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Martensite is formed in carbon steels by the rapid cooling (quenching) of the austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite (FeC). Austenite is gamma-phase iron (γ-Fe), a solid solution of iron and alloying elements. As a result of the quenching, the face-centered cubic austenite transforms to a highly strained body-centered tetragonal form called martensite that is supersaturated with carbon. The shear deformations that result produce a large number of dislocations, which is a primary strengthening mechanism of steels. The highest hardness of a pearlitic steel is 400 Brinell, whereas martensite can achieve 700 Brinell.
The martensitic reaction begins during cooling when the austenite reaches the martensite start temperature (M), and the parent austenite becomes mechanically unstable. As the sample is quenched, an increasingly large percentage of the austenite transforms to martensite until the lower transformation temperature M is reached, at which time the transformation is completed.
For a eutectoid steel (0.76% C), between 6 and 10% of austenite, called retained austenite, will remain. The percentage of retained austenite increases from insignificant for less than 0.6% C steel, to 13% retained austenite at 0.95% C and 30–47% retained austenite for a 1.4% carbon steel. A very rapid quench is essential to create martensite. For a eutectoid carbon steel of thin section, if the quench starting at 750 °C and ending at 450 °C takes place in 0.7 seconds (a rate of 430 °C/s) no pearlite will form, and the steel will be martensitic with small amounts of retained austenite.
For steel with 0–0.6% carbon, the martensite has the appearance of lath and is called lath martensite. For steel with greater than 1% carbon, it will form a plate-like structure called plate martensite. Between those two percentages, the physical appearance of the grains is a mix of the two. The strength of the martensite is reduced as the amount of retained austenite grows. If the cooling rate is slower than the critical cooling rate, some amount of pearlite will form, starting at the grain boundaries where it will grow into the grains until the M temperature is reached, then the remaining austenite transforms into martensite at about half the speed of sound in steel.
In certain alloy steels, martensite can be formed by working the steel at M temperature by quenching to below M and then working by plastic deformations to reductions of cross section area between 20% and 40% of the original. The process produces dislocation densities up to 10/cm. The great number of dislocations, combined with precipitates that originate and pin the dislocations in place, produces a very hard steel. This property is frequently used in toughened ceramics like yttria-stabilized zirconia and in special steels like TRIP steels. Thus, martensite can be thermally induced or stress induced.
The growth of martensite phase requires very little thermal activation energy because the process is a diffusionless transformation, which results in the subtle but rapid rearrangement of atomic positions, and has been known to occur even at cryogenic temperatures. Martensite has a lower density than austenite, so that the martensitic transformation results in a relative change of volume. Of considerably greater importance than the volume change is the shear strain, which has a magnitude of about 0.26 and which determines the shape of the plates of martensite.
Martensite is not shown in the equilibrium phase diagram of the iron-carbon system because it is not an equilibrium phase. Equilibrium phases form by slow cooling rates that allow sufficient time for diffusion, whereas martensite is usually formed by very high cooling rates. Since chemical processes (the attainment of equilibrium) accelerate at higher temperature, martensite is easily destroyed by the application of heat. This process is called tempering. In some alloys, the effect is reduced by adding elements such as tungsten that interfere with cementite nucleation, but more often than not, the nucleation is allowed to proceed to relieve stresses. Since quenching can be difficult to control, many steels are quenched to produce an overabundance of martensite, then tempered to gradually reduce its concentration until the preferred structure for the intended application is achieved. The needle-like microstructure of martensite leads to brittle behavior of the material. Too much martensite leaves steel brittle; too little leaves it soft. | 0 | Metallurgy |
In DNA, regulation of gene expression normally happens at the level of RNA biosynthesis (transcription). It is accomplished through the sequence-specific binding of proteins (transcription factors) that activate or inhibit transcription. Transcription factors may act as activators, repressors, or both. Repressors often act by preventing RNA polymerase from forming a productive complex with the transcriptional initiation region (promoter), while activators facilitate formation of a productive complex. Furthermore, DNA motifs have been shown to be predictive of epigenomic modifications, suggesting that transcription factors play a role in regulating the epigenome.
In RNA, regulation may occur at the level of protein biosynthesis (translation), RNA cleavage, RNA splicing, or transcriptional termination. Regulatory sequences are frequently associated with messenger RNA (mRNA) molecules, where they are used to control mRNA biogenesis or translation. A variety of biological molecules may bind to the RNA to accomplish this regulation, including proteins (e.g., translational repressors and splicing factors), other RNA molecules (e.g., miRNA) and small molecules, in the case of riboswitches. | 1 | Gene expression + Signal Transduction |
There are six operational steam traction engines on the grounds, with a 1913 Buffalo-Pitts steamroller and a 1909 20 horsepower Case undergoing restoration. The operational steam tractors are an 1895 Russell & Co. 15-30 steam tractor, a 1902 Advance 16-30 steam tractor, a 1912 J.I. Case steam tractor, a 1920 Minneapolis steam tractor, and a 1916 15-30 Russell & Co. Most, if not all, of these tractors can be seen steaming around the grounds during the show days. | 0 | Metallurgy |
The csiD promoter (csiD) is essential for the expression of csiD(carbon starvation induced gene), ygaF and the gab genes. The csiD is activated exclusively under carbon starvation conditions and stationary phase during which cAMP accumulates in high concentrations in the cell. The binding of cAMP to the cAMP receptor protein(CRP) causes CRP to bind tightly to a specific DNA site in the csiD promoter, thus activating the transcription of genes downstream of the promoter.
The gabD exerts an additional control over the gabDTP region. The gabD is activated by σ inducing conditions such as hyperosmotic and acidic shifts besides starvation and stationary phase. The gabD promoter on the other hand, is σ dependent and is activated under nitrogen limitation. In nitrogen limiting conditions, the nitrogen regulator Nac binds to a site located just upstream of the promoter expressing the gab genes. The gab genes upon activation produce enzymes that degrade GABA to succinate. | 1 | Gene expression + Signal Transduction |
John Douglas Eshelby FRS (21 December 1916 – 10 December 1981) was a scientist in micromechanics. He made significant contributions to the fields of defect mechanics and micromechanics of inhomogeneous solids for fifty years, including important aspects of the controlling mechanisms of plastic deformation and fracture. | 0 | Metallurgy |
In die casting the most common defects are misruns and cold shuts. These defects can be caused by cold dies, low metal temperature, dirty metal, lack of venting, or excessive lubricant. Other possible defects are gas porosity, shrinkage porosity, hot tears, and flow marks. Flow marks are marks left on the surface of the casting due to poor gating, sharp corners or excessive lubricant. | 0 | Metallurgy |
Many different intermetallic compounds are formed during solidifying of solders and during their reactions with the soldered surfaces. The intermetallics form distinct phases, usually as inclusions in a ductile solid solution matrix, but also can form the matrix itself with metal inclusions or form crystalline matter with different intermetallics. Intermetallics are often hard and brittle. Finely distributed intermetallics in a ductile matrix yield a hard alloy while coarse structure gives a softer alloy. A range of intermetallics often forms between the metal and the solder, with increasing proportion of the metal; e.g. forming a structure of . Layers of intermetallics can form between the solder and the soldered material. These layers may cause mechanical reliability weakening and brittleness, increased electrical resistance, or electromigration and formation of voids. The gold-tin intermetallics layer is responsible for poor mechanical reliability of tin-soldered gold-plated surfaces where the gold plating did not completely dissolve in the solder.
Two processes play a role in a solder joint formation: interaction between the substrate and molten solder, and solid-state growth of intermetallic compounds. The base metal dissolves in the molten solder in an amount depending on its solubility in the solder. The active constituent of the solder reacts with the base metal with a rate dependent on the solubility of the active constituents in the base metal. The solid-state reactions are more complex – the formation of intermetallics can be inhibited by changing the composition of the base metal or the solder alloy, or by using a suitable barrier layer to inhibit diffusion of the metals.
Some example interactions include:
* Gold and palladium readily dissolve in solders. Copper and nickel tend to form intermetallic layers during normal soldering profiles. Indium forms intermetallics as well.
* Indium-gold intermetallics are brittle and occupy about 4 times more volume than the original gold. Bonding wires are especially susceptible to indium attack. Such intermetallic growth, together with thermal cycling, can lead to failure of the bonding wires.
* Copper plated with nickel and gold is often used. The thin gold layer facilitates good solderability of nickel as it protects the nickel from oxidation; the layer has to be thin enough to rapidly and completely dissolve so bare nickel is exposed to the solder.
* Lead-tin solder layers on copper leads can form copper-tin intermetallic layers; the solder alloy is then locally depleted of tin and form a lead-rich layer. The Sn-Cu intermetallics then can get exposed to oxidation, resulting in impaired solderability.
* – common on solder-copper interface, forms preferentially when excess of tin is available; in presence of nickel, compound can be formed
* – common on solder-copper interface, forms preferentially when excess of copper is available, more thermally stable than , often present when higher-temperature soldering occurred
* – common on solder-nickel interface
* – very slow formation
* Sn - at higher concentration of silver (over 3%) in tin forms platelets that can serve as crack initiation sites.
* – β-phase – brittle, forms at excess of tin. Detrimental to properties of tin-based solders to gold-plated layers.
* – forms on the boundary between gold and indium-lead solder, acts as a barrier against further dissolution of gold | 0 | Metallurgy |
The Late Bronze Age remains at Norşuntepe was heavily disturbed by later Iron Age activity, but some larger buildings have been excavated. | 0 | Metallurgy |
Involvement of mediator in various human diseases has been reviewed. Since inhibiting one interaction of a disease-causing signaling pathway with a subunit of mediator may not inhibit general transcription needed for normal function, mediator subunits are attractive candidates for therapeutic drugs. | 1 | Gene expression + Signal Transduction |
Ca ions are usually kept at nanomolar levels in the cytosol of plant cells, and act in a number of signal transduction pathways as second messengers. | 1 | Gene expression + Signal Transduction |
Copper came into use in the Aegean area near the end of the predynastic age of Egypt about 3500 BC. The earliest known implement is a flat celt, which was found on a Neolithic house-floor in the central court of the palace of Knossos in Crete, and is regarded as an Egyptian product. Bronze was not generally used until a thousand years or more later. Its first appearance is probably in the celts and dagger-blades of the Second City of Troy, where it is already the standard alloy of 10% tin. It was not established in Crete until the beginning of the Middle Minoan age (MMI, c. 2000 BC). The Copper Age began in northern Greece and Italy c. 2500 BC, much later than in Crete and Anatolia, and the mature Italian Bronze Age of Terremare culture coincided in time with the Late Aegean (Mycenaean) civilisation (1600–1000 BC). The original sources both of tin and copper in these regions are unknown. | 0 | Metallurgy |
In a 1987 article in New Scientist, Jack Harris reported that oxide jacking has caused significant damage to many historic structures in the United Kingdom, including St Pauls Cathedral, the British Museum and the Albert Memorial in London, Gloucester Cathedral, St. Margarets Church in King's Lynn, Winchester Cathedral, and Blackburn Cathedral.
Harris also wrote that oxide jacking also damaged the ancient Horses of Saint Mark on the exterior of St. Mark's Basilica in Venice. Expansive rusting of iron and steel bolts and reinforcements affected the structural integrity of the copper horse sculptures, which were relocated indoors and replaced with replicas. Poorly-designed early 20th-century renovations also led to oxide jacking damage to the Acropolis of Athens.
In the United States, rusting of iron pegs inserted into holes in the stone entrance stair in order to support handrails resulted in cracking of the steps at the Basilica of the Sacred Heart in Notre Dame, Indiana.
Oxide jacking damaged the terra cotta cornice on the Land Title Building in Philadelphia, designed in 1897 and expanded in 1902 by pioneer skyscraper architect Daniel Burnham. The Land Title complex, with its two interconnected towers, is on the National Register of Historic Places. By 1922, experts on architectural terra cotta were warning that the rusting of embedded iron fasteners could cause decorative building components to fail. This 1902 cornice is nearly high, projects from the facade of the building and is long. The cornice was stabilized, steel anchors subject to rusting were replaced with new stainless steel anchors, and the cornice was completely renovated. The project was completed in 1991.
Flooding in 2007 damaged the modernist Farnsworth House in Plano, Illinois, designed in 1945 by Ludwig Mies van der Rohe, and now owned by the National Trust for Historic Preservation. Among the damage discovered by an architect inspecting the house in 2007 was oxide jacking at the corners of the house's steel framework. The house flooded again in 2008. | 0 | Metallurgy |
In many cases, the splicing process can create a range of unique proteins by varying the exon composition of the same mRNA. This phenomenon is then called alternative splicing. Alternative splicing can occur in many ways. Exons can be extended or skipped, or introns can be retained. It is estimated that 95% of transcripts from multiexon genes undergo alternative splicing, some instances of which occur in a tissue-specific manner and/or under specific cellular conditions. Development of high throughput mRNA sequencing technology can help quantify the expression levels of alternatively spliced isoforms. Differential expression levels across tissues and cell lineages allowed computational approaches to be developed to predict the functions of these isoforms.
