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In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. An RNA-binding repressor binds to the mRNA and prevents translation of the mRNA into protein. This blocking or reducing of expression is called repression. | 1 | Gene expression + Signal Transduction |
When the temperature of concrete exceeds 65 °C for too long a time at an early age, the crystallization of ettringite (AFt) does not occur because of its higher solubility at elevated temperature and the then less soluble mono-sulfate (AFm) is formed. After dissipation of the cement hydration heat, temperature goes back to ambient and the temperature curves of the solubilities of AFt and AFm phases cross over. The mono-sulfate (AFm) now more soluble at low temperature slowly dissolves to recrystallize as the less soluble ettringite (AFt). AFt crystal structure hosts more water molecules than AFm. So, AFt has a higher molar volume than AFm because of its 32 HO molecules. During months, or years, after young concrete cooling, AFt crystallizes very slowly as small acicular needles and can exert a considerable crystallization pressure on the surrounding hardened cement paste (HCP). This leads to the expansion of concrete, to its cracking, and it can ultimately lead to the ruin of the affected structure. The characteristic feature of delayed ettringite formation (DEF) is a random honeycomb cracking pattern similar to this of the alkali-silica reaction (ASR). In fact, this typical crack pattern is common to all expansive internal reactions and also to restrained shrinkage where a rigid substrate or a dense rebar network prevents the movements of a superficial concrete layer. DEF is also known as internal sulfate attack (ISA). External sulfate attack (ESA) also involves ettringite (AFt) formation and deleterious expansion with the same harmful symptoms but requires an external source of sulfate anions in the surrounding terrains or environment. To avoid DEF or ISA reactions, the best way is to use a low CA (tri-calcium aluminate) cement precluding the formation of ettringite (AFt). Sulfate resisting (SR) cements have also a low content in AlO. DEF, or ISA, only affects the hardened cement paste (HCP) and leaves intact the aggregates.
DEF is exacerbated at high pH in cement with a too high content in alkalis and therefore in hydroxides. This is caused by the transformation of ettringite (AFt) into aluminoferrite monosulfate (AFm) under the action of the hydroxyl anions (OH) as schematized as follows:
: AFt + OH → AFm
The complete reaction can be derived from the molecular formulas of the reagents and products involved in the reaction. This reaction favors the dissolution of AFt and the formation of AFm. When combined, it is an aggravating factor of the harmful effect of too high temperatures. To minimize DEF, the use of low-alkali cements is also recommended. The detrimental crystallization of ettringite (AFt) preferentially occurs when concrete is exposed to water infiltrations and that the pH decreases due to the leaching of the (OH) ions: the reaction is reversed as when temperature decreases. | 0 | Metallurgy |
The G protein-coupled receptor is activated by an external signal in the form of a ligand or other signal mediator. This creates a conformational change in the receptor, causing activation of a G protein. Further effect depends on the type of G protein. G proteins are subsequently inactivated by GTPase activating proteins, known as RGS proteins. | 1 | Gene expression + Signal Transduction |
This form of corrosion is usually caused by a combination of corrosion and cyclic stress. Measuring and controlling this is difficult because of the many factors at play including the nature or form of the stress cycle. The stress cycles cause localized work hardening. So avoiding stress concentrators such as holes etc would be good corrosion engineering design. | 0 | Metallurgy |
The functions for eRNA described below have been reported in diverse biological systems, often demonstrated with a small number of specific enhancer-target gene pairs. It is not clear to what extent the functions of eRNA described here can be generalized to most eRNAs. | 1 | Gene expression + Signal Transduction |
In 2010, Dunne was elected a Fellow of the Royal Academy of Engineering (FREng). In 2016, he was awarded the Institute of Materials, Minerals and Mining (IoM3) Harvey Flower Titanium Prize. In 2017, Dunnes Engineering Alloys team shared the Imperial Presidents Award for Outstanding Research Team with Professor Chris Phillips’s team. | 0 | Metallurgy |
Transcription of the msl-2 transcript is regulated by multiple binding sites for fly Sxl at the 5′ UTR. In particular, these poly-uracil sites are located close to a small intron that is spliced in males, but kept in females through splicing inhibition. This splicing inhibition is maintained by Sxl. When present, Sxl will repress the translation of msl2 by increasing translation of a start codon located in a uORF in the 5′ UTR (see above for more information on uORFs). Also, Sxl outcompetes TIA-1 to a poly(U) region and prevents snRNP (a step in alternative splicing) recruitment to the 5′ splice site. | 1 | Gene expression + Signal Transduction |
In some cases, simply changing the way the material is processed can influence the microstructure. An example is the titanium alloy TiAl6V4. Its microstructure and mechanical properties are enhanced using SLM (selective laser melting) which is a 3D printing technique using powder and melting the particles together using high powered laser. Other conventional techniques for improving the microstructure are thermal processes. Those processes rely in the principle that an increase in temperature will induce the reduction or annihilation of pores. Hot isostatic pressing (HIP) is a manufacturing process, used to reduce the porosity of metals and increase the density of many ceramic materials. This improves the material's mechanical properties and workability.
The HIP process exposes the desired material to an isostatic gas pressure as well as high temperature in a sealed vessel (high pressure). The gas used during this process is mostly Argon. The gas needs to be chemically inert so that no reaction occurs between it and the sample. The pressure is achieved by simply applying heat to the hermetically sealed vessel. However, some systems also associate gas pumping to the process to achieve the required pressure level. The pressure applied on the materials is equal and comes from all directions (hence the term “isostatic”). When castings are treated with HIP, the simultaneous application of heat and pressure eliminates internal voids and microporosity through a combination of plastic deformation, creep, and diffusion bonding; this process improves fatigue resistance of the component. | 0 | Metallurgy |
Agricola describes parting silver from gold in this book by using acids. He also describes heating with antimony sulphide (stibium), which would give silver sulphide and a mixture of gold and antimony. The gold and silver can then be recovered with cupellation. Gold can also be parted using salts or using mercury. Large scale cupellation using a cupellation hearth is also covered in this book. | 0 | Metallurgy |
Anodized aluminium surfaces that are not regularly cleaned are susceptible to panel edge staining, a unique type of surface staining that can affect the structural integrity of the metal. | 0 | Metallurgy |
Some reports have suggested that the extrinsic Fas pathway is sufficient to induce complete apoptosis in certain cell types through DISC assembly and subsequent caspase-8 activation. These cells are dubbed Type 1 cells and are characterized by the inability of anti-apoptotic members of the Bcl-2 family (namely Bcl-2 and Bcl-xL) to protect from Fas-mediated apoptosis. Characterized Type 1 cells include H9, CH1, SKW6.4 and SW480, all of which are lymphocyte lineages except the latter, which is a colon adenocarcinoma lineage. However, evidence for crosstalk between the extrinsic and intrinsic pathways exists in the Fas signal cascade.
In most cell types, caspase-8 catalyzes the cleavage of the pro-apoptotic BH3-only protein Bid into its truncated form, tBid. BH-3 only members of the Bcl-2 family exclusively engage anti-apoptotic members of the family (Bcl-2, Bcl-xL), allowing Bak and Bax to translocate to the outer mitochondrial membrane, thus permeabilizing it and facilitating release of pro-apoptotic proteins such as cytochrome c and Smac/DIABLO, an antagonist of inhibitors of apoptosis proteins (IAPs). | 1 | Gene expression + Signal Transduction |
Filamentous fungi, especially Aspergillus and Trichoderma, have long been used to produce diverse industrial enzymes from their own genomes ("native", "homologous") and from recombinant DNA ("heterologous").
More recently, Myceliophthora thermophila C1 has been developed into an expression platform for screening and production of native and heterologous proteins.The expression system C1 shows a low viscosity morphology in submerged culture, enabling the use of complex growth and production media. C1 also does not "hyperglycosylate" heterologous proteins, as Aspergillus and Trichoderma tend to do. | 1 | Gene expression + Signal Transduction |
* Encyclopædia Britannica, 14th ed.
* J. Day & R. F. Tylecote (eds.), The Industrial Revolution in Metals (1991)
* P. W. King, "The Cupola at Bristol", Somerset Araeology and Natural History 140 (for 1997), 37–52
* P. W. King, "Sir Clement Clerke and the Adoption of coal in metallurgy", Transactions of the Newcomen Society 73(1) (2001–2), 33–53 | 0 | Metallurgy |
In terms of structure, GPCRs are characterized by an extracellular N-terminus, followed by seven transmembrane (7-TM) α-helices (TM-1 to TM-7) connected by three intracellular (IL-1 to IL-3) and three extracellular loops (EL-1 to EL-3), and finally an intracellular C-terminus. The GPCR arranges itself into a tertiary structure resembling a barrel, with the seven transmembrane helices forming a cavity within the plasma membrane that serves a ligand-binding domain that is often covered by EL-2. Ligands may also bind elsewhere, however, as is the case for bulkier ligands (e.g., proteins or large peptides), which instead interact with the extracellular loops, or, as illustrated by the class C metabotropic glutamate receptors (mGluRs), the N-terminal tail. The class C GPCRs are distinguished by their large N-terminal tail, which also contains a ligand-binding domain. Upon glutamate-binding to an mGluR, the N-terminal tail undergoes a conformational change that leads to its interaction with the residues of the extracellular loops and TM domains. The eventual effect of all three types of agonist-induced activation is a change in the relative orientations of the TM helices (likened to a twisting motion) leading to a wider intracellular surface and "revelation" of residues of the intracellular helices and TM domains crucial to signal transduction function (i.e., G-protein coupling). Inverse agonists and antagonists may also bind to a number of different sites, but the eventual effect must be prevention of this TM helix reorientation.
The structure of the N- and C-terminal tails of GPCRs may also serve important functions beyond ligand-binding. For example, The C-terminus of M muscarinic receptors is sufficient, and the six-amino-acid polybasic (KKKRRK) domain in the C-terminus is necessary for its preassembly with G proteins. In particular, the C-terminus often contains serine (Ser) or threonine (Thr) residues that, when phosphorylated, increase the affinity of the intracellular surface for the binding of scaffolding proteins called β-arrestins (β-arr). Once bound, β-arrestins both sterically prevent G-protein coupling and may recruit other proteins, leading to the creation of signaling complexes involved in extracellular-signal regulated kinase (ERK) pathway activation or receptor endocytosis (internalization). As the phosphorylation of these Ser and Thr residues often occurs as a result of GPCR activation, the β-arr-mediated G-protein-decoupling and internalization of GPCRs are important mechanisms of desensitization. In addition, internalized "mega-complexes" consisting of a single GPCR, β-arr(in the tail conformation), and heterotrimeric G protein exist and may account for protein signaling from endosomes.
A final common structural theme among GPCRs is palmitoylation of one or more sites of the C-terminal tail or the intracellular loops. Palmitoylation is the covalent modification of cysteine (Cys) residues via addition of hydrophobic acyl groups, and has the effect of targeting the receptor to cholesterol- and sphingolipid-rich microdomains of the plasma membrane called lipid rafts. As many of the downstream transducer and effector molecules of GPCRs (including those involved in negative feedback pathways) are also targeted to lipid rafts, this has the effect of facilitating rapid receptor signaling.
GPCRs respond to extracellular signals mediated by a huge diversity of agonists, ranging from proteins to biogenic amines to protons, but all transduce this signal via a mechanism of G-protein coupling. This is made possible by a guanine-nucleotide exchange factor (GEF) domain primarily formed by a combination of IL-2 and IL-3 along with adjacent residues of the associated TM helices. | 1 | Gene expression + Signal Transduction |
Concrete exposed to seawater is susceptible to its corrosive effects. The effects are more pronounced above the tidal zone than where the concrete is permanently submerged. In the submerged zone, magnesium and hydrogen carbonate ions precipitate a layer of brucite (magnesium hydroxide: Mg(OH)), about 30 micrometers thick, on which a slower deposition of calcium carbonate as aragonite occurs. These mineral layers somewhat protect the concrete from other processes, which includes attack by magnesium, chloride and sulfate ions and carbonatation. Above the water surface, mechanical damage may occur by erosion by waves themselves or sand and gravel they carry, and by crystallization of salts from water soaking into the concrete pores and then drying up. Pozzolanic cements and cements using more than of blast furnace slags as cementitious material are more resistant to seawater than pure Portland cement. Seawater attack presents aspects of both chloride and sulfate attacks. | 0 | Metallurgy |
* Loupe (sidérurgie)
* Krupp-Renn Process
* Direct reduced iron.
