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Phosphoinositide phospholipase C (PLC, EC 3.1.4.11, triphosphoinositide phosphodiesterase, phosphoinositidase C, 1-phosphatidylinositol-4,5-bisphosphate phosphodiesterase, monophosphatidylinositol phosphodiesterase, phosphatidylinositol phospholipase C, PI-PLC, 1-phosphatidyl--myo-inositol-4,5-bisphosphate inositoltrisphosphohydrolase; systematic name 1-phosphatidyl-1-myo-inositol-4,5-bisphosphate inositoltrisphosphohydrolase) is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes. These enzymes belong to a larger superfamily of Phospholipase C. Other families of phospholipase C enzymes have been identified in bacteria and trypanosomes. Phospholipases C are phosphodiesterases.
Phospholipase Cs participate in phosphatidylinositol 4,5-bisphosphate (PIP) metabolism and lipid signaling pathways in a calcium-dependent manner. At present, the family consists of six sub-families comprising a total of 13 separate isoforms that differ in their mode of activation, expression levels, catalytic regulation, cellular localization, membrane binding avidity and tissue distribution. All are capable of catalyzing the hydrolysis of PIP into two important second messenger molecules, which go on to alter cell responses such as proliferation, differentiation, apoptosis, cytoskeleton remodeling, vesicular trafficking, ion channel conductance, endocrine function and neurotransmission. | 1 | Gene expression + Signal Transduction |
According to the IUPAC definition, flocculation is "a process of contact and adhesion whereby the particles of a dispersion form larger-size clusters". Flocculation
is synonymous with agglomeration and coagulation/coalescence.
Basically, coagulation is a process of addition of coagulant to destabilize a stabilized charged particle. Meanwhile, flocculation is a mixing technique that promotes agglomeration and assists in the settling of particles. The most common used coagulant is alum, Al(SO)·14HO.
The chemical reaction involved:
:Al(SO) · 14 HO → 2 Al(OH) + 6 H + 3 + 8 HO
During flocculation, gentle mixing accelerates the rate of particle collision, and the destabilized particles are further aggregated and enmeshed into larger precipitates. Flocculation is affected by several parameters, including mixing speeds, mixing intensity, mixing time and pH. The product of the mixing intensity and mixing time is used to describe flocculation processes. | 0 | Metallurgy |
The first suggestion of ADP-ribosylation surfaced during the early 1960s. At this time, Pierre Chambon and coworkers observed the incorporation of ATP into hen liver nuclei extract. After extensive studies on the acid insoluble fraction, several different research laboratories were able to identify ADP-ribose, derived from NAD, as the incorporated group. Several years later, the enzymes responsible for this incorporation were identified and given the name poly(ADP-ribose)polymerase. Originally, this group was thought to be a linear sequence of ADP-ribose units covalently bonded through a ribose glycosidic bond. It was later reported that branching can occur every 20 to 30 ADP residues.
The first appearance of mono(ADP-ribosyl)ation occurred a year later during a study of toxins: the diphtheria toxin of Corynebacterium diphtheriae was shown to be dependent on NAD in order for it to be completely effective, leading to the discovery of enzymatic conjugation of a single ADP-ribose group by mono(ADP-ribosyl)transferase.
It was initially thought that ADP-ribosylation was a post translational modification involved solely in gene regulation. However, as more enzymes with the ability to ADP-ribosylate proteins were discovered, the multifunctional nature of ADP-ribosylation became apparent. The first mammalian enzyme with poly(ADP-ribose)transferase activity was discovered during the late 1980s. For the next 15 years, it was thought to be the only enzyme capable of adding a chain of ADP-ribose in mammalian cells. During the late 1980s, ADP-ribosyl cyclases, which catalyze the addition of cyclic-ADP-ribose groups to proteins, were discovered. Finally, sirtuins, a family of enzymes that also possess NAD-dependent deacylation activity, were discovered to also possess mono(ADP-ribosyl)transferase activity. | 1 | Gene expression + Signal Transduction |
One of the major issues that hinders the ncRNA therapy is the stability of the single stranded RNA molecule. RNA is typically single stranded therefore slightly unstable as compared to dsDNA molecules. This however can be overcome by fabricating the single stranded RNA to double stranded RNA(dsRNA). This is quite effective as the dsRNA is more stable at room temperature and has a longer shelf life.
Second major issue is the cell/tissue/organ specific targeting of the RNA molecules. Generally, this is overcome by containing the dsRNA in a lipid nanoparticle and using that as a ligand to bind to a receptor on the surface of the target cell. The lipid particles are taken into the liver cells through their specific receptors and this mechanism seems to be effective at targeting the liver cells/cancer.
Another organ with a relatively easy delivery mechanism is the eye. This requires an invasive technique of directly injecting the ncRNA of interest directly into the eye. These techniques are not only invasive but also don’t ensure if all the cells in the target organ are being targeted by the ncRNA of interest.
Additional issues arise once the RNA molecule enters the cell. One of the issues being the immune system. Our immune system can recognize RNA using the intracellular pathogen associated molecular pattern (PAMP) receptors and extracellular toll-like receptors (TLR). Activation of the receptors leads to a cytokine (IFNy-Interferon gamma) mediated immune response. Common applications to overcome the immune response include second generation chemical modifications. This process includes the introduction of small one at a time chemical modifications to avoid the immune response. However, there are some reports of adverse immune responses in clinical trials employing such modified reagents. There’s no fixed answer to issues with immunogenicity and ncRNA therapy.
Modified adenovirus vectors have been used extensively in many clinical trials as a ncRNA delivery mechanism. In particular, adenovirus vector is considered an efficient delivery system due to its stability within live cells and non-pathogenicity. Even though viral transfections have achieved significant results in basic research, one of the issues is the non-specificity leading to off target transfections. Further research needs to be done to improve the accuracy of viral transfections for future tests and clinical trials. | 1 | Gene expression + Signal Transduction |
Pack cementation is a widely used CVD technique that consists of immersing the components to be coated in a metal powder mixture and ammonium halide activators and sealing them in a retort. The entire apparatus is placed inside a furnace and heated in a protective atmosphere to a lower than normal temperature that allows diffusion, due to the halide salts chemical reaction that causes a eutectic bond between the two metals. The surface alloy that is formed due to thermal-diffused ion migration has a metallurgical bond to the substrate and an intermetallic layer found in the gamma layer of the surface alloys.
The traditional pack consists of four components at temperatures below (750 °C):
* Substrate or parts
* Ferrous and non-ferrous powdered alloy: (Ti and/or Al, Si and/or Zn, B and/ or Cr)
* Halide salt activator: Ammonium halide salts
* Relatively inert filler powder (Al2O3, SiO2, or SiC)
This process includes:
* Aluminizing
* Chromizing
* Siliconizing
* Sherardizing
* Boronizing
* Titaniumizing
Pack cementation has reemerged when combined with other chemical processes to lower the temperatures of metal combinations and give intermetallic properties to different alloy combinations for surface treatments. | 0 | Metallurgy |
The borax method of gold extraction has been used by artisanal gold miners in the Benguet area north of Manila in the Philippines for more than 30 years. Some believe it was in practice as early as the 1900s. The method is increasingly being seen as a safe alternative to the widespread use of toxic mercury in artisanal gold mining today. About 30% of the world's mercury emissions comes from small scale mining. Efforts are being made to revive the method and spread its use. As of 2012, around 15,000 artisanal gold miners in a small area of Luzon, the main island in the northern portion of the Philippines, use this method exclusively. The mineral is inexpensive and easily available, and the miners have reportedly found that more gold is recovered through its use. | 0 | Metallurgy |
Archaeometallurgical study has many uses in both the chemical and anthropological fields. Analysis contributes valuable insights into many archaeological questions, from technological choice to social organisation. Any project concerned with the relationship that the human species has had to the metals known to us is an example of archaeometallurgical study. | 0 | Metallurgy |
cAMP is associated with kinases function in several biochemical processes, including the regulation of glycogen, sugar, and lipid metabolism.
In eukaryotes, cyclic AMP works by activating protein kinase A (PKA, or cAMP-dependent protein kinase). PKA is normally inactive as a tetrameric holoenzyme, consisting of two catalytic and two regulatory units (CR), with the regulatory units blocking the catalytic centers of the catalytic units.
Cyclic AMP binds to specific locations on the regulatory units of the protein kinase, and causes dissociation between the regulatory and catalytic subunits, thus enabling those catalytic units to phosphorylate substrate proteins.
The active subunits catalyze the transfer of phosphate from ATP to specific serine or threonine residues of protein substrates. The phosphorylated proteins may act directly on the cell's ion channels, or may become activated or inhibited enzymes. Protein kinase A can also phosphorylate specific proteins that bind to promoter regions of DNA, causing increases in transcription. Not all protein kinases respond to cAMP. Several classes of protein kinases, including protein kinase C, are not cAMP-dependent.
Further effects mainly depend on cAMP-dependent protein kinase, which vary based on the type of cell.
Still, there are some minor PKA-independent functions of cAMP, e.g., activation of calcium channels, providing a minor pathway by which growth hormone-releasing hormone causes a release of growth hormone.
However, the view that the majority of the effects of cAMP are controlled by PKA is an outdated one. In 1998 a family of cAMP-sensitive proteins with guanine nucleotide exchange factor (GEF) activity was discovered. These are termed Exchange proteins activated by cAMP (Epac) and the family comprises Epac1 and Epac2. The mechanism of activation is similar to that of PKA: the GEF domain is usually masked by the N-terminal region containing the cAMP binding domain. When cAMP binds, the domain dissociates and exposes the now-active GEF domain, allowing Epac to activate small Ras-like GTPase proteins, such as Rap1. | 1 | Gene expression + Signal Transduction |
In this example, the following sequence is a region of the human mitochondrial genome with the two overlapping genes MT-ATP8 and MT-ATP6.
When read from the beginning, these codons make sense to a ribosome and can be translated into amino acids (AA) under the vertebrate mitochondrial code:
|Start|AAC GAA AAT CTG TTC GCT TCA ...
|Start|123 123 123 123 123 123 123 ...
| AA | N E N L F A S ...
However, let's change the reading frame by starting one nucleotide downstream (effectively a "+1 frameshift" when considering the 0 position to be the initial position of A):
A|Start|ACG AAA ATC TGT TCG CTT CA...
-|Start|123 123 123 123 123 123 12...
| AA | T K I C S L ...
Because of this +1 frameshifting, the DNA sequence is read differently. The different codon reading frame therefore yields different amino acids. | 1 | Gene expression + Signal Transduction |
Iron smelting—the extraction of usable metal from oxidized iron ores—is more difficult than tin and copper smelting. While these metals and their alloys can be cold-worked or melted in relatively simple furnaces (such as the kilns used for pottery) and cast into molds, smelted iron requires hot-working and can be melted only in specially designed furnaces. Iron is a common impurity in copper ores and iron ore was sometimes used as a flux, thus it is not surprising that humans mastered the technology of smelted iron only after several millennia of bronze metallurgy.
The place and time for the discovery of iron smelting is not known, partly because of the difficulty of distinguishing metal extracted from nickel-containing ores from hot-worked meteoritic iron. The archaeological evidence seems to point to the Middle East area, during the Bronze Age in the 3rd millennium BC. However, wrought iron artifacts remained a rarity until the 12th century BC.
The Iron Age is conventionally defined by the widespread replacement of bronze weapons and tools with those of iron and steel. That transition happened at different times in different places, as the technology spread. Mesopotamia was fully into the Iron Age by 900 BC. Although Egypt produced iron artifacts, bronze remained dominant until its conquest by Assyria in 663 BC. The Iron Age began in India about 1200 BC, in Central Europe about 800 BC, and in China about 300 BC. Around 500 BC, the Nubians, who had learned from the Assyrians the use of iron and were expelled from Egypt, became major manufacturers and exporters of iron. | 0 | Metallurgy |
There are a few limitations of detonation spraying, these are:
* Detonation spraying creates a coating that is mostly mechanically bonded as opposed to being metallurgically bonded, which is a much stronger type of bond.
