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Another type of environmental contaminant can be found in the form of genetically modified organisms (GMOs), specifically when they come in contact with organic agriculture. This sort of contamination can result in the decertification of a farm. This sort of contamination can at times be difficult to control, necessitating mechanisms for compensating farmers where there has been contamination by GMOs. A Parliamentary Inquiry in Western Australia considered a range of options for compensating farmers whose farms had been contaminated by GMOs but ultimately settled on recommending no action. | 0 | Theoretical and Fundamental Chemistry |
Another way of deriving the Gibbs-Duhem equation can be found by taking the extensivity of energy into account. Extensivity implies that
where denotes all extensive variables of the internal energy . The internal energy is thus a first-order homogenous function. Applying Euler's homogeneous function theorem, one finds the following relation when taking only volume, number of particles, and entropy as extensive variables:
Taking the total differential, one finds
Finally, one can equate this expression to the definition of to find the Gibbs-Duhem equation | 0 | Theoretical and Fundamental Chemistry |
Although there is significant insight as to how OPVs work, it is still difficult to relate the devices functionality to local film structures. This difficulty may be attributed to the minimal current generation at a given point within OPVs. Through pc-AFM, OPV devices can be probed at nano-scale level and can help to increase our fundamental knowledge of mechanisms involved in OPVs at nano-scale level. pc-AFM is capable of gathering information such as the mapping of photocurrents, differences in film morphology, determination of donor-acceptor domains, current density-voltage plots, quantum efficiencies, and approximate charge carrier mobilities. One of the other notable characteristics of pc-AFM is its ability to provide concurrent information regarding the topological and photocurrent properties of the device at nano-scale. Using this concurrent sampling method, the sample handling is minimized and can provide more accurate results. In a study by Pingree et al., pc-AFM was used to measure how spatial deviations in the photocurrent generation developed with different processing techniques. The authors were able to compare these photocurrent variations to the duration of the annealing process. They have concluded that lengthening the annealing time allows for improved nano-scale phase separation as well as created a more ordered device. Actual times for the annealing process vary depending on the properties of the polymers used. The authors have shown that external quantum efficiency (EQE) and power conversion efficiency (PCE) levels reach a maximum at certain annealing times whereas while the electron and hole mobilitys do not show the corresponding trends. Therefore, while lengthening the annealing time can increase the photocurrents within the OPV, there is a practical limit to after which the benefits may not be substantial. Besides functional properties, pc-AFM can also be used to interrogate the composition heterogeneity of OPVs when combined with either Raman or infrared (IR) spectroscopy, and it is especially valuable for studying their degradation.
In more recent studies, pc-AFM has been employed to gather information regarding the photoactive regions from the use of quantum dots. Because if their relative ease of use, along with size-tunable excitation attributes, quantum dots have commonly been applied as sensitizers in optoelectronic devices. The authors have studied the photoresponse of sub-surface foundations such as buried indium arsenide (InAs) quantum dots through the implementation of pc-AFM. Through the use of pc-AFM, information regarding quantum dot size, as well as the dispersion of quantum dots within the device, can be recorded in a non-destructive manner. This information can then be used to display local variances in photoactivity relating to heterogeneities within the film morphology. | 0 | Theoretical and Fundamental Chemistry |
Tire derived fuel is usually consumed in the form of shredded or chipped material with most of the metal wire from the tire's steel belts removed. The analytical properties of this refined material are published in TDF Produced From Scrap Tires with 96+% Wire Removed.
Tires are typically composed of about 1 to 1.5% Zinc oxide, which is a well known component used in the manufacture of tires and is also toxic to aquatic and plant life. The chlorine content in tires is due primarily to the chlorinated butyl rubber liner that slows the leak rate of air. The Rubber Manufacturers Association (RMA) is a very good source for compositional data and other information on tires.
The use of TDF for heat production is controversial due to the possibility for toxin production. Reportedly, polychlorinated dibenzodioxins and furans are produced during the combustion process and there is supportive evidence to suggest that this is true under some incineration conditions. Other toxins such as NOx, SOx and heavy metals are also produced, though whether these levels of toxins are higher or lower than conventional coal and oil fired incinerators is not clear. | 1 | Applied and Interdisciplinary Chemistry |
CooA is a heme-containing transcription factor that responds to the presence of carbon monoxide. This protein forms homodimers and is a homolog of cAMP receptor protein. CooA regulates the expression of carbon monoxide dehydrogenase, an enzyme that catalyzes the oxidation of CO to CO. The most well-studied CooA homolog comes from Rhodospirillum rubrum (RrCooA), but the CooA homolog from Carboxydothermus hydrogenoformans (ChCooA) has been studied as well. The main difference between these two CooA homologs is the ferric heme coordination. For RrCooA, the ferric heme iron is bound to a cysteine and the amine of the N-terminal proline, while, in the ferrous state, a ligand switch occurs where a nearby histidine displaces the thiolate. For ChCooA, the heme iron is ligated by a histidine and the N-terminal amine in both the ferric and ferrous states. For both homologs, CO displaces the amine ligand and activates the protein to bind to its target DNA sequence. Several structures of CooA exist: RrCooA in the ferrous state (1FT9), ChCooA in the ferrous, imidazole-bound state (2FMY), and ChCooA in the ferrous, CO-bound state (2HKX). | 1 | Applied and Interdisciplinary Chemistry |
In environments where nuclear safety and radiation protection are required, radioactive contamination is a concern. Radioactive substances can appear on surfaces, or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable, and processes can give rise to their presence in such places. Several examples of radioactive contamination include:
* residual radioactive material remaining at a site after the completion of decommissioning of a site where there was a nuclear reactor, such as a power plant, experimental reactor, isotope reactor, or a nuclear powered ship or submarine
* ingested or absorbed radioactive material that contaminates a biological entity, whether unintentionally or intentionally (such as with radiopharmaceuticals
* escape of elements after nuclear accident, such as the contamination of Iodine-131 and Caesium-137 after the nuclear disaster in Chernobyl, Ukraine.
Note that the term "radioactive contamination" may have a connotation that is not intended. The term refers only to the presence of radioactivity and gives no indication itself of the magnitude of the hazard involved. However, radioactivity can be measured as a quantity in a given location or on a surface, or on a unit area of a surface, such as a square meter or centimeter.
Like environmental monitoring, radiation monitoring can be employed to catch contamination-causing activities before much harm. | 0 | Theoretical and Fundamental Chemistry |
* Chester (closed 24 August 1962)
* Dublin (1801-1922 part of UK system – see Dublin Assay Office)
* Exeter (closed 1883)
* Glasgow (closed 31 March 1964)
* Newcastle (closed 1884)
* Norwich (closed 1702)
* York (closed 1857) | 0 | Theoretical and Fundamental Chemistry |
Over-activation of mTOR signaling significantly contributes to the initiation and development of tumors and mTOR activity was found to be deregulated in many types of cancer including breast, prostate, lung, melanoma, bladder, brain, and renal carcinomas. Reasons for constitutive activation are several. Among the most common are mutations in tumor suppressor PTEN gene. PTEN phosphatase negatively affects mTOR signalling through interfering with the effect of PI3K, an upstream effector of mTOR. Additionally, mTOR activity is deregulated in many cancers as a result of increased activity of PI3K or Akt. Similarly, overexpression of downstream mTOR effectors 4E-BP1, S6K1, S6K2 and eIF4E leads to poor cancer prognosis. Also, mutations in TSC proteins that inhibit the activity of mTOR may lead to a condition named tuberous sclerosis complex, which exhibits as benign lesions and increases the risk of renal cell carcinoma.
Increasing mTOR activity was shown to drive cell cycle progression and increase cell proliferation mainly due to its effect on protein synthesis. Moreover, active mTOR supports tumor growth also indirectly by inhibiting autophagy. Constitutively activated mTOR functions in supplying carcinoma cells with oxygen and nutrients by increasing the translation of HIF1A and supporting angiogenesis. mTOR also aids in another metabolic adaptation of cancerous cells to support their increased growth rate—activation of glycolytic metabolism. Akt2, a substrate of mTOR, specifically of mTORC2, upregulates expression of the glycolytic enzyme PKM2 thus contributing to the Warburg effect. | 1 | Applied and Interdisciplinary Chemistry |
Dioxygen complexes are the precursors to other families of oxygenic ligands. Metal oxo compounds arise from the cleavage of the O–O bond after complexation. Hydroperoxo complexes are generated in the course of the reduction of dioxygen by metals. The reduction of O by metal catalysts is a key half-reaction in fuel cells.
Metal-catalyzed oxidations with O proceed via the intermediacy of dioxygen complexes, although the actual oxidants are often oxo derivatives. The reversible binding of O to metal complexes has been used as a means to purify oxygen from air, but cryogenic distillation of liquid air remains the dominant technology. | 0 | Theoretical and Fundamental Chemistry |
Spliceosomal splicing and self-splicing involve a two-step biochemical process. Both steps involve transesterification reactions that occur between RNA nucleotides. tRNA splicing, however, is an exception and does not occur by transesterification.
Spliceosomal and self-splicing transesterification reactions occur via two sequential transesterification reactions. First, the 2OH of a specific branchpoint nucleotide within the intron, defined during spliceosome assembly, performs a nucleophilic attack on the first nucleotide of the intron at the 5 splice site, forming the lariat intermediate. Second, the 3OH of the released 5 exon then performs a nucleophilic attack at the first nucleotide following the last nucleotide of the intron at the 3' splice site, thus joining the exons and releasing the intron lariat. | 1 | Applied and Interdisciplinary Chemistry |
DNA twist defects are when the addition of one or a few base pairs from one DNA segment are transferred to the next segment resulting in a change of the DNA twist. This will not only change the twist of the DNA but it will also change the length. This twist defect eventually moves around the nucleosome through the transferring of the base pair, this means DNA twists can cause nucleosome sliding. Nucleosome crystal structures have shown that superhelix location 2 and 5 on the nucleosome are commonly found to be where DNA twist defects occur as these are common remodeler binding sites. There are a variety of chromatin remodelers but all share the existence of an ATPase motor which facilitates chromatin sliding on DNA through the binding and hydrolysis of ATP. ATPase has an open and closed state. When the ATPase motor is changing from open and closed states, the DNA duplex changes geometry and exhibits base pair tilting. The initiation of the twist defects via the ATPase motor causes tension to accumulate around the remodeler site. The tension is released when the sliding of DNA has been completed throughout the nucleosome via the spread of two twist defects (one on each strand) in opposite directions. | 1 | Applied and Interdisciplinary Chemistry |
Compounds containing 2 geminal phosphonate groups are known as bisphosphonates. They were first synthesized in 1897 by Von Baeyer and Hofmann and now form the basis for an important class of drugs, used to treat osteoporosis and similar diseases. Examples include HEDP (etidronic acid or Didronel), which is prepared from phosphorous acid and acetic anhydride:
:2 HPO + (CHCO)O → CHC(OH)(POH) + CHCOH | 0 | Theoretical and Fundamental Chemistry |
To describe the Hund's coupling cases, we use the following angular momenta (where boldface letters indicate vector quantities):
*, the electronic orbital angular momentum
*, the electronic spin angular momentum
*, the total electronic angular momentum
*, the rotational angular momentum of the nuclei
*, the total angular momentum of the system (exclusive of nuclear spin)
*, the total angular momentum exclusive of electron (and nuclear) spin
These vector quantities depend on corresponding quantum numbers whose values are shown in molecular term symbols used to identify the states. For example, the term symbol Π denotes a state with S = 1/2, Λ = 1 and J = 3/2. | 0 | Theoretical and Fundamental Chemistry |
Lead contamination in drinking water can be from leaching of lead that was used in old water mains, service lines, pipe joints, plumbing fittings and fixtures. According to WHO, the most significant contributor of lead in water in many countries is the lead service line. | 1 | Applied and Interdisciplinary Chemistry |
Most of the ACE inhibitors on the market today are non-selective towards the two active sites of ACE because their binding to the enzyme is based mostly on the strong fundamental interaction between the zinc atom in the enzyme and the strong chelating group on the inhibitor. The resolution of the 3D structure of germinal ACE, which has only one active site that corresponds with C-domain of the somatic ACE, offers a structural framework for structure-based design approach. Although N- and C-domain have comparable rates in vitro of ACE hydrolyzing, it seems like that in vivo the C-domain is mainly responsible for regulating blood pressure. This indicates that C-domain selective inhibitors could have similar profile to that of a current non-selective inhibitors. Angiotensin I is mainly hydrolyzed by the C-domain in vivo but bradykinin is hydrolyzed by both active sites. Thus, by developing a C-domain selective inhibitor would permit some degradation of bradykinin by the N-domain and this degradation could be enough to prevent accumulation of excess bradykinin which has been observed during attacks of angioedema. C-domain selective inhibition could possibly result in specialized control of blood pressure with less vasodilator-related adverse effects. N-domain selective inhibitors on the other hand give the possibility of opening up novel therapeutic areas. Apparently, the N-domain does not have a big role in controlling blood pressure but it seems to be the principal metabolizing enzyme for AcSDKP, a natural haemoregulatory hormone. | 1 | Applied and Interdisciplinary Chemistry |
Fischer–Tropsch plants associated with biomass or coal or related solid feedstocks (sources of carbon) must first convert the solid fuel into gases. These gases include CO, H, and alkanes. This conversion is called gasification. Synthesis gas ("syngas") is obtained from biomass/coal gasification is a mixture of hydrogen and carbon monoxide. The H:CO ratio is adjusted using the water-gas shift reaction. Coal-based FT plants produce varying amounts of CO, depending upon the energy source of the gasification process. However, most coal-based plants rely on the feed coal to supply all the energy requirements of the process. | 0 | Theoretical and Fundamental Chemistry |
To answer this question one should know the different and important functions of glycans. The following are some of those functions:
*Glycoproteins and Glycolipids found on the cell surface play a critical role in bacterial and viral recognition.