Given this complexity, alternative splicing of pre-mRNA transcripts is regulated by a system of trans-acting proteins (activators and repressors) that bind to cis-acting sites or "elements" (enhancers and silencers) on the pre-mRNA transcript itself. These proteins and their respective binding elements promote or reduce the usage of a particular splice site. The binding specificity comes from the sequence and structure of the cis-elements, e.g. in HIV-1 there are many donor and acceptor splice sites. Among the various splice sites, ssA7, which is 3' acceptor site, folds into three stem loop structures, i.e. Intronic splicing silencer (ISS), Exonic splicing enhancer (ESE), and Exonic splicing silencer (ESSE3). Solution structure of Intronic splicing silencer and its interaction to host protein hnRNPA1 give insight into specific recognition. However, adding to the complexity of alternative splicing, it is noted that the effects of regulatory factors are many times position-dependent. For example, a splicing factor that serves as a splicing activator when bound to an intronic enhancer element may serve as a repressor when bound to its splicing element in the context of an exon, and vice versa. In addition to the position-dependent effects of enhancer and silencer elements, the location of the branchpoint (i.e., distance upstream of the nearest 3’ acceptor site) also affects splicing. The secondary structure of the pre-mRNA transcript also plays a role in regulating splicing, such as by bringing together splicing elements or by masking a sequence that would otherwise serve as a binding element for a splicing factor. | 1 | Gene expression + Signal Transduction |
Chromatin remodeling is the dynamic modification of chromatin architecture to allow access of condensed genomic DNA to the regulatory transcription machinery proteins, and thereby control gene expression. Such remodeling is principally carried out by 1) covalent histone modifications by specific enzymes, e.g., histone acetyltransferases (HATs), deacetylases, methyltransferases, and kinases, and 2) ATP-dependent chromatin remodeling complexes which either move, eject or restructure nucleosomes. Besides actively regulating gene expression, dynamic remodeling of chromatin imparts an epigenetic regulatory role in several key biological processes, egg cells DNA replication and repair; apoptosis; chromosome segregation as well as development and pluripotency. Aberrations in chromatin remodeling proteins are found to be associated with human diseases, including cancer. Targeting chromatin remodeling pathways is currently evolving as a major therapeutic strategy in the treatment of several cancers. | 1 | Gene expression + Signal Transduction |
*TXN2 NM_012473
*TXNDC11 NM_015914
*TXNDC12 NM_015913
*TXNDC15 NM_024715
*TXNDC17 NM_032731
*TXNDC9 NM_005783
*TXNL1 NM_004786
*TXNL4A NM_006701
*TXNL4B NM_017853
*TXNRD1 NM_003330 | 1 | Gene expression + Signal Transduction |
Located in the cell nucleus, the microprocessor complex cleaves primary miRNA (pri-miRNA) into precursor miRNA (pre-miRNA). Its two subunits have been determined as necessary and sufficient for the mediation of the development of miRNAs from the pri-miRNAs. These molecules of around 70 nucleotides contain a stem-loop or hairpin structure. Pri-miRNA substrates can be derived either from non-coding RNA genes or from introns. In the latter case, there is evidence that the microprocessor complex interacts with the spliceosome and that the pri-miRNA processing occurs prior to splicing.
Microprocessor cleavage of pri-miRNAs typically occurs co-transcriptionally and leaves a characteristic RNase III single-stranded overhang of 2-3 nucleotides, which serves as a recognition element for the transport protein exportin-5. Pre-miRNAs are exported from the nucleus to the cytoplasm in a RanGTP-dependent manner and are further processed, typically by the endoribonuclease enzyme Dicer.
Hemin allows for the increased processing of pri-miRNAs through an induced conformational change of the DGCR8 subunit, and also enhances DGCR8's binding specificity for RNA. DGCR8 recognizes the junctions between hairpin structures and single-stranded RNA and serves to orient Drosha to cleave around 11 nucleotides away from the junctions, and remains in contact with the pri-miRNAs following cleavage and dissociation of Drosha.
Although the large majority of miRNAs undergo processing by microprocessor, a small number of exceptions called mirtrons have been described; these are very small introns which, after splicing, have the appropriate size and stem-loop structure to serve as a pre-miRNA. The processing pathways for microRNA and for exogenously derived small interfering RNA converge at the point of Dicer processing and are largely identical downstream. Broadly defined, both pathways constitute RNAi. Microprocessor is also found to be involved in ribosomal biogenesis specifically in the removal of R-loops and activating transcription of ribosomal protein encoding genes. | 1 | Gene expression + Signal Transduction |
The four JAK family members are:
* Janus kinase 1 (JAK1)
* Janus kinase 2 (JAK2)
* Janus kinase 3 (JAK3)
* Tyrosine kinase 2 (TYK2)
Transgenic mice that do not express JAK1 have defective responses to some cytokines, such as interferon-gamma. JAK1 and JAK2 are involved in type II interferon (interferon-gamma) signalling, whereas JAK1 and TYK2 are involved in type I interferon signalling. Mice that do not express TYK2 have defective natural killer cell function. | 1 | Gene expression + Signal Transduction |
Sensitization refers to the precipitation of carbides at grain boundaries in a stainless steel or alloy, causing the steel or alloy to be susceptible to intergranular corrosion or intergranular stress corrosion cracking.
Certain alloys when exposed to a temperature characterized as a sensitizing temperature become particularly susceptible to intergranular corrosion. In a corrosive atmosphere, the grain interfaces of these sensitized alloys become very reactive and intergranular corrosion results. This is characterized by a localized attack at and adjacent to grain boundaries with relatively little corrosion of the grains themselves. The alloy disintegrates (grains fall out) and/or loses its strength.
The photos show the typical microstructure of a normalized (unsensitized) type 304 stainless steel and a heavily sensitized steel. The samples have been polished and etched before taking the photos, and the sensitized areas show as wide, dark lines where the etching fluid has caused corrosion. The dark lines consist of carbides and corrosion products.
Intergranular corrosion is generally considered to be caused by the segregation of impurities at the grain boundaries or by enrichment or depletion of one of the alloying elements in the grain boundary areas. Thus in certain aluminium alloys, small amounts of iron have been shown to segregate in the grain boundaries and cause intergranular corrosion. Also, it has been shown that the zinc content of a brass is higher at the grain boundaries and subject to such corrosion. High-strength aluminium alloys such as the Duralumin-type alloys (Al-Cu) which depend upon precipitated phases for strengthening are susceptible to intergranular corrosion following sensitization at temperatures of about 120 °C. Nickel-rich alloys such as Inconel 600 and Incoloy 800 show similar susceptibility. Die-cast zinc alloys containing aluminum exhibit intergranular corrosion by steam in a marine atmosphere. Cr-Mn and Cr-Mn-Ni steels are also susceptible to intergranular corrosion following sensitization in the temperature range of 420 °C–850 °C. In the case of the austenitic stainless steels, when these steels are sensitized by being heated in the temperature range of about 520 °C to 800 °C, depletion of chromium in the grain boundary region occurs, resulting in susceptibility to intergranular corrosion. Such sensitization of austenitic stainless steels can readily occur because of temperature service requirements, as in steam generators, or as a result of subsequent welding of the formed structure.
Several methods have been used to control or minimize the intergranular corrosion of susceptible alloys, particularly of the austenitic stainless steels. For example, a high-temperature solution heat treatment, commonly termed solution-annealing, quench-annealing or solution-quenching, has been used. The alloy is heated to a temperature of about 1,060 °C to 1,120 °C and then water quenched. This method is generally unsuitable for treating large assemblies, and also ineffective where welding is subsequently used for making repairs or for attaching other structures.
Another control technique for preventing intergranular corrosion involves incorporating strong carbide formers or stabilizing elements such as niobium or titanium in the stainless steels. Such elements have a much greater affinity for carbon than does chromium; carbide formation with these elements reduces the carbon available in the alloy for formation of chromium carbides. Such a stabilized titanium-bearing austenitic chromium-nickel-copper stainless steel is shown in U.S. Pat. No. 3,562,781. Or the stainless steel may initially be reduced in carbon content below 0.03 percent so that insufficient carbon is provided for carbide formation. These techniques are expensive and only partially effective since sensitization may occur with time. The low-carbon steels also frequently exhibit lower strengths at high temperatures. | 0 | Metallurgy |
Prokaryotes use one type of RNA polymerase, transcribing mRNAs that code for more than one type of protein. Transcription, translation and mRNA degradation all happen simultaneously. Transcription termination is essential to define boundaries in transcriptional units, a function necessary to maintain the integrity of the strands and provide quality control. Termination in E. coli may be Rho dependent, utilizing Rho factor, or Rho independent, also known as intrinsic termination. Although most operons in DNA are Rho independent, Rho dependent termination is also essential to maintain correct transcription.
ρ factor
The Rho protein is an RNA translocase that recognizes a cytosine-rich region of the elongating mRNA, but the exact features of the recognized sequences and how the cleaving takes place remain unknown. Rho forms a ring-shaped hexamer and advances along the mRNA, hydrolyzing ATP toward RNA polymerase (5 to 3 with respect to the mRNA). When the Rho protein reaches the RNA polymerase complex, transcription is terminated by dissociation of the RNA polymerase from the DNA. The structure and activity of the Rho protein is similar to that of the F subunit of ATP synthase, supporting the theory that the two share an evolutionary link.
Rho factor is widely present in different bacterial sequences and is responsible for the genetic polarity in E. coli. It works as a sensor of translational status, inhibiting non-productive transcriptions, suppressing antisense transcriptions and resolving conflicts that happen between transcription and replication. The process of termination by Rho factor is regulated by attenuation and antitermination mechanisms, competing with elongation factors for overlapping utilization sites (ruts and nuts), and depends on how fast Rho can move during the transcription to catch up with the RNA polymerase and activate the termination process.
Inhibition of Rho dependent termination by bicyclomycin is used to treat bacterial infections. The use of this mechanism along with other classes of antibiotics is being studied as a way to address antibiotic resistance, by suppressing the protective factors in RNA transcription while working in synergy with other inhibitors of gene expression such as tetracycline or rifampicin. | 1 | Gene expression + Signal Transduction |
Copper tubes are made from the large billets of copper that are gradually worked and drawn down to the required size. As the tubes are drawn they are heat treated to produce the correct mechanical properties. The organic oils and greases used to lubricate the tubes during the drawing processes are broken down during the heat treatment and gradually coat the tube with a film of carbon. If the carbon is left in the bore of the tube then it disrupts the formation of the protective scale and allows the initiation of pits in the wall. The presence of deleterious films, such as carbon, has been prohibited by the British Standards in copper tubes since 1969. All copper tubes for water service are treated, usually by sand (or other nonferrous medium) blasting or acid pickling, to remove any films produced during manufacture with the result that Type 1 pitting initiated by carbon films is now very rare. | 0 | Metallurgy |
Olfactory receptor gene ([https://senselab.med.yale.edu/ordb/ OR]) is normally expressed in human and mouse olfactory tissue with a main function as odorant receptor for the detection of odorants. Individuals with a defect in this gene have disorders of taste and smell. It has been reported that ORs is also expressed on sperms and testis with special emphasis in a manner of ectopic expression. In a study, researchers identified ectopic expression of OR genes in non-olfactory tissues in the mouse model by measuring transcript levels. Here they found relatively low OR gene expression compared to the olfactory tissue, which result indicates that the OR gene in other tissue have no extra function, but they suggest that there is a possibility that small OR subsets can have functional roles in different tissue. | 1 | Gene expression + Signal Transduction |
Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake disks, as they are able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These brake disks are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, the McLaren P1, Bentley, Ferrari, Lamborghini and some specific high-performance Audi cars. Silicon carbide is also used in a sintered form for diesel particulate filters. It is also used as an oil additive to reduce friction, emissions, and harmonics. | 0 | Metallurgy |
Hydrolysis of GTP bound to an (active) G domain-GTPase leads to deactivation of the signaling/timer function of the enzyme. The hydrolysis of the third (γ) phosphate of GTP to create guanosine diphosphate (GDP) and P, inorganic phosphate, occurs by the S2 mechanism (see nucleophilic substitution) via a pentacoordinate transition state and is dependent on the presence of a magnesium ion Mg.
GTPase activity serves as the shutoff mechanism for the signaling roles of GTPases by returning the active, GTP-bound protein to the inactive, GDP-bound state. Most "GTPases" have functional GTPase activity, allowing them to remain active (that is, bound to GTP) only for a short time before deactivating themselves by converting bound GTP to bound GDP. However, many GTPases also use accessory proteins named GTPase-activating proteins or GAPs to accelerate their GTPase activity. This further limits the active lifetime of signaling GTPases. Some GTPases have little to no intrinsic GTPase activity, and are entirely dependent on GAP proteins for deactivation (such as the ADP-ribosylation factor or ARF family of small GTP-binding proteins that are involved in vesicle-mediated transport within cells).
To become activated, GTPases must bind to GTP. Since mechanisms to convert bound GDP directly into GTP are unknown, the inactive GTPases are induced to release bound GDP by the action of distinct regulatory proteins called guanine nucleotide exchange factors or GEFs. The nucleotide-free GTPase protein quickly rebinds GTP, which is in far excess in healthy cells over GDP, allowing the GTPase to enter the active conformation state and promote its effects on the cell. For many GTPases, activation of GEFs is the primary control mechanism in the stimulation of the GTPase signaling functions, although GAPs also play an important role. For heterotrimeric G proteins and many small GTP-binding proteins, GEF activity is stimulated by cell surface receptors in response to signals outside the cell (for heterotrimeric G proteins, the G protein-coupled receptors are themselves GEFs, while for receptor-activated small GTPases their GEFs are distinct from cell surface receptors).
Some GTPases also bind to accessory proteins called guanine nucleotide dissociation inhibitors or GDIs that stabilize the inactive, GDP-bound state.
The amount of active GTPase can be changed in several ways:
# Acceleration of GDP dissociation by GEFs speeds up the accumulation of active GTPase.
# Inhibition of GDP dissociation by guanine nucleotide dissociation inhibitors (GDIs) slows down accumulation of active GTPase.
# Acceleration of GTP hydrolysis by GAPs reduces the amount of active GTPase.
# Artificial GTP analogues like GTP-γ-S, β,γ-methylene-GTP, and β,γ-imino-GTP that cannot be hydrolyzed can lock the GTPase in its active state.
# Mutations (such as those that reduce the intrinsic GTP hydrolysis rate) can lock the GTPase in the active state, and such mutations in the small GTPase Ras are particularly common in some forms of cancer. | 1 | Gene expression + Signal Transduction |
* Cholera toxin is an AB toxin that has five B subunints and one A subunit. The toxin acts by the following mechanism: First, the B subunit ring of the cholera toxin binds to GM1 gangliosides on the surface of target cells. If a cell lacks GM1 the toxin most likely binds to other types of glycans, such as Lewis Y and Lewis X, attached to proteins instead of lipids. | 1 | Gene expression + Signal Transduction |
In the United States, the General Mining Law of 1872 gave rights to explore and mine on public domain land; the original law did not require post-mining reclamation (Woody et al. 2011). Mined land reclamation requirements on federal land depended on state requirements until the passage of the Federal Land Policy and Management Act in 1976. Currently, mining on federal land must have a government-approved mining and reclamation plan before mining can start. Reclamation bonds are required. Mining on either federal, state, or private land is subject to the requirements of the Clean Air Act and the Clean Water Act.
