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Tetsuo Nozoe was born on 16 May 1902 in Sendai to Juichi Nozoe, a lawyer and one-time member of the National Diet, and Toyo Nozoe. Tetsuo's family was Buddhist except of his mother who was a devout Christian. Tetsuo had three sisters and seven brothers, and he was the sixth child in the family. He started doing chemical experiments at home since his junior high school days. Although his parents wanted him to become a medical doctor, and even sent him for premedical classes, he proceeded his education with chemistry. After graduating from high school in Sendai, he entered the Department of Chemistry at Tohoku Imperial University in 1920. In university, he studied organic chemistry under Riko Majima, a leading scientist in organic chemistry in Japan.
In 1926, after graduation he moved to Taihoku, Formosa , where he started working as a researcher at the Camphor Research Laboratories of the Monopoly Bureau and then at the Department of Chemical Industry of the Central Research Institute, both under Government-General of Taipei. In Formosa, Tetsuo was studying the structures of natural compounds, such as saponins, sapogins, sapogenins, triterpenoids and glycosides, especially in plants found locally. In 1937, with the help of ultraviolet–visible spectroscopy he predicted the correct structures for oleanolic acid and hederagenin, common sapogenins. In the same year he became a professor of chemistry at Taihoku Imperial University. The scope of his research in those times included also studying constituents of wool wax and those of other animal skin waxes. He discovered lanolinic acids and agnolinic acids, groups of unusual branched chain fatty acids.
One of the most popular works of Tesuo Nozoe was the research on the chemical constituents of taiwanhinoki (Chamaecyparis taiwanensis, Taiwan cypress), a coniferous tree native to Taiwan. The natural resistance of this and other tree species belonging to Cupressaceae family to fungal wood decay prompted Japanese researchers to study the chemical components of these trees. Nenokichi Hirao, a Japanese chemist, derived a dark-red pigment from hinoki oil and called hinokitin in 1926. Tetsos research led to discovery of a new series of chemical compounds, non-benzoniod aromatic compounds, including hinokitiol. He obtained hinokitiol from hinokitin, and showed that hinokitin is an iron complex of hinokitiol, (CHO)Fe. It was first published in 1936 in a special issue of the Bulletin of the Chemical Society of Japan. After three more years of work in Formosa following the World War II, Tetsuo returned to Japan. As a professor at Tohoku University, he continued his work on hinokitiol. Later in 1948, Holger Erdtman, a Scottish organic chemist, reported isolation of three isomeric monoterpenoids (α-, β-, and γ-thujaplicin) from Thuja plicata (Western red cedar) in his paper published in Nature. After correspondence, both Tetsuo and Holger found that hinokitiol is identical to β-thujaplicin and has a tropolone structure. Tetsuo Nozoe and Holger Erdtman became lifelong friends. In 1951, Nozoe got an opportunity to publish his work on hinokitiol and its derivatives in Nature'. He also studied chemical characteristics of tropones, tropolones, other troponoids, and azulenes. | 0 | Organic Chemistry |
The Dortmund Data Bank (short DDB) is a factual data bank for thermodynamic and thermophysical data. Its main usage is the data supply for process simulation where experimental data are the basis for the design, analysis, synthesis, and optimization of chemical processes. The DDB is used for fitting parameters for thermodynamic models like NRTL or UNIQUAC and for many different equations describing pure component properties, e.g., the Antoine equation for vapor pressures. The DDB is also used for the development and revision of predictive methods like UNIFAC and PSRK. | 7 | Physical Chemistry |
* 2009 Nexxus Young Life Scientist of the Year
* 2013 Royal Society of Chemistry (RSC) Joseph Black Award
* 2016 Top 50 Women in Analytical Science
* 2016 Coblentz Society Craver Award
* 2017 The Analytical Scientist Top 10 Spectroscopists
* 2018 Elected Fellow of the Royal Society of Edinburgh (FRSE)
* 2023 The Analytical Scientist the Power List - Connectors and Interdisciplinarians
Faulds is a Fellow of the Society for Applied Spectroscopy (SAS) and a member of the Young Academy of Scotland (YAS).
In 2019 Faulds was included in the 2019 Power List of The Analytical Scientist. | 3 | Analytical Chemistry |
* The remaining CGN codons are rare in Saccharomyces cerevisiae and absent in Candida glabrata.
* The AUA codon is common in the gene var1 coding for the single mitochondrial ribosomal protein, but rare in genes encoding the enzymes.
* The coding assignments of the AUA (Met or Ile) and CUU (possibly Leu, not Thr) are uncertain in Hansenula saturnus.
* The coding assignment of Thr to CUN is uncertain in Kluyveromyces thermotolerans. | 1 | Biochemistry |
Hormone transport and the involvement of binding proteins is an essential aspect when considering the function of hormones.
The formation of a complex with a binding protein has several benefits: the effective half-life of the bound hormone is increased, and a reservoir of bound hormones is created, which evens the variations in concentration of unbound hormones (bound hormones will replace the unbound hormones when these are eliminated). An example of the usage of hormone-binding proteins is in the thyroxine-binding protein which carries up to 80% of all thyroxine in the body, a crucial element in regulating the metabolic rate. | 1 | Biochemistry |
Certain methyl groups can be deprotonated. For example, the acidity of the methyl groups in acetone () is about 10 times more acidic than methane. The resulting carbanions are key intermediates in many reactions in organic synthesis and biosynthesis. Fatty acids are produced in this way. | 0 | Organic Chemistry |
In organic chemistry, cyclopentanonide is a functional group which is composed of a cyclic ketal of a diol with cyclopentanone. It is seen in amcinonide (triamcinolone acetate cyclopentanonide). | 0 | Organic Chemistry |
Only a small fraction of the light incident on the ocean will be reflected and received by the satellite. The probability for a photon to reflect and exit the ocean decreases exponentially with length of its path through the water because the ocean is an absorbing medium. The more ocean a photon must travel through, the greater its chances of being absorbed by something. After absorption, it will eventually become part of the ocean's heat reservoir. The absorption and scattering characteristics of a water body determine the rate of vertical light attenuation and set a limit to the depths contributing to a satellite signal. A reasonable rule of thumb is that 90 percent of the signal coming from the water that is seen by the satellite is from the first attenuation length. How deep this is depends on the absorption and scattering properties of both the water itself and other constituents in the water. For wavelengths in the near infrared and longer, the penetration depth varies from a metre to a few micrometres. For band 1, the penetration depth will usually be between 1 and 10 metres. If the water has a large turbidity spike below 10 metres, the spike is unlikely to be seen by a satellite.
For very shallow clear water there is a good chance the bottom may be seen. For example, in the Bahamas, the water is quite clear and only a few metres deep, resulting in an apparent high turbidity because the bottom reflects much band 1 light. For areas with consistently high turbidity signals, particularly areas with relatively clear water, part of the signal may be due to bottom reflection. Normally this will not be a problem with a post-hurricane turbidity image since the storm easily resuspends enough sediment such that bottom reflection is negligible.
Clouds are also problematic for the interpretation of satellite derived turbidity. Cloud removal algorithms perform a satisfactory job for pixels that are fully cloudy. Partially cloudy pixels are much harder to identify and typically result in false high turbidity estimates. High turbidity values near clouds are suspect. | 3 | Analytical Chemistry |
Metal oxides excel at catalyzing gas phase reactions by photo-activation, as well as thermal activation of the catalyst. Oxidation of hydrocarbons, alcohols, carbon monoxide, and ammonia occurs when stimulated with light of greater energy than the band gap of the metal oxide. Homophasic and heterophasic light-induced oxygen isotope exchange has also been observed over TiO and ZnO. Homophasic isotope exchange is the production of from and . Heterophasic isotope exchange is the chemisorption of an oxygen isotope to the lattice of the metal oxide (lat), and replacement of one of the oxygens in the gas phase with the lattice oxygen as shown in the following reaction. | 7 | Physical Chemistry |
The main application of size-exclusion chromatography is the fractionation of proteins and other water-soluble polymers, while gel permeation chromatography is used to analyze the molecular weight distribution of organic-soluble polymers. Either technique should not be confused with gel electrophoresis, where an electric field is used to "pull" molecules through the gel depending on their electrical charges. The amount of time a solute remains within a pore is dependent on the size of the pore. Larger solutes will have access to a smaller volume and vice versa. Therefore, a smaller solute will remain within the pore for a longer period of time compared to a larger solute.
Another use of size exclusion chromatography is to examine the stability and characteristics of natural organic matter in water. In this method, Margit B. Müller, Daniel Schmitt, and Fritz H. Frimmel tested water sources from different places in the world to determine how stable the natural organic matter is over a period of time. Even though size exclusion chromatography is widely utilized to study natural organic material, there are limitations. One of these limitations include that there is no standard molecular weight marker; thus, there is nothing to compare the results back to. If precise molecular weight is required, other methods should be used. | 1 | Biochemistry |
Mice treated with tetrahydrocannabinol (THC) show suppression of long-term potentiation in the hippocampus, a process that is essential for the formation and storage of long-term memory. These results may concur with anecdotal evidence suggesting that smoking cannabis impairs short-term memory. Consistent with this finding, mice without the CB receptor show enhanced memory and long-term potentiation indicating that the endocannabinoid system may play a pivotal role in the extinction of old memories. One study found that the high-dose treatment of rats with the synthetic cannabinoid HU-210 over several weeks resulted in stimulation of neural growth in the rats' hippocampus region, a part of the limbic system playing a part in the formation of declarative and spatial memories, but did not investigate the effects on short-term or long-term memory. Taken together, these findings suggest that the effects of endocannabinoids on the various brain networks involved in learning and memory may vary. | 1 | Biochemistry |
The current version, HITRAN2020, contains 55 molecules in the line-by-line portion of HITRAN along with some of their most significant isotopologues (144 isotopologues in total). These data are archived as a multitude of high-resolution line transitions, each containing many spectral parameters required for high-resolution simulations. | 7 | Physical Chemistry |
Plasma electrolytic oxidation (PEO), also known as electrolytic plasma oxidation (EPO) or microarc oxidation (MAO), is an electrochemical surface treatment process for generating oxide coatings on metals. It is similar to anodizing, but it employs higher potentials, so that discharges occur and the resulting plasma modifies the structure of the oxide layer. This process can be used to grow thick (tens or hundreds of micrometers), largely crystalline, oxide coatings on metals such as aluminium, magnesium and titanium. Because they can present high hardness and a continuous barrier, these coatings can offer protection against wear, corrosion or heat as well as electrical insulation.
