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One feature of enzymes is their high specificity. They are specific on a singular substrate, reaction or both together, that means, that the enzymes can catalyze all reactions wherein the substrate can experience.
The enzyme cholesterol 7 alpha hydroxylase catalyzes the reaction that converts cholesterol into cholesterol 7 alpha hydroxylase reducing and oxidizing that molecule. | 1 | Applied and Interdisciplinary Chemistry |
Arash Ghorbani-Choghamarani (born 23 September 1979) is an Iranian chemist and Professor of Chemistry at Bu-Ali Sina University. He is also Deputy of Research and Technology at this university since November 2021.
Ghorbani-Choghamarani is among the most-cited Iranian researchers and is known for his works on organic chemistry, nanochemistry, heterogeneous catalysis, heterocyclic compounds and organic synthesis.
Previously He was professor and Deputy of Education at Ilam University.
Ghorbani-Choghamarani is a winner of Ilam Province Book of the Year for his book Drug Delivery Systems and Their Effectiveness Through Nanotechnology. | 0 | Theoretical and Fundamental Chemistry |
A catalyst increases the rate of a reaction without being consumed in the reaction. The use of a catalyst does not affect the position and composition of the equilibrium of a reaction, because both the forward and backward reactions are sped up by the same factor.
For example, consider the Haber process for the synthesis of ammonia (NH):
:N + 3 H ⇌ 2 NH
In the above reaction, iron (Fe) and molybdenum (Mo) will function as catalysts if present. They will accelerate any reactions, but they do not affect the state of the equilibrium. | 0 | Theoretical and Fundamental Chemistry |
One of the main functions of the chloroplast is its role in photosynthesis, the process by which light is transformed into chemical energy, to subsequently produce food in the form of sugars. Water (HO) and carbon dioxide (CO) are used in photosynthesis, and sugar and oxygen (O) is made, using light energy. Photosynthesis is divided into two stages—the light reactions, where water is split to produce oxygen, and the dark reactions, or Calvin cycle, which builds sugar molecules from carbon dioxide. The two phases are linked by the energy carriers adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADP). | 0 | Theoretical and Fundamental Chemistry |
A boosted fission weapon usually refers to a type of nuclear bomb that uses a small amount of fusion fuel to increase the rate, and thus yield, of a fission reaction. The neutrons released by the fusion reactions add to the neutrons released due to fission, allowing for more neutron-induced fission reactions to take place. The rate of fission is thereby greatly increased such that much more of the fissile material is able to undergo fission before the core explosively disassembles. The fusion process itself adds only a small amount of energy to the process, perhaps 1%.
The alternative meaning is an obsolete type of single-stage nuclear bomb that uses thermonuclear fusion on a large scale to create fast neutrons that can cause fission in depleted uranium, but which is not a two-stage hydrogen bomb. This type of bomb was referred to by Edward Teller as "Alarm Clock", and by Andrei Sakharov as "Sloika" or "Layer Cake" (Teller and Sakharov developed the idea independently, as far as is known). | 0 | Theoretical and Fundamental Chemistry |
The lipophilic group is typically a large hydrocarbon moiety, such as a long chain of the form CH(CH), with n > 4.
The hydrophilic group falls into one of the following categories:
# charged groups
#* anionic. Examples, with the lipophilic part of the molecule represented by R, are:
#** carboxylates: RCO
#** sulfates: RSO
#** sulfonates: RSO
#** phosphates (the charged functional group in phospholipids)
#* cationic. Examples:
#** ammoniums: RNH
# polar, uncharged groups. Examples are alcohols with large R groups, such as diacyl glycerol (DAG), and oligo ethylene glycol with long alkyl chains.
Often, amphiphilic species have several lipophilic parts, several hydrophilic parts, or several of both. Proteins and some block copolymers are such examples.
Amphiphilic compounds have lipophilic (typically hydrocarbon) structures and hydrophilic polar functional groups (either ionic or uncharged).
As a result of having both lipophilic and hydrophilic portions, some amphiphilic compounds may dissolve in water and to some extent in non-polar organic solvents.
When placed in an immiscible biphasic system consisting of aqueous and organic solvents, the amphiphilic compound will partition the two phases. The extent of the hydrophobic and hydrophilic portions determines the extent of partitioning. | 0 | Theoretical and Fundamental Chemistry |
The Rayleigh number describes the behaviour of fluids (such as water or air) when the mass density of the fluid is non-uniform. The mass density differences are usually caused by temperature differences. Typically a fluid expands and becomes less dense as it is heated. Gravity causes denser parts of the fluid to sink, which is called convection. Lord Rayleigh studied the case of Rayleigh-Bénard convection. When the Rayleigh number, Ra, is below a critical value for a fluid, there is no flow and heat transfer is purely by conduction; when it exceeds that value, heat is transferred by natural convection.
When the mass density difference is caused by temperature difference, Ra is, by definition, the ratio of the time scale for diffusive thermal transport to the time scale for convective thermal transport at speed :
This means the Rayleigh number is a type of Péclet number. For a volume of fluid of size in all three dimensions and mass density difference , the force due to gravity is of the order , where is acceleration due to gravity. From the Stokes equation, when the volume of fluid is sinking, viscous drag is of the order , where is the dynamic viscosity of the fluid. When these two forces are equated, the speed . Thus the time scale for transport via flow is . The time scale for thermal diffusion across a distance is , where is the thermal diffusivity. Thus the Rayleigh number Ra is
where we approximated the density difference for a fluid of average mass density , thermal expansion coefficient and a temperature difference across distance .
The Rayleigh number can be written as the product of the Grashof number and the Prandtl number: | 1 | Applied and Interdisciplinary Chemistry |
The reserve pool is not directly connected to the active zone. The increase in presynaptic calcium concentration activates calcium–calmodulin-dependent protein kinase (CaMK). CaMK phosphorylates a protein, synapsin, that mediates the clustering of the reserve pool vesicles and attachment to the cytoskeleton. Phosphorylation of synapsin mobilizes vesicles in the reserve pool and allows them to migrate to the active zone and replenish the readily releasable pool. | 1 | Applied and Interdisciplinary Chemistry |
Figure 3 shows an SEM cross-section of a TE leg. Here it is demonstrated that the thermal bump is structurally identical to a CPB with an extra layer, the TE layer, incorporated into the stack-up. The addition of the TE layer transforms a standard copper pillar bump into a thermal bump. This element, when properly configured electrically and thermally, provides active thermoelectric heat transfer from one side of the bump to the other side. The direction of heat transfer is dictated by the doping type of the thermoelectric material (either a P-type or N-type semiconductor) and the direction of electric current passing through the material. This type of thermoelectric heat transfer is known as the Peltier effect. Conversely, if heat is allowed to pass from one side of the thermoelectric material to the other, a current will be generated in the material in a phenomenon known as the Seebeck effect. The Seebeck effect is essentially the reverse of the Peltier effect. In this mode, electrical power is generated from the flow of heat in the TE element. The structure shown in Figure 3 is capable of operating in both the Peltier and Seebeck modes, though not simultaneously.
Figure 4 shows a schematic of a typical CPB and a thermal bump for comparison. These structures are similar, with both having copper pillars and solder connections. The primary difference between the two is the introduction of either a P- or N-type thermoelectric layer between two solder layers. The solders used with CPBs and thermal bumps can be any one of a number of commonly used solders including, but not limited to, Sn, SnPb eutectic, SnAg or AuSn.
Figure 5 shows a device equipped with a thermal bump. The thermal flow is shown by the arrows labeled “heat.” Metal traces, which can be several micrometres high, can be stacked or interdigitated to provide highly conductive pathways for collecting heat from the underlying circuit and funneling that heat to the thermal bump.
The metal traces shown in the figure for conducting electric current into the thermal bump may or may not be directly connected to the circuitry of the chip. In the case where there are electrical connections to the chip circuitry, on-board temperature sensors and driver circuitry can be used to control the thermal bump in a closed loop fashion to maintain optimal performance. Second, the heat that is pumped by the thermal bump and the additional heat created by the thermal bump in the course of pumping that heat will need to be rejected into the substrate or board. Since the performance of the thermal bump can be improved by providing a good thermal path for the rejected heat, it is beneficial to provide high thermally conductive pathways on the backside of the thermal bump. The substrate could be a highly conductive ceramic substrate like AlN or a metal (e.g., Cu, CuW, CuMo, etc.) with a dielectric. In this case, the high thermal conductance of the substrate will act as a natural pathway for the rejected heat. The substrate might also be a multilayer substrate like a printed wiring board (PWB) designed to provide a high-density interconnect. In this case, the thermal conductivity of the PWB may be relatively poor, so adding thermal vias (e.g. metal plugs) can provide excellent pathways for the rejected heat. | 0 | Theoretical and Fundamental Chemistry |
Crystal formation requires two steps: nucleation and growth. Nucleation is the initiation step for crystallization. At the nucleation phase, protein molecules in solution come together as aggregates to form a stable solid nucleus. As the nucleus forms, the crystal grows bigger and bigger by molecules attaching to this stable nucleus. The nucleation step is critical for crystal formation since it is the first-order phase transition of samples moving from having a high degree of freedom to obtaining an ordered state (aqueous to solid). For the nucleation step to succeed, the manipulation of crystallization parameters is essential. The approach behind getting a protein to crystallize is to yield a lower solubility of the targeted protein in solution. Once the solubility limit is exceeded and crystals are present, crystallization is accomplished. | 0 | Theoretical and Fundamental Chemistry |
The bulk isotope ratio value of stable isotopes for petroleum depict the average isotopic compositions of the oil's components. Carbon stable isotopes are often used in this method. Whether a sample of petroleum originated in a marine environment or a non-marine environment can be seen using this ratio value, as can method distance and age of the oil. | 0 | Theoretical and Fundamental Chemistry |
Coherent Rabi oscillations may also be driven by two-photon transitions. In this case we consider a system with three atomic energy levels, , , and , where represents a so-called intermediate state with corresponding frequency , and an electromagnetic field with two frequency components:
Now, may be much greater than both and , or , as illustrated in the figure on the right.
