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Disubstituted alkenes react with HCN in the presence of strong acids to give formamides, which can be decarbonylated. This method, the Ritter reaction, is used industrially to produce tertiary amines such as tert-octylamine.
Hydroamination of alkenes is also widely practiced. The reaction is catalyzed by zeolite-based solid acids. | 0 | Organic Chemistry |
Analytical thermal desorption, known within the analytical chemistry community simply as "thermal desorption" (TD), is a technique that concentrates volatile organic compounds (VOCs) in gas streams prior to injection into a gas chromatograph (GC). It can be used to lower the detection limits of GC methods, and can improve chromatographic performance by reducing peak widths. | 3 | Analytical Chemistry |
* Cyanogen - ()
* Isocyanogen - ()
* Diisocyanogen - ()
* Paracyanogen - a cyanogen polymer,
* Paraisocyanogen - a cyanogen polymer, | 0 | Organic Chemistry |
As in other social Hymenoptera, bumblebee queens have also been shown to release characteristic pheromones to signal their presence and stop the workers from reproducing. In Bombus terrestris, for example, two studies have shown that workers resorbed oocytes more often and had fewer developing oocytes in their ovaries after treatment with the queen-characteristic cuticular hydrocarbon pentacosane. Similar activity of queen-specific cuticular hydrocarbons has also been documented in Bombus impatiens, as well as in several other species of ants and wasps. | 1 | Biochemistry |
;X-ray diffraction
* [https://web.archive.org/web/20071012172448/http://ndbserver.rutgers.edu/atlas/xray/structures/U/ud0017/ud0017.html NDB ID: UD0017 Database]
*[https://web.archive.org/web/20030803010825/http://ndbserver.rutgers.edu/atlas/xray/index.html X-ray Atlas -database]
* [https://web.archive.org/web/20040105073855/http://ndbserver.rutgers.edu/ftp/NDB/coordinates/na-biol/ PDB files of coordinates for nucleic acid structures from X-ray diffraction by NA (incl. DNA) crystals]
* [https://web.archive.org/web/20040105065152/http://ndbserver.rutgers.edu/ftp/NDB/structure-factors/ Structure factors downloadable files in CIF format]
;Neutron scattering
* ISIS neutron source: [https://web.archive.org/web/19981205225006/http://www.isis.rl.ac.uk/ ISIS pulsed neutron source:A world centre for science with neutrons & muons at Harwell, near Oxford, UK.]
;X-ray microscopy
;Electron microscopy
* [http://www.fidelitysystems.com/Unlinked_DNA.html DNA under electron microscope]
;NMR databases
* [https://web.archive.org/web/20030803005845/http://ndbserver.rutgers.edu/atlas/nmr/index.html NMR Atlas--database]
* [https://web.archive.org/web/20040105082208/http://ndbserver.rutgers.edu/ftp/NDB/coordinates/na-nmr-mmcif/ mmcif downloadable coordinate files of nucleic acids in solution from 2D-FT NMR data]
* [https://web.archive.org/web/20051215062524/http://ndbserver.rutgers.edu/ftp/NDB/nmr-restraints/ NMR constraints files for NAs in PDB format]
;Genomic and structural databases
* [http://www.cbs.dtu.dk/services/GenomeAtlas/ CBS Genome Atlas Database] — contains examples of base skews.
* [https://archive.today/20121129003619/http://tubic.tju.edu.cn/zcurve/ The Z curve database of genomes — a 3-dimensional visualization and analysis tool of genomes].
* [https://web.archive.org/web/20040301074323/http://ndbserver.rutgers.edu/ftp/NDB/models/ DNA and other nucleic acids' molecular models: Coordinate files of nucleic acids molecular structure models in PDB and CIF formats]
;Atomic force microscopy
*[https://web.archive.org/web/20080209123336/http://www.parkafm.com/New_html/resources/01general.php How SPM Works]
*[http://www.rhk-tech.com/results/showcase.php SPM image gallery: AFM STM SEM MFM NSOM, more] | 4 | Stereochemistry |
Those carbenes that have been isolated to date tend to be colorless solids with low melting points. These carbenes tend to sublime at low temperatures under high vacuum.
One of the more useful physical properties is the diagnostic chemical shift of the carbenic carbon atom in the C-NMR spectrum. Typically this peak is in the range between 200 and 300 ppm, where few other peaks appear in the C-NMR spectrum. An example is shown on the left for a cyclic diaminocarbene which has a carbenic peak at 238 ppm.
Upon coordination to metal centers, the C carbene resonance usually shifts highfield, depending on the Lewis acidity of the complex fragment. Based on this observation, Huynh et al. developed a new methodology to determine ligand donor strengths by C NMR analysis of trans-palladium(II)-carbene complexes. The use of a C-labeled N-heterocyclic carbene ligand also allows for the study of mixed carbene-phosphine complexes, which undergo trans-cis-isomerization due to the trans effect. | 0 | Organic Chemistry |
The I. I. Rabi Prize in Atomic, Molecular, and Optical Physics is given by the American Physical Society to recognize outstanding work by mid-career researchers in the field of atomic, molecular, and optical physics. The award was endowed in 1989 in honor of the physicist I. I. Rabi and has been awarded biannually since 1991.
The prize citation reads: | 7 | Physical Chemistry |
As compared to sodium-based liquid metal coolants such as liquid sodium or NaK, lead-based coolants have significantly higher boiling points, meaning a reactor can be operated without risk of coolant boiling at much higher temperatures. This improves thermal efficiency and could potentially allow hydrogen production through thermochemical processes.
Lead and LBE also do not react readily with water or air, in contrast to sodium and NaK which ignite spontaneously in air and react explosively with water. This means that lead- or LBE-cooled reactors, unlike sodium-cooled designs, would not need an intermediate coolant loop, which reduces the capital investment required for a plant.
Both lead and bismuth are also an excellent radiation shield, absorbing gamma radiation while simultaneously being virtually transparent to neutrons. In contrast, sodium forms the potent gamma emitter sodium-24 (half-life 15 hours) following intense neutron radiation, requiring a large radiation shield for the primary cooling loop.
As heavy nuclei, lead and bismuth can be used as spallation targets for non-fission neutron production, as in accelerator transmutation of waste (see energy amplifier).
Both lead-based and sodium-based coolants have the advantage of relatively high boiling points as compared to water, meaning it is not necessary to pressurise the reactor even at high temperatures. This improves safety as it reduces the probability of a loss of coolant accident (LOCA), and allows for passively safe designs. The thermodynamic cycle (Carnot cycle) is also more efficient with a larger difference of temperature. However, a disadvantage of higher temperatures is also the higher corrosion rate of metallic structural components in LBE due to their increased solubility in liquid LBE with temperature (formation of amalgam) and to liquid metal embrittlement. | 8 | Metallurgy |
HDAC3 has been found to be most closely related to HDAC8. HDAC3 contains a non-conserved region in the C-terminal region that was found to be required for transcriptional repression as well as its deacetylase activity. It also contains two regions, one called a Nuclear Localization Signal (NLS) as well as a Nuclear Export Signal (NES). The NLS functions as a signal for nuclear action while an NES functions with HDACs that perform work outside of the nucleus. A presence of both signals for HDAC3 suggests it travels between the nucleus and the cytoplasm. HDAC3 has even been found to interact with the plasma membrane. Silencing Mediator for Retinoic Acid and Thyroid Hormone (SMRT) receptors and Nuclear Receptor Co-Repressor (N-CoR) factors must be utilized by HDAC3 in order to activate it. Upon doing so, it gains the ability to co-precipitate with HDACs 4, 5, and 7. HDAC3 can also be found complexed together with HDAC-related protein (HDRP). HDACs 1 and 3 have been found to mediate Rb-RbAp48 interactions which suggests that it functions in cell cycle progression. HDAC3 also shows involvement in stem cell self-renewal and a transcription independent role in mitosis. | 0 | Organic Chemistry |
Lichens are classified by the fungal component. Lichen species are given the same scientific name (binomial name) as the fungus species in the lichen. Lichens are being integrated into the classification schemes for fungi. The alga bears its own scientific name, which bears no relationship to that of the lichen or fungus. There are about 20,000 identified lichen species, and taxonomists have estimated that the total number of lichen species (including those yet undiscovered) might be as high as 28,000. Nearly 20% of known fungal species are associated with lichens.
"Lichenized fungus" may refer to the entire lichen, or to just the fungus. This may cause confusion without context. A particular fungus species may form lichens with different algae species, giving rise to what appear to be different lichen species, but which are still classified (as of 2014) as the same lichen species.
Formerly, some lichen taxonomists placed lichens in their own division, the Mycophycophyta, but this practice is no longer accepted because the components belong to separate lineages. Neither the ascolichens nor the basidiolichens form monophyletic lineages in their respective fungal phyla, but they do form several major solely or primarily lichen-forming groups within each phylum. Even more unusual than basidiolichens is the fungus Geosiphon pyriforme, a member of the Glomeromycota that is unique in that it encloses a cyanobacterial symbiont inside its cells. Geosiphon is not usually considered to be a lichen, and its peculiar symbiosis was not recognized for many years. The genus is more closely allied to endomycorrhizal genera. Fungi from Verrucariales also form marine lichens with the brown algae Petroderma maculiforme, and have a symbiotic relationship with seaweed (such as rockweed) and Blidingia minima, where the algae are the dominant components. The fungi is thought to help the rockweeds to resist desiccation when exposed to air. In addition, lichens can also use yellow-green algae (Heterococcus) as their symbiotic partner.
