chloroplast biogenesis. In developing plastids, its activity prevents the over-reduction of the plastoquinone pool. Knockout plants for PTOX exhibit phenotypes of variegated leaves with white patches. Without the enzyme, the carotenoid synthesis pathway slows down due to the lack of oxidized plastoquinone with which to oxidize phytoene, a carotenoid intermediate. The colorless compound phytoene accumulates in the leaves, resulting in white patches of cells. PTOX is also thought to determine the redox poise of the developing photosynthetic apparatus and without it, plants fail to assemble organized internal membrane structures in chloroplasts when exposed to high light during early development. | 0 | Theoretical and Fundamental Chemistry |
As river mouths are the site of large-scale sediment deposition and allow for easy travel and ports, many towns and cities are founded there. Many places in the United Kingdom take their names from their positions at the mouths of rivers, such as Plymouth (i.e. mouth of the Plym River), Sidmouth (i.e. mouth of the Sid River), and Great Yarmouth (i.e. mouth of the Yare River); in Celtic, the term is Aber or Inver. Due to rising sea levels as a result of climate change, the coastal cities are at heightened risk of flooding. Sediment starvation in the river compounds this concern. | 1 | Applied and Interdisciplinary Chemistry |
A high-frequency approximation (or "high energy approximation") for scattering or other wave propagation problems, in physics or engineering, is an approximation whose accuracy increases with the size of features on the scatterer or medium relative to the wavelength of the scattered particles.
Classical mechanics and geometric optics are the most common and extreme high frequency approximation, where the wave or field properties of, respectively, quantum mechanics and electromagnetism are neglected entirely.
Less extreme approximations include, the WKB approximation, physical optics, the geometric theory of diffraction, the uniform theory of diffraction, and the physical theory of diffraction. When these are used to approximate quantum mechanics, they are called semiclassical approximations. | 0 | Theoretical and Fundamental Chemistry |
The scanning helium microscope (SHeM) is a novel form of microscopy that uses low-energy (5–100 meV) neutral helium atoms to image the surface of a sample without any damage to the sample caused by the imaging process. Since helium is inert and neutral, it can be used to study delicate and insulating surfaces. Images are formed by rastering a sample underneath an atom beam and monitoring the flux of atoms that are scattered into a detector at each point.
The technique is different from a scanning helium ion microscope, which uses charged helium ions that can cause damage to a surface. | 0 | Theoretical and Fundamental Chemistry |
The Department of Systems and Synthetic Microbiology, headed by Victor Sourjik, aims to elucidate general principles of evolutionary optimization of cellular networks and implement these principles in the design of novel networks in microorganisms. Having a single research group, microbial networks is also led by Sourjik. | 0 | Theoretical and Fundamental Chemistry |
All kinetic and equilibrium isotope effects result from differences in atomic mass. As a result, a reaction that fractionates S will also fractionate S and S, and the fractionation factor for each isotope will be mathematically proportional to its mass. Because of the mathematical relationships of their masses, the observed relationships between δS, δS, and δS in most natural materials are approximately δS = 0.515 × δS and δS = 1.90 × δS. Rarely, natural processes can create deviations from this relationship, and these deviations are reported as ΔS and ΔS values, usually pronounced as "cap delta." These values are typically calculated as follows:
:ΔS = 1000 × [(1 + δS/1000) − (1 + δS 1000) − 1]
:ΔS = 1000 × [(1 + δS/1000) − (1 + δS/1000) − 1]
However, the method for calculating ΔS and ΔS values is not standardized, and can differ among publications. | 0 | Theoretical and Fundamental Chemistry |
In principle, all types of liquids can behave as solvents: liquid noble gases, molten metals, molten salts, molten covalent networks, and molecular liquids. In the practice of chemistry and biochemistry, most solvents are molecular liquids. They can be classified into polar and non-polar, according to whether their molecules possess a permanent electric dipole moment. Another distinction is whether their molecules can form hydrogen bonds (protic and aprotic solvents). Water, the most commonly used solvent, is both polar and sustains hydrogen bonds.
Salts dissolve in polar solvents, forming positive and negative ions that are attracted to the negative and positive ends of the solvent molecule, respectively. If the solvent is water, hydration occurs when the charged solute ions become surrounded by water molecules. A standard example is aqueous saltwater. Such solutions are called electrolytes. Whenever salt dissolves in water ion association has to be taken into account.
Polar solutes dissolve in polar solvents, forming polar bonds or hydrogen bonds. As an example, all alcoholic beverages are aqueous solutions of ethanol. On the other hand, non-polar solutes dissolve better in non-polar solvents. Examples are hydrocarbons such as oil and grease that easily mix, while being incompatible with water.