A two-photon transition is not the same as excitation from the ground to intermediate state, and then out of the intermediate state to the excited state. Instead, the atom absorbs two photons simultaneously and is promoted directly between the initial and final states. There are two necessary conditions for this two-photon process (also known as a Raman process), to be the dominant model of the light-matter interaction:
In words, the sum of the frequencies of the two photons must be on resonance with the transition between the initial and final states, and the individual frequencies of the photons must be detuned from the intermediate state to initial and final state transitions. If the latter condition is not met and , the dominant process will be one governed by rate equations in which the intermediate state is populated and stimulated and Spontaneous emission events from that state prevent the possibility of driving coherent oscillations between the initial and final states.
We may derive the two-photon Rabi frequency by returning to the equations
which now describe excitation between the ground and intermediate states. We know we have the solution
where is the generalized Rabi frequency for the transition from the initial to intermediate state. Similarly for the intermediate to final state transition we have the equations
Now we plug into the above equation for
Such that, upon solving this equation, we find the coefficient to be proportional to:
This is the effective or two-photon Rabi frequency. It is the product of the individual Rabi frequencies for the and transitions, divided by the detuning from the intermediate state . | 0 | Theoretical and Fundamental Chemistry |
Prokaryotes have diversified greatly throughout their long existence. The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct prokaryotic types. For example, in addition to using photosynthesis or organic compounds for energy, as eukaryotes do, prokaryotes may obtain energy from inorganic compounds such as hydrogen sulfide. This enables prokaryotes to thrive in harsh environments as cold as the snow surface of Antarctica, studied in cryobiology, or as hot as undersea hydrothermal vents and land-based hot springs.
Prokaryotes live in nearly all environments on Earth. Some archaea and bacteria are extremophiles, thriving in harsh conditions, such as high temperatures (thermophiles) or high salinity (halophiles). Many archaea grow as plankton in the oceans. Symbiotic prokaryotes live in or on the bodies of other organisms, including humans. Prokaryote have high populations in the soil - including the rhizosphere and rhizosheath. Soil prokaryotes are still heavily undercharacterized despite their easy proximity to humans and their tremendous economic importance to agriculture. | 1 | Applied and Interdisciplinary Chemistry |
During his visit to North America in August 1941, Howard Florey approached the Connaught Laboratories at the University of Toronto, where he met with the director, R. D. Defries, and Ronald Hare. Florey was rebuffed; Defries argued that the laboratories did not have the space, and he expressed his belief that constructing facilities to culture penicillin would be a waste as it would soon be synthesised. The results of clinical trials caused a change of heart, and in August 1943 the Canadian government asked the Connaught Laboratories to initiate mass production of penicillin. The Spadina Building was purchased by the University of Toronto for the purpose, and refurbished at a cost of Canadian $1.2 million (equivalent to Canadian $ million in ), split equally between the university and the government. Penicillin was initially cultured in 200,000 bottles occupying of air-conditioned laboratory space. Production was switched to the deep submergence method in November 1945. | 1 | Applied and Interdisciplinary Chemistry |
Source: [https://www.icheme.org/knowledge/medals-and-prizes/services-to-the-profession/davis-medal/ IChemE]
* 1965 - Arthur Joseph Victor Underwood (1897-1972), consulting chemical engineer
* 1969 - Frank E. Ireland, Chief Alkali Inspector
* 1973 - J. M. Coulson
* 1977 - Sir Denis Rooke
* 1982 - Sir Maurice Hodgson
* 1988 - Sir Geoffrey Allen
* 1991 - Jacques Villermaux
* 1998 - Ian Robinson, CEO, Scottish Power
* 2001 - Sir David Harrison
* 2004 - Sir David King
* 2011 - Andrew N. Liveris
* 2016 - Roland Clift | 1 | Applied and Interdisciplinary Chemistry |
In April 1918, after the attack of German-Austrian troops, most of the equipment and materials of the Yuzovsky plant were evacuated to Tsaritsyn (Volgograd), and detachments of workers retreated with the Red Army.
On May 24, 1918, the plant was nationalized.
In May 1918, during the German occupation, an underground organization of the Russian Communist Party bolsheviks or the RCP(b), led by E. Severyanov, began operating at the plant, and in July 1918 an underground regional committee of six members began operating at the plant.
In December 1919, Soviet power was restored in Yuzovka, on January 30, 1920, a workers' board of all enterprises of the former "Novorossiysk Society of Coal, Iron and Rail Production" (headed by M. S. Titov) was created in Yuzovka, and the restoration of the plant began. On July 6, 1921, the first blast furnace was launched again, by the end of 1921, production at the plant was restored.
In 1924, the plant was named after Joseph Vissarionovich Stalin.
During Industrialization in the Soviet Union, the plant was transformed into a new technical base. During the First Five-Year Plan, mechanization of the mill and a bunker system for blast furnace charging were introduced and technical renovation was initiated; in 1936 the reconstruction of the mill and the construction of the flat furnace mill were completed, the plate and profilerolling mills were mechanized and a new, powerful blooming mill replaced the old rail-rolling mill. | 1 | Applied and Interdisciplinary Chemistry |
Aluminum has been found to compete with iron and magnesium and bind to DNA, membranes, or cell walls, leading to its toxic effect on microbes, such as cyanobacteria, soil bacteria and mycorrhizal fungi.
Aluminium triacetate (Burow's solution) is used as an astringent mild antiseptic. | 1 | Applied and Interdisciplinary Chemistry |
The cell type chosen for this technique depends on the desired application of the cell microcapsules. The cells put into the capsules can be from the patient (autologous cells), from another donor (allogeneic cells) or from other species (xenogeneic cells). The use of autologous cells in microencapsulation therapy is limited by the availability of these cells and even though xenogeneic cells are easily accessible, danger of possible transmission of viruses, especially porcine endogenous retrovirus to the patient restricts their clinical application, and after much debate several groups have concluded that studies should involve the use of allogeneic instead of xenogeneic cells. Depending on the application, the cells can be genetically altered to express any required protein. However, enough research has to be carried out to validate the safety and stability of the expressed gene before these types of cells can be used.
This technology has not received approval for clinical trial because of the high immunogenicity of cells loaded in the capsules. They secrete cytokines and produce a severe inflammatory reaction at the implantation site around the capsules, in turn leading to a decrease in viability of the encapsulated cells. One promising approach being studied is the administration of anti-inflammatory drugs to reduce the immune response produced due to administration of the cell loaded microcapsules. Another approach which is now the focus of extensive research is the use of stem cells such as mesenchymal stem cells for long term cell microencapsulation and cell therapy applications in hopes of reducing the immune response in the patient after implantation. Another issue which compromises long term viability of the microencapsulated cells is the use of fast proliferating cell lines which eventually fill up the entire system and lead to decrease in the diffusion efficiency across the semi-permeable membrane of the capsule. A solution to this could be in the use of cell types such as myoblasts which do not proliferate after the microencapsulation procedure. | 1 | Applied and Interdisciplinary Chemistry |
Guanylin is a 15 amino acid peptide that is secreted by goblet cells in the colon. Guanylin acts as an agonist of the guanylyl cyclase receptor GC-C and regulates electrolyte and water transport in intestinal and renal epithelia. Upon receptor binding, guanylin increases the intracellular concentration of cGMP, induces chloride secretion and decreases intestinal fluid absorption, ultimately causing diarrhoea. The peptide stimulates the enzyme through the same receptor binding
region as the heat-stable enterotoxins.
Researches have found that a loss in guanylin expression can lead to colorectal cancer due to guanylyl cyclase Cs function as an intestinal tumor suppressor. When guanylin expression was measured on over 250 colon cancer patients, more than 85% of patients had a loss of guanylin expression in cancerous tissue samples by 100-1000 times when compared to the same patientss nearby healthy colon tissue. Another study done on genetically engineered mice found that mice on a high calorie diet had reduced guanylin expression in the colon. This loss of expression then resulted in guanylyl cyclase C inhibition and the formation of tumors, therefore linking diet-induced obesity with colorectal cancer. | 1 | Applied and Interdisciplinary Chemistry |
Jinhae Bay is the first of Koreas two major dead zones, hypoxia was first reported in Jinhae Bay in September of 1974. In 2011, a joint study was done to observe and record causes, effects, and what can be done about Koreas hypoxic zones. It was discovered that Jinhae Bay exhibits a seasonal dead zone from early June to late September. This dead zone is caused by "domestic and land use waste and thermal stratification". Jinhae Bay experiences hypoxia largely at the bottom of its bay. The ratios of Phosphorous to Nitrogen is imbalanced at the bottom, where its otherwise balanced at the top, with the exception of early June to late September where the Bay is experiencing eutrophication as a whole. The effects of Jinhae Bay's hypoxia is seen in the marine system surrounding Korea, with a loss of biological diversity, particularly of the calcareous shelled organisms. | 0 | Theoretical and Fundamental Chemistry |
Ellipsometry is an indirect method, i.e. in general the measured and cannot be converted directly into the optical constants of the sample. Normally, a model analysis must be performed, for example the Forouhi Bloomer model. This is one weakness of ellipsometry. Models can be physically based on energy transitions or simply free parameters used to fit the data.