Lichens independently emerged from fungi associating with algae and cyanobacteria multiple times throughout history. | 2 | Environmental Chemistry |
The Federation of the European Biochemical Societies (FEBS) is an international scientific society promoting activities in biochemistry, molecular biology and related research areas in Europe and neighbouring regions. It was founded in 1964 and includes over 35,000 members across 39 Constituent Societies. | 1 | Biochemistry |
Treatment with RO is limited, resulting in low recoveries on high concentration (measured with electrical conductivity) and membrane fouling. RO applicability is limited by conductivity, organics, and scaling inorganic elements such as CaSO, Si, Fe and Ba. Low organic scaling can use two different technologies: spiral wound membrane, and (for high organic scaling, high conductivity and higher pressure (up to 90 bars)), disc tube modules with RO membranes can be used. Disc tube modules were redesigned for landfill leachate purification that is usually contaminated with organic material. Due to the cross-flow, it is given a flow booster pump that recirculates the flow over the membrane between 1.5 and 3 times before it is released as a concentrate. High velocity protects against membrane scaling and allows membrane cleaning. | 3 | Analytical Chemistry |
The EWOC Conference structure consists of a combination of scientific presentations, workshops, topical networking sessions, career panel and also includes a poster session. Examples of Workshops have included Cultivate Belonging in the Workplace for Yourself and Others; How to Create, Build and Leverage Networks for Sustained Leadership and Career Success and Cultural Change to Enable Diversity & Inclusion, the Psychology of Selves: Beyond Imposter Syndrome, Leading through Influence, Allies Help Turn the Tide, Take Control of Your Time: Say No, Negotiate, Delegate, Beyond Pajamas: Coming out of COVID Isolation Mindfully, Beyond Pajamas: Coming out of COVID Isolation Mindfully, and a Discussion Toward Diversity, Equity and Inclusion in Organic Chemistry. Examples of topical networking sessions have focused on Work/Life Balance Discussion, How to start an EWOC Chapter, Publishing like a Boss, Creating a Culture of Safety, Interviewing and choosing a company, and various peer networking discussions for graduate students, postdocs, early career faculty, LGBTQ+, Black, Indigenous, & People of Color (BIPOC), and Allies and Advocates, among others. The virtual format of EWOC has been cited as an example of the benefits of virtual conferences because they are "more accessible to people who couldn’t otherwise attend because of travel costs or restrictions or because they have family obligations that make travel onerous." | 0 | Organic Chemistry |
* B40.200-2008: Thermometers, Direct Reading and Remotes Reading.
* PTC 19.3-1974(R2004): Performance test code for temperature measurement. | 7 | Physical Chemistry |
In chemical and biological defense, activated carbon is impregnated with DABCO for use in filters for masks, collective protection systems, and the like. | 0 | Organic Chemistry |
If R and R (note equation at top of page) are different substituents, there is a new stereocenter formed at the alpha position when an enol converts to its keto form. Depending on the nature of the three R groups, the resulting products in this situation would be diastereomers or enantiomers. | 0 | Organic Chemistry |
The main advantage of diffusion dialysis is the low energy consumption of the unit. This membrane technique operates under normal pressure and does not have a state change. Consequently, the energy required is significantly reduced, which reduces the operating cost. There is also the low installation cost, easy operation and the stability and reliability of the process. Another advantage is that diffusion dialysis does not pollute the environment.
A disadvantage is that a diffusion dialyser has a low processing capability and low processing efficiency. There are other methods such as electrodialysis and reverse osmosis that can achieve better efficiencies than diffusion dialysis. | 1 | Biochemistry |
In the U.S., standard methods have been established by the National Institute for Occupational Safety and Health (NIOSH) and another by U.S. OSHA. Each method uses a single component solvent; butanol and hexane cannot be sampled, however, on the same sample matrix using the NIOSH or OSHA method.
VOCs are quantified and identified by two broad techniques. The major technique is gas chromatography (GC). GC instruments allow the separation of gaseous components. When coupled to a flame ionization detector (FID) GCs can detect hydrocarbons at the parts per trillion levels. Using electron capture detectors, GCs are also effective for organohalide such as chlorocarbons.
The second major technique associated with VOC analysis is mass spectrometry, which is usually coupled with GC, giving the hyphenated technique of GC-MS.
Direct injection mass spectrometry techniques are frequently utilized for the rapid detection and accurate quantification of VOCs. PTR-MS is among the methods that have been used most extensively for the on-line analysis of biogenic and anthropogenic VOCs. PTR-MS instruments based on time-of-flight mass spectrometry have been reported to reach detection limits of 20 pptv after 100 ms and 750 ppqv after 1 min. measurement (signal integration) time. The mass resolution of these devices is between 7000 and 10,500 m/Δm, thus it is possible to separate most common isobaric VOCs and quantify them independently. | 0 | Organic Chemistry |
*1990, American Chemical Society Division of Analytical Chemistry J. Calvin Giddings Award for Excellence in Teaching
*2002, Electrochemical Society Henry B. Linford Award for Distinguished Teaching
*2006, W. George Pinnell Award for Outstanding Service, Indiana University Bloomington
*2007, Elected Fellow of the Electrochemical Society
*2012, Electrochemical Society Division of Organic and Biological Electrochemistry, Manuel M. Baizer Award
*2012, Elected Fellow of the American Association for the Advancement of Science
*2017, Elected Fellow of the American Chemical Society
*2020, American Chemical Society Division of Analytical Chemistry, Roland F. Hirsch Award for Distinguished Service | 3 | Analytical Chemistry |
Space power generation systems must provide consistent and reliable power without large amounts of fuel. As a result, solar and radioisotope fuels (extremely high power density and long lifetime) are ideal. TPVs have been proposed for each. In the case of solar energy, orbital spacecraft may be better locations for the large and potentially cumbersome concentrators required for practical TPVs. However, weight considerations and inefficiencies associated with the more complicated design of TPVs, protected conventional PVs continue to dominate.
The output of isotopes is thermal energy. In the past thermoelectricity (direct thermal to electrical conversion with no moving parts) has been used because TPV efficiency is less than the ~10% of thermoelectric converters. Stirling engines have been deemed too unreliable, despite conversion efficiencies >20%. However, with the recent advances in small-bandgap PVs, TPVs are becoming more promising. A TPV radioisotope converter with 20% efficiency was demonstrated that uses a tungsten emitter heated to 1350 K, with tandem filters and a 0.6 eV bandgap InGaAs PV converter (cooled to room temperature). About 30% of the lost energy was due to the optical cavity and filters. The remainder was due to the efficiency of the PV converter.
Low-temperature operation of the converter is critical to the efficiency of TPV. Heating PV converters increases their dark current, thereby reducing efficiency. The converter is heated by the radiation from the emitter. In terrestrial systems it is reasonable to dissipate this heat without using additional energy with a heat sink. However, space is an isolated system, where heat sinks are impractical. Therefore, it is critical to develop innovative solutions to efficiently remove that heat. Both represent substantial challenges. | 7 | Physical Chemistry |
γ-Amylase () (alternative names: Glucan 1,4-a-glucosidase; amyloglucosidase; exo-1,4-α-glucosidase; glucoamylase; lysosomal α-glucosidase; 1,4-α--glucan glucohydrolase) will cleave α(1–6) glycosidic linkages, as well as the last α-1,4 glycosidic bond at the nonreducing end of amylose and amylopectin, yielding glucose. The γ-amylase has the most acidic optimum pH of all amylases because it is most active around pH 3. They belong to a variety of different GH families, such as glycoside hydrolase family 15 in fungi, glycoside hydrolase family 31 of human MGAM, and glycoside hydrolase family 97 of bacterial forms. | 1 | Biochemistry |
In the 1950s, a series of epidemiological studies were done in the US to determine the relationship between water quality of natural waters and the health of bathers. The results indicated that swimmers were more likely to have gastrointestinal symptoms, eye infections, skin complaints, ear, nose, and throat infections and respiratory illness than non-swimmers and in some cases, higher coliform levels correlated to higher incidence of gastrointestinal illness, although the sample sizes in these studies were small. Since then, studies have been done to confirm causative relations between swimming and certain health outcomes. A review of 22 studies in 1998 confirmed that the health risks for swimmers increased as the number of indicator bacteria increased in recreational waters and that E. coli and enterococci concentrations correlated best with health outcomes among all the indicators studied. The relative risk (RR) of illness for swimmers in polluted freshwater versus swimmers in unpolluted water was between 1–2 for the majority of the data sets reviewed. The same study concluded that bacterial indicators were not well correlated to virus concentrations. | 3 | Analytical Chemistry |
The fundamental thermodynamic relation and statistical mechanical principles can be derived from one another. | 7 | Physical Chemistry |
The Institution of Metallurgists was a British professional association for metallurgists, largely involved in the iron and steel industry. | 8 | Metallurgy |
The magic angle is a particular value of the collection angle of an electron microscope at which the measured energy-loss spectrum "magically" becomes independent of the tilt angle of the sample with respect to the beam direction. The magic angle is not uniquely defined for isotropic samples, but the definition is unique in the (typical) case of small angle scattering on materials with a "c-axis", such as graphite.
