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The echinoderm and flatworm mitochondrial code (translation table 9) is a genetic code used by the mitochondria of certain echinoderm and flatworm species. | 1 | Applied and Interdisciplinary Chemistry |
A primary function of floral scent is to attract pollinators and ensure the reproduction of animal-pollinated plants.
Some families of VOCs presented in floral scents have likely evolved as herbivore repellents. However, these plant defenses are also used by herbivores themselves to locate a plant resource, similar to pollinators attracted by the floral scent. Therefore, flower traits can be subject to antagonistic selection pressures (positive selection by pollinators and negative selection by herbivores). | 1 | Applied and Interdisciplinary Chemistry |
ZMAb is a mixture of three mouse mAbs: m1H3, m2G4, and m4G7. A study published in November 2013 found that EBOV-infected macaque monkeys survived after being given a therapy with a combination of three EBOV surface glycoprotein (EBOV-GP)-specific monoclonal antibodies (ZMAb) within 24 hours of infection. The authors concluded that post-exposure treatment resulted in a robust immune response, with good protection for up to 10 weeks and some protection at 13 weeks. ZMab was created by the NML and licensed to Defyrus, a Toronto-based biodefense company, with further funding by the Public Health Agency of Canada. | 1 | Applied and Interdisciplinary Chemistry |
The earliest hominid remains found around the Caspian Sea are from Dmanisi dating back to around 1.8 Ma and yielded a number of skeletal remains of Homo erectus or Homo ergaster. More later evidence for human occupation of the region came from a number of caves in Georgia and Azerbaijan such as Kudaro and Azykh Caves. There is evidence for Lower Palaeolithic human occupation south of the Caspian from western Alburz. These are Ganj Par and Darband Cave sites.
Neanderthal remains also have been discovered at a cave in Georgia. Discoveries in the Hotu cave and the adjacent Kamarband cave, near the town of Behshahr, Mazandaran south of the Caspian in Iran, suggest human habitation of the area as early as 11,000 years ago. Ancient Greeks focused on the civilization on the south shore – they call it the (H)yr(c/k)anian Sea (, with sources noting the latter word was evolving then to todays Thelessa': late ).
Hafiz-i Abru, a fourteenth century Timurid Empire geographer, has recorded that the destruction of Oxus river dam and irrigation works which diverting the river flow towards Caspian sea, has caused Aral sea to nearly disappeared. | 1 | Applied and Interdisciplinary Chemistry |
Potassium humate is the potassium salt of humic acid. It is manufactured commercially by alkaline extraction of brown coal (lignite) leonardite and is used mainly as a soil conditioner. | 0 | Theoretical and Fundamental Chemistry |
Section D ON Storage and Transport of the IIR is involved in the controlled-temperature logistics and distribution of temperature-sensitive products, from foodstuffs to health products (medicines, vaccines, blood products, organs ...) from artwork to chemicals.
It addresses all issues of equipment and solutions for a durable cold chain from the production or manufacture, to the consumption or use of these products.
Section D thus covers the issues of storage, transportation by land, air or water, packaging, distribution and delivery of these products to the consumer, and the traceability of the cold chain.
The Section is involved in warehouse and platform equipment, devices for temperature-controlled transport, coolants or cool packs, small coolers and refrigerated containers, chillers, refrigerated furnishings, refrigerated cabinets, climate chambers, refrigerators and freezers, but also to thermometers and temperature recorders.
The cold chain involves many temperature ranges, both positive and negative, from -80 °C to + 63 °C.
* Commission D1: Refrigerated Storage
Commission D1 on Refrigerated Storage deals with the storage of all products which require temperature control, such as food and pharmaceuticals. Industrial, commercial and residential storage are also taken into account so that, in cooperation with Commission D2 Refrigerated Transport, the entire cold chain is treated, from raw materials to the final product at our home. Refrigeration plays an essential role for perishable products. While the estimated capacity of refrigerated warehouses was over 500 million cubic meters worldwide in 2014, in some countries global food losses due to the lack of a cold chain are still very important and can reach as much as 20% of the global food supply. At the same time, in heavily industrialised countries, the use of commercial and domestic refrigerators accounts for up to 6% of global electricity consumption.
As a result, the Commission faces important issues in order to promote widespread, energy efficient and environmentally friendly storage systems. New refrigerants, synergies to save or exchange energy with other systems and new technologies are the main focus of its activity. One of the most important themes in these days for this commission is energy efficiency
* Commission D2: Refrigerated Transport
The IIRs Commission D2 on Refrigerated Transport is extremely active. In addition to the IIRs four yearly congress, Commission D2 participates in the IIR Conference on Sustainability and the Cold Chain, held out of synchronisation to the congress.
Every year, Commission D2 CERTE test engineers meet in a European country to discuss refrigerated transport technology and testing issues. This group subsequently advises the United Nations working party on transport of perishable foodstuffs held each year in Geneva. Commission D2 is currently addressing the “Cold Chain for Pharmaceutical Products” and will add this to regular transport discussion and advisory topics. Commission D2 also helps to produce Informatory Notes to assist in areas of technical or regulatory difficulty.
The role of the IIR is well recognized, and in particular, the expertise of the members of Commission D2 makes an important contribution to refrigerated transport issues: reducing food wastage and minimizing emissions. | 0 | Theoretical and Fundamental Chemistry |
A disadvantage with other biofilm processes is that they experience bioclogging and build-up of headloss. Depending on the type of waste and design of the process, several problems can occur during the full-scale process. Some of the disadvantages are:
* Feed pipe/effluent sieve blocking
* Nonhomogeneous mixing
* Carrier voids blocking
* Destroyed carriers
* Carriers accumulating at the effluent sieves
* Carrier overflow | 1 | Applied and Interdisciplinary Chemistry |
Cultures to use cosmetics include the ancient Greeks and the Romans. In the Roman Empire, the use of cosmetics was common amongst prostitutes and rich women. Such adornment was sometimes lamented by certain Roman writers, who thought it to be against the castitas required of women by what they considered traditional Roman values; and later by Christian writers who expressed similar sentiments in a slightly different context. Pliny the Elder mentioned cosmetics in his Naturalis Historia, and Ovid wrote a book on the topic.
Pale faces were a trend during the European Middle Ages. In the 16th century, women would bleed themselves to achieve pale skin. Spanish prostitutes wore pink makeup to contrast pale skin. 13th century Italian women wore red lipstick to show that they were upper class. Use of cosmetics continued in Middle Ages, where the face was whitened and the cheeks rouged. Cosmetics continued to be used in the following centuries, though attitudes towards cosmetics varied throughout time, with the use of cosmetics being openly frowned upon at many points in Western history. In the 19th century, Queen Victoria publicly declared makeup improper, vulgar, and acceptable only for use by actors, with many famous actresses of the time, such as Sarah Bernhardt and Lillie Langtry using makeup.
19th-century fashion ideals of women appearing delicate, feminine and pale were achieved by some through the use of makeup, with some women discreetly using rouge on their cheeks and drops of belladonna to dilate their eyes to appear larger. Though cosmetics were used discreetly by many women, makeup in Western cultures during this time was generally frowned upon, particularly during the 1870s, when Western social etiquette increased in rigidity. Teachers and clergy were specifically forbidden from the use of cosmetic products. | 1 | Applied and Interdisciplinary Chemistry |
The industrial route to acetyl chloride involves the reaction of acetic anhydride with hydrogen chloride:
Propionyl chloride is produced by chlorination of propionic acid with phosgene:
Benzoyl chloride is produced by the partial hydrolysis of benzotrichloride:
Similarly, benzotrichlorides react with carboxylic acids to the acid chloride. This conversion is practiced for the reaction of 1,4-bis(trichloromethyl)benzene to give terephthaloyl chloride: | 0 | Theoretical and Fundamental Chemistry |
In polymer chemistry, materials science, and food science, bloom refers to the migration of one component of a solid mixture to the surface of an article. The process is an example of phase separation or phase aggregation. | 0 | Theoretical and Fundamental Chemistry |
Carbon dioxide in the Earth's atmosphere is essential to life and to most of the planetary biosphere. The average rate of energy capture by photosynthesis globally is approximately 130 terawatts, which is about six times larger than the current power consumption of human civilization. Photosynthetic organisms also convert around 100–115 billion metric tonnes of carbon into biomass per year.
Photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from and water using energy from light. However, not all organisms that use light as a source of energy carry out photosynthesis, since photoheterotrophs use organic compounds, rather than , as a source of carbon. In plants, algae and cyanobacteria, photosynthesis releases oxygen. This is called oxygenic photosynthesis. Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. Some types of bacteria, however, carry out anoxygenic photosynthesis, which consumes but does not release oxygen.
Carbon dioxide is converted into sugars in a process called carbon fixation. Carbon fixation is an endothermic redox reaction, so photosynthesis needs to supply both the source of energy to drive this process and the electrons needed to convert into a carbohydrate. This addition of the electrons is a reduction reaction. In general outline and in effect, photosynthesis is the opposite of cellular respiration, in which glucose and other compounds are oxidized to produce and water, and to release exothermic chemical energy to drive the organism's metabolism. The two processes take place through a different sequence of chemical reactions, however, and in different cellular compartments. | 1 | Applied and Interdisciplinary Chemistry |
An open impeller has a hub with attached vanes and is mounted on a shaft. The vanes do not have a wall, making open impellers slightly weaker than closed or semi-closed impellers. However, as the side plate is not fixed to the inlet side of the vane, the blade stresses are significantly lower. In pumps, the fluid enters the impeller's eye, where vanes add energy and direct it to the nozzle discharge. A close clearance between vanes and pump volute or back plate prevent most of fluid from flowing back. Wear on the bowl and edge of vane can be compensated by adjusting the clearance to maintain efficiency over time. Because the internal parts are visible, open impellers are easier to inspect for damage and maintain than closed impellers. They can also be more easily modified to change flow properties. Open impellers operate on a narrow range of specific speed. Open impellers are usually faster and easier to maintain. For small pumps and those dealing with suspended solids, open impellers are generally used. Sand locking does not occur as easily as with closed type. | 1 | Applied and Interdisciplinary Chemistry |
There is little evidence of the evolution of stomata in the fossil record, but they had appeared in land plants by the middle of the Silurian period. They may have evolved by the modification of conceptacles from plants' alga-like ancestors.
However, the evolution of stomata must have happened at the same time as the waxy cuticle was evolving – these two traits together constituted a major advantage for early terrestrial plants. | 0 | Theoretical and Fundamental Chemistry |
To achieve a near tenfold increase in fusion power density, the design makes use of REBCO superconducting tape for its toroidal field coils. This material enables higher magnetic field strength to contain heated plasma in a smaller volume. In theory, fusion power density is proportional to the fourth power of the magnetic field strength. The most probable candidate material is yttrium barium copper oxide, with a design temperature of , allowing various coolants (e.g. liquid hydrogen, liquid neon, or helium gas) instead of the much more complicated liquid helium refrigeration chosen by ITER. The official SPARC brochure displays a YBCO cable section that is commercially available and that should allow fields up to 30 T.