Direct inversion of and is only possible in very simple cases of isotropic, homogeneous and infinitely thick films. In all other cases a layer model must be established, which considers the optical constants (refractive index or dielectric function tensor) and thickness parameters of all individual layers of the sample including the correct layer sequence. Using an iterative procedure (least-squares minimization) unknown optical constants and/or thickness parameters are varied, and and values are calculated using the Fresnel equations. The calculated and values which match the experimental data best provide the optical constants and thickness parameters of the sample. | 0 | Theoretical and Fundamental Chemistry |
When beer at typical concentration is subjected to reverse osmosis, both water and alcohol pass across the membrane more readily than other components, leaving a "beer concentrate". The concentrate is then diluted with fresh water to restore the non-volatile components to their original intensity. | 0 | Theoretical and Fundamental Chemistry |
Joule heating (also known as resistive, resistance, or Ohmic heating) is the process by which the passage of an electric current through a conductor produces heat.
Joules first law (also just Joules law), also known in countries of the former USSR as the Joule–Lenz law, states that the power of heating generated by an electrical conductor equals the product of its resistance and the square of the current. Joule heating affects the whole electric conductor, unlike the Peltier effect which transfers heat from one electrical junction to another.
Joule-heating or resistive-heating is used in multiple devices and industrial process. The part that converts electricity into heat is called a heating element.
Among the many practical uses are:
* An incandescent light bulb glows when the filament is heated by Joule heating, due to thermal radiation (also called blackbody radiation).
* Electric fuses are used as a safety, breaking the circuit by melting if enough current flows to melt them.
* Electronic cigarettes vaporize propylene glycol and vegetable glycerine by Joule heating.
* Multiple heating devices use Joule heating, such as electric stoves, electric heaters, soldering irons, cartridge heaters.
* Some food processing equipment may make use of Joule heating: running current through food material (which behave as an electrical resistor) causes heat release inside the food. The alternating electrical current coupled with the resistance of the food causes the generation of heat. A higher resistance increases the heat generated. Ohmic heating allows for fast and uniform heating of food products, which maintains quality. Products with particulates heat up faster (compared to conventional heat processing) due to higher resistance. | 0 | Theoretical and Fundamental Chemistry |
The Journal of Photochemistry and Photobiology B: Biology is abstracted and indexed in BIOSIS, Cambridge Scientific Abstracts, Chemical Abstracts, Current Contents, BIOBASE/Current Awareness in Biological Sciences, EMBASE, Embiology, Engineering Index, Metals Abstracts, PASCAL, Physics Abstracts, Physikalische Berichte, Polymer Contents, Science Citation Index, and Scopus. According to the Journal Citation Reports, the journal has a 2016 impact factor of 2.673. | 0 | Theoretical and Fundamental Chemistry |
S-Adenosylmethionine synthetase (), also known as methionine adenosyltransferase (MAT), is an enzyme that creates S-adenosylmethionine (also known as AdoMet, SAM or SAMe) by reacting methionine (a non-polar amino acid) and ATP (the basic currency of energy). | 1 | Applied and Interdisciplinary Chemistry |
* Family papers archive at the National Records of Scotland re the family home at Annacroich https://discovery.nationalarchives.gov.uk/details/c/F19704
* British Medical Journal [https://www.youtube.com/watch?v=aVpHgqX8uI4 video] about the legacy of James Young Simpson including Flockharts role (via [https://www.historyscotland.com/history/sir-james-young-simpson-died-on-this-day-in-history/ History Scotland])'
*Museums and Galleries Edinburgh has an original wax stamp of Flockhart's including his address https://www.edinburghmuseums.org.uk/stories/auld-reekie-retold-surgeon-pharmacist-and-obstetrician | 1 | Applied and Interdisciplinary Chemistry |
The YenR and YenI proteins produced by the gammaproteobacterium Yersinia enterocolitica are similar to Aliivibrio fischeri LuxR and LuxI. YenR activates the expression of a small non-coding RNA, YenS. YenS inhibits YenI expression and acylhomoserine lactone production. YenR/YenI/YenS are involved in the control of swimming and swarming motility. | 1 | Applied and Interdisciplinary Chemistry |
Iodic acid is a white water-soluble solid with the chemical formula . Its robustness contrasts with the instability of chloric acid and bromic acid. Iodic acid features iodine in the oxidation state +5 and is one of the most stable oxo-acids of the halogens. When heated, samples dehydrate to give iodine pentoxide. On further heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine. | 0 | Theoretical and Fundamental Chemistry |
This reactivity is similar to the tendency of ethers with alpha hydrogen atoms to form peroxides. Reaction with chlorine produces alpha-chloroethers. | 0 | Theoretical and Fundamental Chemistry |
The way that porosity develops during the dealloying process has been studied computationally to understand the diffusional pathways on an atomistic level. Firstly, the less noble atoms must be dissolved away from the surface of the alloy. This process is easiest for the lower coordinated atoms, i.e., those bonded to fewer other atoms, usually found as single atoms sitting on the surface ("adatoms"), but it is more difficult for higher coordinated atoms, i.e., those sitting at "steps" or in the bulk of the material. Thus, the slowest step, and that which is most important for determining rate of porosity evolution is the dissolution of these higher coordinated less noble atoms. Just as the less noble metal is less stable as an adatom on the surface, so is an atom of the more noble metal. Therefore, as dissolution proceeds, any more noble atoms will move to more stable positions, like steps, where its coordination is higher. This diffusion process is similar to spinodal decomposition. Eventually, clusters of more noble atoms form this way, and surrounding less noble atoms dissolve away, leaving behind a "bicontinuous structure" and providing a pathway for dissolution to continue deeper into the metal. | 1 | Applied and Interdisciplinary Chemistry |
Synthesis of organoberyllium compounds is limited but literature have shown that beryllium can react with halides, alkyls, alloxides and other organic compounds. Alkylation of beryllium halide is one of the most widely-used method in beryllium chemistry. | 0 | Theoretical and Fundamental Chemistry |
Stochastic effects are those that occur randomly, such as radiation-induced cancer. The consensus of nuclear regulators, governments and the UNSCEAR is that the incidence of cancers due to ionizing radiation can be modeled as increasing linearly with effective dose at a rate of 5.5% per sievert. This is known as the linear no-threshold model (LNT model). Some argue that this LNT model is now outdated and should be replaced with a threshold below which the body's natural cell processes repair damage and/or replace damaged cells. There is general agreement that the risk is much higher for infants and fetuses than adults, higher for the middle-aged than for seniors, and higher for women than for men, though there is no quantitative consensus about this. | 0 | Theoretical and Fundamental Chemistry |
Taylor–Couette flow is a flow between two rotating, infinitely long, coaxial cylinders. The original problem was solved by Stokes in 1845, but Geoffrey Ingram Taylor's name was attached to the flow because he studied its stability in a famous 1923 paper.
The problem can be solved in cylindrical coordinates . Denote the radii of the inner and outer cylinders as and . Assuming the cylinders rotate at constant angular velocities and , then the velocity in the -direction is
This equation shows that the effects of curvature no longer allow for constant shear in the flow domain. | 1 | Applied and Interdisciplinary Chemistry |
Nano fountain probes (NFPs) are fabricated on the wafer-scale using microfabrication techniques allowing for batch fabrication of numerous chips. Through the different generations of devices, design and experimentation improved the device yielding to a robust fabrication process. The highly enhanced feature dimension and shapes is expected to improve the performance in writing and imaging. | 1 | Applied and Interdisciplinary Chemistry |
Project 523 () is a code name for a 1967 secret military project of the Peoples Republic of China to find antimalarial medications. Named after the date the project launched, 23 May, it addressed malaria, an important threat in the Vietnam War. At the behest of Ho Chi Minh, Prime Minister of North Vietnam, Zhou Enlai, the Premier of the Peoples Republic of China, convinced Mao Zedong, Chairman of the Chinese Communist Party, to start the mass project "to keep [the] allies' troops combat-ready", as the meeting minutes put it. More than 500 Chinese scientists were recruited. The project was divided into three streams. The one for investigating traditional Chinese medicine discovered and led to the development of a class of new antimalarial drugs called artemisinins. Launched during and lasting throughout the Cultural Revolution, Project 523 was officially terminated in 1981.
For their high efficacy, safety and stability, artemisinins such as artemether and artesunate became the drugs of choice in treating falciparum malaria. The World Health Organization advocates their combination drugs and includes them in its List of Essential Medicines. Among the scientists of the project, Zhou Yiqing and his team at the Institute of Microbiology and Epidemiology of the Chinese Academy of Military Medical Sciences, were awarded the European Inventor Award of 2009 in the category "Non-European countries" for the development of Coartem (artemether-lumefantrine combination drug). Tu Youyou of the Qinghaosu Research Center, Institute of Chinese Materia Medica, Academy of Traditional Chinese Medicine (now the China Academy of Traditional Chinese Medical Sciences), received both the 2011 Lasker-DeBakey Clinical Medical Research Award and 2015 Nobel Prize in Physiology or Medicine for her role in the discovery of artemisinin. | 1 | Applied and Interdisciplinary Chemistry |
Flutamide has been identified as an agonist of the aryl hydrocarbon receptor. This may be involved in the hepatotoxicity of flutamide. | 0 | Theoretical and Fundamental Chemistry |
The substituents on the diazirine affect which carbene species is generated upon irradiation and subsequent photolytic cleavage. Diazirine substituents that are electron donating in nature can donate electron density to the empty p-orbital of the carbene that will be formed, and hence can stabilize the singlet state. For example, phenyldiazirine produces phenylcarbene in the singlet carbene state whereas p-nitrophenylchlorodiazirine or trifluorophenyldiazirine produce the respective triplet carbene products.
