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A sized screen fraction with a size range coefficient (d95/d5) of 2-5 (optimal 2-3) is fed onto a vibratory feeder which has the function to create a mono-layer, by pre-accelerating the particles. A common misunderstanding in plant design is, that you can use the vibratory feeder to discharge from a buffer bunker but a separate units needs to be applied, since the feed distribution is very important to the efficiency of the sensor-based sorter and different loads on the feeder change its position and vibration characteristics. | 3 | Analytical Chemistry |
The Wimley–White whole residue hydrophobicity scales are significant for two reasons. First, they include the contributions of the peptide bonds as well as the sidechains, providing absolute values. Second, they are based on direct, experimentally determined values for transfer free energies of polypeptides.
Two whole-residue hydrophobicity scales have been measured:
* One for the transfer of unfolded chains from water to the bilayer interface (referred to as the Wimley–White interfacial hydrophobicity scale).
* One for the transfer of unfolded chains into octanol, which is relevant to the hydrocarbon core of a bilayer.
The Stephen H. White website provides an example of whole residue hydrophobicity scales showing the free energy of transfer ΔG(kcal/mol) from water to POPC interface and to n-octanol. These two scales are then used together to make Whole residue hydropathy plots. The hydropathy plot constructed using ΔG − ΔG shows favorable peaks on the absolute scale that correspond to the known TM helices. Thus, the whole residue hydropathy plots illustrate why transmembrane segments prefer a transmembrane location rather than a surface one. | 6 | Supramolecular Chemistry |
Several important anticancer agents both bind to DNA and generate reactive oxygen species. These include adriamycin and other anthracyclines, bleomycin, and cisplatin. These agents may show specific toxicity towards cancer cells because of the low level of antioxidant defenses found in tumors. Recent research demonstrates that redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by pro-oxidant non-genotoxic redox chemotherapeutics.
Photodynamic therapy is used to treat some cancers as well as other conditions. It involves the administration of a photosensitizer followed by exposing the target to appropriate wavelengths of light. The light excites the photosensitizer, causing it to generate reactive oxygen species, which can damage or destroy diseased or unwanted tissue. | 1 | Biochemistry |
In economics, a similar concept also named after Le Chatelier was introduced by American economist Paul Samuelson in 1947. There the generalized Le Chatelier principle is for a maximum condition of economic equilibrium: Where all unknowns of a function are independently variable, auxiliary constraints—"just-binding" in leaving initial equilibrium unchanged—reduce the response to a parameter change. Thus, factor-demand and commodity-supply elasticities are hypothesized to be lower in the short run than in the long run because of the fixed-cost constraint in the short run.
Since the change of the value of an objective function in a neighbourhood of the maximum position is described by the envelope theorem, Le Chatelier's principle can be shown to be a corollary thereof. | 7 | Physical Chemistry |
CREB-regulated transcription coactivator 1 (CRTC1), previously referred to as TORC1 (), is a protein that in humans is encoded by the CRTC1 gene. It is expressed in a limited number of tissues that include fetal brain and liver and adult heart, skeletal muscles, liver and salivary glands and various regions of the adult central nervous system. | 1 | Biochemistry |
The Min System is a mechanism composed of three proteins MinC, MinD, and MinE used by E. coli as a means of properly localizing the septum prior to cell division. Each component participates in generating a dynamic oscillation of FtsZ protein inhibition between the two bacterial poles to precisely specify the mid-zone of the cell, allowing the cell to accurately divide in two. This system is known to function in conjunction with a second negative regulatory system, the nucleoid occlusion system (NO), to ensure proper spatial and temporal regulation of chromosomal segregation and division. | 1 | Biochemistry |
This diagram shows an o-alkylation between phenol and methanol. Unlike the c-alkylation, the o-alkylation replaces the hydrogen atom on the -OH group with the methyl group (from the methanol). The product of the o-alkylation is methoxybenzene, better-known as anisole, and water, which is not shown in the diagram. Anisole is listed as an acute hazard to aquatic life with long-term effects. | 7 | Physical Chemistry |
When blood is used for toxicology testing, drugs of abuse are the usual targets of analysis. Other substances that may be looked for are medications that are known to be prescribed to the individual or poisons if it is suspected. | 1 | Biochemistry |
The naming of monomeric oxyanions follows the following rules.
Here the halogen group (group 7A, 17) is referred to as group VII and the noble gases group (group 8A) is referred to as group VIII.
; If central atom is not in Group VII or VIII
; If central atom is in Group VII or VIII | 7 | Physical Chemistry |
Many diphenylamine derivatives are used as redox indicators that are particularly useful in alkaline redox titrations. The diphenylaminesulfonic acid is a simple prototype redox indicator, owing to its improved aqueous solubility compared with diphenylamine. Attempts have been made to explain the color changes associated with the oxidation of diphenylamine.
In a related application, diphenylamine is oxidized by nitrate to give a similar blue coloration in the diphenylamine test for nitrates. | 3 | Analytical Chemistry |
Soil pH affects the availability of some plant nutrients:
As discussed above, aluminium toxicity has direct effects on plant growth; however, by limiting root growth, it also reduces the availability of plant nutrients. Because roots are damaged, nutrient uptake is reduced, and deficiencies of the macronutrients (nitrogen, phosphorus, potassium, calcium and magnesium) are frequently encountered in very strongly acidic to ultra-acidic soils (pH<5.0). When aluminum levels increase in the soil, it decreases the pH levels. This does not allow for trees to take up water, meaning they cannot photosynthesize, leading them to die. The trees can also develop yellowish colour on their leaves and veins.
Molybdenum availability is increased at higher pH; this is because the molybdate ion is more strongly sorbed by clay particles at lower pH.
Zinc, iron, copper and manganese show decreased availability at higher pH (increased sorption at higher pH).
The effect of pH on phosphorus availability varies considerably, depending on soil conditions and the crop in question. The prevailing view in the 1940s and 1950s was that P availability was maximized near neutrality (soil pH 6.5–7.5), and decreased at higher and lower pH. Interactions of phosphorus with pH in the moderately to slightly acidic range (pH 5.5–6.5) are, however, far more complex than is suggested by this view. Laboratory tests, glasshouse trials and field trials have indicated that increases in pH within this range may increase, decrease, or have no effect on P availability to plants. | 9 | Geochemistry |
The Renwu incident was a soil pollution event at the Formosa Plastics Corporation's Renwu Plant in Kaohsiung, Taiwan.
In 2009, the Taiwanese Environmental Protection Administration (EPA) found that the soil and the groundwater in the area close to Formosa Plastics' Renwu Plant has been polluted by benzene, chloroform, dichloromethane, 1,1,2-Trichloroethane, 1,1-dichloroethylene, tetrachloroethylene, trichloroethylene, and vinylchloride. The pollutants were all present at levels over 20 times the government standard; and most frighteningly, the levels of 1,2-dichloroethane were 30,000 times higher than the standard.
The Formosa Plastics' Renwu Plant had already discovered the soil pollution in 2006, and they had tried to reinforce the structure of their wastewater pit, but the reinforcement work was never completed.
Since the pollution was severe, the residents of the nearby area and an Elected Representative lodged protests, hoping that the Renwu plant could shut down. In April 2010, the EPA proposed a fine on Formosa Plastic' Renwu Plant to NT$150 million (US$4.7 million) for causing soil and groundwater pollution. | 2 | Environmental Chemistry |
An enkephalin is a pentapeptide involved in regulating nociception (pain sensation) in the body. The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body's opioid receptors. Discovered in 1975, two forms of enkephalin have been found, one containing leucine ("leu"), and the other containing methionine ("met"). Both are products of the proenkephalin gene.
* Met-enkephalin is Tyr-Gly-Gly-Phe-Met.
* Leu-enkephalin is Tyr-Gly-Gly-Phe-Leu. | 1 | Biochemistry |
The key elements of any FOCE experimental units are perspex, partially open, chambers, a CO mixing system, sensors to continuously monitor ambient and chamber pH, and a control loop to regulate the addition of gases or liquids to each experimental chamber.
The carbonate chemistry of seawater can be manipulated using different approaches to mimic future conditions. It is possible to directly inject gases (pure CO or CO-enriched air) but this is more difficult than delivering water to achieve precise pH control. Current FOCE systems lower pH using metered addition of CO-enriched seawater into the experimental chambers. pH is controlled as a constant pH offset relative to ambient values, maintaining natural variability, or as a constant value.
Other approaches have been used to manipulate the seawater carbonate chemistry in the field. In pelagic mesocosm experiments, the carbonate chemistry is generally altered at the beginning of the experiment and subsequently drifts as a function of biological processes and air-sea gas transfer. CO bubbling in open water has also been used. This approach does not enable precise control of the carbonate chemistry because it does not include a device to ensure full equilibration of added CO in seawater and its precise control. There are no experimental chambers to regulate water flow, and thus allows for natural near-bottom flow conditions, but it generates highly variable pH under variable current speed or direction. This approach is therefore more similar to natural CO vents than to FOCE systems. This approach can be useful when organisms can not be enclosed in chambers and when they inhabit environments such as estuaries where pCO2 levels are naturally hyper-variable. The approach has inherent limitations but may allow greater replication, at lower cost.
Current users of FOCE systems have organized to release guidelines and best practices information for future users. Furthermore, the Monterey Bay Aquarium Research Institute will release an open source package to transfer FOCE technology to interested researchers ([http://www.xfoce.org xFOCE]). This package will comprise all engineering information required to develop cost effective FOCE systems.
Future development of FOCE systems will include the study of the combined effects of ocean acidification and other environmental factors such as temperature or the concentration of dissolved oxygen. | 9 | Geochemistry |
CrysTBox offers tools for automated processing of diffraction patterns and high-resolution transmission electron microscope images. Since the tools employ algorithms of artificial intelligence and computer vision, they are designed to require minimal operator effort providing higher accuracy compared to manual evaluation. Four analytical tools can be used to index diffraction patterns, measure lattice constants (distances and angles), sample thickness etc. Despite the high level of automation, the user is able to control the whole process and perform individual steps manually if needed. | 3 | Analytical Chemistry |
Clinical neurochemistry is the field of neurological biochemistry which relates biochemical phenomena to clinical symptomatic manifestations in humans. While neurochemistry is mostly associated with the effects of neurotransmitters and similarly functioning chemicals on neurons themselves, clinical neurochemistry relates these phenomena to system-wide symptoms. Clinical neurochemistry is related to neurogenesis, neuromodulation, neuroplasticity, neuroendocrinology, and neuroimmunology in the context of associating neurological findings at both lower and higher level organismal functions. | 1 | Biochemistry |
Depending on the nature of the signal amplification system assays may be of numerous types, to name a few:
#Enzyme assay: Enzymes may be tested by their highly repeating activity on a large number of substrates when loss of a substrate or the making of a product may have a measurable attribute like color or absorbance at a particular wavelength or light or Electrochemiluminescence or electrical/redox activity.
