text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2 values |
|---|---|---|
* Indistinguishable Particles
where N is number of particles, h is Plancks constant, I is moment of inertia, and Z' is the partition function, in various forms: | 0 | Theoretical and Fundamental Chemistry |
Prepainted metal is used in a variety of products. It can be formed for many different applications, including those with T bends, without loss of coating quality. Major industries use prepainted metal in products such as building panels, metal roofs wall panels, garage doors, office furniture (desks, cubicle divider panels, file cabinets, and modular cabinets), home appliances (refrigerators, dishwashers, freezers, range hoods, microwave ovens, and washers and dryers), heating and air-conditioning outer panels and ductwork, commercial appliances, vending machines, foodservice equipment and cooking tins, beverage cans, and automotive panels and parts (fuel tanks, body panels, bumpers), The list continues to grow, with new industries making the switch from post-painted to prepainted processes each year.
Some high-tech, complex coatings are applied with the coil coating process. Coatings for cool metal roofing materials, smog-eating building panels, antimicrobial products, anti-corrosive metal parts, and solar panels use this process. Pretreatments and coatings can be applied with the coil coating process in very precise, thin, uniform layers, and makes some complex coatings feasible and more cost-effective.
The largest market for prepainted metal is in both commercial and residential construction. It is chosen for the quality, low cost, design flexibility, and environmentally beneficial properties. Using prepainted metal can contribute to credit toward LEED certification for sustainable design. A wide arrange of color options are available with prepainted metal, including vibrant colors for modern designs, and natural weathered finishes in rustic expressions. Prepainted metal also can be formed, almost like plastic, in fluid shapes. This flexibility allows architects to achieve unique, expressive designs using metal.
The output of the coil coating industry is a prepainted metal strip. This has numerous applications in various industries, including in:
* The construction industry for both indoor and outdoor applications;
* The automotive and transport industries;
* The production of white goods including washing machines;
* Cabinets for electronic goods;
* Office furniture;
* Lighting envelopes;
* Bakeware. | 1 | Applied and Interdisciplinary Chemistry |
Nitrogenous compounds have a variety of sources including washout of oxides of nitrogen from the atmosphere, some geological inputs and some from macrophyte and algal nitrogen fixation. However, for many rivers in the proximity of humans, the largest input is from sewage whether treated or untreated. The nitrogen derives from breakdown products of proteins found in urine and faeces. These products, being very soluble, often pass through sewage treatment process and are discharged into rivers as a component of sewage treatment effluent. Nitrogen may be in the form of nitrate, nitrite, ammonia or ammonium salts or what is termed albuminoid nitrogen or nitrogen still within an organic proteinoid molecule.
The differing forms of nitrogen are relatively stable in most river systems with nitrite slowly transforming into nitrate in well oxygenated rivers and ammonia transforming into nitrite/ nitrate. However, the process are slow in cool rivers and reduction in concentration may more often be attributed to simple dilution. All forms of nitrogen are taken up by macrophytes and algae and elevated levels of nitrogen are often associated with overgrowths of plants or eutrophication. These can have the effect of blocking channels and inhibiting navigation. However, ecologically, the more significant effect is on dissolved oxygen concentrations which may become super-saturated during daylight due to plant photosynthesis but then drop to very low levels during darkness as plant respiration uses up the dissolved oxygen. Coupled with the release of oxygen in photosynthesis is the creation of bi-carbonate ions which cause a steep rise in pH and this is matched in darkness as carbon dioxide is released through respiration which substantially lowers the pH. Thus high levels of nitrogenous compounds tends to lead to eutrophication with extreme variations in parameters which in turn can substantially degrade the ecological worth of the watercourse.
Ammonium ions also have a toxic effect, especially on fish. The toxicity of ammonia is dependent on both pH and temperature and an added complexity is the buffering effect of the blood/water interface across the gill membrane which masks any additional toxicity over about pH 8.0. The management of river chemistry to avoid ecological damage is particularly difficult in the case of ammonia as a wide range of potential scenarios of concentration, pH and temperature have to be considered and the diurnal pH fluctuation caused by photosynthesis considered. On warm summer days with high-bi-carbonate concentrations unexpectedly toxic conditions can be created. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, chromism is a process that induces a change, often reversible, in the colors of compounds. In most cases, chromism is based on a change in the electron states of molecules, especially the π- or d-electron state, so this phenomenon is induced by various external stimuli which can alter the electron density of substances. It is known that there are many natural compounds that have chromism, and many artificial compounds with specific chromism have been synthesized to date. It is usually synonymous with chromotropism, the (reversible) change in color of a substance due to the physical and chemical properties of its ambient surrounding medium, such as temperature and pressure, light, solvent, and presence of ions and electrons.
Chromism is classified by what kind of stimuli are used. Examples of the major kinds of chromism are as follows.
* thermochromism is chromism that is induced by heat, that is, a change of temperature. This is the most common chromism of all.
* photochromism is induced by light irradiation. This phenomenon is based on the isomerization between two different molecular structures, light-induced formation of color centers in crystals, precipitation of metal particles in a glass, or other mechanisms.
* electrochromism is induced by the gain and loss of electrons. This phenomenon occurs in compounds with redox active sites, such as metal ions or organic radicals.
*solvatochromism depends on the polarity of the solvent. Most solvatochromic compounds are metal complexes.
There are many more chromisms and these are listed below in .
The output from the chromisms described above is observed by a change in the absorption spectra of the chromic material. An increasingly important group of chromisms are those where changes are displayed in their emission spectra. Hence they are called fluorochromisms, exemplified by solvatofluorochromism, electrofluorochromism and mechanofluorochromism. | 0 | Theoretical and Fundamental Chemistry |
It is a suitable discharge option for cakes that are thin and have the tendency to stick with one another. Filter cakes on the drum and discharged roll are pressed against one another to ensure that the thin filter cake is peeled or pulled from the drum. Removal of solids from the discharge roll is done via a knife blade. Roll discharged is used if the desired separation requires high filtration rate, if high solid content slurry is used or if the slurry is easy to filter to produce cake formation or if the discharged solid is sticky or mud-like cake. | 0 | Theoretical and Fundamental Chemistry |
When the interfacial areas are large, the amount of surfactant at the interface cannot be neglected. If, for example, air bubbles are introduced into a solution of a surfactant above CMC, these bubbles, as they rise to the surface, remove surfactants from the bulk to the top of the solution creating a foam column and thus reducing the concentration in bulk to below CMC. This is one of the easiest methods to remove surfactants from effluents (see foam flotation). Thus in foams with sufficient interfacial area are devoid of micelles. Similar reasoning holds for emulsions.
The other situation arises in detergents. One initially starts off with concentrations greater than CMC in water and on adding fabric with large interfacial area, the surfactant concentration drops below CMC and no micelles remain at equilibrium. Therefore, the solubilization plays a minor role in detergents. Removal of oily soil occurs by modification of the contact angles and release of oil in the form of emulsion.
In petroleum industry, CMC is considered prior to injecting surfactant in reservoir regarding enhanced oil recovery (EOR) application. Below the CMC point, interfacial tension between oil and water phase is no longer effectively reduced. If the concentration of the surfactant is kept a little above the CMC, the additional amount covers the dissolution with existing brine in the reservoir. It is desired that the surfactant will work at the lowest interfacial tension (IFT). | 0 | Theoretical and Fundamental Chemistry |
Trithiophosphate is the anion [POS], which has C symmetry. Tetrathiophosphate is the anion [PS], which has T symmetry. | 0 | Theoretical and Fundamental Chemistry |
Stable stratifications can become unstable if layers change density. This can happen due to outside influences (for instance, if water evaporates from a freshwater lens, making it saltier and denser, or if a pot or layered beverage is heated from below, making the bottom layer less dense). However, it can also happen due to internal diffusion of heat (the warmer layer slowly heats the adjacent cooler one) or other physical properties. This often causes mixing at the interface, creating new diffusive layers (see photo of coffee and milk).
Sometimes, two physical properties diffuse between layers simultaneously; salt and temperature, for instance. This may form diffusive layers or even salt fingering, when the surfaces of the diffusive layers become so wavy that there are "fingers" of layers reaching up and down.
Not all mixing is driven by density changes. Other physical forces may also mix stably-stratified layers. Sea spray and whitecaps (foaming whitewater on waves) are examples of water mixed into air, and air into water, respectively. In a fierce storm the air/water boundary may grow indistinct. Some of these wind waves are Kelvin-Helmholtz waves.
Depending on the size of the velocity difference and the size of the density contrast between the layers, Kelvin-Helmholtz waves can look different. For instance, between two layers of air or two layers of water, the density difference is much smaller and the layers are miscible; see black-and-white model video. | 1 | Applied and Interdisciplinary Chemistry |
Observing that microarrays spotted with single molecules did not work well for large genomic DNA molecules, microfluidic devices using soft lithography possessing a series of parallel microchannels were developed. | 1 | Applied and Interdisciplinary Chemistry |
Most aquatic habitats are occupied by fish or other animals requiring certain minimum dissolved oxygen concentrations to survive. Dissolved oxygen concentrations may be measured directly in wastewater, but the amount of oxygen potentially required by other chemicals in the wastewater is termed as oxygen demand. Dissolved or suspended oxidizable organic material in wastewater will be used as a food source. Finely divided material is readily available to microorganisms whose populations will increase to digest the amount of food available. Digestion of this food requires oxygen, so the oxygen content of the water will ultimately be decreased by the amount required to digest the dissolved or suspended food. Oxygen concentrations may fall below the minimum required by aquatic animals if the rate of oxygen utilization exceeds replacement by atmospheric oxygen.
Basically, the reaction for biochemical oxidation may be written as:
:Oxidizable material + bacteria + nutrient + O → CO + HO + oxidized inorganics such as or
Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows:
:S + 2 O →
: + O → | 0 | Theoretical and Fundamental Chemistry |
HOCPCA (3-hydroxycyclopent-1-enecarboxylic acid) is a compound with an affinity for the GHB receptor 39 times greater than that of GHB itself. | 1 | Applied and Interdisciplinary Chemistry |
MMC can be classified into physical MMC and chemical MMC. In the former method, the stationary phase is constructed of two or more types of packing materials. In the chemical method, just one type of packing material containing two or more functionalities is used. | 0 | Theoretical and Fundamental Chemistry |
In geology, solid-state recrystallization is a metamorphic process that occurs under high temperatures and pressures where atoms of minerals are reorganized by diffusion and/or dislocation glide. During this process, the physical structure of the minerals is altered while the composition remains unchanged. This is in contrast to metasomatism, which is the chemical alteration of a rock by hydrothermal and other fluids.