An example of the immiscibility of oil and water is a leak of petroleum from a damaged tanker, that does not dissolve in the ocean water but rather floats on the surface. | 0 | Theoretical and Fundamental Chemistry |
Bohrs model of the atom was essentially a planetary one, with the electrons orbiting around the nuclear "sun". However, the uncertainty principle states that an electron cannot simultaneously have an exact location and velocity in the way that a planet does. Instead of classical orbits, electrons are said to inhabit atomic orbitals'. An orbital is the "cloud" of possible locations in which an electron might be found, a distribution of probabilities rather than a precise location. Each orbital is three dimensional, rather than the two-dimensional orbit, and is often depicted as a three-dimensional region within which there is a 95 percent probability of finding the electron.
Schrödinger was able to calculate the energy levels of hydrogen by treating a hydrogen atoms electron as a wave, represented by the "wave function" , in an electric potential well, , created by the proton. The solutions to Schrödingers equation are distributions of probabilities for electron positions and locations. Orbitals have a range of different shapes in three dimensions. The energies of the different orbitals can be calculated, and they accurately match the energy levels of the Bohr model.
Within Schrödinger's picture, each electron has four properties:
# An "orbital" designation, indicating whether the particle-wave is one that is closer to the nucleus with less energy or one that is farther from the nucleus with more energy;
# The "shape" of the orbital, spherical or otherwise;
# The "inclination" of the orbital, determining the magnetic moment of the orbital around the -axis.
# The "spin" of the electron.
The collective name for these properties is the quantum state of the electron. The quantum state can be described by giving a number to each of these properties; these are known as the electron's quantum numbers. The quantum state of the electron is described by its wave function. The Pauli exclusion principle demands that no two electrons within an atom may have the same values of all four numbers.
The first property describing the orbital is the principal quantum number, , which is the same as in Bohr's model. denotes the energy level of each orbital. The possible values for are integers:
The next quantum number, the azimuthal quantum number, denoted , describes the shape of the orbital. The shape is a consequence of the angular momentum of the orbital. The angular momentum represents the resistance of a spinning object to speeding up or slowing down under the influence of external force. The azimuthal quantum number represents the orbital angular momentum of an electron around its nucleus. The possible values for are integers from 0 to (where is the principal quantum number of the electron):
The shape of each orbital is usually referred to by a letter, rather than by its azimuthal quantum number. The first shape (=0) is denoted by the letter (a mnemonic being "sphere"). The next shape is denoted by the letter and has the form of a dumbbell. The other orbitals have more complicated shapes (see atomic orbital), and are denoted by the letters , , , etc.
The third quantum number, the magnetic quantum number, describes the magnetic moment of the electron, and is denoted by (or simply m). The possible values for are integers from to (where is the azimuthal quantum number of the electron):
The magnetic quantum number measures the component of the angular momentum in a particular direction. The choice of direction is arbitrary; conventionally the z-direction is chosen.
The fourth quantum number, the spin quantum number (pertaining to the "orientation" of the electron's spin) is denoted , with values + or −.
The chemist Linus Pauling wrote, by way of example:
It is the underlying structure and symmetry of atomic orbitals, and the way that electrons fill them, that leads to the organization of the periodic table. The way the atomic orbitals on different atoms combine to form molecular orbitals determines the structure and strength of chemical bonds between atoms.
The field of quantum chemistry was pioneered by physicists Walter Heitler and Fritz London, who published a study of the covalent bond of the hydrogen molecule in 1927. Quantum chemistry was subsequently developed by a large number of workers, including the American theoretical chemist Linus Pauling at Caltech, and John C. Slater into various theories such as Molecular Orbital Theory or Valence Theory. | 1 | Applied and Interdisciplinary Chemistry |
Sensor-based sorting, is an umbrella term for all applications in which particles are detected using a sensor technique and rejected by an amplified mechanical, hydraulic or pneumatic process.
The technique is generally applied in mining, recycling and food processing and used in the particle size range between . Since sensor-based sorting is a single particle separation technology, the throughput is proportional to the average particle size and weight fed onto the machine. | 0 | Theoretical and Fundamental Chemistry |
The compound prepared by treating urea with hydrazine:
:OC(NH) + NH → OC(NH)(NH) + NH
A further reaction can occur to give carbohydrazide:
:OC(NH)(NH) + NH → OC(NH) + NH | 0 | Theoretical and Fundamental Chemistry |
The mechanisms that damage kidneys during hypothermic storage can be sub-divided as follows:
# Injury to the metabolic processes of the cell caused by:
## Cold
## Anoxia when the kidney is warm both before and after the period of hypothermic storage.
## Failure to supply the correct nutrients.
## Toxin accumulation in the perfusate.
## Toxic damage from the storage fluid.
## Washout of essential substrates from the kidney cells.
# Injury to nuclear DNA.
# Mechanical injury to the vascular system of the kidney during hypothermic perfusion.
# Post reimplantation injury. | 1 | Applied and Interdisciplinary Chemistry |
The main distinguishing feature between p90 and p70 is that the 90 kDa family contain two non-identical kinase domains, while the 70 kDa family contain only one kinase domain. | 1 | Applied and Interdisciplinary Chemistry |
Thermophotovoltaic (TPV) energy conversion is a direct conversion process from heat to electricity via photons. A basic thermophotovoltaic system consists of a hot object emitting thermal radiation and a photovoltaic cell similar to a solar cell but tuned to the spectrum being emitted from the hot object.