#Light detection systems that may use amplification e.g. by a photodiode or a photomultiplier tube or a cooled charge coupled device.
#Radioisotope labeled substrates as used in radioimmunoassays and equilibrium dialysis assays and can be detected by the amplification in Gamma counters or X-ray plates, or phosphorimager
#Polymerase Chain Reaction Assays that amplify a DNA (or RNA) target rather than the signal
#Combination Methods Assays may utilize a combination of the above and other amplification methods to improve sensitivity. e.g. Enzyme-linked immunoassay or EIA, enzyme linked immunosorbent assay. | 1 | Biochemistry |
A hidden state of matter is a state of matter which cannot be reached under ergodic conditions, and is therefore distinct from known thermodynamic phases of the material. Examples exist in condensed matter systems, and are typically reached by the non-ergodic conditions created through laser photo excitation.
Short-lived hidden states of matter have also been reported in crystals using lasers. Recently a persistent hidden state was discovered in a crystal of Tantalum(IV) sulfide (TaS), where the state is stable at low temperatures.
A hidden state of matter is not to be confused with hidden order, which exists in equilibrium, but is not immediately apparent or easily observed.
Using ultrashort laser pulses impinging on solid state matter, the system may be knocked out of equilibrium so that not only are the individual subsystems out of equilibrium with each other but also internally. Under such conditions, new states of matter may be created which are not otherwise reachable under equilibrium, ergodic system evolution.
Such states are usually unstable and decay very rapidly, typically in nanoseconds or less. The difficulty is in distinguishing a genuine hidden state from one which is simply out of thermal equilibrium.
Probably the first instance of a photoinduced state is described for the organic molecular compound TTF-CA, which turns from neutral to ionic species as a result of excitation by laser pulses. However, a similar transformation is also possible by the application of pressure, so strictly speaking the photoinduced transition is not to a hidden state under the definition given in the introductory paragraph. A few further examples are given in ref.
Photoexcitation has been shown to produce persistent states in vanadates and manganite materials,
leading to filamentary paths of a modified charge ordered phase which is sustained by a passing current. Transient superconductivity was also reported in cuprates. | 7 | Physical Chemistry |
For dilute thermodynamic conditions, the ideal-gas equation of state (EoS) provides sufficiently accurate results in modelling the fluid thermodynamics. This occurs in general for low values of reduced pressure and high values of reduced temperature, where the term reduced refers to the ratio of a certain thermodynamic quantity and its critical value. For some fluids such as air, the assumption of considering ideal conditions is perfectly reasonable and it is widely used.
On the other hand, when thermodynamic conditions approach condensation and the critical point or when high pressures are involved, real-gas models are needed in order to capture the real fluid behavior. In these conditions, in fact, intermolecular forces and compressibility effects come into play.
A measure of the fluid non-ideality is given by the compressibility factor , defined as
where
* is the pressure [Pa];
* is the specific volume [m/kg];
* is the specific gas constant [J/(kg K)], namely the universal gas constant divided by the fluid's molecular mass;
* is the absolute temperature [K].
The compressibility factor is a dimensionless quantity which is equal to 1 for ideal gases and deviates from unity for increasing levels of non-ideality.
Several non-ideal models exist, from the simplest cubic equations of state (such as the Van der Waals and the Peng-Robinson models) up to complex multi-parameter ones, including the Span-Wagner equation of state.
State-of-the-art equations of state are easily accessible through thermodynamic libraries, such as FluidProp or the open-source software CoolProp. | 7 | Physical Chemistry |
* Decroocq, S and Casserino, M, Polybutenes, Chapter 17 in Rudnick (Ed), Synthetics, Mineral Oils, and Bio-Based Lubricants: Chemistry and Technology, CRC Press (2005), Print , eBook . | 7 | Physical Chemistry |
Several clinical studies have shown that MFGM could positively affect circulating lipids. A single-blind RCT in overweight adults has shown that the effects of milk fat on plasma lipids were modulated by the MFGM content; compared to butter oil (control diet), consumption of whipping cream (MFGM diet) for 8 weeks did not impair the lipoprotein profile. Another double-blind RCT in overweight and obese adults has also shown that MFGM attenuated the negative effects of a high-saturated fats meal by reducing postprandial cholesterol, inflammatory markers and insulin response. A double-blind RCT in normal healthy adults has indicated that one month consumption of buttermilk rich in MFGM led to reduction in serum cholesterol and triacylglycerol levels as well as blood pressure.
MFGM supplementation in infancy is hypothesized to have programming effects that may influence circulating lipid levels later in life. Breastfed infants are known to have a higher total serum cholesterol and LDL cholesterol than formula-fed infants in infancy, but lower levels in adulthood. A clinical study in infants has suggested that MFGM supplementation could narrow the gap between breastfed and formula-fed infants with regard to serum lipid status. Specifically, as compared with a control formula, infants receiving MFGM-supplemented formula had higher total serum cholesterol until 6 months of age, similar to breastfed infants. The LDL:HDL ratio did not differ between the formula-fed groups and was significantly higher in the breastfed reference group as compared with both formula-fed groups. | 1 | Biochemistry |
Leucyl aminopeptidases (, leucine aminopeptidase, LAPs, leucyl peptidase, peptidase S, cytosol aminopeptidase, cathepsin III, L-leucine aminopeptidase, leucinaminopeptidase, leucinamide aminopeptidase, FTBL proteins, proteinates FTBL, aminopeptidase II, aminopeptidase III, aminopeptidase I) are enzymes that preferentially catalyze the hydrolysis of leucine residues at the N-terminus of peptides and proteins. Other N-terminal residues can also be cleaved, however. LAPs have been found across superkingdoms. Identified LAPs include human LAP, bovine lens LAP, porcine LAP, Escherichia coli (E. coli) LAP (also known as PepA or XerB), and the solanaceous-specific acidic LAP (LAP-A) in tomato (Solanum lycopersicum). | 1 | Biochemistry |
*Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, .
*Callen, H.B. (1960/1985). Thermodynamics and an Introduction to Thermostatistics, (1st edition 1960) 2nd edition 1985, Wiley, New York, .
* A translation may be found [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/caratheodory_-_thermodynamics.pdf here]. Also a mostly reliable [https://books.google.com/books?id=xwBRAAAAMAAJ&q=Investigation+into+the+foundations translation is to be found] at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA..
*Giles, R. (1964). Mathematical Foundations of Thermodynamics, Macmillan, New York.
*Guggenheim, E.A. (1949/1967). Thermodynamics. An Advanced Treatment for Chemists and Physicists, fifth revised edition, North-Holland, Amsterdam.
*Guggenheim, E.A. (1949). Statistical basis of thermodynamics, Research, 2: 450–454.
*Gyarmati, I. (1967/1970). Non-equilibrium Thermodynamics. Field Theory and Variational Principles, translated from the 1967 Hungarian by E. Gyarmati and W.F. Heinz, Springer-Verlag, New York.
*Haase, R. (1971). Survey of Fundamental Laws, chapter 1 of Thermodynamics, pages 1–97 of volume 1, ed. W. Jost, of Physical Chemistry. An Advanced Treatise, ed. H. Eyring, D. Henderson, W. Jost, Academic Press, New York, lcn 73–117081.
*Kelvin, Lord (1857). On the alteration of temperature accompanying changes of pressure in fluids, [https://archive.org/stream/mathematicaland03kelvgoog#page/n258/mode/2up Proc. Roy. Soc., June].
*Landsberg, P.T. (1961). Thermodynamics with Quantum Statistical Illustrations, Interscience, New York.
*Lieb, E.H., Yngvason, J. (1999). The physics and mathematics of the second law of thermodynamics, Physics Reports, 314: 1–96, p. 14.
*Planck, M. (1887). Ueber das Princip der Vermehrung der Entropie, Annalen der Physik und Chemie, new series 30: 562–582.
*Planck, M., (1897/1903). [https://archive.org/details/treatiseonthermo00planrich Treatise on Thermodynamics], translated by A. Ogg, Longmans, Green, & Co., London.
*Planck, M. (1935). Bemerkungen über Quantitätsparameter, Intenstitätsparameter und stabiles Gleichgewicht, Physica, 2: 1029–1032.
*Tisza, L. (1966). Generalized Thermodynamics, M.I.T Press, Cambridge MA.
*Uffink, J. (2001). Bluff your way in the second law of thermodynamics, Stud. Hist. Phil. Mod. Phys., 32(3): 305–394, publisher Elsevier Science. | 7 | Physical Chemistry |
Experimentally, G can be determined by stimulating the thyroid with a high thyrotropin concentration (e.g. by means of rhTSH, i.e. recombinant human thyrotropin) and measuring its output in terms of T4 production, or by measuring the serum concentration of protein-bound iodine-131 after administration of radioiodine. These approaches are, however, costly and accompanied by significant exposure to radiation.
In vivo, G can also be estimated from equilibrium levels of TSH and T4 or free T4. In this case it is calculated with
or
[TSH]: Serum thyrotropin concentration (in mIU/L or μIU/mL)<br />
[FT4]: Serum free T4 concentration (in pmol/L)<br />
[TT4]: Serum total T4 concentration (in nmol/L)<br />
: Theoretical (apparent) secretory capacity (SPINA-GT)<br />
: Dilution factor for T4 (reciprocal of apparent volume of distribution, 0.1 L)<br />
: Clearance exponent for T4 (1.1e-6 sec), i. e., reaction rate constant for degradation<br />
K: Binding constant T4-TBG (2e10 L/mol)<br />
K: Binding constant T4-TBPA (2e8 L/mol)<br />
D: EC for TSH (2.75 mU/L)
The method is based on mathematical models of thyroid homeostasis. Calculating the secretory capacity with one of these equations is an inverse problem. Therefore, certain conditions (e.g. stationarity) have to be fulfilled to deliver a reliable result. | 1 | Biochemistry |
When arriving at a site of a surface, an adatom has three options. There is a probability that it will adsorb to the surface (), a probability that it will migrate to another site on the surface (), and a probability that it will desorb from the surface and return to the bulk gas (). For an empty site (θ=0) the sum of these three options is unity.
For a site already occupied by an adatom (θ>0), there is no probability of adsorbing, and so the probabilities sum as:
For the first site visited, the P of migrating overall is the P of migrating if the site is filled plus the P of migrating if the site is empty. The same is true for the P of desorption. The P of adsorption, however, does not exist for an already filled site.
