text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
Ordinary soda-lime glass appears colorless to the naked eye when it is thin, although iron oxide impurities produce a green tint which can be viewed in thick pieces or with the aid of scientific instruments. Further metals and metal oxides can be added to glass during its manufacture to change its color which can enhance its aesthetic appeal. Examples of these additives are listed below:
* Iron(II) oxide may be added to glass resulting in bluish-green glass which is frequently used in beer bottles. Together with chromium it gives a richer green color, used for wine bottles.
* Sulfur, together with carbon and iron salts, is used to form iron polysulfides and produce amber glass ranging from yellowish to almost black. In borosilicate glasses rich in boron, sulfur imparts a blue color. With calcium it yields a deep yellow color.
* Manganese can be added in small amounts to remove the green tint given by iron, or in higher concentrations to give glass an amethyst color. Manganese is one of the oldest glass additives, and purple manganese glass was used since early Egyptian history.
* Manganese dioxide, which is black, is used to remove the green color from the glass; in a very slow process this is converted to sodium permanganate, a dark purple compound. In New England some houses built more than 300 years ago have window glass which is lightly tinted violet because of this chemical change; and such glass panes are prized as antiques. This process is widely confused with the formation of "desert amethyst glass", in which glass exposed to desert sunshine with a high ultraviolet component develops a delicate violet tint. Details of the process and the composition of the glass vary and so do the results, because it is not a simple matter to obtain or produce properly controlled specimens.
* Small concentrations of cobalt (0.025 to 0.1%) yield blue glass. The best results are achieved when using glass containing potash. Very small amounts can be used for decolorizing.
* 2 to 3% of copper oxide produces a turquoise color.
* Nickel, depending on the concentration, produces blue, or violet, or even black glass. Lead crystal with added nickel acquires purplish color. Nickel together with a small amount of cobalt was used for decolorizing of lead glass.
* Chromium is a very powerful colorizing agent, yielding dark green or in higher concentrations even black color. Together with tin oxide and arsenic it yields emerald green glass. Chromium aventurine, in which aventurescence is achieved by growth of large parallel chromium(III) oxide plates during cooling, is made from glass with added chromium oxide in amount above its solubility limit in glass.
* Cadmium together with sulphur forms cadmium sulfide and results in deep yellow color, often used in glazes. However, cadmium is toxic. Together with selenium and sulphur it yields shades of bright red and orange.
* Adding titanium produces yellowish-brown glass. Titanium, rarely used on its own, is more often employed to intensify and brighten other colorizing additives.
* Uranium (0.1 to 2%) can be added to give glass a fluorescent yellow or green color. Uranium glass is typically not radioactive enough to be dangerous, but if ground into a powder, such as by polishing with sandpaper, and inhaled, it can be carcinogenic. When used with lead glass with very high proportion of lead, produces a deep red color.
* Didymium gives green color (used in UV filters) or lilac red. | 0 | Theoretical and Fundamental Chemistry |
Additionally, electron-rich the hydride complex are less proton-like. Thus, as a result, the electronic effects that normally favour the Markovnikov addition to an alkene are less applicable. Thus, electron-rich hydrides are more selective. | 0 | Theoretical and Fundamental Chemistry |
Another class of UV fluorescent bulb is designed for use in "bug zapper" flying insect traps. Insects are attracted to the UV light, which they are able to see, and are then electrocuted by the device. These bulbs use the same UV-A emitting phosphor blend as the filtered blacklight, but since they do not need to suppress visible light output, they do not use a purple filter material in the bulb. Plain glass blocks out less of the visible mercury emission spectrum, making them appear light blue-violet to the naked eye. These lamps are referred to by the designation "blacklight" or "BL" in some North American lighting catalogs. These types are not suitable for applications which require the low visible light output of "BLB" tubes lamps. | 0 | Theoretical and Fundamental Chemistry |
The earliest mention of alchemy in China occurs in connection with fangshi ("masters of the methods") specialists in cosmological and esoteric arts employed by rulers from the 4th century BCE.
The 3rd-century BCE Zhanguo Ce and Han Feizi both record a story about King Qingxiang of Chu (r. 298–263 BCE) being presented a busi zhi yao 不死之藥 "immortality medicine". As the chamberlain was taking the elixir into the palace, a guard asked if it was edible and when he answered yes, the guard grabbed and ate it. The king was angered and condemned the guard to death. A friend of the guard tried to persuade the king, saying, "After all the guard did ask the chamberlain whether it could be eaten before he ate it. Hence the blame attaches to the chamberlain and not to him. Besides what the guest presented was an elixir of life, but if you now execute your servant after eating it, it will be an elixir of death (and the guest will be a liar). Now rather than killing an innocent officer in order to demonstrate a guest's false claim, it would be better to release the guard." This logic convinced the king to let the guard live. | 1 | Applied and Interdisciplinary Chemistry |
The density of saltwater depends on the dissolved salt content as well as the temperature. Ice still floats in the oceans, otherwise, they would freeze from the bottom up. However, the salt content of oceans lowers the freezing point by about 1.9 °C (due to freezing-point depression of a solvent containing a solute) and lowers the temperature of the density maximum of water to the former freezing point at 0 °C. This is why, in ocean water, the downward convection of colder water is not blocked by an expansion of water as it becomes colder near the freezing point. The oceans' cold water near the freezing point continues to sink. So creatures that live at the bottom of cold oceans like the Arctic Ocean generally live in water 4 °C colder than at the bottom of frozen-over fresh water lakes and rivers.
As the surface of saltwater begins to freeze (at −1.9 °C for normal salinity seawater, 3.5%) the ice that forms is essentially salt-free, with about the same density as freshwater ice. This ice floats on the surface, and the salt that is "frozen out" adds to the salinity and density of the seawater just below it, in a process known as brine rejection. This denser saltwater sinks by convection and the replacing seawater is subject to the same process. This produces essentially freshwater ice at −1.9 °C on the surface. The increased density of the seawater beneath the forming ice causes it to sink towards the bottom. On a large scale, the process of brine rejection and sinking cold salty water results in ocean currents forming to transport such water away from the Poles, leading to a global system of currents called the thermohaline circulation. | 1 | Applied and Interdisciplinary Chemistry |
Stereoisomers are compounds that are identical in composition and connectivity but have a different spatial arrangement of atoms around the central atom. A molecule having multiple stereocenters will produce many possible stereoisomers. In compounds whose stereoisomerism is due to tetrahedral (sp) stereogenic centers, the total number of hypothetically possible stereoisomers will not exceed 2, where n is the number of tetrahedral stereocenters. However, this is an upper bound because molecules with symmetry frequently have fewer stereoisomers.
The stereoisomers produced by the presence of multiple stereocenters can be defined as enantiomers (non-superposable mirror images) and diastereomers (non-superposable, non-identical, non-mirror image molecules). Enantiomers and diastereomers are produced due to differing stereochemical configurations of molecules containing the same composition and connectivity (bonding); the molecules must have multiple (two or more) stereocenters to be classified as enantiomers or diastereomers. Enantiomers and diastereomers will produce individual stereoisomers that contribute to the total number of possible stereoisomers.
However, the stereoisomers produced may also give a meso compound, which is an achiral compound that is superposable on its mirror image; the presence of a meso compound will reduce the number of possible stereoisomers. Since a meso compound is superposable on its mirror image, the two "stereoisomers" are actually identical. Resultantly, a meso compound will reduce the number of stereoisomers to below the hypothetical 2 amount due to symmetry.
Additionally, certain configurations may not exist due to steric reasons. Cyclic compounds with chiral centers may not exhibit chirality due to the presence of a two-fold rotation axis. Planar chirality may also provide for chirality without having an actual chiral center present. | 0 | Theoretical and Fundamental Chemistry |
A mixture of two helium isotopes (helium-3 and helium-4) in a certain range of temperatures and concentrations separates into parts. The initial mix of the two isotopes spontaneously separates into -rich and -rich regions. Phase separation also exists in ultracold gas systems. It has been shown experimentally in a two-component ultracold Fermi gas case. The phase separation can compete with other phenomena as vortex lattice formation or an exotic Fulde-Ferrell-Larkin-Ovchinnikov phase. | 0 | Theoretical and Fundamental Chemistry |
Levofloxacin is rapidly and essentially completely absorbed after oral administration, with a plasma concentration profile over time that is essentially identical to that obtained from intravenous administration of the same amount over 60 minutes. As such, the intravenous and oral formulations of levofloxacin are considered interchangeable. Levofloxacin's ability to bind to proteins in the body ranges from 24 to 38%.
The drug undergoes widespread distribution into body tissues. Peak levels in skin are achieved 3 hours after administration and exceed those in plasma by a factor of 2. Similarly, lung tissue concentrations range from two-fold to five-fold higher than plasma concentrations in the 24 hours after a single dose.
The mean terminal plasma elimination half-life of levofloxacin ranges from approximately 6 to 8 hours following single or multiple doses of levofloxacin given orally or intravenously. Elimination occurs mainly via excretion of unmetabolized drug in the urine. Following oral administration, 87% of an administered dose was recovered in the urine as unchanged drug within 2 days. Less than 5% was recovered in the urine as the desmethyl and N-oxide metabolites, the only metabolites identified in humans. | 0 | Theoretical and Fundamental Chemistry |
Early iron smelting used charcoal as both the heat source and the reducing agent. By the 18th century, the availability of wood for making charcoal was limiting the expansion of iron production, so that England became increasingly dependent for a considerable part of the iron required by its industry, on Sweden (from the mid-17th century) and then from about 1725 also on Russia.
Smelting with coal (or its derivative coke) was a long sought objective. The production of pig iron with coke was probably achieved by Dud Dudley around 1619, and with a mixed fuel made from coal and wood again in the 1670s. However this was probably only a technological rather than a commercial success. Shadrach Fox may have smelted iron with coke at Coalbrookdale in Shropshire in the 1690s, but only to make cannonballs and other cast iron products such as shells. However, in the peace after the Nine Years War, there was no demand for these. | 1 | Applied and Interdisciplinary Chemistry |
Calix Ltd has developed a new type of kiln that enables the from the calcination process to be driven off as a pure stream. Calix achieves this by calcining finely ground CaCO continuously down vertical reactor tubes. The reactor tubes are heated from the outside using electricity or fuel ensuring the stream is pure and not contaminated with air or combustion products.