As TPV systems generally work at lower temperatures than solar cells, their efficiencies tend to be low. Offsetting this through the use of multi-junction cells based on non-silicon materials is common, but generally very expensive. This currently limits TPV to niche roles like spacecraft power and waste heat collection from larger systems like steam turbines. | 0 | Theoretical and Fundamental Chemistry |
The flux method is a crystal growth method where starting materials are dissolved in a solvent (flux), and are precipitated out to form crystals of a desired compound. The flux lowers the melting point of the desired compound, analogous to a wet chemistry recrystallization. The flux is molten in a highly stable crucible that does not react with the flux. Metal crucibles, such as platinum, titanium, and niobium are used for the growth of oxide crystals. Ceramic crucibles, such as alumina, zirconia, and boron nitride are used for the growth of metallic crystals. For air-sensitive growths, contents are sealed in ampoules or placed in atmosphere controlled furnaces. | 0 | Theoretical and Fundamental Chemistry |
At the back end of the truck is a powered reel with video cable reinforced with kevlar or steel wire braid. Some trucks also contain a powered winch that booms out from the truck allowing for lowering and retrieval of the inspection equipment from the pipeline. | 1 | Applied and Interdisciplinary Chemistry |
SERS substrates are used to detect the presence of low-abundance biomolecules, and can therefore detect proteins in bodily fluids. Early detection of pancreatic cancer biomarkers was accomplished using SERS-based immunoassay approach. A SERS-base multiplex protein biomarker detection platform in a microfluidic chip is used to detect several protein biomarkers to predict the type of disease and critical biomarkers and increase the chance of differentiating diseases with similar biomarkers like pancreatic cancer, ovarian cancer, and pancreatitis.
This technology has been utilized to detect urea and blood plasma label free in human serum and may become the next generation in cancer detection and screening.
The ability to analyze the composition of a mixture at a nanoscale makes the use of SERS substrates that are beneficial for environmental analysis, pharmaceuticals, material sciences, art and archaeological research, forensic science, drug and explosives detection, food quality analysis, and single algal cell detection.
SERS combined with plasmonic sensing can be used for high-sensitivity quantitative analysis of small molecules in human biofluids, the quantitative detection of biomolecular interaction, the detection of low-level cancer biomarkers via sandwich immunoassay platforms, the label-free characterization of exosomes, and the study of redox processes at a single-molecule level.
SERS is a powerful technique for determining structural information about molecular systems. It has found a wide range of applications in ultra-sensitive chemical sensing and environmental analyses.
A review of the present and future applications of SERS was published in 2020. | 0 | Theoretical and Fundamental Chemistry |
Genomic editing takes place by transfecting cells with the pegRNA and the fusion protein. Transfection is often accomplished by introducing vectors into a cell. Once internalized, the fusion protein nicks the target DNA sequence, exposing a 3’-hydroxyl group that can be used to initiate (prime) the reverse transcription of the RT template portion of the pegRNA. This results in a branched intermediate that contains two DNA flaps: a 3’ flap that contains the newly synthesized (edited) sequence, and a 5’ flap that contains the dispensable, unedited DNA sequence. The 5’ flap is then cleaved by structure-specific endonucleases or 5’ exonucleases. This process allows 3’ flap ligation, and creates a heteroduplex DNA composed of one edited strand and one unedited strand. The reannealed double stranded DNA contains nucleotide mismatches at the location where editing took place. In order to correct the mismatches, the cells exploit the intrinsic mismatch repair mechanism, with two possible outcomes: (i) the information in the edited strand is copied into the complementary strand, permanently installing the edit; (ii) the original nucleotides are re-incorporated into the edited strand, excluding the edit. | 1 | Applied and Interdisciplinary Chemistry |
Due to its high abundance in plants (generally 40% of the total protein content), RuBisCO often impedes analysis of important signaling proteins such as transcription factors, kinases, and regulatory proteins found in lower abundance (10-100 molecules per cell) within plants. For example, using mass spectrometry on plant protein mixtures would result in multiple intense RuBisCO subunit peaks that interfere and hide those of other proteins.