Electron donating substituents can also encourage photoisomerization to the linear diazo compound , rather than the singlet carbene, and hence these compounds are unfavorable for use in biological assays. On the other hand, trifluoroaryldiazirines in particular show favorable stability and photolytic qualities and are most commonly used in biological applications. Carbenes produced from diazirines are quickly quenched by reaction with water molecules, and hence yields for photoreactive crosslinking assays are often low. Yet, as this feature minimizes unspecific labeling, it is actually an advantage of using diazirines. | 0 | Theoretical and Fundamental Chemistry |
One feature of Boussinesq flows is that they look the same when viewed upside-down, provided that the identities of the fluids are reversed. The Boussinesq approximation is inaccurate when the dimensionless density difference is approximately 1, i.e. .
For example, consider an open window in a warm room. The warm air inside is less dense than the cold air outside, which flows into the room and down towards the floor. Now imagine the opposite: a cold room exposed to warm outside air. Here the air flowing in moves up toward the ceiling. If the flow is Boussinesq (and the room is otherwise symmetrical), then viewing the cold room upside down is exactly the same as viewing the warm room right-way-round. This is because the only way density enters the problem is via the reduced gravity which undergoes only a sign change when changing from the warm room flow to the cold room flow.
An example of a non-Boussinesq flow is bubbles rising in water. The behaviour of air bubbles rising in water is very different from the behaviour of water falling in air: in the former case rising bubbles tend to form hemispherical shells, while water falling in air splits into raindrops (at small length scales surface tension enters the problem and confuses the issue). | 1 | Applied and Interdisciplinary Chemistry |
In 2017, the FDA granted deulinoleate ethyl orphan drug designation in the treatment of phospholipase 2G6-associated neurodegeneration (PLAN). | 1 | Applied and Interdisciplinary Chemistry |
When connecting the monosaccharides, the oligosaccharides need to be reducing in order to sequentially connect the glycosyl units. The monosaccharides, in nature prefer ɑ-linkages due to anomeric effect, but the disaccharides with ɑ-linkages are non-reducing thus deactivating the consequent connection of the monosaccharides. In order to make the process of glycosylation continuous and automated, the glycosidic linkages must maintain beta so to keep the structure open to coupling with more glycosyl groups.
It is somewhat more difficult to prepare 1, 2-cis-β-glycosidic linkages stereoselectively. Typically, when non-participating groups on O-2 position, 1, 2-cis-β-linkage can be achieved either by using the historically important halide ion methods, or by using 2-O-alkylated glycosyl donors, commonly thioglycosides or trichloroacetimidates, in nonpolar solvents.
In the early 1990s, it was still the case that the beta mannoside linkage was too challenging to be attempted by amateurs. However, the method introduced by Crich (Scheme 4), with 4,6-benzylidene protection a prerequisite and anomeric alpha triflate a key intermediate leaves this problem essentially solved. The concurrently developed but rather more protracted intramolecular aglycon delivery (IAD) approach is a little-used but nevertheless stereospecific alternative. | 0 | Theoretical and Fundamental Chemistry |
Normality is defined as the molar concentration divided by an equivalence factor . Since the definition of the equivalence factor depends on context (which reaction is being studied), the International Union of Pure and Applied Chemistry and National Institute of Standards and Technology discourage the use of normality. | 0 | Theoretical and Fundamental Chemistry |
Two derivations are presented below. The first is a heuristic argument, based on physical insight. The second is a formal and technical one, requiring basic vector analysis and complex analysis. | 1 | Applied and Interdisciplinary Chemistry |
Spectral directional transmittance in frequency and spectral directional transmittance in wavelength of a surface, denoted T and T respectively, are defined as
where
*L is the spectral radiance in frequency transmitted by that surface;
*L is the spectral radiance received by that surface;
*L is the spectral radiance in wavelength transmitted by that surface;
*L is the spectral radiance in wavelength received by that surface. | 0 | Theoretical and Fundamental Chemistry |
The ICRU/ICRP dose quantities have specific purposes and meanings, but some use common words in a different order. There can be confusion between, for instance, equivalent dose and dose equivalent.
Although the CIPM definition states that the linear energy transfer function (Q) of the ICRU is used in calculating the biological effect, the ICRP in 1990 developed the "protection" dose quantities effective and equivalent dose which are calculated from more complex computational models and are distinguished by not having the phrase dose equivalent in their name. Only the operational dose quantities which still use Q for calculation retain the phrase dose equivalent. However, there are joint ICRU/ICRP proposals to simplify this system by changes to the operational dose definitions to harmonise with those of protection quantities. These were outlined at the 3rd International Symposium on Radiological Protection in October 2015, and if implemented would make the naming of operational quantities more logical by introducing "dose to lens of eye" and "dose to local skin" as equivalent doses.
In the USA there are differently named dose quantities which are not part of the ICRP nomenclature. | 0 | Theoretical and Fundamental Chemistry |
In Europe since early 1980s, cars must be equipped with one or two red rear fog lamps. A single rear fog lamp must be located between the vehicles longitudinal centreline and the outer extent of the drivers side of the vehicle. | 0 | Theoretical and Fundamental Chemistry |
Similar to physical solidification, some chemical crosslinking methods have been developed to produce hydrogel fibers. And the key for the achievement of hydrogel production through the chemical crosslinking method is the effective separation between the formed network and the tube wall. | 0 | Theoretical and Fundamental Chemistry |
Today, the process of fermentation is used for a multitude of everyday applications including medication, beverages and food. Currently, companies like Genencor International uses the production of enzymes involved in fermentation to build a revenue of over $400 million a year. Many medications such as antibiotics are produced by the fermentation process. An example is the important drug cortisone, which can be prepared by the fermentation of a plant steroid known as diosgenin.
The enzymes used in the reaction are provided by the mold Rhizopus nigricans. Just as it is commonly known, alcohol of all types and brands are also produced by way of fermentation and distillation. Moonshine is a classic example of how this is carried out. Finally, foods such as yogurt are made by fermentation processes as well. Yogurt is a fermented milk product that contains the characteristic bacterial cultures Lactobacillus bulgaricus and Streptococcus thermopiles. | 1 | Applied and Interdisciplinary Chemistry |
Victor Moritz Goldschmidt (27 January 1888 – 20 March 1947) was a Norwegian mineralogist considered (together with Vladimir Vernadsky) to be the founder of modern geochemistry and crystal chemistry, developer of the Goldschmidt Classification of elements. | 0 | Theoretical and Fundamental Chemistry |
Aliphatic C-C or C-H bonds can lead to charge delocalization if these bonds are close and antiperiplanar to the leaving group. Corresponding intermediates are referred to a nonclassical ions, with the 2-norbornyl system as the most well known case. | 0 | Theoretical and Fundamental Chemistry |
A lab-on-a-chip is a device that integrates one or several laboratory functions on a single chip that deals with handling particles in hollow microfluidic channels. It has been developed for over a decade. Advantages in handling particles at such a small scale include lowering fluid volume consumption (lower reagents costs, less waste), increasing portability of the devices, increasing process control (due to quicker thermo-chemical reactions) and decreasing fabrication costs. Additionally, microfluidic flow is entirely laminar (i.e., no turbulence). Consequently, there is virtually no mixing between neighboring streams in one hollow channel. In cellular biology convergence, this rare property in fluids has been leveraged to better study complex cell behaviors, such as cell motility in response to chemotactic stimuli, stem cell differentiation, axon guidance, subcellular propagation of biochemical signaling and embryonic development. | 1 | Applied and Interdisciplinary Chemistry |
For small spots of vitiligo, it is possible to use psoralen as drops, applied only on the spots. This method does not have side effects since the amount is very low.
For larger area, the psoralen is taken as a pill, and the amount is high (10 mg); some patients experience nausea and itching after ingesting the psoralen compound. For these patients PUVA bath therapy may be a good option.
Long term use of PUVA therapy with a pill has been associated with higher rates of skin cancer.
The most significant complication of PUVA therapy for psoriasis is squamous cell skin cancer. Two carcinogenic components of the therapy include the nonionizing radiation of UVA light as well as the psoralen intercalation with DNA. Both processes negatively contribute to genome instability. | 0 | Theoretical and Fundamental Chemistry |
The kinetic process of destabilisation can be rather long (up to several months or even years for some products) and it is often required for the formulator to use further accelerating methods in order to reach reasonable development time for new product design. Thermal methods are the most commonly used and consists in increasing temperature to accelerate destabilisation (below critical temperatures of phase and degradation). Temperature affects not only the viscosity, but also interfacial tension in the case of non-ionic surfactants or more generally interactions forces inside the system. Storing a dispersion at high temperatures enables simulation of real life conditions for a product (e.g. tube of sunscreen cream in a car in the summer), but also to accelerate destabilisation processes up to 200 times including vibration, centrifugation and agitation are sometimes used. They subject the product to different forces that pushes the particles / film drainage. However, some emulsions would never coalesce in normal gravity, while they do under artificial gravity. Moreover, segregation of different populations of particles have been highlighted when using centrifugation and vibration. | 0 | Theoretical and Fundamental Chemistry |
The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and efficiency of the cycle increases.
The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low-pressure turbine enters the shell, where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausts for continuous removal of air and gases from the steam side to maintain vacuum.
For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 °C where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of non-condensible air into the closed loop must be prevented.
Typically the cooling water causes the steam to condense at a temperature of about and that creates an absolute pressure in the condenser of about , i.e. a vacuum of about relative to atmospheric pressure. The large decrease in volume that occurs when water vapor condenses to liquid creates the vacuum that generally increases the efficiency of the turbines.
The limiting factor is the temperature of the cooling water and that, in turn, is limited by the prevailing average climatic conditions at the power station's location (it may be possible to lower the temperature beyond the turbine limits during winter, causing excessive condensation in the turbine). Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning.
The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through cooling (OTC) water from a river, lake or ocean. In the United States, about two-thirds of power plants use OTC systems, which often have significant adverse environmental impacts. The impacts include thermal pollution and killing large numbers of fish and other aquatic species at cooling water intakes.