This technology has been successfully piloted in Europe by a cooperative industry group with support from the European Union as the Low Emission Intensity Lime And Cement (LEILAC1) reactor project. The study report concluded that the technology could capture C02 from full scale lime and cement kilns at €14 to €24/t. Transport and storage costs are not included in this estimate and will be dependent upon infrastructure available near the cement or lime plant
A FEED study is underway for a larger commercial demonstration kiln proposed for the Heidelberg Cement plant in Hannover (LEILAC2). This commercial demonstration kiln is designed to capture 100ktpa . A final investment decision for this project is expected early 2022.
This type of kiln is also being studied as a potential method to decarbonise shipping through both looping and single use processes. The single use process would involve using CaCO to be sown over the ocean, thereby permanently capturing addition carbon from the ocean as the CaCO reacts to form Ca(HCO) and reversing ocean acidification. | 1 | Applied and Interdisciplinary Chemistry |
Delapril is a prodrug; it is converted into two active metabolites, 5-hydroxy delapril diacid and delapril diacid. These metabolites bind completely to and inhibit angiotensin-converting enzyme (ACE), hence blocking angiotensin I to angiotensin II conversion. The resulting vasodilation prevents the vasoconstrictive effects of angiotensin II. Angiotensin II-induced aldosterone secretion by the adrenal cortex is also decreased by Delapril, leading to increases in excretion of sodium and therefore increases water outflow. | 0 | Theoretical and Fundamental Chemistry |
Methylene is also a common ligand in coordination compounds, such as copper methylene .
Methylene can bond as a terminal ligand, which is called methylidene, or as a bridging ligand, which is called methanediyl. | 0 | Theoretical and Fundamental Chemistry |
This was developed in the desire for a simpler method. The bed is connected to a wide-diameter u-tube containing a liquid such as kerosene. On pressurizing the space between the u-tube and the bed, the liquid is forced down. The level of liquid then acts as a measure of both pressure and volume flow. The liquid level rises as air leaks out through the bed. The time taken for the liquid level to pass between two pre-set marks on the tube is measured by stop-watch. The mean pressure and mean flowrate can be derived from the dimensions of the tube and the density of the liquid.
A later development used mercury in the u-tube: because of mercury's greater density, the apparatus could be more compact, and electrical contacts in the tube touching the conductive mercury could automatically start and stop a timer. | 1 | Applied and Interdisciplinary Chemistry |
In mathematical finance for volatility smile modeling of options via local volatility, one has the problem of deriving a diffusion coefficient consistent with a probability density obtained from market option quotes. The problem is therefore an inversion of the Fokker–Planck equation: Given the density f(x,t) of the option underlying X deduced from the option market, one aims at finding the local volatility consistent with f. This is an inverse problem that has been solved in general by Dupire (1994, 1997) with a non-parametric solution. Brigo and Mercurio (2002, 2003) propose a solution in parametric form via a particular local volatility consistent with a solution of the Fokker–Planck equation given by a mixture model. More information is available also in Fengler (2008), Gatheral (2008), and Musiela and Rutkowski (2008). | 1 | Applied and Interdisciplinary Chemistry |
Deoxynucleotides (dNTPs) may bind Mg ions and thus affect the concentration of free magnesium ions in the reaction. In addition, excessive amounts of dNTPs can increase the error rate of DNA polymerase and even inhibit the reaction. An imbalance in the proportion of the four dNTPs can result in misincorporation into the newly formed DNA strand and contribute to a decrease in the fidelity of DNA polymerase. | 1 | Applied and Interdisciplinary Chemistry |
The mathematical function used to model cross-correlation curves in FCCS is slightly more complex compared to that used in FCS. One of the primary differences is the effective superimposed observation volume, denoted as in which the G and R channels form a single observation volume:
where and are radial parameters and and are the axial parameters for the G and R channels respectively.
The diffusion time, for a doubly (G and R) fluorescent species is therefore described as follows:
where is the diffusion coefficient of the doubly fluorescent particle.
The cross-correlation curve generated from diffusing doubly labelled fluorescent particles can be modelled in separate channels as follows:
In the ideal case, the cross-correlation function is proportional to the concentration of the doubly labeled fluorescent complex:
with
The cross-correlation amplitude is directly proportional to the concentration of double-labeled (red and green) species. | 0 | Theoretical and Fundamental Chemistry |
Disaccharidases are glycoside hydrolases, enzymes that break down certain types of sugars called disaccharides into simpler sugars called monosaccharides. In the human body, disaccharidases are made mostly in an area of the small intestine's wall called the brush border, making them members of the group of "brush border enzymes".
A genetic defect in one of these enzymes will cause a disaccharide intolerance, such as lactose intolerance or sucrose intolerance. | 1 | Applied and Interdisciplinary Chemistry |
A positron is ejected from the parent nucleus, but the daughter (Z−1) atom still has Z atomic electrons from the parent, i.e. the daughter is a negative ion (at least immediately after the positron emission). Since tables of masses are for atomic masses,
, and, since the mass of the positron is identical to that of the electron, the overall result is that the mass-energy of two electrons is required, and the β decay is energetically possible if and only if the mass of the parent atom exceeds the mass of the daughter atom by at least two electron masses (2m c = 1.022 MeV).
Isotopes which increase in mass under the conversion of a proton to a neutron, or which decrease in mass by less than 2m, cannot spontaneously decay by positron emission. | 0 | Theoretical and Fundamental Chemistry |
A hydraulic accumulator is a pressure storage reservoir in which an incompressible hydraulic fluid is held under pressure that is applied by an external source of mechanical energy. The external source can be an engine, a spring, a raised weight, or a compressed gas. An accumulator enables a hydraulic system to cope with extremes of demand using a less powerful pump, to respond more quickly to a temporary demand, and to smooth out pulsations. It is a type of energy storage device.
Compressed gas accumulators, also called hydro-pneumatic accumulators, are by far the most common type. | 1 | Applied and Interdisciplinary Chemistry |
The most economical source of carbon for recycling into fuel is flue-gas emissions from fossil-fuel combustion where it can be obtained for about US$7.50 per ton. However, this is not carbon-neutral, since the carbon is of fossil origin, therefore moving carbon from the geosphere to the atmosphere. Since carbonic acid in seawater is in chemical equilibrium with atmospheric carbon dioxide, extraction of carbon from seawater has been studied. Researchers have estimated that carbon extraction from seawater would cost about $50 per ton. Carbon capture from ambient air is more costly, at between $94 and $232 per ton and is considered impractical for fuel synthesis or carbon sequestration. Direct air capture is less developed than other methods. Proposals for this method involve using a caustic chemical to react with carbon dioxide in the air to produce carbonates. These can then be broken down and hydrated to release pure CO gas and regenerate the caustic chemical. This process requires more energy than other methods because carbon dioxide is at much lower concentrations in the atmosphere than in other sources.
Researchers have also suggested using biomass as a carbon source for fuel production. Adding hydrogen to the biomass would reduce its carbon to produce fuel. This method has the advantage of using plant matter to cheaply capture carbon dioxide. The plants also add some chemical energy to the fuel from biological molecules. This may be a more efficient use of biomass than conventional biofuel because it uses most of the carbon and chemical energy from the biomass instead of releasing as much energy and carbon. Its main disadvantage is, as with conventional ethanol production, it competes with food production. | 0 | Theoretical and Fundamental Chemistry |
In the Chan–Lam coupling the alkyl, alkenyl or aryl boronic acid reacts with a N–H or O–H containing compound with Cu(II) such as copper(II) acetate and oxygen and a base such as pyridine forming a new carbon–nitrogen bond or carbon–oxygen bond for example in this reaction of 2-pyridone with trans-1-hexenylboronic acid:
The reaction mechanism sequence is deprotonation of the amine, coordination of the amine to the copper(II), transmetallation (transferring the alkyl boron group to copper and the copper acetate group to boron), oxidation of Cu(II) to Cu(III) by oxygen and finally reductive elimination of Cu(III) to Cu(I) with formation of the product. Direct reductive elimination of Cu(II) to Cu(0) also takes place but is very slow. In catalytic systems oxygen also regenerates the Cu(II) catalyst. | 0 | Theoretical and Fundamental Chemistry |
Electromagnets are placed above the sample slide, and an inverted microscope is placed below. The image is captured via a CCD camera and transferred to a computer, where the three-dimensional positions of the magnetic beads are determined. The position of the bead within the horizontal plane of the glass slide, x and y, are determined by real-time correlation of the bead images. The vertical length of the hairpin, measured by the vertical position of the attached magnetic bead, is measured by the bead’s diffraction ring diameter, which increases with distance. | 1 | Applied and Interdisciplinary Chemistry |
Friction loss is a significant engineering concern wherever fluids are made to flow, whether entirely enclosed in a pipe or duct, or with a surface open to the air.
* Historically, it is a concern in aqueducts of all kinds, throughout human history. It is also relevant to sewer lines. Systematic study traces back to Henry Darcy, an aqueduct engineer.
* Natural flows in river beds are important to human activity; friction loss in a stream bed has an effect on the height of the flow, particularly significant during flooding.
* The economies of pipelines for petrochemical delivery are highly affected by friction loss. The Yamal–Europe pipeline carries methane at a volume flow rate of 32.3 × 10 m of gas per year, at Reynolds numbers greater than 50 × 10.
* In hydropower applications, the energy lost to skin friction in flume and penstock is not available for useful work, say generating electricity.