Solid-state recrystallization can be illustrated by observing how snow recrystallizes to ice. When snow is subjected to varying temperatures and pressures, individual snowflakes undergo a physical transformation but their composition remains the same. Limestone is a sedimentary rock that undergoes metamorphic recrystallization to form marble, and clays can recrystallize to muscovite mica. | 0 | Theoretical and Fundamental Chemistry |
Samarium(II) iodide is an inorganic compound with the formula SmI. When employed as a solution for organic synthesis, it is known as Kagan's reagent. SmI is a green solid and forms a dark blue solution in THF. It is a strong one-electron reducing agent that is used in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Gold clusters in cluster chemistry can be either discrete molecules or larger colloidal particles. Both types are described as nanoparticles, with diameters of less than one micrometer. A nanocluster is a collective group made up of a specific number of atoms or molecules held together by some interaction mechanism. Gold nanoclusters have potential applications in optoelectronics and catalysis. | 0 | Theoretical and Fundamental Chemistry |
Vibrational transitions and optical phonon transitions take place in the infrared part of the spectrum, at wavelengths of around 1-30 micrometres. | 0 | Theoretical and Fundamental Chemistry |
Standalone fans are usually powered by an electric motor, often attached directly to the motors output, with no gears or belts. The motor is either hidden in the fans center hub or extends behind it. For big industrial fans, three-phase asynchronous motors are commonly used, may be placed near the fan, and drive it through a belt and pulleys. Smaller fans are often powered by shaded pole AC motors, or brushed or brushless DC motors. AC-powered fans usually use mains voltage, while DC-powered fans typically use low voltage, typically 24V, 12V, or 5 V.
In machines with a rotating part, the fan is often connected to it rather than being powered separately. This is commonly seen in motor vehicles with internal combustion engines, large cooling systems, locomotives, and winnowing machines, where the fan is connected to the drive shaft or through a belt and pulleys. Another common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while the other has a fan mounted on it to cool the motor itself. Window air conditioners commonly use a dual-shaft fan to operate separate fans for the interior and exterior parts of the device.
Where electrical power or rotating parts are not readily available, fans may be driven by other methods. High-pressure gases such as steam can be used to drive a small turbine, and high-pressure liquids can be used to drive a pelton wheel, either which can provide the rotational drive for a fan.
Large, slow-moving energy sources such as a flowing river can also power a fan using a water wheel and a series of step-down gears or pulleys to increase the rotational speed to that which is required for efficient fan operation. | 0 | Theoretical and Fundamental Chemistry |
René Descartes (1596–1650) "mechanical" philosophy of corpuscularism had much in common with atomism, and is considered, in some senses, to be a different version of it. Descartes thought everything physical in the universe to be made of tiny vortices of matter. Like the ancient atomists, Descartes claimed that sensations, such as taste or temperature, are caused by the shape and size of tiny pieces of matter. In Principles of Philosophy (1644) he writes: "The nature of body consists just in extension—not in weight, hardness, colour or the like." The main difference between atomism and Descartes concept was the existence of the void. For him, there could be no vacuum, and all matter was constantly swirling to prevent a void as corpuscles moved through other matter. Another key distinction between Descartes' view and classical atomism is the mind/body duality of Descartes, which allowed for an independent realm of existence for thought, soul, and most importantly, God. | 1 | Applied and Interdisciplinary Chemistry |
EXPOSE has several objectives, specific to each experiments, but all linked to the astrobiology domain. Their collective objective is to better understand the nature and evolution of organic matter present in extraterrestrial environments and their potential implications in astrobiology. These experiments mostly study molecules of cometary interest in order to understand the results of the Rosetta mission, the chemistry of Titan (Cassini–Huygens mission), or the organic chemistry of the Martian environment (Mars Science Laboratory and ExoMars project). | 1 | Applied and Interdisciplinary Chemistry |
PA 11 is a biopolymer derived from natural oil. It is also known under the tradename Rilsan B, commercialized by Arkema. PA 11 belongs to the technical polymers family and is not biodegradable. Its properties are similar to those of PA 12, although emissions of greenhouse gases and consumption of nonrenewable resources are reduced during its production. Its thermal resistance is also superior to that of PA 12. It is used in high-performance applications like automotive fuel lines, pneumatic airbrake tubing, electrical cable antitermite sheathing, flexible oil and gas pipes, control fluid umbilicals, sports shoes, electronic device components, and catheters.
A similar plastic is Polyamide 410 (PA 410), derived 70% from castor oil, under the trade name EcoPaXX, commercialized by DSM.
PA 410 is a high-performance polyamide that combines the benefits of a high melting point (approx. 250 °C), low moisture absorption and excellent resistance to various chemical substances. | 0 | Theoretical and Fundamental Chemistry |
While internal waves of higher magnitudes will often break after crossing over the shelf break, smaller trains will proceed across the shelf unbroken. At low wind speeds these internal waves are evidenced by the formation of wide surface slicks, oriented parallel to the bottom topography, which progress shoreward with the internal waves. Waters above an internal wave converge and sink in its trough and upwell and diverge over its crest. The convergence zones associated with internal wave troughs often accumulate oils and flotsam that occasionally progress shoreward with the slicks. These rafts of flotsam can also harbor high concentrations of larvae of invertebrates and fish an order of magnitude higher than the surrounding waters. | 1 | Applied and Interdisciplinary Chemistry |
Traditional and presently most widespread categorisation of pure working fluids was first used by H. Tabor et al. and O. Badr et al. dating back to the 60s. This three-class classification system sorts pure working fluids into three categories. The base of the classification is the shape of the saturation vapour curve of the fluid in temperature-entropy plane. If the slope of the saturation vapour curve in all states is negative (ds/dT<0), which means that with decreasing saturation temperature the value of entropy increases, the fluid is called wet. If the slope of the saturation vapour curve of the fluid is mainly positive (regardless of a short negative slope somewhat below the critical point), which means that with decreasing saturation temperature the value of entropy also decreases (dT/ds>0), the fluid is dry. The third category is called isentropic, which means constant entropy and refers to those fluids that have a vertical saturation vapour curve (regardless of a short negative slope somewhat below the critical point) in temperature-entropy diagram. According to mathematical approach, it means a (negative) infinite slope (ds/dT=0). The terms of wet, dry and isentropic refer to the quality of vapour after the working fluid undergoes an isentropic (reversible adiabatic) expansion process from saturated vapour state. During an isentropic expansion process the working fluid always ends in the two-phase (also called wet) zone, if it is a wet-type fluid. If the fluid is of dry-type, the isentropic expansion necessarily ends in the superheated (also called dry) steam zone. If the working fluid is of isentropic-type, after an isentropic expansion process the fluid stays in saturated vapour state. The quality of vapour is a key factor in choosing steam turbine or expander for heat engines. See figure for better understanding. | 0 | Theoretical and Fundamental Chemistry |
The large kiln at Crindledykes near Haydon Bridge, Northumbria, was one of more than 300 in the county. It was unique to the area in having four draw arches to a single pot. As production was cut back, the two side arches were blocked up, but were restored in 1989 by English Heritage.
The development of the national rail network made the local small-scale kilns increasingly unprofitable, and they gradually died out through the 19th century. They were replaced by larger industrial plants. At the same time, new uses for lime in the chemical, steel and sugar industries led to large-scale plants. These also saw the development of more efficient kilns.
A lime kiln erected at Dudley, West Midlands (formerly Worcestershire) in 1842 survives as part of the Black Country Living Museum which opened in 1976, although the kilns were last used during the 1920s. It is now among the last in a region which was dominated by coalmining and limestone mining for generations until the 1960s. | 1 | Applied and Interdisciplinary Chemistry |
In 2000, the European Union (EU) enacted similar legislation, Regulation(EC) No 141/2000, which refers to drugs developed to treat rare diseases to as "orphan medicinal products". The EUs definition of an orphan condition is broader than that of the US, in that it also covers some tropical diseases that are primarily found in developing nations. Orphan drug status granted by the European Commission gives marketing exclusivity in the EU for 10 years after approval. The EUs legislation is administered by the Committee on Orphan Medicinal Products of the European Medicines Agency (EMA).
In late 2007 the FDA and EMA agreed to use a common application process for both agencies to make it easier for manufacturers to apply for orphan drug status but, while continuing two separate approval processes. | 1 | Applied and Interdisciplinary Chemistry |
Geranylfarnesyl pyrophosphate is an intermediate used by organisms in the biosynthesis of sesterterpenoids. | 1 | Applied and Interdisciplinary Chemistry |
In froth flotation, the crushed ore is wetted, suspended in a slurry, and mixed with reagents that render the sulfide particles hydrophobic. Typical reagents ("collectors") include potassium ethylxanthate and sodium ethylxanthate, but dithiophosphates and dithiocarbamates are also used. The slurry is introduced to a water-filled aeration tank containing a surfactant such as methylisobutyl carbinol (MIBC). Air is constantly forced through the slurry. The air bubbles attach to the hydrophobic copper sulfide particles, which are conveyed to the surface where the froth is skimmed off. These skimmings are generally subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriously impact the concentrate quality (typically, galena), and the final concentrate sent for smelting. The rock that has not floated off in the flotation cell is either discarded as tailings or further processed to extract other metals such as lead (from galena) and zinc (from sphalerite), should they exist. A variety of measures are taken to improve the efficiency of the froth flotation. Lime is used to raise the pH of the water bath, causing the collector to bond more efficiently to the copper sulfides. The process can produce a concentrates with 27–29% and 37–40% copper contents from chalcopyrite and chalcocite, respectively. | 1 | Applied and Interdisciplinary Chemistry |
The yeast homing endonuclease PI-Sce is a LAGLIDADG-type endonuclease encoded as an intein that splices itself out of another protein (). The high-resolution structure reveals two domains: an endonucleolytic centre resembling the C-terminal domain of Hedgehog proteins, and a Hint domain (Hedgehog/Intein) containing the protein-splicing active site. | 1 | Applied and Interdisciplinary Chemistry |
Some Zintl ions show the ability to activate small molecules. One example from Dehnen and coworkers is the capture of O by the intermetallic cluster [Bi{Ru(cod)}]. Another ruthenium intertermetallic cluster, [Ru@Sn], was used as a precursor to selectively disperse the CO hydrogenation catalyst Ru-SnOx onto CeO, resulting in nearly 100% CO selectivity for methanation.
In materials science, Ge has been used as a source of Ge in lithium ion batteries, where is can be deposited in a microporous layer of alpha-Ge. The discrete nature of Zintl ions opens the possibility for the bottom up synthesis of nanostructured semiconductors and the surface modification of solids. The oxidation and polymerization of Zintl ions may also be a source of new materials. For example, polymerization of Ge clusters was used to create guest free germanium clathrate, in other words a particular, pure Ge. | 0 | Theoretical and Fundamental Chemistry |
To generate an initial state for the prognostic model, a diagnostic model (Kunz, R., 1991) is applied using measured temperature and wind data. Both data can be provided as:
* surface measurements i.e. single measurements directly above the surface (not necessary)
* upper air soundings (i.e., soundings that consist of two or more measurements at different heights) at a constant geographical location is required (with at least one sounding for temperature and wind velocity). | 1 | Applied and Interdisciplinary Chemistry |
A swale is a shady spot, or a sunken or marshy place. In US usage in particular, it is a shallow channel with gently sloping sides. Such a swale may be either natural or human-made. Artificial swales are often infiltration basins, designed to manage water runoff, filter pollutants, and increase rainwater infiltration. Bioswales are swales that involve the inclusion of plants or vegetation in their construction, specifically. | 1 | Applied and Interdisciplinary Chemistry |
A flow battery is a rechargeable fuel cell in which an electrolyte containing one or more dissolved electroactive elements flows through an electrochemical cell that reversibly converts chemical energy directly to electricity. Electroactive elements are "elements in solution that can take part in an electrode reaction or that can be adsorbed on the electrode." Additional electrolyte is stored externally, generally in tanks, and is usually pumped through the cell (or cells) of the reactor, although gravity feed systems are also known. Flow batteries can be rapidly "recharged" by replacing the electrolyte liquid (in a similar way to refilling fuel tanks for internal combustion engines) while simultaneously recovering the spent material for recharging. Many flow batteries use carbon felt electrodes due to its low cost and adequate electrical conductivity, although these electrodes somewhat limit power density due to their low inherent activity toward many redox couples.