*They are involved in cellular signaling pathways and modulate cell function.
*They are important in innate immunity.
*They determine cancer development.
*They orchestrate the cellular fate, inhibit proliferation, regulate circulation and invasion.
*They affect the stability and folding of proteins.
*They affect the pathway and fate of glycoproteins.
*There are many glycan-specific diseases, often hereditary diseases.
There are important medical applications of aspects of glycomics:
*Lectins fractionate cells to avoid graft-versus-host disease in hematopoietic stem cell transplantation.
*Activation and expansion of cytolytic CD8 T cells in cancer treatment.
Glycomics is particularly important in microbiology because glycans play diverse roles in bacterial physiology. Research in bacterial glycomics could lead to the development of:
* novel drugs
* bioactive glycans
* glycoconjugate vaccines | 0 | Theoretical and Fundamental Chemistry |
Tactic and stereoselective polymerizations are traditionally catalyzed by metal-organic complexes. Topochemical polymerization provides an additional choice. In addition, by changing the alignment of the monomer within the crystal, the tacticity/stereochemistry of the polymer product could be easily controlled. An intuitive example is shown in the figure. In topochemical polymerization of 1,3-diene carboxylic acid derivatives, polymers with four different configurations can be prepared. Their structural relationships with the monomer packing are also shown in the figure. | 0 | Theoretical and Fundamental Chemistry |
Because the stereoselectivity of carbocupration is extremely high, the reaction has been applied to the synthesis of pheromones in which the geometric purity of double bonds is critical. One example is the insect pheromone of Cossus cossus, which is synthesized by syn-selective carbocupration of acetylene and alkylation of the resulting organocuprate in the presence of added phosphite. | 0 | Theoretical and Fundamental Chemistry |
The term "inclusion" is also used in the context of metallurgy and metals processing. During the melt stage of processing particles such as oxides can enter or form in the liquid metal which are subsequently trapped when the melt solidifies. The term is usually used negatively such as when the particle could act as a fatigue crack nucleator or as an area of high stress intensity. | 1 | Applied and Interdisciplinary Chemistry |
The phagemid used to transform E. coli cells may be "rescued" from the selected cells by infecting them with VCS-M13 helper phage. The resulting phage particles that are produced contain the single-stranded phagemids and are used to infect XL-1 Blue cells. The double-stranded phagemids are subsequently collected from these XL-1 Blue cells, essentially reversing the process used to produce the original library phage. Finally, the DNA sequences are determined through dideoxy sequencing. | 1 | Applied and Interdisciplinary Chemistry |
The term was coined by Joseph Marius DallaValle in his book Micromeritics: The Technology of Fine Particles (1948). It was derived from the Greek words meaning "small" and meaning "part". The size range which he covered in the book was from 10 to 10 micrometers. Anything smaller than this but bigger than a molecule was referred to at the time as a colloid but is now often referred to as a nanoparticle. Applications included soil physics, mineral physics, chemical engineering, geology, and hydrology. Characteristics discussed included particle size and shape, packing, electrical, optical, chemical and surface science. | 0 | Theoretical and Fundamental Chemistry |
A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although this is debated. Rooftop ponds are another form of green roofs which are used to treat greywater. Vegetation, soil, drainage layer, roof barrier and irrigation system constitute green roof.
Green roofs serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, increasing benevolence, and decreasing stress of the people around the roof by providing a more aesthetically pleasing landscape, and helping to lower urban air temperatures and mitigate the heat island effect. Green roofs are suitable for retrofit or redevelopment projects as well as new buildings and can be installed on small garages or larger industrial, commercial and municipal buildings. They effectively use the natural functions of plants to filter water and treat air in urban and suburban landscapes. There are two types of green roof: intensive roofs, which are thicker, with a minimum depth of , and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are shallow, ranging in depth from , lighter than intensive green roofs, and require minimal maintenance.
The term green roof may also be used to indicate roofs that use some form of green technology, such as a cool roof, a roof with solar thermal collectors or photovoltaic panels. Green roofs are also referred to as eco-roofs, oikosteges, vegetated roofs, living roofs, greenroofs and VCP (Horizontal Vegetated Complex Partitions) | 1 | Applied and Interdisciplinary Chemistry |
Chitin is one of many naturally occurring polymers. It forms a structural component of many animals, such as exoskeletons. Over time it is bio-degradable in the natural environment. Its breakdown may be catalyzed by enzymes called chitinases, secreted by microorganisms such as bacteria and fungi and produced by some plants. Some of these microorganisms have receptors to simple sugars from the decomposition of chitin. If chitin is detected, they then produce enzymes to digest it by cleaving the glycosidic bonds in order to convert it to simple sugars and ammonia.
Chemically, chitin is closely related to chitosan (a more water-soluble derivative of chitin). It is also closely related to cellulose in that it is a long unbranched chain of glucose derivatives. Both materials contribute structure and strength, protecting the organism. | 0 | Theoretical and Fundamental Chemistry |
Several fungi species have radioactive resistance values equal to or greater than more radioresistant bacteria; they perform mycoremediation processes. It was reported that some fungi had the ability of growing into, feeding, generating spores and decomposing pieces of graphite from destroyed reactor No. 4 at the Chernobyl Nuclear Power Station, which is contaminated with high concentrations of cesium, plutonium and cobalt radionuclides. They were called radiotrophic fungi.
Since then, it has been shown that some species of Penicillium, Cladosporium, Paecilomyces and Xerocomus are able to use ionizing radiation as energy through the electronic properties of melanins. In their feeding they bioaccumulate radioisotopes, creating problems on concrete walls of deep geological repositories. Other fungi like oyster mushrooms can bioremediate plutonium-239 and americium-241. | 1 | Applied and Interdisciplinary Chemistry |
TRFLP is one of several molecular methods aimed to generate a fingerprint of an unknown microbial community. Other similar methods include DGGE, TGGE, ARISA, ARDRA, PLFA, etc.
<br>These relatively high throughput methods were developed in order to reduce the cost and effort in analyzing microbial communities using a clone library. The method was first described by Avaniss-Aghajani et al in 1994 and later by Liu in 1997 which employed the amplification of the 16S rDNA target gene from the DNA of several isolated bacteria as well as environmental samples.
<br>Since then the method has been applied for the use of other marker genes such as the functional marker gene pmoA to analyze methanotrophic communities. | 1 | Applied and Interdisciplinary Chemistry |
# Agriculture and Resource Management Council of Australia and New Zealand, “Prediction of Food Intake” In Feeding Standards for Australian Livestock; Ruminants (CSIRO Publishing, 1990) 261.
# Bentley, David, Hegarty, Rodger and Alford, Andrew, “Managing Livestock Enterprises in Australia’s Extensive Rangelands for Greenhouse Gas and Environmental Outcomes: A Pastoral Company Perspective,” Australian Journal of Experimental Agriculture 2, no. 48, (January 2008) 60–64.
# Brightling, Anthony, Brightling, Tony and Fowler, Diane, "Issues with Cattle" In Livestock Diseases in Australia; Diseases of Cattle, Sheep, Goats and Farm Dogs (C.H. Jerram & Associates, 2006) 21.
# Buckley, David, The Cattle Parasite Atlas; A Regional Guide to Cattle Parasite Control in Australia (CSIRO publishing, 2005) 32.
# Cranston, Michael, “Leading Cattle Company The North Australian Pastoral” The North Queensland Register, 13 September 2012, 5.
# Commonwealth Scientific and Industrial Research Organization for the Australian Agricultural Council, Australian Journal of Experimental Agriculture and Animal Husbandry, (Cornell University Publishers, 1979) 261.
# Denniss, Siobhan, A Critique of Environmental Management Systems and their Relevance in the North Australian Pastoral Industry (Melbourne: MTEM Publishers, 2002) 28.
# Derner, Justin D, “Livestock Production Systems,” in Rangeland Systems: Processes, Management and Challenges, ed. David D. Briske, (Springer International Publishing: 2017) 347.
# Dundon, Peter, "Feedlots" In The Australian Feedlot Directory, (Elders Press Ltd, 1994) 12; Quevedo Martin Morgan, “The Beef Cattle Industry” In Australia's Livestock and Meat Industry, (Urbana-Champaign: University of Illinois Press, 1971) 2.
# Eldridge, David J, Poore, Alistair G. B, Ruiz-Colmenero, Marta, Letnic, Mike and Soliveres, Santiago, “Ecosystem structure, function, and composition in rangelands are negatively affected by livestock grazing” In Ecological Applications, Vol. 26 No. 4 (Ecological Society of America, 2016) 1273–1283.
# Gerber, Pierre, Mooney, Harold A. and Dijkman, Jeroen “Livestock in a Changing Landscape” In Experiences and Regional Perspectives, Vol. 2 (Stanford: Island Press, 2010) 23.
# Gerrard, Marjorie A and O’Leary, Patrick, “Union-Avoidance Strategies in the Meat Industry in Australia and the United States” In Frontiers of Labor: Comparative Histories of the United States and Australia, ed. Greg Patmore, (Illinois: University of Illinois Press, 2018), 129.
# Kahn, Lewis and Cottle, David John, “Beef Composition of the Northern Beef Herd” In Beef Cattle Production and Trade (CSIRO publishing, 2014) 180.