The P of migrating from the second site is the P of migrating from the first site and then migrating from the second site, and so we multiply the two values.
Thus the sticking probability () is the P of sticking of the first site, plus the P of migrating from the first site and then sticking to the second site, plus the P of migrating from the second site and then sticking at the third site etc.
There is an identity we can make use of.
The sticking coefficient when the coverage is zero can be obtained by simply setting . We also remember that
If we just look at the P of migration at the first site, we see that it is certainty minus all other possibilities.
Using this result, and rearranging, we find: | 7 | Physical Chemistry |
Joseph Howard Mathews (October 15, 1881 – April 15, 1970) was an American physical chemist, university professor, and expert on firearm identification. Mathews was Chair of the Department of Chemistry at the University of Wisconsin–Madison for 33 years (1919–1952). | 7 | Physical Chemistry |
He was born in Prague, Czechoslovakia, into a family of some wealth and notability. His undergraduate education began in 1938 when he enrolled to study natural sciences at Charles University. His studies were interrupted the following year when universities were shuttered under the German occupation. Working under the supervision of at Bulovka Hospital, and in a rudimentary laboratory in the basement of his parental home, he discovered a polarographic method of measuring fast chemical reactions. He was awarded a doctorate for this research when Charles University reopened in 1945.
In 1943, he joined a research group at the Fragner pharmaceutical company near Prague that was working to develop a penicillin variant. Despite working in secrecy and isolation under onerous wartime restrictions, the group managed to first separate and then test an antimicrobial drug. Wiesners role included ensuring an adequate supply of the antibiotic by extracting and purifying the substance from the test subjects urine following treatment.
From 1946 until 1948 he conducted postgraduate research in organic chemistry under Vladimir Prelog at ETH, Zürich, funded by a Rockefeller fellowship. Wiesner immigrated to Canada in 1948 to take up a position at the University of New Brunswick, Fredericton. Apart from a two-year spell with the pharmaceutical company Ayerst in Montreal, he remained at UNB for the remainder of his career. In 1981, Wiesner became a founding member of the World Cultural Council. He died of lymphoma in 1986. | 0 | Organic Chemistry |
More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has a low transportation cost per unit of nitrogen nutrient. The most common impurity of synthetic urea is biuret, which impairs plant growth. Urea breaks down in the soil to give ammonium ions (). The ammonium is taken up by the plant through its roots. In some soils, the ammonium is oxidized by bacteria to give nitrate (), which is also a nitrogen-rich plant nutrient. The loss of nitrogenous compounds to the atmosphere and runoff is wasteful and environmentally damaging so urea is sometimes modified to enhance the efficiency of its agricultural use. Techniques to make controlled-release fertilizers that slow the release of nitrogen include the encapsulation of urea in an inert sealant, and conversion of urea into derivatives such as urea-formaldehyde compounds, which degrade into ammonia at a pace matching plants' nutritional requirements. | 0 | Organic Chemistry |
In organofluorine chemistry, many perfluorinated compounds are prepared by electrochemical synthesis, which is conducted in liquid HF at voltages near 5–6 V using Ni anodes. The method was invented in the 1930s. Amines, alcohols, carboxylic acids, and sulfonic acids are converted to perfluorinated derivatives using this technology. A solution or suspension of the hydrocarbon in hydrogen fluoride is electrolyzed at 5–6 V to produce high yields of the perfluorinated product. | 7 | Physical Chemistry |
Akin to the chemistry of alcohols, thiols form sulfides, thioacetals, and thioesters, which are analogous to ethers, acetals, and esters respectively. Thiols and alcohols are also very different in their reactivity, thiols being more easily oxidized than alcohols. Thiolates are more potent nucleophiles than the corresponding alkoxides. | 0 | Organic Chemistry |
In 1997, Tamaru group reported the first metal-catalyzed β-carbon elimination of an unstrained compound. Their work revealed a novel Pd(0)-catalyzed ring opening of 4-vinyl cyclic carbonates. They proposed that the reaction is initiated by the elimination of carbon dioxide to form π-allylpalladium intermediate, which is followed by β-decarbopalladation to form dienals and dienones. Since then, this field has bloomed, and a lot of similar reactions were developed and showed their great potential in organic synthesis. The early stage of research in this field has focused on the reaction of M–O–C–C species and β-carbon elimination of the M–N–C–C intermediate was not discovered until the recent ten years. In 2010, Nakamura reported a Cu-catalyzed substitution reaction of propargylic amines with alkynes or other amines as the first example of the transition-metal-catalyzed β-carbon elimination of amines. | 0 | Organic Chemistry |
FACSS presents several awards to both students and professionals. These awards honor scientists who have made significant contributions to the field of Analytical Chemistry.
*FACSS Student Award and Tomas A. Hirshfeld Award [https://web.archive.org/web/20130901023114/http://www.scixconference.org/awards/facss-2012-student-award-and-tomas-a-hirschfeld-award ]
*SAS Student Poster Awards and FACSS Student Poster Awards [http://www.scixconference.org/awards/sas-student-poster-awards-and-facss-poster-awards ]
*FACSS Distinguished Service Award [http://www.scixconference.org/awards/facss-distinguished-service-award ]
*FACSS Innovation Award [http://www.scixconference.org/awards/facss-innovation-awards-paper ]
*Charles Mann Award for Applied Raman Spectroscopy [http://www.scixconference.org/awards/charles-mann-award ]
*Anachem Award [http://www.scixconference.org/awards/anachem-award ]
*Lester W. Strock Award [http://www.scixconference.org/awards/lester-w-strock-award ]
*Applied Spectroscopy William F. Meggers Award [http://www.scixconference.org/awards/applied-spectroscopy-william-f-meggers-award ]
*Ellis R. Lippincott Award [http://www.scixconference.org/awards/ellis-r-lippincott-award ]
* William G. Fateley Student Award
*Coblentz Society Craver Award [http://www.scixconference.org/awards/coblentz-society-craver-award ]
*ACS Div of Analytical Chem Arthur F. Findeis Award for Achievements by a Young Analytical Scientist [http://www.scixconference.org/awards/acs-division-of-analytical-chemistry-award ]
The FACSS Innovation Award was started in 2011 at the Reno meeting. [http://www.spectroscopynow.com/coi/cda/home.cda;jsessionid=D0EEB34B346A80BAF002DDCA366D8255?chId=6] [http://www.spectroscopyeurope.com/] | 7 | Physical Chemistry |
Odd-chain fatty acids (OCFAs) are those fatty acids that contain an odd number of carbon atoms. The most common OCFAs are the saturated C15 and C17 derivatives, respectively pentadecanoic acid and heptadecanoic acid. The synthesis of even-chained fatty acid synthesis is done by assembling acetyl-CoA precursors, however, propionyl-CoA instead of acetyl-CoA is used as the primer for the biosynthesis of long-chain fatty acids with an odd number of carbon atoms.
;Regulation
In B. subtilis, this pathway is regulated by a two-component system: DesK and DesR. DesK is a membrane-associated kinase and DesR is a transcriptional regulator of the des gene. The regulation responds to temperature; when there is a drop in temperature, this gene is upregulated. Unsaturated fatty acids increase the fluidity of the membrane and stabilize it under lower temperatures. DesK is the sensor protein that, when there is a decrease in temperature, will autophosphorylate. DesK-P will transfer its phosphoryl group to DesR. Two DesR-P proteins will dimerize and bind to the DNA promoters of the des gene and recruit RNA polymerase to begin transcription.
Pseudomonas aeruginosa
In general, both anaerobic and aerobic unsaturated fatty acid synthesis will not occur within the same system, however Pseudomonas aeruginosa and Vibrio ABE-1 are exceptions.
While P. aeruginosa undergoes primarily anaerobic desaturation, it also undergoes two aerobic pathways. One pathway utilizes a Δ-desaturase (DesA) that catalyzes a double bond formation in membrane lipids. Another pathway uses two proteins, DesC and DesB, together to act as a Δ-desaturase, which inserts a double bond into a saturated fatty acid-CoA molecule. This second pathway is regulated by repressor protein DesT. DesT is also a repressor of fabAB expression for anaerobic desaturation when in presence of exogenous unsaturated fatty acids. This functions to coordinate the expression of the two pathways within the organism. | 1 | Biochemistry |
His most-cited publications, according to Google Scholar are:
*Lukinavičius, G., K. Umezawa, N. Olivier, A. Honigmann, G. Yang, T. Plass, V. Mueller, L. Reymond, I. R. Corrêa, Z.-G. Luo, C. Schultz, E. A. Lemke, P. Heppenstall, C. Eggeling, S. Manley and K. Johnsson (2013). [https://doi.org/10.1038/nchem.1546 A near-infrared fluorophore for live-cell super-resolution microscopy of cellular proteins]. Nature Chemistry 5(2): 132-139. (cited 837 times)
*Lukinavičius, G., L. Reymond, E. D’Este, A. Masharina, F. Göttfert, H. Ta, A. Güther, M. Fournier, S. Rizzo, H. Waldmann, C. Blaukopf, C. Sommer, D. W. Gerlich, H.-D. Arndt, S. W. Hell and K. Johnsson (2014). [https://doi.org/10.1038/nmeth.2972 Fluorogenic probes for live-cell imaging of the cytoskeleton]. Nature Methods 11(7):731-3. (cited 817 times)
*Dalhoff C., G. Lukinavičius, S. Klimašauskas and E. Weinhold (2006). [https://doi.org/10.1038/nchembio754 Direct transfer of extended groups from synthetic cofactors by DNA methyltransferases]. Nature Chemical Biology 2, 31-2. (cited 252 times)
*Lukinavičius, G., C. Blaukopf, E. Pershagen, A. Schena, L. Reymond, E. Derivery, M. Gonzalez-Gaitan, E. D’Este, S. W. Hell, D. W. Gerlich and Kai Johnsson (2015). [https://doi.org/10.1038/ncomms9497 SiR–Hoechst is a far-red DNA stain for live-cell nanoscopy]. Nature Communications 6, 8497. (Cited 276 times)
*Liutkevičiūtė, Z., G. Lukinavičius, V. Masevičius, D. Daujotytė and S. Klimašauskas (2009). [https://doi.org/10.1038/nchembio.172 Cytosine-5-methyltransferases add aldehydes to DNA]. Nature Chemical Biology 5, 400-402. (cited 173 times) | 1 | Biochemistry |
FCS is sometimes used to study molecular interactions using differences in diffusion times (e.g. the product of an association reaction will be larger and thus have larger diffusion times than the reactants individually); however, FCS is relatively insensitive to molecular mass as can be seen from the following equation relating molecular mass to the diffusion time of globular particles (e.g. proteins):
where is the viscosity of the sample and is the molecular mass of the fluorescent species. In practice, the diffusion times need to be sufficiently different—a factor of at least 1.6—which means the molecular masses must differ by a factor of 4. Dual color fluorescence cross-correlation spectroscopy (FCCS) measures interactions by cross-correlating two or more fluorescent channels (one channel for each reactant), which distinguishes interactions more sensitively than FCS, particularly when the mass change in the reaction is small. | 7 | Physical Chemistry |
Sulfinic acids RSOH are about 1000x more acidic than the corresponding carboxylic acid RCOH. Sulfur is pyramidal, consequently sulfinic acids are chiral. | 0 | Organic Chemistry |
Originally isolated from Pennicillum compactum in 1969, brevianamide A has shown insecticidal activity. Further studies showed that a minor secondary metabolite, brevianamide B, has an epimeric center at the spiro-indoxyl quaternary center. Both were found to fluoresce under long-wave ultraviolet radiation. Furthermore, under irradaton, brevianamide A has been shown to isomerize to brevianamide B. | 0 | Organic Chemistry |
The bottom of the salt pan () is typically composed of clay lined pools, basalt, sand, concrete, or tile. This keeps the salt from coming into contact with the silt beneath and becoming dirty. Every few days, or on occasion daily, the harvester (French: ) pushes or pulls the salt with a long wooden rake. This must be done carefully as the depth of the brine may be as little as and the clay bottom must not be penetrated at the risk of contaminating the salt. The salt is raked toward the sides of the pan where it is then shoveled into a pile and left to dry slightly before storing. of sel gris can be harvested in one day, whereas for fleurs de sel the daily yield is only . | 9 | Geochemistry |
* Medium energy ion scattering (MEIS) and Rutherford backscattering (RBS) spectroscopies involve a similar setup to LEIS but use ions in the energy range of ~100 keV (MEIS) and ~1-2 MeV (RBS) to probe surfaces. Surface sensitivity is lost as a result of the use of higher energy particles, so while MEIS and RBS can still provide information about a sample they are incapable of providing true first-layer sensitivity.
