text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
Bolesatine is a glycoprotein isolated from the Rubroboletus satanas (Boletus satanas Lenz) mushroom which has a lectin function that is specific to the sugar binding site of D-galactose. It is a monomeric protein with a compact globular structure and is thermostable. One tryptophan can be found in its primary sequence along with one disulfide bridge.
Bolesatine causes gastroenteritis in humans and, at high enough concentrations, inhibits protein synthesis. It does not inhibit protein synthesis directly. Instead, it acts as a phosphatase for nucleoside triphosphate, particularly for GTP. At lower concentrations, it is a mitogen to human and rat T lymphocytes. Studies have shown that at low concentrations, protein kinases C (PKC) are activated in vitro and in vero cells, leading to an increase in DNA synthesis activity. | 1 | Applied and Interdisciplinary Chemistry |
Pump–probe microscopy can also measure stimulated emission. In this case, the pump beam drives the electron to an excited state. Then the electron emits a photon when exposed to the probe beam. This interaction increases the probe signal at the detector site. | 0 | Theoretical and Fundamental Chemistry |
Recycling chromatography is mode practiced in both HPLC and CCC. In recycling chromatography, the target compounds are reintroduced into the column after they elute. Each pass through the column increases the number of theoretical plates the compounds experience and enhances chromatographic resolution. Direct recycling must be done with an isocratic solvent system. With this mode, the eluant can be selectively re-chromatographed on the same or a different column in order to facilitate the separation. This process of selective recycling has been termed a "heart-cut" and is especially effective in purifying selected target compounds with some sacrificial loss of recovery. The process of re-separating selected fractions from one chromatography experiment with another chromatographic method has long been practiced by scientists. Recycling and sequential chromatography is a streamlined version of this process. In CCC, the separation characteristics of the column may be modified simply by changing the composition of the biphasic solvent system. | 0 | Theoretical and Fundamental Chemistry |
Halo ketones take part in several reaction types, especially since they are bifunctional, with two electrophilic sites (α-carbon and carbonyl carbon). In one manifestation of this duality, they are precursors to heterocycles. Thiazoles arise from reaction of chloroacetone with thioamides.2-Aminothiazoles are similarly produced by reaction of 2-chloroketones with thioureas. Pyrroles may be synthesized by reaction of halo ketones with dicarbonyls and ammonia in the Hantzsch pyrrole synthesis. | 0 | Theoretical and Fundamental Chemistry |
Currently, the two most prominent areas of co-receptor research are investigations regarding HIV and cancer. HIV research is highly focused on the adaption of HIV strains to a variety of host co-receptors. Cancer research is mostly focused on enhancing the immune response to tumor cells, while some research also involves investigating the receptors expressed by the cancerous cells themselves. | 1 | Applied and Interdisciplinary Chemistry |
There are several examples of covalently linked 2DPs which include the individual layers or sheets of graphite (called graphenes), MoS2, (BN)x and layered covalent organic frameworks. As required by the above definition, these sheets have a periodic internal structure.
A well-known example of a 2D polymer is graphene; whose optical, electronic and mechanical properties have been studied in depth. Graphene has a honeycomb lattice of carbon atoms that exhibit semiconducting properties. A potential repeat unit of graphene is a sp2-hybridized carbon atom. Individual sheets can in principle be obtained by exfoliation procedures, though in reality this is a non-trivial enterprise.
Molybdenumdisulfide can exist in two-dimensional, single or layered polymers where each Mo(IV) center occupies a trigonal prismatic coordination sphere.
Boron nitride polymers are stable in its crystalline hexagonal form where it has a two-dimensional layered structure similar to graphene. There are covalent bonds formed between boron and nitrogen atoms, yet the layers are held together by weak van der Waals interactions, in which the boron atoms are eclipsed over the nitrogen.
Two dimensional covalent organic frameworks (COFs) are one type of microporous coordination polymer that can be fabricated in the 2D plane. The dimensionality and topology of the 2D COFs result from both the shape of the monomers and the relative and dimensional orientations of their reactive groups. These materials contain desirable properties in fields of materials chemistry including thermal stability, tunable porosity, high specific surface area, and the low density of organic material. By careful selection of organic building units, long range π-orbital overlap parallel to the stacking direction of certain organic frameworks can be achieved.
Many covalent organic frameworks derive their topology from the directionality of the covalent linkages, thus small changes in organic linkers can dramatically affect their mechanical and electronic properties. Even small changes in their structure can induce dramatic changes in stacking behavior of molecular semiconductors.
Porphyrins are an additional class of conjugated, heterocyclic macrocycles. Control of monomer assembly through covalent assembly has also been demonstrated using covalent interactions with porphyrins. Upon thermal activation of porphyrin building blocks, covalent bonds form to create a conductive polymer, a versatile route for bottom-up construction of electronic circuits has been demonstrated. | 0 | Theoretical and Fundamental Chemistry |
INSTIs bind tightly and specifically to the IN that is associated with the ends of the DNA by chelating the divalent metal ions (Mg) which is coordinated by the catalytic triad i.e. the DDE motif. The DDE motif is located in the CCD of IN and is the active site of the enzyme and hence INSTIs are so called active site inhibitors. INSTIs bind to a specific site close to the DDE motif of IN, a site that is present only in the conformation that occurs after processing of the 3´ viral DNA ends. Viral DNA may well form a part of the inhibitor binding site. The binding is a form of allosteric inhibition as it implies blockage of a specific integrase-viral DNA complex. This results in selective inhibition of the strand-transfer reaction, with no significant effect on the 3´-processing reaction. INSTIs may therefore be more specific and bind selectively to the target DNA binding site and hence be less toxic than bifunctional inhibitors that are able to bind to both the donor and target binding sites.
INBIs also bind to IN but the mechanism of action is unknown so the binding can not be detailed. | 1 | Applied and Interdisciplinary Chemistry |
Coupling of Pt to H, C, P, F or N has been reported through one up to four bonds (J to J) and is commonly studied to provide additional structural information for platinum complexes. The ~34% abundance of Pt (with the remaining 66% of natural Pt being NMR-inactive) means that this coupling appears in the respective H/P/N/C NMR spectra as satellite peaks (cf. C satellites) which, for example, result in 17:66:17 patterns for singlets.
The trans influence in 16 e square planar Pt complexes has been studied by comparing the magnitude of coupling constants in the cis- and trans- isomers.
Complicated homonuclear couplings ranging from 60 to 9000 Hz for J(Pt–Pt) are of interest in the context of platinum cluster compounds. | 0 | Theoretical and Fundamental Chemistry |
Works by Barenblatt and others have shown that besides the logarithmic law of the wall — the limit for infinite Reynolds numbers — there exist power-law solutions, which are dependent on the Reynolds number.
In 1996, Cipra submitted experimental evidence in support of these power-law descriptions. This evidence itself has not been fully accepted by other experts. In 2001, Oberlack claimed to have derived both the logarithmic law of the wall, as well as power laws, directly from the Reynolds-averaged Navier–Stokes equations, exploiting the symmetries in a Lie group approach. However, in 2014, Frewer et al. refuted these results. | 1 | Applied and Interdisciplinary Chemistry |
A 2012 paper by the Overseas Development Institute reviewed evidence of the economic impacts of green infrastructure in fragile states.
Upfront construction costs for GI were up to 8% higher than non-green infrastructure projects. Climate Finance was not adequately captured by Fragile states for GI investments, and governance issues may further hinder capability to take full advantage.
GI Investments needed strong government participation as well as institutional capacities and capabilities that fragile states may not possess. Potential poverty reduction includes improved agricultural yields and higher rural electrification rates, benefits that can be transmitted to other sectors of the economy not directly linked to the GI investment.
Whilst there are examples of GI investments creating new jobs in a number of sectors, it is unclear what the employment opportunities advantages are in respect to traditional infrastructure investments. The correct market conditions (i.e. labour regulations or energy demand) are also required in order to maximise employment creation opportunities.
Such factors that may not be fully exploited by fragile state governments lacking the capacity to do so. GI investments have a number of co-benefits including increased energy security and improved health outcomes, whilst a potential reduction of a country's vulnerability to the negative effects of climate change being arguably the most important co-benefit for such investments in a fragile state context.
There is some evidence that GI options are taken into consideration during project appraisal. Engagement mostly occurs in projects specifically designed with green goals, hence there is no data showing decision making that leads to a shift towards any green alternative. Comparisons of costs, co-benefits, poverty reduction benefits or employment creation benefits between the two typologies are also not evident.
Currently, an international standard for green infrastructure is developed: SuRe – The Standard for Sustainable and Resilient Infrastructure is a global voluntary standard which integrates key criteria of sustainability and resilience into infrastructure development and upgrade. SuRe is developed by the Swiss Global Infrastructure Basel Foundation and the French bank Natixis as part of a multi-stakeholder process and will be compliant with ISEAL guidelines.
The foundation has also developed the SuRe SmartScan, a simplified version of the SuRe Standard which serves as a self-assessment tool for infrastructure project developers. It provides them with a comprehensive and time-efficient analysis of the various themes covered by the SuRe Standard, offering a solid foundation for projects that are planning to become certified by the SuRe Standard in the future. Upon completion of the SmartScan, project developers receive a spider diagram evaluation, which indicates their project's performance in the different themes and benchmarks the performances with other SmartScan assessed projects. | 1 | Applied and Interdisciplinary Chemistry |
Multiple substituted isotopologues may be used for nuclear magnetic resonance or mass spectrometry experiments, where isotopologues are used to elucidate metabolic pathways in a qualitative (detect new pathways) or quantitative (detect quantitative share of a pathway) approach. A popular example in biochemistry is the use of uniform labelled glucose (U-C glucose), which is metabolized by the organism under investigation (e. g. bacterium, plant, or animal) and whose signatures can later be detected in newly formed amino acid or metabolically cycled products. | 0 | Theoretical and Fundamental Chemistry |
Large amounts of selenium are toxic; however, it is physiologically necessary for animals in extremely small amounts. Many other uncharacterized selenium-containing organic chemicals are also produced by a method similar to that of selenomethionine; some have recently been characterized but remain relatively unknown, such as S-seleno-methyl-glutathione and glutathione-S-selenoglutathione. Due to this, the European Union has questioned the safety and potential toxicity of this food supplement for humans, and it may not be used as an additive after 2002.
[https://www.degruyter.com/document/doi/10.1351/pac200678010105/html G.N Schrauzer], who has written two papers about selenomethionine, claims it should be an essential amino acid, and that the product is completely safe. The European Food Safety Authority does allow the use of selenomethionine as a feed additive for animals. Because organic forms of selenium appear to be excreted from the body slower than inorganic forms, products enriched with organic selenium might detrimentally bioaccumulate in the body. Because selenium-enriched foods contain much more selenium than natural foods, selenium toxicity is a potential problem, and such foods must be treated with caution. The EU allows up to 300 micrograms of selenium per day, but one long-term study of selenium supplementation showed no evidence of toxicity at a dose as high as 800 micrograms per day.
An organic selenium-containing chemical found in selenium yeast has been shown to differ in bioavailability and metabolism compared with common inorganic forms of dietary selenium. Dietary supplementation using selenium yeast is ineffective in the production of antioxidants in bovine milk compared to inorganic selenium (sodium selenate). One study examined if increased selenium in the diet of mutant mice (via a selenium yeast product) caused a higher production of selenium-containing enzymes which have an antioxidant effect. The effect was modest.
