text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
The EFI's primary deliverable is development and dissemination of an integrated sequence/structure strategy for functional assignment. The EFI now offers access to two high-throughput docking tools, a web tool for comparing protein sequences within entire protein families, and a web tool for composing a genome context inventory based on a protein sequence similarity network. Additionally, as the strategy is developed, data and clones generated by the EFI are made freely available via several online resources. | 1 | Biochemistry |
Hagemann's ester, ethyl 2-methyl-4-oxo-2-cyclohexenecarboxylate, is an organic compound that was first prepared and described in 1893 by German chemist Carl Hagemann. The compound is used in organic chemistry as a reagent in the synthesis of many natural products including sterols, trisporic acids, and terpenoids. | 0 | Organic Chemistry |
The color of water varies with the ambient conditions in which that water is present. While relatively small quantities of water appear to be colorless, pure water has a slight blue color that becomes deeper as the thickness of the observed sample increases. The hue of water is an intrinsic property and is caused by selective absorption and scattering of blue light. Dissolved elements or suspended impurities may give water a different color. | 3 | Analytical Chemistry |
Phytochromes (also known as phys) were initially discovered in green plants in 1945. The photoreversible pigment was later found in fungi, mosses, and other algae groups due to the development of whole-genome sequencing, as explained in Peter H. Quails 2010 journal article Phytochromes. As described in Hugo Scheers 1981 journal article Biliproteins, phytochromes function as a sensor of light intensity in ‘high-energy’ reactions, i.e. in higher plants (e.g. underground seedlings), during transformation of heterotrophic blanching growth to autotrophic photosynthetic growth. They carry out this function by monitoring the various parameters of light signals (such as presence/absence, colour, intensity and photoperiodicity). This information is then transduced via intracellular signaling pathways that trigger responses specific to the organism and its development state on both cellular and molecular levels, as explained by Quail. Phytochromes are also responsible for regulating many aspects of a plant's growth, development and reproduction throughout its lifecycle. | 1 | Biochemistry |
In the 1960s through the 1970s, Paul Boyer, a UCLA Professor, developed the binding change, or flip-flop, mechanism theory, which postulated that ATP synthesis is dependent on a conformational change in ATP synthase generated by rotation of the gamma subunit. The research group of John E. Walker, then at the MRC Laboratory of Molecular Biology in Cambridge, crystallized the F catalytic-domain of ATP synthase. The structure, at the time the largest asymmetric protein structure known, indicated that Boyer's rotary-catalysis model was, in essence, correct. For elucidating this, Boyer and Walker shared half of the 1997 Nobel Prize in Chemistry.
The crystal structure of the F showed alternating alpha and beta subunits (3 of each), arranged like segments of an orange around a rotating asymmetrical gamma subunit. According to the current model of ATP synthesis (known as the alternating catalytic model), the transmembrane potential created by (H+) proton cations supplied by the electron transport chain, drives the (H+) proton cations from the intermembrane space through the membrane via the F region of ATP synthase. A portion of the F (the ring of c-subunits) rotates as the protons pass through the membrane. The c-ring is tightly attached to the asymmetric central stalk (consisting primarily of the gamma subunit), causing it to rotate within the alphabeta of F causing the 3 catalytic nucleotide binding sites to go through a series of conformational changes that lead to ATP synthesis. The major F subunits are prevented from rotating in sympathy with the central stalk rotor by a peripheral stalk that joins the alphabeta to the non-rotating portion of F. The structure of the intact ATP synthase is currently known at low-resolution from electron cryo-microscopy (cryo-EM) studies of the complex. The cryo-EM model of ATP synthase suggests that the peripheral stalk is a flexible structure that wraps around the complex as it joins F to F. Under the right conditions, the enzyme reaction can also be carried out in reverse, with ATP hydrolysis driving proton pumping across the membrane.
The binding change mechanism involves the active site of a β subunit's cycling between three states. In the "loose" state, ADP and phosphate enter the active site; in the adjacent diagram, this is shown in pink. The enzyme then undergoes a change in shape and forces these molecules together, with the active site in the resulting "tight" state (shown in red) binding the newly produced ATP molecule with very high affinity. Finally, the active site cycles back to the open state (orange), releasing ATP and binding more ADP and phosphate, ready for the next cycle of ATP production. | 5 | Photochemistry |
In 1901, Joseph Hoeing Kastle and Oliver March Shedd in the U.S. found that biological material could cause the oxidation of phenolphthalin to phenolphthalein in slightly alkaline solutions. In 1903, Erich Meyer in Germany found that blood cells could also trigger the reaction. In 1906, Kastle and Amoss found that chick hemoglobin in blood triggered the reaction. In 1909, Kastle found that the test was sensitive to very dilute samples of blood. However, in 1908, Pozzi-Escot (who by then was living in Lima, Peru) found that the test produced false positive reactions in response to a number of substances besides blood. | 3 | Analytical Chemistry |
Self-cleaning screen media was initially engineered to resolve screen cloth blinding, clogging and pegging problems. The idea was to place crimped wires side by side on a flat surface, creating openings and then, in some way, holding them together over the support bars (crown bars or bucker bars). This would allow the wires to be free to vibrate between the support bars, preventing blinding, clogging and pegging of the cloth. Initially, crimped longitudinal wires on self-cleaning cloth were held together over support bars with woven wire. In the 50s, some manufacturers started to cover the woven cross wires with caulking or rubber to prevent premature wear of the crimps (knuckles on woven wires). One of the pioneer products in this category was ONDAP GOMME made by the French manufacturer Giron. During the mid 90s, Major Wire Industries Ltd., a Quebec manufacturer, developed a “hybrid” self-cleaning screen cloth called Flex-Mat, without woven cross wires. In this product, the crimped longitudinal wires are held in place by polyurethane strips. Rather than locking (impeding) vibration over the support bars due to woven cross wires, polyurethane strips reduce vibration of longitudinal wires over the support bars, thus allowing vibration from hook to hook. Major Wire quickly started to promote this product as a high-performance screen that helped producers screen more in-specification material for less cost and not simply a problem solver. They claimed that the independent vibrating wires helped produce more product compared to a woven wire cloth with the same opening (aperture) and wire diameter. This higher throughput would be a direct result of the higher vibration frequency of each independent wire of the screen cloth (calculated in hertz) compared to the shaker vibration (calculated in RPM), accelerating the stratification of the material bed. Another benefit that helped the throughput increase is that hybrid self-cleaning screen media offered a better open area percentage than woven wire screen media. Due to its flat surface (no knuckles), hybrid self-cleaning screen media can use a smaller wire diameter for the same aperture than woven wire and still lasts as long, resulting in a greater opening percentage. | 8 | Metallurgy |
Surficial processes are the physical and chemical phenomena which cause concentration of ore material within the regolith, generally by the action of the environment. This includes placer deposits, laterite deposits, and residual or eluvial deposits. Superficial deposits processes of ore formation include;
* Erosion of non-ore material.
* Deposition by sedimentary processes, including winnowing, density separation (e.g.; gold placers).
* Weathering via oxidation or chemical attack of a rock, either liberating rock fragments or creating chemically deposited clays, laterites, or supergene enrichment.
* Deposition in low-energy environments in beach environments.
* Sedimentary Exhalative Deposits (SEDEX), formed on the sea floor from metal-bearing brines. | 9 | Geochemistry |
Order strengthening brought about from the interaction of dislocations with ordered precipitates, forming anti-phase boundaries as dislocations move throughout the crystal, can lead to significant increases in strength and creep resistance. For this reason, order strengthening is often exploited for high-temperature creep resistant superalloys used in turbine blades.
Antiphase domains carry with them a surface energy penalty when compared to the perfect lattice due to their chemical disorder, and the presence of these boundaries impedes dislocation motion throughout the crystal, leading to increased strength under shear stress. Figure 3 below shows the process of an edge dislocation propagating through an ordered particle. As the dislocation moves throughout the particle, lattice planes are displaced from their equilibrium configuration, and A-A bonds and B-B bonds are formed throughout the slip plane. This forms a higher energy state than when compared to the equilibrium A-B bonding configuration, and the change in energy is called the anti-phase boundary energy (APBE). This can increase the degree of strengthening created from precipitation hardening, making it more difficult for cutting to occur, and instead increasing the likelihood of Orowan bowing around the precipitate.
<br />
Figure 3: The process of an edge dislocation moving through an ordered precipitate. In (a), the perfectly ordered particle is shown. In (b), the dislocations has moved through part of the particle. In (c), the dislocation exits the precipitate, leading to an increase in surface energy from increased surface area and a higher-energy bonding configuration.
Order strengthening is often characterized by a ratio of the attractive anti-phase boundary energy (APBE) to the repulsive dislocation energy(Gb): . The degree of order strengthening depends on both this ratio and whether the alloy is in the early or late stages of precipitation. When is low, the trailing dislocation moves far behind the leading dislocations, leading to separate cutting of precipitates as seen in Figure 4a. Alternatively, when is high, the trailing dislocation follows close behind the leading dislocation, leading to common cutting as seen in Figure 4b. During the early stages of precipitation, the increase in shear stress can be expressed as:
for low or
for high where G is the shear modulus, f is the volume fraction of precipitates, r is the radius of the precipitate, and b is the burgers vector of the dislocation.
In the later stages of precipitation, the analogous expressions are:
for low or
for high .
<br />
Figure 4: Dislocation motion around precipitates. | 3 | Analytical Chemistry |
The AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface. The cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever according to Hooke's law. Depending on the situation, forces that are measured in AFM include mechanical contact force, van der Waals forces, capillary forces, chemical bonding, electrostatic forces, magnetic forces (see magnetic force microscope, MFM), Casimir forces, solvation forces, etc. Along with force, additional quantities may simultaneously be measured through the use of specialized types of probes (see scanning thermal microscopy, scanning joule expansion microscopy, photothermal microspectroscopy, etc.).
The AFM can be operated in a number of modes, depending on the application. In general, possible imaging modes are divided into static (also called contact) modes and a variety of dynamic (non-contact or "tapping") modes where the cantilever is vibrated or oscillated at a given frequency. | 6 | Supramolecular Chemistry |
Following the work on homeotic mutants by Ed Lewis, the phenomenology of homeosis in animals was further elaborated by discovery of a conserved DNA binding sequence present in many homeotic proteins.
Thus, the 60 amino acid DNA binding protein domain was named the homeodomain, while the 180 bp nucleotide sequence encoding it was named the homeobox. The homeobox gene clusters studied by Ed Lewis were named the Hox genes, although many more homeobox genes are encoded by animal genomes than those in the Hox gene clusters.
The homeotic-function of certain proteins was first postulated to be that of a "selector" as proposed by Antonio Garcia-Bellido.
By definition selectors were imagined to be (transcription factor) proteins that stably determined one of two possible cell fates for a cell and its cellular descendants in a tissue.
While most animal homeotic functions are associated with homeobox-containing factors, not all homeotic proteins in animals are encoded by homeobox genes, and further not all homeobox genes are necessarily associated with homeotic functions or (mutant) phenotypes.