In other words, a flow battery is an electrochemical cell, with the property that the ionic solution (electrolyte) is stored outside of the cell (instead of in the cell around the electrodes) and can be fed into the cell in order to generate electricity. The total amount of electricity that can be generated depends on the volume of electrolyte in the tanks.
Flow batteries are governed by the design principles established by electrochemical engineering.
Redox flow batteries, and to a lesser extent hybrid flow batteries, have the advantages of:
* Independent scaling of energy (tanks) and power (stack), which allows for a cost/weight/etc. optimization for each application
* Long cycle and calendar lives (because there are no solid-to-solid phase transitions, that cause degradation of lithium-ion and related batteries)
* Quick response times
* No need for "equalisation" charging (the overcharging of a battery to ensure all cells have an equal charge)
* No harmful emissions
* Little to no self-discharge during standing
* Full recycling of electroactive materials
Some types also offer easy state-of-charge determination (through voltage dependence on charge), low maintenance and tolerance to overcharge/overdischarge.
They are safe because they typically do not contain flammable electrolytes, and electrolytes can be stored away from the power stack.
Flow batteries have three main disadvantages compared to batteries with solid electroactive materials
* Low energy density (you need large tanks of electrolyte to store useful amounts of energy)
* Low charge and discharge rates (compared to other industrial electrode processes). This means that the electrodes and membrane separators need to be large, which increases the cost of power.
* Flow batteries have a lower energy efficiency, because they operate at higher current densities to minimize the effects of the cross-over (internal self-discharge) and to reduce the cost of power.
Flow batteries typically have a higher energy efficiency than fuel cells, but lower than lithium-ion batteries. | 0 | Theoretical and Fundamental Chemistry |
CDPs climate change program aims to reduce companies greenhouse gas emissions and mitigate climate change risk. CDP requests information on climate risks and low carbon opportunities from the world's largest companies on behalf of over 800 institutional investor signatories with a combined US$100 trillion in assets. | 1 | Applied and Interdisciplinary Chemistry |
The equation for converting Photosynthetic Photon Flux Density (PPFD) to DLI, assuming constant PPFD, is below. </blockquote>whereLight-hours is the number of hours in a day active photons are delivered to the target area, measured in hours.
Note that the factor 3.6·10 is due to the conversion factors coming from μmol being converted to mol and the unit of hours (from Light-Hours) being converted to seconds. | 0 | Theoretical and Fundamental Chemistry |
Green engineering approaches the design of products and processes by applying financially and technologically feasible principles to achieve one or more of the following goals: (1) decrease in the amount of pollution that is generated by a construction or operation of a facility, (2) minimization of human population exposure to potential hazards (including reducing toxicity), (3) improved uses of matter and energy throughout the life cycle of the product and processes, and (4) maintaining economic efficiency and viability. Green engineering can be an overarching framework for all design disciplines. | 1 | Applied and Interdisciplinary Chemistry |
After comparing the metabolic responses between oat plants under an average light intensity to that of oat plants under extreme light intensity, Quiles noted that the amount of PS II produced was of a lower amount in the leaves that underwent chlororespiration in extreme light. Whereas higher levels of PS II were yielded by those leaves that underwent average light intensity. A higher of PS II is more efficient for chemical energy synthesis and thus for a plant's survival. Quiles indicates that although the chlororespiratory pathway is less efficient, it still serves as a back-up response for energy production in plants. Ultimately, Quiles concluded that the intense light on oat plants had caused PS II levels to reduce and thus, initiate an influx of gate-way (NAD(P)H) proteins to start the process of chlororespiration. | 1 | Applied and Interdisciplinary Chemistry |
In order to get more reasonable values for the nuclear masses in the liquid drop model, it is necessary to include shell effects. Soviet physicist Vilen Strutinsky proposed such a method using "shell correction" and corrections for nuclear pairing to the liquid drop model. In this method, the total energy of the nucleus is taken as the sum of the liquid drop model energy, , the shell, , and pairing, , corrections to this energy as:
The shell corrections, just like the liquid drop energy, are functions of the nuclear deformation. The shell corrections tend to lower the ground state masses of spherical nuclei with magic or near-magic numbers of neutrons and protons. They also tend to lower the ground state mass of mid shell nuclei at some finite deformation thus accounting for the deformed nature of the actinides. Without these shell effects, the heaviest nuclei could not be observed, as they would decay by spontaneous fission on a time scale much shorter than we can observe.
This combination of macroscopic liquid drop and microscopic shell effects predicts that for nuclei in the U-Pu region, a double-humped fission barrier with equal barrier heights and a deep secondary minimum will occur. For heavier nuclei, like californium, the first barrier is predicted to be much larger than the second barrier and passage over the first barrier is rate determining. In general, there is ample experimental and theoretical evidence that the lowest energy path in the fission process corresponds to having the nucleus, initially in an axially symmetric and mass (reflection) symmetric shape pass over the first maximum in the fission barrier with an axially asymmetric but mass symmetric shape and then to pass over the second maximum in the barrier with an axially symmetric but mass (reflection) asymmetric shape. Because of the complicated multidimensional character of the fission process, there are no simple formulas for the fission barrier heights. However, there are extensive tabulations of experimental characterizations of the fission barrier heights for various nuclei. | 0 | Theoretical and Fundamental Chemistry |
GGT is expressed in high levels in many different tumors. It is known to accelerate tumor growth and to increase resistance to cisplatin in tumors. | 1 | Applied and Interdisciplinary Chemistry |
In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η (eta). For example, η describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated (otherwise the κ-notation is used). In addition, if the ligand coordinates through multiple atoms that are contiguous then this is considered denticity (not hapticity), and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ (mu), which relates to bridging ligands. | 0 | Theoretical and Fundamental Chemistry |
The Lorentz force, named after Dutch physicist Hendrik Lorentz, for a charged particle q is given (in SI units) by the equation:
where qE describes the electric force due to a present electric field,E, acting on q.
<br>And qv x B describes the magnetic force due to a present magnetic field, B, acting on q when q is moving with velocity v.
<br>Which can also be written as:
where is the electric potential, and A is the magnetic vector potential.
It was Oliver Heaviside who is attributed in 1885 and 1889 to first deriving the correct expression for the Lorentz force of qv x B. Hendrik Lorentz derived and refined the concept in 1892 and gave it his name, incorporating forces due to electric fields.
<br>Rewriting this as the equation of motion for a free particle of charge q mass m,this becomes:
or
in the relativistic case using Lorentz contraction where γ is:
this equation of motion was first verified in 1897 in J. J. Thomson's experiment investigating cathode rays which confirmed, through bending of the rays in a magnetic field, that these rays were a stream of charged particles now known as electrons.
Variations on this basic formula describe the magnetic force on a current-carrying wire (sometimes called Laplace force), the electromotive force in a wire loop moving through a magnetic field (an aspect of Faraday's law of induction), and the force on a particle which might be traveling near the speed of light (relativistic form of the Lorentz force). | 0 | Theoretical and Fundamental Chemistry |
Common nomenclature uses the older names for some organic compounds instead of using the prefixes for the carbon skeleton above. The pattern can be seen below. | 0 | Theoretical and Fundamental Chemistry |
Suksin Lee (; 6 October 1896/7 – 12 December 1944) was a Korean biochemist and physician. He is considered a pioneer of biochemistry in Korea, having been the first Korean to obtain a Ph.D. and to hold a full-time professorship in that field. His studies of glucose metabolism and the chemical composition of common foods contributed to the scientific analysis of nutrition in the Korean diet. | 1 | Applied and Interdisciplinary Chemistry |
: The commonly used markers include simple sequence repeats (or microsatellites), single nucleotide polymorphisms (SNP). The process of identification of plant genotypes is known as genotyping.
Another area that is developing is genotyping by sequencing. | 1 | Applied and Interdisciplinary Chemistry |
The Joule–Thomson coefficient, , is of practical importance because the two end states of a throttling process () lie on a constant enthalpy curve. Although ideal gases, for which , do not change temperature in such a process, real gases do, and it is important in applications to know whether they heat up or cool down.
This coefficient can be found in terms of the previously described derivatives as,
so when is positive the gas temperature decreases when it passes through a throttle, and if it is negative the temperature increases. Therefore the condition defines a curve that separates the region of the plane where from the region where it is less than zero. This curve is called the inversion curve, and its equation is . Using the expression for derived previously for the van der Waals equation this is
Note that for there will be cooling for or in terms of the critical temperature . As Sommerfeld noted, "This is the case with air and with most other gases. Air can be cooled at will by repeated expansion and can finally be liquified."
The inversion curve can be found by solving its equation for , and substituting into the vdW equation. This produces , where, for simplicity, have been replaced by .
The maximum of this, quadratic, curve occurs, with , for
which gives , or , and the corresponding . The zeros of the inversion curve , are, making use of the quadratic formula, , or and ( and ). In terms of the dimensionless variables, the zeros are at and , while the maximum is , and occurs at . Note from Fig. 5 that there is an overlap between the saturation curve and the inversion curve plotted there.
This region is shown enlarged in the right hand graph of the figure. Therefore a van der Waals gas can be liquified by passing it through a throttle under the proper conditions; real gases are liquified in this way. | 0 | Theoretical and Fundamental Chemistry |
* Low-expansion foams, such as aqueous film forming foams (AFFFs), have an expansion ratio of less than 20, are low-viscosity, mobile, and can quickly cover large areas.
* Medium-expansion foams have an expansion ratio of 20–200.
* High-expansion foams have an expansion ratio over 200–1000 and are suitable for enclosed spaces such as hangars, where quick filling is needed.
