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In order to achieve noticeable material strengthening via solution strengthening, one should alloy with solutes of higher shear modulus, hence increasing the local shear modulus in the material. In addition, one should alloy with elements of different equilibrium lattice constants. The greater the difference in lattice parameter, the higher the local stress fields introduced by alloying.
Alloying with elements of higher shear modulus or of very different lattice parameters will increase the stiffness and introduce local stress fields respectively. In either case, the dislocation propagation will be hindered at these sites, impeding plasticity and increasing yield strength proportionally with solute concentration.
Solid solution strengthening depends on:
* Concentration of solute atoms
* Shear modulus of solute atoms
* Size of solute atoms
* Valency of solute atoms (for ionic materials)
For many common alloys, rough experimental fits can be found for the addition in strengthening provided in the form of:
where is a solid solution strengthening coefficient and is the concentration of solute in atomic fractions.
Nevertheless, one should not add so much solute as to precipitate a new phase. This occurs if the concentration of the solute reaches a certain critical point given by the binary system phase diagram. This critical concentration therefore puts a limit to the amount of solid solution strengthening that can be achieved with a given material. | 0 | Metallurgy |
The SIP peptide binding pocket is the docking station of the eight amino acid leaderless peptide signal, speB-inducing peptide (SIP). The binding pocket is a tripartite construction of the C-terminals α12 helix which is a capping helix, TPR3s α6 helix that has a hydrophobic interplay with SIP sidechains, and TPR 4's α8 helix which electrostatically stabilizes SIP. Variations in pH level altered strength of adherence between SIP and the SIP binding pocket with acidic pH levels between 5.5 and 6.5 enhancing adherence and pH levels between 7 and 9 reducing adherence. | 1 | Gene expression + Signal Transduction |
Recyclability is a key factor of a sustainable material. It reduces the need to mine new resources and requires less energy than mining. Copper and its alloys are virtually 100% recyclable and can be recycled infinitely without any loss of quality (i.e., copper does not degrade (i.e., downcycle) after each recycling loop as do most non-metallic materials, if they are recyclable at all). Copper retains much of its primary metal value: premium-grade scrap normally contains at least 95% of the value of primary metal from newly mined ore. Scrap values for competing materials range from about 60% down to 0%. And copper recycling requires only around 20% of the energy needed to extract and process primary metal.
Currently, around 40% of Europe's annual copper demand and about 55% of copper used in architecture come from recycled sources. New copper coil and sheet often have 75%-100% recycled content.
By 1985, more copper was recycled than the total amount of copper that was consumed in 1950. This is due to the relative ease of reusing processing waste and salvaging copper from products after their useful life. | 0 | Metallurgy |
Monoallelic gene expression (MAE) is the phenomenon of the gene expression, when only one of the two gene copies (alleles) is actively expressed (transcribed), while the other is silent. Diploid organisms bear two homologous copies of each chromosome (one from each parent), a gene can be expressed from both chromosomes (biallelic expression) or from only one (monoallelic expression). MAE can be Random monoallelic expression (RME) or Constitutive monoallelic expression (constitutive). Constitutive monoallelic expression occurs from the same specific allele throughout the whole organism or tissue, as a result of genomic imprinting. RME is a broader class of monoallelic expression, which is defined by random allelic choice in somatic cells, so that different cells of the multi-cellular organism express different alleles. | 1 | Gene expression + Signal Transduction |
Shape-memory alloys are applied in medicine, for example, as fixation devices for osteotomies in orthopaedic surgery, as the actuator in surgical tools; active steerable surgical needles for minimally invasive percutaneous cancer interventions in the surgical procedures such as biopsy and brachytherapy, in dental braces to exert constant tooth-moving forces on the teeth, in Capsule Endoscopy they can be used as a trigger for biopsy action.
The late 1980s saw the commercial introduction of Nitinol as an enabling technology in a number of minimally invasive endovascular medical applications. While more costly than stainless steel, the self expanding properties of Nitinol alloys manufactured to BTR (Body Temperature Response), have provided an attractive alternative to balloon expandable devices in stent grafts where it gives the ability to adapt to the shape of certain blood vessels when exposed to body temperature. On average, of all peripheral vascular stents currently available on the worldwide market are manufactured with Nitinol. | 0 | Metallurgy |
Filiform corrosion may be considered as a type of crevice corrosion and is sometimes seen on metals coated with an organic coating (paint). Filiform corrosion is unusual in that it does not weaken or destroy the integrity of the metal but only affects the surface appearance. | 0 | Metallurgy |
Mediator is involved in "looping" of chromatin, which brings distant regions of a chromosome into closer physical proximity. The ncRNA-a mentioned above is involved in such looping. Enhancer RNAs (eRNAs) can function similarly.
In addition to the looping of euchromatin, mediator appears to be involved in formation or maintenance of heterochromatin at centromeres and telomeres. | 1 | Gene expression + Signal Transduction |
Extensive research has been carried out on the metallurgical material from Tell Hammeh. Both excavation and archaeometric analyses were carried out by Dr H.A. Veldhuijzen, first at Leiden University, then since 2001 at the UCL Institute of Archaeology, as a part of the joint excavations conducted by Yarmouk University and Leiden University and co-directed by Prof. Dr. Zeidan Kafafi and Dr. Gerrit Van der Kooij. | 0 | Metallurgy |
Fas signaling pathway involves activating apoptosis (programmed cell death). This happens through the interaction of Fas receptor and Fas ligand. As mentioned, Fas ligand/FasL is a type II transmembrane protein that can exist in both membrane-anchored and soluble forms. The interaction between FasR on an adjacent cell and membrane anchored FasL leads to the trimerization, forming the death-inducing signaling complex (DISC).
Upon ensuing death domain (DD) aggregation, the receptor complex is internalized via the cellular endosomal machinery. This allows the adaptor molecule Fas-associated death domain (FADD) to bind the death domain (DD) of Fas through its own death domain (DD). FADD also contains a death effector domain (DED) near its amino terminus, which facilitates binding to the DED of FADD-like ICE (FLICE), more commonly referred to as caspase-8. FLICE can then self-activate through proteolytic cleavage into p10 and p18 subunits, of which two form the active heterotetramer enzyme. Active caspase-8 is then released from the DISC into the cytosol, where it cleaves other effector caspases, eventually leading to DNA degradation, membrane blebbing, and other hallmarks of apoptosis.
Some reports have suggested that the extrinsic Fas pathway is sufficient to induce complete apoptosis in certain cell types through death-inducing signaling complex (DISC) assembly and subsequent caspase-8 activation. These cells are dubbed Type 1 cells and are characterized by the inability of anti-apoptotic members of the Bcl-2 family (namely Bcl-2 and Bcl-xL) to protect from Fas-mediated apoptosis. Characterized Type 1 cells include H9, CH1, SKW6.4, and SW480, all of which are lymphocyte lineages except for SW480, which is of the colon adenocarcinoma lineage.
Moreover, the pathways in the Fas signal cascade exhibit evidence for crosstalk. In most cell types, caspase-8 catalyzes the cleavage of the pro-apoptotic BH3-only protein Bid into its truncated form, tBid. BH-3 only members of the Bcl-2 family engage exclusively anti-apoptotic members of the family (Bcl-2, Bcl-xL), allowing Bak and Bax to translocate to the outer mitochondrial membrane, thus permeabilizing it and facilitating release of pro-apoptotic proteins such as cytochrome c and Smac/DIABLO, an antagonist of inhibitors of apoptosis proteins (IAPs).