The "magic" angle depends on both the incoming electron energy (which is typically fixed) and the energy loss suffered by the electron. The ratio of the magic angle to the characteristic angle is roughly independent of the energy loss and roughly independent of the particular type of sample considered. | 7 | Physical Chemistry |
The problem of gene regulation could be represented mathematically as the probability of n molecules — RNAP, activators, repressors and inducers — are bound to a target regions.
To compute the probability of bound, it is needed to sum the Boltzmann weights over all possible states of polymerase molecules
on DNA. Here in this deduction is the effective number of RNAP molecules available for binding to the promoter.
This approach is based in statistical thermodynamics of two possible microscopic outcomes:
# one state where all P polymerases molecules are distributed among all the non-specific sites (sites not participating in gene expression)
# a promoter occupied and the remaining P-1 polymerases distributed among the non-specific sites.
The statistical weight of promoter unoccupied Z(P) is defined:
Where the first term is the combinatorial result of taken polymerase of non-specific sites available, and the second term are the Boltzmann weights, where is the energy that represents the average binding energy of RNA polymerase to the genomic background (non-specific sites).
Then, the total statistical weight , can be written as the sum of the state and the RNA polymerase on promoter state:
Where in the state is the binding energy for RNA polymerase on the promoter (where the s stands for specific site).
Finally, to find the probability of a RNA polymerase to binding ( ) to a specific promoter, we divide by which produces:
Where,
An important result of this model is that any transcription factor, regulator or perturbation could be introduced as a term multiplying in the probability of binding equation. This term for any transcriptional factor (here called factor regulators) modify the probability of binding to:
Where is the term for transcriptional factors, and it has the value of for increase of for decrease of the number of RNA polymerase available to bind.
This result has an important significance to represent mathematically all the possible configurations of transcriptional factor by derive different models to estimate (for further developments, see also ). | 1 | Biochemistry |
Schizosaccharomyces pombe is a facultative sexual yeast that can undergo mating when nutrients are limiting. Exposure of S. pombe to hydrogen peroxide, an agent that causes oxidative stress leading to oxidative DNA damage, strongly induces mating, meiosis, and formation of meiotic spores. This finding suggests that meiosis, and particularly meiotic recombination, may be an adaptation for repairing DNA damage. The overall structure of the MAT locus is similar to that in S. cerevisiae. The mating-type switching system is similar, but has evolved independently. | 1 | Biochemistry |
Isomalathion is an impurity found in some batches of malathion. Whereas the structure of malation is, generically, RSP(S)(OCH), the connectivity of isomalathion is RSPO(SCH)(OCH). It arises by heating malathion. Being significantly more toxic to humans than malathion, it has resulted in human poisonings.
In 1976, numerous malaria workers in Pakistan were poisoned by isomalathion. It is an inhibitor of carboxyesterase. | 1 | Biochemistry |
Thermal physics is the combined study of thermodynamics, statistical mechanics, and kinetic theory of gases. This umbrella-subject is typically designed for physics students and functions to provide a general introduction to each of three core heat-related subjects. Other authors, however, define thermal physics loosely as a summation of only thermodynamics and statistical mechanics.
Thermal physics can be seen as the study of system with larger number of atom, it unites thermodynamics to statistical mechanics. | 7 | Physical Chemistry |
DCvC has been used to make molecules with complex topological properties. In the case of Borromean rings, DCvC is used to synthesize a three ring interlocking system. Thermodynamic templates are used to stabilize interlocking macrocycle growth. | 6 | Supramolecular Chemistry |
Veterinary schools, veterinary hospitals, and bovine farming operations in North America often keep a healthy fistulated cow as a microbiota donor. Large animal veterinarians will pull the contents by hand from the healthy cows rumen system to help repopulate the fauna in a sick cows rumen. This process is called transfaunation, or a microbiota transplant.
In Europe, the fistulation of cows to provide rumen contents for transfaunation is considered unethical, and is not practised. Instead, rumen liquor is aspirated through a rumen-fluid collector, consisting of a Frick gag and a flexible hose with a perforated metal tip which serves as a filter. The hose and tip is passed through the gag and down the oesophagus to the rumen. It is normally possible to aspirate five litres of rumen liquor using this device.
Rumen contents from a fistulated cow can also help sheep and goats, which have similar digestive systems.
A 2014 review of rumen transfaunation research indicated that the procedure has been demonstrated to help correct indigestion resulting from illness, surgical correction of displaced abomasum, and ingestion of toxic plants. | 1 | Biochemistry |
Moroidin, a bicyclic octapeptide, has been isolated from Dendrocnide moroides (also called Laportea moroides) and Celosia argentea. The structure of moroidin was confirmed in 2004 by X-ray crystallography. It contains two unusual crosslinks, one between leucine and tryptophan and the other between tryptophan and histidine. These linkages are also present in an analogous family of compounds, the celogentins. | 0 | Organic Chemistry |
In materials science, grain-boundary strengthening (or Hall–Petch strengthening) is a method of strengthening materials by changing their average crystallite (grain) size. It is based on the observation that grain boundaries are insurmountable borders for dislocations and that the number of dislocations within a grain has an effect on how stress builds up in the adjacent grain, which will eventually activate dislocation sources and thus enabling deformation in the neighbouring grain as well. By changing grain size, one can influence the number of dislocations piled up at the grain boundary and yield strength. For example, heat treatment after plastic deformation and changing the rate of solidification are ways to alter grain size. | 8 | Metallurgy |
Gas Engine Row has many large stationary gas engines from the early 1900s. On the row is an operational Fairbanks-Morse mine hoist winding engine, a pumphouse powered by a Fairbanks-Morse engine, a horsepower 1922 Fairbanks-Morse type YV engine connected to a large alternator, an enormous 1914 Chicago-Pneumatic hot-bulb air compressor, an Western engine, a Western engine, a Western engine and many other stationary engines. Almost all of the engines on Gas Engine Row can be seen running during the shows.
Steam Engine Row showcases many different types and sizes of stationary steam engines; from a monstrous Allis Chalmers Corliss engine with a flywheel, to a small J. Lefel & Sons portable engine. They are all powered by steam from two large boilers, nicknamed Pat and Rich, after two long-time museum volunteers who maintain and operate them. | 8 | Metallurgy |
Studies have demonstrated that the oxidative stress generated by arsenic may disrupt the signal transduction pathways of the nuclear transcriptional factors PPARs, AP-1, and NF-κB, as well as the pro-inflammatory cytokines IL-8 and TNF-α. The interference of oxidative stress with signal transduction pathways may affect physiological processes associated with cell growth, metabolic syndrome X, glucose homeostasis, lipid metabolism, obesity, insulin resistance, inflammation, and diabetes-2. Recent scientific evidence has elucidated the physiological roles of the PPARs in the ω- hydroxylation of fatty acids and the inhibition of pro-inflammatory transcription factors (NF-κB and AP-1), pro-inflammatory cytokines (IL-1, -6, -8, -12, and TNF-α), cell4 adhesion molecules (ICAM-1 and VCAM-1), inducible nitric oxide synthase, proinflammatory nitric oxide (NO), and anti-apoptotic factors.
Epidemiological studies have suggested a correlation between chronic consumption of drinking water contaminated with arsenic and the incidence of type 2 diabetes. The human liver after exposure to therapeutic drugs may exhibit hepatic non-cirrhotic portal hypertension, fibrosis, and cirrhosis. However, the literature provides insufficient scientific evidence to show cause and effect between arsenic and the onset of diabetes mellitus Type 2. | 1 | Biochemistry |
Geminal halide hydrolysis is an organic reaction. The reactants are geminal dihalides with a water molecule or a hydroxide ion. The reaction yields ketones from secondary halides or aldehydes from primary halides. | 0 | Organic Chemistry |
For a free ion, e.g. gaseous Ni or Mo, the energy of the d-orbitals are equal in energy; that is, they are "degenerate". In an octahedral complex, this degeneracy is lifted. The energy of the d−y set, which are aimed directly at the ligands are destabilized. On the other hand, the energy of the d, d, and d orbitals, the so-called t set, are stabilized. The labels t and e refer to irreducible representations, which describe the symmetry properties of these orbitals. The energy gap separating these two sets is the basis of crystal field theory and the more comprehensive ligand field theory. The loss of degeneracy upon the formation of an octahedral complex from a free ion is called crystal field splitting or ligand field splitting. The energy gap is labeled Δ, which varies according to the number and nature of the ligands. If the symmetry of the complex is lower than octahedral, the e and t levels can split further. For example, the t and e sets split further in trans-MLL.
Ligand strength has the following order for these electron donors:
:weak: iodine < bromine < fluorine < acetate < oxalate < water < pyridine < cyanide :strong
So called "weak field ligands" give rise to small Δ and absorb light at longer wavelengths. | 4 | Stereochemistry |
A number of bacterial mRNAs have no 5'UTR whatsoever, or a very short one. The complete 70S ribosome, with the help of IF2 (recruiting fMet-tRNA), can simply start translating such a "leaderless" mRNA.
A number of factors modify the efficiency of leaderless initiation. A 5 phosphate group attached to the start codon seems near-essential. AUG is strongly preferred in E. coli, but not necessarily in other species. IF3 inhibits leaderless initiation. A longer 5UTR or one with significant secondary structure also inhibits leaderless initiation. | 1 | Biochemistry |
With these technologies, cold water circulates through a blanket, or torso wraparound vest and leg wraps. To lower temperature with optimal speed, 70% of a persons surface area should be covered with water blankets. The treatment represents the most well studied means of controlling body temperature. Water blankets lower a persons temperature exclusively by cooling a person's skin and accordingly require no invasive procedures.