* Alcohol-resistant foams contain a polymer that forms a protective layer between the burning surface and the foam, preventing foam breakdown by alcohols in the burning fuel. Alcohol-resistant foams are used in fighting fires of fuels containing oxygenates, e.g. methyl tert-butyl ether (MTBE), or fires of liquids based on or containing polar solvents. | 0 | Theoretical and Fundamental Chemistry |
Under certain conditions for some electrochemical cells, especially if they use an aqueous electrolyte, hydrogen ions can be converted into hydrogen atoms and H molecules. In the extreme case, bubbles of hydrogen gas might appear at one of the electrodes. If such a layer of hydrogen or even H gas bubbles appear on the positive plate of a battery, they interfere with the chemical action of the cell. An electrode covered with gases is said to be polarized. Polarization in galvanic cells causes the voltage and thus current to be reduced, especially if the bubbles cover a large fraction of a plate. Depolarizers are substances which are intended to remove the hydrogen, and therefore, they help to keep the voltage at a high level. However, this concept is outdated, since if enough depolarizer is present, it will react directly in most cases by getting electrons from the positive plate of the galvanic cell, i.e. there will be no relevant amount of hydrogen gas present. Therefore, the original concept of polarization does not apply to most batteries, and the depolarizer does not react with hydrogen as H. Still, the term is used today, however, in most cases, it might be replaced with oxidizing agent.
Many different substances have been used as depolarizers; the most notable are listed below. | 0 | Theoretical and Fundamental Chemistry |
Evapoporometry has the significant advantage of requiring only a lab scale, 2-propanol (or another wetting fluid), and a cell in which to contain the sample and 2-propanol. The sample is immersed for some time in 2-propanol prior to measurement to ensure saturation of pores, and is then placed into the cell in an analytical balance and immersed again in 2-propanol, after which the change in mass due to evaporation of the free-standing liquid layer and then draining of liquid from pores is measured by the analytical balance. Instantaneous evaporation rates are calculated from the mass data and input into the above equation to yield a pore-size distribution for the sample. can be used to quantitatively determine value of at which pore draining begins, which is equal to , where is the standard deviation of . This analysis is enabled by the principle that evaporation from small pores will only occur after 2-propanol in larger pores has completely evaporated.
It is important to note that there exists a nanoscale layer of wetting fluid on both the membrane and the test cell material known as the "t-layer," the mass of which is to be excluded from measurement to increase accuracy, otherwise these points may be incorrectly attributed to subnanometer pores. Akhondi et al describe methods for correction of the t-layers of the test cell and membrane, as well as a correction for swelling of membranes during the experiment. The correction for the t-layer of the test cell itself can be made by performing the evapoporometry procedure as described above with an empty test cell, integrating from the start point of pore draining until the point at which = 4 nm to yield the mass of the t-layer. This mass plus the mass of the membrane's t-layer will constitute the endpoint of pore diameter calculation for the principal evapoporometry measurement. | 0 | Theoretical and Fundamental Chemistry |
This way compares with to compare the effects of the imposed the change with and without moderation. The protocol prevents moderation by enforcing that through an adjustment and it observes the no-moderation response Provided that the observed response is indeed that then the principle states that .
In other words, change in the moderating state variable moderates the effect of the driving change in on the responding conjugate variable | 0 | Theoretical and Fundamental Chemistry |
In 1794, Anders Gustav Ekeberg began teaching at Uppsala. He was a supporter of Antoine Lavoisier's proposals for systematizing chemical nomenclature. In 1795 he and Pehr von Afzelius published the first article to introduce the modern names for chemical elements such as hydrogen, nitrogen, and oxygen into the Swedish language, "On the Present State of Chemical Sciences".
He was made docent in chemistry in 1794 and experimentator (laborator) in 1799, working as a demonstrator in the laboratory of Torbern Bergman. In 1798 he lectured on the theory of combustion.
In 1799, he was elected a member of the Royal Swedish Academy of Sciences.
Ekeberg had poor health throughout his life. During his childhood a severe cold had impaired his hearing, which was further weakened over the years, so that it hindered his teaching activities. Subsequently, a gas explosion blinded him in one eye.
Ekeberg was portrayed by his friends and students as a kind and gentle man. He died, unmarried, at the age of 46. | 1 | Applied and Interdisciplinary Chemistry |
Ankyrin repeat and kinase domain containing 1 (ANKK1) also known as protein kinase PKK2 or sugen kinase 288 (SgK288) is an enzyme that in humans is encoded by the ANKK1 gene. The ANKK1 is a member of an extensive family of the Ser/Thr protein kinase family, and protein kinase superfamily involved in signal transduction pathways. | 1 | Applied and Interdisciplinary Chemistry |
Emulsion stability refers to the ability of an emulsion to resist change in its properties over time. There are four types of instability in emulsions: flocculation, coalescence, creaming/sedimentation, and Ostwald ripening. Flocculation occurs when there is an attractive force between the droplets, so they form flocs, like bunches of grapes. This process can be desired, if controlled in its extent, to tune physical properties of emulsions such as their flow behaviour. Coalescence occurs when droplets bump into each other and combine to form a larger droplet, so the average droplet size increases over time. Emulsions can also undergo creaming, where the droplets rise to the top of the emulsion under the influence of buoyancy, or under the influence of the centripetal force induced when a centrifuge is used. Creaming is a common phenomenon in dairy and non-dairy beverages (i.e. milk, coffee milk, almond milk, soy milk) and usually does not change the droplet size. Sedimentation is the opposite phenomenon of creaming and normally observed in water-in-oil emulsions. Sedimentation happens when the dispersed phase is denser than the continuous phase and the gravitational forces pull the denser globules towards the bottom of the emulsion. Similar to creaming, sedimentation follows Stokes' law.
An appropriate surface active agent (or surfactant) can increase the kinetic stability of an emulsion so that the size of the droplets does not change significantly with time. The stability of an emulsion, like a suspension, can be studied in terms of zeta potential, which indicates the repulsion between droplets or particles. If the size and dispersion of droplets does not change over time, it is said to be stable. For example, oil-in-water emulsions containing mono- and diglycerides and milk protein as surfactant showed that stable oil droplet size over 28 days storage at 25 °C. | 0 | Theoretical and Fundamental Chemistry |
There are two different droplet collection schemes: the centrifugal approach and the linear collection scheme. The linear collector is considered to be simpler, more reliable and lighter.
Several different LDR configurations have been proposed and evaluated.
*The spiral LDR employs a generator and collector which rotate at the same angular velocity. This concept was considered more complex due to unnecessary rotation of the collector.
*The enclosed disc LDR contains a droplet generator at the center for creating a disc of droplets. Only the collector rotates. The entire radiator is enclosed by a transparent shroud, which minimizes spacecraft contamination resulting from any errant droplets. This concept was considered more complex due to unnecessary rotation of the collector.
*The annular LDR utilizes a rotating collector to capture an annular sheet of droplets from an annular generator. The annular LDR has an inefficient radiative performance – the sheet radiates to itself more than the droplet sheets of alternate configurations.
*Several proposed variations of the LDR utilize electric fields to control droplet trajectories as in the ink jet printer. The Electrostatic THermal (Energy) Radiator (ETHER) is essentially a proposed variation of the LDR. The droplets are charged and in conjunction with a charge on the spacecraft that is opposite the droplet charge, the droplets will execute a slightly elliptical orbit. This closed trajectory would reduce overall system size. This concept calls for concerns about droplet-plasma interactions. Further, in low Earth orbit the spacecraft will acquire its own potential.
Rectangular and triangular versions of the LDR have been investigated the most.
*The rectangular LDR employs a linear collector which is as wide as the droplet generator. The collector can be two sided, where two droplet sheets traveling in opposite directions impact a single collector. An alternate variation would utilize a one sided collector, with only one generator and droplet sheet. In a rectangular LDR, there is no focusing of the droplet sheet, and the droplet number density remains constant along the flight path. It is the simplest LDR design with the largest radiating area.
*The triangular LDR concept employs a droplet generator to form a converging stream array (sheet) of droplets. The collector, located at the convergence point of the droplet sheet, employs a centrifugal force to capture the droplets. The triangular LDR is inherently less massive, because of the smaller collector. System studies have indicated that a triangular LDR can be 40 percent less massive than a rectangular LDR. However, for any comparable size the triangular LDR has half the area of a rectangular sheet and therefore rejects less heat. Currently, the use of pitot tube pickups has replaced the initial complex rotating seals. Collisions in a focused droplet sheet result in coalescence of the impacting droplets. The triangular LDR is now being developed more extensively.
*The magnetically focused LDR employs a magnetic field to focus streams of droplets directed from the generator toward the collector, thereby assuring that essentially all of the droplets captured, even though some of the streams may be misdirected as they leave the generator. The magnetic focusing means is also effective to suppress splashing of liquid when the droplets impinge on the collector. The magnetically focused LDR was investigated and patented by the Brookhaven National Laboratory (BNL) under a grant by the Department of Energy (Contract DE-AC02-76CH00016). The magnetic means can be achieved with a toroidal shaped electro-magnet or permanent magnets. As only one side of the droplet sheet would be focused by a single permanent magnet, an even number has to be placed across each other adjacent to the collector. A permanent dipole magnet has limited field strength, hence limits radiator size. Electromagnets or (cryogenic cooled) superconducting magnets offer higher field strengths, but may have mass tradeoff. A major conclusion drawn from calculations is that a spacecraft can be maneuvered at accelerations less than 10 g. Higher accelerations require numerous smaller LDRs which will be more massive in the sum, but would to be more likely to survive. | 0 | Theoretical and Fundamental Chemistry |
Organ printing technology can also be combined with microfluidic technology to develop organs-on-chips. These organs-on-chips have the potential to be used for disease models, aiding in drug discovery, and performing high-throughput assays. Organ-on-chips work by providing a 3D model that imitates the natural extracellular matrix, allowing them to display realistic responses to drugs. Thus far, research has been focused on developing liver-on-a-chip and heart-on-a-chip, but there exists the potential to develop an entire body-on-a-chip model.
By combining 3D printed organs, researchers are able to create a body-on-a-chip. The heart-on-a-chip model has already been used to investigate how several drugs with heart rate-based negative side effects, such as the chemotherapeutic drug doxorubicin could affect people on an individual basis. The new body-on-a-chip platform includes liver, heart, lungs, and kidney-on-a-chip. The organs-on-a-chip are separately printed or constructed and then integrated together. Using this platform drug toxicity studies are performed in high throughput, lowering the cost and increasing the efficiency in the drug-discovery pipeline. | 1 | Applied and Interdisciplinary Chemistry |
Going back to Formula 2, calculation of the thermal contact conductance may prove difficult, even impossible, due to the difficulty in measuring the contact area, (A product of surface characteristics, as explained earlier). Because of this, contact conductance/resistance is usually found experimentally, by using a standard apparatus.
The results of such experiments are usually published in Engineering literature, on journals such as [http://scitation.aip.org/ASMEJournals/HeatTransfer/ Journal of Heat Transfer], [http://www.elsevier.com/wps/find/journaldescription.cws_home/210/description#description International Journal of Heat and Mass Transfer], etc. Unfortunately, a centralized database of contact conductance coefficients does not exist, a situation which sometimes causes companies to use outdated, irrelevant data, or not taking contact conductance as a consideration at all.