# Lesslie, Rob and Mewett, Jodie, “Land Use and Management - The Australian Context” in Land Use in Australia: Past, Present and Future, ed. Richard Trackway (Australian National University Press, 2018) 31.
# Meat and Livestock Australia, “Composite Breeds in the Northern Rangelands” In Beef Cattle Nutrition; An Introduction to the Essentials, (Meat and Livestock Australia, 2006) 76.
# Millard, Steve “Experiences with Composites: North Australia Pastoral Company (NAPCO)” Armidale Feeder Steer School; Conference Proceedings and Support Material no.1 (August 2003): 131–133.
# M. Moore, Raymond, “Proceedings” In Australian Grasslands, (Australian National University Press, 1970) 22.
# Pearson, Michael, “Exploring in the 1860s and 1870s,” in Pastoral Australia: Fortunes, Failures and Hard Yakka: A Historical Overview 1788-1967 ed Jane Lennon, (Collingwood: CSIRO publishing, 2010) 103–106.
# Phillips, Amy, “NAPCO for sale; The North Australian Pastoral Company, One of the Largest Cattle Producers and Landholders in Northern Australia, is for Sale” ABC Regional News NSW, 13 May 2013, 3.
# Reid, Robert L, "Agriculture and the Economy" from The Manual of Australian Agriculture (Butterworths publishers, 1990) 1.
# Velado-Alonso, Elena, Morales-Castilla, Ignacio, Rebollo, Salvador and Gómez-Sal, Antonio, “Relationships between the distribution of wildlife and livestock diversity” In Diversity and Distributions, Vol. 26 No. 10, (Wiley Publishers, 2010) 1264. | 1 | Applied and Interdisciplinary Chemistry |
In podsolisation, chelating agents break down clay and release minerals such as iron and aluminium. When iron and aluminium are hydrated they become sesquioxides. The sesquioxides are translocated from the A Horizon, a zone of out-washing, to the B Horizon, a zone of illuviation. Many bases such as calcium and potassium are also leached from the zone along with organic matter and silica. Often minerals like quartz and silica are left behind in the A horizon. What is significantly different about podsols in comparison to other soils is that the bottom of A horizon is known as the AE horizon, which is an eluviated area which has lost sesquioxides. It tends to be an ash gray colour. | 0 | Theoretical and Fundamental Chemistry |
Recursively partitioning is method that creates a decision tree using qualitative data. Understanding the way rules break classes up with a low error of misclassification while repeating each step until no sensible splits can be found. However, recursive partitioning can have poor prediction ability potentially creating fine models at the same rate. | 1 | Applied and Interdisciplinary Chemistry |
In Bayesian statistics, relative entropy can be used as a measure of the information gain in moving from a prior distribution to a posterior distribution: . If some new fact is discovered, it can be used to update the posterior distribution for from to a new posterior distribution using Bayes' theorem:
This distribution has a new entropy:
which may be less than or greater than the original entropy . However, from the standpoint of the new probability distribution one can estimate that to have used the original code based on instead of a new code based on would have added an expected number of bits:
to the message length. This therefore represents the amount of useful information, or information gain, about , that has been learned by discovering .
If a further piece of data, , subsequently comes in, the probability distribution for can be updated further, to give a new best guess . If one reinvestigates the information gain for using rather than , it turns out that it may be either greater or less than previously estimated:
: may be ≤ or > than
and so the combined information gain does not obey the triangle inequality:
: may be
All one can say is that on average, averaging using , the two sides will average out. | 0 | Theoretical and Fundamental Chemistry |
Quinaldine red is an indicator that turns from colorless to red between a pH of 1.0–2.2. The image below shows what color quinaldine red would appear as in a given pH.
It is a cationic molecule that undergoes oxidation at different levels of pH. The rate of oxidation of Quinaldine red is in the first order with respect to the concentration of the oxidizing agent.
Other factors that increases the rate of oxidation includes increasing pH and increased sodium carbonate concentration. The reaction rate eventually levels off due to the maximum formation of the product within the oxidation process.
Quinaldine red also has the ability to fluoresce. Free quinaldine red does not fluoresce in solution when it is not bound to anything, making quinaldine red only visible by fluorescence when it is bound to something. Quinaldine red can exhibit fluorescence when it is bound to nucleic acids, which then emit radiation between 580-650 nm.
Maximum fluorescence of QR is detected from 557 nm to 607 nm. QR and the nucleic acids react quickly under room temperature, and the resulting QR-nucleic acid complex is able to fluorescence. However, fluorescent activity decrease as time goes on. Maximum fluorescence between QR and DNA is found within the pH range of 3.2-3.6, with the optimum being a pH 3.5. The amount of fluorescence seen with the use of QR is linearly related to the concentrations of DNA or RNA. | 0 | Theoretical and Fundamental Chemistry |
Lithium dimethylcuprate exists as a dimer in diethyl ether forming an 8-membered ring. Similarly, lithium diphenylcuprate crystallizes as a dimeric etherate, .
If the Li ions is complexed with the crown ether 12-crown-4, the resulting diorganylcuprate anions adopt a linear coordination geometry at copper.
For the higher order cyanocuprate LiCuCN(CH), the cyanide ligand is coordinated to Li and π-bound to Cu. | 0 | Theoretical and Fundamental Chemistry |
Binding affinity carries a huge importance in medicinal chemistry, as drugs need to bind to the protein effectively within a desired range. However, determining enthalpy changes and optimization of thermodynamic parameters are hugely difficult when designing drugs. ITC troubleshoots this issue easily by deducing the binding affinity, enthalpic/entropic contributions and its binding stoichiometry. | 0 | Theoretical and Fundamental Chemistry |
The Mount Polley mine's tailings facility experienced a dam breach and tailings spill that began 4 August 2014. The four square kilometre tailings pond spilled an estimated 25 billion litres of contaminated materials into Polley Lake, Hazeltine Creek, Quesnel Lake, and Cariboo River, a source of drinking water and major spawning grounds for sockeye salmon. Quesnel Lake is claimed to be the deepest fjord lake in the world, the third deepest lake in North America, and is the major tributary of the Fraser River.
According to Mount Polley mine records filed with Environment Canada in 2013, there were “326 tonnes of nickel, over 400 tonnes of arsenic, 177 tonnes of lead and 18,400 tonnes of copper and its compounds placed in the tailings pond,” in 2012.
By 8 August the sized tailings pond had been emptied of the majority of "process water" from which the crushed rock solids, or "tailings", gradually settle out. The slurry of tailings and process water carried felled trees, mud and debris and wore away the banks of Hazeltine Creek which flows out of Polley Lake and continued into the nearby Quesnel Lake. The spill emptied the tailings pond and caused Polley Lake to rise by . | 1 | Applied and Interdisciplinary Chemistry |
XPS is widely used to generate an empirical formula because it readily yields excellent quantitative accuracy from homogeneous solid-state materials. Absolute quantification requires the use of certified (or independently verified) standard samples, and is generally more challenging, and less common. Relative quantification involves comparisons between several samples in a set for which one or more analytes are varied while all other components (the sample matrix) are held constant. Quantitative accuracy depends on several parameters such as: signal-to-noise ratio, peak intensity, accuracy of relative sensitivity factors, correction for electron transmission function, surface volume homogeneity, correction for energy dependence of electron mean free path, and degree of sample degradation due to analysis. Under optimal conditions, the quantitative accuracy of the atomic percent (at%) values calculated from the major XPS peaks is 90-95% for each peak. The quantitative accuracy for the weaker XPS signals, that have peak intensities 10-20% of the strongest signal, are 60-80% of the true value, and depend upon the amount of effort used to improve the signal-to-noise ratio (for example by signal averaging). Quantitative precision (the ability to repeat a measurement and obtain the same result) is an essential consideration for proper reporting of quantitative results. | 0 | Theoretical and Fundamental Chemistry |
TDS spectrum 1 and 2 are typical examples of a TPD measurement. Both are examples of NO desorbing from a single crystal in high vacuum. The crystal was mounted on a titanium filament and heated with current. The desorbing NO was measured using a mass spectrometer monitoring the atomic mass of 30.
Before 1990 analysis of a TPD spectrum was usually done using a so-called simplified method; the "Redhead" method, assuming the exponential prefactor and the desorption energy to be independent of the surface coverage. After 1990 and with use of computer algorithms TDS spectra were analyzed using the "complete analysis method" or the "leading edge method". These methods assume the exponential prefactor and the desorption energy to be dependent of the surface coverage. Several available methods of analyzing TDS are described and compared in an article by A.M. de JONG and J.W. NIEMANTSVERDRIET. During parameter optimization/estimation, using the integral has been found to create a more well behaved objective function than the differential. | 0 | Theoretical and Fundamental Chemistry |
The cyclic enones include cyclopropenone, cyclobutenone, cyclopentenone, cyclohexenone, and cycloheptenone. | 0 | Theoretical and Fundamental Chemistry |
The surrounding blanket can be a fissile material (enriched uranium or plutonium) or a fertile material (capable of conversion to a fissionable material by neutron bombardment) such as thorium, depleted uranium or spent nuclear fuel. Such subcritical reactors (which also include particle accelerator-driven neutron spallation systems) offer the only currently-known means of active disposal (versus storage) of spent nuclear fuel without reprocessing. Fission by-products produced by the operation of commercial light water nuclear reactors (LWRs) are long-lived and highly radioactive, but they can be consumed using the excess neutrons in the fusion reaction along with the fissionable components in the blanket, essentially destroying them by nuclear transmutation and producing a waste product which is far safer and less of a risk for nuclear proliferation. The waste would contain significantly reduced concentrations of long-lived, weapons-usable actinides per gigawatt-year of electric energy produced compared to the waste from a LWR. In addition, there would be about 20 times less waste per unit of electricity produced. This offers the potential to efficiently use the very large stockpiles of enriched fissile materials, depleted uranium, and spent nuclear fuel. | 0 | Theoretical and Fundamental Chemistry |
Antibodies can also be used to purify their target compounds from mixtures, using the method of immunoprecipitation. | 1 | Applied and Interdisciplinary Chemistry |
Spectroscopic curves can be subjected to numerical differentiation.
When the data points in a curve are equidistant from each other the Savitzky–Golay convolution method may be used. The best convolution function to use depends primarily on the signal-to-noise ratio of the data. The first derivative (slope, ) of all single line shapes is zero at the position of maximum height. This is also true of the third derivative; odd derivatives can be used to locate the position of a peak maximum.
The second derivatives, , of both Gaussian and Lorentzian functions have a reduced half-width. This can be used to apparently improve spectral resolution. The diagram shows the second derivative of the black curve in the diagram above it. Whereas the smaller component produces a shoulder in the spectrum, it appears as a separate peak in the 2nd. derivative. Fourth derivatives, , can also be used, when the signal-to-noise ratio in the spectrum is sufficiently high. | 0 | Theoretical and Fundamental Chemistry |
Modifying lung and macrophage pathology has been shown to have a role in the host-directed therapies for MTB. | 1 | Applied and Interdisciplinary Chemistry |
* Plant cuticle/surface
* Plant cell walls
* Antimicrobial chemicals (for example: polyphenols, sesquiterpene lactones, saponins)
* Antimicrobial peptides
* Enzyme inhibitors
* Detoxifying enzymes that break down pathogen-derived toxins
* Receptors that perceive pathogen presence and activate inducible plant defences | 1 | Applied and Interdisciplinary Chemistry |
Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions. In chemical digestion, enzymes break down food into the small compounds that the body can use.