ARC is planned to be a 270 MWe tokamak reactor with a major radius of , a minor radius of , and an on-axis magnetic field of .
The design point has a fusion energy gain factor Q ≈ 13.6 (the plasma produces 13 times more fusion energy than is required to heat it), yet is fully non-inductive, with a bootstrap fraction of ~63%.
The design is enabled by the ~23 T peak field on coil. External current drive is provided by two inboard RF launchers using of lower hybrid and of ion cyclotron fast wave power. The resulting current drive provides a steady-state core plasma far from disruptive limits. | 0 | Theoretical and Fundamental Chemistry |
In polymer chemistry, chain termination is any chemical reaction that ceases the formation of reactive intermediates in a chain propagation step in the course of a polymerization, effectively bringing it to a halt. | 0 | Theoretical and Fundamental Chemistry |
Both the Arrhenius activation energy and the rate constant k are experimentally determined, and represent macroscopic reaction-specific parameters that are not simply related to threshold energies and the success of individual collisions at the molecular level. Consider a particular collision (an elementary reaction) between molecules A and B. The collision angle, the relative translational energy, the internal (particularly vibrational) energy will all determine the chance that the collision will produce a product molecule AB. Macroscopic measurements of E and k are the result of many individual collisions with differing collision parameters. To probe reaction rates at molecular level, experiments are conducted under near-collisional conditions and this subject is often called molecular reaction dynamics.
Another situation where the explanation of the Arrhenius equation parameters falls short is in heterogeneous catalysis, especially for reactions that show Langmuir-Hinshelwood kinetics. Clearly, molecules on surfaces do not "collide" directly, and a simple molecular cross-section does not apply here. Instead, the pre-exponential factor reflects the travel across the surface towards the active site.
There are deviations from the Arrhenius law during the glass transition in all classes of glass-forming matter. The Arrhenius law predicts that the motion of the structural units (atoms, molecules, ions, etc.) should slow down at a slower rate through the glass transition than is experimentally observed. In other words, the structural units slow down at a faster rate than is predicted by the Arrhenius law. This observation is made reasonable assuming that the units must overcome an energy barrier by means of a thermal activation energy. The thermal energy must be high enough to allow for translational motion of the units which leads to viscous flow of the material. | 0 | Theoretical and Fundamental Chemistry |
It is possible to extend the idea of linear-extrapolation to higher order reconstruction, and an example is shown in the diagram opposite. However, for this case the left and right states are estimated by interpolation of a second-order, upwind biased, difference equation. This results in a parabolic reconstruction scheme that is third-order accurate in space.
We follow the approach of Kermani (Kermani, et al., 2003), and present a third-order upwind biased scheme, where the symbols and again represent scheme dependent functions (of the limited reconstructed cell edge variables). But for this case they are based upon parabolically reconstructed states, i.e.,
and
Where = 1/3 and,
and the limiter function , is the same as above.
Parabolic reconstruction is straight forward to implement and can be used with the Kurganov and Tadmor scheme in lieu of the linear extrapolation shown above. This has the effect of raising the spatial solution of the KT scheme to 3rd order. It performs well when solving the Euler equations, see below. This increase in spatial order has certain advantages over 2nd order schemes for smooth solutions, however, for shocks it is more dissipative - compare diagram opposite with above solution obtained using the KT algorithm with linear extrapolation and Superbee limiter. This simulation was carried out on a mesh of 200 cells using the same KT algorithm but with parabolic reconstruction. Time integration was by RK-4, and the alternative form of van Albada limiter, , was used to avoid spurious oscillations. | 1 | Applied and Interdisciplinary Chemistry |
The 3-hydroxypropionate bicycle, also known as the 3-hydroxypropionate pathway, is a process that allows some bacteria to generate 3-hydroxypropionate using carbon dioxide. It is divided into two parts or reactions. The overall reaction of the 3-hydroxypropionate pathway is 3 HCO3− + 5 ATP + 6 NADPH + 1 quinone → 1 pyruvate + 6 NADP + 1 quinoneH2 + 3 ADP + 3 phosphate + 2 AMP + 2 pyrophosphate. | 1 | Applied and Interdisciplinary Chemistry |
Glycoside hydrolases (or glycosidases), are enzymes that break glycosidic bonds. Glycoside hydrolases typically can act either on α- or on β-glycosidic bonds, but not on both. This specificity allows researchers to obtain glycosides in high epimeric excess, one example being Wen-Ya Lus conversion of D-Glucose to Ethyl β-D-glucopyranoside using naturally-derived glucosidase. It is worth noting that Wen-Ya Lu utilized glucosidase in a reverse manner opposite to the enzymes biological functionality: | 0 | Theoretical and Fundamental Chemistry |
The canonical umpolung reagent is the cyanide ion. The cyanide ion is unusual in that a carbon triply bonded to a nitrogen would be expected to have a (+) polarity due to the higher electronegativity of the nitrogen atom. Yet, the negative charge of the cyanide ion is localized on the carbon, giving it a (-) formal charge. This chemical ambivalence results in umpolung in many reactions where cyanide is involved.
For example, cyanide is a key catalyst in the benzoin condensation, a classical example of polarity inversion.
The net result of the benzoin reaction is that a bond has been formed between two carbons that are normally electrophiles. | 0 | Theoretical and Fundamental Chemistry |
Acid or hydrogen phosphites are called hydrogenphosphonates or acid phosphites. IUPAC recommends the name hydrogenphosphonates). They are anions HP(O)OH. Aypical derivative is the salt [NH][HP(O)OH]. Many related salts are known, e.g., RbHPHO, CsHPHO, TlHPHO. These salts are prepared by treating phosphorous acid with the metal carbonate. These compounds contain a layer polymeric anion consisting of HPO tetrahedra linked by hydrogen bonds. These layers are interleaved by layers of metal cations.
Organic esters of hydrogen phosphites are anions with the formula HP(O)OR (R = organic group). One commercial example is the fungicide fosetyl-Al with the formula [CHOP(H)O]Al. | 0 | Theoretical and Fundamental Chemistry |
Investigation of carbon-neutral fuels has been ongoing for decades. A 1965 report suggested synthesizing methanol from carbon dioxide in air using nuclear power for a mobile fuel depot. Shipboard production of synthetic fuel using nuclear power was studied in 1977 and 1995. A 1984 report studied the recovery of carbon dioxide from fossil fuel plants. A 1995 report compared converting vehicle fleets for the use of carbon-neutral methanol with the further synthesis of gasoline. | 0 | Theoretical and Fundamental Chemistry |
This is a timeline of the history of gunpowder and related topics such as weapons, warfare, and industrial applications. The timeline covers the history of gunpowder from the first hints of its origin as a Taoist alchemical product in China until its replacement by smokeless powder in the late 19th century (from 1884 to the present day). | 1 | Applied and Interdisciplinary Chemistry |
Numerous fields would be able to benefit from the protection of tissue damage by freezing. Businesses are currently investigating the use of these proteins in:
* Increasing freeze tolerance of crop plants and extending the harvest season in cooler climates
* Improving farm fish production in cooler climates
* Lengthening shelf life of frozen foods
* Improving cryosurgery
* Enhancing preservation of tissues for transplant or transfusion in medicine
* Therapy for hypothermia
* Human Cryopreservation (Cryonics)
Unilever has obtained UK, US, EU, Mexico, China, Philippines, Australia and New Zealand approval to use a genetically modified yeast to produce antifreeze proteins from fish for use in ice cream production. They are labeled "ISP" or ice structuring protein on the label, instead of AFP or antifreeze protein. | 1 | Applied and Interdisciplinary Chemistry |
Ammonia is a weak alkali that reacts reversibly with water and alters the pH of the solution into base condition.
:NH + HO NH + OH
On the other hand, if sodium hydroxide is added to adjust the pH of the solution to alkali, the color change occurs faster than when the ammonia is added, as sodium hydroxide is a highly reactive compound.
:NaOH Na + OH
When dry ice is added to water, it sublimes to carbon dioxide gas rapidly because the solution's temperature is warmer than the dry ice (-78.5 °C or -109.3°F). The carbon dioxide gas can be observed as bubbles or clouds above the solution. Because the temperature of the gas is so cold, the water vapor contained in the air above the water condenses into small water droplets, or clouds, suspended in the carbon dioxide gas.
:CO CO
However, some of the dry ice molecules remain in the solution and react reversibly with water molecules to form an acidic solution via the production of hydrogen ions.
:CO + HO HCO + H</sub>
When the acidic solution is mixed together with the alkali present in the solution, the solution, overall, becomes neutral.
:HCO + H + NH + OH NH + HCO + HO (addition of ammonia)
:HCO + H + Na + OH Na + HCO + HO (addition of sodium hydroxide)
The overall chemical equation for neutralization of an aqueous solution of NaOH and carbonic acid is given by:
:2 NaOH + CO NaCO + HO
The color of the solution arises due to the pH indicator. The color of the ammonia-and-water solution at the beginning of the experiment indicates that the solution is alkaline. However, once the dry ice is added, the solution becomes less alkaline as neutralization occurs which causes the color to slowly change as more hydrogen ions are continuously produced from the carbonic acid. | 1 | Applied and Interdisciplinary Chemistry |
Derek Lowe is a medicinal chemist working on preclinical drug discovery in the pharmaceutical industry. Lowe has published a blog about this field, "In the Pipeline", since 2002 and is a columnist for the Royal Society of Chemistrys Chemistry World'. | 1 | Applied and Interdisciplinary Chemistry |
It has been postulated that carbon from a cascade of asteroids (known as the Late Heavy Bombardment), resulting from interaction of Jupiter and Saturn, blasted the surface of young Earth and reacted with nitrogen in Earth's atmosphere to form HCN. | 0 | Theoretical and Fundamental Chemistry |
As ozone in the atmosphere prevents most energetic ultraviolet radiation reaching the surface of the Earth, astronomical data in these wavelengths have to be gathered from satellites orbiting above the atmosphere and ozone layer. Most of the light from young hot stars is in the ultraviolet and so study of these wavelengths is important for studying the origins of galaxies. The Galaxy Evolution Explorer, GALEX, is an orbiting ultraviolet space telescope launched on April 28, 2003, which operated until early 2012. | 0 | Theoretical and Fundamental Chemistry |
One major complications to the use of herbicides for weed control is the ability of plants to evolve herbicide resistance, rendering the herbicides ineffective against target plants. Out of 31 known herbicide modes of action, weeds have evolved resistance to 21. 268 plant species are known to have evolved herbicide resistance at least once. Herbicide resistance was first observed in 1957, and since has evolved repeatedly in weed species from 30 families across the globe. Weed resistance to herbicides has become a major concern in crop production worldwide.