The coating is a chemical conversion of the substrate metal into its oxide, and grows both inwards and outwards from the original metal surface. Because it grows inward into the substrate, it has excellent adhesion to the substrate metal. A wide range of substrate alloys can be coated, including all wrought aluminum alloys and most cast alloys, although high levels of silicon can reduce coating quality. | 8 | Metallurgy |
Cyclodextrins (CDs) are cyclic oligosaccharides of six, seven, or eight glucose units designated as α, β, and γ cyclodextrins respectively. Depicted in the diagram below. Daniel Armstrong is considered the pioneer of micelle and cyclodextrin-based separations. Cyclodextrins are covalently attached to silica by Armstrong process and provide stable CSPs. The primary hydroxyl groups are used to anchor the CD molecules to the modified silica surface. CDs are chiral because of innate chirality of the building blocks, glucose units. In cyclodextrin the glucose units are α-(1,4)- connected. The shape of CD looks like a shortened cone (see the sketch). The inner surface of the cone forms moderately hydrophobic pocket. The width of the CD-cavity is identified with the quantity of glucose units present. In cyclodextrins, secondary hydroxyl groups (OH-2 and - 3) line the upper rim of the cavity, and an essential 6-hydroxyl group is positioned at the lower rim. The hydroxyl group offer chiral binding points, which appear to be fundamental for enantioselectivity. Apolar glyosidic oxygen makes the pit hydrophobic and guarantees inclusion complexing of the hydrophobic moiety of analytes. Interactions between the polar area of an analyte and secondary hydroxyl groups at the mouth of the pit, joined with the hydrophobic connections inside the pit, give a unique two-point fit and lead to enantioselectivity.
Selectivity of a cyclodextrin phase is dependent on two key factors namely the size and structure of the analyte since it is based on a simple fit-unfit geometric criteria. An aromatic ring or cycloalkyl ring should be attached near the stereogenic center of the analyte. Substituents at or near the analyte chiral center must be able to interact with the hydroxyl groups at the entrance of the CD cavity through H-bonding. α-Cyclodextrin holds small aromatic molecules, whereas β-cyclodextrin incorporates both naphthyl groups and substituted phenyl groups. The aqueous compatibility of CD and its unique molecular structure make the CD- bonded phase highly suitable for use in chiral HPLC analysis of drugs. One further benefit of CD is that they are generally less expensive than the other CSPs. Some of the major shortcomings of CD CSPs is that it is limited to compounds that can enter into CD cavity, minor structural changes in analyte leads to unpredictable effect on resolution, often poor efficiency and cannot invert elution order.
Enantiomers of propranolol, metoprolol, chlorpheniramine, verapamil, hexobarbitaI, methadone and much more drugs have been separated using immobilized β-cyclodextrin.
Initially natural CDs have been used as the chiral selector. Later, modified cyclodextrin structures have been prepared by derivatizing the secondary hydroxyl groups present on the CD molecule. Incorporation of these additional functional groups may improve the chiral recognition capability by possibly modifying the chiral pocket and creating extra auxiliary interaction site. This approach enabled to expand the range of target chiral analytes that could be separated. A number of chiral pharmaceuticals has been resolved using derivatized CDs including ibuprofen, suprofen, flurbiprofen from NSAID category and b-blockers like metoprolol and atenolol. A brief list of cyclodextrin-based chiral stationary stationary phases available in the market is furnished in the table below. | 4 | Stereochemistry |
Surface stress was first defined by Josiah Willard Gibbs (1839–1903) as the amount of the reversible work per unit area needed to elastically stretch a pre-existing surface. Depending upon the convention used, the area is either the original, unstretched one which represents a constant number of atoms, or sometimes is the final area; these are atomistic versus continuum definitions. Some care is needed to ensure that the definition used is also consistent with the elastic strain energy, and misinterpretations and disagreements have occurred in the literature.
A similar term called "surface free energy", the excess free energy per unit area needed to create a new surface, is sometimes confused with "surface stress". Although surface stress and surface free energy of liquid–gas or liquid–liquid interface are the same, they are very different in solid–gas or solid–solid interface. Both terms represent an energy per unit area, equivalent to a force per unit length, so are sometimes referred to as "surface tension", which contributes further to the confusion in the literature. | 7 | Physical Chemistry |
Foldit's developers wanted to attract as many people as possible to the cause of protein folding. So, rather than only building a useful science tool, they used gamification (the inclusion of gaming elements) to make Foldit appealing and engaging to the general public.
As a protein structure is modified, a score is calculated based on how well-folded the protein is, and a list of high scores for each puzzle is maintained. Foldit users may create and join groups, and members of groups can share puzzle solutions. Groups have been found to be useful in training new players. A separate list of group high scores is maintained. | 1 | Biochemistry |
Typical stages in 5S rRNA (also termed class I) gene initiation:
*TFIIIA (Transcription Factor for polymerase III A) binds to the intragenic (lying within the transcribed DNA sequence) 5S rRNA control sequence, the C Block (also termed box C).
*TFIIIA serves as a platform that replaces the A and B Blocks for positioning TFIIIC in an orientation with respect to the start site of transcription that is equivalent to what is observed for tRNA genes.
*Once TFIIIC is bound to the TFIIIA-DNA complex, the assembly of TFIIIB proceeds as described for tRNA transcription. | 1 | Biochemistry |
Mycoremediation can even be used for fire management with the encapsulation method. This process consists of using fungal spores coated with agarose in a pellet form, which is introduced to a substrate in the burnt forest, breaking down toxins and stimulating growth. | 2 | Environmental Chemistry |
The olfactory receptor neuron has a fast working negative feedback response upon depolarization. When the neuron is depolarizing, the CNG ion channel is open allowing sodium and calcium to rush into the cell. The influx of calcium begins a cascade of events within the cell. Calcium first binds to calmodulin to form CaM. CaM will then bind to the CNG channel and close it, stopping the sodium and calcium influx. CaMKII will be activated by the presence of CaM, which will phosphorylate ACIII and reduce cAMP production. CaMKII will also activate phosphodiesterase, which will then hydrolyze cAMP. The effect of this negative feedback response inhibits the neuron from further activation when another odor molecule is introduced. | 1 | Biochemistry |
In eukaryote cells, RNA polymerase III (also called Pol III) is a protein that transcribes DNA to synthesize 5S ribosomal RNA, tRNA, and other small RNAs.
The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose expression is required in all cell types and most environmental conditions. Therefore, the regulation of Pol III transcription is primarily tied to the regulation of cell growth and the cell cycle and thus requires fewer regulatory proteins than RNA polymerase II. Under stress conditions, however, the protein Maf1 represses Pol III activity. Rapamycin is another Pol III inhibitor via its direct target TOR. | 1 | Biochemistry |
The Tafel equation is an equation in electrochemical kinetics relating the rate of an electrochemical reaction to the overpotential. The Tafel equation was first deduced experimentally and was later shown to have a theoretical justification. The equation is named after Swiss chemist Julius Tafel.
Where an electrochemical reaction occurs in two half reactions on separate electrodes, the Tafel equation is applied to each electrode separately. On a single electrode the Tafel equation can be stated as:
where
* the plus sign under the exponent refers to an anodic reaction, and a minus sign to a cathodic reaction,
* : overpotential, V
* : "Tafel slope", V
* : current density, A/m
* : "exchange current density", A/m.
A verification plus further explanation for this equation can be found here. The Tafel equation is an approximation of the Butler-Volmer equation in the case of . Also, at a given electrode the Tafel equation assumes that the reverse half reaction rate is negligible compared to the forward reaction rate. | 7 | Physical Chemistry |
During World War II, various chloroalkanes were in standard use in military aircraft, although these early halons suffered from excessive toxicity. Nevertheless, after the war they slowly became more common in civil aviation as well. In the 1960s, fluoroalkanes and bromofluoroalkanes became available and were quickly recognized as being highly effective fire-fighting materials. Much early research with Halon 1301 was conducted under the auspices of the US Armed Forces, while Halon 1211 was, initially, mainly developed in the UK. By the late 1960s they were standard in many applications where water and dry-powder extinguishers posed a threat of damage to the protected property, including computer rooms, telecommunications switches, laboratories, museums and art collections. Beginning with warships, in the 1970s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel.
By the early 1980s, bromofluoroalkanes were in common use on aircraft, ships, and large vehicles as well as in computer facilities and galleries. However, concern was beginning to be expressed about the impact of chloroalkanes and bromoalkanes on the ozone layer. The Vienna Convention for the Protection of the Ozone Layer did not cover bromofluoroalkanes under the same restrictions, instead, the consumption of bromofluoroalkanes was frozen at 1986 levels. This is due to the fact that emergency discharge of extinguishing systems was thought to be too small in volume to produce a significant impact, and too important to human safety for restriction. | 2 | Environmental Chemistry |
A few stable nitronium salts with anions of weak nucleophilicity can be isolated. These include nitronium perchlorate , nitronium tetrafluoroborate , nitronium hexafluorophosphate , nitronium hexafluoroarsenate , and nitronium hexafluoroantimonate . These are all very hygroscopic compounds.
