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The core RNA polymerase (consisting of 2 alpha (α), 1 beta (β), 1 beta-prime (β'), and 1 omega (ω) subunits) binds a sigma factor to form a complex called the RNA polymerase holoenzyme. It was previously believed that the RNA polymerase holoenzyme initiates transcription, while the core RNA polymerase alone synthesizes RNA. Thus, the accepted view was that sigma factor must dissociate upon transition from transcription initiation to transcription elongation (this transition is called "promoter escape"). This view was based on analysis of purified complexes of RNA polymerase stalled at initiation and at elongation. Finally, structural models of RNA polymerase complexes predicted that, as the growing RNA product becomes longer than ~15 nucleotides, sigma must be "pushed out" of the holoenzyme, since there is a steric clash between RNA and a sigma domain. However, σ can remain attached in complex with the core RNA polymerase in early elongation and sometimes throughout elongation. Indeed, the phenomenon of promoter-proximal pausing indicates that sigma plays roles during early elongation. All studies are consistent with the assumption that promoter escape reduces the lifetime of the sigma-core interaction from very long at initiation (too long to be measured in a typical biochemical experiment) to a shorter, measurable lifetime upon transition to elongation. | 1 | Gene expression + Signal Transduction |
In molecular biology and genetics, transcription coregulators are proteins that interact with transcription factors to either activate or repress the transcription of specific genes. Transcription coregulators that activate gene transcription are referred to as coactivators while those that repress are known as corepressors. The mechanism of action of transcription coregulators is to modify chromatin structure and thereby make the associated DNA more or less accessible to transcription. In humans several dozen to several hundred coregulators are known, depending on the level of confidence with which the characterisation of a protein as a coregulator can be made. One class of transcription coregulators modifies chromatin structure through covalent modification of histones. A second ATP dependent class modifies the conformation of chromatin. | 1 | Gene expression + Signal Transduction |
Paracrine signaling through fibroblast growth factors and its respective receptors utilizes the receptor tyrosine pathway. This signaling pathway has been highly studied, using Drosophila eyes and human cancers.
Binding of FGF to FGFR phosphorylates the idle kinase and activates the RTK pathway. This pathway begins at the cell membrane surface, where a ligand binds to its specific receptor. Ligands that bind to RTKs include fibroblast growth factors, epidermal growth factors, platelet-derived growth factors, and stem cell factor. This dimerizes the transmembrane receptor to another RTK receptor, which causes the autophosphorylation and subsequent conformational change of the homodimerized receptor. This conformational change activates the dormant kinase of each RTK on the tyrosine residue. Due to the fact that the receptor spans across the membrane from the extracellular environment, through the lipid bilayer, and into the cytoplasm, the binding of the receptor to the ligand also causes the trans phosphorylation of the cytoplasmic domain of the receptor.
An adaptor protein (such as SOS) recognizes the phosphorylated tyrosine on the receptor. This protein functions as a bridge which connects the RTK to an intermediate protein (such as GNRP), starting the intracellular signaling cascade. In turn, the intermediate protein stimulates GDP-bound Ras to the activated GTP-bound Ras. GAP eventually returns Ras to its inactive state. Activation of Ras has the potential to initiate three signaling pathways downstream of Ras: Ras→Raf→MAP kinase pathway, PI3 kinase pathway, and Ral pathway. Each pathway leads to the activation of transcription factors which enter the nucleus to alter gene expression. | 1 | Gene expression + Signal Transduction |
In molecular biology, a twintron is an intron-within-intron excised by sequential splicing reactions. A twintron is presumably formed by the insertion of a mobile intron into an existing intron. | 1 | Gene expression + Signal Transduction |
*2001 – Chester F. Carlson Award, American Society for Engineering Education
*2006 – Distinguished Alumni Award, University of Minnesota
*2006 – Distinguished Service Award, American Society for Engineering Education
*2014 – Honorary Doctorate, University of Technology Malaysia
*2015 – Lifetime Achievement Award, American Society for Engineering Education
*2023 – Hall of Fame, American Society for Engineering Education | 0 | Metallurgy |
Corepressors present many potential avenues for drugs to target a vast range of diseases.
BCL6 upregulation is observed in cancers such as diffuse large B-cell lymphomas (DLBCLs), colorectal cancer, and lung cancer. BCL-6 corepressor, SMRT, NCoR, and other corepressors are able to interact with and transcriptionally repress BCL6. Small-molecule compounds, such as synthetic peptides that target BCL6 and corepressor interactions, as well as other protein-protein interaction inhibitors, have been shown to effectively kill cancer cells.
Activated liver X receptor (LXR) forms a complex with corepressors to suppress the inflammatory response in rheumatoid arthritis, making LXR agonists like GW3965 a potential therapeutic strategy. Ursodeoxycholic acid (UDCA), by upregulating the corepressor small heterodimer partner interacting leucine zipper protein (SMILE), inhibits the expression of IL-17, an inflammatory cytokine, and suppresses Th17 cells, both implicated in rheumatoid arthritis. This effect is dose-dependent in humans, and UCDA is thought to be another prospective agent of rheumatoid arthritis therapy. | 1 | Gene expression + Signal Transduction |
The oldest anodizing process uses chromic acid. It is widely known as the Bengough-Stuart process but, due to the safety regulations regarding air quality control, is not preferred by vendors when the additive material associated with type II doesn't break tolerances. In North America, it is known as Type I because it is so designated by the MIL-A-8625 standard, but it is also covered by AMS 2470 and MIL-A-8625 Type IB. In the UK it is normally specified as Def Stan 03/24 and used in areas that are prone to come into contact with propellants etc. There are also Boeing and Airbus standards. Chromic acid produces thinner, 0.5 μm to 18 μm (0.00002" to 0.0007") more opaque films that are softer, ductile, and to a degree self-healing. They are harder to dye and may be applied as a pretreatment before painting. The method of film formation is different from using sulfuric acid in that the voltage is ramped up through the process cycle. | 0 | Metallurgy |
A bimetallic strip is a strip that consists of two strips of different metals which expand at different rates as they are heated. They are used to convert a temperature change into mechanical displacement. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled.
The invention of the bimetallic strip is generally credited to John Harrison, an eighteenth-century clockmaker who made it for his third marine chronometer (H3) of 1759 to compensate for temperature-induced changes in the balance spring. Harrison's invention is recognized in the memorial to him in Westminster Abbey, England. | 0 | Metallurgy |
The TET proteins also have activities that are independent of DNA demethylation. These include, for instance, TET2 interaction with O-linked N-acetylglucosamine (O-GlcNAc) transferase to promote histone O-GlcN acylation to affect transcription of target genes. | 1 | Gene expression + Signal Transduction |
Tyrosine phosphorylation sites in growth factor receptors serve two major purposes—to control the state of activity of the kinase and to create binding sites for downstream signal transduction molecules, which in many cases also are substrates for the kinase. The second part of the tyrosine kinase domain in the PDGFβ receptor is phosphorylated at Tyr-857, and mutant receptors carrying phenylalanine at this position have reduced kinase activity. Tyr-857 has therefore been assigned a role in positive regulation of kinase activity. Sites of tyrosine phosphorylation involved in binding signal transduction molecules have been identified in the juxtamembrane domain, the kinase insert, and in the C-terminal tail in the PDGFβ receptor. The phosphorylated tyrosine residue and in general three adjacent C-terminal amino acid residues form specific binding sites for signal transduction molecules. Binding to these sites involves a common conserved stretches, denoted the Src homology (SH) 2 domain and/or Phosphotyrosine Binding Domains (PTB). The specificity of these interactions appears to be very high, since mutant receptors carrying phenylalanine residues in one or several of the different phosphorylation sites generally lack the capacity to bind the targeted signal transduction molecule. The signal transduction molecules are either equipped with different enzymatic activities, or they are adaptor molecules, which in some but not all cases are found in complexes with subunits that carry a catalytic activity. Upon interaction with the activated receptor, the catalytic activities become up-regulated, through tyrosine phosphorylation or other mechanisms, generating a signal that may be unique for each type of signal transduction molecule.
Examination of the different signaling cascades induced by RTKs established Ras/mitogen-activated protein kinase (MAPK), PI-3 kinase, and phospholipase-γ (PLCγ) pathways as key downstream mediators of PDGFR signaling. In addition, reactive oxygen species (ROS)-dependent STAT3 activation has been established to be a key downstream mediator of PDGFR signaling in vascular smooth muscle cells. | 1 | Gene expression + Signal Transduction |
In steel industry
There are mainly two types of MTC in steel industry, as for steel plates or steel pipes, there must be specific inspection scope or lists:
# MTC EN 10204 3.1 :MTC 3.1 is issued by the manufacturer in which they declare that the products supplied are in compliance with the requirements of the order and in which they supply test results. This is the most common MTC in steel industry, when there is no extra requirement of customer for TPI inspection and witness of production and inspection of tests.
# MTC EN 10204 3.2 :MTC 3.2 refers to the report prepared by both the manufacturers authorized inspection representative, independent of the manufacturing department and either the purchasers authorized inspection representative or the inspector designated by the official regulations and in which they declare that the products supplied are in compliance with the requirements of the order and in which test results are supplied. | 0 | Metallurgy |
Electric resistance corrosion probes are used in different types for different applications of online corrosion monitoring. The corrosion rate of these probes can be measured online or transferred to the control system by using corrosion handheld or fixed data loggers or by corrosion transmitters.
The general type of ER probes element are as below:
* flush type
* cylindrical
* spiral loop
* wire loop
* tube loop
ER probes can be provided by adapter in order to connect to data logger or transmitters. The length of probes is dependent on the mounting and monitoring position. | 0 | Metallurgy |
Sterlite Industries ("Sterlite"), a subsidiary of Vedanta Resources, built a copper smelter in Tuticorin using an ISASMELT furnace and Peirce-Smith converters. The smelter was commissioned in 1996 and was designed to produce 60,000 t/y of copper (450,000 t/y of copper concentrate), but by increasing the oxygen content of the lance air and making modifications to other equipment, the ISASMELT furnace feed rate was increased to the point where the smelter was producing 180,000 t/y of copper.
Sterlite commissioned a new ISASMELT furnace in May 2005 that was designed to treat 1.3 million t/y of copper concentrate, and the smelters production capacity was expanded to 300,000 t/y of copper. The new plant reached its design capacity, measured over a three-month period, six months after it started treating its first feed. Vedantas website states that the new ISASMELT furnace was successfully ramped up "in a record period of 45 days".
Since then Sterlite decided to further expand its copper production by installing a third ISASMELT smelter and new refinery using IsaKidd technology. The new smelter has a design capacity of 1.36 million t/y of copper concentrate (containing 400,000 t/y of copper), processed through a single ISASMELT furnace. | 0 | Metallurgy |
Hot blast was the single most important advance in fuel efficiency of the blast furnace and was one of the most important technologies developed during the Industrial Revolution. Hot blast was patented by James Beaumont Neilson at Wilsontown Ironworks in Scotland in 1828. Within a few years of the introduction, hot blast was developed to the point where fuel consumption was cut by one-third using coke or two-thirds using coal, while furnace capacity was also significantly increased. Within a few decades, the practice was to have a "stove" as large as the furnace next to it into which the waste gas (containing CO) from the furnace was directed and burnt. The resultant heat was used to preheat the air blown into the furnace.