Water blankets possess several undesirable qualities. They are susceptible to leaking, which may represent an electrical hazard since they are operated in close proximity to electrically powered medical equipment. The Food and Drug Administration also has reported several cases of external cooling blankets causing significant burns to the skin of person. Other problems with external cooling include overshoot of temperature (20% of people will have overshoot), slower induction time versus internal cooling, increased compensatory response, decreased patient access, and discontinuation of cooling for invasive procedures such as the cardiac catheterization.
If therapy with water blankets is given along with two litres of cold intravenous saline, people can be cooled to in 65 minutes. Most machines now come with core temperature probes. When inserted into the rectum, the core body temperature is monitored and feedback to the machine allows changes in the water blanket to achieve the desired set temperature. In the past some of the models of cooling machines have produced an overshoot in the target temperature and cooled people to levels below , resulting in increased adverse events. They have also rewarmed patients at too fast a rate, leading to spikes in intracranial pressure. Some of the new models have more software that attempt to prevent this overshoot by utilizing warmer water when the target temperature is close and preventing any overshoot. Some of the new machines now also have 3 rates of cooling and warming; a rewarming rate with one of these machines allows a patient to be rewarmed at a very slow rate of just an hour in the "automatic mode", allowing rewarming from to over 24 hours. | 1 | Biochemistry |
A termolecular (or trimolecular) reaction in solutions or gas mixtures involves three reactants simultaneously colliding, with appropriate orientation and sufficient energy. However the term trimolecular is also used to refer to three body association reactions of the type:
Where the M over the arrow denotes that to conserve energy and momentum a second reaction with a third body is required. After the initial bimolecular collision of A and B an energetically excited reaction intermediate is formed, then, it collides with a M body, in a second bimolecular reaction, transferring the excess energy to it.
The reaction can be explained as two consecutive reactions:
These reactions frequently have a pressure and temperature dependence region of transition between second and third order kinetics.
Catalytic reactions are often three-component, but in practice a complex of the starting materials is first formed and the rate-determining step is the reaction of this complex into products, not an adventitious collision between the two species and the catalyst. For example, in hydrogenation with a metal catalyst, molecular dihydrogen first dissociates onto the metal surface into hydrogen atoms bound to the surface, and it is these monatomic hydrogens that react with the starting material, also previously adsorbed onto the surface.
Reactions of higher molecularity are not observed due to very small probability of simultaneous interaction between 4 or more molecules. | 7 | Physical Chemistry |
ECOTOX is considered to be more comprehensive in that it holds results from toxicity tests of single chemicals on aquatic and terrestrial plants and animals. Data can be found on both freshwater and marine taxa. ECOTOX collects data from previously EPA established databases , TERRATOX, and PHYTOTOX which individually provide aquatic, terrestrial species and plant data respectively. Data large is collected from peer-reviewed literature however some amount of data is sourced from grey literature. Using the Quick Database Query function enables searches by chemical, taxonomic name, effect, and publication year. Data from ECOTOX is used to provide reference parameters to current toxicity studies and serves as a regulatory guideline. | 1 | Biochemistry |
In organic chemistry, hydroboration refers to the addition of a hydrogen-boron bond to certain double and triple bonds involving carbon (, , , and ). This chemical reaction is useful in the organic synthesis of organic compounds.
Hydroboration produces organoborane compounds that react with a variety of reagents to produce useful compounds, such as alcohols, amines, or alkyl halides. The most widely known reaction of the organoboranes is oxidation to produce alcohols typically by hydrogen peroxide. This type of reaction has promoted research on hydroboration because of its mild condition and a wide scope of tolerated alkenes. Another research subtheme is metal-catalysed hydroboration.
The development of this technology and the underlying concepts were recognized by the Nobel Prize in Chemistry to Herbert C. Brown. He shared the prize with Georg Wittig in 1979 for his pioneering research on organoboranes as important synthetic intermediates. A complement to hydroboration is carboboration, where a carbon moiety is incorporated rather than hydrogen. | 0 | Organic Chemistry |
Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides. Biopesticides fall into three major classes:
* Microbial pesticides which consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes are also often classed as microbial pesticides, even though they are multi-cellular.
* Biochemical pesticides or herbal pesticides are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial diseases.
* Plant-incorporated protectants (PIPs) have genetic material from other species incorporated into their genetic material (i.e. GM crops). Their use is controversial, especially in many European countries. | 2 | Environmental Chemistry |
is a biweekly peer-reviewed scientific journal published by Elsevier. It was established in 1950 and is sponsored by the Geochemical Society and the Meteoritical Society. The editor-in-chief is Jeffrey Catalano (Washington University in St. Louis). The journal covers topics in Earth geochemistry, planetary geochemistry, cosmochemistry and meteoritics.
Publishing formats include original research articles and invited reviews and occasional editorials, book reviews, and announcements. In addition, the journal publishes short comments (4 pages) targeting specific articles and designed to improve understanding of the target article by advocating a different interpretation supported by the literature, followed by a response by the author. | 9 | Geochemistry |
:The symmetry of a crystalline material has profound impacts on its emergent properties, including electronic band structure, electromagnetic behavior, and mechanical properties . Crystal symmetry is described and categorized by the crystal system, lattice, and space group of the material. Determination of these attributes is an important aspect of crystallography.
:Precession electron diffraction enables much more direct determination of space group symmetries over other forms of electron diffraction. Because of the increased number of reflections in both the zero order Laue zone and higher order Laue zones, the geometric relationship between Laue zones is more readily determined. This provides three-dimensional information about the crystal structure that can be used to determine its space group. Furthermore, because the PED technique is insensitive to slight misorientation from the zone axis, it provides the practical benefit of more robust data collection. | 3 | Analytical Chemistry |
The forces between the atoms in a solid can take a variety of forms. For example, a crystal of sodium chloride (common salt) is made up of ionic sodium and chlorine, which are held together by ionic bonds. In diamond or silicon, the atoms share electrons and form covalent bonds. In metals, electrons are shared in metallic bonding. Some solids, particularly most organic compounds, are held together with van der Waals forces resulting from the polarization of the electronic charge cloud on each molecule. The dissimilarities between the types of solid result from the differences between their bonding. | 7 | Physical Chemistry |
Mars is fundamentally an igneous planet. Rocks on the surface and in the crust consist predominantly of minerals that crystallize from magma. Most of our current knowledge about the mineral composition of Mars comes from spectroscopic data from orbiting spacecraft, in situ analyses of rocks and soils from six landing sites, and study of the Martian meteorites. Spectrometers currently in orbit include THEMIS (Mars Odyssey), OMEGA (Mars Express), and CRISM (Mars Reconnaissance Orbiter). The two Mars exploration rovers each carry an Alpha Particle X-ray Spectrometer (APXS), a thermal emission spectrometer (Mini-TES), and Mössbauer spectrometer to identify minerals on the surface.
On October 17, 2012, the Curiosity rover on the planet Mars at "Rocknest" performed the first X-ray diffraction analysis of Martian soil. The results from the rover's CheMin analyzer revealed the presence of several minerals, including feldspar, pyroxenes and olivine, and suggested that the Martian soil in the sample was similar to the "weathered basaltic soils" of Hawaiian volcanoes. | 9 | Geochemistry |
The first ideas about light being used in photosynthesis were proposed by Colin Flannery in 1779 who recognized it was sunlight falling on plants that was required, although Joseph Priestley had noted the production of oxygen without the association with light in 1772. Cornelis Van Niel proposed in 1931 that photosynthesis is a case of general mechanism where a photon of light is used to photo decompose a hydrogen donor and the hydrogen being used to reduce .
Then in 1939, Robin Hill demonstrated that isolated chloroplasts would make oxygen, but not fix , showing the light and dark reactions occurred in different places. Although they are referred to as light and dark reactions, both of them take place only in the presence of light. This led later to the discovery of photosystems I and II. | 5 | Photochemistry |
Ammonium phosphomolybdate, anion, was reported in 1826. The isostructural phosphotungstate anion was characterized by X-ray crystallography 1934. This structure is called the Keggin structure after its discoverer.
The 1970's witnessed the introduction of quaternary ammonium salts of POMs. This innovation enabled systematic study without the complications of hydrolysis and acid/base reactions. The introduction of O NMR spectroscopy allowed the structural characterization of POMs in solution.
Ramazzoite, the first example of a mineral with a polyoxometalate cation, was described in 2016 in Mt. Ramazzo Mine, Liguria, Italy. | 7 | Physical Chemistry |
Heme biosynthesis is used as biomarker in environmental toxicology studies. While excess production of porphyrins indicate organochlorine exposure, lead inhibits ALA dehydratase enzyme. | 1 | Biochemistry |
A sample (analyte) is injected into a flowing carrier solution stream that is forced by a peristaltic pump. The injection of the sample is done under controlled dispersion in known volumes. The carrier solution and sample then meet at mixing points with reagents and react. The reaction time is controlled by a pump and reaction coil. The reaction product then flows through a detector. Most often, the detector is a spectrophotometer as the reactions usually produce a colored product. One can then determine the amount of an unknown material in the sample as it is proportional to the absorption spectrum given by the spectrophotometer. After moving through the detector, the sample then flows to waste.