One solution proposed to reclamation problems is the privatization of the land to be mined (Woody et al. 2011). | 0 | Metallurgy |
The zinc coating, when intact, prevents corrosive substances from reaching the underlying iron. Additional electroplating such as a chromate conversion coating may be applied to provide further surface passivation to the substrate material. | 0 | Metallurgy |
Compared with vertebrates, insects and crustaceans possess a number of structurally unusual hormones such as the juvenile hormone, a sesquiterpenoid. | 1 | Gene expression + Signal Transduction |
Cell-free production of proteins is performed in vitro using purified RNA polymerase, ribosomes, tRNA and ribonucleotides. These reagents may be produced by extraction from cells or from a cell-based expression system. Due to the low expression levels and high cost of cell-free systems, cell-based systems are more widely used. | 1 | Gene expression + Signal Transduction |
The phosphatome includes proteins that are structurally closely related to phosphatases but lack catalytic activity. These retain biological function, and may regulate pathways that involve active phosphatases, or bind to phosphorylated substrates without cleaving them. Examples include [https://www.ncbi.nlm.nih.gov/gene/6815 STYX], where the phosphatase domain has become a phospho-tyrosine binding domain, and [https://www.ncbi.nlm.nih.gov/gene/2580 GAK], whose inactive phosphatase domain instead binds phospholipids. | 1 | Gene expression + Signal Transduction |
The preferred method of iron production in Europe until the development of the puddling process in 1783–84. Cast iron development lagged in Europe because wrought iron was the desired product and the intermediate step of producing cast iron involved an expensive blast furnace and further refining of pig iron to cast iron, which then required a labor and capital intensive conversion to wrought iron.
Through a good portion of the Middle Ages, in Western Europe, iron was still being made by the working of iron blooms into wrought iron. Some of the earliest casting of iron in Europe occurred in Sweden, in two sites, Lapphyttan and Vinarhyttan, between 1150 and 1350. Some scholars have speculated the practice followed the Mongols across Russia to these sites, but there is no clear proof of this hypothesis, and it would certainly not explain the pre-Mongol datings of many of these iron-production centres. In any event, by the late 14th century, a market for cast iron goods began to form, as a demand developed for cast iron cannonballs. | 0 | Metallurgy |
The below list is not exhaustive, but here are some examples of popular cyclic corrosion test standards,
*[https://webstd.volvo.com/webstd/docs/1027,149 ACT 1] (Volvo)
*[https://webstd.volvo.com/webstd/docs/1027,1449 ACT 2] (Volvo)
*CETP 00.00-L-467 (Ford)
*D17 2028 (Renault)
*JASO M 609
*SAE J 2334
*VDA 621-415 | 0 | Metallurgy |
The steam engine was applied to power blast air, overcoming a shortage of water power in areas where coal and iron ore were located. This was first done at Coalbrookdale where a steam engine replaced a horse-powered pump in 1742. Such engines were used to pump water to a reservoir above the furnace. The first engines used to blow cylinders directly was supplied by Boulton and Watt to John Wilkinson's New Willey Furnace. This powered a cast iron blowing cylinder, which had been invented by his father Isaac Wilkinson. He patented such cylinders in 1736, to replace the leather bellows, which wore out quickly. Isaac was granted a second patent, also for blowing cylinders, in 1757. The steam engine and cast iron blowing cylinder led to a large increase in British iron production in the late 18th century. | 0 | Metallurgy |
Particular advantages of the powder technology include:
# Very high levels of purity and uniformity in starting materials
# Preservation of purity, due to the simpler subsequent fabrication process (fewer steps) that it makes possible
# Stabilization of the details of repetitive operations, by control of grain size during the input stages
# Absence of binding contact between segregated powder particles – or "inclusions" (called stringering) – as often occurs in melting processes
# No deformation needed to produce directional elongation of grains
# Capability to produce materials of controlled, uniform porosity.
# Capability to produce nearly net-shaped objects.
# Capability to produce materials which cannot be produced by any other technology.
# Capability to fabricate high-strength material like turbine blades.
# After sintering the mechanical strength to handling becomes higher.
The literature contains many references on sintering dissimilar materials to produce solid/solid-phase compounds or solid/melt mixtures at the processing stage. Almost any substance can be obtained in powder form, through either chemical, mechanical or physical processes, so basically any material can be obtained through sintering. When pure elements are sintered, the leftover powder is still pure, so it can be recycled. | 0 | Metallurgy |
The International Institute of Welding Technology IIW published the Guideline "Recommendations for the HFMI Treatment" in October 2016. An overview of higher frequency hammers (HFMI) is presented, and recommendations for the correct application of the method and quantitative measurements for quality assurance the guideline provides the basis for measurements of HFMI improved welded joints on the basis of all known stress calculation concepts.
In numerous experiments at various institutes and universities an 80 to 100 percent increase of fatigue strength and a 5 – to 15-fold increase in weld-life could be demonstrated. The most extensive research project was from 2006 to 2009 "REFRESH – life extension of existing and new welded steel structures (P702). In this research project, the HiFIT device was developed and made ready for production. This report is available in book form at the FOSTA (Forschungsvereinigung Stahlanwendung e.V.) and can be ordered under the number . The book contains detailed scientific verifications and validations. | 0 | Metallurgy |
The identification of the genetic basis for the causative agent of a disease can be an important component of understanding its effects and spread. Location and content of structural genes can elucidate the evolution of virulence, as well as provide necessary information for treatment. Likewise understanding the specific changes in structural gene sequences underlying a gain or loss of virulence aids in understanding the mechanism by which diseases affect their hosts.
For example, Yersinia pestis (the bubonic plague) was found to carry several virulence and inflammation-related structural genes on plasmids. Likewise, the structural gene responsible for tetanus was determined to be carried on a plasmid as well. Diphtheria is caused by a bacterium, but only after that bacterium has been infected by a bacteriophage carrying the structural genes for the toxin.
In Herpes simplex virus, the structural gene sequence responsible for virulence was found in two locations in the genome despite only one location actually producing the viral gene product. This was hypothesized to serve as a potential mechanism for strains to regain virulence if lost through mutation.
Understanding the specific changes in structural genes underlying a gain or loss of virulence is a necessary step in the formation of specific treatments, as well the study of possible medicinal uses of toxins. | 1 | Gene expression + Signal Transduction |
In genetics, a master regulator gene is a regulator gene at the top of a gene regulation hierarchy, particularly in regulatory pathways related to cell fate and differentiation. | 1 | Gene expression + Signal Transduction |
The principal manuscripts are:
* The Lucca MS, Lucca, Biblioteca Capitolare Feliniana, Codex 490, the oldest witness, c. 800.
* The Sélestat MS, Sélestat, Bibliothèque Humaniste, MS 17. A very full yet old witness, early ninth century.
* The Codex Matritensis (Madrid codex), Madrid, Biblioteca Nacional, MS A.16 (Was: MS A.19), c. 1130.
* The Phillipps-Corning Manuscript, Corning Museum of Glass, MS 5, late twelfth century.
These are simply among the fullest witnesses - there are dozens more that preserve extracts. | 0 | Metallurgy |
*MCM3AP possibly a primase
*XRCC5 NM_021141 Ku80
*XRCC6 NM_001469 Homo sapiens thyroid autoantigen: Single-stranded DNA-dependent ATP-dependent helicase. Has a role in chromosome translocation. | 1 | Gene expression + Signal Transduction |
A gene product is the biochemical material, either RNA or protein, resulting from expression of a gene. A measurement of the amount of gene product is sometimes used to infer how active a gene is. Abnormal amounts of gene product can be correlated with disease-causing alleles, such as the overactivity of oncogenes which can cause cancer.
A gene is defined as "a hereditary unit of DNA that is required to produce a functional product". Regulatory elements include:
* Promoter region
* TATA box
* Polyadenylation sequences
* Enhancers
These elements work in combination with the open reading frame to create a functional product. This product may be transcribed and be functional as RNA or is translated from mRNA to a protein to be functional in the cell. | 1 | Gene expression + Signal Transduction |
Single nucleotide polymorphisms (SNPs) in TCF7L2 gene have shown an increase in susceptibility to schizophrenia in Arab, European and Chinese Han populations. In the Chinese Han population, SNP rs12573128 in TCF7L2 is the variant that was associated with an increase in schizophrenia risk. This marker is used as a pre-diagnostic marker for schizophrenia. TCF7L2 has also been reported as a risk gene in autism spectrum disorder and has been linked to it in recent large-scale genetic studies.
The mechanism behind TCF7L2s involvement in the emergence of neurodevelopmental disorders is not fully understood, as there have been few studies characterizing its role in brain development in detail. It was shown that during embryogenesis TCF7L2 is involved in the development of fish-specific habenula asymmetry in Danio rerio, and that the dominant negative TCF7L2 isoform influences cephalic separation in the embryo by inhibiting the posteriorizing effect of the Wnt pathway. It was also shown that in Tcf7l2' knockout mice the number of proliferating cells in cortical neural progenitor cells is reduced. In contrast, no such effect was found in the midbrain.
More recently it was shown that TCF7L2 plays a crucial role in both the embryonic development and postnatal maturation of the thalamus through direct and indirect regulation of many genes previously reported to be important for both processes. In late gestation TCF7L2 regulates the expression of many thalamus-enriched transcription factors (e.g. Foxp2, Rora, Mef2a, Lef1, Prox1), axon guidance molecules (e.g. Epha1, Epha4, Ntng1, Epha8) and cell adhesion molecules (e.g. Cdh6, Cdh8, Cdhr1). Accordingly, a total knockout of Tcf7l2 in mice leads to improper growth of thalamocortical axons, changed anatomy and improper sorting of the cells in the thalamo-habenular region. In the early postnaral period TCF7L2 starts to regulate the expression of many genes necessary for the acquisition of characteristic excitability patterns in the thalamus, mainly ion channels, neurotransmitters and their receptors and synaptic vescicle proteins (e.g. Cacna1g, Kcnc2, Slc17a7, Grin2b), and an early postnatal knockout of Tcf7l2 in mouse thalamus leads to significant reduction in the number and frequency of action potentials generated by the thalamocortical neurons. The mechanism that leads to the change in TCF7L2 target genes between gestation and early postnatal period is unknown. It is likely that a perinatal change in the proportion of TCF7L2 isoforms expressed in the thalamus is partially responsible. Abnormalities in the anatomy of the thalamus and the activity of its connections to the cerebral cortex are frequently detected in patients with schizophrenia and autism. Such abnormalities could arise from developmental aberrations in patients with unfavorable mutations of TCF7L2, further strengthening the link between TCF7L2 and neurodevelopmental disorders. | 1 | Gene expression + Signal Transduction |
In the 16th century, heap leaching became commonly used to extract copper as well as saltpeter, from organic matter. Primarily used in Germany and Spain, pyrite would be brought to the surface and left out in the open. The pyrite would be set outside for months at a time, where rain and air exposure would lead to chemical weathering. A solution containing copper sulfide would be collected in a basin, then precipitated in a process called cementation, resulting in metallic copper. Heap leaching, in this natural chemical-free form, was further developed to obtain different, more economically viable, types of ore. This was done by incorporating chemical lixiviation, which applies more chemical manipulation and technique to heap leaching.
From 1767-1867, the production of potash in Quebec became an important industry to supply France's glass and soap manufacturers. Potash was most frequently made from the ash remains of wood-burning stoves and fireplaces, which were agitated with water and filtered. Once evaporated, the remains would be potash. 400 tons of hardwood would be required to burn to yield one ton of potash.
In 1858, Adolf von Patera, an Austrian metallurgist, utilized lixiviation to separate soluble and insoluble compounds from silver in an aqueous solution.The technique of Patera's lixiviation was further developed by American E. H. Russell around 1884, creating the "Russell Process". In 1887, when the cyanidation process was patented in England, it began to be incorporated into the existing leaching process, creating the more specific cyanide leaching.
In 1887, when the cyanidation process was patented in England, it began to phase out the existing Russell Process. Cyanidation was much more efficient and had a recovery rate of up to 90%.
Leading up to World War I, many new ideas for leaching processes were experimented. This included using ammonia solutions for copper sulfides, and nitric acid for leaching sulfide ores. Most of these ideas were phased out into obscurity due to the high cost of the leaching agents required. | 0 | Metallurgy |
TGFB1I1 has been shown to interact with:
* Androgen receptor,
* Dopamine transporter
* Hsp27,
* PTK2B,
* PTK2, and
* PTPN12. | 1 | Gene expression + Signal Transduction |
While the mechanism by which survivin may regulate cell mitosis and cytokinesis is not known, the observations made on its localization during mitosis suggests strongly that it is involved in some way in the cytokinetic process.
Proliferating Daoy cells were placed on a glass coverslip, fixed and stained with fluorescent antibodies for survivin and alpha-tubulin. Immunoflourescence using confocal microscopy was used to look at the localization of survivin and tubulin during the cell-cycle to look for any patterns of survivin expression. Survivin was absent in interphase, but present in the G2-M phase.