Additionally, the c-FLIP protein, structurally resembling caspase-8 but lacking enzymatic activity, plays a dual role in Fas-induced apoptosis. At low concentrations, c-FLIP is believed to promote caspase-8 activation. There is a possibility it is because caspase-8 binds to c-FLIP with higher affinity than to itself (caspase-8 homo-dimerization). However, at high concentrations, c-FLIP reduces the proteolytic activity of caspase-8, potentially by competing for binding to FADD. This dual role underscores the complexity of Fas signaling and its regulation by c-FLIP at different concentrations. | 1 | Gene expression + Signal Transduction |
The two N-terminal cysteines of CXC chemokines (or α-chemokines) are separated by one amino acid, represented in this name with an "X". There have been 17 different CXC chemokines described in mammals, that are subdivided into two categories, those with a specific amino acid sequence (or motif) of glutamic acid-leucine-arginine (or ELR for short) immediately before the first cysteine of the CXC motif (ELR-positive), and those without an ELR motif (ELR-negative). ELR-positive CXC chemokines specifically induce the migration of neutrophils, and interact with chemokine receptors CXCR1 and CXCR2. An example of an ELR-positive CXC chemokine is interleukin-8 (IL-8), which induces neutrophils to leave the bloodstream and enter into the surrounding tissue. Other CXC chemokines that lack the ELR motif, such as CXCL13, tend to be chemoattractant for lymphocytes. CXC chemokines bind to CXC chemokine receptors, of which seven have been discovered to date, designated CXCR1-7. | 1 | Gene expression + Signal Transduction |
Center-surround antagonism refers to antagonistic interactions between center and surround regions of the receptive fields of photoreceptor cells in the retina. Center surround antagonism enables edge detection and contrast enhancement within the visual cortex. | 1 | Gene expression + Signal Transduction |
Experimental work on precious metals is limited by the cost of experimentation and by the well-understood technical processes involved. Gold and silver are produced in a similar manner to copper with the additional process of cupellation. Platinum is mostly an issue in South America and is typically left out from experimental archaeometallurgy because of its traditional use as a powdered metal as an additive to produce alloys. | 0 | Metallurgy |
This book describes the miner and the finding of veins. Agricola assumes that his audience is the mine owner, or an investor in mines. He advises owners to live at the mine and to appoint good deputies. It is recommended to buy shares in mines that have not started to produce as well as existing mines to balance the risks. The next section of this book recommends areas where miners should search. These are generally mountains with wood available for fuel and a good supply of water. A navigable river can be used to bring fuel, but only gold or gemstones can be mined if no fuel is available. The roads must be good and the area healthy. Agricola describes searching streams for metals and gems that have been washed from the veins. He also suggests looking for exposed veins and also describes the effects of metals on the overlying vegetation. He recommends trenching to investigate veins beneath the surface. He then describes dowsing with a forked twig although he rejects the method himself. The passage is the first written description of how dowsing is done. Finally he comments on the practice of naming veins or shafts. | 0 | Metallurgy |
Fretting refers to wear and sometimes corrosion damage of loaded surfaces in contact while they encounter small oscillatory movements tangential to the surface. Fretting is caused by adhesion of contact surface asperities, which are subsequently broken again by the small movement. This breaking causes wear debris to be formed.
If the debris and/or surface subsequently undergo chemical reaction, i.e., mainly oxidation, the mechanism is termed fretting corrosion. Fretting degrades the surface, leading to increased surface roughness and micropits, which reduces the fatigue strength of the components.
The amplitude of the relative sliding motion is often in the order of micrometers to millimeters, but can be as low as 3 nanometers.
Typically fretting is encountered in shrink fits, bearing seats, bolted parts, splines, and dovetail connections. | 0 | Metallurgy |
In these processes, iron ore is brought into contact with reducing gases produced and heated by a separate plant in a closed enclosure. As a result, these processes are naturally suited to the use of natural gas. | 0 | Metallurgy |
The TGF-β pathway regulates many cellular processes in developing embryo and adult organisms, including cell growth, differentiation, apoptosis, and homeostasis. There are five kinds of type II receptors and seven types of type I receptors in humans and other mammals. These receptors are known as "dual-specificity kinases" because their cytoplasmic kinase domain has weak tyrosine kinase activity but strong serine/threonine kinase activity. When a TGF-β superfamily ligand binds to the type II receptor, it recruits a type I receptor and activates it by phosphorylating the serine or threonine residues of its "GS" box. This forms an activation complex that can then phosphorylate SMAD proteins. | 1 | Gene expression + Signal Transduction |
Deflocculation is the exact opposite of flocculation, also sometimes known as peptization. Sodium silicate (NaSiO) is a typical example. Usually in higher pH ranges in addition to low ionic strength of solutions and domination of monovalent metal cations the colloidal particles can be dispersed.
The additive that prevents the colloids from forming flocs is called a deflocculant. For deflocculation imparted through electrostatic barriers, the efficacy of a deflocculant can be gauged in terms of zeta potential. According to the Encyclopedic Dictionary of Polymers deflocculation is "a state or condition of a dispersion of a solid in a liquid in which each solid particle remains independent and unassociated with adjacent particles (much like emulsifier). A deflocculated suspension shows zero or very low yield value".
Deflocculation can be a problem in wastewater treatment plants as it commonly causes sludge settling problems and deterioration of the effluent quality. | 0 | Metallurgy |
Early European bloomeries were relatively small, primarily due to the mechanical limits of human-powered bellows and the amount of force possible to apply with hand-driven sledge hammers. Those known archaeologically from the pre-Roman Iron Age tend to be in the 2 kg range, produced in low shaft furnaces. Roman-era production often used furnaces tall enough to create a natural draft effect (into the range of 200 cm tall), and increasing bloom sizes into the range of 10–15 kg. Contemporary experimenters had routinely made blooms using Northern European-derived "short-shaft" furnaces with blown air supplies in the 5–10 kg range The use of waterwheels, spreading around the turn of the first millennium and used to power more massive bellows, allowed the bloomery to become larger and hotter, with associated trip hammers allowing the consolidation forging of the larger blooms created. Progressively larger bloomeries were constructed in the late 14th century, with a capacity of about 15 kg on average, though exceptions did exist. European average bloom sizes quickly rose to 300 kg, where they levelled off until the demise of the bloomery.
As a bloomerys size is increased, the iron ore is exposed to burning charcoal for a longer time. When combined with the strong air blast required to penetrate the large ore and charcoal stack, this may cause part of the iron to melt and become saturated with carbon in the process, producing unforgeable pig iron, which requires oxidation to be reduced into cast iron, steel, and iron. This pig iron was considered a waste product detracting from the largest bloomeries yield, and early blast furnaces, identical in construction, but dedicated to the production of molten iron, were not built until the 14th century.
Bloomery type furnaces typically produced a range of iron products from very low-carbon iron to steel containing around 0.2–1.5% carbon. The master smith had to select pieces of low-carbon iron, carburize them, and pattern-weld them together to make steel sheets. Even when applied to a noncarburized bloom, this pound, fold, and weld process resulted in a more homogeneous product and removed much of the slag. The process had to be repeated up to 15 times when high-quality steel was needed, as for a sword. The alternative was to carburize the surface of a finished product. Each welding's heat oxidises some carbon, so the master smith had to make sure enough carbon was in the starting mixture.
In England and Wales, despite the arrival of the blast furnace in the Weald in about 1491, bloomery forges, probably using waterpower for the hammer and the bellows, were operating in the West Midlands region beyond 1580. In Furness and Cumberland, they operated into the early 17th century and the last one in England (near Garstang) did not close until about 1770.
One of the oldest-known blast furnaces in Europe has been found in Lapphyttan in Sweden, carbon-14 dated to be from the 12th century. The oldest bloomery in Sweden, also found in the same area, has been carbon-14 dated to 700 BCE.