Resistance to herbicides is often attributed to overuse as well as the strong evolutionary pressure on the affected weeds. Three agricultural practices account for the evolutionary pressure upon weeds to evolve resistance: monoculture, neglecting non-herbicide weed control practices, and reliance on one herbicide for weed control. To minimize resistance, rotational programs of herbicide application, where herbicides with multiple modes of action are used, have been widely promoted. In particular, glyphosate resistance evolved rapidly in part because when glyphosate use first began, it was continuously and heavily relied upon for weed control. This caused incredibly strong selective pressure upon weeds, encouraging mutations conferring glyphosate resistance to persist and spread.
However, in 2015, an expansive study showed an increase in herbicide resistance as a result of rotation, and instead recommended mixing multiple herbicides for simultaneous application. As of 2023, the effectiveness of combining herbicides is also questioned, particularly in light of the rise of non-target site resistance.
Plants developed resistance to atrazine and to ALS-inhibitors relatively early, but more recently, glyphosate resistance has dramatically risen. Marestail is one weed that has developed glyphosate resistance. Glyphosate-resistant weeds are present in the vast majority of soybean, cotton and corn farms in some U.S. states. Weeds that can resist multiple other herbicides are spreading. Few new herbicides are near commercialization, and none with a molecular mode of action for which there is no resistance. Because most herbicides could not kill all weeds, farmers rotate crops and herbicides to stop the development of resistant weeds.
A 2008–2009 survey of 144 populations of waterhemp in 41 Missouri counties revealed glyphosate resistance in 69%. Weeds from some 500 sites throughout Iowa in 2011 and 2012 revealed glyphosate resistance in approximately 64% of waterhemp samples. As of 2023, 58 weed species have developed glyphosate resistance. Weeds resistant to multiple herbicides with completely different biological action modes are on the rise. In Missouri, 43% of waterhemp samples were resistant to two different herbicides; 6% resisted three; and 0.5% resisted four. In Iowa 89% of waterhemp samples resist two or more herbicides, 25% resist three, and 10% resist five.
As of 2023, Palmer amaranth with resistance to six different herbicide modes of action has emerged. Annual bluegrass collected from a golf course in the U.S. state of Tennessee was found in 2020 to be resistant to seven herbicides at once. Rigid ryegrass and annual bluegrass share the distinction of the species with confirmed resistance to the largest number of herbicide modes of action, both with confirmed resistance to 12 different modes of action; however, this number references how many forms of herbicide resistance are known to have emerged in the species at some point, not how many have been found simultaneously in a single plant.
In 2015, Monsanto released crop seed varieties resistant to both dicamba and glyphosate, allowing for use of a greater variety of herbicides on fields without harming the crops. By 2020, five years after the release of dicamba-resistant seed, the first example of dicamba-resistant Palmer amaranth was found in one location. | 1 | Applied and Interdisciplinary Chemistry |
Ferrocene-containing dendrimers can be synthesized by both convergent and divergent methods. Some of the first dendrimers of this type, were made by attaching ferrocene units to small silicon containing dendrimers.
Dendrimers with peripheral ferrocene groups are usually synthesized by attaching ferrocene to the core by either olefin metathesis or by hydrosilylation. As an example, tetraallylsilane undergoes Pt-catalyzed hydrosilylation to form the core. This core was then reacted with ferrocenyllithium to form 1. Convergent approaches can also be used to make dendrimers with peripheral ferrocene. As an example, figure 1 shows a 54-ferrocene dendrimer which was synthesized by a fast convergent approach.
Dendrimers with ferrocene cores have been synthesized by decorating suitably functionalized ferrocenes, e.g., decaallylferrocene.
synthesis
Ferrocene-containing dendrimers can be synthesized by convergence and diffusion methods. By linking ferrocene units to small silicon-containing dendrimers, some of these first-type dendrimers can be made. [3]
Dendritic macromolecules with peripheral ferrocene groups are usually synthesized by linking ferrocene to the core through olefin metathesis or hydrosilylation [1]. For example, tetraallyl silane undergoes Pt-catalyzed hydrosilylation to form a core. The core is then reacted with ferrocenyl lithium to form 1. [4]. The convergence method can also be used to make dendrimers with peripheral ferrocene.
en.china.cn is a good place to supply polymer resin | 0 | Theoretical and Fundamental Chemistry |
The ETS (Erythroblast Transformation Specific)family is divided into 12 subfamilies, which are listed below: | 1 | Applied and Interdisciplinary Chemistry |
CellCognition has been used in RNAi-based screening, applied in basic cell cycle study, and extended to unsupervised modeling. | 1 | Applied and Interdisciplinary Chemistry |
A loading control is a protein used as a control in a Western blotting experiment. Typically, loading controls are proteins with high and ubiquitous expression, such as beta-actin or GADPH. They are used to make sure that the protein has been loaded equally across all wells. | 1 | Applied and Interdisciplinary Chemistry |
According to some twentieth-century philosophers, unit-point atomism was the philosophy of the Pythagoreans, a conscious repudiation of Parmenides and the Eleatics. It stated that atoms were infinitesimally small ("point") yet possessed corporeality. It was a predecessor of Democritean atomism. Most recent students of presocratic philosophy, such as Kurt von Fritz, Walter Burkert, Gregory Vlastos, Jonathan Barnes, and Daniel W. Graham have rejected that any form of atomism can be applied to the early Pythagoreans (before Ecphantus of Syracuse).
Unit-point atomism was invoked in order to make sense of a statement ascribed to Zeno of Elea in Platos Parmenides: "these writings of mine were meant to protect the arguments of Parmenides against those who make fun of him. . . My answer is addressed to the partisans of the many. . ." The anti-Parmenidean pluralists were supposedly unit-point atomists whose philosophy was essentially a reaction against the Eleatics. This hypothesis, however, to explain Zenos paradoxes, has been thoroughly discredited. | 1 | Applied and Interdisciplinary Chemistry |
Polymeric micelles are drug carriers formed by the aggregation of some amphiphile\amphiphilic molecule with an amphiphilic block copolymer. These carriers form at some high concentration specific to the compounds used, called the critical micelle concentration. The addition of an amphiphilic block copolymer effectively lowers this critical micelle concentration by shifting the monomer exchange equilibrium. These carriers are comparable to liposomes, however the lack of an aqueous core makes polymeric micelles less accommodating to a wide variety of drugs. | 1 | Applied and Interdisciplinary Chemistry |
• DIN EN ISO 6988 Metallic and other inorganic coatings - Test with sulfur dioxide with general moisture condensation, March 1997.
• DIN 50018 testing in an alternating condensation climate with an atmosphere containing sulfur dioxide, June 1997.
• The importance of corrosion test procedures with special consideration of the SO test according to DIN 50018, Wilhelm Kesternich, published in Materials and Corrosion Volume 16, Issue 3, pages 193-201, March 1965. | 1 | Applied and Interdisciplinary Chemistry |
*Selection of transverse magnetization (I, S, I etc.):
(+)gradient 180°(x) (+)gradient
*Suppression of transverse magnetization (I, S, I etc.):
(+)gradient 180°(x) (-)gradient | 0 | Theoretical and Fundamental Chemistry |
A unilamellar liposome is a spherical liposome, a vesicle, bounded by a single bilayer of an amphiphilic lipid or a mixture of such lipids, containing aqueous solution inside the chamber. Unilamellar liposomes are used to study biological systems and to mimic cell membranes, and are classified into three groups based on their size: small unilamellar liposomes/vesicles (SUVs) that with a size range of 20–100 nm, large unilamellar liposomes/vesicles (LUVs) with a size range of 100–1000 nm and giant unilamellar liposomes/vesicles (GUVs) with a size range of 1–200 µm. GUVs are mostly used as models for biological membranes in research work. Animal cells are 10–30 µm and plant cells are typically 10–100 µm. Even smaller cell organelles such as mitochondria are typically 1–2 µm. Therefore, a proper model should account for the size of the specimen being studied. In addition, the size of vesicles dictates their membrane curvature which is an important factor in studying fusion proteins. SUVs have a higher membrane curvature and vesicles with high membrane curvature can promote membrane fusion faster than vesicles with lower membrane curvature such as GUVs.
The composition and characteristics of the cell membrane varies in different cells (plant cells, mammalian cells, bacterial cells, etc). In a membrane bilayer, often the composition of the phospholipids is different between the inner and outer leaflets. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and sphingomyelin are some of the most common lipids most animal cell membranes. These lipids are widely different in charge, length, and saturation state. The presence of unsaturated bonds (double bonds) in lipids for example, creates a kink in acyl chains which further changes the lipid packing and results in a looser packing. Therefore, the composition and sizes of the unilamellar liposomes must be chosen carefully based on the subject of the study.
Each lipid bilayer structure is comparable to lamellar phase lipid organization in biological membranes, in general. In contrast, multilamellar liposomes (MLVs), consist of many concentric amphiphilic lipid bilayers analogous to onion layers, and MLVs may be of variable sizes up to several micrometers. | 0 | Theoretical and Fundamental Chemistry |
Diboryne or a compound with boron-boron triple bond was first isolated as a N-heterocyclic carbene supported complex (NHC-BB-NHC) in the Braunschweig group, and its unique, peculiar bonding structure thereupon catalyzed new research to computationally assess the nature of this at that time controversial triple bond.
A few years later, Köppe and Schnöckel published an article arguing that the B-B bond should be defined as a 1.5 bond based on thermodynamic view and rigid force constant calculations. That same year, Grunenberg reassessed the B-B bond using generalized compliance constants of which he claimed better suited as a bond strength descriptor.
The calculated relaxed force constants show a clear trend as the bond order between the B-B bond increases, which advocates the existence of the triple bond in Braunschweig's compound. | 0 | Theoretical and Fundamental Chemistry |
Biocurious planned to tweak the biobrick containing six genes, including luciferin-regenerating enzyme and luciferase from fireflies. During initial development, they would use Agrobacterium to test the transfer of the genetic circuit. When producing the final product, they intended to instead use a gene gun to avoid issues related to regulation of GM plants. Over the course of the project, several plants were mentioned as being recipients, including Arabidopsis thaliana, Nicotiana tabacum, and roses. Issues surrounding the production included the difficulty of moving the six component genes of the metabolic pathway, increasing the dim light produced by the plant following insertion, and preventing the pathway from being silenced. | 1 | Applied and Interdisciplinary Chemistry |
In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently large fraction of the population (e.g. 1% or more), many publications do not apply such a frequency threshold.
For example, a G nucleotide present at a specific location in a reference genome may be replaced by an A in a minority of individuals. The two possible nucleotide variations of this SNP – G or A – are called alleles.
SNPs can help explain differences in susceptibility to a wide range of diseases across a population. For example, a common SNP in the CFH gene is associated with increased risk of age-related macular degeneration. Differences in the severity of an illness or response to treatments may also be manifestations of genetic variations caused by SNPs. For example, two common SNPs in the APOE gene, rs429358 and rs7412, lead to three major APO-E alleles with different associated risks for development of Alzheimer's disease and age at onset of the disease.