Hot blast enabled the use of raw anthracite coal, which was difficult to light, in the blast furnace. Anthracite was first tried successfully by George Crane at Ynyscedwyn Ironworks in south Wales in 1837. It was taken up in America by the Lehigh Crane Iron Company at Catasauqua, Pennsylvania, in 1839. Anthracite use declined when very high capacity blast furnaces requiring coke were built in the 1870s. | 0 | Metallurgy |
In general, if an excitatory synapse is strong enough, an action potential in the presynaptic neuron will trigger an action potential in the postsynaptic cell. In many cases the excitatory postsynaptic potential (EPSP) will not reach the threshold for eliciting an action potential. When action potentials from multiple presynaptic neurons fire simultaneously, or if a single presynaptic neuron fires at a high enough frequency, the EPSPs can overlap and summate. If enough EPSPs overlap, the summated EPSP can reach the threshold for initiating an action potential. This process is known as summation, and can serve as a high pass filter for neurons.
On the other hand, a presynaptic neuron releasing an inhibitory neurotransmitter, such as GABA, can cause an inhibitory postsynaptic potential (IPSP) in the postsynaptic neuron, bringing the membrane potential farther away from the threshold, decreasing its excitability and making it more difficult for the neuron to initiate an action potential. If an IPSP overlaps with an EPSP, the IPSP can in many cases prevent the neuron from firing an action potential. In this way, the output of a neuron may depend on the input of many different neurons, each of which may have a different degree of influence, depending on the strength and type of synapse with that neuron. John Carew Eccles performed some of the important early experiments on synaptic integration, for which he received the Nobel Prize for Physiology or Medicine in 1963. | 1 | Gene expression + Signal Transduction |
As yttrium is chemically similar to lanthanides, it occurs in the same ores (rare-earth minerals) and is extracted by the same refinement processes. A slight distinction is recognized between the light (LREE) and the heavy rare-earth elements (HREE), but the distinction is not perfect. Yttrium is concentrated in the HREE group because of its ion size, though it has a lower atomic mass.
Rare-earth elements (REEs) come mainly from four sources:
* Carbonate and fluoride containing ores such as the LREE bastnäsite ((Ce, La, etc.)(CO)F) contain an average of 0.1% of yttrium compared to the 99.9% for the 16 other REEs. The main source for bastnäsite from the 1960s to the 1990s was the Mountain Pass rare earth mine in California, making the United States the largest producer of REEs during that period. The name "bastnäsite" is actually a group name, and the Levinson suffix is used in the correct mineral names, e.g., bästnasite-(Y) has Y as a prevailing element.
* Monazite ((Ce, La, etc.)PO), which is mostly phosphate, is a placer deposit of sand created by the transportation and gravitational separation of eroded granite. Monazite as an LREE ore contains 2% (or 3%) yttrium. The largest deposits were found in India and Brazil in the early 20th century, making those two countries the largest producers of yttrium in the first half of that century. Of the monazite group, the Ce-dominant member, monazite-(Ce), is the most common one.
* Xenotime, a REE phosphate, is the main HREE ore containing as much as 60% yttrium as yttrium phosphate (YPO). This applies to xenotime-(Y). The largest mine is the Bayan Obo deposit in China, making China the largest exporter for HREE since the closure of the Mountain Pass mine in the 1990s.
* Ion absorption clays or Lognan clays are the weathering products of granite and contain only 1% of REEs. The final ore concentrate can contain as much as 8% yttrium. Ion absorption clays are mostly in southern China. Yttrium is also found in samarskite and fergusonite (which also stand for group names).
One method for obtaining pure yttrium from the mixed oxide ores is to dissolve the oxide in sulfuric acid and fractionate it by ion exchange chromatography. With the addition of oxalic acid, the yttrium oxalate precipitates. The oxalate is converted into the oxide by heating under oxygen. By reacting the resulting yttrium oxide with hydrogen fluoride, yttrium fluoride is obtained. When quaternary ammonium salts are used as extractants, most yttrium will remain in the aqueous phase. When the counter-ion is nitrate, the light lanthanides are removed, and when the counter-ion is thiocyanate, the heavy lanthanides are removed. In this way, yttrium salts of 99.999% purity are obtained. In the usual situation, where yttrium is in a mixture that is two-thirds heavy-lanthanide, yttrium should be removed as soon as possible to facilitate the separation of the remaining elements.
Annual world production of yttrium oxide had reached by 2001; by 2014 it had increased to . Global reserves of yttrium oxide were estimated in 2014 to be more than . The leading countries for these reserves included Australia, Brazil, China, India, and the United States. Only a few tonnes of yttrium metal are produced each year by reducing yttrium fluoride to a metal sponge with calcium magnesium alloy. The temperature of an arc furnace of greater than 1,600 °C is sufficient to melt the yttrium. | 0 | Metallurgy |
Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable for use as solder should have a lower melting point than the pieces to be joined. The solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics.
Soft solder typically has a melting point range of , and is commonly used in electronics, plumbing, and sheet metal work. Alloys that melt between are the most commonly used. Soldering performed using alloys with a melting point above is called "hard soldering", "silver soldering", or brazing.
In specific proportions, some alloys are eutectic — that is, the alloys melting point is the lowest possible for a mixture of those components, and coincides with the freezing point. Non-eutectic alloys can have markedly different solidus and liquidus' temperatures, as they have distinct liquid and solid transitions. Non-eutectic mixtures often exist as a paste of solid particles in a melted matrix of the lower-melting phase as they approach high enough temperatures. In electrical work, if the joint is disturbed while in this "pasty" state before it fully solidifies, a poor electrical connection may result; use of eutectic solder reduces this problem. The pasty state of a non-eutectic solder can be exploited in plumbing, as it allows molding of the solder during cooling, e.g. for ensuring watertight joint of pipes, resulting in a so-called "wiped joint".
For electrical and electronics work, solder wire is available in a range of thicknesses for hand-soldering (manual soldering is performed using a soldering iron or soldering gun), and with cores containing flux. It is also available as a room temperature paste, as a preformed foil shaped to match the workpiece which may be more suited for mechanized mass-production, or in small "tabs" that can be wrapped around the joint and melted with a flame where an iron isn't usable or available, as for instance in field repairs. Alloys of lead and tin were commonly used in the past and are still available; they are particularly convenient for hand-soldering. Lead-free solders have been increasing in use due to regulatory requirements plus the health and environmental benefits of avoiding lead-based electronic components. They are almost exclusively used today in consumer electronics.
Plumbers often use bars of solder, much thicker than the wire used for electrical applications, and apply flux separately; many plumbing-suitable soldering fluxes are too corrosive (or conductive) to be used in electrical or electronic work. Jewelers often use solder in thin sheets, which they cut into snippets. | 0 | Metallurgy |
In most cases, unidirectional transcription of enhancer regions generates long (>4kb) and polyadenylated eRNAs. Enhancers that generate polyA+ eRNAs have a lower H3K4me1/me3 ratio in their chromatin signature than 2D-eRNAs. PolyA+ eRNAs are distinct from long multiexonic poly transcripts (meRNAs) that are generated by transcription initiation at intragenic enhancers. These long non-coding RNAs, which accurately reflect the host gene's structure except for the alternative first exon, display poor coding potential. As a result, polyA+ 1D-eRNAs may represent a mixed group of true enhancer-templated RNAs and multiexonic RNAs. | 1 | Gene expression + Signal Transduction |
Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame).
Thermal spraying can provide thick coatings (approx. thickness range is 20 microns to several mm, depending on the process and feedstock), over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapor deposition. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. They are fed in powder or wire form, heated to a molten or semimolten state and accelerated towards substrates in the form of micrometer-size particles. Combustion or electrical arc discharge is usually used as the source of energy for thermal spraying. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances.
Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro-hardness, bond strength and surface roughness. Generally, the coating quality increases with increasing particle velocities. | 0 | Metallurgy |
The Shapiro–Senapathy algorithm has been used to determine the various aberrant splicing mechanisms in genes due to deleterious mutations in the splice sites, which cause numerous diseases. Deleterious splice site mutations impair the normal splicing of the gene transcripts, and thereby make the encoded protein defective. A mutant splice site can become “weak” compared to the original site, due to which the mutated splice junction becomes unrecognizable by the spliceosomal machinery. This can lead to the skipping of the exon in the splicing reaction, resulting in the loss of that exon in the spliced mRNA (exon-skipping). On the other hand, a partial or complete intron could be included in the mRNA due to a splice site mutation that makes it unrecognizable (intron inclusion). A partial exon-skipping or intron inclusion can lead to premature termination of the protein from the mRNA, which will become defective leading to diseases. The S&S has thus paved the way to determine the mechanisms by which a deleterious mutation could lead to a defective protein, resulting in different diseases depending on which gene is affected. | 1 | Gene expression + Signal Transduction |
Several Bioconductor packages, for the R software, provide the facility for creating MA plots. These include affy (ma.plot, mva.pairs), limma (plotMA), marray (maPlot), and edgeR(maPlot)
Similar "RA" plots can be generated using the raPlot function in the caroline [https://cran.r-project.org/ CRAN] R package.
An interactive MA plot to filter genes by M, A and p-values, search by names or with a lasso, and save selected genes, is available as an R-Shiny code [https://github.com/alisheharyar/Enhanced_MA_Plot Enhanced-MA-Plot]. | 1 | Gene expression + Signal Transduction |
The major role of chemokines is to act as a chemoattractant to guide the migration of cells. Cells that are attracted by chemokines follow a signal of increasing chemokine concentration towards the source of the chemokine. Some chemokines control cells of the immune system during processes of immune surveillance, such as directing lymphocytes to the lymph nodes so they can screen for invasion of pathogens by interacting with antigen-presenting cells residing in these tissues. These are known as homeostatic chemokines and are produced and secreted without any need to stimulate their source cells. Some chemokines have roles in development; they promote angiogenesis (the growth of new blood vessels), or guide cells to tissues that provide specific signals critical for cellular maturation. Other chemokines are inflammatory and are released from a wide variety of cells in response to bacterial infection, viruses and agents that cause physical damage such as silica or the urate crystals that occur in gout. Their release is often stimulated by pro-inflammatory cytokines such as interleukin 1. Inflammatory chemokines function mainly as chemoattractants for leukocytes, recruiting monocytes, neutrophils and other effector cells from the blood to sites of infection or tissue damage. Certain inflammatory chemokines activate cells to initiate an immune response or promote wound healing. They are released by many different cell types and serve to guide cells of both innate immune system and adaptive immune system. | 1 | Gene expression + Signal Transduction |
Increased intracellular levels of lactate can act as a signalling hormone, inducing changes in gene expression that will upregulate genes involved in lactate removal. These genes include MCT1, cytochrome c oxidase (COX), and other enzymes involved in the lactate oxidation complex. Additionally, lactate will increase levels of peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC1-α), suggesting that lactate stimulates mitochondrial biogenesis. | 1 | Gene expression + Signal Transduction |
Etching is the immersion of the part into the chemical bath, and the action of the chemical on the part to be milled. The time spent immersed in the chemical bath determines the depth of the resulting etch; this time is calculated via the formula:
where E is the rate of etching (usually abbreviated to etch rate), s is the depth of the cut required, and t is the total immersion time. Etch rate varies based on factors such as the concentration and composition of the etchant, the material to be etched, and temperature conditions. Due to its inconstant nature, etch rate is often determined experimentally immediately prior to the etching process. A small sample of the material to be cut, of the same material specification, heat-treatment condition, and approximately the same thickness is etched for a certain time; after this time, the depth of the etch is measured and used with the time to calculate the etch rate. Aluminium is commonly etched at rates around , and magnesium about | 0 | Metallurgy |
The expansion of the corrosion products (iron oxides) of carbon steel reinforcement structures may induce internal mechanical stress (tensile stress) that cause the formation of cracks and disrupt the concrete structure. If rebars have been improperly installed or have inadequate concrete cover at surfaces exposed to the elements, oxide jacking and spalling can occur during the structures lifetime: flat fragments of concrete are detached from the concrete mass as a result of the rebars corrosion.