Bloomeries survived in Spain and southern France as Catalan forges into the mid-19th century, and in Austria as the to 1775. | 0 | Metallurgy |
The most widely used anodizing specification in the US is a U.S. military spec, MIL-A-8625, which defines three types of aluminium anodizing. Type I is chromic acid anodizing, Type II is sulphuric acid anodizing, and Type III is sulphuric acid hard anodizing. Other anodizing specifications include more MIL-SPECs (e.g., MIL-A-63576), aerospace industry specs by organizations such as SAE, ASTM, and ISO (e.g., AMS 2469, AMS 2470, AMS 2471, AMS 2472, AMS 2482, ASTM B580, ASTM D3933, ISO 10074, and BS 5599), and corporation-specific specs (such as those of Boeing, Lockheed Martin, Airbus and other large contractors). AMS 2468 is obsolete. None of these specifications define a detailed process or chemistry, but rather a set of tests and quality assurance measures which the anodized product must meet. BS 1615 guides the selection of alloys for anodizing. For British defense work, a detailed chromic and sulfuric anodizing processes are described by DEF STAN 03-24/3 and DEF STAN 03-25/3 respectively. | 0 | Metallurgy |
FAIRE-Seq (Formaldehyde-Assisted Isolation of Regulatory Elements) is a method in molecular biology used for determining the sequences of DNA regions in the genome associated with regulatory activity. The technique was developed in the laboratory of Jason D. Lieb at the University of North Carolina, Chapel Hill. In contrast to DNase-Seq, the FAIRE-Seq protocol doesn't require the permeabilization of cells or isolation of nuclei, and can analyse any cell type. In a study of seven diverse human cell types, DNase-seq and FAIRE-seq produced strong cross-validation, with each cell type having 1-2% of the human genome as open chromatin. | 1 | Gene expression + Signal Transduction |
Cyclic adenosine monophosphate (cAMP, cyclic AMP, or 3,5-cyclic adenosine monophosphate) is a second messenger, or cellular signal occurring within cells, that is important in many biological processes. cAMP is a derivative of adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway. | 1 | Gene expression + Signal Transduction |
In another setting, the chambers are connected side by side horizontally (Zigmond chamber) or as concentric rings on a slide (Dunn chamber) Concentration gradient develops on a narrow connecting bridge between the chambers and the number of migrating cells is also counted on the surface of the bridge by light microscope. In some cases the bridge between the two chambers is filled with agar and cells have to "glide" in this semisolid layer. | 1 | Gene expression + Signal Transduction |
Romans used many methods to create metal objects. Like Samian ware, moulds were created by making a model of the desired shape (whether through wood, wax, or metal), which would then be pressed into a clay mould. In the case of a metal or wax model, once dry, the ceramic could be heated and the wax or metal melted until it could be poured from the mould (this process utilising wax is called the “lost wax“ technique). By pouring metal into the aperture, exact copies of an object could be cast. This process made the creation of a line of objects quite uniform. This is not to suggest that the creativity of individual artisans did not continue; rather, unique handcrafted pieces were normally the work of small, rural metalworkers on the peripheries of Rome using local techniques (Tylecote 1962).
There is archaeological evidence throughout the Empire demonstrating the large scale excavations, smelting, and trade routes concerning metals. With the Romans came the concept of mass production; this is arguably the most important aspect of Roman influence in the study of metallurgy. Three particular objects produced en masse and seen in the archaeological record throughout the Roman Empire are brooches called fibulae, worn by both men and women (Bayley 2004), coins, and ingots (Hughes 1980). These cast objects can allow archaeologists to trace years of communication, trade, and even historic/stylistic changes throughout the centuries of Roman power. | 0 | Metallurgy |
The histone code is a hypothesis that the transcription of genetic information encoded in DNA is in part regulated by chemical modifications to histone proteins, primarily on their unstructured ends. Together with similar modifications such as DNA methylation it is part of the epigenetic code.
Cumulative evidence suggests that such code is written by specific enzymes which can (for example) methylate or acetylate DNA (writers), removed by other enzymes having demethylase or deacetylase activity (erasers), and finally readily identified by proteins (readers) that are recruited to such histone modifications and bind via specific domains, e.g., bromodomain, chromodomain. These triple action of writing, reading and erasing establish the favorable local environment for transcriptional regulation, DNA-damage repair, etc.
The critical concept of the histone code hypothesis is that the histone modifications serve to recruit other proteins by specific recognition of the modified histone via protein domains specialized for such purposes, rather than through simply stabilizing or destabilizing the interaction between histone and the underlying DNA. These recruited proteins then act to alter chromatin structure actively or to promote transcription.
A very basic summary of the histone code for gene expression status is given below (histone nomenclature is described here): | 1 | Gene expression + Signal Transduction |
There are ten known isoforms of adenylyl cyclases in mammals:
These are also sometimes called simply AC1, AC2, etc., and, somewhat confusingly, sometimes Roman numerals are used for these isoforms that all belong to the overall AC class III. They differ mainly in how they are regulated, and are differentially expressed in various tissues throughout mammalian development. | 1 | Gene expression + Signal Transduction |
Prior to the formation of the lactate shuttle hypothesis, lactate had long been considered a byproduct resulting from glucose breakdown through glycolysis in times of anaerobic metabolism. As a means of regenerating oxidized NAD, lactate dehydrogenase catalyzes the conversion of pyruvate to lactate in the cytosol, oxidizing NADH to NAD, regenerating the necessary substrate needed to continue glycolysis. Lactate is then transported from the peripheral tissues to the liver by means of the Cori Cycle where it is reformed into pyruvate through the reverse reaction using lactate dehydrogenase. By this logic, lactate was traditionally considered a toxic metabolic byproduct that could give rise to fatigue and muscle pain during times of anaerobic respiration. Lactate was essentially payment for ‘oxygen debt’ defined by Hill and Lupton as the ‘total amount of oxygen used, after cessation of exercise in recovery therefrom’. | 1 | Gene expression + Signal Transduction |
In eukaryotic transcription of mRNAs, terminator signals are recognized by protein factors that are associated with the RNA polymerase II and which trigger the termination process. The genome encodes one or more polyadenylation signals. Once the signals are transcribed into the mRNA, the proteins cleavage and polyadenylation specificity factor (CPSF) and cleavage stimulation factor (CstF) transfer from the carboxyl terminal domain of RNA polymerase II to the poly-A signal. These two factors then recruit other proteins to the site to cleave the transcript, freeing the mRNA from the transcription complex, and add a string of about 200 A-repeats to the 3' end of the mRNA in a process known as polyadenylation. During these processing steps, the RNA polymerase continues to transcribe for several hundred to a few thousand bases and eventually dissociates from the DNA and downstream transcript through an unclear mechanism; there are two basic models for this event known as the torpedo and allosteric models. | 1 | Gene expression + Signal Transduction |
The Museum Weavers are housed in a barn, featuring more than 50 working looms for weaving. Members of this club meet weekly to learn and practice weaving, rug-making and rope-making. | 0 | Metallurgy |
Nuclear receptor-interacting protein 1 (NRIP1) also known as receptor-interacting protein 140 (RIP140) is a protein that in humans is encoded by the NRIP1 gene. | 1 | Gene expression + Signal Transduction |
Hydrogen probes are used to monitor the penetration of hydrogen into steels, which can cause brittleness, porosity or decarbonization. | 0 | Metallurgy |
Wrought iron is no longer made. The particles of slag present in the iron after preparation by puddling were drawn into long fibres during the forging or rolling process. The proportion of slag was intended to be about 3%, but the process was difficult to control and examples with up to 10% slag were produced. | 0 | Metallurgy |
Considerable effort and research continues to be made into discovering and refining better methods of tailings disposal. Research at the Porgera Gold Mine is focusing on developing a method of combining tailings products with coarse waste rock and waste muds to create a product that can be stored on the surface in generic-looking waste dumps or stockpiles. This would allow the current use of riverine disposal to cease. Considerable work remains to be done. However, co-disposal has been successfully implemented by several designers including AMEC at, for example, the Elkview Mine in British Columbia. | 0 | Metallurgy |
Signal transducer and activator of transcription 1 (STAT1) is a transcription factor which in humans is encoded by the STAT1 gene. It is a member of the STAT protein family. | 1 | Gene expression + Signal Transduction |
The fim switch in Escherichia coli is the mechanism by which the fim gene cluster, encoding Type I Pili, is transcriptionally controlled.