The concept of homeotic selectors was further elaborated or at least qualified by Michael Akam in a so-called "post-selector gene" model that incorporated additional findings and "walked back" the "orthodoxy" of selector-dependent stable binary switches.
The concept of tissue compartments is deeply intertwined with the selector model of homeosis because the selector-mediated maintenance of cell fate can be restricted into different organizational units of an animal's body plan.
In this context, newer insights into homeotic mechanisms were found by Albert Erives and colleagues by focusing on enhancer DNAs that are co-targeted by homeotic selectors and different combinations of developmental signals.
This work identifies a protein biochemical difference between the transcription factors that function as homeotic selectors versus the transcription factors that function as effectors of developmental signaling pathways, such as the Notch signaling pathway and the BMP signaling pathway.
This work proposes that homeotic selectors function to "license" enhancer DNAs in a restricted tissue compartment so that the enhancers are enabled to read-out developmental signals, which are then integrated via polyglutamine-mediated aggregation. | 1 | Biochemistry |
The Codon Adaptation Index (CAI) is the most widespread technique for analyzing codon usage bias. As opposed to other measures of codon usage bias, such as the effective number of codons (Nc), which measure deviation from a uniform bias (null hypothesis), CAI measures the deviation of a given protein coding gene sequence with respect to a reference set of genes. CAI is used as a quantitative method of predicting the level of expression of a gene based on its codon sequence. | 1 | Biochemistry |
First-row metal complexes tend to undergo reductive elimination faster than second-row metal complexes, which tend to be faster than third-row metal complexes. This is due to bond strength, with metal-ligand bonds in first-row complexes being weaker than metal-ligand bonds in third-row complexes. Additionally, electron-poor metal centers undergo reductive elimination faster than electron-rich metal centers since the resulting metal would gain electron density upon reductive elimination. | 0 | Organic Chemistry |
Zeta potential titration is a titration of heterogeneous systems, for example colloids and emulsions. Solids in such systems have very high surface area. This type of titration is used to study the zeta potential of these surfaces under different conditions. Details of zeta potential definition and measuring techniques can be found in the International Standard. | 7 | Physical Chemistry |
Whilst the method of PDC electrolysis has been proven by Ghoroghichian and Bockris in 1952 and 1985 to work extremely well in theory, it is difficult to replicate with consistently positive results in practical experimentation. Hence, the many mechanisms that have been patented are unable to be repeated and used in industry.
According to Shabaan, during the pulse-off period, if the electrolytic cell is not constructed properly, the current polarity can reverse. This can cause the cathode to deteriorate. In electrolysis, the cathode is where the reduction of hydrogen occurs, forming the desired hydrogen gas. Any loss in mass can reduce the speed and effectiveness of the electrolytic reaction, reducing the overall efficiency of the pulse electrolysis method.
Shaaban also states that due to expected internal losses, such as through heat, the current density required will increase, which increases the required voltage. As a result, greater over potentials are needed that further converts to heat. | 7 | Physical Chemistry |
Alvaro Alonso Barba was a secular Catholic priest and metallurgist born in Lepe in 1569.
Antonio (1786) says, "Baeticus ex oppido Lepe, apud Potosi"; hence Barba is assumed to be of Andalusian origin, from the ancient Roman province of Baetica.
He lived at Potosí during the period when its silver mines were most productive and luxury among the Spanish residents and mine owners had nearly reached its height. Barba divided his time between his priestly duties and a close study of the ores of this region and their treatment. There had been, since 1570, a complete revolution in the treatment of silver ores, through the application of mercury, and a number of improvements followed, of which Barba had knowledge.
In 1609, he invented the pan amalgamation process (in Spanish the cazo or fondo process) for extracting silver from ore by mixing it with salt and mercury and heating it in shallow copper vessels. In 1640 he published in Madrid a book entitled Arte de los Metales, the earliest work on South American ores and minerals. It includes information on mineral localities in Bolivia. The book has been republished in Spanish, French, English and German. | 8 | Metallurgy |
Faulds studied forensic and analytical science at the University of Strathclyde, graduating with a BSc in 1998. She remained at Strathclyde for her doctoral studies and in 2003 received her PhD for research on the detection of drugs of substance abuse using surface-enhanced Raman spectroscopy (SERS). | 3 | Analytical Chemistry |
Alloys of vanadium, nickel, and titanium have a high hydrogen solubility, and can therefore absorb significant amounts of hydrogen. This can lead to hydride formation, resulting in irregular volume expansion and reduced ductility (because metallic hydrides are fragile ceramic materials). This is a particular issue when looking for non-palladium-based alloys for use in hydrogen separation membranes. | 7 | Physical Chemistry |
An example of splicing aberration (exon skipping) caused by a mutation in the donor splice site in the exon 8 of MLH1 gene that led to colorectal cancer is given below. This example shows that a mutation in a splice site within a gene can lead to a profound effect in the sequence and structure of the mRNA, and the sequence, structure and function of the encoded protein, leading to disease. | 1 | Biochemistry |
* The advantages of an oxidation-reduction reactor in gas chromatography include
* The reactor ensures uniform sensitivity to most organic molecules, leading to consistent and reliable detection across a wide range of analytes.
* By eliminating the need for multiple calibrations and standards, the reactor increases the accuracy of quantification, reducing errors and enhancing the reliability of analytical results.
* Reduction in calibration requirements decreases the cost of ownership and saves time, making the analytical process more efficient.
* The reactor enables the quantification of complex mixtures even when standards are not available, provided retention times are known or can be estimated, thereby expanding the applicability of gas chromatography.
* Unlike traditional methanizers, which primarily convert CO and CO2, oxidation-reduction reactors can convert a broader range of organic compounds to methane, leading to a more comprehensive response and improved sensitivity for a wide variety of analytes.
* These reactors are more resistant to poisoning by compounds containing nitrogen and oxygen, ensuring consistent performance even in the presence of interfering substances.
* Compared to packed column versions of methanizers, oxidation-reduction reactors typically produce sharper peaks, enhancing resolution and improving the quality of chromatographic separation. | 3 | Analytical Chemistry |
Pharmacogenetics focuses on identifying genetic variations including SNPs associated with differential responses to treatment. Many drug metabolizing enzymes, drug targets, or target pathways can be influenced by SNPs. The SNPs involved in drug metabolizing enzyme activities can change drug pharmacokinetics, while the SNPs involved in drug target or its pathway can change drug pharmacodynamics. Therefore, SNPs are potential genetic markers that can be used to predict drug exposure or effectiveness of the treatment. Genome-wide pharmacogenetic study is called pharmacogenomics. Pharmacogenetics and pharmacogenomics are important in the development of precision medicine, especially for life-threatening diseases such as cancers. | 1 | Biochemistry |
* Evalyn Bostock, (1917–1944) British actress who died from accidentally drinking carbon tetrachloride after mistaking it for her drink while working in a photographic darkroom.
* Harry Edwards (1887–1952), an American director who died from carbon tetrachloride poisoning shortly after directing his first television production.
* Zilphia Horton, (1910–1952) American musician and activist who died from accidentally drinking a glass full of carbon tetrachloride-based typewriter cleaning fluid that she mistook for water.
* Margo Jones, (1911–1955) American stage director who was exposed to the fumes of carbon tetrachloride that was used to clean off paint from a carpet. She died a week later from kidney failure.
* Jim Beck, (1919–1956), American record producer, died after exposure to carbon tetrachloride fumes that he was exposed to during cleaning recording equipment.
* Tommy Tucker, (1933–1982) American blues singer, died after using carbon tetrachloride in floor refinishing. | 2 | Environmental Chemistry |
N-linked glycans are extremely important in proper protein folding in eukaryotic cells. Chaperone proteins in the endoplasmic reticulum, such as calnexin and calreticulin, bind to the three glucose residues present on the core N-linked glycan. These chaperone proteins then serve to aid in the folding of the protein that the glycan is attached to. Following proper folding, the three glucose residues are removed, and the glycan moves on to further processing reactions. If the protein fails to fold properly, the three glucose residues are reattached, allowing the protein to re-associate with the chaperones. This cycle may repeat several times until a protein reaches its proper conformation. If a protein repeatedly fails to properly fold, it is excreted from the endoplasmic reticulum and degraded by cytoplasmic proteases.
N-linked glycans also contribute to protein folding by steric effects. For example, cysteine residues in the peptide may be temporarily blocked from forming disulfide bonds with other cysteine residues, due to the size of a nearby glycan. Therefore, the presence of a N-linked glycan allows the cell to control which cysteine residues will form disulfide bonds.
N-linked glycans also play an important role in cell-cell interactions. For example, tumour cells make N-linked glycans that are abnormal. These are recognized by the CD337 receptor on Natural Killer cells as a sign that the cell in question is cancerous.
Within the immune system the N-linked glycans on an immune cell's surface will help dictate that migration pattern of the cell, e.g. immune cells that migrate to the skin have specific glycosylations that favor homing to that site. The glycosylation patterns on the various immunoglobulins including IgE, IgM, IgD, IgE, IgA, and IgG bestow them with unique effector functions by altering their affinities for Fc and other immune receptors. Glycans may also be involved in "self" and "non self" discrimination, which may be relevant to the pathophysiology of various autoimmune diseases; including rheumatoid arthritis and type 1 diabetes.
The targeting of degradative lysosomal enzymes is also accomplished by N-linked glycans. The modification of an N-linked glycan with a mannose-6-phosphate residue serves as a signal that the protein to which this glycan is attached should be moved to the lysosome. This recognition and trafficking of lysosomal enzymes by the presence of mannose-6-phosphate is accomplished by two proteins: CI-MPR (cation-independent mannose-6-phosphate receptor) and CD-MPR (cation-dependent mannose-6-phosphate receptor). | 0 | Organic Chemistry |
Speculations about the chemical structure and properties of hypothetical non-carbon-based life have been a recurring theme in science fiction. Silicon is often used as a substitute for carbon in fictional lifeforms because of its chemical similarities. In cinematic and literary science fiction, when man-made machines cross from non-living to living, this new form is often presented as an example of non-carbon-based life. Since the advent of the microprocessor in the late 1960s, such machines are often classed as "silicon-based life". Other examples of fictional "silicon-based life" can be seen in the 1967 episode "The Devil in the Dark" from Star Trek: The Original Series, in which a living rock creatures biochemistry is based on silicon. In the 1994 The X-Files' episode "Firewalker", in which a silicon-based organism is discovered in a volcano.
In the 1984 film adaptation of Arthur C. Clarkes 1982 novel 2010: Odyssey Two', a character argues, "Whether we are based on carbon or on silicon makes no fundamental difference; we should each be treated with appropriate respect."