Concrete, like most consolidated hard rocks, is a material very resistant to compression but which cannot withstand tension, especially internal tensions. Its tensile strength is about 10 times lower than its compressive strength. In itself carbonated concrete is a very solid material because its compressive strength increases due to its porosity decrease by the precipitation of calcium carbonate (calcite, ). In the absence of steel reinforcement bars and without the formation of expansive reaction products inducing tensile stress inside the concrete matrix, pure concrete is most often a long-lasting material. An illustration of the concrete intrinsic durability is the dome of the Pantheon building in Rome made with Roman concrete more than 2000 years ago.
When atmospheric carbon dioxide (), or carbonate ions (, dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, ) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite). Below a pH value of about 9.5 – 10, the solubility of iron oxides present at the surface of carbon steel increases and they start to dissolve. As a consequence, they no longer protect the underlying metallic iron against oxidation by atmospheric oxygen and the reinforcement bars are no longer passivated against corrosion. It is the considerable forces internally created by the expansion of the iron corrosion products (about 6 – 7 times less dense than metallic iron, so 6 – 7 times more voluminous) that cause the cracks in the concrete matrix and destroy reinforced concrete. In the absence of iron (and without some harmful chemical degradation reactions also producing expansive products) concrete would probably be one of the most durable materials. However, steel reinforcement bars are necessary to take over the tensile efforts to which concrete is submitted in most engineering structures and stainless steel would be too costly a metal to replace carbon steel. Zinc-galvanization or epoxy-coating can improve the corrosion resistance of rebar, but have also other disadvantages such as their lower surface adhesion to concrete (risk of slip), the possible formation of cathodic and anodic zones conducive to galvanic corrosion if the protective coating is locally punctured or damaged, and their higher costs. | 0 | Metallurgy |
Dye runs a Youtube channel, personal blog, and has courses on Coursera to teach metallurgy, mathematics and data analysis, continuum mechanics, and engineering Alloys. Dye also is a scientific witness to the Science and Technology Committee of the UK parliament. | 0 | Metallurgy |
The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer. Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (AlO), the rest being a mixture of silica, various iron oxides, and titanium dioxide. The aluminium oxide must be further purified before it can be refined into aluminium.
The Bayer process is also the main source of gallium as a byproduct despite low extraction yields. | 0 | Metallurgy |
The capping enzyme is part of the covalent nucleotidyl transferases superfamily, which also includes DNA ligases and RNA ligases. The enzymes of this superfamily share the following similarities:
* Conserved regions known as motifs I, II, III, IIIa, IV, V and VI, which are arranged in the same order and similar spacing
* A lysine containing motif KxDG (motif I)
* A covalent lysyl-NMP intermediate
The capping enzyme is composed of two domains, a nucleotidyl transferase (NTase) domain and a C-terminal oligonucleotide binding (OB) domain. The NTase domain, conserved in capping enzymes, DNA and RNA ligases, is made up 5 motifs, I, III, IIIa, IV and V. Motif I or KxDG is the active site where the covalent (lysyl)-N-GMP intermediate is formed. Both the NTase and OB domains undergo conformational changes that assist in the capping reaction.
Capping enzymes are found in the nucleus of eukaryotic cells. Depending on the organism, the capping enzyme is either a monofunctional or bifunctional polypeptide. The guanylyltransferases (Ceg1) of Saccharomyces cerevisiae is encoded by the CEG1 gene and is composed of 459 amino acids (53-kD). The RNA triphosphatase (Cet1) is a separate 549 amino acid polypeptide (80-kD), encoded by the CET1 gene. The human capping enzyme is an example of a bifunctional polypeptide, which has both triphosphatase (N-terminal) and guanylyltransferase (C-terminal) domains. The human mRNA guanylyltransferase domain of the capping enzyme is composed of seven helices and fifteen β strands that are grouped into three, five and seven strands, arranged as antiparallel β sheets. The enzyme structure has three sub-domains referred to hinge, base and lid. The GTP binding site is located between the hinge and base domain. The lid domain determines the conformation of the active site cleft, which consists of the GTP binding site, phosphoamide linking lysine and surrounding residues. The guanylyltransferase domain is linked to the triphosphatase domain via a 25 amino acid flexible loop structure. | 1 | Gene expression + Signal Transduction |
Defective Fas-mediated apoptosis may lead to oncogenesis as well as drug resistance in existing tumors. Germline mutation of Fas is associated with autoimmune lymphoproliferative syndrome (ALPS), a childhood disorder of apoptosis.
Increases in Fas-mediated signaling have been implicated in the pathology of low-risk myelodysplastic syndromes (MDS) and glioblastoma.
More recently, FasL-mediated apoptosis of T cells has also been suggested as an immune-evasive mechanism by which tumors can suppress T cell infiltration similar to inhibitory immune checkpoints such as PD-1 and CTLA-4. | 1 | Gene expression + Signal Transduction |
The equilibrium phase diagram of the alloy formed between the two components tantalum and tungsten is a binary diagram, where the two components are totally soluble on each other. In this diagram the melting temperature of the two elements are shown. It can be seen that there are two lines, representing the solidus and liquidus. | 0 | Metallurgy |
The preparation of ceramic specimens for microstructural analysis consists of five broad steps: sawing, embedding, grinding, polishing and etching. The tools and consumables for ceramographic preparation are available worldwide from metallography equipment vendors and laboratory supply companies. | 0 | Metallurgy |
Sulfuric acid produced by microorganisms will interact with the surface of the structure material. For ordinary Portland cement, it reacts with the calcium hydroxide in concrete to form calcium sulfate. This change simultaneously destroys the polymeric nature of calcium hydroxide and substitutes a larger molecule into the matrix causing pressure and spalling of the adjacent concrete and aggregate particles. The weakened crown may then collapse under heavy overburden loads. Even within a well-designed sewer network, a rule of thumb in the industry suggests that 5% of the total length may/will suffer from biogenic corrosion. In these specific areas, biogenic sulfide corrosion can deteriorate metal or several millimeters per year of concrete (see Table).
For calcium aluminate cements, processes are completely different because they are based on another chemical composition. At least three different mechanisms contribute to the better resistance to biogenic corrosion:
* The first barrier is the larger acid neutralizing capacity of calcium aluminate cements vs. ordinary Portland Cement; one gram of calcium aluminate cement can neutralize around 40% more acid than a gram of ordinary Portland Cement. For a given production of acid by the biofilm, a calcium aluminate cement concrete will last longer.
* The second barrier is due to the precipitation, when the surficial pH gets below 10, of a layer of alumina gel (AH3 in cement chemistry notation). AH3 is a stable compound down to a pH of 4 and it will form an acid-resistant barrier as long as the surface pH is not lowered below 3-4 by the bacterial activity.
* The third barrier is the bacteriostatic effect locally activated when the surface reaches pH values less than 3–4. At this level, the alumina gel is no longer stable and will dissolve, liberating aluminum ions. These ions will accumulate in the thin biofilm. Once the concentration reaches 300-500 ppm, it will produce a bacteriostatic effect on bacteria metabolism. In other word, bacteria will stop oxidizing the sulfur from HS to produce acid, and the pH will stop decreasing.
A mortar made of calcium aluminate cement combined with
calcium aluminate aggregates, i.e. a 100% calcium aluminate material, will last much longer as aggregates can also limit microorganisms’ growth and inhibits the acid generation at the source itself. | 0 | Metallurgy |
*How to model it: Problem Solving for the Computer Age (1990) ISBN 978-0808779704
*Active Learning: Cooperation in the College Classroom (1991) ISBN 978-0939603145
*Cooperative learning: Increasing college faculty instructional productivity (1991) ISBN 978-1878380095
*New paradigms for College Teaching (1997) ISBN 978-0939603268
*Teamwork and Project Management, 4th edition, (2014) ISBN 978-0073534909 | 0 | Metallurgy |
The Gibson assembly method is a relatively straightforward DNA assembly method, requiring only a few additional reagents: the 5 T5 exonuclease, Phusion DNA polymerase, and Taq DNA ligase. The DNA fragments to be assembled are synthesised to have overlapping 5 and 3' ends in the order that they are to be assembled in. These reagents are mixed together with the DNA fragments to be assembled at 50 °C and the following reactions occur:
# The T5 exonuclease chews back DNA from the 5 end of each fragment, exposing 3 overhangs on each DNA fragment.
# The complementary overhangs on adjacent DNA fragments anneal via complementary base pairing.
# The Phusion DNA polymerase fills in any gaps where the fragments anneal.
# Taq DNA ligase repairs the nicks on both DNA strands.
Because the T5 exonuclease is heat labile, it is inactivated at 50 °C after the initial chew back step. The product is thus stable, and the fragments assembled in the desired order. This one-pot protocol can assemble up to 5 different fragments accurately, while several commercial providers have kits to accurately assemble up to 15 different fragments in a two-step reaction. However, while the Gibson assembly protocol is fast and uses relatively few reagents, it requires bespoke DNA synthesis as each fragment has to be designed to contain overlapping sequences with the adjacent fragments and amplified via PCR. This reliance on PCR may also affect the fidelity of the reaction when long fragments, fragments with high GC content or repeat sequences are used. | 1 | Gene expression + Signal Transduction |
Despite the widespread classification of genes as either structural or regulatory, these categories are not an absolute division. Recent genetic discoveries call into question the distinction between regulatory and structural genes.
The distinction between regulatory and structural genes can be attributed to the original 1959 work on Lac operon protein expression. In this instance, a single regulatory protein was detected that affected the transcription of the other proteins now known to compose the Lac operon. From this point forward, the two types of coding sequences were separated.
However, increasing discoveries of gene regulation suggest greater complexity. Structural gene expression is regulated by numerous factors including epigenetics (e.g. methylation), RNAi, and more. Regulatory and structural genes can be epigenetically regulated identically, so not all regulation is coded for by “regulatory genes”.