* In refrigeration applications, energy is expended pumping the coolant fluid through pipes or through the condenser. In split systems, the pipes carrying the coolant take the place of the air ducts in HVAC systems. | 1 | Applied and Interdisciplinary Chemistry |
Compounds or materials that are easily transformed (often by biological activity) are termed labile. For example, labile phosphate is that fraction of soil phosphate that is readily transformed into soluble or plant-available phosphate. Labile organic matter is the soil organic matter that is easily decomposed by microorganisms. | 1 | Applied and Interdisciplinary Chemistry |
The decay correct might be used this way: a group of 20 animals is injected with a compound of interest on a Monday at 10:00 a.m. The compound is chemically joined to the isotope copper-64, which has a known half-life of 12.7 hours, or 764 minutes. After one hour, the 5 animals in the "one hour" group are killed, dissected, and organs of interest are placed in sealed containers to await measurement. This is repeated for another 5 animals, at 2 hours, and again at 4 hours. At this point, (say, 4:00 p.m., Monday) all the organs collected so far are measured for radioactivity (a proxy of the distribution of the compound of interest). The next day (Tuesday), the "24 hour" group would be killed and dissected at 10:00 a.m., then measured for radioactivity, (say at 11:00 a.m.). In order to compare ALL the groups together, the data from the "24 hour" must be decay corrected: the radioactivity measured on the second day must be "adjusted" in order to allow a comparison to measurements from an earlier time, but of the same original material.
In this case, "time zero" is Monday, 4:00 p.m., when the first three groups (1,2, and 4 hour animals organs) were measured. The "24 hour" group was measured at 11:00 a.m. Tuesday, which is 19 hours after the first groups.
Start by calculating the decay constant "K". Substitute 12.7 (hours, the half-life of copper-64) for , giving
Next, multiply this value of "K" by the time elapsed between the first and second measures of radioactivity, 19 hours: (0.0546 x 19) = 1.0368.
Change the sign, to make it -1.0368, then find the "inverse Ln"; in this case 0.3546.
This value is in the denominator of the decay correcting fraction, so it is the same as multiplying the numerator by its inverse (), which is 2.82.
(A simple way to check if you are using the decay correct formula right is to put in the value of the half-life in place of "t". After you perform the inverse Ln, the value should be very close to 0.5. When divided into the value "A" (for uncorrected counts), it effectively doubles them, which is the necessary correction after one half-life has occurred.)
In this case, the uncorrected values will be multiplied by 2.82, which corrects for 19 hours elapsing (between one and two half-lives).
If the radiation measured has dropped by half between the 4 hour sample and the 24 hour sample we might think that the concentration of compound in that organ has dropped by half; but applying the decay correct we see that the concentration is 0.5*2.82 so it has actually increased by 40% in that period. | 0 | Theoretical and Fundamental Chemistry |
The gene for the LHCGR is found on chromosome 2 p21 in humans, close to the FSH receptor gene. It consists of 70 kbp (versus 54 kpb for the FSHR). The gene is similar to the gene for the FSH receptor and the TSH receptor. | 1 | Applied and Interdisciplinary Chemistry |
No study has led to the isolation of true human sex pheromones. While humans are highly dependent upon visual cues, when in close proximity, smells also play a role in sociosexual behaviors. An inherent difficulty in studying human pheromones is the need for cleanliness and odorlessness in human participants. | 1 | Applied and Interdisciplinary Chemistry |
There are a wide range of types of package plants, often serving small communities or industrial plants that may use hybrid treatment processes often involving the use of aerobic sludge to treat the incoming sewage. In such plants the primary settlement stage of treatment may be omitted. In these plants, a biotic floc is created which provides the required substrate. Package plants are designed and fabricated by specialty engineering firms in dimensions that allow for their transportation to the job site in public highways, typically width and height of . Length varies with capacity with larger plants being fabricated in pieces and welded on site. Steel is preferred over synthetic materials (e.g., plastic) for its durability. Package plants are commonly variants of extended aeration, to promote the "fit and forget" approach required for small communities without dedicated operational staff. There are various standards to assist with their design.
To use less space, treat difficult waste, and intermittent flows, a number of designs of hybrid treatment plants have been produced. Such plants often combine at least two stages of the three main treatment stages into one combined stage. In the UK, where a large number of wastewater treatment plants serve small populations, package plants are a viable alternative to building a large structure for each process stage. In the US, package plants are typically used in rural areas, highway rest stops and trailer parks.
Package plants may be referred to as high charged or low charged. This refers to the way the biological load is processed. In high charged systems, the biological stage is presented with a high organic load and the combined floc and organic material is then oxygenated for a few hours before being charged again with a new load. In the low charged system the biological stage contains a low organic load and is combined with flocculate for longer times. | 1 | Applied and Interdisciplinary Chemistry |
Serotonylation is the process by which serotonin effects the exocytosis of alpha-granules from platelets (also known as thrombocytes). This involves the serotonylation of small GTPases such as Rab4 and RhoA. It has been suggested that "further understanding of the specific hormonal role of 5-HT in hemostasis and thrombosis is important to possibly prevent and treat deleterious hemorrhagic and cardiovascular disorders." Serotonylation has recently identified as playing a critical role in pulmonary hypertension.
Serotonylation also through small GTPases is involved in the process by which serotonin controls the release of insulin from beta cells in the pancreas and so the regulation of blood glucose levels. This role helps explain why defects in transglutaminase can lead to glucose intolerance. Though small GTPases are involved, the existence of a large amount of protein-bound serotonin suggests the presence of yet unidentified other serotonylation interactions.
Serotonylation of proteins other than small GTPases underlies the regulation of vascular smooth muscle "tone" in blood vessels including the aorta. This may occur through serotonylation modifying proteins integral to the contractility and the cytoskeleton such as alpha-actin, beta-actin, gamma-actin, myosin heavy chain and filamin A | 1 | Applied and Interdisciplinary Chemistry |
One conference specific to Pharmaceutical Bioinformatics is "International Conference on Pharmaceutical Bioinformatics" (ICPB) (http://www.icpb.net) | 1 | Applied and Interdisciplinary Chemistry |
Peer-reviewed test methods have been published by government agencies and private research organizations. Approved published methods must be used when testing to demonstrate compliance with regulatory requirements. | 1 | Applied and Interdisciplinary Chemistry |
The Sir Hans Krebs Lecture and Medal is awarded annually by the Federation of European Biochemical Societies (FEBS) for outstanding achievements in Biochemistry and Molecular Biology or related sciences.
It was endowed by the Lord Rank Centre for Research and named after the German-born British biochemist Sir Hans Adolf Krebs, well known for identifying the urea and citric acid cycles. The awardee receives a silver medal and presents one of the plenary lectures at the FEBS Congress. | 1 | Applied and Interdisciplinary Chemistry |
Although quite stable, the blue ammonia solutions containing solvated electrons degrade rapidly in the presence of catalysts to give colorless solutions of sodium amide:
:2 [Na(NH)]e → H + 2 NaNH + 10 NH
Electride salts can be isolated by the addition of macrocyclic ligands such as crown ether and cryptands to solutions containing solvated electrons. These ligands strongly bind the cations and prevent their re-reduction by the electron.
:[Na(NH)]e + cryptand → [Na(cryptand)]e+ 6 NH
The solvated electron reacts with oxygen to form a superoxide radical (O). With nitrous oxide, solvated electrons react to form hydroxyl radicals (HO). | 0 | Theoretical and Fundamental Chemistry |
In the 1980s, the U.S. Department of Energy began a vigorous multiyear program, culminating in a 1992 50 MW demonstration coal combustor at the Component Development and Integration Facility (CDIF) in Butte, Montana. This program also had significant work at the Coal-Fired-In-Flow-Facility (CFIFF) at University of Tennessee Space Institute.
This program combined four parts:
# An integrated MHD topping cycle, with channel, electrodes, and current control units developed by AVCO, later known as Textron Defence of Boston. This system was a Hall effect duct generator heated by pulverized coal, with a potassium ionisation seed. AVCO had developed the famous Mk. V generator, and had significant experience.
# An integrated bottoming cycle, developed at the CDIF.
# A facility to regenerate the ionization seed was developed by TRW. Potassium carbonate is separated from the sulphate in the fly ash from the scrubbers. The carbonate is removed, to regain the potassium.
# A method to integrate MHD into preexisting coal plants. The Department of Energy commissioned two studies. Westinghouse Electric performed a study based on the Scholtz Plant of Gulf Power in Sneads, Florida. The MHD Development Corporation also produced a study based on the J.E. Corrette Plant of the Montana Power Company of Billings, Montana.
Initial prototypes at the CDIF were operated for short durations, with various coals: Montana Rosebud, and a high-sulphur corrosive coal, Illinois No. 6. A great deal of engineering, chemistry, and material science was completed. After the final components were developed, operational testing completed with 4,000 hours of continuous operation, 2,000 on Montana Rosebud, 2,000 on Illinois No. 6. The testing ended in 1993. | 1 | Applied and Interdisciplinary Chemistry |
Aspects of the carbonate-silicate cycle have changed through Earth history as a result of biological evolution and tectonic changes. Generally, the formation of carbonates has outpaced that of silicates, effectively removing carbon dioxide from the atmosphere. The advent of carbonate biomineralization near the Precambrian-Cambrian boundary would have allowed more efficient removal of weathering products from the ocean. Biological processes in soils can significantly increase weathering rates. Plants produce organic acids that increase weathering. These acids are secreted by root and mycorrhizal fungi, as well as microbial plant decay. Root respiration and oxidation of organic soil matter also produce carbon dioxide, which is converted to carbonic acid, which increases weathering.
Tectonics can induce changes in the carbonate-silicate cycle. For example, the uplift of major mountain ranges, such as Himalayas and the Andes, is thought to have initiated the Late Cenozoic Ice Age due to increased rates of silicate weathering and draw down of carbon dioxide.
Seafloor weather is linked both to solar luminosity and carbon dioxide concentration. However, it presented a challenge to modelers who have tried to relate the rate of outgassing and subduction to the related rates of seafloor change. Proper, uncomplicated proxy data is difficult to attain for such questions. For example, sediment cores, from which scientists can deduce past sea levels, are not ideal because sea levels change as a result of more than just seafloor adjustment. Recent modeling studies have investigated the role of seafloor weathering on the early evolution of life, showing that relatively fast seafloor creation rates worked to draw down carbon dioxide levels to a moderate extent.