In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva. Saliva, a liquid secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. The saliva also contains mucus, which lubricates the food; the electrolyte hydrogencarbonate (), which provides the ideal conditions of pH for amylase to work; and other electrolytes (, , ). About 30% of starch is hydrolyzed into disaccharide in the oral cavity (mouth). After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus. It will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. In infants and toddlers, gastric juice also contains rennin to digest milk proteins. As the first two chemicals may damage the stomach wall, mucus and bicarbonates are secreted by the stomach. They provide a slimy layer that acts as a shield against the damaging effects of chemicals like concentrated hydrochloric acid while also aiding lubrication. Hydrochloric acid provides acidic pH for pepsin. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which is waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Pepsin breaks down proteins into peptides or proteoses, which is further broken down into dipeptides and amino acids by enzymes in the small intestine. Studies suggest that increasing the number of chews per bite increases relevant gut hormones and may decrease self-reported hunger and food intake.
When the pyloric sphincter valve opens, partially digested food (chyme) enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues. When the chyme is fully digested, it is absorbed into the blood. 95% of nutrient absorption occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon (large intestine) where the pH is slightly acidic (about 5.6 ~ 6.9). Some vitamins, such as biotin and vitamin K (KMK7) produced by bacteria in the colon are also absorbed into the blood in the colon. Absorption of water, simple sugar and alcohol also takes place in stomach. Waste material (feces) is eliminated from the rectum during defecation. | 1 | Applied and Interdisciplinary Chemistry |
Heinz Otto Schild (1906–1984) held the Chair of Pharmacology from 1961 to 1973.
He was born in Fiume (now Rijeka, Croatia), in 1908, when it was part of the Austro-Hungarian empire. He qualified in medicine in Munich and then worked with Straub, the leading German pharmacologist of the time. By good fortune, Schild had been accepted as a visiting worker by Sir Henry Dale and was in England when the National Socialists came to power in Germany. He decided to stay in Britain and became an assistant in the Department of Pharmacology in Edinburgh, then headed by A.J. Clark. When J. H. Gaddum was appointed to the chair at UCL, he invited Schild to join him as a Demonstrator. So began his long association with UCL, interrupted only by his bizarre internment on the Isle of Man as an ‘enemy alien’ at the outbreak of the Second World War. Following his release (greatly aided by F.R Wintons and Sir Henry Dales appeals to the Home Office) he returned to his work in the department, then based in Leatherhead, and in 1961 became Winton's successor as Head of Department and Professor of Pharmacology.
Schild made major contributions to receptor pharmacology, to the understanding of the mechanism of histamine release and to bioassay. Like Gaddum and Clark, he used quantitative approaches whenever possible. His name is immortalised by the Schild equation. He built on the work of Clark and Gaddum on competitive antagonism, by realising that the null method was key to extraction of physical equilibrium constants from simple functional experiments. Rather than looking at the depression by antagonist of the response to a fixed agonist concentration, he measured the dose-ratio, the factor by which the agonist concentration had to be increased in order to restore a given response in the presence of the antagonist. By measuring the dose-ratio as a function of antagonist, it was possible to estimate the dissociation equilibrium constant for the combination of the antagonist with its receptor. Crucially the estimate is not dependent on the nature of the agonist. Although Schild's derivation used the simplest possible model, it was subsequently shown that his equation is valid under much more general conditions.
A.J. Clarks textbook was continued by Schild as Clarks Applied Pharmacology by Wilson & Schild.
Heinz Schild was a generous and kindly Head of department. He appointed the third female member of academic staff, Dr M. Maureen Dale, a co-author of Rang & Dales Pharmacology. He oversaw the planning and introduction of a three-year B.Sc. course in Pharmacology which began in 1967 and continues to this day. Medical students were able to enter its final year and Schild, who never lost sight of the roots of the subject in medicine, was delighted that many took this opportunity. | 1 | Applied and Interdisciplinary Chemistry |
Many women of sub-Saharan Africa choose to foster their children to infertile women. IVF enables these infertile women to have their own children, which imposes new ideals to a culture in which fostering children is seen as both natural and culturally important. Many infertile women are able to earn more respect in their society by taking care of the children of other mothers, and this may be lost if they choose to use IVF instead. As IVF is seen as unnatural, it may even hinder their societal position as opposed to making them equal with fertile women. It is also economically advantageous for infertile women to raise foster children as it gives these children greater ability to access resources that are important for their development and also aids the development of their society at large. If IVF becomes more popular without the birth rate decreasing, there could be more large family homes with fewer options to send their newborn children. This could result in an increase of orphaned children and/or a decrease in resources for the children of large families. This would ultimately stifle the childrens and the communitys growth.
In the US, the pineapple has emerged as a symbol of IVF users, possibly because some people thought, without scientific evidence, that eating pineapple might slightly increase the success rate for the procedure. | 1 | Applied and Interdisciplinary Chemistry |
The essential idea in the Boussinesq approximation is the elimination of the vertical coordinate from the flow equations, while retaining some of the influences of the vertical structure of the flow under water waves. This is useful because the waves propagate in the horizontal plane and have a different (not wave-like) behaviour in the vertical direction. Often, as in Boussinesq's case, the interest is primarily in the wave propagation.
This elimination of the vertical coordinate was first done by Joseph Boussinesq in 1871, to construct an approximate solution for the solitary wave (or wave of translation). Subsequently, in 1872, Boussinesq derived the equations known nowadays as the Boussinesq equations.
The steps in the Boussinesq approximation are:
*a Taylor expansion is made of the horizontal and vertical flow velocity (or velocity potential) around a certain elevation,
*this Taylor expansion is truncated to a finite number of terms,
*the conservation of mass (see continuity equation) for an incompressible flow and the zero-curl condition for an irrotational flow are used, to replace vertical partial derivatives of quantities in the Taylor expansion with horizontal partial derivatives.
Thereafter, the Boussinesq approximation is applied to the remaining flow equations, in order to eliminate the dependence on the vertical coordinate.
As a result, the resulting partial differential equations are in terms of functions of the horizontal coordinates (and time).
As an example, consider potential flow over a horizontal bed in the plane, with the horizontal and the vertical coordinate. The bed is located at , where is the mean water depth. A Taylor expansion is made of the velocity potential around the bed level :
where is the velocity potential at the bed. Invoking Laplace's equation for , as valid for incompressible flow, gives:
since the vertical velocity is zero at the – impermeable – horizontal bed . This series may subsequently be truncated to a finite number of terms. | 1 | Applied and Interdisciplinary Chemistry |
Small molecules, proteins, and nucleic acids have been found to stimulate levels of frameshifting. For example, the mechanism of a negative feedback loop in the polyamine synthesis pathway is based on polyamine levels stimulating an increase in +1 frameshifts, which results in production of an inhibitory enzyme. Certain proteins which are needed for codon recognition or which bind directly to the mRNA sequence have also been shown to modulate frameshifting levels. MicroRNA (miRNA) molecules may hybridize to a RNA secondary structure and affect its strength. | 1 | Applied and Interdisciplinary Chemistry |
CMTM6 localizes with and binds to cell PD-L1 protein located on cell surface membranes thereby maintaining PD-L1'S expression at this site; it also localizes with PD-L1 protein located in recycling endosomes and thereby prevents PD-L1 from being degraded by lysosomal enzymes. These actions increase and maintain high levels of PD-L1 on cell surface membranes. PD-L1 protein on the surface of normal cells binds to PD-1 receptors on a type of cytotoxic T cells (i.e. CD8+ T cells) and thereby blocks these T-cells from organizing an immune response that would kill them. This PD-L1/CD8+ T cell circuit is one of several immune checkpoint mechanisms for maintaining self-tolerance, i.e. for preventing CD8+ T cells from attacking normal cells. Tumor cells may employ this immune-evading tactic: they may express PD-L1 and thereby block CD8+ T cell-mediated immune responses to themselves. In effect, the robust expression of PD-L1 helps not only normal cells but also cancer cells to evade immune destruction. | 1 | Applied and Interdisciplinary Chemistry |
Hydrocarbons are a class of molecule that is defined by functional groups called hydrocarbyls that contain only carbon and hydrogen, but vary in the number and order of double bonds. Each one differs in type (and scope) of reactivity.
There are also a large number of branched or ring alkanes that have specific names, e.g., tert-butyl, bornyl, cyclohexyl, etc. Hydrocarbons may form charged structures: positively charged carbocations or negative carbanions. Carbocations are often named -um. Examples are tropylium and triphenylmethyl cations and the cyclopentadienyl anion. | 0 | Theoretical and Fundamental Chemistry |
A common sulfinamide is tert-butanesulfinamide (Ellmans sulfinamide), p-toluenesulfinamide (Davis sulfinamide), and 2,4,6-trimethylbenzenesulfinamide.
Sulfinamides arise in nature by the addition of nitroxyl (HNO) to thiols:
:RSH + HNO → RS(O)NH | 0 | Theoretical and Fundamental Chemistry |
The Racah parameters are defined as
where are Slater integrals
and are the Slater-Condon parameters
where is the normalized radial part of an electron orbital, and | 0 | Theoretical and Fundamental Chemistry |
A fast current of water flowing over a rock near the surface of a stream or river can create a rooster tail—such commotions at the waters surface are avoided by boaters due to the near surface obstruction. Propellers on boats can produce a rooster tail of water in their wake, in the form of a fountain which shoots into the air behind the boat. The faster a boat goes, the larger the rooster tails become. The efficiency of a boats hull design can be judged by the magnitude of the rooster tail—larger rooster tails indicate less efficient designs. If a water skier is in tow, the skis also throw off a rooster tail. Airplanes lifting off from a lake produce lengthening rooster tails behind their amphibious floats as their speed increases, until the plane lifts off the surface. | 1 | Applied and Interdisciplinary Chemistry |
In general, in prokaryotes the lifetime of mRNA is much shorter than in eukaryotes. Prokaryotes degrade messages by using a combination of ribonucleases, including endonucleases, 3 exonucleases, and 5 exonucleases. In some instances, small RNA molecules (sRNA) tens to hundreds of nucleotides long can stimulate the degradation of specific mRNAs by base-pairing with complementary sequences and facilitating ribonuclease cleavage by RNase III. It was recently shown that bacteria also have a sort of 5 cap consisting of a triphosphate on the 5 end. Removal of two of the phosphates leaves a 5 monophosphate, causing the message to be destroyed by the exonuclease RNase J, which degrades 5 to 3'. | 1 | Applied and Interdisciplinary Chemistry |
The original CAGE method (Shiraki et al., 2003) was using CAP Trapper for capturing the 5′ ends, oligo-dT primers for synthesizing the cDNAs, the type IIs restriction enzyme MmeI for cleaving the tags, and the Sanger method for sequencing them.
Random reverse-transcription primers were introduced in 2006 by Kodzius et al. to better detect the non-polyadenylated RNAs.
In DeepCAGE (Valen et al., 2008), the tag concatemers were sequenced at a higher throughput on the 454 “next-generation” sequencing platform.
In 2008, barcode multiplexing was added to the DeepCAGE protocol (Maeda et al., 2008).
In nanoCAGE (Plessy et al., 2010), the 5′ ends or RNAs were captured with the template-switching method instead of CAP Trapper, in order to analyze smaller starting amounts of total RNA. Longer tags were cleaved with the type III restriction enzyme EcoP15I and directly sequenced on the Solexa (then Illumina) platform without concatenation.
The CAGEscan methodology (Plessy et al., 2010), where the enzymatic tag cleavage is skipped, and the 5′ cDNAs sequenced paired-end, was introduced in the same article to connect novel promoters to known annotations.