* Direct reduction (blast furnace)
* Histoire de la production de l'acier. | 0 | Metallurgy |
It has been shown by Fulda et al. that the naturally occurring compound resveratrol (a polyphenol found in grapes and red wine) can be used as a sensitizer for anticancer drug-induced apoptosis by the action of causing cell cycle arrest. This cell cycle arrest causes a dramatic decline in survivin levels in the cells, as it is known from the literature that survivin expression is highly linked with the cell cycle phase state. Thus, the decrease in survivin, which is a contributing factor to chemotherapy resistance and apoptosis induction therapies, would render the cancer cells more prone to such cancer treatments. Fulda et al. have demonstrated the benefits of resveratrol through a series of experiments. First, the authors of the paper tested the intrinsic cytotoxic effects of resveratrol. They found that it induced moderate apoptosis levels only in SHEP neuroblastoma cells. After, they tested resveratrol in combination with several different known anticancer agents. They found a consistent increase in the level of apoptosis induced by the drugs when resveratrol was also present. Moreover, they varied the order with which either the drugs or resveratrol was introduced to the cancer cells to determine whether the sequence of treatment had any important effect. It was found that the highest levels of apoptosis induction were observed when resveratrol was added prior to anticancer drug treatment. Next, the authors tested for any differential sensitivity to apoptosis linked to the phase of the cell cycle the cells were in. Analysis by flow cytometry revealed an accumulation of cells in S phase upon treatment with resveratrol. The cells were also halted in different phases of the cell cycle using special compounds and then treated with the anticancer drugs. They found that cells halted in S phase were significantly more sensitive to the cytotoxic effects of the drugs.
To determine the involvement of survivin in resveratrol-mediated sensitization, the authors decided to test whether downregulation of the specific survivin protein expression would confer a similar effect on the phenotype of resveratrol-treated cells. In terms of seeing at which level resveratrol worked, they did a northern blot and found that resveratrol treatment resulted in a decrease in survivin mRNA levels, thus implying resveratrol's inhibitory action at the transcriptional level. To further see whether survivin played a key role in sensitization of the cancer cells to cytotoxic drugs, survivin antisense oligonucleotides were used to knock down any survivin mRNA, and, thus, its possibility to be translated is also eliminated. siRNAs for survivin are complements in sequence to the mRNA sequence encoding survivin. When these siRNAs for survivin are introduced into cells, they will bind to the respective complementary mRNA and, thus, prevent its translation since the mRNA is now impeded from proper physical interaction with the translational machinery. In this way, the siRNAs for survivin effectively downregulates survivin expression level in the cell. Cells treated with antisense oligonucleotides for survivin showed similar sensitization to cytotoxic drugs as cells treated with resveratrol, which offers support for the mechanism of action of resveratrol. | 1 | Gene expression + Signal Transduction |
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses from one neuron to another, playing a key role in enabling rapid and direct communication by creating circuits. In addition, a synapse serves as a junction where both the transmission and processing of information occur, making it a vital means of communication between neurons. Neurons are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together and carry out the signaling process. In many synapses, the presynaptic part is located on an axon and the postsynaptic part is located on a dendrite or soma. Astrocytes also exchange information with the synaptic neurons, responding to synaptic activity and, in turn, regulating neurotransmission. Synapses (at least chemical synapses) are stabilized in position by synaptic adhesion molecules (SAMs) projecting from both the pre- and post-synaptic neuron and sticking together where they overlap; SAMs may also assist in the generation and functioning of synapses. Moreover, SAMs coordinate the formation of synapses, with various types working together to achieve the remarkable specificity of synapses. In essence, SAMs function in both excitatory and inhibitory synapses, likely serving as devices for signal transmission. | 1 | Gene expression + Signal Transduction |
Pigmentation patterns provide one of the most striking and easily scored differences between different species of animals. Pigmentation of the Drosophila wing has proven to be a particularly amenable system for studying the development of complex pigmentation phenotypes. The Drosophila guttifera wing has 12 dark pigmentation spots and 4 lighter gray intervein patches. Pigment spots arise from expression of the yellow gene, whose product produces black melanin. Recent work has shown that two enhancers in the yellow gene produce gene expression in precisely this pattern – the vein spot enhancer drives reporter gene expression in the 12 spots, and the intervein shade enhancer drives reporter expression in the 4 distinct patches. These two enhancers are responsive to the Wnt signaling pathway, which is activated by wingless expression at all of the pigmented locations. Thus, in the evolution of the complex pigmentation phenotype, the yellow pigment gene evolved enhancers responsive to the wingless signal and wingless expression evolved at new locations to produce novel wing patterns. | 1 | Gene expression + Signal Transduction |
CAF-1 functions as a histone chaperone that mediates the first step in nucleosome formation by tetramerizing and depositing newly synthesized histone H3/H4 onto DNA rapidly behind replication forks. H3 and H4 are synthesized in the cytoplasm. Several studies have shown that the interaction between CAF-1 and PCNA (proliferating cell nuclear antigen, which stabilizes CAF-1 at replication forks, is important for CAF-1's role in nucleosome assembly
The three subunits work together to make the complex function. The human subunit (p150) interacts with PCNA, which acts as a sliding clamp, to help the CAF-1 complex interact with the DNA replication fork. Additionally, p150 along with PCNA performs nucleotide excision repair to fix any damaged DNA. P60 interacts with ASF1a/b, which is a histone chaperone for H3/H4. p48 has roles outside of CAF-1, but when involved with the complex, it binds to H4.
p60 attracts ASF1a/b which is a chaperone for H3/H4 and this is in the complex with p150 which interacts with PCNA to attach to the replication fork. The CAF-1 complex adds the histones to the DNA ahead of the replication fork.
A mutation in p150 that results in a loss of function would lead to double stranded breaks, interruptions in the replication fork and translocations. In p60, loss of function would mean the histone chaperone for H3/H4 would not interact with the complex. A mutation like this in either subunit would result in loss of function for the CAF-1 complex as a whole. However, loss of function in p48 would alter how well the complex is able to chaperone chromatin, but would not stop it as a whole. | 1 | Gene expression + Signal Transduction |
Enterococcus faecalis is an opportunistic, Gram-positive bacteria that forms biofilm in glass. This process is also known as forming a biofilm in vitro. The presence of (Esp), a certain cell surface protein, aids the formation of a biofilm by Enterococcus faecalis. | 1 | Gene expression + Signal Transduction |
A similar process (environmental stress cracking) occurs in polymers, when products are exposed to specific solvents or aggressive chemicals such as acids and alkalis. As with metals, attack is confined to specific polymers and particular chemicals. Thus polycarbonate is sensitive to attack by alkalis, but not by acids. On the other hand, polyesters are readily degraded by acids, and SCC is a likely failure mechanism. Polymers are susceptible to environmental stress cracking where attacking agents do not necessarily degrade the materials chemically.
Nylon is sensitive to degradation by acids, a process known as hydrolysis, and nylon mouldings will crack when attacked by strong acids.
For example, the fracture surface of a fuel connector showed the progressive growth of the crack from acid attack (Ch) to the final cusp (C) of polymer. In this case the failure was caused by hydrolysis of the polymer by contact with sulfuric acid leaking from a car battery. The degradation reaction is the reverse of the synthesis reaction of the polymer:
Cracks can be formed in many different elastomers by ozone attack, another form of SCC in polymers. Tiny traces of the gas in the air will attack double bonds in rubber chains, with natural rubber, styrene-butadiene rubber, and nitrile butadiene rubber being most sensitive to degradation. Ozone cracks form in products under tension, but the critical strain is very small. The cracks are always oriented at right angles to the strain axis, so will form around the circumference in a rubber tube bent over. Such cracks are dangerous when they occur in fuel pipes because the cracks will grow from the outside exposed surfaces into the bore of the pipe, so fuel leakage and fire may follow. Ozone cracking can be prevented by adding anti-ozonants to the rubber before vulcanization. Ozone cracks were commonly seen in automobile tire sidewalls, but are now seen rarely thanks to the use of these additives. On the other hand, the problem does recur in unprotected products such as rubber tubing and seals. | 0 | Metallurgy |
Isothermal transformation diagrams (also known as time-temperature-transformation (TTT) diagrams) are plots of temperature versus time (usually on a logarithmic scale). They are generated from percentage transformation-vs time measurements, and are useful for understanding the transformations of an alloy steel at elevated temperatures.
An isothermal transformation diagram is only valid for one specific composition of material, and only if the temperature is held constant during the transformation, and strictly with rapid cooling to that temperature. Though usually used to represent transformation kinetics for steels, they also can be used to describe the kinetics of crystallization in ceramic or other materials. Time-temperature-precipitation diagrams and time-temperature-embrittlement diagrams have also been used to represent kinetic changes in steels.
Isothermal transformation (IT) diagram or the C-curve is associated with mechanical properties, microconstituents/microstructures, and heat treatments in carbon steels. Diffusional transformations like austenite transforming to a cementite and ferrite mixture can be explained using the sigmoidal curve; for example the beginning of pearlitic transformation is represented by the pearlite start (P) curve. This transformation is complete at P curve. Nucleation requires an incubation time. The rate of nucleation increases and the rate of microconstituent growth decreases as the temperature decreases from the liquidus temperature reaching a maximum at the bay or nose of the curve. Thereafter, the decrease in diffusion rate due to low temperature offsets the effect of increased driving force due to greater difference in free energy. As a result of the transformation, the microconstituents, pearlite and bainite, form; pearlite forms at higher temperatures and bainite at lower.
Austenite is slightly undercooled when quenched below Eutectoid temperature. When given more time, stable microconstituents can form: ferrite and cementite. Coarse pearlite is produced when atoms diffuse rapidly after phases that form pearlite nucleate. This transformation is complete at the pearlite finish time (P).
However, greater undercooling by rapid quenching results in formation of martensite or bainite instead of pearlite. This is possible provided the cooling rate is such that the cooling curve intersects the martensite start temperature or the bainite start curve before intersecting the Pcurve. The martensite transformation being a diffusionless shear transformation is represented by a straight line to signify the martensite start temperature. | 0 | Metallurgy |
The extent to which a solid is crystalline (crystallinity) has important effects on its physical properties. Sulfur, while usually polycrystalline, may also occur in other allotropic forms with completely different properties. Although crystallites are referred to as grains, powder grains are different, as they can be composed of smaller polycrystalline grains themselves. Generally, polycrystals cannot be superheated; they will melt promptly once they are brought to a high enough temperature. This is because grain boundaries are amorphous, and serve as nucleation points for the liquid phase. By contrast, if no solid nucleus is present as a liquid cools, it tends to become supercooled. Since this is undesirable for mechanical materials, alloy designers often take steps against it (by grain refinement).
Material fractures can be either intergranular or a transgranular fracture. There is an ambiguity with powder grains: a powder grain can be made of several crystallites. Thus, the (powder) "grain size" found by laser granulometry can be different from the "grain size" (rather, crystallite size) found by X-ray diffraction (e.g. Scherrer method), by optical microscopy under polarised light, or by scanning electron microscopy (backscattered electrons).
If the individual crystallites are oriented completely at random, a large enough volume of polycrystalline material will be approximately isotropic. This property helps the simplifying assumptions of continuum mechanics to apply to real-world solids. However, most manufactured materials have some alignment to their crystallites, resulting in texture that must be taken into account for accurate predictions of their behavior and characteristics. When the crystallites are mostly ordered with a random spread of orientations, one has a mosaic crystal. Abnormal grain growth, where a small number of crystallites are significantly larger than the mean crystallite size, is commonly observed in diverse polycrystalline materials, and results in mechanical and optical properties that diverge from similar materials having a monodisperse crystallite size distribution with a similar mean crystallite size.
Coarse grained rocks are formed very slowly, while fine grained rocks are formed quickly, on geological time scales. If a rock forms very quickly, such as from the solidification of lava ejected from a volcano, there may be no crystals at all. This is how obsidian forms. | 0 | Metallurgy |
During the Mississippian period (800–1600 CE, varying locally), elites at major political and religious centers throughout the midwestern and southeastern United States used copper ornamentation as a sign of their status by crafting the sacred material into representations connected with the Chiefly Warrior cult of the Southeastern Ceremonial Complex (S.E.C.C.).