* Secondary ion mass spectrometry (SIMS) involves the detection of ionic species ejected from a surface as a result of energetic particle impact. While SIMS is capable of giving depth profiles of the elemental composition of a sample, it is an inherently destructive method and is generally does not give structural information.
* X-ray photoelectron spectroscopy (XPS) is capable of surface elemental analysis, but samples a much more broad region of a sample than LEIS and so is not able to distinguish the first layer from subsurface layers. Since XPS relies on ejection of core-level electrons from atoms it is unable to detect hydrogen or helium atoms in a sample.
* Low-energy electron diffraction (LEED) is often used in combination with LEIS in order to facilitate proper sample alignment. LEED can give detailed structural information about a sample including surface superstructures and alignment of adsorbates. LEED is not element-specific and so cannot be used to determine surface elemental composition.
* Auger electron spectroscopy (AES) involves the detection of electrons emitted as a result of core hole excitation and relaxation processes. Since the process involves core levels it is insensitive to hydrogen and helium atoms. AES results may typically be used to infer information on the chemical environment of particular atoms in a surface. | 7 | Physical Chemistry |
In the study of heat transfer, radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation.
Radiative cooling has been applied in various contexts throughout human history, including ice making in India and Iran, heat shields for spacecraft, and in architecture. In 2014, a scientific breakthrough in the use of photonic metamaterials made daytime radiative cooling possible. It has since been proposed as a strategy to mitigate local and global warming caused by greenhouse gas emissions known as passive daytime radiative cooling. | 7 | Physical Chemistry |
Perfect mixing is a term heavily used in relation to the definition of models that predict the behavior of chemical reactors. Perfect mixing assumes that there are no spatial gradients in a given physical envelope, such as:
* concentration (with respect to any chemical species)
* temperature
* chemical potential
* catalytic activity | 7 | Physical Chemistry |
Between 100 million and 280 million tons of phosphogypsum waste are estimated to be produced annually as a consequence of the processing of phosphate rock for the production of phosphate fertilizers. In addition to being useless and abundant, phosphogypsum is radioactive due to the presence of naturally occurring uranium and thorium, and their daughter isotopes. Depending on the price achievable on the uranium market, extraction of the uranium content may be economically lucrative even absent other incentives, such as reducing the harm the radioactive heavy metals do to the environment. | 8 | Metallurgy |
Alcohol and carboxylic acids react in the so-called Fischer esterification. The reaction usually requires a catalyst, such as concentrated sulfuric acid:
Other types of ester are prepared in a similar manner for example, tosyl (tosylate) esters are made by reaction of the alcohol with p-toluenesulfonyl chloride in pyridine. | 0 | Organic Chemistry |
In 2013 Green and a team of researchers launched the BabySeq Project to study the ethical and medical consequences of sequencing a newborn´s DNA.
As of 2015, whole genome and exome sequencing as a newborn screening tool were deliberated. and in 2021, further discussed.
In 2021, the NIH funded BabySeq2, an implementation study that expanded the BabySeq project, enrolling 500 infants from diverse families and track the effects of their genomic sequencing on their pediatric care.
In 2023, the Lancet opined that in the UK "focusing on improving screening by upgrading targeted gene panels might be more sensible in the short term. Whole genome sequencing in the long term deserves thorough examination and universal caution." | 1 | Biochemistry |
Surface plasmons have been used to enhance the surface sensitivity of several spectroscopic measurements including fluorescence, Raman scattering, and second-harmonic generation. In their simplest form, SPR reflectivity measurements can be used to detect molecular adsorption, such as polymers, DNA or proteins, etc. Technically, it is common to measure the angle of minimum reflection (angle of maximum absorption). This angle changes in the order of 0.1° during thin (about nm thickness) film adsorption. (See also the Examples.) In other cases the changes in the absorption wavelength is followed. The mechanism of detection is based on the adsorbing molecules causing changes in the local index of refraction, changing the resonance conditions of the surface plasmon waves. The same principle is exploited in the recently developed competitive platform based on loss-less dielectric multilayers (DBR), supporting surface electromagnetic waves with sharper resonances (Bloch surface waves).
If the surface is patterned with different biopolymers, using adequate optics and imaging sensors (i.e. a camera), the technique can be extended to surface plasmon resonance imaging (SPRI). This method provides a high contrast of the images based on the adsorbed amount of molecules, somewhat similar to Brewster angle microscopy (this latter is most commonly used together with a Langmuir–Blodgett trough).
For nanoparticles, localized surface plasmon oscillations can give rise to the intense colors of suspensions or sols containing the nanoparticles. Nanoparticles or nanowires of noble metals exhibit strong absorption bands in the ultraviolet–visible light regime that are not present in the bulk metal. This extraordinary absorption increase has been exploited to increase light absorption in photovoltaic cells by depositing metal nanoparticles on the cell surface. The energy (color) of this absorption differs when the light is polarized along or perpendicular to the nanowire. Shifts in this resonance due to changes in the local index of refraction upon adsorption to the nanoparticles can also be used to detect biopolymers such as DNA or proteins.
Related complementary techniques include plasmon waveguide resonance, QCM, extraordinary optical transmission, and dual-polarization interferometry. | 7 | Physical Chemistry |
Humans express four epoxide hydrolase isozymes: mEH, sEH, EH3, and EH4. These isozymes are known (mEH and sEH) or presumed (EH3 and EH4) to share a common structure that includes containing an Alpha/beta hydrolase fold and a common reaction mechanism wherein they add water to epoxides to form vicinal cis (see (cis-trans isomerism); see (epoxide#Olefin (alkene) oxidation using organic peroxides and metal catalysts)) diol products. They differ, however, in subcellular location, substrate preferences, tissue expression, and/or function. | 1 | Biochemistry |
The electrochemical promotion of catalysis (EPOC) effect in the realm of chemistry refers to the pronounced enhancement of catalytic reactions or significant changes in the catalytic properties of a conductive catalyst in the presence of electrical currents or interfacial potentials. Also known as Non-faradaic electrochemical modification of catalytic activity (the NEMCA effect), it can increase in catalytic activity (up to 90-fold) and selectivity of a gas exposed electrode on a solid electrolyte cell upon application of a potential. This phenomenon is well documented and has been observed on various surfaces (Ni, Au, Pt, Pd, IrO2, RuO2) supported by O, Na and proton conducting solid electrolytes.
The EPOC effect can also be utilized in a reverse manner in order to influence the selectivity of versatile heterogeneous catalytic reactions. In most cases, the electronically conductive catalyst is in metallic or metal oxide states in the form of a porous film deposited on a solid electrolyte (O or mixed O electronic conductor). The EPOC effect was firstly discovered by M. Stoukides and C. Vayenas in the early 1980s and have been widely studied by various research groups for more than 100 heterogeneous catalytic reactions of mostly gaseous molecules. The EPOC effect has been evaluated as an important phenomenon which can closely link electrocatalysis and thermal catalysis. | 7 | Physical Chemistry |
Generally, the Fischer–Tropsch process is operated in the temperature range of . Higher temperatures lead to faster reactions and higher conversion rates but also tend to favor methane production. For this reason, the temperature is usually maintained at the low to middle part of the range. Increasing the pressure leads to higher conversion rates and also favors the formation of long-chained alkanes, both of which are desirable. Typical pressures range from one to several tens of atmospheres. Even higher pressures would be favorable, but the benefits may not justify the additional costs of high-pressure equipment, and higher pressures can lead to catalyst deactivation via coke formation.
A variety of synthesis-gas compositions can be used. For cobalt-based catalysts the optimal H:CO ratio is around 1.8–2.1. Iron-based catalysts can tolerate lower ratios, due to the intrinsic water-gas shift reaction activity of the iron catalyst. This reactivity can be important for synthesis gas derived from coal or biomass, which tend to have relatively low H:CO ratios (< 1). | 0 | Organic Chemistry |
β-aryl elimination is much less common and understood than β-alkyl elimination. Examples are reported to occur from metal alkoxide and amido complexes. A theoretical study showed that these reactions are driven by consequent extensive conjugation system. A very recent example of catalytic β-aryl elimination which leads to enantioselective synthesis of biaryl atropisomers is driven by release of distorted ring string. | 0 | Organic Chemistry |
A common spectroscopic method for analysis is Fourier transform infrared spectroscopy (FTIR), where chemical bonds can be detected through their characteristic infrared absorption frequencies or wavelengths. These absorption characteristics make infrared analyzers an invaluable tool in geoscience, environmental science, and atmospheric science. For instance, atmospheric gas monitoring has been facilitated by the development of commercially available gas analyzers which can distinguish between carbon dioxide, methane, carbon monoxide, oxygen, and nitric oxide.