There are also examples of proteins that do not decidedly fit either category, such as chaperone proteins. These proteins aid in the folding of other proteins, a seemingly regulatory role. Yet these same proteins also aid in the movement of their chaperoned proteins across membranes, and have now been implicated in immune responses (see Hsp60) and in the apoptotic pathway (see Hsp70).
More recently, microRNAs were found to be produced from the internal transcribed spacers of rRNA genes. Thus an internal component of a structural gene is, in fact, regulatory. Binding sites for microRNAs were also detected within coding sequences of genes. Typically interfering RNAs target the 3’UTR, but inclusion of binding sites within the sequence of the protein itself allows the transcripts of these proteins to effectively regulate the microRNAs within the cell. This interaction was demonstrated to have an effect on expression, and thus again a structural gene contains a regulatory component. | 1 | Gene expression + Signal Transduction |
One of the few known cases of a functional system in which ephaptic coupling is responsible for an observable physiological event is in the Purkinje cells of the rat cerebellum. It was demonstrated in this study that the basket cells which encapsulate some regions of Purkinje fibers can cause inhibitory effects on the Purkinje cells. The firing of these basket cells, which occurs more rapidly than in the Purkinje cells, draws current across the Purkinje cell and generates a passive hyperpolarizing potential which inhibits the activity of the Purkinje cell. Although the exact functional role of this inhibition is still unclear, it may well have a synchronizing effect in the Purkinje cells as the ephaptic effect will limit the firing time.
A similar ephaptic effect has been studied in the Mauthner cells of teleosts. | 1 | Gene expression + Signal Transduction |
Consequences of loss of pRb function is dependent on cell type and cell cycle status, as pRb's tumor suppressive role changes depending on the state and current identity of the cell.
In G0 quiescent stem cells, pRb is proposed to maintain G0 arrest although the mechanism remains largely unknown. Loss of pRb leads to exit from quiescence and an increase in the number of cells without loss of cell renewal capacity. In cycling progenitor cells, pRb plays a role at the G1, S, and G2 checkpoints and promotes differentiation. In differentiated cells, which make up the majority of cells in the body and are assumed to be in irreversible G0, pRb maintains both arrest and differentiation.
Loss of pRb therefore exhibits multiple different responses within different cells that ultimately all could result in cancer phenotypes. For cancer initiation, loss of pRb may induce cell cycle re-entry in both quiescent and post-mitotic differentiated cells through dedifferentiation. In cancer progression, loss of pRb decreases the differentiating potential of cycling cells, increases chromosomal instability, prevents induction of cellular senescence, promotes angiogenesis, and increases metastatic potential.
Although most cancers rely on glycolysis for energy production (Warburg effect), cancers due to pRb loss tend to upregulate oxidative phosphorylation. The increased oxidative phosphorylation can increase stemness, metastasis, and (when enough oxygen is available) cellular energy for anabolism.
In vivo, it is still not entirely clear how and which cell types cancer initiation occurs with solely loss of pRb, but it is clear that the pRb pathway is altered in large number of human cancers.[110] In mice, loss of pRb is sufficient to initiate tumors of the pituitary and thyroid glands, and mechanisms of initiation for these hyperplasia are currently being investigated. | 1 | Gene expression + Signal Transduction |
The discovery that a hormone can influence phosphoinositide metabolism was made by Mabel R. Hokin (1924–2003) and her husband Lowell E. Hokin in 1953, when they discovered that radioactive P phosphate was incorporated into the phosphatidylinositol of pancreas slices when stimulated with acetylcholine. Up until then phospholipids were believed to be inert structures only used by cells as building blocks for construction of the plasma membrane.
Over the next 20 years, little was discovered about the importance of PIP metabolism in terms of cell signaling, until the mid-1970s when Robert H. Michell hypothesized a connection between the catabolism of PIP and increases in intracellular calcium (Ca) levels. He hypothesized that receptor-activated hydrolysis of PIP produced a molecule that caused increases in intracellular calcium mobilization. This idea was researched extensively by Michell and his colleagues, who in 1981 were able to show that PIP is hydrolyzed into DAG and IP by a then unknown phosphodiesterase. In 1984 it was discovered that IP acts as a secondary messenger that is capable of traveling through the cytoplasm to the endoplasmic reticulum (ER), where it stimulates the release of calcium into the cytoplasm.
Further research provided valuable information on the IP pathway, such as the discovery in 1986 that one of the many roles of the calcium released by IP is to work with DAG to activate protein kinase C (PKC). It was discovered in 1989 that phospholipase C (PLC) is the phosphodiesterase responsible for hydrolyzing PIP into DAG and IP. Today the IP signaling pathway is well mapped out, and is known to be important in regulating a variety of calcium-dependent cell signaling pathways. | 1 | Gene expression + Signal Transduction |
Silicon carbide is used as a raw ingredient in some glazes applied to ceramics. At high temperatures it can reduce metal oxides forming silica and carbon dioxide. This can be used to make the glaze foam and crater due to the evolved carbon dioxide gas, or to reduce the colorant oxides and achieve colors such as copper reds otherwise only possible in a fuel powered reduction firing in an electric kiln. | 0 | Metallurgy |
Metal casting processes uses the following terminology:
*Pattern: An approximate duplicate of the final casting used to form the mold cavity.
*Molding material: The material that is packed around the pattern and then the pattern is removed to leave the cavity where the casting material will be poured.
*Flask: The rigid wood or metal frame that holds the molding material.
**Cope: The top half of the pattern, flask, mold, or core.
**Drag: The bottom half of the pattern, flask, mold, or core.
*Core: An insert in the mold that produces internal features in the casting, such as holes.
**Core print: The region added to the pattern, core, or mold used to locate and support the core.
*Mold cavity: The combined open area of the molding material and core, where the metal is poured to produce the casting.
*Riser: An extra void in the mold that fills with molten material to compensate for shrinkage during solidification.
*Gating system: The network of connected channels that deliver the molten material to the mold cavities.
**Pouring cup or pouring basin: The part of the gating system that receives the molten material from the pouring vessel.
**Sprue: The pouring cup attaches to the sprue, which is the vertical part of the gating system. The other end of the sprue attaches to the runners.
**Runners: The horizontal portion of the gating system that connects the sprues to the gates.
**Gates: The controlled entrances from the runners into the mold cavities.
*Vents: Additional channels that provide an escape for gases generated during the pour.
*Parting line or parting surface: The interface between the cope and drag halves of the mold, flask, or pattern.
*Draft: The taper on the casting or pattern that allow it to be withdrawn from the mold
*Core box: The mold or die used to produce the cores.
*Chaplet: Long vertical holding rod for core that after casting it become the integral part of casting, provide the support to the core.
Some specialized processes, such as die casting, use additional terminology. | 0 | Metallurgy |
The mammalian target of rapamycin (mTOR), also referred to as the mechanistic target of rapamycin, and sometimes called FK506-binding protein 12-rapamycin-associated protein 1 (FRAP1), is a kinase that in humans is encoded by the MTOR gene. mTOR is a member of the phosphatidylinositol 3-kinase-related kinase family of protein kinases.
mTOR links with other proteins and serves as a core component of two distinct protein complexes, mTOR complex 1 and mTOR complex 2, which regulate different cellular processes. In particular, as a core component of both complexes, mTOR functions as a serine/threonine protein kinase that regulates cell growth, cell proliferation, cell motility, cell survival, protein synthesis, autophagy, and transcription. As a core component of mTORC2, mTOR also functions as a tyrosine protein kinase that promotes the activation of insulin receptors and insulin-like growth factor 1 receptors. mTORC2 has also been implicated in the control and maintenance of the actin cytoskeleton. | 1 | Gene expression + Signal Transduction |
The active zone is present in all chemical synapses examined so far and is present in all animal species. The active zones examined so far have at least two features in common, they all have protein dense material that project from the membrane and tethers synaptic vesicles close to the membrane and they have long filamentous projections originating at the membrane and terminating at vesicles slightly farther from the presynaptic membrane. The protein dense projections vary in size and shape depending on the type of synapse examined. One striking example of the dense projection is the ribbon synapse (see below) which contains a "ribbon" of protein dense material that is surrounded by a halo of synaptic vesicles and extends perpendicular to the presynaptic membrane and can be as long as 500 nm. The glutamate synapse contains smaller pyramid like structures that extend about 50 nm from the membrane. The neuromuscular synapse contains two rows of vesicles with a long proteinaceous band between them that is connected to regularly spaced horizontal ribs extending perpendicular to the band and parallel with the membrane. These ribs are then connected to the vesicles which are each positioned above a peg in the membrane (presumably a calcium channel). Previous research indicated that the active zone of glutamatergic neurons contained a highly regular array of pyramid shaped protein dense material and indicated that these pyramids were connected by filaments. This structure resembled a geometric lattice where vesicles were guided into holes of the lattice. This attractive model has come into question by recent experiments. Recent data shows that the glutamatergic active zone does contain the dense protein material projections but these projections were not in a regular array and contained long filaments projecting about 80 nm into the cytoplasm.
There are at least five major scaffold proteins that are enriched in the active zone; UNC13B/Munc13, RIMS1 (Rab3-interacting molecule), Bassoon, Piccolo/aczonin, ELKS, and liprins-α. These scaffold proteins are thought to be the constituents of the dense pyramid like structures of the active zone and are thought to bring the synaptic vesicles into close proximity to the presynaptic membrane and the calcium channels. The protein ELKS binds to the cell adhesion protein, β-neurexin, and other proteins within the complex such as Piccolo and Bassoon. β-neurexin then binds to cell adhesion molecule, neuroligin located on the postsynaptic membrane. Neuroligin then interacts with proteins that bind to postsynaptic receptors. Protein interactions like that seen between Piccolo/ELKS/β-neurexin/neuroligin ensures that machinery that mediates vesicle fusion is in close proximity to calcium channels and that vesicle fusion is adjacent to postsynaptic receptors. This close proximity vesicle fusion and postsynaptic receptors ensures that there is little delay between the activation of the postsynaptic receptors and the release of neurotransmitters. | 1 | Gene expression + Signal Transduction |
Depending on the type of ligand a co-receptor binds, its location and function can vary. Various ligands include interleukins, neurotrophic factors, fibroblast growth factors, transforming growth factors, vascular endothelial growth factors and epidermal growth factors. Co-receptors prominent in embryonic tissue have an essential role in morphogen gradient formation or tissue differentiation. Co-receptors localized in endothelial cells function to enhance cell proliferation and cell migration.
With such variety in regards to location, co-receptors can participate in many different cellular activities. Co-receptors have been identified as participants in cell signalling cascades, embryonic development, cell adhesion regulation, gradient formation, tissue proliferation and migration. | 1 | Gene expression + Signal Transduction |
Bauxite tailings is a waste product generated in the industrial production of aluminium. Making provision for the approximately 77 million tons that is produced annually is one of the most significant problems for the aluminium mining industry. | 0 | Metallurgy |
;For aluminium
* sodium hydroxide
* Keller's reagent
;For steels
* hydrochloric and nitric acids
* ferric chloride for stainless steels
* Nital (a mixture of nitric acid and ethanol, methanol, or methylated spirits for mild steels.