* Detonation spraying is a line of sight process meaning that components generally need to be coated before being put to use or assembled. This is because the detonation gun needs to be able to access the surface to be able to apply an effective coating.
* The coatings despite being considerably strong in compression are weak under tension, meaning they can't be applied to malleable or expanding components.
* The coatings tend to fatigue under pinpoint loading.
*Detonation guns are quite large and loud.
*Detonation spraying has to be performed at a location specifically designed for it, as the gun is reasonable large and it is a loud process that produces substantial noise. For this reason, it is usually installed in a sound-proof room (with concrete walls 45 cm thick).
*The process involves a considerable amount of mechanisation and automation because the operator can't be in the room whilst the D-gun is in operation. | 0 | Metallurgy |
In addition to activating PKC, diacylglycerol has a number of other functions in the cell:
* a source for prostaglandins
* a precursor of the endocannabinoid 2-arachidonoylglycerol
* an activator of a subfamily of transient receptor potential canonical (TRPC) cation channels, TRPC3/6/7. | 1 | Gene expression + Signal Transduction |
LacI finds its target operator DNA surprisingly fast. In vitro the search is 10-100 times faster than the theoretical upper limit for two particles searching for each other via diffusion in three dimensions (3D). To explain the fast search, it was hypothesized that LacI and other transcription factors (TFs) find their binding sites by facilitated diffusion, a combination of free diffusion in 3D and 1D-sliding on the DNA. During sliding the repressor is in contact with the DNA helix, sliding around and tracking its major groove, which speeds up the search process by extending the target length when the TF slides in onto the operator from the side. In vivo single-molecule experiments with E.coli cells have now tested and verified the facilitated diffusion model, and shown that the TF scans on average 45 bp during each sliding event, before the TF detaches spontaneously and resumes exploring the genome in 3D. These experiments also suggest that LacI slides over the O operator several times before binding, meaning that different DNA sequences can have different probabilities to be recognized at each encounter with the TF. This implies a trade-off between fast search on nonspecific sequences and binding to specific sequences. In vivo and in vitro experiments have shown that it is this probability to recognize the operator that changes with DNA sequence, while the time the TF remains in the bound conformation on the operator changes less with sequence. The TF often leaves the sequence it is intended to regulate, but at a strong target site, it almost always make a very short journey before finding the way back again. On the macroscopic scale, this looks like a stable interaction. This binding mechanism explains how DNA binding proteins manage to quickly search through the genome of the cell without getting stuck too long at sequences that resemble the true target.
An all-atom molecular dynamics simulation suggests that the transcription factor encounters a barrier of 1 kT during sliding and 12 kT for dissociation, implying that the repressor will slide over 8 bp on average before dissociating. The in vivo search model for the lac repressor includes intersegment transfer and hopping as well as crowding by other proteins which make the genome in E.coli cells less accessible for the repressor. The existence of hopping, where the protein slips out of the major groove of DNA to land in another nearby groove along the DNA chain, has been proven more directly in vitro, where the lac repressor has been observed to bypass operators, flip orientation, and rotate with a longer pitch than the 10.5 bp period of DNA while moving along it. | 1 | Gene expression + Signal Transduction |
Chemical milling is normally performed in a series of five steps: cleaning, masking, scribing, etching, and demasking. [https://www.youtube.com/watch?v=YtnUZanxtLs Video of chemical milling process] [https://www.fotofab.com/photo-etching-process/ Learn more about the video] | 0 | Metallurgy |
RNAP was discovered independently by Charles Loe, Audrey Stevens, and Jerard Hurwitz in 1960. By this time, one half of the 1959 Nobel Prize in Medicine had been awarded to Severo Ochoa for the discovery of what was believed to be RNAP, but instead turned out to be polynucleotide phosphorylase. | 1 | Gene expression + Signal Transduction |
The explorations in the foothills of the Kopetdag revealed well developed irrigation systems with water control arrangements which resulted in prosperous, well settled large regional centres. The largest of these settlements is Namazga-Tepe with an area of 50 ha. The excavations done at this site lead to the discovery of six distinct periods. Named Namazgadepe I to VI, the periods extended over the late 5th millennium to early 3rd millennium BC. In the process of development over these centuries, the transition observed was from Chalcolithic period to Early Bronze Age with urban characteristics in the settlements. Dwelling houses also emerged from chaotically planned one room houses to larger houses with many rooms with the interiors painted (lac paintings) and with a hearth. Defensive forts were part of the settlements. Chalcolithic stone amulets with geometric shapes, pottery traditions with two-tiered furnaces for firing ceramics, terracotta figurines, stamp seals of clay and stone, and centres of metallurgical production were uncovered. Rosette and zoomorphic patterns were unearthed, representing various periods, both at Namazga-Tepe and also at other settlements in the foothills of the Kopetdag mountains. These are clearly indicative of the village cultures of Central Asia. | 0 | Metallurgy |
Adenylate-uridylate-rich elements (AU-rich elements; AREs) are found in the 3' untranslated region (UTR) of many messenger RNAs (mRNAs) that code for proto-oncogenes, nuclear transcription factors, and cytokines. AREs are one of the most common determinants of RNA stability in mammalian cells.
AREs are defined as a region with frequent adenine and uridine bases in a mRNA. They usually target the mRNA for rapid degradation.
ARE-directed mRNA degradation is influenced by many exogenous factors, including phorbol esters, calcium ionophores, cytokines, and transcription inhibitors. These observations suggest that AREs play a critical role in the regulation of gene transcription during cell growth and differentiation, and the immune response.
AREs have been divided into three classes with different sequences. The best characterised adenylate uridylate (AU)-rich Elements have a core sequence of AUUUA within U-rich sequences (for example WWWU(AUUUA)UUUW where W is A or U). This lies within a 50–150 base sequence, repeats of the core AUUUA element are often required for function.
A number of different proteins (e.g. HuA, HuB, HuC, HuD, HuR) bind to these elements and stabilise the mRNA while others (AUF1, TTP, BRF1, TIA-1, TIAR, and KSRP) destabilise the mRNA, miRNAs may also bind to some of them. HuD (also called ELAVL4) binds to AREs and increases the half-life of ARE-bearing mRNAs in neurons during brain development and plasticity.
AREsite—a database for ARE containing genes—has recently been developed with the aim to provide detailed bioinformatic characterization of AU-rich elements. | 1 | Gene expression + Signal Transduction |
One of the earliest smelted iron artifacts, a dagger with an iron blade found in a Hattic tomb in Anatolia, dated from 2500 BC. About 1500 BC, increasing numbers of non-meteoritic, smelted iron objects appeared in Mesopotamia, Anatolia and Egypt. Nineteen meteoric iron objects were found in the tomb of Egyptian ruler Tutankhamun, who died in 1323 BC, including an iron dagger with a golden hilt, an Eye of Horus, the mummys head-stand and sixteen models of an artisans tools. An Ancient Egyptian sword bearing the name of pharaoh Merneptah as well as a battle axe with an iron blade and gold-decorated bronze shaft were both found in the excavation of Ugarit.
Although iron objects dating from the Bronze Age have been found across the Eastern Mediterranean, bronzework appears to have greatly predominated during this period. As the technology spread, iron came to replace bronze as the dominant metal used for tools and weapons across the Eastern Mediterranean (the Levant, Cyprus, Greece, Crete, Anatolia and Egypt).
Iron was originally smelted in bloomeries, furnaces where bellows were used to force air through a pile of iron ore and burning charcoal. The carbon monoxide produced by the charcoal reduced the iron oxide from the ore to metallic iron. The bloomery, however, was not hot enough to melt the iron, so the metal collected in the bottom of the furnace as a spongy mass, or bloom. Workers then repeatedly beat and folded it to force out the molten slag. This laborious, time-consuming process produced wrought iron, a malleable but fairly soft alloy.
Concurrent with the transition from bronze to iron was the discovery of carburization, the process of adding carbon to wrought iron. While the iron bloom contained some carbon, the subsequent hot-working oxidized most of it. Smiths in the Middle East discovered that wrought iron could be turned into a much harder product by heating the finished piece in a bed of charcoal, and then quenching it in water or oil. This procedure turned the outer layers of the piece into steel, an alloy of iron and iron carbides, with an inner core of less brittle iron. | 0 | Metallurgy |
Sand casting has many defects that can occur due to the mould failing. The mould usually fails because of one of two reasons: the wrong material is used or it is improperly rammed.
The first type is mould erosion, which is the wearing away of the mould as the liquid metal fills the mould. This type of defect usually only occurs in sand castings because most other casting processes have more robust moulds. The castings produced have rough spots and excess material. The moulding sand becomes incorporated into the casting metal and decreases the ductility, fatigue strength, and fracture toughness of the casting. This can be caused by a sand with too little strength or a pouring velocity that is too fast. The pouring velocity can be reduced by redesigning the gating system to use larger runners or multiple gates. A related source of defects are drops, in which part of the moulding sand from the cope drops into the casting while it is still a liquid. This also occurs when the mould is not properly rammed.
The second type of defect is metal penetration, which occurs when the liquid metal penetrates into the moulding sand. This causes a rough surface finish. This is caused by sand particles which are too coarse, lack of mould wash, or pouring temperatures that are too high. An alternative form of metal penetration into the mould known as veining is caused by cracking of the sand.
If the pouring temperature is too high or a sand of low melting point is used then the sand can fuse to the casting. When this happens the surface of the casting produced has a brittle, glassy appearance.
A run out occurs when the liquid metal leaks out of the mould because of a faulty mould or flask.
s are a thin layer of metal that sits proud of the casting. They are easy to remove and always reveal a underneath, which is an indentation in the casting surface. s are similar to buckles, except they are thin line indentations and not associated with scabs. Another similar defect is s, which are buckles that occur in the cope of sand castings. All of these defects are visual in nature and are no reason to scrap the workpiece. These defects are caused by overly high pouring temperatures or deficiencies of carbonaceous material.
A swell occurs when the mould wall gives way across a whole face, and is caused by an improperly rammed mould.
occurs when metallic oxides interact with impurities in silica sands. The result is sand particles embedded in the surface of the finished casting. This defect can be avoided by reducing the temperature of the liquid metal, by using a mould wash, and by using various additives in the sand mixture. | 0 | Metallurgy |
While the mechanical behavior of ceramics is often dominated by flaws, i.e. porosity, instead of grain size, grain-size strengthening is also observed in high-density ceramic specimens. Additionally, nanocrystalline ceramics have been shown to sinter more rapidly than bulk ceramics, leading to higher densities and improved mechanical properties, although extended exposure to the high pressures and elevated temperatures required to sinter the part to full density can result in coarsening of the nanostructure.