These pili are virulence factors involved in adhesion, especially important in uropathogenic Escherichia coli. The gene undergoes phase variation mediated via two recombinases and is a model example of site specific inversion. | 1 | Gene expression + Signal Transduction |
The discovery of this type of mechanism to control the expression of genes in a biosynthetic operon lead to its identification in a wide variety of such operons for which repressors had never been discovered. For example: | 1 | Gene expression + Signal Transduction |
Fresh domestic sewage entering a wastewater collection system contains proteins including organic sulfur compounds oxidizable to sulfates and may contain inorganic sulfates. Dissolved oxygen is depleted as bacteria begin to catabolize organic material in sewage. In the absence of dissolved oxygen and nitrates, sulfates are reduced to hydrogen sulfide as an alternative source of oxygen for catabolizing organic waste by sulfate reducing bacteria (SRB), identified primarily from the obligate anaerobic species Desulfovibrio.
Hydrogen sulfide production depends on various physicochemical, topographic and hydraulic parameters such as:
* Sewage oxygen concentration. The threshold is 0.1 mg.l; above this value, sulfides produced in sludge and sediments are oxidized by oxygen; below this value, sulfides are emitted in the gaseous phase.
* Temperature. The higher the temperature, the faster the kinetics of HS production.
* Sewage pH. It must be included between 5.5 and 9 with an optimum at 7.5-8.
* Sulfate concentration.
* Nutrients concentration, associated to the biochemical oxygen demand.
* Conception of the sewage As HS is formed only in anaerobic conditions. Slow flow and long retention time gives more time to aerobic bacteria to consume all available dissolved oxygen in water, creating anaerobic conditions. The flatter the land, the less slope can be given to the sewer network, and this favors slower flow and more pumping stations (where retention time is generally longer) | 0 | Metallurgy |
One well-studied eRNA is the eRNA of the enhancer that interacts with the promoter of the prostate specific antigen (PSA) gene. The PSA eRNA is strongly up-regulated by the androgen receptor. High PSA eRNA then has a domino effect. PSA eRNA binds to and activates the positive transcription elongation factor P-TEFb protein complex which can then phosphorylate RNA polymerase II (RNAP II), initiating its activity in producing mRNA. P-TEFb can also phosphorylate the negative elongation factor NELF (which pauses RNAP II within 60 nucleotides after mRNA initiation begins). Phosphorylated NELF is released from RNAP II, then allowing RNAP II to have productive mRNA progression (see Figure). Up-regulated PSA eRNA thereby increases expression of 586 androgen receptor-responsive genes. Knockdown of PSA eRNA or deleting a set of nucleotides from PSA eRNA causes decreased presence of phosphorylated (active) RNAP II at these genes causing their reduced transcription.
The negative elongation factor NELF protein can also be released from its interaction with RNAP II by direct interaction with some eRNAs. Schaukowitch et al. showed that the eRNAs of two immediate early genes (IEGs) directly interacted with the NELF protein to release NELF from the RNAP II paused at the promoters of these two genes, allowing these two genes to then be expressed.
In addition, eRNAs appear to interact with as many as 30 other proteins. | 1 | Gene expression + Signal Transduction |
Small GTPases, also known as small G-proteins, bind GTP and GDP likewise, and are involved in signal transduction. These proteins are homologous to the alpha (α) subunit found in heterotrimers, but exist as monomers. They are small (20-kDa to 25-kDa) proteins that bind to guanosine triphosphate (GTP). This family of proteins is homologous to the Ras GTPases and is also called the Ras superfamily GTPases. | 1 | Gene expression + Signal Transduction |
The deposits consist of a multitude of pancake-like splats called lamellae, formed by flattening of the liquid droplets. As the feedstock powders typically have sizes from micrometers to above 100 micrometers, the lamellae have thickness in the micrometer range and lateral dimension from several to hundreds of micrometers. Between these lamellae, there are small voids, such as pores, cracks and regions of incomplete bonding. As a result of this unique structure, the deposits can have properties significantly different from bulk materials. These are generally mechanical properties, such as lower strength and modulus, higher strain tolerance, and lower thermal and electrical conductivity. Also, due to the rapid solidification, metastable phases can be present in the deposits. | 0 | Metallurgy |
The alkA gene product is a glycosylase that can repair a variety of lesions, removing a base from the sugar-phosphate backbone, producing an abasic site. | 1 | Gene expression + Signal Transduction |
RNA polymerase II (also called RNAP II and Pol II) is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. In humans, RNAP II consists of seventeen protein molecules (gene products encoded by POLR2A-L, where the proteins synthesized from POLR2C, POLR2E, and POLR2F form homodimers). | 1 | Gene expression + Signal Transduction |
Scholarly information about the use of gold in early Philippine history comes mostly from artifacts that have been discovered in various sites in the Philippines, and from historical accounts from the early Spanish colonial period. Archeological excavation sites include ones in Batangas, Mindoro, Luzon, Samar, Butuan and Surigao. | 0 | Metallurgy |
The Mark IV Cell design was introduced in 2009. It included the following improvements:
* a flexible hose for easier alignment of the downcomer
* clamping of the slurry lens onto the downcomer (see Figure 10)
* stainless steel quick-release clamps in the downcomer assembly
* long-lasting rubber flaps in the AISE valves. | 0 | Metallurgy |
Recent excavations in Middle Ganga Valley done by archaeologist Rakesh Tewari show iron working in India may have begun as early as 1800 BCE. Archaeological sites in India, such as Malhar, Dadupur, Raja Nala Ka Tila and Lahuradewa in the state of Uttar Pradesh show iron implements in the period between 1800 BCE – 1200 BCE. Sahi (1979: 366) concluded that by the early 13th century BCE, iron smelting was definitely practiced on a bigger scale in India, suggesting that the date the technology's inception may well be placed as early as the 16th century BCE.
The Black and Red Ware culture was another early Iron Age archaeological culture of the northern Indian subcontinent. It is dated to roughly the 12th – 9th centuries BCE, and associated with the post-Rigvedic Vedic civilization. It extended from the upper Gangetic plain in Uttar Pradesh to the eastern Vindhya range and West Bengal.
Perhaps as early as 500 BCE, although certainly by 200 CE, high quality steel was being produced in southern India by what Europeans would later call the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in crucibles and heated until the iron melted and absorbed the carbon. The resulting high-carbon steel, called fūlāḏ by the Arabs () and wootz by later Europeans, was exported throughout much of Asia and Europe.
Will Durant wrote in The Story of Civilization I: Our Oriental Heritage: | 0 | Metallurgy |
The U.S. Institute of Medicine (IOM) established Recommended Dietary Allowances (RDAs) for calcium in 1997 and updated those values in 2011. See table. The
European Food Safety Authority (EFSA) uses the term Population Reference Intake (PRIs) instead of RDAs and sets slightly different numbers: ages 4–10 800 mg, ages 11–17 1150 mg, ages 18–24 1000 mg, and >25 years 950 mg.
Because of concerns of long-term adverse side effects such as calcification of arteries and kidney stones, the IOM and EFSA both set Tolerable Upper Intake Levels (ULs) for the combination of dietary and supplemental calcium. From the IOM, people ages 9–18 years are not supposed to exceed 3,000 mg/day; for ages 19–50 not to exceed 2,500 mg/day; for ages 51 and older, not to exceed 2,000 mg/day. The EFSA set UL at 2,500 mg/day for adults but decided the information for children and adolescents was not sufficient to determine ULs. | 1 | Gene expression + Signal Transduction |
The Jameson Cell has been found to be particularly effective in cleaning and recovering fine coal particles. For example, at BHP Coal's Goonyella mine (now part of the BHP Mitsubishi Alliance) eight Cells were installed to replace the entire 32 mechanical cell flotation circuit in 1995 in its 1800 t/h coal flotation plant. The result was an overall increase in yield for the plant of 3.5% (better than the predicted yield of 2.1% that was used to justify the project) and the production of a low-ash product.