In JoJolion, the eighth part of the larger JoJos Bizarre Adventure' series, a mysterious race of silicon-based lifeforms "Rock Humans" serve as the primary antagonists. | 1 | Biochemistry |
*[http://pid.nci.nih.gov/PID/2006/061114/full/pid.2006.001.shtml An Introduction to the NCI-Nature Pathway Interaction Database]
*[http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000425 Identification of Key Processes Underlying Cancer Phenotypes Using Biologic Pathway Analysis] | 1 | Biochemistry |
Charge exchange (or charge exchange collision) is a process in which a neutral atom or molecule collides with an ion, resulting in the neutral atom acquiring the charge of the ion. The reaction is typically expressed as
This reaction has various diagnostic applications, such as in plasma physics and mass spectrometry. | 7 | Physical Chemistry |
In vertebrates, the majority of gene promoters contain a CpG island with numerous CpG sites. When many of a gene's promoter CpG sites are methylated the gene becomes silenced. Colorectal cancers typically have 3 to 6 driver mutations and 33 to 66 hitchhiker or passenger mutations. However, transcriptional silencing may be of more importance than mutation in causing progression to cancer. For example, in colorectal cancers about 600 to 800 genes are transcriptionally silenced by CpG island methylation (see regulation of transcription in cancer). Transcriptional repression in cancer can also occur by other epigenetic mechanisms, such as altered expression of microRNAs. In breast cancer, transcriptional repression of BRCA1 may occur more frequently by over-expressed microRNA-182 than by hypermethylation of the BRCA1 promoter (see Low expression of BRCA1 in breast and ovarian cancers). | 1 | Biochemistry |
In 1925, Coward received a Rockefeller Fellowship to continue her studies and research on vitamin A in the Department of Agricultural Chemistry at the University of Wisconsin–Madison under Dr. Harry Steenbock. On her return to Britain, she was appointed head of the Nutrition Department of the Royal Pharmaceutical Society's pharmacological laboratories, the position which she remained until her retirement in 1950. In 1937 she was elected as an honorary member of the Pharmaceuticals Society. | 3 | Analytical Chemistry |
Surprisal (a term coined in this context by Myron Tribus) was first introduced to better understand the specificity of energy release and selectivity of energy requirements of elementary chemical reactions. This gave rise to a series of new experiments which demonstrated that in elementary reactions, the nascent products could be probed and that the energy is preferentially released and not statistically distributed. Surprisal analysis was initially applied to characterize a small three molecule system that did not seemingly conform to principles of thermodynamics and a single dominant constraint was identified that was sufficient to describe the dynamic behavior of the three molecule system. Similar results were then observed in nuclear reactions, where differential states with varying energy partitioning are possible. Often chemical reactions require energy to overcome an activation barrier. Surprisal analysis is applicable to such applications as well. Later, surprisal analysis was extended to mesoscopic systems, bulk systems and to dynamical processes. | 7 | Physical Chemistry |
One famous intercalation host is graphite, which intercalates potassium as a guest. Intercalation expands the van der Waals gap between sheets, which requires energy. Usually this energy is supplied by charge transfer between the guest and the host solid, i.e., redox. Two potassium graphite compounds are KC and KC. Carbon fluorides (e.g., (CF) and (CF)) are prepared by reaction of fluorine with graphitic carbon. The color is greyish, white, or yellow. The bond between the carbon and fluorine atoms is covalent, thus fluorine is not intercalated. Such materials have been considered as a cathode in various lithium batteries.
Treating graphite with strong acids in the presence of oxidizing agents causes the graphite to oxidise. Graphite bisulfate, [C][HSO], is prepared by this approach using sulfuric acid and a little nitric acid or chromic acid. The analogous graphite perchlorate can be made similarly by reaction with perchloric acid. | 6 | Supramolecular Chemistry |
In August 2012, Ferrier celebrated his 80th birthday and retired a second time. Later that year, the Ferrier Trust was set up in his honour, to bring a scientist to New Zealand each year, to engage with chemistry students and lecture. Peppi Prasit, a Ferrier PhD graduate and founder of Amira Pharmaceuticals and Inception Sciences in the US, was the trust's foundation donor. He was able to attend the inaugural Ferrier Lecture in March 2013. | 0 | Organic Chemistry |
Since its founding in 1959, EAS has become a premier venue for analysts to learn about new technologies, new applications for older technologies, and developments in such diverse fields as bioanalysis, pharmaceutical analysis, forensic science, laboratory management, and environmental analysis. Throughout the years, the EAS has been the place where innovations in analytical science have been introduced to the community of analytical scientists.
The first EAS was held in 1959 at the Hotel New Yorker in New York City, with 1200 attendees at 12 technical sessions. The exposition had 38 exhibitors who displayed the latest in analytical supplies and instrumentation. During the early years in New York, the EAS was held at various hotels in the city, as the attendance grew. At the 10th EAS, a workshop on electrochemical techniques was the origin of the exhibitor workshops, which later would become a standard feature of the EAS program. By the 15th symposium, major awards were given out as part of the program of the Symposium, including the Meggers Memorial Award, the Hassler Award in Applied Spectroscopy, and the Anachem Award.
In 1973, the EAS was suspended to support the emerging FACSS (Federation of Analytical Chemistry and Spectroscopy Societies), whose meetings were held at a similar time of the year. After two years, an EAS mini-symposium was held, and in 1977, the EAS returned to its original format in New York City. During the late 1970s and the 1980s, the EAS was moved from location to location New York City, as attendance continued to expand. During this period, the Governing Board of the Eastern Analytical Symposium began to present its own awards for excellence in analysis. In 1986, the first EAS Award for Outstanding Contributions in the Fields of Analytical Chemistry was presented to Professor George Morrison, who - aside from his many scientific contributions - had been instrumental in the early development of EAS. At the same meeting, the EAS Award for Outstanding Contributions to Separations Science was presented to Professor Csaba Horvath. In subsequent years, EAS awards of contributions to other areas would be added to recognize contributions to various areas of analysis. Currently, the EAS presents the six major awards listed above to distinguished scientists from around the world at the annual Symposium.
As the 1990s dawned, it became necessary for the Eastern Analytical Symposium to find a venue for the meeting to meet the needs of a growing meeting. In 1990, the EAS moved to the then-new Garden State Convention and Exhibit Center in Somerset, New Jersey. As the symposium continued to grow, even the GSCEC seemed limited. In 2000, the EAS was moved to the Atlantic City Convention Center, where it remained for two years. However, beginning in the early 2000s, it was decided to move the EAS back to the Garden State Convention and Exhibit Center.
Although the Eastern Analytical Symposium started as a regional meeting, where persons interested in practical analytical chemistry from laboratories in the Northeast could meet to discuss problems of common interest, it has grown to international stature, with attendance from analysts from laboratories in companies and universities across the world. The Symposium has further grown to emphasize a wide variety of technologies and areas of application that could only be dreamed of in 1959. Applications to traditional areas of analysis are still represented among the talks, but unique to the Eastern Analytical Symposium are areas such as cultural heritage and forensic science. As the 21st century has dawned, EAS continues to provide an inclusive home for practical analytical studies, to educate about the latest technologies, and to inform its audience about the current state of analysis.
After several decades of holding the meeting in Somerset, NJ, the annual symposium was moved to nearby Princeton, NJ in 2017. | 7 | Physical Chemistry |
The modification of inert surfaces of polyolefins, polyesters, and polyamides by grafting functional vinyl monomers has been used to increase hydrophobicity, dye absorption, and polymer adhesion. This photografting method is generally used during continuous filament or thin film processing. On a bulk commercial scale, the grafting technique is referred to as photoinitiated lamination, where desired surfaces are joined by grafting a polymeric adhesion network between the two films. The low adhesion and absorption of polyolefins, polyesters, and polyamides is improved by UV-irradiation of an initiator and monomer transferred through the vapor phase to the substrate. Functionalization of porous surfaces have seen great success with high temperature photografting techniques.
In microfluidic chips, functionalizing channels allows directed flow to preserve lamellar behavior between and within junctions. The adverse turbulent flow in microfluidic applications can compound component failure modes due to the increased level of channel interdependency and network complexity. In addition, the imprinted design of microfluidic channels can be reproduced for photografting the corresponding channels with a high degree of accuracy. | 7 | Physical Chemistry |
The discovery that the β chemokines RANTES, MIP (macrophage inflammatory proteins) 1α and 1β (now known as CCL5, CCL3 and CCL4 respectively) suppress HIV-1 provided the initial connection and indicated that these molecules might control infection as part of immune responses in vivo, and that sustained delivery of such inhibitors have the capacity of long-term infection control. The association of chemokine production with antigen-induced proliferative responses, more favorable clinical status in HIV infection, as well as with an uninfected status in subjects at risk for infection suggests a positive role for these molecules in controlling the natural course of HIV infection. | 1 | Biochemistry |
One resolution to irreversibility is to say that the constant increase of entropy we observe happens only because of the initial state of our universe. Other possible states of the universe (for example, a universe at heat death equilibrium) would actually result in no increase of entropy. In this view, the apparent T-asymmetry of our universe is a problem in cosmology: why did the universe start with a low entropy? This view, supported by cosmological observations (such as the isotropy of the cosmic microwave background) connects this problem to the question of initial conditions of the universe. | 7 | Physical Chemistry |
Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal
fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). Material is removed from the work piece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the or , while the other is called the workpiece-electrode, or . The process depends upon the tool and work piece not making physical contact. Extremely hard materials like carbides, ceramics, titanium alloys and heat treated tool steels that are very difficult to machine using conventional machining can be precisely machined by EDM.
When the voltage between the two electrodes is increased, the intensity of the electric field in the volume between the electrodes becomes greater, causing dielectric break down of the liquid, and produces an electric arc. As a result, material is removed from the electrodes. Once the current stops (or is stopped, depending on the type of generator), new liquid dielectric is conveyed into the inter-electrode volume, enabling the solid particles (debris) to be carried away and the insulating properties of the dielectric to be restored. Adding new liquid dielectric in the inter-electrode volume is commonly referred to as . After a current flow, the voltage between the electrodes is restored to what it was before the breakdown, so that a new liquid dielectric breakdown can occur to repeat the cycle. | 8 | Metallurgy |
The racemic parent compound racemorphan was first described in a Swiss and US patent application from Hoffmann-La Roche in 1946 and 1947, respectively; a patent was granted in 1950. A resolution of the two isomers of racemorphan with tartaric acid was published in 1952, and dextromethorphan was successfully tested in 1954 as part of US Navy and CIA-funded research on nonaddictive substitutes for codeine. Dextromethorphan was approved by the FDA in 1958 as an over-the-counter antitussive. As had been initially hoped, dextromethorphan was a solution for some of the problems associated with the use of codeine phosphate as a cough suppressant, such as sedation and opiate dependence, but like the dissociative anesthetics phencyclidine and ketamine, dextromethorphan later became associated with nonmedical use.
During the 1960s and 1970s, dextromethorphan became available in an over-the-counter tablet form by the brand name Romilar. In 1973, Romilar was taken off the shelves after a burst in sales because of frequent misuse. A few years later, products with an unpleasant taste were introduced (such as Robitussin, Vicks-44, and Dextrotussion), but later the same manufacturers began producing products with a better taste. The advent of widespread internet access in the 1990s allowed users to rapidly disseminate information about dextromethorphan, and online discussion groups formed around use and acquisition of the drug. As early as 1996, dextromethorphan hydrobromide powder could be purchased in bulk from online retailers, allowing users to avoid consuming dextromethorphan in syrup preparations.