The large volume fraction of grain boundaries associated with nanocrystalline materials causes interesting behavior in ceramic systems, such as superplasticity in otherwise brittle ceramics. The large volume fraction of grain boundaries allows for a significant diffusional flow of atoms via Coble creep, analogous to the grain boundary sliding deformation mechanism in nanocrystalline metals. Because the diffusional creep rate scales as and linearly with the grain boundary diffusivity, refining the grain size from 10 μm to 10 nm can increase the diffusional creep rate by approximately 11 orders of magnitude. This superplasticity could prove invaluable for the processing of ceramic components, as the material may be converted back into a conventional, coarse-grained material via additional thermal treatment after forming. | 0 | Metallurgy |
Self-cleaning screen media was initially engineered to resolve screen cloth blinding, clogging and pegging problems. The idea was to place crimped wires side by side on a flat surface, creating openings and then, in some way, holding them together over the support bars (crown bars or bucker bars). This would allow the wires to be free to vibrate between the support bars, preventing blinding, clogging and pegging of the cloth. Initially, crimped longitudinal wires on self-cleaning cloth were held together over support bars with woven wire. In the 50s, some manufacturers started to cover the woven cross wires with caulking or rubber to prevent premature wear of the crimps (knuckles on woven wires). One of the pioneer products in this category was ONDAP GOMME made by the French manufacturer Giron. During the mid 90s, Major Wire Industries Ltd., a Quebec manufacturer, developed a “hybrid” self-cleaning screen cloth called Flex-Mat, without woven cross wires. In this product, the crimped longitudinal wires are held in place by polyurethane strips. Rather than locking (impeding) vibration over the support bars due to woven cross wires, polyurethane strips reduce vibration of longitudinal wires over the support bars, thus allowing vibration from hook to hook. Major Wire quickly started to promote this product as a high-performance screen that helped producers screen more in-specification material for less cost and not simply a problem solver. They claimed that the independent vibrating wires helped produce more product compared to a woven wire cloth with the same opening (aperture) and wire diameter. This higher throughput would be a direct result of the higher vibration frequency of each independent wire of the screen cloth (calculated in hertz) compared to the shaker vibration (calculated in RPM), accelerating the stratification of the material bed. Another benefit that helped the throughput increase is that hybrid self-cleaning screen media offered a better open area percentage than woven wire screen media. Due to its flat surface (no knuckles), hybrid self-cleaning screen media can use a smaller wire diameter for the same aperture than woven wire and still lasts as long, resulting in a greater opening percentage. | 0 | Metallurgy |
A key concept that might be used for applications is the (numerical) derivative of the solid fraction fs with temperature. A numerical example using a copper zinc alloy at composition Zn 30% in weight is proposed as an example here using the opposite sign for using both temperature and its derivative in the same graph.
Kozlov and Schmid-Fetzer have calculated numerically the derivative of the Scheil curve in an open paper https://iopscience.iop.org/article/10.1088/1757-899X/27/1/012001 and applied it to the growth restriction factor Q in Al-Si-Mg-Cu alloys. | 0 | Metallurgy |
Spalling is a common mechanism of rock weathering, and occurs at the surface of a rock when there are large shear stresses under the surface. This form of mechanical weathering can be caused by freezing and thawing, unloading, thermal expansion and contraction, or salt deposition. | 0 | Metallurgy |
Circle-Throw Vibrating Equipment is a shaker or a series of shakers as to where the drive causes the whole structure to move. The structure extends to a maximum throw or length and then contracts to a base state. A pattern of springs are situated below the structure to where there is vibration and shock absorption as the structure returns to the base state.
This type of equipment is used for very large particles, sizes that range from pebble size on up to boulder size material. It is also designed for high volume output. As a scalper, this shaker will allow oversize material to pass over and fall into a crusher such a cone crusher, jaw crusher, or hammer mill. The material that passes the screen by-passes the crusher and is conveyed and combined with the crush material.
Also this equipment is used in washing processes, as material passes under spray bars, finer material and foreign material is washed through the screen. This is one example of wet screening. | 0 | Metallurgy |
Smaller arc furnaces may be adequately cooled by circulation of air over structural elements of the shell and roof, but larger installations require intensive forced cooling to maintain the structure within safe operating limits. The furnace shell and roof may be cooled either by water circulated through pipes which form a panel, or by water sprayed on the panel elements. Tubular panels may be replaced when they become cracked or reach their thermal stress life cycle.
Spray cooling is the most economical and is the highest efficiency cooling method. A spray cooling piece of equipment can be relined almost endlessly. Equipment that lasts 20 years is the norm. While a tubular leak is immediately noticed in an operating furnace due to the pressure loss alarms on the panels, at this time there exists no immediate way of detecting a very small volume spray cooling leak. These typically hide behind slag coverage and can hydrate the refractory in the hearth, leading to a break out of molten metal or in the worst case a steam explosion. | 0 | Metallurgy |
Uncontrolled growth is a necessary step for the development of all cancers. In many cancers (e.g. melanoma), a defect in the MAP/ERK pathway leads to that uncontrolled growth. Many compounds can inhibit steps in the MAP/ERK pathway, and therefore are potential drugs for treating cancer, such as Hodgkin disease.
The first drug licensed to act on this pathway is sorafenib — a Raf kinase inhibitor. Other Raf inhibitors include SB590885, PLX4720, XL281, RAF265, encorafenib, dabrafenib, and vemurafenib.
Some MEK inhibitors include cobimetinib, CI-1040, PD0325901, binimetinib (MEK162), selumetinib, and trametinib (GSK1120212)
It has been found that acupoint-moxibustion has a role in relieving alcohol-induced gastric mucosal injury in a mouse model, which may be closely associated with its effects in up-regulating activities of the epidermal growth factor/ERK signal transduction pathway.
RAF-ERK pathway is also involved in the pathophysiology of Noonan syndrome, a polymalformative disease.
Protein microarray analysis can be used to detect subtle changes in protein activity in signaling pathways. The developmental syndromes caused by germline mutations in genes that alter the RAS components of the MAP/ERK signal transduction pathway are called RASopathies. | 1 | Gene expression + Signal Transduction |
The following genes are analogous or homologous between Drosophila melanogaster (in bold) and human TNFR1 signalling:
* Imd: human orthologue = RIP1
* Tak1: human orthologue = Tak1
* TAB2: human orthologue = TAB2
* Dredd: human orthologue = caspase-8
* FADD: human orthologue = FADD
* Key/Ikkγ: human orthologue = NEMO
* Ird5: human orthologue = IKK2
* Relish: human orthologues = p65/p50 and IκB
* Iap2: human orthologue = cIAP2
* UEV1a: human orthologue = UEV1a
* bend: human orthologue = UBC13 | 1 | Gene expression + Signal Transduction |
The nucleolus within the nucleus can be targeted with a sequence called a nucleolar localization signal (abbreviated NoLS or NOS). | 1 | Gene expression + Signal Transduction |
HMG proteins are thought to play a significant role in various human disorders. Disruptions and rearrangements in the genes coding for some of the HMG proteins are associated with some common benign tumors. Antibodies to HMG proteins are found in patients with autoimmune diseases. The SRY gene on the Y Chromosome, responsible for male sexual differentiation, contains an HMG-Box domain. A member of the HMG family of proteins, HMGB1, has also been shown to have an extracellular activity as a chemokine, attracting neutrophils and mononuclear inflammatory cells to the infected liver. The high-mobility group protein such as HMO1 alters DNA architecture by binding, bending and looping. Furthermore, these HMG-box DNA-binding proteins increase the flexibility of the DNA upon binding.
In mammalian cells, the HMG non-histone proteins can modulate the activity of major DNA repair pathways including base excision repair, mismatch repair, nucleotide excision repair and double-strand break repair. | 1 | Gene expression + Signal Transduction |
High-carbon steel has approximately 0.6 to 1.0% carbon content. It is very strong, used for springs, edged tools, and high-strength wires. | 0 | Metallurgy |
Scaffold proteins act in at least four ways: tethering signaling components, localizing these components to specific areas of the cell, regulating signal transduction by coordinating positive and negative feedback signals, and insulating correct signaling proteins from competing proteins. | 1 | Gene expression + Signal Transduction |
The CAG promoter is a strong synthetic promoter frequently used to drive high levels of gene expression in mammalian expression vectors.
CAG promoter was constructed in the lab of Dr Jun-ichi Miyazaki from the following sequences:
:(C) the cytomegalovirus (CMV) early enhancer element,
:(A) the promoter, the first exon and the first intron of chicken beta-actin gene,
:(G) the splice acceptor of the rabbit beta-globin gene
The resulting synthetic element was used in the pCAGGS expression vector. The initiation codon located at the proximal region of the second exon was disrupted by digesting with NcoI restriction enzyme and replacing the site with a HindIII linker.
Although the whole construct is commonly referred to as the "CAG promoter", it is not a promoter in a strict sense, as it includes a part of the transcribed sequence (the first exon and the first intron of chicken beta-actin gene) and enhancer elements. In addition to the CMV immediate early enhancer, the intron of the chicken beta actin gene contains an enhancer element, which is highly conserved among vertebrates. The 3' part of the promoter has high GC content and is thus refractory to PCR amplification.
Some of the CAG promoter's functions as an effective tool that increases and maintains the expression level of recombinant proteins, as well as increases the expression of transgenes under low temperature conditions. | 1 | Gene expression + Signal Transduction |
A key characteristic of amorphous brazing foils (ABFs) is their relatively low melting points, which typically range from 830 to 1200°C. This attribute is crucial for their application as filler metals in brazing. Due to their ductility and flexibility, ABFs present a viable alternative to filler metals in paste or powder form. This substitution offers notable advantages, such as the elimination of soot formation, a common drawback associated with residual organic solvents in paste-based fillers. Additionally, ABFs help minimize the formation of surface oxides, an issue frequently encountered with gas-atomized powder fillers, thereby enhancing the quality and integrity of the brazed joint. | 0 | Metallurgy |
The Anti-apoptotic Ras signaling cascade is an intracellular signal transduction cascade
that involves the Ras protein and inhibits apoptosis. It is the target of the cancer drug gefitinib.
It may refer to the PI3K/AKT pathway.
It may refer to the MAPK/ERK pathway which involves ras and can affect apoptosis.
The anti-apoptotic STAT pathway does not involve Ras. | 1 | Gene expression + Signal Transduction |
Clustering of genes in prokaryotes was known for a long time. Their genes are grouped in operons, genes within operons share a common promoter unit. These genes are mostly functionally related. The genome of prokaryotes is relatively very simple and compact. In eukaryotes the genome is huge and only a small amount of it are functionally genes, furthermore the genes are not arranged in operons. Except for nematodes and trypanosomes; although their operons are different from the prokaryotic operons. In eukaryotes each gene has a transcription regulation site of its own. Therefore, genes don't have to be in close proximity to be co-expressed. Therefore, it was long assumed that eukaryotic genes were randomly distributed across the genome due to the high rate of chromosome rearrangements. But because the complete sequence of genomes became available it became possible to absolutely locate a gene and measure its distance to other genes.
The first eukaryote genome ever sequenced was that of Saccharomyces cerevisiae, or budding yeast, in 1996. Half a year after that Velculescu et al. (1997) published a research in which they had integrated SAGE data with the now available genome map. During a cell cycle different genes are active in a cell. Therefore, they used SAGE data from three moments of the cell cycle (log phase, S phase-arrested and G2/M-phase arrested cells). Because in yeast all genes have a promoter unit of their own it was not suspected that genes would cluster near to each other but they did. Clusters were present on all 16 yeast chromosomes.
A year later Cho et al. also reported (although in more detail) that certain genes are located near to each other in yeast. | 1 | Gene expression + Signal Transduction |
The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen. The iron is the reducing agent (gives up electrons) while the oxygen is the oxidizing agent (gains electrons). The rate of corrosion is affected by water and accelerated by electrolytes, as illustrated by the effects of road salt on the corrosion of automobiles. The key reaction is the reduction of oxygen:
:O + 4 + 2 → 4
Because it forms hydroxide ions, this process is strongly affected by the presence of acid. Likewise, the corrosion of most metals by oxygen is accelerated at low pH. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows:
:Fe → Fe + 2
The following redox reaction also occurs in the presence of water and is crucial to the formation of rust:
:4 Fe + O → 4 Fe + 2 O
In addition, the following multistep acid–base reactions affect the course of rust formation:
:Fe + 2 HO ⇌ Fe(OH) + 2
:Fe + 3 HO ⇌ Fe(OH) + 3
as do the following dehydration equilibria:
:Fe(OH) ⇌ FeO +
:Fe(OH) ⇌ FeO(OH) +
:2 FeO(OH) ⇌ FeO +
From the above equations, it is also seen that the corrosion products are dictated by the availability of water and oxygen. With limited dissolved oxygen, iron(II)-containing materials are favoured, including FeO and black lodestone or magnetite (FeO). High oxygen concentrations favour ferric materials with the nominal formulae Fe(OH)O. The nature of rust changes with time, reflecting the slow rates of the reactions of solids.
Furthermore, these complex processes are affected by the presence of other ions, such as Ca, which serve as electrolytes which accelerate rust formation, or combine with the hydroxides and oxides of iron to precipitate a variety of Ca, Fe, O, OH species.