Observations of so-called deep time indicate that Earth has a relatively insensitive rock weathering feedback, allowing for large temperature swings. With about twice as much carbon dioxide in the atmosphere, paleoclimate records show that global temperatures reached up to 5 to 6 °C higher than current temperatures. However, other factors such as changes in orbital/solar forcing contribute to global temperature change in the paleo-record.
Human emissions of CO have been steadily increasing, and the consequent concentration of CO in the Earth system has reached unprecedented levels in a very short amount of time. Excess carbon in the atmosphere that is dissolved in seawater can alter the rates of carbonate-silicate cycle. Dissolved CO may react with water to form bicarbonate ions, HCO, and hydrogen ions, H. These hydrogen ions quickly react with carbonate, CO to produce more bicarbonate ions and reduce the available carbonate ions, which presents an obstacle to the carbon carbonate precipitation process. Put differently, 30% of excess carbon emitted into the atmosphere is absorbed by the oceans. Higher concentrations of carbon dioxide in the oceans work to push the carbonate precipitation process in the opposite direction (to the left), producing less CaCO. This process, which harms shell-building organisms, is called ocean acidification. | 0 | Theoretical and Fundamental Chemistry |
The first organoniobium compound fully characterized was , however the paramagnetic Nb(IV) metallocenes such as niobocene dichloride are more prevalent. Complexes are typically prepared by treatment of with NaCp to form the bis(cyclopentadienyl) complex followed by further functionalization. Derivatives of pentamethylcyclopentadiene are also known, such as .
Niobium carbonyls supported by Cp ligands can be prepared at various oxidation states of Nb and serve as useful precursors in niobium carbonyl chemistry. | 0 | Theoretical and Fundamental Chemistry |
Signal transduction mediated by the superfamily of GPCRs dates back to the origin of multicellularity. Mammalian-like GPCRs are found in fungi, and have been classified according to the GRAFS classification system based on GPCR fingerprints. Identification of the superfamily members across the eukaryotic domain, and comparison of the family-specific motifs, have shown that the superfamily of GPCRs have a common origin. Characteristic motifs indicate that three of the five GRAFS families, Rhodopsin, Adhesion, and Frizzled, evolved from the Dictyostelium discoideum cAMP receptors before the split of opisthokonts. Later, the Secretin family evolved from the Adhesion GPCR receptor family before the split of nematodes. Insect GPCRs appear to be in their own group and Taste2 is identified as descending from Rhodopsin. Note that the Secretin/Adhesion split is based on presumed function rather than signature, as the classical Class B (7tm_2, ) is used to identify both in the studies. | 1 | Applied and Interdisciplinary Chemistry |
The Hamiltonian for a single spin evolving under a chemical shift of angular frequency is
which means that in an ensemble of many such spins with slightly different chemical shifts, there is a dephasing of the magnetisation in the - plane. Consider the pulse sequence
where is a time interval. Starting in an equilibrium state with all the polarisation along the -axis, the evolution of an individual spin in the ensemble is
Hence this sequence refocuses the transverse magnetisation produced by the first pulse, independent of the value of the chemical shift.
As an indication of the utility of the formalism, suppose instead that we tried to reach the same result using states only and therefore the Schrödinger time evolution operators. This amounts to trying to simplify the unitary propagator taking the initial state to the final state as , where explicitly
Essentially we want to find the propagator in the form , that is as a single exponential of a combination of operators, because that gives the effective Hamiltonian acting during the sequence. Since the arguments of the exponentials in the original form of the propagator do not commute, this amounts to solving a specific example of the Baker–Campbell–Hausdorff (BCH) problem. In this relatively simple case we can solve the BCH problem using the fact that for unitary operator , operator and function , as well as the mathematical similarity of the spin operators with the physical rotation generators, which allow us to write
Hence and only the effect of the 180° pulse remains, which agrees with the product operator treatment. For larger sequences of pulses this state treatment quickly becomes even more unwieldy, unless more advanced methods such as exact effective Hamiltonian theory (which gives closed-form expressions for the entangled propagators via the Cayley-Hamilton theorem and eigendecompositions) are used. | 0 | Theoretical and Fundamental Chemistry |
Surfactant protein B is an essential lipid-associated protein found in pulmonary surfactant. Without it, the lung would not be able to inflate after a deep breath out. It rearranges lipid molecules in the fluid lining the lung so that tiny air sacs in the lung, called alveoli, can more easily inflate. | 0 | Theoretical and Fundamental Chemistry |
Following the first publication, Pockels' studies of surface films accelerated. She continued to correspond with Lord Rayleigh. These communications emphasized her findings concerning the importance of purity and cleanliness of the equipment, including a recognition of difficulties in her own experimentation regarding previously unrecognized contamination.
Pockels pointed out that even airborne dust can affect results with her experimental apparatus. She recognized that impurities can affect reproducibility of experimental findings. Pockels developed a refined method of assessing monolayer films consisting of deposition of the compound on interest as a solution in benzene on the water surface in her sliding trough. Through this line of experimentation, she measured the thickness of certain monolayer films as being 13Å. With the aid of Lord Rayleigh, Pockelss second publication appeared in the journal Nature' in 1892.
Pockels described the calming effect that oils can have on bodies of water, an effect first investigated in the published literature by Benjamin Franklin. Her research extended to investigations of other surface phenomena including capillarity and contact angles.
Pockels published 14 scientific papers, mostly in German journals, the last one being published in 1926. She was eventually recognized as a pioneer in the emerging field of surface science. Following the death of her brother, Friedrich Carl Alwin Pockels in 1913 and her own ill health, Agnes Pockels lost contact with many professional scientists and ceased original research.
Pockels never received a formal appointment for her scientific endeavors. Nevertheless, she published a number of scholarly papers and eventually received recognition as a pioneer in the new field of surface science. Commentators wrote: "When Langmuir received the Nobel Prize for Chemistry in 1932, for his work in investigating monolayers on solids and on liquids, part of his achievement was [...] founded on original experiments first made with a button and a thin tray, by a young lady of 18 who had had no formal scientific training." | 0 | Theoretical and Fundamental Chemistry |
The first use of the term ‘transcription factory’ was used in 1993 by [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC413307/Jackson] and his colleagues who noticed that transcription occurred at discrete sites in the nucleus. This contradicted the original view that transcription occurred at an even distribution throughout the nucleus. | 1 | Applied and Interdisciplinary Chemistry |
Reactive transport modeling in porous media refers to the creation of computer models integrating chemical reaction with transport of fluids through the Earth's crust. Such models predict the distribution in space and time of the chemical reactions that occur along a flowpath. Reactive transport modeling in general can refer to many other processes, including reactive flow of chemicals through tanks, reactors, or membranes; particles and species in the atmosphere; gases exiting a smokestack; and migrating magma. | 0 | Theoretical and Fundamental Chemistry |
The Science History Institute presents a number of annual awards to recognize outstanding contributions to science and technology by researchers, business leaders and entrepreneurs.
The annual Heritage Day Awards honor achievements in science and technology and comprise the Othmer Gold Medal,
the Richard J. Bolte Sr. Award for Supporting Industries and, in conjunction with The Chemists' Club of New York, the
Winthrop-Sears Medal.
The annual Affiliate Partnership Awards, presented in conjunction with affiliate organizations, recognize achievement with the
Biotechnology Heritage Award,
the Franklin-Lavoisier Prize,
the Petrochemical Heritage Award
and the Pittcon Heritage Award.
The Roy G. Neville Prize in Bibliography or Biography recognizes a biographical work in the field of chemical or molecular science. Established in 2006, the prize is awarded biennially. | 1 | Applied and Interdisciplinary Chemistry |
In experimental biophysics, the activity of molecular motors is observed with many different experimental approaches, among them:
* Fluorescent methods: fluorescence resonance energy transfer (FRET), fluorescence correlation spectroscopy (FCS), total internal reflection fluorescence (TIRF).
* Magnetic tweezers can also be useful for analysis of motors that operate on long pieces of DNA.
* Neutron spin echo spectroscopy can be used to observe motion on nanosecond timescales.
* Optical tweezers (not to be confused with molecular tweezers in context) are well-suited for studying molecular motors because of their low spring constants.
* Scattering techniques: single particle tracking based on dark field microscopy or interferometric scattering microscopy (iSCAT)
* Single-molecule electrophysiology can be used to measure the dynamics of individual ion channels.
Many more techniques are also used. As new technologies and methods are developed, it is expected that knowledge of naturally occurring molecular motors will be helpful in constructing synthetic nanoscale motors. | 0 | Theoretical and Fundamental Chemistry |
The GUS assay does not require the presence of any cofactors or ions for function. Beta-glucuronidase can function through a wide range of pH values, and is fairly resistant to thermal inactivation. However, GUS is susceptible to inhibition from certain heavy metal ions, such as Cu and Zn.
Additionally, the interpretation of the assay is limited by the movement of diX-indigo throughout the cell. DiX-indigo, can associate with lipids to diffuse far from the site of enzyme activity, which shows a lack of cytosolic localization and irregularity of substrate penetration. This can potentially lead to an incorrect interpretation of GUS protein localization. Despite a lack of cellular localization, nuclear localization of GUS has been well observed. GUS assays can be carried out in the presence of potassium ferricyanide to prevent the stain from diffusing. | 1 | Applied and Interdisciplinary Chemistry |
NMOR is a component of tobacco products. As of 2014, detectable levels of NMOR are present in tobacco products in the United States and China. The presence of NMOR and other n-nitrosoamines is not limited to cigarettes, but is found in smokeless tobacco products (snuff tobacco, Snus, etc.) as well. Volatile nitrosamines, including NMOR, are detectable in the urine of tobacco smokers. | 0 | Theoretical and Fundamental Chemistry |
This quantity can be calculated from the slope of the function of two concentration cells, without or with ionic transport.