FDA panels considered moving dextromethorphan to prescription status due to its potential for abuse, but voted against the recommendation in September 2010, citing lack of evidence that making it prescription-only would curb abuse. Some states have restricted the sale of dextromethorphan to adults or put other restrictions on its purchase in place, similar to those for pseudoephedrine. As of January 1, 2012, dextromethorphan is prohibited for sale to minors in the State of California and in the State of Oregon as of January 1, 2018, except with a doctor's prescription. Several other states have also begun regulating sales of dextromethorphan to minors.
In Indonesia, the National Agency of Drug and Food Control (BPOM-RI) prohibited single-component dextromethorphan drug sales with or without prescription. Indonesia is the only country in the world that makes single-component dextromethorphan illegal even by prescription and violators may be prosecuted by law. National Anti-Narcotics Agency (BNN RI) has even threatened to revoke pharmacies and drug stores licenses if they still stock dextromethorphan, and will notify the police for criminal prosecution. As a result of this regulation, 130 medications have been withdrawn from the market, but those containing multicomponent dextromethorphan can still be sold over the counter. | 4 | Stereochemistry |
The guaifenesin developed by Eldon Boyd is still commonly used today as an expectorant, sold over the counter, and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections. Guaifenesin is a component of Mucinex, Robitussin DAC, Cheratussin DAC, Robitussin AC, Cheratussin AC, Benylin, DayQuil Mucous Control, Meltus, and Bidex 400.
Seirogan is a popular Kampo medicine in Japan, used as an anti-diarrheal, and has 133 mg wood creosote from beech, pine, maple or oak wood per adult dose as its primary ingredient. Seirogan was first used as a gastrointestinal medication by the Imperial Japanese Army in Russia during the Russo-Japanese War of 1904 to 1905.
Creomulsion is a cough medicine in the United States, introduced in 1925, that is still sold and contains beechwood creosote. Beechwood creosote is also found under the name kreosotum or kreosote. | 7 | Physical Chemistry |
The majority of these twintrons have been characterized within the Euglena chloroplast genome but these elements have also been found in cryptomonad algae (Pyrenomonas salina), and group I intron based twintrons (group I inserted within a group I intron) have been described in Didymium iridis. Since the discovery of the psbF twintron, several categories of twintrons have been characterized. A twintron can be simple (external intron interrupted by 1 internal intron), or complex (external intron interrupted by multiple internal introns). Most probably, the internal and external introns comprising the twintron element are from the same category; group I internal to group I, group II internal to group II, and group III internal to group III. Mixed twintrons (consisting of introns belonging to different categories) were characterized from the Euglena gracilis
rps3 gene in which an internal group II intron is found to interrupt an external group III intron. In Rhodomonas salina (=Pyrenomonas salina) twintrons (nested group II/group III introns) were identified where the internal intron lost its splicing capacity, essentially merging with the outer intron forming one splicing unit. Recently, two novel twintrons have been uncovered within the fungal mitochondrial genome, one at position mS917 of the Cryphonectria parasitica mt-rns gene, where a group ID intron encoding a LAGLIDADG ORF invaded another ORF-less group ID intron. Another twintron complex was detected at position mS1247 of the Chaetomium thermophilumhere mt-rns gene, a group IIA1 intron invaded the open reading frame embedded within a group IC2 intron. The mS1247 twintron represents the first recorded fungal mitochondrial mixed twintron consisting of group II intron as an internal intron and a group I intron as an external intron. In mS1247 twintron, splicing of the internal group IIA1 intron reconstitutes the open reading frame encoded within the group IC2 intron and thus facilitates the expression of the encoded homing endonuclease. The mS1247 twintron encod ORF have been biochemically characterized and the results showed that it is an active homing endonuclease that could potentially mobilize the twintron to rns genes that have not yet been invaded by this mobile composite element. | 1 | Biochemistry |
In England and Wales acceptable levels for drinking water supply are listed in the "Water Supply (Water Quality) Regulations 2000." | 3 | Analytical Chemistry |
Protein synthesis within chloroplasts relies on two RNA polymerases. One is coded by the chloroplast DNA, the other is of nuclear origin. The two RNA polymerases may recognize and bind to different kinds of promoters within the chloroplast genome. The ribosomes in chloroplasts are similar to bacterial ribosomes. | 5 | Photochemistry |
Member countries include: Australia, Austria, Belgium, Brazil, Canada, Czech Republic, China, Denmark, Finland, France, Germany, Hungary, Italy, Japan, Luxembourg, Netherlands, Norway, Portugal, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, and the United States. | 8 | Metallurgy |
Oxidative phosphorylation (UK , US ) or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing chemical energy in order to produce adenosine triphosphate (ATP). In eukaryotes, this takes place inside mitochondria. Almost all aerobic organisms carry out oxidative phosphorylation. This pathway is so pervasive because it releases more energy than alternative fermentation processes such as anaerobic glycolysis.
The energy stored in the chemical bonds of glucose is released by the cell in the citric acid cycle, producing carbon dioxide and the energetic electron donors NADH and FADH. Oxidative phosphorylation uses these molecules and O to produce ATP, which is used throughout the cell whenever energy is needed. During oxidative phosphorylation, electrons are transferred from the electron donors to a series of electron acceptors in a series of redox reactions ending in oxygen, whose reaction releases half of the total energy.
In eukaryotes, these redox reactions are catalyzed by a series of protein complexes within the inner membrane of the cells mitochondria, whereas, in prokaryotes, these proteins are located in the cells outer membrane. These linked sets of proteins are called the electron transport chain. In eukaryotes, five main protein complexes are involved, whereas in prokaryotes many different enzymes are present, using a variety of electron donors and acceptors.
The energy transferred by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane, in a process called electron transport. This generates potential energy in the form of a pH gradient and the resulting electrical potential across this membrane. This store of energy is tapped when protons flow back across the membrane and down the potential energy gradient, through a large enzyme called ATP synthase in a process called chemiosmosis. The ATP synthase uses the energy to transform adenosine diphosphate (ADP) into adenosine triphosphate, in a phosphorylation reaction. The reaction is driven by the proton flow, which forces the rotation of a part of the enzyme. The ATP synthase is a rotary mechanical motor.
Although oxidative phosphorylation is a vital part of metabolism, it produces reactive oxygen species such as superoxide and hydrogen peroxide, which lead to propagation of free radicals, damaging cells and contributing to disease and, possibly, aging and senescence. The enzymes carrying out this metabolic pathway are also the target of many drugs and poisons that inhibit their activities. | 1 | Biochemistry |
VMA is found in the urine, along with other catecholamine metabolites, including homovanillic acid (HVA), metanephrine, and normetanephrine. In timed urine tests the quantity excreted (usually per 24 hours) is assessed along with creatinine clearance, and the quantity of cortisols, catecholamines, and metanephrines excreted is also measured. | 1 | Biochemistry |
Pseudoephedrine was on the International Olympic Committees (IOC) banned substances list until 2004, when the World Anti-Doping Agency (WADA) list replaced the IOC list. Although WADA initially only monitored' pseudoephedrine, it went back onto the "banned" list on 1 January 2010.
Pseudoephedrine is excreted through urine, and concentration in urine of this drug shows a large inter-individual spread; that is, the same dose can give a vast difference in urine concentration for different individuals. Pseudoephedrine is approved to be taken up to 240 mg per day. In seven healthy male subjects this dose yielded a urine concentration range of 62.8 to 294.4 microgram per milliliter (µg/mL) with mean ± standard deviation 149 ± 72 µg/mL. Thus, normal dosage of 240 mg pseudoephedrine per day can result in urine concentration levels exceeding the limit of 150 µg/mL set by WADA for about half of all users. Furthermore, hydration status does not affect urinary concentration of pseudoephedrine.
Canadian rower Silken Laumann was stripped of her 1995 Pan American Games team gold medal after testing positive for pseudoephedrine.
In February 2000, Elena Berezhnaya and Anton Sikharulidze won gold at the 2000 European Figure Skating Championships but were stripped of their medals after Berezhnaya tested positive. This resulted in a three-month disqualification from the date of the test, and the medal being stripped. She stated that she had taken cold medication approved by a doctor but had failed to inform the ISU as required. The pair missed the World Championships that year as a result of the disqualification.
Romanian gymnast Andreea Răducan was stripped of her gold medal at the 2000 Summer Olympic Games after testing positive. She took two pills given to her by the team coach for a cold. Although she was stripped of the overall gold medal, she kept her other medals, and, unlike in most other doping cases, was not banned from competing again; only the team doctor was banned for a number of years. Ion Țiriac, the president of the Romanian Olympic Committee, resigned over the scandal.
In the 2010 Winter Olympic Games, the IOC issued a reprimand against the Slovak ice hockey player Lubomir Visnovsky for usage of pseudoephedrine.
In the 2014 Winter Olympic Games Team Sweden and Washington Capitals ice hockey player Nicklas Bäckström was prevented from playing in the final for usage of pseudoephedrine. Bäckström claimed he was using it as allergy medication. In March 2014, the IOC Disciplinary Commission decided that Bäckström would be awarded the silver medal. In January 2015 Bäckström, the IOC, WADA and the IIHF agreed to a settlement in which he accepted a reprimand but was cleared of attempting to enhance his performance. | 4 | Stereochemistry |
Research into the phenomenon of ocean acidification, as well as awareness raising about the problem, has been going on for several decades. The fundamental research really began with the creation of the pH scale by Danish chemist Søren Peder Lauritz Sørensen in 1909. By around the 1950s the massive role of the ocean in absorbing fossil fuel CO was known to specialists, but not appreciated by the greater scientific community. Throughout much of the 20th century, the dominant focus has been the beneficial process of oceanic CO uptake, which has enormously ameliorated climate change. The concept of "too much of a good thing" has been late in developing and was triggered only by some key events, and the oceanic sink for heat and CO is still critical as the primary buffer against climate change.
In the early 1970s questions over the long-term impact of the accumulation of fossil fuel CO in the sea were already arising around the world and causing strong debate. Researchers commented on the accumulation of fossil CO in the atmosphere and sea and drew attention to the possible impacts on marine life. By the mid-1990s, the likely impact of CO levels rising so high with the inevitable changes in pH and carbonate ion became a concern of scientists studying the fate of coral reefs.
By the end of the 20th century the trade-offs between the beneficial role of the ocean in absorbing some 90 % of all heat created, and the accumulation of some 50 % of all fossil fuel CO emitted, and the impacts on marine life were becoming more clear. By 2003, the time of planning for the "First Symposium on the Ocean in a High-CO World" meeting to be held in Paris in 2004, many new research results on ocean acidification were published.
In 2009, members of the InterAcademy Panel called on world leaders to "Recognize that reducing the build up of in the atmosphere is the only practicable solution to mitigating ocean acidification". The statement also stressed the importance to "Reinvigorate action to reduce stressors, such as overfishing and pollution, on marine ecosystems to increase resilience to ocean acidification".
For example, research in 2010 found that in the 15-year period 1995–2010 alone, acidity had increased 6 percent in the upper 100 meters of the Pacific Ocean from Hawaii to Alaska.
According to a statement in July 2012 by Jane Lubchenco, head of the U.S. National Oceanic and Atmospheric Administration "surface waters are changing much more rapidly than initial calculations have suggested. It's yet another reason to be very seriously concerned about the amount of carbon dioxide that is in the atmosphere now and the additional amount we continue to put out."