The onset of rusting can also be detected in the laboratory with the use of ferroxyl indicator solution. The solution detects both Fe ions and hydroxyl ions. Formation of Fe ions and hydroxyl ions are indicated by blue and pink patches respectively. | 0 | Metallurgy |
The processive polyadenylation complex in the nucleus of eukaryotes works on products of RNA polymerase II, such as precursor mRNA. Here, a multi-protein complex (see components on the right) cleaves the 3′-most part of a newly produced RNA and polyadenylates the end produced by this cleavage. The cleavage is catalysed by the enzyme CPSF and occurs 10–30 nucleotides downstream of its binding site. This site often has the polyadenylation signal sequence AAUAAA on the RNA, but variants of it that bind more weakly to CPSF exist. Two other proteins add specificity to the binding to an RNA: CstF and CFI. CstF binds to a GU-rich region further downstream of CPSF's site. CFI recognises a third site on the RNA (a set of UGUAA sequences in mammals) and can recruit CPSF even if the AAUAAA sequence is missing. The polyadenylation signal – the sequence motif recognised by the RNA cleavage complex – varies between groups of eukaryotes. Most human polyadenylation sites contain the AAUAAA sequence, but this sequence is less common in plants and fungi.
The RNA is typically cleaved before transcription termination, as CstF also binds to RNA polymerase II. Through a poorly understood mechanism (as of 2002), it signals for RNA polymerase II to slip off of the transcript. Cleavage also involves the protein CFII, though it is unknown how. The cleavage site associated with a polyadenylation signal can vary up to some 50 nucleotides.
When the RNA is cleaved, polyadenylation starts, catalysed by polyadenylate polymerase. Polyadenylate polymerase builds the poly(A) tail by adding adenosine monophosphate units from adenosine triphosphate to the RNA, cleaving off pyrophosphate. Another protein, PAB2, binds to the new, short poly(A) tail and increases the affinity of polyadenylate polymerase for the RNA. When the poly(A) tail is approximately 250 nucleotides long the enzyme can no longer bind to CPSF and polyadenylation stops, thus determining the length of the poly(A) tail. CPSF is in contact with RNA polymerase II, allowing it to signal the polymerase to terminate transcription. When RNA polymerase II reaches a "termination sequence" (⁵TTTATT on the DNA template and ⁵AAUAAA on the primary transcript), the end of transcription is signaled. The polyadenylation machinery is also physically linked to the spliceosome, a complex that removes introns from RNAs. | 1 | Gene expression + Signal Transduction |
ASF/SF2 has been shown to interact with:
* CDC5L,
* CLK1,
* PSIP1,
* SFRS2,
* SRPK1,
* SRPK2,
* TOP1,
* U2 small nuclear RNA auxiliary factor 1, and
* snRNP70. | 1 | Gene expression + Signal Transduction |
The GAIN domain (G-protein-coupled receptor (GPCR) autoproteolysis-inducing domain) is a protein domain found in a number of cell surface receptors, including adhesion-GPCRs and polycystic kidney disease proteins PKD1 and PKD2. The domain is involved in the self-cleavage of these transmembrane receptors, and has been shown to be crucial for their function . Point mutations within the GAIN domain of PKD1 and GPR56 are known to cause polycystic kidney disease and polymicrogyria, respectively. | 1 | Gene expression + Signal Transduction |
Coherent grain boundaries are those in which the crystal lattice of adjacent grains is continuous across the boundary. In other words, the crystallographic orientation of the grains on either side of the boundary is related by a small rotation or translation. Coherent grain boundaries are typically observed in materials with small grain sizes or in highly ordered materials such as single crystals. Because the crystal lattice is continuous across the boundary, there are no defects or dislocations associated with coherent grain boundaries. As a result, they do not act as barriers to the motion of dislocations and have little effect on the strength of a material. However, they can still affect other properties such as diffusion and grain growth.
When solid solutions become supersaturated and precipitation occurs, tiny particles are formed. These particles typically have interphase boundaries that match up with the matrix, despite differences in interatomic spacing between the particle and the matrix. This creates a coherency strain, which causes distortion. Dislocations respond to the stress field of a coherent particle in a way similar to how they interact with solute atoms of different sizes. It is worth noting that the interfacial energy can also influence the kinetics of phase transformations and precipitation processes. For instance, the energy associated with a strained coherent interface can reach a critical level as the precipitate grows, leading to a transition from a coherent to a disordered (non-coherent) interface. This transition occurs when the energy associated with maintaining the coherency becomes too high, and the system seeks a lower energy configuration. This happens when particle dispersion is introduced into a matrix. Dislocations pass through small particles and bow between large particles or particles with disordered interphase boundaries. The predominant slip mechanism determines the contribution to strength, which depends on factors such as particle size and volume fraction. | 0 | Metallurgy |
The D-gun atomises the powder feedstock into extremely small particles (80–95% of particles by total number are of size <100 nm). This means proper extraction facilities are required for inhalation safety purposes. Also isolation of the D-gun is recommended to avoid operators breathing in the dangerous dust and fumes. If operators are to enter the room they should wear appropriate dust masks or respirators. Many of the compounds used as the feedstock in detonation spraying are detrimental to human health if ingested or inhaled. Airborne metals from the detonation gun in particular are harmful to the lungs. Exposure to cadmium for example can cause harm to the kidneys and lungs, vomiting, loss of consciousness and even reduced fertility. Also heavy metals have been shown in recent studies to be carcinogenic such as lead, nickel, chromium, and cadmium. Some serious lung conditions caused by metal dust inhalation include:
* Silicosis - a lung disease cause by inhaling silica present in the feedstock compounds.
* Siderosis - (silver polishers lung or welders lung), a lung disease cause by inhaling iron present in the feedstock compounds.
* Alzheimer's - a memory loss disease more common among the elderly has been shown by some studies to be caused by high levels of exposure to aluminum (among many other causes). However, it must be noted that these studies were not conclusive, and others have proven otherwise.
* Metal fume fever - this can occur in some individuals following exposure certain metal compounds (such as copper, zinc, magnesium and aluminum alloys or oxides) that have a particularly unpleasant odour. The fumes are caused as a byproduct when the metals are heated and can trigger a fever-like reaction that may need medical attention. | 0 | Metallurgy |
Since multiple studies have shown that RNA Pol II can be found at a very large number of extragenic regions, it is possible that eRNAs simply represent the product of random “leaky” transcription and carry no functional significance. The non-specific activity of RNA Pol II would therefore allow extragenic transcriptional noise at sites where chromatin is already in an open and transcriptionally competent state. This would explain even tissue-specific eRNA expression as open sites are tissue-specific as well. | 1 | Gene expression + Signal Transduction |
It is crucial to note that although most of the gene deserts explored here are essential, it could be that the majority of the contents in gene deserts are still likely to be inessential and disposable. Naturally, this is not to say that the roles that gene deserts play are inessential or unimportant, rather than their functions may include buffering effects. An example of essential gene deserts with inessential DNA content are the telomeres that protect the ends of genomes. Telomeres can be categorized as true gene deserts, given that they solely contain repeats of TTAGGG (in humans) and do not have apparent protein-coding functions. Without these telomeres, human genomes would be severely mutated within a fixed number of cell cycles. On the other hand, since telomeres do not code for proteins, their loss ensures that there is no effect in important processes. Therefore, the term “junk” DNA should no longer be applied to any region of the genome; every portion of the genome should play a role in protecting, regulating, or repairing the protein coding regions that determine the functions of life. Although there is still much to learn about the nooks and crannies of the immense (yet limited) human genome, with the aid of various new technologies and the synthesis of the full human genome, we may perhaps unravel a great collection of secrets in the approaching years about the marvels of our genetic code. | 1 | Gene expression + Signal Transduction |
Up-regulated expression of genes in mammals can be initiated when signals are transmitted to the promoters associated with the genes. Cis-regulatory DNA sequences that are located in DNA regions distant from the promoters of genes can have very large effects on gene expression, with some genes undergoing up to 100-fold increased expression due to such a cis-regulatory sequence. These cis-regulatory sequences include enhancers, silencers, insulators and tethering elements. Among this constellation of sequences, enhancers and their associated transcription factor proteins have a leading role in the regulation of gene expression.
Enhancers are sequences of the genome that are major gene-regulatory elements. Enhancers control cell-type-specific gene expression programs, most often by looping through long distances to come in physical proximity with the promoters of their target genes. In a study of brain cortical neurons, 24,937 loops were found, bringing enhancers to promoters. Multiple enhancers, each often at tens or hundred of thousands of nucleotides distant from their target genes, loop to their target gene promoters and coordinate with each other to control expression of their common target gene.
The schematic illustration in this section shows an enhancer looping around to come into close physical proximity with the promoter of a target gene. The loop is stabilized by a dimer of a connector protein (e.g. dimer of CTCF or YY1), with one member of the dimer anchored to its binding motif on the enhancer and the other member anchored to its binding motif on the promoter (represented by the red zigzags in the illustration). Several cell function specific transcription factor proteins (in 2018 Lambert et al. indicated there were about 1,600 transcription factors in a human cell) generally bind to specific motifs on an enhancer and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern the level of transcription of the target gene. Mediator (coactivator) (a complex usually consisting of about 26 proteins in an interacting structure) communicates regulatory signals from enhancer DNA-bound transcription factors directly to the RNA polymerase II (RNAP II) enzyme bound to the promoter.
Enhancers, when active, are generally transcribed from both strands of DNA with RNA polymerases acting in two different directions, producing two eRNAs as illustrated in the Figure. An inactive enhancer may be bound by an inactive transcription factor. Phosphorylation of the transcription factor may activate it and that activated transcription factor may then activate the enhancer to which it is bound (see small red star representing phosphorylation of a transcription factor bound to an enhancer in the illustration). An activated enhancer begins transcription of its RNA before activating a promoter to initiate transcription of messenger RNA from its target gene. | 1 | Gene expression + Signal Transduction |
Several, so-called mTOR/PI3K dual inhibitors (TPdIs), have been developed and are in early-stage preclinical trials and show promising results. Their development has been benefited from previous studies with PI3K-selective inhibitors. The activity of these small molecules from rapalog activity differs in the way by blocking both mTORC1-dependent phospholylation of S6K1 and mTORC2-dependent phosphorylation of AKT Ser473 residue.
Dual mTOR/PI3K inhibitors include dactolisib, voxtalisib, BGT226, SF1126, PKI-587 and many more. For example, Novartis has developed the compound NVPBE235 that was reported to inhibit tumor growth in various preclinical models. It enhances antitumor activity of some other drugs such as vincristine. Dactolisib seems to inhibit effectively both wild-type and mutant form of PI3KCA, which suggests its use towards wide types of tumors. Studies have shown superior antiproliferative activity to rapalogs and in vivo models have confirmed these potent antineoplastic effects of dual mTOR/PI3K inhibitors. These inhibitors target isoforms of PI3K (p110α, β and γ) along with ATP-binding sites of mTORC1 and mTORC2 by blocking PI3K/AKT signaling, even in cancer types with mutations in this pathway. | 1 | Gene expression + Signal Transduction |
After the war, Birger Solberg resumed control, but the economics and equipment of the facility had become unfavorable. Feeling empathy for the former workers, he devised a new business plan based on collecting German plane wrecks and other debris in middle-Norway and re-melting them.
The facility was closed on December 20, 2002 and production moved to Mo i Rana. | 0 | Metallurgy |
In 1964 Impalco decided to offer Fulmer for sale.