Selenium supplementation in yeast form has been shown to increase pig selenium-containing antioxidant enzymes, broiler growth and meat quality, the shelf life of turkey and rooster semen, and possibly cattle fertility.
Selenium supplementation in animal feeds may be profitable for agribusinesses. It may be possible to market selenium-fortified foods to consumers as functional foods, such as selenium-enriched eggs, meat, or milk. | 1 | Applied and Interdisciplinary Chemistry |
A similar concept is being attempted by TAE Technologies, formerly Tri-Alpha Energy (TAE), based largely on the ideas of Norman Rostoker, a professor at University of California, Irvine. Early publications from the early 1990s show devices using conventional intersecting storage rings and refocussing arrangements, but later documents from 1996 on use a very different system firing fuel ions into a field-reversed configuration (FRC).
The FRC is a self-stable arrangement of plasma which geometry looks like a mix of a vortex ring and a thick-walled tube. The magnetic fields keep the particles trapped between the tube walls, circulating rapidly. TAE intends to first produce a stable FRC, and then use accelerators to fire additional fuel ions into it so they become trapped. The ions make up for any radiative losses from the FRC, and inject more magnetic helicity into the FRC to keep its shape. The ions from the accelerators collide to produce fusion.
When the concept was first revealed, it garnered several negative reviews in the journals. These issues were explained away and the construction of several small experimental devices followed. , the best-reported performance of the system is approximately 10 away from breakeven. In early 2019, it was announced that the system would instead be developed using conventional D-T fuels and the company changed its name to TAE. | 0 | Theoretical and Fundamental Chemistry |
They named element 75 rhenium (Latin Rhenus meaning "Rhine"). Rhenium was the last element to be discovered having a stable isotope. The existence of a yet undiscovered element at this position in the periodic table had been predicted by Henry Moseley in 1914. In 1925 they reported that they detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite. In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite. These achievements led to Walter and Ida being awarded the German Chemical Society's prestigious Liebig Medal in 1931. In 2018 a memorial medal "Fidelitas ad Scientiam" was issued by ISTR for Anniversary of Re discovery https://www.pinterest.ru/pin/747879081861611384/. | 1 | Applied and Interdisciplinary Chemistry |
Before modern PCR methods existed, it was almost impossible to analyze degraded DNA samples. Methods like restriction fragment length polymorphism or RFLP Restriction fragment length polymorphism, which was the first technique used for DNA analysis in forensic science, required high molecular weight DNA in the sample in order to get reliable data. High molecular weight DNA, however, is lacking in degraded samples, as the DNA is too fragmented to carry out RFLP accurately. It was only when PCR techniques were invented that analysis of degraded DNA samples were able to be carried out Polymerase chain reaction. Multiplex PCR in particular made it possible to isolate and to amplify the small fragments of DNA that are still left in degraded samples. When multiplex PCR methods are compared to the older methods like RFLP, a vast difference can be seen. Multiplex PCR can theoretically amplify less than 1 ng of DNA, but RFLP had to have a least 100 ng of DNA in order to carry out an analysis. | 1 | Applied and Interdisciplinary Chemistry |
Ion channels may be classified by gating, i.e. what opens and closes the channels. For example, voltage-gated ion channels open or close depending on the voltage gradient across the plasma membrane, while ligand-gated ion channels open or close depending on binding of ligands to the channel. | 1 | Applied and Interdisciplinary Chemistry |
In this process, the dispersed phase is forced through the pores of a microporous membrane directly into the continuous phase. Emulsified droplets are formed and detached at the end of the pores with a drop-by-drop mechanism. The advantages of membrane emulsification over conventional emulsification processes are that it enables one to obtain very fine emulsions of controlled droplet sizes and narrow droplet size distributions. Successful emulsification can be carried out with much less consumption of emulsifier and energy, and because of the lowered shear stress effect, membrane emulsification allows the use of shear-sensitive ingredients, such as starch and proteins. The membrane emulsification process is generally carried out in cross-flow (continuous or batch) mode or in a stirred cell (batch).
A major limiting factor of ME was the low dispersed phase flux. In order to expand the industrial applications, the productivity of this method had to be increased. Some research has been aimed at solving this problem and others, such as membrane fouling.
High dispersed phase flux has now been shown to be possible using single-pass annular gap crossflow membranes. | 0 | Theoretical and Fundamental Chemistry |
Methyl cyanoformate is the organic compound with the formula CHOC(O)CN. It is used as a reagent in organic synthesis as a source of the methoxycarbonyl group, in which context it is also known as Manders reagent. When a lithium enolate is generated in diethyl ether or methyl t-butyl ether, treatment with Manders reagent will selectively afford the C-acylation product. Thus, for enolate acylation reactions in which C- vs. O-selectivity is a concern, methyl cyanoformate is often used in place of more common acylation reagent like methyl chloroformate.
Methyl cyanoformate is also an ingredient in Zyklon A. It has lachrymatory effects. | 0 | Theoretical and Fundamental Chemistry |
Consider a system composed of water that contains an organic electrolyte RNaz and an inorganic electrolyte NaCl that both dissociate completely such that:
The Gibbs Adsorption equation in terms of the relative surface excess becomes:
The Relation Between Surface Tension and The Surface Excess Concentration becomes:
where is the coefficient of the Gibbs adsorption. Values of are calculated using the Double layer (interfacial) models of Helmholtz, Gouy, and Stern.
Substances can have different effects on surface tension as shown :
* No effect, for example sugar
* Increase of surface tension, inorganic salts
* Decrease surface tension progressively, alcohols
* Decrease surface tension and, once a minimum is reached, no more effect: surfactants
Therefore, the Gibbs isotherm predicts that inorganic salts have negative surface concentrations. However, this view has been challenged extensively in recent years due to a combination of more precise interfacially sensitive experiments and theoretical models, both of which predict an increase in surface propensity of the halides with increasing size and polarizability. As such, surface tension is not a reliable method for determining the relative propensity of ions toward the air-water interface.
A method for determining surface concentrations is needed in order to prove the validity of the model: two different techniques are normally used: ellipsometry and following the decay of C present in the surfactant molecules. | 0 | Theoretical and Fundamental Chemistry |
Two staff members from ABC Radio also joined the expedition:
* Colin Simpson
* Raymond Frank Giles - Sound Recorder | 1 | Applied and Interdisciplinary Chemistry |
Gentian violet has antibacterial, antifungal, antihelminthic, antitrypanosomal, antiangiogenic, and antitumor properties. It is used medically for these properties, in particular for dentistry, and is also known as "pyoctanin" (or "pyoctanine"). It is commonly used for:
* Marking the skin for surgery preparation and allergy testing;
* Treating Candida albicans and related fungal infections, such as thrush, yeast infections, various types of tinea (ringworm, athlete's foot, jock itch);
* Treating impetigo; it was used primarily before the advent of antibiotics, but still useful to persons who may be allergic to penicillin.
In resource-limited settings, gentian violet is used to manage burn wounds, inflammation of the umbilical cord stump (omphalitis) in the neonatal period, oral candidiasis in HIV-infected patients and mouth ulcers in children with measles. | 0 | Theoretical and Fundamental Chemistry |
A common application is to a layer of liquid, such as water, when there is a temperature difference across this layer. This could be due to the liquid evaporating or being heated from below. There is a surface tension at the surface of a liquid that depends on temperature, typically as the temperature increases the surface tension decreases. Thus if due to a small fluctuation temperature, one part of the surface is hotter than another, there will be flow from the hotter part to the colder part, driven by this difference in surface tension, this flow is called the Marangoni effect. This flow will transport thermal energy, and the Marangoni number compares the rate at which thermal energy is transported by this flow to the rate at which thermal energy diffuses.
For a liquid layer of thickness , viscosity and thermal diffusivity , with a surface tension which changes with temperature at a rate , the Marangoni number can be calculated using the following formula:
When Ma is small thermal diffusion dominates and there is no flow, but for large Ma, flow (convection) occurs, driven by the gradients in the surface tension. This is called Bénard-Marangoni convection. | 1 | Applied and Interdisciplinary Chemistry |
Recent developments in LED technology have led to commercially available UV-C LEDs. UV-C LEDs use semiconductors to emit light between 255 nm and 280 nm. The wavelength emission is tuneable by adjusting the material of the semiconductor. , the electrical-to-UV-C conversion efficiency of LEDs was lower than that of mercury lamps. The reduced size of LEDs opens up options for small reactor systems allowing for point-of-use applications and integration into medical devices. Low power consumption of semiconductors introduce UV disinfection systems that utilized small solar cells in remote or Third World applications.
UV-C LEDs don't necessarily last longer than traditional germicidal lamps in terms of hours used, instead having more-variable engineering characteristics and better tolerance for short-term operation. A UV-C LED can achieve a longer installed time than a traditional germicidal lamp in intermittent use. Likewise, LED degradation increases with heat, while filament and HID lamp output wavelength is dependent on temperature, so engineers can design LEDs of a particular size and cost to have a higher output and faster degradation or a lower output and slower decline over time. | 0 | Theoretical and Fundamental Chemistry |
Arsenic can sublime readily at high temperatures.
Cadmium and zinc sublime much more than other common materials, so they are not suitable materials for use in vacuum. | 0 | Theoretical and Fundamental Chemistry |
Finger-stick ketone meters allow instant testing of beta-hydroxybutyrate levels in the blood, similar to glucometers. Beta-hydroxybutrate levels in blood can also be measured in a laboratory. | 1 | Applied and Interdisciplinary Chemistry |
The use of coal-tar creosote on a commercial scale began in 1838, when a patent covering the use of creosote oil to treat timber was taken out by inventor John Bethell. The "Bethell process"—or as it later became known, the full-cell process—involves placing wood to be treated in a sealed chamber and applying a vacuum to remove air and moisture from wood "cells". The wood is then pressure-treated to imbue it with creosote or other preservative chemicals, after which vacuum is reapplied to separate the excess treatment chemicals from the timber. Alongside the zinc chloride-based "Burnett process", use of creosoted wood prepared by the Bethell process became a principal way of preserving railway timbers (most notably railway sleepers) to increase the lifespan of the timbers, and avoiding having to regularly replace them.
Besides treating wood, it was also used for lighting and fuel. In the beginning, it was only used for lighting needed in harbour and outdoor work, where the smoke that was produced from burning it was of little inconvenience. By 1879, lamps had been created that ensured a more complete combustion by using compressed air, removing the drawback of the smoke. Creosote was also processed into gas and used for lighting that way. As a fuel, it was used to power ships at sea and blast furnaces for different industrial needs, once it was discovered to be more efficient than unrefined coal or wood. It was also used industrially for the softening of hard pitch, and burned to produce lamp black. By 1890, the production of creosote in the United Kingdom totaled approximately 29,900,000 gallons per year.
In 1854, Alexander McDougall and Robert Angus Smith developed and patented a product called McDougalls Powder as a sewer deodorant; it mainly consisted of carbolic acid derived from creosote. McDougall, in 1864, experimented with his solution to remove entozoa parasites from cattle pasturing on a sewage farm. This later led to widespread use of creosote as a cattle wash and sheep dip. External parasites would be killed in a creosote diluted dip, and drenching tubes would be used to administer doses to the animals stomachs to kill internal parasites.
Creosoted wood blocks were a common road-paving material in the late 19th and early 20th centuries, but ultimately fell out of favor because they did not generally hold up well enough over time.