This ornamentation includes Mississippian copper plates, repousséd plates of beaten copper now found as far afield as Alabama, Florida, Georgia, Illinois, Mississippi, Oklahoma, and Tennessee. Some of the more famous of the plates are of raptorial birds and avian-themed dancing warriors. These plates, such as the Rogan plates from Etowah, the Spiro plates from the Spiro in Oklahoma, and the Wulfing cache from southeast Missouri, were instrumental in the development of the archaeological concept known as the S.E.C.C.
The only Mississippian culture site where a copper workshop has been located by archaeologists is Cahokia in western Illinois, where a copper workshop dating to the Moorehead Phase () was identified at Mound 34. Gregory Perino identified the site in 1956 and archaeologists subsequently excavated it.
Numerous copper fragments were found at the site; metallographic analysis indicated that Mississippian copper workers worked copper into thin sheet through repeated hammering and annealing, a process that could be successful over open-pit wood fires.
After the collapse of the Mississippian way of life in the 1500s with the advent of European colonization, copper still retained a place in Native American religious life as a special material. Copper was traditionally regarded as sacred by many historic period Eastern tribes. Copper nuggets are included in medicine bundles among Great Lakes tribes. Among 19th century Muscogee Creeks, a group of copper plates carried along the Trail of Tears are regarded as some of the tribe's most sacred items. | 0 | Metallurgy |
Experimental archaeometallurgy is a subset of experimental archaeology that specifically involves past metallurgical processes most commonly involving the replication of copper and iron objects as well as testing the methodology behind the production of ancient metals and metal objects. Metals and elements used primarily as alloying materials, such as tin, lead, and arsenic, are also a part of experimental research. | 0 | Metallurgy |
The (p)ppGpp levels of the host seem to act as a sensor for phage lambda development, primarily affecting transcription. Modest ppGpp levels inhibit pR and active pE, pI, and paQ promoters in vivo and have effects in vitro that seem to favor lysogeny. In contrast, absent or high concentrations of (p)ppGpp favor lysis. Modest ppGpp levels favor lysogeny by leading to low HflB (FtsH). When ppGpp is either absent or high, HflB protease levels are high; this leads to lower CII (a lysogeny-promoting phage protein)
and favors lysis. | 1 | Gene expression + Signal Transduction |
Although the origins of iron working in Africa have been the subject of scholarly interest since the 1860s, it is still not known whether this technology diffused into sub-Saharan Africa from the Mediterranean region, or whether it was invented there independently of iron working elsewhere. Although some nineteenth-century European scholars favored an indigenous invention of iron working in sub-Saharan Africa, archaeologists writing between 1945 and 1965 mostly favored diffusion of iron smelting technology from Carthage across the Sahara to West Africa and/or from Meroe on the upper Nile to central Africa. This in turn has been questioned by more recent research which argues for an independent invention.
The invention of radiocarbon dating in the late 1950s enabled dating of metallurgical sites by the charcoal fuel used for smelting and forging. By the late 1960s some surprisingly early radiocarbon dates had been obtained for iron smelting sites in both Niger and central Africa (Rwanda, Burundi), reviving the view that iron-making was independently invented by Africans in sub-Saharan Africa as far back as 3600 BCE. These dates preceded the known antiquity of ironworking in Carthage or Meroe, weakening the diffusion hypothesis. In the 1990s, evidence was found of Phoenician iron smelting in the western Mediterranean (900–800 BCE), though specifically in North Africa it seems to date only to the 5th to 4th centuries BCE, or the 7th century BCE at the earliest, contemporary to or later than the oldest known iron metallurgy dates from sub-Saharan Africa. According to archaeometallurgist Manfred Eggert, "Carthage cannot be reliably considered the point of origin for sub-Saharan iron ore reduction." It is still not known when iron working was first practiced in Kush and Meroe in modern Sudan, but the earliest known iron metallurgy dates from Meroe and Egypt do not predate those from sub-Saharan Africa, and thus the Nile Valley is also considered unlikely to be the source of sub-Saharan iron metallurgy.
From the mid-1970s there were new claims for independent invention of iron smelting in central Niger and from 1994 to 1999 UNESCO funded an initiative "Les Routes du Fer en Afrique/The Iron Routes in Africa" to investigate the origins and spread of iron metallurgy in Africa. This funded both the conference on early iron in Africa and the Mediterranean and a volume, published by UNESCO, that generated some controversy because it included only authors sympathetic to the independent-invention view.
Two reviews of the evidence from the mid-2000s found technical flaws in the studies claiming independent invention, raising three major issues. The first was whether the material dated by radiocarbon was in secure archaeological association with iron-working residues. Many of the dates from Niger, for example, were on organic matter in potsherds that were lying on the ground surface together with iron objects. The second issue was the possible effect of "old carbon": wood or charcoal much older than the time at which iron was smelted. This is a particular problem in Niger, where the charred stumps of ancient trees are a potential source of charcoal, and have sometimes been misidentified as smelting furnaces. A third issue is the weaker precision of the radiocarbon method for dates between 800 and 400 BCE, attributable to irregular production of radiocarbon in the upper atmosphere. Unfortunately most radiocarbon dates for the initial spread of iron metallurgy in sub-Saharan Africa fall within this range.
Controversy flared again in 2007 with the publication of excavations by Étienne Zangato and colleagues in the Central African Republic. At Oboui they excavated an undated iron forge yielding eight consistent radiocarbon dates of 2000 BCE. This would make Oboui the oldest iron-working site in the world, and more than a thousand years older than any other dated evidence of iron in Central Africa. Opinion among African archaeologists is sharply divided. Some specialists accept this interpretation, but archaeologist Bernard Clist has argued that Oboui is a highly disturbed site, with older charcoal having been brought up to the level of the forge by the digging of pits into older levels. Clist also raised questions about the unusually good state of preservation of metallic iron from the site. However, archaeologists such as Craddock, Eggert, and Holl have argued that such disturbance or disruption is highly unlikely given the nature of the site. Additionally, Holl, regarding the state of preservation, argues that this observation was based on published illustrations representing a small unrepresentative number of atypically well-preserved objects selected for publication. At Gbabiri, also in the Central African Republic, Eggert has found evidence of an iron reduction furnace and blacksmith workshop with earliest dates of 896–773 BCE and 907–796 BCE respectively.
In north-central Burkina Faso, remains of an iron smelting furnace near Douroula was also dated to the 8th century BCE, leading to the creation of the Ancient Ferrous Metallurgy Sites of Burkina Faso World Heritage Site. In the Nsukka region of southeast Nigeria (now Igboland), archaeological sites containing iron smelting furnaces and slag have been excavated dating to 750 BCE in Opi (Augustin Holl 2009) and 2,000 BCE in Lejja (Pamela Eze-Uzomaka 2009). According to Augustin Holl (2018), there is evidence of ironworking dated to 2,153–2,044 BCE and 2,368–2,200 BCE from the site of Gbatoro, Cameroon.
Archaeometallurgical scientific knowledge and technological development originated in numerous centers of Africa; the centers of origin were located in West Africa, Central Africa, and East Africa; consequently, as these origin centers are located within inner Africa, these archaeometallurgical developments are thus native African technologies. Iron metallurgical development occurred 2631 BCE – 2458 BCE at Lejja, in Nigeria, 2136 BCE – 1921 BCE at Obui, in Central Africa Republic, 1895 BCE – 1370 BCE at Tchire Ouma 147, in Niger, and 1297 BCE – 1051 BCE at Dekpassanware, in Togo.
In 2014, archaeo-metallurgist Manfred Eggert argued that, though still inconclusive, the evidence overall suggests an independent invention of iron metallurgy in sub-Saharan Africa. In a 2018 study, archaeologist Augustin Holl also argues that an independent invention is most likely.
While the origins of iron smelting are difficult to date by radiocarbon, there are fewer problems with using it to track the spread of ironworking after 400 BCE. In the 1960s it was suggested that iron working was spread by speakers of Bantu languages, whose original homeland has been located by linguists in the Benue River valley of eastern Nigeria and Western Cameroon. Although some assert that no words for iron or ironworking can be traced to reconstructed proto-Bantu, place-names in West Africa suggest otherwise, for example (Okuta) Ilorin, literally "site of iron-work". The linguist Christopher Ehret argues that the first words for iron-working in Bantu languages were borrowed from Central Sudanic languages in the vicinity of modern Uganda and Kenya, while Jan Vansina argues instead that they originated in non-Bantu languages in Nigeria, and that iron metallurgy spread southwards and eastwards to Bantu speakers, who had already dispersed into the Congo rainforest and the Great Lakes region. Archaeological evidence clearly indicates that starting in the first century BCE, iron and cereal agriculture (millet and sorghum) spread together southward from southern Tanzania and northern Zambia, all the way to the eastern Cape region of present South Africa by the third or fourth century CE. It seems highly probable that this occurred through migrations of Bantu-speaking peoples. | 0 | Metallurgy |
Hydrogen-reduced iron is used as a source of food-grade iron powder, for food fortification and for oxygen scavenging. This elemental form is not absorbed as well as ferrous forms, but the oxygen-scavenging function keeps it attractive. Purity standards for this use are established in 1977. | 0 | Metallurgy |
The ciliate, dasycladacean and Hexamita nuclear code (translation table 6) is a genetic code used by certain ciliate, dasycladacean and Hexamita species.
The ciliate macronuclear code has not been determined completely. The codon UAA is known to code for Gln only in the Oxytrichidae. | 1 | Gene expression + Signal Transduction |
S&S has also been used in RNA splicing research in many animals and plants.
The mRNA splicing plays a fundamental role in gene functional regulation. Very recently, it has been shown that A to G conversions at splice sites can lead to mRNA mis-splicing in Arabidopsis. The splicing and exon–intron junction prediction coincided with the GT/AG rule (S&S) in the Molecular characterization and evolution of carnivorous sundew (Drosera rotundifolia L.) class V b-1,3-glucanase. Unspliced (LSDH) and spliced (SSDH) transcripts of NAD+ dependent sorbitol dehydroge nase (NADSDH) of strawberry (Fragaria ananassa Duch., cv. Nyoho) were investigated for phytohormonal treatments.
Ambra1 is a positive regulator of autophagy, a lysosome-mediated degradative process involved both in physiological and pathological conditions. Nowadays, this function of Ambra1 has been characterized only in mammals and zebrafish. Diminution of rbm24a or rbm24b gene products by morpholino knockdown resulted in significant disruption of somite formation in mouse and zebrafish. Dr.Senapathy algorithm used extensively to study intron-exon organization of fut8 genes. The intron-exon boundaries of Sf9 fut8 were in agreement with the consensus sequence for the splicing donor and acceptor sites concluded using S&S. | 1 | Gene expression + Signal Transduction |
Transcription initiation at the P promoter occurs in the presence of high arabinose and low glucose concentrations. Upon arabinose binding to AraC, the N-terminal arm of AraC is released from its DNA binding domain via a “light switch” mechanism. This allows AraC to dimerize and bind the I and I operators. The AraC-arabinose dimer at this site contributes to activation of the Ppromoter. Additionally, CAP binds to two CAP binding sites upstream of the I and I operators and helps activate the P promoter. In the presence of both high arabinose and high glucose concentrations however, low cAMP levels prevent CAP from activating the P promoter. It is hypothesized that P promoter activation by CAP and AraC is mediated through contacts between the C-terminal domain of the α-subunit of RNA polymerase and the CAP and AraC proteins.
Without arabinose, and regardless of glucose concentration, the P and Ppromoters are repressed by AraC. The N-terminal arm of AraC interacts with its DNA binding domain, allowing two AraC proteins to bind to the O and I operator sites. The Ooperator is situated within the araC gene. An AraC dimer also binds to the O operator and represses the P promoter via a negative autoregulatory feedback loop. The two bound AraC proteins dimerize and cause looping of the DNA. The looping prevents binding of CAP and RNA Polymerase, which normally activate the transcription of both P and P.