A 2013 study found acidity was increasing at a rate 10 times faster than in any of the evolutionary crises in Earth's history.
The "Third Symposium on the Ocean in a High- World" took place in Monterey, California, in 2012. The summary for policy makers from the conference stated that "Ocean acidification research is growing rapidly".
In a synthesis report published in Science in 2015, 22 leading marine scientists stated that from burning fossil fuels is changing the oceans chemistry more rapidly than at any time since the Great Dying (Earths most severe known extinction event). Their report emphasized that the 2 °C maximum temperature increase agreed upon by governments reflects too small a cut in emissions to prevent "dramatic impacts" on the world's oceans. | 9 | Geochemistry |
Not all compounds with alternating double and single bonds are aromatic. Cyclooctatetraene, for example, possesses alternating single and double bonds. The molecule typically adopts a "tub" conformation. Because the p orbitals of the molecule do not align themselves well in this non-planar molecule, the π bonds are essentially isolated and not conjugated. The lack of conjugation allows the 8 π electron molecule to avoid antiaromaticity, a destabilizing effect associated with cyclic, conjugated systems containing 4n π (n = 0, 1, 2, ...) electrons. This effect is due to the placement of two electrons into two degenerate nonbonding (or nearly nonbonding) orbitals of the molecule, which, in addition to drastically reducing the thermodynamic stabilization of delocalization, would either force the molecule to take on triplet diradical character, or cause it to undergo Jahn-Teller distortion to relieve the degeneracy. This has the effect of greatly increasing the kinetic reactivity of the molecule. Because of the lack of long-range interactions, cyclooctatetraene takes on a nonplanar conformation and is nonaromatic in character, behaving as a typical alkene. In contrast, derivatives of the cyclooctatetraene dication and dianion have been found to be planar experimentally, in accord with the prediction that they are stabilized aromatic systems with 6 and 10 π electrons, respectively. Because antiaromaticity is a property that molecules try to avoid whenever possible, only a few experimentally observed species are believed to be antiaromatic. Cyclobutadiene and cyclopentadienyl cation are commonly cited as examples of antiaromatic systems. | 7 | Physical Chemistry |
Imines may be reduced enantioselectively using stoichiometric amounts of chiral metal hydrides. Such methods have the advantage that they are easy to implement. Reduction with hydrosilanes is a second alternative to transition-metal catalyzed hydrogenation. | 0 | Organic Chemistry |
Once again, the conformation and position of groups (ie. substituents) larger than a singular hydrogen are critical to the overall stability of the molecule. The larger the group, the less likely to prefer the axial position on its respective carbon. Maintaining said position with a larger size costs more energy from the molecule as a whole because of steric repulsion between the large groups' nonbonded electron pairs and the electrons of the smaller groups (ie. hydrogens). Such steric repulsions are absent for equatorial groups. The cyclohexane model thus assesses steric size of functional groups on the basis of gauche interactions. The gauche interaction will increase in energy as the size of the substituent involved increases. For example, a t-butyl substituent would sustain a higher energy gauche interaction as compared to a methyl group, and therefore, contribute more to the instability of the molecule as a whole.
In comparison, a staggered conformation is thus preferred; the larger groups would maintain the equatorial position and lower the energy of the entire molecule. This preference for the equatorial position among bulkier groups lowers the energy barriers between different conformations of the ring. When the molecule is activated, there will be a loss in entropy due to the stability of the larger substituents. Therefore, the preference of the equatorial positions by large molecules (such as a methyl group) inhibits the reactivity of the molecule and thus makes the molecule more stable as a whole. | 4 | Stereochemistry |
Strict carnivores manage vitamin A differently than omnivores and herbivores. Carnivores are more tolerant of high intakes of retinol because those species have the ability to excrete retinol and retinyl esters in urine. Carnivores also have the ability to store more in the liver, due to a higher ratio of liver HSCs to hepatocytes compared to omnivores and herbivores. For humans, liver content can range from 20 to 30 μg/gram wet weight. Notoriously, polar bear liver is acutely toxic to humans because content has been reported in range of 2,215 to 10,400 μg/g wet weight. As noted, in humans, retinol circulates bound to RBP4. Carnivores maintain R-RBP4 within a tight range while also having retinyl esters in circulation. Bound retinol is delivered to cells while the esters are excreted in the urine. In general, carnivore species are poor converters of ionone-containing carotenoids, and pure carnivores such as felidae (cats) lack the cleaving enzyme entirely. They must have retinol or retinyl esters in their diet. | 1 | Biochemistry |
Dead zones can be classified by type, and are identified by the length of their occurrence:
* Permanent dead zones are deep water occurrences that rarely exceed 2 milligrams per liter.
* Temporary dead zones are short lived dead zones lasting hours or days.
* Seasonal dead zones are annually occurring, typically in warm months of summer and autumn.
* Diel cycling hypoxia is a specific seasonal dead zone that only becomes hypoxic during the night
The type of dead zone can, in some ways, be categorized by the time required for the water to return to full health. This time frame depends on the intensity of eutrophication and level of oxygen depletion. A water body that sinks to anoxic conditions and experiences extreme reduction in community diversity will have to travel a much longer path to return to full health. A water body that only experiences mild hypoxia and maintains community diversity and maturity will require a much shorter path length to return to full health. | 9 | Geochemistry |
Volatile suspended solids (VSS) is an analytical parameter representing, loosely, the undissolved organic matter in a water sample. More technically, it a water quality parameter obtained from the loss on ignition of total suspended solids. This ignition generally takes place in an oven at a temperature of 550 °C to 600 °C. It represents the amount of volatile matter present in the undissolved solid fraction of the measured solution. | 3 | Analytical Chemistry |
the Atlantic Station project in Atlanta, was the largest brownfield redevelopment in the United States. Dayton, like many other cities in the region, is developing Tech Town in order to attract technology-based firms to Dayton and revitalize the downtown area. In Homestead, Pennsylvania, the site once occupied by Carnegie Steel has been converted into a successful commercial center, The Waterfront.
Pittsburgh, Pennsylvania, has successfully converted numerous former steel mill sites into high-end residential, shopping, and offices. Examples of brownfield redevelopment in Pittsburgh include:
* In Pittsburgh's Squirrel Hill neighborhood, a former slag dump for steel mills was turned into a $243 million residential development called Summerset at Frick Park.
* In Pittsburgh's South Side neighborhood, a former LTV Steel mill site was transformed into Southside Works, a mixed-use development that includes high-end entertainment, retail, offices, and housing.
* In the Hazelwood (Pittsburgh) neighborhood, a former Jones and Laughlin steel mill site was transformed into a $104 million office park called Pittsburgh Technology Center.
* In Herrs Island, a island on the western bank of the Allegheny River, a former rail stop for livestock and meatpacking was transformed into Washingtons Landing, a waterfront center for commerce, manufacturing, recreation and upscale housing | 2 | Environmental Chemistry |
Polyprotein processing is adopted by 45% of plant viruses, such as the Potyviridae and Tymoviridae. The ribosome translates a single protein from the viral genome. Within the polyprotein is an enzyme (or enzymes) with proteinase function that is able to cleave the polyprotein into the various single proteins or just cleave away the protease, which can then cleave other polypeptides producing the mature proteins. | 1 | Biochemistry |
Salmonella encodes a LuxR homolog, SdiA, but does not encode an AHL synthase. SdiA detects AHLs produced by other species of bacteria including Aeromonas hydrophila, Hafnia alvei, and Yersinia enterocolitica. When AHL is detected, SdiA regulates the rck operon on the Salmonella virulence plasmid (pefI-srgD-srgA-srgB-rck-srgC) and a single gene horizontal acquisition in the chromosome srgE. Salmonella does not detect AHL when passing through the gastrointestinal tracts of several animal species, suggesting that the normal microbiota does not produce AHLs. However, SdiA does become activated when Salmonella transits through turtles colonized with Aeromonas hydrophila or mice infected with Yersinia enterocolitica. Therefore, Salmonella appears to use SdiA to detect the AHL production of other pathogens rather than the normal gut flora. | 1 | Biochemistry |
Static fatigue describes how prolonged and constant cyclic stress weakens a material until it breaks apart, which is called failure. Static fatigue is sometimes called "delayed fracture". The damage occurs at a lower stress level than the stress level needed to create a normal tensile fracture. Static fatigue can involve plastic deformation or crack growth. For example, repeated stress can create small cracks that grow and eventually break apart plastic, glass, or ceramic materials. The material reaches failure faster by increasing cyclic stress. Static fatigue varies with material type and environmental factors, such as moisture presence and temperature. | 8 | Metallurgy |
The GUS assay, as well as other reporter gene systems, can be used for other kinds of studies other than the classical promoter activity assay. Reporter systems have been used for the determination of the efficiency of gene delivery systems, the intracellular localization of a gene product, the detection of protein-protein or protein-DNA interactions, the efficiency of translation initiation signals and the success of molecular cloning efforts. | 1 | Biochemistry |
In Earth's atmosphere, carbon dioxide is a trace gas that plays an integral part in the greenhouse effect, carbon cycle, photosynthesis and oceanic carbon cycle. It is one of several greenhouse gases in the atmosphere of Earth. The current global average concentration of carbon dioxide (CO) in the atmosphere is 421 ppm as of May 2022 (0.04%). This is an increase of 50% since the start of the Industrial Revolution, up from 280 ppm during the 10,000 years prior to the mid-18th century. The increase is due to human activity. Burning fossil fuels is the main cause of these increased CO concentrations and also the main cause of climate change. Other large sources of CO from human activities include cement production, deforestation, and biomass burning.
Carbon dioxide is a greenhouse gas. It absorbs and emits infrared radiation at its two infrared-active vibrational frequencies. The two wavelengths are 4.26 μm (2,347 cm) (asymmetric stretching vibrational mode) and 14.99 μm (667 cm) (bending vibrational mode). CO plays a significant role in influencing Earths surface temperature through the greenhouse effect. Light emission from the Earths surface is most intense in the infrared region between 200 and 2500 cm, as opposed to light emission from the much hotter Sun which is most intense in the visible region. Absorption of infrared light at the vibrational frequencies of atmospheric traps energy near the surface, warming the surface of Earth and its lower atmosphere. Less energy reaches the upper atmosphere, which is therefore cooler because of this absorption.
The increase in atmospheric concentrations of and other long-lived greenhouse gases such as methane increase the absorption and emission of infrared radiation by the atmosphere. This has led to a rise in average global temperature and ocean acidification. Another direct effect is the CO fertilization effect. The increase in atmospheric concentrations of causes a range of further effects of climate change on the environment and human living conditions.