During the different stages of mitosis, one could see that survivin follows a certain localization pattern. At prophase and metaphase, survivin is mainly nuclear in location. During prophase, as the chromatin condenses so that it is visible under the microscope, survivin starts to move to the centromeres. At prometaphase when the nuclear membrane dissociates and spindle microtubules cross over the nuclear region, survivin stays put at the centromeres. At metaphase, when the chromosomes align at the middle plate and are pulled with high tension to either pole by the kinetochore attachments, survivin then associates with the kinetochores. At anaphase as separation of the chromatids happens, the kinetochore microtubules shorten as the chromosomes move towards to the spindle poles and survivin also moves along to the midplate. Survivin thus accumulates at the midplate at telophase. Finally, survivin localizes to the midbody at the cleavage furrow. | 1 | Gene expression + Signal Transduction |
The following excerpt from Takashi Fujii (1960) summarises well the limits of the Vegard’s law in the context of mineralogy and also makes the link with the Gladstone–Dale equation: | 0 | Metallurgy |
Dislocations require proper lattice ordering to move through a material. At grain boundaries, there is a lattice mismatch, and every atom that lies on the boundary is uncoordinated. This stops dislocations that encounter the boundary from moving. | 0 | Metallurgy |
The strength of a material is dependent on how easily dislocations in its crystal lattice can be propagated. These dislocations create stress fields within the material depending on their character. When solute atoms are introduced, local stress fields are formed that interact with those of the dislocations, impeding their motion and causing an increase in the yield stress of the material, which means an increase in strength of the material. This gain is a result of both lattice distortion and the modulus effect.
When solute and solvent atoms differ in size, local stress fields are created that can attract or repel dislocations in their vicinity. This is known as the size effect. By relieving tensile or compressive strain in the lattice, the solute size mismatch can put the dislocation in a lower energy state. In substitutional solid solutions, these stress fields are spherically symmetric, meaning they have no shear stress component. As such, substitutional solute atoms do not interact with the shear stress fields characteristic of screw dislocations. Conversely, in interstitial solid solutions, solute atoms cause a tetragonal distortion, generating a shear field that can interact with edge, screw, and mixed dislocations. The attraction or repulsion of the dislocation to the solute atom depends on whether the atom sits above or below the slip plane. For example, consider an edge dislocation encountering a smaller solute atom above its slip plane. In this case, the interaction energy is negative, resulting in attraction of the dislocation to the solute. This is due to the reduced dislocation energy by the compressed volume lying above the dislocation core. If the solute atom were positioned below the slip plane, the dislocation would be repelled by the solute. However, the overall interaction energy between an edge dislocation and a smaller solute is negative because the dislocation spends more time at sites with attractive energy. This is also true for solute atom with size greater than the solvent atom. Thus, the interaction energy dictated by the size effect is generally negative.
The elastic modulus of the solute atom can also determine the extent of strengthening. For a “soft” solute with elastic modulus lower than that of the solvent, the interaction energy due to modulus mismatch (U) is negative, which reinforce the size interaction energy (U). In contrast, U is positive for a “hard” solute, which results in lower total interaction energy than a soft atom. Even though the interaction force is negative (attractive) in both cases when the dislocation is approaching the solute. The maximum force (F) necessary to tear dislocation away from the lowest energy state (i.e. the solute atom) is greater for the soft solute than the hard one. As a result, a soft solute will strengthen a crystal more than a hard solute due to the synergistic strengthening by combining both size and modulus effects.
The elastic interaction effects (i.e. size and modulus effects) dominate solid-solution strengthening for most crystalline materials. However, other effects, including charge and stacking fault effects, may also play a role. For ionic solids where electrostatic interaction dictates bond strength, charge effect is also important. For example, addition of divalent ion to a monovalent material may strengthen the electrostatic interaction between the solute and the charged matrix atoms that comprise a dislocation. However, this strengthening is to a less extent than the elastic strengthening effects. For materials containing a higher density of stacking faults, solute atoms may interact with the stacking faults either attractively or repulsively. This lowers the stacking fault energy, leading to repulsion of the partial dislocations, which thus makes the material stronger.
Surface carburizing, or case hardening, is one example of solid solution strengthening in which the density of solute carbon atoms is increased close to the surface of the steel, resulting in a gradient of carbon atoms throughout the material. This provides superior mechanical properties to the surface of the steel without having to use a higher-cost material for the component. | 0 | Metallurgy |
SUI1 is a translation initiation factor that directs the ribosome to the translation start site, helped by eIF2 and the initiator Met-tRNA. SUI1 ensures that translation initiation commences from the correct start codon (usually AUG), by stabilizing the pre-initiation complex around the start codon. SUI1 promotes a high initiation fidelity for the AUG codon, discriminating against non-AUG codons.
In E. coli however, it seems that the SUI1 homolog YciH is an inhibitor of translation during stress instead. | 1 | Gene expression + Signal Transduction |
The invertebrate mitochondrial code ([https://www.ncbi.nlm.nih.gov/Taxonomy/Utils/wprintgc.cgi?chapter=tgencodes#SG5 translation table 5]) is a genetic code used by the mitochondrial genome of invertebrates. Mitochondria contain their own DNA and reproduce independently from their host cell. Variation in translation of the mitochondrial genetic code occurs when DNA codons result in non-standard amino acids has been identified in invertebrates, most notably arthropods. This variation has been helpful as a tool to improve upon the phylogenetic tree of invertebrates, like flatworms. | 1 | Gene expression + Signal Transduction |
Specific control of the lac genes depends on the availability of the substrate lactose to the bacterium. The proteins are not produced by the bacterium when lactose is unavailable as a carbon source.
The lac genes are organized into an operon; that is, they are oriented in the same direction immediately adjacent on the chromosome and are co-transcribed into a single polycistronic mRNA molecule. Transcription of all genes starts with the binding of the enzyme RNA polymerase (RNAP), a DNA-binding protein, which binds to a specific DNA binding site, the promoter, immediately upstream of the genes. Binding of RNA polymerase to the promoter is aided by the cAMP-bound catabolite activator protein (CAP, also known as the cAMP receptor protein). However, the lacI gene (regulatory gene for lac operon) produces a protein that blocks RNAP from binding to the operator of the operon. This protein can only be removed when allolactose binds to it, and inactivates it. The protein that is formed by the lacI gene is known as the lac repressor. The type of regulation that the lac operon undergoes is referred to as negative inducible, meaning that the gene is turned off by the regulatory factor (lac repressor) unless some molecule (lactose) is added. Once the repressor is removed, RNAP then proceeds to transcribe all three genes (lacZYA) into mRNA. Each of the three genes on the mRNA strand has its own Shine-Dalgarno sequence, so the genes are independently translated. The DNA sequence of the E. coli lac operon, the lacZYA mRNA, and the lacI genes are available from GenBank [https://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=146575 (view)].
The first control mechanism is the regulatory response to lactose, which uses an intracellular regulatory protein called the lactose repressor to hinder production of β-galactosidase in the absence of lactose. The lacI gene coding for the repressor lies nearby the lac operon and is always expressed (constitutive). If lactose is missing from the growth medium, the repressor binds very tightly to a short DNA sequence just downstream of the promoter near the beginning of lacZ called the lac operator. The repressor binding to the operator interferes with binding of RNAP to the promoter, and therefore mRNA encoding LacZ and LacY is only made at very low levels. When cells are grown in the presence of lactose, however, a lactose metabolite called allolactose, made from lactose by the product of the lacZ gene, binds to the repressor, causing an allosteric shift. Thus altered, the repressor is unable to bind to the operator, allowing RNAP to transcribe the lac genes and thereby leading to higher levels of the encoded proteins.
The second control mechanism is a response to glucose, which uses the catabolite activator protein (CAP) homodimer to greatly increase production of β-galactosidase in the absence of glucose. Cyclic adenosine monophosphate (cAMP) is a signal molecule whose prevalence is inversely proportional to that of glucose. It binds to the CAP, which in turn allows the CAP to bind to the CAP binding site (a 16 bp DNA sequence upstream of the promoter on the left in the diagram below, about 60 bp upstream of the transcription start site), which assists the RNAP in binding to the DNA. In the absence of glucose, the cAMP concentration is high and binding of CAP-cAMP to the DNA significantly increases the production of β-galactosidase, enabling the cell to hydrolyse lactose and release galactose and glucose.
More recently inducer exclusion was shown to block expression of the lac operon when glucose is present. Glucose is transported into the cell by the PEP-dependent phosphotransferase system. The phosphate group of phosphoenolpyruvate is transferred via a phosphorylation cascade consisting of the general PTS (phosphotransferase system) proteins HPr and EIA and the glucose-specific PTS proteins EIIA and EIIB, the cytoplasmic domain of the EII glucose transporter. Transport of glucose is accompanied by its phosphorylation by EIIB, draining the phosphate group from the other PTS proteins, including EIIA. The unphosphorylated form of EIIA binds to the lac permease and prevents it from bringing lactose into the cell. Therefore, if both glucose and lactose are present, the transport of glucose blocks the transport of the inducer of the lac operon. | 1 | Gene expression + Signal Transduction |
The 5 UTR of prokaryotes consists of the Shine–Dalgarno sequence (5-AGGAGGU-3'). This sequence is found 3-10 base pairs upstream from the initiation codon. The initiation codon is the start site of translation into protein. | 1 | Gene expression + Signal Transduction |
Certain gene deserts are heavy regulators, while others may be deleted without any effect. As a possible classification, gene deserts can be broken down into two subtypes: stable and variable. Stable gene deserts have fewer repeats and have relatively higher Guanine to Cytosine (GpC) content than observed in variable gene deserts.
Guanine and cytosine content is indicative of protein-coding functionality. For example, in a study on chromosomes 2 and 4, which have been linked to several genetic diseases, there were elevated GpC content in certain regions. Mutations in these GC-rich regions caused a variety of diseases, revealing the necessary integrity of these genes. High density CpG regions serve as regulatory regions for DNA methylation. Therefore, essential coding genes should be represented by high-CpG regions. In particular, regions with high GC content should tend to have high densities of genes that are devoted mainly to the essential housekeeping and tissue specific processes. These processes would require the most protein production to express functionality. Stable gene deserts, which have higher levels of GC content, should therefore contain the essential enhancer sequences. This could determine the conservatory functions of stable gene deserts.
On the other hand, approximately 80% of gene deserts have low GpC contents, indicating that they have very few essential genes. Thus, the majority of gene deserts are variable gene deserts, which may have alternate functions. One prevalent theory regarding the origins of gene deserts postulates that gene deserts are accumulations of essential genes that act as a distance. This may hold true, as given the low numbers of essential genes within them, these regions would have been less conserved. As a result, due to the prevalence of cytosine to thymine conversions, the [http://genome.sph.umich.edu/wiki/SNP_Call_Set_Properties most common SNP], would cause a gradual separation between the few essential genes within variable gene deserts. These essential sequences would have been maintained and conserved, leading to small regions of high density that regulate at a distance. GC content is therefore indication for the presence of coding or regulatory processes in DNA.
While stable gene deserts have higher GC content, this relative value is only an average. Within stable gene deserts, although the ends contain very high levels of GC content, the main bulk of the DNA contains even less GC content than observed in variable gene deserts. This indicates that there are very few highly conserved regions in stable gene deserts that do not recombine, or do so at very low rates. Given that the ends of the stable gene deserts have particularly high levels of GC contents, these sequences must be extremely conserved. This conservation may in turn cause the flanking genes to also have higher conservation rates. Thus, stable genes should be directly linked to at least one of their flanking genes and cannot be separated from coding sequences by recombination events. Most gene deserts appear to cluster in pairs around a small number of genes. This clustering creates long loci that have very low gene density; small regions with high numbers of genes are surrounded by long stretches of gene deserts, creating a low gene average. Therefore, the minimized probability of recombination events in these long loci creates syntenic blocks that are inherited together over time. These syntenic blocks can be conserved for very long periods of time, preventing loss of essential material, even while the distance between essential genes may grow in time.
Although this effect should theoretically be amplified through the even lower GC-content in variable gene deserts (thereby truly minimalizing gene density), the gene conservation rates in variable gene deserts are even lower than observed in stable gene deserts—in fact, the rate is far lower than the rest of the genome. A possible explanation for this phenomenon is that variable gene deserts may be recently evolved regions that have not yet been fixed into stable gene deserts. Therefore, shuffling may still occur before stabilizing regions within the variable gene deserts begin to cluster as whole units. There are a few exceptions to this minimal rate of conservation, as a few GC gene deserts are subjected to hypermethylation, which greatly reduces the accessibility to the DNA, thus effectively protecting the region from recombination. However, these occur rarely in observation.
Although stable and variable gene deserts differ in content and function, both wield conservatory abilities. It is possible that since most variable gene deserts have regulatory elements that can act at a distance, conservation of the entire gene desert into a sytenic locus would not have been necessary, so long as these regulatory elements themselves were conserved as units. Given the particularly low levels of GC content, the regulatory elements would therefore be in a minimal gene density situation as observed similarly in flanking stable gene deserts, with the same effect. Thus, both types of gene deserts serve to retain essential genes within the genome. | 1 | Gene expression + Signal Transduction |
The presynaptic bouton has an efficiently orchestrated process to fuse vesicles to the presynaptic membrane to release neurotransmitters and regenerate neurotransmitter vesicles. This process called the synaptic vesicle cycle maintains the number of vesicles in the presynaptic bouton and allows the synaptic terminal to be an autonomous unit. The cycle begins with (1) a region of the golgi apparatus is pinched off to form the synaptic vesicle and this vesicle is transported to the synaptic terminal. At the terminal (2) the vesicle is filled with neurotransmitter. (3) The vesicle is transported to the active zone and docked in close proximity to the plasma membrane. (4) During an action potential the vesicle is fused with the membrane, releases the neurotransmitter and allows the membrane proteins previously on the vesicle to diffuse to the periactive zone. (5) In the periactive zone the membrane proteins are sequestered and are endocytosed forming a clathrin coated vesicle. (6) The vesicle is then filled with neurotransmitter and is then transported back to the active zone.