Detail of sample dispersion
When a sample is injected into the carrier stream it has the rectangular flow. As the sample is carried through the mixing and reaction zone, the width of the flow profile increases as the sample disperses into the carrier stream. Dispersion results from two processes: convection due to the flow of the carrier stream and diffusion due to a concentration gradient between the sample and the carrier stream. Convection of the sample occurs by laminar flow, in which the linear velocity of the sample at the tube's walls is zero, while the sample at the center of the tube moves with a linear velocity twice that of the carrier stream. The result is the parabolic flow profile, before the sample passes through a detector to a waste container. | 3 | Analytical Chemistry |
Fluorescence spectroscopy is a technique that is used to assay a sample using a fluorescent probe. DNA nucleotides themselves are not good candidates for this technique because they do not readily re-emit light upon light excitation. A fluorescent marker is needed to detect base flipping. 2-Aminopurine is a base that is structurally similar to adenine, but is very fluorescent when flipped out from the DNA duplex. It is commonly used to detect base flipping and has an excitation at 305‑320 nm and emission at 370 nm so that it well separated from the excitations of proteins and DNA. Other fluorescent probes used to study DNA base flipping are 6MAP (4‑amino‑6‑methyl‑7(8H)‑pteridone) and Pyrrolo‑C (3-[β-D-2-ribofuranosyl]-6-methylpyrrolo[2,3-d]pyrimidin-2(3H)-one). Time-resolved fluorescence spectroscopy is also employed to provide a more detailed picture of the extent of base flipping as well as the conformational dynamics occurring during base flipping. | 1 | Biochemistry |
Thermal radiation is a phenomenon that can burn skin and ignite flammable materials. The time to a damage from exposure to thermal radiation is a function of the rate of delivery of the heat. Radiative heat flux and effects are given as follows: | 7 | Physical Chemistry |
Octasulfur is an inorganic substance with the chemical formula . It is an odourless and tasteless yellow solid, and is a major industrial chemical. It is the most common allotrope of sulfur and occurs widely in nature. | 1 | Biochemistry |
The Jameson Cell is a high-intensity froth flotation cell that was invented by Laureate Professor Graeme Jameson of the University of Newcastle (Australia) and developed in conjunction with Mount Isa Mines Limited ("MIM", a subsidiary of MIM Holdings Limited and now part of the Glencore group of companies). | 8 | Metallurgy |
Deamination of guanine results in the formation of xanthine. Xanthine, however, still pairs with cytosine. | 1 | Biochemistry |
Although polyadenylation is seen in almost all organisms, it is not universal. However, the wide distribution of this modification and the fact that it is present in organisms from all three domains of life implies that the last universal common ancestor of all living organisms, it is presumed, had some form of polyadenylation system. A few organisms do not polyadenylate mRNA, which implies that they have lost their polyadenylation machineries during evolution. Although no examples of eukaryotes that lack polyadenylation are known, mRNAs from the bacterium Mycoplasma gallisepticum and the salt-tolerant archaean Haloferax volcanii lack this modification.
The most ancient polyadenylating enzyme is polynucleotide phosphorylase. This enzyme is part of both the bacterial degradosome and the archaeal exosome, two closely related complexes that recycle RNA into nucleotides. This enzyme degrades RNA by attacking the bond between the 3′-most nucleotides with a phosphate, breaking off a diphosphate nucleotide. This reaction is reversible, and so the enzyme can also extend RNA with more nucleotides. The heteropolymeric tail added by polynucleotide phosphorylase is very rich in adenine. The choice of adenine is most likely the result of higher ADP concentrations than other nucleotides as a result of using ATP as an energy currency, making it more likely to be incorporated in this tail in early lifeforms. It has been suggested that the involvement of adenine-rich tails in RNA degradation prompted the later evolution of polyadenylate polymerases (the enzymes that produce poly(A) tails with no other nucleotides in them).
Polyadenylate polymerases are not as ancient. They have separately evolved in both bacteria and eukaryotes from CCA-adding enzyme, which is the enzyme that completes the 3′ ends of tRNAs. Its catalytic domain is homologous to that of other polymerases. It is presumed that the horizontal transfer of bacterial CCA-adding enzyme to eukaryotes allowed the archaeal-like CCA-adding enzyme to switch function to a poly(A) polymerase. Some lineages, like archaea and cyanobacteria, never evolved a polyadenylate polymerase.
Polyadenylate tails are observed in several RNA viruses, including Influenza A, Coronavirus, Alfalfa mosaic virus, and Duck Hepatitis A. Some viruses, such as HIV-1 and Poliovirus, inhibit the cells poly-A binding protein (PABPC1) in order to emphasize their own genes expression over the host cell's. | 1 | Biochemistry |
Since the energy states of valence tautomers affect the IVCT band, the strength of electronic interaction between the sites, known as α (the mixing coefficient), can be determined by analysis of the IVCT band. Depending on the value of α, mixed valence complexes are classified into three groups:
*class I: α ~ 0, the complex has no interaction between redox sites. No IVCT band is observed. The oxidation states of the two metal sites are distinct and do not readily interconvert.
*class II: 0 = 0.707, intermediate interaction between sites. An IVCT band is observed. The oxidation states of the two metal sites are distinct, but they readily interconvert. This is by far the most common class of intervalence complexes.
*class III: α > = 0.707, interaction between redox sites is very strong. It is better to consider these sites as one united site, not as two isolated sites. An IVCT band is observed. The oxidation states of the two metal sites are essentially equivalent. In these situations, the two metals are often best described as having the same half integer oxidation state. | 7 | Physical Chemistry |
It crystallizes as a tetrameric cubane-type cluster. It crystallises from tetrahydrofuran/pentane at −20°C as [tBuOK·tBuOH], which consists of straight chains linked by hydrogen bonding. Sublimation of [tBuOK·tBuOH] affords the tetramer [tBuOK], which adopts a cubane-like structure. Mild Lewis basic solvents such as THF and diethyl ether do not break up the tetrameric structure, which persists in the solid, in solution and even in the gas phase. | 0 | Organic Chemistry |
The sigma-2 receptor takes part in a number of normal-function roles, including cell proliferation, autophagy, cholesterol homeostasis, and both non-neuronal and neuronal signaling. Much of sigma-2 receptor function relies on signaling cascades. The receptor's interaction with EGFR and PGRMC1 proteins allow for sigma-2 receptors to play diverse roles within cell through Ras, PLC, and PI3K signaling. | 1 | Biochemistry |
The trace amount of samples collected from crime scenes can be amplified by MDA to the quantity that is enough for forensic DNA analysis, which is commonly used in identifying victims and suspects. | 1 | Biochemistry |
Slippery sequences can potentially make the reading ribosome "slip" and skip a number of nucleotides (usually only 1) and read a completely different frame thereafter. In programmed −1 ribosomal frameshifting, the slippery sequence fits a X_XXY_YYH motif, where XXX is any three identical nucleotides (though some exceptions occur), YYY typically represents UUU or AAA, and H is A, C or U. In the case of +1 frameshifting, the slippery sequence contains codons for which the corresponding tRNA is more rare, and the frameshift is favored because the codon in the new frame has a more common associated tRNA. One example of a slippery sequence is the polyA on mRNA, which is known to induce ribosome slippage even in the absence of any other elements. | 1 | Biochemistry |
One of the primary functions of carbaminohemoglobin is to enable the transport of carbon dioxide in the bloodstream. When carbon dioxide is produced as a waste product of cellular metabolism in tissues, the compound is diffused into the bloodstream and it works to react with hemoglobin.
When the binding of molecules occurs to form carbaminohemoglobin, it allows for the transport of carbon dioxide from the tissues to the lungs. One it is in the lungs, carbon dioxide is released from carbaminohemoglobin and can be let out from the body during the exhalation process. This complete process is very important for maintaining the balance of gases in the blood and to ensure that gas exchange is being transported between tissues and organs. | 1 | Biochemistry |
;Aldehydes and ketones
Polymeric hydrosilanes, such as polymethylhydrosiloxane (PHMS), may be employed to facilitate separation of the reduced products from silicon-containing byproducts.
Enantioselective reductions of ketones may be accomplished through the use of catalytic amounts of chiral transition metal complexes. In some cases, the transition metal simply serves as a Lewis acid that coordinates to the ketone oxygen; however, some metals (most notably copper) react with hydrosilanes to afford metal hydride intermediates, which act as the active reducing agent.
In the presence of rhodium catalyst 1 and rhodium trichloride, 2-phenylcyclohexanone is reduced with no diastereoselectivity but high enantioselectivity.
;Esters
Esters may be reduced to alcohols under conditions of nucleophilic activation with caesium or potassium fluoride.
Aldehydes undergo hydrosilylation in the presence of hydrosilanes and fluoride. The resulting silyl ethers can be hydrolyzed with 1 M hydrochloric acid. Optimal yields of the hydrosilylation are obtained when the reaction is carried out in very polar solvents. | 0 | Organic Chemistry |
Vicinal difunctionalization refers to a chemical reaction involving transformations at two adjacent centers (most commonly carbons). This transformation can be accomplished in α,β-unsaturated carbonyl compounds via the conjugate addition of a nucleophile to the β-position followed by trapping of the resulting enolate with an electrophile at the α-position. When the nucleophile is an enolate and the electrophile a proton, the reaction is called Michael addition. | 0 | Organic Chemistry |
Reversible photochromics are also found in applications such as toys, cosmetics, clothing and industrial applications. If necessary, they can be made to change between desired colors by combination with a permanent pigment. | 5 | Photochemistry |
Symplekin (SYMPK) is a scaffolding protein that mediates the interaction between CPSF and CstF.