2% Nital is common etchant for plain carbon steels.
;For copper
* cupric chloride
* ferric chloride
* ammonium persulfate
* ammonia
* 25-50% nitric acid.
* hydrochloric acid and hydrogen peroxide
;For silica
* hydrofluoric acid | 0 | Metallurgy |
In cell biology, protein kinase A (PKA) is a family of serine-threonine kinase whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism. It should not be confused with 5'-AMP-activated protein kinase (AMP-activated protein kinase). | 1 | Gene expression + Signal Transduction |
A spoil tip (also called a boney pile, culm bank, gob pile, waste tip or bing) is a pile built of accumulated spoil – waste material removed during mining. Spoil tips are not formed of slag, but in some areas, such as England and Wales, they are referred to as slag heaps. In Scotland the word bing is used. In North American English the term is mine dump or mine waste dump.
The term "spoil" is also used to refer to material removed when digging a foundation, tunnel, or other large excavation. Such material may be ordinary soil and rocks (after separation of coal from waste), or may be heavily contaminated with chemical waste, determining how it may be disposed of. Clean spoil may be used for land reclamation.
Spoil is distinct from tailings, which is the processed material that remains after the valuable components have been extracted from ore. | 0 | Metallurgy |
Boeing, General Electric Aircraft Engines, Goodrich Corporation, NASA, Texas A&M University and All Nippon Airways developed the Variable Geometry Chevron using a NiTi SMA. Such a variable area fan nozzle (VAFN) design would allow for quieter and more efficient jet engines in the future. In 2005 and 2006, Boeing conducted successful flight testing of this technology.
SMAs are being explored as vibration dampers for launch vehicles and commercial jet engines. The large amount of hysteresis observed during the superelastic effect allow SMAs to dissipate energy and dampen vibrations. These materials show promise for reducing the high vibration loads on payloads during launch as well as on fan blades in commercial jet engines, allowing for more lightweight and efficient designs. SMAs also exhibit potential for other high shock applications such as ball bearings and landing gear.
There is also strong interest in using SMAs for a variety of actuator applications in commercial jet engines, which would significantly reduce their weight and boost efficiency. Further research needs to be conducted in this area, however, to increase the transformation temperatures and improve the mechanical properties of these materials before they can be successfully implemented. A review of recent advances in high-temperature shape-memory alloys (HTSMAs) is presented by Ma et al.
A variety of wing-morphing technologies are also being explored. | 0 | Metallurgy |
The Kidd Process development team modified its cathode plates to cope with high-corrosion environments, such as the liberator cells used to remove contaminants in refineries and some high-corrosion environments in electrowinning plants.
The design of the plate features a stainless-steel jacket that surrounds a solid-copper hanger bar, protecting it from corrosion. A corrosion-resistant resin inside the stainless steel jacket protects the conductive interior weld between the header bar and the plate. The hanger bar is then finished with high-quality sealing to prevent ingress of electrolytes into the conductive interior weld.
This corrosion resistance electrode is marketed as the HP cathode plate. | 0 | Metallurgy |
Self-splicing occurs for rare introns that form a ribozyme, performing the functions of the spliceosome by RNA alone. There are three kinds of self-splicing introns, Group I, Group II and Group III. Group I and II introns perform splicing similar to the spliceosome without requiring any protein. This similarity suggests that Group I and II introns may be evolutionarily related to the spliceosome. Self-splicing may also be very ancient, and may have existed in an RNA world present before protein.
Two transesterifications characterize the mechanism in which group I introns are spliced:
# 3OH of a free guanine nucleoside (or one located in the intron) or a nucleotide cofactor (GMP, GDP, GTP) attacks phosphate at the 5 splice site.
# 3OH of the 5 exon becomes a nucleophile and the second transesterification results in the joining of the two exons.
The mechanism in which group II introns are spliced (two transesterification reaction like group I introns) is as follows:
# The 2OH of a specific adenosine in the intron attacks the 5 splice site, thereby forming the lariat
# The 3OH of the 5 exon triggers the second transesterification at the 3' splice site, thereby joining the exons together. | 1 | Gene expression + Signal Transduction |
Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide () anion, and another anion such as carbonate (), chloride (), or sulfate (), in a layered double hydroxide structure. The most studied varieties are
* carbonate green rust – GR(): [()] · [·2].
* chloride green rust – GR(): [()] · [·n].
* sulfate green rust – GR(): [()] · [·2].
Other varieties reported in the literature are bromide , fluoride , iodide , nitrate , and selenate.
Green rust was first recognized as a corrosion crust on iron and steel surfaces. It occurs in nature as the mineral fougerite. | 0 | Metallurgy |
High-temperature corrosion typically occurs in environments that have heat and chemical such as hydrocarbon fuel sources but also other chemicals enable this form of corrosion.
Thus it can occur in boilers, automotive engines driven by diesel or gasoline, metal production furnaces and flare stacks from oil and gas production. High temperature oxidation of metals would also be included. | 0 | Metallurgy |
Bioleaching is the extraction or liberation of metals from their ores through the use of living organisms. Bioleaching is one of several applications within biohydrometallurgy and several methods are used to treat ores or concentrates containing copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt.
Bioleaching falls into two broad categories. The first, is the use of microorganisms to oxidize refractory minerals to release valuable metals such and gold and silver. Most commonly the minerals that are the target of oxidization are pyrite and arsenopyrite.
The second category is leaching of sulphide minerals to release the associated metal, for example, leaching of pentlandite to release nickel, or the leaching of chalcocite, covellite or chalcopyrite to release copper. | 0 | Metallurgy |
This - Calphad calculated value of numerical derivative - Q has some interesting applications in the field of metal solidification. In fact, Q reflects the phase diagram of the alloy system and its reciprocal has been found to have a relationship with grain size d on solidification, which empirically has been found in some cases to be linear:
where a and b are constants, as illustrated with some examples from the literature for Mg and Al alloys. Before Calphad use, Q values were calculated from the conventional relationship:
Q=m*c0(k−1)
where m is the slope of the liquidus, c0 is the solute concentration, and k is the equilibrium distribution coefficient.
More recently some other possible correlation of Q with grain size d have been found, for instance:
where B is a constant independent of alloy composition. | 0 | Metallurgy |
Aluminium surface composites with enhanced surface properties can be fabricated using FSP. Aluminium surface composites fabricated with the optimum friction stir processing parameters show better mechanical properties and corrosion resistance. The processing parameters such as tool rotational speed and tool shoulder diameter affects the surface properties. Higher surface hardness is exhibited by the surface composites fabricated at higher tool rotational speed and lower tool shoulder diameter. The properties of the composite materials can be altered by changing the type of reinforcement. Reinforcement particles aids in the grain size refinement as well as the property enhancement in the processed materials. The surface composite properties can be varied by changing the reinforcement particles based on the end application. The reinforcement phases can be metallic, ceramic, or polymer materials. | 0 | Metallurgy |
Ferrouranium, also called ferro-uranium, is a ferroalloy, an alloy of iron and uranium, after World War II usually depleted uranium. | 0 | Metallurgy |
Construction of a 15 t/h demonstration copper ISASMELT plant began in 1986. The design was based on MIM's 250 kg/h test work and operating experience with the lead ISASMELT pilot plant. It cost A$11 million and was commissioned in April 1987. The initial capital cost was recovered in the first 14 months of operation.
As with the lead ISASMELT pilot plant, the copper ISASMELT demonstration plant was integrated into copper smelter operations and justified by the 20% (30,000 t/y) increase in copper production that it provided. It quickly treated the entire backlog of converter slag concentrate, which could not be treated at high rates in the reverberatory furnaces without generating magnetite ("FeO") accretions that would necessitate shutting down the reverberatory furnaces for their removal.
The demonstration copper ISASMELT plant was used to further develop the copper process. Refractory life was initially shorter than expected and considerable effort was devoted to understanding the reasons and attempting to extend the life of the refractories. At the end of the life of the demonstration plant, the longest refractory life achieved was 90 weeks.
Lance life was also low initially. Inexperienced operators could destroy a lance in as little as 10 minutes. However, as a result of modifications to the lance design, the development of techniques to determine the position of the lance in the bath, and a rise in the operating experience, the typical lance life was extended to a week.
The demonstration plant was commissioned with high-pressure (700 kPag) air injected down the lance. Later, after extensive testing of low-pressure lance designs and trials using oxygen enrichment of the lance air, a 70 t/d oxygen plant and a 5 Nm3/s blower with a discharge pressure of 146 kPag were purchased. The new lance design was capable of operating at pressures below 100 kPag. Using enrichment of the oxygen in the lance air to 35%, the demonstration plant throughput was lifted to 48 t/h of concentrate, and the gross energy used during smelting was reduced from 25.6 GJ/t of contained copper to 4.1 GJ/t. | 0 | Metallurgy |
Rapamycin (Sirolimus) inhibits mTORC1, resulting in the suppression of cellular senescence. This appears to provide most of the beneficial effects of the drug (including life-span extension in animal studies). Suppression of insulin resistance by sirtuins accounts for at least some of this effect. Impaired sirtuin 3 leads to mitochondrial dysfunction.
Rapamycin has a more complex effect on mTORC2, inhibiting it only in certain cell types under prolonged exposure. Disruption of mTORC2 produces the diabetic-like symptoms of decreased glucose tolerance and insensitivity to insulin. | 1 | Gene expression + Signal Transduction |
One of the key elements of promoters inhibited by (p)ppGpp is the presence of a GC-rich discriminator, defined as a region between TATA-box (-10 box) and +1 nt (where +1 is the transcription start site). Promoters negatively regulated by ppGpp have a 16-bp linker, in contrast with the 17-bp consensus. Promoters activated by ppGpp seem to have an AT-rich discriminator and linger linkers (for example, the his promoter linker is 18 bp). | 1 | Gene expression + Signal Transduction |
Promoters are important gene regulatory elements used in tuning synthetically designed genetic circuits and metabolic networks. For example, to overexpress an important gene in a network, to yield higher production of target protein, synthetic biologists design promoters to upregulate its expression. Automated algorithms can be used to design neutral DNA or insulators that do not trigger gene expression of downstream sequences. | 1 | Gene expression + Signal Transduction |
The third piece has a fractured top surface, which indicates that a fourth piece of the original pillar is missing. Klaus Roessler (1995) estimated the length of this piece at . Henry Cousens hypothesized that the fourth piece had a garuda figure (the Paramara royal emblem) or a trishula (trident) at the top. As Bhoja was a Shaivite king, R. Balasubramaniam analyzed Shaivite iconography to conclude that the top had a trishula.
Balasubramaniam also theorizes that an iron pillar in front of Mandus Jami Masjid might be a re-shaped version of the Dhar pillars missing piece. This pillar is called Allaudins Sang' (spear) after Alauddin Khalji. | 0 | Metallurgy |
A brass mill is a mill which processes brass. Brass mills are common in England; many date from long before the Industrial Revolution.