At that time Dr (later Sir) James Taylor, who was Chairman of Imperial Metal Industries (IMI), was also the Honorary Treasurer of the Institute of Physics and the Physical Society (IOP). He proposed that IOP should acquire Fulmer and thus become the first Learned Society to own a commercial research company. The Council of the IOP, in recommending the purchase of Fulmer to its membership, expressed the intention that, after providing for equipment needs, income from the investment in Fulmer was to be used to support the scientific and educational work of the IOP. The purchase was made possible by a grant from ICI, to be repaid over ten years from Fulmer profits. Thus, in 1965, IOP became the owner of Fulmer. | 0 | Metallurgy |
A third element was presently supplied in the rich repertory of decorative motives, Egyptian and Assyrian, that was brought to Europe by Phoenician traders or fetched from Asia by adventurous Greeks. A vast amount of oriental merchandise found its way into Greece and Italy around 800 BC. There is some uncertainty about the place of manufacture of much of the surviving bronze work, but the same doubt serves to emphasize the close resemblance that these pieces, Phoenician, Greek or Etruscan, bear to their Assyrian or Egyptian models. Foremost among them are the bowls and shields from the Idaean cave in Crete. These interesting bowls are embossed with simple bands of animals, the shields with bold and complicated designs of purely oriental character. It is unlikely that a Greek craftsman in this vigorous Geometric age could suppress his style and produce mechanical copies such as these. So in Etruscan graves beside inscribed Phoenician bowls there have been found great cauldrons, adorned with jutting heads of lions and griffins, and set on conical stands which are embossed with Assyrian winged monsters. | 0 | Metallurgy |
There are many types of defects which result from many different causes. Some of the solutions to certain defects can be the cause for another type of defect.
The following defects can occur in sand castings. Most of these also occur in other casting processes. | 0 | Metallurgy |
Grev Brook; Bill Bowyer; David Davies; Mike Dewey; Bill Flavell; Philipp Gross; Eddie Sugars; GI Williams | 0 | Metallurgy |
Fas ligand or FasL is a type II transmembrane protein belonging to the tumor necrosis factor superfamily (TNFSF). It is homotrimeric, which means it consists of three identical polypeptides. It has a long cytoplasmic domain, a stalk region, a transmembrane domain (TM), a TNF homology domain (THD) responsible for the homotrimerization. Including a C-terminal region involved in binding to CD95, also known as the fas receptor.
FasL binds to fas, leading to the formation of fas:FasL assemble. This interaction initiates the formation of the death-inducing signaling complex, resulting in apoptosis.
FasL is expressed on various cell types, including T cells, natural killer cells, monocytes, neutrophils, and vascular endothelial cells. FasL exists in both membrane-anchored and soluble forms. | 1 | Gene expression + Signal Transduction |
The Wohlwill process is an industrial-scale chemical procedure used to refine gold to the highest degree of purity (99.999%). The process was invented in 1874 by Emil Wohlwill. This electrochemical process involves using a cast gold ingot, often called a doré bar, of 95%+ gold to serve as an anode. Lower percentages of gold in the anode will interfere with the reaction, especially when the contaminating metal is silver or one of the platinum group elements. The cathodes for this reaction are small sheets of pure (24k) gold sheeting or stainless steel. Current is applied to the system, and electricity travels through the electrolyte of chloroauric acid. Gold and other metals are dissolved at the anode, and pure gold (coming through the chloroauric acid by ion transfer) is plated onto the gold cathode. When the anode is dissolved, the cathode is removed and melted or otherwise processed in the manner required for sale or use. The resulting gold is 99.999% pure, and of higher purity than gold produced by the other common refining method, the Miller process, which produces gold of 99.5% purity.
For industrial gold production the Wohlwill process is necessary for highest purity gold applications. When lower purity gold is required, refiners often utilize the Miller process for its relative ease and quicker turnaround times and because it does not require a large inventory of gold, in the form of chloroauric acid. | 0 | Metallurgy |
In soldering metals, flux serves a threefold purpose: it removes any oxidized metal from the surfaces to be soldered, seals out air thus preventing further oxidation, and improves the wetting characteristics of the liquid solder. Some fluxes are corrosive, so the parts have to be cleaned with a damp sponge or other absorbent material after soldering to prevent damage. Several types of flux are used in electronics.
A number of standards exist to define the various flux types. The principal standard is J-STD-004.
Various tests, including the ROSE test, may be used after soldering to check for the presence of ionic or other contaminants that could cause short circuits or other problems. | 0 | Metallurgy |
In genetics, a promoter is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter. The RNA transcript may encode a protein (mRNA), or can have a function in and of itself, such as tRNA or rRNA. Promoters are located near the transcription start sites of genes, upstream on the DNA (towards the 5' region of the sense strand).
Promoters can be about 100–1000 base pairs long, the sequence of which is highly dependent on the gene and product of transcription, type or class of RNA polymerase recruited to the site, and species of organism.
Promoters control gene expression in bacteria and eukaryotes. RNA polymerase must attach to DNA near a gene for transcription to occur. Promoter DNA sequences provide an enzyme binding site. The -10 sequence is TATAAT. -35 sequences are conserved on average, but not in most promoters.
Artificial promoters with conserved -10 and -35 elements transcribe more slowly. All DNAs have "Closely spaced promoters". Divergent, tandem, and convergent orientations are possible. Two closely spaced promoters will likely interfere. Regulatory elements can be several kilobases away from the transcriptional start site in gene promoters (enhancers).
In eukaryotes, the transcriptional complex can bend DNA, allowing regulatory sequences to be placed far from the transcription site. The distal promoter is upstream of the gene and may contain additional regulatory elements with a weaker influence. RNA polymerase II (RNAP II) bound to the transcription start site promoter can start mRNA synthesis. It also typically contains CpG islands, a TATA box, and TFIIB recognition elements.
Hypermethylation downregulates both genes, while demethylation upregulates them. Non-coding RNAs are linked to mRNA promoter regions. Subgenomic promoters range from 24 to 100 nucleotides (Beet necrotic yellow vein virus). Gene expression depends on promoter binding. Unwanted gene changes can increase a cell's cancer risk.
MicroRNA promoters often contain CpG islands. DNA methylation forms 5-methylcytosines at the 5' pyrimidine ring of CpG cytosine residues. Some cancer genes are silenced by mutation, but most are silenced by DNA methylation. Others are regulated promoters. Selection may favor less energetic transcriptional binding.
Variations in promoters or transcription factors cause some diseases. Misunderstandings can result from using a canonical sequence to describe a promoter. | 1 | Gene expression + Signal Transduction |
Steel which utilizes the EPS process to remove surface scale shows few differences from steel which utilizes acid pickling to remove surface scale. "Downstream" industrial processes such as galvanizing, cold reducing and painting of EPS-processed steel strip show it to be interchangeable with acid-pickled steel strip. This also holds true for common sheet metal fabrication processes, such as laser cutting, plasma cutting, stamping, welding, bending, and roll forming – no meaningful difference between steel strip using the EPS process and steel strip using acid pickling.
An area where the difference between EPS-processed steel strip and acid-pickled steel strip is apparent is visual appearance. Steel which has undergone EPS processing exhibits a more uniform, lustrous appearance, as shown in Figure 4. In the EPS process, the impact of the abrasive particles on the steel surface serves to "smooth out" minor surface imperfections such as scratches, pits, roll marks and silicone streaks.
Another area of difference between EPS-treated steel strip and acid-pickled steel strip is rust resistance. Conventional acid-pickled steel strip is frequently coated with a thin film of oil to serve as a barrier to contact with oxygen so as to prevent rusting. EPS-processed steel is inherently rust-inhibitive and, therefore, needs no oil or other coating to prevent rusting. Many "downstream" processes and steel fabrication processes must have the steel's oil coating (or other surface contaminants) removed as a precursor step of the process. Use of EPS-treated steel in these processes precludes the need for any such "oil-stripping" precursor step, thereby simplifying the process. | 0 | Metallurgy |
Immediate manifestations of caustic substance ingestions include erosions of mucosal surfaces of the gastrointestinal tract or airway (which can cause bleeding if the erosions extend to a blood vessel), mouth and tongue swelling, drooling or hypersalivation, nausea, vomiting, dyspnea, dysphonia/aphonia irritation of the eyes and skin. Perforation of the esophagus can lead to mediastinitis or perforation of the stomach or bowel can lead to peritonitis Swelling of the airway or laryngospasm can occur leading to compromised breathing. Injuries affecting the respiratory system include aspiration pneumonia and laryngeal sores. Signs of respiratory compromise include stridor and a change in a person's voice.
Later manifestations of caustic substance ingestions include esophageal strictures or stenosis; which can result in chronic pain and malnutrition. Esophageal strictures more commonly occur after more severe mucosal injury, occurring in to 71% and 100% of grade 2b and 3 mucosal lesions respectively. Remote manifestations of caustic ingestions include esophageal cancer. People who have a history of caustic substance ingestion are 1000-3000 times more likely to develop esophageal cancer with most cases occurring 10–30 years after the ingestion. | 0 | Metallurgy |
Sources of manganese ore generally also contain iron oxides. As manganese is harder to reduce than iron, during the reduction of manganese ore, iron is also reduced and mixed with the manganese in the melt, unlike other oxides such as SiO, AlO and CaO.
Reduction is achieved using a submerged arc furnance. There are two main industrial procedures to perform the reduction, the discard slag method (or flux method) and the duplex method (or fluxless method). Despite the name, the differences in the method are not in the addition of flux, but rather in the number of stages required. In the flux method, basic fluxes such as CaO are added in order to electrolytically reduce the manganese ore:
The remaining slag after the reduction process has approximately 15-20% manganese content, which is usually discarded.
In the fluxless method, carbon reduction is also used in the first stage, but the fluxes added do not necessarily increase the activity of the manganese. As a result, the remaining slag has a concentration of 30% to 50% of the manganese. This is then reprocessed with quartzite to make silicomanganese alloys. The resultant discarded slag has a manganese content of less than 5%, increasing the yield. As a result, this method is used more often in industry.
In both methods, due to the addition of carbon as an reducing agent, the alloy produced is referred to as high-carbon ferromanganese (HCFM), with a carbon content of up to 6%.
A correct mix of coke, flux and ore composition is required to give high yield and reliable furnance operation, by achieving the desired chemical properties, viscosity and smelting temperature in the resulting melt. Since the iron to manganese ratio of natural manganese sources vary greatly, mixing ores from several sources is sometimes done to give a certain desired ratio.
In the manufacture of steel, low-carbon ferromanganese (LCFM) is preferred due to the ability to accurately control the amount of carbon in the resultant steel. To arrive at LCFM from HCFM, there are also two main methods: silicothermal reduction and oxygen refinement.
In silicothermal reduction, silicomanganese from the second step of the duplex process is used as a reductant. After a variety of mixing and meting steps to reduce the silicon content, a low-carbon allow with less than 0.8% carbon and 1% silicon by weight can be obtained.
In the oxygen refinement method, HCFM is melted and heated to a high temperature of . Oxygen is then blown in to oxidise the carbon into CO and CO. The disadvantage of this process is that the metal is also oxidised at these high temperatures. Manganese oxide collects mainly in the form of MnO in the dust blown out from the crucible. | 0 | Metallurgy |
* Williams, H. (trans.), A sixteenth-century German treatise: Von Stahel und Eysen. 1532, Technical studies in the field of the fine arts, 4.2 (October, 1935), 63-92.
* Smith, Cyril Stanley (ed.), Sources for the History of the Science of Steel, 1532-1786, Society for the History of Technology, 4 (Cambridge, Mass.: Society for the History of Technology, 1968), pp. 7–19. | 0 | Metallurgy |
The noble metals are siderophiles (iron-lovers). They tend to sink into the Earth's core because they dissolve readily in iron either as solid solutions or in the molten state. Most siderophile elements have practically no affinity whatsoever for oxygen: indeed, oxides of gold are thermodynamically unstable with respect to the elements.