Two later methods for creosoting wood were introduced after the turn of the century, referred to as empty-cell processes, because they involve compressing the air inside the wood so that the preservative can only coat the inner cell walls rather than saturating the interior cell voids. This is a less effective, though usually satisfactory, method of treating the wood, but is used because it requires less of the creosoting material. The first method, the "Rüping process" was patented in 1902, and the second, the "Lowry process" was patented in 1906. Later in 1906, the "Allardyce process" and "Card process" were patented to treat wood with a combination of both creosote and zinc chloride. In 1912, it was estimated that a total of 150,000,000 gallons were produced in the US per year. | 0 | Theoretical and Fundamental Chemistry |
In 1952, Stanley Miller and Harold Urey carried out a chemical experiment to demonstrate how organic molecules could have formed spontaneously from inorganic precursors under prebiotic conditions like those posited by the Oparin–Haldane hypothesis. It used a highly reducing (lacking oxygen) mixture of gases—methane, ammonia, and hydrogen, as well as water vapor—to form simple organic monomers such as amino acids. Bernal said of the Miller–Urey experiment that "it is not enough to explain the formation of such molecules, what is necessary, is a physical-chemical explanation of the origins of these molecules that suggests the presence of suitable sources and sinks for free energy." However, current scientific consensus describes the primitive atmosphere as weakly reducing or neutral, diminishing the amount and variety of amino acids that could be produced. The addition of iron and carbonate minerals, present in early oceans, however, produces a diverse array of amino acids. Later work has focused on two other potential reducing environments: outer space and deep-sea hydrothermal vents. | 0 | Theoretical and Fundamental Chemistry |
In the United States, vancomycin is approved by the Food and Drug Administration for either intravenous or oral administration. | 0 | Theoretical and Fundamental Chemistry |
The MPTP was originally discovered by Haworth and Hunter in 1979 and has been found to be involved in neurodegeneration, hepatotoxicity from Reye-related agents, cardiac necrosis and nervous and muscular dystrophies among other deleterious events inducing cell damage and death.
MPT is one of the major causes of cell death in a variety of conditions. For example, it is key in neuronal cell death in excitotoxicity, in which overactivation of glutamate receptors causes excessive calcium entry into the cell. MPT also appears to play a key role in damage caused by ischemia, as occurs in a heart attack and stroke. However, research has shown that the MPT pore remains closed during ischemia, but opens once the tissues are reperfused with blood after the ischemic period, playing a role in reperfusion injury.
MPT is also thought to underlie the cell death induced by Reye's syndrome, since chemicals that can cause the syndrome, like salicylate and valproate, cause MPT. MPT may also play a role in mitochondrial autophagy. Cells exposed to toxic amounts of Ca ionophores also undergo MPT and death by necrosis. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a reactivity series (or reactivity series of elements) is an empirical, calculated, and structurally analytical progression of a series of metals, arranged by their "reactivity" from highest to lowest. It is used to summarize information about the reactions of metals with acids and water, single displacement reactions and the extraction of metals from their ores. | 0 | Theoretical and Fundamental Chemistry |
Mansfield was born in Lambeth, London on 9 October 1933, to Sidney George (b. 1904, d. 1966) and Lillian Rose Mansfield (b. 1905, d. 1984; née Turner). Mansfield was the youngest of three sons, Conrad (b. 1925) and Sidney (b. 1927).
Mansfield grew up in Camberwell. During World War II he was evacuated from London, initially to Sevenoaks and then twice to Torquay, Devon, where he was able to stay with the same family on both occasions. On returning to London after the war he was told by a school master to take the 11+ exam. Having never heard of the exam before, and having no time to prepare, Mansfield failed to gain a place at the local Grammar school. His mark was, however, high enough for him to go to a Central School in Peckham. At the age of 15 he was told by a careers teacher that science wasnt for him. He left school shortly afterwards to work as a printers assistant.
At the age of 18, having developed an interest in rocketry, Mansfield took up a job with the Rocket Propulsion Department of the Ministry of Supply in Westcott, Buckinghamshire. Eighteen months later he was called up for National Service. | 0 | Theoretical and Fundamental Chemistry |
Underwater archaeology is a subfield of archaeology that focuses on the exploration of submerged archaeological sites in seas, rivers, and other bodies of water. In 1988, the Maryland Maritime Archeology Program (MMAP) was established with the goal to manage and explore the various underwater archaeological sites that line the Chesapeake Bay. This was in response to the National Abandoned Shipwreck Act passed in 1987, which gave ownership of historically significant shipwrecks to those states with proper management programs.
Water makes up 25% of the State of Maryland and there are over 550 submerged archaeological sites that have been located across the Chesapeake Bay and its surrounding watersheds. Ranging from 12,000-year-old, precolonial native settlements to shipwrecks from as recent as World War II, the MMAP researches thousands of years worth of history in these archaeological sites. Susan Langley has been Marylands State Underwater Archaeologist, one of only nine state-appointed underwater archaeologists in the United States, since assuming the role in 1995. Before Langley was hired, only 1% of the underwater archaeological sites in the bay area had been examined. Over the next 10 years, Langley made significant improvements to the MMAP's marine technology, allowing her and her team to explore 34% of the underwater archaeological sites by 2004. | 1 | Applied and Interdisciplinary Chemistry |
Afovirsen is an oligonucleotide capable of antisense interactions with mRNA of human papillomavirus. It has been investigated as a tool for diagnostics and therapeutics. | 0 | Theoretical and Fundamental Chemistry |
Kilju is often mixed with juice or some other beverage to mask off tastes, of which there can be several.
Compared to wines, kilju most closely resembles Beaujolais nouveau, which is drunk after only a few weeks of fermentation. However, properly made kilju will not easily turn into vinegar, lacking the nutrients necessary for further fermentation. It is possible to drink kilju years after it was made if it has been properly stored. In fact as white wines, it ages well into 2-3a, especially when made from impure cane sugar, molasses included (fariinisokeri), or if brewed partially from oat malt and hops, as an extra strong beer. | 1 | Applied and Interdisciplinary Chemistry |
The most widely used tensile test method is used to characterize the mechanical properties of materials. From any complete tensile test record, one can obtain important information about the materials elastic properties, the character and extent of plastic deformation, yield, and tensile strengths and toughness. The information obtained from one test justifies the extensive use of tensile tests in engineering materials research. Therefore, investigations of EMR emissions are mainly based on the tensile test of the specimens. From experiments, it can be shown that tensile crack formation excites more intensive EMR than shear cracking, increasing the elasticity, strength, and loading rate during uniaxial loading increases amplitude. Poissons ratio is a key parameter for EMR characterization during triaxial compression. If the Poisson's ratio is lower, it is harder for the material to strain transversally and hence there is a higher probability of new fractures. | 0 | Theoretical and Fundamental Chemistry |
Polymers can be fractionated on an analytical scale by size exclusion chromatography (SEC), Matrix-assisted laser desorption/ionization (MALDI) or field flow fractionation (FFF). These methods are used to determine the molecular weight distribution. | 0 | Theoretical and Fundamental Chemistry |
The Hill plot is the rearrangement of the Hill equation into a straight line.
Taking the reciprocal of both sides of the Hill equation, rearranging, and inverting again yields: . Taking the logarithm of both sides of the equation leads to an alternative formulation of the Hill-Langmuir equation:
This last form of the Hill equation is advantageous because a plot of versus yields a linear plot, which is called a Hill plot. Because the slope of a Hill plot is equal to the Hill coefficient for the biochemical interaction, the slope is denoted by . A slope greater than one thus indicates positively cooperative binding between the receptor and the ligand, while a slope less than one indicates negatively cooperative binding.
Transformations of equations into linear forms such as this were very useful before the widespread use of computers, as they allowed researchers to determine parameters by fitting lines to data. However, these transformations affect error propagation, and this may result in undue weight to error in data points near 0 or 1. This impacts the parameters of linear regression lines fitted to the data. Furthermore, the use of computers enables more robust analysis involving nonlinear regression. | 1 | Applied and Interdisciplinary Chemistry |
Dialysis is generally performed in clipped bags of dialysis tubing or in a variety of formatted dialyzers. The choice of the dialysis set up used is largely dependent on the size of the sample and the preference of the user.
Dialysis tubing is the oldest and generally the least expensive format used for dialysis in the lab. Tubing is cut and sealed with a clip at one end, then filled and sealed with a clip on the other end. Tubing provides flexibility but has increased concerns regarding handling, sealing and sample recovery. Dialysis tubing is typically supplied either wet or dry in rolls or pleated telescoped tubes.
A wide variety of dialysis devices (or dialyzers) are available from several vendors. Dialyzers are designed for specific sample volume ranges and provide greater sample security and improved ease of use and performance for dialysis experiments over tubing. The most common preformatted dialyzers are Slide-A-Lyzer, Float-A-Lyzer, and the Pur-A-lyzer/D-Tube/GeBAflex Dialyzers product lines. | 1 | Applied and Interdisciplinary Chemistry |
A Frost diagram or Frost–Ebsworth diagram is a type of graph used by inorganic chemists in electrochemistry to illustrate the relative stability of a number of different oxidation states of a particular substance. The graph illustrates the free energy vs oxidation state of a chemical species. This effect is dependent on pH, so this parameter also must be included. The free energy is determined by the oxidation–reduction half-reactions. The Frost diagram allows easier comprehension of these reduction potentials than the earlier-designed Latimer diagram, because the “lack of additivity of potentials” was confusing. The free energy ΔG° is related to the reduction potential E shown in the graph by the formula: or , where n is the number of transferred electrons, and F is the Faraday constant ). The Frost diagram is named after , who originally invented it as a way to "show both free energy and oxidation potential data conveniently" in a 1951 paper. | 0 | Theoretical and Fundamental Chemistry |
Solomon received an Associate of Sydney Technical College, (equivalent to a Diploma of Chemistry) in 1950 and went on to complete a Bachelor of Science (BSc (Hons)) in 1952 from the New South Wales University of Technology (now the University of New South Wales), a Master of Science (MSc) from the same university in 1955, and a PhD from the University of New South Wales in 1959 with a thesis entitled Studies on the Chemistry of Carbonyl Compounds. In 1968 he was awarded a DSc from the University of New South Wales for his thesis Studies on the Chemistry of Coating Compounds. He also received an Honorary Doctorate in Applied Science from the University of Melbourne in 2005, one of only seven awarded in the university's history. | 0 | Theoretical and Fundamental Chemistry |
The original technique of chromosome jumping was developed in the laboratories of Collins and Weissman at Yale University in New Haven, U.S. and the laboratories of Poustka and Lehrach at the European Molecular Biology Laboratory in Heidelberg, Germany.
Collins and Weissman's method described above encountered some early limitations. The main concern was with avoiding non-circularized fragments. Two solutions were suggested: either screening junction fragments with a given probe or adding a second size-selection step after the ligation to separate single circular clones (monomers) from clones ligated to each other (multimers). The authors also suggested that other markers such as the λ cos site or antibiotic resistance genes should be considered (instead of the amber suppressor tRNA gene) to facilitate selection of junction clones.
Poustka and Lehrach suggested that full digestion with rare-cutting restrictions enzymes (such as NotI) should be used for the first step of the library construction instead of partial digestion with a frequently cutting restriction enzyme. This would significantly reduce the number of clones from millions to thousands. However, this could create problems with circularizing the DNA fragments since these fragments would be very long, and would also lose the flexibility in choice of end points that one gets in partial digests. One suggestion for overcoming these problems would be to combine the two methods, i.e. to construct a jumping library from DNA fragments digested partially with a commonly cutting restriction enzyme and completely with a rare cutting restriction enzyme and circularizing them into plasmids cleaved with both enzymes. Several of these "combination" libraries were completed in 1986.