Ultraviolet (UV) spectroscopy is used where strong absorption of UV radiation occurs in a substance. Such groups are known as chromophores and include aromatic groups, conjugated system of bonds, carbonyl groups and so on. Nuclear magnetic resonance spectroscopy detects hydrogen atoms in specific environments, and complements both infrared (IR) spectroscopy and UV spectroscopy. The use of Raman spectroscopy is growing for more specialist applications.
There are also derivative methods such as infrared microscopy, which allows very small areas to be analyzed in an optical microscope.
One method of elemental analysis that is important in forensic analysis is energy-dispersive X-ray spectroscopy (EDX) performed in the environmental scanning electron microscope (ESEM). The method involves analysis of back-scattered X-rays from the sample as a result of interaction with the electron beam. Automated EDX is further used in a range of automated mineralogy techniques for identification and textural mapping. | 7 | Physical Chemistry |
In genetic engineering, a gene gun or biolistic particle delivery system is a device used to deliver exogenous DNA (transgenes), RNA, or protein to cells. By coating particles of a heavy metal with a gene of interest and firing these micro-projectiles into cells using mechanical force, an integration of desired genetic information can be introduced into desired cells. The technique involved with such micro-projectile delivery of DNA is often referred to as biolistics, short for "biological ballistics".
This device is able to transform almost any type of cell and is not limited to the transformation of the nucleus; it can also transform organelles, including plastids and mitochondria. | 1 | Biochemistry |
The Advisory Group on Greenhouse Gases, created in 1986, was an advisory body for the review of studies into the greenhouse effect. The group was created by the International Council of Scientific Unions, the United Nations Environment Programme, and the World Meteorological Organization to follow up on the recommendations of the International conference of the Assessment of the role of carbon dioxide and of other greenhouse gases in climate variations and associated impacts, held at Villach, Austria, in October 1985.
The seven-member panel included Swedish meteorologist Bert Bolin and Canadian climatologist Kenneth Hare.
The group held its last meeting in 1990. It was gradually replaced by the Intergovernmental Panel on Climate Change. | 2 | Environmental Chemistry |
The Journal of Organometallic Chemistry is a peer-reviewed scientific journal published by Elsevier, covering research on organometallic chemistry. According to the Journal Citation Reports, the journal has a 2021 impact factor of 2.345. | 0 | Organic Chemistry |
The coefficient lies always in range values equal to 0 or 1), value 1 indicates ideal equal-spreading of the spots, for example (0.25,0.5,0.75) for three solutes, or (0.2,0.4,0.6,0.8) for four solutes.
This coefficient was proposed as an alternative to earlier approaches, such as D (separation response), I (performance index) or S (informational entropy). Besides its stable range, the advantage is a stable distribution as a random variable, regardless of compounds investigated.
In contrast to the similar concept called Retention distance, R is insensitive to R values close to 0 or 1, or close to themselves. If two values are not separated, it still indicates some uniformity of chromatographic system. For example, the R values (0,0.2,0.2,0.3) (two compounds not separated at 0.2 and one at the start ) result in R equal to 0.3609. | 3 | Analytical Chemistry |
One way that Zero Carbon World aims to meet its objectives is the donation of Electric Vehicle Charging stations to various organisations around the UK. Sites that install donated chargers get added to the charity's ZeroNet EV charger map. | 2 | Environmental Chemistry |
adopts three structures, depending on the temperature and the state (solid, liquid, gas). Solid has a sheet-like layered structure with cubic close-packed chloride ions. In this framework, the Al centres exhibit octahedral coordination geometry. Yttrium(III) chloride adopts the same structure, as do a range of other compounds. When aluminium trichloride is in its melted state, it exists as the dimer , with tetracoordinate aluminium. This change in structure is related to the lower density of the liquid phase (1.78 g/cm) versus solid aluminium trichloride (2.48 g/cm). dimers are also found in the vapour phase. At higher temperatures, the dimers dissociate into trigonal planar monomer, which is structurally analogous to boron trifluoride|. The melt conducts electricity poorly, unlike more ionic halides such as sodium chloride.
Aluminium chloride monomer belongs to the point group D in its monomeric form and D in its dimeric form. | 0 | Organic Chemistry |
Push–pull technology involves use of behaviour-modifying stimuli to manipulate the distribution and abundance of stemborers and beneficial insects for management of stemborer pests. It is based on in-depth understanding of chemical ecology, agrobiodiversity, plant-plant and insect-plant interactions, and involves intercropping a cereal crop with a repellent intercrop such as Desmodium uncinatum (silverleaf) (push), with an attractive trap plant such as Napier grass (pull) planted as a border crop around this intercrop. Gravid stemborer females are repelled from the main crop and are simultaneously attracted to the trap crop. | 1 | Biochemistry |
The results of the investigations are internationally evaluated by the members in specialist committees and made available to practice and the responsible bodies at regional and state level, as well as to the European Uninion for legislative and approval procedures. | 1 | Biochemistry |
This compound is originated from mevalonic acid pathway which produce dimethylallyl diphosphate (DMAPP) from acetyl-CoA. Three DMAPPs, or one DMAPP and two isopentenyl diphosphate (IPP), are made into a farnesyl diphosphate (FPP), which is the fundamental precursor of sesquiterpene, and then sesquiterpene cyclise enzymes cause it a cyclization. The synthesis up to here is well known, though process after the first cyclization was unclear.
Anislactone-type sesquiterpenes which merrilactone A belongs to has been thought to be biosynthesized from majucin since they have γ-lactone. However, this pathway has trouble to elucidate some configurations and other feature they have. The biosynthesis shown in the figure was newly proposed and solved these problems.
The point of this pathway is that seco-prezizaane, anislactone and tashironin group which are all found in Illicium are all derived from the same intermediate 6. This is expected to be able to give all characteristic sesquiterpenes in Illicium plants a reasonable explanation of biosynthesis. | 0 | Organic Chemistry |
Crithidia luciliae are haemoflaggelate single celled protists. They are used as a substrate in immunofluorescence for the detection of anti-dsDNA antibodies. They possess an organelle known as the kinetoplast which is a large mitochondrion with a network of interlocking circular dsDNA molecules. After incubation with serum containing anti-dsDNA antibodies and fluorescent-labelled anti-human antibodies, the kinetoplast will fluoresce. The lack of other nuclear antigens in this organelle means that using C. luciliae as a substrate allows for the specific detection of anti-dsDNA antibodies. | 1 | Biochemistry |
Going back to Formula 2, calculation of the thermal contact conductance may prove difficult, even impossible, due to the difficulty in measuring the contact area, (A product of surface characteristics, as explained earlier). Because of this, contact conductance/resistance is usually found experimentally, by using a standard apparatus.
The results of such experiments are usually published in Engineering literature, on journals such as [http://scitation.aip.org/ASMEJournals/HeatTransfer/ Journal of Heat Transfer], [http://www.elsevier.com/wps/find/journaldescription.cws_home/210/description#description International Journal of Heat and Mass Transfer], etc. Unfortunately, a centralized database of contact conductance coefficients does not exist, a situation which sometimes causes companies to use outdated, irrelevant data, or not taking contact conductance as a consideration at all.
[http://sourceforge.net/projects/cocoe/ CoCoE] (Contact Conductance Estimator), a project founded to solve this problem and create a centralized database of contact conductance data and a computer program that uses it, was started in 2006. | 7 | Physical Chemistry |
The wide-ranged biological purposes of bio-luminescence include but are not limited to attraction of mates, defense against predators, and warning signals. In the case of bioluminescent bacteria, bio-luminescence mainly serves as a form of dispersal. It has been hypothesized that enteric bacteria (bacteria that survive in the guts of other organisms) - especially those prevalent in the depths of the ocean - employ bio-luminescence as an effective form of distribution. After making their way into the digestive tracts of fish and other marine organisms and being excreted in fecal pellets, bioluminescent bacteria are able to utilize their bio-luminescent capabilities to lure in other organisms and prompt ingestion of these bacterial-containing fecal pellets. The bio-luminescence of bacteria thereby ensures their survival, persistence, and dispersal as they are able to enter and inhabit other organisms. | 1 | Biochemistry |
The method is similar to the cyanide method above, except sulfuric acid is used to dissolve copper from its ores. The acid is recycled from the solvent extraction circuit (see solvent extraction-electrowinning, SX/EW) and reused on the leach pad. A byproduct is iron(II) sulfate, jarosite, which is produced as a byproduct of leaching pyrite, and sometimes even the same sulfuric acid that is needed for the process. Both oxide and sulfide ores can be leached, though the leach cycles are much different and sulfide leaching requires a bacterial, or bio-leach, component.
In 2011 leaching, both heap leaching and in-situ leaching, produced 3.4 million metric tons of copper, 22 percent of world production. The largest copper heap leach operations are in Chile, Peru, and the southwestern United States.
Although heap leaching is a low cost-process, it normally has recovery rates of 60-70%. It is normally most profitable with low-grade ores. Higher-grade ores are usually put through more complex milling processes where higher recoveries justify the extra cost. The process chosen depends on the properties of the ore.
The final product is cathode copper. | 8 | Metallurgy |
FSL have been used to create human red cell kodecytes that have been used to detect and identify blood group allo-antibodies as ABO sub-group mimics, ABO quality control systems, serologic teaching kits and a syphilis diagnostic. Kodecytes have also demonstrated that FSL-FLRO4 is a suitable reagent for labelling packed red blood cells (PRBC) at any point during routine storage and look to facilitate the development of immunoassays and transfusion models focused on addressing the mechanisms involved in tansfusion-related immunomodulation (TRIM). Murine kodecytes have been experimentally used to determine in vivo cell survival, and create model transfusion reactions. Zebrafish kodecytes have been used to determine real time in vivo cell migration. Kodecytes have been used to create influenza diagnostics. Kodecytes which have been modified with FSL-GB3 were unable to be infected with the HIV virus. | 1 | Biochemistry |
Some synapses dispense with the "middleman" of the neurotransmitter, and connect the presynaptic and postsynaptic cells together. When an action potential reaches such a synapse, the ionic currents flowing into the presynaptic cell can cross the barrier of the two cell membranes and enter the postsynaptic cell through pores known as connexons. Thus, the ionic currents of the presynaptic action potential can directly stimulate the postsynaptic cell. Electrical synapses allow for faster transmission because they do not require the slow diffusion of neurotransmitters across the synaptic cleft. Hence, electrical synapses are used whenever fast response and coordination of timing are crucial, as in escape reflexes, the retina of vertebrates, and the heart. | 7 | Physical Chemistry |
Mechanistically, eukaryotic translation termination matches its prokaryotic counterpart. In this case, termination of the polypeptide chain is achieved through the hydrolytic action of a heterodimer consisting of release factors, eRF1 and eRF3. Translation termination is said to be leaky in some cases as noncoding-tRNAs may compete with release factors to bind stop codons. This is possible due to the matching of 2 out 3 bases within the stop codon by tRNAs that may occasionally outcompete release factor base pairing. An example of regulation at the level of termination is functional translational readthrough of the lactate dehydrogenase gene LDHB. This readthrough provides a peroxisomal targeting signal that localizes the distinct LDHBx to the peroxisome. | 1 | Biochemistry |
DiProDB is a database designed to collect and analyse thermodynamic, structural and other dinucleotide properties. | 4 | Stereochemistry |
The non-covalent interactions between antiparallel strands in DNA can be broken in order to "open" the double helix when biologically important mechanisms such as DNA replication, transcription, DNA repair or protein binding are set to occur. The area of partially separated DNA is known as the denaturation bubble, which can be more specifically defined as the opening of a DNA double helix through the coordinated separation of base pairs.