The solid form of dinitrogen pentoxide, , actually consists of nitronium and nitrate ions, so it is an ionic compound, nitronium nitrate , not a molecular solid. However, dinitrogen pentoxide in liquid or gaseous state is molecular and does not contain nitronium ions. | 0 | Organic Chemistry |
The Merv Oasis had been extensively explored in 1904 by an American team; however, the reports published were of a preliminary nature. During the period 1940–50, the Asian Republics started establishing archaeological institutions in their respective countries. Among them, the South Turkmenistan Complex Archaeological Expedition was established in 1946 by Masson under the aegis of the Turkmenistan Academy of Sciences to carry out explorations at several locations. These explorations included:
* 1947-1952: exploration by Alexey Okladnikov of mesolithic sites
* 1940s and 1950s: Eneolithic and Bronze Age excavations by Boris Kuftin
* 1955-62: excavations by V.M. Masson, I.N. Khlopin, and Viktor Sarianidi of neolithic sites at many locations, including Jietun at the Geoksur Oasis
* Since 1965: Bronze Age excavations by Masson covering, among others, the site at Altyndepe
* Excavations by G. N. Lisitsyna to investigate the prehistoric economies and irrigation systems.
* 1977-92: explorations by Khlopin in the Sumbar Valley
Since 1992, excavations have been carried out by a joint project titled “Turkmen-British-Merv Project”. This has yielded historical data on fortifications and a residential complex of the Hellenistic, Parthina and Sassanian period. | 8 | Metallurgy |
The pyridinium dichromate (PDC) or Cornforth reagent is a pyridinium salt of dichromate with the chemical formula [CHNH][CrO]. This compound is named after the Australian-British chemist Sir John Warcup Cornforth (b. 1917) who introduced it in 1962. The Cornforth reagent is a strong oxidizing agent which can convert primary and secondary alcohols to aldehydes and ketones respectively. In its chemical structure and functions it is closely related to other compounds made from hexavalent chromium oxide, such as pyridinium chlorochromate and Collins reagent. Because of their toxicity, these reagents are rarely used nowadays. | 0 | Organic Chemistry |
Coronaviruses are enveloped viruses with a positive-sense RNA genome and with a nucleocapsid of helical symmetry. They infect the upper respiratory and gastrointestinal tract of mammals and birds. They are the cause of a wide range of diseases in cats, dog, pigs, rodents, cattle and humans. Transmission is by the faecal-oral route. | 1 | Biochemistry |
The most common synthesis method of gold(III) bromide is heating gold and excess liquid bromine at 140 °C:
Alternatively, the halide-exchange reaction of gold(III) chloride with hydrobromic acid has also been proven successful in synthesizing gold(III) bromide:
This reaction is driven by the production of the relatively more stable hydrochloric acid compared with hydrobromic acid. | 3 | Analytical Chemistry |
Phosgene is an insidious poison as the odor may not be noticed and symptoms may be slow to appear.
The odor detection threshold for phosgene is 0.4 ppm, four times the threshold limit value (time weighted average). Its high toxicity arises from the action of the phosgene on the , and groups of the proteins in pulmonary alveoli (the site of gas exchange), respectively forming ester, amide and thioester functional groups in accord with the reactions discussed above. This results in disruption of the blood–air barrier, eventually causing pulmonary edema. The extent of damage in the alveoli does not primarily depend on phosgene concentration in the inhaled air, with the dose (amount of inhaled phosgene) being the critical factor. Dose can be approximately calculated as "concentration" × "duration of exposure". Therefore, persons in workplaces where there exists risk of accidental phosgene release usually wear indicator badges close to the nose and mouth. Such badges indicate the approximate inhaled dose, which allows for immediate treatment if the monitored dose rises above safe limits.
In case of low or moderate quantities of inhaled phosgene, the exposed person is to be monitored and subjected to precautionary therapy, then released after several hours. For higher doses of inhaled phosgene (above 150 ppm × min) a pulmonary edema often develops which can be detected by X-ray imaging and regressive blood oxygen concentration. Inhalation of such high doses can eventually result in fatality within hours up to 2–3 days of the exposure.
The risk connected to a phosgene inhalation is based not so much on its toxicity (which is much lower in comparison to modern chemical weapons like sarin or tabun) but rather on its typical effects: the affected person may not develop any symptoms for hours until an edema appears, at which point it could be too late for medical treatment to assist. Nearly all fatalities as a result of accidental releases from the industrial handling of phosgene occurred in this fashion. On the other hand, pulmonary edemas treated in a timely manner usually heal in the mid- and longterm, without major consequences once some days or weeks after exposure have passed. Nonetheless, the detrimental health effects on pulmonary function from untreated, chronic low-level exposure to phosgene should not be ignored; although not exposed to concentrations high enough to immediately cause an edema, many synthetic chemists (e.g. Leonidas Zervas) working with the compound were reported to experience chronic respiratory health issues and eventual respiratory failure from continuous low-level exposure.
If accidental release of phosgene occurs in an industrial or laboratory setting, it can be mitigated with ammonia gas; in the case of liquid spills (e.g. of diphosgene or phosgene solutions) an absorbent and sodium carbonate can be applied. | 0 | Organic Chemistry |
In July 2020 researchers report the discovery of chemolithoautotrophic bacterial culture that feeds on the metal manganese after performing unrelated experiments and named its bacterial species Candidatus Manganitrophus noduliformans and Ramlibacter lithotrophicus. | 1 | Biochemistry |
The term radiative cooling is generally used for local processes, though the same principles apply to cooling over geological time, which was first used by Kelvin to estimate the age of the Earth (although his estimate ignored the substantial heat released by radioisotope decay, not known at the time, and the effects of convection in the mantle). | 7 | Physical Chemistry |
The diffuse series used to be called the first subordinate series, with the sharp series being the second subordinate, both being subordinate to (less intense than) the principal series. | 7 | Physical Chemistry |
PEP carboxylase is mainly subject to two levels of regulation: phosphorylation and allostery. Figure 3 shows a schematic of the regulatory mechanism.
Phosphorylation by phosphoenolpyruvate carboxylase kinase turns the enzyme on, whereas phosphoenolpyruvate carboxylase phosphatase turns it back off. Both kinase and phosphatase are regulated by transcription. It is further believed that malate acts as a feedback inhibitor of kinase expression levels, and as an activator for phosphatase expression (transcription). Since oxaloacetate is converted to malate in CAM and organisms, high concentrations of malate activate phosphatase expression - the phosphatase subsequently de-phosphorylates and thus de-actives PEP carboxylase, leading to no further accumulation of oxaloacetate and thus no further conversion of oxaloacetate to malate. Hence malate production is down-regulated.
The main allosteric inhibitors of PEP carboxylase are the carboxylic acids malate (weak) and aspartate (strong). Since malate is formed in the next step of the CAM and cycles after PEP carboxylase catalyses the condensation of CO and PEP to oxaloacetate, this works as a feedback inhibition pathway. Oxaloacetate and aspartate are easily inter-convertible through a transaminase mechanism; thus high concentrations of aspartate are also a pathway of feedback inhibition of PEP carboxylase.
The main allosteric activators of PEP carboxylase are acetyl-CoA and fructose-1,6-bisphosphate (F-1,6-BP). Both molecules are indicators of increased glycolysis levels, and thus positive feed-forward effectors of PEP carboxylase. They signal the need to produce oxaloacetate to allow more flux through the citric acid cycle. Additionally, increased glycolysis means a higher supply of PEP is available, and thus more storage capacity for binding CO in transport to the Calvin cycle. It is also noteworthy that the negative effectors aspartate competes with the positive effector acetyl-CoA, suggesting that they share an allosteric binding site.
Studies have shown that energy equivalents such as AMP, ADP and ATP have no significant effect on PEP carboxylase.
The magnitudes of the allosteric effects of these different molecules on PEP carboxylase activity depend on individual organisms. | 5 | Photochemistry |
When brickwork is persistently wet, as in foundations, retaining walls, parapets and chimneys, sulfates in bricks and mortar may in time crystallise and expand and cause mortar and renderings to disintegrate. To minimise this effect specialised brickwork with low sulfate levels should be used. Acid sulfates that are located within the subsoil strata has the same effects on the foundations of a building. Adequate protection can exist using a polythene sheeting to encase the foundations or using a sulfate-resistant Portland cement. To identify the pH level of the ground a soil investigation must take place. | 9 | Geochemistry |
The commercial synthesis of halothane starts from trichloroethylene, which is reacted with hydrogen fluoride in the presence of antimony trichloride at 130 °C to form 2-chloro-1,1,1-trifluoroethane. This is then reacted with bromine at 450 °C to produce halothane. | 4 | Stereochemistry |
Alzheimers disease involves the progressive degeneration of the brain, severely impacting mental faculties. Since the Ca hypothesis of Alzheimers was proposed in 1994, several studies have shown that disruptions in Ca signaling are the primary cause of Alzheimers disease. Familial Alzheimers disease has been strongly linked to mutations in the presenilin 1 (PS1), presenilin 2 (PS2), and amyloid precursor protein (APP) genes. All of the mutated forms of these genes observed to date have been found to cause abnormal Ca signaling in the ER. Mutations in PS1 have been shown to increase IP-mediated Ca release from the ER in several animal models. Calcium channel blockers have been used to treat Alzheimer's disease with some success, and the use of lithium to decrease IP turnover has also been suggested as a possible method of treatment. | 1 | Biochemistry |
Due to the ability to introduce diverse functionality into COFs’ structure, catalytic sites can be fine-tuned in conjunction with other advantageous properties like conductivity and stability to afford efficient and selective catalysts. COFs have been used as heterogeneous catalysts in organic, electrochemical, as well as photochemical reactions. | 6 | Supramolecular Chemistry |
A biotransducer is the recognition-transduction component of a biosensor system. It consists of two intimately coupled parts; a bio-recognition layer and a physicochemical transducer, which acting together converts a biochemical signal to an electronic or optical signal. The bio-recognition layer typically contains an enzyme or another binding protein such as antibody. However, oligonucleotide sequences, sub-cellular fragments such as organelles (e.g. mitochondria) and receptor carrying fragments (e.g. cell wall), single whole cells, small numbers of cells on synthetic scaffolds, or thin slices of animal or plant tissues, may also comprise the bio-recognition layer. It gives the biosensor selectivity and specificity. The physicochemical transducer is typically in intimate and controlled contact with the recognition layer. As a result of the presence and biochemical action of the analyte (target of interest), a physico-chemical change is produced within the biorecognition layer that is measured by the physicochemical transducer producing a signal that is proportionate to the concentration of the analyte. The physicochemical transducer may be electrochemical, optical, electronic, gravimetric, pyroelectric or piezoelectric. Based on the type of biotransducer, biosensors can be classified as shown to the right. | 1 | Biochemistry |
When applied globally, PDRC can lower rising temperatures to slow and reverse global warming. Aili et al. concludes that "widescale adoption of radiative cooling could reduce air temperature near the surface, if not the whole atmosphere." To address global warming, PDRCs must be designed "to ensure that the emission is through the atmospheric transparency window and out to space, rather than just to the atmosphere, which would allow for local but not global cooling."