In 1991, Zabarovsky et al. proposed a new approach for construction of jumping libraries. This approach included the use of two separate λ vectors for library construction, and a partial filling-in reaction that removes the need for a selectable marker. This filling-in reaction worked by destroying the specific cohesive ends (resulting from restriction digests) of the DNA fragments that were nonligated and noncircularized, thus preventing them from cloning into the vectors, in a more energy-efficient and accurate manner. Furthermore, this improved technique required less DNA to start with, and also produced a library that could be transferred into a plasmid form, making it easier to store and replicate. Using this new approach, they successfully constructed a human NotI jumping library from a lymphoblastoid cell line and a human chromosome 3-specific NotI jumping library from a human chromosome 3 and mouse hybrid cell line. | 1 | Applied and Interdisciplinary Chemistry |
If the cylinder has variable radius in the axial direction, the -axis, , then the solution to the first-order approximation in terms of the three-dimensional velocity potential is
where is the modified Bessel function of the first kind of order one. | 1 | Applied and Interdisciplinary Chemistry |
In 1825, Johann Friedrich Engelhart discovered that the ratio of iron to protein is identical in the hemoglobins of several species. From the known atomic mass of iron, he calculated the molecular mass of hemoglobin to n × 16000 (n = number of iron atoms per hemoglobin molecule, now known to be 4), the first determination of a proteins molecular mass. This "hasty conclusion" drew ridicule from colleagues who could not believe that any molecule could be so large. However, Gilbert Smithson Adair confirmed Engelharts results in 1925 by measuring the osmotic pressure of hemoglobin solutions.
Although blood had been known to carry oxygen since at least 1794, the oxygen-carrying property of hemoglobin was described by Hünefeld in 1840. In 1851, German physiologist Otto Funke published a series of articles in which he described growing hemoglobin crystals by successively diluting red blood cells with a solvent such as pure water, alcohol or ether, followed by slow evaporation of the solvent from the resulting protein solution. Hemoglobin's reversible oxygenation was described a few years later by Felix Hoppe-Seyler.
With the development of X-ray crystallography, it became possible to sequence protein structures. In 1959, Max Perutz determined the molecular structure of hemoglobin. For this work he shared the 1962 Nobel Prize in Chemistry with John Kendrew, who sequenced the globular protein myoglobin.
The role of hemoglobin in the blood was elucidated by French physiologist Claude Bernard.
The name hemoglobin is derived from the words heme and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme group. Each heme group contains one iron atom, that can bind one oxygen molecule through ion-induced dipole forces. The most common type of hemoglobin in mammals contains four such subunits. | 0 | Theoretical and Fundamental Chemistry |
Phosgene oxime, or CX, is an organic compound with the formula . It is a potent chemical weapon, specifically a nettle agent, which is a type of blister agent. The compound itself is a colorless solid, but impure samples are often yellowish liquids. It has a strong, disagreeable and irritating odor. It is used as a reagent in organic chemistry. | 1 | Applied and Interdisciplinary Chemistry |
Oxoguanine glycosylase (OGG1) catalyses the first step in base excision repair of the oxidatively damaged base 8-OHdG. OGG1 finds 8-OHdG by sliding along the linear DNA at 1,000 base pairs of DNA in 0.1 seconds. OGG1 very rapidly finds 8-OHdG. OGG1 proteins bind to oxidatively damaged DNA with a half maximum time of about 6 seconds. When OGG1 finds 8-OHdG it changes conformation and complexes with 8-OHdG in its binding pocket. OGG1 does not immediately act to remove the 8-OHdG. Half maximum removal of 8-OHdG takes about 30 minutes in HeLa cells in vitro, or about 11 minutes in the livers of irradiated mice. DNA oxidation by reactive oxygen species preferentially occurs at a guanine in a methylated CpG site, because of a lowered ionization potential of guanine bases adjacent to 5-methylcytosine. TET1 binds (is recruited to) the OGG1 bound to 8-OHdG (see figure). This likely allows TET1 to demethylate an adjacent methylated cytosine. When human mammary epithelial cells (MCF-10A) were treated with HO, 8-OHdG increased in DNA by 3.5-fold and this caused about 80% demethylation of the 5-methylcytosines in the MCF-10A genome. | 1 | Applied and Interdisciplinary Chemistry |
Prime editing efficiency can be increased with the use of engineered pegRNAs (epegRNAs). One common issue with traditional pegRNAs is degradation of the 3 end, leading to decreased PE efficiency. epegRNAs have a structured RNA motif added to their 3 end to prevent degradation. | 1 | Applied and Interdisciplinary Chemistry |
is prepared by chlorination of Mo metal but also chlorination of . The unstable hexachloride is not produced in this way.
is reduced by acetonitrile to afford an orange acetonitrile complex, . This complex in turn reacts with THF to give , a precursor to other molybdenum-containing complexes.
Molybdenum(IV) bromide is prepared by treatment of with hydrogen bromide:
The reaction proceeds via the unstable molybdenum(V) bromide, which releases bromine at room temperature.
is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form . In organic synthesis, the compound finds occasional use in chlorinations, deoxygenation, and oxidative coupling reactions. | 0 | Theoretical and Fundamental Chemistry |
Olavi Erämetsä (born Enwald; 10 October 1906 Lahti, Finland - 3 January 1974 Helsinki, Finland) was a Finnish chemist at the Helsinki University of Technology (TKK, now part of Aalto University). He served as a lecturer in analytical chemistry (1940-1946) before succeeding Yrjö Kauko as professor of inorganic chemistry (1947-1973).
Erämetsä was a major initiator of geochemical research in rare earths and trace elements at TKK from 1947 to 1973.
In 1965, he reported the isolation of the element promethium from natural sources.
Erämetsä studied the presence of trace elements including rare earths in soils and plants such as lichens and mosses. He also studied their presence in the human body, gathering epidemiological evidence about environmental factors and their possible effects on human health.
Erämetsä was the Chairman of the Finnish Chemistry Society in 1945–1946, a Founding Member of the Finnish Academy of Engineering in 1957 and a Member of the Finnish Academy of Sciences as of 1961. | 1 | Applied and Interdisciplinary Chemistry |
The same capability of natural organic matter that helps with water retention in soil creates problems for current water purification methods. In water, organic matter can still bind to metal ions and minerals. These bound molecules are not necessarily stopped by the purification process, but do not cause harm to any humans, animals, or plants. However, because of the high level of reactivity of organic matter, by-products that do not contain nutrients can be made. These by-products can induce biofouling, which essentially clogs water filtration systems in water purification facilities, as the by-products are larger than membrane pore sizes. This clogging problem can be treated by chlorine disinfection (chlorination), which can break down residual material that clogs systems. However, chlorination can form disinfection by-products.
Water with organic matter can be disinfected with ozone-initiated radical reactions. The ozone (three oxygens) has very strong oxidation characteristics. It can form hydroxyl radicals (OH) when it decomposes, which will react with the organic matter to shut down the problem of biofouling. | 0 | Theoretical and Fundamental Chemistry |
Particle deposition can be followed by various experimental techniques. Direct observation of deposited particles is possible with an optical microscope, scanning electron microscope, or the atomic force microscope. Optical microscopy has the advantage that the deposition of particles can be followed in real time by video techniques and the sequence of images can be analyzed quantitatively. On the other hand, the resolution of optical microscopy requires that the particle size investigated exceeds at least 100 nm.
An alternative is to use surface sensitive techniques to follow particle deposition, such as reflectivity, ellipsometry, surface plasmon resonance, or quartz crystal microbalance. These techniques can provide information on the amount of particles deposited as a function of time with good accuracy, but they do not permit to obtain information concerning the lateral arrangement of the particles.
Another approach to study particle deposition is to investigate their transport in a chromatographic column. The column is packed with large particles or with a porous medium to be investigated. Subsequently, the column is flushed with the solvent to be investigated, and the suspension of the small particles is injected at the column inlet. The particles are detected at the outlet with a standard chromatographic detector. When particles deposit in the porous medium, they will not arrive at the outlet, and from the observed difference the deposition rate coefficient can be inferred. | 0 | Theoretical and Fundamental Chemistry |
Three different samples of recycled glass with different gradation curves produced from residential and industrial waste glass streams in Victoria were studied in this research to investigate their usage as a construction material in geotechnical applications. The Fine Recycled Glass (FRG) and Medium recycled Glass (MRG) were classified well graded (SW-SM) while Coarse Recycled Glass (CRG) was classified poorly graded (GP) according to Unified Soil Classifications System (USCS). Recycled glass specific gravity values were found to be approximately 10% lower than the values attributed to natural aggregate reported by Das (2007).
Results of standard and modified proctor compaction tests showed a higher maximum dry unit weight for MRG sample compared to FRG sample while the optimum water content of MRG was found to be lower than FRG sample. LA abrasion tests proved that the abrasion resistance of FRG and MRG samples is close to those of construction and demolition material, whereas CRG showed a higher LA abrasion value. Post compaction gradation curve analysis of FRG and MRG samples proves their stability during engineering operations including handling, spreading and especially compacting. The CRG source consisted of a sizable amount of elongated and flat shaped particles and high debris content. It was also found that the CRG source possesses little ability to absorb and hold moisture which impacts on its compaction behavior. These characteristics along with perceptible change in gradation curves of the CRG samples after compaction, and its high segregation potential led the authors to conclude that CRG source is not an ideal material for geotechnical engineering applications. On the other hand, FRG and MRG samples proved appropriate characteristics close to those of natural aggregate within the same soil classification.
CBR tests indicate the superior shear resistance of MRG as compared to FRG. Direct shear test results indicate that the internal friction angle of MRG is slightly higher than those of FRG. The internal friction angle values obtained for FRG and MRG samples through direct shear test are comparable to those of natural sand and gravel mixtures with angular particles. Consolidated Drained CD triaxial shear test results confirmed the findings of direct shear tests. By and large FRG and MRG samples showed the geotechnical engineering behavior of natural well graded sand and gravel mixtures.
Hydraulic conductivity tests showed that FRG and MRG samples have medium permeability with good drainage characteristics. TC and Assessment of Safety Level and Safety Performance (ASLP) proved that FRG and MRG samples comply with requirements issued by EPA Victoria for using aggregates as fill material. Results of this study advocate using recycled glass in a range of geotechnical engineering applications. | 0 | Theoretical and Fundamental Chemistry |
When white light passes through a polarizer, the extent of rotation of light depends on its wavelength. Short wavelengths are rotated more than longer wavelengths, per unit of distance. Because the wavelength of light determines its color, the variation of color with distance through the tube is observed. This dependence of specific rotation on wavelength is called optical rotatory dispersion.
In all materials the rotation varies with wavelength. The variation is caused by two quite different phenomena. The first accounts in most cases for the majority of the variation in rotation and should not strictly be termed rotatory dispersion. It depends on the fact that optical activity is actually circular birefringence. In other words, a substance which is optically active transmits right circularly polarized light with a different velocity from left circularly polarized light.
In addition to this pseudodispersion which depends on the material thickness, there is a true rotatory dispersion which depends on the variation with wavelength of the indices of refraction for right and left circularly polarized light.