The first model that attempted to describe the thermodynamics of the denaturation bubble was introduced in 1966 and called the Poland-Scheraga Model. This model describes the denaturation of DNA strands as a function of temperature. As the temperature increases, the hydrogen bonds between the base pairs are increasingly disturbed and "denatured loops" begin to form. However, the Poland-Scheraga Model is now considered elementary because it fails to account for the confounding implications of DNA sequence, chemical composition, stiffness and torsion.
Recent thermodynamic studies have inferred that the lifetime of a singular denaturation bubble ranges from 1 microsecond to 1 millisecond. This information is based on established timescales of DNA replication and transcription. Currently, biophysical and biochemical research studies are being performed to more fully elucidate the thermodynamic details of the denaturation bubble. | 1 | Biochemistry |
The bronze-colored material is one of the strongest reducing agents known. It has also been used as a catalyst in polymerizations and as a coupling reagent for aryl halides to biphenyls. In one study, freshly prepared was treated with 1-iodododecane delivering a modification (micrometre scale carbon platelets with long alkyl chains sticking out providing solubility) that is soluble in chloroform. Another potassium graphite compound, , has been used as a neutron monochromator. A new essential application for potassium graphite was introduced by the invention of the potassium-ion battery. Like the lithium-ion battery, the potassium-ion battery should use a carbon-based anode instead of a metallic anode. In this circumstance, the stable structure of potassium graphite is an important advantage. | 6 | Supramolecular Chemistry |
Apart from life sciences, specialty chemicals -and therefore also their active ingredients, commodities or fine chemicals, as the case may be- are used ubiquitously, in both industrial applications, such as biocides and corrosion inhibitors in cooling water towers, and consumer applications, such as personal care and household products. The active ingredients extend from high-price / low-volume fine chemicals, used for liquid crystal displays to large-volume / low-price amino acids used as feed additives.
fine chemicals merchant market size, growth potential
Examples of applications in eight areas, ranging from adhesives to specialty polymers, are listed in Table 8. Overall, the attractiveness for the fine chemical industry is smaller than the life science industry. The total market, expressed in finished product sales, amounts to $150–200 billion, or about one fourth of the pharma market. The embedded fine chemicals account for an estimated $15 billion (see Table 5). Further disadvantages are the backward integration of the big players, e.g. Akzo-Nobel, Netherlands; Ajinomoto, Japan; Danone, France; Everlight Chemical Industrial Corp., Taiwan; Evonik-Degussa, Germany; Givaudan and Nestlé, Switzerland, Novozymes, Denmark, Procter & Gamble, and Unilever USA. Last but not least, innovation is rather based on new formulations of existing products, rather than the development of new fine chemicals. It is most likely to happen in application areas unrelated to human health (where NCEs are subject to very extensive testing). | 0 | Organic Chemistry |
In 2017, a new method to purify processing bodies was published. Hubstenberger et al. used fluorescence-activated particle sorting (a method based on the ideas of fluorescence-activated cell sorting) to purify processing bodies from human epithelial cells. From these purified processing bodies they were able to use mass spectrometry and RNA sequencing to determine which proteins and RNAs are found in processing bodies, respectively. This study identified 125 proteins that are significantly associated with processing bodies. Notably this work provided the most compelling evidence up to this date that P-bodies might not be the sites of degradation in the cell and instead used for storage of translationally repressed mRNA. This observation was further supported by single molecule imaging of mRNA by the Chao group in 2017.
In 2018, Youn et al. took a proximity labeling approach called BioID to identify and predict the processing body proteome. They engineered cells to express several processing body-localized proteins as fusion proteins with the BirA* enzyme. When the cells are incubated with biotin, BirA* will biotinylate proteins that are nearby, thus tagging the proteins within processing bodies with a biotin tag. Streptavidin was then used to isolate the tagged proteins and mass spectrometry to identify them. Using this approach, Youn et al. identified 42 proteins that localize to processing bodies. | 1 | Biochemistry |
Two main theories exist on microtubule movement within the cell: dynamic instability and treadmilling. Dynamic instability occurs when the microtubule assembles and disassembles at one end only, while treadmilling occurs when one end polymerizes while the other end disassembles. | 1 | Biochemistry |
The second generation of mTOR inhibitors is known as ATP-competitive mTOR kinase inhibitors. mTORC1/mTORC2 dual inhibitors such as torin-1, torin-2 and vistusertib, are designed to compete with ATP in the catalytic site of mTOR. They inhibit all of the kinase-dependent functions of mTORC1 and mTORC2 and block the feedback activation of PI3K/AKT signaling, unlike rapalogs, which only target mTORC1. Development of these drugs has reached clinical trials, although some, such as vistusertib, have been discontinued. Like rapalogs, they decrease protein translation, attenuate cell cycle progression, and inhibit angiogenesis in many cancer cell lines and also in human cancer. In fact, they have been proven to be more potent than rapalogs.
Theoretically, the most important advantages of these mTOR inhibitors is the considerable decrease of AKT phosphorylation on mTORC2 blockade and in addition to a better inhibition on mTORC1. However, some drawbacks exist. Even though these compounds have been effective in rapamycin-insensitive cell lines, they have only shown limited success in KRAS driven tumors. This suggests that combinational therapy may be necessary for the treatment of these cancers. Another drawback is also their potential toxicity. These facts have raised concerns about the long term efficacy of these types of inhibitors.
The close interaction of mTOR with the PI3K pathway has also led to the development of mTOR/PI3K dual inhibitors. Compared with drugs that inhibit either mTORC1 or PI3K, these drugs have the benefit of inhibiting mTORC1, mTORC2, and all the catalytic isoforms of PI3K. Targeting both kinases at the same time reduces the upregulation of PI3K, which is typically produced with an inhibition on mTORC1. The inhibition of the PI3K/mTOR pathway has been shown to potently block proliferation by inducing G1 arrest in different tumor cell lines. Strong induction of apoptosis and autophagy has also been seen. Despite good promising results, there are preclinical evidence that some types of cancers may be insensitive to this dual inhibition. The dual PI3K/mTOR inhibitors are also likely to have increased toxicity. | 1 | Biochemistry |
In titrations, the concentration of analyte in solution can be determined by titrating the standard solution against the analyte solution to determine the threshold of neutralization. For example, to calculate the concentration of hydrogen chloride, a standard solution of known concentration, such as 0.5 M sodium hydroxide, is titrated against the hydrogen chloride solution. | 3 | Analytical Chemistry |
These depend upon analysis of the "halo" of diffracted light produced when a laser beam passes through a dispersion of particles in air or in a liquid. The angle of diffraction increases as particle size decreases, so that this method is particularly good for measuring sizes between 0.1 and 3,000 μm. Advances in sophisticated data processing and automation have allowed this to become the dominant method used in industrial PSD determination. This technique is relatively fast and can be performed on very small samples. A particular advantage is that the technique can generate a continuous measurement for analyzing process streams.
Laser diffraction measures particle size distributions by measuring the angular variation in intensity of light scattered as a laser beam passes through a dispersed particulate sample. Large particles scatter light at small angles relative to the laser beam and small particles scatter light at large angles. The angular scattering intensity data is then analyzed to calculate the size of the particles responsible for creating the scattering pattern, using the Mie theory or Fraunhofer approximation of light scattering. The particle size is reported as a volume equivalent sphere diameter. | 7 | Physical Chemistry |
In boardsports (e.g., surfing, skateboarding and snowboarding), one stands erect on a single, lightweight board that slides along the ground or on water. The need for balance causes one to position the body perpendicular to the direction of motion, with one foot leading the other. As with handedness, when this task is repetitively performed, one tends to naturally choose a particular foot for the leading position. | 4 | Stereochemistry |
This unusual triad occurs only in one superfamily of amidases. In this case, the lysine acts to polarise the middle serine. The middle serine then forms two strong hydrogen bonds to the nucleophilic serine to activate it (one with the side chain hydroxyl and the other with the backbone amide). The middle serine is held in an unusual cis orientation to facilitate precise contacts with the other two triad residues. The triad is further unusual in that the lysine and cis-serine both act as the base in activating the catalytic serine, but the same lysine also performs the role of the acid member as well as making key structural contacts. | 1 | Biochemistry |
Research has shown that men largely view themselves as "passive contributors" since they have "less physical involvement" in IVF treatment. Despite this, many men feel distressed after seeing the toll of hormonal injections and ongoing physical intervention on their female partner. Fertility was found to be a significant factor in a man's perception of his masculinity, driving many to keep the treatment a secret. In cases where the men did share that he and his partner were undergoing IVF, they reported to have been teased, mainly by other men, although some viewed this as an affirmation of support and friendship. For others, this led to feeling socially isolated. In comparison with females, males showed less deterioration in mental health in the years following a failed treatment. However, many men did feel guilt, disappointment and inadequacy, stating that they were simply trying to provide an "emotional rock" for their partners. | 1 | Biochemistry |
Silver nanoparticles are experimentally shown to inhibit autotrophic nitrifying bacterial growth (86±3%) more than Ag ions (42±7%) or AgCl colloids (46±4%). Silver nanoparticle-inhibited heterotrophic growth (55±8%) in Escherichia coli is best observed at lower concentrations, between 1.0 uM and 4.2 uM. This is less than Ag ions (~100%), but greater than AgCl colloids (66±6%). The actual cause of these results is undetermined as growth conditions and cell properties differ between nitrifying bacteria and heterotrophic E. coli. Studies conducted in natural lake environments show less response from bacterioplankton than in laboratory environments when exposed to similar concentrations of silver nanoparticles. This may be due to the binding of free Ag ions to dissolved organic matter in lake environments, rendering the Ag unavailable.