In mammalian CPSF, both cleavage factor I (CFI) and cleavage and polyadenylation specificity factor (CPSF) are required for cleavage and polyadenylation whereas cleavage stimulation factor (CstF) is only essential for the cleavage step. CPSF and CstF travel along with RNA polymerase II (RNAP II) during nascent gene transcription in search of the PAS.
Cleavage factor I (CFI) is made of 25 (CPSF5), 59 (CPSF7), and 68 (CPSF6) kDa proteins. Cleavage factor II (CFII) is made of Pcf11, Clp1, and cleavage stimulation factor (CstF). CFII binds to the RNAP II C-terminal domain and other CpA factors.
Cleavage stimulation factor (CstF) has three subunits: CstF77 (CstF3), CstF50 (CstF1), and CstF64 (CstF2 and CstF2T). CstF recognizes the PAS that is 20 nucleotides downstream the signaling region of the cleavage site, which is a GU-rich sequence motif followed by U-rich sequences. CstF contributes to the selection of the cleavage site, as well as alternative polyadenylation. | 1 | Biochemistry |
A Levich constant (B) is often used in order to simplify the Levich equation. Furthermore, B is readily extracted from rotating disk electrode experimental data.
The B can be defined as:
where
* n is the number of moles of electrons transferred in the half reaction (number)
* F is the Faraday constant (C/mol)
* A is the electrode area (cm)
* D is the diffusion coefficient (see Fick's law of diffusion) (cm/s)
* v is the kinematic viscosity (cm/s)
* C is the analyte concentration (mol/cm) | 7 | Physical Chemistry |
The leaving group X in the organic partner is usually a halide, although triflate, tosylate and other pseudohalide have been used. Chloride is an ideal group due to the low cost of organochlorine compounds. Frequently, however, C–Cl bonds are too inert, and bromide or iodide leaving groups are required for acceptable rates. The main group metal in the organometallic partner usually is an electropositive element such as tin, zinc, silicon, or boron. | 0 | Organic Chemistry |
Extending the wavelength range for CD experiments had been both considered and instigated as far back as 1970. Three research groups had created their own "in-house" CD machines, with specialist lamps as their light source, to enable measurements in this range. Synchrotron radiation (SR) had been proposed for use as the light source at a meeting in Brookhaven National Laboratory on Long Island in 1972, however, it took a few years more before this came to fruition. Two research papers in 1980 reported the collection of CD data using SR as the light source for the experiments. Specifically, spectra were obtained in wavelength regions into the VUV range, from ~100 nanometers (nm) to ~200 nm, largely unavailable to laboratory-based bench-top spectrophotometers. Sutherland et. al. focussed on the development of a versatile spectrophotometer capable of measuring CD, amongst other properties, in the VUV region of the spectrum, while Snyder and Rowe collected CD data from a small organic compound in the wavelength range 130.5 nm to 205 nm. | 7 | Physical Chemistry |
A number of methods of measuring distribution coefficients have been developed, including the shake-flask, separating funnel method, reverse-phase HPLC, and pH-metric techniques. | 7 | Physical Chemistry |
Alarm signals need not be communicated only by auditory means. For example, many animals may use chemosensory alarm signals, communicated by chemicals known as pheromones. Minnows and catfish release alarm pheromones (Schreckstoff) when injured, which cause nearby fish to hide in dense schools near the bottom. At least two species of freshwater fish produce chemicals known as disturbance cues, which initiates a coordinated antipredator defence by increasing group cohesion in response to fish predators. Chemical communication about threats is also known among plants, though it is debated to what extent this function has been reinforced by actual selection. Lima beans release volatile chemical signals that are received by nearby plants of the same species when infested with spider mites. This message allows the recipients to prepare themselves by activating defense genes, making them less vulnerable to attack, and also attracting another mite species that is a predator of spider mites (indirect defence). Although it is conceivable that other plants are only intercepting a message primarily functioning to attract "bodyguards", some plants spread this signal on to others themselves, suggesting an indirect benefit from increased inclusive fitness.
Deceptive chemical alarm signals are also employed. For example, the wild potato, Solanum berthaultii, emits the aphid alarm-pheromone, (E)-β-farnesene, from its leaves, which functions as a repellent against the green peach aphid, Myzus persicae. | 1 | Biochemistry |
The degree of coordinative unsaturation of a surface cation measures the number of bonds involving the cation that have to be broken to form a surface. As the degree of coordinative unsaturation increases, more bonds are broken and the metal cation becomes destabilized. The destabilization of the cation increases the surface Gibbs energy, which decreases the overall stability. For example, the rutile (110) surface is more stable than the rutile (100) and (001) surfaces because it has a lower degree of coordinative unsaturation. | 7 | Physical Chemistry |
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the main examples of polynucleotides. They arise by condensation of nucleotides. Their backbones form by the condensation of a hydroxy group on a ribose with the phosphate group on another ribose. This linkage is called a phosphodiester bond. The condensation is catalyzed by enzymes called polymerases. DNA and RNA can be millions of nucleotides long thus allowing for the genetic diversity of life. The bases project from the pentose-phosphate polymer backbone and are hydrogen bonded in pairs to their complementary partners (A with T and G with C). This creates a double helix with pentose phosphate backbones on either side, thus forming a secondary structure. | 0 | Organic Chemistry |
Charles M. Schwab (1862–1939) and Eugene Grace (1876–1960) made Bethlehem Steel the second-largest American steel company by the 1920s. Schwab had been the operating head of Carnegie Steel and US Steel. In 1903 he purchased the small firm Bethlehem Steel, and in 1916 made Grace president. Innovation was the keynote at a time when U.S. Steel under Judge Elbert Henry Gary moved slowly. Bethlehem concentrated on government contracts, such as ships and naval armor, and on construction beams, especially for skyscrapers and bridges. Its subsidiary Bethlehem Shipbuilding Corporation operated 15 shipyards in World War II. It produced 1,121 ships, more than any other builder during the war and nearly one-fifth of the U.S. Navy's fleet. Its peak employment was 180,000 workers, out of a company-wide wartime peak of 300,000. After 1945 Bethlehem doubled its steel capacity, a measure of the widespread optimism in the industry. However the company ignored the new technologies then being developed in Europe and Japan. Seeking labor peace in order to avoid strikes, Bethlehem like the other majors agreed to large wage and benefits increases that kept its costs high. After Grace retired the executives concentrated on short term profits and postponed innovations that led to long-term inefficiency. It went bankrupt in 2001. | 8 | Metallurgy |
In the field of engineering, the hydrophobicity (or dewetting ability) of a flat surface (e.g., a counter top in kitchen or a cooking pan) can be measured by the contact angle of water droplet. A University of Nebraska-Lincoln team recently devised a computational approach that can relate the molecular hydrophobicity scale of amino-acid chains to the contact angle of water nanodroplet. The team constructed planar networks composed of unified amino-acid side chains with native structure of the beta-sheet protein. Using molecular dynamics simulation, the team is able to measure the contact angle of water nanodroplet on the planar networks (caHydrophobicity).
On the other hand, previous studies show that the minimum of excess chemical potential of a hard-sphere solute with respect to that in the bulk exhibits a linear dependence on cosine value of contact angle. Based on the computed excess chemical potentials of the purely repulsive methane-sized Weeks–Chandler–Andersen solute with respect to that in the bulk, the extrapolated values of cosine value of contact angle are calculated(ccHydrophobicity), which can be used to quantify the hydrophobicity of amino acid side chains with complete wetting behaviors. | 6 | Supramolecular Chemistry |
Synthesis of DDQ involves cyanation of chloranil. J. Thiele and F. Günther first reported a 6-step preparation in 1906. The substance did not receive interest until its potential as a dehydrogenation agent was discovered. A single-step chlorination from 2,3-dicyanohydroquinone was reported in 1965. | 0 | Organic Chemistry |
EXPOSE is a multi-user facility mounted outside the International Space Station (ISS) dedicated to astrobiology. EXPOSE was developed by the European Space Agency (ESA) for long-term spaceflights and was designed to allow exposure of chemical and biological samples to outer space while recording data during exposure.