For wavelengths that are absorbed by the optically active sample, the two circularly polarized components will be absorbed to differing extents. This unequal absorption is known as circular dichroism. Circular dichroism causes incident linearly polarized light to become elliptically polarized. The two phenomena are closely related, just as are ordinary absorption and dispersion. If the entire optical rotatory dispersion spectrum is known, the circular dichroism spectrum can be calculated, and vice versa. | 0 | Theoretical and Fundamental Chemistry |
The main part of a centrifugal compressor is the impeller. An open impeller has no cover, therefore it can work at higher speeds. A compressor with a covered impeller can have more stages than one that has an open impeller. | 1 | Applied and Interdisciplinary Chemistry |
Three main types of cheese rely on moulds for their characteristic properties: blue cheese, soft ripened cheese (such as camembert and brie) and rind-washed cheese (such as époisses and taleggio).
To make blue cheese, the cheese is treated with a mould, usually Penicillium roqueforti, while it is still in the loosely pressed curd form. As the cheese matures, the mould grows, creating blue veins within it which gives the cheese its characteristic flavour. Examples include stilton, roquefort and gorgonzola.
Soft ripened cheese such as brie and camembert are made by allowing P. camemberti to grow on the outside of the cheese, which causes them to age from the outside in. The mould forms a soft white crust, and the interior becomes runny with a strong flavour.
Rind-washed cheeses like limburger also ripen inwards, but here, as the name suggests, they are washed with brine and other ingredients such as beer and wine which contain mould. This also makes them attractive to bacteria, which add to the flavour.
Traditionally, inoculations of sausages with moulds were done with the indigenous biota of the slaughters. Different moulds (such as P. chrysogenum and P. nalgiovense) can be used to ripen surfaces of sausages. The mould cultures develop the aroma and improve the texture of the sausages. They also contribute to shortening of the ripening period and preserving the natural quality. This expands the shelf life of the meat product.
In the past, soy sauce has been made by mixing soybeans and other grains with a mould (Aspergillus oryzae or A. sojae) and yeast. This mixture was then left to ferment in the sun. Today soy sauce is made under controlled conditions. The key flavour ingredients formed in this process are salts of the amino acid glutamic acid, notably monosodium glutamate. | 1 | Applied and Interdisciplinary Chemistry |
The reaction of cyclopropylmethamine with sodium nitrite in dilute aqueous perchloric acid solution yielded a mixture of 48% cyclopropylmethyl alcohol, 47% cyclobutanol, and 5% homoallylic alcohol (but-3-en-1-ol). In the non-classical perspective, the positive charge is delocalized throughout the carbocation intermediate structure via resonance, resulting in partial (electron-deficient) bonds. Evidently, the relatively low yield of the homoallylic alcohol implies that the homoallylic structure is the weakest resonance contributor. | 0 | Theoretical and Fundamental Chemistry |
There are two common mathematical descriptions of the work hardening phenomenon. Hollomon's equation is a power law relationship between the stress and the amount of plastic strain:
where σ is the stress, K is the strength index or strength coefficient, ε is the plastic strain and n is the strain hardening exponent. Ludwik's equation is similar but includes the yield stress:
If a material has been subjected to prior deformation (at low temperature) then the yield stress will be increased by a factor depending on the amount of prior plastic strain ε:
The constant K is structure dependent and is influenced by processing while n is a material property normally lying in the range 0.2–0.5. The strain hardening index can be described by:
This equation can be evaluated from the slope of a log(σ) – log(ε) plot. Rearranging allows a determination of the rate of strain hardening at a given stress and strain: | 1 | Applied and Interdisciplinary Chemistry |
Different methods to determine the endpoint include:
*Indicator: A substance that changes color in response to a chemical change. An acid–base indicator (e.g., phenolphthalein) changes color depending on the pH. Redox indicators are also used. A drop of indicator solution is added to the titration at the beginning; the endpoint has been reached when the color changes.
*Potentiometer: An instrument that measures the electrode potential of the solution. These are used for redox titrations; the potential of the working electrode will suddenly change as the endpoint is reached.
*pH meter: A potentiometer with an electrode whose potential depends on the amount of H ion present in the solution. (This is an example of an ion-selective electrode.) The pH of the solution is measured throughout the titration, more accurately than with an indicator; at the endpoint there will be a sudden change in the measured pH.
*Conductivity: A measurement of ions in a solution. Ion concentration can change significantly in a titration, which changes the conductivity. (For instance, during an acid–base titration, the H and OH ions react to form neutral HO.) As total conductance depends on all ions present in the solution and not all ions contribute equally (due to mobility and ionic strength), predicting the change in conductivity is more difficult than measuring it.
*Color change: In some reactions, the solution changes color without any added indicator. This is often seen in redox titrations when the different oxidation states of the product and reactant produce different colors.
*Precipitation: If a reaction produces a solid, a precipitate will form during the titration. A classic example is the reaction between Ag and Cl to form the insoluble salt AgCl. Cloudy precipitates usually make it difficult to determine the endpoint precisely. To compensate, precipitation titrations often have to be done as "back" titrations (see below).
*Isothermal titration calorimeter: An instrument that measures the heat produced or consumed by the reaction to determine the endpoint. Used in biochemical titrations, such as the determination of how substrates bind to enzymes.
*Thermometric titrimetry: Differentiated from calorimetric titrimetry because the heat of the reaction (as indicated by temperature rise or fall) is not used to determine the amount of analyte in the sample solution. Instead, the endpoint is determined by the rate of temperature change.
*Spectroscopy: Used to measure the absorption of light by the solution during titration if the spectrum of the reactant, titrant or product is known. The concentration of the material can be determined by Beer's Law.
*Amperometry: Measures the current produced by the titration reaction as a result of the oxidation or reduction of the analyte. The endpoint is detected as a change in the current. This method is most useful when the excess titrant can be reduced, as in the titration of halides with Ag. | 0 | Theoretical and Fundamental Chemistry |
Mao has authored numerous publications spanning the areas of nanomanufacturing, nanofabrication, and nanochemistry, including articles in peer-reviewed journals. | 1 | Applied and Interdisciplinary Chemistry |
The term sequestration is based on the Latin sequestrare, which means set aside or surrender. It is derived from sequester, a depositary or trustee, one in whose hands a thing in dispute was placed until the dispute was settled. In English "sequestered" means secluded or withdrawn.
In law, sequestration is the act of removing, separating, or seizing anything from the possession of its owner under process of law for the benefit of creditors or the state. | 0 | Theoretical and Fundamental Chemistry |
The racemic parent compound racemorphan was first described in a Swiss and US patent application from Hoffmann-La Roche in 1946 and 1947, respectively; a patent was granted in 1950. A resolution of the two isomers of racemorphan with tartaric acid was published in 1952, and dextromethorphan was successfully tested in 1954 as part of US Navy and CIA-funded research on nonaddictive substitutes for codeine. Dextromethorphan was approved by the FDA in 1958 as an over-the-counter antitussive. As had been initially hoped, dextromethorphan was a solution for some of the problems associated with the use of codeine phosphate as a cough suppressant, such as sedation and opiate dependence, but like the dissociative anesthetics phencyclidine and ketamine, dextromethorphan later became associated with nonmedical use.
During the 1960s and 1970s, dextromethorphan became available in an over-the-counter tablet form by the brand name Romilar. In 1973, Romilar was taken off the shelves after a burst in sales because of frequent misuse. A few years later, products with an unpleasant taste were introduced (such as Robitussin, Vicks-44, and Dextrotussion), but later the same manufacturers began producing products with a better taste. The advent of widespread internet access in the 1990s allowed users to rapidly disseminate information about dextromethorphan, and online discussion groups formed around use and acquisition of the drug. As early as 1996, dextromethorphan hydrobromide powder could be purchased in bulk from online retailers, allowing users to avoid consuming dextromethorphan in syrup preparations.
FDA panels considered moving dextromethorphan to prescription status due to its potential for abuse, but voted against the recommendation in September 2010, citing lack of evidence that making it prescription-only would curb abuse. Some states have restricted the sale of dextromethorphan to adults or put other restrictions on its purchase in place, similar to those for pseudoephedrine. As of January 1, 2012, dextromethorphan is prohibited for sale to minors in the State of California and in the State of Oregon as of January 1, 2018, except with a doctor's prescription. Several other states have also begun regulating sales of dextromethorphan to minors.
In Indonesia, the National Agency of Drug and Food Control (BPOM-RI) prohibited single-component dextromethorphan drug sales with or without prescription. Indonesia is the only country in the world that makes single-component dextromethorphan illegal even by prescription and violators may be prosecuted by law. National Anti-Narcotics Agency (BNN RI) has even threatened to revoke pharmacies and drug stores licenses if they still stock dextromethorphan, and will notify the police for criminal prosecution. As a result of this regulation, 130 medications have been withdrawn from the market, but those containing multicomponent dextromethorphan can still be sold over the counter. | 0 | Theoretical and Fundamental Chemistry |
The S.I. unit for the mold constant is seconds per metre squared (). According to Askeland, the constant is usually 2, however Degarmo claims it is between 1.5 and 2. The mold constant can be calculated using the following formula:
Where
: = melting or freezing temperature of the liquid (in kelvins),
: = initial temperature of the mold (in kelvins),
: = superheat (in kelvins),
: = latent heat of fusion (in ),
: = thermal conductivity of the mold (in ),
: = density of the mold (in ),
: = specific heat of the mold (in ),
: = density of the metal (in ),
: = specific heat of the metal (in ).
It is most useful in determining if a riser will solidify before the casting, because if the riser solidifies first then defects like shrinkage or porosity can form. | 1 | Applied and Interdisciplinary Chemistry |
According to the VSEPR theory of molecular bonding, the preferred geometry of a molecule is that in which both bonding and non-bonding electrons are as far apart as possible. In molecules, it is quite common for these angles to be somewhat compressed or expanded compared to their optimal value. This strain is referred to as angle strain, or Baeyer strain. The simplest examples of angle strain are small cycloalkanes such as cyclopropane and cyclobutane, which are discussed below. Furthermore, there is often eclipsing or Pitzer strain in cyclic systems. These and possible transannular interactions were summarized early by H.C. Brown as internal strain, or I-Strain. Molecular mechanics or force field approaches allow to calculate such strain contributions, which then can be correlated e.g. with reaction rates or equilibria. Many reactions of alicyclic compounds, including equilibria, redox and solvolysis reactions, which all are characterized by transition between sp2 and sp3 state at the reaction center, correlate with corresponding strain energy differences SI (sp2 -sp3). The data reflect mainly the unfavourable vicinal angles in medium rings, as illustrated by the severe increase of ketone reduction rates with increasing SI (Figure 1). Another example is the solvolysis of bridgehead tosylates with steric energy differences between corresponding bromide derivatives (sp3) and the carbenium ion as sp2- model for the transition state. (Figure 2)
In principle, angle strain can occur in acyclic compounds, but the phenomenon is rare. | 0 | Theoretical and Fundamental Chemistry |
Structural symmetry of a molecule can be defined mathematically as a permutation of the atoms that exchanges at least two atoms but does not change the molecule's structure. Two atoms then can be said to be structurally equivalent if there is a structural symmetry that takes one to the other.
Thus, for example, all four hydrogen atoms of methane are structurally equivalent, because any permutation of them will preserve all the bonds of the molecule.