The present atmospheric concentration of is the highest for 14 million years. Concentrations of in the atmosphere were as high as 4,000 ppm during the Cambrian period about 500 million years ago, and as low as 180 ppm during the Quaternary glaciation of the last two million years. Reconstructed temperature records for the last 420 million years indicate that atmospheric concentrations peaked at approximately 2,000 ppm. This peak happened during the Devonian period (400 million years ago). Another peak occurred in the Triassic period (220–200 million years ago). | 2 | Environmental Chemistry |
In coordination chemistry and crystallography, the geometry index or structural parameter () is a number ranging from 0 to 1 that indicates what the geometry of the coordination center is. The first such parameter for 5-coordinate compounds was developed in 1984. Later, parameters for 4-coordinate compounds were developed. | 3 | Analytical Chemistry |
BARDS has significant potential as an analytical technique. Applications researched so far include:
* Batch consistency analysis
* Blend uniformity analysis
* Polymorph and pseudopolymorph discrimination
* Monitoring of supersaturation of solutions and rates of outgassing | 7 | Physical Chemistry |
Golfomycin A is a synthetic enediyne molecule designed in an attempt to create a more easily manufactured antitumor antibiotic. DNA strand-scission induced by golfomycin A is pH dependent. Preliminary in vitro studies have demonstrated that golfomycin A can reduce carcinomas in bladder cells. | 0 | Organic Chemistry |
The vapor-compression cycle is used in most household refrigerators as well as in many large commercial and industrial refrigeration systems. Figure 1 provides a schematic diagram of the components of a typical vapor-compression refrigeration system.
The thermodynamics of the cycle can be analyzed on a diagram as shown in Figure 2. In this cycle, a circulating refrigerant such as a low boiling hydrocarbon or hydrofluorocarbons enters the compressor as a vapour. From point 1 to point 2, the vapor is compressed at constant entropy and exits the compressor as a vapor at a higher temperature, but still below the vapor pressure at that temperature. From point 2 to point 3 and on to point 4, the vapor travels through the condenser which cools the vapour until it starts condensing, and then condenses the vapor into a liquid by removing additional heat at constant pressure and temperature. Between points 4 and 5, the liquid refrigerant goes through the expansion valve (also called a throttle valve) where its pressure abruptly decreases, causing flash evaporation and auto-refrigeration of, typically, less than half of the liquid.
That results in a mixture of liquid and vapour at a lower temperature and pressure as shown at point 5. The cold liquid-vapor mixture then travels through the evaporator coil or tubes and is completely vaporized by cooling the warm air (from the space being refrigerated) being blown by a fan across the evaporator coil or tubes. The resulting refrigerant vapour returns to the compressor inlet at point 1 to complete the thermodynamic cycle.
The above discussion is based on the ideal vapour-compression refrigeration cycle, and does not take into account real-world effects like frictional pressure drop in the system, slight thermodynamic irreversibility during the compression of the refrigerant vapor, or non-ideal gas behavior, if any. Vapor compression refrigerators can be arranged in two stages in cascade refrigeration systems, with the second stage cooling the condenser of the first stage. This can be used for achieving very low temperatures.
More information about the design and performance of vapor-compression refrigeration systems is available in the classic Perrys Chemical Engineers Handbook. | 7 | Physical Chemistry |
The situation on rough surfaces is much more complicated. The main characteristic of the wetting properties of rough surfaces is the so-called apparent contact angle (APCA). It is well known that the APCA usually measured are different from those predicted by the Young equation. Two main hypotheses were proposed in order to explain this discrepancy, namely the Wenzel and Cassie wetting models. According to the traditional Cassie model, air can remain trapped below the drop, forming "air pockets". Thus, the hydrophobicity of the surface is strengthened because the drop sits partially on air. On the other hand, according to the Wenzel model the roughness increases the area of a solid surface, which also geometrically modifies the wetting properties of this surface. Transition from Cassie to Wenzel regime is also called wetting transition. Under certain external stimuli, such as pressure or vibration, the Cassie air trapping wetting state could be converted into the Wenzel state. Apart from external stimuli, intrinsic contact angle of the liquid (below or above 90 degree), liquid volatility, structure of cavities (reentrant or non-reentrant, connected or unconnected) are known to be important factors determining the rate of wetting transition. It is well accepted that the Cassie air trapping wetting regime corresponds to a higher energetic state, and the Cassie–Wenzel transition is irreversible. However, the mechanism of the transition remains unclear. It was suggested that the Cassie–Wenzel transition occurs via a nucleation mechanism starting from the drop center. On the other hand, recent experiments showed that the Cassie–Wenzel transition is more likely to be due to the displacement of a triple line under an external stimulus. The existence of so-called impregnating Cassie wetting state also has to be considered. Understanding wetting transitions is of a primary importance for design of superhydrophobic surfaces. | 7 | Physical Chemistry |
The three types of coatings are: diffusion coatings, overlay coatings, and thermal barrier coatings. Diffusion coatings, mainly constituted with aluminide or platinum-aluminide, is the most common. MCrAlX-based overlay coatings (M=Ni or Co, X=Y, Hf, Si) enhance resistance to corrosion and oxidation. Compared to diffusion coatings, overlay coatings are more expensive, but less dependent on substrate composition, since they must be carried out by air or vacuum plasma spraying (APS/VPS) or electron beam physical vapour deposition (EB-PVD). Thermal barrier coatings provide by far the best enhancement in working temperature and coating life. It is estimated that modern TBC of thickness 300 μm, if used in conjunction with a hollow component and cooling air, has the potential to lower metal surface temperatures by a few hundred degrees. | 8 | Metallurgy |
Molecular breeding resources (including multiomics data) are available for:
* Some of the millets
* Wheat | 1 | Biochemistry |
Townsend's early experimental apparatus consisted of planar parallel plates forming two sides of a chamber filled with a gas. A direct current high-voltage source was connected between the plates; the lower plate being the cathode while the other was the anode. He forced the cathode to emit electrons using the photoelectric effect by irradiating it with X-rays, and he found that the current flowing through the chamber depended on the electric field between the plates. However, this current showed an exponential increase as the plate gaps became small, leading to the conclusion that the gas ions were multiplying as they moved between the plates due to the high electric field.
Townsend observed currents varying exponentially over ten or more orders of magnitude with a constant applied voltage when the distance between the plates was varied. He also discovered that gas pressure influenced conduction: he was able to generate ions in gases at low pressure with a much lower voltage than that required to generate a spark. This observation overturned conventional thinking about the amount of current that an irradiated gas could conduct.
The experimental data obtained from his experiments are described by the following formula
where
* is the current flowing in the device,
* is the photoelectric current generated at the cathode surface,
* is Euler's number
* is the first Townsend ionisation coefficient, expressing the number of ion pairs generated per unit length (e.g. meter) by a negative ion (anion) moving from cathode to anode,
* is the distance between the plates of the device.
The almost constant voltage between the plates is equal to the breakdown voltage needed to create a self-sustaining avalanche: it decreases when the current reaches the glow discharge regime. Subsequent experiments revealed that the current rises faster than predicted by the above formula as the distance increases: two different effects were considered in order to better model the discharge: positive ions and cathode emission. | 7 | Physical Chemistry |
Sulfuranes are relatively specialized functional group that feature tetravalent sulfur, with the formula SR Likewise, persulfuranes feature hexavalent SR.
One of the few all-carbon persulfuranes has two methyl and two biphenylene ligands:
It is prepared from the corresponding sulfurane 1 with xenon difluoride / boron trifluoride in acetonitrile to the sulfuranyl dication 2 followed by reaction with methyllithium in tetrahydrofuran to (a stable) persulfurane 3 as the cis isomer. X-ray diffraction shows C−S bond lengths ranging between 189 and 193 pm (longer than the standard bond length) with the central sulfur atom in a distorted octahedral molecular geometry. | 9 | Geochemistry |
Well-known acyl compounds are the acyl chlorides, such as acetyl chloride (CHCOCl) and benzoyl chloride (CHCOCl). These compounds, which are treated as sources of acylium cations, are good reagents for attaching acyl groups to various substrates. Amides (RC(O)NR′) and esters (RC(O)OR′) are classes of acyl compounds, as are ketones (RC(O)R′) and aldehydes (RC(O)H), where R and R′ stand for organyl (or hydrogen in the case of formyl). | 0 | Organic Chemistry |
Another benefit of using conductive polymers as a coating for neural devices is the ease of synthesis and flexibility in processing. Conducting polymers can be directly "deposited onto electrode surfaces with precisely controlled morphologies". There are two current ways conducting polymers can be deposited onto electrode surfaces which are chemical polymerization and electrochemical polymerization. In the application for neural implants, electrochemical polymerization is used because of its ability to create thin films and the ease of synthesis. Films can be formed on the order of 20 nm. Electrochemical polymerization (electrochemical deposition) is performed using a three-electrode configuration in a solution of the monomer of the desired polymer, a solvent, and an electrolyte (dopant). In the case of depositing a polymer coating onto electrode a common dopant used is poly (styrene sulfonate) or PSS because of its stability and biocompatibility. Two common conductive polymers being investigated for coatings use PSS as a dopant to be electrochemically deposited onto the electrode surface (see sections below). | 7 | Physical Chemistry |
Some Chinese cookware is seasoned at a much higher temperature than conventional seasoning at 450 °C. More akin to bluing, this type of seasoning mainly involves a chemical change of the iron pan itself and not the oil. When beef tallow is heated at this temperature, it evaporates on the iron surface and increases the partial pressure of O (oxygen gas) on the pot surface. This transport of oxygen encourages the formation of FeO nanoballs. The surface formed is broadly speaking hydrophobic and oleophilic, but is more versatile in that it temporarily turns hydrophilic on contact with high-water ingredients. | 7 | Physical Chemistry |
Qualitative filter paper is used in qualitative analytical techniques to determine materials. There are different grades of qualitative filter paper according to different pore size. There are total 13 different grades of qualitative filter paper. The largest pore size is grade 4; the smallest pore size is grade 602 h; the most commonly used grades are grade 1 to grade 4.
Grade 1 qualitative filter paper has the pore size of 11 μm. This grade of filter paper is widely used for many different fields in agricultural analysis, air pollution monitoring and other similar experiments.
Grade 2 qualitative filter paper has the pore size of 8 μm. This grade of filter paper requires more filtration time than Grade 1 filter paper. This filter paper is used for monitoring specific contaminants in the atmosphere and soil testing.
Grade 3 qualitative filter paper has the pore size of 6 μm. This grade of filter paper is very suitable for carrying samples after filtration.
Grade 4 qualitative filter paper has the pore size of 20~25 μm. This grade of filter paper has the largest pore size among all standard qualitative filter papers. It is very useful as rapid filter for cleanup of geological fluids or organic extracts during experiment.
Grade 602 h qualitative filter paper has the pore size of 2 μm. This grade of filter paper has the smallest pore size among all standard qualitative filter papers. It is used for collecting or removing fine particles. | 3 | Analytical Chemistry |
In biochemistry, the KIX domain (kinase-inducible domain (KID) interacting domain) or CREB binding domain is a protein domain of the eukaryotic transcriptional coactivators CBP and P300. It serves as a docking site for the formation of heterodimers between the coactivator and specific transcription factors. Structurally, the KIX domain is a globular domain consisting of three α-helices and two short 3-helices.