[http://sourceforge.net/projects/cocoe/ CoCoE] (Contact Conductance Estimator), a project founded to solve this problem and create a centralized database of contact conductance data and a computer program that uses it, was started in 2006. | 0 | Theoretical and Fundamental Chemistry |
Glycans, or polysaccharides, are instrumental in many facets of biology, from decorations on cell membranes being involved in cell signaling and interaction to post-translational modifications on proteins warranting function. Yet even though sugars are the most abundant class of organic molecules found on earth, the study of their structure and function are not as well known as other biological molecules such as proteins and ribonucleic acids. This is partly due to the fact that glycans have no direct biosynthetic template in the genome, as opposed to protein, and thus have not been as effectively elucidated by the age of genomics. Furthermore, the polymeric nature of glycans presents a challenge to study, as there are plethora of combinations of linkages (unlike in DNA and protein) and many different types of monosaccharides and isomers.
Seeing as glycans play a key role in the biology of organisms, translational glycobiology thus aims to utilize them both as targets for drugs or as drugs themselves. New or improved glycan products arise as more is learned about the complex biological and chemical roles glycans play, paralleled by advancements in the carbohydrate synthesis toolbox. | 1 | Applied and Interdisciplinary Chemistry |
Hyperthecosis, or ovarian hyperthecosis, is hyperplasia of the theca interna of the ovary. Hyperthecosis occurs when an area of luteinization occurs along with stromal hyperplasia. The luteinized cells produce androgens, which may lead to hirsutism and virilization (or masculinization) in affected women.
The term hyperthecosis refers to the presence of nests of luteinized theca cells in the ovarian stroma due to differentiation of the ovarian interstitial cells into steroidogenically active luteinized stromal cells. These nests or islands of luteinized theca cells are scattered throughout the stroma of the ovary, rather than being confined to areas around cystic follicles as in polycystic ovary syndrome (PCOS). These luteinized theca cells result in greater production of androgens.
Seen as a severe form of PCOS, the clinical features of hyperthecosis are similar to those of PCOS. Women with hyperthecosis often have more markedly elevated testosterone, more hirsutism, and are much more likely to be virilized. While elevated androgens in postmenopausal women is rare, hyperthecosis can present in both premenopausal or postmenopausal women. Women with hyperthecosis may or may not have always had underlying PCOS. | 1 | Applied and Interdisciplinary Chemistry |
The second description of the flow field state within the pipe is the turbulence intensity. According to an experiment in 1994, the metering errors may exist even when the velocity flow profile is fully developed with perfect pipe flow conditions. Conversely, it was found zero metering error at times when the velocity profile was not fully developed. Hence this behavior was referred to the turbulence intensity of the gas flow that can cause metering bias error. This behavior accounts in part for the less than adequate performance of the conventional tube bundle. | 1 | Applied and Interdisciplinary Chemistry |
Majeed returned to Pakistan in 1974 after India had conducted a surprise nuclear test, codenamed "Pokhran-I". At the Pakistan Institute of Nuclear Science and Technology (PINSTECH) he was assigned to the Nuclear Chemistry Division led by Iqbal Hussain Qureshi. In 1974, Majeed was a part of Munir Ahmad Khans team that had supervised the criticality of the second nuclear pile —PARR-II reactor. After the construction of the third nuclear pile—PARR-III, also known as The New-Labs; Majeed was the first technical director, and was part of a team that supervised the reactors criticality. An expert in plutonium technology, Majeed, as junior scientist, is known for his contribution in the plutonium reprocessing plant and plutonium nuclear fuel cycle technology. Majeed was also a part of a team at the New Labs that had succeeded in attaining fresh supplies of weapons-grade plutonium isotopes, produced by the reactor. In 1990, Majeed was promoted and was made Director-general of Nuclear Chemistry Division (NCD) by Munir Ahmad Khan. Throughout the 1990s, Majeed was responsible for underground work of the nuclear reactor Khushab-I, and the CHASNUPP-I commercial nuclear power plant. There, he was the director of Radiation and Nuclear Safety Division and was omitted from the weapons development teams.
He published extensively in the 1980s and 1990s on nuclear detectors and the use of x-ray diffraction, fluorescence, and crystallography to study a wide variety of materials and elements, including stainless steel, uranium, plutonium, and thorium. Due to his work for the State, he was conferred with the Tamgha-e-Imtiaz awarded by the Prime Minister of Pakistan, Nawaz Sharif, in 1998. | 0 | Theoretical and Fundamental Chemistry |
In the simplest case, one considers a two-layer fluid in which a slab of fluid with uniform density overlies a slab of fluid with uniform density . Arbitrarily the interface between the two layers is taken to be situated at The fluid in the upper and lower layers are assumed to be irrotational. So the velocity in each layer is given by the gradient of a velocity potential, and the potential itself satisfies Laplace's equation:
Assuming the domain is unbounded and two-dimensional (in the plane), and assuming the wave is periodic in with wavenumber the equations in each layer reduces to a second-order ordinary differential equation in . Insisting on bounded solutions the velocity potential in each layer is
and
with the amplitude of the wave and its angular frequency. In deriving this structure, matching conditions have been used at the interface requiring continuity of mass and pressure. These conditions also give the dispersion relation:
in which the reduced gravity is based on the density difference between the upper and lower layers:
with the Earth's gravity. Note that the dispersion relation is the same as that for deep water surface waves by setting | 1 | Applied and Interdisciplinary Chemistry |
In acidic medium, H ions and water are added to balance each half-reaction.
For example, when manganese reacts with sodium bismuthate.
:Unbalanced reaction: Mn + NaBiO → Bi +
:Oxidation: 4 HO + Mn → + 8 H + 5 e
:Reduction: 2 e + 6 H + → Bi + 3 HO
Finally, the reaction is balanced by multiplying the stoichiometric coefficients so the numbers of electrons in both half reactions match
:8 HO + 2 Mn → 2 + 16 H + 10 e
:10 e + 30 H + 5 → 5 Bi + 15 HO
and adding the resulting half reactions to give the balanced reaction:
:14 H + 2 Mn + 5 NaBiO → 7 HO + 2 + 5 Bi + 5 Na | 0 | Theoretical and Fundamental Chemistry |
Halothane was first synthesized by C. W. Suckling of Imperial Chemical Industries in 1951 at the ICI Widnes Laboratory and was first used clinically by M. Johnstone in Manchester in 1956. Initially, many pharmacologists and anaesthesiologists had doubts about the safety and efficacy of the new drug. But halothane, which required specialist knowledge and technologies for safe administration, also afforded British anaesthesiologists the opportunity to remake their speciality as a profession during a period, when the newly established National Health Service needed more specialist consultants. In this context, halothane eventually became popular as a nonflammable general anesthetic replacing other volatile anesthetics such as trichloroethylene, diethyl ether and cyclopropane. In many parts of the world it has been largely replaced by newer agents since the 1980s but is still widely used in developing countries because of its lower cost.
Halothane was given to many millions of people worldwide from its introduction in 1956 through the 1980s. Its properties include cardiac depression at high levels, cardiac sensitization to catecholamines such as norepinephrine, and potent bronchial relaxation. Its lack of airway irritation made it a common inhalation induction agent in pediatric anesthesia.
Its use in developed countries has been mostly replaced by newer anesthetic agents such as sevoflurane. It is not commercially available in the United States. | 0 | Theoretical and Fundamental Chemistry |
A rudimentary understanding of muscle tissue began to develop as early as 1835, when embryonic myogenesis was first described. In the 1860s, it was shown that muscle is capable of regeneration and an experimental regeneration was conducted to better understand the specific method by which this was done in vivo. Following this discovery, muscle generation and degeneration in man were described for the first time. Researchers consequently assessed several aspects of muscle regeneration in vivo, including "the continuous or discontinuous regeneration depending on tissue type" to increase functional understanding of the phenomena. It was not until the 1960s, however, that researchers determined what components were required for muscle regeneration. | 1 | Applied and Interdisciplinary Chemistry |
The first step in understanding the chemistry of freshwater is to establish the relevant concentrations of the parameters of interest. Conventionally this is done by taking representative samples of the water for subsequent analysis in a laboratory. However, in-situ monitoring using hand-held analytical equipment or using bank-side monitoring stations are also used. | 1 | Applied and Interdisciplinary Chemistry |
Superfluid is the state of matter that exhibits frictionless flow, zero viscosity, also known as inviscid flow.
To date, helium is the only fluid to exhibit superfluidity that has been discovered. Helium-4 becomes a superfluid once it is cooled to below 2.2K, a point known as the lambda point. At temperatures above the lambda point, helium exists as a liquid exhibiting normal fluid dynamic behavior. Once it is cooled to below 2.2K it begins to exhibit quantum behavior. For example, at the lambda point there is a sharp increase in heat capacity, as it is continued to be cooled, the heat capacity begins to decrease with temperature. In addition, the thermal conductivity is very large, contributing to the excellent coolant properties of superfluid helium. Similarly, Helium-3 is found become a superfluid at 2.491mK. | 1 | Applied and Interdisciplinary Chemistry |
Caesium-137, along with other radioactive isotopes caesium-134, iodine-131, xenon-133, and strontium-90, were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Chernobyl disaster and the Fukushima Daiichi disaster.
Caesium-137 in the environment is substantially anthropogenic (human-made). Caesium-137 is produced from the nuclear fission of plutonium and uranium, and decays into barium-137. By observing the characteristic gamma rays emitted by this isotope, one can determine whether the contents of a given sealed container were made before or after the first atomic bomb explosion (Trinity test, 16 July 1945), which spread some of it into the atmosphere, quickly distributing trace amounts of it around the globe. This procedure has been used by researchers to check the authenticity of certain rare wines, most notably the purported "Jefferson bottles". Surface soils and sediments are also dated by measuring the activity of Cs. | 0 | Theoretical and Fundamental Chemistry |
*Assess kidney function before and during treatment where appropriate.
*Renovascular hypertension
*Surgery/anesthesia
*An analysis on the PROGRESS trial showed that perindopril has key benefits in reducing cardiovascular events by 30% in patients with chronic kidney disease defined as a CrCl <60ml/min. A 2016 and 2017 meta-analysis review looking at ACE inhibitors demonstrated a reduction in cardiovascular events but also slowed the decline of renal failure by 39% when compared to placebo. These studies included patients with moderate to severe kidney disease and those on dialysis.
*Its renoprotective benefits of decreasing blood pressure and removing filtration pressure is highlighted in a 2016 review. ACE inhibitor can result in an initial increase of serum creatinine, but mostly returns to baseline in a few weeks in majority of patients. It has been suggested that increased monitoring, especially in advanced kidney failure, will minimise any related risk and improve long-term benefits.
*Use cautiously in patients with sodium or volume depletion due to potential excessive hypotensive effects of renin-angiotensin blockade causing symptomatic hypotension. Careful monitoring or short-term dose reduction of diuretics prior to commencing perindopril is recommended to prevent this potential effect. A diuretic may later be given in combination if necessary; potassium-sparing diuretics are not recommended in combination with perindopril due to the risk of hyperkalaemia.