;Examples of brass mills include:
*Brassmill (Ross on Wye)
*Saltford Brass Mill | 0 | Metallurgy |
RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein-coding genes in living cells. It consists of RNA polymerase II, a subset of general transcription factors, and regulatory proteins known as SRB proteins.
Part of the assembly of the holoenzyme is referred to as the preinitiation complex, because its assembly takes place on the gene promoter before the initiation of transcription. The mediator complex acts as a bridge between RNA polymerase II and the transcription factors. | 1 | Gene expression + Signal Transduction |
Flocculation and sedimentation are widely employed in the purification of drinking water as well as in sewage treatment, storm-water treatment and treatment of industrial wastewater streams. Typical treatment processes consist of grates, coagulation, flocculation, sedimentation, granular filtration and disinfection. As the demand for eco-friendly solutions in the flocculation process continues to grow, biopolymers are emerging as a highly promising solution. Among these, chitosan stands out for its exceptional properties, making it a top contender in this environmentally-conscious endeavor. Chitosan is not only biodegradable but also exhibits a unique ability to bind with a wide range of contaminants, including heavy metals and organic pollutants, effectively removing them from water sources. | 0 | Metallurgy |
A method employing very gentle cell lysis in yeast followed by co-immunoprecipitation with an antibody to a mediator subunit (Med 17) has confirmed almost all previously reported or predicted interactions and revealed many previously unsuspected specific interactions of various proteins with mediator. | 1 | Gene expression + Signal Transduction |
The emerging understanding of the role of eNSCs in the adult mammalian brain suggested the relevance of these cells to disease. To address this issue, experiments were performed where the activation of eNSCs was induced in models of disease. This allowed the study of the consequences of activating eNSCs in the diseased brain. Several lines of evidence implicate the STAT3-Ser/Hes3 signaling axis in various diseases:
:* Activation of the signaling pathway by Delta4 in combination with basic fibroblast growth factor (bFGF) induces motor and sensory skill improvements in adult rat models of ischemic stroke (PMCAO model).
:* This signaling pathway may mediate pro-survival functions of macrophage migration inhibitory factor on neural stem cells.
:* Activation of the signaling pathway by Delta4, Angiopoietin 2, insulin, or a combination of the three and a JAK inhibitor induces motor skill improvements in adult rat models of Parkinson's disease (6-hydroxydopamine model).
:* RNA interference (“knockdown”) of Hes3 in cultures of cells with cancer stem cell properties from patients with glioblastoma multiforme reduces cell number.
:* Mice lacking Hes3 exhibit increased sensitivity to particular paradigms of pancreatic islet damage, suggesting roles in diabetes. | 1 | Gene expression + Signal Transduction |
It appears that growth factors, amino acids, ATP, and oxygen levels regulate mTOR signaling. Several downstream pathways that regulate cell-cycle progression, translation, initiation, transcriptional stress responses, protein stability, and survival of cells are signaling through mTOR.
The serine/threonine kinase mTOR is a downstream effector of the PI3K/AKT pathway, and forms two distinct multiprotein complexes, mTORC1 and mTORC2. These two complexes have a separate network of protein partners, feedback loops, substrates, and regulators. mTORC1 consists of mTOR and two positive regulatory subunits, raptor and mammalian LST8 (mLST8), and two negative regulators, proline-rich AKT substrate 40 (PRAS40) and DEPTOR. mTORC2 consists of mTOR, mLST8, mSin1, protor, rictor, and DEPTOR.
mTORC1 is sensitive to rapamycin but mTORC2 is considered to be resistant and is generally insensitive to nutrients and energy signals. mTORC2 is activated by growth factors, phosphorylates PKCα, AKT and paxillin, and regulates the activity of the small GTPase, Rac, and Rho related to cell survival, migration and regulation of the actin cytoskeleton.
The mTORC1 signaling cascade is activated by phosphorylated AKT and results in phosphorylation of S6K1, and 4EBP1, which lead to mRNA translation. | 1 | Gene expression + Signal Transduction |
Bisson (2000) thought that because of coppers redness, luminosity and sound, it was valued by Africans. For many African cultures, the redness could be with life giving powers. Bisson (2000) also noted that the redness is a symbol of transition and it association with transition could explain why the wide use of copper in rituals in various African states. Also, its ability to reflect sunlight is suggested represent aggression and liminal boundaries between states, thus emphasizing its transformative properties. Finally, because of coppers use in bells and drums, it is thought to aid in the summoning spirits, when the instruments are played. | 0 | Metallurgy |
In addition to reinitiation, uORFs contribute to translation initiation based on:
* The nucleotides of an uORF may code for a codon that leads to a highly structured mRNA, causing the ribosome to stall.
* cis- and trans- regulation on translation of the main protein coding sequence.
* Interactions with IRES sites. | 1 | Gene expression + Signal Transduction |
As noted above, human cells do not express TLR11, but mice cells do. Mouse-specific TLR11 recognizes uropathogenic E.coli and the apicomplexan parasite Toxoplasma gondii. With Toxoplasma its ligand is the protein profilin and the ligand for E. coli is flagellin. The flagellin from the enteropathogen Salmonella is also recognized by TLR11.
As mouse TLR11 is able to recognize Salmonella effectively, normal mice do not get infected by oral Salmonella Typhi, which causes food- and waterborne gastroenteritis and typhoid fever in humans. TLR11 deficient knockout mice, on the other hand, are efficiently infected. As a result, this knockout mouse can act as a disease model of human typhoid fever. | 1 | Gene expression + Signal Transduction |
HIV-1 is a retrovirus that relies on myristoylation of one of its structural proteins in order to successfully package its genome, assemble and mature into a new infectious particle. Viral matrix protein, the N-terminal–most domain of the gag polyprotein, is myristoylated. This myristoylation modification targets gag to the membrane of the host cell. Utilizing the myristoyl-electrostatic switch, including a basic patch on the matrix protein, gag can assemble at lipid rafts at the plasma membrane for viral assembly, budding and further maturation. In order to prevent viral infectivity, myristoylation of the matrix protein could become a good drug target. | 1 | Gene expression + Signal Transduction |
Controversy has swirled around the provenance of the copper oxhide ingots. Lead isotope analysis (LIA) suggests that the late LBA ingots (that is, after 1250 BC) are composed of Cypriot copper, specifically copper from the Apilki mine and its surrounding area. The Gelidonya ingots' ratios are consistent with Cypriot ores while the Uluburun ingots fall on the periphery of the Cypriot isotopic field. On the other hand, Late Minoan I ingots found on Crete have Paleozoic lead isotope ratios and are more consistent with ore sources in Afghanistan, Iran, or Central Asia. The controversy settles on the validity of LIA. Paul Budd argues that LBA copper is the product of such extensive mixing and recycling that LIA, which works best for metals from a single ore deposit, is unfeasible.
Some scholars worry that the 1250 BC date is too limiting. They note that Cyprus was smelting copper on a large scale in the early LBA and had the potential to export the metal to Crete and other places at this time. Furthermore, copper ore is more plentiful on Cyprus than on Sardinia and far more plentiful than on Crete. Archaeologists have discovered numerous Cypriot exports to Sardinia including metalworking tools and prestige metal objects.
Due to the heavy corrosion of tin oxhide ingots and the limited data for lead isotopic studies of tin, the provenance of the tin ingots has been uncertain. The fact that scholars have been unable to pinpoint Bronze Age tin ore deposits compounds this problem. | 0 | Metallurgy |
The Old Copper Complex in North America has been radiometrically dated to 9500 BP—i.e., about 7480 BCE—making it one of the oldest known examples of copper extraction in the world. The earliest evidence of the cold-hammering of native copper comes from the excavation at Çayönü Tepesi in eastern Anatolia, which dates between 7200 to 6600 BCE. Among the various items considered to be votive or amulets, there was one that looked like a fishhook and one like an awl. Another find, at Shanidar Cave in Mergasur, Iraq, contained copper beads, and dates back to 8,700 BCE.
One of the world's oldest known copper mines, as opposed to usage of surface deposits, is at Timna Valley, Israel, and has been used since the fourth millennium BC, with surface deposit usage occurring in the fifth and sixth millennium.
The Pločnik archaeological site in southeastern Europe (Serbia) contains the oldest securely dated evidence of copper making at high temperature, from 5,000 BCE. The find in June 2010 extends for an additional 500 years, dated to 5th millennium BCE, representing the earlier record of copper smelting from Rudna Glava (Serbia). | 0 | Metallurgy |
However, this system of calculation gives only the mass of pure gold contained in an alloy. The term 18-karat gold means that the alloys mass consists of 75% of gold and 25% of other metals. The quantity of gold by volume' in a less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm for gold, 10.49 g/cm for silver and 8.96 g/cm for copper. | 0 | Metallurgy |
In colloidal chemistry, flocculation is a process by which colloidal particles come out of suspension to sediment in the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended, under the form of a stable dispersion (where the internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation) and are not truly dissolved in solution.
Coagulation and flocculation are important processes in water treatment with coagulation aimed to destabilize and aggregate particles through chemical interactions between the coagulant and colloids, and flocculation to sediment the destabilized particles by causing their aggregation into floc. | 0 | Metallurgy |
In bacteria, the promoter contains two short sequence elements approximately 10 (Pribnow Box) and 35 nucleotides upstream from the transcription start site.
* The sequence at -10 (the -10 element) has the consensus sequence TATAAT.
* The sequence at -35 (the -35 element) has the consensus sequence TTGACA.
* The above consensus sequences, while conserved on average, are not found intact in most promoters. On average, only 3 to 4 of the 6 base pairs in each consensus sequence are found in any given promoter. Few natural promoters have been identified to date that possess intact consensus sequences at both the -10 and -35; artificial promoters with complete conservation of the -10 and -35 elements have been found to transcribe at lower frequencies than those with a few mismatches with the consensus.
* The optimal spacing between the -35 and -10 sequences is 17 bp.
* Some promoters contain one or more upstream promoter element (UP element) subsites (consensus sequence 5-AAAAAARNR-3 when centered in the -42 region; consensus sequence 5-AWWWWWTTTTT-3 when centered in the -52 region; W = A or T; R = A or G; N = any base).
The above promoter sequences are recognized only by RNA polymerase holoenzyme containing sigma-70. RNA polymerase holoenzymes containing other sigma factors recognize different core promoter sequences.
upstream downstream
5-XXXXXXXPPPPPPXXXXXXPPPPPPXXXXGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGXXXX-3
-35 -10 Gene to be transcribed | 1 | Gene expression + Signal Transduction |
The common technique of cleaning silverware by immersion of the silver or sterling silver (or even just silver plated objects) and a piece of aluminium (foil is preferred because of its much greater surface area than that of ingots, although if the foil has a "non-stick" face, this must be removed with steel wool first) in a hot electrolytic bath (usually composed of water and sodium bicarbonate, i.e., household baking soda) is an example of galvanic corrosion. Silver darkens and corrodes in the presence of airborne sulfur molecules, and the copper in sterling silver corrodes under a variety of conditions. These layers of corrosion can be largely removed through the electrochemical reduction of silver sulfide molecules: the presence of aluminium (which is less noble than either silver or copper) in the bath of sodium bicarbonate strips the sulfur atoms off the silver sulfide and transfers them onto and thereby corrodes the piece of aluminium foil (a much more reactive metal), leaving elemental silver behind. No silver is lost in the process. | 0 | Metallurgy |
Sensitive electronic equipment are vulnerable to interference and unauthorized surveillance. These products also require protection from high voltages. Radio frequency (RF) shielding can address these issues by reducing the transmission of electric or magnetic fields from one space to another.