Recently, one efficient method for precipitating out RuBisCO involves the usage of protamine sulfate solution. Other existing methods for depleting RuBisCO and studying lower abundance proteins include fractionation techniques with calcium and phytate, gel electrophoresis with polyethylene glycol, affinity chromatography, and aggregation using DTT, though these methods are more time-consuming and less efficient when compared to protamine sulfate precipitation. | 0 | Theoretical and Fundamental Chemistry |
Despite the presence of the de novo pathway, the salvage reactions are essential in humans; a lack of niacin in the diet causes the vitamin deficiency disease pellagra. This high requirement for NAD results from the constant consumption of the coenzyme in reactions such as posttranslational modifications, since the cycling of NAD between oxidized and reduced forms in redox reactions does not change the overall levels of the coenzyme.
The major source of NAD in mammals is the salvage pathway which recycles the nicotinamide produced by enzymes utilizing NAD. The first step, and the rate-limiting enzyme in the salvage pathway is nicotinamide phosphoribosyltransferase (NAMPT), which produces nicotinamide mononucleotide (NMN). NMN is the immediate precursor to NAD+ in the salvage pathway.
Besides assembling NAD de novo from simple amino acid precursors, cells also salvage preformed compounds containing a pyridine base. The three vitamin precursors used in these salvage metabolic pathways are nicotinic acid (NA), nicotinamide (Nam) and nicotinamide riboside (NR). These compounds can be taken up from the diet and are termed vitamin B or niacin. However, these compounds are also produced within cells and by digestion of cellular NAD. Some of the enzymes involved in these salvage pathways appear to be concentrated in the cell nucleus, which may compensate for the high level of reactions that consume NAD in this organelle. There are some reports that mammalian cells can take up extracellular NAD from their surroundings, and both nicotinamide and nicotinamide riboside can be absorbed from the gut.
The salvage pathways used in microorganisms differ from those of mammals. Some pathogens, such as the yeast Candida glabrata and the bacterium Haemophilus influenzae are NAD auxotrophs – they cannot synthesize NAD – but possess salvage pathways and thus are dependent on external sources of NAD or its precursors. Even more surprising is the intracellular pathogen Chlamydia trachomatis, which lacks recognizable candidates for any genes involved in the biosynthesis or salvage of both NAD and NADP, and must acquire these coenzymes from its host. | 0 | Theoretical and Fundamental Chemistry |
In mathematics, a stereographic projection is a perspective projection of the sphere, through a specific point on the sphere (the pole or center of projection), onto a plane (the projection plane) perpendicular to the diameter through the point. It is a smooth, bijective function from the entire sphere except the center of projection to the entire plane. It maps circles on the sphere to circles or lines on the plane, and is conformal, meaning that it preserves angles at which curves meet and thus locally approximately preserves shapes. It is neither isometric (distance preserving) nor equiareal (area preserving).
The stereographic projection gives a way to represent a sphere by a plane. The metric induced by the inverse stereographic projection from the plane to the sphere defines a geodesic distance between points in the plane equal to the spherical distance between the spherical points they represent. A two-dimensional coordinate system on the stereographic plane is an alternative setting for spherical analytic geometry instead of spherical polar coordinates or three-dimensional cartesian coordinates. This is the spherical analog of the Poincaré disk model of the hyperbolic plane.
Intuitively, the stereographic projection is a way of picturing the sphere as the plane, with some inevitable compromises. Because the sphere and the plane appear in many areas of mathematics and its applications, so does the stereographic projection; it finds use in diverse fields including complex analysis, cartography (see stereographic map projection), geology, and photography. Sometimes stereographic computations are done graphically using a special kind of graph paper called a stereographic net, shortened to stereonet, or Wulff net. | 0 | Theoretical and Fundamental Chemistry |
In the United States, drug costs are partially unregulated, but instead are the result of negotiations between drug companies and insurance companies.
High prices have been attributed to monopolies given to manufacturers by the government. New drug development costs continue to rise as well. Despite the enormous advances in science and technology, the number of new blockbuster drugs approved by the government per billion dollars spent has halved every 9 years since 1950. | 1 | Applied and Interdisciplinary Chemistry |
* Photo-reflectance measures differential reflectivities as small as one part per million, whereas ellipsometry and/or standard reflectance measure differential reflectivities on the order of one part per thousand.
* Photo-reflectance spectra exhibits sharp derivative-like structures localized at interband transition energies, whereas ellipsometry and/or standard reflectance exhibit broad slowly varying spectra.
* The photo-reflectance response at a particular wavelength typically arises from specific interband transitions confined to specific materials within the sample.
* By using phase-locked detection methods, ambient (nonsynchronous) light does not influence photo-reflectance measurements.
* By using a laser probe beam, the refractive part of the photo-reflectance response can be isolated without the necessity to take spectroscopic data or perform a fit procedure.
* Laser photo-reflectance has been proven in statistical process control for microelectronics manufacturing for over three decades. | 0 | Theoretical and Fundamental Chemistry |
Mezlocillin can be made in a variety of ways including reaction of ampicillin with chlorocarbamate 1 in the presence of triethylamine. Chlorocarbamate 1 itself is made from ethylenediamine by reaction with phosgene to form the cyclic urea followed by monoamide formation with methanesulfonyl chloride and then reaction of the other nitrogen atom with phosgene and trimethylsilylchloride.