Since then, Jameson Cells have been installed in many coal preparation plants around the world, with the largest installation at the Curragh coal mine in Australia, where 12 Cells treat over 5 million t/y of coal fines.
The Cell can also be applied to coal preparation plant tailings to recover fine coal previously discarded. | 0 | Metallurgy |
The initial laser systems used during the development of laser peening were large research lasers providing high-energy pulses at very low pulse frequencies. Since the mid-late 1990s, lasers designed specifically for laser peening featured steadily smaller size and higher pulse frequencies, both of these more desirable for production environments. The laser peening systems include both rod laser systems and a slab laser system. The rod laser systems can be separated roughly into three primary groups, recognizing that there is some overlap between them: (1) high-energy low-repetition rate lasers operating typically at 10–40 J per pulse with 8–25 ns pulse length at nominally 0.5–1 Hz rep rate, nominal spot sizes of 2 to 8 mm; (2) intermediate energy, intermediate repetition rate lasers operating at 3–10 J with 10–20 ns pulse width at 10 Hz rep rate, nominal spot sizes of 1–4 mm; (3) low-energy, high-repetition rate lasers operating at per pulse with ≤10 ns pulse length at 60+ Hz rep rate, spot size. The slab laser system operates in the range of 10–25 J per pulse with 8–25 ns pulse duration at 3–5 Hz rep rate, nominal spot sizes of 2–5 mm. The commercial systems include rod lasers represented by all three groups and the slab laser system.
For each laser peening system the output beam from the laser is directed into a laser peening cell containing the work pieces or parts to be processed. The peening cell contains the parts handling system and provides the safe environment necessary for efficient commercial laser peening. The parts to be processed are usually introduced into the cell in batches. The parts are then picked and placed in the beam path by robots or other customized parts handling systems. Within the work cell, the beam is directed to the surface of the work piece via an optical chain of mirrors and/or lenses. If tape is used, it is applied before the part enters the work cell, whereas water or RapidCoater overlays are applied within the cell individually for each spot. The workpiece, or sometimes the laser beam, is repositioned for each shot as necessary via a robot or other parts handling system. When the selected areas on each part have been processed, the batch is replaced in the work cell by another. | 0 | Metallurgy |
The process of DNA replication inherently places cells at risk of acquiring mutations. Thus, caretaker genes are vitally important to cellular health. Rounds of cell replication allow fixation of mutated genes into the genome. Caretaker genes provide genome stability by preventing the accumulation of these mutations.
Factors that contribute to genome stabilization include proper cell-cycle checkpoints, DNA repair pathways, and other actions that ensure cell survival following DNA damage. Specific DNA maintenance operations encoded by caretaker genes include nucleotide excision repair, base excision repair, non-homologous end joining recombination pathways, mismatch repair pathways, and telomere metabolism.
Loss of function mutations in caretaker genes allow mutations in other genes to survive that can result in increased conversion of a normal cell to a neoplastic cell, a cell that; (1) divides more often than it should or (2) does not die when conditions warrant cell death. Thus, caretaker genes do not directly regulate cell proliferation. Instead, they prevent other mutations from surviving for example by slowing the cell division process to enable DNA repair to complete, or by initiating apoptosis of the cell. In genetic knock-out and rescue experiments, restoration of a caretaker gene from the mutated form to the wildtype version does not limit tumorigenesis. This is because caretaker genes only indirectly contribute to the pathway to cancer.
Cells deficient in a DNA repair process tend to accumulate unrepaired DNA damages. Cells defective in apoptosis tend to survive even with excessive DNA damage, thus permitting replication of the damaged DNA and consequently carcinogenic mutations. Some key caretaker proteins that contribute to cell survival by acting in DNA repair processes when the level of damage is manageable, become executioners by inducing apoptosis when there is excess DNA damage.
Inactivation of caretaker genes is environmentally equivalent to exposing the cell to mutagens incessantly. For example, a mutation in a caretaker gene coding for a DNA repair pathway that leads to the inability to properly repair DNA damage could allow uncontrolled cell growth. This is the result of mutations of other genes that accumulate unchecked as a result of faulty gene products encoded by the caretakers.
In addition to providing genomic stability, caretakers also provide chromosomal stability. Chromosomal instability resulting from dysfunctional caretaker genes is the most common form of genetic instability that leads to cancer in humans. In fact, it has been proposed that these caretaker genes are responsible for many hereditary predispositions to cancers.
In individuals predisposed to cancer via mutations in caretaker genes, a total of three subsequent somatic mutations are required to acquire the cancerous phenotype. Mutations must occur in the remaining normal caretaker allele in addition to both alleles of gatekeeper genes within that cell for the said cell to turn to neoplasia. Thus, the risk of cancer in these affected populations is much less when compared to cancer risk in families predisposed to cancer via the gatekeeper pathway. | 1 | Gene expression + Signal Transduction |
Conformal compound coatings stop the whiskers from penetrating a barrier, reaching a nearby termination and forming a short. | 0 | Metallurgy |
Laser peening uses the dynamic mechanical effects of a shock wave imparted by a laser to modify the surface of a target material. It does not utilize thermal effects. Fundamentally, laser peening can be accomplished with only two components: a transparent overlay and a high-energy pulsed laser system. The transparent overlay confines the plasma formed at the target surface by the laser beam. It is also often beneficial to use a thin overlay, opaque to the laser beam, between the water overlay and the target surface. This opaque overlay can provide either or each of three benefits: protect the target surface from potentially detrimental thermal effects from the laser beam, provide a consistent surface for the laser beam-material interaction and, if the overlay impedance is less than that of the target surface, increase the magnitude of the shock wave entering the target. However, there are situations where an opaque overlay is not used; in the Toshiba process, LPwC, or where the tradeoff between decreased cost and possibly somewhat lowered surface residual stress allows superficial grinding or honing after laser peening to remove the thin thermally effected layer.
The laser peening process originated with high-energy Nd-glass lasers producing pulse energies up to 50 J (more commonly 5 to 40 J) with pulse durations of 8 to 25 ns. Laser spot diameters on target are typically in the range of 2 to 7 mm. The processing sequence begins by applying the opaque overlay on the workpiece or target surface. Commonly used opaque overlay materials are black or aluminum tape, paint or a proprietary liquid, RapidCoater. The tape or paint is generally applied over the entire area to be processed, while the RapidCoater is applied over each laser spot just before triggering the laser pulse. After application of the opaque overlay, the transparent overlay is placed over it. The transparent overlay used in production processing is water; it is cheap, easily applied, readily conforms to most complex surface geometries, and is easily removed. It is applied to the surface just before triggering the laser pulse. Quartz or glass overlays produce much higher pressures than water, but are limited to flat surfaces, must be replaced after each shot and would be difficult to handle in a production setting. Clear tape may be used, but requires labor to apply and is difficult to conform to complex surface features. The transparent overlay allows the laser beam to pass through it without appreciable absorption of the laser energy or dielectric breakdown. When the laser is triggered, the beam passes through the transparent overlay and strikes the opaque overlay, immediately vaporizing a thin layer of the overlay material. This vapor is trapped in the interface between the transparent and opaque overlays. The continued delivery of energy during the laser pulse rapidly heats and ionizes the vapor, converting it into a rapidly expanding plasma. The rising pressure exerted on the opaque overlay surface by the expanding plasma enters the target surface as a high-amplitude stress wave or shock wave. Without a transparent overlay, the unconfined plasma plume moves away from the surface and the peak pressure is considerably lower. If the amplitude of the shock wave is above the Hugoniot Elastic Limit (HEL), i.e., the dynamic yield strength, of the target, the material plastically deforms during passage of the shock wave. The magnitude of the plastic strain decreases with distance from the surface as the peak pressure of the shock wave attenuates, i.e., decreases, and becomes zero when the peak pressure falls below the HEL. After the shock wave passes, the residual plastic strain creates a compressive residual stress gradient below the target surface, highest at or immediately below the surface and decreasing with depth. By varying the laser power density, pulse duration, and number of successive shots on an area, a range of surface compressive stress magnitudes and depths can be achieved. The magnitude of surface stresses are comparable to shot peening, but the depths are much greater, ranging up to 5 mm when using multiple shots on a spot. Generally spot densities of about 10 spots/cm to 40 spots/cm are applied. The compressive stress depth achieved with the most common processing parameters ranges from deep. The deep compressive stresses are due to the shock wave peak pressure being maintained above the HEL to greater depths than for other peening technologies.