Copper is an excellent material for RF shielding because it absorbs radio and magnetic waves. Other useful properties for RF shielding is that copper has a high electrical conductivity, is ductile, malleable, and solders easily.
RF shielding enclosures filter a range of frequencies for specific conditions. Properly designed and constructed copper enclosures satisfy most RF shielding needs, from computer and electrical switching rooms to hospital CAT-scan and MRI facilities. Special attention needs to be addressed regarding potential shield penetrations, such as doors, vents, and cables.
A shield can be effective against one type of electromagnetic field but not against another. For example, a copper foil or screen RF shield will be minimally effective against power frequency magnetic fields. A power frequency magnetic shield could offer little reduction of radio frequency fields. The same is true for different RF frequencies. A simple large-mesh screen shield can work well for lower frequencies, but can be ineffective for microwaves.
Sheet copper for RF shielding can be formed into essentially any shape and size. Electrical connection to a grounding system provides an effective RF enclosure. | 0 | Metallurgy |
Complex metallic alloys is an umbrella term for intermetallic compounds with a relatively large unit cell. There is no precise definition of how large the unit cell of a complex metallic alloy has to be, but the broadest definition includes Zintl phases, skutterudites, and Heusler compounds on the most simple end, and quasicrystals on the more complex end. | 0 | Metallurgy |
Polymerase III terminates transcription at small polyUs stretch (5-6). In eukaryotes, a hairpin loop is not required, but may enhance termination efficiency in humans. In Saccharomyces cerevisiae, it was found that termination of transcription occurred in the sequence T7GT6 and was progressive. The presence of transcripts with five, six, and seven U residues and the slow readthrough of the T7 stretch suggest that the incorporation of a single G into the RNA chain served to reset elongation rates either entirely or substantially. | 1 | Gene expression + Signal Transduction |
The second generation of mTOR inhibitors is known as ATP-competitive mTOR kinase inhibitors. mTORC1/mTORC2 dual inhibitors such as torin-1, torin-2 and vistusertib, are designed to compete with ATP in the catalytic site of mTOR. They inhibit all of the kinase-dependent functions of mTORC1 and mTORC2 and block the feedback activation of PI3K/AKT signaling, unlike rapalogs, which only target mTORC1. Development of these drugs has reached clinical trials, although some, such as vistusertib, have been discontinued. Like rapalogs, they decrease protein translation, attenuate cell cycle progression, and inhibit angiogenesis in many cancer cell lines and also in human cancer. In fact, they have been proven to be more potent than rapalogs.
Theoretically, the most important advantages of these mTOR inhibitors is the considerable decrease of AKT phosphorylation on mTORC2 blockade and in addition to a better inhibition on mTORC1. However, some drawbacks exist. Even though these compounds have been effective in rapamycin-insensitive cell lines, they have only shown limited success in KRAS driven tumors. This suggests that combinational therapy may be necessary for the treatment of these cancers. Another drawback is also their potential toxicity. These facts have raised concerns about the long term efficacy of these types of inhibitors.
The close interaction of mTOR with the PI3K pathway has also led to the development of mTOR/PI3K dual inhibitors. Compared with drugs that inhibit either mTORC1 or PI3K, these drugs have the benefit of inhibiting mTORC1, mTORC2, and all the catalytic isoforms of PI3K. Targeting both kinases at the same time reduces the upregulation of PI3K, which is typically produced with an inhibition on mTORC1. The inhibition of the PI3K/mTOR pathway has been shown to potently block proliferation by inducing G1 arrest in different tumor cell lines. Strong induction of apoptosis and autophagy has also been seen. Despite good promising results, there are preclinical evidence that some types of cancers may be insensitive to this dual inhibition. The dual PI3K/mTOR inhibitors are also likely to have increased toxicity. | 1 | Gene expression + Signal Transduction |
Platelet-derived growth factor receptors (PDGF-R) are cell surface tyrosine kinase receptors for members of the platelet-derived growth factor (PDGF) family. PDGF subunits -A and -B are important factors regulating cell proliferation, cellular differentiation, cell growth, development and many diseases including cancer. There are two forms of the PDGF-R, alpha and beta each encoded by a different gene. Depending on which growth factor is bound, PDGF-R homo- or heterodimerizes. | 1 | Gene expression + Signal Transduction |
A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein). A term derived from the lac operon, structural genes are typically viewed as those containing sequences of DNA corresponding to the amino acids of a protein that will be produced, as long as said protein does not function to regulate gene expression. Structural gene products include enzymes and structural proteins. Also encoded by structural genes are non-coding RNAs, such as rRNAs and tRNAs (but excluding any regulatory miRNAs and siRNAs). | 1 | Gene expression + Signal Transduction |
The silicothermic reduction of dolomite was first developed by Amati in 1938 at the University of Padua. Immediately afterward, an industrial production was established in Bolzano (Italy), using what is now better known as the Bolzano process.
A few years later in 1939, when Canada and its allies entered WW2, they were short on supplies that required magnesium such as bombs, other military devices and aluminum alloys needed for aircraft. Dr. Lloyd Montgomery Pidgeon at the National Research Council was able to create a method for extracting magnesium from dolomite in a vacuum at high temperature with ferrosilicon as the reducing agent. At this time, the ferrosilicon method was known, however it had yet to be commercialized. By early 1942, a successful pilot test took place.
Since then, the Pidgeon process has continually been widely used, especially in China, the worlds largest magnesium producer. | 0 | Metallurgy |
In 1787, part-time chemist Carl Axel Arrhenius found a heavy black rock in an old quarry near the Swedish village of Ytterby (now part of the Stockholm Archipelago). Thinking it was an unknown mineral containing the newly discovered element tungsten, he named it ytterbite and sent samples to various chemists for analysis.
Johan Gadolin at the University of Åbo identified a new oxide (or "earth") in Arrhenius sample in 1789, and published his completed analysis in 1794. Anders Gustaf Ekeberg confirmed the identification in 1797 and named the new oxide yttria. In the decades after Antoine Lavoisier developed the first modern definition of chemical elements, it was believed that earths could be reduced to their elements, meaning that the discovery of a new earth was equivalent to the discovery of the element within, which in this case would have been yttrium'.
Friedrich Wöhler is credited with first isolating the metal in 1828 by reacting a volatile chloride that he believed to be yttrium chloride with potassium.
In 1843, Carl Gustaf Mosander found that samples of yttria contained three oxides: white yttrium oxide (yttria), yellow terbium oxide (confusingly, this was called erbia at the time) and rose-colored erbium oxide (called terbia at the time). A fourth oxide, ytterbium oxide, was isolated in 1878 by Jean Charles Galissard de Marignac. New elements were later isolated from each of those oxides, and each element was named, in some fashion, after Ytterby, the village near the quarry where they were found (see ytterbium, terbium, and erbium). In the following decades, seven other new metals were discovered in "Gadolin's yttria". Since yttria was found to be a mineral and not an oxide, Martin Heinrich Klaproth renamed it gadolinite in honor of Gadolin.
Until the early 1920s, the chemical symbol Yt was used for the element, after which Y came into common use.
In 1987, yttrium barium copper oxide was found to achieve high-temperature superconductivity. It was only the second material known to exhibit this property, and it was the first-known material to achieve superconductivity above the (economically important) boiling point of nitrogen. | 0 | Metallurgy |
A subgenomic promoter is a promoter added to a virus for a specific heterologous gene, resulting in the formation of mRNA for that gene alone. Many positive-sense RNA viruses produce these subgenomic mRNAs (sgRNA) as one of the common infection techniques used by these viruses and generally transcribe late viral genes. Subgenomic promoters range from 24 nucleotide (Sindbis virus) to over 100 nucleotides (Beet necrotic yellow vein virus) and are usually found upstream of the transcription start. | 1 | Gene expression + Signal Transduction |
Another drug delivery system that has shown potential for chemotactic applicability is protocells. In general, protocells are artificial cells that mimic living cells but cannot reproduce and have genetic mutations like living cells do. Moreover, protocells combine the advantages of liposomes with that of mesoporous silica nanoparticles. These advantages include but are not limited to stability, large capacity for various cargos, low toxicity, immunogenicity, and the ability to circulate the blood for long periods. Thus, researchers aim to create a tunable chemotactic protocell that can move towards or away from a chemical signal. In fact, researchers have devised a way to use the enzymes catalase, urease, and ATPase to move the protocell closer or further away from the reactant, giving them direction and movement control of these protocells. Overall, the development of chemotactic controlled protocols holds great promise for the targeted delivery of drugs to specific areas of the body, potentially increasing treatment efficacy while minimizing side effects. However, more research is needed to fully understand the capabilities and limitations of protocells as drug delivery systems and optimize their design and functionality for specific applications. | 1 | Gene expression + Signal Transduction |
Transcription regulation at about 60% of promoters is controlled by methylation of cytosines within CpG dinucleotides (where 5’ cytosine is followed by 3’ guanine or CpG sites). 5-methylcytosine (5-mC) is a methylated form of the DNA base cytosine (see Figure). 5-mC is an epigenetic marker found predominantly within CpG sites. About 28 million CpG dinucleotides occur in the human genome. In most tissues of mammals, on average, 70% to 80% of CpG cytosines are methylated (forming 5-methylCpG or 5-mCpG). Methylated cytosines within 5’cytosine-guanine 3’ sequences often occur in groups, called CpG islands. About 60% of promoter sequences have a CpG island while only about 6% of enhancer sequences have a CpG island. CpG islands constitute regulatory sequences, since if CpG islands are methylated in the promoter of a gene this can reduce or silence gene transcription.
DNA methylation regulates gene transcription through interaction with methyl binding domain (MBD) proteins, such as MeCP2, MBD1 and MBD2. These MBD proteins bind most strongly to highly methylated CpG islands. These MBD proteins have both a methyl-CpG-binding domain as well as a transcription repression domain. They bind to methylated DNA and guide or direct protein complexes with chromatin remodeling and/or histone modifying activity to methylated CpG islands. MBD proteins generally repress local chromatin such as by catalyzing the introduction of repressive histone marks, or creating an overall repressive chromatin environment through nucleosome remodeling and chromatin reorganization.
Transcription factors are proteins that bind to specific DNA sequences in order to regulate the expression of a gene. The binding sequence for a transcription factor in DNA is usually about 10 or 11 nucleotides long. As summarized in 2009, Vaquerizas et al. indicated there are approximately 1,400 different transcription factors encoded in the human genome by genes that constitute about 6% of all human protein encoding genes. About 94% of transcription factor binding sites (TFBSs) that are associated with signal-responsive genes occur in enhancers while only about 6% of such TFBSs occur in promoters.