With HeliScopeCAGE (Kanamori-Katayama et al., 2011), the CAP-trapped CAGE protocol was changed to skip the enzymatic tag cleavage and sequence directly the capped 5′ ends on the HeliScope platform, without PCR amplification. It was then automated by Itoh et al. in 2012.
In 2012, the standard CAGE protocol was updated by Takahashi et al. to cleave tags with EcoP15I and sequence them on the Illumina-Solexa platform.
In 2013, Batut et al. combined CAP trapper, template switching, and 5′-phosphate-dependent exonuclease digestion in RAMPAGE to maximize promoter specificity.
In 2014, Murata et al. published the nAnTi-CAGE protocol, where capped 5′ ends are sequenced on the Illumina platform with no PCR amplification and no tag cleavage.
In 2017, Poulain et al. updated the nanoCAGE protocol to use the tagmentation method (based on Tn5 transposition) for multiplexing.
In 2018, Cvetesic et al. increased the sensitivity of CAP-trapped CAGE by introducing selectively degradable carrier RNA (SLIC-CAGE, "Super-Low Input Carrier-CAGE").
In 2021, Takahashi et al. simplified the sequencing of CAGE libraries on Illumina sequencers by skipping second-strand synthesis directly loading single-strand cDNAs (Low Quantity Single Strand CAGE, "LQ-ssCAGE"). | 1 | Applied and Interdisciplinary Chemistry |
Research and education in chemistry has been conducted at the department since 1778, when the first Laboratorium Chymicum was established. Since then, the chemists have moved several times. In 1962, Universitetets Kemiske Laboratorium moved to its present location in the H.C. Ørsted Institute (HCØ), named after Hans Christian Ørsted who discovered electromagnetism in 1820. | 1 | Applied and Interdisciplinary Chemistry |
Threaded pipes can provide an effective seal for pipes transporting liquids, gases, steam, and hydraulic fluid. These threads are now used in materials other than steel and brass, including PTFE, PVC, nylon, bronze, and cast iron.
The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other, as opposed to parallel/straight thread fittings or compression fittings in which the threads merely hold the pieces together and do not provide a seal. The various types of pipe threads are designed for use both with or without thread sealants, as [https://casadasvalvulasmg.com.br/roscas-bsp-e-npt-aplicacao-de-cada-uma/ particular applications demand]. The sealants, where used, are typically thread seal tape thread sealant or a thread seal paste pipe dope (sometimes similar in composition to plumber's putty).
Because the thread body is tapered (), a larger diameter keeps compressing into a smaller diameter and finally forms a seal (no clearance remains between the crests and roots of the threads because of the taper). This means that NPT fittings should be burr-free and lubricated using a lubricant like lubricating paste or thread seal tape. The use of tape also helps to limit corrosion on the threads, which otherwise can make future disassembly nearly impossible.
Commonly used sizes are , , , , , 1, , , 2, , 3, 4, 5, and 6 inch, as pipe and fittings by most US suppliers. Sizes smaller than inch are occasionally used for compressed air, while sizes larger than 6 inches are often joined by other methods. | 1 | Applied and Interdisciplinary Chemistry |
While not knowing the structure trying to predict how the ligands will bind to the receptor. With the use of pharmacophore features each ligand identified donor, and acceptors. Equating features are overlaid, however given it is unlikely there is a single correct solution. | 1 | Applied and Interdisciplinary Chemistry |
In electrochemistry, exchange current density is a parameter used in the Tafel equation, Butler–Volmer equation and other electrochemical kinetics expressions. The Tafel equation describes the dependence of current for an electrolytic process to overpotential.
The exchange current density is the current in the absence of net electrolysis and at zero overpotential. The exchange current can be thought of as a background current to which the net current observed at various overpotentials is normalized. For a redox reaction written as a reduction at the equilibrium potential, electron transfer processes continue at electrode/solution interface in both directions. The cathodic current is balanced by the anodic current. This ongoing current in both directions is called the exchange current density. When the potential is set more negative than the formal potential, the cathodic current is greater than the anodic current. Written as a reduction, cathodic current is positive. The net current density is the difference between the cathodic and anodic current density.
Exchange current densities reflect intrinsic rates of electron transfer between an analyte and the electrode. Such rates provide insights into the structure and bonding in the analyte and the electrode. For example, the exchange current densities for platinum and mercury electrodes for reduction of protons differ by a factor of 10, indicative of the excellent catalytic properties of platinum. Owing to this difference, mercury is the preferred electrode material at reducing (cathodic) potentials in aqueous solution. | 0 | Theoretical and Fundamental Chemistry |
Van der Waals strain is strain resulting from Van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their Van der Waals radii.
Van der Waals strain is also called Van der Waals repulsion and is related to steric hindrance. One of the most common forms of this strain is eclipsing hydrogen, in alkanes. | 0 | Theoretical and Fundamental Chemistry |
The transition between the ground and the excited state is based on the Franck–Condon principle, that the electronic transition is very fast compared with the motion in the lattice. The energy transitions can then be symbolized by vertical arrows between the ground and excited state, that is, there is no motion along the configurational coordinates during the transition. Figure 2 is an energy diagram for interpreting absorption and emission with and without phonons in terms of the configurational coordinate . The energy transitions originate at the lowest phonon energy level of the electronic states. As represented in the figure, the largest wavefunction overlap (and therefore largest transition probability) occurs when the photon energy is equal to the energy difference between the two electronic states () plus three quanta of lattice mode vibrational energy (). This three-phonon transition is mirrored in emission when the excited state quickly decays to its zero-point lattice vibration level by means of a radiationless process, and from there to the ground state via photon emission. The zero-phonon transition is depicted as having a lower wavefunction overlap and therefore a lower transition probability.
In addition to the Franck-Condon assumption, three other approximations are commonly assumed and are implicit in the figures. The first is that each lattice vibrational mode is well described by a quantum harmonic oscillator. This approximation is implied in the parabolic shape of the potential wells of Figure 2, and in the equal energy spacing between phonon energy levels. The second approximation is that only the lowest (zero-point) lattice vibration is excited. This is called the low temperature approximation and means that electronic transitions do not originate from any of the higher phonon levels. The third approximation is that the interaction between the chromophore and the lattice is the same in both the ground and the excited state. Specifically, the harmonic oscillator potential is equal in both states. This approximation, called linear coupling, is represented in Figure 2 by two equally shaped parabolic potentials and by equally spaced phonon energy levels in both the ground and excited states.
The strength of the zero-phonon transition arises in the superposition of all of the lattice modes. Each lattice mode has a characteristic vibrational frequency which leads to an energy difference between phonons . When the transition probabilities for all the modes are summed, the zero-phonon transitions always add at the electronic origin (), while the transitions with phonons contribute at a distribution of energies. Figure 3 illustrates the superposition of transition probabilities of several lattice modes. The phonon transition contributions from all lattice modes constitute the phonon sideband.
The frequency separation between the maxima of the absorption and fluorescence phonon sidebands is the phonon contribution to the Stokes’ shift. | 0 | Theoretical and Fundamental Chemistry |
He was awarded the Louisa Gross Horwitz Prize from Columbia University in 1991, the Louis-Jeantet Prize for Medicine in 1993, the Otto Warburg Medal in 1999 and half of the Nobel Prize in Chemistry in 2002 for "his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution". He received the Bijvoet Medal of the Bijvoet Center for Biomolecular Research of Utrecht University in 2008. He was elected a Foreign Member of the Royal Society (ForMemRS) in 2010. He was also awarded the 2018 Fray International Sustainability Award at SIPS 2018 by FLOGEN Star Outreach. | 0 | Theoretical and Fundamental Chemistry |
CARS is used for species selective microscopy and combustion diagnostics. The first exploits the selectivity of vibrational spectroscopy. More recently, CARS microscopy has been utilized as a method for non-invasive imaging of lipids in biological samples, both in vivo and in vitro. Moreover, RP-CARS, a particular implementation of the Coherent anti-Stokes Raman spectroscopy microscopy, is used to study myelin and myelopathies. In 2020, Scully and team used femtosecond adaptive spectroscopic techniques via CARS to identify individual virus particles. | 0 | Theoretical and Fundamental Chemistry |
In dielectric spectroscopy, large frequency dependent contributions to the dielectric response, especially at low frequencies, may come from build-ups of charge. This Maxwell–Wagner–Sillars polarization (or often just Maxwell-Wagner polarization), occurs either at inner dielectric boundary layers on a mesoscopic scale, or at the external electrode-sample interface on a macroscopic scale. In both cases this leads to a separation of charges (such as through a depletion layer). The charges are often separated over a considerable distance (relative to the atomic and molecular sizes), and the contribution to dielectric loss can therefore be orders of magnitude larger than the dielectric response due to molecular fluctuations. | 0 | Theoretical and Fundamental Chemistry |
If one wants to use a theory based on plane parallel layers, optimally the samples would be describable as layers. But a particulate sample often looks a jumbled maze of particles of various sizes and shapes, showing no structured pattern of any kind, and certainly not literally divided into distinct, identical layers. Even so, it is a tenet of Representative Layer Theory that for spectroscopic purposes, we may treat the complex sample as if it were a series of layers, each one representative of the sample as a whole. | 0 | Theoretical and Fundamental Chemistry |
In solid state physics, a superstructure is some additional structure that is superimposed on a higher symmetry crystalline structure. A typical and important example is ferromagnetic ordering.
In a wider sense, the term "superstructure" is applied to polymers and proteins to describe ordering on a length scale larger than that of monomeric segments. | 0 | Theoretical and Fundamental Chemistry |
Standard solutions are commonly used to determine the concentration of an analyte species via calibration curve. A calibration curve is obtained by measuring a series of standard solutions with known concentrations, which can be used to determine the concentration of an unknown sample using linear regression analysis. For example, by comparing the absorbance values of a solution with an unknown concentration to a series of standard solutions with varying concentrations, the concentration of the unknown can be determined using Beer's Law.
Any form of spectroscopy can be used in this way so long as the analyte species has substantial absorbance in the spectra. The standard solution is a reference guide to discover the molarity of unknown species.
The matrix effect can negatively affect the efficiency of a calibration curve due to interactions between matrix and the analyte response. The matrix effect can be reduced by the addition of internal standards to the standard solutions, or by using the standard addition method. | 0 | Theoretical and Fundamental Chemistry |
In fluid mechanics, dynamic similarity is the phenomenon that when there are two geometrically similar vessels (same shape, different sizes) with the same boundary conditions (e.g., no-slip, center-line velocity) and the same Reynolds and Womersley numbers, then the fluid flows will be identical. This can be seen from inspection of the underlying Navier-Stokes equation, with geometrically similar bodies, equal Reynolds and Womersley Numbers the functions of velocity (u’,v’,w’) and pressure (P’) for any variation of flow. | 1 | Applied and Interdisciplinary Chemistry |
For over 150 years, scientists from all around the world have known about the crystallization of protein molecules.
In 1840, Friedrich Ludwig Hünefeld accidentally discovered the formation of crystalline material in samples of earthworm blood held under two glass slides and occasionally observed small plate-like crystals in desiccated swine or human blood samples. These crystals were named as haemoglobin, by Felix Hoppe-Seyler in 1864. The seminal findings of Hünefeld inspired many scientists in the future.
In 1851, Otto Funke described the process of producing human haemoglobin crystals by diluting red blood cells with solvents, such as pure water, alcohol or ether, followed by slow evaporation of the solvent from the protein solution. In 1871, William T. Preyer, Professor at University of Jena, published a book entitled Die Blutkrystalle (The Crystals of Blood), reviewing the features of haemoglobin crystals from around 50 species of mammals, birds, reptiles and fishes.