There may be instances where it is cost effective not to apply the opaque overlay and laser peen the bare surface of the work piece directly. When laser peening a bare, metallic surface a thin, micrometer-range, layer of surface material is vaporized. The rapid rise in temperature causes surface melting to a depth dependent on pulse energy and duration, and target melting point. On aluminum alloys this depth is nominally 10–20 μm, but on steels and other higher melting point alloys the depths may be just a few micrometers. Due to the short duration of the pulse, the in-depth heating of the surface is limited to a few tens of micrometers due to the rapid quenching effect of the cold substrate. Some superficial surface staining of the work piece may occur, typically from oxidation products. These detrimental effects of bare surface processing, both aesthetic and metallurgical, can be removed after laser peening by light grinding or honing. With an opaque overlay in place, the target surface experiences temperature rises of less than on a nanosecond time scale.
Laser pulses are generally applied sequentially on the target to treat areas larger than the laser spot size. Laser pulse shapes are customizable to circular, elliptical, square, and other profiles to provide the most convenient and efficient processing conditions. The spot size applied depends on a number of factors that include material HEL, laser system characteristics and other processing factors. The area to be laser peened is usually determined by the part geometry, the extent of the fatigue critical area and considerations of moving the compensating tensile stresses out of this area.
The more recently developed laser peening process, the Toshiba LPwC process, varies in significant ways from the process described above. The LPwC process utilizes low-energy high-frequency Nd-YAG lasers producing pulse energies of and pulse durations of , using spot sizes diameter. Because the process originally was intended to operate in large water-filled vessels, the wave frequency was doubled to halve the wavelength to 532 nm. The shorter wavelength decreases the absorption of beam energy while traveling through water to the target. Due to access constraints, no opaque overlay is applied to the target surface. This factor, combined with the small spot size, requires many shots to achieve a significant surface compressive stress and depths of 1 mm. The first layers applied produce a tensile surface stress due to surface melting, although a compressive stress is developed below the melt layer. However, as more layers are added, the increasing subsurface compressive stress "bleeds" back through the melted surface layer to produce the desired surface compressive stress. Depending on material properties and the desired compressive stresses, generally about 18 spots/mm to 70 spots/mm or greater spot densities are applied, about 100 times the spot densities of the high-pulse-energy process. The effects of the higher spot densities on processing times are compensated for in part by the higher pulse frequency, 60 Hz, of the low-energy lasers. Newer generations of these laser systems are projected to operate at higher frequencies. This low-energy process achieves compressive residual stress magnitudes and depths equivalent to the high-energy process with nominal depths of . However, the smaller spot size will not permit depths deeper than this. | 0 | Metallurgy |
Many waters in both the UK and Europe are capable of supporting Type 1 pitting but no problems will be experienced unless a pit is initiated in the wall of the tube. When a copper tube is initially filled with a hard water salts deposit on the wall and the copper slowly reacts with the water producing a thin protective layer of mixed corrosion products and hardness scale. If any pitting of the tube is to occur then this film must be locally disrupted. There are three mechanisms that allow the disruption of the protective deposits. The most well known, although now the least common, is the presence of carbon films on the bore. Stagnation and flux residues are the most common initiation mechanisms that have led to Type 1 pitting failures in the last ten years. | 0 | Metallurgy |
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This process is not 100% efficient. At the Lautenthal, Altenau, and Sankt Andreasberg smelting-works in the Upper Harz between 1857 and 1860 25% of the silver, 25.1% of the lead and 9.3% of the copper was lost. Some of this is lost in slag that is not worth reusing, some is lost by what is termed ‘burning’, and some of the silver is lost to the refined copper. It is clear therefore that a constant supply of lead was needed to make up for that lost at various stages. | 0 | Metallurgy |
The largest subunit of Pol II (Rpb1) has a domain at its C-terminus called the CTD (C-terminal domain). This is the target of kinases and phosphatases. The phosphorylation of the CTD is an important regulation mechanism, as this allows attraction and rejection of factors that have a function in the transcription process. The CTD can be considered as a platform for transcription factors.
The CTD consists of repetitions of an amino acid motif, YSPTSPS, of which Serines and Threonines can be phosphorylated. The number of these repeats varies; the mammalian protein contains 52, while the yeast protein contains 26. Site-directed-mutagenesis of the yeast protein has found at least 10 repeats are needed for viability. There are many different combinations of phosphorylations possible on these repeats and these can change rapidly during transcription. The regulation of these phosphorylations and the consequences for the association of transcription factors plays a major role in the regulation of transcription.
During the transcription cycle, the CTD of the large subunit of RNAP II is reversibly phosphorylated. RNAP II containing unphosphorylated CTD is recruited to the promoter, whereas the hyperphosphorylated CTD form is involved in active transcription. Phosphorylation occurs at two sites within the heptapeptide repeat, at Serine 5 and Serine 2. Serine 5 phosphorylation is confined to promoter regions and is necessary for the initiation of transcription, whereas Serine 2 phosphorylation is important for mRNA elongation and 3'-end processing. | 1 | Gene expression + Signal Transduction |
The Arthashastra lays down the role of the Director of Metals, the Director of Forest Produce and the Director of Mining. It is the duty of the Director of Metals to establish factories for different metals. The Director of Mines is responsible for the inspection of mines. The Arthashastra also refers to counterfeit coins. | 0 | Metallurgy |
Bacteria depend on transcription-translation coupling for genome integrity, termination of transcription and control of mRNA stability. Consequently, artificial disruption of transcription-translation coupling impairs the fitness of bacteria. Without coupling, genome integrity is compromised as stalled transcription complexes interfere with DNA replication and induce DNA breaks. Lack of coupling produces premature transcription termination, likely due to increased binding of termination factor Rho. Degradation of prokaryotic mRNAs is accelerated by loss of coupled translation due to increased availability of target sites of RNase E. It has also been suggested that coupling of transcription with translation is an important mechanism of preventing formation of deleterious R-loops. While transcription-translation coupling is likely prevalent across prokaryotic organisms, not all species are dependent on it. Unlike Escherichia coli, in Bacillus subtilis transcription significantly outpaces translation, and coupling consequently does not occur. | 1 | Gene expression + Signal Transduction |
The cam is actuated by a user by rotating the handle, causing a cam to lift the weight and let it fall freely on the frame attached to the ram head. This produces a standard compacting action to a pre-measured amount of sand. Demonstration of this apparatus can be seen here:
Variety of standard specimen for Green Sand and Silicate based (CO)sand are prepared using a sand rammer along with accessories
The object for producing the standard cylindrical specimen is to have the specimen become 2 inches high (plus or minus 1/32 inch) with three rams of the machine. After the specimen has been prepared inside the specimen tube, the specimen can be used for various standard sand tests such as the permeability test, the green sand compression test, the shear test, or other standard foundry tests.
The sand rammer machine can be used to measure compactability of prepared sand by filling the specimen tube with prepared sand so that it is level with the top of the tube. The tube is then placed under the ram head in the shallow cup and rammed three times. Compactability in percentage is then calculated from the resultant height of the sand inside the specimen tube.