PDRC is not proposed as a standalone solution to global warming, but to be coupled with a global reduction in emissions and transition off of fossil fuel energy. Otherwise, "the radiative balance will not last long, and the potential financial benefits of mitigation will not fully be realized because of continued ocean acidification, air pollution, and redistribution of biomass" from high remaining levels of atmospheric , as per Munday, who summarized the global implementation of PDRC as follows:The estimated total surface area coverage is 5×10 m or about half the size of the Sahara Desert. Global implementation may be more predictable if distributed in a decentralized manner, rather than in a few heavily centralized locations on the Earth's surface. Mandal et al. refers to this as a "distributed geoengineering" strategy that can mitigate "weather disruptions that may arise from large-scale, centralized geoengineering." Desert climates have the highest radiative cooling potential due to low year-round humidity and cloud cover while tropical climates have a lower cooling potential due to the presence of humidity and cloud cover.
Total costs for global implementation have been estimated at $1.25 to $2.5 trillion or about 3% of global GDP, with probable reductions in price at scale. This has been described as "a small investment compared to the estimated $20 trillion global benefits predicted by limiting global warming to 1.5°C rather than 2°C," as per Munday. Low-cost scalable materials have been developed for widescale implementation, although some challenges toward commercialization remain.
Some studies have recommended efforts to focus on maximizing the solar reflectance or albedo of surfaces from very low values to high values, so long as a thermal emittance of at least 90% can be achieved. For example, while the albedo of an urban rooftop may be 0.2, increasing reflectivity to 0.9 is far more impactful than increasing an already reflective surface to be more reflective, such as from 0.9 to 0.97. | 7 | Physical Chemistry |
Muon spin rotation and relaxation are mostly performed with positive muons. They are well suited to the study of magnetic fields at the atomic scale inside matter, such as those produced by various kinds of magnetism and/or superconductivity encountered in compounds occurring in nature or artificially produced by modern material science.
The London penetration depth is one of the most important parameters characterizing a superconductor because its inverse square provides a measure of the density n of Cooper pairs. The dependence of n on temperature and magnetic field directly indicates the symmetry of the superconducting gap. Muon spin spectroscopy provides a way to measure the penetration depth, and so has been used to study high-temperature cuprate superconductors since their discovery in 1986.
Other important fields of application of µSR exploit the fact that positive muons capture electrons to form muonium atoms which behave chemically as light isotopes of the hydrogen atom. This allows investigation of the largest known kinetic isotope effect in some of the simplest types of chemical reactions, as well as the early stages of formation of radicals in organic chemicals. Muonium is also studied as an analogue of hydrogen in semiconductors, where hydrogen is one of the most ubiquitous impurities. | 7 | Physical Chemistry |
The molar conductivity of an electrolyte solution is defined as its conductivity divided by its molar concentration.
where:
: κ is the measured conductivity (formerly known as specific conductance),
: c is the molar concentration of the electrolyte.
The SI unit of molar conductivity is siemens metres squared per mole (S m mol). However, values are often quoted in S cm mol. In these last units, the value of Λ may be understood as the conductance of a volume of solution between parallel plate electrodes one centimeter apart and of sufficient area so that the solution contains exactly one mole of electrolyte. | 7 | Physical Chemistry |
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavior of the receiving individuals. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Pheromones are used by many organisms, from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. The ecological functions and evolution of pheromones are a major topic of research in the field of chemical ecology. | 1 | Biochemistry |
The mechanism consists of three well-differentiated reactions:
# Phenol O-acylation with formation of a tetrahedral intermediate
# Intramolecular aldol condensation to cyclize and to form a hydroxydihydrochromone
# Elimination of the hydroxyl group to form the chromone (or coumarin) | 0 | Organic Chemistry |
SLC25 is a gene that is essential for the synthesis of a wide range of mitochondrial transporters, such as citrate shuttle. Mutations in this gene can result in dysfunctional mitochondria. This leads to significant decrease in the energy production of our body cells, causing severe metabolic diseases. It can cause severe symptoms in organs or tissues that have high energy demand. These organs include the liver, brain, heart, kidneys. They require abundant functional mitochondria to function. Mitochondrial disorders caused by defective or reduced SLC25 gene expression can cause diseases, such as CAC deficiency, HHH syndrome, AGC2 deficiency (CTLN2/NICCD), , Congenital Amish microcephaly, Early epileptic encephalopathy, AAC1 deficiency, PiC (isoform A) deficiency, AGC1 deficiency, Neuropathy with striatal necrosis, and Congenital sideroblastic anaemia.
In addition, SLC25 gene is crucial for the survival of organisms because of its high frequency in the genomics of different organisms. It indicates that this gene is favourable for the survival of a species in response to the environmental features, so it is preserved and passed along the generation. In other words, the gene is positively selected for evolution. Not only is SLC25 gene found in humans, but also in other animals, or even microorganisms like bacteria and viruses. It shows that this gene is conserved among different species. This might provide evidence for the significance and essentiality of the gene in the survival of organisms. | 1 | Biochemistry |
The functional group, the spacer and the lipid tail components of the FSL Kode construct can each be individually designed resulting in FSL Kode constructs with specific biological functions. The functional head group is usually the bioactive component of the construct and the various spacers and lipids influence and effect its presentation, orientation and location on a surface. Critical to the definition of an FSL Kode construct is the requirement to be dispersible in water, and spontaneously and stably incorporate into cell membranes. Other lipid bioconjugates that include components similar to FSLs but do not have these features are not termed as Function-Spacer-Lipid Kode constructs. | 1 | Biochemistry |
Sea foam, ocean foam, beach foam, or spume is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter (including proteins, lignins, and lipids) derived from sources such as the offshore breakdown of algal blooms. These compounds can act as surfactants or foaming agents. As the seawater is churned by breaking waves in the surf zone adjacent to the shore, the surfactants under these turbulent conditions trap air, forming persistent bubbles that stick to each other through surface tension.
Sea foam is a global phenomenon, and it varies depending on location and the potential influence of the surrounding marine, freshwater, and/or terrestrial environments. Due to its low density and persistence, foam can be blown by strong on-shore winds inland, towards the beach. Human activities, such as production, transport or spillage of petroleum products or detergents, can also contribute to the formation of sea foam. | 9 | Geochemistry |
In eukaryotes, N-linked glycans are derived from a core 14-sugar unit assembled in the cytoplasm and endoplasmic reticulum. First, two N-acetylglucosamine residues are attached to dolichol monophosphate, a lipid, on the external side of the endoplasmic reticulum membrane. Five mannose residues are then added to this structure. At this point, the partially finished core glycan is flipped across the endoplasmic reticulum membrane, so that it is now located within the reticular lumen. Assembly then continues within the endoplasmic reticulum, with the addition of four more mannose residues. Finally, three glucose residues are added to this structure. Following full assembly, the glycan is transferred en bloc by the glycosyltransferase oligosaccharyltransferase to a nascent peptide chain, within the reticular lumen. This core structure of N-linked glycans, thus, consists of 14 residues (3 glucose, 9 mannose, and 2 N-acetylglucosamine).
Image: https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=glyco.figgrp.469
Dark squares are N-acetylglucosamine; light circles are mannose; dark triangles are glucose. | 0 | Organic Chemistry |
De re metallica (Latin for On the Nature of Metals [Minerals]) is a book in Latin cataloguing the state of the art of mining, refining, and smelting metals, published a year posthumously in 1556 due to a delay in preparing woodcuts for the text. The author was Georg Bauer, whose pen name was the Latinized Georgius Agricola ("Bauer" and "Agricola" being respectively the German and Latin words for "farmer"). The book remained the authoritative text on mining for 180 years after its publication. It was also an important chemistry text for the period and is significant in the history of chemistry.
Mining was typically left to professionals, craftsmen and experts who were not eager to share their knowledge. Much experiential knowledge had been accumulated over the course of time. This knowledge was consecutively handed down orally within a small group of technicians and mining overseers. In the Middle Ages these people held the same leading role as the master builders of the great cathedrals, or perhaps also alchemists. It was a small, cosmopolitan elite within which existing knowledge was passed on and further developed but not shared with the outside world. Only a few writers from that time wrote anything about mining itself. Partly, that was because this knowledge was very difficult to access. Most writers also found it simply not worth the effort to write about it. Only in the Renaissance did this perception begin to change. With the improved transport and the invention of the printing press knowledge spread much more easily and faster than before. In 1500, the first printed book dedicated to mining engineering, called the Nützlich Bergbüchleyn ("The Useful Little Mining Book”) by Ulrich Rülein von Calw, was published. The most important works in this genre were, however, the twelve books of De Re Metallica by Georgius Agricola, published in 1556.
Agricola had spent nine years in the Bohemian town of Joachimsthal (now Jáchymov in the Czech Republic). After Joachimsthal, he spent the rest of his life in Chemnitz in Saxony, another prominent mining town in the Ore Mountains.