The endocytosis mechanism is slower than the exocytosis mechanism. This means that in intense activity the vesicle in the terminal can become depleted and no longer available to be released. To help prevent the depletion of synaptic vesicles the increase in calcium during intense activity can activate calcineurin which dephosphorylate proteins involved in clathrin-mediated endocytosis. | 1 | Gene expression + Signal Transduction |
Non-systematic, less-recognized and often unverified syntheses of silicon carbide include:
* César-Mansuète Despretz's passing an electric current through a carbon rod embedded in sand (1849)
* Robert Sydney Marsden's dissolution of silica in molten silver in a graphite crucible (1881)
* Paul Schuetzenberger's heating of a mixture of silicon and silica in a graphite crucible (1881)
* Albert Colson's heating of silicon under a stream of ethylene (1882). | 0 | Metallurgy |
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, where it was one of the great enabling technologies of the 20th century. It has been described as "the single most important operation used for the recovery and upgrading of sulfide ores". The development of froth flotation has improved the recovery of valuable minerals, such as copper- and lead-bearing minerals. Along with mechanized mining, it has allowed the economic recovery of valuable metals from much lower-grade ore than previously. | 0 | Metallurgy |
The earliest surviving bimetallic strip was made by the eighteenth-century clockmaker John Harrison who is generally credited with its invention. He made it for his third marine chronometer (H3) of 1759 to compensate for temperature-induced changes in the balance spring. It should not be confused with the bimetallic mechanism for correcting for thermal expansion in his gridiron pendulum. His earliest examples had two individual metal strips joined by rivets but he also invented the later technique of directly fusing molten brass onto a steel substrate. A strip of this type was fitted to his last timekeeper, H5. Harrison's invention is recognized in the memorial to him in Westminster Abbey, England. | 0 | Metallurgy |
Flow-accelerated corrosion (FAC), also known as flow-assisted corrosion, is a corrosion mechanism in which a normally protective oxide layer on a metal surface dissolves in a fast flowing water. The underlying metal corrodes to re-create the oxide, and thus the metal loss continues.
By definition, the rate of FAC depends on the flow velocity. FAC often affects carbon steel piping carrying ultra-pure, deoxygenated water or wet steam. Stainless steel does not suffer from FAC. FAC of carbon steel halts in the presence of small amount of oxygen dissolved in water. FAC rates rapidly decrease with increasing water pH.
FAC has to be distinguished from erosion corrosion because the fundamental mechanisms for the two corrosion modes are different. FAC does not involve impingement of particles, bubbles, or cavitation which cause the mechanical (often crater-like) wear on the surface. By contrast to mechanical erosion, FAC involves dissolution of normally poorly soluble oxide by combined electrochemical, water chemistry and mass-transfer phenomena. Nevertheless, the terms FAC and erosion are sometimes used interchangeably because the actual mechanism may, in some cases, be unclear.
FAC was the cause of several high-profile accidents in power plants, for example, a rupture of a high-pressure condensate line in Virginia Power's Surry nuclear plant in 1986, that resulted in four fatalities and four injuries. | 0 | Metallurgy |
Slip bands or stretcher-strain marks are localized bands of plastic deformation in metals experiencing stresses. Formation of slip bands indicates a concentrated unidirectional slip on certain planes causing a stress concentration. Typically, slip bands induce surface steps (e.g., roughness due persistent slip bands during fatigue) and a stress concentration which can be a crack nucleation site. Slip bands extend until impinged by a boundary, and the generated stress from dislocations pile-up against that boundary will either stop or transmit the operating slip depending on its (mis)orientation.
Formation of slip bands under cyclic conditions is addressed as persistent slip bands (PSBs) where formation under monotonic condition is addressed as dislocation planar arrays (or simply slip-bands, see Slip bands in the absence of cyclic loading section). Slip-bands can be simply viewed as boundary sliding due to dislocation glide that lacks (the complexity of ) PSBs high plastic deformation localisation manifested by tongue- and ribbon-like extrusion. And, where PSBs normally studied with (effective) Burgers vector aligned with the extrusion plane because a PSB extends across the grain and exacerbates during fatigue; a monotonic slip-band has a Burger’s vector for propagation and another for plane extrusions both controlled by the conditions at the tip. | 0 | Metallurgy |
It was given a Royal Charter in 1975. In 1977 it became the sixteenth constituent of the •Council of Engineering Institutions, which became the Engineering Council in 1981. | 0 | Metallurgy |
Silver overlay is an electroplated coating of silver on a non-conductive surface such as porcelain or glass. Most techniques used to create silver overlay involve the use of special flux which contains silver and turpentine oil. This is then painted on the glass ornament as a design. After the painting is complete, the entire ornament is fired under relatively low heat, it is then cleaned after being quenched and cooled, then it is placed in a solution of silver. A low voltage current is run through the solution and the silver binds in the design, creating a permanent fusion of the silver with the glass.
A much older technique of overlay, which was commonly used in the Indian subcontinent since ancient times, involves the use of a silver sheet wrapped around the ornament and then the design beaten onto the sheet or it may be burnished. This technique renders the design silhouetted against a dark backdrop and was commonly called the Aftabi design technique. This technique of overlay predates the technique that is common today, but without the use of electroplating, it was a time consuming and tedious process, which could only be accomplished by skilled artisans. | 0 | Metallurgy |
As stated above, the STAT3-Ser/Hes3 signaling axis regulates the number of neural stem cells (as well as other cell types) in culture. This prompted experiments to determine if the same pathway can also regulate the number of naturally resident (endogenous) neural stem cells in the adult rodent brain. If so, this would generate a new experimental approach to study the effects of increasing the number of endogenous neural stem cells (eNSCs). For example, would this lead to the replacement of lost cells by newly generated cells from eNSCs? Or, could this lead to the rescue of damaged neurons in models of neurodegenerative disease, since eNSCs are known to produce factors that can protect injured neurons?
Various treatments that input into the STAT3-Ser/Hes3 signaling axis (Delta4, Angiopoietin 2, insulin, or a combined treatment consisting of all three factors and an inhibitor of JAK) induce the increase in numbers of endogenous neural stem cells as well as behavioral recovery in models of neurodegenerative disease. Several pieces of evidence suggest that in the adult brain, pharmacological activation of the STAT3-Ser/Hes3 signaling axis protects compromised neurons through increased neurotrophic support provided by activated neural stem cells / neural precursor cells, which can be identified by their expression of Hes3:
:* These treatments increase the number of Hes3+ cells by several-fold.
:* Hes3+ cells can be isolated and placed in culture where they exhibit stem cell properties.
:* In culture and in vivo, Hes3+ cells express Shh, which supports the survival of certain neurons [Hes3+ cells may also express other pro-survival factors, yet unidentified].
:* The distribution of Hes3+ cells in the adult brain is widespread and can be found in close physical proximity to different types of neurons.
:* Diverse treatments that converge to the STAT3-Ser/Hes3 signaling axis exert similar effects in the normal brain (increase in the number of Hes3+ cells) and in the compromised brain (increase in the number of Hes3+ cells, oppose neuronal death, and improve behavioral state).
:* Macrophage migration inhibitory factor stimulates this signaling pathway and promotes the survival of neural stem cells.
:* Mice genetically engineered to lack the Hes3 gene exhibit differences in the amount of myelin basic protein (a protein expressed on myelinating oligodendrocytes), relative to normal mice; Hes3-lacking mice also exhibit a different regulation of this protein after oligodendrocyte damage induced by the chemical cuprizone. | 1 | Gene expression + Signal Transduction |
Alternative U-to-C mRNA editing was first reported in WT1 (Wilms Tumor-1) transcripts, and non-classic G-A mRNA changes were first observed in HNRNPK (heterogeneous nuclear ribonucleoprotein K) transcripts in both malignant and normal colorectal samples. The latter changes were also later seen alongside non-classic U-to-C alterations in brain cell TPH2 (tryptophan hydroxylase 2) transcripts. Although the reverse amination might be the simplest explanation for U-to-C changes, transamination and transglycosylation mechanisms have been proposed for plant U-to-C editing events in mitochondrial transcripts. A recent study reported novel G-to-A mRNA changes in WT1 transcripts at two hotspots, proposing the APOBEC3A (apolipoprotein B mRNA editing enzyme, catalytic polypeptide 3A) as the enzyme implicated in this class of alternative mRNA editing. It was also shown that alternative mRNA changes were associated with canonical WT1 splicing variants, indicating their functional significance. | 1 | Gene expression + Signal Transduction |
Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature mRNA for translation. In many bacteria, the poly(A) tail promotes degradation of the mRNA. It, therefore, forms part of the larger process of gene expression.
The process of polyadenylation begins as the transcription of a gene terminates. The 3′-most segment of the newly made pre-mRNA is first cleaved off by a set of proteins; these proteins then synthesize the poly(A) tail at the RNA's 3′ end. In some genes these proteins add a poly(A) tail at one of several possible sites. Therefore, polyadenylation can produce more than one transcript from a single gene (alternative polyadenylation), similar to alternative splicing.
The poly(A) tail is important for the nuclear export, translation and stability of mRNA. The tail is shortened over time, and, when it is short enough, the mRNA is enzymatically degraded. However, in a few cell types, mRNAs with short poly(A) tails are stored for later activation by re-polyadenylation in the cytosol. In contrast, when polyadenylation occurs in bacteria, it promotes RNA degradation. This is also sometimes the case for eukaryotic non-coding RNAs.
mRNA molecules in both prokaryotes and eukaryotes have polyadenylated 3′-ends, with the prokaryotic poly(A) tails generally shorter and fewer mRNA molecules polyadenylated. | 1 | Gene expression + Signal Transduction |
Etching reveals and delineates grain boundaries and other microstructural features that are not apparent on the as-polished surface. The two most common types of etching in ceramography are selective chemical corrosion, and a thermal treatment that causes relief. As an example, alumina can be chemically etched by immersion in boiling concentrated phosphoric acid for 30–60 s, or thermally etched in a furnace for 20–40 min at in air. The plastic encapsulation must be removed before thermal etching. The alumina in Fig. 1 was thermally etched.
Alternatively, non-cubic ceramics can be prepared as thin sections, also known as petrography, for examination by polarized transmitted light microscopy. In this technique, the specimen is sawed to ~1 mm thick, glued to a microscope slide, and ground or sawed (e.g., by microtome) to a thickness (x) approaching 30 µm. A cover slip is glued onto the exposed surface. The adhesives, such as epoxy or Canada balsam resin, must have approximately the same refractive index (η ≈ 1.54) as glass. Most ceramics have a very small absorption coefficient (α ≈ 0.5 cm for alumina in Fig. 2) in the Beer–Lambert law below, and can be viewed in transmitted light. Cubic ceramics, e.g. yttria-stabilized zirconia and spinel, have the same refractive index in all crystallographic directions and appear, therefore, black when the microscope's polarizer is 90° out of phase with its analyzer.
: (Beer–Lambert eqn)
Ceramographic specimens are electrical insulators in most cases, and must be coated with a conductive ~10-nm layer of metal or carbon for electron microscopy, after polishing and etching. Gold or Au-Pd alloy from a sputter coater or evaporative coater also improves the reflection of visible light from the polished surface under a microscope, by the Fresnel formula below. Bare alumina (η ≈ 1.77, k ≈ 10) has a negligible extinction coefficient and reflects only 8% of the incident light from the microscope, as in Fig. 1. Gold-coated (η ≈ 0.82, k ≈ 1.59 @ λ = 500 nm) alumina reflects 44% in air, 39% in immersion oil.
: (Fresnel eqn).. | 0 | Metallurgy |
Archaeological evidence has not revealed metal smelting or alloying of metals by pre-Columbian native peoples north of the Rio Grande; however, they did use native copper extensively. | 0 | Metallurgy |
* A 32-inch diameter gas transmission pipeline, north of Natchitoches, Louisiana, belonging to the Tennessee Gas Pipeline exploded and burned from SCC on March 4, 1965, killing 17 people. At least 9 others were injured, and 7 homes 450 feet from the rupture were destroyed.
* SCC caused the catastrophic collapse of the Silver Bridge in December 1967, when an eyebar suspension bridge across the Ohio river at Point Pleasant, West Virginia, suddenly failed. The main chain joint failed and the entire structure fell into the river, killing 46 people who were traveling in vehicles across the bridge. Rust in the eyebar joint had caused a stress corrosion crack, which went critical as a result of high bridge loading and low temperature. The failure was exacerbated by a high level of residual stress in the eyebar. The disaster led to a nationwide reappraisal of bridges.
* USS Hartford submarine periscope: In 2009, the periscope of the submarine USS Hartford failed due to SCC. The periscope is used to provide a view of the surface while the submarine is submerged. The failure occurred when the periscope was extended through the hull of the submarine, causing seawater to enter the periscopes seal. The seawater caused SCC to occur in the periscopes steel support structure, which led to the periscope falling back into the submarine. Fortunately, there were no injuries, but the submarine had to be taken out of service for repairs.
* Trans-Alaska Pipeline: In 2001, a section of the Trans-Alaska Pipeline failed due to SCC. The pipeline is used to transport crude oil from the North Slope of Alaska to the Valdez Marine Terminal. The failure occurred when a 34-foot section of the pipeline ruptured, causing a spill of over 285,000 gallons of crude oil. The investigation into the failure found that SCC had occurred in the pipeline due to the presence of water and bacteria, which had created a corrosive environment.
* Aloha Airlines Flight 243: In 1988, Aloha Airlines Flight 243 experienced a partial fuselage failure due to SCC. The Boeing 737-200 was flying from Hilo to Honolulu, Hawaii when a section of the fuselage ruptured, causing a decompression event. The investigation into the failure found that SCC had occurred in the aluminum skin of the fuselage due to the repeated pressurization and depressurization cycles of the aircraft. The incident led to changes in maintenance procedures and inspections for aircraft to prevent similar failures in the future. | 0 | Metallurgy |
;AIME
*Sir Henry Ayers foundation president, 1893
*Uriah Dudley foundation general secretary 1893–1897
*David Lauder Stirling (c. 1871 – 30 August 1949); president 1894, secretary 1906–1941 or later; also secretary, Victorian Chamber of Mines 1898–1945
*H. W. Ferd Kayser (mine manager Mount Bischoff Tin Mining Company), vice-president 1894, president 1898, 1899
*Alexander Montgomery (government geologist in New Zealand, Tasmania, and Western Australia), president 1895
*Ernest Lidgey geological surveyor in Victoria; conducted Australia's first geophysical surveys; president 1901
*Samuel Henry McGowan (c. 1845 – 13 May 1921), accountant specializing in gold mining companies, mayor of Bendigo 1899–1900; president 1902
*F. Danvers Power, lecturer at Sydney University, president 1897, 1904.