In 1909, the physiologist Edward T. Reichert, together with the mineralogist Amos P. Brown, published a treatise on the preparation, physiology and geometrical characterization of haemoglobin crystals from several hundreds animals, including extinct species such as the Tasmanian wolf. Increasing protein crystals were found.
In 1934, John Desmond Bernal and his student Dorothy Hodgkin discovered that protein crystals surrounded by their mother liquor gave better diffraction patterns than dried crystals. Using pepsin, they were the first to discern the diffraction pattern of a wet, globular protein. Prior to Bernal and Hodgkin, protein crystallography had only been performed in dry conditions with inconsistent and unreliable results. This is the first X‐ray diffraction pattern of a protein crystal.
In 1958, the structure of myoglobin (a red protein containing heme), determined by X-ray crystallography, was first reported by John Kendrew. Kendrew shared the 1962 Nobel Prize in Chemistry with Max Perutz for this discovery.
Now, based on the protein crystals, the structures of them play a significant role in biochemistry and translational medicine. | 0 | Theoretical and Fundamental Chemistry |
Methylthioadenosine nucleosidase are enzymes that catalyse the hydrolytic deadenylation reaction of 5'-methylthioadenosine and S-adenosylhomocysteine. It is also regarded as an important target for antibacterial drug discovery because it is important in the metabolic system of bacteria and only produced by bacteria. Given the different distance between nitrogen atom of adenine and the ribose anomeric carbon (see in the diagram in this section), the transition state structure can be defined by early or late dissociation stage. Based on the finding of different transition state structures, Schramm and coworkers designed two transition state analogues mimicking the early and late dissociative transition state. The early and late transition state analogue shown binding affinity (Kd) of 360 and 140 pM, respectively. | 1 | Applied and Interdisciplinary Chemistry |
Arthur John Birch, AC CMG FRS FAA (3 August 1915 – 8 December 1995) was an Australian organic chemist.
Birch developed the Birch reduction of aromatic rings (by treatment with lithium metal and ammonia) which is widely used in synthetic organic chemistry. The Birch Reduction enables the modification of steroids. In 1948 Birch published the first total synthesis of a male sex hormone (19-nortestosterone), as the first member of a new structural series. This series later comprised the first oral contraceptive pill, which was made by others. The Birch reduction also allows for the development of other steroid drugs and antibiotics – he also made the first simple synthesis of the ring A-B structure of cholesterol. Birch published over 440 scientific papers and reports. | 0 | Theoretical and Fundamental Chemistry |
Electrophilic aromatic substitution is famously affected by EWGs. The effect is transmitted by inductive and resonance effects. Benzene with an EWG typically undergoes electrophilic substitution at meta positions. Overall the rates are diminished. thus EWGs are called deactivating.
When it comes to nucleophilic substitution reactions, electron-withdrawing groups are more prone to nucleophilic substitution. For example, chlorodinitrobenzene is far more susceptible to reactions displacing chloride compared to chlorobenzene. | 0 | Theoretical and Fundamental Chemistry |
The BBE-like enzyme's optimum pH is 8.9, this means it works in an alkaline medium, but the isoelectric point of the homogeneous enzyme is located at pH 4.9, which is a rather an acid medium. This value was obtained with isoelectric focusing and chromatofocusing techniques.
The enzyme broad temperature range is between 40-50 degrees Celsius. The molecular weight of the protein was determined by two processes that show two different results: by SDS gel electrophoresis comes to be 54 kD, and by gel filtration on AcA 54 the enzyme corresponds to a molecular weight of 49 kD, adopting globular shape. A purification study shows that the true molecular weight is in the range of 52 ±4 kD.
On the other hand, total activity decreases drastically during the stationary phase. | 1 | Applied and Interdisciplinary Chemistry |
Clore received his undergraduate degree with first class honours in biochemistry from University College London in 1976 and medical degree from UCL Medical School in 1979. After completing house physician and house surgeon appointments at University College Hospital and St Charles Hospital (part of the St. Marys Hospital group), respectively, he was a member of the scientific staff of the Medical Research Council National Institute for Medical Research from 1980 to 1984. He received his PhD from the National Institute for Medical Research in Physical Biochemistry in 1982. He was awarded a joint Lister Institute Research Fellowship from the Lister Institute of Preventive Medicine which he held from 1982 to 1984 at the Medical Research Council. In 1984 he joined the Max Planck Institute for Biochemistry in Martinsried, Germany, where he headed the Biological NMR department from 1984 to 1988.
In 1988, Clore was recruited to the National Institutes of Health (NIH) Laboratory of Chemical Physics (National Institute of Diabetes and Digestive and Kidney Diseases) located in Bethesda, Maryland, U.S., where he interacted closely in the late 1980s and early 1990s with NIH colleagues Ad Bax, Angela Gronenborn and Dennis Torchia on the development of multidimensional heteronuclear NMR spectroscopy and a structural biology effort aimed at proteins involved in the pathogenesis of HIV/AIDS. He has remained at the NIH ever since and is currently a NIH Distinguished Investigator and Chief of the Section on Molecular and Structural Biophysics at the NIH. He is an elected Member of the United States National Academy of Sciences, a Fellow of the Royal Society, a Fellow of the American Academy of Arts and Sciences, and a Foreign Member of the Academia Europaea (Biochemistry and Molecular Biology Section). Clore's citation upon election to the Royal Society reads: | 0 | Theoretical and Fundamental Chemistry |
The preferred method of iron production in Europe until the development of the puddling process in 1783–84. Cast iron development lagged in Europe because wrought iron was the desired product and the intermediate step of producing cast iron involved an expensive blast furnace and further refining of pig iron to cast iron, which then required a labor and capital intensive conversion to wrought iron.
Through a good portion of the Middle Ages, in Western Europe, iron was still being made by the working of iron blooms into wrought iron. Some of the earliest casting of iron in Europe occurred in Sweden, in two sites, Lapphyttan and Vinarhyttan, between 1150 and 1350. Some scholars have speculated the practice followed the Mongols across Russia to these sites, but there is no clear proof of this hypothesis, and it would certainly not explain the pre-Mongol datings of many of these iron-production centres. In any event, by the late 14th century, a market for cast iron goods began to form, as a demand developed for cast iron cannonballs. | 1 | Applied and Interdisciplinary Chemistry |
Leached pulp and carbon are transferred in a countercurrent flow arrangement involving a series of tanks, usually numbering 4 to 6. In the final tank, fresh or barren carbon is put in contact with low grade or tailings solution. At this tank the fresh carbon has a high affinity for gold and can remove trace amounts of gold (to levels below 0.01 mg/L Au in solution).
As it moves up the train, the carbon loads to higher and higher concentrations of gold, as it comes in contact with higher grade solutions. Typically concentrations as high as 4000 to 8000 grams of gold per tonne of carbon (g/t Au) can be achieved on the final loaded carbon, as it comes in contact with freshly leached ore and pregnant leach solution (PLS). | 1 | Applied and Interdisciplinary Chemistry |
The list below provides a few more commonly known applications of pharmacogenomics:
* Improve drug safety, and reduce ADRs;
* Tailor treatments to meet patients' unique genetic pre-disposition, identifying optimal dosing;
* Improve drug discovery targeted to human disease; and
* Improve proof of principle for efficacy trials.
Pharmacogenomics may be applied to several areas of medicine, including pain management, cardiology, oncology, and psychiatry. A place may also exist in forensic pathology, in which pharmacogenomics can be used to determine the cause of death in drug-related deaths where no findings emerge using autopsy.
In cancer treatment, pharmacogenomics tests are used to identify which patients are most likely to respond to certain cancer drugs. In behavioral health, pharmacogenomic tests provide tools for physicians and care givers to better manage medication selection and side effect amelioration. Pharmacogenomics is also known as companion diagnostics, meaning tests being bundled with drugs. Examples include KRAS test with cetuximab and EGFR test with gefitinib. Beside efficacy, germline pharmacogenetics can help to identify patients likely to undergo severe toxicities when given cytotoxics showing impaired detoxification in relation with genetic polymorphism, such as canonical 5-FU. In particular, genetic deregulations affecting genes coding for DPD, UGT1A1, TPMT, CDA and CYP2D6 are now considered as critical issues for patients treated with 5-FU/capecitabine, irinotecan, mercaptopurine/azathioprine, gemcitabine/capecitabine/AraC and tamoxifen, respectively.
In cardiovascular disorders, the main concern is response to drugs including warfarin, clopidogrel, beta blockers, and statins. In patients with CYP2C19, who take clopidogrel, cardiovascular risk is elevated, leading to medication package insert updates by regulators. In patients with type 2 diabetes, haptoglobin (Hp) genotyping shows an effect on cardiovascular disease, with Hp2-2 at higher risk and supplemental vitamin E reducing risk by affecting HDL.
In psychiatry, as of 2010, research has focused particularly on 5-HTTLPR and DRD2. | 1 | Applied and Interdisciplinary Chemistry |
Due to radioactive nucleotides have similar properties to their stable, inactive, counterparts similar analytical chemistry separation techniques can be used. These separation methods include precipitation, Ion Exchange, Liquid Liquid extraction, Solid Phase extraction, Distillation, and Electrodeposition. | 0 | Theoretical and Fundamental Chemistry |
The necessity for a subject to exert maximum effort in order to accurately measure V̇O max can be dangerous in those with compromised respiratory or cardiovascular systems; thus, sub-maximal tests for estimating V̇O max have been developed. | 1 | Applied and Interdisciplinary Chemistry |
SEM is used to examine morphology of fabricated surfaces, enabling the comparison of natural surfaces with synthetic surfaces. The size of nanotopography can be measured. To prepare samples for SEM, surfaces are often sputter coated using platinum, gold/palladium, or silver, which reduces sample damage and charging and improves edge resolution. | 0 | Theoretical and Fundamental Chemistry |
Chemical Engineering and Biotechnology Abstracts (CEABA-VTB) is an abstracting and indexing service that is published by DECHEMA, BASF, and Bayer Technology Services, all based in Germany. This is a bibliographic database that covers multiple disciplines. | 1 | Applied and Interdisciplinary Chemistry |
Site energy is the term used in North America for the amount of end-use energy of all forms consumed at a specified location. This can be a mix of primary energy (such as natural gas burned at the site) and secondary energy (such as electricity). Site energy is measured at the campus, building, or sub-building level and is the basis for energy charges on utility bills.
Source energy, in contrast, is the term used in North America for the amount of primary energy consumed in order to provide a facility’s site energy. It is always greater than the site energy, as it includes all site energy and adds to it the energy lost during transmission, delivery, and conversion. While source or primary energy provides a more complete picture of energy consumption, it cannot be measured directly and must be calculated using conversion factors from site energy measurements. For electricity, a typical value is three units of source energy for one unit of site energy. However, this can vary considerably depending on factors such as the primary energy source or fuel type, the type of power plant, and the transmission infrastructure. One full set of conversion factors is available as technical reference from Energy STAR.