Single nucleotide substitutions with an allele frequency of less than 1% are sometimes called single-nucleotide variants (SNVs). "Variant" may also be used as a general term for any single nucleotide change in a DNA sequence, encompassing both common SNPs and rare mutations, whether germline or somatic. The term SNV has therefore been used to refer to point mutations found in cancer cells. DNA variants must also commonly be taken into consideration in molecular diagnostics applications such as designing PCR primers to detect viruses, in which the viral RNA or DNA sample may contain SNVs. However, this nomenclature uses arbitrary distinctions (such as an allele frequency of 1%) and is not used consistently across all fields; the resulting disagreement has prompted calls for a more consistent framework for naming differences in DNA sequences between two samples. | 1 | Applied and Interdisciplinary Chemistry |
Bertram Boltwood was born on July 27, 1870, in the Amherst, Massachusetts home of his grandfather, Lucius Boltwood. After relocating from England in the 17th century, the Boltwood family was active in the Amherst community for generations. Lucius was the son of a farmer who worked his way through Williams College to become a lawyer. He was a founder of Amherst College and ran for Governor of Massachusetts as an early member of the Liberty Party in 1841. Thomas Kast Boltwood, son of Lucius, was a lawyer who died in 1872 when his son Bertram was 2 years old. Bertram Boltwood was emotionally close with his mother, Margaret Mathilda, and he grew up in her hometown of Castleton, NY. She prepared him to attend Yale, his father's alma mater, by placing him in private school at a young age, followed by the Albany Academy.
Boltwood’s childhood reveals influences and inclinations that foreshadow the scientist he became as an adult. As a boy, he was interested in mechanical gadgets and enjoyed hobbies such as fishing, photography, and minerals. The latter was likely the influence of his uncle, Charles Upham Shepard, who was a mineralogist and a chemist. His personality was reportedly light-hearted, and he was known to play practical jokes in his youth. He was often reminded of a familial tie to Ralph Waldo Emerson through his paternal great grandmother’s sister (Emerson’s mother Ruth Haskins), and it was expected that Boltwood would study and succeed in line with the family legacy. | 0 | Theoretical and Fundamental Chemistry |
The dopped stone is ground at precise angles and indexes on cutting laps of progressively finer grit, and then the process is repeated a final time to polish each facet. Accurate repetition of angles in the cutting and polishing process is aided by the angle readout and index gear. The physical process of polishing is a subject of debate. One commonly accepted theory is that the fine abrasive particles of a polishing compound produce abrasions smaller than the wavelengths of light, thus making the minute scratches invisible. Since gemstones have two sides (the crown and pavilion), a device often called a "transfer jig" is used to flip the stone so that each side may be cut and polished. | 0 | Theoretical and Fundamental Chemistry |
Over time, many parts of the chloroplast genome were transferred to the nuclear genome of the host, a process called endosymbiotic gene transfer.
As a result, the chloroplast genome is heavily reduced compared to that of free-living cyanobacteria. Chloroplasts may contain 60–100 genes whereas cyanobacteria often have more than 1500 genes in their genome. Contrarily, there are only a few known instances where genes have been transferred to the chloroplast from various donors, including bacteria.
Endosymbiotic gene transfer is how we know about the lost chloroplasts in many chromalveolate lineages. Even if a chloroplast is eventually lost, the genes it donated to the former hosts nucleus persist, providing evidence for the lost chloroplasts existence. For example, while diatoms (a heterokontophyte) now have a red algal derived chloroplast, the presence of many green algal genes in the diatom nucleus provide evidence that the diatom ancestor (probably the ancestor of all chromalveolates too) had a green algal derived chloroplast at some point, which was subsequently replaced by the red chloroplast.
In land plants, some 11–14% of the DNA in their nuclei can be traced back to the chloroplast, up to 18% in Arabidopsis, corresponding to about 4,500 protein-coding genes. There have been a few recent transfers of genes from the chloroplast DNA to the nuclear genome in land plants. | 0 | Theoretical and Fundamental Chemistry |
The newly formed primordial germ cells (PGC) in the implanted embryo devolve from the somatic cells at about day 7 of embryogenesis in the mouse. At this point the PGCs have high levels of methylation. These cells migrate from the epiblast toward the gonadal ridge. As reviewed by Messerschmidt et al., the majority of PGCs are arrested in the G phase of the cell cycle while they migrate toward the hindgut during embryo days 7.5 to 8.5. Then demethylation of the PGCs takes place in two waves. There is both passive and active, TET-dependent demethylation of the primordial germ cells. At day 9.5 the primordial germ cells begin to rapidly replicate going from about 200 PGCs at embryo day 9.5 to about 10,000 PGCs at day 12.5. During days 9.5 to 12.5 DNMT3a and DNMT3b are repressed and DNMT1 is present in the nucleus at a high level. But DNMT1 is unable to methylate cytosines during days 9.5 to 12.5 because the UHRF1 gene (also known as NP95) is repressed and UHRF1 is an essential protein needed to recruit DNMT1 to replication foci where maintenance DNA methylation takes place. This is a passive, dilution form of demethylation.
In addition, from embryo day 9.5 to 13.5 there is an active form of demethylation. As indicated in the Figure of the demethylation pathway above, two enzymes are central to active demethylation. These are a ten-eleven translocation (TET) methylcytosine dioxygenase and thymine-DNA glycosylase (TDG). One particular TET enzyme, TET1, and TDG are present at high levels from embryo day 9.5 to 13.5, and are employed in active TET-dependent demethylation during gametogenesis. PGC genomes display the lowest levels of DNA methylation of any cells in the entire life cycle of the mouse by embryonic day 13.5. | 1 | Applied and Interdisciplinary Chemistry |
The colored fraction of DOC (CDOM) absorbs light in the blue and UV-light range and therefore influences plankton productivity both negatively by absorbing light, that otherwise would be available for photosynthesis, and positively by protecting plankton organisms from harmful UV-light. However, as the impact of UV damage and ability to repair is extremely variable, there is no consensus on how UV-light changes might impact overall plankton communities. The CDOM absorption of light initiates a complex range of photochemical processes, which can impact nutrient, trace metal and DOC chemical composition, and promote DOC degradation. | 1 | Applied and Interdisciplinary Chemistry |
*one ATP by direct phosphorylation of GDP
*two ATP from oxidation of FADH
*three ATP at a time for the NADH + H produced within the α-ketoglutarate dehydrogenase reaction, the malate dehydrogenase reaction and the malate decarboxylase reaction.
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Due to low glutamate dehydrogenase and glutamate pyruvate transaminase activities, in tumor cells the conversion of glutamate to alpha-ketoglutarate mainly takes place via glutamate oxaloacetate transaminase. | 1 | Applied and Interdisciplinary Chemistry |
A post column oxidation-reduction reactor is a chemical reactor that performs derivatization to improve the measurement of organic molecules. It is used in gas chromatography (GC), after the column, and before a flame ionization detector (FID), to make the detector response uniform for all organic molecules.
The reactor converts the carbon atoms of organic molecules in GC column effluents into methane before reaching the FID. The resulting detector response is uniform on a per-carbon basis and avoids the need for response factors and calibration standards for each molecule. It can improve the response of the FID to many molecules with poor/low response including carbon monoxide (CO), carbon dioxide (CO), hydrogen cyanide (HCN), formamide (CHNO), formaldehyde (CHO) and formic acid (CHO), because these molecules are converted to methane. | 0 | Theoretical and Fundamental Chemistry |
The RFU peak height depends on the amount of DNA being analyzed. When the amount of DNA is very low, then
it can be difficult to separate a true low-level RFU peak from signal noise or other technical artifacts. As a result, many forensic DNA laboratories have set minimum RFU peak-height levels in "scoring" the analysis of alleles.
There are no firm industry-wide rules for establishing minimum RFU threshold values. Each laboratory, in general, has established its own threshold levels as one aspect of its particular validation procedure. Many laboratories have established both lower and upper thresholds for data interpretation, as a window of minimum and maximum readings.
Some threshold levels can be derived experimentally based on the equipment's known signal-to-noise ratios, or a threshold can be defined to match published data or the manufacturer specifications. The company which sells the most widely used equipment for STR typing, Applied Biosystems, Inc. (ABI), has recommended a peak-height minimum of 150 RFU, advising how peaks below that level should be judged with caution. However, many forensic laboratories which have ABI systems have defined lower thresholds, often only 50 to 100 RFU, as determined by their own studies.
Many different factors can affect a laboratory's choice of thresholds. For instance, there might be regulatory guidelines in specific jurisdictions. Also, different kinds of instruments vary in sensitivity (such as slab gel instruments being less sensitive than capillary electrophoresis (CE) instruments). Individual instruments, of a particular model type, have also been known to differ in performance (e.g. differences among various ABI 310 units, all of the same model). Capillary electrophoresis instruments generally provide better resolution compared gel-based systems, as well having better sensitivity. In addition, some laboratories have set different threshold standards depending on which instruments in the lab are used for an analysis.
Setting an upper maximum threshold is critical when analyzing DNA data within high quantity samples. Samples with large amounts of amplified DNA will report high RFU levels that might oversaturate an instrument's sensitivity to measure the results. In such cases, an accurate measurement of the relative peak heights and/or areas might be unattainable. Oversaturation can be a problem when analyzing mixed samples. | 1 | Applied and Interdisciplinary Chemistry |
Evaporation is a phase transition from the liquid phase to vapor (a state of substance below critical temperature) that occurs at temperatures below the boiling temperature at a given pressure. Evaporation occurs on the surface. Evaporation only occurs when the partial pressure of vapor of a substance is less than the equilibrium vapor pressure. For example, due to constantly decreasing pressures, vapor pumped out of a solution will eventually leave behind a cryogenic liquid. | 0 | Theoretical and Fundamental Chemistry |
GC–MS is becoming the tool of choice for tracking organic pollutants in the environment. The cost of GC–MS equipment has decreased significantly, and the reliability has increased at the same time, which has contributed to its increased adoption in environmental studies. | 0 | Theoretical and Fundamental Chemistry |
Unfortunately, the probabilities and cannot be measured directly. Instead, we assay the relative population of folded molecules using various structural probes, e.g., absorbance at 287 nm (which reports on the solvent exposure of tryptophan and tyrosine), far-ultraviolet circular dichroism (180-250 nm, which reports on the secondary structure of the protein backbone), dual polarisation interferometry (which reports the molecular size and fold density) and near-ultraviolet fluorescence (which reports on changes in the environment of tryptophan and tyrosine). However, nearly any probe of folded structure will work; since the measurement is taken at equilibrium, there is no need for high time resolution. Thus, measurements can be made of NMR chemical shifts, intrinsic viscosity, solvent exposure (chemical reactivity) of side chains such as cysteine, backbone exposure to proteases, and various hydrodynamic measurements.