*Robert C. Sticht general manager, Mount Lyell Mining & Railway Company, president 1905, 1915, vice-president 1909
*G. D. Delprat (manager of the Broken Hill mine), president 1906
*Dr. Alfred William Howitt, C.M.G., F.G.S., the eminent naturalist, was president 1907
*Frank A. Moss, (general manager of Kalgurli Gold Mines), president 1907
*C. F. Courtney (general manager of the Sulphide Corporation), president 1908
*Richard Hamilton, (general manager of the Great Boulder Proprietary mine), president 1909, vice-president 1910
*G. A. Richard (of Mount Morgan, Queensland), president 1910
*Herman Carl Bellinger from US; mine manager, Cobar 1909–1914, president 1912
*James Hebbard (manager of the Central Mine, Broken Hill), president 1913
*John Warren (mining) (manager of Block 10, Broken Hill), vice-president 1894, president 1902
*Hyman Herman (director of the Victorian geological survey), joined 1897, president 1914, remained councillor to 1959.
*Robert Silvers Black, (general manager of Kalgurli Gold Mines), president 1917
*J. W. Sutherland metallurgist at Lake View Consols and Golden Horse Shoe gold mines; president 1918
*Professor D. B. Waters of Otago, New Zealand, vice-president 1917,1918 (absent for most of this period — he was with New Zealand Tunnelling Company in France).
;AIMM
*R. W. Chapman, vice-president 1906, president 1920
*Colin Fraser (later Sir Colin), president 1923
*H. W. Gepp, later Sir Herbert William Gepp, president 1924
*Ernest W. Skeats (professor of geology, University of Melbourne), vice-president 1924, president 1925
*David Lauder Stirling, general secretary 1922–45
*R. M. Murray (general manager, Mount Lyell Mining & Railway Company), president 1927
*Alfred Stephen Kenyon, treasurer 1897, secretary 1906, president 1928
*E. C. Andrews (New South Wales Government Geologist), president 1929
*William Edward Wainwright (general manager of Broken Hill South), president 1919, 1930, vice-president 1916–18, 1933, 1934
*Wiliam Harley Wainwright son of W. E. Wainwright, (chief metallurgist, BHP) life member
*Essington Lewis (managing director of BHP) vice-president 1932, president 1935
*Andrew Fairweather, president 1932 (succeeded W. E. Mainwright at Broken Hill South mine and as General Manager)
*Professor J. Neill Greenwood (dean of Melbourne University Faculty of Applied Science), president 1936,1937
*Donald Yates, superintendent of Broken Hill Associated Smelters Pty., president 1937
*Julius Kruttschnitt (general manager, Mount Isa Mines) president 1939
*Oliver H. Woodward (general manager, North Mine, Broken Hill) active in tunnelling operations WWI, president 1940
*Arthur H. P. Moline (1877–1965) (succeeded R. M. Murray as general manager, Mount Lyell, in 1944), president 1945
*Asdruebal James Keast (general manager, Zinc Corporation; Australian Aluminium Production Commission 1951–55), president 1946, vice-president 1947
*Frank R. Hockey / Francis Richard Hockey (general superintendent, BHP), president 1947, vice-president 1949,1950
*F. F. Espie / Frank Fancett Espie (general superintendent, Western Mining Corporation), president 1948
*Godfrey Bernard O'Malley, vice-president 1943–46
*Maurice Alan Edgar Mawby (director of exploration, Zinc Corporation, Limited), vice-president 1950,1951, president 1953,1954
*Ian Munro McLennan (General Manager, BHP), president 1951
*Beryl Elaine Jacka MBE, typist 1936; assistant general secretary 1945–52, secretary 1952–1976
*Gordon Colvin Lindesay Clark CMG | 0 | Metallurgy |
The product of the blast furnace is pig iron, which contains 4–5% carbon and usually some silicon. To produce a forgeable product a further process was needed, usually described as fining, rather than refining. From the 16th century, this was undertaken in a finery forge. At the end of the 18th century, this began to be replaced by puddling (in a puddling furnace), which was in turn gradually superseded by the production of mild steel by the Bessemer process. | 0 | Metallurgy |
Polysulfides are a class of chemical compounds derived from anionic chains of sulfur atoms. There are two main classes of polysulfides: inorganic and organic. The inorganic polysulfides have the general formula . These anions are the conjugate bases of polysulfanes . Organic polysulfides generally have the formulae , where R is an alkyl or aryl group. | 0 | Metallurgy |
The Schikorr reaction can occur in the process of anaerobic corrosion of iron and carbon steel in various conditions.
Anaerobic corrosion of metallic iron to give iron(II) hydroxide and hydrogen:
:3 (Fe + 2 HO → Fe(OH) + H)
followed by the Schikorr reaction:
:3 Fe(OH) → FeO + 2 HO + H
give the following global reaction:
:3 Fe + 6 HO → FeO + 2 HO + 4 H
:3 Fe + 4 HO → FeO + 4 H
At low temperature, the anaerobic corrosion of iron can give rise to the formation of "green rust" (fougerite) an unstable layered double hydroxide (LDH). In function of the geochemical conditions prevailing in the environment of the corroding steel, iron(II) hydroxide and green rust can progressively transform in iron(II,III) oxide, or if bicarbonate ions are present in solution, they can also evolve towards more stable carbonate phases such as iron carbonate (FeCO), or iron(II) hydroxycarbonate (Fe(OH)(CO), chukanovite) isomorphic to copper(II) hydroxycarbonate (Cu(OH)(CO), malachite) in the copper system. | 0 | Metallurgy |
Protein–protein interaction screening refers to the identification of Protein–protein interaction with high-throughput screening methods such as computer- and/or robot-assisted plate reading, flow cytometry analyzing.
The interactions between proteins are central to virtually every process in a living cell. Information about these interactions improves understanding of diseases and can provide the basis for new therapeutic approaches. | 1 | Gene expression + Signal Transduction |
One of the most common base analogs is 5-bromouracil (5BU), the abnormal base found in the mutagenic nucleotide analog BrdU. When a nucleotide containing 5-bromouracil is incorporated into the DNA, it is most likely to pair with adenine; however, it can spontaneously shift into another isomer which pairs with a different nucleobase, guanine. If this happens during DNA replication, a guanine will be inserted as the opposite base analog, and in the next DNA replication, that guanine will pair with a cytosine. This results in a change in one base pair of DNA, specifically a transition mutation.
Additionally, nitrous acid (HNO2) is a potent mutagen that acts on replicating and non-replicating DNA. It can cause deamination of the amino groups of adenine, guanine and cytosine. Adenine is deaminated to hypoxanthine, which base pairs to cytosine instead of thymine. Cytosine is deaminated to uracil, which base pairs with adenine instead of guanine. Deamination of guanine is not mutagenic. Nitrous acid-induced mutations also are induced to mutate back to wild-type. | 1 | Gene expression + Signal Transduction |
The strength, , of dislocation is dependent on the shear modulus, G, the magnitude of the Burgers vector, b, and the dislocation density, :
where is the intrinsic strength of the material with low dislocation density and is a correction factor specific to the material.
As shown in Figure 1 and the equation above, work hardening has a half root dependency on the number of dislocations. The material exhibits high strength if there are either high levels of dislocations (greater than 10 dislocations per m) or no dislocations. A moderate number of dislocations (between 10 and 10 dislocations per m) typically results in low strength. | 0 | Metallurgy |
Archaeometallurgical scientific knowledge and technological development originated in numerous centers of Africa; the centers of origin were located in West Africa, Central Africa, and East Africa; consequently, as these origin centers are located within inner Africa, these archaeometallurgical developments are thus native African technologies. Iron metallurgical development occurred 2631 BCE – 2458 BCE at Lejja, in Nigeria, 2136 BCE – 1921 BCE at Obui, in Central Africa Republic, 1895 BCE – 1370 BCE at Tchire Ouma 147, in Niger, and 1297 BCE – 1051 BCE at Dekpassanware, in Togo.
Though there is some uncertainty, some archaeologists believe that iron metallurgy was developed independently in sub-Saharan Africa (possibly in West Africa).
Inhabitants of Termit, in eastern Niger, smelted iron around 1500 BC.
In the region of the Aïr Mountains in Niger there are also signs of independent copper smelting between 2500 and 1500 BC. The process was not in a developed state, indicating smelting was not foreign. It became mature about 1500 BC.
Archaeological sites containing iron smelting furnaces and slag have also been excavated at sites in the Nsukka region of southeast Nigeria in what is now Igboland: dating to 2000 BC at the site of Lejja (Eze-Uzomaka 2009) and to 750 BC and at the site of Opi (Holl 2009). The site of Gbabiri (in the Central African Republic) has yielded evidence of iron metallurgy, from a reduction furnace and blacksmith workshop; with earliest dates of 896–773 BC and 907–796 BC respectively. Similarly, smelting in bloomery-type furnaces appear in the Nok culture of central Nigeria by about 550 BC and possibly a few centuries earlier.
There is also evidence that carbon steel was made in Western Tanzania by the ancestors of the Haya people as early as 2,300 to 2,000 years ago (about 300 BC or soon after) by a complex process of "pre-heating" allowing temperatures inside a furnace to reach 1300 to 1400 °C.
Iron and copper working spread southward through the continent, reaching the Cape around AD 200. The widespread use of iron revolutionized the Bantu-speaking farming communities who adopted it, driving out and absorbing the rock tool using hunter-gatherer societies they encountered as they expanded to farm wider areas of savanna. The technologically superior Bantu-speakers spread across southern Africa and became wealthy and powerful, producing iron for tools and weapons in large, industrial quantities.
The earliest records of bloomery-type furnaces in East Africa are discoveries of smelted iron and carbon in Nubia that date back between the 7th and 6th centuries BC, particularly in Meroe where there are known to have been ancient bloomeries that produced metal tools for the Nubians and Kushites and produced surplus for their economy. | 0 | Metallurgy |
In molecular biology, housekeeping genes are typically constitutive genes that are required for the maintenance of basic cellular function, and are expressed in all cells of an organism under normal and patho-physiological conditions. Although some housekeeping genes are expressed at relatively constant rates in most non-pathological situations, the expression of other housekeeping genes may vary depending on experimental conditions.
The origin of the term "housekeeping gene" remains obscure. Literature from 1976 used the term to describe specifically tRNA and rRNA. For experimental purposes, the expression of one or multiple housekeeping genes is used as a reference point for the analysis of expression levels of other genes. The key criterion for the use of a housekeeping gene in this manner is that the chosen housekeeping gene is uniformly expressed with low variance under both control and experimental conditions. Validation of housekeeping genes should be performed before their use in gene expression experiments such as RT-PCR. Recently a web-based database of [http://www.housekeeping.unicamp.br/?homePageHuman human] and [http://www.housekeeping.unicamp.br/?homePageMouse mouse] housekeeping genes and reference genes/transcripts, named [http://www.housekeeping.unicamp.br/ Housekeeping and Reference Transcript Atlas] (HRT Atlas), was developed to offer updated list of housekeeping genes and reliable candidate reference genes/transcripts for RT-qPCR data normalization. This database can be accessed at http://www.housekeeping.unicamp.br. | 1 | Gene expression + Signal Transduction |
On some other instances in biology (not necessarily about cell signaling), the term "Scaffold protein" is used in a broader sense, where a protein holds several things together for any purpose.
;In chromosome folding: Chromosome scaffold has important role to hold the chromatin into compact chromosome. Chromosome scaffold is made of proteins including condensin, topoisomerase IIα and kinesin family member 4 (KIF4) Chromosome scaffold constituent proteins are also called scaffold protein.
;In enzymatic reaction: Large multifunctional enzymes that performs a series or chain of reaction in a common pathway, sometimes called scaffold proteins. such as Pyruvate dehydrogenase.
;In molecule shape formation: An enzyme or structural protein that holds several molecules together to hold them in proper spatial arrangement, such as Iron sulphur cluster scaffold proteins.
;Structural scaffold: In cytoskeleton and ECM, the molecules provide mechanical scaffold. Such as type 4 collagen | 1 | Gene expression + Signal Transduction |
The first step should always be an investigation to determine the cause of the deterioration. The general principles of repair include arresting and preventing further degradation; treating exposed steel reinforcement; and filling fissures or holes caused by cracking or left after the loss of spalled or damaged concrete.
Various techniques are available for the repair, protection and rehabilitation of concrete structures, and specifications for repair principals have been defined systematically. The selection of the appropriate approach will depend on the cause of the initial damage (e.g. impact, excessive loading, movement, corrosion of the reinforcement, chemical attack, or fire) and whether the repair is to be fully load bearing or simply cosmetic.
Repair principles which do not improve the strength or performance of concrete beyond its original (undamaged) condition include replacement and restoration of concrete after spalling and delamination; strengthening to restore structural load-bearing capacity; and increasing resistance to physical or mechanical attack.
Repair principles for arresting and preventing further degradation include control of anodic areas; cathodic protection, cathodic control; increasing resistivity; preserving or restoring passivity; increasing resistance to chemical attack; protection against ingress of adverse agents; and moisture control.
Techniques for filling holes left by the removal of spalled or damaged concrete include mortar repairs; flowing concrete repairs and sprayed concrete repairs. The filling of cracks, fissures or voids in concrete for structural purposes (restoration of strength and load-bearing capability), or non-structural reasons (flexible repairs where further movement is expected, or alternately to resist water and gas permeation) typically involves the injection of low viscosity resins or grouts based on epoxy, PU or acrylic resins, or micronised cement slurries.