Either site or source energy can be an appropriate metric when comparing or analyzing energy use of different facilities. The U.S Energy Information Administration, for example, uses primary (source) energy for its energy overviews but site energy for its Commercial Building Energy Consumption Survey and Residential Building Energy Consumption Survey. The US Environmental Protection Agency's Energy STAR program recommends using source energy, and the US Department of Energy uses site energy in its definition of a zero net energy building. | 0 | Theoretical and Fundamental Chemistry |
Prof. Dr. Petko Stoyanov Dimitrov () (16 September 1944 – 29 April 2023) was a Bulgarian marine geologist and oceanographer from the Institute of Oceanology - Bulgarian Academy of Sciences in Varna. He has been an early proponent of the Black Sea deluge hypothesis which gained public notoriety at the end of the XXc. | 0 | Theoretical and Fundamental Chemistry |
El-Shall was born in Cairo, Egypt, and spent his early life in Cairo. He is the grandson of Sheikh Mahmud Shaltut. He earned his B.S. degree in chemistry in 1976, and M.S. degree in physical chemistry in 1980 both from Cairo University. El-Shall earned his doctoral degree in physical chemistry from Georgetown University in 1985. | 0 | Theoretical and Fundamental Chemistry |
The biosynthesis of trabectedin in Candidatus Endoecteinascidia frumentensis starts with a fatty acid loading onto the acyl-ligase domain of the EtuA3 module. A cysteine and glycine are then loaded as canonical NRPS amino acids. A tyrosine residue is modified by the enzymes EtuH, EtuM1, and EtuM2 to add a hydroxyl at the meta position of the phenol, and adding two methyl groups at the para-hydroxyl and the meta carbon position. This modified tyrosine reacts with the original substrate via a Pictet-Spengler reaction, where the amine group is converted to an imine by deprotonation, then attacks the free aldehyde to form a carbocation that is quenched by electrons from the methyl-phenol ring. This is done in the EtuA2 T-domain. This reaction is done a second time to yield a dimer of modified tyrosine residues that have been further cyclized via Pictet-Spengler reaction, yielding a bicyclic ring moiety. The EtuO and EtuF3 enzymes continue to post-translationally modify the molecule, adding several functional groups and making a sulfide bridge between the original cysteine residue and the beta-carbon of the first tyrosine to form ET-583, ET-597, ET-596, and ET-594 which have been previously isolated. A third O-methylated tyrosine is added and cyclized via Pictet-Spengler to yield the final product. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, syn- and anti-addition are different ways in which substituent molecules can be added to an alkene () or alkyne (). The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction.
The type of addition that occurs depends on multiple different factors of a reaction, and is defined by the final orientation of the substituents on the parent molecule. Syn and anti addition are related to Markovnikovs rule for the orientation of a reaction, which refers to the bonding preference of different substituents for different carbons on an alkene or alkyne. In order for a reaction to follow Markovnikovs rule, the intermediate carbocation of the mechanism of a reaction must be on the more-substituted carbon, allowing the substituent to bond to the more-stable carbocation and the more-substituted carbon.
Syn addition is the addition of two substituents to the same side (or face) of a double bond or triple bond, resulting in a decrease in bond order but an increase in number of substituents. Generally the substrate will be an alkene or alkyne. An example of syn addition would be the oxidation of an alkene to a diol by way of a suitable oxidizing agent such as osmium tetroxide, , or potassium permanganate, .
Anti addition is in direct contrast to syn addition. In anti addition, two substituents are added to opposite sides (or faces) of a double bond or triple bond, once again resulting in a decrease in bond order and increase in number of substituents. The classical example of this is bromination (any halogenation) of alkenes. An anti addition reaction results in a trans-isomer of the products, as the substituents are on opposite faces of the bond.
Depending on the substrate double bond, addition can have different effects on the molecule. After addition to a straight-chain alkene such as ethene (), the resulting alkane will rapidly and freely rotate around its single sigma bond under normal conditions (i.e. room temperature). Thus whether substituents are added to the same side (syn) or opposite sides (anti) of a double can usually be ignored due to free rotation. However, if chirality or the specific absolute orientation of the substituents needs to be taken into account, knowing the type of addition is significant. Unlike straight-chain alkenes, cycloalkene syn addition allows stable addition of substituents to the same side of the ring, where they remain together. The cyclic locked ring structure prevents free rotation.
Syn elimination and anti elimination are the reverse processes of syn and anti addition. These result in a new double bond, such as in E elimination. | 0 | Theoretical and Fundamental Chemistry |
To facilitate further preparation, the sawed specimen is usually embedded (or mounted or encapsulated) in a plastic disc, 25, 32 or 38 mm in diameter. A thermosetting solid resin, activated by heat and compression, e.g. mineral-filled epoxy, is best for most applications. A castable (liquid) resin such as unfilled epoxy, acrylic or polyester may be used for porous refractory ceramics or microelectronic devices. The castable resins are also available with fluorescent dyes that aid in fluorescence microscopy. The left and right specimens in Fig. 3 were embedded in mineral-filled epoxy. The center refractory in Fig. 3 was embedded in castable, transparent acrylic. | 1 | Applied and Interdisciplinary Chemistry |
Consider a system composed of chemical species (e.g. water splitting) in thermodynamic equilibrium at constant pressure and thermodynamic temperature T:
:::::HO(l) H(g) + 1/2 O(g) (1)
Equilibrium is displaced to the right only if energy (enthalpy change ΔH for water-splitting) is provided to the system under strict conditions imposed by thermodynamics:
* one fraction must be provided as work, namely the Gibbs free energy change ΔG of the reaction: it consists of "noble" energy, i.e. under an organized state where matter can be controlled, such as electricity in the case of the electrolysis of water. Indeed, the generated electron flow can reduce protons (H) at the cathode and oxidize anions (O) at the anode (the ions exist because of the chemical polarity of water), yielding the desired species.
* the other one must be supplied as heat, i.e. by increasing the thermal agitation of the species, and is equal by definition of the entropy to the absolute temperature T times the entropy change ΔS of the reaction.
Hence, for an ambient temperature T° of 298K (kelvin) and a pressure of 1 atm (atmosphere (unit)) (ΔG° and ΔS° are respectively equal to 237 kJ/mol and 163 J/mol/K, relative to the initial amount of water), more than 80% of the required energy ΔH must be provided as work in order for water-splitting to proceed.
If phase transitions are neglected for simplicity's sake (e.g. water electrolysis under pressure to keep water in its liquid state), one can assume that ΔH et ΔS do not vary significantly for a given temperature change. These parameters are thus taken equal to their standard values ΔH° et ΔS° at temperature T°. Consequently, the work required at temperature T is,
As ΔS° is positive, a temperature increase leads to a reduction of the required work. This is the basis of high-temperature electrolysis. This can also be intuitively explained graphically.
Chemical species can have various excitation levels depending on the absolute temperature T, which is a measure of the thermal agitation. The latter causes shocks between atoms or molecules inside the closed system such that energy spreading among the excitation levels increases with time, and stop (equilibrium) only when most of the species have similar excitation levels (a molecule in a highly excited level will quickly return to a lower energy state by collisions) (Entropy (statistical thermodynamics)).
Relative to the absolute temperature scale, the excitation levels of the species are gathered based on standard enthalpy change of formation considerations; i.e. their stabilities. As this value is null for water but strictly positive for oxygen and hydrogen, most of the excitation levels of these last species are above the ones of water. Then, the density of the excitation levels for a given temperature range is monotonically increasing with the species entropy. A positive entropy change for water-splitting means far more excitation levels in the products. Consequently,
* A low temperature (T°), thermal agitation allow mostly the water molecules to be excited as hydrogen and oxygen levels required higher thermal agitation to be significantly populated (on the arbitrary diagram, 3 levels can be populated for water vs 1 for the oxygen/hydrogen subsystem),
* At high temperature (T), thermal agitation is sufficient for the oxygen/hydrogen subsystem excitation levels to be excited (on the arbitrary diagram, 4 levels can be populated for water vs 8 for the oxygen/hydrogen subsystem). According to the previous statements, the system will thus evolve toward the composition where most of its excitation levels are similar, i.e. a majority of oxygen and hydrogen species.
One can imagine that if T were high enough in Eq.(3), ΔG could be nullified, meaning that water-splitting would occur even without work (thermolysis of water). Though possible, this would require tremendously high temperatures: considering the same system naturally with steam instead of liquid water (ΔH° = 242 kJ/mol; ΔS° = 44 J/mol/K) would hence give required temperatures above 3000K, that make reactor design and operation extremely challenging.
Hence, a single reaction only offers one freedom degree (T) to produce hydrogen and oxygen only from heat (though using Le Chatelier's principle would also allow to slightly decrease the thermolysis temperature, work must be provided in this case for extracting the gas products from the system) | 0 | Theoretical and Fundamental Chemistry |
Gans theory or Mie-Gans theory is the extension of Mie theory for the case of spheroidal particles. It gives the scattering characteristics of both oblate and prolate spheroidal particles much smaller than the excitation wavelength.
Since it is a solution of the Maxwell equations it should technically not be called a theory.
The theory is named after Richard Gans who first published the solution for gold particles in 1912 in an article entitled "Über die Form ultramikroskopischer Goldteilchen". A subsequent article in 1915 discussed the case of silver particles.
In Gans theory, the absorption is only dependent on the aspect ratio of the particles and not on the absolute dimensions. This dependence is introduced through so called polarization- or shape factors related to the three dimensions of the particle. For the case of spheroids, this reduces to only two different factors since the particle is rotational symmetric around one axis.
It is currently being applied in the field of nanotechnology to characterize silver and gold nanorods. A popular alternative for this is the Discrete dipole approximation (DDA) method. Gans theory gives the exact solution for spheroidal particles; real nanorods, however, have a more cylindrical shape. Using DDA, it is possible to better model the exact shape of the particles. As the name suggests, this will only give an approximation. | 0 | Theoretical and Fundamental Chemistry |
A [1,j]-sigmatropic rearrangement is also a two component pericyclic reaction: one component is the π-system, the other component is the migrating group. The simplest case is a [1,j]-hydride shift across a π-system where j is odd. In this case, as the hydrogen has only a spherically symmetric s orbital, the reaction must be suprafacial with respect to the hydrogen. The total number of electrons involved is (j + 1) as there are (j − 1)/2 π-bond plus the σ bond involved in the reaction. If j = 4n − 1 then it must be antarafacial, and if j = 4n + 1, then it must be suprafacial. This agrees with experiment that [1,3]-hydride shifts are generally not observed as the symmetry-allowed antarafacial process is not feasible, but [1,5]-hydride shifts are quite facile.
For a [1,j]-alkyl shift, where the reaction can be antarafacial (i.e. invert stereochemistry) with respect to the carbon center, the same rules apply. If j = 4n − 1 then the reaction is symmetry-allowed if it is either antarafacial with respect to the π-system, or inverts stereochemistry at the carbon. If j = 4n + 1 then the reaction is symmetry-allowed if it is suprafacial with respect to the π-system and retains stereochemistry at the carbon center.
On the right is one of the first examples of a [1,3]-sigmatropic shift to be discovered, reported by Berson in 1967. In order to allow for inversion of configuration, as the σ bond breaks, the C(H)(D) moiety twists around at the transition state, with the hybridization of the carbon approximating sp, so that the remaining unhybridized p orbital maintains overlap with both carbons 1 and 3. | 0 | Theoretical and Fundamental Chemistry |
A characteristic reaction of is its easy hydrolysis, signaled by the release of HCl vapors and titanium oxides and oxychlorides. Titanium tetrachloride has been used to create naval smokescreens, as the hydrochloric acid aerosol and titanium dioxide that is formed scatter light very efficiently. This smoke is corrosive, however.