The book was greatly influential, and for more than a century after it was published, De Re Metallica remained a standard treatise used throughout Europe. The German mining technology it portrayed was acknowledged as the most advanced at the time, and the metallic wealth produced in German mining districts was the envy of many other European nations. The book was reprinted in a number of Latin editions, as well as in German and Italian translations. Publication in Latin meant that it could be read by any educated European of the time. The 292 superb woodcut illustrations and the detailed descriptions of machinery made it a practical reference for those wishing to replicate the latest in mining technology.
The drawings from which the woodcuts were made were done by an artist in Joachimsthal named Blasius Weffring or Basilius Wefring. The woodcuts were then prepared in the Froben publishing house by Hans Rudolf Manuel Deutsch and Zacharias Specklin.
In 1912, the first English translation of De Re Metallica was privately published in London by subscription. The translators were Herbert Hoover, a mining engineer (and later President of the United States), and his wife, Lou Henry Hoover, a geologist and Latinist. The translation is notable not only for its clarity of language, but for the extensive footnotes, which detail the classical references to mining and metals. Subsequent translations into other languages, including German, owe much to the Hoover translations, as their footnotes detail their difficulties with Agricola's invention of several hundred Latin expressions to cover Medieval German mining and milling terms that were unknown to classical Latin. The most important translation—outside English—was the one published by the Deutsches Museum in Munich. | 8 | Metallurgy |
The mathematical definition given by H.T. Odum is formally analogous to the definition provided on the maximum power theorem article. (For a brief explanation of Odums approach to the relationship between ecology and electronics see Ecological Analog of Ohms Law) | 7 | Physical Chemistry |
The commercial development of the Cell occurred indirectly as a result of problems being experienced in MIMs Mount Isa lead–zinc concentrator (sometimes referred to as a "mill" in the mining industry). MIM had been operating a lead–zinc concentrator at Mount Isa since 1931, although lead–zinc ore was substituted with copper ore for a time between mid-1943 and mid-1946. Over time, the lead, zinc and other mineral grains in the ore became progressively finer, the ore grade decreased and it became more difficult to treat. These trends, combined with an increase in the concentrators throughput, significantly reduced the concentrator's performance in the 1980s, resulting in a "tense" period of "an endless circle of circuit changes, reagent changes, operator changes, metallurgist changes, and so on". The decreasing grain size and pushing the grinding circuit beyond its design throughput meant a reduction in the degree of separation of the individual mineral grains (referred to as "liberation") during grinding. From 1984 to 1991, the liberation of sphalerite (the zinc-bearing mineral, ZnS) decreased from almost 70% to just over 50%. This decrease in liberation resulted in a reduction in the recovery of zinc to saleable zinc concentrate.
The initial response to the problem of decreased zinc recovery was in 1986 to start to produce a lower-grade concentrate that was a mixture of zinc and lead (known in the industry as a "bulk concentrate" and referred to at Mount Isa as the "low-grade middlings concentrate"). This concentrate typically contained 34% zinc and 13% lead, compared to the normal zinc concentrate composition of at least 50% zinc and less than 3% lead.
By producing the bulk concentrate, the total recovery of zinc for sale was maintained at over 70% until 1989. However, the high lead content meant that the bulk concentrate could not be treated by the electrolytic zinc process, and it had to be sold to zinc smelters using the more-expensive Imperial Smelting Process. Initially, MIM received good revenue from its bulk concentrate, but as the nature of the ore continued to deteriorate, the production of the bulk concentrate increased and saturated the market. Payment terms declined until MIM received less than half the payment for zinc in the bulk concentrate than it received for zinc in the zinc concentrate.
The problems in the concentrator also affected the performance of MIMs Mount Isa lead smelter. The lead–zinc ore also contained increasing amounts of fine-grained, carbonaceous pyrite (FeS). This material was naturally hydrophobic and floated without the aid of a collector into the lead concentrate, diluting it. The additional sulfur from the pyrite in the lead concentrate reduced the lead smelters lead production because the ability to eliminate sulfur from the concentrate was lead smelter's capacity bottleneck.
As part of the effort to try to fix the problems, MIM installed some column flotation cells in the zinc concentrate and bulk concentrate sections of the plant. In those days, the air was introduced into flotation columns using air spargers, usually in the form of a bag or sheath around a pipe. The spargers were high-maintenance items, and their performance was critical to the operation of the column. | 8 | Metallurgy |
Since 5β-coprostanol is formed from cholesterol in the vertebrate gut, the ratio of the product over reactant can be used to indicate the degree of faecal matter in samples. Raw untreated sewage typically has a 5β-coprostanol / cholesterol ratio of ~10 which decreases through a sewage treatment plant (STP) such that in the discharged liquid wastewaters the ratio is ~2. Undiluted STP wastewaters may be identified by this high ratio. As the faecal matter is dispersed in the environment, the ratio will decrease as more (non-faecal) cholesterol from animals is encountered. Grimalt & Albaiges () have suggested that samples with a 5β-coprostanol / cholesterol greater than 0.2 may be considered as contaminated by faecal material. | 2 | Environmental Chemistry |
Point mutations usually take place during DNA replication. DNA replication occurs when one double-stranded DNA molecule creates two single strands of DNA, each of which is a template for the creation of the complementary strand. A single point mutation can change the whole DNA sequence. Changing one purine or pyrimidine may change the amino acid that the nucleotides code for.
Point mutations may arise from spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens. Mutagens can be physical, such as radiation from UV rays, X-rays or extreme heat, or chemical (molecules that misplace base pairs or disrupt the helical shape of DNA). Mutagens associated with cancers are often studied to learn about cancer and its prevention.
There are multiple ways for point mutations to occur. First, ultraviolet (UV) light and higher-frequency light have ionizing capability, which in turn can affect DNA. Reactive oxygen molecules with free radicals, which are a byproduct of cellular metabolism, can also be very harmful to DNA. These reactants can lead to both single-stranded and double-stranded DNA breaks. Third, bonds in DNA eventually degrade, which creates another problem to keep the integrity of DNA to a high standard. There can also be replication errors that lead to substitution, insertion, or deletion mutations. | 1 | Biochemistry |
Controversy about, and shortages of, injected HCG for weight loss have led to substantial Internet promotion of "homeopathic HCG" for weight control. The ingredients in these products are often obscure, but if prepared from true HCG via homeopathic dilution, they contain either no HCG at all or only trace amounts. Moreover, it is highly unlikely that oral HCG is bioavailable due to the fact that digestive protease enzymes and hepatic metabolism renders peptide-based molecules (such as insulin and human growth hormone) biologically inert. HCG can likely only enter the bloodstream through injection.
The United States Food and Drug Administration has stated that over-the-counter products containing HCG are fraudulent and ineffective for weight loss. They are also not protected as homeopathic drugs and have been deemed illegal substances. HCG is classified as a prescription drug in the United States and it has not been approved for over-the-counter sales by the FDA as a weight loss product or for any other purposes, and therefore neither HCG in its pure form nor any preparations containing HCG may be sold legally in the country except by prescription. In December 2011, FDA and FTC started to take actions to pull unapproved HCG products from the market. In the aftermath, some suppliers started to switch to "hormone-free" versions of their weight loss products, where the hormone is replaced with an unproven mixture of free amino acids or where radionics is used to transfer the "energy" to the final product. | 1 | Biochemistry |
Transportable semi-mobile installations have gained increasing popularity in the last two decades. They are enabled by the fact that complete sensor-based sorting systems are relatively compact in relation to the capacity in tonnes per hour. This is mainly because little infrastructure is needed. The picture shows a containerised sensor-based sorter which is applied in Chromitite sorting. The system is operated in conjunction with a Diesel-powered mobile crusher and screen. Material handling of the feed, undersize fraction, product and waste fraction is conducted using a wheel loader. The system is powered by a Diesel generator and a compressor station delivers the instrument quality air needed for the operation.
Semi-mobile installations are applied primarily to minimise material handling and save transport costs. Another reason for choosing the semi-mobile option for an installation is bulk testing of new ore bodies. Capacity of a system very much depends on the size fraction sorted, but a 250tph capacity is a good estimate for semi-mobile installations, considering a capacity of 125tph sorter feed and 125tph undersize material. During the last decade both generic plant designs and customised designs have been developed, for example in the framework of the i2mine project. | 3 | Analytical Chemistry |
Chemerin peptides are short peptides (on the order of 9 amino acids) that are produced from the carboxyl terminus of the chemokine chemerin. They display the same activities as chemerin, although at higher efficacy and potency.
A particular synthetic chemerin-derived peptide, termed C15, was developed at Oxford University. It showed anti-inflammatory activities. Intraperitoneal administration of C15 (0.32 ng/kg) to mice before zymosan challenge conferred significant protection against zymosan-induced peritonitis, suppressing neutrophil (63%) and monocyte (62%) recruitment with a concomitant reduction in proinflammatory mediator expression.
C15 was found to promote phagocytosis and efferocytosis in peritoneal macrophages at picomolar concentrations. C15 enhanced macrophage clearance of microbial particles and apoptotic cells by factor of 360% in vitro | 1 | Biochemistry |
Quantasomes are particles found in the thylakoid membrane of chloroplasts in which photosynthesis takes place. They are embedded in a paracrystalline array on the surface of thylakoid discs in chloroplasts. They are composed of lipids and proteins that include various photosynthetic pigments and redox carriers. For this reason they are considered to be photosynthetic units. They occur in 2 sizes: the smaller quantasome is thought to represent the site of photosystem I, the larger to represent the site of photosystem II. | 5 | Photochemistry |
* Rockefeller Public Service Award (1953)
* Society of Women Engineers Achievement Award (1966)
* Businessweek’s list of 100 Top Corporate Women (1976) | 7 | Physical Chemistry |
The Randle cycle, also known as the glucose fatty-acid cycle, is a metabolic process involving the competition of glucose and fatty acids for substrates. It is theorized to play a role in explaining type 2 diabetes and insulin resistance.