The heat absorbed by the circulating cooling water in the condenser tubes must also be removed to maintain the ability of the water to cool as it circulates. This is done by pumping the warm water from the condenser through either natural draft, forced draft or induced draft cooling towers (as seen in the adjacent image) that reduce the temperature of the water by evaporation, by about 11 to 17 °C (20 to 30 °F)—expelling waste heat to the atmosphere. The circulation flow rate of the cooling water in a 500 MW unit is about 14.2 m/s (500 ft/s or 225,000 US gal/min) at full load.
The condenser tubes are typically made stainless steel or other alloys to resist corrosion from either side. Nevertheless, they may become internally fouled during operation by bacteria or algae in the cooling water or by mineral scaling, all of which inhibit heat transfer and reduce thermodynamic efficiency. Many plants include an automatic cleaning system that circulates sponge rubber balls through the tubes to scrub them clean without the need to take the system off-line.
The cooling water used to condense the steam in the condenser returns to its source without having been changed other than having been warmed. If the water returns to a local water body (rather than a circulating cooling tower), it is often tempered with cool raw water to prevent thermal shock when discharged into that body of water.
Another form of condensing system is the air-cooled condenser. The process is similar to that of a radiator and fan. Exhaust heat from the low-pressure section of a steam turbine runs through the condensing tubes, the tubes are usually finned and ambient air is pushed through the fins with the help of a large fan. The steam condenses to water to be reused in the water-steam cycle. Air-cooled condensers typically operate at a higher temperature than water-cooled versions. While saving water, the efficiency of the cycle is reduced (resulting in more carbon dioxide per megawatt-hour of electricity).
From the bottom of the condenser, powerful condensate pumps recycle the condensed steam (water) back to the water/steam cycle. | 1 | Applied and Interdisciplinary Chemistry |
Parkinsons disease is characterized by the death of cells that produce dopamine, a neurotransmitter. An enzyme called monoamine oxidase (MAO) breaks down neurotransmitters. MAO has two forms, MAO-A and MAO-B. MAO-B is generally believed to break down dopamine; however, recent evidence suggests that MAO-A may mostly or entirely be responsible for dopamine metabolism. Rasagiline prevents the breakdown of dopamine by irreversibly binding to MAO-B. Dopamine is therefore more available, somewhat compensating for the diminished quantities made in the brains of people with Parkinsons.
Selegiline was the first selective MAO-B inhibitor. It is partly metabolized to levomethamphetamine (l-methamphetamine), one of the two enantiomers of methamphetamine, in vivo. While these metabolites may contribute to selegilines ability to inhibit reuptake of the neurotransmitters dopamine and norepinephrine, they have also been associated with orthostatic hypotension and hallucinations in some people. Rasagiline metabolizes into 1(R')-aminoindan which has no amphetamine-like characteristics and has neuroprotective properties in cells and in animal models.
It is selective for MAO type B over type A by a factor of fourteen. | 0 | Theoretical and Fundamental Chemistry |
Molten polymers are non-Newtonian fluids with high viscosities, and the interaction between their thermal and mechanical degradation can be complex. At low temperatures, the polymer-melt is more viscous and more prone to mechanical degradation via shear stress. At higher temperatures, the viscosity is reduced, but thermal degradation is increased. Friction at points of high sheer can also cause localised heating, leading to additional thermal degradation.
Mechanical degradation can be reduced by the addition of lubricants, also referred to as processing aids or flow aids. These can reduce friction against the processing machinery but also between polymer chains, resulting in a decrease in melt-viscosity. Common agents are high-molecular-weight waxes (paraffin wax, wax esters, etc.) or metal stearates (i.e.zinc stearate). | 0 | Theoretical and Fundamental Chemistry |
One of the largest deliberate PCB spills in American history occurred in the summer of 1978 when 31,000 gallons (117 m^3) of PCB-contaminated oil were illegally sprayed by the Ward PCB Transformer Company in swaths along the roadsides of some of North Carolina highway shoulders in 14 counties and at the Fort Liberty Army Base. The crime, known as "the midnight dumpings", occurred over nearly two weeks, as drivers of a black-painted tanker truck drove down one side of rural Piedmont highways spraying PCB-laden waste and then up the other side the following night.
Under Governor James B. Hunt, Jr., state officials then erected large, yellow warning signs along the contaminated highways that read: "CAUTION: PCB Chemical Spills Along Highway Shoulders". The illegal dumping is believed to have been motivated by the passing of the Toxic Substances Control Act (TSCA), which became effective on August 2, 1978, and increased the expense of chemical waste disposal.
Within a couple of weeks of the crime, Robert Burns and his sons, Timothy and Randall, were arrested for dumping the PCBs along the roadsides. Burns was a business partner of Robert "Buck" Ward Jr., of the Ward PCB Transformer Company, in Raleigh. Burns and sons pleaded guilty to state and Federal criminal charges; Burns received a three to five-year prison sentence. Ward was acquitted of state charges in the dumping, but was sentenced to 18 months prison time for violation of TSCA.
Cleanup and disposal of the roadside PCBs generated controversy, as the Governor's plan to pick up the roadside PCBs and to bury them in a landfill in rural Warren County were strongly opposed in 1982 by local residents.
In October 2013, at the request of the South Carolina Department of Health and Environmental Control (SCDHEC), the City of Charlotte, North Carolina, decided to stop applying sewage sludge to land while authorities investigated the source of PCB contamination.
In February 2014, the City of Charlotte admitted PCBs have entered their sewage treatment centers as well.
After the 2013 SCDHEC had issued emergency regulations, the City of Charlotte discovered high levels of PCBs entering its sewage waste water treatment plants, where sewage is converted to sewage sludge. The city at first denied it had a problem, then admitted an "event" occurred in February 2014, and in April that the problem had occurred much earlier. The city stated that its very first test with a newly changed test method revealed very high PCB levels in its sewage sludge farm field fertilizer. Because of the widespread use of the contaminated sludge, SCDHEC subsequently issued PCB fish advisories for nearly all streams and rivers bordering farm fields that had been applied with city waste. | 1 | Applied and Interdisciplinary Chemistry |
A line vortex of strength is given by
where is the circulation around any simple closed contour enclosing the vortex. The velocity field in polar coordinates are
i.e., a purely azimuthal flow. | 1 | Applied and Interdisciplinary Chemistry |
Despite their many advantages, the use of PPGs in total syntheses are relatively rare. Nevertheless, PPGs’ "orthogonality" to common synthetic reagents, as well as the possibility of conducting a "traceless reagent process", has proven useful in natural product synthesis. Two examples include the syntheses of ent-Fumiquinazoline and (-)-diazonamide A. The syntheses required irradiation at 254 and 300 nm, respectively. | 0 | Theoretical and Fundamental Chemistry |
The need to use two compressors in a booster set-up tends to increase the cost of a refrigeration system. A two staged system also needs synchronization, pressure control and lubrication. To reduce these costs, specialized equipment has been developed.
Economizer screw compressors are built by several manufacturers like Refcomp, Mycom, Bitzer and York. These machines merge both compressors of a two staged system into one screw compressor with two inputs: the main suction and an interstage side entrance for higher pressure gas. This means there is no need to install two compressors and still benefit from the booster concept.
There are two types of economizer setups for these compressors, flash and subcooling. The latter works like a two staged booster with subcooling. The flash economizer is different because it doesn't use a heat exchanger to produce the subcooling. Instead, it has a flash chamber or tank, in which flash gas is produced to lower the temperature of the liquid before the expansion. The flash gas that is produced in this tank leaves the liquid line and goes to the economizer entrance of the screw compressor. | 0 | Theoretical and Fundamental Chemistry |
The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating. However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry. | 0 | Theoretical and Fundamental Chemistry |
The patio process is a process for extracting silver from ore. Smelting, or refining, is most often necessary because silver is only infrequently found as a native element like some metals nobler than the redox couple 2 + 2 ⇌ (gold, mercury, ...). Instead, it is made up of a larger ore body. Thus, smelting, or refining, is necessary to reduce the compound containing the cation into metallic Ag and to remove other byproducts to get at pure silver. The process, which uses mercury amalgamation to recover silver from ore, was first used at scale by Bartolomé de Medina in Pachuca, Mexico, in 1554. It replaced smelting as the primary method of extracting silver from ore at Spanish colonies in the Americas. Although some knowledge of amalgamation techniques were likely known since the classical era, it was in the New World that it was first used on a large industrial scale. Other amalgamation processes were later developed, importantly the pan amalgamation process, and its variant, the Washoe process. The silver separation process generally differed from gold parting and gold extraction, although amalgamation with mercury is also sometimes used to extract gold. While gold was often found in the Americas as a native metal or alloy, silver was often found as a compound such as silver chloride and silver sulfide, and therefore required mercury amalgamation for refinement. | 1 | Applied and Interdisciplinary Chemistry |
Archaerhodopsin proteins are a family of retinal-containing photoreceptors found in the archaea genera Halobacterium and Halorubrum. Like the homologous bacteriorhodopsin (bR) protein, archaerhodopsins harvest energy from sunlight to pump H ions out of the cell, establishing a proton motive force that is used for ATP synthesis. They have some structural similarities to the mammalian G protein-coupled receptor protein rhodopsin, but are not true homologs.
Archaerhodopsins differ from bR in that the claret membrane, in which they are expressed, includes bacterioruberin, a second chromophore thought to protect against photobleaching. Also, bR lacks the omega loop structure observed at the N-terminus of the structures of several archaerhodopsins.