To convert these observations into the probabilities and , one generally assumes that the observable adopts one of two values, or , corresponding to the native or unfolded state, respectively. Hence, the observed value equals the linear sum
By fitting the observations of under various solution conditions to this functional form, one can estimate and , as well as the parameters of . The fitting variables and are sometimes allowed to vary linearly with the solution conditions, e.g., temperature or denaturant concentration, when the asymptotes of are observed to vary linearly under strongly folding or strongly unfolding conditions. | 0 | Theoretical and Fundamental Chemistry |
Colloid-facilitated transport designates a transport process by which colloidal particles serve as transport vector
of diverse contaminants in the surface water (sea water, lakes, rivers, fresh water bodies) and in underground water circulating in fissured rocks
(limestone, sandstone, granite, ...). The transport of colloidal particles in surface soils and in the ground can also occur, depending on the soil structure, soil compaction, and the particles size, but the importance of colloidal transport was only given sufficient attention during the 1980 years.
Radionuclides, heavy metals, and organic pollutants, easily sorb onto colloids suspended in water and that can easily act as contaminant carrier.
Various types of colloids are recognised: inorganic colloids (clay particles, silicates, iron oxy-hydroxides, ...), organic colloids (humic and fulvic substances). When heavy metals or radionuclides form their own pure colloids, the term "Eigencolloid" is used to designate pure phases, e.g., Tc(OH), Th(OH), U(OH), Am(OH). Colloids have been suspected for the long range transport of plutonium on the Nevada Nuclear Test Site. They have been the subject of detailed studies for many years. However, the mobility of inorganic colloids is very low in compacted bentonites and in deep clay formations
because of the process of ultrafiltration occurring in dense clay membrane.
The question is less clear for small organic colloids often mixed in porewater with truly dissolved organic molecules. | 0 | Theoretical and Fundamental Chemistry |
The terms saturated vs unsaturated are often applied to the fatty acid constituents of fats. The triglycerides (fats) that comprise tallow are derived from the saturated stearic and monounsaturated oleic acids. Many vegetable oils contain fatty acids with one (monounsaturated) or more (polyunsaturated) double bonds in them. | 0 | Theoretical and Fundamental Chemistry |
The first published attempt to use plasma emissions as a source for spectroscopic analysis were in 1956 by Eugen Bădărău. In 1964 Stanley Greenfield working at Albright & Wilson was the first to use ICP for non experimental analysis. The first commercial machine was produced by KONTRON in 1975. | 0 | Theoretical and Fundamental Chemistry |
Proteins can be engineered to improve the chance of successful protein crystallization by using techniques like Surface Entropy Reduction or engineering in crystal contacts. Frequently, problematic cysteine residues can be replaced by alanine to avoid disulfide-mediated aggregation, and residues such as lysine, glutamate, and glutamine can be changed to alanine to reduce intrinsic protein flexibility, which can hinder crystallization.. | 0 | Theoretical and Fundamental Chemistry |
In a turbulent flow, there is a range of scales of the time-varying fluid motion. The size of the largest scales of fluid motion (sometimes called eddies) are set by the overall geometry of the flow. For instance, in an industrial smoke stack, the largest scales of fluid motion are as big as the diameter of the stack itself. The size of the smallest scales is set by the Reynolds number. As the Reynolds number increases, smaller and smaller scales of the flow are visible. In a smokestack, the smoke may appear to have many very small velocity perturbations or eddies, in addition to large bulky eddies. In this sense, the Reynolds number is an indicator of the range of scales in the flow. The higher the Reynolds number, the greater the range of scales. The largest eddies will always be the same size; the smallest eddies are determined by the Reynolds number.
What is the explanation for this phenomenon? A large Reynolds number indicates that viscous forces are not important at large scales of the flow. With a strong predominance of inertial forces over viscous forces, the largest scales of fluid motion are undamped—there is not enough viscosity to dissipate their motions. The kinetic energy must "cascade" from these large scales to progressively smaller scales until a level is reached for which the scale is small enough for viscosity to become important (that is, viscous forces become of the order of inertial ones). It is at these small scales where the dissipation of energy by viscous action finally takes place. The Reynolds number indicates at what scale this viscous dissipation occurs. | 1 | Applied and Interdisciplinary Chemistry |
Increases in glucose concentration excite and induce vasodilation in ventrolateral preoptic nucleus neurons of the hypothalamus via astrocytic release of adenosine that is blocked by A2A receptor antagonists like caffeine. Evidence also suggests that the small rise in blood glucose that occurs after a meal is sensed by glucose-inhibited neurons in the lateral hypothalamus. These orexin-expressing neurons appear to be hyperpolarised (inhibited) by a glucose-activated potassium channel. This inhibition is hypothesized to then reduce output from orexigenic neurons to aminergic, cholinergic, and glutamatergic arousal pathways of the brain, thus decreasing the activity of those pathways. | 1 | Applied and Interdisciplinary Chemistry |
Manapurathu Verghese George (3 October 1928 - 9 December 2019) was an Indian photochemist and an emeritus professor of the National Institute for Interdisciplinary Science and Technology (NIIST). He was known for establishing the Photochemistry Research Unit at NIIST and his studies on the mechanism of organic reactions. He is a recipient of the 1992 TWAS Award and an elected fellow of The World Academy of Sciences, the Indian National Science Academy and the Indian Academy of Sciences. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 1973, for his contributions to chemical sciences. | 0 | Theoretical and Fundamental Chemistry |
Synthetic radionuclides are deliberately synthesised using nuclear reactors, particle accelerators or radionuclide generators:
* As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of neutrons present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is iridium-192. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high neutron cross-section.
* Particle accelerators such as cyclotrons accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate protons at a target to produce positron-emitting radionuclides, e.g. fluorine-18.
* Radionuclide generators contain a parent radionuclide that decays to produce a radioactive daughter. The parent is usually produced in a nuclear reactor. A typical example is the technetium-99m generator used in nuclear medicine. The parent produced in the reactor is molybdenum-99. | 0 | Theoretical and Fundamental Chemistry |
Transition metal carbon dioxide complexes undergo a variety of reactions. Metallacarboxylic acids protonate at oxygen and eventually convert to metal carbonyl complexes:
:[LMCO] + 2 H → [LMCO] + HO
This reaction is relevant to the potential catalytic conversion of CO to fuels. | 0 | Theoretical and Fundamental Chemistry |
The practice of designating hemes with upper case letters was formalized in a footnote in a paper by Puustinen and Wikstrom, which explains under which conditions a capital letter should be used: "we prefer the use of capital letters to describe the heme structure as isolated. Lowercase letters may then be freely used for cytochromes and enzymes, as well as to describe individual protein-bound heme groups (for example, cytochrome bc, and aa3 complexes, cytochrome b, heme c of the bc complex, heme a of the aa complex, etc)." In other words, the chemical compound would be designated with a capital letter, but specific instances in structures with lowercase. Thus cytochrome oxidase, which has two A hemes (heme a and heme a) in its structure, contains two moles of heme A per mole protein. Cytochrome bc, with hemes b, b, and c, contains heme B and heme C in a 2:1 ratio. The practice seems to have originated in a paper by Caughey and York in which the product of a new isolation procedure for the heme of cytochrome aa3 was designated heme A to differentiate it from previous preparations: "Our product is not identical in all respects with the heme a obtained in solution by other workers by the reduction of the hemin a as isolated previously (2). For this reason, we shall designate our product heme A until the apparent differences can be rationalized." In a later paper, Caughey's group uses capital letters for isolated heme B and C as well as A. | 1 | Applied and Interdisciplinary Chemistry |
Chemical reaction models transform physical knowledge into a mathematical formulation that can be utilized in computational simulation of practical problems in chemical engineering. Computer simulation provides the flexibility to study chemical processes under a wide range of conditions. Modeling of a chemical reaction involves solving conservation equations describing convection, diffusion, and reaction source for each component species. | 1 | Applied and Interdisciplinary Chemistry |
Chemotaxis assays are experimental tools for evaluation of chemotactic ability of prokaryotic or eukaryotic cells.
A wide variety of techniques have been developed. Some techniques are qualitative - allowing an investigator to approximately determine a cell's chemotactic affinity for an analyte - while others are quantitative, allowing a precise measurement of this affinity. | 1 | Applied and Interdisciplinary Chemistry |
In three-dimensional Euclidean space, the densest packing of equal spheres is achieved by a family of structures called close-packed structures. One method for generating such a structure is as follows. Consider a plane with a compact arrangement of spheres on it. Call it A. For any three neighbouring spheres, a fourth sphere can be placed on top in the hollow between the three bottom spheres. If we do this for half of the holes in a second plane above the first, we create a new compact layer. There are two possible choices for doing this, call them B and C. Suppose that we chose B. Then one half of the hollows of B lies above the centers of the balls in A and one half lies above the hollows of A which were not used for B. Thus the balls of a third layer can be placed either directly above the balls of the first one, yielding a layer of type A, or above the holes of the first layer which were not occupied by the second layer, yielding a layer of type C. Combining layers of types A, B, and C produces various close-packed structures.
Two simple arrangements within the close-packed family correspond to regular lattices. One is called cubic close packing (or face-centred cubic, "FCC")—where the layers are alternated in the ABCABC... sequence. The other is called hexagonal close packing ("HCP"), where the layers are alternated in the ABAB... sequence. But many layer stacking sequences are possible (ABAC, ABCBA, ABCBAC, etc.), and still generate a close-packed structure. In all of these arrangements each sphere touches 12 neighboring spheres, and the average density is
In 1611, Johannes Kepler conjectured that this is the maximum possible density amongst both regular and irregular arrangements—this became known as the Kepler conjecture. Carl Friedrich Gauss proved in 1831 that these packings have the highest density amongst all possible lattice packings. In 1998, Thomas Callister Hales, following the approach suggested by László Fejes Tóth in 1953, announced a proof of the Kepler conjecture. Hales proof is a proof by exhaustion involving checking of many individual cases using complex computer calculations. Referees said that they were "99% certain" of the correctness of Hales proof. On 10 August 2014, Hales announced the completion of a formal proof using automated proof checking, removing any doubt. | 0 | Theoretical and Fundamental Chemistry |
Lasso peptide biosynthesis requires at least three genes, referred to as the A, B, and C proteins. The A gene encodes the precursor peptide, which is modified by the B and C proteins into the mature natural product. The B protein is an adenosine triphosphate-dependent cysteine protease that cleaves the leader region from the precursor peptide. The C protein displays homology to asparagine synthetase and is thought to activate the carboxylic acid side chain of a glutamate or aspartate residue via adenylylation. The N-terminal amine formed by the B protein (protease) then reacts with this activated side chain to form the macrocycle-forming isopeptide bond. The exact steps and reaction intermediates in lasso peptide biosynthesis remain unknown due to experimental difficulties associated with the proteins. Commonly, the B protein is referred to as the lasso protease, and the C protein is referred to as the lasso cyclase.