A rammer is mounted on a base block on a solid foundation, which provides vibration damping to ensure consistent ramming. | 0 | Metallurgy |
Different elements serve different roles in the solder alloy:
* Antimony is added to increase strength without affecting wettability. Prevents tin pest. Should be avoided on zinc, cadmium, or galvanized metals as the resulting joint is brittle.
* Bismuth significantly lowers the melting point and improves wettability. In presence of sufficient lead and tin, bismuth forms crystals of with melting point of only 95 °C, which diffuses along the grain boundaries and may cause a joint failure at relatively low temperatures. A high-power part pre-tinned with an alloy of lead can therefore desolder under load when soldered with a bismuth-containing solder. Such joints are also prone to cracking. Alloys with more than 47% Bi expand upon cooling, which may be used to offset thermal expansion mismatch stresses. Retards growth of tin whiskers. Relatively expensive, limited availability.
* Copper improves resistance to thermal cycle fatigue, and improves wetting properties of the molten solder. It also slows down the rate of dissolution of copper from the board and part leads in the liquid solder. Copper in solders forms intermetallic compounds. Supersaturated (by about 1%) solution of copper in tin may be employed to inhibit dissolution of thin-film under-bump metallization of BGA chips, e.g. as .
* Nickel can be added to the solder alloy to form a supersaturated solution to inhibit dissolution of thin-film under-bump metallization. In tin-copper alloys, small addition of Ni (<0.5 wt%) inhibits the formation of voids and interdiffusion of Cu and Sn elements. Inhibits copper dissolution, even more in synergy with bismuth. Nickel presence stabilizes the copper-tin intermetallics, inhibits growth of pro-eutectic β-tin dendrites (and therefore increases fluidity near the melting point of copper-tin eutectic), promotes shiny bright surface after solidification, inhibits surface cracking at cooling; such alloys are called "nickel-modified" or "nickel-stabilized". Small amounts increase melt fluidity, most at 0.06%. Suboptimal amounts may be used to avoid patent issues. Fluidity reduction increase hole filling and mitigates bridging and icicles.
* Cobalt is used instead of nickel to avoid patent issues in improving fluidity. Does not stabilize intermetallic growths in solid alloy.
* Indium lowers the melting point and improves ductility. In presence of lead it forms a ternary compound that undergoes phase change at 114 °C. Very high cost (several times of silver), low availability. Easily oxidizes, which causes problems for repairs and reworks, especially when oxide-removing flux cannot be used, e.g. during GaAs die attachment. Indium alloys are used for cryogenic applications, and for soldering gold as gold dissolves in indium much less than in tin. Indium can also solder many nonmetals (e.g. glass, mica, alumina, magnesia, titania, zirconia, porcelain, brick, concrete, and marble). Prone to diffusion into semiconductors and cause undesired doping. At elevated temperatures easily diffuses through metals. Low vapor pressure, suitable for use in vacuum systems. Forms brittle intermetallics with gold; indium-rich solders on thick gold are unreliable. Indium-based solders are prone to corrosion, especially in presence of chloride ions.
* Lead is inexpensive and has suitable properties. Worse wetting than tin. Toxic, being phased out. Retards growth of tin whiskers, inhibits tin pest. Lowers solubility of copper and other metals in tin.
* Silver provides mechanical strength, but has worse ductility than lead. In absence of lead, it improves resistance to fatigue from thermal cycles. Using SnAg solders with HASL-SnPb-coated leads forms phase with melting point at 179 °C, which moves to the board-solder interface, solidifies last, and separates from the board. Addition of silver to tin significantly lowers solubility of silver coatings in the tin phase. In eutectic tin-silver (3.5% Ag) alloy and similar alloys (e.g. SAC305) it tends to form platelets of , which, if formed near a high-stress spot, may serve as initiating sites for cracks and cause poor shock and drop performance; silver content needs to be kept below 3% to inhibit such problems. High ion mobility, tends to migrate and form short circuits at high humidity under DC bias. Promotes corrosion of solder pots, increases dross formation.
* Tin is the usual main structural metal of the alloy. It has good strength and wetting. On its own it is prone to tin pest, tin cry, and growth of tin whiskers. Readily dissolves silver, gold and to less but still significant extent many other metals, e.g. copper; this is a particular concern for tin-rich alloys with higher melting points and reflow temperatures.
* Zinc lowers the melting point and is low-cost. However, it is highly susceptible to corrosion and oxidation in air, therefore zinc-containing alloys are unsuitable for some purposes, e.g. wave soldering, and zinc-containing solder pastes have shorter shelf life than zinc-free. Can form brittle Cu-Zn intermetallic layers in contact with copper. Readily oxidizes which impairs wetting, requires a suitable flux.
* Germanium in tin-based lead-free solders influences formation of oxides; at below 0.002% it increases formation of oxides. Optimal concentration for suppressing oxidation is at 0.005%. Used in e.g. Sn100C alloy. Patented.
* Rare-earth elements, when added in small amounts, refine the matrix structure in tin-copper alloys by segregating impurities at the grain boundaries. However, excessive addition results in the formation of tin whiskers; it also results in spurious rare earth phases, which easily oxidize and deteriorate the solder properties.
* Phosphorus is used as antioxidant to inhibit dross formation. Decreases fluidity of tin-copper alloys. | 0 | Metallurgy |
The addition of the myristoyl group proceeds via a nucleophilic addition-elimination reaction. First, myristoyl coenzyme A (CoA) is positioned in its binding pocket of NMT so that the carbonyl faces two amino acid residues, phenylalanine 170 and leucine 171. This polarizes the carbonyl so that there is a net positive charge on the carbon, making it susceptible to nucleophilic attack by the glycine residue of the protein to be modified. When myristoyl CoA binds, NMT reorients to allow binding of the peptide. The C-terminus of NMT then acts as a general base to deprotonate the NH, activating the amino group to attack at the carbonyl group of myristoyl-CoA. The resulting tetrahedral intermediate is stabilized by the interaction between a positively charged oxyanion hole and the negatively charged alkoxide anion. Free CoA is then released, causing a conformational change in the enzyme that allows the release of the myristoylated peptide. | 1 | Gene expression + Signal Transduction |
Some forms of ribosomal pause are reversible without needing to discard the translated peptide and mRNA. This sort, usually described as a slowdown, is usually caused by polyproline stretches (resolved by EFP or eIF5A) and uncharged tRNA. Slowdowns are important for the cell to control how much protein is produced; it also aids co-translational folding of the nascent polypeptide on the ribosome, and delays protein translation while its encoding mRNA; this can trigger ribosomal frameshifting.
More severe "stalls" can be caused an actual lack of tRNA or by the mRNA terminating without a stop codon. In this case, ribosomal quality control (RQC) performs crisis rescue by translational abandonment. This releases the ribosome from the mRNA. The incomplete polypeptide is targeted for destruction; in eukaryotes, mRNA no-go decay is also triggered.
It is difficult for RQC machinery to differentiate between a slowdown and a stall. It is possible for a mRNA sequence that normally produces a protein slowly to produce nothing instead due to intervention by RQC under different conditions. | 1 | Gene expression + Signal Transduction |
The most common anodizing processes, for example, sulphuric acid on aluminium, produce a porous surface which can accept dyes easily. The number of dye colours is almost endless; however, the colours produced tend to vary according to the base alloy. The most common colours in the industry, due to them being relatively cheap, are yellow, green, blue, black, orange, purple and red. Though some may prefer lighter colours, in practice they may be difficult to produce on certain alloys such as high-silicon casting grades and 2000-series aluminium-copper alloys. Another concern is the "lightfastness" of organic dyestuffs—some colours (reds and blues) are particularly prone to fading. Black dyes and gold produced by inorganic means (ferric ammonium oxalate) are more lightfast. Dyed anodizing is usually sealed to reduce or eliminate dye bleed out. White color cannot be applied due to the larger molecule size than the pore size of the oxide layer.