One novel proposal for the repair of cracks is to use bacteria. BacillaFilla is a genetically engineered bacterium designed to repair damaged concrete, filling in the cracks, and making them whole again. | 0 | Metallurgy |
* Measurement of the emissivities of gases at temperatures up to 1000 °C. Emissivity values were required for gaseous aluminium chlorides as part of the development of the sub-halide distillation process mentioned above. A flowing column of the gas to be measured, heated in a refractory tube, was maintained at a fixed length by gas barriers at each end, formed by balanced opposing streams of argon. The radiation emitted by the gas was measured by a thermopile. A diaphragm was set up to shield this sensor from radiation emitted by the furnace and other hot parts of the equipment. The whole apparatus was mounted on a water-cooled optical bench.
* X-ray diffraction determination of the structures of liquid metals. There was a need for structural studies of liquid sodium and sodium-potassium alloys because these were used as coolants in fast-breeder reactors. Fulmer developed a high temperature x-ray diffractometer for investigating the structures of liquid metals and alloys. In addition to its studies of liquid alkali metals, Fulmer discovered that certain eutectics, such as those in the gold-silicon and gold-germanium systems, have a structure in the liquid phase that has to be disrupted on crystallization. This gives rise to considerable supercooling which results in multiple nucleation, and hence a very fine grain size in the resulting polycrystalline alloy.
* Production of high purity austenitic stainless steel. High purity austenitic stainless steel was of interest as a potential cladding material for nuclear fuel elements. Fulmer produced high purity chromium by electro-deposition from a fluoride bath. Zone refining using induction heating was used to produce high-purity iron and nickel and to remove oxygen from chromium. Impurity levels of 1-40 parts per million were achieved.
* Chromium with improved ductility. Uses of chromium as a high temperature material are limited by its brittleness. Starting with electro-deposited flakes of high purity chromium, investigators at Fulmer used argon-arc melting to form electrodes for ingot production in a consumable electrode furnace. Ingots were then heated in an inert or hydrogen atmosphere and extruded to give a fine grained structure. Critical warm working, below the recrystallization temperature, then gave improved room-temperature ductility.
* Statistical studies of the strength of ceramics. The strength of brittle materials such as ceramics is inherently variable. Fulmer undertook numerous strength tests on sets of nominally identical specimens of engineering ceramics such as silicon nitride and silicon carbide. They devised graphical techniques for finding the probability distribution of test results and contributed to criteria for engineering design with these materials. | 0 | Metallurgy |
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.
mRNA is created during the process of transcription, where an enzyme (RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA). This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence. These are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. This exon sequence constitutes mature mRNA. Mature mRNA is then read by the ribosome, and the ribosome creates the protein utilizing amino acids carried by transfer RNA (tRNA). This process is known as translation. All of these processes form part of the central dogma of molecular biology, which describes the flow of genetic information in a biological system.
As in DNA, genetic information in mRNA is contained in the sequence of nucleotides, which are arranged into codons consisting of three ribonucleotides each. Each codon codes for a specific amino acid, except the stop codons, which terminate protein synthesis. The translation of codons into amino acids requires two other types of RNA: transfer RNA, which recognizes the codon and provides the corresponding amino acid, and ribosomal RNA (rRNA), the central component of the ribosome's protein-manufacturing machinery.
The concept of mRNA was developed by Sydney Brenner and Francis Crick in 1960 during a conversation with François Jacob. In 1961, mRNA was identified and described independently by one team consisting of Brenner, Jacob, and Matthew Meselson, and another team led by James Watson. While analyzing the data in preparation for publication, Jacob and Jacques Monod coined the name "messenger RNA". | 1 | Gene expression + Signal Transduction |
In friction stir processing (FSP), a rotating tool is used with a pin and a shoulder to a single piece of material to make specific property enhancement, such as improving the materials toughness or flexibility, in a specific area in the micro-structure of the material via fine grain of a second material with properties that improve the first.(Ma) Friction between the tool and workpieces results in localized heating that softens and plasticizes the workpiece. A volume of processed material is produced by movement of materials from the front of the pin to the back of the pin. During this process, the material undergoes intense plastic deformation and this results in significant grain refinement. (Mishra) FSP changes physical properties without changing physical state which helps engineers create things such as “high-strain-rate superplasticity”. The grain refinement occurs on the base material improving properties of the first material, while mixing with the second material. This allows for a variety of materials to be altered to be changed for things that may require other difficult to acquire conditions. The processes branches off of friction stir welding (FSW) which uses the same process to weld two pieces of different materials together without heating, melting, or having to change the materials physical state. | 0 | Metallurgy |
The original Jameson Cell design had the following features:
* small (200 mm diameter) downcomers
* no wash water
* no tailings recycle
* no bubble dispersers
* low capacity.
In 1994 MIM launched the Mark II model Cell. It incorporated the following changes:
* the downcomer diameter was increased to 280 mm
* wash-water trays were included for froth washing
* a tailings recycle system was added to maintain constant downcomer flow and higher recoveries
* conical bubble dispersers were added
* increased depth of tank from the bottom of the downcomer
* increased distance between the downcomers.
These changes resulted in a higher capacity design.
One of the problems encountered with the Mark I Cell was that its performance was reduced if the feed rate to the cell varied, which was a common occurrence arising from normal fluctuations in operating concentrators. This problem was resolved by recycling some of the tailings to the cell feed via an external splitter box called an "External Recycle Mechanism" or "ERM" box separate to the flotation cell. Thus, when the production of the feed stream to the Jameson Cell decreased as a result of a fluctuation elsewhere in the concentrator, a higher percentage of the tailings was automatically recycled to the downcomers, producing a constant flow rate, hence feed pressure, to the cell. This had the added benefit of giving a proportion of the tailings (typically 40%) a second pass through the system, which resulted in higher recoveries. In coal fines flotation, this allowed a single Cell to achieve the same recovery of combustibles as had previously been achieved in some two-stage Cell systems.
Subsequently, an internal recycling system, referred to as the "internal recycle control" or "IRC" was developed. This was mainly used in integrated rectangular cells (see Figure 6), where the feed tank and tailings recycling system could easily be built in a single unit with the flotation cell. This system reduced the cell installation costs and made the cell more compact.
During this period, the orifice diameter was increased from the 28 mm design used in 1990 to 34 mm with the Mark II model and 38 mm in 1997. This, together with the larger Mark II downcomer diameter, allowed the slurry flow per downcomer to be doubled from 30 m/h in 1990 to 60 m/h in 1997.
The increased distance between the downcomers reduced the interaction of aerated slurry discharging from adjacent downcomers. This interaction could reduce overall cell recovery by causing particles collected by bubbles in the downcomer to detach in the pulp tank.
There was significant turbulence in the areas beneath the downcomers. that could result in particles detaching from bubbles. These turbulent areas were calmed by the addition of conical diffusers beneath each downcomer. They allowed uniform bubble rise velocities across the surface of the cell by slowing the superficial gas velocity in the high void-fraction area immediately around the downcomer and provided a more even bubble dispersion. It was reported that the diffusers reduced the turbulence by 69% compared with a standard downcomer with no diffuser. | 0 | Metallurgy |
In metazoans, small interfering RNAs (siRNAs) processed by Dicer are incorporated into a complex known as the RNA-induced silencing complex or RISC. This complex contains an endonuclease that cleaves perfectly complementary messages to which the siRNA binds. The resulting mRNA fragments are then destroyed by exonucleases. siRNA is commonly used in laboratories to block the function of genes in cell culture. It is thought to be part of the innate immune system as a defense against double-stranded RNA viruses. | 1 | Gene expression + Signal Transduction |
Processing of mRNA differs greatly among eukaryotes, bacteria, and archaea. Non-eukaryotic mRNA is, in essence, mature upon transcription and requires no processing, except in rare cases. Eukaryotic pre-mRNA, however, requires several processing steps before its transport to the cytoplasm and its translation by the ribosome. | 1 | Gene expression + Signal Transduction |
The formation of raw iron ore pellets, also known as pelletizing, has the objective of producing pellets in an appropriate band of sizes and with mechanical properties high usefulness during the stresses of transference, transport, and use. For example, waste materials are ground before being heated and introduced into a press for compression. Both mechanical force and thermal processes are used to produce the correct pellet properties. From an equipment point of view there are two alternatives for industrial production of iron ore pellets: the drum and the pelletizing disk. | 0 | Metallurgy |
A longitudinal facial crack is a specialized type of defect that only occurs in continuous casting processes. This defect is caused by uneven cooling, both primary cooling and secondary cooling, and includes molten steel qualities, such as the chemical composition being out of specification, cleanliness of the material, and homogeneity. | 0 | Metallurgy |
The half-Heusler compounds have distinctive properties and high tunability which makes the class very promising as thermoelectric materials. A study has predicted that there can be as many as 481 stable half-Heusler compounds using high-throughput ab initio calculation combine with machine learning techniques. The particular half-Heusler compounds of interest as thermoelectric materials (space group ) are the semiconducting ternary compounds with a general formula XYZ where X is a more electropositive transition metal (such as Ti or Zr), Y is a less electropositive transition metal (such Ni or Co), and Z is heavy main group element (such as Sn or Sb). This flexible range of element selection allows many different combinations to form a half-Heusler phase and enables a diverse range of material properties.
Half-Heusler thermoelectric materials have distinct advantages over many other thermoelectric materials; low toxicity, inexpensive element, robust mechanical properties, and high thermal stability make half-Heusler thermoelectrics an excellent option for mid-high temperature application. However, the high thermal conductivity, which is intrinsic to highly symmetric HH structure, has made HH thermoelectric generally less efficient than other classes of TE materials. Many studies have focused on improving HH thermoelectric by reducing the lattice thermal conductivity and zT > 1 has been repeatedly recorded. | 0 | Metallurgy |
CK1δ and CK1ε were thought to be generally redundant in circadian cycle length and protein stability. Recent research, however, has shown that CK1δ deficiency lengthens circadian period while CK1ε deficiency does not. Also, CK1α has recently been suggested to play a role redundant to CK1δ in phosphorylating PER1 although this is not consistent with other data | 1 | Gene expression + Signal Transduction |
Ridges (regions of increased gene expression) are domains of the genome with a high gene expression; the opposite of ridges are antiridges. The term was first used by Caron et al. in 2001. Characteristics of ridges are:
*Gene dense
*Contain many C and G nucleobases
*Genes have short introns
*High SINE repeat density
*Low LINE repeat density | 1 | Gene expression + Signal Transduction |
Powder metallurgy is a class of modern processing techniques in which metals are first powdered, and then formed into the desired shape by heating below the melting point. This is in contrast to casting, which occurs with molten metal. Superalloy manufacturing often employs powder metallurgy because of its material efficiency - typically much less waste metal must be machined away from the final product—and its ability to facilitate mechanical alloying. Mechanical alloying is a process by which reinforcing particles are incorporated into the superalloy matrix material by repeated fracture and welding. | 0 | Metallurgy |
Jameson's research into flotation began when he was at Imperial College London, in 1969. A colleague, Dr J. A. Kitchener of the Royal School of Mines, pointed out that many of the new mineral deposits being found around the world required fine grinding to separate the valuable particles from the rock in which they were embedded, and the flotation technologies available at the time were relatively inefficient for recovering fine particles. Kitchener felt that improvements could best be achieved by an increased knowledge of the physics of flotation, rather than the chemistry of the reagents. Jameson had gained some expertise in the properties of bubbles and particles in suspensions whilst a PhD student at Cambridge. He began research into the fluid mechanics of the flotation process and set in train a series of experimental projects into the effect of particle diameter and bubble size on the flotation rate constant. Much of the research was conducted by honours students in chemical engineering. Jameson accepted the challenge of coming up with practical solutions to remedy the situation, if these could be identified.
Jameson's research showed that the kinetics of flotation of fine particles was a strong function of the bubble diameter and that the way to improve recoveries was to use small bubbles in the order of 300 microns (μm) in diameter. What was needed was a practical method of making such bubbles in large quantities, of the order of billions per second. The device needed to be simple to construct and operate, capable of running for long periods with minimal maintenance, and should be resistant to blockage by stray large particles in the feed. He began to look at the theory of bubble breakup in sheared flows, that is, in flow fields in which layers of liquid slide over each other. Lewis and Davidson had recently published a theory to predict the maximum size of bubbles in a well-characterised flow environment. By balancing the forces acting on a bubble in a shearing flow, including the disruptive dynamic stresses from the liquid motion and the restoring force of surface tension, it was possible to predict the critical shear rate required to produce a bubble of given size. Jameson then looked for simple and practical ways of generating the required shear rates, and found inspiration in the kitchen sink. If a jet of water from a tap plunges into a basin full of water, a shear layer develops around the jet, that entrains air from the atmosphere into the water, and at the same time, breaks up the entrained air into fine bubbles. The effect is magnified if there is a detergent in the water. Detergents, known as frothers, are used in flotation to prevent bubble coalescence, and to create stable froths. By the correct choice of jet velocity and diameter, it is possible to provide a controlled shear environment that can generate bubbles of a suitable size for flotation, with the added advantage that the air is naturally aspirated by the jet, so there is no need for a compressor or blower. Thus the idea of the Jameson Cell was born.
After a number of failures, the radical new process for flotation emerged in the laboratory at the University of Newcastle. Jameson filed a provisional patent application in 1986. After an initial trial at the Renison Bell tin mine in Tasmania, certain design features were modified. He led a further plant trial with a small cell in the lead-zinc concentrator at Mt Isa Mines Ltd in Queensland, initially working alone. The plant metallurgists took an interest in the technology and helped to refine it, particularly checking the scale-up procedures that Jameson had devised. In 1988 a recent graduate was assigned full-time for a year to verify and validate the performance of the Cell. In 1989 a worldwide exclusive license was negotiated between Tunra Ltd on behalf of the University of Newcastle, Jameson, and MIM Holdings Limited, for the use of the Cell for metallurgical purposes. Summary papers on the theory and practice have been published.
There have been ongoing significant changes to the design of the Cell since it was first developed in the late 1980s. | 0 | Metallurgy |
A growing number of ligands that can be used to activate RASSLs / DREADDs are commercially available.