It was named for Philip Randle, who described it in 1963. | 1 | Biochemistry |
A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry derives from two Greek words, γωνία (gōnía) angle and μέτρον (métron) measure. The protractor is a commonly used type in the fields of mechanics, engineering, and geometry.
The first known description of a goniometer, based on the astrolabe, was by Gemma Frisius in 1538. | 7 | Physical Chemistry |
The Heck reaction is the palladium-catalyzed coupling of an aryl or alkenyl halide with an alkene to form a substituted alkene. Intramolecular variants of the reaction may be used to generate cyclic products containing endo or exo double bonds. Ring sizes produced by the intramolecular Heck reaction range from four to twenty-seven atoms. Additionally, in the presence of a chiral palladium catalyst, the intramolecular Heck reaction may be used to establish tertiary or quaternary stereocenters with high enantioselectivity. A number of tandem reactions, in which the intermediate alkylpalladium complex is intercepted either intra- or intermolecularly before β-hydride elimination, have also been developed. | 0 | Organic Chemistry |
In order for neuroproteomics to function correctly, proteins must be separated in terms of the proteome from which they came. For example, one set might be under normal conditions, while another might be under diseased conditions. Proteins are commonly separated using two-dimensional polyacrylamide gel electrophoresis (2D PAGE). For this technique, proteins are run across an immobile gel with a pH gradient until they stop at the point where their net charge is neutral. After separating by charge in one direction, sodium dodecyl sulfate is run in the other direction to separate the proteins by size. A two-dimensional map is created using this technique that can be used to match additional proteins later.
One can usually match the function of a protein by identifying in an 2D PAGE in simple proteomics because many intracellular somatic pathways are known. In neuroproteomics, however, many proteins combine to give an end result that may be neurological disease or breakdown. It is necessary then to study each protein individually and find a correlation between the different proteins to determine the cause of a neurological disease. New techniques are being developed that can identify proteins once they are separated out using 2D PAGE. | 1 | Biochemistry |
It follows immediately that
Substituting Equation 3 back into Equation 1 gives a relationship for the efficiency in terms of temperature:
This is identical to the efficiency formula for Carnot cycle, which effectively employs the ideal gas scale. This means that the two scales equal numerically at every point. | 7 | Physical Chemistry |
Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles.
Example locations are Cape Cod Bay, Chongming Dongtan Reserve in Shanghai, China, Banc d'Arguinpreserve in Mauritania, The Bristol Channel in the United Kingdom, Mandø Island in the Wadden Sea in Denmark, Florida Bay, San Francisco Bay, Bay of Fundy, Casco Bay, Penobscot Bay, and Morro Bay.
Bay mud manifests low shear strength, high compressibility and low permeability, making it hazardous to build upon in seismically active regions like the San Francisco Bay Area.
Typical bulk density of bay mud is approximately 1.3 grams per cubic centimetre.
Bay muds often have a high organic content, consisting of decayed organisms at lower depths, but may also contain living creatures when they occur at the upper soil layer and become exposed by low tides; then, they are called mudflats, an important ecological zone for shorebirds and many types of marine organisms. Great attention was not given to the incidence of deeper bay muds until the 1960s and 1970s when development encroachment on certain North American bays intensified, requiring geotechnical design of foundations.
Bay mud has its own official geological abbreviation: the designation for Quaternary older bay mud is Qobm and the acronym for Quaternary younger bay mud is Qybm. An alluvial layer is often found overlying the older bay mud.
In relation to shipping channels, it is often necessary to dredge bay bottoms and barge the excavated material to an alternate location. In this case chemical analyses are usually performed on the bay mud to determine whether there are elevated levels of heavy metals, PCBs or other toxic substances known to accumulate in a benthic environment. It is not uncommon to dredge the same channel repeatedly (over a span of ten to thirty years) since further settling sediments are prone to redeposit on an open estuarine valley floor. | 2 | Environmental Chemistry |
Endocrinologists have traditionally classified hormones as anabolic or catabolic, depending on which part of metabolism they stimulate. The classic anabolic hormones are the anabolic steroids, which stimulate protein synthesis and muscle growth, and insulin. | 1 | Biochemistry |
PCBs or biphenyl cannot provide energy for microbes, so they are primary energy and carbon sources. As stated before it takes months sometimes for microorganisms to activate their gene for dichlorine after the first exposure to PCBs. It has been proposed to use analogs to promote the activation of genes. However, even after the metabolic pathway is activated, the intermediates of the pathway create a bottleneck effect due to their toxicity. Also, there is the possibility that BP pathway leads to protoanemonin which is a dead-end metabolite that cannot be utilized by cells. Due to the high energy cost of this pathway, if no preferred energy source present in the system, cells will not activate this pathway. | 1 | Biochemistry |
* Kuipers graduated in 1986 in biology at Utrecht University.
* In 1988 Kuipers obtained an EMBO Fellowship for three month at the lab of Dr. J. Gallay of the University of Paris-Sud in Orsay (Paris) to study time-resolved Fluorescence.
* In 1989 Kuipers received a SHELL fellowship to give lectures in the United States at Prof. Mahendra Jain (Newark), Prof. Michael Gelb (Seattle) and Prof. Yang (San Francisco) and on a conference about Time Resolved Fluorescence.
* In 1990 Kuipers obtained his doctorate at the University of Utrecht in biochemistry with the thesis Probing the mechanism of pancreatic phospholipase A2 by protein engineering.
* From 1990 to 1997 he worked as a project leader on molecular genetics at the Department of Biophysical Chemistry of NIZO food research, a contract research center in Ede (The Netherlands).
* From 1997 to 1999 he was head of genetics and research leader of the section Microbial Ingredients of the same institute.
* From 1999 Kuipers is professor and head of the ‘Molecular Genetics of Prokaryotes’ group of the Groningen Biomolecular Sciences and Biotechnology Institute (GBB) of the University of Groningen. | 0 | Organic Chemistry |
Levomethamphetamine crosses the blood-brain-barrier and acts as a norepinephrine transporter inhibitor and TAAR1 agonist, functioning as a selective norepinephrine releasing agent (with limited effects on the release of dopamine), thus levomethamphetamine affects the central nervous system, although its effects are qualitatively distinct relative to those of dextromethamphetamine. It does not possess the same potential for euphoria or addiction that dextromethamphetamine possesses. Among its physiological effects are the vasoconstriction that makes it useful for nasal decongestion. | 4 | Stereochemistry |
Isaac Lewis Pulvermacher was a physicist and inventor originally concerned with the electric telegraph. He first published details of his chain in August 1850 in German and in the winter of that same year came to Britain to demonstrate the machine to notable physicians. He visited London and Edinburgh on this trip. He gives his residence as Breslau, Kingdom of Prussia in his 1853 US patent. Prior to this, however, he had arrived in Britain from Vienna and all the British sources of the time describe him as "of Vienna". | 7 | Physical Chemistry |
Deficiency of this enzyme will increase the possibility of cholesterol gallstones.
Disruption of CYP7A1 from classic bile acid synthesis in mice leads to either increased postnatal death or a milder phenotype with elevated serum cholesterol. The latter is similar to the case in humans, where CYP7A1 mutations associate with high plasma low-density lipoprotein and hepatic cholesterol content, as well as deficient bile acid excretion. There is also a synergy between plasma low-density lipoprotein cholesterol (LDL-C) and risks of coronary artery disease (CAD). Glucose signaling also induces CYP7A1 gene transcription by epigenetic regulation of the histone acetylation status. Glucose induction of bile acid synthesis have an important implication in metabolic control of glucose, lipid, and energy homeostasis under normal and diabetic conditions. CYP7A1-rs3808607 and apolipoprotein E (APOE) isoform are associated with the extent of reduction in circulating LDL cholesterol in response to plant sterol consumption and could serve as potential predictive genetic markers to identify individuals who would derive maximum LDL cholesterol lowering with plant sterol consumption. Genetic variations in CYP7A1 influence its expression and thus may affect the risk of gallstone disease and gallbladder cancer.
One of the many lipid lowering effects of the fibrate drug class is mediated through the inhibition of transcription of this enzyme. This inhibition leads to more cholesterol in the bile, which is the body's only route of cholesterol excretion. This also increases the risk of cholesterol gallstone formation.
Inhibition of CYP7A1 is thought to be involved in or responsible for the hepatotoxicity associated with ketoconazole. The levorotatory enantiomer of ketoconazole, levoketoconazole, shows 12-fold reduced potency in inhibition of this enzyme, and is under development for certain indications (e.g., Cushing's syndrome) as a replacement for ketoconazole with reduced toxicity and improved tolerability and safety. | 1 | Biochemistry |
Nucleic acids (including RNA and DNA) are nucleotide polymers synthesized by polymerase enzymes during either transcription or DNA replication. Following 5-3 synthesis of the backbone, individual nitrogenous bases are capable of interacting with one another via hydrogen bonding, thus allowing for the formation of higher-order structures. Nucleic acid denaturation occurs when hydrogen bonding between nucleotides is disrupted, and results in the separation of previously annealed strands. For example, denaturation of DNA due to high temperatures results in the disruption of base pairs and the separation of the double stranded helix into two single strands. Nucleic acid strands are capable of re-annealling when "normal" conditions are restored, but if restoration occurs too quickly, the nucleic acid strands may re-anneal imperfectly resulting in the improper pairing of bases. | 1 | Biochemistry |
*It can be prepared by Jones oxidation of cyclooctanol.
*It can also be produced by ketonization reaction starting with azelaic acid. | 0 | Organic Chemistry |
A cylinder lens consists of several cylinders whose sides are thin walls. Each cylinder lines up parallel to the optical axis into which electrons enter. There are small gaps put between the cylinders. When each cylinder has a different voltage, the gap between the cylinders works as a lens. The magnification is able to be changed by choosing different voltage combinations. Although the magnification of two cylinder lenses can be changed, the focal point is also changed by this operation. Three cylinder lenses achieve the change of the magnification while holding the object and image positions because there are two gaps that work as lenses. Although the voltages have to change depending on the electron kinetic energy, the voltage ratio is kept constant when the optical parameters are not changed.
