text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
There has been some confusion in the literature on the use of the term “M30”. Although it should be very clear that “M30” is a monoclonal antibody (“M”) that detects the antigen “ccK18”/“K18-Asp396” people sometimes refer to the antigen as “M30”. This is incorrect.
It is clear that the use of the term “M30” in connection with “keratin” means the monoclonal antibody M30® or (possibly, but erroneously) the neo-epitope DALD396 on K18 recognized by the M30® monoclonal. “M30” is not a biological entity expressed in cells but a (patent protected) monoclonal antibody.
Caspase-cleaved fragment of keratin 18 = ccK18
Keratin 18 = K18 (or CK18)
M30® = the antibody that recognizes a neoepitope on ccK18
M65® ELISA = an ELISA composed of two antibodies (M5 and M6) for conventional epitopes of K18
M30®, Apoptosense®, M65®, EpiDeath®, and PEVIVA® are registered trademarks, including U.S. Trademarks 4,577,969, 2,749,204, 1,009,048, and 896,269. Additionally, VLVBio™ holds additional Trademarks in most countries worldwide. | 1 | Biochemistry |
Baldwins rules also apply to aldol cyclizations involving enolates. Two new descriptors need to be defined: enolendo and enolexo', which refer to whether both carbons of the enolate C-C fragment are incorporated into the ring formed or not, respectively.
The rules are the following: | 4 | Stereochemistry |
Redox zonation refers to how the processes that transfer terminal electrons as a result of organic matter degradation vary depending on time and space. Certain reactions will be favored over others due to their energy yield as detailed in the energy acceptor cascade detailed above. In oxic conditions, in which oxygen is readily available, aerobic respiration will be favored due to its high energy yield. Once the use of oxygen through respiration exceeds the input of oxygen due to bioturbation and diffusion, the environment will become anoxic and organic matter will be broken down via other means, such as denitrification and manganese reduction. | 9 | Geochemistry |
The effect of crystal symmetry on misorientations is to reduce the fraction of the full orientation space necessary to uniquely represent all possible misorientation relationships. For example, cubic crystals (i.e. FCC) have 24 symmetrically related orientations. Each of these orientations is physically indistinguishable, though mathematically distinct. Therefore, the size of orientation space is reduced by a factor of 24. This defines the fundamental zone (FZ) for cubic symmetries. For the misorientation between two cubic crystallites, each possesses its 24 inherent symmetries. In addition, there exists a switching symmetry, defined by:
which recognizes the invariance of misorientation to direction; A→B or B→A. The fraction of the total orientation space in the cubic-cubic fundamental zone for misorientation is then given by:<br />
or 1/48 the volume of the cubic fundamental zone. This also has the effect of limiting the maximum unique misorientation angle to 62.8°<br />
<br />
Disorientation describes the misorientation with the smallest possible rotation angle out of all symmetrically equivalent misorientations that fall within the FZ (usually specified as having an axis in the standard stereographic triangle for cubics). Calculation of these variants involves application of crystal symmetry operators to each of the orientations during the calculation of misorientation.<br />
<br />
where O denotes one of the symmetry operators for the material. | 3 | Analytical Chemistry |
Hemoglycin (previously termed hemolithin) is a space polymer that is the first polymer of amino acids found in meteorites. | 7 | Physical Chemistry |
In organic chemistry a halohydrin (also a haloalcohol or β-halo alcohol) is a functional group in which a halogen and a hydroxyl are bonded to adjacent carbon atoms, which otherwise bear only hydrogen or hydrocarbyl groups (e.g. 2-chloroethanol, 3-chloropropane-1,2-diol). The term only applies to saturated motifs, as such compounds like 2-chlorophenol would not normally be considered halohydrins. Megatons of some chlorohydrins, e.g. propylene chlorohydrin, are produced annually as precursors to polymers.
Halohydrins may be categorized as chlorohydrins, bromohydrins, fluorohydrins or iodohydrins depending on the halogen present. | 0 | Organic Chemistry |
The liquid ordered phase can be defined as:
* fluid and lamellar phase, including the Wide angle X-ray scattering pattern centered by broad diffraction peak at 4.2Å
* acyl hydrocarbon chains are in the all-trans state
* rapid lateral diffusion
* H-NMR quadrupolar splitting is ca. 50 kHz | 1 | Biochemistry |
María del Coral Barbas Arribas (or Arriba) is a professor at the Universidad CEU San Pablo in Madrid, Spain who is known for her research on metabolomics and integration of chemical data. | 3 | Analytical Chemistry |
In coastal areas the groundwater and seawater flows are driven by a variety of factors. Both types of water can circulate in marine sediments due to tidal pumping, waves, bottom currents or density driven transport processes. Meteoric freshwaters can discharge along confined and unconfined aquifers into the sea or the oppositional process of seawater intruding into groundwater charged aquifers can take place. The flow of both fresh and sea water is primarily controlled by the hydraulic gradients between land and sea and differences in the densities between both waters and the permeabilities of the sediments.
According to Drabbe and Badon-Ghijben (1888) and Herzberg (1901), the thickness of a freshwater lens below sea level (z) corresponds with the thickness of the freshwater level above sea level (h) as:
z= ρf/((ρs-ρf))*h
With z being the thickness between the saltwater-freshwater interface and the sea level, h being the thickness between the top of the freshwater lens and the sea level, ρf being the density of freshwater and ρs being the density of saltwater. Including the densities of freshwater (ρf = 1.00 g •cm-3) and seawater (ρs = 1.025 g •cm-3) equation (2) simplifies to:
z=40*h
Together with Darcy's Law, the length of a salt wedge from the shoreline into the hinterland can be calculated:
L= ((ρs-ρf)Kf m)/(ρf Q)
With Kf being the hydraulic conductivity, m the aquifer thickness and Q the discharge rate. Assuming an isotropic aquifer system the length of a salt wedge solely depends on the hydraulic conductivity, the aquifer thickness and is inversely related to the discharge rate. These assumptions are only valid under hydrostatic conditions in the aquifer system. In general the interface between fresh and saline water forms a zone of transition due to diffusion/dispersion or local anisotropy. | 9 | Geochemistry |
No known natural processes generate trifluoroacetic acid. In the environment, trifluoroacetic acid may be formed by photooxidation of the commonly used refrigerant 1,1,1,2-tetrafluoroethane (R-134a). Moreover, it is formed as an atmospheric degradation product of almost all fourth-generation synthetic refrigerants, also called hydrofluoroolefins (HFO), such as 2,3,3,3-tetrafluoropropene.
Trifluoroacetic acid degrades very slowly in the environment. Median concentrations of a few micrograms per liter have been found in beer and tea. Sea water contains about 200 ng of TFA per liter. No biodegradation mechanism for the compound is known in water, although biotransformation apparently decarboxylates the acid to fluoroform.
Trifluoroacetic acid is mildly phytotoxic. | 0 | Organic Chemistry |
In physics and chemistry, a selection rule, or transition rule, formally constrains the possible transitions of a system from one quantum state to another. Selection rules have been derived for electromagnetic transitions in molecules, in atoms, in atomic nuclei, and so on. The selection rules may differ according to the technique used to observe the transition. The selection rule also plays a role in chemical reactions, where some are formally spin-forbidden reactions, that is, reactions where the spin state changes at least once from reactants to products.
In the following, mainly atomic and molecular transitions are considered. | 7 | Physical Chemistry |
The issues dealing with recovery of the often expensive catalyst after product formation poses a serious drawback for large-scale applications of homogeneous catalysis. Structures known as metallodendrimers combine the advantages of homogeneous and heterogeneous catalysts, as they are soluble and well defined on the molecular level, and yet they can be recovered by precipitation, ultrafiltration, or ultracentrifugation. Some recent examples can be found about the use of dendritic palladium complex catalysts for the copper-free Sonogashira reaction. Thus, several generations of bidentate phosphine palladium(II) polyamino dendritic catalysts have been used solubilized in triethylamine for the coupling of aryl iodides and bromides at 25-120 °C, and of aryl chlorides, but in very low yields.
The dendrimeric catalysts could usually be recovered by simple precipitation and filtration and reused up to five times, with diminished activity produced by dendrimer decomposition and not by palladium leaching being observed. These dendrimeric catalysts showed a negative dendritic effect; that is, the catalyst efficiency decreases as the dendrimer generation increases. A recyclable polymeric phosphine ligand is obtained from ring-opening metathesis polymerization of a norbornene derivative, and has been used in the copper co-catalyzed Sonogashira reaction of methyl p-iodobenzoate and phenylacetylene using as a palladium source. Despite recovery by filtration, polymer catalytic activity decreased by approximately 4-8% in each recycle experiment. | 0 | Organic Chemistry |
In 1945 there were 38 furnaces worldwide, each with a capacity of 1 Mt/year. The process was favored in Germany due to the autarky policy of the Nazi regime, which prioritized the use of low-quality domestic iron ore. The transfer of technology between Nazi Germany and Imperial Japan led to the Japanese Empire benefiting from this process. Furnaces were installed in the co-prosperity sphere and operated by Japanese technicians. By the eve of the Pacific War, the process was being used in four steelworks in Japan.
After World War II all installations in Germany, China, and North Korea were dismantled, with 29 furnaces sent to the USSR as war reparations. Only the Japanese and Czechoslovakian plants remained functional.
In the 1950s Krupp rebuilt several large furnaces in Spain, Greece, and Germany. The Czechoslovakians were the primary drivers, constructing 16 furnaces and increasing process efficiency. The Great Soviet Encyclopedia reports that over 65 industrial plants, ranging from 60 to 110 meters in length and 3.6 to 4.6 meters in diameter, were constructed between 1930 and 1950. By 1960, 50 furnaces were producing 2 million tons per year in several countries. | 8 | Metallurgy |
For example, the common restriction enzyme EcoRI recognizes the palindromic sequence GAATTC and cuts between the G and the A on both the top and bottom strands. This leaves an overhang (an end-portion of a DNA strand with no attached complement) known as a sticky end on each end of AATT. The overhang can then be used to ligate in (see DNA ligase) a piece of DNA with a complementary overhang (another EcoRI-cut piece, for example).
Some restriction enzymes cut DNA at a restriction site in a manner which leaves no overhang, called a blunt end. Blunt ends are much less likely to be ligated by a DNA ligase because the blunt end doesnt have the overhanging base pair that the enzyme can recognize and match with a complementary pair. Sticky ends of DNA however are more likely to successfully bind with the help of a DNA ligase because of the exposed and unpaired nucleotides. For example, a sticky end trailing with AATTG is more likely to bind with a ligase than a blunt end where both the 5 and 3' DNA strands are paired. In the case of the example the AATTG would have a complementary pair of TTAAC which would reduce the functionality of the DNA ligase enzyme. | 1 | Biochemistry |
Salbutamol is sold as a racemic mixture. The (R)-(−)-enantiomer (CIP nomenclature) is shown in the image at right (top), and is responsible for the pharmacologic activity; the (S)-(+)-enantiomer (bottom) blocks metabolic pathways associated with elimination of itself and of the pharmacologically active enantiomer (R). The slower metabolism of the (S)-(+)-enantiomer also causes it to accumulate in the lungs, which can cause airway hyperreactivity and inflammation. Potential formulation of the R form as an enantiopure drug is complicated by the fact that the stereochemistry is not stable, but rather the compound undergoes racemization within a few days to weeks, depending on pH.
The direct separation of Salbutamol enantiomers and the control of enantiomeric purity has been described by thin-layer chromatography. | 4 | Stereochemistry |
In physical chemistry, the Evans–Polanyi principle (also referred to as the Bell–Evans–Polanyi principle, Brønsted–Evans–Polanyi principle, or Evans–Polanyi–Semenov principle) observes that the difference in activation energy between two reactions of the same family is proportional to the difference of their enthalpy of reaction.
This relationship can be expressed as
where
: is the activation energy of a reference reaction of the same class,
: is the enthalpy of reaction,
: characterizes the position of the transition state along the reaction coordinate (such that ).
The Evans–Polanyi model is a linear energy relationship that serves as an efficient way to calculate activation energy of many reactions within a distinct family. The activation energy may be used to characterize the kinetic rate parameter of a given reaction through application of the Arrhenius equation.
The Evans–Polanyi model assumes that the pre-exponential factor of the Arrhenius equation and the position of the transition state along the reaction coordinate are the same for all reactions belonging to a particular reaction family. | 7 | Physical Chemistry |
Hyper-IL-6 has been used to test which cells depend on Interleukin-6 trans-signaling in their response to the cytokine Interleukin-6. To this end, cells were treated with Interleukin-6 and alternatively with Hyper-IL-6. Cells, which respond to Interleukin-6 alone do express an Interleukin-6 receptor whereas cells, which only respond to Hyper-IL-6 but not to Interleukin-6 alone depend in their response to the cytokine on Interleukin-6 trans-signaling. It turned out that hematopoietic stem cells, neural cells, smooth muscle cells and endothelial cells are typical target cells of Interleukin-6 trans-signaling. | 1 | Biochemistry |
If the concentration of a reactant remains constant (because it is a catalyst, or because it is in great excess with respect to the other reactants), its concentration can be included in the rate constant, leading to a pseudo–first-order (or occasionally pseudo–second-order) rate equation. For a typical second-order reaction with rate equation if the concentration of reactant B is constant then where the pseudo–first-order rate constant The second-order rate equation has been reduced to a pseudo–first-order rate equation, which makes the treatment to obtain an integrated rate equation much easier.
One way to obtain a pseudo-first order reaction is to use a large excess of one reactant (say, [B]≫[A]) so that, as the reaction progresses, only a small fraction of the reactant in excess (B) is consumed, and its concentration can be considered to stay constant. For example, the hydrolysis of esters by dilute mineral acids follows pseudo-first order kinetics, where the concentration of water is constant because it is present in large excess:
The hydrolysis of sucrose () in acid solution is often cited as a first-order reaction with rate The true rate equation is third-order, however, the concentrations of both the catalyst and the solvent are normally constant, so that the reaction is pseudo–first-order. | 7 | Physical Chemistry |
William Bayliss and Ernest Starling, a physiologist and biologist, respectively, wanted to see if the nervous system had an impact on the digestive system. They knew that the pancreas was involved in the secretion of digestive fluids after the passage of food from the stomach to the intestines, which they believed to be due to the nervous system. They cut the nerves to the pancreas in an animal model and discovered that it was not nerve impulses that controlled secretion from the pancreas. It was determined that a factor secreted from the intestines into the bloodstream was stimulating the pancreas to secrete digestive fluids. This was named secretin: a hormone. | 1 | Biochemistry |
The function of this intron in the vectors is unknown, but it is theorized that it might be involved in splicing or translation efficiency.
Vectors such as pME18s contain it. | 1 | Biochemistry |
The 43S preinitiation complex (43S PIC) is a ribonucleoprotein complex that exists during an early step of eukaryotic translation initiation. The 43S PIC contains the small ribosomal subunit (40S) bound by the initiation factors eIF1, eIF1A, eIF3, and the eIF2-Met-tRNA-GTP ternary complex (eIF2-TC). | 1 | Biochemistry |
The earliest sources of tin in the Early Bronze Age in the Near East are still unknown and the subject of much debate in archaeology.) Possibilities include minor now-depleted sources in the Near East, trade from Central Asia, Sub-Saharan Africa, Europe, or elsewhere.
It is possible that as early as 2500 BC, the Ore Mountains had begun exporting tin, using the well established Baltic amber trade route to supply Scandinavia as well as the Mediterranean with tin. By 2000 BC, the extraction of tin in Britain, France, Spain, and Portugal had begun and tin was traded to the Mediterranean sporadically from all these sources. Evidence of tin trade in the Mediterranean can be seen in a number of Bronze Age shipwrecks containing tin ingots such as the Uluburun off the coast of Turkey dated 1300 BC which carried over 300 copper bars weighing 10 tons, and approximately 40 tin bars weighing 1 ton. Evidence of direct tin trade between Europe and the Eastern Mediterranean has been demonstrated through the analysis of tin ingots dated to the 13th-12th centuries BC from sites in Israel, Turkey and modern-day Greece; tin ingots from Israel, for example, have been found to share chemical composition with tin from Cornwall and Devon (Great Britain).
While Sardinia does not appear to have much in terms of significant sources of tin, it does have rich copper and other mineral wealth and served as a centre for metals trade during the Bronze Age and likely actively imported tin from the Iberian Peninsula for export to the rest of the Mediterranean.
By classical Greek times, the tin sources were well established. Greece and the Western Mediterranean appear to have traded their tin from European sources, while the Middle East acquired their tin from Central Asian sources through the Silk Road. For example, Iron Age Greece had access to tin from Iberia by way of the Phoenicians who traded extensively there, from the Erzgebirge by way of the Baltic Amber Road overland route, or from Brittany and Cornwall through overland routes from their colony at Massalia (modern day Marseilles) established in the 6th century BC. In 450 BC, Herodotus described tin as coming from Northern European islands named the Cassiterides along the extreme borders of the world, suggesting very long-distance trade, likely from Britain, northwestern Iberia, or Brittany, supplying tin to Greece and other Mediterranean cultures. The idea that the Phoenicians went to Cornwall for its tin and supplied it to the whole of the Mediterranean has no archaeological basis and is largely considered a myth.
The early Roman world was mainly supplied with tin from its Iberian provinces of Gallaecia and Lusitania and to a lesser extent Tuscany. Pliny mentions that in 80 BC, a senatorial decree halted all mining on the Italian Peninsula, stopping any tin mining activity in Tuscany and increasing Roman dependence on tin from Brittany, Iberia, and Cornwall. After the Roman conquest of Gaul, Brittany's tin deposits saw intensified exploitation after the first century BC. With the exhaustion of the Iberian tin mines, Cornwall became a major supplier of tin for the Romans after the 3rd century AD.
Throughout the medieval period, demand for tin increased as pewter gained popularity. Brittany and Cornwall remained the major producers and exporters of tin throughout the Mediterranean through to modern times. | 8 | Metallurgy |
The malate dehydrogenase family contains L-lactate dehydrogenase and L-2-hydroxyisocaproate dehydrogenases. L-lactate dehydrogenases catalyzes the conversion of L-lactate to pyruvate, the last step in anaerobic glycolysis. The N-terminus is a Rossmann NAD-binding fold and the C-terminus is an unusual alpha+beta fold. | 1 | Biochemistry |
In addition to treating copper concentrates, ISASMELT furnaces have also been built to treat secondary (scrap) copper materials. | 8 | Metallurgy |
Most analytical techniques use a calibration curve. There are a number of advantages to this approach. First, the calibration curve provides a reliable way to calculate the uncertainty of the concentration calculated from the calibration curve (using the statistics of the least squares line fit to the data).
Second, the calibration curve provides data on an empirical relationship. The mechanism for the instrument's response to the analyte may be predicted or understood according to some theoretical model, but most such models have limited value for real samples. (Instrumental response is usually highly dependent on the condition of the analyte, solvents used and impurities it may contain; it could also be affected by external factors such as pressure and temperature.)
Many theoretical relationships, such as fluorescence, require the determination of an instrumental constant anyway, by analysis of one or more reference standards; a calibration curve is a convenient extension of this approach. The calibration curve for a particular analyte in a particular (type of) sample provides the empirical relationship needed for those particular measurements.
The chief disadvantages are (1) that the standards require a supply of the analyte material, preferably of high purity and in known concentration, and (2) that the standards and the unknown are in the same matrix. Some analytes - e.g., particular proteins - are extremely difficult to obtain pure in sufficient quantity. Other analytes are often in complex matrices, e.g., heavy metals in pond water. In this case, the matrix may interfere with or attenuate the signal of the analyte. Therefore, a comparison between the standards (which contain no interfering compounds) and the unknown is not possible. The method of standard addition is a way to handle such a situation. | 1 | Biochemistry |
Different phases of digestion take place including: the cephalic phase, gastric phase, and intestinal phase.
The cephalic phase occurs at the sight, thought and smell of food, which stimulate the cerebral cortex. Taste and smell stimuli are sent to the hypothalamus and medulla oblongata. After this it is routed through the vagus nerve and release of acetylcholine. Gastric secretion at this phase rises to 40% of maximum rate. Acidity in the stomach is not buffered by food at this point and thus acts to inhibit parietal (secretes acid) and G cell (secretes gastrin) activity via D cell secretion of somatostatin.
The gastric phase takes 3 to 4 hours. It is stimulated by distension of the stomach, presence of food in stomach and decrease in pH. Distention activates long and myenteric reflexes. This activates the release of acetylcholine, which stimulates the release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach. Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin, which in turn stimulates parietal cells to secrete gastric acid. Gastric acid is about 0.5% hydrochloric acid, which lowers the pH to the desired pH of 1–3. Acid release is also triggered by acetylcholine and histamine.
The intestinal phase has two parts, the excitatory and the inhibitory. Partially digested food fills the duodenum. This triggers intestinal gastrin to be released. Enterogastric reflex inhibits vagal nuclei, activating sympathetic fibers causing the pyloric sphincter to tighten to prevent more food from entering, and inhibits local reflexes. | 1 | Biochemistry |
The first real collections of crystal models were produced by Romé de lIsle. He actually offered sets of small (ca 3 cm) models made of "terra cotta" in order to stimulate the sales of the expensive four-volume set of his book "Cristallographie'" (1783). The models were manufactured by his co-workers Arnould Carangeot, Lhermina and Swebach-Desfontaines, who produced numerous large sets (up to 448 models in each set). In order to exactly transfer interplanar angles from natural crystals to the terra cotta models, Carangeot invented and designed a prototype of a contact goniometer. This instrument, that proved to be an invaluable tool in geometric crystallography, enabled the measurement of interplanar angles with a precision of about half a degree.
Teylers Museum in Haarlem has a complete set of these terracotta models that were bought in Paris (in 1785) by Martin van Marum, the first director of the museum. After over 200 years, this collection is still complete and in perfect condition at Teylers Museum. | 3 | Analytical Chemistry |
The first method to detect A-to-I RNA modifications, developed in 1997, was inosine-specific cleavage. RNA samples are treated with glyoxal and borate to specifically modify all G bases, and subsequently enzymatically digested to by RNase T1, which cleaves after I sites. The amplification of these fragments then allows analysis of cleavage sites and inference of A-to-I modification.
. It was used to prove the position of inosine at specific sites rather than identify novel sites or transcriptome-wide profiles. | 1 | Biochemistry |
Mantle oxidation state (redox state) applies the concept of oxidation state in chemistry to the study of the Earth's mantle. The chemical concept of oxidation state mainly refers to the valence state of one element, while mantle oxidation state provides the degree of decreasing of increasing valence states of all polyvalent elements in mantle materials confined in a closed system. The mantle oxidation state is controlled by oxygen fugacity and can be benchmarked by specific groups of redox buffers.
Mantle oxidation state changes because of the existence of polyvalent elements (elements with more than one valence state, e.g. Fe, Cr, V, Ti, Ce, Eu, C and others). Among them, Fe is the most abundant (~8 wt% of the mantle) and its oxidation state largely reflects the oxidation state of mantle. Examining the valence state of other polyvalent elements could also provide the information of mantle oxidation state.
It is well known that the oxidation state can influence the partitioning behavior of elements and liquid water between melts and minerals, the speciation of C-O-H-bearing fluids and melts, as well as transport properties like electrical conductivity and creep.
The formation of diamond requires both reaching high pressures and high temperatures and a carbon source. The most common carbon source in deep Earth is not elemental carbon and redox reactions need to be involved in diamond formation. Examining the oxidation state can help us predict the P-T conditions of diamond formation and elucidate the origin of deep diamonds. | 9 | Geochemistry |
Selenium also plays a role in the functioning of the thyroid gland. It participates as a cofactor for the three thyroid hormone deiodinases. These enzymes activate and then deactivate various thyroid hormones and their metabolites. It may inhibit Hashimotos disease, an auto-immune disease in which the bodys own thyroid cells are attacked by the immune system. A reduction of 21% on TPO antibodies was reported with the dietary intake of 0.2 mg of selenium. | 1 | Biochemistry |
Integration was the watchword as the various processes were brought together by large corporations, from mining the iron ore to shipping the finished product to wholesalers. The typical steelworks was a giant operation, including blast furnaces, Bessemer converters, open-hearth furnaces, rolling mills, coke ovens and foundries, as well as supported transportation facilities. The largest ones were operated in the region from Chicago to St. Louis to Baltimore, Philadelphia and Buffalo. Smaller operations appeared in Birmingham, Alabama, and in California.
The industry grew slowly but other industries grew even faster, so that by 1967, as the downward spiral began, steel accounted for 4.4% of manufacturing employment and 4.9% of manufacturing output. After 1970 American steel producers could no longer compete effectively with low-wage producers elsewhere. Imports and local mini-mills undercut sales.
Per-capita steel consumption in the U.S. peaked in 1977, then fell by half before staging a modest recovery to levels well below the peak.
Most mills were closed. Bethlehem went bankrupt in 2001. In 1984, Republic merged with Jones and Laughlin Steel Company; the new firm went bankrupt in 2001. US Steel diversified into oil (Marathon Oil was spun off in 2001). Finally US Steel reemerged in 2002 with plants in three American locations (plus one in Europe) that employed fewer than one-tenth the 168,000 workers of 1902. By 2001 steel accounted for only 0.8% of manufacturing employment and 0.8% of manufacturing output.
The world steel industry peaked in 2007. That year, ThyssenKrupp spent $12 billion to build the two most modern mills in the world, in Alabama and Brazil. The worldwide great recession starting in 2008, however, with its heavy cutbacks in construction, sharply lowered demand and prices fell 40%. ThyssenKrupp lost $11 billion on its two new plants, which sold steel below the cost of production. Finally in 2013, ThyssenKrupp offered the plants for sale at under $4 billion. | 8 | Metallurgy |
*PPID Peptidyl-prolyl cis-trans isomerase D
*PPIE Peptidyl-prolyl cis-trans isomerase E
*PPIF Peptidyl-prolyl cis-trans isomerase F
*PPIG Peptidyl-prolyl cis-trans isomerase G
*PPIH Cyclophilin H
*CANX Calnexin. Folding of glycoproteins within endoplasmic reticulum
*CAPN1 Calpain subunit
*CAPN7
*CAPNS1 Calpain protease subunit
*NACA Nascent polypeptide associated complex alpha polypeptide
*NACA2
*PFDN2 Prefoldin 2
*PFDN4 Prefoldin 4
*PFDN5 Prefoldin 5
*PFDN6 Prefoldin 6
*SNX2 Sorting nexin 2
*SNX3 Sorting nexin 3
*SNX4 Sorting nexin 4
*SNX5 Sorting nexin 5
*SNX6 Sorting nexin 6
*SNX9 Sorting nexin 9
*SNX12 Sorting nexin 12
*SNX13 Sorting nexin 13
*SNX17 Sorting nexin 17
*SNX18 Sorting nexin 18
*SNX19 Sorting nexin 19
*SNX25 Sorting nexin 25
*SSR1 Translocon-associated protein TRAPA. Protein translocation in ER
*SSR2 Translocon-associated protein TRAPB. Protein translocation in ER
*SSR3 Translocon-associated protein TRAPG. Protein translocation in ER
*SUMO1 Protein targeting
*SUMO3 Protein targeting | 1 | Biochemistry |
Drospirenone is a progestin and antiandrogen medication which is used in birth control pills to prevent pregnancy and in menopausal hormone therapy, among other uses. It is available both alone under the brand name Slynd and in combination with an estrogen under the brand name Yasmin among others. The medication is an analog of the drug spironolactone. Drospirenone is taken by mouth.
Common side effects include acne, headache, breast tenderness, weight increase, and menstrual changes. Rare side effects may include high potassium levels and blood clots (when taken as a combined oestrogen-progestogen pill), among others. Drospirenone is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone. It has additional antimineralocorticoid and antiandrogenic activity and no other important hormonal activity. Because of its antimineralocorticoid activity and lack of undesirable off-target activity, drospirenone is said to more closely resemble bioidentical progesterone than other progestins.
Drospirenone was patented in 1976 and introduced for medical use in 2000. It is available widely throughout the world. The medication is sometimes referred to as a "fourth-generation" progestin. It is available as a generic medication. In 2020, a formulation of drospirenone with ethinylestradiol was the 145th most commonly prescribed medication in the United States, with more than 4million prescriptions. | 4 | Stereochemistry |
Flotation processes are described in ancient Greek and Persian literature. During the late 19th century, the process basics were discovered through a slow evolutionary phase. During the first decade of the 20th century, a more rapid investigation of oils, froths, and agitation led to proven workplace applications, especially in Broken Hill, Australia, that brought the technological innovation known as “froth flotation.” During the early 20th century, froth flotation revolutionized mineral processing.
Initially, naturally occurring chemicals such as fatty acids and oils were used as flotation reagents in large quantities to increase the hydrophobicity of the valuable minerals. Since then, the process has been adapted and applied to a wide variety of materials to be separated, and additional collector agents, including surfactants and synthetic compounds have been adopted for various applications. | 8 | Metallurgy |
This phenomenon came to light with the advent of technologies, such as MS2 tagging and single molecule RNA fluorescence in situ hybridisation, to detect RNA production in single cells, through precise measurements of RNA number or RNA appearance at the gene. Other, more widespread techniques, such as Northern blotting, microarrays, RT-PCR and RNA-Seq, measure bulk RNA levels from homogenous population extracts. These techniques lose dynamic information from individual cells and give the impression that transcription is a continuous smooth process. Observed at an individual cell level, transcription is irregular, with strong periods of activity interspersed by long periods of inactivity. | 1 | Biochemistry |
Thermoresponsive polymers can be used as stationary phase in liquid chromatography. Here, the polarity of the stationary phase can be varied by temperature changes, altering the power of separation without changing the column or solvent composition. Thermally related benefits of gas chromatography can now be applied to classes of compounds that are restricted to liquid chromatography due to their thermolability. In place of solvent gradient elution, thermoresponsive polymers allow the use of temperature gradients under purely aqueous isocratic conditions. The versatility of the system is controlled not only through changing temperature, but through the addition of modifying moieties that allow for a choice of enhanced hydrophobic interaction, or by introducing the prospect of electrostatic interaction. These developments have already introduced major improvements to the fields of hydrophobic interaction chromatography, size exclusion chromatography, ion exchange chromatography, and affinity chromatography separations as well as pseudo-solid phase extractions ("pseudo" because of phase transitions). | 3 | Analytical Chemistry |
Bacterial anaerobic corrosion typically impacts metallic substrates but may also occur in concrete. Corrosion of concrete mediums leads to considerable losses in industrial settings. When considering the corrosion of concrete there is significant documentation of structural degradation in concrete wastewater infrastructure where wastewater is collected or treated. Similarly, biofilms are important for bacterial anaerobic corrosion of metals in wastewater pipes.
For bacterial anaerobic corrosion there is general corrosion of substrates as well as another form of corrosion known as pitting. In both general or pitting corrosion, the breakdown process occurs in aqueous conditions. Bacteria tend to form biofilms as their primary means of corroding metals, with different bacteria dominating across different settings. In municipal wastewater, Desulfovibrio desulfuricans is the main contributor to corrosion. | 8 | Metallurgy |
In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. Nam et al. demonstrated the direct condensation of nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Also, a plausible prebiotic process for synthesizing pyrimidine and purine ribonucleosides and ribonucleotides using wet-dry cycles was presented by Becker et al. | 0 | Organic Chemistry |
When an excess of Ba is added to a non-ionic surfactant of the alkyl propylene oxide derivative type, a pseudo-cationic complex is formed. This may be titrated with standard sodium tetraphenylborate. Two moles tetraphenylborate react with one mole of the Ba/ non-ionic surfactant complex. | 3 | Analytical Chemistry |
Hematological abnormalities often associate with chronic liver diseases. Both iron overload and iron deficient anemia have been reported in patients with liver cirrhosis. The former is mainly due to reduced hepcidin level caused by the decreased synthetic capacity of the liver, while the latter is due to acute and chronic bleeding caused by portal hypertension. Inflammation is also present in patients with advanced chronic liver disease. As a consequence, elevated hepatic and serum ferritin levels are consistently reported in chronic liver diseases.
Studies showed association between high serum ferritin levels and increased risk of short-term mortality in cirrhotic patients with acute decompensation and acute-on-chronic liver failure. An other study found association between high serum ferritin levels and increased risk of long-term mortality in compensated and stable decompensated cirrhotic patients. The same study demonstrated that increased serum ferritin levels could predict the development of bacterial infection in stable decompensated cirrhotic patients, while in compensated cirrhotic patients the appearance of the very first acute decompensation episode showed higher incidence in patients with low serum ferritin levels. This latter finding was explaind by the association between chronic bleeding and increased portal pressure. | 1 | Biochemistry |
The metabolism of progesterone is rapid and extensive and occurs mainly in the liver, though enzymes that metabolize progesterone are also expressed widely in the brain, skin, and various other extrahepatic tissues. Progesterone has an elimination half-life of only approximately 5 minutes in circulation. The metabolism of progesterone is complex, and it may form as many as 35 different unconjugated metabolites when it is ingested orally. Progesterone is highly susceptible to enzymatic reduction via reductases and hydroxysteroid dehydrogenases due to its double bond (between the C4 and C5 positions) and its two ketones (at the C3 and C20 positions).
The major metabolic pathway of progesterone is reduction by 5α-reductase and 5β-reductase into the dihydrogenated 5α-dihydroprogesterone and 5β-dihydroprogesterone, respectively. This is followed by the further reduction of these metabolites via 3α-hydroxysteroid dehydrogenase and 3β-hydroxysteroid dehydrogenase into the tetrahydrogenated allopregnanolone, pregnanolone, isopregnanolone, and epipregnanolone. Subsequently, 20α-hydroxysteroid dehydrogenase and 20β-hydroxysteroid dehydrogenase reduce these metabolites to form the corresponding hexahydrogenated pregnanediols (eight different isomers in total), which are then conjugated via glucuronidation and/or sulfation, released from the liver into circulation, and excreted by the kidneys into the urine. The major metabolite of progesterone in the urine is the 3α,5β,20α isomer of pregnanediol glucuronide, which has been found to constitute 15 to 30% of an injection of progesterone. Other metabolites of progesterone formed by the enzymes in this pathway include 3α-dihydroprogesterone, 3β-dihydroprogesterone, 20α-dihydroprogesterone, and 20β-dihydroprogesterone, as well as various combination products of the enzymes aside from those already mentioned. Progesterone can also first be hydroxylated (see below) and then reduced. Endogenous progesterone is metabolized approximately 50% into 5α-dihydroprogesterone in the corpus luteum, 35% into 3β-dihydroprogesterone in the liver, and 10% into 20α-dihydroprogesterone.
Relatively small portions of progesterone are hydroxylated via 17α-hydroxylase (CYP17A1) and 21-hydroxylase (CYP21A2) into 17α-hydroxyprogesterone and 11-deoxycorticosterone (21-hydroxyprogesterone), respectively, and pregnanetriols are formed secondarily to 17α-hydroxylation. Even smaller amounts of progesterone may be also hydroxylated via 11β-hydroxylase (CYP11B1) and to a lesser extent via aldosterone synthase (CYP11B2) into 11β-hydroxyprogesterone. In addition, progesterone can be hydroxylated in the liver by other cytochrome P450 enzymes which are not steroid-specific. 6β-Hydroxylation, which is catalyzed mainly by CYP3A4, is the major transformation, and is responsible for approximately 70% of cytochrome P450-mediated progesterone metabolism. Other routes include 6α-, 16α-, and 16β-hydroxylation. However, treatment of women with ketoconazole, a strong CYP3A4 inhibitor, had minimal effects on progesterone levels, producing only a slight and non-significant increase, and this suggests that cytochrome P450 enzymes play only a small role in progesterone metabolism. | 0 | Organic Chemistry |
In an Iowa prairie restoration project, meadow voles experienced an initial population increase during the initial stage of vegetation succession (old field dominated by foxtail grass (Setaria spp.), red clover (Trifolium pratense), annual ragweed (Ambrosia artemisiifolia), alfalfa (Medicago sativa), and thistles (Cirsium spp.). However, populations reached their peak abundance during the perennial grass stage of succession from old field to tallgrass prairie. Meadow vole habitat devoid of tree cover and grasses dominated the herb layer. with low tolerance for habitat variation (i. e., a species that is intolerant of variations in habitat, is restricted to few habitats, and/or uses habitats less evenly than tolerant species).
In most areas, meadow voles clearly prefer habitat with dense vegetation. In tallgrass prairie at Pipestone National Monument, they were positively associated with dense vegetation and litter. The variables important to meadow vole habitat in Virginia include vegetative cover reaching a height of 8 to 16 inches (20–41 cm) and presence of litter. Meadow voles appeared to be randomly distributed within a grassland habitat in southern Quebec. Grant and Morris were not able to establish any association of meadow vole abundance with particular plant species. They were also unable to distinguish between food and cover as the determining factor in meadow vole association with dense vegetation. In South Dakota, meadow voles prefer grasslands to Rocky Mountain juniper (Juniperus scopulorum) woodlands. In New Mexico, meadow voles were captured in stands of grasses, wild rose (Rosa sp.), prickly pear (Opuntia sp.), and various forbs; meadow voles were also captured in wet areas with tall marsh grasses.
Open habitat with a thick mat of perennial grass favors voles. In west-central Illinois, they were the most common small mammals on Indian grass (Sorghastrum nutans)-dominated and switchgrass (Panicum virgatum)-dominated study plots. They were present in very low numbers on orchard grass (Dactylis glomerata)-dominated plots. The most stable population occurred on unburned big bluestem (Andropogon gerardii)-dominated plots. In Ontario, meadow voles and white-footed mice (Peromyscus leucopus) occur together in ecotones. Meadow voles were the most common small mammals in oak savanna/tallgrass prairie dominated by northern pin oak (Quercus ellipsoidalis) and grasses including bluejoint reedgrass (Calamagrostis canadensis), prairie cordgrass (Sporobolus michauxianus), big bluestem, switchgrass, and Indian grass.
In Michigan, strip clearcuts in a conifer swamp resulted in an increase in the relative abundance of meadow voles. They were most abundant in clearcut strip interiors and least abundant in uncut strip interiors. Slash burning did not appear to affect meadow vole numbers about 1.5 years after treatment. | 2 | Environmental Chemistry |
Zinc can be present in six different forms in soil namely; water soluble zinc, exchangeable zinc, organically bound zinc, carbonate bound zinc, aluminium and manganese oxide bound zinc and residual fractions of zinc.
In toxic conditions, species of Calluna, Erica and Vaccinium can grow in zinc-metalliferous soils, because translocation of toxic ions is prevented by the action of ericoid mycorrhizal fungi. | 1 | Biochemistry |
Depending on the location of the catenane structures in the polymer chain, the polycatenanes can be divided into main-chain polycatenanes and side-chain polycatenanes.
Main-chain polycatenanes are linear catenanes in which the rings are interlocked with one another in a large number of units. They can also be a series of oligomers linked physically even if not interlocked together. The stability of the structure is not only given by mechanical bonds but also hydrogen bonds and π-π interactions between the rings.
On the other hand, the Side-Chain Polycatenanes, are polycatenanes with ramifications where more oligomers are connected on the same cycle with respect to the main backbone. This type of catenane is synthesised functionalizing the macrocycles so that there is a directionality with the possibility to control the ramification.
There are other types of polycatenanes like the ones based on cyclic polymers, where the macrocyles are interlocked to the cyclic polymers, or the polycatenane networks, when catenanes are interlocked to each other into a net. | 6 | Supramolecular Chemistry |
More so than thiophenol, benzeneselenol is easily oxidized by air. The facility of this reaction reflects the weakness of the Se-H bond, bond dissociation energy of which is estimated to be between 67 and 74 kcal/mol. In contrast, the S-H BDE for thiophenol is near 80 kcal/mol. The product is diphenyl diselenide as shown in this idealized equation:
The presence of the diselenide in benzeneselenol is indicated by a yellow coloration. The diselenide can be converted back to the selenol by reduction followed by acidification of the resulting .
PhSeH is acidic with a pK of 5.9. Thus at neutral pH, it is mostly ionized:
It is approximately seven times more acidic than the related thiophenol. Both compounds dissolve in water upon the addition of base. The conjugate base is , a potent nucleophile. | 0 | Organic Chemistry |
Organism cloning (also called reproductive cloning) refers to the procedure of creating a new multicellular organism, genetically identical to another. In essence this form of cloning is an asexual method of reproduction, where fertilization or inter-gamete contact does not take place. Asexual reproduction is a naturally occurring phenomenon in many species, including most plants and some insects. Scientists have made some major achievements with cloning, including the asexual reproduction of sheep and cows. There is a lot of ethical debate over whether or not cloning should be used. However, cloning, or asexual propagation, has been common practice in the horticultural world for hundreds of years. | 1 | Biochemistry |
Raman scattering is another phenomenon that involves inelastic scattering of light caused by the vibrational properties of matter. The detected range of frequency shifts and other effects are very different compared to Brillouin scattering. In Raman scattering, photons are scattered by the effect of vibrational and rotational transitions in the bonds between first-order neighboring atoms, while Brillouin scattering results from the scattering of photons caused by large scale, low-frequency phonons. The effects of the two phenomena provide very different information about the sample: Raman spectroscopy can be used to determine the transmitting mediums chemical composition and molecular structure, while Brillouin scattering can be used to measure the materials properties on a larger scale – such as its elastic behavior. The frequency shifts from Brillouin scattering, a technique known as Brillouin spectroscopy, are detected with an interferometer while Raman scattering uses either an interferometer or a dispersive (grating) spectrometer. | 7 | Physical Chemistry |
Manganese deficiency in humans results in a number of medical problems. Manganese is a vital element of nutrition in very small quantities (adult male daily intake 2.3 milligrams). However poisoning may occur when greater amounts are ingested. | 1 | Biochemistry |
In B. Neritina, bryostatin biosynthesis is carried out through a type I polyketide synthase cluster, bry. BryR is the secondary metabolism homolog of HMG-CoA synthase, which is the PKS in bacterial primary metabolism. In the bryostatin pathway, the BryR module catalyzes β-Branching between a local acetoacetyl acceptor acyl carrier protein (ACP-a) and an appropriate donor BryU acetyl-ACP (ACP-d).
The first step involves the loading of a malonyl unit onto a discrete BryU ACP-d within an initial BryA module. The extended BryU product in BryA is then loaded onto a cysteine sidechain of BryR for interaction with ACP-a. Upon interaction, BryR then catalyzes β-Branching, facilitating an aldol reaction between the alpha-carbon of the BryU unit and the β-ketone of ACP-a, yielding a product similar to HMGS products in primary metabolism. After β-Branching, subsequent dehydration by a BryT enoyl-CoA hydratase homolog (ECH), as well as BryA O-methylation and BryB double bond isomerization of the generated HMGS product, are carried out in specific domains of the bry cluster. These post-β-Branching steps generate the vinyl methylester moieties which are found in all natural product bryostatins. Finally, BryC and BryD are responsible for further extension, pyran ring closure, and cyclization of the HMGS product to produce the novel bryostatin product.
In the presence of BryR, ACP-d conversion to holo-ACP-d was observed prior to β-Branching. BryR was shown to have high specificity for ACP-d only after this conversion. Specificity for these protein-bound groups is a feature that differentiates the HMGS homologs found in primary metabolism, where HMGS typically acts on substrates linked to Coenzyme A, from those found in non-ribosomal peptide synthase (NRPS) or PKS pathways such as the bryostatin pathway. | 0 | Organic Chemistry |
Anodizing can also be performed in borate or tartrate baths in which aluminium oxide is insoluble. In these processes, the coating growth stops when the part is fully covered, and the thickness is linearly related to the voltage applied. These coatings are free of pores, relative to the sulfuric and chromic acid processes. This type of coating is widely used to make electrolytic capacitors because the thin aluminium films (typically less than 0.5 μm) would risk being pierced by acidic processes. | 8 | Metallurgy |
ADO is defined as the random non-amplification of one of the alleles present in a heterozygous sample. Some studies have reported the ADO rate of the MDA products to be 0–60%. This drawback decreases the accuracy of genotyping of single sample and misdiagnosis in other MDA involved applications. ADO appears to be independent of the fragment sizes and has been reported to have a similar rate in other single-cell techniques. Possible solutions are the use of different lysis conditions or to carry out multiple rounds of amplifications from the diluted MDA products since PCR mediated amplification from cultured cells has been reported to give lower ADO rates. | 1 | Biochemistry |
Vital effects are biological impacts on geochemical records. Many marine organisms, ranging from zooplankton (e.g. foraminifera) to phytoplankton (e.g diatoms) to reef builders (e.g. coral), create shells or skeletons from chemical compounds dissolved in seawater. This process, which is also called biomineralization, therefore records the chemical signature of seawater during the time of shell formation. However, different species have different metabolism and physiology, causing them to create their shells in different ways. These biological distinctions cause species to record slightly different chemical signatures in their shells; these differences are known as vital effects. | 9 | Geochemistry |
The atomization of molten materials produces a large amount of dust and fumes made up of very fine particles (ca. 80–95% of the particles by number <100 nm). Proper extraction facilities are vital not only for personal safety, but to minimize entrapment of re-frozen particles in the sprayed coatings. The use of respirators fitted with suitable filters is strongly recommended where equipment cannot be isolated.
Certain materials offer specific known hazards:. The Toxicity from thermal spray aerosols is dependent on the metal profile of the thermal spray.
#Finely divided metal particles are potentially pyrophoric and harmful when accumulated in the body.
#Certain materials e.g. aluminum, zinc and other base metals may react with water to evolve hydrogen. This is potentially explosive and special precautions are necessary in fume extraction equipment.
#Fumes of certain materials, notably zinc and copper alloys, have a disagreeable odour and may cause a fever-type reaction in certain individuals (known as metal fume fever). This may occur some time after spraying and usually subsides rapidly. If it does not, medical advice must be sought.
#Fumes of reactive compounds can dissociate and create harmful gasses. Respirators should be worn in these areas and gas meters should be used to monitor the air before respirators are removed. | 8 | Metallurgy |
RuBP acts as an enzyme inhibitor for the enzyme rubisco, which regulates the net activity of carbon fixation. When RuBP is bound to an active site of rubisco, the ability to activate via carbamylation with and is blocked. The functionality of rubisco activase involves removing RuBP and other inhibitory bonded molecules to re-enable carbamylation on the active site. | 5 | Photochemistry |
On selection as a remedy, implementation of SVE involves the following elements: system design, operation, optimization, performance assessment, and closure. Several guidance documents provide information on these implementation aspects. EPA and U.S. Army Corps of Engineers (USACE) guidance documents establish an overall framework for design, operation, optimization, and closure of a SVE system. The Air Force Center for Engineering and the Environment (AFCEE) guidance presents actions and considerations for SVE system optimization, but has limited information related to approaches for SVE closure and meeting remediation goals. Guidance from the Pacific Northwest National Laboratory (PNNL) supplements these documents by discussing specific actions and decisions related to SVE optimization, transition, and/or closure.
Design and operation of a SVE system is relatively straightforward, with the major uncertainties having to do with subsurface geology/formation characteristics and the location of contamination. As time goes on, it is typical for a SVE system to exhibit a diminishing rate of contaminant extraction due to mass transfer limitations or removal of contaminant mass. Performance assessment is a key aspect to provide input for decisions about whether the system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. Assessment of rebound and mass flux provide approaches to evaluate system performance and obtain information on which to base decisions. | 2 | Environmental Chemistry |
If the person's lithium toxicity is mild or moderate, lithium dosage is reduced or stopped entirely. If the toxicity is severe, lithium may need to be removed from the body. The removal of lithium is done in a hospital emergency department. It may involve:
*Gastric lavage. A tube is placed through the nose or mouth into the stomach. The tube is used to remove lithium that has not been digested yet. It may also be used to put medicines directly into the stomach to help stop lithium from being absorbed.
*Use of an artificial kidney to clean the blood (dialysis). This is usually done only in the most severe cases.
*Diuretic medications such as furosemide and hydration via intravenous normal saline appear to be effective in speeding the removal of lithium and also rehydrate patients who've lost fluids.
*Hemodialysis. Hemodialysis is widely advocated as a means of reducing the risk of permanent neurological sequelae following lithium poisoning. Although hemodialysis clearly enhances the elimination of lithium, it is unclear whether this translates into improved patient outcomes.
People may be sent home once their blood serum lithium level is less than 1.5 mEq/L and they have no symptoms. | 1 | Biochemistry |
The primary molecular mechanism behind an oscillating gene is best described as a transcription/translation feedback loop. This loop contains both positive regulators, which increase gene expression, and negative regulators, which decrease gene expression. The fundamental elements of these loops are found across different phyla. In the mammalian circadian clock, for example, transcription factors CLOCK and BMAL1 are the positive regulators. CLOCK and BMAL1 bind to the E-box of oscillating genes, such as Per1, Per2, and Per3 and Cry1 and Cry2, and upregulate their transcription. When the PERs and CRYs form a heterocomplex in the cytoplasm and enter the nucleus again, they inhibit their own transcription. This means that over time the mRNA and protein levels of PERs and CRYs, or any other oscillating gene under this mechanism, will oscillate.
There also exists a secondary feedback loop, or stabilizing loop, which regulates the cyclic expression of Bmal1. This is caused by two nuclear receptors, REV-ERB and ROR, which suppresses and activates Bmal1 transcription, respectively.
In addition to these feedback loops, post-translational modifications also play a role in changing the characteristics of the circadian clock, such as its period. Without any type of feedback repression, the molecular clock would have a period of just a few hours. Casein kinase members CK1ε and CK1δ were both found to be mammalian protein kinases involved in circadian regulation. Mutations in these kinases are associated with familial advanced sleep phase syndrome (FASPS). In general, phosphorylation is necessary for the degradation of PERs via ubiquitin ligases. In contrast, phosphorylation of BMAL1 via CK2 is important for accumulation of BMAL1. | 1 | Biochemistry |
Based on characteristic that molecules usually have extraordinarily larger Stokes shift when ESIPT occurs, various applications have been developed using red-shifted fluorescence. Applications include turn-on photoluminescence sensor, photochromic, non-destructive optical memory, and white-light emitting materials.
Because phenol does not form a ketal under normal conditions because it does not tautomerize to any useful extent; however under ESIPT in the presence of an alcohol, e.g. ethylene glycol, it became possible to trap 1,4-Dioxaspiro[4.5]deca-6,8-diene [23783-59-7]. | 5 | Photochemistry |
Hellenistic and Graeco-Roman forms are more conventional, and the new motives that belong to these periods are mostly floral. Busts and masks are the usual handle-plaques and spouts; heads and limbs of various animals are allotted certain decorative functions, as for instance the spirited mules' heads mentioned by Juvenal, which formed the elbow-rests of dining couches. These structural pieces are frequently inlaid with silver and niello. Bronze chairs and tables were commonly used in Hellenistic and Roman houses, and largely took the place of monumental vases that were popular in earlier days. Small household articles, such as lamps, when made of bronze are usually Roman, and a peculiarly Roman class of personal ornaments is a large bronze brooch inlaid with coloured enamels, a technique which seems to have had a Gaulish origin. | 8 | Metallurgy |
In the petroleum refining and petrochemical industries, the initialism BTX refers to mixtures of benzene, toluene, and the three xylene isomers, all of which are aromatic hydrocarbons. The xylene isomers are distinguished by the designations ortho – (or o –), meta – (or m –), and para – (or p –) as indicated in the adjacent diagram. If ethylbenzene is included, the mixture is sometimes referred to as BTEX.
The BTX aromatics are very important petrochemical materials. Global consumption of benzene, estimated at more than 40,000,000 tons in 2010, showed an unprecedented growth of more than 3,000,000 tons from the level seen in 2009. Likewise, the para-xylene consumption showed unprecedented growth in 2010, growing by 2,800,000 tons, a full ten percent growth from 2009.
Toluene is also a valuable petrochemical for use as a solvent and intermediate in chemical manufacturing processes and as a high octane gasoline component. | 7 | Physical Chemistry |
It is presumed that Chesapeake Bay was once inhabited by Paleoindians 11,000 years ago. For thousands of years, Native American societies lived in villages of wooden longhouses close to water bodies where they fished and farmed the land. Agricultural products included beans, corn, tobacco, and squash. Villages often lasted between 10 and 20 years before being abandoned due to local resources such as firewood running out or soil depleting. To produce enough food, labor was divided with men hunting while the women supervised the village's farming. All village members took part in the harvesting of fish and shellfish from the local bodies of water. As time went on, communities around Chesapeake Bay formed confederations such as the Powhatan, the Piscataway, and the Nanticoke. Each of these confederations consisted of a collection of smaller tribes falling under the leadership of a central chief. | 2 | Environmental Chemistry |
Cesium chloride is a simple cubic crystal lattice with a basis of Cs at (0,0,0) and Cl at (1/2, 1/2, 1/2) (or the other way around, it makes no difference). Equation () becomes
We then arrive at the following result for the structure factor for scattering from a plane :
and for scattered intensity, | 3 | Analytical Chemistry |
In thermodynamics, a quantity that is well defined so as to describe the path of a process through the equilibrium state space of a thermodynamic system is termed a process function, or, alternatively, a process quantity, or a path function. As an example, mechanical work and heat are process functions because they describe quantitatively the transition between equilibrium states of a thermodynamic system.
Path functions depend on the path taken to reach one state from another. Different routes give different quantities. Examples of path functions include work, heat and arc length. In contrast to path functions, state functions are independent of the path taken. Thermodynamic state variables are point functions, differing from path functions. For a given state, considered as a point, there is a definite value for each state variable and state function.
Infinitesimal changes in a process function are often indicated by to distinguish them from infinitesimal changes in a state function which is written . The quantity is an exact differential, while is not, it is an inexact differential. Infinitesimal changes in a process function may be integrated, but the integral between two states depends on the particular path taken between the two states, whereas the integral of a state function is simply the difference of the state functions at the two points, independent of the path taken.
In general, a process function may be either holonomic or non-holonomic. For a holonomic process function, an auxiliary state function (or integrating factor) may be defined such that is a state function. For a non-holonomic process function, no such function may be defined. In other words, for a holonomic process function, may be defined such that is an exact differential. For example, thermodynamic work is a holonomic process function since the integrating factor (where is pressure) will yield exact differential of the volume state function . The second law of thermodynamics as stated by Carathéodory essentially amounts to the statement that heat is a holonomic process function since the integrating factor (where is temperature) will yield the exact differential of an entropy state function . | 7 | Physical Chemistry |
The Occupational Safety and Health Administration (OSHA) is the regulatory body covering worker safety. OSHA puts forth permissible exposure limit (PEL) 20 ppb for MDI and detailed technical guidance on exposure assessment.
The National Institutes of Health (NIOSH) is the agency responsible for providing the research and recommendations regarding workplace safety, while OSHA is more of an enforcement body. NIOSH is responsible for producing the science that can result in recommended exposure limits (REL), which can be lower than the PEL. OSHA is tasked with enforcement and defending the enforceable limits (PELs). In 1992, when OSHA reduced the PEL for TDI to the NIOSH REL, the PEL reduction was challenged in court, and the reduction was reversed.
The Environmental Protection Agency (EPA) is also involved in the regulation of isocyanates with regard to the environment and also non-worker persons that might be exposed.
The American Conference of Governmental Industrial Hygienists (ACGIH) is a non-government organization that publishes guidance known as threshold limit values (TLV) for . The TLV is not an OSHA-enforceable value, unless the PEL is the same. | 0 | Organic Chemistry |
1,1,1,2-Tetrafluoroethane is also being considered as an organic solvent, both in liquid and supercritical fluid.
It is used in the resistive plate chamber particle detectors in the Large Hadron Collider. It is also used for other types of particle detectors, e.g. some cryogenic particle detectors. It can be used as an alternative to sulfur hexafluoride in magnesium smelting as a shielding gas. | 2 | Environmental Chemistry |
The following steps convert in a conventional n-type DSSC photons (light) to current:
The efficiency of a DSSC depends on four energy levels of the component: the excited state (approximately LUMO) and the ground state (HOMO) of the photosensitizer, the Fermi level of the TiO electrode and the redox potential of the mediator (I/I) in the electrolyte. | 5 | Photochemistry |
Even if there is no oxygen present, glycolysis can continue to generate ATP. However, for glycolysis to continue to produce ATP, there must be NAD+ present, which is responsible for oxidizing glucose. This is achieved by recycling NADH back to NAD+. When NAD+ is reduced to NADH, the electrons from NADH are eventually transferred to a separate organic molecule, transforming NADH back to NAD+. This process of renewing the supply of NAD+ is called fermentation, which falls into two categories. | 1 | Biochemistry |
The reaction is a possible candidate for prebiotic early-Earth conditions and, therefore, is of interest in the research of the origin of life. It has been found that some non-consecutive steps of the cycle can be catalyzed by minerals through photochemistry, while entire two and three-step sequences can be promoted by metal ions such as iron (as reducing agents) under acidic conditions. In addition, these organisms that undergo photochemistry can and do utilize the citric acid cycle. However, the conditions are extremely harsh and require 1 M hydrochloric or 1 M sulfuric acid and strong heating at 80–140 °C.
Along with these possibilities of the rTCA cycle contributing to early life and biomolecules, it is thought that the rTCA cycle could not have been completed without the use of enzymes. The kinetic and thermodynamic parameters of the reduction of highly oxidized species to push the rTCA cycle are seemingly unlikely without the necessary action of biological catalysts known as enzymes. The rate of some of the reactions in the rTCA cycle likely would have been too slow to contribute significantly to the formation of life on Earth without enzymes. Considering the thermodynamics of the rTCA cycle, the increase in Gibbs free energy going from product to reactant would make pyrophosphate an unlikely energy source for the conversion of pyruvate to oxaloacetate as the reaction is too endoergic. However, it is suggested that a nonenzymatic precursor to the Krebs cycle, glyoxylate cycle, and reverse Krebs cycle might have originated, where oxidation and reduction reactions cooperated. The later use of carboxylation utilizing ATP could have given rise to parts of reverse Krebs cycle.
It is suggested that the reverse Krebs cycle was incomplete, even in the last universal common ancestor. Many reactions of the reverse Krebs cycle, including thioesterification and hydrolysis, could have been catalyzed by iron-sulfide minerals at deep sea alkaline hydrothermal vent cavities. More recently, aqueous microdroplets have been shown to promote reductive carboxylation reactions in the reverse Krebs cycle. | 1 | Biochemistry |
When the transition involves more than one charged particle, the transition dipole moment is defined in an analogous way to an electric dipole moment: The sum of the positions, weighted by charge. If the ith particle has charge q and position operator r, then the transition dipole moment is: | 5 | Photochemistry |
The most commonly used PCMs are salt hydrates, fatty acids and esters, and various paraffins (such as octadecane). Recently also ionic liquids were investigated as novel PCMs.
As most of the organic solutions are water-free, they can be exposed to air, but all salt based PCM solutions must be encapsulated to prevent water evaporation or uptake. Both types offer certain advantages and disadvantages and if they are correctly applied some of the disadvantages becomes an advantage for certain applications.
They have been used since the late 19th century as a medium for thermal storage applications. They have been used in such diverse applications as refrigerated transportation for rail and road applications and their physical properties are, therefore, well known.
Unlike the ice storage system, however, the PCM systems can be used with any conventional water chiller both for a new or alternatively retrofit application. The positive temperature phase change allows centrifugal and absorption chillers as well as the conventional reciprocating and screw chiller systems or even lower ambient conditions utilizing a cooling tower or dry cooler for charging the TES system.
The temperature range offered by the PCM technology provides a new horizon for the building services and refrigeration engineers regarding medium and high temperature energy storage applications. The scope of this thermal energy application is wide-ranging of solar heating, hot water, heating rejection (i.e., cooling tower), and dry cooler circuitry thermal energy storage applications.
Since PCMs transform between solid–liquid in thermal cycling, encapsulation naturally became the obvious storage choice.
*Encapsulation of PCMs
**Macro-encapsulation: Early development of macro-encapsulation with large volume containment failed due to the poor thermal conductivity of most PCMs. PCMs tend to solidify at the edges of the containers preventing effective heat transfer.
**Micro-encapsulation: Micro-encapsulation on the other hand showed no such problem. It allows the PCMs to be incorporated into construction materials, such as concrete, easily and economically. Micro-encapsulated PCMs also provide a portable heat storage system. By coating a microscopic sized PCM with a protective coating, the particles can be suspended within a continuous phase such as water. This system can be considered a phase change slurry (PCS).
**Molecular-encapsulation is another technology, developed by Dupont de Nemours that allows a very high concentration of PCM within a polymer compound. It allows storage capacity up to 515 kJ/m for a 5 mm board (103 MJ/m). Molecular-encapsulation allows drilling and cutting through the material without any PCM leakage.
As phase change materials perform best in small containers, therefore they are usually divided in cells. The cells are shallow to reduce static head – based on the principle of shallow container geometry. The packaging material should conduct heat well; and it should be durable enough to withstand frequent changes in the storage material's volume as phase changes occur. It should also restrict the passage of water through the walls, so the materials will not dry out (or water-out, if the material is hygroscopic). Packaging must also resist leakage and corrosion. Common packaging materials showing chemical compatibility with room temperature PCMs include stainless steel, polypropylene, and polyolefin.
Nanoparticles such as carbon nanotubes, graphite, graphene, metal and metal oxide can be dispersed in PCM. It is worth noting that inclusion of nanoparticles will not only alter thermal conductivity characteristic of PCM but also other characteristics as well, including latent heat capacity, sub-cooling, phase change temperature and its duration, density and viscosity. The new group of PCMs called NePCM. NePCMs can be added to metal foams to build even higher thermal conductive combination. | 7 | Physical Chemistry |
RECODE is a database of "programmed" frameshifts, bypassing and codon redefinition used for gene expression. | 1 | Biochemistry |
Continuous dynamic recrystallization is common in materials with high stacking-fault energies. It occurs when low angle grain boundaries form and evolve into high angle boundaries, forming new grains in the process. For continuous dynamic recrystallization there is no clear distinction between nucleation and growth phases of the new grains.
Continuous Dynamic Recrystallization has 4 main characteristics:
* As strain increases, stress increases
* As strain increases, subgrain boundary misorientation increases
* As low angle grain boundaries evolve into high angle grain boundaries, the misorientation increases homogeneously
* As deformation increases, crystallite size decreases
There are three main mechanisms of continuous dynamic recrystallization:
First, continuous dynamic recrystallization can occur when low angle grain boundaries are assembled from dislocations formed within the grain. When the material is subjected to continued stress, the misorientation angle increases until the critical angle is achieved, creating a high angle grain boundary. This evolution can be promoted by the pinning of subgrain boundaries.
Second, continuous dynamic recrystallization can occur through subgrain rotation recrystallization; subgrains rotate increasing the misorientation angle. Once the misorientation angle exceeds the critical angle, the former subgrains qualify as independent grains.
Third, continuous dynamic recrystallization can occur due to deformation caused by microshear bands. Subgrains are assembled by dislocations within the grain formed during work hardening. If microshear bands are formed within the grain, the stress they introduce rapidly increases the misorientation of low angle grain boundaries, transforming them into high angle grain boundaries. However, the impact of microshear bands are localized, so this mechanism preferentially impacts regions which deform heterogeneously, such as microshear bands or areas near pre-existing grain boundaries. As recrystallization proceeds, it spreads out from these zones, generating a homogenous, equiaxed microstructure. | 8 | Metallurgy |
A cryophorus is a glass container containing liquid water and water vapor. It is used in physics courses to demonstrate rapid freezing by evaporation. A typical cryophorus has a bulb at one end connected to a tube of the same material. When the liquid water is manipulated into the bulbed end and the other end is submerged into a freezing mixture (such as liquid nitrogen), the gas pressure drops as it is cooled. The liquid water begins to evaporate, producing more water vapor. Evaporation causes the water to cool rapidly to its freezing point and it solidifies suddenly.
Wollaston's cryophorus was a precursor to the modern heat pipe. | 7 | Physical Chemistry |
The extensive use of gold during early Philippine history is well-documented, both in the archeological record and in the various written accounts from precolonial and early Spanish colonial times. Gold was used throughout the Philippine archipelago in various decorative and ceremonial items, as clothing, and also as currency.
Gold was readily available throughout the Philippine archipelago, and gold items were valued as symbols of power and markers of elite status, although studies of grave artifacts suggest that these items were not as valued in precolonial Philippines as traded ornaments were. Gold was plentiful enough that local elites did not feel the need to acquire large amounts of it, and only sought it as the need arose, by trading with settlements which produced it through low intensity mining.
Among the most prominent sites for gold mining in early Philippine history were Aringay-Tonglo-Balatok trade route covering the Cordillera Mountain Range and the Lingayen gulf towns of Agoo and Aringay; the mines of Paracale on the Bicol Peninsula which were a major source of gold for the trading centers of the Visayan islands, particularly Panay and Cebu; and the Butuan-Surigao area, particularly along the Agusan river on the island of Mindanao, which made Butuan (historical polity) an important trading center. | 8 | Metallurgy |
1,2-Dichlorotetrafluoroethane, or R-114, also known as cryofluorane (INN), is a chlorofluorocarbon (CFC) with the molecular formula ClFCCFCl. Its primary use has been as a refrigerant. It is a non-flammable gas with a sweetish, chloroform-like odor with the critical point occurring at 145.6 °C and 3.26 MPa. When pressurized or cooled, it is a colorless liquid. It is listed on the Intergovernmental Panel on Climate Change's list of ozone depleting chemicals, and is classified as a Montreal Protocol Class I, group 1 ozone depleting substance.
When used as a refrigerant, R-114 is classified as a medium pressure refrigerant.
The U.S. Navy uses R-114 in its centrifugal chillers in preference to R-11 to avoid air and moisture leakage into the system. While the evaporator of an R-11 charged chiller runs at a vacuum during operation, R-114 yields approximately 0 psig operating pressure in the evaporator.
Manufactured and sold R-114 was usually mixed with the non symmetrical isomer 1,1-dichlorotetrafluoroethane (CFC-114a), as separation of the two isomers is difficult. | 2 | Environmental Chemistry |
Quasi-equilibrium is different from classical chemical equilibrium, but can be described using a similar thermodynamic treatment. Consider the reaction below
where complete equilibrium is achieved between all the species in the system including activated complexes, [AB] . Using statistical mechanics, concentration of [AB] can be calculated in terms of the concentration of A and B.
TST assumes that even when the reactants and products are not in equilibrium with each other, the activated complexes are in quasi-equilibrium with the reactants. As illustrated in Figure 2, at any instant of time, there are a few activated complexes, and some were reactant molecules in the immediate past, which are designated [AB] (since they are moving from left to right). The remainder of them were product molecules in the immediate past ([AB]).
In TST, it is assumed that the flux of activated complexes in the two directions are independent of each other. That is, if all the product molecules were suddenly removed from the reaction system, the flow of [AB] stops, but there is still a flow from left to right. Hence, to be technically correct, the reactants are in equilibrium only with [AB], the activated complexes that were reactants in the immediate past. | 7 | Physical Chemistry |
In addition to common uses previously mentioned, FRET and BRET are also effective in the study of biochemical reaction kinetics. FRET is increasingly used for monitoring pH dependent assembly and disassembly and is valuable in the analysis of nucleic acids encapsulation. This technique can be used to determine factors affecting various types of nanoparticle formation as well as the mechanisms and effects of nanomedicines. | 1 | Biochemistry |
The objective of this study was to compare different tumor markers and their diagnostic value. The tumor markers tested in this experiment were CA 19-9, CA 242 and CEA tumor markers. The data revealed that although each marker have its own level of specificity and correspond to a cancer, all three makers together increase diagnostic value. | 1 | Biochemistry |
The sea surface microlayer (SML) is the boundary interface between the atmosphere and ocean, covering about 70% of Earth's surface. With an operationally defined thickness between 1 and , the SML has physicochemical and biological properties that are measurably distinct from underlying waters. Recent studies now indicate that the SML covers the ocean to a significant extent, and evidence shows that it is an aggregate-enriched biofilm environment with distinct microbial communities. Because of its unique position at the air-sea interface, the SML is central to a range of global marine biogeochemical and climate-related processes.
The sea surface microlayer is the boundary layer where all exchange occurs between the atmosphere and the ocean. The chemical, physical, and biological properties of the SML differ greatly from the sub-surface water just a few centimeters beneath.
Despite the huge extent of the ocean's surface, until now relatively little attention has been paid to the sea surface microlayer (SML) as the ultimate interface where heat, momentum and mass exchange between the ocean and the atmosphere takes place. Via the SML, large-scale environmental changes in the ocean such as warming, acidification, deoxygenation, and eutrophication potentially influence cloud formation, precipitation, and the global radiation balance. Due to the deep connectivity between biological, chemical, and physical processes, studies of the SML may reveal multiple sensitivities to global and regional changes.
Understanding the processes at the ocean's surface, in particular involving the SML as an important and determinant interface, could provide an essential contribution to the reduction of uncertainties regarding ocean-climate feedbacks. As of 2017, processes occurring within the SML, as well as the associated rates of material exchange through the SML, remained poorly understood and were rarely represented in marine and atmospheric numerical models. | 7 | Physical Chemistry |
Downregulation of protein kinase A occurs by a feedback mechanism and uses a number of cAMP hydrolyzing phosphodiesterase (PDE) enzymes, which belong to the substrates activated by PKA. Phosphodiesterase quickly converts cAMP to AMP, thus reducing the amount of cAMP that can activate protein kinase A. PKA is also regulated by a complex series of phosphorylation events, which can include modification by autophosphorylation and phosphorylation by regulatory kinases, such as PDK1.
Thus, PKA is controlled, in part, by the levels of cAMP. Also, the catalytic subunit itself can be down-regulated by phosphorylation. | 1 | Biochemistry |
This way also uses two experimental protocols, and , to compare the index effect with the effect of moderation alone. The index protocol is executed first; the response of prime interest, is observed, and the response of the moderating variable is also measured. With that knowledge, then the fixed driver, moderation imposed protocol enforces that with the driving variable held fixed; the protocol also, through an adjustment imposes a change (learnt from the just previous measurement) in the moderating variable, and measures the change Provided that the moderated response is indeed that then the principle states that the signs of and are opposite.
Again, in other words, change in the moderating state variable opposes the effect of the driving change in on the responding conjugate variable | 7 | Physical Chemistry |
The compound was first described by Carl Wilhelm Scheele in 1780, who obtained it by the dry distillation of mucic acid. For this reason it was initially known as pyromucic acid. This was the first known synthesis of a furan compound, the second being furfural in 1821.
Despite this, it was furfural which came to set naming conventions for later furans. | 0 | Organic Chemistry |
Rhodizonic acid is a chemical compound with formula or . It can be seen as a twofold enol and fourfold ketone of cyclohexene, more precisely 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone.
Rhodizonic acid is usually obtained in the form of a dihydrate . The latter is actually 2,3,5,5,6,6-hexahydroxycyclohex-2-ene-1,4-dione, where two of the original ketone groups are replaced by two pairs of geminal diols. The orange to deep-red and highly hygroscopic anhydrous acid can be obtained by low-pressure sublimation of the dihydrate.
Like many other enols, rhodizonic acid can lose the hydrogen cations from the hydroxyls (pK = , pK = at 25 °C), yielding the hydrogen rhodizonate anion and the rhodizonate anion . The latter is aromatic and symmetric, as the double bond and the negative charges are delocalized and evenly distributed over the six CO units. Rhodizonates tend to have various shades of red, from yellowish to purplish.
Rhodizonic acid has been used in chemical assays for barium, lead, and other metals. In particular, the sodium rhodizonate test can be used to detect gunshot residue (which contains lead) in a subject's hands, and to distinguish arrow wounds from gunshot wounds for hunting regulation enforcement. | 3 | Analytical Chemistry |
A hand boiler functions similar to the "drinking bird" toy: The upper and lower bulbs of the device are at different temperatures, and therefore the vapor pressure in the two bulbs is different. Since the lower bulb is warmer, the vapor pressure in it is higher. The difference in vapor pressure forces the liquid from the lower bulb to the upper bulb. Thus:
where:<br>
= the height of the column of fluid above the fluid's level in the lower bulb<br>
= the difference in vapor pressure between the two bulbs (which can be determined via the Antoine equation)<br>
= the density of the liquid<br>
= the acceleration of gravity at the Earth's surface
The liquid inside a hand boiler (ethanol) does not actually boil. The "boiling" is caused by the relationship between the temperature and pressure of a gas. As the temperature of a gas in a closed container rises, the pressure also rises. There must be a temperature (and pressure) difference between the two large chambers for the liquid to move. When held upright (with the smaller bulb on top), the liquid will move from the bulb with the higher pressure to the bulb with lower pressure. As the gas continues to expand, the gas will then bubble through the liquid, making it appear to boil. The fact that the liquid is volatile (easily vaporized) makes the hand boiler more effective. Adding heat to the liquid produces more gas, also increasing pressure in the closed container.
Sometimes a hand boiler is used to show properties of distillation. Since the liquid both evaporates and condenses at relatively cool temperatures while in an enclosed system, the boiler can be turned upside down, and the top end can be placed in ice water. The gaseous form of the liquid will condense in the cooled chamber. Since the liquid is often colored with dye, but the dye does not evaporate or condense at the same temperature, the liquid that condenses in the cooled chamber is colorless, leaving the pigment behind. | 7 | Physical Chemistry |
ASTM International has an international standard for artificial seawater: ASTM D1141-98 (Original Standard ASTM D1141-52). It is used in many research testing labs as a reproducible solution for seawater such as tests on corrosion, oil contamination, and detergency evaluation. | 9 | Geochemistry |
* The analyst wishes to simplify the conduct of a variety of titrations by using one sensor for all. For example, a laboratory might conduct routinely acid/base, redox, complexometric, sulfate and chloride titrations. A single thermometric sensor in conjunction with an autosampler will enable all titrations to be performed in the same carousel load without having to change titration sensors. After preparation of the samples and placing in the carousel, the analyst assigns the appropriate thermometric method to the beaker position in the carousel.
* The titration environment is considered unsuitable for conventional titration sensors. For example, glass membrane pH electrodes must be kept adequately hydrated for proper operation. The use of such electrodes in substantially non-aqueous media as in the determination of trace acids in lipids and lubricating oils can lead to loss of performance as the membrane fouls and dehydrates, and/or if the reference junction is partly or completely blocked. It is often necessary to keep a number of electrodes cycling through a rejuvenation program in order to keep up with an analytical workload. Thermometric sensors have no electrochemical interaction with the titrating solution, and therefore can be used on a continuous basis with essentially no maintenance. Similarly, the potentiometric titration of sulfate with barium chloride in various industrial samples can lead to rapid degradation of the indicating barium ion selective electrode.
* A thermometric titration methodology which cannot be emulated using other types of titration sensors will deliver superior or results otherwise unobtainable by other techniques. Examples are the determination of fluoride by titration with boric acid, the analysis of orthophosphate by titration with magnesium ions, and the direct titration of aluminium with fluoride ions. | 3 | Analytical Chemistry |
Underwater air retaining surfaces are of great interest for technical applications. If a transfer of the effect to a technical surface is successful, ship hulls could be coated with this surface to reduce friction between ship and water resulting in less fuel consumption, fuel costs and reduction of its negative environmental impact (antifouling effect by the air layer). In 2007 first test boats already achieved a ten percent friction reduction and the principle was subsequently patented. By now scientists assume a friction reduction of over 30%.
The underlying principle is schematically shown in a figure. Two flow profiles of laminar flow in water over a solid surface and water flowing over an air retaining surface are compared here.
If water flows over a smooth solid surface, the velocity at the surface is zero due to the friction between water and surface molecules. If an air layer is situated between the solid surface and the water the velocity is higher than zero. The lower viscosity of air (55 times lower than the viscosity of water) reduces the transmission of friction forces by the same factor.
Researchers are currently working on the development of a biomimetic, permanently air retaining surface modeled on S. molesta to reduce friction on ships. Salvinia-Effect surfaces have been proven to quickly and efficiently adsorb oil and can be used for oil-water separation applications | 7 | Physical Chemistry |
Carly Joanne Stevens has been awarded B.Sc. and M.Sc. degrees. In 2004 her PhD was awarded by the Open University for her work on the effects of nitrogen on grassland ecology supervised by Nancy Dise, David Gowing and Owen Mountford. It was carried out in collaboration with the NERC Centre for Ecology and Hydrology, Monks Wood. Prior to her appointment at University of Lancaster, Stevens was a research fellow at the Open University. | 9 | Geochemistry |
Typical spiral concentrators will use a slurry from about 20%-40% solids by weight, with a particle size somewhere between 0.75—1.5mm (17-340 mesh), though somewhat larger particle sizes are sometimes used. The spiral separator is less efficient at the particle sizes of 0.1—0.074mm however. For efficient separation, the density difference between the heavy minerals and the light minerals in the feedstock should be at least 1 g/cm; and because the separation is dependent upon size and density, spiral separators are most effective at purifying ore if its particles are of uniform size and shape. A spiral separator may process a couple tons per hour of ore, per flight, and multiple flights may be stacked in the same space as one, to improve capacity.
Many things can be done to improve the separation efficiency, including:
* changing the rate of material feed
*changing the grain size of the material
*changing the slurry mass percentage
*adjusting the cutter bar positions
*running the output of one spiral separator (often, a third, intermediate, cut) through a second.
*adding washwater inlets along the length of the spiral, to aid in separating light minerals
*adding multiple outlets along the length, to improve the ability of the spiral to remove heavy contaminants
*adding ridges on the sluice at an angle to the direction of flow. | 3 | Analytical Chemistry |
* [https://www.fs.usda.gov/rmrs/air-soil-and-water-resources-and-quality Rocky Mountain Research Station - Air, soil, and water resources and quality]
* [https://www.nimss.org/projects/18621 NRSP3: The National Atmospheric Deposition Program (NADP)] | 2 | Environmental Chemistry |
Characterization of microstructures has also been performed using x-ray diffraction (XRD) techniques for many years. XRD can be used to determine the percentages of various phases present in a specimen if they have different crystal structures. For example, the amount of retained austenite in a hardened steel is best measured using XRD (ASTM E 975). If a particular phase can be chemically extracted from a bulk specimen, it can be identified using XRD based on the crystal structure and lattice dimensions. This work can be complemented by EDS and/or WDS analysis where the chemical composition is quantified. But EDS and WDS are difficult to apply to particles less than 2-3 micrometers in diameter. For smaller particles, diffraction techniques can be performed using the TEM for identification and EDS can be performed on small particles if they are extracted from the matrix using replication methods to avoid detection of the matrix along with the precipitate. | 8 | Metallurgy |
Pepper spray, oleoresin capsicum spray, OC spray, capsaicin spray, or capsicum spray is a lachrymator (tear gas) product containing the compound capsaicin as the active ingredient that irritates the eyes to cause burning and pain sensations, as well as temporary blindness. Its inflammatory effects cause the eyes to close, temporarily taking away vision. This temporary blindness allows officers to more easily restrain subjects and permits people in danger to use pepper spray in self-defense for an opportunity to escape. It also causes temporary discomfort and burning of the lungs which causes shortness of breath. Pepper spray is used as a less lethal weapon in policing, riot control, crowd control, and self-defense, including defense against dogs and bears.
Pepper spray was engineered originally for defense against bears, mountain lions, wolves and other dangerous predators, and is often referred to colloquially as bear spray.
Kamran Loghman, the person who developed it for use in riot control, wrote the guide for police departments on how it should be used. It was successfully adapted, except for improper usages such as when police sprayed peaceful protestors at University of California, Davis in 2011. Loghman commented, "I have never seen such an inappropriate and improper use of chemical agents", prompting court rulings completely barring its use on docile persons. | 1 | Biochemistry |
Quorum sensing is used by bacteria to form biofilms. Quorum sensing is used by bacteria to form biofilms because the process determines if the minimum number of bacteria necessary for biofilm formation are present. The criteria to form a biofilm is dependent on a certain density of bacteria rather than a certain number of bacteria being present. When aggregated in high enough densities, some bacteria may form biofilms to protect themselves from biotic or abiotic threats. Quorum sensing is used by both Gram-positive and Gram-negative bacteria because it aids cellular reproduction. Once in a biofilm, bacteria can communicate with other bacteria of the same species. Bacteria can also communicate with other species of bacteria. This communication is enabled through autoinducers used by the bacteria.
Additionally, certain responses can be generated by the host organism in response to the certain bacterial autoinducers. Despite the fact that specific bacterial quorum sensing systems are different, for example the target genes, signal relay mechanisms, and chemical signals used between bacteria, the ability to coordinate gene expression for a specific species of bacteria remains the same. This ability alludes to the larger idea that bacteria have potential to become a multicellular bacterial body.
Secondly, biofilms may also serve to transport nutrients into the microbial community or transport toxins out by means of channels that permeate the extracellular polymeric matrix (like cellulose) that holds the cells together. Finally, biofilms are an ideal environment for horizontal gene transfer through either conjugation or environmental DNA (eDNA) that exists in the biofilm matrix.
The process of biofilm development is often triggered by environmental signals, and bacteria are proven to require flagella to successfully approach a surface, adhere to it, and form the biofilm. As cells either replicate or aggregate in a location, the concentration of autoinducers outside of the cells increases until a critical mass threshold is reached. At this point, it is energetically unfavorable for intracellular autoinducers to leave the cell and they bind to receptors and trigger a signaling cascade to initiate gene expression and begin secreting an extracellular polysaccharide to encase themselves inside. | 1 | Biochemistry |
Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation, or with chemical reaction with another constituent of the solution, such as acid or alkali. Each solubility equilibrium is characterized by a temperature-dependent solubility product which functions like an equilibrium constant. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios. | 7 | Physical Chemistry |
The importance of these untranslated regions of mRNA is just beginning to be understood. Various medical studies are being conducted that have found connections between mutations in untranslated regions and increased risk for developing a particular disease, such as cancer. For example, associations between polymorphisms in the HLA-G 3′UTR region and development of colorectal cancer have been discovered. Single Nucleotide Polymorphisms in the 3 UTR of another gene have also been associated with susceptibility to preterm birth. Mutations in the 3 UTR of the APP gene are related to development of cerebral amyloid angiopathy. | 1 | Biochemistry |
Ribosome-mediated attenuation is a gene expression mechanism in which a transcriptional termination signal is regulated by translation. Attenuation occurs at the start of some prokaryotic operons at sequences called "attenuators", which have been identified in operons encoding amino acid biosynthesis enzymes, pyrimidine biosynthesis enzymes and antibiotic resistance factors. The attenuator functions via a set of mRNA sequence elements that coordinate the status of translation to a transcription termination signal:
* A short open reading frame encoding a "leader peptide"
* A transcription pause sequence
* A "control region"
* A transcription termination signal
Once the start of the leader open reading frame has been transcribed, RNA polymerase pauses due to folding of the nascent mRNA. This programmed arrest of transcription gives time for translation of the leader peptide to commence, and transcription to resume once coupled to translation. The downstream "control region" then modulates the elongation rate of either the ribosome or RNA polymerase. The factor determining this depends on the function of the downstream genes (e.g. the operon encoding enzymes involved in the synthesis of histidine contains a series of histidine codons is the control region). The role of the control region is to modulate whether transcription remains coupled to translation depending on the cellular state (e.g. a low availability of histidine slows translation leading to uncoupling, while high availability of histidine permits efficient translation and maintains coupling). Finally, the transcription terminator sequence is transcribed. Whether transcription is coupled to translation determines whether this stops transcription. The terminator requires folding of the mRNA, and by unwinding mRNA structures the ribosome elects the formation of either of two alternative structures: the terminator, or a competing fold termed the "antiterminator".
For amino acid biosynthesis operons, these allow the gene expression machinery to sense the abundance of the amino acid produced by the encoded enzymes, and adjust the level of downstream gene expression accordingly: transcription occurring only if the amino acid abundance is low and the demand for the enzymes is therefore high. Examples include the histidine (his) and tryptophan (trp) biosynthetic operons.
The term "attenuation" was introduced to describe the his operon. While it is typically used to describe biosynthesis operons of amino acids and other metabolites, programmed transcription termination that does not occur at the end of a gene was first identified in λ phage. The discovery of attenuation was significant as it represented a regulatory mechanism distinct from repression. The trp operon is regulated by both attenuation and repression, and was the first evidence that gene expression regulation mechanisms can be overlapping or redundant. | 1 | Biochemistry |
Ex situ conservation, while helpful in humankinds efforts to sustain and protect our environment, is rarely enough to save a species from extinction. It is to be used as a last resort, or as a supplement to in situ conservation because it cannot recreate the habitat as a whole: the entire genetic variation of a species, its symbiotic counterparts, or those elements which, over time, might help a species adapt to its changing surroundings. Instead, ex situ conservation removes the species from its natural ecological contexts, preserving it under semi-isolated conditions whereby natural evolution and adaptation processes are either temporarily halted or altered by introducing the specimen to an unnatural habitat. In the case of cryogenic storage methods, the preserved specimens adaptation processes are (quite literally) frozen altogether. The downside to this is that, when re-released, the species may lack the genetic adaptations and mutations which would allow it to thrive in its ever-changing natural habitat.
Furthermore, ex situ conservation techniques are often costly, with cryogenic storage being economically infeasible in most cases since species stored in this manner cannot provide a profit but instead slowly drain the financial resources of the government or organization determined to operate them. Seedbanks are ineffective for certain plant genera with recalcitrant seeds that do not remain fertile for long periods of time. Diseases and pests foreign to the species, to which the species has no natural defense, may also cripple crops of protected plants in ex situ plantations and in animals living in ex situ breeding grounds. These factors, combined with the specific environmental needs of many species, some of which are nearly impossible to recreate by man, make ex situ conservation impossible for a great number of the world's endangered flora and fauna. | 1 | Biochemistry |
The difference between the two heating values depends on the chemical composition of the fuel. In the case of pure carbon or carbon monoxide, the two heating values are almost identical, the difference being the sensible heat content of carbon dioxide between 150 °C and 25 °C (sensible heat exchange causes a change of temperature, while latent heat is added or subtracted for phase transitions at constant temperature. Examples: heat of vaporization or heat of fusion). For hydrogen, the difference is much more significant as it includes the sensible heat of water vapor between 150 °C and 100 °C, the latent heat of condensation at 100 °C, and the sensible heat of the condensed water between 100 °C and 25 °C. All in all, the higher heating value of hydrogen is 18.2% above its lower heating value (142MJ/kg vs. 120MJ/kg). For hydrocarbons, the difference depends on the hydrogen content of the fuel. For gasoline and diesel the higher heating value exceeds the lower heating value by about 10% and 7%, respectively, and for natural gas about 11%.
A common method of relating HHV to LHV is:
where H is the heat of vaporization of water, n is the number of moles of water vaporized and n is the number of moles of fuel combusted.
* Most applications that burn fuel produce water vapor, which is unused and thus wastes its heat content. In such applications, the lower heating value must be used to give a benchmark for the process.
* However, for true energy calculations in some specific cases, the higher heating value is correct. This is particularly relevant for natural gas, whose high hydrogen content produces much water, when it is burned in condensing boilers and power plants with flue-gas condensation that condense the water vapor produced by combustion, recovering heat which would otherwise be wasted. | 7 | Physical Chemistry |
An article published in Nature Materials demonstrated cell efficiencies of 8.2% using a new solvent-free liquid redox electrolyte consisting of a melt of three salts, as an alternative to using organic solvents as an electrolyte solution. Although the efficiency with this electrolyte is less than the 11% being delivered using the existing iodine-based solutions, the team is confident the efficiency can be improved. | 5 | Photochemistry |
The PECT effect was first reported by Dr. F Lincoln Vogel in 1981 when studying how intercalation voltages could be used to provide an actuation force in graphitized carbon fibres. The research used sulphate (SO) ions from sulfuric acid to intercalate into the microstructure of carbon fibers, forming graphite intercalation compounds (GICs). It was hypothesized that an axial strain of up to 2% should be possible, however only 0.2% was observed due to experimental limitations.
The effect is often explained by the theories of Larché and Cahn who derived mathematical formulations for the equilibrium relationships between the electric potential, chemical potential, and mechanical stress in solid materials. In summary the theory states that solid materials under mechanical stress undergo a change in chemical potential, which in turn affects their electrical potential. | 7 | Physical Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.