Mutants of Archaerhodopsin-3 (AR3) are used as tools in optogenetics for neuroscience research. | 0 | Theoretical and Fundamental Chemistry |
Aerobic granulation technology for the application in wastewater treatment is widely developed at laboratory scales. The large-scale experience is growing rapidly and multiple institutions are making efforts to improve this technology:
* Since 1999 Royal HaskoningDHV (former DHV Water), Delft University of technology (TUD), STW (Dutch Foundation for Applied Technology) and STOWA (Dutch Foundation for Applied Water Research) have been cooperating closely on the development of the aerobic granular sludge technology ([http://www.royalhaskoningdhv.com/en-gb/nereda Nereda]). In September 2003, a first extensive pilot plant research was executed at STP Ede, the Netherlands with focus on obtaining stable granulation and biological nutrient removal. Following the positive outcome together with six Dutch Water Boards the parties decided to establish a Public-Private Partnership (PPP)- the National Nereda Research Program [http://www.neredannop.nl (NNOP)]- to mature, further scale-up and implement several full-scale units. As part of this PPP extensive pilot tests have been executed between 2003 and 2010 at multiple sewage treatment plants. Currently more than 20 plants are running or under construction across 3 continents.
* From the basis of the aerobic granular sludge but using a contention system for the granules, a sequencing batch biofilter granular reactor (SBBGR) with a volume of 3.1m was developed by IRSA (Istituto di Ricerca Sulle Acque, Italy). Different studies were carried out in this plant treating sewage at an Italian wastewater treatment plant.
* The use of aerobic granules prepared in laboratory, as a starter culture, before adding in main system, is the base of the technology ARGUS (Aerobic granules upgrade system) developed by EcoEngineering Ltd.. The granules are cultivated on-site in small bioreactors called propagators and fill up only 2 to 3% of the main bioreactor or fermentor (digestor) capacity. This system is being used in a pilot plant with a volume of 2.7 m located in one Hungarian pharmaceutical industry.
* The Group of Environmental Engineering and Bioprocesses from the University of Santiago de Compostela is currently operating a 100 L pilot plant reactor.
The feasibility study showed that the aerobic granular sludge technology seems very promising (de Bruin et al., 2004. Based on total annual costs a GSBR (Granular sludge sequencing batch reactors) with pre-treatment and a GSBR with post-treatment proves to be more attractive than the reference activated sludge alternatives (6–16%).
A sensitivity analysis shows that the GSBR technology is less sensitive to land price and more sensitive to rain water flow. Because of the high allowable volumetric load the footprint of the GSBR variants is only 25% compared to the references. However, the GSBR with only primary treatment cannot meet the present effluent standards for municipal wastewater, mainly because of exceeding the suspended solids effluent standard caused by washout of not well settleable biomass. | 1 | Applied and Interdisciplinary Chemistry |
In the wake of the Castle Bravo detonation, a new research section was added to the Castle Bravo Weapons Effects research section. Program 4, "Biomedical effects," was to include one project, Project 4.1, titled "Study of Response of Human Beings exposed to Significant Beta and Gamma Radiation due to Fall-out from High-Yield Weapons." Eugene P. Cronkite of the National Naval Medical Center was designated as Project Officer. Cronkite's instructions stressed the importance of secrecy surrounding the project:
The purpose of the project, as a 1982 Defense Nuclear Agency report explained, was both medical as well as for research purposes: | 0 | Theoretical and Fundamental Chemistry |
Since glycans play an important role in intercellular interactions and protein, they serve as viable targets for various therapeutic interactions. Multiple current therapeutics aim to take advantage of their role in signaling pathways, and target their biosynthesis or engineer related glycoproteins. These interactions can be controlled by encouraging or inhibiting the presence of those glycans that mediate signaling, which is the mechanism of action for a number of extant drugs, including heparin, erythropoietin, the antivirals oseltamivir and zanamivir, and the Hib vaccine. Furthermore, the glycans themselves can serve as drugs and there is ongoing research and development to engineer more effective ones. | 1 | Applied and Interdisciplinary Chemistry |
A: α-naphthol – 5 g
*Absolute ethyl alcohol – 100 mL – 0.6 mL – 3 parts
*B: KOH – 40 g
*Distilled water – 100 mL – 0.2 mL – 1 part | 0 | Theoretical and Fundamental Chemistry |
Homogeneous broadening is a type of emission spectrum broadening in which all atoms radiating from a specific level under consideration radiate with equal opportunity. If an optical emitter (e.g. an atom) shows homogeneous broadening, its spectral linewidth is its natural linewidth, with a Lorentzian profile. | 0 | Theoretical and Fundamental Chemistry |
Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low-melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal. For higher melting point metals and alloys such as steel and silver, oxidized impurities melt and float making them easy to pour off.
With wrought iron, hammering and later rolling remove some dross.
With tin and lead the dross can be removed by adding sodium hydroxide pellets, which dissolve the oxides and form a slag. If floating, dross can also be skimmed off.
Dross, as a solid, is distinguished from slag, which is a liquid. Dross product is not entirely waste material; for example, aluminium dross can be recycled and is also used in secondary steelmaking for slag deoxidation. | 1 | Applied and Interdisciplinary Chemistry |
Circuit-breakers can be placed at portions of a circuit in series to the path of current it will affect. If more current than expected goes through the circuit-breaker, the circuit breaker "opens" the circuit and stops all current. A fuse is a common type of circuit breaker that involves direct effect of Joule-overheating. A fuse is always placed in series with the path of current it will affect. Fuses usually consist of a thin strand of wire of definite-material. When more that the rated current flows through the fuse, the wire melts and breaks the circuit. | 0 | Theoretical and Fundamental Chemistry |
Hydroxyl radicals are highly reactive and undergo chemical reactions that make them short-lived. When biological systems are exposed to hydroxyl radicals, they can cause damage to cells, including those in humans, where they can react with DNA, lipids, and proteins. | 0 | Theoretical and Fundamental Chemistry |
Mucoadhesion involves several types of bonding mechanisms, and it is the interaction between each process that allows for the adhesive process. The major categories are wetting theory, adsorption theory, diffusion theory, electrostatic theory, and fracture theory. Specific processes include mechanical interlocking, electrostatic, diffusion interpenetration, adsorption and fracture processes. | 1 | Applied and Interdisciplinary Chemistry |
Recent work demonstrates MTTF prediction using a machine learning model. The work uses a neural network-based supervised learning approach with current density, interconnect length, interconnect temperature as input features to the model. | 0 | Theoretical and Fundamental Chemistry |
Electron excitation is the movement of an electron to a higher energy state. This can either be done by photoexcitation (PE), where the original electron absorbs the photon and gains all the photon's energy or by electrical excitation (EE), where the original electron absorbs the energy of another, energetic electron. Within a semiconductor crystal lattice, thermal excitation is a process where lattice vibrations provide enough energy to move electrons to a higher energy band. When an excited electron falls back to a lower energy state again, it is called electron relaxation. This can be done by radiation of a photon or giving the energy to a third spectator particle as well.
In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state. The excited state, in general, is in relation to the ground state, where the excited state is at a higher energy level than the ground state. | 0 | Theoretical and Fundamental Chemistry |
It is common in electrochemistry and solid-state physics to discuss both the chemical potential and the electrochemical potential of the electrons. However, in the two fields, the definitions of these two terms are sometimes swapped. In electrochemistry, the electrochemical potential of electrons (or any other species) is the total potential, including both the (internal, nonelectrical) chemical potential and the electric potential, and is by definition constant across a device in equilibrium, whereas the chemical potential of electrons is equal to the electrochemical potential minus the local electric potential energy per electron. In solid-state physics, the definitions are normally compatible with this, but occasionally the definitions are swapped.
This article uses the electrochemistry definitions. | 0 | Theoretical and Fundamental Chemistry |
Substituted derivatives of porphine are called porphyrins. Many porphyrins are found in nature with the dominant example being protoporphyrin IX. Many synthetic porphyrins are also known, including octaethylporphyrin and tetraphenylporphyrin. | 1 | Applied and Interdisciplinary Chemistry |
The compound is stable on a temperature up to approximately . If the temperature is higher than that value, the following reaction, known as Rammelsberg's reaction, occurs: | 0 | Theoretical and Fundamental Chemistry |
A key characteristic of ATM is the orientation of the polarized electric field of THz light at the sample. In particular, unlike other microspectroscopy techniques like scattering scanning near-field optical microscopy (s-SNOM), the electric field of the interrogating THz field is parallel to the surface of the sample. In s-SNOM, the shape of the oscillating metallic probe tip directs the THz polarization into a direction predominantly perpendicular to the sample surface. | 0 | Theoretical and Fundamental Chemistry |
The deviation from ideality is taken to be a function of the potential energy resulting from the electrostatic interactions between ions and their surrounding clouds. To calculate this energy two steps are needed.
The first step is to specify the electrostatic potential for ion j by means of Poisson's equation
ψ(r) is the total potential at a distance, r, from the central ion and ρ(r) is the averaged charge density of the surrounding cloud at that distance. To apply this formula it is essential that the cloud has spherical symmetry, that is, the charge density is a function only of distance from the central ion as this allows the Poisson equation to be cast in terms of spherical coordinates with no angular dependence.
The second step is to calculate the charge density by means of a Boltzmann distribution.
where k is Boltzmann constant and T is the temperature. This distribution also depends on the potential ψ(r) and this introduces a serious difficulty in terms of the superposition principle. Nevertheless, the two equations can be combined to produce the Poisson–Boltzmann equation.