The results will contribute to our understanding of photobiological processes in simulated radiation climates of planets (e.g. early Earth, early and present Mars, and the role of the ozone layer in protecting the biosphere from harmful UV-B radiation), as well as studies of the probabilities and limitations for life to be distributed beyond its planet of origin. EXPOSE data support long-term in situ studies of microbes in artificial meteorites, as well as of microbial communities from special ecological niches. Some EXPOSE experiments investigated to what extent particular terrestrial organisms are able to cope with extraterrestrial environmental conditions. Others tested how organic molecules react when subjected for a prolonged period of time to unfiltered solar light. | 1 | Biochemistry |
Each of the three widely used methods for diagnosing HIV infection has been developed using recombinant DNA. The antibody test (ELISA or western blot) uses a recombinant HIV protein to test for the presence of antibodies that the body has produced in response to an HIV infection. The DNA test looks for the presence of HIV genetic material using reverse transcription polymerase chain reaction (RT-PCR). Development of the RT-PCR test was made possible by the molecular cloning and sequence analysis of HIV genomes. [https://www.cdc.gov/hiv/topics/testing/index.htm HIV testing page from US Centers for Disease Control (CDC)] | 1 | Biochemistry |
In the GeneCalling protocol, mRNAs are first isolated from a given sample and processed into fragments for analysis. This usually involves the synthesis and subdivision of double-stranded cDNAs from polyA RNA. Distinct sets of restriction enzymes can then be used to digest sets of the divided cDNAs and resulting fragments ligated to labelled adapters to be amplified by PCR. PCR products are then purified and subjected to gel electrophoresis on a mounted platform employing stationary laser excitation and a multi-colour charge-coupled device imaging system. A fluorescent label at the 5' end of one of the PCR primers allows for visualization of the PCR fragments, and the cDNAs are subjected to several isolated and identical restriction digests to generate a merged profile based on peak height and variance. The merged digestion profiles from the cDNA preparations are then compared to locate differentially expressed fragments (such as between normal tissue and diseased or drug responsive tissue); these profiles are compared by means of various internet-ready databases such as GeneScape. | 1 | Biochemistry |
The earliest rationale for the effects of hypothermia as a neuroprotectant focused on the slowing of cellular metabolism resulting from a drop in body temperature. For every one degree Celsius drop in body temperature, cellular metabolism slows by 5–7%. Accordingly, most early hypotheses suggested that hypothermia reduces the harmful effects of ischemia by decreasing the body's need for oxygen. The initial emphasis on cellular metabolism explains why the early studies almost exclusively focused on the application of deep hypothermia, as these researchers believed that the therapeutic effects of hypothermia correlated directly with the extent of temperature decline.
In the special case of infants with perinatal asphyxia, it appears that apoptosis is a prominent cause of cell death and that hypothermia therapy for neonatal encephalopathy interrupts the apoptotic pathway. In general, cell death is not directly caused by oxygen deprivation, but occurs indirectly as a result of the cascade of subsequent events. Cells need oxygen to create ATP, a molecule used by cells to store energy, and cells need ATP to regulate intracellular ion levels. ATP is used to fuel both the importation of ions necessary for cellular function and the removal of ions that are harmful to cellular function. Without oxygen, cells cannot manufacture the necessary ATP to regulate ion levels and thus cannot prevent the intracellular environment from approaching the ion concentration of the outside environment. It is not oxygen deprivation itself that precipitates cell death, but rather without oxygen the cell can not make the ATP it needs to regulate ion concentrations and maintain homeostasis.
Notably, even a small drop in temperature encourages cell membrane stability during periods of oxygen deprivation. For this reason, a drop in body temperature helps prevent an influx of unwanted ions during an ischemic insult. By making the cell membrane more impermeable, hypothermia helps prevent the cascade of reactions set off by oxygen deprivation. Even moderate dips in temperature strengthen the cellular membrane, helping to minimize any disruption to the cellular environment. It is by moderating the disruption of homeostasis caused by a blockage of blood flow that many now postulate, results in hypothermia's ability to minimize the trauma resultant from ischemic injuries.
Targeted temperature management may also help to reduce reperfusion injury, damage caused by oxidative stress when the blood supply is restored to a tissue after a period of ischemia. Various inflammatory immune responses occur during reperfusion. These inflammatory responses cause increased intracranial pressure, which leads to cell injury and in some situations, cell death. Hypothermia has been shown to help moderate intracranial pressure and therefore to minimize the harmful effects of a patients inflammatory immune responses during reperfusion. The oxidation that occurs during reperfusion also increases free radical production. Since hypothermia reduces both intracranial pressure and free radical production, this might be yet another mechanism of action for hypothermias therapeutic effect. Overt activation of N-methyl-D-aspartate (NMDA) receptors following brain injuries can lead to calcium entry which triggers neuronal death via the mechanisms of excitotoxicity. | 1 | Biochemistry |
Acid–base extraction is a subclass of liquid–liquid extractions and involves the separation of chemical species from other acidic or basic compounds. It is typically performed during the work-up step following a chemical synthesis to purify crude compounds and results in the product being largely free of acidic or basic impurities. A separatory funnel is commonly used to perform an acid-base extraction.
Acid-base extraction utilizes the difference in solubility of a compound in its acid or base form to induce separation. Typically, the desired compound is changed into its charged acid or base form, causing it to become soluble in aqueous solution and thus be extracted from the non-aqueous (organic) layer. Acid-base extraction is a simple alternative to more complex methods like chromatography. It is not possible to separate chemically similar acids or bases using this simple method. | 7 | Physical Chemistry |
Functional groups containing heteroatoms in low oxidation states can be oxidised by trifluoroperacetic acid. Common cases include the oxidation of iodine (for example, the formation of the hypervalent iodine compound from iodobenzene mentioned earlier), nitrogen, sulfur, and selenium.
In the case of nitrogen-containing compounds, known transformations include oximes and aromatic primary amines to nitro compounds (even with electron-withdrawing substituents, for example, pentafluoroaniline to pentafluoronitrobenzene), nitrosamines to nitramines, formation of aromatic N-oxides and aromatic azine N-oxides, and conversion of nitroso compounds to nitro compounds or nitramines. For example, a mixture of hydrogen peroxide and trifluoroperacetic acid oxidises the nitroso-substituted pyrimidine 4,6-diamino-5-nitrosopyrimidine-2-thiol to its nitro analogue while also removing the thiol moiety by oxidative hydrolytic desulfurization:
In the case of chalcogen elements, sulfide moieties (R–S–R) can be oxidised by trifluoroperacetic acid to sulfoxide (R–S(O)–R) and/or sulfone (R–S(O)–R) forms, depending on the conditions used. In the analogous selenium system, trifluoroperacetic acid oxidation of selenoethers (R–Se–R) produces selones (R–Se(O)–R) without the formation of the related selenoxides (R–Se(O)–R) as an isolable product, a reaction which is particularly effective when the R is an aryl group. A general approach to the formation of sulfinyl chlorides (RS(O)Cl) is the reaction of the corresponding thiol with sulfuryl chloride (). In cases where the sulfenyl chloride (RSCl) results instead, a subsequent trifluoroperacetic acid oxidation affords the desired product, as in the case of 2,2,2-trifluoro-1,1-diphenylethanethiol:
The trifluoroperacetic acid oxidation of thiophene illustrates competing pathways for reaction, with both S-oxidation and epoxidation being possible. The major pathway initially forms the sulfoxide, but this chemical promptly undergoes a Diels-Alder-type dimerisation before any further oxidation occurs—neither thiophene-S-oxide or thiophene-S,S-dioxide are found among the products of the reaction. The dimer can then be oxidized further, converting one of the S-oxide moieties to an S,S-dioxide. In the minor reaction pathway, a Prilezhaev epoxidation results in the formation of thiophene-2,3-epoxide that rapidly rearranges to the isomer thiophene-2-one. Trapping experiments demonstrate that this epoxide pathway is not an alternative reaction of the S-oxide intermediate, and isotopic labeling experiments demonstrate that a 1,2-hydride shift (an NIH shift) occurs and thus that a cationic intermediate is involved. The choice of trifluoroperacetic acid preparation method is important as water suppresses the minor reaction pathway, likely because it acts as a competing base. | 0 | Organic Chemistry |
Transcriptional noise is a primary cause of the variability (noise) in gene expression occurring between cells in isogenic populations (see also cellular noise) . A proposed source of transcriptional noise is transcriptional bursting although other sources of heterogeneity, such as unequal separation of cell contents at mitosis are also likely to contribute considerably. Bursting transcription, as opposed to simple probabilistic models of transcription, reflects multiple states of gene activity, with fluctuations between states separated by irregular intervals, generating uneven protein expression between cells. Noise in gene expression can have tremendous consequences on cell behaviour, and must be mitigated or integrated. In certain contexts, such as establishment of viral latency, the survival of microbes in rapidly changing stressful environments, or several types of scattered differentiation, the variability may be essential. Variability also impacts upon the effectiveness of clinical treatment, with resistance of bacteria and yeast to antibiotics demonstrably caused by non-genetic differences. Variability in gene expression may also contribute to resistance of sub-populations of cancer cells to chemotherapy and appears to be a barrier to curing HIV. | 1 | Biochemistry |
Transparent conducting electrodes are essential components of solar cells. It is either a continuous film of indium tin oxide or a conducting wire network, in which wires are charge collectors while voids between wires are transparent for light. An optimum density of wire network is essential for the maximum solar cell performance as higher wire density blocks the light transmittance while lower wire density leads to high recombination losses due to more distance traveled by the charge carriers. | 7 | Physical Chemistry |
Spectroscopy is a sufficiently broad field that many sub-disciplines exist, each with numerous implementations of specific spectroscopic techniques. The various implementations and techniques can be classified in several ways. | 7 | Physical Chemistry |
Viral RdRps were discovered in the early 1960s from studies on mengovirus and polio virus when it was observed that these viruses were not sensitive to actinomycin D, a drug that inhibits cellular DNA-directed RNA synthesis. This lack of sensitivity suggested that there is a virus-specific enzyme that could copy RNA from an RNA template and not from a DNA template. | 1 | Biochemistry |
COC has unique electrical properties that resist dielectric breakdown and have a very low dielectric loss over time. Because of this COC is used in filter media that require a charge retention to work properly. | 7 | Physical Chemistry |
Pentosidine is a biomarker for advanced glycation endproducts, or AGEs. It is a well characterized and easily detected member of this large class of compounds. | 1 | Biochemistry |
Professor Zagal is also a man of many talents: he sings and plays several instruments, including the guitar and the scottish bagpipes. He also writes poetry, paints and draws cartoons. He played Caiphas in the Opera Rock Jesus Christ Superstar in the early 70s. He has been a volunteer firemen with the 14th British and Commonwealth Fire & Rescue Company in Santiago since 1972 and is also the official piper of his company. Some of his caricatures have been published in the magazine “Interface” of the Electrochemical Society and in the Journal of the Serbian Chemical Society. He is a devoted train enthusiast. He has built large replicas or working steam locomotive and full size freight wagons. He also collects full size railway items including 12 wagons and 2 locomotives, one steam and an electric locomotive. With other enthusiasts he started in the 80s the "Chilean Association for the Preservation of the Railways". With two other enthusiasts he owns the "Puangue Station" which is one of the few preserved railway stations in rural areas. | 7 | Physical Chemistry |
Because many definitions of standard temperature and pressure differ in temperature significantly from standard laboratory temperatures (e.g. 0 °C vs. ~25 °C), reference is often made to "standard laboratory conditions" (a term deliberately chosen to be different from the term "standard conditions for temperature and pressure", despite its semantic near identity when interpreted literally). However, what is a "standard" laboratory temperature and pressure is inevitably geography-bound, given that different parts of the world differ in climate, altitude and the degree of use of heat/cooling in the workplace. For example, schools in New South Wales, Australia use 25 °C at 100 kPa for standard laboratory conditions.