Some lasso peptide biosynthetic gene clusters also require an additional protein of unknown function for biosynthesis. Additionally, lasso peptide gene clusters usually include an ABC transporter (D protein) or an isopeptidase, although these are not strictly required for lasso peptide biosynthesis and are sometimes absent. No X-ray crystal structure is yet known for any lasso peptide biosynthetic protein.
The biosynthesis of lasso peptides is particularly interesting due to the inaccessibility of the threaded-lasso topology to chemical peptide synthesis. | 1 | Applied and Interdisciplinary Chemistry |
Resonance Raman spectroscopy explains the huge enhancement of Raman scattering intensity. Intermolecular and intramolecular charge transfers significantly enhance Raman spectrum peaks. In particular, the enhancement is huge for species adsorbing the metal surface due to the high-intensity charge transfers from the metal surface with wide band to the adsorbing species. This resonance Raman enhancement is dominant in SERS for species on small nanoclusters with considerable band gaps, because surface plasmon appears only in metal surface with near-zero band gaps. This chemical mechanism probably occurs in concert with the electromagnetic mechanism for metal surface. | 0 | Theoretical and Fundamental Chemistry |
Marius Clore was educated at the Lycee Francais Charles de Gaulle in Kensington, London, University College London and UCL Medical School. Marius Clores father was the film producer Leon Clore whose credits include The French Lieutenants Woman. | 0 | Theoretical and Fundamental Chemistry |
Thermite usage is hazardous due to the extremely high temperatures produced and the extreme difficulty in smothering a reaction once initiated. Small streams of molten iron released in the reaction can travel considerable distances and may melt through metal containers, igniting their contents. Additionally, flammable metals with relatively low boiling points such as zinc (with a boiling point of 907 °C, which is about 1,370 °C below the temperature at which thermite burns) could potentially spray superheated boiling metal violently into the air if near a thermite reaction.
If, for some reason, thermite is contaminated with organics, hydrated oxides and other compounds able to produce gases upon heating or reaction with thermite components, the reaction products may be sprayed. Moreover, if the thermite mixture contains enough empty spaces with air and burns fast enough, the super-heated air also may cause the mixture to spray. For this reason it is preferable to use relatively crude powders, so the reaction rate is moderate and hot gases could escape the reaction zone.
Preheating of thermite before ignition can easily be done accidentally, for example by pouring a new pile of thermite over a hot, recently ignited pile of thermite slag. When ignited, preheated thermite can burn almost instantaneously, releasing light and heat energy at a much higher rate than normal and causing burns and eye damage at what would normally be a reasonably safe distance.
The thermite reaction can take place accidentally in industrial locations where workers use abrasive grinding and cutting wheels with ferrous metals. Using aluminium in this situation produces a mixture of oxides that can explode violently.
Mixing water with thermite or pouring water onto burning thermite can cause a steam explosion, spraying hot fragments in all directions.
Thermites main ingredients were also utilized for their individual qualities, specifically reflectivity and heat insulation, in a paint coating or dope for the German zeppelin Hindenburg, possibly contributing to its fiery destruction. This was a theory put forward by the former NASA scientist Addison Bain, and later tested in small scale by the scientific reality-TV show MythBusters with semi-inconclusive results (it was proven not to be the fault of the thermite reaction alone, but instead conjectured to be a combination of that and the burning of hydrogen gas that filled the body of the Hindenburg). The MythBusters' program also tested the veracity of a video found on the Internet, whereby a quantity of thermite in a metal bucket was ignited while sitting on top of several blocks of ice, causing a sudden explosion. They were able to confirm the results, finding huge chunks of ice as far as 50 m from the point of explosion. Co-host Jamie Hyneman conjectured that this was due to the thermite mixture aerosolizing, perhaps in a cloud of steam, causing it to burn even faster. Hyneman also voiced skepticism about another theory explaining the phenomenon: that the reaction somehow separated the hydrogen and oxygen in the ice and then ignited them. This explanation claims that the explosion is due to the reaction of high temperature molten aluminium with water. Aluminium reacts violently with water or steam at high temperatures, releasing hydrogen and oxidizing in the process. The speed of that reaction and the ignition of the resulting hydrogen can easily account for the explosion verified. This process is akin to the explosive reaction caused by dropping metallic potassium into water. | 0 | Theoretical and Fundamental Chemistry |
From 1901 to 1938, Sørensen was head of the prestigious Carlsberg Laboratory, Copenhagen. While working at the Carlsberg Laboratory he studied the effect of ion concentration on proteins and, because the concentration of hydrogen ions was particularly important, he introduced the pH-scale as a simple way of expressing it in 1909. The article in which he introduced the scale (using the notation ) was published in French and Danish as well as in German described two methods for measuring acidity which Sørensen and his students had refined. The first method was based on electrodes, whereas the second involved comparing the colours of samples and a preselected set of indicators. (Sørensen, 1909).
:From p. 134: "Die Größe der Wasserstoffionenkonzentration … und die Bezeichnung für den numerischen Wert des Exponent dieser Potenz benütze." (The magnitude of the hydrogen ion concentration is accordingly expressed by the normality factor of the solution concerned, based on the hydrogen ions, and this factor is written in the form of a negative power of 10. By the way, as I refer [to it] in a following section (see p. 159), I just want to point out here that I use the name "hydrogen ion exponent" and the notation for the numerical value of the exponent of this power.)
:From pp. 159–160: "Für die Zahl p schlage ich den Namen "Wasserstoffionenexponent" … Normalitätsfaktors der Lösung verstanden." (For the number p I suggest the name "hydrogen ion exponent" and the notation . By the hydrogen ion exponent () of a solution is thus understood the Briggsian logarithm of the reciprocal value of the normality factor of the solution, based on the hydrogen ions, and this factor is written in the form of a negative power of 10).
:Starting on p. 139, "4. Meßmethoden zur Bestimmung der Wasserstoffionenkonzentration." (4. Methods of measurement for the determination of hydrogen ion concentration.), Sørensen reviewed a series of methods for measuring hydrogen ion concentration. He rejected all of them except two.
:From p. 144: "Es gibt noch zwei Verfahrungsweisen, … bzw. die colorimetrische Methode genannt." (There are still two procedures by which the hydrogen or hydroxyl ion concentration of a solution can be determined; namely, gas chain measurement and determination by means of indicators, also called the electrometric or colorimetric method.) On pp. 145–146, Sørensen outlined the electrometric and colorimetric methods:
::From p. 145: "Die elektrometrische Methode. Wird eine mit Platin-schwarz bedeckte Platinplatte in eine wäßerige … von der Wasserstoffionenkonzentration der Lösung abhängt.)" (The electrometric method. If a platinum plate that's covered with platinum black is dipped into an aqueous – acidic, neutral, or alkaline – solution and if the solution is saturated with hydrogen, then one finds, between the platinum plate and the solution, a voltage difference whose magnitude depends on the hydrogen ion concentration of the solution according to a law.
::From pp. 145: "Die colorimetrische Methode. Der Umschlag des Indicators bei einer gewöhnlichen Titrierung bedeutet ja, wie bekannt, daß die Konzentration der Wasserstoffionen der vorliegenden Lösung eine gewisse Größe von der einen oder der anderen Seite her erreicht oder überschritten hat." (The colorimetric method. The sudden change of the indicator during a typical titration means, as is known, that the concentration of hydrogen ions in the solution at hand has reached or exceeded – from one direction or the other – a certain magnitude.)
: p. 146: "Die Grundlage ist seit langer Zeit bekannt, … eine vollständige Reihe Indikatoren mit Umschlagspunkten bei den verschiedensten Ionenkonzentrationen zusammenzustellen." (The basis [of the colorimetric method] has been known for a long time, but the scattered material was first struggled through and perfected at certain points by the beautiful investigations of Hans Friedenthal [1870-1942] and Eduard Salm, so that it became possible for them to assemble a complete series of indicators with transition points at the most varied ion concentrations.)
:On pp. 150ff, the electrometric method is detailed; and on pp. 201ff, the colorimetric method is detailed. | 0 | Theoretical and Fundamental Chemistry |
The main use of concrete is for producing absolutes. The general process of producing absolutes includes extracting the concrete with ethanol, using cold filtration to remove residue, then distilling off the ethanol.
Absolutes are highly concentrated and aromatic oily mixtures. They are similar to essential oils, but are more soluble and have longer lasting odours. Absolutes are completely soluble in ethanol and can be used as perfume ingredients. In contrast to this, concretes are only partially soluble in ethanol due its composition of heavier substances. Therefore, they cannot directly produce perfume without being made into an absolute first. Moreover, because of their insoluble character, they are also used in soap perfumery. | 0 | Theoretical and Fundamental Chemistry |
Chlorophylls and carotenoids are important in light-harvesting complexes present in plants. Chlorophyll b is almost identical to chlorophyll a, except it has a formyl group in place of a methyl group. This small difference makes chlorophyll b absorb light with wavelengths between 400 and 500 nm more efficiently. Carotenoids are long linear organic molecules that have alternating single and double bonds along their length. Such molecules are called polyenes. Two examples of carotenoids are lycopene and β-carotene. These molecules also absorb light most efficiently in the 400 – 500 nm range.
Due to their absorption region, carotenoids appear red and yellow and provide most of the red and yellow colours present in fruits and flowers.
The carotenoid molecules also serve a safeguarding function. Carotenoid molecules suppress damaging photochemical reactions, in particular those including oxygen, which exposure to sunlight can cause. Plants that lack carotenoid molecules quickly die upon exposure to oxygen and light. | 0 | Theoretical and Fundamental Chemistry |
Chlorophyll fluorescence can measure most types of plant stress. Chlorophyll fluorescence can be used as a proxy of plant stress because environmental stresses, e.g. extremes of temperature, light and water availability, can reduce the ability of a plant to metabolise normally. This can mean an imbalance between the absorption of light energy by chlorophyll and the use of energy in photosynthesis.
* Favaretto et al. (2010) investigated adaptation to a strong light environment in pioneer and late successional species, grown under 100% and 10% light. Numerous parameters, including chlorophyll a fluorescence, were measured. A greater decline in under full sun light in the late-successional species than in the pioneer species was observed. Overall, their results show that pioneer species perform better under high-sun light than late- successional species, suggesting that pioneer plants have more potential tolerance to photo-oxidative damage.
* Neocleous and Vasilakakis (2009) investigated the response of raspberry to boron and salt stress. An chlorophyll fluorometer was used to measure , and . The leaf chlorophyll fluorescence was not significantly affected by NaCl concentration when B concentration was low. When B was increased, leaf chlorophyll fluorescence was reduced under saline conditions. It could be concluded that the combined effect of B and NaCl on raspberries induces a toxic effect in photochemical parameters.