*Combination with neuroleptics or imipramine-type drugs may increase the blood pressure lowering effect. Serum lithium concentrations may rise during lithium therapy. | 0 | Theoretical and Fundamental Chemistry |
Switzerland built an extensive network of fallout shelters, not only through extra hardening of government buildings such as schools, but also through a building regulation requiring nuclear shelters in residential buildings since the 1960s (the first legal basis in this sense dates from 4 October 1963). Later, the law ensured that all residential buildings built after 1978 contained a nuclear shelter able to withstand a blast from a 12-megaton explosion at a distance of 700 metres. The Federal Law on the Protection of the Population and Civil Protection still requires that every inhabitant should have a place in a shelter close to where they live.
The Swiss authorities maintained large communal shelters (such as the Sonnenberg Tunnel until 2006) stocked with over four months of food and fuel. The reference Nuclear War Survival Skills declared that, as of 1986, "Switzerland has the best civil defense system, one that already includes blast shelters for over 85% of all its citizens." As of 2006, there were about 300,000 shelters built in private residences, institutions and hospitals, as well as 5,100 public shelters for a total of 8.6 million places, a level of coverage equal to 114% of the population.
In Switzerland, most residential shelters are no longer stocked with the food and water required for prolonged habitation and a large number have been converted by the owners to other uses (e.g., wine cellars, ski rooms, gyms). But the owner still has the obligation to ensure the maintenance of the shelter. | 0 | Theoretical and Fundamental Chemistry |
with:
*σ is surface tension of the mixture
*σ is surface tension of pure water
*a is component specific constant (see table below)
*x is mole fraction of the solvated component
The equation can be rearranged to be explicit in a:
This allows the direct calculation of that component specific parameter a from experimental data.
The equation can also be written as:
with:
*γ is surface tension of the mixture
*γ is surface tension of pure water
*R is ideal gas constant 8.31 J/(mol*K)
*T is temperature in K
*ω is cross-sectional area of the surfactant molecules at the surface
The surface tension of pure water is dependent on temperature. At room temperature (298 K), it is equal to 71.97 mN/m | 0 | Theoretical and Fundamental Chemistry |
Empirical correlations are simple mathematical expressions intended to approximate a liquid's properties over a range of experimental conditions, such as varying temperature and pressure. They are constructed by fitting simple functional forms to experimental data. For example, the temperature-dependence of liquid viscosity is sometimes approximated by the function , where and are fitting constants. Empirical correlations allow for extremely efficient estimates of physical properties, which can be useful in thermophysical simulations. However, they require high quality experimental data to obtain a good fit and cannot reliably extrapolate beyond the conditions covered by experiments. | 0 | Theoretical and Fundamental Chemistry |
During his years working as a physician Michaelis a friend (Peter Rona) built a compact lab, in the hospital, and over the course of five years – Michaelis successfully became published over 100 times. During his research in the hospital, he was the first to view the different types of inhibition; specifically using fructose and glucose as inhibitors of maltase activity. Maltase breaks maltose into two units of glucose. Findings from that experiment allowed for the divergence of non-competitive and competitive inhibition. Non-competitive inhibition affects the k value (but not the K) on any given graph; this inhibitor binds to a site that has specificity for the certain molecule. Michaelis determined that when the inhibitor is bound, the enzyme would become inactivated.
Like many other scientists of their time, Leonor Michaelis and Maud Menten worked on a reaction that was used to change the composition of sucrose and make it lyse into two products – fructose and glucose. The enzyme involved in this reaction is called invertase, and it is the enzyme the kinetics of which have been supported by Michaelis and Menten to be revolutionary for the kinetics of other enzymes. While expressing the rate of the reaction studied, they derived an equation that described the rate in a way which suggested that it is mostly dependent on the enzyme concentration, as well as on presence of the substrate, but only to a certain extent.
Adrian Brown and Victor Henri laid the groundwork for the discoveries in enzyme kinetics that Michaelis and Menten are known for. Brown theoretically envisioned the mechanism now accepted for enzyme kinetics, but did not have the quantitative data to make a claim. Victor Henri made significant contributions to enzyme kinetics during his doctoral thesis, however he lacked noting the importance of hydrogen ion concentration and mutarotation of glucose. The goal of Henris thesis was to compare his knowledge of enzyme-catalysed reactions to the recognized laws of physical chemistry. Henri is credited with being the first to write the equation that is now known as the Michaelis-Menten equation. Using glucose and fructose in the catalytic reactions controlled by maltase and invertase, Leonor Michaelis was the first scientist to distinguish the different types of inhibition by using the pH scale which did not exist in Henris time.
Particularly during their work on describing the rate of this reaction they also tested and extrapolated on the idea of another scientist, Victor Henri, that enzyme they were using had some affinity for both products of this reaction – fructose and glucose. Using Henris methods, Michaelis and Menten nearly perfected this concept of initial-rate method for steady-state experiments. They were studying inhibition when they found that non-competitive (mixed) inhibition is characterized by its effect on k (catalyst rate) while competitive is characterized by its effect on velocity (V). In the Michaelis and Menten experiments they heavily focused on pH effects of invertase using hydrogen ions. Invertase is an enzyme found in extracellular yeast and catalyzed reactions by hydrolysis or inverting a sucrose (mixture of sucrose and fructose) to “invert sugar.” The main reason for using invertase was that it could be easily assayed and experiments could be done in quicker manner. Sucrose rotates in polarimeter as dextroratatory-D whereas invert sugar is levorotatory-L. This made tracking the inversion of sugar relatively simple. They also found that α-D-glucose is released in reactions catalyzed by invertase which is very unstable and spontaneously changes to β-D-glucose. Although, these are both in the dextrorotatory form, this is where they noted that glucose can change spontaneously, also known as mutarotation. Failing to take this into consideration was one of the main reasons Henris experiments fell short. Using invertase to catalyze sucrose inversion, they could see how fast the enzyme was reacting by polarimetry; therefore, non-competitive inhibition was found to occur in the reaction where sucrose was inverted with invertase. | 1 | Applied and Interdisciplinary Chemistry |
Most of the air—including ~88% of the CO—is located in the lower part of the atmosphere known as troposphere. The troposphere is thicker in the equator and thinner at the poles, but the global mean of its thickness is around 11 km.
Inside the troposphere, the temperature drops approximately linearly at a rate of 6.5 Celsius degrees per km, from a global mean of 288 Kelvin (15 Celsius) on the ground to 220 K (-53 Celsius). At higher altitudes, up to 20 km, the temperature is approximately constant; this layer is called the tropopause.
The troposphere and tropopause together consist of ~99% of the atmospheric CO. Inside the troposphere, the CO drops with altitude approximately exponentially, with a typical length of 6.3 km; this means that the density at height y is approximately proportional to exp(-y/6.3 km), and it goes down to 37% at 6.3 km, and to 17% at 11 km. Higher through the tropopause, density continues dropping exponentially, albeit faster, with a typical length of 4.2 km. | 1 | Applied and Interdisciplinary Chemistry |
The first attempt for the total synthesis of hydrastine was reported by Sir Robert Robinson and co-workers in 1931. Following studies where the synthesis of the key lactonic amide intermediate (structure 4 in figure) was the most troublesome, the major breakthrough was achieved in 1981 when J. R. Falck and co-workers reported a four-step total synthesis of hydrastine from simple starting materials. The key step in the Falck synthesis was using a Passerini reaction to construct the lactonic amide intermediate 4.
Starting from a simple phenylbromide variant 1, alkylation reaction with lithium methylisocyanide gives the isocyanide intermediate 2. Reacting isocyanide intermediate 2 with opianic acid 3 initiated the intramolecular Passerini reaction to give the key lactonic amide intermediate 4. The tetrahydro-isoquinolin ring was formed by first a ring-closure reaction under dehydration conditions using POCl3 and then a catalyzed hydrogenation using PtO2 as the catalyst. Finally, hydrastine was synthesized by installing the N-methyl group via reductive amination reaction with formaldehyde. | 0 | Theoretical and Fundamental Chemistry |
Cryobiology is a bimonthly peer-reviewed scientific journal covering cryobiology. It was established in 1964 and is published by Elsevier on behalf of the Society for Cryobiology, of which it is the official journal. The editor-in-chief is D.M. Rawson (University of Bedfordshire). According to the Journal Citation Reports, the journal has a 2017 impact factor of 2.050. | 1 | Applied and Interdisciplinary Chemistry |
In principle, full genome sequencing can provide the raw nucleotide sequence of an individual organism's DNA at a single point in time. However, further analysis must be performed to provide the biological or medical meaning of this sequence, such as how this knowledge can be used to help prevent disease. Methods for analyzing sequencing data are being developed and refined.
Because sequencing generates a lot of data (for example, there are approximately six billion base pairs in each human diploid genome), its output is stored electronically and requires a large amount of computing power and storage capacity.
While analysis of WGS data can be slow, it is possible to speed up this step by using dedicated hardware. | 1 | Applied and Interdisciplinary Chemistry |
In the Hunsdiecker reaction, carboxylic acids are converted to organic halide, whose carbon chain is shortened by one carbon atom with respect to the carbon chain of the particular carboxylic acid. The carboxylic acid is first converted to its silver salt, which is then oxidized with halogen:
Many organometallic compounds react with halogens to give the organic halide: | 0 | Theoretical and Fundamental Chemistry |
As a consequence of low receptivity, C NMR spectroscopy suffers from complications not encountered in proton NMR spectroscopy. Many measures can be implemented to compensate for the low receptivity of this nucleus. For example, high field magnets with internal bores are capable of accepting larger sample tubes (typically 10 mm in diameter for C NMR versus 5 mm for H NMR). Relaxation reagents allow more rapid pulsing. A typical relaxation agent is chromium(III) acetylacetonate. For a typical sample, recording a C NMR spectrum may require several hours, compared to 15–30 minutes for H NMR. The nuclear dipole is weaker, the difference in energy between alpha and beta states is one-quarter that of proton NMR, and the Boltzmann population difference is correspondingly less. One final measure to compensate for low receptivity is isotopic enrichment.
Some NMR probes, called cryoprobes, offer 20x signal enhancement relative to ordinary NMR probes. In cryoprobes, the RF generating and receiving electronics are maintained at ~ 25K using helium gas, which greatly enhances their sensitivity. The trade-off is that cryoprobes are costly. | 0 | Theoretical and Fundamental Chemistry |
Surface plasmon resonance (SPR) has been widely used for measuring protein adsorption with high sensitivity. This technique is based on the excitation of surface plasmons, longitudinal electromagnetic waves originated at the interface between metals and dielectrics. The deposition on the conducting surface of molecules and thin layers within 200 nm modifies the dielectric properties of the system and thus the SPR response, signaling the presence of molecules on a metal surface. | 1 | Applied and Interdisciplinary Chemistry |
In an open system, there is an exchange of energy and matter between the system and the surroundings. The presence of reactants in an open beaker is an example of an open system. Here the boundary is an imaginary surface enclosing the beaker and reactants. It is named closed, if borders are impenetrable for substance, but allow transit of energy in the form of heat, and isolated, if there is no exchange of heat and substances. The open system cannot exist in the equilibrium state. To describe deviation of the thermodynamic system from equilibrium, in addition to constitutive variables that was described above, a set of internal variables have been introduced. The equilibrium state is considered to be stable and the main property of the internal variables, as measures of non-equilibrium of the system, is their trending to disappear; the local law of disappearing can be written as relaxation equation for each internal variable
where is a relaxation time of a corresponding variable. It is convenient to consider the initial value equal to zero.