Likewise, all six hydrogens of ethane () are structurally equivalent to each other, as are the two carbons; because any hydrogen can be switched with any other, either by a permutation that swaps just those two atoms, or by a permutation that swaps the two carbons and each hydrogen in one methyl group with a different hydrogen on the other methyl. Either operation preserves the structure of the molecule. That is the case also for the hydrogen atoms cyclopentane, allene, 2-butyne, hexamethylenetetramine, prismane, cubane, dodecahedrane, etc.
On the other hand, the hydrogen atoms of propane are not all structurally equivalent. The six hydrogens attached to the first and third carbons are equivalent, as in ethane, and the two attached to the middle carbon are equivalent to each other; but there is no equivalence between these two equivalence classes. | 0 | Theoretical and Fundamental Chemistry |
Detonation of a nuclear weapon involves bringing fissile material into its optimal supercritical state very rapidly. During part of this process, the assembly is supercritical, but not yet in an optimal state for a chain reaction. Free neutrons, in particular from spontaneous fissions, can cause the device to undergo a preliminary chain reaction that destroys the fissile material before it is ready to produce a large explosion, which is known as predetonation.
To keep the probability of predetonation low, the duration of the non-optimal assembly period is minimized and fissile and other materials are used that have low spontaneous fission rates. In fact, the combination of materials has to be such that it is unlikely that there is even a single spontaneous fission during the period of supercritical assembly. In particular, the gun method cannot be used with plutonium (see nuclear weapon design). | 0 | Theoretical and Fundamental Chemistry |
First-generation Glycoazodyes are synthesized using glucose, galactose or lactose as the sugar group. The point of esterification is controlled by selectively protecting alcohol groups on the sugar, or by choosing an azo dye with a different alcohol group position. Either the dye or the sugar group can be succinylated by reacting a free alcohol group with succinic anhydride. The resulting hemisuccinate then reacts with a free alcohol group on either the dye or the sugar. The condensation product is then deprotected. | 0 | Theoretical and Fundamental Chemistry |
The purpose of this technique is to analyze the activity of a gene transcription promoter (in terms of expression of a so-called reporter gene under the regulatory control of that promoter) either in a quantitative manner, involving some measure of activity, or qualitatively (on versus off) through visualization of its activity in different cells, tissues, or organs. The technique utilizes the uidA gene of Escherichia coli, which codes for the enzyme, β-glucuronidase; this enzyme, when incubated with specific colorless or non-fluorescent substrates, can convert them into stable colored or fluorescent products. The presence of the GUS-induced color indicates where the gene has been actively expressed. In this way, strong promoter activity produces much staining and weak promoter activity produces less staining.
The uidA gene can also be fused to a gene of interest, creating a gene fusion. The insertion of the uidA gene will cause production of GUS, which can then be detected using various glucuronides as substrates. | 1 | Applied and Interdisciplinary Chemistry |
Welan gum is an exopolysaccharide used as a rheology modifier in industrial applications such as cement manufacturing. It is produced by fermentation of sugar by bacteria of the genus Alcaligenes. The molecule consists of repeating tetrasaccharide units with single branches of L-mannose or L-rhamnose. In solution, the gum retains viscosity at elevated temperature, and is stable in a wide pH range, in the presence of calcium ion, and with high concentration of glycols. | 0 | Theoretical and Fundamental Chemistry |
The Illinois Plant is called the Lacassane Coastal Prairie Mitigation Bank and the Ragley property, in conjunction with the "Calcasieu Mitigation Bank" and partnered with Ecosystem Investment Partners (EIP), is known as the Bill Jackson Longleaf Savannah Mitigation Bank. Both have been designated (through The Lacassane Company) by the Corps of Engineers as a mitigation bank providing ecosystem services to the public in the form of Environmental mitigation (compensatory mitigation) to ensure the no net loss wetlands policy is followed to prevent Biodiversity loss that keeps the greenhouse debt in check. The Lacassane Company partnered with The Coastal Plain Conservancy to hold conservation servitudes on the land. The banks are monitored and maintained by Wildlands, Inc., an environmental consulting and plant propagation company.
The company operations now include land leases for waterfowl (Waterfowl Limited Liability Company) and other hunting, cattle grazing, alligator hide and egg harvesting, oil and gas exploration, and wetland projects. A pumping system through canals, laterals, the Bell City ditch, the Lacassine Bayou and the Mermentau River provides irrigation for the farming operations. The company's SIC code (Lessors of Real Property, NEC) is 6519 and the NAICS CODE (Lessors of Other Real Estate Property) is 531190. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the Taylor microscale, which is sometimes called the turbulence length scale, is a length scale used to characterize a turbulent fluid flow. This microscale is named after Geoffrey Ingram Taylor. The Taylor microscale is the intermediate length scale at which fluid viscosity significantly affects the dynamics of turbulent eddies in the flow. This length scale is traditionally applied to turbulent flow which can be characterized by a Kolmogorov spectrum of velocity fluctuations. In such a flow, length scales which are larger than the Taylor microscale are not strongly affected by viscosity. These larger length scales in the flow are generally referred to as the inertial range. Below the Taylor microscale the turbulent motions are subject to strong viscous forces and kinetic energy is dissipated into heat. These shorter length scale motions are generally termed the dissipation range.
Calculation of the Taylor microscale is not entirely straightforward, requiring formation of certain flow correlation function(s), then expanding in a Taylor series and using the first non-zero term to characterize an osculating parabola. The Taylor microscale is proportional to , while the Kolmogorov microscale is proportional to , where is the integral scale Reynolds number. A turbulence Reynolds number calculated based on the Taylor microscale is given by
where is the root mean square of the velocity fluctuations.
The Taylor microscale is given as
where is the kinematic viscosity, and is the rate of energy dissipation. A relation with turbulence kinetic energy can be derived as
The Taylor microscale gives a convenient estimation for the fluctuating strain rate field | 1 | Applied and Interdisciplinary Chemistry |
PROTACs achieve degradation through "hijacking" the cell's ubiquitin–proteasome system (UPS) by bringing together the target protein and an E3 ligase.
First, the E1 activates and conjugates the ubiquitin to the E2. The E2 then forms a complex with the E3 ligase. The E3 ligase targets proteins and covalently attaches the ubiquitin to the protein of interest. Eventually, after a ubiquitin chain is formed, the protein is recognized and degraded by the 26S proteasome. PROTACs take advantage of this cellular system by putting the protein of interest in close proximity to the E3 ligase to catalyze degradation.
Unlike traditional inhibitors, PROTACs have a catalytic mechanism, with the PROTAC itself being recycled after the target protein is degraded. | 1 | Applied and Interdisciplinary Chemistry |
Nesfatin-1 is a polypeptide encoded in the N-terminal region of the protein precursor, Nucleobindin-2 (NUCB2).
Recombinant human Nesfatin-1 is a 9.7 kDa protein containing 82 amino acid residues. Nesfatin-1 is expressed in the hypothalamus, in other areas of the brain, and in pancreatic islets, gastric endocrine cells and adipocytes. | 1 | Applied and Interdisciplinary Chemistry |
LASNEX is a computer program that simulates the interactions between x-rays and a plasma, along with many effects associated with these interactions. The program is used to predict the performance of inertial confinement fusion (ICF) devices such as the Nova laser or proposed particle beam "drivers".
Versions of LASNEX have been used since the late 1960s or early 1970s, and the program has been constantly updated. LASNEXs existence was mentioned in John Nuckolls seminal paper in Nature in 1972 that first widely introduced the ICF concept, saying it was "...like breaking an enemy code. It tells you how many divisions to bring to bear on a problem."
LASNEX uses a 2-dimensional finite element method (FEM) for calculations, breaking down the experimental area into a grid of arbitrary polygons. Each node on the grid records values for various parameters in the simulation. Values for thermal (low-energy) electrons and ions, super-thermal (high-energy and relativistic) electrons, x-rays from the laser, reaction products and the electric and magnetic fields were all stored for each node. The simulation engine then evolves the system forward through time, reading values from the nodes, applying formulas, and writing them back out. The process is very similar to other FEM systems, like those used in aerodynamics.
In spite of numerous problems in very early ICF research, LASNEX offered clear suggestions that slight increases in performance would be all that was needed to reach ignition. By the late 1970s further work with LASNEX indicated that the issue was not energy as much as the number of laser beams, and suggested that the Shiva laser with 10 kJ of energy in 20 beams would reach ignition. It did not, failing to contain the Rayleigh–Taylor instability. A review of the progress by The New York Times the following year noted that the system "fell short of the more optimistic estimates by a factor of 10,000".
Real-world results from the Shiva project were then used to tune the LASNEX code, which now predicted that a somewhat larger machine, the Nova laser, would reach ignition. It did not; although Nova demonstrated fusion reactions on a large scale, it was far from ignition.
Novas results were also used to tune the LASNEX system, which once again predicted that ignition could be reached, this time with a significantly larger machine. Given the past failures and rising costs, the Department of Energy decided to directly test the concept with a series of underground nuclear tests known as "Halite" and "Centurion", depending on which lab was handling the experiment. Halite/Centurion placed typical ICF targets in hohlraums, metal cylinders intended to smooth out the drivers energy so it shines on the fuel target evenly. The hohlraum/fuel assemblies were then placed at various distances from a small atomic bomb, detonation of which released significant quantities of x-rays. These x-rays heated the hohlraums until they glowed in the x-ray spectrum (having been heated "x-ray hot" as opposed to "white hot") and it was this smooth x-ray illumination that started the fusion reactions within the fuel. These results demonstrated that the amount of energy needed to cause ignition was approximately 100 MJ, about 25 times greater than any machine that was being considered.
The data from Halite/Centurion was used to further tune LASNEX, which then predicted that careful shaping of laser pulse would reduce the energy required by a factor of about 100 times, between 1 and 2 MJ, so a design with a total output of 4 MJ began to be on the safe side. This emerged as the National Ignition Facility concept. In 2022, NIF achieved ignition, triggering a self-sustaining fusion reaction which released 3.15 MJ of energy using 2.05 MJ of laser energy.
For these reasons, LASNEX is somewhat controversial in the ICF field. More accurately, LASNEX generally predicted a device's low-energy behaviour quite closely, but becomes increasingly inaccurate as the energy levels are increased.
Advanced 3D versions of the same basic concept, like ICF3D and HYDRA, continue to drive modern ICF design, and likewise have failed to closely match experimental performance. | 0 | Theoretical and Fundamental Chemistry |
RNA sequencing has taken over microarray and SAGE technology in recent years, as noted in 2016, and has become the most efficient way to study transcription and gene expression. This is typically done by next-generation sequencing.
A subset of sequenced RNAs are small RNAs, a class of non-coding RNA molecules that are key regulators of transcriptional and post-transcriptional gene silencing, or RNA silencing. Next-generation sequencing is the gold standard tool for non-coding RNA discovery, profiling and expression analysis. | 1 | Applied and Interdisciplinary Chemistry |
Thermosetting plastics are generally stronger than thermoplastic materials due to the three-dimensional network of bonds (crosslinking), and are also better suited to high-temperature applications up to the decomposition temperature since they keep their shape as strong covalent bonds between polymer chains cannot be broken easily. The higher the crosslink density and aromatic content of a thermoset polymer, the higher the resistance to heat degradation and chemical attack. Mechanical strength and hardness also improve with crosslink density, although at the expense of brittleness. They normally decompose before melting.
Hard, plastic thermosets may undergo permanent or plastic deformation under load. Elastomers, which are soft and springy or rubbery and can be deformed and revert to their original shape on loading release.