Within toothpaste, Ag ions have been shown to have a stronger effect on gram-negative bacteria than on gram-positive bacteria. In comparison to other nanoparticles, such as gold, silver tends to have a broader antimicrobial effect, which is another reason why it is incorporated into so many products. Ag is less effective on gram-positive bacteria due to the thick layer of peptidoglycan around them that gram-negative species lack. Approximately half of the peptidoglycan wall is composed of teichoic acids linked by phosphodiester bonds, which results in an overall negative charge in the peptidoglycan layer. This negative charge may trap the positive Ag and prevent them from entering the cell and disrupting the flow of electrons. | 2 | Environmental Chemistry |
As a dis-Ability rights activist, Perera has promoted the concept of establishing a society that does not marginalise or discriminate against people on the basis of limited mobility, either for short time, or long time or life time in attending to normal day-to-day life – the principal problem in this context.
He is a fervent advocate of built environments and facilities that are a joy rather than a trial to use by everyone. He has constantly used the weapon of persuasion to convince people that the cumulative result of even small changes could be substantial.
Perera has also pioneered the campaign in Sri Lanka for accessible tourism, recognising it as an overlooked growth market and new profit resource for Sri Lanka.
Perera was also instrumental in proposing to the Sri Lanka Standards Institution (SLSI) and paving the way in persuading them to establish the first Sri Lanka standard for design in building construction SLS ISO TR 9527:2006 in 2007, a fact which Dr. A. R. L. Wijesekera, the then Chairman SLSI, recognised as an achievement of national importance. | 3 | Analytical Chemistry |
Mammalian cell expression systems are essential for the transient production of recombinant proteins and their complementary post-translational modifications. In fact, approximately half of the current commercially available therapeutic proteins are produced in mammalian cells. However, mammalian cell systems' slow growth, precise growth requirements, and potential risk of infection by animal viruses present a number of challenges. As a result, a growing number of mammalian cell lines have been established to serve as hosts for transient recombinant protein production. | 1 | Biochemistry |
Generally, and except for specific continuous-filtering or continuous-cultivating versions, algae scrubbers require the algae to be removed ("harvested") periodically from the scrubber. This removal of algae has the effect of removing undesired nutrients from the water because the algae used the nutrients in order to grow. The algae is generally removed either:
*Every 7 to 21 days, or
*When it is black, or
*When it fills up the scrubber, or
*When it starts letting go, or
*When nutrients start to rise in the water.
For waterfall versions, the screen is removed from the pipe and cleaned in a sink with running water. The pipe is removed also, and the slot is cleaned with a toothbrush, to remove any algae that have grown up into it. After the algae are removed, the screen and pipe are put back in the scrubber. For upflow versions, the cleaning method depends on the type:
Glass-attached version: The magnet portion outside the glass is removed, and the inside portion is lifted out of the water. If the growth is thick green hair algae, then it is just removed by hand. If the growth is thin green hair (as occurs in freshwater) or dark slime, then the inside unit is taken to the sink and cleaned with a toothbrush. After cleaning, the inside and outside parts are put back into place on the glass.
Floating-surface version: If the growth is thick green hair algae then it is just removed by hand by lifting the LED lid up and pulling the growth out. If the growth is thin green hair or dark slime, then the floating portion is taken to the sink and cleaned with a toothbrush.
Drop-in version: The entire unit is lifted out of the water, and the lid is removed. If the growth is thick green hair algae then it is just removed by hand. If the growth is thin green hair or dark slime, then the whole unit is taken to the sink and cleaned with a toothbrush.
If the screen is not cleaned like this periodically, the algae will get too thick and block light and flow from reaching the "roots" of the algae, and these areas will die and let go, putting nutrients back into the water. | 5 | Photochemistry |
Deep-sea hydrothermal vents and their associated fauna were first discovered along the Galapagos Rift in the eastern Pacific in 1977. Vents are now known to occur along all active mid ocean ridges and back-arc spreading centres, from fast to ultra-slow spreading ridges. The interest in chemosynthetic environments was strengthened by the discovery of chemosynthetic-based fauna at cold seeps along the base of the Florida Escarpment in 1983. Cold seeps occur along active and passive continental margins. More recently, the study of chemosynthetic fauna has extended to the communities that develop in other reducing habitats such as whale falls, sunken wood and areas of oxygen minima when they intersect with the margin or seamounts.
Since the first discovery of hydrothermal vents, more than 600 species have been described from vents and seeps. This is equivalent of 1 new description every 2 weeks(!). As biologists, geochemists, and physicists combine research efforts in these systems, new species will certainly be discovered. Moreover, because of the extreme conditions of the vent and seep habitat, certain species may have specific physiological adaptations with interesting results for the biochemical and medical industry.
These globally distributed, ephemeral and insular habitats that support endemic faunas offer natural laboratories for studies on dispersal, isolation and evolution. Here, hydrographic and topographic controls on biodiversity and biogeography might be much more readily resolved than in systems where climate and human activity obscure their role. In addition, hydrothermal vents have been suggested to be the habitat of the origin of life. These hypotheses are being used by ChEss researchers in collaboration with NASA to develop programmes to search for life in planets or moons of the outer space. | 9 | Geochemistry |
On 5 October 2016, Ranga Dias and Isaac F. Silvera of Harvard University released claims of experimental evidence that solid metallic hydrogen had been synthesized in the laboratory at a pressure of around using a diamond anvil cell. This manuscript was available in October 2016, and a revised version was subsequently published in the journal Science in January 2017.
In the preprint version of the paper, Dias and Silvera write:
Silvera stated that they did not repeat their experiment, since more tests could damage or destroy their existing sample, but assured the scientific community that more tests are coming. He also stated that the pressure would eventually be released, in order to find out whether the sample was metastable (i.e., whether it would persist in its metallic state even after the pressure was released).
Shortly after the claim was published in Science, Nature news division published an article stating that some other physicists regarded the result with skepticism. Prominent members of the high pressure research community criticized the claimed results, questioning the claimed pressures or the presence of metallic hydrogen at the pressures claimed.
In February 2017, it was reported that the sample of claimed metallic hydrogen was lost, after the diamond anvils it was contained between broke.
In August 2017, Silvera and Dias issued an erratum to the Science article, regarding corrected reflectance values due to variations between the optical density of stressed natural diamonds and the synthetic diamonds used in their pre-compression diamond anvil cell.
In June 2019 a team at the Commissariat à l'énergie atomique et aux énergies alternatives (French Alternative Energies & Atomic Energy Commission) claimed to have created metallic hydrogen at around 425GPa using a toroidal profile diamond anvil cell produced using electron beam machining.
W. Ferreira et al. (including Dias and Silvera) released a preprint in September 2022 claiming to have repeated the experiment, finding metallisation of hydrogen between 477 and 491 GPa. This time, the pressure was released to assess the question of metastability. They reported that metallic hydrogen was not found to be metastable to zero pressure, and that transformation to the molecular phase likely occurred between 113 and 84 GPa. The authors plan to study the metallisation and metastability of deuterium in the future. | 7 | Physical Chemistry |
Salahuddin was President of Society of Biological Chemists SBC (India) from 1989 to 1990; a Member of the editorial board of Indian Journal of Biochemistry and Biophysics(1985–1988); Visiting Associate Professor, University of Maryland 1975; Member of Protein Society, Bethesda, USA(1995-1997); Member of the New York Academy of Science, New York(1995-1996); Member of the executive committee of the Society of Biological Chemists, India(1974-1975); Member of the executive committee of Indian Biophysical Society, India (1991–1993); Member of the Guha Research Conference, India (1987–1992); and Member of Sigma Xi (USA). | 1 | Biochemistry |
Phenols undergo esterification. Phenol esters are active esters, being prone to hydrolysis. Phenols are reactive species toward oxidation. Oxidative cleavage, for instance cleavage of 1,2-dihydroxybenzene to the monomethylester of 2,4 hexadienedioic acid with oxygen, copper chloride in pyridine Oxidative de-aromatization to quinones also known as the Teuber reaction. and oxone. In reaction depicted below 3,4,5-trimethylphenol reacts with singlet oxygen generated from oxone/sodium carbonate in an acetonitrile/water mixture to a para-peroxyquinole. This hydroperoxide is reduced to the quinole with sodium thiosulfate.
Phenols are oxidized to hydroquinones in the Elbs persulfate oxidation.
Reaction of naphtols and hydrazines and sodium bisulfite in the Bucherer carbazole synthesis. | 0 | Organic Chemistry |
Scleroderma, polymyositis, and dermatomyositis elicit little or no CRP response. CRP levels also tend not to be elevated in systemic lupus erythematosus (SLE) unless serositis or synovitis is present. Elevations of CRP in the absence of clinically significant inflammation can occur in kidney failure. CRP level is an independent risk factor for atherosclerotic disease. Patients with high CRP concentrations are more likely to develop stroke, myocardial infarction, and severe peripheral vascular disease. Elevated level of CRP can also be observed in inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis.
High levels of CRP has been associated to point mutation Cys130Arg in the APOE gene, coding for apolipoprotein E, establishing a link between lipid values and inflammatory markers modulation. | 1 | Biochemistry |
Triethyloxonium tetrafluoroborate is prepared from boron trifluoride, diethyl ether and epichlorohydrin:
where the Et stands for ethyl. The trimethyloxonium salt is available from dimethyl ether via an analogous route. These salts do not have long shelf-lives at room temperature. They degrade by hydrolysis:
The propensity of trialkyloxonium salts for alkyl-exchange can be advantageous. For example, trimethyloxonium tetrafluoroborate, which reacts sluggishly due to its low solubility in most compatible solvents, may be converted in situ to higher alkyl/more soluble oxoniums, thereby accelerating alkylation reactions.