CNO is the prototypical DREADD activator. CNO activates the excitatory Gq- coupled DREADDs: hM3Dq, hM1Dq and hM5Dq and also the inhibitory hM4Di and hM2Di G-coupled DREADDs. CNO also activates the G-coupled DREADD (GsD) and the β-arrestin preferring DREADD: rM3Darr (Rq(R165L).
Recent findings suggest that systemically administered CNO does not readily cross the blood-brain-barrier in vivo and converts to clozapine which itself activates DREADDs. Clozapine is an atypical antipsychotic which has been indicated to show high DREADD affinity and potency. Subthreshold injections of clozapine itself can be utilised to induce preferential DREADD-mediated behaviors. Therefore, when using CNO, care must be taken in experimental design and proper controls should be incorporated.
DREADD agonist 21, also known as Compound 21, represents an alternative agonist for muscarinic-based DREADDs and an alternative to CNO. It has been reported that Compound 21 has excellent bioavailability, pharmacokinetic properties and brain penetrability and does not undergo reverse metabolism to clozapine. Another known agonist is perlapine, a hypnotic drug approved for treating insomnia in Japan. It acts as an activator of G-, G-, and G DREADDs that has structural similarity to CNO. A more recent agonist of hM3Dq and hM4Di is deschloroclozapine (DCZ).
On the other hand, SalB B is a potent and selective activator of KORD.
JHU37160 and JHU37152 have been marketed commercially as novel DREADD ligands, active in vivo, with high potency and affinity for hM3Dq and hM4Di DREADDs.
Diihydrochloride salts of DREADDs ligands that are water-soluble (but with differing stabilities in solution) have also been commercially developed (see for aqueous stability). | 1 | Gene expression + Signal Transduction |
Fas ligand has been shown to interact with:
* CASP8,
* EZR,
* FADD,
* FNBP1,
* FYN,
* FAS,
* Grb2,
* PACSIN2, and
* TNFRSF6B. | 1 | Gene expression + Signal Transduction |
Yttrium is used in the production of a large variety of synthetic garnets, and yttria is used to make yttrium iron garnets (, also "YIG"), which are very effective microwave filters which were recently shown to have magnetic interactions more complex and longer-ranged than understood over the previous four decades. Yttrium, iron, aluminium, and gadolinium garnets (e.g. and ) have important magnetic properties. YIG is also very efficient as an acoustic energy transmitter and transducer. Yttrium aluminium garnet ( or YAG) has a hardness of 8.5 and is also used as a gemstone in jewelry (simulated diamond). Cerium-doped yttrium aluminium garnet (YAG:Ce) crystals are used as phosphors to make white LEDs.
YAG, yttria, yttrium lithium fluoride (), and yttrium orthovanadate () are used in combination with dopants such as neodymium, erbium, ytterbium in near-infrared lasers. YAG lasers can operate at high power and are used for drilling and cutting metal. The single crystals of doped YAG are normally produced by the Czochralski process. | 0 | Metallurgy |
Staff at BRM began work on an alternative to the conventional reverberatory cupellation furnace in the early 1980s. This included a review of the available technology, including the top-blown rotary converter ("TBRC"), on which test work was undertaken.
One of the first areas investigated was the use of oxygen-enriched blast air in the reverberatory furnace. This was “found to be of marginal benefit and not economically viable."
The BRM staff subsequently tried to increase the oxygen transfer rate by using lances submerged in the bath of the reverberatory furnace and found that there was some benefit in doing this. However, the wear rate of the lances was excessive and it was realized that the basic design of the furnace, with its shallow bath, was not conducive to the development of a high-intensity reactor.
The concept then evolved into a new furnace design, one that had a deep bath, in contrast to the reverberatory furnace design.
Initial tests of the bottom injection of oxygen were carried out on a small scale at Imperial College, London, using a nitrogen-shrouded tuyere. These showed that under certain conditions a protective accretion would form at the tip of the injector, and that oxygen utilization was high, with the oxidation reactions generating sufficient heat to keep the furnace hot until the final stages of refining when the impurity levels were low.
Additionally, the test work on the TBRC had shown that it had a high rate of refractory wear, due to the washing action of the slag caused by the rotation of the furnace, which provided additional pressure to develop an alternate process. The TBRC test work also resulted in low oxygen utilization (about 60%).
Based on the success of the small-scale tests, and with calculations indicating that the new design would have significant energy savings over the reverberatory furnace, the BRM staff built a 1.5 t pilot plant with a working volume of 150 liters (“L”). The oxygen injector was a fixed tuyere, located at corner of the base with the side wall, with an annular nitrogen shroud.
The initial pilot plant tests showed that it was difficult to maintain the protective accretion that had been generated in the small-scale tests, due to the variation in temperature and bullion composition that occurred throughout the cupelling cycle. Without the accretion, the nitrogen shroud could not provide sufficient protection to the injector, and it burned back to the level of the refractory lining, which resulted in damage to the lining.
The solution eventually developed was the concept of the moveable lance system in place of the fixed tuyere that had been used initially. The lance was pushed further into the furnace as its tip was worn away.
The initial lance advancing system was manual, but the current automated system was subsequently developed.
Once a sustainable system had been developed in the pilot plant, and after three years of pilot plant development, a commercial, 3 t-scale BBOC was commissioned at BRM in 1986. Its use reduced the fuel consumption per tonne of silver by 85%, from 30 gigajoules per tonne (“GJ/t”) to 4.5 GJ/t and the exhaust gas volume from 32 000 Nm/h to 7500 Nm/h. | 0 | Metallurgy |
Among the faculty members who have worked at the Graduate Institute of Ferrous Technology, several Professors are distinguished world-widely:
** Sir Professor Harshad_Bhadeshia
** Professor Frédéric Barlat
** Professor Nack Joon KIM
** Professor Bruno De Cooman
** Prof. Yasushi Sasaki
** Prof. Hae-Geon Lee
** Prof. Chong Soo Lee | 0 | Metallurgy |
LOV domains have been found to control gene expression through DNA binding and
to be involved in redox-dependent regulation, like e.g. in the bacterium Rhodobacter sphaeroides. Notably, LOV-based optogenetic tools have been gaining wide popularity in recent years to control a myriad of cellular events, including cell motility, subcellular organelle distribution, formation of membrane contact sites, microtubule dynamics, transcription, and protein degradation. | 1 | Gene expression + Signal Transduction |
Lamina-associated domains (LADs) are parts of the chromatin that heavily interact with the lamina, a network-like structure at the inner membrane of the nucleus. LADs consist mostly of transcriptionally silent chromatin, being enriched with trimethylated Lys27 on histone H3, (i.e. H3K27me3); which is a common posttranslational histone modification of heterochromatin. LADs have CTCF-binding sites at their periphery. | 1 | Gene expression + Signal Transduction |
In the early 1950s, divers found the remains of a shipwreck in Cape Gelidonya, off the coast of Turkey. The remains included a substantial amount of copper oxhide ingot material: 34 in full, five in half, 12 corners, and of random fragments. Twenty-four full copper oxhide ingots have stamps on their centers—usually of a circle containing intersecting lines. These stamps were likely made when the metal was soft. In addition, the ship contained numerous complete and incomplete copper bun-shaped ingots, rectangular tin bars, and Cypriot agricultural tools made of scrap bronze. Radiocarbon dating of brushwood from the ship gives an approximate date of 1200 BC. | 0 | Metallurgy |
From 1875 to 1920 American steel production grew from 380,000 tons to 60 million tons annually, making the U.S. the world leader. The annual growth rates in steel 1870–1913 were 7.0% for the US; 1.0% for Britain; 6.0% for Germany; and 4.3% for France, Belgium, and Russia, the other major producers. This explosive American growth rested on solid technological foundations and the continuous rapid expansion of urban infrastructures, office buildings, factories, railroads, bridges and other sectors that increasingly demanded steel. The use of steel in automobiles and household appliances came in the 20th century.
Some key elements in the growth of steel production included the easy availability of iron ore, and coal. Iron ore of fair quality was abundant in the eastern states, but the Lake Superior region contained huge deposits of exceedingly rich ore; the Marquette Iron Range was discovered in 1844; operations began in 1846. Other ranges were opened by 1910, including the Menominee, Gogebic, Vermilion, Cuyuna, and, greatest of all, (in 1892) the Mesabi range in Minnesota. This iron ore was shipped through the Great Lakes to ports such as Chicago, Detroit, Cleveland, Erie and Buffalo for shipment by rail to the steel mills. Abundant coal was available in Pennsylvania, West Virginia, and Ohio. Manpower was short. Few Native Americans wanted to work in the mills, but immigrants from Britain and Germany (and later from Eastern Europe) arrived in great numbers.
In 1869 iron was already a major industry, accounting for 6.6% of manufacturing employment and 7.8% of manufacturing output. By then the central figure was Andrew Carnegie, who made Pittsburgh the center of the industry. He sold his operations to US Steel in 1901, which became the world's largest steel corporation for decades.
In the 1880s, the transition from wrought iron puddling to mass-produced Bessemer steel greatly increased worker productivity. Highly skilled workers remained essential, but the average level of skill declined. Nevertheless, steelworkers earned much more than ironworkers despite their fewer skills. Workers in an integrated, synchronized mass production environment wielded greater strategic power, for the greater cost of mistakes bolstered workers' status. The experience demonstrated that the new technology did not decrease worker bargaining leverage by creating an interchangeable, unskilled workforce. | 0 | Metallurgy |
Autocrine signaling is a form of cell signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on that same cell, leading to changes in the cell. This can be contrasted with paracrine signaling, intracrine signaling, or classical endocrine signaling. | 1 | Gene expression + Signal Transduction |
Developments in the United States had been less than spectacular. Butterss failures, as well as others, was followed after 1904, with Scotsman Stanley MacQuistens process (a surface tension based method), which was developed with a modicum of success in Nevada and Idaho, but this would not work when slimes were present, a major fault. Henry E. Wood of Denver had developed his flotation process along the same lines in 1907, patented 1911, with some success on molybdenum ores. For the most part, however, these were isolated attempts without fanfare for what can only be called marginal successes.
In 1911, James M. Hyde, a former employee of Minerals Separation, Ltd., modified the Minerals Separation process and installed a test plant in the Butte and Superior Mill in Basin, Montana, the first such installation in the USA. In 1912, he designed the Butte & Superior zinc works, Butte, Montana, the first great flotation plant in America. Minerals Separation, Ltd., which had set up an office in San Francisco, sued Hyde for infringement as well as the Butte & Superior company, both cases were eventually won by the firm in the U. S. Supreme Court. Daniel Cowan Jackling and partners, who controlled Butte & Superior, also refuted the Minerals Separation patent and funded the ensuing legal battles that lasted over a decade. They - Utah Copper (Kennecott), Nevada Consolidated, Chino Copper, Ray Con and other Jackling firms - eventually settled, in 1922, paying a substantial fee for licenses to use the Minerals Separation process. One unfortunate result of the dispute was professional divisiveness among the mining engineering community for a generation.
In 1913, the Minerals Separation paid for a test plant for the Inspiration Copper Company at Miami, Arizona. Built under the San Francisco office director, Edward Nutter, it proved a success. Inspiration engineer L. D. Ricketts ripped out a gravity concentration mill and replaced it with the Minerals Separation process, the first major use of the process at an American copper mine. A major holder of Inspiration stock were men who controlled the great Anaconda mine of Butte. They immediately followed the Inspiration success to build a Minerals Separation licensed plant at Butte, in 1915–1916, a major statement about the final acceptance of the Minerals Separation patented process.
John M. Callow, of General Engineering of Salt Lake City, had followed flotation from technical papers and the introduction in both the Butte and Superior Mill, and at Inspiration Copper in Arizona and determined that mechanical agitation was a drawback to the existing technology. Introducing a porous brick with compressed air, and a mechanical stirring mechanism, Callow applied for a patent in 1914 (some say that Callow, a Jackling partisan, invented his cell as a means to avoid paying royalties to Minerals Separation, which firms using his cell eventually were forced to do by the courts). This method, known as Pneumatic Flotation, was recognized as an alternative to the Minerals Separation process of flotation concentration. The American Institute of Mining Engineers presented Callow the James Douglas Gold Medal in 1926 for his contributions to the field of flotation. By that time, flotation technology was changing, especially with the discovery of the use of xanthates and other reagents, which made the Callow cell and his process obsolete.
Montana Tech professor Antoine Marc Gaudin defined the early period of flotation as the mechanical phase while by the late 1910s it entered the chemical phase. Discoveries in reagents, especially the use of xanthates patented by Minerals Separations chemist Cornelius H. Keller, not so much increased the capture of minerals through the process as making it far more manageable in day-to-day operations. Minerals Separation's initial flotation patents ended 1923, and new ones for chemical processes gave it a significant position into the 1930s. During this period the company also developed and patented flotation processes for iron out of its Hibbing lab and of phosphate in its Florida lab. Another rapid phase of flotation process innovation did not occur until after 1960.
In the 1960s the froth flotation technique was adapted for deinking recycled paper.
The success of the process is evinced by the number of claimants as "discoverers" of flotation. In 1961, American engineers celebrated "50 years of flotation" and enshrined James Hyde and his Butte & Superior mill. In 1977, German engineers celebrated the "hundredth anniversary of flotation" based on the brothers Bessel patent of 1877. The historic Glasdir copper mine site advertises its tours in Wales as site of the "discovery of flotation" based upon the Elmore brothers work. Recent writers, because of the interest in celebrating women in science, champion Carrie Everson of Denver as mother of the process based on her 1885 patent. Omitted from this list are the engineers, metallurgists and chemists of Minerals Separation, Ltd., which, at least in the American and Australian courts, won control of froth flotation patents as well as right of claimant as discoverers of froth flotation. But, as historian Martin Lynch writes, "Mineral Separation would eventually prevail after taking the case to the US Supreme Court [and the House of Lords], and in so doing earned for itself the cordial detestation of many in the mining world." | 0 | Metallurgy |