The EMF of transport concentration cell involves both the transport number of the cation and its activity coefficient:
where and are activities of HCl solutions of right and left hand electrodes, respectively, and is the transport number of . | 0 | Theoretical and Fundamental Chemistry |
Floriana Tuna is a Romanian chemist and a Senior Research Fellow in the Department of Chemistry at The University of Manchester. Her research in general is based on inorganic chemistry and magnetochemistry, specifically on molecular magnetism, EPR spectroscopy and quantum computing. | 0 | Theoretical and Fundamental Chemistry |
JAK inhibitors are used for the treatment of atopic dermatitis and rheumatoid arthritis. They are also being studied in psoriasis, polycythemia vera, alopecia, essential thrombocythemia, ulcerative colitis, myeloid metaplasia with myelofibrosis and vitiligo. Examples are tofacitinib, baricitinib, upadacitinib and filgotinib.
In 2014 researchers discovered that oral JAK inhibitors, when administered orally, could restore hair growth in some subjects and that applied to the skin, effectively promoted hair growth. | 1 | Applied and Interdisciplinary Chemistry |
At distances on the scale of the wavelength of a radiated electromangetic wave or smaller, Planck's law is not accurate. For objects this small and close together, the quantum tunneling of EM waves has a significant impact on the rate of radiation.
A more sophisticated framework involving electromagnetic theory must be used for smaller distances from the thermal source or surface. For example, although far-field thermal radiation at distances from surfaces of more than one wavelength is generally not coherent to any extent, near-field thermal radiation (i.e., radiation at distances of a fraction of various radiation wavelengths) may exhibit a degree of both temporal and spatial coherence.
Planck's law of thermal radiation has been challenged in recent decades by predictions and successful demonstrations of the radiative heat transfer between objects separated by nanoscale gaps that deviate significantly from the law predictions. This deviation is especially strong (up to several orders in magnitude) when the emitter and absorber support surface polariton modes that can couple through the gap separating cold and hot objects. However, to take advantage of the surface-polariton-mediated near-field radiative heat transfer, the two objects need to be separated by ultra-narrow gaps on the order of microns or even nanometers. This limitation significantly complicates practical device designs.
Another way to modify the object thermal emission spectrum is by reducing the dimensionality of the emitter itself. This approach builds upon the concept of confining electrons in quantum wells, wires and dots, and tailors thermal emission by engineering confined photon states in two- and three-dimensional potential traps, including wells, wires, and dots. Such spatial confinement concentrates photon states and enhances thermal emission at select frequencies. To achieve the required level of photon confinement, the dimensions of the radiating objects should be on the order of or below the thermal wavelength predicted by Plancks law. Most importantly, the emission spectrum of thermal wells, wires and dots deviates from Plancks law predictions not only in the near field, but also in the far field, which significantly expands the range of their applications. | 0 | Theoretical and Fundamental Chemistry |
In his 1884 dissertation, Svante Arrhenius put forth his explanation of solid crystalline salts disassociating into paired charged particles when dissolved, for which he won the 1903 Nobel Prize in Chemistry. Arrheniuss explanation was that in forming a solution, the salt dissociates into charged particles, to which Michael Faraday (1791-1867) had given the name "ions" many years earlier. Faradays belief had been that ions were produced in the process of electrolysis. Arrhenius proposed that, even in the absence of an electric current, solutions of salts contained ions. He thus proposed that chemical reactions in solution were reactions between ions.
Shortly after Arrhenius's hypothesis of ions, Franz Hofmeister and Siegmund Lewith found that different ion types displayed different effects on such things as the solubility of proteins. A consistent ordering of these different ions on the magnitude of their effect arises consistently in many other systems as well. This has since become known as the Hofmeister series.
While the origins of these effects are not abundantly clear and have been debated throughout the past century, it has been suggested that the charge density of these ions is important and might actually have explanations originating from the work of Charles-Augustin de Coulomb over 200 years ago. | 0 | Theoretical and Fundamental Chemistry |
Trimethylsilyl azide is commercially available. It may be prepared by the reaction of trimethylsilyl chloride and sodium azide: | 0 | Theoretical and Fundamental Chemistry |
Classically radicals form by one-electron reductions. Typically one-electron reduced organic compounds are unstable. Stability is conferred to the radical anion when the charge can be delocalized. Examples include alkali metal naphthenides, anthracenides, and ketyls. | 1 | Applied and Interdisciplinary Chemistry |
Chromosomal landing is a genetic technique used to identify and isolate clones in a genetic library. Chromosomal landing reduces the problem of analyzing large, and/or highly repetitive genomes by minimizing the need for chromosome walking. It is based on the principle that the expected average between-marker distances can be smaller than the average insert length of a clone library containing the gene of interest.
From the abstract of :
:The strategy of chromosome walking is based on the assumption that it is difficult and time consuming to find DNA markers that are physically close to a gene of interest. Recent technological developments invalidate this assumption for many species. As a result, the mapping paradigm has now changed such that one first isolates one or more DNA marker(s) at a physical distance from the targeted gene that is less than the average insert size of the genomic library being used for clone isolation. The DNA marker is then used to screen the library and isolate (or land on) the clone containing the gene, without any need for chromosome walking and its associated problems. Chromosome landing, together with the technology that has made it possible, is likely to become the main strategy by which map-based cloning is applied to isolate both major genes and genes underlying quantitative traits in plant species. | 1 | Applied and Interdisciplinary Chemistry |
As briefly mentioned in Section: Impact on Models for large-scale Ocean Circulation, the surface currents can be calculated by forcing surface winds into a general circulation model. The case of a model which is also forced by relative wind stress can be visualized in Figure 5. Firstly, the satellite data is used to input the 10m wind velocity into the calculation of the relative wind stress. However, if the parameterization for relative wind stress is used, this will result in a coupled problem. The ocean model requires the relative wind stress to output the ocean current velocity, which in turn the calculation of relies on. This coupled system needs to be formulated as an inverse problem.
Another consequence is that, depending on the parameterization used for the wind stress, a different vector field will be inputted into the ocean model and, consequently, a different value of will be outputted by the ocean model. Therefore, if a different wind field is used for the calculations of and then it could be that . In other words, there may be a negative bias when calculating the work done on the ocean using the resting ocean approximation. On the global scale, however, the literature has found an over rather than underestimation, as previously mentioned. | 1 | Applied and Interdisciplinary Chemistry |
In boiling water reactors (BWR), the fuel is similar to PWR fuel except that the bundles are "canned". That is, there is a thin tube surrounding each bundle. This is primarily done to prevent local density variations from affecting neutronics and thermal hydraulics of the reactor core. In modern BWR fuel bundles, there are either 91, 92, or 96 fuel rods per assembly depending on the manufacturer. A range between 368 assemblies for the smallest and 800 assemblies for the largest BWR in the U.S. form the reactor core. Each BWR fuel rod is backfilled with helium to a pressure of about . | 0 | Theoretical and Fundamental Chemistry |
Tornadoes and dust devils display localised vortex flow. Their fluid motion is similar to tropical cyclones but on a much smaller scale so that the Coriolis effect is not significant. The primary flow is circular around the vertical axis of the tornado or dust devil. As with all vortex flow, the speed of the flow is fastest at the core of the vortex. In accordance with Bernoullis principle where the wind speed is fastest the air pressure is lowest; and where the wind speed is slowest the air pressure is highest. Consequently, near the center of the tornado or dust devil the air pressure is low. There is a pressure gradient toward the center of the vortex. This gradient, coupled with the slower speed of the air near the earths surface, causes a secondary flow toward the center of the tornado or dust devil, rather than in a purely circular pattern.
The slower speed of the air at the surface prevents the air pressure from falling as low as would normally be expected from the air pressure at greater heights. This is compatible with Bernoulli's principle. The secondary flow is toward the center of the tornado or dust devil, and is then drawn upward by the significantly lower pressure several thousands of feet above the surface in the case of a tornado, or several hundred feet in the case of a dust devil. Tornadoes can be very destructive and the secondary flow can cause debris to be swept into a central location and carried to low altitudes.
Dust devils can be seen by the dust stirred up at ground level, swept up by the secondary flow and concentrated in a central location. The accumulation of dust then accompanies the secondary flow upward into the region of intense low pressure that exists outside the influence of the ground. | 1 | Applied and Interdisciplinary Chemistry |
In 1987, an elderly couple was exposed to sulfuryl fluoride in their house already cleared for reentry. While the fumigation company opened windows and doors, and aerated the house with fans, sulfuryl fluoride level was not measured. It was not detected when the air was sampled 12 days after aeration. The couple experienced weakness, nausea and shortness of breath that evening. The man suffered a seizure and died the following day. His wife's condition got worse with pulmonary edema, and she died after a cardiovascular arrest 6 days later.
In 2015, a 10-year-old boy suffered severe brain damage and lost function of his left arm and leg after his home was treated with sulfuryl fluoride and insufficiently aerated, prompting a criminal investigation by the Department of Justice and the Florida Department of Agricultural and Consumer Services. Two pest control workers later pled guilty to charges of misuse of the pesticide resulting in the boy's poisoning, and were each sentenced to one year in prison.
In 2016, a 24-year-old man who allegedly entered an apartment that was being fumigated in Fremont, California to commit a burglary was exposed to sulfuryl fluoride and chloropicrin and died shortly thereafter. According to a police officer, he experienced labored breathing and was sweating before he collapsed just a few steps from the first floor window of the apartment he allegedly burglarized. | 1 | Applied and Interdisciplinary Chemistry |
The treatment given so far is for a system not subject to an external electric field. When conductivity is measured the system is subject to an oscillating external field due to the application of an AC voltage to electrodes immersed in the solution. Debye and Hückel modified their theory in 1926 and their theory was further modified by Lars Onsager in 1927. All the postulates of the original theory were retained. In addition it was assumed that the electric field causes the charge cloud to be distorted away from spherical symmetry. After taking this into account, together with the specific requirements of moving ions, such as viscosity and electrophoretic effects, Onsager was able to derive a theoretical expression to account for the empirical relation known as Kohlrausch's Law, for the molar conductivity, Λ.
is known as the limiting molar conductivity, K is an empirical constant and c is the electrolyte concentration. Limiting here means "at the limit of the infinite dilution").