* Lu and Zhang (1999) studied heat stress in wheat plants and found that temperature stability in the Photosystem II of water-stressed leaves correlates positively to the resistance in metabolism during photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
* Amsterdam
* The Hague
* Groningen
* Zwolle
* Breda
* Middleburg
* Maastricht
* Alkmaar
* Utrecht
* Rotterdam
* Leeuwarden
* Arnhem
* Den Bosch
* Schoonhoven
* Roermond
* Roosendaal
* Joure | 0 | Theoretical and Fundamental Chemistry |
This depends upon a relationship between the specific surface area and the resistance to gas-flow of a porous bed of powder. The method is simple and quick, and yields a result that often correlates well with the chemical reactivity of a powder. However, it fails to measure much of the deep surface texture. | 0 | Theoretical and Fundamental Chemistry |
The Bilbao Crystallographic Server came to life in 1997 as a scientific project by the [https://web.archive.org/web/20120127074622/http://lcdx00.wm.lc.ehu.es/lama/ Departments of Condensed Matter Physics and Applied Physics II] of the University of the Basque Country (EHU) under the supervision of J. Manuel Perez-Mato (EHU) and Mois I. Aroyo (EHU), in coordination with Gotzon Madariaga (EHU) and Hans Wondratschek (Karlsruhe Institute of Technology, Germany) with funding from the Basque government and several ministries of the Spanish government. The initial code was written by then Ph.D. students Eli Kroumova (EHU) and Svet Ivantchev (EHU) and the very first shells related to retrieval tools, group-subgroup relations and space group representations have soon appeared online.
Afterwards, in collaboration with Harold T. Stokes and Dorian M. Hatch from Brigham Young University, USA, the server extended its services to include symmetry modes analysis. Asen K. Kirov, a Ph.D. student from Sofia University, Bulgaria contributed to the server, working on programs dedicated to irreducible representations and extinction rules.
In 2001, Ph.D. student Cesar Capillas began his research on the server and became the main developer and system administrator focusing on structure relations, such as pseudosymmetry and phase transitions. Danel Orobengoa, also a Ph.D. student, joined the developer team in 2005 and worked mainly on symmetry modes, k-vector classification tables and non-characteristic orbits (in collaboration with Massimo Nespolo of the Nancy-Université, France), writing his Ph.D. thesis on the applications of the server for ferroic materials.
In 2009, Ph.D. student Gemma de la Flor and post-doc Emre S. Tasci were recruited for the development team: de la Flor working mainly on the identification and interpretation of symmetry operations, structure comparison and Tasci becoming the new system administrator and main developer, focusing in the structure relations concerning phase transitions. The Bilbao Crystallographic Server team took its current (2012) line-up in 2010 with the addition of Ph.D. student Samuel Vidal Gallego, his main research field being the magnetic space groups. | 0 | Theoretical and Fundamental Chemistry |
G proteins were discovered in 1980 when Alfred G. Gilman and Martin Rodbell investigated stimulation of cells by adrenaline. They found that when adrenaline binds to a receptor, the receptor does not stimulate enzymes (inside the cell) directly. Instead, the receptor stimulates a G protein, which then stimulates an enzyme. An example is adenylate cyclase, which produces the second messenger cyclic AMP. For this discovery, they won the 1994 Nobel Prize in Physiology or Medicine.
Nobel prizes have been awarded for many aspects of signaling by G proteins and GPCRs. These include receptor antagonists, neurotransmitters, neurotransmitter reuptake, G protein-coupled receptors, G proteins, second messengers, the enzymes that trigger protein phosphorylation in response to cAMP, and consequent metabolic processes such as glycogenolysis.
Prominent examples include (in chronological order of awarding):
* The 1947 Nobel Prize in Physiology or Medicine to Carl Cori, Gerty Cori and Bernardo Houssay, for their discovery of how glycogen is broken down to glucose and resynthesized in the body, for use as a store and source of energy. Glycogenolysis is stimulated by numerous hormones and neurotransmitters including adrenaline.
* The 1970 Nobel Prize in Physiology or Medicine to Julius Axelrod, Bernard Katz and Ulf von Euler for their work on the release and reuptake of neurotransmitters.
* The 1971 Nobel Prize in Physiology or Medicine to Earl Sutherland for discovering the key role of adenylate cyclase, which produces the second messenger cyclic AMP.
* The 1988 Nobel Prize in Physiology or Medicine to George H. Hitchings, Sir James Black and Gertrude Elion "for their discoveries of important principles for drug treatment" targeting GPCRs.
* The 1992 Nobel Prize in Physiology or Medicine to Edwin G. Krebs and Edmond H. Fischer for describing how reversible phosphorylation works as a switch to activate proteins, and to regulate various cellular processes including glycogenolysis.
* The 1994 Nobel Prize in Physiology or Medicine to Alfred G. Gilman and Martin Rodbell for their discovery of "G-proteins and the role of these proteins in signal transduction in cells".
* The 2000 Nobel Prize in Physiology or Medicine to Eric Kandel, Arvid Carlsson and Paul Greengard, for research on neurotransmitters such as dopamine, which act via GPCRs.
* The 2004 Nobel Prize in Physiology or Medicine to Richard Axel and Linda B. Buck for their work on G protein-coupled olfactory receptors.
* The 2012 Nobel Prize in Chemistry to Brian Kobilka and Robert Lefkowitz for their work on GPCR function. | 1 | Applied and Interdisciplinary Chemistry |
Scolytus multistriatus, one of the vectors of the Dutch elm disease, uses vanillin as a signal to find a host tree during oviposition. | 0 | Theoretical and Fundamental Chemistry |
A transcriptor is a transistor-like device composed of DNA and RNA rather than a semiconducting material such as silicon. Prior to its invention in 2013, the transcriptor was considered an important component to build biological computers. | 1 | Applied and Interdisciplinary Chemistry |
The pyridinium dichromate (PDC) or Cornforth reagent is a pyridinium salt of dichromate with the chemical formula [CHNH][CrO]. This compound is named after the Australian-British chemist Sir John Warcup Cornforth (b. 1917) who introduced it in 1962. The Cornforth reagent is a strong oxidizing agent which can convert primary and secondary alcohols to aldehydes and ketones respectively. In its chemical structure and functions it is closely related to other compounds made from hexavalent chromium oxide, such as pyridinium chlorochromate and Collins reagent. Because of their toxicity, these reagents are rarely used nowadays. | 0 | Theoretical and Fundamental Chemistry |
Trichlorofluoromethane was first widely used as a refrigerant. Because of its high boiling point compared to most refrigerants, it can be used in systems with a low operating pressure, making the mechanical design of such systems less demanding than that of higher-pressure refrigerants R-12 or R-22.
Trichlorofluoromethane is used as a reference compound for fluorine-19 NMR studies.
Trichlorofluoromethane was formerly used in the drinking bird novelty, largely because it has a boiling point of . The replacement, dichloromethane, boiling point , requires a higher ambient temperature to work.
Prior to the knowledge of the ozone depletion potential of chlorine in refrigerants and other possible harmful effects on the environment, trichlorofluoromethane was sometimes used as a cleaning/rinsing agent for low-pressure systems. | 1 | Applied and Interdisciplinary Chemistry |
*Large quantities are in some cases required to remove impurities
*May pose barriers on small scale reactions by "clogging up" the test tube reaction
*Dependent upon reagent to be removed | 0 | Theoretical and Fundamental Chemistry |
Isocyanates also can react with themselves. Aliphatic diisocyanates can trimerise to from substituted isocyanuric acid groups. This can be seen in the formation of polyisocyanurate resins (PIR) which are commonly used as rigid thermal insulation. Isocyanates participate in Diels–Alder reactions, functioning as dienophiles. | 0 | Theoretical and Fundamental Chemistry |
While there are many methods of detecting fake precious metals, there are realistically only two options available for verifying the marked fineness of metal as being reasonably accurate: assaying the metal (which requires destroying it), or using X-ray fluorescence (XRF). XRF will measure only the outermost portion of the piece of metal and so may get misled by thick plating.
That becomes a concern because it would be possible for an unscrupulous refiner to produce precious metals bars that are slightly less pure than marked on the bar. A refiner doing $1 billion of business each year that marked .980 pure bars as .999 fine would make about an extra $20 million in profit. In the United States, the actual purity of gold articles must be no more than .003 less than the marked purity (e.g. .996 fine for gold marked .999 fine), and the actual purity of silver articles must be no more than .004 less than the marked purity. | 1 | Applied and Interdisciplinary Chemistry |
Dexpramipexole is a first-in-class oral investigational medicine that lowers blood and tissue eosinophils before they can cause damage in the target organ. Dexpramipexole is being developed by [https://areteiatx.com/ Areteia Therapeutics] and has the potential to be the first oral treatment ever approved for eosinophilic asthma.
The eosinophil-targeting effects of oral dexpramipexole were discovered during its clinical development. Across five clinical trials, dexpramipexole has consistently been shown to significantly reduce blood eosinophil counts. | 0 | Theoretical and Fundamental Chemistry |
The study of network motifs was pioneered by Holland and Leinhardt who introduced the concept of a triad census of networks. They introduced methods to enumerate various types of subgraph configurations, and test whether the subgraph counts are statistically different from those expected in random networks.
This idea was further generalized in 2002 by Uri Alon and his group when network motifs were discovered in the gene regulation (transcription) network of the bacteria E. coli and then in a large set of natural networks. Since then, a considerable number of studies have been conducted on the subject. Some of these studies focus on the biological applications, while others focus on the computational theory of network motifs.
The biological studies endeavor to interpret the motifs detected for biological networks. For example, in work following, the network motifs found in E. coli were discovered in the transcription networks of other bacteria as well as yeast and higher organisms. A distinct set of network motifs were identified in other types of biological networks such as neuronal networks and protein interaction networks.
The computational research has focused on improving existing motif detection tools to assist the biological investigations and allow larger networks to be analyzed. Several different algorithms have been provided so far, which are elaborated in the next section in chronological order.
Most recently, the acc-MOTIF tool to detect network motifs was released. | 1 | Applied and Interdisciplinary Chemistry |
For water at standard temperature (25 C) the net cell reaction may be written:
Using Gibbs potentials ( kJ/mol), the thermodynamic voltage at standard conditions is
: 1.229 Volt (2 electrons needed to form H(g))
Just as the combustion of hydrogen and oxygen generates heat, the reverse reaction generating hydrogen and oxygen will absorb heat. The thermoneutral voltage is (using kJ/mol):
: 1.481 Volts. | 0 | Theoretical and Fundamental Chemistry |
Chaotropicity describes the entropic disordering of lipid bilayers and other biomacromolecules which is caused by substances dissolved in water. According to the original usage and work carried out on cellular stress mechanisms and responses, chaotropic substances do not necessarily disorder the structure of water.