Solution of this equation is far from straightforward. Debye and Hückel expanded the exponential as a truncated Taylor series to first order. The zeroth order term vanishes because the solution is on average electrically neutral (so that Σ n z = 0), which leaves us with only the first order term. The result has the form of the Helmholtz equation
which has an analytical solution. This equation applies to electrolytes with equal numbers of ions of each charge. Nonsymmetrical electrolytes require another term with ψ. For symmetrical electrolytes, this reduces to the modified spherical Bessel equation
The coefficients and are fixed by the boundary conditions. As , must not diverge, so . At , which is the distance of the closest approach of ions, the force exerted by the charge should be balanced by the force of other ions, imposing , from which is found, yielding
The electrostatic potential energy, , of the ion at is
This is the potential energy of a single ion in a solution. The multiple-charge generalization from electrostatics gives an expression for the potential energy of the entire solution (see also: Debye–Hückel equation). The mean activity coefficient is given by the logarithm of this quantity as follows (see also: Extensions of the theory)
where I is the ionic strength and a is a parameter that represents the distance of closest approach of ions. For aqueous solutions at 25 °C A = 0.51 moldm and B = 3.29 nmmoldm
The most significant aspect of this result is the prediction that the mean activity coefficient is a function of ionic strength rather than the electrolyte concentration. For very low values of the ionic strength the value of the denominator in the expression above becomes nearly equal to one. In this situation the mean activity coefficient is proportional to the square root of the ionic strength. This is known as the Debye–Hückel limiting law. | 0 | Theoretical and Fundamental Chemistry |
The Cauchy problem for the 1d Kuramoto–Sivashinsky equation is well-posed in the sense of Hadamard—that is, for given initial data , there exists a unique solution that depends continuously on the initial data.
The 1d Kuramoto–Sivashinsky equation possesses Galilean invariance—that is, if is a solution, then so is , where is an arbitrary constant. Physically, since is a velocity, this change of variable describes a transformation into a frame that is moving with constant relative velocity . On a periodic domain, the equation also has a reflection symmetry: if is a solution, then is also a solution. | 1 | Applied and Interdisciplinary Chemistry |
The internodes are the myelin segments and the gaps between are referred to as nodes. The size and the spacing of the internodes vary with the fiber diameter in a curvilinear relationship that is optimized for maximal conduction velocity. The size of the nodes span from 1–2 μm whereas the internodes can be up to (and occasionally even greater than)1.5 millimetres long, depending on the axon diameter and fiber type.
The structure of the node and the flanking paranodal regions are distinct from the internodes under the compact myelin sheath, but are very similar in CNS and PNS. The axon is exposed to the extra-cellular environment at the node and is constricted in its diameter. The decreased axon size reflects a higher packing density of neurofilaments in this region, which are less heavily phosphorylated and are transported more slowly. Vesicles and other organelles are also increased at the nodes, which suggest that there is a bottleneck of axonal transport in both directions as well as local axonal-glial signaling.
When a longitudinal section is made through a myelinating Schwann cell at the node, three distinctive segments are represented: the stereotypic internode, the paranodal region, and the node itself. In the internodal region, the Schwann cell has an outer collar of cytoplasm, a compact myelin sheath, and inner collar of cytoplasm, and the axolemma. At the paranodal regions, the paranodal cytoplasm loops contact thickenings of the axolemma to form septate –like junctions. In the node alone, the axolemma is contacted by several Schwann microvilli and contains a dense cytoskeletal undercoating. | 1 | Applied and Interdisciplinary Chemistry |
Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions. They are natural catalysts and are ubiquitous, in plants, animals and microorganisms where they catalyze processes that are vital to living organisms. They are intimately involved in numerous biotechnological processes, such as cheese making, beer brewing and winemaking, that date back to the dawn of civilization. Recent advances in biotechnology, particularly in genetic and protein engineering, and genetics have provided the basis for the efficient development of enzymes with improved properties for established applications and novel, tailor-made enzymes for completely new applications where enzymes were not previously used.
Today, enzymes are widely applied in many different industries and the number of applications continues to increase. Examples include food (baking, dairy products, starch conversion) and beverage (beer, wine, fruit and vegetable juices) processing, animal feed, textiles, pulp and paper, detergents, biosensors, cosmetics, health care and nutrition, waste water treatment, pharmaceutical and chemical manufacture and, more recently, biofuels such as biodiesel. The main driver for the widespread application of enzymes is their small environmental footprint.
Many traditional chemical conversions used in various industries suffer from inherent drawbacks from both an economic and environmental viewpoint. Non-specific reactions can afford low product yields, copious amounts of waste and impure products. The need for elevated temperatures and pressures leads to high energy consumption and high capital investment costs. Disposal of unwanted by-products may be difficult and/or expensive and hazardous solvents may be required. In stark contrast, enzymatic reactions are performed under mild conditions of temperature and pressure, in water as solvent, and exhibit very high rates and are often highly specific. Moreover, they are produced from renewable raw materials and are biodegradable. In addition, the mild operating conditions of enzymatic processes mean that they can be performed in relatively simple equipment and are easy to control. In short, they reduce the environmental footprint of manufacturing by reducing the consumption of energy and chemicals and concomitant generation of waste.
In the production of fine chemicals, flavors and fragrances, agrochemicals and pharmaceuticals an important benefit of enzymes is the high degree of chemoselectivity, regioselectivity and enantioselectivity which they exhibit. Particularly, their ability to catalyze the formation of products in high enantiopurity, by an exquisite stereochemical control, is of the utmost importance in these industries.
Notwithstanding all these desirable characteristic features of enzymes, their widespread industrial application is often hampered by their lack of long term operational stability and shelf-storage life, as well as by their cumbersome recovery and re-use. These drawbacks can be generally overcome by enzyme immobilization. A major present challenge in industrial biocatalysis is the development of stable, robust and preferably insoluble biocatalysts. | 0 | Theoretical and Fundamental Chemistry |
Most cordials were of European origin, first produced in Italian apothecaries during the Renaissance, where the art of distilling was refined during the 15th and 16th centuries. It is from this origin that cordials are frequently referred to in French as Liqueurs dltalie', it is also from this that we have liqueurs. From the Renaissance onwards, cordials were usually based on alcohol in which certain herbs, spices or other ingredients were allowed to steep. The first cordials arrived in England in the late 15th century and were called distilled cordial waters. These were strictly used as alcoholic medicines, prescribed in small doses to invigorate and revitalise the heart, body and spirit as well as cure diseases. By the 18th century cordials were being imbibed for their intoxicating effects and medicinal virtues, and were fast becoming recreational drinks, eventually evolving into liqueurs.
Though cordials originated on the continent, a number of British "sweet drams" achieved popularity in Europe. | 1 | Applied and Interdisciplinary Chemistry |
Hatchett was awarded the Copley Medal by the Royal Society in 1798. In 1828, he was recognized by the Royal Institution. Hatchett, Humphry Davy, William Thomas Brande, William Hyde Wollaston, Michael Faraday and John Frederic Daniell received a gold medal for their discoveries in chemistry. The award was given by John Fuller, founder of the Institution's Fullerian Chair of Chemistry.
In 1979, the Companhia Brasileira de Metalurgia e Mineração established the Charles Hatchett Award.
It is presented by the Institute of Materials, Minerals and Mining ("IOM3") (London), yearly, to a noted metallurgist. The award is given for "the best research on the science and technology of niobium and its alloys". The medal is cast in pure niobium. | 1 | Applied and Interdisciplinary Chemistry |
Three minerals exist that are industrially relevant sources of fluorine: fluorite, fluorapatite, and cryolite. | 0 | Theoretical and Fundamental Chemistry |
Vi capsular polysaccharide vaccine (ViCPS) against typhoid caused by the Typhi serotype of Salmonella enterica. Instead of being a protein, the Vi antigen is a bacterial capsule polysacchide, made up of a long sugar chain linked to a lipid. Capsular vaccines like ViCPS tend to be weak at eliciting immune responses in children. Making a conjugate vaccine by linking the polysacchide with a toxoid increases the efficacy. | 1 | Applied and Interdisciplinary Chemistry |
The Journal of Organometallic Chemistry is a peer-reviewed scientific journal published by Elsevier, covering research on organometallic chemistry. According to the Journal Citation Reports, the journal has a 2021 impact factor of 2.345. | 0 | Theoretical and Fundamental Chemistry |
One mechanism of regulating CTCF is via methylation of its DNA sequence. CTCF protein is known to favourably bind to unmethylated sites, so it follows that methylation of CpG islands is a point of epigenetic regulation. An example of this is seen in the Igf2-H19 imprinted locus where methylation of the paternal imprinted control region (ICR) prevents CTCF from binding. A second mechanism of regulation is through regulating proteins that are required for fully functioning CTCF insulators. These proteins include, but are not limited to cohesin, RNA polymerase, and CP190. | 1 | Applied and Interdisciplinary Chemistry |
P is made by neutron bombardment of S
:S + n → P + p
It decays by beta decay with a half-life of 14.29 days. It is commonly used to study protein phosphorylation by kinases in biochemistry.
P is made in relatively low yield by neutron bombardment of P. It is also a beta-emitter, with a half-life of 25.4 days. Though more expensive than P, the emitted electrons are less energetic, permitting better resolution in, for example, DNA sequencing.
Both isotopes are useful for labeling nucleotides and other species that contain a phosphate group. | 0 | Theoretical and Fundamental Chemistry |
Muon spin rotation and relaxation are mostly performed with positive muons. They are well suited to the study of magnetic fields at the atomic scale inside matter, such as those produced by various kinds of magnetism and/or superconductivity encountered in compounds occurring in nature or artificially produced by modern material science.
The London penetration depth is one of the most important parameters characterizing a superconductor because its inverse square provides a measure of the density n of Cooper pairs. The dependence of n on temperature and magnetic field directly indicates the symmetry of the superconducting gap. Muon spin spectroscopy provides a way to measure the penetration depth, and so has been used to study high-temperature cuprate superconductors since their discovery in 1986.