The KIX domain was originally discovered in 1996 as the specific and minimal region in CBP that binds and interacts with phosphorylated CREB to activate transcription. It was thus first termed CREB-binding domain. However, when it was later discovered that it also binds many other proteins, the more general name KIX domain became favoured. The KIX domain contains two separate binding sites: the "c-Myb site", named after the oncoprotein c-Myb, and the "MLL site", named after the proto-oncogene MLL (Mixed Lineage Leukemia, KMT2A).
The paralogous coactivators CBP (CREBBP) and P300 (EP300) are recruited to DNA-bound transcription factors to activate transcription. Coactivators can associate with promoters and enhancers in the DNA only indirectly through protein-protein contacts with transcription factors. CBP and P300 activate transcription synergistically in two ways: first, by remodelling and relaxing chromatin through their intrinsic histone acetyltransferase activity, and second, by recruiting the basal transcription machinery, such as RNA polymerase II.
The KIX domain belongs to the proposed GACKIX domain superfamily. GACKIX comprises structurally and functionally highly homologous domains in related proteins. It is named after the protein GAL11 / ARC105 (MED15), the plant protein CBP-like, and the KIX domain from CBP and P300. Additional instances include RECQL5 and related plant proteins. All of these contain a KIX domain or KIX-related domain that interacts with the transactivation domain of many different transcription factors. The distinction between a KIX domain, a KIX-related domain and a GACKIX domain is subject to an ongoing debate and not clearly defined. | 1 | Biochemistry |
The full quantum-mechanical treatment of bremsstrahlung is very involved. The "vacuum case" of the interaction of one electron, one ion, and one photon, using the pure Coulomb potential, has an exact solution that was probably first published by A. Sommerfeld in 1931. This analytical solution involves complicated mathematics, and several numerical calculations have been published, such as by Karzas and Latter. Other approximate formulas have been presented, such as in recent work by Weinberg and Pradler and Semmelrock.
This section gives a quantum-mechanical analog of the prior section, but with some simplifications to illustrate the important physics. We give a non-relativistic treatment of the special case of an electron of mass , charge , and initial speed decelerating in the Coulomb field of a gas of heavy ions of charge and number density . The emitted radiation is a photon of frequency and energy . We wish to find the emissivity which is the power emitted per (solid angle in photon velocity space * photon frequency), summed over both transverse photon polarizations. We express it as an approximate classical result times the free−free emission Gaunt factor g accounting for quantum and other corrections:
if , that is, the electron does not have enough kinetic energy to emit the photon. A general, quantum-mechanical formula for exists but is very complicated, and usually is found by numerical calculations. We present some approximate results with the following additional assumptions:
* Vacuum interaction: we neglect any effects of the background medium, such as plasma screening effects. This is reasonable for photon frequency much greater than the plasma frequency with the plasma electron density. Note that light waves are evanescent for and a significantly different approach would be needed.
* Soft photons: , that is, the photon energy is much less than the initial electron kinetic energy.
With these assumptions, two unitless parameters characterize the process: , which measures the strength of the electron-ion Coulomb interaction, and , which measures the photon "softness" and we assume is always small (the choice of the factor 2 is for later convenience). In the limit , the quantum-mechanical Born approximation gives:
In the opposite limit , the full quantum-mechanical result reduces to the purely classical result
where is the Euler–Mascheroni constant. Note that which is a purely classical expression without Planck's constant .
A semi-classical, heuristic way to understand the Gaunt factor is to write it as where and are maximum and minimum "impact parameters" for the electron-ion collision, in the presence of the photon electric field. With our assumptions, : for larger impact parameters, the sinusoidal oscillation of the photon field provides "phase mixing" that strongly reduces the interaction. is the larger of the quantum-mechanical de Broglie wavelength and the classical distance of closest approach where the electron-ion Coulomb potential energy is comparable to the electron's initial kinetic energy.
The above approximations generally apply as long as the argument of the logarithm is large, and break down when it is less than unity. Namely, these forms for the Gaunt factor become negative, which is unphysical. A rough approximation to the full calculations, with the appropriate Born and classical limits, is | 7 | Physical Chemistry |
Dianins compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) was first prepared by Aleksandr Dianin in 1914. This compound is a condensation isomer of bisphenol A and acetone and of special importance in host–guest chemistry because it can form a large variety of clathrates with suitable guest molecules. One example is the clathrate of Dianins compound with morpholine. Slow evaporation of a solution containing both organic compounds yields crystals. Each asymmetric unit cell making up the crystal contains six chroman molecules of which two are deprotonated and two protonated morpholine molecules. The six chroman molecules are racemate pairs. | 6 | Supramolecular Chemistry |
The weighted sum of partial specific volumes of a mixture or solution is an inverse of density of the mixture namely the specific volume of the mixture. | 1 | Biochemistry |
Homing endonucleases are always indicated with a prefix that identifies their genomic origin, followed by a hyphen: "I-" for homing endonucleases encoded within an intron, "PI-" (for "protein insert") for those encoded within an intein. Some authors have proposed using the prefix "F-" ("freestanding") for viral enzymes and other natural enzymes not encoded by introns nor inteins, and "H-" ("hybrid") for enzymes synthesized in a laboratory. Next, a three-letter name is derived from the binominal name of the organism, taking one uppercase letter from the genus name and two lowercase letters from the specific name. (Some mixing is usually done for hybrid enzymes.) Finally, a Roman numeral distinguishes different enzymes found in the same organism:
* PI-TliII () is the second-identified enzyme encoded by an intein found in the archaea Thermococcus litoralis.
* H-DreI () is the first synthetic homing endonuclease, created in a laboratory from the enzymes I-DmoI () and I-CreI (), taken respectively from Desulfurococcus mobilis and Chlamydomonas reinhardtii. | 1 | Biochemistry |
Nanorobots have the potential to transform drug delivery processes and biological computing. Llopis-Lorente and co. developed a nanorobot that can perform logic operations and process information on glucose and urea. Thubagere and coworkers designed a DNA molecular nanorobot capable of sorting chemical cargo. The system could work without additional power as the robot was capable of walking across the DNA origami surface on its two feet. It also had an arm to transport cargo.
Molecular sequential logic is exemplified by Margulies et al., where they demonstrate a molecular keypad lock resembling the processing capabilities of an electronic security device which is equivalent to incorporates several interconnected AND logic gates in parallel. The molecule mimics an electronic keypad of an automated teller machine (ATM). The output signals are dependent not only on the combination of inputs but also on the correct order of inputs; i.e. the correct password must be entered. The molecule was designed using pyrene and fluorescein fluorophores connected by a siderophore, which binds to Fe(III), and the acidic of the solution changes the fluorescence properties of the fluorescein fluorophore.
Molecular logic gate systems can theoretically overcome the problems arising when semiconductors approach nano-dimensions. Molecular logic gates are more versatile than their silicon counterparts, with phenomena such as superposed logic unavailable to semiconductor electronics. Dry molecular gates, such as the one demonstrated by Avouris and colleagues, prove to be possible substitutes for semiconductor devices due to their small size, similar infrastructure, and data processing abilities. Avouris revealed a NOT logic gate composed of a bundle of carbon nanotubes. The nanotubes are doped differently in adjoining regions creating two complementary field effect transistors, and the bundle operates as a NOT logic gate only when satisfactory conditions are met. | 6 | Supramolecular Chemistry |
Laser peening (LP), or laser shock peening (LSP), is a surface engineering process used to impart beneficial residual stresses in materials. The deep, high-magnitude compressive residual stresses induced by laser peening increase the resistance of materials to surface-related failures, such as fatigue, fretting fatigue, and stress corrosion cracking. Laser shock peening can also be used to strengthen thin sections, harden surfaces, shape or straighten parts (known as laser peen forming), break up hard materials, compact powdered metals and for other applications where high-pressure, short duration shock waves offer desirable processing results. | 8 | Metallurgy |
UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva. For example, ejaculated fluids or saliva can be detected by high-power UV sources, irrespective of the structure or colour of the surface the fluid is deposited upon. UV–vis microspectroscopy is also used to analyze trace evidence, such as textile fibers and paint chips, as well as questioned documents.
Other applications include the authentication of various collectibles and art, and detecting counterfeit currency. Even materials not specially marked with UV sensitive dyes may have distinctive fluorescence under UV exposure or may fluoresce differently under short-wave versus long-wave ultraviolet. | 5 | Photochemistry |
In 2013, the International Agency for Research on Cancer (IARC) classified dioxin-like PCBs as human carcinogens.
According to the U.S. EPA, PCBs have been shown to cause cancer in animals and evidence supports a cancer-causing effect in humans. Per the EPA, studies have found increases in malignant melanoma and rare liver cancers in PCB workers.
In 2013, the IARC determined that the evidence for PCBs causing non-Hodgkin lymphoma is "limited" and "not consistent". In contrast an association between elevated blood levels of PCBs and non-Hodgkin lymphoma had been previously accepted. PCBs may play a role in the development of cancers of the immune system because some tests of laboratory animals subjected to very high doses of PCBs have shown effects on the animals' immune system, and some studies of human populations have reported an association between environmental levels of PCBs and immune response. | 2 | Environmental Chemistry |
A disequilibrium in the abundance of gas species in an atmosphere can be interpreted as a biosignature. Life has greatly altered the atmosphere on Earth in a way that would be unlikely for any other processes to replicate. Therefore, a departure from equilibrium is evidence for a biosignature. For example, the abundance of methane in the Earth's atmosphere is orders of magnitude above the equilibrium value due to the constant methane flux that life on the surface emits. Depending on the host star, a disequilibrium in the methane abundance on another planet may indicate a biosignature. | 2 | Environmental Chemistry |
No applications have been found thus far, although physicist Andreas Hermann states that if the state of matter could be recreated in other materials, it could have many different applications. | 7 | Physical Chemistry |
Carboranes (or carbaboranes) are electron-delocalized (non-classically bonded) clusters composed of boron, carbon and hydrogen atoms. Like many of the related boron hydrides, these clusters are polyhedra or fragments of polyhedra. Carboranes are one class of heteroboranes.
In terms of scope, carboranes can have as few as 5 and as many as 14 atoms in the cage framework. The majority have two cage carbon atoms. The corresponding C-alkyl and B-alkyl analogues are also known in a few cases. | 7 | Physical Chemistry |
Tributyltin azide is an organotin compound with the formula (CH)SnN. It is a colorless solid although older samples can appear as yellow oils. The compound is used as a reagent in organic synthesis. | 0 | Organic Chemistry |
CORROSION es una banda de Thrash metal Paraguaya ceada en 1992 en Asunción
con partes de los integrantes de la Banda de Thrash Rawhide.Tiene como influencias a las tipicas bandas de metal como Slayer,Mettalica,Dorsal Atlantica,etc
La banda Se creo en 1992 con las cenizas de Rawhide,Lanzaron un Demo + Bonus tracks Y un LP album de studio(Report of Explotation) Despues de su ultima gira en 1995 en varios escenarios de Paraguay y Sao paulo y entre eso se disolvieron por problemas personales.
Luego en 2013 volvieron haciendo un concierto en el estadio de Sol de America con varios grupos de Thrash Muy conocidos...
En 2021 Lanzaron un Boxset de Report of Explotation.