Alcohols react with to give alkoxides with the formula (R = alkyl, n = 1, 2, 4). As indicated by their formula, these alkoxides can adopt complex structures ranging from monomers to tetramers. Such compounds are useful in materials science as well as organic synthesis. A well known derivative is titanium isopropoxide, which is a monomer. Titanium bis(acetylacetonate)dichloride results from treatment of titanium tetrachloride with excess acetylacetone:
Organic amines react with to give complexes containing amido (-containing) and imido (-containing) complexes. With ammonia, titanium nitride is formed. An illustrative reaction is the synthesis of tetrakis(dimethylamido)titanium , a yellow, benzene-soluble liquid: This molecule is tetrahedral, with planar nitrogen centers. | 0 | Theoretical and Fundamental Chemistry |
Radiation therapy works by damaging the DNA of cancer cells and can cause them to undergo mitotic catastrophe. This DNA damage is caused by one of two types of energy, photon or charged particle. This damage is either direct or indirect ionization of the atoms which make up the DNA chain. Indirect ionization happens as a result of the ionization of water, forming free radicals, notably hydroxyl radicals, which then damage the DNA.
In photon therapy, most of the radiation effect is through free radicals. Cells have mechanisms for repairing single-strand DNA damage and double-stranded DNA damage. However, double-stranded DNA breaks are much more difficult to repair, and can lead to dramatic chromosomal abnormalities and genetic deletions. Targeting double-stranded breaks increases the probability that cells will undergo cell death. Cancer cells are generally less differentiated and more stem cell-like; they reproduce more than most healthy differentiated cells, and have a diminished ability to repair sub-lethal damage. Single-strand DNA damage is then passed on through cell division; damage to the cancer cells' DNA accumulates, causing them to die or reproduce more slowly.
One of the major limitations of photon radiation therapy is that the cells of solid tumors become deficient in oxygen. Solid tumors can outgrow their blood supply, causing a low-oxygen state known as hypoxia. Oxygen is a potent radiosensitizer, increasing the effectiveness of a given dose of radiation by forming DNA-damaging free radicals. Tumor cells in a hypoxic environment may be as much as 2 to 3 times more resistant to radiation damage than those in a normal oxygen environment. Much research has been devoted to overcoming hypoxia including the use of high pressure oxygen tanks, hyperthermia therapy (heat therapy which dilates blood vessels to the tumor site), blood substitutes that carry increased oxygen, hypoxic cell radiosensitizer drugs such as misonidazole and metronidazole, and hypoxic cytotoxins (tissue poisons), such as tirapazamine. Newer research approaches are currently being studied, including preclinical and clinical investigations into the use of an oxygen diffusion-enhancing compound such as trans sodium crocetinate as a radiosensitizer.
Charged particles such as protons and boron, carbon, and neon ions can cause direct damage to cancer cell DNA through high-LET (linear energy transfer) and have an antitumor effect independent of tumor oxygen supply because these particles act mostly via direct energy transfer usually causing double-stranded DNA breaks. Due to their relatively large mass, protons and other charged particles have little lateral side scatter in the tissue – the beam does not broaden much, stays focused on the tumor shape, and delivers small dose side-effects to surrounding tissue. They also more precisely target the tumor using the Bragg peak effect. See proton therapy for a good example of the different effects of intensity-modulated radiation therapy (IMRT) vs. charged particle therapy. This procedure reduces damage to healthy tissue between the charged particle radiation source and the tumor and sets a finite range for tissue damage after the tumor has been reached. In contrast, IMRT's use of uncharged particles causes its energy to damage healthy cells when it exits the body. This exiting damage is not therapeutic, can increase treatment side effects, and increases the probability of secondary cancer induction. This difference is very important in cases where the close proximity of other organs makes any stray ionization very damaging (example: head and neck cancers). This X-ray exposure is especially bad for children, due to their growing bodies, and while depending on a multitude of factors, they are around 10 times more sensitive to developing secondary malignancies after radiotherapy as compared to adults. | 0 | Theoretical and Fundamental Chemistry |
Greek prefixes in alphabetical order indicate ring size.
Lactones are usually named according to the precursor acid molecule (aceto = 2 carbon atoms, propio = 3, butyro = 4, valero = 5, capro = 6, etc.), with a -lactone suffix and a Greek letter prefix that specifies the number of carbon atoms in the heterocycle — that is, the distance between the relevant -OH and the -COOH groups along said backbone. The first carbon atom after the carbon in the -COOH group on the parent compound is labelled α, the second will be labeled β, and so forth. Therefore, the prefixes also indicate the size of the lactone ring: α-lactone = 3-membered ring, β-lactone = 4-membered, γ-lactone = 5-membered, δ-lactone = 6-membered, etc. Macrocyclic lactones are known as macrolactones.
The other suffix used to denote a lactone is -olide, used in substance class names like butenolide, macrolide, cardenolide or bufadienolide.
To obtain the preferred IUPAC names, lactones are named as heterocyclic pseudoketones by adding the suffix one, dione, thione, etc. and the appropriate multiplicative prefixes to the name of the heterocyclic parent hydride. | 0 | Theoretical and Fundamental Chemistry |
#The sample is dissolved, if it is not already in solution.
#The solution may be treated to adjust the pH (so that the proper precipitate is formed, or to suppress the formation of other precipitates). If it is known that species are present which interfere (by also forming precipitates under the same conditions as the analyte), the sample might require treatment with a different reagent to remove these interferents.
#The precipitating reagent is added at a concentration that favors the formation of a "good" precipitate (see below). This may require low concentration, extensive heating (often described as "digestion"), or careful control of the pH. Digestion can help reduce the amount of coprecipitation.
#After the precipitate has formed and been allowed to "digest", the solution is carefully filtered. The filter is used to collect the precipitate; smaller particles are more difficult to filter.
#*Depending on the procedure followed, the filter might be a piece of ashless filter paper in a fluted funnel, or a filter crucible. Filter paper is convenient because it does not typically require cleaning before use; however, filter paper can be chemically attacked by some solutions (such as concentrated acid or base), and may tear during the filtration of large volumes of solution.
#*The alternative is a crucible whose bottom is made of some porous material, such as sintered glass, porcelain or sometimes metal. These are chemically inert and mechanically stable, even at elevated temperatures. However, they must be carefully cleaned to minimize contamination or carryover(cross-contamination). Crucibles are often used with a mat of glass or asbestos fibers to trap small particles.
#*After the solution has been filtered, it should be tested to make sure that the analyte has been completely precipitated. This is easily done by adding a few drops of the precipitating reagent; if a precipitate is observed, the precipitation is incomplete.
#After filtration, the precipitate – including the filter paper or crucible – is heated, or charred. This accomplishes the following:
#*The remaining moisture is removed (drying).
#*Secondly, the precipitate is converted to a more chemically stable form. For instance, calcium ion might be precipitated using oxalate ion, to produce calcium oxalate (CaCO); it might then be heated to convert it into the oxide (CaO). It is vital that the empirical formula of the weighed precipitate be known, and that the precipitate be pure; if two forms are present, the results will be inaccurate.
#*The precipitate cannot be weighed with the necessary accuracy in place on the filter paper; nor can the precipitate be completely removed from the filter paper to weigh it. The precipitate can be carefully heated in a crucible until the filter paper has burned away; this leaves only the precipitate. (As the name suggests, "ashless" paper is used so that the precipitate is not contaminated with ash.)
#After the precipitate is allowed to cool (preferably in a desiccator to keep it from absorbing moisture), it is weighed (in the crucible). To calculate the final mass of the analyte, the starting mass of the empty crucible is subtracted from the final mass of the crucible containing the sample. Since the composition of the precipitate is known, it is simple to calculate the mass of analyte in the original sample. | 0 | Theoretical and Fundamental Chemistry |
A Rieke metal is a highly reactive metal powder generated by reduction of a metal salt with an alkali metal. These materials are named after Reuben D. Rieke, who first described the recipes for their preparation. Among the many metals that have been generated by this method are Mg, Ca, Ti, Fe, Co, Ni, Cu, Zn, and In, which in turn are called Rieke-magnesium, Rieke-calcium, etc.
Rieke metals are highly reactive because they have high surface area and lack surface oxides that can retard reaction of bulk materials. The particles are very small, ranging from 1-2 μm down to 0.1 μm or less. Some metals like nickel and copper give black colloidal suspensions that do not settle, even with centrifugation, and cannot be filtered. Other metals such as magnesium and cobalt give larger particles, but these are found to be composed mainly of the alkali salt by-product, with the metal dispersed in them as much finer particles or even as an amorphous phase. | 0 | Theoretical and Fundamental Chemistry |
The Fenton reaction has different implications in biology because it involves the formation of free radicals by chemical species naturally present in the cell under in vivo conditions. Transition-metal ions such as iron and copper can donate or accept free electrons via intracellular reactions and so contribute to the formation, or at the contrary to the scavenging, of free radicals. Superoxide ions and transition metals act in a synergistic way in the appearance of free radical damages. Therefore, although the clinical significance is still unclear, it is one of the viable reasons to avoid iron supplementation in patients with active infections, whereas other reasons include iron-mediated infections. | 1 | Applied and Interdisciplinary Chemistry |
The drug should be used with caution in those with liver or kidney failure, due to metabolism in the liver (to the active molecule desmetramadol) and elimination by the kidneys. | 0 | Theoretical and Fundamental Chemistry |
Knowles was educated at Toller Porcorum primary school, Beaminster School and St Catharine's College, Cambridge, graduating from the university in 1988, with triple first class honours in natural sciences (taking Materials Science and Metallurgy in Part II). He then went on to complete a PhD in 1991 - on the topic of the fatigue and fracture behaviour of aluminium-lithium based composites - under the supervision of Dr Julia King (now Baroness Brown of Cambridge). | 1 | Applied and Interdisciplinary Chemistry |
sarcoplasmic reticulum - satellite DNA - scientific notation - SDS-PAGE - second messenger - second messenger system - secondary structure - secretin - selectin - sensory receptor - sequence (biology) - sequence homology - sequence motif - sequencing - serine - serotonin - serotonin receptor - serpin - sexual reproduction - SH3 domain - SI - sigma factor - signal peptide - signal recognition particle - signal sequence - signal transduction - sincalide - skeleton - skin - smooth ER - sodium channel - sodium-hydrogen antiporter - soluble - solution - solvation - solvent - somatomedin - somatomedin receptor - somatostatin - somatostatin receptor - somatotropin - somatotropin receptor - somatotropin-releasing hormone - somatropin - sp1 transcription factor - spectrin - spectroscopy - src gene - src-family kinase - SSRI - starch - stem cell - stereochemistry - steroid 17alpha-monooxygenase - steroid 21-monooxygenase - steroid receptor - stimulatory gs G-protein - stoichiometry - structural biology - structural domain - Structural formula - structural motif - substance P - substrate - sugar - sulfur - supercoil - superfamily - superoxide - surface immunoglobulin - surface plasmon resonance - suspension (chemistry) - synapse - synthetic vaccine - systems biology | 1 | Applied and Interdisciplinary Chemistry |
Iron, usually as Fe is a common constituent of river waters at very low levels. Higher iron concentrations in acidic springs or an anoxic hyporheic zone may cause visible orange/brown staining or semi-gelatinous precipitates of dense orange iron bacterial floc carpeting the river bed. Such conditions are very deleterious to most organisms and can cause serious damage in a river system.
Coal mining is also a very significant source of Iron both in mine-waters and from stocking yards of coal and from coal processing. Long abandoned mines can be a highly intractable source of high concentrations of Iron. Low levels of iron are common in spring waters emanating from deep-seated aquifers and maybe regarding as health giving springs. Such springs are commonly called Chalybeate springs and have given rise to a number of Spa towns in Europe and the United States. | 1 | Applied and Interdisciplinary Chemistry |
The simplest thiophosphates have the formula [PSO]. These trianions are only observed at very high pH, instead they exist in protonated form with the formula [HPSO] (x = 0, 1, 2, or 3 and (n = 1, 2, or 3). | 0 | Theoretical and Fundamental Chemistry |
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