EGR1 protein is a particular transcription factor that is important for regulation of methylation of CpG islands. An EGR1 transcription factor binding site is frequently located in enhancer or promoter sequences. There are about 12,000 binding sites for EGR1 in the mammalian genome and about half of EGR1 binding sites are located in promoters and half in enhancers. The binding of EGR1 to its target DNA binding site is insensitive to cytosine methylation in the DNA.
While only small amounts of EGR1 transcription factor protein are detectable in cells that are un-stimulated, translation of the EGR1 gene into protein at one hour after stimulation is drastically elevated. Expression of EGR1 transcription factor proteins, in various types of cells, can be stimulated by growth factors, neurotransmitters, hormones, stress and injury. In the brain, when neurons are activated, EGR1 proteins are up-regulated and they bind to (recruit) the pre-existing TET1 enzymes which are highly expressed in neurons. TET enzymes can catalyse demethylation of 5-methylcytosine. When EGR1 transcription factors bring TET1 enzymes to EGR1 binding sites in promoters, the TET enzymes can demethylate the methylated CpG islands at those promoters. Upon demethylation, these promoters can then initiate transcription of their target genes. Hundreds of genes in neurons are differentially expressed after neuron activation through EGR1 recruitment of TET1 to methylated regulatory sequences in their promoters.
The methylation of promoters is also altered in response to signals. The three mammalian DNA methyltransferasess (DNMT1, DNMT3A, and DNMT3B) catalyze the addition of methyl groups to cytosines in DNA. While DNMT1 is a “maintenance” methyltransferase, DNMT3A and DNMT3B can carry out new methylations. There are also two splice protein isoforms produced from the DNMT3A gene: DNA methyltransferase proteins DNMT3A1 and DNMT3A2.
The splice isoform DNMT3A2 behaves like the product of a classical immediate-early gene and, for instance, it is robustly and transiently produced after neuronal activation. Where the DNA methyltransferase isoform DNMT3A2 binds and adds methyl groups to cytosines appears to be determined by histone post translational modifications.
On the other hand, neural activation causes degradation of DNMT3A1 accompanied by reduced methylation of at least one evaluated targeted promoter. | 1 | Gene expression + Signal Transduction |
*AMPP Annual Conference
*Area Conferences
*Coatings+ (will retire after 2021)
*CORROSION (will retire after 2022) | 0 | Metallurgy |
The lost-wax technique came to be known in the Mediterranean during the Bronze Age. It was a major metalworking technique utilized in the ancient Mediterranean world, notably during the Classical period of Greece for large-scale bronze statuary and in the Roman world.
Direct imitations and local derivations of Oriental, Syro-Palestinian and Cypriot figurines are found in Late Bronze Age Sardinia, with a local production of figurines from the 11th to 10th century BC. The cremation graves (mainly 8th-7th centuries BC, but continuing until the beginning of the 4th century) from the necropolis of Paularo (Italian Oriental Alps) contained fibulae, pendants and other copper-based objects that were made by the lost-wax process. Etruscan examples, such as the bronze anthropomorphic handle from the Bocchi collection (National Archaeological Museum of Adria), dating back to the 6th to 5th centuries BC, were made by cire perdue. Most of the handles in the Bocchi collection, as well as some bronze vessels found in Adria (Rovigo, Italy) were made using the lost-wax technique. The better known lost-wax produced items from the classical world include the "Praying Boy" (in the Berlin Museum), the statue of Hera from Vulci (Etruria), which, like most statues, was cast in several parts which were then joined. Geometric bronzes such as the four copper horses of San Marco (Venice, probably 2nd century) are other prime examples of statues cast in many parts.
Examples of works made using the lost-wax casting process in Ancient Greece largely are unavailable due to the common practice in later periods of melting down pieces to reuse their materials. Much of the evidence for these products come from shipwrecks. As underwater archaeology became feasible, artifacts lost to the sea became more accessible. Statues like the Artemision Bronze Zeus or Poseidon (found near Cape Artemision), as well as the Victorious Youth (found near Fano), are two such examples of Greek lost-wax bronze statuary that were discovered underwater.
Some Late Bronze Age sites in Cyprus have produced cast bronze figures of humans and animals. One example is the male figure found at Enkomi. Three objects from Cyprus (held in the Metropolitan Museum of Art in New York) were cast by the lost-wax technique from the 13th and 12th centuries BC, namely, the amphorae rim, the rod tripod, and the cast tripod.
Other, earlier examples that show this assembly of lost-wax cast pieces include the bronze head of the Chatsworth Apollo and the bronze head of Aphrodite from Satala (Turkey) from the British Museum. | 0 | Metallurgy |
Anodizing can produce yellowish integral colours without dyes if it is carried out in weak acids with high voltages, high current densities, and strong refrigeration. Shades of colour are restricted to a range which includes pale yellow, gold, deep bronze, brown, grey, and black. Some advanced variations can produce a white coating with 80% reflectivity. The shade of colour produced is sensitive to variations in the metallurgy of the underlying alloy and cannot be reproduced consistently.
Anodizing in some organic acids, for example malic acid, can enter a runaway situation, in which the current drives the acid to attack the aluminium far more aggressively than normal, resulting in huge pits and scarring. Also, if the current or voltage are driven too high, burning can set in; in this case, the supplies act as if nearly shorted and large, uneven and amorphous black regions develop.
Integral colour anodizing is generally done with organic acids, but the same effect has been produced in laboratories with very dilute sulfuric acid. Integral colour anodizing was originally performed with oxalic acid, but sulfonated aromatic compounds containing oxygen, particularly sulfosalicylic acid, have been more common since the 1960s. Thicknesses of up to 50 μm can be achieved. Organic acid anodizing is called Type IC by MIL-A-8625. | 0 | Metallurgy |
Vacuum metallurgy is the field of materials technology that deals with making, shaping, or treating metals in a controlled atmosphere, at pressures significantly less than normal atmospheric pressure. The purpose of vacuum metallurgy is to prevent contamination of metal by gases in the atmosphere. Alternatively, in some processes, a reactive gas may be introduced into the process to become part of the resultant product. Examples of vacuum metallurgy include vacuum degassing of molten steel in steelmaking operations, vacuum deposition of thin metal layers in manufacture of optics and semiconductors, vacuum casting, vacuum arc remelting of alloys, and vacuum induction melting. | 0 | Metallurgy |
Properly designed copper roofs minimize movements due to thermal changes. Coppers low thermal expansion, 40% less than zinc and lead, helps to prevent deterioration and failure. Also, coppers high melting point ensures that it will not creep or stretch as some other metals do.
On small gable roofs, thermal movement is relatively minor and usually is not an issue. On wide-span buildings over and when long panels are used, an allowance for thermal expansion may be necessary. This enables the roof to "float" over supporting substructures while remaining secure. | 0 | Metallurgy |
(AD 800/900–1450)
Utilitarian and ceremonial objects; objects of personal adornment
#Amapa, Nayarit
#Apatzingán, Michoacán
#Atoyac, Jalisco
#Cojumatlán, Michoacán
#Coyuca de Catalán, Guerrero
#Culiacán, Sinaloa
#Jiquilpan, Michoacán
#Peñitas, Nayarit
#Río Balsas, Guerrero
#Tancitaro, Michoacán
#Telpalcátepec, Michoacán
#Tepic, Nayarit
#Texmelincan, Guerrero
#Tuxcacuesco, Jalisco
#Tzintzuntzan, Michoacán
#Yestla, Guerrero
#Zacpu, Michoacán
#Zamora, Michoacán | 0 | Metallurgy |
The acetyltransferase activity and cellular location of PCAF are regulated through acetylation of PCAF itself. PCAF may be autoacetylated (acetylated by itself) or by p300. Acetylation leads to migration to the nucleus and enhances its acetyltransferase activity. PCAF interacts with and is deacetylated by HDAC3, leading to a reduction in PCAF acetyltransferase activity and cytoplasmic localisation. | 1 | Gene expression + Signal Transduction |
If chloride ions have penetrated beyond the surface more rigorous treatment is required.
This typically involves soaking in acetone to displace any water in the specimen. Then soaking in a benzotriazole (BTA)–ethanol solution to chelate the copper and make it unreactive. Pits and holes may be filled with zinc powder, which is then painted over with shellac coloured to look like the specimen. | 0 | Metallurgy |
Non-Smad signaling proteins contribute to the responses of the TGF-β pathway in three ways. First, non-Smad signaling pathways phosphorylate the Smads. Second, Smads directly signal to other pathways by communicating directly with other signaling proteins, such as kinases. Finally, the TGF-β receptors directly phosphorylate non-Smad proteins. | 1 | Gene expression + Signal Transduction |
Sulfur concrete, sometimes named thioconcrete or sulfurcrete, is a composite construction material, composed mainly of sulfur and aggregate (generally a coarse aggregate made of gravel or crushed rocks and a fine aggregate such as sand). Cement and water, important compounds in normal concrete, are not part of sulfur concrete. The concrete is heated above the melting point of elemental sulfur () at ca. in a ratio of between 12% and 25% sulfur, the rest being aggregate.
Low-volatility (i.e., with a high boiling point) organic admixtures (sulfur modifiers), such as dicyclopentadiene (DCPD), styrene, turpentine, or furfural, are also added to the molten sulfur to inhibit its crystallization and to stabilize its polymeric structure after solidification.
In the absence of modifying agents, elemental sulfur crystallizes in its most stable allotropic (polymorphic) crystal phase at room temperature. With the addition of some modifying agents, elemental sulfur forms a copolymer (linear chains with styrene, cross-linking structure with DCPD) and remains plastic.
Sulfur concrete then achieves high mechanical strength within of cooling. It does not require a prolonged curing period like conventional cement concrete, which after setting (a few hours) must still harden to reach its expected nominal strength at 28 days. The rate of hardening of sulfur concrete depends on its cooling rate and also on the nature and concentration of modifying agents (cross-linking process). Its hardening is governed by the fairly rapid liquid/solid state change and associated phase transition processes (the added modifiers maintaining the plastic state while avoiding its recrystallization). It is a thermoplastic material whose physical state depends on temperature. It can be recycled and reshaped in a reversible way, simply by remelting it at high temperature.
A sulfur concrete patent was already registered in 1900 by McKay. Sulfur concrete was studied in the 1920s and 1930s and received renewed interest in the 1970s because of the accumulation of large quantities of sulfur as a by-product of the hydrodesulfurization process of oil and gas production and its low cost. | 0 | Metallurgy |
Earl Sutherland of Vanderbilt University won a Nobel Prize in Physiology or Medicine in 1971 "for his discoveries concerning the mechanisms of the action of hormones", especially epinephrine, via second messengers (such as cyclic adenosine monophosphate, cyclic AMP). | 1 | Gene expression + Signal Transduction |
Several sets of data can be collected during the experimental process of smelting including fuel consumption rates, the effects of variation in furnace airflow,
temperatures, production time, and chemical composition. | 0 | Metallurgy |
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