ASTM International has published Standard ASTM E41- Terminology Relating to Conditioning and hundreds of special conditions for particular materials and test methods. Other standards organizations also have specialized standard test conditions. | 7 | Physical Chemistry |
The quantum fluctuations of the electromagnetic field have important physical consequences. In addition to the Casimir effect, they also lead to a splitting between the two energy levels and (in term symbol notation) of the hydrogen atom which was not predicted by the Dirac equation, according to which these states should have the same energy. Charged particles can interact with the fluctuations of the quantized vacuum field, leading to slight shifts in energy; this effect is called the Lamb shift. The shift of about is roughly of the difference between the energies of the 1s and 2s levels, and amounts to 1,058 MHz in frequency units. A small part of this shift (27 MHz ≈ 3%) arises not from fluctuations of the electromagnetic field, but from fluctuations of the electron–positron field. The creation of (virtual) electron–positron pairs has the effect of screening the Coulomb field and acts as a vacuum dielectric constant. This effect is much more important in muonic atoms. | 7 | Physical Chemistry |
Proteins can also be cross-linked artificially using small-molecule crosslinkers. This approach has been used to elucidate protein–protein interactions. Crosslinkers bind only surface residues in relatively close proximity in the native state. Common crosslinkers include the imidoester crosslinker dimethyl suberimidate, the N-Hydroxysuccinimide-ester crosslinker BS3 and formaldehyde. Each of these crosslinkers induces nucleophilic attack of the amino group of lysine and subsequent covalent bonding via the crosslinker. The zero-length carbodiimide crosslinker EDC functions by converting carboxyls into amine-reactive isourea intermediates that bind to lysine residues or other available primary amines. SMCC or its water-soluble analog, Sulfo-SMCC, is commonly used to prepare antibody-hapten conjugates for antibody development. An in-vitro cross-linking method is PICUP (photo-induced cross-linking of unmodified proteins). Typical reagents are ammonium persulfate (APS), an electron acceptor, the photosensitizer tris-bipyridylruthenium (II) cation (). In in-vivo crosslinking of protein complexes, cells are grown with [[photoreactive diazirine analogs to leucine and methionine, which are incorporated into proteins. Upon exposure to ultraviolet light, the diazirines are activated and bind to interacting proteins that are within a few ångströms of the photo-reactive amino acid analog (UV cross-linking). | 7 | Physical Chemistry |
Conditions for hydroformylation catalysis can induce degradation of supporting organophosphorus ligands. Triphenylphosphine is subject to hydrogenolysis, releasing benzene and diphenylphosphine. The insertion of carbon monoxide in an intermediate metal-phenyl bond can lead to the formation of benzaldehyde or by subsequent hydrogenation to benzyl alcohol. One of the ligands phenyl-groups can be replaced by propene, and the resulting diphenylpropylphosphine ligand can inhibit the hydroformylation reaction due to its increased basicity. | 0 | Organic Chemistry |
In practice, simple idealized thermodynamic cycles are usually made out of four thermodynamic processes. Any thermodynamic processes may be used. However, when idealized cycles are modeled, often processes where one state variable is kept constant, such as:
* adiabatic (constant heat)
* isothermal (constant temperature)
* isobaric (constant pressure)
* isochoric (constant volume)
* isentropic (constant entropy)
* isenthalpic (constant enthalpy)
Some example thermodynamic cycles and their constituent processes are as follows: | 7 | Physical Chemistry |
Methyl violet 10B has six methyl groups. It is known in medicine as Gentian violet (or crystal violet or pyoctanin(e)) and is the active ingredient in a Gram stain, used to classify bacteria. It is used as a pH indicator, with a range between 0 and 1.6. The protonated form (found in acidic conditions) is yellow, turning blue-violet above pH levels of 1.6.
Methyl violet 10B inhibits the growth of many Gram positive bacteria, except streptococci. When used in conjunction with nalidixic acid (which destroys gram-negative bacteria), it can be used to isolate the streptococci bacteria for the diagnosis of an infection. | 3 | Analytical Chemistry |
Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is often used in organic electrons and have strong NIR absorption. In 2012, Liu’s group first reported PEGylated PEDOT:PSS polymeric nanoparticle (PEDOT:PSS-PEG) for near-infrared photothermal therapy of cancer. PEDOT:PSS-PEG nanoparticles have high stability in vivo and long blood circulation half-life of 21.4 ± 3.1 h. The PTT in animals showed no appreciable side effects for the tested dose and an excellent therapeutic efficacy under the 808 nm laser irradiation. Kang et al. synthesized magneto-conjugated polymer core−shell MNP@PEDOT:PSS nanoparticles for multimodal imaging-guided PTT. Furthermore, PEDOT:PSS NPs can not only serve as PTAs but also as a drug carrier to load various types of drugs, such as SN38, chemotherapy drugs DOX and photodynamic agent chlorin e6 (Ce6), thus achieving synergistic cancer therapy. | 5 | Photochemistry |
In the United States, the regulation of F-gases falls under the authority of the Environmental Protection Agency's overall attempts to combat greenhouse gases. The United States has put forward a joint proposal with Mexico and the Federated States of Micronesia for a phase-down of HFCs by 2030. The American Innovation and Manufacturing Act is federal legislation that mandates at 85% reduction in the production and consumption of HFC refrigerants by 2035, in compliance with the Kigali Amendment. | 2 | Environmental Chemistry |
A sequence contig is a continuous (not contiguous) sequence resulting from the reassembly of the small DNA fragments generated by bottom-up sequencing strategies. This meaning of contig is consistent with the original definition by Rodger Staden (1979). The bottom-up DNA sequencing strategy involves shearing genomic DNA into many small fragments ("bottom"), sequencing these fragments, reassembling them back into contigs and eventually the entire genome ("up"). Because current technology allows for the direct sequencing of only relatively short DNA fragments (300–1000 nucleotides), genomic DNA must be fragmented into small pieces prior to sequencing. In bottom-up sequencing projects, amplified DNA is sheared randomly into fragments appropriately sized for sequencing. The subsequent sequence reads, which are the data that contain the sequences of the small fragments, are put into a database. The assembly software then searches this database for pairs of overlapping reads. Assembling the reads from such a pair (including, of course, only one copy of the identical sequence) produces a longer contiguous read (contig) of sequenced DNA. By repeating this process many times, at first with the initial short pairs of reads but then using increasingly longer pairs that are the result of previous assembly, the DNA sequence of an entire chromosome can be determined.
Today, it is common to use paired-end sequencing technology where both ends of consistently sized longer DNA fragments are sequenced. Here, a contig still refers to any contiguous stretch of sequence data created by read overlap. Because the fragments are of known length, the distance between the two end reads from each fragment is known. This gives additional information about the orientation of contigs constructed from these reads and allows for their assembly into scaffolds in a process called scaffolding.
Scaffolds consist of overlapping contigs separated by gaps of known length. The new constraints placed on the orientation of the contigs allows for the placement of highly repeated sequences in the genome. If one end read has a repetitive sequence, as long as its mate pair is located within a contig, its placement is known. The remaining gaps between the contigs in the scaffolds can then be sequenced by a variety of methods, including PCR amplification followed by sequencing (for smaller gaps) and BAC cloning methods followed by sequencing for larger gaps. | 1 | Biochemistry |
DNA banking is the secure, long term storage of an individual’s genetic material. DNA is most commonly extracted from blood, but can also be obtained from saliva and other tissues. DNA banks allow for conservation of genetic material and comparative analysis of an individuals genetic information. Analyzing an individuals DNA can allow scientists to predict genetic disorders, as used in preventive genetics or gene therapy, and prove that person's identity, as used in the criminal justice system. There are multiple methods for testing and analyzing genetic information including restriction fragment length polymorphism (RFLP) and polymerase chain reactions (PCR). | 1 | Biochemistry |
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