The chaotropic activities of solutes in the aqueous phase (e.g. ethanol, butanol, urea, MgCl, and phenol) have been quantified using an agar-gelation assay. Whereas chaotropicity was first applied to studies of ions, it is equally applicable to alcohols, aromatics, ion mixtures, and other solutes. Furthermore, hydrophobic substances known to stress cellular systems (including benzene and toluene) can chaotropically disorder macromolecules and induce a chaotrope-stress response in microbial cells, even though they partition into the hydrophobic domains of macromolecular systems. | 1 | Applied and Interdisciplinary Chemistry |
A buffer solution contains an acid and its conjugate base or a base and its conjugate acid. Addition of the conjugate ion will result in a change of pH of the buffer solution. For example, if both sodium acetate and acetic acid are dissolved in the same solution they both dissociate and ionize to produce acetate ions. Sodium acetate is a strong electrolyte, so it dissociates completely in solution. Acetic acid is a weak acid, so it only ionizes slightly. According to Le Chatelier's principle, the addition of acetate ions from sodium acetate will suppress the ionization of acetic acid and shift its equilibrium to the left. Thus the percent dissociation of the acetic acid will decrease, and the pH of the solution will increase. The ionization of an acid or a base is limited by the presence of its conjugate base or acid.
: NaCHCO(s) → Na(aq) + CHCO(aq)
: CHCOH(aq) H(aq) + CHCO(aq)
This will decrease the hydronium concentration, and thus the common-ion solution will be less acidic than a solution containing only acetic acid. | 0 | Theoretical and Fundamental Chemistry |
Agarose gel electrophoresis is most commonly done horizontally in a subaquaeous mode whereby the slab gel is completely submerged in buffer during electrophoresis. It is also possible, but less common, to perform the electrophoresis vertically, as well as horizontally with the gel raised on agarose legs using an appropriate apparatus. The buffer used in the gel is the same as the running buffer in the electrophoresis tank, which is why electrophoresis in the subaquaeous mode is possible with agarose gel.
For optimal resolution of DNA greater than 2kb in size in standard gel electrophoresis, 5 to 8 V/cm is recommended (the distance in cm refers to the distance between electrodes, therefore this recommended voltage would be 5 to 8 multiplied by the distance between the electrodes in cm). Voltage may also be limited by the fact that it heats the gel and may cause the gel to melt if it is run at high voltage for a prolonged period, especially if the gel used is LMP agarose gel. Too high a voltage may also reduce resolution, as well as causing band streaking for large DNA molecules. Too low a voltage may lead to broadening of band for small DNA fragments due to dispersion and diffusion.
Since DNA is not visible in natural light, the progress of the electrophoresis is monitored using colored dyes. Xylene cyanol (light blue color) comigrates large DNA fragments, while Bromophenol blue (dark blue) comigrates with the smaller fragments. Less commonly used dyes include Cresol Red and Orange G which migrate ahead of bromophenol blue. A DNA marker is also run together for the estimation of the molecular weight of the DNA fragments. Note however that the size of a circular DNA like plasmids cannot be accurately gauged using standard markers unless it has been linearized by restriction digest, alternatively a supercoiled DNA marker may be used. | 1 | Applied and Interdisciplinary Chemistry |
In the Black Sea, sapropels are distributed at a depth of 500 to 2200 m, and in different morpholithological zones they have different thicknesses. Deep sea sediments are called the sediments formed outside the zone of influence of hydrogenic factors such as wind-driven waves and internal waves as well as of the transgressive and regressive cycles of the Black Sea basin. Here, under the conditions of relative stagnation, can be observed uninterrupted cross-sections because this area was under the sea level during the entire Pleistocene and Holocene. Deep sea organogenic mineral sediments (DSOMS) are those sediments that contain more than 3% organic carbon. The sapropels form a single horizon with constant thickness typical of the Black Sea basin. Analogues of the sapropels on the continental shelf and the upper part of the continental slope are the green aleurite-pelite, oozes with accumulation of plant detritus and decomposed shells of Mytilus galloprovincialis. The transition from aleurite-pelitic oozes to sapropels is facial. The organic matter in the sapropels is of heterogeneous origin. They are composed primarily of planktogenic organisms (about 80%) and continental organic matter (20%). The planktonic organisms are well preserved in most cases under the conditions of the hydrogen sulfide zone. The main components of the sapropels are the dinoflagellate cysts, diatom algae, coccolithophorids, peridiniales. The mineral part of sapropel muds is represented by a poly-component mixture of clay minerals. The minerals illite and montmorillonite predominate, chlorite and kaolinite occur in subordinate quantities. Individual grains of quartz, feldspar, volcanic glass and others are rarely found among them. Carbonate minerals are mainly represented by calcite and dolomite. It is generally accepted that the main source of hydrogen sulfide in the Black Sea today are the processes of anaerobic decomposition of organic matter by sulfate-reducing bacteria (SRB). The organic substance that is fixed at the bottom of the basin in the form of organogenic-mineral sediments (sapropels) is a product of the mass extinction of the plankton biomass as a result of the Black Sea flood. There is an excess of a huge amount of organic matter, which creates favorable conditions for the development of bacterial sulfate reduction. | 0 | Theoretical and Fundamental Chemistry |
An airfoil at a given angle of attack will have what is called a pressure distribution. This pressure distribution is simply the pressure at all points around an airfoil. Typically, graphs of these distributions are drawn so that negative numbers are higher on the graph, as the for the upper surface of the airfoil will usually be farther below zero and will hence be the top line on the graph. | 1 | Applied and Interdisciplinary Chemistry |
NanoPutians are a series of organic molecules whose structural formulae resemble human forms. James Tour's research group designed and synthesized these compounds in 2003 as a part of a sequence on chemical education for young students. The compounds consist of two benzene rings connected via a few carbon atoms as the body, four acetylene units each carrying an alkyl group at their ends which represents the hands and legs, and a 1,3-dioxolane ring as the head. Tour and his team at Rice University used the NanoPutians in their NanoKids educational outreach program. The goal of this program was to educate children in the sciences in an effective and enjoyable manner. They have made several videos featuring the NanoPutians as anthropomorphic animated characters.
Construction of the structures depends on Sonogashira coupling and other synthetic techniques. By replacing the 1,3-dioxolane group with an appropriate ring structure, various other types of putians have been synthesized, e.g. NanoAthlete, NanoPilgrim, and NanoGreenBeret. Placing thiol (R-SH) functional groups at the end of the legs enables them to "stand" on a gold surface.
"NanoPutian" is a portmanteau of nanometer, a unit of length commonly used to measure chemical compounds, and lilliputian, a fictional race of humans in the novel Gulliver's Travels by Jonathan Swift. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin A deficiency (VAD) caused night blindness is a reversible difficulty for the eyes to adjust to dim light. It is common in young children who have a diet inadequate in retinol and beta-carotene. A process called dark adaptation typically causes an increase in photopigment amounts in response to low levels of illumination. This increases light sensitivity by up to 100,000 times compared to normal daylight conditions. Significant improvement in night vision takes place within ten minutes, but the process can take up to two hours to reach maximal effect. People expecting to work in a dark environment wore red-tinted goggles or were in a red light environment to not reverse the adaptation because red light does not deplete rhodopsin versus what occurs with yellow or green light. | 1 | Applied and Interdisciplinary Chemistry |
Methylene blue has been described as "the first fully synthetic drug used in medicine." Methylene blue was first prepared in 1876 by German chemist Heinrich Caro.
Its use in the treatment of malaria was pioneered by Paul Guttmann and Paul Ehrlich in 1891. During this period before the first World War, researchers like Ehrlich believed that drugs and dyes worked in the same way, by preferentially staining pathogens and possibly harming them. Changing the cell membrane of pathogens is in fact how various drugs work, so the theory was partially correct although far from complete. Methylene blue continued to be used in the second World War, where it was not well liked by soldiers, who observed, "Even at the loo, we see, we pee, navy blue." Antimalarial use of the drug has recently been revived. It was discovered to be an antidote to carbon monoxide poisoning and cyanide poisoning in 1933 by Matilda Brooks.
The blue urine was used to monitor psychiatric patients compliance with medication regimes. This led to interest - from the 1890s to the present day - in the drugs antidepressant and other psychotropic effects. It became the lead compound in research leading to the discovery of chlorpromazine. | 0 | Theoretical and Fundamental Chemistry |
β-Catenin was initially discovered in the early 1990s as a component of a mammalian cell adhesion complex: a protein responsible for cytoplasmatic anchoring of cadherins. But very soon, it was realized that the Drosophila protein armadillo – implicated in mediating the morphogenic effects of Wingless/Wnt – is homologous to the mammalian β-catenin, not just in structure but also in function. Thus, β-catenin became one of the first examples of moonlighting: a protein performing more than one radically different cellular function. | 1 | Applied and Interdisciplinary Chemistry |
Proteins are characterized by amide linkages (-N(H)-C(O)-) formed by the condensation of amino acids. The sequence of the amino acids in the polypeptide backbone is known as the primary structure of the protein. Like almost all polymers, protein fold and twist, forming into the secondary structure, which is rigidified by hydrogen bonding between the carbonyl oxygens and amide hydrogens in the backbone, i.e. C=O---HN. Further interactions between residues of the individual amino acids form the protein's tertiary structure. For this reason, the primary structure of the amino acids in the polypeptide backbone is the map of the final structure of a protein, and it therefore indicates its biological function. Spatial positions of backbone atoms can be reconstructed from the positions of alpha carbons using computational tools for the backbone reconstruction. | 0 | Theoretical and Fundamental Chemistry |
Most aquo complexes are mono-nuclear, with the general formula , with or 3; they have an octahedral structure. The water molecules function as Lewis bases, donating a pair of electrons to the metal ion and forming a dative covalent bond with it. Typical examples are listed in the following table.
Tutton's salts are crystalline compounds with the generic formula (where , , , , , or ). Alums, , are also double salts. Both sets of salts contain hexa-aquo metal cations. | 0 | Theoretical and Fundamental Chemistry |
Alkaloids are bitter-tasting chemicals, widespread in nature, and often toxic. There are several classes with different modes of action as drugs, both recreational and pharmaceutical. Medicines of different classes include atropine, scopolamine, and hyoscyamine (all from nightshade), the traditional medicine berberine (from plants such as Berberis and Mahonia), caffeine (Coffea), cocaine (Coca), ephedrine (Ephedra), morphine (opium poppy), nicotine (tobacco), reserpine (Rauvolfia serpentina), quinidine and quinine (Cinchona), vincamine (Vinca minor), and vincristine (Catharanthus roseus). | 1 | Applied and Interdisciplinary Chemistry |
An excess of free fatty acids in liver cells plays a role in Nonalcoholic Fatty Liver Disease (NAFLD). In the liver, it is the type of fatty acid, not the quantity, that determines the extent of the lipotoxic effects. In hepatocytes, the ratio of monounsaturated fatty acids and saturated fatty acids leads to apoptosis and liver damage. There are several potential mechanisms by which the excess fatty acids can cause cell death and damage. They may activate death receptors, stimulate apoptotic pathways, or initiate cellular stress response in the endoplasmic reticulum. These lipotoxic effects have been shown to be prevented by the presence of excess triglycerides within the hepatocytes. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits