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Mikael Bols (born July 28, 1961) is a synthetic organic chemist who is mainly known for his work on carbohydrates and artificial enzymes. | 0 | Organic Chemistry |
In sports where endurance is an important component in performance, such as road cycling, rowing, cross-country skiing, swimming, and long-distance running, world-class athletes typically have high V̇O max values. Elite male runners can consume up to 85 mL/(kg·min), and female elite runners can consume about 77 mL/(kg·min).
High values in absolute terms for humans may be found in rowers, as their greater bulk makes up for a slightly lower V̇O max per body weight. Elite oarsmen measured in 1984 had V̇O max values of 6.1±0.6 L/min and oarswomen 4.1±0.4 L/min. New Zealand sculler Rob Waddell has one of the highest absolute V̇O max levels ever tested. | 1 | Biochemistry |
Many other deoxyribozymes have since been developed that catalyze DNA phosphorylation, DNA adenylation, DNA deglycosylation, porphyrin metalation, thymine dimer photoreversion
and DNA cleavage. | 7 | Physical Chemistry |
In 1964, Israeli physician Jacob Sheskin administered thalidomide to a patient critically ill with leprosy. The patient exhibited erythema nodosum leprosum (ENL), a painful skin condition, one of the complications of leprosy. The treatment was attempted despite the ban on thalidomide's use, and results were favourable: the patient slept for hours and was able to get out of bed without aid upon awakening. A clinical trial studying the use of thalidomide in leprosy soon followed.
Thalidomide has been used by Brazilian physicians as the drug of choice for the treatment of severe ENL since 1965, and by 1996, at least 33 cases of thalidomide embryopathy were recorded in people born in Brazil after 1965. Since 1994, the production, dispensing, and prescription of thalidomide have been strictly controlled, requiring women to use two forms of birth control and submit to regular pregnancy tests. Despite this, cases of thalidomide embryopathy continue, with at least 100 cases identified in Brazil between 2005 and 2010. 5.8 million thalidomide pills were distributed throughout Brazil in this time period, largely to poor Brazilians in areas with little access to healthcare, and these cases have occurred despite the controls.
In 1998, the FDA approved the drugs use in the treatment of ENL. Because of thalidomides potential for causing birth defects, the drug may be distributed only under tightly controlled conditions. The FDA required that Celgene Corporation, which planned to market thalidomide under the brand name Thalomid, establish a system for thalidomide education and prescribing safety (STEPS) oversight program. The conditions required under the program include limiting prescription and dispensing rights to authorized prescribers and pharmacies only, keeping a registry of all patients prescribed thalidomide, providing extensive patient education about the risks associated with the drug, and providing periodic pregnancy tests for women who take the drug.
In 2010, the World Health Organization stated that it did not recommend thalidomide for leprosy due to the difficulty of adequately controlling its use, and due to the availability of clofazimine. | 4 | Stereochemistry |
Achieving balance in telomere length is challenging. While extended telomeres can reverse some aspects of cellular aging, excessively long telomeres may lead to cellular instability and dysfunction. It is important to strike the right balance to avoid unintended consequences. | 1 | Biochemistry |
FSL constructs have a wide range of uses and they have been used to modify the following:
* Cells – blood cells, culture lines, embryos, spermatozoa
* Viruses – influenza, measles, varicella
* Organisms – parasites, microbes, zebrafish
* Liposomes – also micelles, lipid particles
* Surfaces/fibres – hydrophobic or hydrophilic membranes/fibres, paper, nitrocellulose, cotton, silk, glass, Teflon, silica, magnetic beads (microspheres) etc.
* Solutions – saline, plasma/serum, culture media | 1 | Biochemistry |
* Chapter (Molecular Spectroscopy), Section (Vibration-rotation spectra) and page numbers may be different in different editions. | 7 | Physical Chemistry |
This is an assembly of three microchannel plates with channels aligned in a Z shape. Single MCPs can have gain up to 10,000 (40dB) but this system can provide gain more than 10 million (70dB). | 7 | Physical Chemistry |
Peptides can be cyclized on a solid support. A variety of cyclization reagents can be used such as HBTU/HOBt/DIEA, PyBop/DIEA, PyClock/DIEA. Head-to-tail peptides can be made on the solid support. The deprotection of the C-terminus at some suitable point allows on-resin cyclization by amide bond formation with the deprotected N-terminus. Once cyclization has taken place, the peptide is cleaved from resin by acidolysis and purified.
The strategy for the solid-phase synthesis of cyclic peptides is not limited to attachment through Asp, Glu or Lys side chains. Cysteine has a very reactive sulfhydryl group on its side chain. A disulfide bridge is created when a sulfur atom from one Cysteine forms a single covalent bond with another sulfur atom from a second cysteine in a different part of the protein. These bridges help to stabilize proteins, especially those secreted from cells. Some researchers use modified cysteines using S-acetomidomethyl (Acm) to block the formation of the disulfide bond but preserve the cysteine and the protein's original primary structure. | 1 | Biochemistry |
The CH vertices of closo-dicarbadodecaboranes undergo deprotonation upon treatment with organolithium reagents:
: CBH + 2 BuLi → LiCBH + 2 BuH
These dilithiated compounds react with a variety of electrophiles, e.g. chlorophosphines, chlorosilanes, and sulfur. Many of the same compounds can be produced by hydroboration of alkynes:
:LiCBH + 2 RX → RCBH + 2LiX
:LBH + RCR → RCBH + 2L (L = MeCN, etc.)
ortho-Carborane can be converted to highly reactive carborynes with the formula BCH. | 7 | Physical Chemistry |
Paper chromatography is an analytical method used to separate coloured chemicals or substances. It is now primarily used as a teaching tool, having been replaced in the laboratory by other chromatography methods such as thin-layer chromatography (TLC).
The setup has three components. The mobile phase is a solution that travels up the stationary phase by capillary action. The mobile phase is generally a mixture of non-polar organic solvent, while the stationary phase is polar inorganic solvent water. Here paper is used to support the stationary phase, water. Polar water molecules are held inside the void space of the cellulose network of the host paper. The difference between TLC and paper chromatography is that the stationary phase in TLC is a layer of adsorbent (usually silica gel, or aluminium oxide), and the stationary phase in paper chromatography is less absorbent paper.
A paper chromatography variant, two-dimensional chromatography, involves using two solvents and rotating the paper 90° in between. This is useful for separating complex mixtures of compounds having similar polarity, for example, amino acids. | 3 | Analytical Chemistry |
Chemical labeling or the use of chemical tags utilizes the interaction between a small molecule and a specific genetic amino acid sequence. Chemical labeling is sometimes used as an alternative for GFP. Synthetic proteins that function as fluorescent probes are smaller than GFPs, and therefore can function as probes in a wider variety of situations. Moreover, they offer a wider range of colors and photochemical properties. With recent advancements in chemical labeling, Chemical tags are preferred over fluorescent proteins due to the architectural and size limitations of the fluorescent proteins characteristic β-barrel. Alterations of fluorescent proteins would lead to loss of fluorescent properties. | 1 | Biochemistry |
Eszopiclone acts on benzodiazepine binding site situated on GABA neurons as a positive allosteric modulator.
Eszopiclone is rapidly absorbed after oral administration, with serum levels peaking between .45 and 1.3 hours. The elimination half-life of eszopiclone is approximately 6 hours and it is extensively metabolized by oxidation and demethylation. Approximately 52% to 59% of a dose is weakly bound to plasma protein. Cytochrome P450 (CYP) isozymes CYP3A4 and CYP2E1 are involved in the biotransformation of eszopiclone; thus, drugs that induce or inhibit these CYP isozymes may affect the metabolism of eszopiclone. Less than 10% of the orally administered dose is excreted in the urine as racemic zopiclone. In terms of benzodiazepine receptor binding and relevant potency, 3 mg of eszopiclone is equivalent to 10 mg of diazepam. | 4 | Stereochemistry |
Catastrophin (Catastrophe-related protein) is a term use to describe proteins that are associated with the disassembly of microtubules. Catastrophins affect microtubule shortening, a process known as microtubule catastrophe. | 1 | Biochemistry |
Compounds where phosphorus exists in a formal oxidation state of less than III are uncommon, but examples are known for each class. Organophosphorus(0) species are debatably illustrated by the carbene adducts, [P(NHC)], where NHC is an N-heterocyclic carbene. With the formulae (RP) and (RP), respectively, compounds of phosphorus(I) and (II) are generated by reduction of the related organophosphorus(III) chlorides:
:5 PhPCl + 5 Mg → (PhP) + 5 MgCl
:2 PhPCl + Mg → PhP-PPh + MgCl
Diphosphenes, with the formula RP, formally contain phosphorus-phosphorus double bonds. These phosphorus(I) species are rare but are stable provided that the organic substituents are large enough to prevent catenation. Many mixed-valence compounds are known, e.g. the cage P(CH). | 0 | Organic Chemistry |
VIPA was proposed and named by Shirasaki in 1996. Prior to the publication in the paper, a preliminary presentation was given by Shirasaki at a conference. This presentation was reported in Laser Focus World. The details of this new approach to producing angular dispersion were described in the patent. Since then, in the first ten years, the VIPA was of particular interest in the field of optical fiber communication technology. The VIPA was first applied to optical wavelength division multiplexing (WDM) and a wavelength demultiplexer was demonstrated for a channel spacing of 0.8 nm, which was a standard channel spacing at the time. Later, a much smaller channel separation of 24 pm and a 3 dB bandwidth of 6 pm were achieved by Weiner in 2005 at 1550 nm wavelength range. For another application, by utilizing the wavelength-dependent length of the light path due to the angular dispersion of the VIPA, the compensation of chromatic dispersion of fibers was studied and demonstrated (Shirasaki, 1997). The compensation was further developed for tunable systems by using adjustable mirrors or a spatial light modulator (Weiner, 2006). Using the VIPA, compensation of polarization mode dispersion was also achieved (Weiner, 2008). Furthermore, pulse shaping using the combination of a VIPA for high-resolution wavelength splitting/recombining and a SLM was demonstrated (Weiner, 2010).
A drawback of the VIPA is its limited free spectral range due to the high diffraction order. To expand the functional wavelength range, Shirasaki combined a VIPA with a regular diffraction grating in 1997 to provide a broadband two-dimensional spectral disperser. This configuration can be a high performance substitute for diffraction gratings in many grating applications. After the mid 2000s, the two-dimensional VIPA disperser has been used in various fields and devices, such as high-resolution WDM (Weiner, 2004), a laser frequency comb (Diddams, 2007), a spectrometer (Nugent-Glandorf, 2012), an astrophysical instrument (Le Coarer, 2017), Brillouin spectroscopy in biomechanics (Scarcelli, 2008, Rosa, 2018, and Margueritat, 2020), other Brillouin spectroscopy (Loubeyre, 2022 and Wu, 2023), beam scanning (Ford, 2008), microscopy (Jalali, 2009), tomography imaging (Ellerbee, 2014), metrology (Bhattacharya, 2015), fiber laser (Xu, 2020), LiDAR (Fu, 2021), and surface measurement (Zhu, 2022). | 7 | Physical Chemistry |
In organic chemistry, carbonyl allylation describes methods for adding an allyl anion to an aldehyde or ketone to produce a homoallylic alcohol. The carbonyl allylation was first reported in 1876 by Alexander Zaitsev and employed an allylzinc reagent. | 0 | Organic Chemistry |
Hess's Law states that the sum of the energy changes of all thermochemical equations included in an overall reaction is equal to the overall energy change. Since ΔH is a state function and is not dependent on how reactants become products as a result, steps (in the form of several thermochemical equations) can be used to find the ΔH of the overall reaction. For instance:
:Reaction 1: C + O → CO
This reaction is the result of two steps (a reaction sequence):
:C + ½O → CO
:ΔH = −110.5 kJ
:CO + ½O → CO
:ΔH = −283.0 kJ
Adding these two reactions together results in Reaction 1, which allows ΔH to be found, so whether or not agents in the reaction sequence are equal to each other is verified. The reaction sequences are then added together. In the following example, CO is not in Reaction 1 and equals another reaction.
:C + ½O + ½O → CO
and
:C + O → CO, Reaction (1)
To solve for ΔH, the ΔHs of the two equations in the reaction sequence are added together:
:(−110.5 kJ) + (−283.0 kJ) = (−393.5 kJ) = ΔH of Reaction (1)
Another example involving thermochemical equations is that when methane gas is combusted, heat is released, making the reaction exothermic. In the process, 890.4 kJ of heat is released, so the heat is written as a product of the reaction. | 7 | Physical Chemistry |
Since many algal blooms are caused by a major influx of nutrient-rich runoff into a water body, programs to treat wastewater, reduce the overuse of fertilizers in agriculture and reducing the bulk flow of runoff can be effective for reducing severe algal blooms at river mouths, estuaries, and the ocean directly in front of the river's mouth.
The nitrates and phosphorus in fertilizers cause algal blooms when they run off into lakes and rivers after heavy rains. Modifications in farming methods have been suggested, such as only using fertilizer in a targeted way at the appropriate time exactly where it can do the most good for crops to reduce potential runoff. A method used successfully is drip irrigation, which instead of widely dispersing fertilizers on fields, drip-irrigates plant roots through a network of tubes and emitters, leaving no traces of fertilizer to be washed away. Drip irrigation also prevents the formation of algal blooms in reservoirs for drinking water while saving up to 50% of water typically used by agriculture.
There have also been proposals to create buffer zones of foliage and wetlands to help filter out the phosphorus before it reaches water. Other experts have suggested using conservation tillage, changing crop rotations, and restoring wetlands. It is possible for some dead zones to shrink within a year under proper management.
There have been a few success stories in controlling chemicals. After Norway's lobster fishery collapsed in 1986 due to low oxygen levels, for instance, the government in neighboring Denmark took action and reduced phosphorus output by 80 percent which brought oxygen levels closer to normal. Similarly, dead zones in the Black Sea and along the Danube River recovered after phosphorus applications by farmers were reduced by 60%.
Nutrients can be permanently removed from wetlands harvesting wetland plants, reducing nutrient influx into surrounding bodies of water. Research is ongoing to determine the efficacy of floating mats of cattails in removing nutrients from surface waters too deep to sustain the growth of wetland plants.
In the U.S., surface runoff is the largest source of nutrients added to rivers and lakes, but is mostly unregulated under the federal Clean Water Act. Locally developed initiatives to reduce nutrient pollution are underway in various areas of the country, such as the Great Lakes region and the Chesapeake Bay. To help reduce algal blooms in Lake Erie, the State of Ohio presented a plan in 2016 to reduce phosphorus runoff. | 3 | Analytical Chemistry |
In mammals, the eIF4E•G•A trimeric complex can be directly purified from cells, while only the two subunit eIF4E•G can be purified from yeast cells. eIF4E binds the mG 5 cap and the eIF4G scaffold, connecting the mRNA 5 terminus to a hub of other initiation factors and mRNA. The interaction of eIF4G•A is thought to guide the formation of a single-stranded RNA landing pad for the 43S preinitiation complex (43S PIC) via eIF4A's RNA helicase activity.
The eIF4F proteins interact with a number of different binding partners, and there are multiple genetic isoforms of eIF4A, eIF4E, and eIF4G in the human genome. In mammals, eIF4F is bridged to the 40S ribosomal subunit by eIF3 via eIF4G, while budding yeast lacks this connection. Interactions between eIF4G and PABP are thought to mediate the circularization of mRNA particles.
Approximate molecular weight for human proteins.
In addition to the major proteins encompassing the eIF4F trimer, the eIF4F complex functionally interacts with proteins including eIF4B and eIF4H. The unusual isoform of eIF4G, eIF4G2 or DAP5, also appears to perform a non-canonical translation function. | 1 | Biochemistry |
One of the possible ways to measure the content of single cells is nano-DESI (nanospray desorption electrospray ionization). Unlike desorption electrospray ionization, which is a desorption technique, nano-DESI is a liquid extraction technique that enables the sampling of small surfaces, therefore suitable for single-cell analysis. In nano-DESI, two fused silica capillaries are set up in a V-shaped form, closing an angle of approx. 85 degrees. The two capillaries are touching therefore a liquid bridge can be formed between them and enable the sampling of surfaces as small as a single cell. The primary capillary delivers the solvent to the sample surface where the extraction happens and the secondary capillary directs the solvent with extracted molecules to the MS inlet. Nano-DESI mass spectrometry (MS) enables sensitive molecular profiling and quantification of endogenous species as small as a few hundred fmol-s in single cells in a higher throughput manner. Lanekoff et al. identified 14 amino acids, 6 metabolites, and several lipid molecules from single cheek cells using nano-DESI MS. | 1 | Biochemistry |
* Enerkem from Canada produces renewable Methanol with a capacity of 100 000 t/a. The methanol is produced from municipal solid waste.
* Celanese announced in May 2021 the plan to produce methanol from CO at site Clear Lake, Texas. Herefore 180 000 tons of CO per year shall be used. | 2 | Environmental Chemistry |
Diradicals are usually triplets. The phrases singlet and triplet are derived from the multiplicity of states of diradicals in electron spin resonance: a singlet diradical has one state (S = 0, M = 2*0+1 = 1, m = 0) and exhibits no signal in EPR and a triplet diradical has 3 states (S = 1, M = 2*1+1 = 3, m = -1; 0; 1) and shows in EPR 2 peaks (if no hyperfine splitting). The triplet state has total spin quantum number S = 1 and is paramagnetic. Therefore, diradical species display a triplet state when the two electrons are unpaired and display the same spin. When the unpaired electrons with opposite spin are antiferromagnetically coupled, diradical species can display a singlet state (S = 0) and be diamagnetic. | 0 | Organic Chemistry |
Fish emulsion is a fertilizer emulsion that is produced from the fluid remains of fish processed for fish oil and fish meal industrially. | 9 | Geochemistry |
Alkaline water electrolysis is a type of electrolyzer that is characterized by having two electrodes operating in a liquid alkaline electrolyte. Commonly, a solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH) at 25-40 wt% is used. These electrodes are separated by a diaphragm, separating the product gases and transporting the hydroxide ions (OH) from one electrode to the other. A recent comparison showed that state-of-the-art nickel based water electrolyzers with alkaline electrolytes lead to competitive or even better efficiencies than acidic polymer electrolyte membrane water electrolysis with platinum group metal based electrocatalysts.
The technology has a long history in the chemical industry. The first large-scale demand for hydrogen emerged in late 19th century for lighter-than-air aircraft, and before the advent of steam reforming in the 1930s, the technique was competitive. | 7 | Physical Chemistry |
Hammond died on January 6, 1908, aged 74. He is interred in Mount Auburn Cemetery, Cambridge, Massachusetts. | 8 | Metallurgy |
Bolaamphiphiles (also known as bolaform surfactants,
bolaphiles, or alpha-omega-type surfactants) are amphiphilic molecules that have hydrophilic groups at both ends of a sufficiently long hydrophobic hydrocarbon chain. Compared to single-headed amphiphiles, the introduction of a second head-group generally induces a higher solubility in water, an increase in the critical micelle concentration (cmc), and a decrease in aggregation number. The aggregate morphologies of bolaamphiphiles include spheres, cylinders, disks, and vesicles. Bolaamphiphiles are also known to form helical structures that can form monolayer microtubular self-assemblies. | 7 | Physical Chemistry |
In 2014, researchers at California NanoSystems Institute discovered using kesterite and perovskite improved electric power conversion efficiency for solar cells.
In December 2022, it was reported that MIT researchers had developed ultralight fabric solar cells. These cells offer a weight one-hundredth that of traditional panels while generating 18 times more power per kilogram. Thinner than a human hair, these cells can be laminated onto various surfaces, such as boat sails, tents, tarps, or drone wings, to extend their functionality. Using ink-based materials and scalable techniques, researchers coat the solar cell structure with printable electronic inks, completing the module with screen-printed electrodes. Tested on high-strength fabric, the cells produce 370 watts-per-kilogram, representing an improvement over conventional solar cells. | 7 | Physical Chemistry |
The first reported metallic glass was an alloy (AuSi) produced at Caltech by W. Klement (Jr.), Willens and Duwez in 1960. This and other early glass-forming alloys had to be cooled extremely rapidly (in the order of one mega-kelvin per second, 10 K/s) to avoid crystallization. An important consequence of this was that metallic glasses could only be produced in a limited number of forms (typically ribbons, foils, or wires) in which one or more dimensions were small so that heat could be extracted quickly enough to achieve the necessary cooling rates. As a result, metallic glass specimens (with a few exceptions) were limited to thicknesses of less than one hundred micrometers.
Mg-Zn-Ca based metallic glasses are a relatively new group of amorphous metals, possessing commercial and technical advantages over early compositions. Gu and co-workers produced the first Mg-Zn-Ca BMG in 2005, reporting high glass forming ability, high strength and most importantly exceptional plasticity. This lanthanide-free, Mg-based glass attracted immediate interest due to its low density and cost, and particularly because of its uncharacteristically high ductility. This property was unexpected for such compositions, as the constituent elements are found to be of relatively low Poisson ratio, and hence contribute little to the inherent plasticity of the glass. This unlikely asset was seized upon by Li in 2008, who made use of the Poisson ratio principle and increased Mg content at the expense of Zn to further enhance plasticity. Further improvements were achieved by incremental addition of Ca to the Mg72Zn28 binary composition, producing numerous ternary alloys along the 350 °C isotherm of the Mg-Zn-Ca system.
Ternary Ca-Mg-Zn bulk metallic glasses were also discovered in 2005. Similar to the Mg-Zn-Ca, these two amorphous alloys are both bioresorbable metallic glasses and are based on the same Mg-Zn-Ca ternary system. The elements are displayed in order of decreasing atomic concentration. Hence, the distinction between these two metallic glasses lies in their most dominant element, namely Ca and Mg. These Ca-based bulk glassy alloys had compositions of CaMgZn, CaMgZn, and CaMgZn, where X = 0, 5 and 10; Y = 0, 5, 7.5, 10, and 15; and Z = 0, 5, 7.5, 10, and 15. Critical casting thicknesses of up to 10 mm were achieved. | 8 | Metallurgy |
Archaea have variants of the Entner-Doudoroff Pathway. These variants are called the semiphosphorylative ED (spED) and the nonphosphorylative ED (npED):
* spED is found in halophilic euryachaea and Clostridium species.
* In spED, the difference is where phosphorylation occurs. In the standard ED, phosphorylation occurs at the first step from glucose to G-6-P. In spED, the glucose is first oxidized to gluconate via a glucose dehydrogenase. Next, gluconate dehydratase converts gluconate into 2-keto-3-deoxy-gluconate (KDG). The next step is where phosphorylation occurs as KDG kinase converts KDG into KDPG. KDPG is then cleaved into glyceraldehyde 3-phosphate (GAP) and pyruvate via KDPG aldolase and follows the same EMP pathway as the standard ED. This pathway produces the same amount of ATP as the standard ED.
* npED is found in thermoacidophilic Sulfolobus, Euryarchaeota Tp. acidophilum, and Picrophilus species.
* In npED, there is no phosphorylation at all. The pathway is the same as spED but instead of phosphorylation occurring at KDG, KDG is instead cleaved GA and pyruvate via KDG aldolase. From here, GA is oxidized via GA dehydrogenase into glycerate. The glycerate is phosphorylated by glycerate kinase into 2PG. 2PG then follows the same pathway as ED and is converted into pyruvate via ENO and PK. In this pathway though, there is no ATP produced.
Some archaea such as Crenacraeota Sul. solfacaricus and Tpt. tenax have what is called branched ED. In branched ED, the organism have both spED and npED that are both operative and work in parallel. | 1 | Biochemistry |
Sybren Otto (Groningen, 3 August 1971) is Professor of Systems chemistry at the Stratingh Institute for Chemistry, University of Groningen. | 0 | Organic Chemistry |
In humans, the Hex-mediated GnT-I-dependent truncation pathway is known to facilitate, at least in some tissues including neutrophils, the production of paucimannosidic proteins. Human Hex isoenzymes are assembled with alpha and beta subunits encoded by the HEXA and HEXB genes, respectively. From these two subunits, isoenzymes such as Hex A (one alpha and one beta subunit), Hex B (two beta subunits) and Hex S (two alpha subunits) are generated. Both Hex A and Hex B are reported to play important functional roles in human, particularly in the lysosomal degradation of gangliosides. Recently, both HEXA and HEXB were documented to mediate protein paucimannosylation in human neutrophils and may therefore also be the main driver for the elevated production of paucimannosidic proteins during cancer development. Recent in vitro observations have suggested other noncanonical truncation pathways with direct core fucosylation of paucimannosidic proteins in vertebrates, but this remains to be validated Hex A and Hex B isoenzymes are mainly present in the azurophilic granules of human neutrophils as a result of a proposed targeting-by-timing mechanism that supposedly directs these enzymes to this compartment during neutrophil development. Recently, granule-specific glycosylation was shown in neutrophils featuring prominent paucimannosylation in the azurophilic granules an observation that was suggested to arise from a "glycosylation-by-timing" mechanism yet to be documented. More widely across vertebrate species, the biosynthesis of paucimannosidic proteins remains largely unstudied. | 1 | Biochemistry |
There are two common types of paint used today. The first are water-based paints such as latex and acrylic paint, and the second are oil-based paints. The paint of choice will depend on the substrate to be painted upon and the desired end result. All paints have the same basic structure:
* Pigment – This is the part of the paint that is seen by the eye. The pigment gives the paint opacity and color. The pigments of all paints contain a white base composed of titanium dioxide (TiO) or zinc oxide (ZnO). Dyes are added to the pigment to attain the desired color.
*Binder – the binder is the glue that holds the paint together. This is usually a polymer that upon drying will polymerize to keep the pigments homogeneous and adhered to the substrate.
*Solvent – this is the bulk of the paint, it is used to keep the paint workable when it is wet. After paint is applied to a surface the solvent evaporates, the pigment and binder will coalesce together to form a uniform coating. The solvent is water for water-based paints, and an oil for oil-based paints.
There actually is no chemical bond between paint and an underlying surface. Paint adheres simply through physical forces like Van der Waals. When paint is first applied to a surface it goes on as a thick wet coating. As the solvent is allowed to evaporate out, the pigment plates which are attracted to one another stack up to form layers. The binder polymerizes essentially locking the pigment plates together. What remains is a uniform coating of binder and pigment. Anti-graffiti coatings make paints unable to adhere to the surface. | 7 | Physical Chemistry |
A Soxhlet extractor has three main sections: a percolator (boiler and reflux) which circulates the solvent, a thimble (usually made of thick filter paper) which retains the solid to be extracted, and a siphon mechanism, which periodically empties the condensed solvent from the thimble back into the percolator. | 3 | Analytical Chemistry |
Imipenem acts as an antimicrobial through inhibiting cell wall synthesis of various Gram-positive and Gram-negative bacteria. It remains very stable in the presence of β-lactamase (both penicillinase and cephalosporinase) produced by some bacteria, and is a strong inhibitor of β-lactamases from some Gram-negative bacteria that are resistant to most β-lactam antibiotics. | 4 | Stereochemistry |
Ions that hit the doorknob release secondary electrons. A high voltage (about ) between the doorknob and the scintillator accelerates the electrons onto the phosphor screen, where they are converted to photons. These photons are detected by the photomultiplier.
The advantage of the Daly detector is that the photomultiplier can be separated by a window, which lets the photons through from the high vacuum of the mass spectrometer, thus preventing an otherwise possible contamination and extending life span of the detector. The Daly detector also allows a higher acceleration after the field-free region of a time-of-flight mass spectrometer flight tube, which can improve the sensitivity for heavy ions. | 5 | Photochemistry |
Paired receptors transduce extracellular signals through opposing intracellular signaling pathways. Canonically, inhibitory receptors recruit phosphatases through their ITIM motifs, inhibiting the function of cells in which they are expressed. By contrast, activating receptors interact with adaptor proteins such as DAP-12 bearing an ITAM motif, which in turn recruit kinases such as Syk and ZAP70.
Ligands for paired receptors can be very diverse. They are often proteins; the best-characterized are the MHC class I molecules, but a number of other endogenous molecules have been described as ligands for at least one family of paired receptors, and in a few cases in the LILR family, even intact bacteria or viruses can serve as ligands. Lipids such as phosphatidylethanolamine and phosphatidylserine, sugars and sialylated glycans, and nucleic acids can all serve as ligands for some paired receptors.
The binding affinity of paired receptors' extracellular domains for their ligands is generally fairly weak, with dissociation constants (K) in the micromolar (μM) range. However, the inhibitory member of a pair usually binds with higher affinity than the activating member. This can produce a competitive inhibition effect, in which the inhibitory member of the pair out-competes its activating counterpart for ligand binding; other mechanisms of interference with activation, such as disrupting dimerization, have also been described. Thus the net baseline signal from the pair is usually inhibitory, but may be modulated through differences in expression, surface density, subcellular localization, or other factors.
In NK cells, ligands for inhibitory receptors are often MHC class I (MHC-I) molecules, while those for activating receptors may include signals of abnormality or infection such as proteins from pathogens or tumors, or molecules associated with cell stress. Endogenous ligands for inhibitory receptors are better characterized than those for activating receptors. Paired receptor signaling may represent maintenance of homeostasis such that immune responses to normal host cells are inhibited, while responses to abnormal or pathogenic molecules in the environment are activating. NK activation in the absence of inhibitory receptor signals from endogenous ligands is a molecular mechanism for the missing-self hypothesis of NK activation. | 1 | Biochemistry |
TADs are defined as regions whose DNA sequences preferentially contact each other. They were discovered in 2012 using chromosome conformation capture techniques including Hi-C. They have been shown to be present in multiple species, including fruit flies (Drosophila), mouse, plants, fungi and human genomes. In bacteria, they are referred to as Chromosomal Interacting Domains (CIDs). | 1 | Biochemistry |
Earths core is believed to be mostly an alloy of iron and nickel. The density indicates that it also contains a significant amount of lighter elements. Elements such as hydrogen would be stable in the Earths core, however the conditions at the formation of the core would not be suitable for its inclusion. Carbon is a very likely constituent of the core. Preferential partitioning of the carbon isotopeC into the metallic core, during its formation, may explain why there seems to be more C on the surface and mantle of the Earth compared to other solar system bodies (−5‰ compared to -20‰). The difference can also help to predict the value of the carbon proportion of the core.
The outer core has a density around 11 cm, and a mass of 1.3×10kg. It contains roughly 10 kg of carbon.
Carbon dissolved in liquid iron affect the solution of other elements. Dissolved carbon changes lead from a siderophile to a lithophile. It has the opposite effect on tungsten and molybdenum, causing more tungsten or molybdenum to dissolve in the metallic phase. The measured amounts of these elements in the rocks compared to the Solar System can be explained by a 0.6% carbon composition of the core.
The inner core is about 1221 km in radius. It has a density of 13 g cm, and a total mass of 9×10 kg and a surface area of 18,000,000 square kilometers. Experiments with mixtures under pressure and temperature attempt to reproduce the known properties of the inner and outer core. Carbides are among the first to precipitate from a molten metal mix, and so the inner core may be mostly iron carbides, FeC or FeC. At atmospheric pressure (100 kPa) the iron-FeC eutectic point is at 4.1% carbon. This percentage decreases as pressure increases to around 50 GPa. Above that pressure the percentage of carbon at the eutectic increases. The pressure on the inner core ranges from 330 GPa to 360 GPa at the centre of the Earth. The temperature at the inner core surface is about 6000 K. The material of the inner core must be stable at the pressure and temperature found there, and more dense than that of the outer core liquid. Extrapolations show that either FeC or FeC match the requirements. FeC is 8.4% carbon, and FeC is 6.7% carbon. The inner core is growing by about 1 mm per year, or adding about 18 cubic kilometres per year. This is about 18×10kg of carbon added to the inner core every year. It contains about 8×10 kg of carbon. | 9 | Geochemistry |
In chemistry, mechanically interlocked molecular architectures (MIMAs) are molecules that are connected as a consequence of their topology. This connection of molecules is analogous to keys on a keychain loop. The keys are not directly connected to the keychain loop but they cannot be separated without breaking the loop. On the molecular level, the interlocked molecules cannot be separated without the breaking of the covalent bonds that comprise the conjoined molecules; this is referred to as a mechanical bond. Examples of mechanically interlocked molecular architectures include catenanes, rotaxanes, molecular knots, and molecular Borromean rings. Work in this area was recognized with the 2016 Nobel Prize in Chemistry to Bernard L. Feringa, Jean-Pierre Sauvage, and J. Fraser Stoddart.
The synthesis of such entangled architectures has been made efficient by combining supramolecular chemistry with traditional covalent synthesis, however mechanically interlocked molecular architectures have properties that differ from both "supramolecular assemblies" and "covalently bonded molecules". The terminology "mechanical bond" has been coined to describe the connection between the components of mechanically interlocked molecular architectures. Although research into mechanically interlocked molecular architectures is primarily focused on artificial compounds, many examples have been found in biological systems including: cystine knots, cyclotides or lasso-peptides such as microcin J25 which are proteins, and a variety of peptides. | 6 | Supramolecular Chemistry |
Researchers at the Center for Exploitation of Solar Energy at the University of Copenhagen Department of Chemistry are studying the photochromic dihydroazulene–vinylheptafulvene system as a method to harvest and store solar energy. | 5 | Photochemistry |
The most widely used tensile test method is used to characterize the mechanical properties of materials. From any complete tensile test record, one can obtain important information about the materials elastic properties, the character and extent of plastic deformation, yield, and tensile strengths and toughness. The information obtained from one test justifies the extensive use of tensile tests in engineering materials research. Therefore, investigations of EMR emissions are mainly based on the tensile test of the specimens. From experiments, it can be shown that tensile crack formation excites more intensive EMR than shear cracking, increasing the elasticity, strength, and loading rate during uniaxial loading increases amplitude. Poissons ratio is a key parameter for EMR characterization during triaxial compression. If the Poisson's ratio is lower, it is harder for the material to strain transversally and hence there is a higher probability of new fractures. | 5 | Photochemistry |
* Barium chloride tests for sulfates
* Acidified silver nitrate solution tests for halide ions
* The Beilstein test tests for halides qualitatively
* The bead test tests for certain metals
* The Carius halogen method measures halides quantitatively.
* Chemical tests for cyanide test for the presence of cyanide, CN
* Copper sulfate tests for the presence of water
* Flame tests test for metals
* The Gilman test tests for the presence of a Grignard reagent
* The Kjeldahl method quantitatively determines the presence of nitrogen
* Nessler's reagent tests for the presence of ammonia
* Ninhydrin tests for ammonia or primary amines
* Phosphate tests test for phosphate
* The sodium fusion test tests for the presence of nitrogen, sulfur, and halides in a sample
* The Zerewitinoff determination tests for any acidic hydrogen
* The Oddy test tests for acid, aldehydes, and sulfides
* Gunzberg's test tests for the presence of hydrochloric acid
* Kelling's test tests for the presence of lactic acid | 3 | Analytical Chemistry |
Mukaiyama became an assistant professor at the Tokyo Institute of Technology in 1958 and earned his full professorship in 1963. During this time, his main focus was on organophosphorus chemistry. While examining deoxygenation reactions involving phosphines, Mukaiyama found that the mercury(II) acetate employed as a catalyst would react with phosphorus(III) compounds to produce acetic anhydride. This initial example expanded into the concept of the redox condensation reaction, in which a weak acid and weak base catalyze a condensation by means of a redox reaction – this would become a primary research focus for Mukaiyama for much of his career. In the original reaction, the phosphine served as the reducing agent by accepting oxygen, while the mercury(II) was the oxidation agent that accepted hydrogens, resulting in the condensation of carboxylic acids with the loss of a molecule of water.
This framework was expanded to include the formation of a variety of other functional groups, including esters and amides, but the most significant was the synthesis of phosphoric esters using DEAD and an alcohol in 1967. The same year that paper was published, Mukaiyama's co-author and former student Oyo Mitsunobu attacked the products of the reaction with a carboxylic acid in the presence of triphenylphosphine to yield an ester, creating what is now known as the Mitsunobu reaction. | 0 | Organic Chemistry |
The copper is of high purity, although earlier examples are sometimes composed of arsenical copper. Tylecote suggested that they are not primary smelting products and instead were refined and recast. The macrostructure of a half section example from Gillan, Cornwall shows a columnar structure that probably indicates slow cooling in a reheating furnace or a warm mold, rather than from pouring into a cold mold. | 8 | Metallurgy |
Manufacturing or fabrication errors occur during the processing of the material or component. For metal parts, casting defects are common, such as cold shut, hot tears or slag inclusions. It can also be surface treatment problems, processing parameters such as ramming a sand mold or wrong temperature during hardening. | 8 | Metallurgy |
Denaturing High Performance Liquid Chromatography (DHPLC) is a method of chromatography for the detection of base substitutions, small deletions or insertions in the DNA. Thanks to its speed and high resolution, this method is particularly useful for finding polymorphisms in DNA.
In practice, the analysis begins with a standard PCR in order to amplify the fragment of interest. If the amplified region that exhibits the polymorphism(s) is heterozygous, two kinds of fragments corresponding to the allele and the wild polymorphic allele will be present in the PCR product. This first step is followed by a step of denaturation–renaturation to create hetero- and homoduplexes from the two allele populations in the PCR. To find a homozygous polymorphism, proceed in the same way by premixing a DNA wild population to a population of polymorphic DNA to obtain heteroduplexes after the denaturation–renaturation step.
Heteroduplexes are actually double strands of DNA containing a strand from the wild-type allele and a sprig from the polymorphic allele. The formation of such DNA fragments then causes the appearance of a "mismatch" or bad pairing where the polymorphism is located.
These "mismatches" in the heteroduplex are the basis for the polymorphism detection by DHPLC. Heteroduplexes are thermally less stable than their corresponding homoduplexes, and the single DNA strands will therefore be disconnected by chromatography when subjected to a sufficiently high temperature. The consequence of this double strand instability will be a mismatch of the two DNA strands in the region of polymorphism when DNA is heated to the DNA melting temperature. This mismatch will therefore decrease the interaction with the column and will result in a reduced retention time compared to the homoduplexes in the chromatographic separation process.
To observe the phenomenon of separation, the DHPLC method uses a column of a non-grafted porous stationary phase composed of polystyrene-divinylbenzene alkyl. The stationary phase is electrically neutral and hydrophobic. The DNA, however, is negatively charged at its phosphate groups and therefore can adsorb itself on the column. In order to make the adsorption possible, triethylammonium acetate (TEAA) is used. The positively charged ammonium ion of these molecules interacts with the DNA, and the alkyl chain with the hydrophobic surface of the solid phase.
Therefore, when heteroduplexes are partially denaturated by heating, the negative charges undergo partial relocation and the interaction force between DNA heteroduplexes and column decreases in comparison to the strength of interaction of the homoduplexes. These will therefore be eluted less rapidly by the mobile phase (consisting of acetonitrile). | 3 | Analytical Chemistry |
Jehle pointed out that, when immersed in a liquid and intermingled with other molecules, charge fluctuation forces favor the association of identical molecules as nearest neighbors. In accord with this principle, the multiple copies of a polypeptide encoded by a gene often undergo molecular recognition with each other to form an ordered multi-polypeptide protein structure. When such a protein is formed from polypeptides produced by two different mutant alleles of a particular gene, the protein composed of a mixture of polypeptides may exhibit greater functional activity than the multi-polypeptide protein formed by each of the mutants alone. In such a case, the phenomenon is referred to as intragenic complementation.
Intragenic complementation (also called inter-allelic complementation) has been demonstrated in many different genes in a variety of organisms. Crick and Orgel analyzed of the results of such studies and came to the conclusion that intragenic complementation, in general, arises from the interaction of differently defective polypeptide monomers when they form an ordered aggregate they called a “multimer.” | 6 | Supramolecular Chemistry |
Many alkoxides can be prepared by anodic dissolution of the corresponding metals in water-free alcohols in the presence of electroconductive additive. The metals may be Co, Ga, Ge, Hf, Fe, Ni, Nb, Mo, La, Re, Sc, Si, Ti, Ta, W, Y, Zr, etc. The conductive additive may be lithium chloride, quaternary ammonium halide, or other. Some examples of metal alkoxides obtained by this technique: , , , , , , and . | 0 | Organic Chemistry |
Freezing is a common method of food preservation that slows both food decay and the growth of micro-organisms. Besides the effect of lower temperatures on reaction rates, freezing makes water less available for bacteria growth. Freezing is one of the oldest and most widely used methods of food preservation; since as long ago as 1842, freezing has been used in an ice and salt brine. In freezing, flavours, smell and nutritional content generally remain unchanged. Freezing became commercially applicable after the advent (introduction) of mechanical refrigeration. Freezing has been successfully employed for long term preservation of many foods providing a significantly extended shelf-life. Freezing preservation is generally regarded as superior to canning and dehydration with respect to retention in sensory attributes and nutritive attributes. | 1 | Biochemistry |
Some histidine kinases are hybrids that contain an internal receiver domain. In these cases, a hybrid HK autophosphorylates and then transfers the phosphoryl group to its own internal receiver domain, rather than to a separate RR protein. The phosphoryl group is then shuttled to histidine phosphotransferase (HPT) and subsequently to a terminal RR, which can evoke the desired response. This system is called a phosphorelay. Almost 25% of bacterial HKs are of the hybrid type, as are the large majority of eukaryotic HKs. | 1 | Biochemistry |
The electronegativity of an atom changes depending on the hybridization of the orbital employed in bonding. Electrons in s orbitals are held more tightly than electrons in p orbitals. Hence, a bond to an atom that employs an sp hybrid orbital for bonding will be more heavily polarized to that atom when the hybrid orbital has more s character. That is, when electronegativities are compared for different hybridization schemes of a given element, the order holds (the trend should apply to non-integer hybridization indices as well). While this holds true in principle for any main-group element, values for the hybridization-specific electronegativity are most frequently cited for carbon. In organic chemistry, these electronegativities are frequently invoked to predict or rationalize bond polarities in organic compounds containing double and triple bonds to carbon. | 3 | Analytical Chemistry |
Fresh blastocyst (day 5 to 6) stage transfer seems to be more effective than cleavage (day 2 or 3) stage transfer in assisted reproductive technologies. The Cochrane study showed a small improvement in live birth rate per couple for blastocyst transfers. This would mean that for a typical rate of 31% in clinics that use early cleavage stage cycles, the rate would increase to 32% to 41% live births if clinics used blastocyst transfer. Recent systematic review showed that along with selection of embryo, the techniques followed during transfer procedure may result in successful pregnancy outcome. The following interventions are supported by the literature for improving pregnancy rates:
Abdominal ultrasound guidance for embryo transfer
Removal of cervical mucus
Use of soft embryo transfer catheters
Placement of embryo transfer tip in the upper or middle (central) area of the uterine cavity, greater than 1 cm from the fundus, for embryo expulsion
Immediate ambulation once the embryo transfer procedure is completed | 1 | Biochemistry |
The Green Revolution of the 1960s and 70s introduced sturdier plants that could support the heavier grain loads resulting from intensive fertilizer use. Pesticide imports by 11 Southeast Asian countries grew nearly sevenfold in value between 1990 and 2010, according to FAO statistics, with disastrous results. Rice farmers become accustomed to spraying soon after planting, triggered by signs of the leaf folder moth, which appears early in the growing season. It causes only superficial damage and doesnt reduce yields. In 1986, Indonesia banned 57 pesticides and completely stopped subsidizing their use. Progress was reversed in the 2000s, when growing production capacity, particularly in China, reduced prices. Rice production in Asia more than doubled. But it left farmers believing more is better—whether it's seed, fertilizer, or pesticides.
The brown planthopper, Nilaparvata lugens, the farmers' main target, has become increasingly resistant. Since 2008, outbreaks have devastated rice harvests throughout Asia, but not in the Mekong Delta. Reduced spraying allowed natural predators to neutralize planthoppers in Vietnam. In 2010 and 2011, massive planthopper outbreaks hit 400,000 hectares of Thai rice fields, causing losses of about $64 million. The Thai government is now pushing the "no spray in the first 40 days" approach.
By contrast early spraying kills frogs, spiders, wasps and dragonflies that prey on the later-arriving and dangerous planthopper and produced resistant strains. Planthoppers now require pesticide doses 500 times greater than originally. Overuse indiscriminately kills beneficial insects and decimates bird and amphibian populations. Pesticides are suspected of harming human health and became a common means for rural Asians to commit suicide.
In 2001, scientists challenged 950 Vietnamese farmers to try IPM. In one plot, each farmer grew rice using their usual amounts of seed and fertilizer, applying pesticide as they chose. In a nearby plot, less seed and fertilizer were used and no pesticides were applied for 40 days after planting. Yields from the experimental plots was as good or better and costs were lower, generating 8% to 10% more net income. The experiment led to the "three reductions, three gains" campaign, claiming that cutting the use of seed, fertilizer and pesticide would boost yield, quality and income. Posters, leaflets, TV commercials and a 2004 radio soap opera that featured a rice farmer who gradually accepted the changes. It didnt hurt that a 2006 planthopper outbreak hit farmers using insecticides harder than those who didnt. Mekong Delta farmers cut insecticide spraying from five times per crop cycle to zero to one.
The Plant Protection Center and the International Rice Research Institute (IRRI) have been encouraging farmers to grow flowers, okra and beans on rice paddy banks, instead of stripping vegetation, as was typical. The plants attract bees and a tiny wasp that eats planthopper eggs, while the vegetables diversify farm incomes.
Agriculture companies offer bundles of pesticides with seeds and fertilizer, with incentives for volume purchases. A proposed law in Vietnam requires licensing pesticide dealers and government approval of advertisements to prevent exaggerated claims. Insecticides that target other pests, such as Scirpophaga incertulas (stem borer), the larvae of moth species that feed on rice plants allegedly yield gains of 21% with proper use. | 9 | Geochemistry |
When a defective gene causes gaps to appear in the metabolic recycling process for purines and pyrimidines, these chemicals are not metabolised properly, and adults or children can suffer from any one of twenty-eight hereditary disorders, possibly some more as yet unknown. Symptoms can include gout, anaemia, epilepsy, delayed development, deafness, compulsive self-biting, kidney failure or stones, or loss of immunity.
Purine metabolism can have imbalances that can arise from harmful nucleotide triphosphates incorporating into DNA and RNA which further lead to genetic disturbances and mutations, and as a result, give rise to several types of diseases. Some of the diseases are:
#Severe immunodeficiency by loss of adenosine deaminase.
#Hyperuricemia and Lesch–Nyhan syndrome by the loss of hypoxanthine-guanine phosphoribosyltransferase.
#Different types of cancer by an increase in the activities of enzymes like IMP dehydrogenase. | 1 | Biochemistry |
Different related definitions of an ideal solution have been proposed. The simplest definition is that an ideal solution is a solution for which each component obeys Raoult's law for all compositions. Here is the vapor pressure of component above the solution, is its mole fraction and is the vapor pressure of the pure substance at the same temperature.
This definition depends on vapor pressure, which is a directly measurable property, at least for volatile components. The thermodynamic properties may then be obtained from the chemical potential μ (which is the partial molar Gibbs energy g) of each component. If the vapor is an ideal gas,
The reference pressure may be taken as = 1 bar, or as the pressure of the mix, whichever is simpler.
On substituting the value of from Raoult's law,
This equation for the chemical potential can be used as an alternate definition for an ideal solution.
However, the vapor above the solution may not actually behave as a mixture of ideal gases. Some authors therefore define an ideal solution as one for which each component obeys the fugacity analogue of Raoult's law . Here is the fugacity of component in solution and is the fugacity of as a pure substance. Since the fugacity is defined by the equation
this definition leads to ideal values of the chemical potential and other thermodynamic properties even when the component vapors above the solution are not ideal gases. An equivalent statement uses thermodynamic activity instead of fugacity. | 7 | Physical Chemistry |
Normal glass does not transmit below 350 nm, so it is not used for optics in solar-blind systems. Instead calcium fluoride, fused silica, and magnesium fluoride are used as they are transparent to shorter wavelengths. | 5 | Photochemistry |
Genetic evidence suggesting that RNAP was the target of ppGpp came from the discovery that M+ mutants (also called stringent RNAP mutants) display in vitro and in vivo mimicry of physiology and transcription regulation conferred by (p)ppGpp, even in its absence. Cross-linking ppGpp to RNAP reinforced this notion. Structural details of an association between ppGpp and RNAP came from the analysis of cocrystals that positioned ppGpp in the secondary channel of RNAP near the catalytic center. | 1 | Biochemistry |
Syngenta was the Chinese owned worldwide leader in agrochemical sales in 2013 at approximately US$10.9 billion, followed by Bayer CropScience, BASF, Dow AgroSciences, Monsanto, and then DuPont with about $3.6 billion. It is still in the worldwide leading position based on sales of year 2019. Based on a statistics by statistica, In 2019, the agrochemical market worldwide was worth approximately $234.2 billion. This is expected to increase to more than $300 billion in 2025. | 2 | Environmental Chemistry |
The term dross derives from the Old English word dros, meaning the scum produced when smelting metals (extracting them from their ores). By the 15th century it had come to refer to rubbish in general. Dregs, and the geological term druse are also thought to be etymologically related. Popular non-metalworking uses of the word are derogatory:
*poorly written or plagiarized journalism - "a dross article"; "utter/complete/terrible dross" (adjective/noun), a stronger term than filler
*undesirable, unprofitable work - "lets hone in on the lions share and outsource the dross"; synonyms: corvée, hiding-to-nothing, and drudgery which are growing archaisms in business (noun); as strong a term as dogsbody work | 8 | Metallurgy |
Fluctuation electron microscopy is another transmission electron microscopy based technique that is sensitive to the medium range order of amorphous materials. Structural fluctuations arising from different forms of medium range order can be detected with this method. Fluctuation electron microscopy experiments can be done in conventional or scanning transmission electron microscope mode. | 7 | Physical Chemistry |
SCORE is especially used as detection method in bio- and chemosensors. It is a label-free technique like Reflectometric interference spectroscopy (RIfS), Bio-layer Interferometry (BLI) and Surface plasmon resonance (SPR), which allows time-resolved observation of binding events on the sensor surface without the use of fluorescence or radioactive labels.
The SCORE technology was commercialised by Biametrics GmbH, a service provider and instrument manufacturer with headquarters in Tübingen, Germany. In January 2020, Biametrics GmbH and its technology was acquired by BioCopy Holding AG, headquartered in Aadorf, Switzerland. | 7 | Physical Chemistry |
A promiscuous activity is a non-native activity the enzyme did not evolve to do, but arises due to an accommodating conformation of the active site. However, the main activity of the enzyme is a result not only of selection towards a high catalytic rate towards a particular substrate to produce a particular product, but also to avoid the production of toxic or unnecessary products. For example, if a tRNA syntheses loaded an incorrect amino acid onto a tRNA, the resulting peptide would have unexpectedly altered properties, consequently to enhance fidelity several additional domains are present. Similar in reaction to tRNA syntheses, the first subunit of tyrocidine synthetase (tyrA) from Bacillus brevis adenylates a molecule of phenylalanine in order to use the adenyl moiety as a handle to produce tyrocidine, a cyclic non-ribosomal peptide. When the specificity of enzyme was probed, it was found that it was highly selective against natural amino acids that were not phenylalanine, but was much more tolerant towards unnatural amino acids. Specifically, most amino acids were not catalysed, whereas the next most catalysed native amino acid was the structurally similar tyrosine, but at a thousandth as much as phenylalanine, whereas several unnatural amino acids where catalysed better than tyrosine, namely D-phenylalanine, β-cyclohexyl-L-alanine, 4-amino-L-phenylalanine and L-norleucine.
One peculiar case of selected secondary activity are polymerases and restriction endonucleases, where incorrect activity is actually a result of a compromise between fidelity and evolvability. For example, for restriction endonucleases incorrect activity (star activity) is often lethal for the organism, but a small amount allows new functions to evolve against new pathogens. | 1 | Biochemistry |
It has been suggested that nitrogen removal by oyster reefs could generate net benefits for sources facing nitrogen emission restrictions, similar to other nutrient trading scenarios. Specifically, if oysters maintain nitrogen levels in estuaries below thresholds that would lead to the imposition of emission limits, oysters effectively save the sources the compliance costs they otherwise would incur. Several studies have shown that oysters and mussels have the capacity to dramatically impact nitrogen levels in estuaries. Filter feeding activity is considered beneficial to water quality by controlling phytoplankton density and sequestering nutrients, which can be removed from the system through shellfish harvest, buried in the sediments, or lost through denitrification. Foundational work toward the idea of improving marine water quality through shellfish cultivation was conducted by Odd Lindahl et al., using mussels in Sweden. In the United States, shellfish restoration projects have been conducted on the East, West and Gulf coasts. | 2 | Environmental Chemistry |
The fine chemical industry has undergone several boom and bust phases during its almost 30 years of existence. The biggest boom took place in the late 1990s, when high-dosage, high volume anti-AIDS drugs and COX-2 inhibitors gave a big boost to custom manufacturing. After the end of the "irrational exuberance" in 2000, the industry suffered a first bust in 2003, as a result of capacity expansions, the advent of Asian competitors and a ruinous M&A activity, several billion dollars of shareholder value were destroyed. The most recent –minor- boom is associated with stockpiling of GlaxoSmithKlines Relenza (zanamivir) and Roches Tamiflu (oseltamivir phosphate) by many countries in order to prepare for a possible avian flu epidemic. Surprisingly, the main cause for the 2009 slump had not been the general recession, but slow-downs of the growth and, even more so, inventory adjustments by the pharma industry. They resulted in postponements or cancellations of orders. The unfavorable development was in sharp contrast to the very optimistic growth forecasts, which many fine chemical companies, had announced. They had been based on equally promising sector reports from investment banks, which in turn had evolved from forward projections of the preceding boom period. In most cases, these projections have been missed by a large margin.
At the end of the "irrational exuberance" at the turn of the millennium and again in 2009 almost half of the industry achieved a return on sales (ROS) of more than 10%, and less than 10% an ROS below 5%. In the worst years, 2003 and 2009, almost half of the companies suffered from an ROS of less than 5%. Whereas during the period under review, 2000–2009. the average EBITDA / sales and EBIT / sales ratios of representative companies, resp. divisions were 15% and 7%, respectively, in the period 2000–2009, the numbers were 20% and 10–13% in the boom, and 10% and 5% in the bust phases. The factor 2 between the high and low numbers reflects the volatility of the industry's profitability. All in all, the average Western fine-chemical firms have been making a return below the cost of capital, i.e. they are not reinvestment grade. | 0 | Organic Chemistry |
Because of its mineral complexity and coarse grain size, sel gris can be used both as a cooking salt and a finishing salt. Being much denser than table and kosher salt, there is a lot more salt in an equivalent volume of sel gris.
Because it is a moist salt, it does not suck all the moisture out of food when used as a finishing salt, unlike kosher salt (which is designed to absorb blood and other fluids from meat). | 9 | Geochemistry |
The catalytic properties of eukaryotic complex I are not simple. Two catalytically and structurally distinct forms exist in any given preparation of the enzyme: one is the fully competent, so-called “active” A-form and the other is the catalytically silent, dormant, “inactive”, D-form. After exposure of idle enzyme to elevated, but physiological temperatures (>30 °C) in the absence of substrate, the enzyme converts to the D-form. This form is catalytically incompetent but can be activated by the slow reaction (k~4 min) of NADH oxidation with subsequent ubiquinone reduction. After one or several turnovers the enzyme becomes active and can catalyse physiological NADH:ubiquinone reaction at a much higher rate (k~10 min). In the presence of divalent cations (Mg, Ca), or at alkaline pH the activation takes much longer.
The high activation energy (270 kJ/mol) of the deactivation process indicates the occurrence of major conformational changes in the organisation of the complex I. However, until now, the only conformational difference observed between these two forms is the number of cysteine residues exposed at the surface of the enzyme. Treatment of the D-form of complex I with the sulfhydryl reagents N-Ethylmaleimide or DTNB irreversibly blocks critical cysteine residues, abolishing the ability of the enzyme to respond to activation, thus inactivating it irreversibly. The A-form of complex I is insensitive to sulfhydryl reagents.
It was found that these conformational changes may have a very important physiological significance. The inactive, but not the active form of complex I was susceptible to inhibition by nitrosothiols and peroxynitrite. It is likely that transition from the active to the inactive form of complex I takes place during pathological conditions when the turnover of the enzyme is limited at physiological temperatures, such as during hypoxia, ischemia or when the tissue nitric oxide:oxygen ratio increases (i.e. metabolic hypoxia). | 1 | Biochemistry |
The Henderson–Hasselbalch equation, when applied to the carbonic acid-bicarbonate buffer system in the extracellular fluids, states that:
where:
* is the negative logarithm (or cologarithm) of molar concentration of hydrogen ions in the extracellular fluid.
* is the cologarithm of the acid dissociation constant of carbonic acid. It is equal to 6.1.
* is the molar concentration of bicarbonate in the blood plasma.
* is the molar concentration of carbonic acid in the extracellular fluid.
However, since the carbonic acid concentration is directly proportional to the partial pressure of carbon dioxide () in the extracellular fluid, the equation can be rewritten as follows:
where:
* is the negative logarithm of molar concentration of hydrogen ions in the extracellular fluid.
* is the molar concentration of bicarbonate in the plasma.
* is the partial pressure of carbon dioxide in the blood plasma.
The pH of the extracellular fluids can thus be controlled by the regulation of and the other metabolic acids. | 7 | Physical Chemistry |
This way compares with to compare the effects of the imposed the change with and without moderation. The protocol prevents moderation by enforcing that through an adjustment and it observes the no-moderation response Provided that the observed response is indeed that then the principle states that .
In other words, change in the moderating state variable moderates the effect of the driving change in on the responding conjugate variable | 7 | Physical Chemistry |
In applications, typically represents the "true" distribution of data, observations, or a precisely calculated theoretical distribution, while typically represents a theory, model, description, or approximation of . In order to find a distribution that is closest to , we can minimize the KL divergence and compute an information projection.
While it is a statistical distance, it is not a metric, the most familiar type of distance, but instead it is a divergence. While metrics are symmetric and generalize linear distance, satisfying the triangle inequality, divergences are asymmetric and generalize squared distance, in some cases satisfying a generalized Pythagorean theorem. In general does not equal , and the asymmetry is an important part of the geometry. The infinitesimal form of relative entropy, specifically its Hessian, gives a metric tensor that equals the Fisher information metric; see . Relative entropy satisfies a generalized Pythagorean theorem for exponential families (geometrically interpreted as dually flat manifolds), and this allows one to minimize relative entropy by geometric means, for example by information projection and in maximum likelihood estimation.
The relative entropy is the Bregman divergence generated by the negative entropy, but it is also of the form of an -divergence. For probabilities over a finite alphabet, it is unique in being a member of both of these classes of statistical divergences. | 7 | Physical Chemistry |
The first implementation of a/LCI used a Michelson interferometer, the same model used in the famous Michelson–Morley experiment. The Michelson interferometer splits one beam of light into two paths, one reference path and one sampling path, and recombines them again to produce a waveform resulting from interference. The difference between the reference beam and the sampling beam thus reveal the properties of the sample in the way it scatters light.
The early a/LCI device used a movable mirror and lens in the reference arm so that researchers could replicate different angles and depths in the reference beam as they occurred in the collected backscattered light. This allowed isolation of the backscattered light at varying depths of reflection in the sample.
In order to transform the data into measurements of cell structure, angular scattering distributions are then compared to the predictions of Mie theory—which calculates the size of spheres relative to their light scattering patterns.
The a/LCI technique was first validated in studies of polystyrene microspheres, the sizes of which were known and relatively homogeneous. A later study expanded the signal processing method to compensate for the nonspherical and inhomogeneous nature of cell nuclei.
This early system required up to 40 minutes to acquire the data for a 1 mm² point in a sample, but proved the feasibility of the idea. | 7 | Physical Chemistry |
In 2020, the FDA granted orphan drug designation RT001 for the treatment of patients with progressive supranuclear palsy (PSP). PSP is a disease involving modification and dysfunction of tau protein; RT001's mechanism of action both lowers lipid peroxidation and prevents mitochondrial cell death of neurons which is associated with disease onset and progression. | 1 | Biochemistry |
Another application of sputtering is to etch away the target material. One such example occurs in secondary ion mass spectrometry (SIMS), where the target sample is sputtered at a constant rate. As the target is sputtered, the concentration and identity of sputtered atoms are measured using mass spectrometry. In this way the composition of the target material can be determined and even extremely low concentrations (20 µg/kg) of impurities detected. Furthermore, because the sputtering continually etches deeper into the sample, concentration profiles as a function of depth can be measured. | 7 | Physical Chemistry |
Thermodynamic stability applies to a particular system. The reactivity of a chemical substance is a description of how it might react across a variety of potential chemical systems and, for a given system, how fast such a reaction could proceed.
Chemical substances or states can persist indefinitely even though they are not in their lowest energy state if they experience metastability - a state which is stable only if not disturbed too much. A substance (or state) might also be termed "kinetically persistent" if it is changing relatively slowly (and thus is not at thermodynamic equilibrium, but is observed anyway). Metastable and kinetically persistent species or systems are not considered truly stable in chemistry. Therefore, the term chemically stable should not be used by chemists as a synonym of unreactive because it confuses thermodynamic and kinetic concepts. On the other hand, highly chemically unstable species tend to undergo exothermic unimolar decompositions at high rates. Thus, high chemical instability may sometimes parallel unimolar decompositions at high rates. | 7 | Physical Chemistry |
In 1890, , a 28-year-old assistant in Berlin, published instructions for folding a piece of paper to represent two forms of cyclohexane he called symmetrical and asymmetrical (what we would now call chair and boat). He clearly understood that these forms had two positions for the hydrogen atoms (again, to use modern terminology, axial and equatorial), that two chairs would probably interconvert, and even how certain substituents might favor one of the chair forms (). Because he expressed all this in mathematical language, few chemists of the time understood his arguments. He had several attempts at publishing these ideas, but none succeeded in capturing the imagination of chemists. His death in 1893 at the age of 31 meant his ideas sank into obscurity. It was only in 1918 that , based on the molecular structure of diamond that had recently been solved using the then very new technique of X-ray crystallography, was able to successfully argue that Sachse's chair was the pivotal motif. Derek Barton and Odd Hassel shared the 1969 Nobel Prize in Chemistry for work on the conformations of cyclohexane and various other molecules. | 4 | Stereochemistry |
Feringa was born as the son of farmer Geert Feringa (1918–1993) and his wife Lies Feringa née Hake (1924–2013). Feringa was the second of ten siblings in a Catholic family. He spent his youth on the family's farm, which is directly on the border with Germany, in Barger-Compascuum in the Bourtange moor. He is of Dutch and German descent. Among his ancestors is the settler Johann Gerhard Bekel. Together with his wife Betty Feringa, he has three daughters. He lives in Paterswolde near Groningen. | 4 | Stereochemistry |
Consider the example of polyethylene terephthalate (PET or "polyester"). The monomers which could be used to create this polymer are ethylene glycol and terephthalic acid:
HO-CH-CH-OH
and
HOOC-CH-COOH
In the polymer, there are two structural units, which are
-O-CH-CH-O-
and
-CO-CH-CO-
The repeat unit is
-CH-CH-O-CO-CH-CO-O- | 7 | Physical Chemistry |
Black-brown pigment was observed by Johann Heinrich Meckel in 1847, in the blood and spleen of a person suffering from insanity. However, it was not until 1849 that the presence of this pigment was connected to infection with malaria. Initially, it was thought that this pigment was produced by the body in response to infection, but Charles Louis Alphonse Laveran realized in 1880 that "malaria pigment" is, instead, produced by the parasites, as they multiplied within the red blood cell. The link between pigment and malaria parasites was used by Ronald Ross to identify the stages in the Plasmodium life cycle that occur within the mosquito, since, although these forms of the parasite are different in appearance to the blood stages, they still contain traces of pigment.
Later, in 1891, T. Carbone and W.H. Brown (1911) published papers linking the hemoglobin degradation with pigment production, describing the malaria pigment as a form of hematin and disproving the widely held idea that it is related to melanin. Brown observed that all melanins were bleaching rapidly with potassium permanganate, while with this reagent malarial pigment manifests not the slightest sign of a true bleach reaction. The name "hemozoin" was proposed by Louis Westenra Sambon. In the 1930s several authors identified hemozoin as a pure crystalline form of α-hematin and showed that the substance did not contain proteins within the crystals, but no explanation for the solubility differences between malaria pigment and α-hematin crystals was given. | 1 | Biochemistry |
This gene encodes a member of the STAT-induced STAT inhibitor (SSI), also known as suppressor of cytokine signalling (SOCS), family. SSI family members are cytokine-inducible negative regulators of cytokine signaling. The expression of this gene can be induced by a subset of cytokines, including IL2, IL3 erythropoietin (EPO), GM-CSF, and interferon-gamma (IFN-γ). The protein encoded by this gene functions downstream of cytokine receptors, and takes part in a negative feedback loop to attenuate cytokine signaling. Knockout studies in mice suggested the role of this gene as a modulator of IFN-γ action, which is required for normal postnatal growth and survival.
Several recent viral studies have shown that viral genes, such as Tax gene product (Tax), encoded by HTLV-1, could hijack SOCS1 to inhibit host antiviral pathways, as a strategy to evade host immunity. | 1 | Biochemistry |
Inhibition of fatty acid oxidation requires that ACC is active. Both AMPK and MCD are inactive and glucose uptake is stimulated. The LCFAs are then rerouted to esterification. These conditions exist in tissues rich in oxygen, in which AMPK is inactive and glucose inactivates the AMPK (researched in skeletal muscle).
The inhibition of MCD suppresses the oxidation of fatty acids and stimulates glucose oxidation. In a study on MCD deficient mice there was no difference in the oxidation of fatty acids and glucose in the heart under aerobic conditions. It is theorized that the overexpression of fatty acids being used makes up for the lack of MCD. | 1 | Biochemistry |
Freeze-dried samples of Caldora penicillata had EtOAc−MeOH and HO−EtOH applied to them in order to extract Caldoramide. The extracts were partitioned with n-BuOH and HO and then fractions were taken based on solubility in either EtOAc or BuOH. Caldoramide was extracted from the BuOH soluble fraction. | 1 | Biochemistry |
For higher grade applications such as ferrous metals, coal and industrial minerals, sensor-based ore sorting can be applied to create a final product. Pre-condition is, that the liberation allows for the creation of a sellable product. Undersize material is usually bypassed as product, but can also be diverted to the waste fraction, if the composition does not meet the required specifications. This is case and application dependent. | 3 | Analytical Chemistry |
Keene P. Dimick Award in Chromatography, Third International Symposium on Supercritical Fluid Chromatography Award for Pioneering Work in the Development of SFC; Marcel J.E. Golay Award and Medal, International Symposium on Capillary Chromatography; American Chemical Society Award in Separation Science and Technology; American Chemical Society Exceptional Achievement Award as a Capillary Gas Chromatography Short Course Instructor; R&D 100 Award for technologically significant new product: -PAGE Polyacrylamide Gel-filled Capillaries for Capillary Electrophoresis”; Jan E. Purkynje Memorial Medal of the Czech Academy of Sciences; R&D Magazine Scientist of the Year Award; M.S. Tswett Memorial Medal of the Russian Academy of Sciences; A.J.P. Martin Gold Medal of the Chromatographic Society of Great Britain; Theophilus Redwood Award, The Royal Society of Chemistry, Great Britain; Distinguished Teaching and Mentoring Award of the University Graduate School, Indiana University; Elected as a Foreign Member of the Royal Society of Sciences (Sweden); College of Arts & Sciences Distinguished Faculty Award, Indiana University. | 3 | Analytical Chemistry |
Bioconjugation of TGF-β to iron oxide nanoparticles and its activation through magnetic hyperthermia in-vitro has been reported. This was done by using 1-(3-dimethylaminopropyl)ethylcarbodiimide combined with N-Hydroxysuccinimide to form primary amide bonds with the free primary amines on the growth factor. Carbon nanotubes have been successfully used in conjunction with bioconjugation to link TGF-β followed by an activation with near-infrared light. Typically, these reactions have involved the use of a crosslinker, but some of these add molecular space between the compound of interest and base material and in turn causes higher degrees of non-specific binding and unwanted reactivity. | 1 | Biochemistry |
In biological systems, methylation is accomplished by enzymes. Methylation can modify heavy metals and can regulate gene expression, RNA processing, and protein function. It is a key process underlying epigenetics. Sources of methyl groups include S-methylmethionine, methyl folate, methyl B12. | 0 | Organic Chemistry |
After the RNase cleavage of the last six nucleotides, the next step is phosphorylation of the 5'-end via Kinase. Then the next cycle of ligation can be repeated. | 1 | Biochemistry |
Explosive yields can be affected by the introduction of mechanical loads or the application of temperature; such damages are called insults. The mechanism of a thermal insult at low temperatures on an explosive is primarily thermomechanical, at higher temperatures it is primarily thermochemical. | 7 | Physical Chemistry |
Amazake, beer, bread, choujiu, gamju, injera, kvass, makgeolli, murri, ogi, rejuvelac, sake, sikhye, sourdough, sowans, rice wine, malt whisky, grain whisky, idli, dosa, Bangla (drink)
vodka, boza, and chicha, among others. | 1 | Biochemistry |
The Polyelectrolyte theory of the gene is a proposed generic biosignature. In 2002, Steven A. Benner and Daniel Hutter proposed that for a linear genetic biopolymer dissolved in water, such as DNA, to undergo Darwinian evolution anywhere in the universe, it must be a polyelectrolyte, a polymer containing repeating ionic charges. Benner and others proposed methods for concentrating and analyzing these polyelectrolyte genetic biopolymers on Mars, Enceladus, and Europa. | 2 | Environmental Chemistry |
There are several ways of exposure to these hepatotoxins that humans can encounter one of which is through recreational activities like swimming, surfing, fishing, and other activities involving direct contact with contaminated water. Another rare, yet extremely toxic, route of exposure that has been identified by scientists is through hemodialysis surgeries. One of the fatal cases for microcystic intoxication through hemodialysis was studied in Brazil where 48% of patients that received the surgery in a specific period of time died because the water used in the procedure was found to be contaminated.
Microcystins are chemically stable over a wide range of temperature and pH, possibly as a result of their cyclic structure.
Microcystin-LR water contamination is resistant to boiling and microwave treatments.
Microcystin-producing bacteria algal blooms can overwhelm the filter capacities of water treatment plants. Some evidence shows the toxin can be transported by irrigation into the food chain. | 2 | Environmental Chemistry |
The majority of mRNAs in E. coli are prefaced with a Shine-Dalgarno (SD) sequence. The SD sequence is recognized by an complementary "anti-SD" region on the 16S rRNA component of the 30S subunit. In the canonical model, the 30S ribosome is first joined up with the three initiation factors, forming an unstable "pre-initiation complex". The mRNA then pairs up with this anti-SD region, causing it to form a double-stranded RNA structure, roughly positioning the start codon at the P site. An initiating tRNA arrives and is positioned with the help of IF2, starting the translation.
There are a lot of uncertainties even in the canonical model. The initiation site has been shown to be not strictly limited to AUG. Well-known coding regions that do not have AUG initiation codons are those of lacI (GUG) and lacA (UUG) in the E. coli lac operon. Two studies have independently shown that 17 or more non-AUG start codons may initiate translation in E. coli. Nevertheless, AUG seems to at least be the strongest initiation codon among all possibilities.
The SD sequence also does not appear strictly necessary, as a wide range of mRNAs lack them and are still translated, with an entire phylum of bacteria (Bacteroidetes) using no such sequence. Simply SD followed by AUG is also not sufficient to initiate translation. It does, at least, function as a very important initiating signal in E. coli. | 1 | Biochemistry |
A continuous cooling transformation (CCT) phase diagram is often used when heat treating steel. These diagrams are used to represent which types of phase changes will occur in a material as it is cooled at different rates. These diagrams are often more useful than time-temperature-transformation diagrams because it is more convenient to cool materials at a certain rate (temperature-variable cooling), than to cool quickly and hold at a certain temperature (isothermal cooling). | 8 | Metallurgy |
Corrosion engineering groups have formed around the world to educate, prevent, slow, and manage corrosion. These include the National Association of Corrosion Engineers (NACE), the European Federation of Corrosion (EFC), The Institute of Corrosion in the UK and the Australasian Corrosion Association. The corrosion engineer's main task is to economically and safely manage the effects of corrosion of materials. | 8 | Metallurgy |
In a combustion analyser, half of the sample is injected into a chamber where it is acidified, usually with phosphoric acid, to turn all of the inorganic carbon into carbon dioxide as per the following reaction:
: CO + HO ⇌ HCO ⇌H + HCO ⇌ 2H + CO
This is then sent to a detector for measurement. The other half of the sample is injected into a combustion chamber which is raised to between 600–700 °C, some even up to 1200 °C. Here, all the carbon reacts with oxygen, forming carbon dioxide. It is then flushed into a cooling chamber, and finally into the detector. Usually, the detector used is a non-dispersive infrared spectrophotometer. By finding the total inorganic carbon and subtracting it from the total carbon content, the amount of organic carbon is determined. | 3 | Analytical Chemistry |
Non-metallic inclusions, the presence of which defines purity of steel, are classified by chemical and mineralogical content, by stability and by origin. By chemical content non-metallic inclusions are divided into the following groups:
#sulfides (simple — FeS, MnS, AlS, CaS, MgS, ZrS and others; compound — FeS·FeO, MnS·MnO and others);
#nitrides (simple — ZrN, TiN, AlN, CeN and others; compound — Nb(C, N), V(c, N) and others), which can be found in alloyed steel and has strong nitride-generative elements in its content: titanium, aluminium, vanadium, cerium and others;
#silicates
#oxides (simple — FeO, MnO, CrO, SiO, AlO, TiO and others; compound — FeO·FeO, FeO·AlO, FeO·CrO, MgO·AlO, 2FeO·SiO and others;
The majority of inclusions in metals are oxides and sulfides since the content of phosphorus is very small.
Silicates are very detrimental to steels, especially if it has to undergo heat treatment at a later stage.
Usually nitrides are present in special steels that contain an element with a high affinity to nitrogen.
By mineralogical content, oxygen inclusions divide into the following main groups:
* Free oxides — FeO, MnO, CrO, SiO (quartz), AlO (corundum) and others
* Spinels — compound oxides formed by bi and trivalent elements
Ferrites, chromites and aluminates are in this group.
*silicates, which are present in steel like a glass or SiO with admixture of iron, manganese, chromium, aluminium and tungsten oxides and also crystalline silicates. Silicates are the biggest group among non-metallic inclusions. In liquid steel non-metallic inclusions are in solid or liquid condition. It depends on the melting temperature.
By stability, non-metallic inclusions are either stable or unstable. Unstable inclusions are those that dissolve in dilute acids (less than 10%concentration). Unstable inclusions are iron and manganese sulfides and also some free oxides.
Present-day levels of steel production allow to move off from the metal different inclusions. However, in general the content of inclusions in different steels varies within wide limits and has a big influence on the metal properties. | 8 | Metallurgy |
Because secondary structure of the 5’ end of mRNA influences translational efficiency, synonymous changes at this region on the mRNA can result in profound effects on gene expression. Codon usage in noncoding DNA regions can therefore play a major role in RNA secondary structure and downstream protein expression, which can undergo further selective pressures. In particular, strong secondary structure at the ribosome-binding site or initiation codon can inhibit translation, and mRNA folding at the 5’ end generates a large amount of variation in protein levels. | 1 | Biochemistry |
The quantum tunneling dynamics in water was reported as early as 1992. At that time it was known that there are motions which destroy and regenerate the weak hydrogen bond by internal rotations of the substituent water monomers. On 18 March 2016, it was reported that the hydrogen bond can be broken by quantum tunneling in the water hexamer. Unlike previously reported tunneling motions in water, this involved the concerted breaking of two hydrogen bonds. Later in the same year, the discovery of the quantum tunneling of water molecules was reported. | 2 | Environmental Chemistry |
As mentioned, negative resists are photopolymers that become insoluble upon exposure to radiation. They have found a variety of commercial applications, especially in the area of designing and printing small chips for electronics. A characteristic found in most negative tone resists is the presence of multifunctional branches on the polymers used. Radiation of the polymers in the presence of an initiator results in the formation of a chemically resistant network polymer. A common functional group used in negative resists is epoxy functional groups. An example of a widely used polymer of this class is SU-8. SU-8 was one of the first polymers used in this field, and found applications in wire board printing. In the presence of a cationic photoinitiator photopolymer, SU-8 forms networks with other polymers in solution. Basic scheme shown below.
SU-8 is an example of an intramolecular photopolymerization forming a matrix of cross-linked material. Negative resists can also be made using co-polymerization. In the event that two different monomers, or oligomers, are in solution with multiple functionalities, it is possible for the two to polymerize and form a less soluble polymer.
Manufacturers also use light curing systems in OEM assembly applications such as specialty electronics or medical device applications. | 5 | Photochemistry |
The detection efficiency for electrons is essentially 100% for most scintillators. But because electrons can make large angle scatterings (sometimes backscatterings), they can exit the detector without depositing their full energy in it. The back-scattering is a rapidly increasing function of the atomic number Z of the scintillator material. Organic scintillators, having a lower Z than inorganic crystals, are therefore best suited for the detection of low-energy (< 10 MeV) beta particles. The situation is different for high energy electrons: since they mostly lose their energy by bremsstrahlung at the higher energies, a higher-Z material is better suited for the detection of the bremsstrahlung photon and the production of the electromagnetic shower which it can induce. | 5 | Photochemistry |
Tic100 is a nuclear encoded protein thats 871 amino acids long. The 871 amino acids collectively weigh slightly less than 100 thousand daltons, and since the mature protein probably doesnt lose any amino acids when itself imported into the chloroplast (it has no cleavable transit peptide), it was named Tic100. Tic100 is found at the edges of the 1 million dalton complex on the side that faces the chloroplast intermembrane space. | 5 | Photochemistry |
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