Onsager's expression is
where A and B are constants that depend only on known quantities such as temperature, the charges on the ions and the dielectric constant and viscosity of the solvent. This is known as the Debye–Hückel–Onsager equation. However, this equation only applies to very dilute solutions and has been largely superseded by other equations due to Fuoss and Onsager, 1932 and 1957 and later. | 0 | Theoretical and Fundamental Chemistry |
Multiplex ligation-dependent probe amplification was invented by Jan Schouten, a Dutch scientist. The method was first described in 2002 in the scientific journal Nucleic Acid Research. The first applications included the detection of exon deletions in the human genes BRCA1, MSH2 and MLH1, which are linked to hereditary breast and colon cancer. Now MLPA is used to detect hundreds of hereditary disorders, as well as for tumour profiling. | 1 | Applied and Interdisciplinary Chemistry |
Hot corrosion can affect gas turbines operating in high salt environments (e.g., near the ocean). Salts, including chlorides and sulfates, are ingested by the turbines and deposited in the hot sections of the engine; other elements present in fuels also form salts, e.g. vanadates. The heat from the engine melts these salts which then can flux the passivating oxide layers on the metal components of the engine, allowing corrosion to occur at an accelerated rate. | 1 | Applied and Interdisciplinary Chemistry |
The roasting process is generally undertaken in combination with reverberatory furnaces. In the roaster, the copper concentrate is partially oxidised to produce "calcine". Sulfur dioxide is liberated. The stoichiometry of the reaction is:
Roasting generally leaves more sulfur in the calcined product (15% in the case of the roaster at Mount Isa Mines) than a sinter plant leaves in the sintered product (about 7% in the case of the Electrolytic Refining and Smelting smelter).
As of 2005, roasting is no longer common in copper concentrate treatment because its combination with reverberatory furnaces is not energy efficient and the SO concentration in the roaster offgas is too dilute for cost-effective capture. Direct smelting is now favored, and uses the following smelting technologies: flash smelting, Isasmelt, Noranda, Mitsubishi or El Teniente furnaces. | 1 | Applied and Interdisciplinary Chemistry |
The sievert is used in external radiation protection for equivalent dose (the external-source, whole-body exposure effects, in a uniform field), and effective dose (which depends on the body parts irradiated).
These dose quantities are weighted averages of absorbed dose designed to be representative of the stochastic health effects of radiation, and use of the sievert implies that appropriate weighting factors have been applied to the absorbed dose measurement or calculation (expressed in grays).
The ICRP calculation provides two weighting factors to enable the calculation of protection quantities.
: 1. The radiation factor W, which is specific for radiation type R – This is used in calculating the equivalent dose H which can be for the whole body or for individual organs.
: 2. The tissue weighting factor W, which is specific for tissue type T being irradiated. This is used with W to calculate the contributory organ doses to arrive at an effective dose E for non-uniform irradiation.
When a whole body is irradiated uniformly only the radiation weighting factor W is used, and the effective dose equals the whole body equivalent dose. But if the irradiation of a body is partial or non-uniform the tissue factor W is used to calculate dose to each organ or tissue. These are then summed to obtain the effective dose. In the case of uniform irradiation of the human body, these summate to 1, but in the case of partial or non-uniform irradiation, they will summate to a lower value depending on the organs concerned; reflecting the lower overall health effect. The calculation process is shown on the accompanying diagram. This approach calculates the biological risk contribution to the whole body, taking into account complete or partial irradiation, and the radiation type or types.
The values of these weighting factors are conservatively chosen to be greater than the bulk of experimental values observed for the most sensitive cell types, based on averages of those obtained for the human population. | 0 | Theoretical and Fundamental Chemistry |
Random packing was used as early as 1820. Originally the packing material consisted of glass spheres, however in 1850 they were replaced by a more porous pumice stone and pieces of coke. | 1 | Applied and Interdisciplinary Chemistry |
In one study, the human health and environmental costs due to pesticides in the United States was estimated to be $9.6 billion: offset by about $40 billion in increased agricultural production.
Additional costs include the registration process and the cost of purchasing pesticides: which are typically borne by agrichemical companies and farmers respectively. The registration process can take several years to complete (there are 70 different types of field tests) and can cost $50–70 million for a single pesticide. At the beginning of the 21st century, the United States spent approximately $10 billion on pesticides annually. | 1 | Applied and Interdisciplinary Chemistry |
The American Society of Mechanical Engineers (ASME) publishes the following Tri-Harmonized Standard:
* ASSE 1002/ASME A112.1002/CSA B125.12 on Performance Requirements for Anti-Siphon Fill Valves (Ballcocks) for Gravity Water Closet Flush Tanks | 1 | Applied and Interdisciplinary Chemistry |
The Indian National Chemistry Olympiad (INChO for short) is an Olympiad in Chemistry held in India.
The theory part of the INChO examination is held in end-January/beginning of February of every year. It is conducted by the Indian Association of Chemistry Teachers. School students (usually of standards 11 and 12) first need to qualify the National Standard Examination in Chemistry (NSEC) held in November of the preceding year. Among the 30,000+ students who sit for the NSEC, only the top 1% are selected for the INChO.
About 35 students are selected from the written examination. A total of 30 students are chosen from these to attend the Orientation-Cum-Selection-Camp (OCSC), chemistry, held at HBCSE, Mumbai.
Most students qualifying for the INChO are those completing their twelfth standard. However, in some cases, students have been selected for INChO at the end of the eleventh or tenth standard. | 1 | Applied and Interdisciplinary Chemistry |
The alkA gene product is a glycosylase that can repair a variety of lesions, removing a base from the sugar-phosphate backbone, producing an abasic site. | 1 | Applied and Interdisciplinary Chemistry |
In the cases of carbon dioxide cooled graphite moderated reactors such as magnox and AGR power reactors an important corrosion reaction is the reaction of a molecule of carbon dioxide with graphite (carbon) to form two molecules of carbon monoxide. This is one of the processes which limits the working life of this type of reactor. | 0 | Theoretical and Fundamental Chemistry |
Proton beams can be used for writing (proton beam writing) through either the hardening of a polymer (by proton induced cross-linking), or through the degradation of a proton sensitive material. This may have important effects in the field of nanotechnology. | 0 | Theoretical and Fundamental Chemistry |
Substrates can be classified according to their polarity. Nonpolar substrates are dominated by alkenes. Polar substrates include ketones, enamines ketimines. | 0 | Theoretical and Fundamental Chemistry |
When a concrete structure is heavily reinforced, the very dense rebar network can block the contraction movement of the protecting concrete cover located above the external layer of reinforcement bars due to the natural drying shrinkage process. As a consequence, a network of fissures with the characteristic honeycomb pattern also typical for the cracks resulting from the expansive chemical reactions (ASR, DEF, ESA) forms.
The formation of fissures in the concrete cover above the reinforcement bars represents a preferential pathway for the ingress of water and aggressive agents such as carbon dioxide| (lowering of pH around the rebar) and chloride anions (pitting corrosion) into concrete. The physical formation of cracks therefore favors the chemical degradation of concrete and aggravates steel corrosion. Physical and chemical degradation processes are intimately coupled, and the presence of water infiltrations also accelerates the formation of expansive products of harmful swelling chemical reactions (iron corrosion products, ASR, DEF, ISA, ESA).
Different approaches and methods have been developed to attempt to quantitatively estimate the influence of cracks in concrete structures on carbonation and chloride penetration. Their aim is to avoid underestimating the penetration depth of these harmful chemical agents and to calculate a sufficient thickness for the concrete cover to protect the rebar against corrosion during the whole service life of the concrete structure. | 1 | Applied and Interdisciplinary Chemistry |
He was appointed lecturer in chemistry at the University of Glasgow in 1787, and professor of medicine in 1789.
In January 1788, on the proposal of John Walker, Daniel Rutherford and Alexander Monro, he was elected a Fellow of the Royal Society of Edinburgh.
In 1791–1792 Hope completed experiments on the chemical element strontium, proposing the name Stronities for it, after Strontian, the west highland village where he found strontianite. The element was later renamed to Strontium. On 4 November 1793, Hope presented his findings, An account of a Mineral from Strontian and of a Peculiar Species of Earth which it contains, to the Royal Society of Edinburgh.
In the experiment that bears his name, Hope determined the maximum density of water and explained why icebergs float. | 1 | Applied and Interdisciplinary Chemistry |
Due to being described by a multi-component order parameter, numerous types of
topological defects (vortices) can appear in spinor condensates
Homotopy theory provides a natural description of topological defects, and is regularly employed to understand
vortices in spinor condensates. | 0 | Theoretical and Fundamental Chemistry |
In the history of thermodynamics, Thermodynamik chemischer Vorgänge (Chemical thermodynamic process) is a sequence of three papers (1882–1883) written by German physicist Hermann von Helmholtz. It is one of the founding papers in thermodynamics, along with Josiah Willard Gibbss 1876 paper "On the Equilibrium of Heterogeneous Substances'". Together they form the foundation of chemical thermodynamics as well as a large part of physical chemistry.
It was published in three parts in Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin ["Proceedings of the Royal Prussian Academy of Sciences"], and is available on HathiTrust and online archive of the Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin.
* First part: Die Thermodynamik chemischer Vorgänge, Submitted on 2 February 1882.
* Second part: Zur Thermodynamik chemischer Vorgänge, subtitled Folgerungen die galvanische Polarisation betreffend ["Conclusions concerning galvanic polarization"]. Submitted on 27 July 1882.
** (yes, the word "Die" was turned to "Zur", which might cause bibliographical confusion)
* Third part: Zur Thermodynamik chemischer Vorgänge, subtitled Versuche an Chlorzink-Kalomel-Elementen ["Experiments on zinc chloride calomel elements"]. Submitted on 31 May 1883. | 0 | Theoretical and Fundamental Chemistry |
Isobutyl nitrite is one of the compounds used as poppers, an inhalant drug that induces a brief euphoria.