The spacing between the O and I operator sites is critical. Adding or removing 5 base pairs between the O and I operator sites abrogates AraC mediated repression of the P promoter. The spacing requirement arises from the double helix nature of DNA, in which a complete turn of the helix is about 10.5 nucleotides. Therefore, adding or removing 5 base pairs between the O and I operator sites rotates the helix roughly 180 degrees. This reverses the direction that the Ooperator faces when the DNA is looped and prevents dimerization of the O bound AraC with the bound I araC. | 1 | Gene expression + Signal Transduction |
In addition to water and ammonia, the clouds in the atmospheres of the gas giant planets contain ammonium sulfides. The reddish-brownish clouds are attributed to polysulfides, arising from the exposure of the ammonium sulfides to light. | 0 | Metallurgy |
The majority of miRNAs act in the cytoplasm and mediate mRNA degradation or translational arrest. However, some plant miRNAs have been shown to act directly to promote DNA methylation. miRNAs come from hairpin precursors generated by the RNaseIII enzymes Drosha and Dicer. Both miRNA and siRNA form either the RNA-induced silencing complex (RISC) or the nuclear form of RISC known as RNA-induced transcriptional silencing complex (RITS). The volume of literature on miRNA within the framework of RNAi is extensive. | 1 | Gene expression + Signal Transduction |
Hydrometallurgy is concerned with processes involving aqueous solutions to extract metals from ores. The first step in the hydrometallurgical process is leaching, which involves dissolution of the valuable metals into the aqueous solution and or a suitable solvent. After the solution is separated from the ore solids, the extract is often subjected to various processes of purification and concentration before the valuable metal is recovered either in its metallic state or as a chemical compound. This may include precipitation, distillation, adsorption, and solvent extraction. The final recovery step may involve precipitation, cementation, or an electrometallurgical process. Sometimes, hydrometallurgical processes may be carried out directly on the ore material without any pretreatment steps. More often, the ore must be pretreated by various mineral processing steps, and sometimes by pyrometallurgical processes. | 0 | Metallurgy |
*Patricia A. M. Huntington. [http://www.meteorman.org/Cape%20York.pdf Robert E Peary and the Cape York meteorites] | 0 | Metallurgy |
James Beaumont Neilson, previously foreman at Glasgow gas works, invented the system of preheating the blast for a furnace. He found that by increasing the temperature of the incoming air to 300 degrees Fahrenheit, he could reduce the fuel consumption from 8.06 tons of coal to 5.16 tons of coal per ton of produced iron with further reductions at even higher temperatures. He, with partners including Charles Macintosh, patented this in 1828. Initially the heating vessel was made of wrought iron plates, but these oxidized, and he substituted a cast iron vessel.
On the basis of a January 1828 patent, Thomas Botfield has a historical claim as the inventor of the hot blast method. Neilson is credited as inventor of hot blast, because he won patent litigation. Neilson and his partners engaged in substantial litigation to enforce the patent against infringers. The spread of this technology across Britain was relatively slow. By 1840, 58 ironmasters had taken out licenses, yielding a royalty income of £30,000 per year. By the time the patent expired there were 80 licenses. In 1843, just after it expired, 42 of the 80 furnaces in south Staffordshire were using hot blast, and uptake in south Wales was even slower.
Other advantages of hot blast were that raw coal could be used instead of coke. In Scotland, the relatively poor "black band" ironstone could be profitably smelted. It also increased the daily output of furnaces. In the case of Calder ironworks from 5.6 tons per day in 1828 to 8.2 in 1833, which made Scotland the lowest cost steel producing region in Britain in the 1830s.
Early hot blast stoves were troublesome, as thermal expansion and contraction could cause breakage of pipes. This was somewhat remedied by supporting the pipes on rollers. It was also necessary to devise new methods of connecting the blast pipes to the tuyeres, as leather could no longer be used.
Ultimately this principle was applied even more efficiently in regenerative heat exchangers, such as the Cowper stove (which preheat incoming blast air with waste heat from flue gas; these are used in modern blast furnaces), and in the open hearth furnace (for making steel) by the Siemens-Martin process.
Independently, George Crane and David Thomas, of the Yniscedwyn Works in Wales, conceived of the same idea, and Crane filed for a British patent in 1836. They began producing iron by the new process on February 5, 1837. Crane subsequently bought Gessenhainer's patent and patented additions to it, controlling the use of the process in both Britain and the US. While Crane remained in Wales, Thomas moved to the US on behalf of the Lehigh Coal & Navigation Company and founded the Lehigh Crane Iron Company to utilize the process. | 0 | Metallurgy |
The completed assembly of the holoenzyme with transcription factors and RNA polymerase II bound to the promoter forms the eukaryotic transcription initiation complex. Transcription in the archaea domain is similar to transcription in eukaryotes.
Transcription begins with matching of NTPs to the first and second in the DNA sequence. This, like most of the remainder of transcription, is an energy-dependent process, consuming adenosine triphosphate (ATP) or other NTP. | 1 | Gene expression + Signal Transduction |
A not often used definition of glaze is the highly sintered compacted oxide layer formed due to the sliding of either two metallic surfaces (or sometimes a metal surface and ceramic surface) at high temperatures (normally several hundred degrees Celsius) in oxidizing conditions. The sliding or tribological action generates oxide debris that can be compacted against one or both sliding surfaces and, under the correct conditions of load, sliding speed and oxide chemistry as well as (high) temperature, sinter together to form a glaze layer. The glaze formed in such cases is actually a crystalline oxide, with a very small crystal or grain size having been shown to approach nano-scale levels. Such glaze layers were originally thought to be amorphous oxides of the same form as ceramic glazes, hence the name glaze is still currently used.
Such glazes have attracted limited attention due to their ability to protect the metallic surfaces on which they may form, from wear under the high temperature conditions in which they are generated. This high temperature wear protection allows potential use at temperatures beyond the range of conventional hydrocarbon-based, silicone-based or even solid lubricants such as molybdenum disulfide (the latter useful up to about short term). Once they form, little further damage occurs unless there is a dramatic change in sliding conditions.
Such glazes work by providing a mechanically resistant layer, which prevents direct contact between the two sliding surfaces. For example, when two metals slide against each other, there can be a high degree of adhesion between the surfaces. The adhesion may be sufficient to result in metallic transfer from one surface to the other (or removal and ejection of such material) - effectively adhesive wear (also referred to as severe wear). With the glaze layer present, such severe adhesive interactions cannot occur and wear may be greatly reduced. The continued generation of oxidized debris during the more gradual wear that results (entitled mild wear) can sustain the glaze layer and maintain this low wear regime.
However, their potential application has been hampered as they have only successfully been formed under the very sliding conditions where they are meant to offer protection. A limited amount of sliding damage (referred to as run in wear - actually a brief period of adhesive or severe wear) needs to occur before the oxides are generated and such glaze layers can form. Efforts at encouraging their early formation have met with very limited success, and the damage inflicted during the run in period is one factor preventing this technique being used for practical applications.
As oxide generated is effectively the result of the tribochemical decay of one or both of the metallic (or ceramic) surfaces in contact, the study of compacted oxide layer glazes is sometimes referred to as part of the more general field of high temperature corrosion.
The generation of oxides during high temperature sliding wear does not automatically lead to the production of a compacted oxide layer glaze. Under certain conditions (potentially due to non-ideal conditions of sliding speed, load, temperature or oxide chemistry / composition), the oxide may not sinter together and instead the loose oxide debris may assist or enhance the removal of material by abrasive wear. A change in conditions may also see a switch from the formation of a loose, abrasive oxide to the formation of wear protective compacted oxide glaze layers and vice versa, or even the reappearance of adhesive or severe wear. Due to the complexities of the conditions controlling the types of wear observed, there have been a number of attempts to map types of wear with reference to sliding conditions in order to help better understand and predict them. | 0 | Metallurgy |
In cancers, loss of expression of genes occurs about 10 times more frequently by transcription silencing (caused by promoter hypermethylation of CpG islands) than by mutations. As Vogelstein et al. point out, in a colorectal cancer there are usually about 3 to 6 driver mutations and 33 to 66 hitchhiker or passenger mutations. In contrast, in colon tumors compared to adjacent normal-appearing colonic mucosa, there are about 600 to 800 heavily methylated CpG islands in promoters of genes in the tumors while these CpG islands are not methylated in the adjacent mucosa.
Using gene set enrichment analysis, 569 out of 938 gene sets were hypermethylated and 369 were hypomethylated in cancers. Hypomethylation of CpG islands in promoters results in increased transcription of the genes or gene sets affected.
One study listed 147 specific genes with colon cancer-associated hypermethylated promoters and 27 with hypomethylated promoters, along with the frequency with which these hyper/hypo-methylations were found in colon cancers. At least 10 of those genes had hypermethylated promoters in nearly 100% of colon cancers. They also indicated 11 microRNAs whose promoters were hypermethylated in colon cancers at frequencies between 50% and 100% of cancers. MicroRNAs (miRNAs) are small endogenous RNAs that pair with sequences in messenger RNAs to direct post-transcriptional repression. On average, each microRNA represses or inhibits transcriptional expression of several hundred target genes. Thus microRNAs with hypermethylated promoters may be allowing enhanced transcription of hundreds to thousands of genes in a cancer. | 1 | Gene expression + Signal Transduction |
Prp24 has a human homolog, SART3. SART3 is a tumor rejection antigen (SART3 stands for "squamous cell carcinoma antigen recognized by T cells, gene 3). The RRMs 1 and 2 in yeast are similar to RRMs in human SART3. The C-terminal domain is also highly conserved from yeast to humans. This protein, like Prp24, interacts with the LSm proteins for the recycling of U6 into the U4/U6 snRNP. It has been proposed that SART3 target U6 to a Cajal body or a nuclear inclusion as the site of assembly of the U4/U6 snRNP. SART3 is located on chromosome 12, and a mutation is likely the cause of disseminated superficial actinic porokeratosis. | 1 | Gene expression + Signal Transduction |
Antibody (or immunoglobulin) structure is made up of two heavy-chains and two light-chains. These chains are held together by disulfide bonds. The arrangement or processes that put together different parts of this antibody molecule play important role in antibody diversity and production of different subclasses or classes of antibodies. The organization and processes take place during the development and differentiation of B cells. That is, the controlled gene expression during transcription and translation coupled with the rearrangements of immunoglobulin gene segments result in the generation of antibody repertoire during development and maturation of B cells. | 1 | Gene expression + Signal Transduction |
High-Mobility Group or HMG is a group of chromosomal proteins that are involved in the regulation of DNA-dependent processes such as
transcription, replication, recombination, and DNA repair. | 1 | Gene expression + Signal Transduction |
The Fas receptor, also known as Fas, FasR, apoptosis antigen 1 (APO-1 or APT), cluster of differentiation 95 (CD95) or tumor necrosis factor receptor superfamily member 6 (TNFRSF6), is a protein that in humans is encoded by the FAS gene. Fas was first identified using a monoclonal antibody generated by immunizing mice with the FS-7 cell line. Thus, the name Fas is derived from FS-7-associated surface antigen.
The Fas receptor is a death receptor on the surface of cells that leads to programmed cell death (apoptosis) if it binds its ligand, Fas ligand (FasL). It is one of two apoptosis pathways, the other being the mitochondrial pathway. | 1 | Gene expression + Signal Transduction |
Pewter, being a softer material, can be manipulated in various ways such as being cast, hammered, turned, spun and engraved.
Given that pewter is soft at room temperature, a pewter bell does not ring clearly. Cooling it in liquid nitrogen hardens it and enables it to ring, but also makes it more brittle. | 0 | Metallurgy |
The transcriptome is the set of all RNA transcripts, including coding and non-coding, in an individual or a population of cells. The term can also sometimes be used to refer to all RNAs, or just mRNA, depending on the particular experiment. The term transcriptome is a portmanteau of the words transcript and genome; it is associated with the process of transcript production during the biological process of transcription.
The early stages of transcriptome annotations began with cDNA libraries published in the 1980s. Subsequently, the advent of high-throughput technology led to faster and more efficient ways of obtaining data about the transcriptome. Two biological techniques are used to study the transcriptome, namely DNA microarray, a hybridization-based technique and RNA-seq, a sequence-based approach. RNA-seq is the preferred method and has been the dominant transcriptomics technique since the 2010s. Single-cell transcriptomics allows tracking of transcript changes over time within individual cells.
Data obtained from the transcriptome is used in research to gain insight into processes such as cellular differentiation, carcinogenesis, transcription regulation and biomarker discovery among others. Transcriptome-obtained data also finds applications in establishing phylogenetic relationships during the process of evolution and in in vitro fertilization. The transcriptome is closely related to other -ome based biological fields of study; it is complementary to the proteome and the metabolome and encompasses the translatome, exome, meiome and thanatotranscriptome which can be seen as ome fields studying specific types of RNA transcripts. There are quantifiable and conserved relationships between the Transcriptome and other -omes, and Transcriptomics data can be used effectively to predict other molecular species, such as metabolites. There are numerous publicly available transcriptome databases. | 1 | Gene expression + Signal Transduction |
The preinitiation complex (abbreviated PIC) is a complex of approximately 100 proteins that is necessary for the transcription of protein-coding genes in eukaryotes and archaea. The preinitiation complex positions RNA polymerase II (Pol II) at gene transcription start sites, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription.
The minimal PIC includes RNA polymerase II and six general transcription factors: TFA, TFB, TFD, TFE, TFF, and TFH. Additional regulatory complexes (such as the mediator coactivator and chromatin remodeling complexes) may also be components of the PIC.
Preinitiation complexes are also formed during RNA Polymerase I and RNA Polymerase III transcription. | 1 | Gene expression + Signal Transduction |
GPCRs downstream signals have been shown to possibly interact with integrin signals, such as FAK. Integrin signaling will phosphorylate FAK, which can then decrease GPCR G activity. | 1 | Gene expression + Signal Transduction |
Each of the most important fragments of Cape York has its own name (listed in order of discovery date by foreigners):
# Ahnighito (the Tent), , 1884–1897, Meteorite Island, 76°04N – 64°58W
# Woman, , 1897, Saveruluk, 76°09N – 64°56W
# Dog, , 1897, Saveruluk, 76°09N – 64°56W
# Savik I, , 1913, Savequarfik, 76°08N – 64°36W
# Thule, , summer 1955, Thule, 76°32N – 67°33W
# Savik II, , 1961, Savequarfik, 76°08N – 64°36W
# Agpalilik (the Man), , 1963, Agpalilik, 76°09N – 65°10W
# Tunorput, , 1984 | 0 | Metallurgy |
Although nonsense-mediated mRNA decay reduces nonsense codons, mutations can occur that lead to various health problems and diseases in humans. A dominant-negative or deleterious gain-of-function mutation can occur if premature terminating (nonsense) codons are translated. NMD is becoming increasingly evident in the way it modifies phenotypic consequences because of the broad way it controls gene expression. For instance, the blood disorder Beta thalassemia is inherited and caused by mutations within the upstream region of the β-globin gene. An individual carrying only one affected allele will have no or extremely low levels of the mutant β-globin mRNA. An even more severe form of the disease can occur called thalassemia intermedia or ‘inclusion body’ thalassemia. Instead of decreased mRNA levels, a mutant transcript produces truncated β chains, which in turn leads to a clinical phenotype in the heterozygote.
Nonsense-mediated decay mutations can also contribute to Marfan syndrome. This disorder is caused by mutations in the fibrillin 1 (FBN1) gene and is resulted from a dominant negative interaction between mutant and wild-type fibrillin-1 gene. | 1 | Gene expression + Signal Transduction |
As mentioned above, the deformed structure is often a 3-D cellular structure with walls consisting of dislocation tangles. As recovery proceeds these cell walls will undergo a transition towards a genuine subgrain structure. This occurs through a gradual elimination of extraneous dislocations and the rearrangement of the remaining dislocations into low-angle grain boundaries.
Sub-grain formation is followed by subgrain coarsening where the average size increases while the number of subgrains decreases. This reduces the total area of grain boundary and hence the stored energy in the material. Subgrain coarsen shares many features with grain growth.
If the sub-structure can be approximated to an array of spherical subgrains of radius R and boundary energy γ; the stored energy is uniform; and the force on the boundary is evenly distributed, the driving pressure P is given by:
Since γ is dependent on the boundary misorientation of the surrounding subgrains, the driving pressure generally does not remain constant throughout coarsening. | 0 | Metallurgy |
A B2 intermetallic compound has equal numbers of atoms of two metals such as aluminium and iron, arranged as two interpenetrating simple cubic lattices of the component metals. | 0 | Metallurgy |
mTOR inhibitors may be useful for treating/preventing several age-associated conditions, including neurodegenerative diseases such as Alzheimers disease and Parkinsons disease. After a short-term treatment with the mTOR inhibitors dactolisib and everolimus, in elderly (65 and older), treated subjects had a reduced number of infections over the course of a year.
Various natural compounds, including epigallocatechin gallate (EGCG), caffeine, curcumin, berberine, quercetin, resveratrol and pterostilbene, have been reported to inhibit mTOR when applied to isolated cells in culture. As yet no high quality evidence exists that these substances inhibit mTOR signaling or extend lifespan when taken as dietary supplements by humans, despite encouraging results in animals such as fruit flies and mice. Various trials are ongoing. | 1 | Gene expression + Signal Transduction |
Beginning in 1618, the government on an almost continual basis organized expeditions to the Urals and Siberia to search for ore deposits. Also, the practice of issuing permits was used, which made it possible to search for ores throughout the territory of the state.
In the 16th-17th centuries, primitive blast furnaces were built by peasant families in the forests adjacent to their villages. The resulting metal pieces were processed into iron in forges or sold. It is known that 40 years before the arrival of Georg Wilhelm de Gennin to the Urals, the peasants of the Aramil settlement smelted iron in small furnaces and sold it, paying tithes to the district office. Even at the beginning of the 18th century, the smelting of ore in small blast furnaces was widespread in many regions of the Urals. In 1720-1722, the artisanal farms of the Kungur district produced 3 thousand poods of iron, 203 poods of strip iron and 897 poods of other varieties. Subsequently, artisanal metallurgical production was legally prohibited on the initiative of G. W. de Gennin.
In the 1630s, with the involvement of foreign engineers, the construction of arms metallurgical factories began in the central part of Russia. Despite the construction of more than 20 state and private factories in the central region in the 17th century, the country experienced a shortage of metal and continued to buy it abroad. In 1629, 25 thousand poods of iron bars were bought in Sweden. To meet the needs of the Ural and Siberian enterprises (primarily salt-making) and settlements settled by Russians, iron was purchased in the central regions. At the same time, the cost of the metal increased sharply with the distance to the east due to transport costs. The impetus for the development of the Ural industry at the beginning of the 17th century was the plans of the authorities to create metallurgical enterprises in the eastern regions of Russia. After his trip abroad, Peter I, realizing the shortage of coal in the central regions and the need to strengthen weapons potential, ordered the construction of mining plants in the Urals, providing them with engineers from Tula, Kashira and other factories. The Ural factories were built on the model of factories in central Russia, which, in turn, were created using the French, German and Swedish types. The rapid development of the metallurgical industry in the Urals in the 17th-18th centuries was facilitated by the abundance of rich natural alloyed (copper, chromium and vanadium) ores in the region, as well as the availability of accessible forest and water resources. The lack of railways led to the development of a large number of small mines. Iron ore reserves were considered practically inexhaustible, while copper ore reserves, on the contrary, were quickly depleted, which led to the closure of 40 copper smelters in the Western Urals in the late 17th - first half of the 18th century.
In the absence of their own specialists in mining and metallurgy, craftsmen were invited from abroad, but they worked mainly in the central regions of the country. In 1618-1622, the Englishman John Water, and in 1626 Fritsch, Gerold and Bulmerr, together with Russian attendants, carried out fruitless expeditions to search for ores in the region of the upper Kama and the Pechora. Others such as the Bergman brothers also unsuccessfully searched for ore in 1626 in the Cherdyn region. Only in 1635, the Saxon, Aris Petzold, and the Moscow merchant Nadia Sveteshnikov found two copper deposits, which became the basis of the first copper smelter in the Urals - Pyskorsky. Failures of geological exploration expeditions at the beginning of the 17th century forced the state to weaken its monopoly on exploration for non-ferrous and precious metals. Major rewards were promised for the found deposits. This decision was followed by a series of discoveries of new deposits of copper and iron in the Urals. In particular, thanks to local residents who brought samples of bog ore to the offices of the Turin and Tobolsk governors for a fee, the deposits of the first iron-making plant in the Urals - Nitsynsky - were discovered. In the 1670s, the expeditions, not finding ore in the Penza district, began to advance to the Urals and found silver ores along the banks of the Kama, Yayva and Kosva.
Government incentives for the found ores led to a sharp increase in exploration activity in the Urals. In the second half of the 17th century, the focus of the search shifted from the Kama region to the Verkhotursky district, where a number of large copper and iron deposits were discovered. In 1669-1674, the state organized an expedition to the Trans-Urals to search for silver and gold ores. During the expedition, no suitable ore was found. Rich ores were found only at the end of the 17th century far beyond the Urals, in the valley of the Argun River, on the basis of which, in 1704, the first Russian silver-smelting Nerchinsk plant was launched.
In general, the Ural metallurgy in the 17th century did not go beyond the limits of artisanal production, the central regions received greater development during this period. | 0 | Metallurgy |
The quenching process produces a high strength bar from inexpensive low carbon steel. The process quenches the surface layer of the bar, which pressurizes and deforms the crystal structure of intermediate layers, and simultaneously begins to temper the quenched layers using the heat from the bar's core.
Steel billets 130mm² ("pencil ingots") are heated to approximately 1200°C to 1250°C in a reheat furnace. Then, they are progressively rolled to reduce the billets to the final size and shape of reinforcing bar. After the last rolling stand, the billet moves through a quench box. The quenching converts the billet's surface layer to martensite, and causes it to shrink. The shrinkage pressurizes the core, helping to form the correct crystal structures. The core remains hot, and austenitic. A microprocessor controls the water flow to the quench box, to manage the temperature difference through the cross-section of the bars. The correct temperature difference assures that all processes occur, and bars have the necessary mechanical properties.
The bar leaves the quench box with a temperature gradient through its cross section. As the bar cools, heat flows from the bars centre to its surface so that the bars heat and pressure correctly tempers an intermediate ring of martensite and bainite.
Finally, the slow cooling after quenching automatically tempers the austenitic core to ferrite and pearlite on the cooling bed.
These bars therefore exhibit a variation in microstructure in their cross section, having strong, tough, tempered martensite in the surface layer of the bar, an intermediate layer of martensite and bainite, and a refined, tough and ductile ferrite and pearlite core.
When the cut ends of TMT bars are etched in Nital (a mixture of nitric acid and methanol), three distinct rings appear: 1. A tempered outer ring of martensite, 2. A semi-tempered middle ring of martensite and bainite, and 3. a mild circular core of bainite, ferrite and pearlite. This is the desired micro structure for quality construction rebar.
In contrast, lower grades of rebar are twisted when cold, work hardening them to increase their strength. However, after thermo mechanical treatment (TMT), bars do not need more work hardening. As there is no twisting during TMT, no torsional stress occurs, and so torsional stress cannot form surface defects in TMT bars. Therefore TMT bars resist corrosion better than cold, twisted and deformed (CTD) bars.
After thermomechanical processing, some grades in which TMT Bars can be covered includes Fe: 415 /500 /550/ 600. These are much stronger compared with conventional CTD Bars and give up to 20% more strength to concrete structure with same quantity of steel. | 0 | Metallurgy |
Offshore wind turbines are subject to challenging environmental conditions, including corrosive saltwater, high wind forces, and potential electrical currents. These conditions can contribute to bearing failures and impact the reliability and maintenance of wind turbines. Several factors that can lead to bearing failures, such as corrosion, fatigue, wear, improper lubrication, high electric currents, and the need for improved materials and designs to ensure the longevity and performance of bearings in offshore wind turbines. WECs negatively affects the reliability of bearings, not only in the wind industry but also in various other industrial applications such as electric motors, paper machines, industrial gearboxes, pumps, ship propulsion systems, and the automotive sector. 60% of wind turbines failures are liked to WEC.
In October 2018, a workshop on WECs was organised in Düsseldorf by a junior research group funded by the German Federal Ministry of Education and Research (BMBF). Representatives from academia and industry gathered to discuss the mechanisms behind WEC formation in wind turbines, focusing on the fundamental material processes causing this phenomenon. | 0 | Metallurgy |
Permutation re-sampling requires a computationally demanding number of permutations to get reliable estimates of the p-values for the most differentially expressed genes, if n is large. Eisinga, Breitling and Heskes (2013) provide the exact probability mass distribution of the rank product statistic. Calculation of the exact p-values offers a substantial improvement over permutation approximation, most significantly for that part of the distribution rank product analysis is most interested in, i.e., the thin right tail. However, exact statistical significance of large rank products may take unacceptable long amounts of time to compute. Heskes, Eisinga and Breitling (2014) provide a method to determine accurate approximate p-values of the rank product statistic in a computationally fast manner. | 1 | Gene expression + Signal Transduction |
Using a glass pipette, the photolysed cell is isolated by aspiration. Cells are lysed and affinity purification is performed using streptavidin-coated beads that bind, immobilize and purify the biotinylated TIVA tag. | 1 | Gene expression + Signal Transduction |
When iron is in contact with water and oxygen, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of chemical reactions. Iron metal is relatively unaffected by pure water or by dry oxygen. As with other metals, like aluminium, a tightly adhering oxide coating, a passivation layer, protects the bulk iron from further oxidation. The conversion of the passivating ferrous oxide layer to rust results from the combined action of two agents, usually oxygen and water.
Other degrading solutions are sulfur dioxide in water and carbon dioxide in water. Under these corrosive conditions, iron hydroxide species are formed. Unlike ferrous oxides, the hydroxides do not adhere to the bulk metal. As they form and flake off from the surface, fresh iron is exposed, and the corrosion process continues until either all of the iron is consumed or all of the oxygen, water, carbon dioxide or sulfur dioxide in the system are removed or consumed.
When iron rusts, the oxides take up more volume than the original metal; this expansion can generate enormous forces, damaging structures made with iron. See economic effect for more details. | 0 | Metallurgy |
For the bacteria to use quorum sensing constitutively, they must possess three abilities: secretion of a signaling molecule, secretion of an autoinducer (to detect the change in concentration of signaling molecules), and regulation of gene transcription as a response. This process is highly dependent on the diffusion mechanism of the signaling molecules. QS signaling molecules are usually secreted at a low level by individual bacteria. At low cell density, the molecules may just diffuse away. At high cell density, the local concentration of signaling molecules may exceed its threshold level, and trigger changes in gene expression. | 1 | Gene expression + Signal Transduction |
Below is a table of the handbooks published by ASM International as of April 2023. These handbooks are recognized as a standard reference in the field of materials science. | 0 | Metallurgy |
Synapses are typically formed where two neurons come in very close proximity. Ephaptic coupling may therefore arise across the synaptic cleft. Prominent examples are the fish Mauthner cell, the chick ciliary ganglion, the mammalian cerebellar basket synapse, and the mammalian, developing calyx of Held synapse. | 1 | Gene expression + Signal Transduction |
A silencer is a sequence-specific element that induces a negative effect on the transcription of its particular gene. There are many positions in which a silencer element can be located in DNA. The most common position is found upstream of the target gene where it can help repress the transcription of the gene. This distance can vary greatly between approximately -20 bp to -2000 bp upstream of a gene. Certain silencers can be found downstream of a promoter located within the intron or exon of the gene itself. Silencers have also been found within the 3 prime untranslated region (3' UTR) of mRNA. | 1 | Gene expression + Signal Transduction |
* 999.95: what most dealers would buy as if 100% pure; the most common purity for platinum bullion coins and bars
* 999—three nines fine
* 950: the most common purity for platinum jewelry
* 900—one nine fine | 0 | Metallurgy |
Several techniques exist to produce pre-alloyed powder, such as Grade 5. In the hydride-dehydride process feedstock such as solid scrap, billet or machined turnings are processed to remove contaminants, hydrogenated to produce brittle material then ground under argon in a vibratory ball mill, typically at 400 °C for 4 hours at a pressure of 1 psi for Ti Grade 5. The resulting particles are angular and measure between 50 and 300 μm. Cold compaction after dehydrogenation of the powder, followed by either vacuum hot pressing (in this case the dehydrogenation process can be bypassed as hydrogen is removed under vacuum) or HIP and a final vacuum anneal, produces powders with hydrogen below 125 ppm. The possible presence of contaminants makes these powders unsuitable for use in critical aircraft applications.
In the plasma rotating electrode process (PREP), the feedstock, such as Ti Grade 5, is in the form of a rotating bar which is arced with gas plasma. The molten metal is centrifugally flung off the bar, cools down and is collected. The powders produced are spherical; between 100 and 300 μm is size, with good packing and flow characteristics, making the powder ideal for high quality, near net shapes produced by HIP, such as aviation parts and porous coatings on hip prostheses.
In the titanium gas atomisation (TGA) process, titanium is vacuum induction skull melted in a water cooled copper crucible, the metal tapped and the molten metal stream atomized with a stream of high pressure inert gas. The tiny droplets are spherical and measure between 50 and 350 μm. The TGA process has been used to produce a wide variety of materials such as commercially pure (CP) titanium, conventional alpha-beta and beta alloys.
In plasma atomization (PA) process, a titanium wire is atomized by 3 inert gas plasma jets to form spherical metal powders. The distribution of diameter obtained in the PA process ranges between 0–200 μm and the powders obtained is very pure. The PA process specializes in the production of high temperature melting material as titanium (CP-Ti, Ti-6Al-4V), niobium, molybdenum, tantalum and many more. | 0 | Metallurgy |
Relative little is known about the normal functions and pathological actions of the CKLF2, CKLF3, and CKLF4 isoforms. | 1 | Gene expression + Signal Transduction |
The regions of the rpoB gene which are susceptible to mutations are typically well conserved, indicating they are important for life. This makes it very likely that mutations within these regions have some effect on the overall fitness of the organism. These physiological changes can include a reduced rate of growth, increased sensitivity to increases or decreases in temperature, and alterations to the properties of RNA chain elongation and transcription termination. Such changes are not universal across all bacteria, though. A mutation in codon 450 of M. tuberculosis leads to a minor loss of fitness, while the corresponding mutation in S. aureus results in bacteria barely able to survive.
In Neisseria meningitidis rpoB mutations have been observed to increase expression of enzymes which are involved in metabolizing carbohydrates, as well as enzymes involved in the citric acid cycle and in transcription elongation. At the same time enzymes involved in ATP production, cell division, and lipid metabolism are all downregulated, or expressed at a lower than normal level.
In M. tuberculosis mutations in the rpoB gene can significantly upregulate polyketide synthase, potentially indicating increased production of phthiocerol dimycocerosate, a lipid produced by M. tuberculosis and implicated in virulence of the bacteria. Mutations also impact promoter binding, elongation, termination, and transcription-coupled repair processes in the RNA polymerase itself. Because of this, rpoB mutations were used to study transcription mechanisms before interest shifted to their ability to impart antibiotic resistance. Particular mutations can even result in strains of M. tuberculosis which grow better in the presence of rifampicin than they do when the antibiotic is not present.
In bacteria which are used to produce naturally occurring antibiotics such as erythromycin (Saccharopolyspora erythraea) and vancomycin (Amycolatopsis orientalis) certain rpoB mutations can increase the production of antibiotic by bacteria with those mutations. | 1 | Gene expression + Signal Transduction |
Season cracking is a form of stress-corrosion cracking of brass cartridge cases originally reported from British forces in India. During the monsoon season, military activity was temporarily reduced, and ammunition was stored in stables until the dry weather returned. Many brass cartridges were subsequently found to be cracked, especially where the case was crimped to the bullet. It was not until 1921 that the phenomenon was explained by Moor, Beckinsale and Mallinson: ammonia from horse urine, combined with the residual stress in the cold-drawn metal of the cartridges, was responsible for the cracking.
Season cracking is characterised by deep brittle cracks which penetrate into affected components. If the cracks reach a critical size, the component can suddenly fracture, sometimes with disastrous results. However, if the concentration of ammonia is very high, then attack is much more severe, and attack over all exposed surfaces occurs. The problem was solved by annealing the brass cases after forming so as to relieve the residual stresses. | 0 | Metallurgy |
In materials science, the Zener–Hollomon parameter, typically denoted as Z, is used to relate changes in temperature or strain-rate to the stress-strain behavior of a material. It has been most extensively applied to the forming of steels at increased temperature, when creep is active. It is given by
where is the strain rate, Q is the activation energy, R is the gas constant, and T is the temperature. The Zener–Hollomon parameter is also known as the temperature compensated strain rate, since the two are inversely proportional in the definition. It is named after Clarence Zener and John Herbert Hollomon, Jr. who established the formula based on the stress-strain behavior in steel.
When plastically deforming a material, the flow stress depends heavily on both the strain-rate and temperature. During forming processes, Z may help determine appropriate changes in strain-rate or temperature when the other variable is altered, in order to keep material flowing properly. Z has also been applied to some metals over a large range of strain rates and temperatures and shown comparable microstructures at the end-of-processing, as long as Z remained similar. This is because the relative activity of various deformation mechanisms is typically inversely proportional to temperature or strain-rate, such that decreasing strain rate or increasing temperature will increase Z and promote plastic deformation. | 0 | Metallurgy |
Caretaker genes encode products that stabilize the genome. Fundamentally, mutations in caretaker genes lead to genomic instability. Tumor cells arise from two distinct classes of genomic instability: mutational instability arising from changes in the nucleotide sequence of DNA and chromosomal instability arising from improper rearrangement of chromosomes.
Changes in the genome that allow uncontrolled cell proliferation or cell immortality are responsible for cancer. It is believed that the major changes in the genome that lead to cancer arise from mutations in tumor suppressor genes. In 1997, Kinzler and Bert Vogelstein grouped these cancer susceptibility genes into two classes: "caretakers" and "gatekeepers". In 2004, a third classification of tumor suppressor genes was proposed by Franziska Michor, Yoh Iwasa, and Martin Nowak; "landscaper" genes.
In contrast to caretaker genes, gatekeeper genes encode gene products that act to prevent growth of potential cancer cells and prevent accumulation of mutations that directly lead to increased cellular proliferation.
The third classification of genes, the landscapers, encode products that, when mutated, contribute to the neoplastic growth of cells by fostering a stromal environment conducive to unregulated cell proliferation. | 1 | Gene expression + Signal Transduction |
An autoreceptor is a type of receptor located in the membranes of nerve cells. It serves as part of a negative feedback loop in signal transduction. It is only sensitive to the neurotransmitters or hormones released by the neuron on which the autoreceptor sits. Similarly, a heteroreceptor is sensitive to neurotransmitters and hormones that are not released by the cell on which it sits. A given receptor can act as either an autoreceptor or a heteroreceptor, depending upon the type of transmitter released by the cell on which it is embedded.
Autoreceptors may be located in any part of the cell membrane: in the dendrites, the cell body, the axon, or the axon terminals.
Canonically, a presynaptic neuron releases a neurotransmitter across a synaptic cleft to be detected by the receptors on a postsynaptic neuron. Autoreceptors on the presynaptic neuron will also detect this neurotransmitter and often function to control internal cell processes, typically inhibiting further release or synthesis of the neurotransmitter. Thus, release of neurotransmitter is regulated by negative feedback. Autoreceptors are usually G protein-coupled receptors (rather than transmitter-gated ion channels) and act via a second messenger. | 1 | Gene expression + Signal Transduction |
Tumor angiogenesis rely on interactions between endothelial vascular growth factors which can all activate the PI3K/AKT/mTOR in endothelial cells, pericytes, or cancer cells. Example of these growth factors are angiopoietin 1 (ANG1), ANG 2, basic fibroblast growth factor (bFGF), ephrin-B2, vascular endothelial growth factor (VEGF), and members of the tumor growth factor-β (TGFβ) superfamily. One of the major stimuli of angiogenesis is hypoxia, resulting in activation of hypoxia-inducible transcription factors (HIFs) and expression of ANG2, bFGF, PDGF, VEGF, and VEGFR. Inhibition of HIF1α translation by preventing PDGF/PDGFR and VEGF/VEGFR can result from mTOR inhibition. A G0-G1 cell-cycle blockage can be the consequence of inactivation of mTOR in hypoxia-activated pericytes and endothelial cells.
There is some evidence that extended therapy with rapamycin may have effect on AKT and mTORC2 as well. | 1 | Gene expression + Signal Transduction |
Homologous paired receptors are located in the same gene cluster and are thought to have evolved through gene duplication. Sequence features such as the presence of an ITIM-like sequence in the 3' untranslated region of some activating receptors imply that the activating members of the pair likely evolved from the inhibitory members. A number of pathogens interact with the inhibitory member of a pair as a means of immune evasion or viral entry, suggesting that activating members with similar binding competencies may be an evolutionary response to this mechanism. This hypothesis is known as the "counterbalance theory" and these evolutionary dynamics represent an evolutionary arms race between pathogens and the host immune system. The evolutionary pressures on some paired-receptor families have been described as examples of the "Red Queen" effect.
Including non-paired examples, over 300 potential immune inhibitory receptors have been identified in the human genome. There are strong indications that paired receptors are rapidly and recently evolving. These genetic regions have high levels of gene polymorphism, and the gene repertoires found in the genomes of closely related lineages vary significantly. The selective pressure experienced by the host from pathogens is thought to underlie this rapid evolution.
Although paired receptors are best characterized as part of the human and mouse immune systems, they have also been studied in other organisms. The chicken (Gallus gallus domesticus) genome contains a number of examples including a very large family, the chicken Ig-like receptors (CHIR) with over 100 members. Paired receptor evolution has also been studied in Xenopus (clawed frog) species. The adaptive immune system is unique to jawed vertebrates, but an example of a paired receptor family has been identified in a jawless vertebrate, termed agnathan paired receptors resembling Ag receptors (APAR) in the hagfish. | 1 | Gene expression + Signal Transduction |
A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, osmium, iridium) are most often so classified. Silver, copper, and mercury are sometimes included as noble metals, but each of these usually occurs in nature combined with sulfur.
In more specialized fields of study and applications the number of elements counted as noble metals can be smaller or larger. In physics, there are only three noble metals: copper, silver, and gold. In dentistry, silver is not always considered a noble metal because it is subject to corrosion when present in the mouth. In chemistry, the term noble metal is sometimes applied more broadly to any metallic or semimetallic element that does not react with a weak acid and give off hydrogen gas in the process. This broader set includes copper, mercury, technetium, rhenium, arsenic, antimony, bismuth, polonium, gold, the six platinum group metals, and silver.
__TOC__ | 0 | Metallurgy |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V) | 1 | Gene expression + Signal Transduction |
Performance-based approaches provide for a real design of durability, based on models describing the evolution in time of degradation processes, and the definition of times at which defined limit states will be reached. To consider the wide variety of service life influencing factors and their variability, performance-based approaches address the problem from a probabilistic or semiprobabilistic point of view.
The performance-based service life model proposed by the European project DuraCrete, and by FIB Model Code for Service Life Design, is based on a probabilistic approach, similar to the one adopted for structural design. Environmental factors are considered as loads S(t), while material properties such as chloride penetration resistance are considered as resistances R(t) as shown in Figure 2. For each degradation process, design equations are set to evaluate the probability of failure of predefined performances of the structure, where acceptable probability is selected on the basis of the limit state considered. The degradation processes are still described with the models previously defined for carbonation-induced and chloride-induced corrosion, but to reflect the statistical nature of the problem, the variables are considered as probability distribution curves over time. To assess some of the durability design parameters, the use of accelerated laboratory test is suggested, such as the so called Rapid Chloride Migration Test to evaluate chloride penetration resistance of concrete '. Through the application of corrective parameters, the long-term behaviour of the structure in real exposure conditions may be evaluated.
The use of probabilistic service life models allows to implement a real durability design that could be implemented in the design stage of structures. This approach is of particular interest when an extended service life is required (>50 years) or when the environmental exposure conditions are particularly aggressive. Anyway, the applicability of this kind of models is still limited. The main critical issues still concern, for instance, the individuation of accelerated laboratory tests able to characterize concrete performances, reliable corrective factors to be used for the evaluation of long-term durability performances and the validation of these models based on real long-term durability performances. | 0 | Metallurgy |
Development of the Albion process started during the early nineties led by Mount Isa Mines. It was first patented in 1993. Several pilot plant projects were conducted in 1994 and 1995 which tested the feasibility of using the technology to process high arsenic gold and copper ore.
The Albion Process has been successfully installed in seven projects globally:
* GPM Gold Project (Gold, Armenia)
* Las Lagunas Tailings (Gold, Dominican Republic)
* Sable Copper Project (Copper, Chalcopyrite, Zambia)
* Asturiana de Zinc (Zinc, Spain)
* Nordenham Zinc Refinery (Zinc, Germany)
* McArthur River (Zinc, Australia) | 0 | Metallurgy |
Common roll-to-roll coating processes include:
* Air knife coating
* Anilox coater
* Flexo coater
* Gap Coating
** Knife-over-roll coating
* Gravure coating
* Hot melt coating- when the necessary coating viscosity is achieved by temperature rather than solution of the polymers etc. This method commonly implies slot-die coating above room temperature, but it also is possible to have hot-melt roller coating; hot-melt metering-rod coating, etc.
* Immersion dip coating
* Kiss coating
* Metering rod (Meyer bar) coating
* Roller coating
** Forward roller coating
** Reverse roll coating
* Silk Screen coater
** Rotary screen
*Slot Die coating - Slot die coating was originally developed in the 1950s. Slot die coating has a low operational cost and is an easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste. Slot die coating technology is used to deposit a variety of liquid chemistries onto substrates of various materials such as glass, metal, and polymers by precisely metering the process fluid and dispensing it at a controlled rate while the coating die is precisely moved relative to the substrate. The complex inner geometry of conventional slot dies require machining or can be accomplished with 3-D printing.
*Extrusion coating - generally high pressure, often high temperature, and with the web travelling much faster than the speed of the extruded polymer
**Curtain coating- low viscosity, with the slot vertically above the web and a gap between slot-die and web.
** Slide coating- bead coating with an angled slide between the slot-die and the bead. Commonly used for multilayer coating in the photographic industry.
** Slot die bead coating- typically with the web backed by a roller and a very small gap between slot-die and web.
** Tensioned-web slot-die coating- with no backing for the web.
* Inkjet printing
* Lithography
* Flexography | 0 | Metallurgy |
Plasma electrolytic oxidation is a similar process, but where higher voltages are applied. This causes sparks to occur and results in more crystalline/ceramic type coatings. | 0 | Metallurgy |
A protein phosphatase is a phosphatase enzyme that removes a phosphate group from the phosphorylated amino acid residue of its substrate protein. Protein phosphorylation is one of the most common forms of reversible protein posttranslational modification (PTM), with up to 30% of all proteins being phosphorylated at any given time. Protein kinases (PKs) are the effectors of phosphorylation and catalyse the transfer of a γ-phosphate from ATP to specific amino acids on proteins. Several hundred PKs exist in mammals and are classified into distinct super-families. Proteins are phosphorylated predominantly on Ser, Thr and Tyr residues, which account for 79.3, 16.9 and 3.8% respectively of the phosphoproteome, at least in mammals. In contrast, protein phosphatases (PPs) are the primary effectors of dephosphorylation and can be grouped into three main classes based on sequence, structure and catalytic function. The largest class of PPs is the phosphoprotein phosphatase (PPP) family comprising PP1, PP2A, PP2B, PP4, PP5, PP6 and PP7, and the protein phosphatase Mg- or Mn-dependent (PPM) family, composed primarily of PP2C. The protein Tyr phosphatase (PTP) super-family forms the second group, and the aspartate-based protein phosphatases the third. The protein pseudophosphatases form part of the larger phosphatase family, and in most cases are thought to be catalytically inert, instead functioning as phosphate-binding proteins, integrators of signalling or subcellular traps. Examples of membrane-spanning protein phosphatases containing both active (phosphatase) and inactive (pseudophosphatase) domains linked in tandem are known, conceptually similar to the kinase and pseudokinase domain polypeptide structure of the JAK pseudokinases. A complete comparative analysis of human phosphatases and pseudophosphatases has been completed by Manning and colleagues, forming a companion piece to the ground-breaking analysis of the human kinome, which encodes the complete set of ~536 human protein kinases. | 1 | Gene expression + Signal Transduction |
The Bengal Iron Works was founded at Kulti, Bengal, in 1870 which began its production in 1874 followed by The Tata Iron and Steel Company (TISCO) was established by Dorabji Tata in 1907, as part of his father's conglomerate. By 1939 it operated the largest steel plant in the British Empire. The company launched a major modernization and expansion program in 1951.
Prime Minister Jawaharlal Nehru, a believer in socialism, decided that the technological revolution in India needed maximization of steel production. He, therefore, formed a government owned company, Hindustan Steel Limited (HSL) and set up three steel plants in the 1950s.
The Indian steel industry began expanding into Europe in the 21st century. In January 2007 Indias Tata Steel made a successful $11.3 billion offer to buy European steel maker Corus Group. In 2006 Mittal Steel (based in London but with Indian management) merged with Arcelor after a takeover bid for $34.3 billion to become the worlds biggest steel maker, ArcelorMittal (based in Luxembourg City), with 10% of the world's output. | 0 | Metallurgy |
The VAR process is used on many different materials. Certain applications almost always use a material that has been VAR treated. A list of materials that may be VAR treated include:
*Stainless Steel
*Alloy Steel
**4340 & 4330+V
**300M
**AF1410
**Aermet 100
**M50
**BG42
**Nitralloy
**16NCD13
**35NCD16
**HY-100
**HY-180
**HY-TUF
**D6AC
**Maraging steels
**UT-18
**HP 9-4-30
*Titanium
**Ti-6Al-4V
**Ti-10V-2Al-3Fe
**Ti-5Al-5V-5Mo-3Cr
*Invar
*Nitinol
*Nickel superalloys
**Inconel alloys
**Hastelloy alloys
**Rene alloys
**RR1000
*Zirconium
*Niobium
*Platinum
*Tantalum
*Rhodium
Note that pure titanium and most titanium alloys are double or triple VAR processed. Nickel-based super alloys for aerospace applications are usually VAR processed. Zirconium and niobium alloys used in the nuclear industry are routinely VAR processed. Pure platinum, tantalum, and rhodium may be VAR processed. | 0 | Metallurgy |
Thermopiles are used for measuring the intensity of incident radiation, typically visible or infrared light, which heats the hot junctions, while the cold junctions are on a heat sink. It is possible to measure radiative intensities of only a few μW/cm with commercially available thermopile sensors. For example, some laser power meters are based on such sensors; these are specifically known as thermopile laser sensor.
The principle of operation of a thermopile sensor is distinct from that of a bolometer, as the latter relies on a change in resistance. | 0 | Metallurgy |
Overload, shocks and vibrations (bridges, roads submitted to intense truck traffic...) can induce mechanical stress and deformations in concrete structures and be responsible for the mechanical degradation of concrete. Beside the long-term drying shrinkage of concrete, pre-stressed and post-tensioned civil engineering structures (bridges, primary containment domes of nuclear power plants can also undergo slow concrete creep and deformation. | 0 | Metallurgy |
False brinelling is a bearing damage caused by fretting, with or without corrosion, that causes imprints that look similar to brinelling, but are caused by a different mechanism. False brinelling may occur in bearings which act under small oscillations or vibrations.
The basic cause of false brinelling is that the design of the bearing does not have a method for redistribution of lubricant without large rotational movement of all bearing surfaces in the raceway. Lubricant is pushed out of a loaded region during small oscillatory movements and vibration where the bearings surfaces repeatedly do not move very far. Without lubricant, wear is increased when the small oscillatory movements occur again. It is possible for the resulting wear debris to oxidize and form an abrasive compound which further accelerates wear. | 0 | Metallurgy |
Knowles was awarded a Fellowship of the Institute of Materials, Minerals and Mining (FIMMM) in 2004 in recognition of his contributions to the field of materials science. In 2015, he was also made Fellow of the Royal Academy of Engineering (FREng). He holds two European patents and has authored over 100 academic papers - five of which have been cited over 100 times - and he has also given a number of invited lectures and conference keynotes | 0 | Metallurgy |
Nowadays, several Calphad softwares are available - in a framework of computational thermodynamics - to simulate solidification in systems with more than two components; these have recently been defined as Calphad Tools for the Metallurgy of Solidification. In recent years, Calphad-based methodologies have reached maturity in several important fields of metallurgy, and especially in solidification-related processes such as semi-solid casting, 3d printing, and welding, to name a few. While there are important studies devoted to the progress of Calphad methodology, there is still space for a systematization of the field, which proceeds from the ability of most Calphad-based software to simulate solidification curves and includes both fundamental and applied studies on solidification, to be substantially appreciated by a wider community than today. The three applied fields mentioned above could be widened by specific successful examples of simple modeling related to the topic of this issue, with the aim of widening the application of simple and effective tools related to Calphad and Metallurgy. See also "Calphad Tools for the Metallurgy of Solidification" in an ongoing issue of an Open Journal. https://www.mdpi.com/journal/metals/special_issues/Calphad_Solidification
Given a specific chemical composition, using a software for computational thermodynamics - which might be open or commercial - the calculation of the Scheil curve is possible if a thermodynamic database is available. A good point in favour of some specific commercial softwares is that the install is easy indeed and you can use it on a windows based system - for instance with students or for self training.