Conventional thermoset plastics or elastomers cannot be melted and re-shaped after they are cured. This usually prevents recycling for the same purpose, except as filler material. New developments involving thermoset epoxy resins which on controlled and contained heating form crosslinked networks permit repeatedly reshaping, like silica glass by reversible covalent bond exchange reactions on reheating above the glass transition temperature. There are also thermoset polyurethanes shown to have transient properties and which can thus be reprocessed or recycled. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 3.862. | 1 | Applied and Interdisciplinary Chemistry |
Single reversible solid oxide cells can be arranged in series to form stacks. Single stacks can be then arranged in modules to reach power capabilities in the order of kilowatts or megawatts.
One of the most challenging aspects in designing large rSOC systems for energy storage purposes is the thermal integration. When the rSOC is operated in electrolysis mode, thermal power is needed for the operation of the system. Thermal power must be provided at two different temperature levels. Heat is needed for water operation, and additional heat at high temperature may be needed if the SOEC modality is endothermic. The latter requirement can be avoided if the rSOC is operated with an exothermic reaction in SOEC modality, with a negative effect on the roundtrip efficiency. On the other hand, when the rSOC is operated in fuel cell mode, the reaction is characterized by a high exothermicity. A number of works in the scientific literature have proposed the exploitation of a Thermal energy storage (TES) to ease the thermal integration of the system.
Excess heat from the SOFC operation can be recovered and stored in a TES, and later used for the SOEC operation. Thermal energy storage typologies and heat transfer fluids that have been considered for this purpose are those used for Concentrated solar power (CSP) technologies. Diathermic oil can be used to store heat at relatively low temperature (for instance, 180°C) and exploited for water evaporation. Alternatively, phase-change materials characterized by high fusion points can be used to store heat at high temperature and enable the endothermic operation in the electrolysis mode. In this case, usually, rSOCs operate at different temperature levels in the two modalities (for example, 850°C in SOFC mode and 800°C in SOEC mode).
If carbonaceous chemistries are employed, the beneficial effect of methane synthesis inside the cell can be exploited to reduce the heat request of the electrolysis mode. In this regard, systems operating at high pressure and lower temperature (20 bar and 650°C) have been proposed to reduce or even eliminate the thermal power requirement of the rSOC system. Alternatively, the production of methane can be favored in external reactors. The methanation reaction is exothermic and favored at low temperature.
The syngas that produced by the co-electrolysis can undergo a further reaction in one or multiple methanation reactors to produce methane and generate low-temperature heat for water evaporation. In addition, the formation of methane in such systems may be beneficial to the size of the tanks used for storing the fuels. In fact, methane is characterized by a higher volumetric energy density than hydrogen in the gaseous form.
When computing the roundtrip efficiencies of rSOC systems, the definition must take into account the net electric consumption (or additional electric production) of other components inside the system. The set of these component is regarded as balance of plant (BOP), and may comprehend pumps, compressors, expanders or fans, needed for fluid circulation and processing inside the system. Therefore, the system roundtrip efficiency can be defined as:
where:
* is the electric power produced in SOFC mode;
* is the electric power consumed in SOEC mode;
* is the net electric power consumption (negative) or production (positive) by the BOP in FC mode;
* is the net electric power consumption (negative) or production (positive) by the BOP in EC mode.
The roundtrip efficiencies achievable with rSOC systems operating with steam and hydrogen can reach values in the order of 60%. On the other hand, systems exploiting the beneficial effects of methane formation, either inside the rSOC or in external reactors, can reach rountrip efficiencies in the order of 70% and beyond. | 0 | Theoretical and Fundamental Chemistry |
In these cycles and engines the working fluid are always like liquid:
*Stirling cycle (Malone engine)
*Heat Regenerative Cyclone | 0 | Theoretical and Fundamental Chemistry |
Chiral molecules can be described as ones with a set of stereoisomers or left and right-handed enantiomers. As defined by Lord Kelvin, a molecule has chirality “if its image in a plane mirror, ideally realized, cannot be brought to coincide with itself.” In other words, a chiral molecule is asymmetrical in the sense that its mirror image will not be an exact copy of itself. Chirality is key to understand in many fields such as drug development as one enantiomer of a drug may cause severe adverse effects while the other provides relief from an ailment. This is significant in terms of Fischer Projections as chirality is an important factor to consider when both drawing and reading them. A great benefit of the model is the ability to interpret chirality with ease based on the orientation of the substituents. Slight changes in the formatting of these models can cause the stereochemistry to be interpreted differently thereby meaning that the molecule has been depicted incorrectly. Fischer Projections provide aid in visualizing chirality as well as where substituents are oriented within space which is why their application can be useful to many. | 0 | Theoretical and Fundamental Chemistry |
TPCK is an irreversible inhibitor of chymotrypsin. Also inhibits some cysteine proteases such as caspase, papain, bromelain or ficin. It does not inhibit trypsin or zymogens.
TPCK is observed covalently bound in the active site of Caspase 3 in the crystal structure of the complex solved in 2010. The chloromethyl group reacts with the active site cysteine to form a covalent bond with the loss of the chlorine.
TPCK is chosen for the chemical labelling of active histidine in enzyme analysis. The phenylalanine moiety is bound to the enzyme because of specificity for aromatic amino acid residues at the active site (as in chymotrypsin, in which it binds to the Histidine-57 residue in the active site). | 1 | Applied and Interdisciplinary Chemistry |
A majority of the adhesion GPCRs are orphan receptors and work is underway to de-orphanize many of these receptors. Adhesion GPCRs get their name from their N-terminal domains that have adhesion-like domains, such as EGF, and the belief that they interact cell to cell and cell to extra cellular matrix. While ligands for many receptors are still not known, researchers are utilizing drug libraries to investigate compounds that can activate GPCRs and using these data for future ligand research.
One adhesion GPCR, GPR56, has a known ligand, collagen III, which is involved in neural migration inhibition. GPR56 has been shown to be the cause of polymicrogyria in humans and may play a role in cancer metastasis. The binding of collagen III to GPR56 occurs on the N-terminus and has been narrowed down to a short stretch of amino acids. The N-terminus of GPR56 is naturally glycosylated, but this glycosylation is not necessary for collagen III binding. Collagen III, results in GPR56 to signal through Gα12/13 activating RhoA. | 1 | Applied and Interdisciplinary Chemistry |
The zooplanktonic Calanus spp. are not only important for moving carbon out of the photic zone and into the deep ocean, but these lipid-rich organisms play a critical role in the success of many marine species that depend on them as food. They comprise the majority of diets for fishes, seabirds and even large mammals such as whales. Copepods can account for about 70–90% of total zooplankton biomass, depending on region. Additionally, their eggs are a main source of food for commercially important fish stocks. The copepod eggs are buoyant and will rise to the sea surface, but are susceptible to predation by fish and other organisms. Copepods also provide the benthic community with food via sinking fecal pellets, meaning that as fish and smaller invertebrates excrete waste, that waste falls to the sea floor and organisms on the sea floor compete for the pellets as food. The role of copepods in the food web is crucially intertwined amongst other organisms.
Copepod abundance, specifically the C. finmarchicus, has a direct impact on the endangered right whales of the North Atlantic. North Atlantic right whales rely on copepods as their primary prey in order to meet their nutritional needs. To meet the right whales energetic requirements they need about 500 kg of C. finmarchicus a day. Each copepod measures about 2–4 millimetres long which is about the size of a grain of rice and they weigh, on average, between 1.0274 and 1.0452 g cm. A loss in C. finmarchicus has the potential to affect the right whales migration, reproduction, and/or ability to successfully nurse their young (only for lactating females). | 0 | Theoretical and Fundamental Chemistry |
Hemoglobin can be tracked noninvasively, to build an individual data set tracking the hemoconcentration and hemodilution effects of daily activities for better understanding of sports performance and training. Athletes are often concerned about endurance and intensity of exercise. The sensor uses light-emitting diodes that emit red and infrared light through the tissue to a light detector, which then sends a signal to a processor to calculate the absorption of light by the hemoglobin protein.
This sensor is similar to a pulse oximeter, which consists of a small sensing device that clips to the finger. | 0 | Theoretical and Fundamental Chemistry |
* Reliance on accurate species identification - When using visual identification in the field, there is the potential for species to be misidentified, which could lead to incorrect analysis and conclusions. To reduce the likelihood of such errors, many monitoring organisations utilise laboratory verification of sample specimens for quality control purposes.
* Species specific - It can be difficult to draw comparisons between results unless the same indicator organism has been used in each study, as every species has an individual niche and associated ideal conditions. Even similar species (as defined by either taxonomy or niche) may have different reactions and different thresholds for change.
* External influences - Changes in population size or health caused by external factors may be incorrectly interpreted as resulting from changes in the environment. For example, a reduction in population that occurs due to disease, but coincides with a change in environmental conditions, could be misconstrued as resulting from the latter change.
* Misleading results - Survival of species usually regarded as sensitive can lead to the conclusion that there has been little change or contamination of an environment, which may be incorrect. An example of this is amphibians, which have traditionally been considered a highly sensitive class in regards to environmental changes, however, some research indicates that this may only be true for phenols, with amphibians having similar sensitivity to other contaminants (e.g. heavy metals) as other aquatic taxonomic groups, such as bivalves. | 1 | Applied and Interdisciplinary Chemistry |
Cycloalkenes with a small ring have about 20° more bond angle strain than a cycloalkane of the same size. This is because the bond angle for an alkene, C-C=C, is 122°, while the bond angle for an alkane, C-C-C, is 112°. When these carbons form a small ring, the alkene which has a larger bond angle will have to compress more than the alkane causing more bond angle strain.
Cycloalkenes have a lower melting point than cycloalkanes of the same size. The lowered melting point is due to the double bond preventing the compound from compact packing.
Cycloalkenes generally reflect physical properties of their cycloalkane. In physical states, only the smaller cycloalkenes are gases while the others are mostly liquid. These molecules are also more reactive than cycloalkanes due to increased electron density shifts of the double bond. | 0 | Theoretical and Fundamental Chemistry |
Along with several other NSAIDs, chronic ibuprofen use has been found correlated with risk of progression to hypertension in women, though less than for paracetamol (acetaminophen), and myocardial infarction (heart attack), particularly among those chronically using higher doses. On 9 July 2015, the US FDA toughened warnings of increased heart attack and stroke risk associated with ibuprofen and related NSAIDs; the NSAID aspirin is not included in this warning. The European Medicines Agency (EMA) issued similar warnings in 2015. | 0 | Theoretical and Fundamental Chemistry |
The optical properties (details of absorption and emission spectra) of many coordination complexes can be explained by Crystal Field Theory. Often, however, the deeper colors of metal complexes arise from more intense charge-transfer excitations. | 0 | Theoretical and Fundamental Chemistry |
In 1954, Herbert Fröhlich proposed a microscopic theory, in which energy gaps at ±k would form below a transition temperature as a result of the interaction between the electrons and phonons of wavevector Q=2k. Conduction at high temperatures is metallic in a quasi-1-D conductor, whose Fermi surface consists of fairly flat sheets perpendicular to the chain direction at ±k. The electrons near the Fermi surface couple strongly with the phonons of nesting wave number Q = 2k. The 2k mode thus becomes softened as a result of the electron-phonon interaction. The 2k phonon mode frequency decreases with decreasing temperature, and finally goes to zero at the Peierls transition temperature. Since phonons are bosons, this mode becomes macroscopically occupied at lower temperatures, and is manifested by a static periodic lattice distortion. At the same time, an electronic CDW forms, and the Peierls gap opens up at ±k. Below the Peierls transition temperature, a complete Peierls gap leads to thermally activated behavior in the conductivity due to normal uncondensed electrons.