Copper, silver, gold, and the six platinum group metals are the only native metals that occur naturally in relatively large amounts. | 0 | Metallurgy |
ECgene in computational biology is a database of genomic annotations taking alternative splicing events into consideration. | 1 | Gene expression + Signal Transduction |
There may be a general misconception between the term corrosion inspection and corrosion monitoring, but inspection means frequent checkpoints to check for changes or deviations from predicted results, while corrosion monitoring is a continuous check to control and act quickly against change. In inspection, the purpose is to evaluate or estimate the corrosion time in order to replace or correct the corrosion, while in corrosion monitoring, the purpose is to take care of the change in order to prevent corrosion and to improve the ways of prevention. | 0 | Metallurgy |
Archaeometallurgy is the study of the past use and production of metals by humans. It is a sub-discipline of archaeology and archaeological science. | 0 | Metallurgy |
(p)ppGpp, guanosine pentaphosphate and tetraphosphate, also known as the "magic spot" nucleotides, are alarmones involved in the stringent response in bacteria that cause the inhibition of RNA synthesis when there is a shortage of amino acids. This inhibition by (p)ppGpp decreases translation in the cell, conserving amino acids present. Furthermore, ppGpp and pppGpp cause the up-regulation of many other genes involved in stress response such as the genes for amino acid uptake (from surrounding media) and biosynthesis. | 1 | Gene expression + Signal Transduction |
In metallurgy, solid solution strengthening is a type of alloying that can be used to improve the strength of a pure metal. The technique works by adding atoms of one element (the alloying element) to the crystalline lattice of another element (the base metal), forming a solid solution. The local nonuniformity in the lattice due to the alloying element makes plastic deformation more difficult by impeding dislocation motion through stress fields. In contrast, alloying beyond the solubility limit can form a second phase, leading to strengthening via other mechanisms (e.g. the precipitation of intermetallic compounds). | 0 | Metallurgy |
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Cleavage factors are two closely associated protein complexes involved in the cleavage of the 3' untranslated region of a newly synthesized pre-messenger RNA (mRNA) molecule in the process of gene transcription. The cleavage is the first step in adding a polyadenine tail to the pre-mRNA, which is one of the necessary post-transcriptional modifications necessary for producing a mature mRNA molecule.
In mammals, the two cleavage factors are known as CFIm and CFIIm. The proteins that constitute these complexes are recruited to the cleavage site by cleavage and polyadenylation specificity factor and cleavage stimulatory factor, and form a larger complex that also includes polyadenine polymerase, which performs the polyadenylation reaction. | 1 | Gene expression + Signal Transduction |
In addition to the role of the lactate shuttle in supplying NAD+ substrate for β-oxidation in the peroxisomes, the shuttle also regulates FFA mobilization by controlling plasma lactate levels. Research has demonstrated that lactate functions to inhibit lipolysis in fat cells through activation of an orphan G-protein couple receptor (GPR81) that acts as a lactate sensor, inhibiting lipolysis in response to lactate . | 1 | Gene expression + Signal Transduction |
Transvection is an epigenetic phenomenon that results from an interaction between an allele on one chromosome and the corresponding allele on the homologous chromosome. Transvection can lead to either gene activation or repression. It can also occur between nonallelic regions of the genome as well as regions of the genome that are not transcribed.
The first observation of mitotic (i.e. non-meiotic) chromosome pairing was discovered via microscopy in 1908 by Nettie Stevens. Edward B. Lewis at Caltech discovered transvection at the bithorax complex in Drosophila in the 1950s. Since then, transvection has been observed at a number of additional loci in Drosophila, including the genes known as white, decapentaplegic, eyes absent, vestigial, and yellow.
As defined by Lewis, "Operationally, transvection is occurring if the phenotype of a given genotype can be altered solely by disruption of somatic (or meiotic) pairing. Such disruption can generally be accomplished by introduction of a heterozygous rearrangement that disrupts pairing in the relevant region but has no position effect of its own on the phenotype" (cited by Ting Wu and Jim Morris, 1999). Recently, pairing-mediated phenomena have been observed in species other than Drosophila, including mice, humans, plants, nematodes, insects, and fungi. In light of these findings, transvection may represent a potent and widespread form of gene regulation.
Transvection appears to be dependent upon chromosome pairing. In some cases, if one allele is placed on a different chromosome by a translocation, transvection does not occur. Transvection can sometimes be restored in a translocation homozygote, where both alleles may once again be able to pair. Restoration of phenotype has been observed at bithorax, decapentaplegic, eyes absent, and vestigial, and with transgenes of white. In some cases, transvection between two alleles leads to intragenic complementation while disruption of transvection disrupts the complementation.
Transvection is believed to occur through a variety of mechanisms. In one mechanism, the enhancers of one allele activate the promoter of a paired second allele. Other mechanisms include pairing-sensitive silencing and enhancer bypass of a chromatin insulator through pairing-mediated changes in gene structure.
The physiological relevance of transvection has recently been documented in the context of sex-biased gene expression. In Drosophila, transvection acts on the female X-linked gene yellow, which is homozygous in females (XX) versus hemizygous in males (XY). | 1 | Gene expression + Signal Transduction |
A boundary can be described by the orientation of the boundary to the two grains and the 3-D rotation required to bring the grains into coincidence. Thus a boundary has 5 macroscopic degrees of freedom. However, it is common to describe a boundary only as the orientation relationship of the neighbouring grains. Generally, the convenience of ignoring the boundary plane orientation, which is very difficult to determine, outweighs the reduced information.
The relative orientation of the two grains is described using the rotation matrix:
Using this system the rotation angle θ is:
while the direction [uvw] of the rotation axis is:
The nature of the crystallography involved limits the misorientation of the boundary. A completely random polycrystal, with no texture, thus has a characteristic distribution of boundary misorientations (see figure). However, such cases are rare and most materials will deviate from this ideal to a greater or lesser degree. | 0 | Metallurgy |
The Euglena photoreceptor was identified as a blue-light-activated adenylyl cyclase. Excitation of this receptor protein results in the formation of cyclic adenosine monophosphate (cAMP) as a second messenger. Chemical signal transduction ultimately triggers changes in flagellar beat patterns and cell movement.
The archaeal-type rhodopsins of Chlamydomonas contain an all-trans retinylidene chromatophore which undergoes photoisomerization to a 13-cis isomer. This activates a photoreceptor channel, leading to a change in membrane potential and cellular calcium ion concentration. Photoelectric signal transduction ultimately triggers changes in flagellar strokes and thus cell movement. | 1 | Gene expression + Signal Transduction |
SMAs find a variety of applications in civil structures such as bridges and buildings. In the form of rebars or plates, they can be used for flexural, shear and seismic strengthening of concrete and steel structures. Another application is Intelligent Reinforced Concrete (IRC), which incorporates SMA wires embedded within the concrete. These wires can sense cracks and contract to heal micro-sized cracks. Also the active tuning of structural natural frequency using SMA wires to dampen vibrations is possible, as well as the usage of SMA fibers in concrete. | 0 | Metallurgy |
The first stage is called roughing, which produces a rougher concentrate. The objective is to remove the maximum amount of the valuable mineral at as coarse a particle size as practical. Grinding costs energy. The goal is to release enough gangue from the valuable mineral to get a high recovery. Some concentrators use a preflotation step to remove low density impurities such as carbonaceous dust. The rougher concentrate is normally subjected to further stages of flotation to reject more of the undesirable minerals that also reported to the froth, in a process known as cleaning. The resulting material is often subject to further grinding (usually called regrinding). Regrinding is often undertaken in specialized regrind mills, such as the IsaMill. The rougher flotation step is often followed by a scavenger flotation step that is applied to the rougher tailings to further recover any of the target minerals. | 0 | Metallurgy |
* bicarbonate derived from carbonic anhydrase (CA)-dependent hydration.
* CO metabolism
* Enters through membrane-transporting proteins or cystic fibrosis transmembrane conductance regulators.
* Calcium enters by voltage-dependent Ca channels or by release from the endoplasmic reticulum.
* Hydrogencarbonate and calcium activates sAC in the nucleus.
* sAC inside mitochondria is activated by metabolically generated CO through carbonic anhydrase. | 1 | Gene expression + Signal Transduction |
Because the ligaments of these materials are essentially small metallic samples, they are themselves expected to be quite ductile; although, the entire nano-porous material is often observed to be brittle in tension. Dislocation behavior is extensive within the ligaments (just as would be expected in a metal): a high density. of partial dislocations, stacking faults and twins have been observed both in simulation and in TEM. However, the morphology of the ligaments makes bulk dislocation motion very difficult; the limited size of each ligament and complex connectivity within the nano-porous structure means that a dislocation cannot freely travel long distances and thus induce large-scale plasticity. | 0 | Metallurgy |
Depletion gilding is a method for producing a layer of nearly pure gold on an object made of gold alloy by removing the other metals from its surface. It is sometimes referred to as a "surface enrichment" process. | 0 | Metallurgy |
A coin assayer is often assigned to each mint or assay office to determine and assure that all coins produced at the mint have the correct content or purity of each metal specified, usually by law, to be contained in them. This was particularly important when gold and silver coins were produced for circulation and used in daily commerce. Few nations, however, persist in minting silver or gold coins for general circulation. For example, the U.S. discontinued the use of gold in coinage in 1933. The U.S. was one of the last nations to discontinue the use of silver in circulating coins after its 1970 A.D. half dollar coin, although the amount of silver used in smaller denomination coins was ended after 1964. Even with the half dollar, the amount of silver used in the coins was reduced from 90% in 1964 and earlier to 40% between 1965 and 1970. Copper, nickel, cupro-nickel and brass alloys now predominate in coin making. Notwithstanding, several national mints, including the Perth Mint in Australia, the Austrian Mint, the British Royal Mint, the Royal Canadian Mint, the South African Mint, and the U.S. Mint continue to produce precious metal bullion coins for collectors and investors. The precious metal purity and content of these coins is guaranteed by the respective mint or government, and, therefore, the assay of the raw materials and finished coins is an important quality control.
In the UK, the Trial of the Pyx is a ceremonial procedure for ensuring that newly minted coins conform to required standards. | 0 | Metallurgy |
Hydrogen forms whenever molten aluminium comes into contact with water vapor, and easily dissolves into the melt. The gas tends to come out of the solution and forms bubbles when the melt solidifies.
The detrimental effects arising from the presence of an excess of dissolved hydrogen in aluminium are numerous. Hydrogen causes porosity in aluminum products leading to many casting defects, reduced mechanical properties like fatigue and lower corrosion resistance. Several methods are used to reduce the amount of dissolved hydrogen from the melt, such as furnace fluxing prior to the casting process or using in-line degassing equipment during the casting process. | 0 | Metallurgy |
The elements of a eukaryotic and prokaryotic 5′ UTR differ greatly. The prokaryotic 5′ UTR contains a ribosome binding site (RBS), also known as the Shine–Dalgarno sequence (AGGAGGU), which is usually 3–10 base pairs upstream from the initiation codon. In contrast, the eukaryotic 5′ UTR contains the Kozak consensus sequence (ACCAUGG), which contains the initiation codon. The eukaryotic 5′ UTR also contains cis-acting regulatory elements called upstream open reading frames (uORFs) and upstream AUGs (uAUGs) and termination codons, which have a great impact on the regulation of translation (see below). Unlike prokaryotes, 5′ UTRs can harbor introns in eukaryotes. In humans, ~35% of all genes harbor introns within the 5′ UTR. | 1 | Gene expression + Signal Transduction |
CK1δ and CK1ε have been shown to be relevant in human disease. Recent findings indicate that pharmaceutical inhibition of CK1 may be a promising therapeutic for aberrant circadian rhythm. Mutations and variants of the CK1ε phosphorylation site of PER2 are associated with cases of Familial Advanced Sleep Phase Syndrome (FASPS). Similarly, length variations in the CK1ε phosphorylation site of PER3 have been found to correlate with morningness and eveningness; longer alleles are associated with early risers while shorter alleles are associated with late risers. Additionally, 75% of patients with Delayed sleep phase syndrome are homozygous for the shorter allele.