The closely related analogue azlocillin is made in essentially the same manner as mezlocillin. but with omission of the methylation step. | 0 | Theoretical and Fundamental Chemistry |
The interface between a crystal and its vapor can be molecularly sharp at temperatures well below the melting point. An ideal crystalline surface grows by the spreading of single layers, or equivalently, by the lateral advance of the growth steps bounding the layers. For perceptible growth rates, this mechanism requires a finite driving force (or degree of supercooling) in order to lower the nucleation barrier sufficiently for nucleation to occur by means of thermal fluctuations. In the theory of crystal growth from the melt, Burton and Cabrera have distinguished between two major mechanisms: | 0 | Theoretical and Fundamental Chemistry |
In physics and thermodynamics, the Redlich–Kwong equation of state is an empirical, algebraic equation that relates temperature, pressure, and volume of gases. It is generally more accurate than the van der Waals equation and the ideal gas equation at temperatures above the critical temperature. It was formulated by Otto Redlich and Joseph Neng Shun Kwong in 1949. It showed that a two-parameter, cubic equation of state could well reflect reality in many situations, standing alongside the much more complicated Beattie–Bridgeman model and Benedict–Webb–Rubin equation that were used at the time. The Redlich–Kwong equation has undergone many revisions and modifications, in order to improve its accuracy in terms of predicting gas-phase properties of more compounds, as well as in better simulating conditions at lower temperatures, including vapor–liquid equilibria. | 0 | Theoretical and Fundamental Chemistry |
Anodizing will raise the surface since the oxide created occupies more space than the base metal converted. This will generally not be of consequence except where there are tight tolerances. If so, the thickness of the anodizing layer has to be taken into account when choosing the machining dimension. A general practice on engineering drawing is to specify that "dimensions apply after all surface finishes". This will force the machine shop to take into account the anodization thickness when performing the final machining of the mechanical part before anodization. Also in the case of small holes threaded to accept screws, anodizing may cause the screws to bind, thus the threaded holes may need to be chased with a tap to restore the original dimensions. Alternatively, special oversize taps may be used to precompensate for this growth. In the case of unthreaded holes that accept fixed-diameter pins or rods, a slightly oversized hole to allow for the dimension change may be appropriate. Depending on the alloy and thickness of the anodized coating, the same may have a significantly negative effect on fatigue life. Conversely, anodizing may increase fatigue life by preventing corrosion pitting. | 1 | Applied and Interdisciplinary Chemistry |
Carbon is a necessary component of all known life. C, a stable isotope of carbon, is abundantly produced in stars due to three factors:
# The decay lifetime of a Be nucleus is four orders of magnitude larger than the time for two He nuclei (alpha particles) to scatter.
# An excited state of the C nucleus exists a little (0.3193 MeV) above the energy level of Be + He. This is necessary because the ground state of C is 7.3367 MeV below the energy of Be + He; a Be nucleus and a He nucleus cannot reasonably fuse directly into a ground-state C nucleus. However, Be and He use the kinetic energy of their collision to fuse into the excited C (kinetic energy supplies the additional 0.3193 MeV necessary to reach the excited state), which can then transition to its stable ground state. According to one calculation, the energy level of this excited state must be between about 7.3 MeV and 7.9 MeV to produce sufficient carbon for life to exist, and must be further "fine-tuned" to between 7.596 MeV and 7.716 MeV in order to produce the abundant level of C observed in nature. The Hoyle state has been measured to be about 7.65 MeV above the ground state of C.
# In the reaction C + He → O, there is an excited state of oxygen which, if it were slightly higher, would provide a resonance and speed up the reaction. In that case, insufficient carbon would exist in nature; almost all of it would have converted to oxygen.
Some scholars argue the 7.656 MeV Hoyle resonance, in particular, is unlikely to be the product of mere chance. Fred Hoyle argued in 1982 that the Hoyle resonance was evidence of a "superintellect"; Leonard Susskind in The Cosmic Landscape rejects Hoyle's intelligent design argument. Instead, some scientists believe that different universes, portions of a vast "multiverse", have different fundamental constants: according to this controversial fine-tuning hypothesis, life can only evolve in the minority of universes where the fundamental constants happen to be fine-tuned to support the existence of life. Other scientists reject the hypothesis of the multiverse on account of the lack of independent evidence. | 0 | Theoretical and Fundamental Chemistry |
Steel pipe (or black iron pipe) was once the most popular choice for supply of water and flammable gases. Steel pipe is still used in many homes and businesses to convey natural gas or propane fuel, and is a popular choice in fire sprinkler systems due to its high heat resistance. In commercial buildings, steel pipe is used to convey heating or cooling water to heat exchangers, air handlers, variable air volume (VAV) devices, or other HVAC equipment.