One should get some open, chiefly binary, databases (extension *.tdb), one could find - after registering - at Computational Phase Diagram Database (CPDDB) of the National Institute for Materials Science of Japan, NIMS https://cpddb.nims.go.jp/index_en.html. They are available - for free - and the collection is rather complete; in fact currently 507 binary systems are available in the thermodynamic data base (tdb) format.
Some wider and more specific alloy systems partly open - with tdb compatible format - are available with minor corrections for Pandat use at Matcalc https://www.matcalc.at/index.php/databases/open-databases. | 0 | Metallurgy |
ppGpp and pppGpp were first identified by Michael Cashel in 1969. These nucleotides were found to accumulate rapidly in Escherichia coli cells starved for amino acids and inhibit synthesis of ribosomal and transfer RNAs. It is now known that (p)ppGpp is also produced in response to other stressors including carbon and phosphate starvation. Historically, literature surrounding (p)ppGpp have given conflicting findings and information on its role in bacterial stress responses. | 1 | Gene expression + Signal Transduction |
In the United States in 1964, the Federal Trade Commission proscribed the use of the word leakproof or the phrase "guaranteed leakproof" in advertisements for or on the packages of dry-cell batteries, as they had determined that no manufacturer had yet developed a battery that was truly impervious to leaking. The FTC repealed this ban in 1997. | 0 | Metallurgy |
Genes can be silenced by multiple methylation of CpG sites in the CpG islands of their promoters.[11] Even if silencing of a gene is initiated by another mechanism, this often is followed by methylation of CpG sites in the promoter CpG island to stabilize the silencing of the gene.[11] On the other hand, hypomethylation of CpG islands in promoters can result in gene over-expression.
Causes of DNA hypermethylation are:
- Mediation of mutated K-ras induced jun protein (Serra RW. et al. 2014; Leppä S. et al. 1998)
- the inhibitory effect of lnRNA on miRNAs causing demethylation - their "absorption" in the sponge effect or direct repression of demethylation factors TET1 and TGD (Thakur S. Brenner C. 2017; Ratti M. et al. 2020; Morita S. et al. 2013)
- Activation of DNA methylases (Kwon JJ. et al. 2018)
- Changes in isocitrate dehydrogenase (Christensen BC. et al. 2011)
- Effects of viruses (Wang X. et al. )
Causes of DNA hypomethylation:
- The effect of mutated K-ras on long non-coding RNAs, which, when acting, a) directly inhibits the activity or translation of genes encoding DNA methylases (Sarkar D. et al. 2015) b) rather, "sponges" absorb miRNAs (Ratti M. et al. 2020 ), which should ensure the functioning of DNA methylases
- The effect of mutated K-Ras through the activation of the myc-ODC axis, the mTor complex, with the consequence of the synthesis of polyamines, the activation of which, figuratively speaking, "pumps out" single-carbon fragments from the Methionine cycle and creates a lack of substrate for DNA methylation, leading to a hypomethylated state of DNA (Урба К. 1991 )
- Changes in the activity of methylases DNMT1/3A/3B, their relocalization (Hoffmann MJ, Schulz WA. 2005; Nishiyama A. et al. 2021)
- Changes in TET performance (Nishiyama A. et al. 2021)
- Changes in the synthesis of SAM from methionine due to changes in the enzymes MAT (Frau M. et al. 2013)
- Changes in serine catabolism (Snell K., Weber G. 1986), causing more intensive removal of homocysteine from the methionine cycle, when serine binds to homocysteine (Урба К. 1991)
- Other, unspecified reasons for supplying the Met cycle with single-carbon fragments, causing e.g. "methyl trap" phenomenon (Shane B. Stokstad EL. 1985; Zheng Y, Cantley LC. 2019), sietin and with disorders of vitamin B12 metabolism, disruption of the spare methionine resynthesis pathway (Ouyang Y. et al. 2020; Ozyerli-Goknar E, Bagci-Onder T. 2021; Barekatain, Yasaman et al. 2021) or other monocarbon fragment metabolism disorders (Urba K. 1991). | 1 | Gene expression + Signal Transduction |
Tetrathionate's structure can be visualized by following three edges of a rectangular cuboid, as in the diagram below. The structure shown is the configuration of in BaSO·2HO and NaSO·2HO. Dihedral S–S–S–S angles approaching 90° are common in polysulfides. | 0 | Metallurgy |
The furnace comprises three distinct zones:
* Firstly, the preheating zone heats the ore to 800 °C using the hot fumes within the furnace. Ore reduction occurs only if temperatures exceed 900-1,000 °C, while the coal releases its most volatile constituents.
* Secondly, the reduction zone is situated in the middle of the furnace, where coal and iron oxides combine to produce carbon monoxide. The carbon monoxide is released from the charge, generating a gaseous layer that shields the charge against the oxidizing air circulating above. As a consequence, this excessive gas is combusted, raising the temperature of the furnace walls, which then transfer the heat back to the charge due to rotary motion. The temperature eventually increases to 800 – 1,200 °C. Subsequently, the iron oxides are gradually altered into ferronickel or metallic iron. The metal produced is in the form of metallic sponge particles that are finely dispersed in the powdery gangue.
* Reduction is complete by the end of the furnace, and there is a minimal amount of CO produced. This is due to the fact that the charge is no longer protected from oxidation by the air blown in at the base of the furnace. As a result, a violent but shallow reoxidation of the iron occurs. Some of the oxidized iron is returned to the core of the charge by rotation where it is further reduced with residual coal. The remaining material mixes with waste to create a thick slag that cannot blend with the produced metal. This extremely hot reaction melts the non-oxidized iron and nickel, which clump together forming nodules named Luppen.
Control of temperature is critical in regards to the ores physicochemical characteristics. Overly high temperatures or unsuitable granulometry lead to the creation of rings of sintered material that accumulate on the walls of the furnace. Typically, a ring of iron-poor slag, known as slag, is formed at two-thirds of the distance along the furnace. Similarly, a metal ring usually forms around ten meters from the outlet. These rings disturb the flow of materials and gas, diminishing the furnaces useful capacity, sometimes completely obstructing it. The process's revival is hindered by the formation of a ring, particularly in China. In the early 21st century, industrialists abandoned its adoption after recognizing how critical and challenging managing this parameter was.
While slag melting consumes energy, it enables us to govern the charges behavior in the furnace. Additionally, we need a minimum of 800 to 1,000 kg of slag per ton of iron to prevent Luppen from growing too big. Slag limits coal segregation as coal is much less dense than ore and would float to the surface of the mixture. It transforms into a paste that guards the metal against oxidation when heated and simplifies both Luppen' processing and furnace cleaning during maintenance shutdowns through vitrification when it gets cold. | 0 | Metallurgy |
Deformation mechanisms are commonly characterized as brittle, ductile, and brittle-ductile. The driving mechanism responsible is an interplay between internal (e.g. composition, grain size and lattice-preferred orientation) and external (e.g. temperature and fluid pressure) factors. These mechanisms produce a range of micro-structures studied in rocks to constrain the conditions, rheology, dynamics, and motions of tectonic events. More than one mechanism may be active under a given set of conditions and some mechanisms can develop independently. Detailed microstructure analysis can be used to define the conditions and timing under which individual deformation mechanisms dominate for some materials. Common deformation mechanisms processes include:
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(recovery) | 0 | Metallurgy |
Dye completed a Bachelor of Arts degree in Natural Sciences in 1997 at the University of Cambridge, followed by a PhD on the Mechanical effects of welding superalloys in 2000, supervised by Roger Reed. | 0 | Metallurgy |
Although the FGF family of paracrine factors has a broad range of functions, major findings support the idea that they primarily stimulate proliferation and differentiation. To fulfill many diverse functions, FGFs can be alternatively spliced or even have different initiation codons to create hundreds of different FGF isoforms.
One of the most important functions of the FGF receptors (FGFR) is in limb development. This signaling involves nine different alternatively spliced isoforms of the receptor. Fgf8 and Fgf10 are two of the critical players in limb development. In the forelimb initiation and limb growth in mice, axial (lengthwise) cues from the intermediate mesoderm produces Tbx5, which subsequently signals to the same mesoderm to produce Fgf10. Fgf10 then signals to the ectoderm to begin production of Fgf8, which also stimulates the production of Fgf10. Deletion of Fgf10 results in limbless mice.
Additionally, paracrine signaling of Fgf is essential in the developing eye of chicks. The fgf8 mRNA becomes localized in what differentiates into the neural retina of the optic cup. These cells are in contact with the outer ectoderm cells, which will eventually become the lens.
Phenotype and survival of mice after knockout of some FGFR genes: | 1 | Gene expression + Signal Transduction |
Dimetcote is popular in the marine industry. The inorganic zinc coating of Dimetcote can protect metal components from moisture. | 0 | Metallurgy |
The vesicular monoamine transporter (VMAT) is a transport protein integrated into the membranes of synaptic vesicles of presynaptic neurons. It transports monoamine neurotransmitters – such as dopamine, serotonin, norepinephrine, epinephrine, and histamine – into the vesicles, which release the neurotransmitters into synapses, as chemical messages to postsynaptic neurons. VMATs utilize a proton gradient generated by V-ATPases in vesicle membranes to power monoamine import.
Pharmaceutical drugs that target VMATs have possible applications for many conditions, leading to a plethora of biological research, including hypertension, drug addiction, psychiatric disorders, Parkinson's disease, and other neurological disorders. Many drugs that target VMATs act as inhibitors and alter the kinetics of the protein. Much research regarding the effects of altered VMATs on biological systems is still ongoing. | 1 | Gene expression + Signal Transduction |
After the first bond is synthesized, the RNA polymerase must clear the promoter. During this time, there is a tendency to release the RNA transcript and produce truncated transcripts. This is called abortive initiation and is common for both eukaryotes and prokaryotes. Abortive initiation continues to occur until the σ factor rearranges, resulting in the transcription elongation complex (which gives a 35 bp-moving footprint). The σ factor is released before 80 nucleotides of mRNA are synthesized. Once the transcript reaches approximately 23 nucleotides, it no longer slips and elongation can occur. | 1 | Gene expression + Signal Transduction |
Adenosine-to-inosine (A-to-I) modifications contribute to nearly 90% of all editing events in RNA. The deamination of adenosine is catalyzed by the double-stranded RNA-specific adenosine deaminase (ADAR), which typically acts on pre-mRNAs. The deamination of adenosine to inosine disrupts and destabilizes the dsRNA base pairing, therefore rendering that particular dsRNA less able to produce siRNA, which interferes with the RNAi pathway.
The wobble base pairing causes deaminated RNA to have a unique but different structure, which may be related to the inhibition of the initiation step of RNA translation. Studies have shown that I-RNA (RNA with many repeats of the I-U base pair) recruits methylases that are involved in the formation of heterochromatin and that this chemical modification heavily interferes with miRNA target sites. There is active research into the importance of A-to-I modifications and their purpose in the novel concept of epitranscriptomics, in which modifications are made to RNA that alter their function. A long established consequence of A-to-I in mRNA is the interpretation of I as a G, therefore leading to functional A-to-G substitution, e.g. in the interpretation of the genetic code by ribosomes. Newer studies, however, have weakened this correlation by showing that inosines can also be decoded by the ribosome (although in a lesser extent) as adenosines or uracils. Furthermore, it was shown that I's lead to the stalling of ribosomes on the I-rich mRNA.
The development of high-throughput sequencing in recent years has allowed for the development of extensive databases for different modifications and edits of RNA. RADAR (Rigorously Annotated Database of A-to-I RNA editing) was developed in 2013 to catalog the vast variety of A-to-I sites and tissue-specific levels present in humans, mice, and flies. The addition of novel sites and overall edits to the database are ongoing. The level of editing for specific editing sites, e.g. in the filamin A transcript, is tissue-specific. The efficiency of mRNA-splicing is a major factor controlling the level of A-to-I RNA editing. Interestingly, ADAR1 and ADAR2 also affect alternative splicing via both A-to-I editing ability and dsRNA binding ability. | 1 | Gene expression + Signal Transduction |
Stainless steel is a material which is difficult to solder because of its stable, self-healing surface oxide layer and its low thermal conductivity. A solution of zinc chloride in hydrochloric acid is a common flux for stainless steels; it has however to be thoroughly removed afterwards as it would cause pitting corrosion. Another highly effective flux is phosphoric acid; its tendency to polymerize at higher temperatures however limits its applications. | 0 | Metallurgy |
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