Mutations in CK1 have been shown to alter circadian behavior in other mammals, as well. In 1988, the golden hamster tau mutant, which has a freerunning period of 22hrs, was the first mammalian circadian mutant discovered. Twelve years later in 2000, the tau mutation was mapped to CK1ε. Since its discovery, the tau mutant has proven to be a valuable research tool in circadian biology. CK1ɛ, a T178C substitution, is a gain-of function mutation that causes an increase in degradation of PER, but not CRY. This creates a disruption in the PER-regulated feedback loop and consequently an acceleration of molecular oscillations. Homozygous mutants (CK1ε(tau/tau)) show a significant decrease in period, both in vivo (behaviorally) and in vitro (measured by firing rates of the suprachiasmatic nucleus). Recent research has also identified a link between mutations in the CK1δ gene and familial migraine and advanced sleep phase, a finding that was replicated in mice migraine models. | 1 | Gene expression + Signal Transduction |
The Scythians emerged as a people prior to the 7th Century BC, when they were first mentioned in historical records. The Scythian civilization consisted of a number of distinct tribal groups scattered across the Pontic Steppes, Caucasus, and Central Asia. Though primarily a nomadic people, the Scythians established a number of settlements across their territory; these establishments in turn allowed for the development of a sedentary society and the accompanying development of trade skills, including metalworking.
Scythian knowledge of metalworking likely originated with the peoples of Iran and China, with this knowledge spreading along trade routes and arriving in the steppes from the 2nd to 1st Millennium BC. Early Scythian metallurgy was centered around bronzeworking, as these skills had already been widely adopted by the Scythians neighbors. The Minusinsk Basin of Siberia has been speculated as the origin point for the raw materials used in Bronze-age Scythian metallurgy, and Scythian access to this region fueled the peoples later centuries of expansion. During the 8th Century BC Scythians were often employed by nations in the Near East and these returning soldiers may have brought knowledge of iron-working back to their homeland, and by the start of the 6th-century BC the practice was widespread in the Pontic steppes. In addition to bronze and iron working, gold and copper-working were also present in Scythian society; in his commentary on the Scythian people, Greek historian Herodotus remarked on their fondness for making things from gold and copper.
Metallurgy held a major place in Scythian society as metalworkers were needed to produce material goods to support the Scythian way of life. As a nomadic society with broad borders, the Scythians often raided neighboring peoples and as such required metal weaponry - particularly iron swords and bronze arrowheads. It has been speculated that the Scythian's use of stylized metal adornments may have been copied from their opponents during these conflicts. In addition, jewelry and other adornment was in demand among all classes of society, as can be seen with the discovery of metal adornments in the burial tombs attributed to the Scythians. One notable aspect of Scythian clothing was the widespread use of metal belts.
Other signs of Scythian metalworking can be found throughout sites attributed to the people. Several notable Scythian archeological sites contain the remnants of metalworking operations; at one settlement along the Dnieper, remnants of blast furnaces and slag have been found, implying the existence of a large metallurgical center. Studies of other Scythian sites have also led to the remains of metal workshops and tools being found, further supporting the theory that the Scythians were organized craftspeople. Scythian metalworkers were particularly renowned for the high quality of their copper crafting. During war, portable molds were brought to forge arrowheads for the Scythian cavalry. Scythian metallurgy also influenced the metallurgy of the Koban people of the North Caucasus. | 0 | Metallurgy |
Sigma B was the first anti-sigma factor identified in a bacterium. It is found in Bacillus subtilis and other similar bacteria. Sigma B is a stress response factor that plays a role in survival and against destruction that could be caused by other organisms such as mammals. General stress responses that are controlled by Sigma B are stimulated by things like temperature, salt concentration, energy depletion, etc. Once activated, Sigma B binds to the RNAP and recognizes a promoter, causing inhibition of the stimuli. Because Sigma B orthologs are conserved in various gram-positive bacteria, this anti-sigma factor plays an essential role in the evolution of different bacteria and their ability to respond to stressing factors. Scientist have found that the anti- sigma factor, Sigma B controls more than 150 genes that are influential in stress response. | 1 | Gene expression + Signal Transduction |
Taking results gathered largely from ‘real world’ exposure sites, automotive companies, led originally by the Japanese automobile industry, developed their own Cyclic Corrosion Tests. These have evolved in different ways for different vehicle manufacturers, and such tests still remain largely industry specific, with no truly international CCT standard. However, they all generally require most of the following conditions to be created, in a repeating sequence or ‘cycle’, though not necessarily in the following order:
• A salt spray ‘pollution’ phase. This may be similar to the traditional salt spray test although in some cases direct impingement by the salt solution on the test specimens, or even complete immersion in salt water, is required. However, this ‘pollution’ phase is generally shorter in duration than a traditional salt spray test.
• An air drying phase. Depending on the test, this may be conducted at ambient temperature, or at an elevated temperature, with or without control over the relative humidity and usually by introducing a continuous supply of relatively fresh air around the test samples at the same time. It is generally required that the samples under test should be visibly ‘dry’ at the end of this test phase.
• A condensation humidity ‘wetting’ phase. This is usually conducted at an elevated temperature and generally a high humidity of 95-100%RH. The purpose of this phase is to promote the formation of condensation on the surfaces of the samples under test.
• A controlled humidity/humidity cycling phase. This requires the tests samples to be exposed to a controlled temperature and controlled humidity climate, which can either be constant or cycling between different levels. When cycling between different levels, the rate of change may also be specified.
The above list is not exhaustive, since some automotive companies may also require other climates to be created in sequence as well, for example; sub-zero refrigeration, but it does list the most common requirements. | 0 | Metallurgy |
Further alloys with low melting points are at , at and at . The alloy consisting of 40.8 % caesium, 11.8 % sodium and 47.4 % potassium has a melting point of . | 0 | Metallurgy |
As outlined above, the Kidd Process did not use wax on its permanent cathodes. This highlighted disadvantages associated with the use of wax by the Isa Process. Cathode copper consumers applied pressure to producers to remove residual wax from the cathode copper, and the use of wax also created “housekeeping” problems for Isa Process operators.
Consequently, MIM commenced a development program in 1997 aimed at eliminating the use of wax. This resulted in a new process called the Isa 2000 technology, which was able to produce single-sheet cathode (as opposed to the Kidd taco shell cathode) without using wax.
This was achieved by machining a 90° “V”-groove into the bottom edge of the cathode. The groove weakens the structure of the copper growing at the bottom edge of the cathode plate because the copper crystals grow perpendicular to the cathode plate from opposite sides of the groove, causing them to intersect at right angles to each other. A discontinuity in the structure is formed at the intersection that results in a weak zone, along which the copper splits during stripping.
Figure 4 is a microscope view of the cross-section a copper cathode growing at the tip of a cathode plate. The yellow lines show the orientation and direction of crystal growth. | 0 | Metallurgy |
Histone methylation was initially considered an effectively irreversible process as the half-life of the histone methylation was approximately equal to the histone half-life. Histone lysine demethylase LSD1 (later classified as KDM1A) was first identified in 2004 as a nuclear amine oxidase homolog. Two main classes of histone lysine demethylases exist, defined by their mechanisms: flavin adenine dinucleotide (FAD)-dependent amine oxidases and α-ketoglutarate-dependent hydroxylases.
Histone lysine demethylases possess a variety of domains that are responsible for histone recognition, DNA binding, methylated amino acid substrate binding and catalytic activity. These include:
* FAD-dependent amine oxidase domains containing the active catalytic site of KDM1
* Jumonji-C domains containing the active catalytic site of KDM2 through KDM8
* Jumonji-N domains responsible for Jumonji-C domain conformation stability
* SWIRM (SWI3P, RSC8P and Moira) domains proposed as an anchor site for histone substrates and responsible for chromatin stability
* PHD, CXXC and C5HC2 zinc finger domains responsible for histone recognition and binding
Histone lysine demethylases are classified according to their domains and unique substrate specificities. The lysine substrates and identified according to their position in the corresponding histone amino acid sequence and methylation state (for example, H3K9me3 refers to trimethylated histone 3 lysine 9.)
;KDM1:The KDM1 homologs include KDM1A and KDM1B. KDM1A demethylates H3K4me1/2 and H3K9me1/2, and KDM1B emethylates H3K4me1/2. KDM1 activity is critical to embryogenesis and tissue-specific differentiation, as well as oocyte growth. Deletion of the gene for KDM1A can have effects on the growth and differentiation of embryonic stem cells and is universally lethal in knockout mice. KDM1A gene expression is observed to be upregulated in some cancers, and so KDM1A inhibition has therefore been considered a possible epigenetic treatment for cancer.:KDM1B, however, is mostly involved in oocyte development. Deletion of this gene leads to maternal effect lethality in mice. Orthologs of KDM1 in D. melanogaster and C. elegans appear to function similarly to KDM1B rather than KDM1A.
;KDM2:The KDM2 homologs include KDM2A and KDM2B. KDM2A and KDM2B demethylate H3K4me3 and H3K36me2/3. KDM2A has roles in either promoting or inhibiting tumor function, and KDM2B has roles in oncogenesis. KDM2A and KDM2B possess CXXC zinc finger domains responsible for binding to unmethylated CpG islands, and it is believed that they may bind to many gene regulatory elements in the absence of sequence-specific transcription factors.:Overexpressed KDM2B has been observed in human lymphoma and adenocarcinoma, and underexpressed KDM2B has been observed in human prostate cancer and glioblastoma. KDM2B has been additionally shown to prevent senescence in some cells through ectopic expression.
;KDM3:The KDM3 homologs include KDM3A, KDM3B and KDM3C. KDM3A, KDM3B and KDM3C demethylate H3K9me1/2. KDM3A has roles in spermatogenesis and metabolic functions, however, the activity of KDM3B and KDM3C are not specifically known.:Knockdown studies of KDM3A in mice resulted in male infertility and adult onset-obesity. Additional studies have indicated that KDM3A may play a role in regulation of androgen receptor-dependent genes as well as genes involved in pluripotency, indicating a potential role for KDM3A in tumorigenesis.
;KDM4:The KDM4 homologs include KDM4A, KDM4B, KDM4C, KDM4D, KDM4E and KDM4F. KDM4A, KDM4B and KDM4C demethylate H3K9me2/3, H3K9me3 and H3K36me2/3, and KDM4D, KDM4E and KDM4F demethylate H3K9me2/3. KDM4A, KDM4B, KDM4C and KDM4D have roles in tumorigenesis, however, the activity of KDM4E and KDM4F are not specifically known.. KDM4B upregulation has bee observed in medulloblastoma, and KDM4C amplification has been documented in oesophageal squamous carcinoma, medulloblastoma and breast cancer. Other gene expression data has also suggested KDM4A, KDM4B, and KDM4C are overexpressed in prostate cancer.
;KDM5:The KDM5 homologs includes KDM5A, KDM5B, KDM5C and KDM5D. KDM5A, KDM5B, KDM5C and KDM5D demethylate H3K4me2/3. The KDM5 family appears to regulate key developmental functions, including cellular differentiation, mitochondrial function and cell cycle progression. KDM5B and KDM5C have also shown to interaction with PcG proteins, which are involved in transcriptional repression. KDM5C mutations on the X-chromosome have also been observed in patients with X-linked intellectual disability. Depletion of KDM5C homologs in D. rerio have shown brain-patterning defects and neuronal cell death.
;KDM6:The KDM6 family includes KDM6A, KDM6B and KDM6C. KDM6A and KDM6B demethylate H3K27me2/3, and KDM4C demethylates H3K27me3. KDM6A and KDM6B possess tumor-suppressive characteristics. KDM6A knockdowns in fibroblasts lead to an immediate increase in fibroblast population. KDM6B expressed in fibroblasts induces oncogenes of the Ras/Raf/MEK/ERK pathway. Point mutations of KDM6A have been identified as one cause of Kabuki syndrome, a congenital disorder resulting in intellectual disability. Deletion of KDM6A in D. rerio results in decreased expression of HOX genes, which play a role in regulating body patterning during development. In mammalian studies, KDM6A has been shown to regulate HOX genes as well. Mutation of KDM5B disrupt gonad development in C.elegans. Other studies have shown that KDM6B expression is upregulated in activated macrophages and dynamically expressed during differentiation of stem cells. | 1 | Gene expression + Signal Transduction |
TFIIIB remains bound to DNA following the initiation of transcription by Pol III, unlike bacterial σ factors and most of the basal transcription factors for Pol II transcription. This leads to a high rate of transcriptional reinitiation of Pol III-transcribed genes. One study conducted on Saccharomyces cerevisiae found the average rate of chain elongation was 21 to 22 nucleotides per second, with the fastest being 29 nucleotides per second. These rates were comparable to elongation rates of RNA polymerase II found by an in vivo study conducted on Drosophila. The analysis of the individual steps of RNA chain elongation depicted that adding U and A to U-terminated RNA chains was slow. | 1 | Gene expression + Signal Transduction |
The grain macrostructure in ingots and most castings have three distinct regions or zones: the chill zone, columnar zone, and equiaxed zone. The image below depicts these zones.