Steel pipe is sometimes joined using threaded connections, where tapered threads (see National Pipe Thread) are cut into the end of the tubing segment, sealant is applied in the form of thread sealing compound or thread seal tape (also known as PTFE or Teflon tape), and it is then threaded into a corresponding threaded fitting using two pipe wrenches. Beyond domestic or light commercial settings, steel pipe is often joined by welding, or by use of mechanical couplings made by companies such as Victaulic or Anvil International (formerly Grinnell) that hold the pipe joint together via a groove pressed or cut (a rarely used older practice), into the ends of the pipes.
Other variations of steel pipe include various stainless steel and chrome alloys. In high-pressure situations these are usually joined by TIG welding.
In Canada, with respect to natural gas (NG) and propane (LP gas), black iron pipe (BIP) is commonly used to connect an appliance to the supply. It must however be marked (either painted yellow or yellow banding attached at certain intervals) and certain restrictions apply to which nominal pipe size (NPS) can be put through walls and buildings. With propane in particular, BIP can be run from an exterior tank (or cylinder) provided it is well protected from the weather, and an anode-type of protection from corrosion is in place when the pipe is to be installed underground. | 1 | Applied and Interdisciplinary Chemistry |
In the process industry, there exist a variety of cases where a high pressure jet release incident can occur. LNG storage facilities or NG pipeline systems leakage can degenerate into a jet fire and, through a domino effect, cause heavy damage to the workforce, equipment and surrounding environment. For different scenarios that may happen, safety protocols have to be engineered that aim to set minimum distances between equipment and the workforce, along with preventive systems that reduce the danger of the potential incidental scenario. The following are some of the most common scenarios that may be encountered in an industrial environment:
*Jet-Ground interaction: this is one of the most common scenarios, where the free jet does not interact with any other obstacle apart from the ground. Although the jet can dissipate to concentrations below its LFL after roughly 16 meters with no interactions (interaction with concrete and at stagnant pressure of 65 bar, a common pressure for NG pipelines, with an orifice size of 2.54 mm), as the jet gets closer to the ground and makes contact with it, a dragging effect leads to a further extension. The jet has the tendency of bending downwards if close enough to the ground because of lower pressure zones below it.
*Jet-horizontal tank interaction: jet-tank interaction will depend of the type of material used. For cylindrical steel tanks, the distance from the exit plane will have an effect with the interaction, along with its angle with respect to the axis of the jet and the height of the release of the jet. Generally, when the jet impinges the horizontal tank along the axis of the tank, the jet is brought downwards, allowing an interaction with the ground. This will often lead to the extension of the jet at its LFL concentration with respect to its free jet (the same scenario is simulated with no other obstacles but the ground). Furthermore, crosswise extension is also expected.
*Jet-vertical tank interaction: for a cylindrical steel tank, the distance from the exit plane will have an effect with the interaction. Generally, when the jet impinges the vertical tank along the axis of the tank, the obstacle will act as a limiting factor for the extension of the jet at its LFL concentration with respect to its free jet. The impact with the tank will generate more eddies downstream the tail of the jet and limit ground interaction (at low enough flow rates and speeds), speeding up dilution of the gas below its lower flammable limit.
*Jet-horizontal tandem tank interaction: by adding a second horizontal tank behind the first, a shortening effect is achieved. The presence of the second obstacle leads to eddy generation after the first, promoting dissipation. Moreover, the second obstacle may have a detachment effect of the jet from the ground, as it will tend to adhere to the round surface of the second tank due to the coanda effect. Distance between the two tanks will have an effect, since, after a certain distance, the second obstacle will no longer have an effect on the cloud at LFL concentration.
*Jet-vertical tandem tank interaction: by adding a second vertical tank behind the first, a shortening effect will generally be achieved. The presence of the second obstacle leads to eddy generation after the first, promoting dissipation. Contrary to the previous scenario, the second obstacle can allow for jet-ground interaction and elongate the jet, a quality that be worsen due to the coanda effect. Distance between the two tanks will have an effect, since, after a certain distance, the second obstacle will no longer have an effect on the cloud at LFL concentration. | 1 | Applied and Interdisciplinary Chemistry |
Lead compounds are sometimes called developmental candidates. This is because the discovery and selection of lead compounds occurs prior to preclinical and clinical development of the candidate. | 1 | Applied and Interdisciplinary Chemistry |
Coinduction in anesthesia is a pharmacological tool whereby a combination of sedative drugs may be used to greater effect than a single agent, achieving a smoother onset of general anesthesia. The use of coinduction allows lower doses of the same anesthetic agents to be used which provides enhanced safety, faster recovery, fewer side-effects, and more predictable pharmacodynamics. Coinduction is used in human medicine and veterinary medicine as standard practice to provide optimum anesthetic induction. The onset or induction phase of anesthesia is a critical period involving the loss of consciousness and reactivity in the patient, and is arguably the most dangerous period of a general anesthetic. A great variety of coinduction combinations are in use and selection is dependent on the patient's age and health, the specific situation, and the indication for anesthesia. As with all forms of anesthesia the resources available in the environment are a key factor.