While a charged particle is in an electric field force acts upon it. The faster the particle the smaller the accumulated impulse. For a collimated beam the focal length is given as the initial impulse divided by the accumulated (perpendicular) impulse by the lens. This makes the focal length of a single lens a function of the second order of the speed of the charged particle. Single lenses as known from photonics are not easily available for electrons.
The cylinder lens consists of defocusing lens, a focusing lens and a second defocusing lens, with the sum of their refractive powers being zero. But because there is some distance between the lenses, the electron makes three turns and hits the focusing lens at a position farther away from the axis and so travels through a field with greater strength. This indirectness leads to the fact that the resulting refractive power is the square of the refractive power of a single lens. | 7 | Physical Chemistry |
For a face-centered cubic unit cell, the number of atoms is four. A line can be drawn from the top corner of a cube diagonally to the bottom corner on the same side of the cube, which is equal to 4r. Using geometry, and the side length, a can be related to r as:
Knowing this and the formula for the volume of a sphere, it becomes possible to calculate the APF as follows: | 3 | Analytical Chemistry |
Responses are polyclonal in nature as each clone somewhat specializes in producing antibodies against a given epitope, and because, each antigen contains multiple epitopes, each of which in turn can be recognized by more than one clone of B cells. To be able to react to innumerable antigens, as well as multiple constituent epitopes, the immune system requires the ability to recognize a very great number of epitopes in all, i.e., there should be a great diversity of B cell clones. | 1 | Biochemistry |
For most protein antigens, the production of antibodies by B lymphocytes is dependent on stimulation of helper T cells. However bacterial polysaccharides and lipopolysaccharides, and some polymeric proteins, can stimulate B lymphocytes without involvement of helper T cells. The non-protein microbial antigens cannot stimulate classical T cell response by themselves, but they are able to elicit the production of antibodies, so that is why we call them T cell or thymus independent antigens.
T independent antigens are divided into 2 classes by the mechanism of activating B cells. | 1 | Biochemistry |
In organic chemistry, nitroamines are organic compounds with the general chemical structure . They consist of a nitro group () bonded to an amine. The parent inorganic compound, where both R substituents are hydrogen, is nitramide, . | 0 | Organic Chemistry |
The nitrogen in ammonia has 5 valence electrons and bonds with three hydrogen atoms to complete the octet. This would result in the geometry of a regular tetrahedron with each bond angle equal to cos(−) ≈ 109.5°. However, the three hydrogen atoms are repelled by the electron lone pair in a way that the geometry is distorted to a trigonal pyramid (regular 3-sided pyramid) with bond angles of 107°. In contrast, boron trifluoride is flat, adopting a trigonal planar geometry because the boron does not have a lone pair of electrons. In ammonia the trigonal pyramid undergoes rapid nitrogen inversion. | 4 | Stereochemistry |
A number of different structural domains that fold mostly on their own have been found in the APP sequence. The extracellular region, much larger than the intracellular region, is divided into the E1 and E2 domains, linked by an acidic domain (AcD); E1 contains two subdomains including a growth factor-like domain (GFLD) and a copper-binding domain (CuBD) interacting tightly together. A serine protease inhibitor domain, absent from the isoform differentially expressed in the brain, is found between acidic region and E2 domain. The complete crystal structure of APP has not yet been solved; however, individual domains have been successfully crystallized, the growth factor-like domain, the copper-binding domain, the complete E1 domain and the E2 domain. | 1 | Biochemistry |
Like mitochondria, chloroplasts use the potential energy stored in an H, or hydrogen ion, gradient to generate ATP energy. The two photosystems capture light energy to energize electrons taken from water, and release them down an electron transport chain. The molecules between the photosystems harness the electrons' energy to pump hydrogen ions into the thylakoid space, creating a concentration gradient, with more hydrogen ions (up to a thousand times as many) inside the thylakoid system than in the stroma. The hydrogen ions in the thylakoid space then diffuse back down their concentration gradient, flowing back out into the stroma through ATP synthase. ATP synthase uses the energy from the flowing hydrogen ions to phosphorylate adenosine diphosphate into adenosine triphosphate, or ATP. Because chloroplast ATP synthase projects out into the stroma, the ATP is synthesized there, in position to be used in the dark reactions. | 5 | Photochemistry |
Tetrabutylammonium tribromide, abbreviated to TBATB, is a pale orange solid with the formula [N(CH)]Br. It is a salt of the lipophilic tetrabutylammonium cation and the linear tribromide anion. The salt is sometimes used as a reagent used in organic synthesis as a conveniently weighable, solid source of bromine. | 0 | Organic Chemistry |
In general, the most important requisite is to calibrate the incubation time of the assay both to the model cell and the ligand to be evaluated. Too short incubation time results in no cells in the sample, while too long time perturbs the concentration gradients and measures more chemokinetic than chemotactic responses.
The most commonly used techniques are grouped into two main groups: | 1 | Biochemistry |
The ABO blood group system is determined by what type of glycosyltransferases are expressed in the body.
The ABO gene locus expressing the glycosyltransferases has three main allelic forms: A, B, and O. The A allele encodes 1-3-N-acetylgalactosaminyltransferase that bonds α-N-acetylgalactosamine to D-galactose end of H antigen, producing the A antigen. The B allele encodes 1-3-galactosyltransferase that joins α-D-galactose bonded to D-galactose end of H antigen, creating the B antigen. In case of O allele the exon 6 contains a deletion that results in a loss of enzymatic activity. The O allele differs slightly from the A allele by deletion of a single nucleotide - Guanine at position 261. The deletion causes a frameshift and results in translation of an almost entirely different protein that lacks enzymatic activity. This results in H antigen remaining unchanged in case of O groups.
The combination of glycosyltransferases by both alleles present in each person determines whether there is an AB, A, B or O blood type. | 0 | Organic Chemistry |
Although the energy formula of Rydberg series is a result of hydrogen-like atom structure, Rydberg states are also present in molecules. Wave functions of high Rydberg states are very diffuse and span diameters that approach infinity. As a result, any isolated neutral molecule behaves like a hydrogen-like atom at the Rydberg limit. For molecules with multiple stable monovalent cations, multiple Rydberg series may exist. Because of the complexity of molecular spectra, low-lying Rydberg states of molecules are often mixed with valence states with similar energy and are thus not pure Rydberg states. | 7 | Physical Chemistry |
In addition to undergoing S2-type reactions, alkyl halides and similar substrates can add to a metal center via a radical mechanism, although some details remain controversial. Reactions which are generally accepted to proceed by a radical mechanism are known however. One example was proposed by Lednor and co-workers.
;Initiation
:[[Azobisisobutyronitrile|[(CH)C(CN)N]]] → 2 (CH)(CN)C + N
:(CH)(CN)C + PhBr → (CH)(CN)CBr + Ph
;Propagation
:Ph + [Pt(PPh)] → [Pt(PPh)Ph]
:[Pt(PPh)Ph] + PhBr → [Pt(PPh)PhBr] + Ph | 0 | Organic Chemistry |
The Helferich method may refer to:
#Glycosylation of an alcohol using a glycosyl acetate as glycosyl donor and a Lewis acid (e.g. a metal halide) as promoter
#Glycosylation of an alcohol using a glycosyl halide as a glycosyl donor and a mercury salt as promoter (cf the Koenigs-Knorr reaction, which uses silver salts as promoters). | 0 | Organic Chemistry |
Baker's yeast (BY) has been utilized for the kinetic resolution of α-stereogenic carbonyl compounds. The enzyme selectively reduces one enantiomer, yielding a highly enantioenriched alcohol and ketone, as shown below.
Bakers yeast has also been used in the kinetic resolution of secondary benzylic alcohols by oxidation. While excellent ees of the recovered alcohol have been reported, they typically require >60% conversion, resulting in diminished yields. Bakers yeast has also been used in the kinetic resolution via reduction of β-ketoesters. However, given the success of Noyoris resolution of the same substrates, detailed later in this article, this has not seen much use. | 4 | Stereochemistry |
Gene nomenclature has been established by the HUGO Gene Nomenclature Committee (HGNC), a committee of the Human Genome Organisation, for each known human gene in the form of an approved gene name and symbol (short-form abbreviation), which can be accessed through a database maintained by HGNC. Symbols are chosen to be unique, and each gene has only one symbol (although approved symbols sometimes change). Symbols are preferably kept consistent with other members of a gene family and with homologs in other species, particularly the mouse due to its role as a common model organism. | 1 | Biochemistry |
Together with hydrogen (H), oxygen is evolved by the electrolysis of water. The point of water electrolysis is to store energy in the form of hydrogen gas, a clean-burning fuel. The "oxygen evolution reaction (OER) is the major bottleneck [to water electrolysis] due to the sluggish kinetics of this four-electron transfer reaction." All practical catalysts are heterogeneous.
Electrons (e) are transferred from the cathode to protons to form hydrogen gas. The half reaction, balanced with acid, is:
:2 H + 2e → H
At the positively charged anode, an oxidation reaction occurs, generating oxygen gas and releasing electrons to the anode to complete the circuit:
:2 HO → O + 4 H + 4e
Combining either half reaction pair yields the same overall decomposition of water into oxygen and hydrogen:
:Overall reaction:
:2 HO → 2 H + O | 5 | Photochemistry |
If the diffusing particles are hindered by obstacles or pushed by a force (molecular motors, flow, etc.) the dynamics is often not sufficiently well-described by the normal diffusion model, where the mean squared displacement (MSD) grows linearly with time. Instead the diffusion may be better described as anomalous diffusion, where the temporal dependence of the MSD is non-linear as in the power-law:
where is an anomalous diffusion coefficient. "Anomalous diffusion" commonly refers only to this very generic model, and not the many other possibilities that might be described as anomalous. Also, a power law is, in a strict sense, the expected form only for a narrow range of rigorously defined systems, for instance when the distribution of obstacles is fractal. Nonetheless a power law can be a useful approximation for a wider range of systems.