Isobutyl nitrite is known to cause methemoglobinemia. Severe methemoglobinemia may be treated with methylene blue. | 0 | Theoretical and Fundamental Chemistry |
There is very little known about the mechanism of action of these drugs. However, it was shown in 2015 that a possible mechanism of action of these drugs in colorectal cancer-initiating cells is through activating dsRNA expression which leads to the activation of the MDA5/MAVS RNA recognition pathway inducing some sort of viral mimicry inside the cell. | 1 | Applied and Interdisciplinary Chemistry |
The docking of IP to its receptor, which is called the inositol trisphosphate receptor (InsP3R), was first studied using deletion mutagenesis in the early 1990s. Studies focused on the N-terminus side of the IP receptor. In 1997 researchers localized the region of the IP receptor involved with binding of IP to between amino acid residues 226 and 578 in 1997. Considering that IP is a negatively charged molecule, positively charged amino acids such as arginine and lysine were believed to be involved. Two arginine residues at position 265 and 511 and one lysine residue at position 508 were found to be key in IP docking. Using a modified form of IP, it was discovered that all three phosphate groups interact with the receptor, but not equally. Phosphates at the 4th and 5th positions interact more extensively than the phosphate at the 1st position and the hydroxyl group at the 6th position of the inositol ring. | 1 | Applied and Interdisciplinary Chemistry |
The values for the octanol-water system in the following table are from the Dortmund Data Bank. They are sorted by the partition coefficient, smallest to largest (acetamide being hydrophilic, and 2,2,4,4,5-pentachlorobiphenyl lipophilic), and are presented with the temperature at which they were measured (which impacts the values).
Values for other compounds may be found in a variety of available reviews and monographs. Critical discussions of the challenges of measurement of log P and related computation of its estimated values (see below) appear in several reviews. | 0 | Theoretical and Fundamental Chemistry |
The age of a water parcel can be estimated by the CFC partial pressure (pCFC) age or SF partial pressure (pSF) age. The pCFC age of a water sample is defined as:
where [CFC] is the measured CFC concentration (pmol kg) and F is the solubility of CFC gas in seawater as a function of temperature and salinity. The CFC partial pressure is expressed in units of 10–12 atmospheres or parts-per-trillion (ppt). The solubility measurements of CFC-11 and CFC-12 have been previously measured by Warner and Weiss Additionally, the solubility measurement of CFC-113 was measured by Bu and Warner and SF by Wanninkhof et al. and Bullister et al. Theses authors mentioned above have expressed the solubility (F) at a total pressure of 1 atm as:
where F = solubility expressed in either mol l or mol kg atm,
T = absolute temperature,
S = salinity in parts per thousand (ppt),
a, a, a, b, b, and b are constants to be determined from the least squares fit to the solubility measurements. This equation is derived from the integrated Van 't Hoff equation and the logarithmic Setchenow salinity dependence.
It can be noted that the solubility of CFCs increase with decreasing temperature at approximately 1% per degree Celsius.
Once the partial pressure of the CFC (or SF) is derived, it is then compared to the atmospheric time histories for CFC-11, CFC-12, or SF in which the pCFC directly corresponds to the year with the same. The difference between the corresponding date and the collection date of the seawater sample is the average age for the water parcel. The age of a parcel of water can also be calculated using the ratio of two CFC partial pressures or the ratio of the SF partial pressure to a CFC partial pressure. | 1 | Applied and Interdisciplinary Chemistry |
Naphthenic acids, mixtures of long chain and cyclic carboxylic acids extracted from petroleum, form lipophilic complexes (often called salts) with transition metals. These metal naphthenates, have the formula M(naphthenate), or MO(naphthenate), have diverse applications including synthetic detergents, lubricants, corrosion inhibitors, fuel and lubricating oil additives, wood preservatives, insecticides, fungicides, acaricides, wetting agents, thickening agent, and oil drying agents. Industrially useful naphthenates include those of aluminium, magnesium, calcium, barium, cobalt, copper, lead, manganese, nickel, vanadium, and zinc.< Illustrative is the use of cobalt naphthenate for the oxidation of tetrahydronaphthalene to the hydroperoxide.
Like naphthenic acid, 2-ethylhexanoic acid forms lipophilic complexes that are used in organic and industrial chemical synthesis. They function as catalysts in polymerizations as well as for oxidation reactions as oil drying agents. | 0 | Theoretical and Fundamental Chemistry |
Digallane (systematically named digallane(6)) is an inorganic compound with the chemical formula (also written or ). It is the dimer of the monomeric compound gallane. The eventual preparation of the pure compound, reported in 1989,
was hailed as a "tour de force." Digallane had been reported as early as 1941 by Wiberg; however, this claim could not be verified by later work by Greenwood and others. This compound is a colorless gas that decomposes above 0 °C.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
The formation of stable nanoclusters such as Buckminsterfullerene (C) has been suggested to have occurred during the early universe. The first set of experiments to form nanoclusters can be traced back to 1950s and 1960s. During this period, nanoclusters were produced from intense molecular beams at low temperature by supersonic expansion. The development of laser vaporization technique made it possible to create nanoclusters of a clear majority of the elements in the periodic table. Since 1980s, there has been tremendous work on nanoclusters of semiconductor elements, compound clusters and transition metal nanoclusters. | 0 | Theoretical and Fundamental Chemistry |
In Chaetomium thermophilum, a complex of a metabolon exists between fatty acid synthase and a MDa carboxylase, and was observed using chemical cross-linking coupled to mass spectrometry and visualized by cryo-electron microscopy. The Fatty acid synthesis metabolon in C. thermophilum is highly flexible, and although a high-resolution structure of Fatty acid synthase was possible, the metabolon was highly flexible, hindering high-resolution structure determination. | 1 | Applied and Interdisciplinary Chemistry |
Recently the late-stage sulfoximidation of electron-rich arenes by photoredox catalysis was reported and several examples were discussed. | 0 | Theoretical and Fundamental Chemistry |
Although they have excellent environmental credentials, waterborne polyurethane dispersions tend to suffer from lower mechanical strength than other resins. The use of polycarbonate based polyols in the synthesis can help overcome this weakness. The wear and corrosion resistance is also not as good and hence they are often hybridized. Other strategies used to overcome some of the weaknesses include molecular design and mixing/compounding with inorganic rather than polymeric materials. The use of an anionic or cationic center or indeed a hydrophilic non-ionic manufacturing technique tends to result in a permanent inbuilt water resistance weakness. Research is being conducted and techniques developed to combat this weakness. Simple blending has also been employed. This has the advantage in that if no new molecule has been formed but merely blending with existing registered raw materials, then that is a way around the work required to get registration of the material under various country regimes such as REACH in Europe and TSCA in the United States. Because of the surface tension of water being so high, pinholes and other problems of air-entrainment tend to be more common and need special additives to combat. They also tend not to be manufactured with biobased polyols because vegetable based polyols don't have performance enhancing functional groups. Modification is possible to achieve this and enable even greener versions.
Drying, curing and cross-linking is also not usually as good and hence research is proceeding in the area of post crosslinking to improve these features. | 0 | Theoretical and Fundamental Chemistry |
The types and sizes of bioaerosols vary in marine environments and occur largely because of wet-discharges caused by changes in osmotic pressure or surface tension. Some types of marine originated bioaerosols excrete dry-discharges of fungal spores that are transported by the wind.
One instance of impact on marine species was the 1983 die off of Caribbean sea fans and sea urchins that correlated with dust storms originating in Africa. This correlation was determined by the work of microbiologists and a Total Ozone Mapping Spectrometer, which identified bacteria, viral, and fungal bioaerosols in the dust clouds that were tracked over the Atlantic Ocean. Another instance in of this occurred in 1997 when El Niño possibly impacted seasonal trade wind patterns from Africa to Barbados, resulting in similar die offs. Modeling instances like these can contribute to more accurate predictions of future events. | 0 | Theoretical and Fundamental Chemistry |
When a nucleus has a spin quantum number, I, greater than 1/2 it has a quadrupole moment. In that case, coupling of nuclear spin angular momentum with rotational angular momentum causes splitting of the rotational energy levels. If the quantum number J of a rotational level is greater than I, levels are produced; but if J is less than I, levels result. The effect is one type of hyperfine splitting. For example, with N () in HCN, all levels with J > 0 are split into 3. The energies of the sub-levels are proportional to the nuclear quadrupole moment and a function of F and J. where , . Thus, observation of nuclear quadrupole splitting permits the magnitude of the nuclear quadrupole moment to be determined.
This is an alternative method to the use of nuclear quadrupole resonance spectroscopy. The selection rule for rotational transitions becomes | 0 | Theoretical and Fundamental Chemistry |
Bay muds occur in bays and estuaries throughout the temperate regions of the world. In North America, prominent instances are: (a) the Stellwagen Bank formed 16,000 to 9000 BCE by glaciation of Cape Cod Bay in Massachusetts, (b) Florida Bay, (c) in California Morro Bay and San Francisco Bay and (d) Knik & Turnagain Arms in Anchorage, Alaska. In the United Kingdom large bay mud occurrences are found at Morecambe Bay, Bridgwater Bay and Bristol Bay. Straddling Denmark, the Netherlands and Germany is the Wadden Sea, a major formation underlain by bay muds.
In Asia the Chongming Dongtan Nature Reserve in Shanghai, China, is an example of a large scale bay mud formation. The Atlantic coast of Africa holds the Banc dArguin, a World Heritage nature preserve in the country of Mauritania. Banc dArguin is a vast area underlain by bay mud. | 1 | Applied and Interdisciplinary Chemistry |
RNAPII can exist in two forms: RNAPII0, with a highly phosphorylated CTD, and RNAPIIA, with a nonphosphorylated CTD. Phosphorylation occurs principally on Ser2 and Ser5 of the repeats, although these positions are not equivalent. The phosphorylation state changes as RNAPII progresses through the transcription cycle: The initiating RNAPII is form IIA, and the elongating enzyme is form II0. While RNAPII0 does consist of RNAPs with hyperphosphorylated CTDs, the pattern of phosphorylation on individual CTDs can vary due to differential phosphorylation of Ser2 versus Ser5 residues and/or to differential phosphorylation of repeats along the length of the CTD. The PCTD (phosphoCTD of an RNAPII0) physically links pre-mRNA processing to transcription by tethering processing factors to elongating RNAPII, e.g., 5′-end capping, 3′-end cleavage, and polyadenylation.