__TOC__ | 1 | Applied and Interdisciplinary Chemistry |
AT receptors are mainly found in the heart, adrenal glands, brain, liver and kidneys. Their main role is to regulate blood pressure as well as fluid and electrolyte balance. <br />
AT receptors are highly expressed in the developing fetus but they decline rapidly after birth. In the adult, AT receptors are present only at low levels and are mostly found in the heart, adrenal glands, uterus, ovaries, kidneys and brain. | 1 | Applied and Interdisciplinary Chemistry |
N-demethylation of 3° amines is by the von Braun reaction, which uses BrCN as the reagent to give the corresponding nor- derivatives. A modern variation of the von Braun reaction was developed, where BrCN was superseded by ethyl chloroformate. The preparation of Paxil from arecoline is an application of this reaction, as well as the synthesis of GSK-372,475, for example.
The N-demethylation of imipramine gives desipramine. | 0 | Theoretical and Fundamental Chemistry |
*[http://www.epa.gov/owow/showcase/whiteriver/river_bend/riverbend.html EPA - River Bend Project]
*[https://web.archive.org/web/20021231051820/http://dnr.metrokc.gov/wlr/flood/maintenance.html Levee and Revetment Routine Maintenance]
*[http://www.fhwa.dot.gov/engineering/hydraulics/pubs/hec/hec11si.pdf US DOT - Design of Riprap Revetment] | 1 | Applied and Interdisciplinary Chemistry |
Redox reactions are prevalent for the transition elements. Two classes of redox reaction are considered: atom-transfer reactions, such as oxidative addition/reductive elimination, and electron-transfer. A fundamental redox reaction is "self-exchange", which involves the degenerate reaction between an oxidant and a reductant. For example, permanganate and its one-electron reduced relative manganate exchange one electron:
:[MnO] + [Mn*O] → [MnO] + [Mn*O] | 0 | Theoretical and Fundamental Chemistry |
Similar to intermolecular reactions, intramolecular reactions can show significant stereoselectivity from the ground state conformation of the molecule. In the intramolecular Diels-Alder reaction depicted below, the lowest energy conformation yields the observed product. The structure minimizing repulsive steric interactions provides the observed product by having the lowest barrier to a transition state for the reaction. Though no external attack by a reagent occurs, this reaction can be thought of similarly to those modeled with peripheral attack; the lowest energy conformation is the most likely to react for a given reaction.
The lowest energy conformations of macrocycles also influence intramolecular reactions involving transannular bond formation. In the intramolecular Michael addition sequence below, the ground state conformation minimizes transannular interactions by placing the sp centers at the appropriate vertices, while also minimizing diaxial interactions. | 0 | Theoretical and Fundamental Chemistry |
An eccentric reducer is a fitting used in piping systems between two pipes of different diameters. The same fitting can be used in reverse as an eccentric increaser or expander. They are used where the diameter of the pipe on the upstream side of the fitting (i.e. where flow is coming from) is larger than the downstream side, and where there is a danger that vapour may accumulate. Unlike a concentric reducer, which resembles a cone, eccentric reducers have an edge that is parallel to the connecting pipe, referred to as the flat side. This parallel edge results in the two pipes having offset center lines. Because eccentric reducers are asymmetrical, they create asymmetrical flow conditions; flow is faster along the angled side, resulting in increased pressure.
Horizontal liquid reducers are always eccentric, with the flat side on the top, which prevents the build up of air bubbles in the system, (unless on control set, same as PV, TV, HV, LV) or in a pipe rack. In a pipe rack, the flat side of an eccentric reducer is on the bottom, so that the position of the bottom of the pipe will be constant, and supported by the rack. Eccentric reducers are used at the suction side of pumps to ensure air does not accumulate in the pipe. The gradual accumulation of air in a concentric reducer could result in a large bubble that could eventually cause the pump to stall or cause cavitation when drawn into the pump.
Horizontal gas reducers are always eccentric, bottom flat, which allows condensed water or oil to drain at low points.
Reducers in vertical lines are generally concentric unless the layout dictates otherwise. | 1 | Applied and Interdisciplinary Chemistry |
The curve is usually best described by a sigmoid plot, using a formula of the kind:
A hemoglobin molecule can bind up to four oxygen molecules in a reversible method.
The shape of the curve results from the interaction of bound oxygen molecules with incoming molecules. The binding of the first molecule is difficult. However, this facilitates the binding of the second, third and fourth, this is due to the induced conformational change in the structure of the hemoglobin molecule induced by the binding of an oxygen molecule.