The FCS autocorrelation function for anomalous diffusion is:
where the anomalous exponent is the same as above, and becomes a free parameter in the fitting.
Using FCS, the anomalous exponent has been shown to be an indication of the degree of molecular crowding (it is less than one and smaller for greater degrees of crowding). | 7 | Physical Chemistry |
HCFC-142b is used as a refrigerant, as a blowing agent for foam plastics production, and as feedstock to make polyvinylidene fluoride (PVDF). It was introduced to replace the chlorofluorocarbons (CFCs) that were initially undergoing a phase-out per the Montreal Protocol, but HCFCs still have a significant ozone-depletion ability. As of year 2020, HCFC's are replaced by non ozone depleting HFCs within many applications.
In the United States, the EPA stated that HCFCs could be used in "processes that result in the transformation or destruction of the HCFCs", such as using HCFC-142b as a feedstock to make PVDF. HCFCs could also be used in equipment that was manufactured before January 1, 2010. The point of these new regulations was to phase-out HCFCs in much the same way that CFCs were phased out. HCFC-142b production in non article 5 countries like the United States was banned on January 1, 2020, under the Montreal Protocol. | 2 | Environmental Chemistry |
Whole cell and tissue analysis is possible using a microPIXE beam, this method is also referred to as nuclear microscopy. | 7 | Physical Chemistry |
This specific sulfinamide chiral auxiliary was initially developed by Jonathan A. Ellman, and its use has been explored extensively by his group. Thus, it is often referred to as Ellmans auxiliary or Ellmans sulfinamide. | 4 | Stereochemistry |
Pigments absorb light. Soap bubbles show a prism of different colors on their surfaces. These colors result from the way light interacts with differing thicknesses of the bubble's film, a phenomenon called structural color. Part of Qingchen Shen and Silvia Vignolini’s research focuses on identifying the causes behind different types of structural colors in nature. In one case, her group found that cellulose nanocrystals (CNCs), which are derived from the cellulose found in plants, could be made into iridescent, colorful films without any added pigment. They made films with vibrant blue, green and red colors that, when placed under sunlight, were an average of nearly 7 F cooler than the surrounding air. A square meter of the film generated over 120 Watts of cooling power. | 7 | Physical Chemistry |
The term "fine chemicals" was in use as early as 1908. The emergence of the fine chemical industry as a distinct entity dates to the late 1970s, when the overwhelming success of the histamine H receptor antagonists Tagamet (cimetidine) and Zantac (ranitidine hydrochloride) created a strong demand for advanced organic chemicals used in their manufacture. As the in-house production capacities of the originators, the pharmaceutical companies Smith, Kline, & French and Glaxo, could not keep pace with the rapidly increasing requirements, both companies (now merged as GlaxoSmithKline) outsourced part of the manufacturing to chemical companies experienced in producing relatively sophisticated organic molecules. Lonza, Switzerland, which already had supplied an early intermediate, methyl acetoacetate, during drug development, soon became the main supplier of more and more advanced precursors. The signature of a first, simple supply contract is generally acknowledged as the historical document marking the beginning of the fine chemical industry.
In subsequent years, the business developed and Lonza was the first fine chemical company entering in a strategic partnership with SKF. In a similar way, Fine Organics, UK became the supplier of the thioethyl-N'-methyl-2-nitro-1,1-ethenediamine moiety of ranitidine, the second H2 receptor antagonist, marketed as Zantac by Glaxo. Other pharmaceutical and agrochemical companies gradually followed suit and started outsourcing the procurement of fine chemicals. An example in case is F.I.S., Italy, which partnered with Roche, Switzerland for custom manufacturing precursors of the benzodiazepine class of tranquilizers, such as Librium (chlordiazepoxide HCl) and Valium (diazepam).
The growing complexity and potency of new pharmaceuticals and agrochemicals requiring production in multipurpose, instead of dedicated plants and, more recently, the advent of biopharmaceuticals had a major impact on the demand for fine chemicals and the evolution of the fine chemical industry as a distinct entity. For many years, the life science industry continued considering captive production of the active ingredients of their drugs and agrochemicals as a core competency. Outsourcing was used only in exceptional cases, such as capacity shortfalls, processes requiring hazardous chemistry or new products, where uncertainties existed about the chance of a successful launch. | 0 | Organic Chemistry |
He worked as part of the DNA synthesis group at Genentech from 1986 to 1990, before joining Gilead in 1990 as Director of Organic Chemistry. In 1993, he began work, as head of a team, to create Tamiflu. In 1996, clinical studies were carried out on the drug, which was the first orally active commercially developed anti-influenza medication. Explaining the motivation behind this, he said, "We decided to create a pill and not a medication to inhale because especially people who suffer from influenza struggle with breathing difficulties. And the agent would only reach the lung," Three years later, the right to market and develop Tamiflu were sold to Roche, with Bischofberger and Gilead retaining the intellectual rights to it.
Bischofberger has publicly displayed pessimism over the risk viruses pose, saying, "I think the threat by new bacterial or viral agents is higher than the potential of a nuclear war." | 0 | Organic Chemistry |
In one study, it was estimated that for every dollar ($1) that is spent on pesticides for crops can yield up to four dollars ($4) in crops saved. This means based that, on the amount of money spent per year on pesticides, $10 billion, there is an additional $40 billion savings in crop that would be lost due to damage by insects and weeds. In general, farmers benefit from having an increase in crop yield and from being able to grow a variety of crops throughout the year. Consumers of agricultural products also benefit from being able to afford the vast quantities of produce available year-round. | 2 | Environmental Chemistry |
Flavin mononucleotide is a prosthetic group found in, among other proteins, NADH dehydrogenase, E.coli nitroreductase and old yellow enzyme. | 1 | Biochemistry |
Hydrolysis is related to energy metabolism and storage. All living cells require a continual supply of energy for two main purposes: the biosynthesis of micro and macromolecules, and the active transport of ions and molecules across cell membranes. The energy derived from the oxidation of nutrients is not used directly but, by means of a complex and long sequence of reactions, it is channeled into a special energy-storage molecule, adenosine triphosphate (ATP). The ATP molecule contains pyrophosphate linkages (bonds formed when two phosphate units are combined) that release energy when needed. ATP can undergo hydrolysis in two ways: Firstly, the removal of terminal phosphate to form adenosine diphosphate (ADP) and inorganic phosphate, with the reaction:
Secondly, the removal of a terminal diphosphate to yield adenosine monophosphate (AMP) and pyrophosphate. The latter usually undergoes further cleavage into its two constituent phosphates. This results in biosynthesis reactions, which usually occur in chains, that can be driven in the direction of synthesis when the phosphate bonds have undergone hydrolysis. | 7 | Physical Chemistry |
The main compartment of the titration cell contains the anode solution plus the analyte. The anode solution consists of an alcohol (ROH), a base (B), sulfur dioxide () and KI. Typical alcohols that may be used include ethanol, diethylene glycol monoethyl ether, or methanol, sometimes referred to as Karl Fischer grade. A common base is imidazole.
The titration cell also consists of a smaller compartment with a cathode immersed in the anode solution of the main compartment. The two compartments are separated by an ion-permeable membrane.
The Pt anode generates from the KI when current is provided through the electric circuit. The net reaction as shown below is oxidation of by . One mole of is consumed for each mole of . In other words, 2 moles of electrons are consumed per mole of water.
The end point is detected most commonly by a bipotentiometric titration method. A second pair of Pt electrodes is immersed in the anode solution. The detector circuit maintains a constant current between the two detector electrodes during titration. Prior to the equivalence point, the solution contains but little . At the equivalence point, excess appears and an abrupt voltage drop marks the end point. The amount of charge needed to generate I and reach the end point can then be used to calculate the amount of water in the original sample. | 3 | Analytical Chemistry |
Ellipsometry measures the complex reflectance ratio of a system, which may be parametrized by the amplitude component and the phase difference . The polarization state of the light incident upon the sample may be decomposed into an s and a p component (the s component is oscillating perpendicular to the plane of incidence and parallel to the sample surface, and the p component is oscillating parallel to the plane of incidence). The amplitudes of the s and p components, after reflection and normalized to their initial value, are denoted by and respectively. The angle of incidence is chosen close to the Brewster angle of the sample to ensure a maximal difference in and . Ellipsometry measures the complex reflectance ratio (a complex quantity), which is the ratio of over :
Thus, is the amplitude ratio upon reflection, and is the phase shift (difference). (Note that the right side of the equation is simply another way to represent a complex number.) Since ellipsometry is measuring the ratio (or difference) of two values (rather than the absolute value of either), it is very robust, accurate, and reproducible. For instance, it is relatively insensitive to scatter and fluctuations and requires no standard sample or reference beam. | 7 | Physical Chemistry |
P1 was discovered in 1951 by Giuseppe Bertani in Salvador Lurias laboratory, but the phage was little studied until Ed Lennox, also in Lurias group, showed in 1954–5 that it could transduce genetic material between host bacteria. This discovery led to the phage being used for genetic exchange and genome mapping in E. coli, and stimulated its further study as a model organism. In the 1960s, Hideo Ikeda and Jun-ichi Tomizawa showed the phages DNA genome to be linear and double-stranded, with redundancy at the ends. In the 1970s, Nat Sternberg characterised the Cre–lox' site-specific recombination system, which allows the linear genome to circularise to form a plasmid after infection. During the 1980s, Sternberg developed P1 as a vector for cloning large pieces of eukaryotic DNA. A P1 gene map based on a partial DNA sequence was published in 1993 by Michael Yarmolinsky and Małgorzata Łobocka, and the genome was completely sequenced by Łobocka and colleagues in 2004. | 1 | Biochemistry |
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