The specific contribution to the thermodynamics of open non-equilibrium systems was made by Ilya Prigogine, who investigated a system of chemically reacting substances. In this case the internal variables appear to be measures of incompleteness of chemical reactions, that is measures of how much the considered system with chemical reactions is out of equilibrium. The theory can be generalized, to consider any deviations from the equilibrium state, such as structure of the system, gradients of temperature, difference of concentrations of substances and so on, to say nothing of degrees of completeness of all chemical reactions, to be internal variables.
The increments of Gibbs free energy and entropy at and are determined as
The stationary states of the system exist due to exchange of both thermal energy and a stream of particles. The sum of the last terms in the equations presents the total energy coming into the system with the stream of particles of substances that can be positive or negative; the quantity is chemical potential of substance . The middle terms in equations (2) and (3) depict energy dissipation (entropy production) due to the relaxation of internal variables , while are thermodynamic forces.
This approach to the open system allows describing the growth and development of living objects in thermodynamic terms. | 0 | Theoretical and Fundamental Chemistry |
Based on the IUPAC definition, radical polymerization is a chain polymerization in which the kinetic-chain carriers are radicals. Usually, the growing chain end bears an unpaired electron. Free radicals can be initiated by many methods such as heating, redox reactions, ultraviolet radiation, high energy irradiation, electrolysis, sonication, and plasma.
Free radical polymerization is very important in polymer chemistry. It is one of the most developed methods in chain-growth polymerization. Currently, most polymers in our daily life are synthesized by free radical polymerization, including polyethylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, styrene butadiene rubber, nitrile rubber, neoprene, etc. | 0 | Theoretical and Fundamental Chemistry |
In information theory, the Kraft–McMillan theorem establishes that any directly decodable coding scheme for coding a message to identify one value out of a set of possibilities can be seen as representing an implicit probability distribution over , where is the length of the code for in bits. Therefore, relative entropy can be interpreted as the expected extra message-length per datum that must be communicated if a code that is optimal for a given (wrong) distribution is used, compared to using a code based on the true distribution : it is the excess entropy.
where is the cross entropy of and , and is the entropy of (which is the same as the cross-entropy of P with itself).
The relative entropy can be thought of geometrically as a statistical distance, a measure of how far the distribution is from the distribution . Geometrically it is a divergence: an asymmetric, generalized form of squared distance. The cross-entropy is itself such a measurement (formally a loss function), but it cannot be thought of as a distance, since is not zero. This can be fixed by subtracting to make agree more closely with our notion of distance, as the excess loss. The resulting function is asymmetric, and while this can be symmetrized (see ), the asymmetric form is more useful. See for more on the geometric interpretation.
Relative entropy relates to "rate function" in the theory of large deviations.
Arthur Hobson proved that relative entropy is the only measure of difference between probability distributions that satisfies some desired properties, which are the canonical extension to those appearing in a commonly used characterization of entropy. Consequently, mutual information is the only measure of mutual dependence that obeys certain related conditions, since it can be defined in terms of Kullback–Leibler divergence. | 0 | Theoretical and Fundamental Chemistry |
We will consider the fundamentals of the MUSCL scheme by considering the following simple first-order, scalar, 1D system, which is assumed to have a wave propagating in the positive direction,
Where represents a state variable and represents a flux variable.
The basic scheme of Godunov uses piecewise constant approximations for each cell, and results in a first-order upwind discretisation of the above problem with cell centres indexed as . A semi-discrete scheme can be defined as follows,
This basic scheme is not able to handle shocks or sharp discontinuities as they tend to become smeared. An example of this effect is shown in the diagram opposite, which illustrates a 1D advective equation with a step wave propagating to the right. The simulation was carried out with a mesh of 200 cells and used a 4th order Runge–Kutta time integrator (RK4).
To provide higher resolution of discontinuities, Godunovs scheme can be extended to use piecewise linear approximations of each cell, which results in a central difference scheme that is second-order' accurate in space. The piecewise linear approximations are obtained from
Thus, evaluating fluxes at the cell edges we get the following semi-discrete scheme
where and are the piecewise approximate values of cell edge variables, i.e.,
Although the above second-order scheme provides greater accuracy for smooth solutions, it is not a total variation diminishing (TVD) scheme and introduces spurious oscillations into the solution where discontinuities or shocks are present. An example of this effect is shown in the diagram opposite, which illustrates a 1D advective equation , with a step wave propagating to the right. This loss of accuracy is to be expected due to Godunov's theorem. The simulation was carried out with a mesh of 200 cells and used RK4 for time integration.
MUSCL based numerical schemes extend the idea of using a linear piecewise approximation to each cell by using slope limited left and right extrapolated states. This results in the following high resolution, TVD discretisation scheme,
Which, alternatively, can be written in the more succinct form,
The numerical fluxes correspond to a nonlinear combination of first and second-order approximations to the continuous flux function.
The symbols and represent scheme dependent functions (of the limited extrapolated cell edge variables), i.e.,
where, using downwind slopes:
and
The function is a limiter function that limits the slope of the piecewise approximations to ensure the solution is TVD, thereby avoiding the spurious oscillations that would otherwise occur around discontinuities or shocks - see Flux limiter section. The limiter is equal to zero when and is equal to unity when . Thus, the accuracy of a TVD discretization degrades to first order at local extrema, but tends to second order over smooth parts of the domain.
The algorithm is straight forward to implement. Once a suitable scheme for has been chosen, such as the Kurganov and Tadmor scheme (see below), the solution can proceed using standard numerical integration techniques. | 1 | Applied and Interdisciplinary Chemistry |
Electromigration decreases the reliability of integrated circuits (ICs). It can cause the eventual loss of connections or failure of a circuit. Since reliability is critically important for space travel, military purposes, anti-lock braking systems, medical equipment like Automated External Defibrillators and is even important for personal computers or home entertainment systems, the reliability of chips (ICs) is a major focus of research efforts.
Due to difficulty of testing under real conditions, Black's equation is used to predict the life span of integrated circuits.
To use Blacks equation, the component is put through high temperature operating life (HTOL) testing. The components expected life span under real conditions is extrapolated from data gathered during the testing.
Although electromigration damage ultimately results in failure of the affected IC, the first symptoms are intermittent glitches, and are quite challenging to diagnose. As some interconnects fail before others, the circuit exhibits seemingly random errors, which may be indistinguishable from other failure mechanisms (such as electrostatic discharge damage). In a laboratory setting, electromigration failure is readily imaged with an electron microscope, as interconnect erosion leaves telltale visual markers on the metal layers of the IC.
With increasing miniaturization, the probability of failure due to electromigration increases in VLSI and ULSI circuits because both the power density and the current density increase. Specifically, line widths will continue to decrease over time, as will wire cross-sectional areas. Currents are also reduced due to lower supply voltages and shrinking gate capacitances. However, as current reduction is constrained by increasing frequencies, the more marked decrease in cross-sectional areas (compared to current reduction) will give rise to increased current densities in ICs going forward.
In advanced semiconductor manufacturing processes, copper has replaced aluminium as the interconnect material of choice. Despite its greater fragility in the fabrication process, copper is preferred for its superior conductivity. It is also intrinsically less susceptible to electromigration. However, electromigration (EM) continues to be an ever-present challenge to device fabrication, and therefore the EM research for copper interconnects is ongoing (though a relatively new field).
In modern consumer electronic devices, ICs rarely fail due to electromigration effects. This is because proper semiconductor design practices incorporate the effects of electromigration into the ICs layout. Nearly all IC design houses use automated EDA tools to check and correct electromigration problems at the transistor layout-level. When operated within the manufacturers specified temperature and voltage range, a properly designed IC device is more likely to fail from other (environmental) causes, such as cumulative damage from gamma-ray bombardment.
Nevertheless, there have been documented cases of product failures due to electromigration. In the late 1980s, one line of Western Digitals desktop drives suffered widespread, predictable failure 12–18 months after field usage. Using forensic analysis of the returned bad units, engineers identified improper design-rules in a third-party suppliers IC controller. By replacing the bad component with that of a different supplier, WD was able to correct the flaw, but not before significant damage to the company's reputation.
Electromigration can be a cause of degradation in some power semiconductor devices such as low voltage power MOSFETs, in which the lateral current through the source contact metallisation (often aluminium) can reach the critical current densities during overload conditions. The degradation of the aluminium layer causes an increase in on-state resistance, and can eventually lead to complete failure. | 0 | Theoretical and Fundamental Chemistry |
Calmodulin is a small, highly conserved protein that is 148 amino acids long (16.7 kDa). The protein has two approximately symmetrical globular domains (the N- and C- domains) each containing a pair of EF hand motifs separated by a flexible linker region for a total of four Ca binding sites, two in each globular domain. In the Ca-free state, the helices that form the four EF-hands are collapsed in a compact orientation, and the central linker is disordered; in the Ca-saturated state, the EF-hand helices adopt an open orientation roughly perpendicular to one another, and the central linker forms an extended alpha-helix in the crystal structure, but remains largely disordered in solution. The C-domain has a higher binding affinity for Ca than the N-domain.
Calmodulin is structurally quite similar to troponin C, another Ca-binding protein containing four EF-hand motifs. However, troponin C contains an additional alpha-helix at its N-terminus, and is constitutively bound to its target, troponin I. It therefore does not exhibit the same diversity of target recognition as does calmodulin. | 1 | Applied and Interdisciplinary Chemistry |
Because there are no known naturally occurring deoxyribozymes, most known deoxyribozyme sequences have been discovered through a high-throughput in vitro selection technique, similar to SELEX.
in vitro selection utilizes a "pool" of a large number of random DNA sequences (typically 10–10 unique strands) that can be screened for a specific catalytic activity. The pool is synthesized through solid phase synthesis such that each strand has two constant regions (primer binding sites for PCR amplification) flanking a random region of a certain length, typically 25–50 bases long. Thus the total number of unique strands, called the sequence space, is 4 where N denotes the number of bases in the random region. Because 4 ≈ 10, there is no practical reason to choose random regions of less than 25 bases in length, while going above this number of bases means that the total sequence space cannot be surveyed. However, since there are likely many potential candidates for a given catalytic reaction within the sequence space, random regions of 50 and even higher have successfully yielded catalytic deoxyribozymes.