The chill zone is named so because it occurs at the walls of the mold where the wall chills the material. Here is where the nucleation phase of the solidification process takes place. As more heat is removed the grains grow towards the center of the casting. These are thin, long columns that are perpendicular to the casting surface, which are undesirable because they have anisotropic properties. Finally, in the center the equiaxed zone contains spherical, randomly oriented crystals. These are desirable because they have isotropic properties. The creation of this zone can be promoted by using a low pouring temperature, alloy inclusions, or inoculants. | 0 | Metallurgy |
The process begins by preparing the puddling furnace. This involves bringing the furnace to a low temperature and then fettling it. Fettling is the process of painting the grate and walls around it with iron oxides, typically hematite; this acts as a protective coating keeping the melted metal from burning through the furnace. Sometimes finely pounded cinder was used instead of hematite. In this case the furnace must be heated for 4–5 hours to melt the cinder and then cooled before charging.
Either white cast iron or refined iron is then placed in hearth of the furnace, a process known as charging. For wet puddling, scrap iron and/or iron oxide is also charged. This mixture is then heated until the top melts, allowing for the oxides to begin mixing; this usually takes 30 minutes. This mixture is subjected to a strong current of air and stirred by long bars with hooks on one end, called puddling bars or rabbles, through doors in the furnace. This helps the iron-III (the species acting as an oxidiser) from the oxides to react with impurities in the pig iron, notably silicon, manganese (to form slag) and to some degree sulfur and phosphorus, which form gases that escape with the exhaust of the furnace.
More fuel is then added and the temperature is raised. The iron completely melts and the carbon starts to burn off. When wet puddling, the formation of carbon monoxide (CO) and carbon dioxide () due to reactions with the added iron oxide will cause bubbles to form that cause the mass to appear to boil. This process causes the slag to puff up on top, giving the rabbler a visual indication of the progress of the combustion. As the carbon burns off, the melting temperature of the mixture rises from , so the furnace has to be continually fed during this process. The melting point increases since the carbon atoms within the mixture act as a solute in solution which lowers the melting point of the iron mixture (like road salt on ice).
Working as a two-man crew, a puddler and helper could produce about 1500 kg of iron in a 12-hour shift. The strenuous labour, heat and fumes caused puddlers to have a very short life expectancy, with most dying in their 30s. Puddling was never able to be automated because the puddler had to sense when the balls had "come to nature". | 0 | Metallurgy |
This is the most common use for galvanized metal, and hundreds of thousands of tons of steel products are galvanized annually worldwide. In developed countries most larger cities have several galvanizing factories, and many items of steel manufacture are galvanized for protection. Typically these include: street furniture, building frameworks, balconies, verandahs, staircases, ladders, walkways, and more. Hot dip galvanized steel is also used for making steel frames as a basic construction material for steel frame buildings. | 0 | Metallurgy |
Figure 2 illustrates the most common type of DDRNAI DNA construct, designed to express a shRNA. This figure consists of a promoter sequence driving the expression of sense and antisense sequences separated by a loop sequence, followed by a transcriptional terminator. The antisense sequence processed from the shRNA can bind to the target RNA and specify its degradation. shRNA constructs typically encode sense and antisense sequences of 20–30 nucleotides. Flexibility in construct design is possible; for example, the positions of sense and antisense sequences can be reversed, and other modifications and additions can alter intracellular shRNA processing. Moreover, a variety of promoter loop and terminator sequences can be used.
A beneficial variant is a multi-cassette (Figure 2b). Designed to express two or more shRNAs, they can simultaneously target multiple sequences for degradation hence particularly a useful strategy for targeting viruses. Natural sequence variations can render a single shRNA-target site unrecognizable, preventing RNA degradation. Multi-cassette constructs that target multiple sites within the same viral RNA circumvent this issue. | 1 | Gene expression + Signal Transduction |
Trans-regulatory elements (TRE) are DNA sequences encoding upstream regulators (ie. trans-acting factors), which may modify or regulate the expression of distant genes. Trans-acting factors interact with cis-regulatory elements to regulate gene expression. TRE mediates expression profiles of a large number of genes via trans-acting factors. While TRE mutations affect gene expression, it is also one of the main driving factors for evolutionary divergence in gene expression. | 1 | Gene expression + Signal Transduction |
The physical presence of introns promotes cellular resistance to starvation via intron enhanced repression of ribosomal protein genes of nutrient-sensing pathways. | 1 | Gene expression + Signal Transduction |
One challenge when synthesising a metallic glass is that the techniques often only produce very small samples, due to the need for high cooling rates. 3D-printing methods have been suggested as a method to create larger bulk samples. Selective laser melting (SLM) is one example of an additive manufacturing method that has been used to make iron based metallic glasses. Laser foil printing (LFP) is another method where foils of the amorphous metals are stacked and welded together, layer by layer. | 0 | Metallurgy |
Discovered in 1953 by Jacques Monod and colleagues, the trp operon in E. coli was the first repressible operon to be discovered. While the lac operon can be activated by a chemical (allolactose), the tryptophan (Trp) operon is inhibited by a chemical (tryptophan). This operon contains five structural genes: trp E, trp D, trp C, trp B, and trp A, which encodes tryptophan synthetase. It also contains a promoter which binds to RNA polymerase and an operator which blocks transcription when bound to the protein synthesized by the repressor gene (trp R) that binds to the operator. In the lac operon, lactose binds to the repressor protein and prevents it from repressing gene transcription, while in the trp operon, tryptophan binds to the repressor protein and enables it to repress gene transcription. Also unlike the lac operon, the trp operon contains a leader peptide and an attenuator sequence which allows for graded regulation. This is an example of the corepressible model. | 1 | Gene expression + Signal Transduction |
GenePattern is a freely available computational biology open-source software package originally created and developed at the Broad Institute for the analysis of genomic data. Designed to enable researchers to develop, capture, and reproduce genomic analysis methodologies, GenePattern was first released in 2004. GenePattern is currently developed at the University of California, San Diego. | 1 | Gene expression + Signal Transduction |
RNA editing through the addition and deletion of uracil has been found in kinetoplasts from the mitochondria of Trypanosoma brucei.
Because this may involve a large fraction of the sites in a gene, it is sometimes called "pan-editing" to distinguish it from topical editing of one or a few sites.
Pan-editing starts with the base-pairing of the unedited primary transcript with a guide RNA (gRNA), which contains complementary sequences to the regions around the insertion/deletion points. The newly formed double-stranded region is then enveloped by an editosome, a large multi-protein complex that catalyzes the editing. The editosome opens the transcript at the first mismatched nucleotide and starts inserting uridines. The inserted uridines will base-pair with the guide RNA, and insertion will continue as long as A or G is present in the guide RNA and will stop when a C or U is encountered. The inserted nucleotides cause a frameshift, and result in a translated protein that differs from its gene.
The mechanism of the editosome involves an endonucleolytic cut at the mismatch point between the guide RNA and the unedited transcript. The next step is catalyzed by one of the enzymes in the complex, a terminal U-transferase, which adds Us from UTP at the 3 end of the mRNA. The opened ends are held in place by other proteins in the complex. Another enzyme, a U-specific exoribonuclease, removes the unpaired Us. After editing has made mRNA complementary to gRNA, an RNA ligase rejoins the ends of the edited mRNA transcript. As a consequence, the editosome can edit only in a 3 to 5' direction along the primary RNA transcript. The complex can act on only a single guide RNA at a time. Therefore, a RNA transcript requiring extensive editing will need more than one guide RNA and editosome complex. | 1 | Gene expression + Signal Transduction |
E3 ubiquitin-protein ligase TRIM33, also known as (ectodermin homolog and tripartite motif-containing 33) is a protein encoded in the human by the gene TRIM33, a member of the tripartite motif family.
TRIM33 is thought to be a transcriptional corepressor. However unlike the related TRIM24 and TRIM28 proteins, few transcription factors such as SMAD4 that interact with TRIM33 have been identified. | 1 | Gene expression + Signal Transduction |
The red component of color television cathode ray tubes is typically emitted from an yttria () or yttrium oxide sulfide () host lattice doped with europium (III) cation (Eu) phosphors. The red color itself is emitted from the europium while the yttrium collects energy from the electron gun and passes it to the phosphor. Yttrium compounds can serve as host lattices for doping with different lanthanide cations. Tb can be used as a doping agent to produce green luminescence. As such yttrium compounds such as yttrium aluminium garnet (YAG) are useful for phosphors and are an important component of white LEDs.
Yttria is used as a sintering additive in the production of porous silicon nitride.
Yttrium compounds are used as a catalyst for ethylene polymerization. As a metal, yttrium is used on the electrodes of some high-performance spark plugs. Yttrium is used in gas mantles for propane lanterns as a replacement for thorium, which is radioactive. | 0 | Metallurgy |
* Chromatin structure oriented factors:<br />(HMTs (Histone MethylTransferases)):<br /> COMPASS§† – (COMplex of Proteins ASsociated with Set1) – Methylates lysine 4 of histone H3: Is responsible of repression/silencing of transcription. A normal part of cell growth and transcription regulation within RNAP II.
* Set2 – Methylates lysine 36 of histone H3: Set2 is involved in regulation transcription elongation through its direct contact with the CTD.<br /> (interesting irrelevant example: Dot1*‡ – Methylates lysine 79 of histone H3.)
* Bre1 – Ubiquinates (adds ubiquitin to) lysine 123 of histone H2B. Associated with pre-initiation and allowing RNA Pol II binding. | 1 | Gene expression + Signal Transduction |
Morpholinos do not trigger the degradation of their target RNA molecules, unlike many antisense structural types (e.g., phosphorothioates, siRNA). Instead, Morpholinos act by "steric blocking", binding to a target sequence within an RNA, inhibiting molecules that might otherwise interact with the RNA. Morpholino oligos are often used to investigate the role of a specific mRNA transcript in an embryo. Developmental biologists inject Morpholino oligos into eggs or embryos of zebrafish, African clawed frog (Xenopus), sea urchin and killifish (F. heteroclitus) producing morphant embryos, or electroporate Morpholinos into chick embryos at later development stages. With appropriate cytosolic delivery systems, Morpholinos are effective in cell culture. Vivo-Morpholinos, in which the oligo is covalently linked to a delivery dendrimer, enter cells when administered systemically in adult animals or in tissue cultures. | 1 | Gene expression + Signal Transduction |
The process of splat quenching involves rapid quenching or cooling of molten metal. A typical procedure for splat quenching involves pouring the molten metal between two cooled copper rollers that are circulated with water to transfer the heat away from the metal, causing it to almost instantaneously solidify.
A more efficient splat quenching technique is Duwezs and Willens gun technique. Their technique produces higher rates of cooling of the droplet of metal because the sample is propelled at high velocities and hits a quencher plate causing its surface area to increase which immediately solidifies the metal. This allows for a wider range of metals that can be quenched and be given amorphous-like features instead of the general iron alloy.
Another technique involves the consecutive spraying of the molten metal onto a chemical vapor deposition surface. However, the layers do not fuse together as desired and this causes oxides to be contained in the structure and pores to form around the structure. Manufacturing companies take an interest in the resultant products because of their near-net shaping capabilities. | 0 | Metallurgy |