Ser5 phosphorylation (Ser5PO) near the 5′ ends of genes depends principally on the kinase activity of TFIIH (Kin28 in yeast; CDK7 in metazoans). The transcription factor TFIIH is a kinase and will hyperphosphorylate the CTD of RNAP, and in doing so, causes the RNAP complex to move away from the initiation site. Subsequent to the action of TFIIH kinase, Ser2 residues are phosphorylated by CTDK-I in yeast (CDK9 kinase in metazoans). Ctk1 (CDK9) acts in complement to phosphorylation of serine 5 and is, thus, seen in middle to late elongation.
CDK8 and cyclin C (CCNC) are components of the RNA polymerase II holoenzyme that phosphorylate the carboxy-terminal domain (CTD). CDK8 regulates transcription by targeting the CDK7/cyclin H subunits of the general transcription initiation factor IIH (TFIIH), thereby providing a link between the mediator and the basal transcription machinery.
The gene CTDP1 encodes a phosphatase that interacts with the carboxy-terminus of transcription initiation factor TFIIF, a transcription factor that regulates elongation as well as initiation by RNA polymerase II.
Also involved in the phosphorylation and regulation of the RPB1 CTD is cyclin T1 (CCNT1). Cyclin T1 tightly associates and forms a complex with CDK9 kinase, both of which are involved in the phosphorylation and regulation.
: ATP + [DNA-directed RNA polymerase II] <=> ADP + [DNA-directed RNA polymerase II] phosphate : catalyzed by CDK9 EC 2.7.11.23.
TFIIF and FCP1 cooperate for RNAPII recycling. FCP1, the CTD phosphatase, interacts with RNA polymerase II. Transcription is regulated by the state of phosphorylation of a heptapeptide repeat. The nonphosphorylated form, RNAPIIA, is recruited to the initiation complex, whereas the elongating polymerase is found with RNAPII0. RNAPII cycles during transcription. CTD phosphatase activity is regulated by two GTFs (TFIIF and TFIIB). The large subunit of TFIIF (RAP74) stimulates the CTD phosphatase activity, whereas TFIIB inhibits TFIIF-mediated stimulation. Dephosphorylation of the CTD alters the migration of the largest subunit of RNAPII (RPB1). | 1 | Applied and Interdisciplinary Chemistry |
Since the 1940s, the DLVO theory has been used to explain phenomena found in colloidal science, adsorption and many other fields. Due to the more recent popularity of nanoparticle research, DLVO theory has become even more popular because it can be used to explain behavior of both material nanoparticles such as fullerene particles and microorganisms. | 0 | Theoretical and Fundamental Chemistry |
The following process models are commonly applied to geometallurgy:
* The Bond equation
* The SPI calibration equation, CEET
* FLEET*
* SMC model
* Aminpro-Grind, Aminpro-Flot models | 1 | Applied and Interdisciplinary Chemistry |
Usually the time-of-flight tube used in mass spectrometry is praised for simplicity, but for precision measurements of charged low energy particles the electric and the magnetic field in the tube has to be controlled within 10 mV and 1 nT respectively.
The work function homogeneity of the tube can be controlled by a Kelvin probe. The magnetic field can be measured by a fluxgate compass. High frequencies are passively shielded and damped by radar absorbent material. To generate arbitrary low frequencies field the screen is parted into plates (overlapping and connected by capacitors) with bias voltage on each plate and a bias current on coil behind plate whose flux is closed by an outer core. In this way the tube can be configured to act as a weak achromatic quadrupole lens with an aperture with a grid and a delay line detector in the diffraction plane to do angle resolved measurements. Changing the field the angle of the field of view can be changed and a deflecting bias can be superimposed to scan through all angles.
When no delay line detector is used focusing the ions onto a detector can be accomplished through the use of two or three einzel lenses placed in the vacuum tube located between the ion source and the detector.
The sample should be immersed into the tube with holes and apertures for and against stray light to do magnetic experiments and to control the electrons from their start. | 0 | Theoretical and Fundamental Chemistry |
As a strong base, TBD fully deprotonates most phenols, carboxylic acids, and some C-acids. It catalyzes a variety of reactions including Michael reactions, Henry reactions (nitroaldol reactions), transesterification reactions, and Knoevenagel condensations.
Deprotonation at the 7-position gives a particularly electron-rich ligand as manifested in the redox properties of ditungsten tetra(hpp). | 0 | Theoretical and Fundamental Chemistry |
Two basic sets of theorems exists, one for flux and another for concentrations. The concentration connectivity theorems are divided again depending on whether the system species is different from the local species . | 1 | Applied and Interdisciplinary Chemistry |
The d electron count or number of d electrons is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex. The d electron count is an effective way to understand the geometry and reactivity of transition metal complexes. The formalism has been incorporated into the two major models used to describe coordination complexes; crystal field theory and ligand field theory, which is a more advanced version based on molecular orbital theory. However the d electron count of an atom in a complex is often different from the d electron count of a free atom or a free ion of the same element. | 0 | Theoretical and Fundamental Chemistry |
As with any piece of instrumentation or equipment, there are many aspects of maintenance that need to be encompassed by daily, weekly and annual procedures. The frequency of maintenance is typically determined by the sample volume and cumulative run time that the instrument is subjected to.
One of the first things that should be carried out before the calibration of the ICP-MS is a sensitivity check and optimization. This ensures that the operator is aware of any possible issues with the instrument and if so, may address them before beginning a calibration. Typical indicators of sensitivity are Rhodium levels, Cerium/Oxide ratios and DI water blanks. One common standard practice is to measure a standard tuning solution provided by the ICP manufacturer every time the plasma torch is started. Then the instrument is auto-calibrated for optimum sensitivity and the operator obtains a report providing certain parameters such as sensitivity, mass resolution and estimated amount of oxidized species and double-positive charged species.
One of the most frequent forms of routine maintenance is replacing sample and waste tubing on the peristaltic pump, as these tubes can get worn fairly quickly resulting in holes and clogs in the sample line, resulting in skewed results. Other parts that will need regular cleaning and/or replacing are sample tips, nebulizer tips, sample cones, skimmer cones, injector tubes, torches and lenses. It may also be necessary to change the oil in the interface roughing pump as well as the vacuum backing pump, depending on the workload put on the instrument. | 0 | Theoretical and Fundamental Chemistry |
Researchers have been using carbon nanotubes (CNTs) to mimic the papillae of lotus leaves. CNT nanoforests can be made using chemical vapor deposition techniques. CNT’s can be applied on a surface to modify its water contact angle. Lau et al. created vertical CNT forests with a polytetrafluroethylene (PTFE) coating that was both stable and superhydrophobic with an advancing and receding contact angle of 170° and 160°. Jung and Bhushan have created a superhydrophobic surface by spray coating CNTs with an epoxy resin. The spacing and alignment of the CNTs have been shown to impact the degree of hydrophobicity a surface has. Sun et al., have found that CNTs aligned vertically with a medium spacing display the best hydrophobic properties. Small and large spacing shows increased drop spreading, while horizontal orientation may even display hydrophilic properties.
Glass silica beads in an epoxy resin, and the electrochemical deposition of gold into dendritic structures has also created synthetic biomimetic surfaces similar to lotus leaves. | 0 | Theoretical and Fundamental Chemistry |
This naming method generally follows established IUPAC organic nomenclature. Hydrides of the main group elements (groups 13–17) are given -ane base names, e.g. borane, BH. Acceptable alternative names for some of the parent hydrides are water rather than oxidane and ammonia rather than azane. In these cases the base name is intended to be used for substituted derivatives.
This section of the recommendations covers the naming of compounds containing rings and chains. | 0 | Theoretical and Fundamental Chemistry |
For a Morpholino to be effective, it must be delivered past the cell membrane into the cytosol of a cell. Once in the cytosol, Morpholinos freely diffuse between the cytosol and nucleus, as demonstrated by the nuclear splice-modifying activity of Morpholinos observed after microinjection into the cytosol of cells. Different methods are used for delivery into embryos, into cultured cells or into adult animals. A microinjection apparatus is usually used for delivery into an embryo, with injections most commonly performed at the single-cell or few-cell stage; an alternative method for embryonic delivery is electroporation, which can deliver oligos into tissues of later embryonic stages. Common techniques for delivery into cultured cells include the Endo-Porter peptide (which causes the Morpholino to be released from endosomes), the Special Delivery system (no longer commercially available, used a Morpholino-DNA heteroduplex and an ethoxylated polyethylenimine delivery reagent), electroporation, or scrape loading.
Delivery into adult tissues is usually difficult, though there are a few systems allowing useful uptake of unmodified Morpholino oligos (including uptake into muscle cells with Duchenne muscular dystrophy or the vascular endothelial cells stressed during balloon angioplasty). Though they permeate through intercellular spaces in tissues effectively, unconjugated PMOs have limited distribution into the cytosol and nuclear spaces within healthy tissues following IV administration. Systemic delivery into many cells in adult organisms can be accomplished by using covalent conjugates of Morpholino oligos with cell-penetrating peptides, and, while toxicity has been associated with moderate doses of the peptide conjugates, they have been used in vivo for effective oligo delivery at doses below those causing observed toxicity. An octa-guanidinium dendrimer attached to the end of a Morpholino can deliver the modified oligo (called a Vivo-Morpholino) from the blood to the cytosol. Delivery-enabled Morpholinos, such as peptide conjugates and Vivo-Morpholinos, show promise as therapeutics for viral and genetic diseases. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.