In its simplest form, the oxyhemoglobin dissociation curve describes the relation between the partial pressure of oxygen (x axis) and the oxygen saturation (y axis). Hemoglobin's affinity for oxygen increases as successive molecules of oxygen bind. More molecules bind as the oxygen partial pressure increases until the maximum amount that can be bound is reached. As this limit is approached, very little additional binding occurs and the curve levels out as the hemoglobin becomes saturated with oxygen. Hence the curve has a sigmoidal or S-shape. At pressures above about 60 mmHg, the standard dissociation curve is relatively flat, which means that the oxygen content of the blood does not change significantly even with large increases in the oxygen partial pressure. To get more oxygen to the tissue would require blood transfusions to increase the hemoglobin count (and hence the oxygen-carrying capacity), or supplemental oxygen that would increase the oxygen dissolved in plasma.
Although binding of oxygen to hemoglobin continues to some extent for pressures about 50 mmHg, as oxygen partial pressures decrease in this steep area of the curve, the oxygen is unloaded to peripheral tissue readily as the hemoglobin's affinity diminishes.
The partial pressure of oxygen in the blood at which the hemoglobin is 50% saturated, typically about 26.6 mmHg (3.5 kPa) for a healthy person, is known as the P. The P is a conventional measure of hemoglobin affinity for oxygen. In the presence of disease or other conditions that change the hemoglobin oxygen affinity and, consequently, shift the curve to the right or left, the P changes accordingly. An increased P indicates a rightward shift of the standard curve, which means that a larger partial pressure is necessary to maintain a 50% oxygen saturation. This indicates a decreased affinity. Conversely, a lower P indicates a leftward shift and a higher affinity.
The plateau portion of the oxyhemoglobin dissociation curve is the range that exists at the pulmonary capillaries (minimal reduction of oxygen transported until the p(O) falls 50 mmHg).
The steep portion of the oxyhemoglobin dissociation curve is the range that exists at the systemic capillaries (a small drop in systemic capillary p(O) can result in the release of large amounts of oxygen for the metabolically active cells).
To see the relative affinities of each successive oxygen as you remove/add oxygen from/to the hemoglobin from the curve compare the relative increase/decrease in p(O) needed for the corresponding increase/decrease in s(O). | 1 | Applied and Interdisciplinary Chemistry |
The largest use of vanillin is as a flavoring, usually in sweet foods. The ice cream and chocolate industries together comprise 75% of the market for vanillin as a flavoring, with smaller amounts being used in confections and baked goods.
Vanillin is also used in the fragrance industry, in perfumes, and to mask unpleasant odors or tastes in medicines, livestock fodder, and cleaning products. It is also used in the flavor industry, as a very important key note for many different flavors, especially creamy profiles such as cream soda.
Additionally, vanillin can be used as a general-purpose stain for visualizing spots on thin-layer chromatography plates. This stain yields a range of colors for these different components.
Vanillin–HCl staining can be used to visualize the localisation of tannins in cells.
Vanillin is becoming a popular choice for the development of bio-based plastics. | 0 | Theoretical and Fundamental Chemistry |
The function of this intron in the vectors is unknown, but it is theorized that it might be involved in splicing or translation efficiency.
Vectors such as pME18s contain it. | 1 | Applied and Interdisciplinary Chemistry |
Which friction factor formula may be applicable depends upon the type of flow that exists:
*Laminar flow
*Transition between laminar and turbulent flow
*Fully turbulent flow in smooth conduits
*Fully turbulent flow in rough conduits
*Free surface flow. | 1 | Applied and Interdisciplinary Chemistry |
Composite metal foam panels, manufactured using 2 mm steel hollow spheres embedded in a stainless steel matrix and processed using a powder metallurgy technique, were used together with boron carbide ceramic and aluminium 7075 or Kevlar back panels to fabricate a new composite armour system. This composite armour was tested against NIJ-Type III and Type IV threats using NIJ 0101.06 ballistic test standard. The highly functional layer-based design allowed the composite metal foam to absorb the ballistic kinetic energy effectively, where the CMF layer accounted for 60–70% of the total energy absorbed by the armour system and allowed the composite armour system to show superior ballistic performance for both Type III and IV threats. The results of this testing program suggests that CMF can be used to reduce the weight and increase the performance of armour for Type III and Type IV threats. | 0 | Theoretical and Fundamental Chemistry |
The Flory–Stockmayer Theory predicts the gel point for the system consisting of three types of monomer units
:linear units with two A-groups (concentration ),
:linear units with two B groups (concentration ),
:branched A units (concentration ).
The following definitions are used to formally define the system
The theory states that the gelation occurs only if , where
is the critical value for cross-linking and is presented as a function of ,
or, alternatively, as a function of ,
One may now substitute expressions for into definition of and obtain
the critical values of that admit gelation. Thus gelation occurs if
alternatively, the same condition for reads,
The both inequalities are equivalent and one may use the one that is more convenient. For instance, depending on which conversion or is resolved analytically. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.