The pool is first subjected to a selection step, during which the catalytic strands are separated from the non-catalytic strands. The exact separation method will depend on the reaction being catalyzed. As an example, the separation step for ribonucleotide cleavage often utilizes affinity chromatography, in which a biological tag attached to each DNA strand is removed from any catalytically active strands via cleavage of a ribonucleotide base. This allows the catalytic strands to be separated by a column that specifically binds the tag, since the non-active strands will remain bound to the column while the active strands (which no longer possess the tag) flow through. A common set-up for this is a biotin tag with a streptavidin affinity column. Gel electrophoresis based separation can also be used in which the change in molecular weight of strands upon the cleavage reaction is enough to cause a shift in the location of the reactive strands on the gel. After the selection step, the reactive pool is amplified via polymerase chain reaction (PCR) to regenerate and amplify the reactive strands, and the process is repeated until a pool of sufficient reactivity is obtained. Multiple rounds of selection are required because some non-catalytic strands will inevitably make it through any single selection step. Usually 4–10 rounds are required for unambiguous catalytic activity, though more rounds are often necessary for more stringent catalytic conditions. After a sufficient number of rounds, the final pool is sequenced and the individual strands are tested for their catalytic activity. The dynamics of the pool can be described through mathematical modeling, which shows how oligonucleotides undergo competitive binding with the targets and how the evolutionary outcome can be improved through fine tuning of parameters.
Deoxyribozymes obtained through in vitro selection will be optimized for the conditions during the selection, such as salt concentration, pH, and the presence of cofactors. Because of this, catalytic activity only in the presence of specific cofactors or other conditions can be achieved using positive selection steps, as well as negative selection steps against other undesired conditions. | 0 | Theoretical and Fundamental Chemistry |
Marco Fontani (born 5 May 1969 in Florence) is a chemist and chemistry historian, author of over 120 publications in materials chemistry, organometallic chemistry, electrochemistry and the history of chemistry. He is also a member of the board of directors of the Italian National Society of History of Chemistry (Gruppo Nazionale di Storia e Fondamenti della Chimica).
He wrote the books: The Lost Elements: The Periodic Tables Shadow Side and Chemistry and Chemists in Florence: From the Last of the Medici Family to the European Magnetic Resonance Center'. Both edited in Italian and English.
He has been working at the Department of Organic Chemistry at the University of Florence since 2003. | 1 | Applied and Interdisciplinary Chemistry |
The gradient of the line between any two points on a Frost diagram gives the potential for the reaction. A species that lies in a peak, above the gradient of the two points on either side, denotes a species unstable with respect to disproportionation, and a point that falls below the gradient of the line joining its two adjacent points lies in a thermodynamic sink, and is intrinsically stable. | 0 | Theoretical and Fundamental Chemistry |
Honorary Membership of the Czech Society for Mass Spectrometry; Lifetime Achievement Award in Chromatography by the LC-GC Magazine, Europe; Giorgio Nota Award, Italian Chemical Society; Heyrovsky Medal in Chemical Sciences, Prague, Czech Republic. | 0 | Theoretical and Fundamental Chemistry |
In astrophysics and nuclear physics, nuclear pasta is a theoretical type of degenerate matter that is postulated to exist within the crusts of neutron stars. If it exists, nuclear pasta would be the strongest material in the universe. Between the surface of a neutron star and the quark–gluon plasma at the core, at matter densities of 10 g/cm, nuclear attraction and Coulomb repulsion forces are of comparable magnitude. The competition between the forces leads to the formation of a variety of complex structures assembled from neutrons and protons. Astrophysicists call these types of structures nuclear pasta because the geometry of the structures resembles various types of pasta. | 0 | Theoretical and Fundamental Chemistry |
The solidifying behavior depends on the alloy composition. Pure metals solidify at a certain temperature, forming crystals of one phase. Eutectic alloys also solidify at a single temperature, all components precipitating simultaneously in so-called coupled growth. Non-eutectic compositions on cooling start to first precipitate the non-eutectic phase; dendrites when it is a metal, large crystals when it is an intermetallic compound. Such a mixture of solid particles in a molten eutectic is referred to as a mushy state. Even a relatively small proportion of solids in the liquid can dramatically lower its fluidity.
The temperature of total solidification is the solidus of the alloy, the temperature at which all components are molten is the liquidus.
The mushy state is desired where a degree of plasticity is beneficial for creating the joint, allowing filling larger gaps or being wiped over the joint (e.g. when soldering pipes). In hand soldering of electronics it may be detrimental as the joint may appear solidified while it is not yet. Premature handling of such joint then disrupts its internal structure and leads to compromised mechanical integrity. | 1 | Applied and Interdisciplinary Chemistry |
A calculation of the β emission decay rate is quite different from a calculation of α decay. In α decay the nucleons of the original nucleus are used to form the final state α particle (He). In β decay the β and neutrino particles are the result of a nucleon transformation into its isospin complement ( or ). Below is a list of the differences:
#The β electron and neutrino did not exist before the decay.
#The β electron and neutrino are relativistic (nuclear decay energy is usually not enough to make heavy α nucleus relativistic).
#The light decay products can have continuous energy distributions. (before assuming the α carried away most of the energy was usually a good approximation).
The β decay rate calculation was developed by Fermi in 1934 and was based on Pauli's neutrino hypothesis.
Fermis Golden Rule says that the transition rate is given by a transition matrix element (or "amplitude") weighted by the phase space and Plancks constant such that
From this analysis we can conclude that the Gamow–Teller nuclear transition from 0 → ±1 is a weak perturbation of the system's interaction Hamiltonian. This assumption appears to be true based on the very short time scale (10 s) it takes for the formation of quasi-stationary nuclear states compared with the time it takes for a β decay (half lives ranging from seconds to days).
The matrix element between parent and daughter nuclei in such a transition is:
with the interaction Hamiltonian forming 2 separate states from the perturbation. | 0 | Theoretical and Fundamental Chemistry |
Support for the Bulletin of the Chemical Society of Japan (BCSJ) began in 1926. Other publications of the society include:
* Bioscience, Biotechnology, and Biochemistry
* Chemistry Letters | 1 | Applied and Interdisciplinary Chemistry |
The hexahydrate consists of octahedral cation centers and chloride anions () as counterions. Hydrogen bonds link the cation and anions.
The hydrated form of aluminium chloride has an octahedral molecular geometry, with the central aluminium ion surrounded by six water ligand molecules. Being coordinatively saturated, the hydrate is of little value as a catalyst in Friedel-Crafts alkylation and related reactions. | 0 | Theoretical and Fundamental Chemistry |
Controversy about, and shortages of, injected HCG for weight loss have led to substantial Internet promotion of "homeopathic HCG" for weight control. The ingredients in these products are often obscure, but if prepared from true HCG via homeopathic dilution, they contain either no HCG at all or only trace amounts. Moreover, it is highly unlikely that oral HCG is bioavailable due to the fact that digestive protease enzymes and hepatic metabolism renders peptide-based molecules (such as insulin and human growth hormone) biologically inert. HCG can likely only enter the bloodstream through injection.
The United States Food and Drug Administration has stated that over-the-counter products containing HCG are fraudulent and ineffective for weight loss. They are also not protected as homeopathic drugs and have been deemed illegal substances. HCG is classified as a prescription drug in the United States and it has not been approved for over-the-counter sales by the FDA as a weight loss product or for any other purposes, and therefore neither HCG in its pure form nor any preparations containing HCG may be sold legally in the country except by prescription. In December 2011, FDA and FTC started to take actions to pull unapproved HCG products from the market. In the aftermath, some suppliers started to switch to "hormone-free" versions of their weight loss products, where the hormone is replaced with an unproven mixture of free amino acids or where radionics is used to transfer the "energy" to the final product. | 1 | Applied and Interdisciplinary Chemistry |
The Buchner–Curtius–Schlotterbeck reaction is the reaction of aldehydes or ketones with aliphatic diazoalkanes to form homologated ketones. It was first described by Eduard Buchner and Theodor Curtius in 1885 and later by Fritz Schlotterbeck in 1907. Two German chemists also preceded Schlotterbeck in discovery of the reaction, Hans von Pechmann in 1895 and Viktor Meyer in 1905. The reaction has since been extended to the synthesis of β-keto esters from the condensation between aldehydes and diazo esters. The general reaction scheme is as follows:
The reaction yields two possible carbonyl compounds (I and II) along with an epoxide (III). The ratio of the products is determined by the reactant used and the reaction conditions. | 0 | Theoretical and Fundamental Chemistry |
Superhydrophobic coatings can be made from many different materials. The following are known possible bases for the coating:
* Manganese oxide polystyrene (MnO/PS) nano-composite
* Zinc oxide polystyrene (ZnO/PS) nano-composite
* Precipitated calcium carbonate
* Carbon nano-tube structures
* Silica nano-coating
* Fluorinated silanes and Fluoropolymer coatings.
The silica-based coatings are perhaps the most cost effective to use. They are gel-based and can be easily applied either by dipping the object into the gel or via aerosol spray. In contrast, the oxide polystyrene composites are more durable than the gel-based coatings, however the process of applying the coating is much more involved and costly. Carbon nano-tubes are also expensive and difficult to produce with current technology. Thus, the silica-based gels remain the most economically viable option at present. | 0 | Theoretical and Fundamental Chemistry |
A way to experimentally determine wetting is to look at the contact angle (), which is the angle connecting the solid–liquid interface and the liquid–gas interface (as in the figure).
: If , the liquid completely wets the substrate.
: If , high wetting occurs.
: If , low wetting occurs.
: If , the liquid does not wet the substrate at all.
The Young equation relates the contact angle to interfacial energy:
where is the interfacial energy between the solid and gas phases, the interfacial energy between the substrate and the liquid, is the interfacial energy between the liquid and gas phases, and is the contact angle between the solid–liquid and the liquid–gas interface. | 0 | Theoretical and Fundamental Chemistry |
Wayne Campbell at Massey University, New Zealand, has experimented with a wide variety of organic dyes based on porphyrin. In nature, porphyrin is the basic building block of the hemoproteins, which include chlorophyll in plants and hemoglobin in animals. He reports efficiency on the order of 5.6% using these low-cost dyes. | 0 | Theoretical and Fundamental Chemistry |
Pipe cutting or pipe profiling is a mechanized industrial process that removes material from pipe or tubing to create a desired profile. Typical profiles include straight cuts, mitres, saddles and midsection holes. These complex cuts are usually required to allow a tight fit between two parts that are to be joined via arc welding. | 1 | Applied and Interdisciplinary Chemistry |
In the U.S., the value of prescriptions increased over the period of 1995 to 2005 by 3.4 billion annually, a 61 percent increase. Retail sales of prescription drugs jumped 250 percent from $72 billion to $250 billion, while the average price of prescriptions more than doubled from $30 to $68. | 1 | Applied and Interdisciplinary Chemistry |
Copper(II) borate is an inorganic compound with the formula Cu(B O). It has previously studied due to its photocatalytic properties. | 0 | Theoretical and Fundamental Chemistry |
Noddack was born in Berlin. He became professor for physical chemistry at the University of Freiburg in 1935 and in 1941 at the Reichsuniversität Straßburg. After World War II he changed to the University of Bamberg and in 1956 he became director of the newly founded Research Institute for geochemistry there. He died in Berlin. | 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.