This reagent is useful for esterification of carboxylic acids under conditions where acid-catalyzed reactions are infeasible: | 0 | Organic Chemistry |
A total synthesis reported by Eli Lilly and the University of Southampton in 2007 also starts from isovanillin. The aldehyde group in its derivative 1 is converted to its amine by reductive amination with methylamine which is then protected as a BOC group in 2. The remainder of the carbon framework is added with chiral propargyl alcohol 3 (introducing the 4a stereocenter and obtained by chiral synthesis of the ketone with R-Alpine borane) in a Mitsunobu reaction to aryl ether 4. The trimethylsilyl protective group is removed by potassium carbonate in methanol and the subsequent enyne metathesis reaction with Grubbs' catalyst gives diene 5. A hydroboration–oxidation reaction converts 5 to alcohol 6 and an intramolecular Heck reaction affords tricycle 7 with alkene isomerization and establishment of the 8a stereocenter with correct stereochemistry based on chiral induction. The allyl alcohol group in 8 is introduced by selenoxide oxidation with an excess of the desired diastereomer. In the final step to galanthamine 9 the hydroxyl group is activated as the triflate and the amine group as the mesylate for intramolecular azepine ring closure via nucleophilic substitution (with 6% epimer formation). | 0 | Organic Chemistry |
Denudation is the process of wearing away the top layers of Earths landscape. Because the rate of denudation is normally too small to directly measure, it can be indirectly determined by measuring the sediment load of the streams that drain the area in question. This is possible because any material that passes through a certain point on a stream is guaranteed to have come from somewhere in the streams drainage basin upstream of that point. As topographic relief increases, the dissolved load's contribution to the total stream load decreases due to the fact that on steeper surfaces, rain is less likely to infiltrate the rocks, leading to less chemical weathering, which decreases the dissolved load. | 9 | Geochemistry |
Nonbonded 1,3-diaxial interaction energies are commonly used to approximate strain energy in cyclic molecules, as values for these interactions are available. By taking the difference in nonbonded interactions for each conformer, the equilibrium enthalpy can be estimated. The strain energy for methylidenecyclohexane has been calculated to be 4.5 kcalmol using estimations for 1,3-diaxial strain (0.9 kcalmol), methyl/hydrogen allylic strain (1.3kcalmol), and methyl/methyl allylic strain (7.6 kcalmol) values.
The strain energy in 1,8-dimethylnaphthalene was calculated to be 7.6 kcalmol and around 12-15 kcalmol for 4,5-dimethylphenanthrene. Allylic strain tends to be greater for cyclic molecules compared to olefins as strain energy increases with increasing rigidity of the system. An in depth summary of allylic strain in six membered rings has been presented in a review by Johnson, F. | 4 | Stereochemistry |
One of the hallmarks of cancer is altered metabolism or deregulating cellular energetics. Cancers cells often have reprogrammed their glucose metabolism to perform lactic acid fermentation, in the presence of oxygen, rather than send the pyruvate made through glycolysis to the mitochondria. This is referred to as the Warburg effect and is associated with high consumption of glucose and a high rate of glycolysis. ATP production in these cancer cells is often only through the process of glycolysis and pyruvate is broken down by the fermentation process in the cell's cytoplasm.
This phenomenon is often seen as counterintuitive, since cancer cells have higher energy demands due to the continued proliferation and respiration produces significantly more ATP than glycolysis alone (fermentation produces no additional ATP). Typically, there is an up-regulation in glucose transporters and enzymes in the glycolysis pathway (also seen in yeast). There are many parallel aspects of aerobic fermentation in tumor cells that are also seen in Crabtree-positive yeasts. Further research into the evolution of aerobic fermentation in yeast such as S. cerevisiae can be a useful model for understanding aerobic fermentation in tumor cells. This has a potential for better understanding cancer and cancer treatments. | 1 | Biochemistry |
In cell biology, microtubule-associated proteins (MAPs) are proteins that interact with the microtubules of the cellular cytoskeleton. MAPs are integral to the stability of the cell and its internal structures and the transport of components within the cell. | 1 | Biochemistry |
Electromethanogenesis is a form of electrofuel production where methane is produced by direct biological conversion of electrical current and carbon dioxide.
Methane producing technologies garnered interest from the scientific community prior to 2000, but electromethanogenesis did not become a significant area of interest until 2008. Publications concerning catalytic methanation have increased from 44 to over 130 since 2008. Electromethanogenesis has drawn more research due to its proposed applications. The production of methane from electrical current may provide an approach to renewable energy storage. Electrical current produced from renewable energy sources may, through electromethanogenesis, be converted into methane which may then be used as a biofuel. It may also be a useful method for the capture of carbon dioxide which may be used for air purification.
In nature, methane formation occurs biotically and abiotically. Abiogenic methane is produced on a smaller scale and the required chemical reactions do not necessitate organic materials. Biogenic methane is produced in anaerobic natural environments where methane forms as the result of the breakdown of organic materials by microbes—or microorganisms. Researchers have found that the biogenic methane production process can be replicated in a laboratory environment through electromethanogenesis. The reduction of CO in electromethanogenesis is facilitated by an electrical current at a biocathode in a microbial electrolysis cell (MEC) and with the help of microbes and electrons (Equation 1) or abiotically produced hydrogen (Equation 2).
(1) CO + 8H + 8e ↔ CH + 2HO
(2) CO + 4H ↔ CH + 2HO | 7 | Physical Chemistry |
A number of alloys with the L1 structure (e.g., NiAl, NiGa, NiGe, NiSi), show yield strength anomalies. The L1 structure is a derivative of the face-centered cubic crystal structure. For these alloys, the active slip system below the peak is ⟨110⟩{111} while the active system at higher temperatures is ⟨110⟩{010}. The hardening mechanism in these alloys is the cross slip of screw dislocations from (111) to (010) crystallographic planes. This cross slip is thermally activated, and the screw dislocations are much less mobile on the (010) planes, so the material is strengthened as temperatures increases and more screw dislocations are in the (010) plane. A similar mechanism has been proposed for some B2 alloys that have yield strength anomalies (e.g., CuZn, FeCo, NiTi, CoHf, CoTi, CoZr).
The yield strength anomaly mechanism in Ni-based superalloys is similar. In these alloys, screw superdislocations undergo thermally activated cross slip onto {100} planes from {111} planes. This prevents motion of the remaining parts of the dislocations on the (111)[-101] slip system. Again, with increasing temperature, more cross-slip occurs, so dislocation motion is more hindered and yield strength increases. | 8 | Metallurgy |
Studies on how people transform the substances that they ingest began in the mid-nineteenth century, with chemists discovering that organic chemicals such as benzaldehyde could be oxidized and conjugated to amino acids in the human body. During the remainder of the nineteenth century, several other basic detoxification reactions were discovered, such as methylation, acetylation, and sulfonation.
In the early twentieth century, work moved on to the investigation of the enzymes and pathways that were responsible for the production of these metabolites. This field became defined as a separate area of study with the publication by Richard Williams of the book Detoxication mechanisms in 1947. This modern biochemical research resulted in the identification of glutathione S-transferases in 1961, followed by the discovery of cytochrome P450s in 1962, and the realization of their central role in xenobiotic metabolism in 1963. | 1 | Biochemistry |
The major tissue systems present are
* The epidermis, which covers the upper and lower surfaces
* The mesophyll tissue, which consists of photosynthetic cells rich in chloroplasts. (also called chlorenchyma)
* The arrangement of veins (the vascular tissue)
These three tissue systems typically form a regular organization at the cellular scale. Specialized cells that differ markedly from surrounding cells, and which often synthesize specialized products such as crystals, are termed idioblasts. | 5 | Photochemistry |
Anfinsens dogma, also known as the thermodynamic hypothesis, is a postulate in molecular biology. It states that, at least for a small globular protein in its standard physiological environment, the native structure is determined only by the proteins amino acid sequence. The dogma was championed by the Nobel Prize Laureate Christian B. Anfinsen from his research on the folding of ribonuclease A. The postulate amounts to saying that, at the environmental conditions (temperature, solvent concentration and composition, etc.) at which folding occurs, the native structure is a unique, stable and kinetically accessible minimum of the free energy. In other words, there are three conditions for formation of a unique protein structure:
*Uniqueness – Requires that the sequence does not have any other configuration with a comparable free energy. Hence the free energy minimum must be unchallenged.
*Stability – Small changes in the surrounding environment cannot give rise to changes in the minimum configuration. This can be pictured as a free energy surface that looks more like a funnel (with the native state in the bottom of it) rather than like a soup plate (with several closely related low-energy states); the free energy surface around the native state must be rather steep and high, in order to provide stability.
*Kinetical accessibility – Means that the path in the free energy surface from the unfolded to the folded state must be reasonably smooth or, in other words, that the folding of the chain must not involve highly complex changes in the shape (like knots or other high order conformations). Basic changes in the shape of the protein happen dependent on their environment, shifting shape to suit their place. This creates multiple configurations for biomolecules to shift into. | 1 | Biochemistry |
The precise mechanism of action of modafinil for narcolepsy and other sleep disorders remains unclear. Although modafinil may have interactions with neurotransmitter systems, its exact mode of action is not fully understood.
From laboratory research, modafinil has little to no affinity for serotonin or norepinephrine transporters and does not directly interact with these systems. However, studies have shown that elevated concentrations of norepinephrine and serotonin can occur as an indirect effect following modafinil administration due to increased extracellular dopamine activity. Unlike traditional psychostimulant drugs, such as cocaine or amphetamine, modafinil shows low potential for causing euphoria due to differences in how it interacts with dopamine transporters at a cellular level.
In addition to its influence on dopaminergic pathways, modafinil may impact other neurotransmitter systems, such as orexin or hypocretin. Orexin neurons play a crucial role in promoting wakefulness and regulating arousal states. Modafinil may increase signaling within hypothalamic orexin pathways, potentially contributing to its wake-promoting effects. | 4 | Stereochemistry |
In the 1940s Craig invented the first apparatus to conduct countercurrent partitioning; he called this the countercurrent distribution Craig apparatus. The apparatus consists of a series of glass tubes that are designed and arranged such that the lighter liquid phase is transferred from one tube to the next. The next major milestone was droplet countercurrent chromatography (DCCC). It uses only gravity to move the mobile phase through the stationary phase which is held in long vertical tubes connected in series. The modern era of CCC began with the development of the planetary centrifuge by Ito which was first introduced in 1966 as a closed helical tube which was rotated on a "planetary" axis as is turned on a "sun" axis.
Centrifugal partition chromatography was introduced in Japan in 1982; the first instrument was built at Sanki Eng. Ltd. in Kyoto. The first instrument consisted of twelve cartridges arranged around the rotor of a centrifuge; the inner volume of each cartridge was about 15 mL for 50 channels. In 1999 Kromaton developed the first FCPC with radial cells. During cell development, the Z cell was completed in 2005 and the twin cell in 2009. In 2017 RotaChrom designed its top performing CPC cells through computed fluid dynamic simulation software. After thousands of simulations, this tool revealed the drawbacks of conventional CPC cell designs and highlighted the unparallel load capacity and scalable cell design of RotaChrom. | 3 | Analytical Chemistry |
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