However, a CDW whose wavelength is incommensurate with the underlying atomic lattice, i.e., where the CDW wavelength is not an integer multiple of the lattice constant, would have no preferred position, or phase φ, in its charge modulation ρ + ρcos[2kx – φ]. Fröhlich thus proposed that the CDW could move and, moreover, that the Peierls gaps would be displaced in momentum space along with the entire Fermi sea, leading to an electric current proportional to dφ/dt. However, as discussed in subsequent sections, even an incommensurate CDW cannot move freely, but is pinned by impurities. Moreover, interaction with normal carriers leads to dissipative transport, unlike a superconductor. | 0 | Theoretical and Fundamental Chemistry |
Golfomycin A is a synthetic enediyne molecule designed in an attempt to create a more easily manufactured antitumor antibiotic. DNA strand-scission induced by golfomycin A is pH dependent. Preliminary in vitro studies have demonstrated that golfomycin A can reduce carcinomas in bladder cells. | 0 | Theoretical and Fundamental Chemistry |
When treated with sodium borohydride, molybdate is reduced to molybdenum(IV) oxide:
:NaMoO + NaBH + 2HO → NaBO + MoO + 2NaOH + 3H
Sodium molybdate reacts with the acids of dithiophosphates:
:NaMoO + → [MoO(SP(OR))]
which further reacts to form [MoO(SP(OR))]. | 0 | Theoretical and Fundamental Chemistry |
Lithium tert-butoxide is the metalorganic compound with the formula LiOC(CH). A white solid, it is used as a strong base in organic synthesis. The compound is often depicted as a salt, and it often behaves as such, but it is not ionized in solution. Both octameric and hexameric forms have been characterized by X-ray crystallography | 0 | Theoretical and Fundamental Chemistry |
Now, given the considerations of background, peak shape functions, integrated intensity, and non-linear least squares minimization, the parameters used in the Rietveld refinement which put these things together can be introduced. Below are the groups of independent least squares parameters generally refined in a Rietveld refinement.
* Background parameters: usually 1 to 12 parameters.
* Sample displacement: sample transparency, and zero shift corrections. (move peak position)
* Multiple peak shape parameters.
** FWHM parameters: i.e. Caglioti parameters (see section 3.1.2)
** Asymmetry parameters (FCJ parameters)
* Unit cell dimensions
** one to six parameters (a, b, c, α, β, γ), depending on the crystal family/system, for each present phase.
* Preferred orientation, and sometimes absorption, porosity, and extinction coefficients, which can be independent for each phase.
* Scale factors (for each phase)
* Positional parameters of all independent atoms in the crystal model (generally 0 to 3 per atom).
* Population parameters
** Occupation of site positions by atoms.
* Atomic displacement parameters
** Isotropic and anisotropic (temperature) parameters.
Each Rietveld refinement is unique and there is no prescribed sequence of parameters to include in a refinement. It is up to the user to determine and find the best sequence of parameters for refinement. It is worth noting that it is rarely possible to refine all relevant variables simultaneously from the beginning of a refinement, nor near the end since the least squares fitting will be destabilized or lead to a false minimum. It is important for the user to determine a stopping point for a given refinement. Given the complexity of Rietveld refinement it is important to have a clear grasp of the system being studied (sample, and instrumentation) to ensure that results are accurate, realistic, and meaningful. High data quality, a large enough range, and a good model – to serve as the initial approximation in the least squares fitting – are necessary for a successful, reliable, and meaningful Rietveld refinement. | 0 | Theoretical and Fundamental Chemistry |
The strength and range of the electric force and the good conductivity of plasmas usually ensure that the densities of positive and negative charges in any sizeable region are equal ("quasineutrality"). A plasma with a significant excess of charge density, or, in the extreme case, is composed of a single species, is called a non-neutral plasma. In such a plasma, electric fields play a dominant role. Examples are charged particle beams, an electron cloud in a Penning trap and positron plasmas. | 0 | Theoretical and Fundamental Chemistry |
seconds, particles, usually neutrons, are "boiled" off. That is, it remains together until enough energy happens to be concentrated in one neutron to escape the mutual attraction. The excited quasi-bound nucleus is called a compound nucleus.
*Low energy (e, e' xn), (γ, xn) (the xn indicating one or more neutrons), where the gamma or virtual gamma energy is near the giant dipole resonance. These increase the need for radiation shielding around electron accelerators. | 0 | Theoretical and Fundamental Chemistry |
When the process needed is more dehumidification or drying, the Cromer cycle can be enhanced by using the free heat available from the condensing side of the reverse Carnot refrigeration cycle. This heat, sometimes called "hot gas bypass" can be added before the desiccant wheel to enhance the drying of the wheel at location 1 of Figure 1 (but after the filter), called pre-heat. Hot gas bypass heat can also be added to the process at location 4, called reheat, which delivers warmer but even lower RH supply air. Either one or both hot gas bypass locations can be used. When a Cromer cycle air conditioning system is enhanced with hot gas bypass, it is typically referred to as "active" Cromer cycle air-conditioning. When the cycle is used as equipment designed for dehumidification or drying, it is typically called a Cromer cycle dehumidifier or Cromer cycle dryer.
R&D magazine recognized the Cromer cycle in 2006 with an R&D 100 Award in the mechanical/materials category, recognizing the year's 100 most significant technological innovations. | 0 | Theoretical and Fundamental Chemistry |
On 16 December 2014, NASA reported the Curiosity rover detected a "tenfold spike", likely localized, in the amount of methane in the Martian atmosphere. Sample measurements taken "a dozen times over 20 months" showed increases in late 2013 and early 2014, averaging "7 parts of methane per billion in the atmosphere." Before and after that, readings averaged around one-tenth that level.
In addition, high levels of organic chemicals, particularly chlorobenzene, were detected in powder drilled from one of the rocks, named "Cumberland", analyzed by the Curiosity rover. | 0 | Theoretical and Fundamental Chemistry |
Shortly after the publication of Kirkendall's paper, L.S. Darken published an analysis of diffusion in binary systems much like the one studied by Smigelskas and Kirkendall. By separating the actual diffusive flux of the materials from the movement of the interface relative to the markers, Darken found the marker velocity to be
where and are the diffusion coefficients of the two materials and is an atomic fraction.
One consequence of this equation is that the movement of an interface varies linearly with the square root of time, which is exactly the experimental relationship discovered by Smigelskas and Kirkendall.
Darken also developed a second equation that defines a combined chemical diffusion coefficient in terms of the diffusion coefficients of the two interfacing materials:
This chemical diffusion coefficient can be used to mathematically analyze Kirkendall effect diffusion via the Boltzmann-Matano method. | 1 | Applied and Interdisciplinary Chemistry |
Soil organic matter is anything in the soil of biological origin. Carbon is its key component comprising about 58% by weight. Simple assessment of total organic matter is obtained by measuring organic carbon in soil. Living organisms (including roots) contribute about 15% of the total organic matter in soil. These are critical to operation of the soil carbon cycle. What follows refers to the remaining 85% of the soil organic matter - the non-living component.
As shown below, non-living organic matter in soils can be grouped into four distinct categories on the basis of size, behaviour and persistence. These categories are arranged in order of decreasing ability to decompose. Each of them contribute to soil health in different ways.
Dissolved organic matter (DOM): is the organic matter which dissolves in soil water. It comprises the relatively simple organic compounds (e.g. organic acids, sugars and amino acids) which easily decompose. It has a turnover time of less than 12 months. Exudates from plant roots (mucilages and gums) are included here.
Particulate organic matter (POM): is the organic matter that retains evidence of its original cellular structure, and is discussed further in the next section.
Humus: is usually the largest proportion of organic matter in soil, contributing 45 to 75%. Typically it adheres to soil minerals, and plays an important role structuring soil. Humus is the end product of soil organism activity, is chemically complex, and does not have recognisable characteristics of its origin. Humus is of very small unit size and has large surface area in relation to its weight. It holds nutrients, has high water holding capacity and significant cation exchange capacity, buffers pH change and can hold cations. Humus is quite slow to decompose and exists in soil for decades.
Resistant organic matter: has a high carbon content and includes charcoal, charred plant materials, graphite and coal. Turnover times are long and estimated in hundreds of years. It is not biologically active but contributes positively to soil structural properties, including water holding capacity, cation exchange capacity and thermal properties. | 0 | Theoretical and Fundamental Chemistry |
Although the chemical composition of the primitive mantle cannot be directly measured at its source, researchers have been able to estimate primitive mantle characteristics using a few methods. One methodology involves the analysis of chondritic meteorites that represent early Earth chemical composition and creating models using the analyzed chemical characteristics and assumptions describing inner-Earth dynamics. This approach is based on the assumption that early planetary bodies in the solar system formed under similar conditions, giving them comparable chemical compositions. The more direct methodology is to observe trends in the chemical makeup of upper mantle peridotites and interpret the hypothetical composition of the primitive mantle based on these trends. This is done by matching the peridotite compositional trends to the distribution of refractory lithophile elements (which are not affected by core-mantle differentiation) in chondritic meteorites. Both methods have limitations based on the assumptions made about inner-earth, as well as statistical uncertainties in the models used to quantify the data.
The two approaches detailed above yield weight percentages that follow the same general trends when compared to the depleted (or homogeneous) mantle: the primitive mantle has significantly higher concentrations of SiO AlO, NaO, and CaO, and significantly lower concentrations of MgO. More importantly, both approaches show that the primitive mantle has much greater concentrations of refractory lithophile elements (e.g Al, Ba, Be, Ca, Hf, Nb, Sc, Sr, Ta, Th, Ti, U, Y, Zr, and rare earth elements). The exact concentrations of these compounds and refractory lithophile elements depends on the estimation method used. Methods using peridotite analysis yield a much smaller primitive mantle weight percentage for SiO and significantly larger primitive mantle weight percentages for MgO and AlO than those estimated using direct chondritic meteorite analysis. The estimated concentrations of refractory lithophile elements obtained from the two methods vary as well, usually 0.1-5 ppm. | 0 | Theoretical and Fundamental Chemistry |
Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosystem, enzymes capture photons of light to energize electrons that are then transferred through a variety of coenzymes and cofactors to reduce plastoquinone to plastoquinol. The energized electrons are replaced by oxidizing water to form hydrogen ions and molecular oxygen.
By replenishing lost electrons with electrons from the splitting of water, photosystem II provides the electrons for all of photosynthesis to occur. The hydrogen ions (protons) generated by the oxidation of water help to create a proton gradient that is used by ATP synthase to generate ATP. The energized electrons transferred to plastoquinone are ultimately used to reduce to NADPH or are used in non-cyclic electron flow. DCMU is a chemical often used in laboratory settings to inhibit photosynthesis. When present, DCMU inhibits electron flow from photosystem II to plastoquinone. | 0 | Theoretical and Fundamental Chemistry |
1,1,2-Trichloro-1,2,2-trifluoroethane, also called trichlorotrifluoroethane (often abbreviated as TCTFE) or CFC-113, is a chlorofluorocarbon. It has the formula . This colorless, volatile liquid is a versatile solvent. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.