Other important fields of application of µSR exploit the fact that positive muons capture electrons to form muonium atoms which behave chemically as light isotopes of the hydrogen atom. This allows investigation of the largest known kinetic isotope effect in some of the simplest types of chemical reactions, as well as the early stages of formation of radicals in organic chemicals. Muonium is also studied as an analogue of hydrogen in semiconductors, where hydrogen is one of the most ubiquitous impurities. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many organic compounds. It is a very stable group in most molecules. While the methyl group is usually part of a larger molecule, bounded to the rest of the molecule by a single covalent bond (), it can be found on its own in any of three forms: methanide anion (), methylium cation () or methyl radical (). The anion has eight valence electrons, the radical seven and the cation six. All three forms are highly reactive and rarely observed. | 0 | Theoretical and Fundamental Chemistry |
Circular DNA are more strongly affected by ethidium bromide concentration than linear DNA if ethidium bromide is present in the gel during electrophoresis. All naturally occurring DNA circles are underwound, but ethidium bromide which intercalates into circular DNA can change the charge, length, as well as the superhelicity of the DNA molecule, therefore its presence during electrophoresis can affect its movement in gel. Increasing ethidium bromide intercalated into the DNA can change it from a negatively supercoiled molecule into a fully relaxed form, then to positively coiled superhelix at maximum intercalation. Agarose gel electrophoresis can be used to resolve circular DNA with different supercoiling topology. | 1 | Applied and Interdisciplinary Chemistry |
The dynamics of the MPI can be described by finding the time evolution of the state of the atom which is described by the Schrödinger equation. The form of this equation in the electric field gauge, assuming the single active electron (SAE) approximation and using dipole approximation, is the following
where is the electric field of the laser and is the static Coulomb potential of the atomic core at the position of the active electron. By finding the exact solution of equation (1) for a potential ( the magnitude of the ionization potential of the atom), the probability current is calculated. Then, the total MPI rate from short-range potential for linear polarization, , is found from
where is the frequency of the laser, which is assumed to be polarized in the direction of the axis. The effect of the ionic potential, which behaves like ( is the charge of atomic or ionic core) at a long distance from the nucleus, is calculated through first order correction on the semiclassical action. The result is that the effect of ionic potential is to increase the rate of MPI by a factor of
Where and is the peak electric field of laser. Thus, the total rate of MPI from a state with quantum numbers and in a laser field for linear polarization is calculated to be
where is the Keldysh's adiabaticity parameter and . The coefficients , and are given by
The coefficient is given by
where
The ADK model is the limit of the PPT model when approaches zero (quasi-static limit). In this case, which is known as quasi-static tunnelling (QST), the ionization rate is given by
In practice, the limit for the QST regime is . This is justified by the following consideration. Referring to the figure, the ease or difficulty of tunneling can be expressed as the ratio between the equivalent classical time it takes for the electron to tunnel out the potential barrier while the potential is bent down. This ratio is indeed , since the potential is bent down during half a cycle of the field oscillation and the ratio can be expressed as
where is the tunneling time (classical time of flight of an electron through a potential barrier, and is the period of laser field oscillation. | 0 | Theoretical and Fundamental Chemistry |
* [https://archive.org/details/diegeschichtlich00farbuoft Die geschichtliche Entwicklung der Chemie] (The historical development of chemistry), Berlin: Springer 1921
* as translator and editor with Moritz Färber: Der skeptische Chemiker von Robert Boyle, Ostwalds Klassiker der exakten Wissenschaften; No. 229, 1928 (See Robert Boyles The Sceptical Chymist'.)
* Evolution of Chemistry: A History of Its Ideas, Methods, and Materials, New York: Ronald Press, 1952, 2nd Edition, 1969
* Nobel Prize Winners in Chemistry, 1953, [https://archive.org/details/nobelprizewinner00farb/page/n5 revised edition, 1962]
* as editor: Great Chemists, Interscience 1961
* Milestones of Modern Chemistry: Original Reports of the Discoveries, 1966 | 1 | Applied and Interdisciplinary Chemistry |
Ox gall is gall, usually obtained from cows, that is an ingredient in bile soap and mixed with alcohol and used as the wetting agent in paper marbling, engraving, lithography, and watercolor painting. It is a greenish-brown liquid mixture containing cholesterol, lecithin, taurocholic acid, and glycocholic acid. | 0 | Theoretical and Fundamental Chemistry |
Latest generation transmissometer technology makes use of a co-located forward scatter visibility sensor on the transmitter unit to allow for higher accuracies over an Extended Meteorological Optical Range or EMOR. After 10,000 meters the accuracy of transmissometer technology diminishes, and at higher visibilities forward scatter visibility sensor technology is more accurate. The co-location of the two sensors allows for the most accurate technology to be used when reporting current visibility. The forward scatter sensor also enables auto-alignment and auto-calibration of the transmissometer device. Hence it is very useful for oceanography and water optics study. | 0 | Theoretical and Fundamental Chemistry |
The advantage of “arming” and “disarming” glycosyl donors lies in their synthetic use. By disarming the glycosyl, a selective coupling can be achieved. The disarmed portion of the disaccharide can then be armed through selective deprotection. The disaccharide can then be coupled to a disarmed sugar. This process can be repeated as many times as necessary to achieve an efficient synthesis of a desired oligosaccharide with minimal loss of material to undesired coupling. This can be especially useful in “one-pot” synthetic methods. In these methods, multiple sugars are added to the reaction mixture. One of the sugars is armed as the glycosyl donor, and reacts quickly with a glycosyl acceptor. The non-reducing sugar then acts as a glycosyl acceptor as a protecting group that is easily lost in solution reveals a free hydroxyl group. This reacts with a donor that was disarmed, forming the oxocarbenium ion at a slower rate, producing the desired trisaccharide. | 0 | Theoretical and Fundamental Chemistry |
The analysis of slag is based on its shape, texture, isotopic signature, chemical and mineralogical characteristics. Analytical tools like Optical Microscope, scanning electron microscope (SEM), X-ray Fluorescence (XRF), X-ray diffraction (XRD) and inductively coupled plasma-mass spectrometry (ICP-MS) are widely employed in the study of slag. | 1 | Applied and Interdisciplinary Chemistry |
The process for TLC is similar to paper chromatography but provides faster runs, better separations, and the choice between different stationary phases. Plates can be labelled before or after the chromatography process with a pencil or other implement that will not interfere with the process.
There are four main stages to running a thin-layer chromatography plate:
Plate preparation: Using a capillary tube, a small amount of a concentrated solution of the sample is deposited near the bottom edge of a TLC plate. The solvent is allowed to completely evaporate before the next step. A vacuum chamber may be necessary for non-volatile solvents. To make sure there is sufficient compound to obtain a visible result, the spotting procedure can be repeated. Depending on the application, multiple different samples may be placed in a row the same distance from the bottom edge; each sample will move up the plate in its own "lane."
Development chamber preparation: The development solvent or solvent mixture is placed into a transparent container (separation/development chamber) to a depth of less than 1 centimetre. A strip of filter paper (aka "wick") is also placed along the container wall. This filter paper should touch the solvent and almost reach the top of the container. The container is covered with a lid and the solvent vapors are allowed to saturate the atmosphere of the container. Failure to do so results in poor separation and non-reproducible results.
Development: The TLC plate is placed in the container such that the sample spot(s) are not submerged into the mobile phase. The container is covered to prevent solvent evaporation. The solvent migrates up the plate by capillary action, meets the sample mixture, and carries it up the plate (elutes the sample). The plate is removed from the container before the solvent reaches the top of the plate; otherwise, the results will be misleading. The solvent front, the highest mark the solvent has travelled along the plate, is marked.
Visualization: The solvent evaporates from the plate. Visualization methods include UV light, staining, and many more. | 0 | Theoretical and Fundamental Chemistry |
The capillary length or capillary constant, is a length scaling factor that relates gravity and surface tension. It is a fundamental physical property that governs the behavior of menisci, and is found when body forces (gravity) and surface forces (Laplace pressure) are in equilibrium.
The pressure of a static fluid does not depend on the shape, total mass or surface area of the fluid. It is directly proportional to the fluid's specific weight – the force exerted by gravity over a specific volume, and its vertical height. However, a fluid also experiences pressure that is induced by surface tension, commonly referred to as the Young-Laplace pressure. Surface tension originates from cohesive forces between molecules, and in the bulk of the fluid, molecules experience attractive forces from all directions. The surface of a fluid is curved because exposed molecules on the surface have fewer neighboring interactions, resulting in a net force that contracts the surface. There exists a pressure difference either side of this curvature, and when this balances out the pressure due to gravity, one can rearrange to find the capillary length.
In the case of a fluid–fluid interface, for example a drop of water immersed in another liquid, the capillary length denoted or is most commonly given by the formula,
where is the surface tension of the fluid interface, is the gravitational acceleration and is the mass density difference of the fluids. The capillary length is sometimes denoted in relation to the mathematical notation for curvature. The term capillary constant is somewhat misleading, because it is important to recognize that is a composition of variable quantities, for example the value of surface tension will vary with temperature and the density difference will change depending on the fluids involved at an interface interaction. However if these conditions are known, the capillary length can be considered a constant for any given liquid, and be used in numerous fluid mechanical problems to scale the derived equations such that they are valid for any fluid. For molecular fluids, the interfacial tensions and density differences are typically of the order of and respectively resulting in a capillary length of mm for water and air at room temperature on earth. On the other hand, the capillary length would be mm for water-air on the moon. For a soap bubble, the surface tension must be divided by the mean thickness, resulting in a capillary length of about meters in air! The equation for can also be found with an extra term, most often used when normalising the capillary height. | 1 | Applied and Interdisciplinary Chemistry |
: Once genes or markers are identified, they can be used for genotyping and selection decisions can be made. | 1 | Applied and Interdisciplinary Chemistry |
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