En 1992 lanzaron un demo + Bonus tracks llamado Reinos Depredados,luego Grabaron el Famoso album de Studio como LP Report of Explotation en 1993 Grabado en brazil en el estudio de Nas Nuvens de Río de Janeiro y fue lanzado bajo el sello de Dynamo brazil.
# Reinos Depredados
# Aventon de la muerte
# Escucha tu Conciencia
# Corrosion
# Freneticos
Bonus tracks
# Reinos Depredados (estudio demo)
# Intro - Aventón de la Muerte (en vivo)
# Reinos Depredados (en vivo)
# For Whom the Bell Tolls (Metallica Cover) (live)
# Noema (live)
# Escucha a Tu Conciencia (live)
# Frenéticos (live)
# Himno a la Alegría (live)
# Huellas de Corrosión (live)
# Skeletons of Society (Slayer cover) (live)
# Reinos Depredados [Bis] (live)
# Aventón de la Muerte [Bis] (live)
# Letragia Ancestral (studio version)
Duracion:
# Zeitgeist
# Genesis of Terror
# Deforested Kingdoms
# Castle of sir jan
B Side
# Listen to your conciensce
# Noema
# Hitch-Hicking Death
# Signs Of Corrosion
# Tesay Ro
# Letergia Ancestral
# Letergia Ancestral
# Reinos depredados
# Escucha Tu Conciencia
# Deforested Kingdoms
# Signs of corrosion | 8 | Metallurgy |
α-Hydroxyketones, or acyloins, are an important synthetic motifs present in many natural products. α-Hydroxyketones have been synthesized in many ways, including reduction of α-diketones, substitution of a hydroxyl for a leaving group and direct oxidation of an enolate. Oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide) (MoOPH) and N-sulfonyloxaziridines are the most common electrophilic sources of oxygen implemented in this process. One advantage of using N-sulfonyloxaziridines is that higher chiral induction is almost invariably observed relative to MoOPH and other oxidants. High yield (77–91%) and dr (95:5 – 99:1) are reported for α-hydroxylation with the Evans chiral auxiliary with N'-sulfonyloxaziridine as the electrophile. Chiral induction has been demonstrated with many other chiral ketones and ketones with chiral auxiliaries, including [http://upload.wikimedia.org/wikipedia/commons/0/03/SAMP_RAMP_Struktur.svg SAMP and RAMP].
Extensive work has been reported on asymmetric hydroxylation of prochiral enolates with camphorsulfonyloxaziridine derivatives, achieving moderate to high enantiomeric excess. The commonly accepted proposed transition state that justifies this stereochemical outcome involves an open transition state where the steric bulk of R determines the face of approach.
The selectivity of some hydroxylations may be drastically improved in some cases with the addition of coordinating groups alpha to the oxaziridine ring as oxaziridines 3b and 3c in the table above. In these instances it is proposed that the reaction proceeds through a closed transition state where the metal oxyanion is stabilized by chelation from the sulfate and coordinating groups on the camphor skeleton.
α-Hydroxylation with oxaziridines has been widely implemented in total synthesis. It is a key step in both the Holton Taxol total synthesis and the Wender Taxol total synthesis. Additionally, Forsyth implemented the transformation in his synthesis of the C3-C14 (substituted 1,7-Dioxaspiro[5.5]undec-3-ene) System of okadaic acid. | 0 | Organic Chemistry |
The International Association for the Properties of Water and Steam (IAPWS) is an international non-profit association of national organizations concerned with the properties of water and steam, particularly thermophysical properties and other aspects of high-temperature steam, water and aqueous mixtures that are relevant to thermal power cycles and other industrial applications.
The organization publishes a range of releases. Specifically, these relate to the thermal and expansion properties of steam.
Both free software and commercial software implementations of the IAPWS correlations are available. | 7 | Physical Chemistry |
Wu et al. reported a C–X cross coupling using CuX (X= Br, Cl) and a silver catalyst to obtain aryl halides. | 0 | Organic Chemistry |
BAC contigs are constructed by aligning BAC regions of known overlap via a variety of methods. One common strategy is to use sequence-tagged site (STS) content mapping to detect unique DNA sites in common between BACs. The degree of overlap is roughly estimated by the number of STS markers in common between two clones, with more markers in common signifying a greater overlap. Because this strategy provides only a very rough estimate of overlap, restriction digest fragment analysis, which provides a more precise measurement of clone overlap, is often used. In this strategy, clones are treated with one or two restriction enzymes and the resulting fragments separated by gel electrophoresis. If two clones, they will likely have restriction sites in common, and will thus share several fragments. Because the number of fragments in common and the length of these fragments is known (the length is judged by comparison to a size standard), the degree of overlap can be deduced to a high degree of precision. | 1 | Biochemistry |
The effect of non-depolarizing neuromuscular-blocking drugs may be reversed with acetylcholinesterase inhibitors, neostigmine, and edrophonium, as commonly used examples. Of these, edrophonium has a faster onset of action than neostigmine, but it is unreliable when used to antagonize deep neuromuscular block. Acetylcholinesterase inhibitors increase the amount of acetylcholine in the neuromuscular junction, so a prerequisite for their effect is that the neuromuscular block is not complete, because in case every acetylcholine receptor is blocked then it does not matter how much acetylcholine is present.
Sugammadex is a newer drug for reversing neuromuscular block by rocuronium and vecuronium in general anaesthesia. It is the first selective relaxant binding agent (SRBA). | 1 | Biochemistry |
Many traditional solids exhibit different properties when they shrink to nanometer sizes. For example, nanoparticles of usually yellow gold and gray silicon are red in color; gold nanoparticles melt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064 °C); and metallic nanowires are much stronger than the corresponding bulk metals. The high surface area of nanoparticles makes them extremely attractive for certain applications in the field of energy. For example, platinum metals may provide improvements as automotive fuel catalysts, as well as proton exchange membrane (PEM) fuel cells. Also, ceramic oxides (or cermets) of lanthanum, cerium, manganese and nickel are now being developed as solid oxide fuel cells (SOFC). Lithium, lithium-titanate and tantalum nanoparticles are being applied in lithium ion batteries. Silicon nanoparticles have been shown to dramatically expand the storage capacity of lithium ion batteries during the expansion/contraction cycle. Silicon nanowires cycle without significant degradation and present the potential for use in batteries with greatly expanded storage times. Silicon nanoparticles are also being used in new forms of solar energy cells. Thin film deposition of silicon quantum dots on the polycrystalline silicon substrate of a photovoltaic (solar) cell increases voltage output as much as 60% by fluorescing the incoming light prior to capture. Here again, surface area of the nanoparticles (and thin films) plays a critical role in maximizing the amount of absorbed radiation. | 7 | Physical Chemistry |
The reagent is prepared from chlorosulfonylisocyanate by reaction with methanol and triethylamine in benzene: | 0 | Organic Chemistry |
Initial salting in at low concentrations is explained by the Debye–Huckel theory. Proteins are surrounded by the salt counterions (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing activity of the solvent, which in turn leads to increasing solubility. This theory predicts that the logarithm of solubility is proportional to the square root of the ionic strength.
The behavior of proteins in solutions at high salt concentrations is explained by John Gamble Kirkwood. The abundance of the salt ions decreases the solvating power of salt ions, resulting in the decrease in the solubility of the proteins and precipitation results.
At high salt concentrations, the solubility is given by the following empirical expression.
:log S = B − KI
where S is the solubility of the protein, B is a constant (function of protein, pH and temperature), K is the salting out constant (function of pH, mixing and salt), and I is the ionic strength of the salt. This expression is an approximation to that proposed by Long and McDevit. | 3 | Analytical Chemistry |
Brominated haloalkanes were first used during World War II in fire extinguishers for aircraft and tanks. BCF was introduced as an effective gaseous fire suppression agent in the mid-1960s for use around highly valuable materials in places such as museums, mainframe rooms, and telecommunication switching centers. BCFs were also widely used in the maritime industries in the engine rooms of ships and also in the transport industry in vehicles. Its efficiency as a fire extinguishing agent has also led it to be the predominant choice of fire extinguishing agent on commercial aircraft and is typically found in cylindrical hand-held canisters. Its advantages as a fire extinguishing agent are that it has lower toxicity than chemicals such as carbon tetrachloride and that since it is a covalently bonded compound, it does not form conductive ions, therefore being usable on electrical equipment.
BCF is an excellent fire extinguishing agent, as it is a streaming agent with low toxicity, a low pressure, liquefied gas, and effective on all common types of fires, A, B, and C. It is mainly used in portable and wheeled extinguishers, and small spot protection units for aviation and marine engine applications, and was never widely used in fixed systems like Halon 1301 was.
BCF has fairly low toxicity. The lethal concentration for 15 minute exposure is about 32%. | 2 | Environmental Chemistry |
Tertiary phosphines are often used as ligands in coordination chemistry. The binding of phosphines bind to metals, which serve as Lewis acids. For example, silver chloride reacts with triphenylphosphine to 1;1 and 1:2 complexes:
:PPh + AgCl → ClAgPPh
:PPh + ClAgPPh → ClAg(PPh)
The adducts formed from phosphines and borane are useful reagents. These phosphine-boranes are air-stable, but the borane protecting group can be removed by treatment with amines. | 0 | Organic Chemistry |
Therapeutic monoclonal antibodies act through multiple mechanisms, such as blocking of targeted molecule functions, inducing apoptosis in cells which express the target, or by modulating signalling pathways. | 1 | Biochemistry |
An autapse is a chemical or electrical synapse from a neuron onto itself. It can also be described as a synapse formed by the axon of a neuron on its own dendrites, in vivo or in vitro. | 1 | Biochemistry |
The Westinghouse Lamp Plant located in Bloomfield, New Jersey, was one of the lamp manufacturing plants of Westinghouse Electric Corporation. The plant had a major involvement in supplying uranium metal for the world's first self-sustaining chain reaction in Chicago (Chicago Pile-1) in the early phase of the Manhattan Project to create the first atomic bomb. | 8 | Metallurgy |
Stein Bjornar Jacobsen (born 1950) is a Norwegian-American geochemist who works within cosmochemistry.
Hailing from Drammen, he finished a cand.mag. degree at the University of Oslo before studying geology in California with a Rotary grant. Jacobsen became a professor of geochemistry at Harvard University.
He was an inducted into the Norwegian Academy of Science and Letters in 1994. In 2009 he was inducted into the American Academy of Arts and Sciences, mainly for using "the distribution of long-lived and extinct radioisotopes to date the formation of the earth's core and to define the effects of core separation on the early history of the core-mantle-crust system". | 9 | Geochemistry |
Some evidence shows that alternatives to pesticides can be equally effective as the use of chemicals. A study of Maize fields in northern Florida found that the application of composted yard waste with high carbon to nitrogen ratio to agricultural fields was highly effective at reducing the population of plant-parasitic nematodes and increasing crop yield, with yield increases ranging from 10% to 212%; the observed effects were long-term, often not appearing until the third season of the study. Additional silicon nutrition protects some horticultural crops against fungal diseases almost completely, while insufficient silicon sometimes leads to severe infection even when fungicides are used.
Pesticide resistance is increasing and that may make alternatives more attractive. | 2 | Environmental Chemistry |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.