Alternatively, metal (usually tin) can be electrolytically deposited in the pores of the anodic coating to provide more lightfast colours. Metal dye colors range from pale champagne to black. Bronze shades are commonly used for architectural metals. Alternatively, the colour may be produced integral to the film. This is done during the anodizing process using organic acids mixed with the sulfuric electrolyte and a pulsed current.
Splash effects are created by dying the unsealed porous surface in lighter colours and then splashing darker colour dyes onto the surface. Aqueous and solvent-based dye mixtures may also be alternately applied since the coloured dyes will resist each other and leave spotted effects.
Another interesting coloring method is anodizing interference coloring. The thin oil film resting on the waters surface displays a rainbow hue due to the interference between light reflected from the water-oil interface and the oil films surface. Because the oil films thickness isnt regulated, the resulting rainbow color appears random.
In the anodizing coloring of aluminum, desired colors are achieved by depositing a controllably thick metal layer (typically tin) at the base of the porous structure. This involves reflections on the aluminum substrate and the upper metal surface. The color resulting from interference shifts from blue, green, and yellow to red as the deposited metal layer thickens. Beyond a specific thickness, the optical interference vanishes, and the color turns bronze. Interference-colored anodized aluminum parts exhibit a distinctive quality: their color varies when viewed from different angles. The interference coloring involves a 3-step process: sulfuric acid anodizing, electrochemical modification of the anodic pore, and metal (tin) deposition. | 0 | Metallurgy |
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains.
Bacillite is a type of crystallite. It is rodlike with parallel longulites. | 0 | Metallurgy |
Nanocrystalline materials can be prepared in several ways. Methods are typically categorized based on the phase of matter the material transitions through before forming the nanocrystalline final product. | 0 | Metallurgy |
eIF2 is a heterotrimer of a total molar mass of 126 kDa that is composed of the three sub-units: α (sub-unit 1), β (sub-unit 2), and γ (sub-unit 3).
The sequences of all three sub-units are highly conserved (pairwise amino acid identities for each sub-unit range from 47 to 72% when comparing the proteins of Homo sapiens and Saccharomyces cerevisiae).
The α-subunit contains the main target for phosphorylation, a serine at position 51. It also contains a S1 motif domain, which is a potential RNA binding-site. Therefore, the α-subunit can be considered the regulatory subunit of the trimer.
The β-subunit contains multiple phosphorylation sites (residues 2, 13, 67, 218). What is important to consider is that there are also three lysine clusters in the N-terminal domain (NTD), which are important for the interaction with eIF2B. Moreover, the sequence of the protein comprises a zinc finger motif that was shown to play a role in both ternary complex and 43S preinitiation complex formation. There are also two guanine nucleotide-binding sequences that have not been shown to be involved in the regulation of eIF2 activity. The β-subunit is also believed to interact with both tRNA and mRNA.
The γ-subunit comprises three guanine nucleotide-binding sites and is known to be the main docking site for GTP/GDP. It also contains a tRNA-binding cavity that has been shown by X-ray crystallography. A zinc knuckle motif is able to bind one Zn cation. It is related to some elongation factors like EF-Tu. | 1 | Gene expression + Signal Transduction |
The atmosphere of Early Earth is widely speculated to have been reducing. The Miller–Urey experiment, related to some hypotheses for the origin of life, entailed reactions in a reducing atmosphere composed of a mixed atmosphere of methane, ammonia and hydrogen sulfide. Some hypotheses for the origin of life invoke a reducing atmosphere consisting of hydrogen cyanide (HCN). Experiments show that HCN can polymerize in the presence of ammonia to give a variety of products including amino acids. The same principle applies to Mars, Venus and Titan.
Cyanobacteria are suspected to be the first photoautotrophs that evolved oxygenic photosynthesis, which over the latter half of the Archaen eon eventually depleted all reductants in the Earth's oceans, terrestrial surface and atmsophere, gradually increasing the oxygen concentration in the atmosphere, changing it to what is known as an oxidizing atmosphere. This rising oxygen initially led to a 300 million-year-long ice age that devastated the then-mostly anaerobe-dominated biosphere, forcing the surviving anaerobic colonies to evolve into symbiotic microbial mats with the newly evolved aerobes. Some aerobic bacteria eventually became endosymbiont within other anaerobes (likely archaea), and the resultant symbiogenesis led to the evolution of a completely new lineage of life — the eukaryotes, who took advantage of mitochondrial aerobic respiration to power their cellular activities, allowing life to thrive and evolve into ever more complex forms. The increased oxygen in the atmosphere also eventually created the ozone layer, which shielded away harmful ionizing ultraviolet radiation that otherwise would have photodissociated away surface water and rendered life impossible on land and the ocean surface.
In contrast to the hypothesized early reducing atmosphere, evidence exists that Hadean atmospheric oxygen levels were similar to those of today. These results suggests prebiotic building blocks were delivered from elsewhere in the galaxy. The results however do not run contrary to existing theories on life's journey from anaerobic to aerobic organisms. The results quantify the nature of gas molecules containing carbon, hydrogen, and sulphur in the earliest atmosphere, but they shed no light on the much later rise of free oxygen in the air. | 0 | Metallurgy |
The number of RNAPs in bacterial cells (e.g., E. coli) have been shown to be smaller than the number of sigma factors. Consequently, if a certain sigma factor is overexpressed, not only will increase the expression levels of genes whose promoters have preference for that sigma factor, but it will also reduce the probability that genes with promoters with preference for other sigma factors.
Meanwhile, transcription initiation has two major rate limiting steps: the closed and the open complex formation. However, only the dynamics of the first step depends on the concentration of sigma factors. Interestingly, the fastest is the closed complex formation relative to the open complex formation, the less responsive is a promoter to changes in sigma factors’ concentration (see for a model and empirical data of this phenomenon). | 1 | Gene expression + Signal Transduction |
Due to the scattered nature of tin deposits around the world and its essential nature for the creation of tin bronze, tin trade played an important role in the development of cultures throughout ancient times. Archaeologists have reconstructed parts of the extensive trade networks of ancient cultures from the Bronze Age to modern times using historical texts, archaeological excavations, and trace element and lead isotope analysis to determine the origins of tin objects around the world. | 0 | Metallurgy |
The first ncRNA therapeutic drug approved by food and drug administration (FDA) (1998) and the European medicine agency (EMA) (1999) is called Fomivirsen or Vitravene. The target organ is the eye and works against the cytomegalovirus (CMV) retinitis in immunocompromised patients. The drug functions as an antisense oligonucleotide and binds to the complementary sequence of the mRNA that inhibits the replication of human cytomegalovirus. This therapy can also be categorized as Antisense oligonucleotide (ASO) therapy.
There have been many ASO RNA therapeutics that have been approved by FDA and/or EMA over the years, but it wasn’t until 2018 that the EMA approved the drug called Patisiran/Onpattro. The drug uses ds-siRNA as a mechanism of action and is deemed effective against hereditary transthyretin amyloidosis. The mechanism specifically targets the Transthyretin (TTR) mRNA.
RNA therapeutic targets are not limited to mature mRNA but have been used to target mRNA at different stages of maturation. One such example is Nusinersen (Spinaraza), it functions as an ASO and targets pre-mRNA before splicing that corresponds to Survival of motor neuron 2 gene (SMN 2). This drug therapy was approved by FDA and EMA in 2016 and 2017 respectively.
There are some drugs that have been approved by FDA and not by EMA. This can be seen in the case of an ASO type therapeutics called Eteplirsen (Exondys51) which has been approved by FDA in 2016 but not by EMA. It targets pre-mRNA corresponding to Dystrophin (DMD) and works against Duchenne muscular dystrophy.
There are many additional therapeutics that have been developed and are either in phase I or II of the clinical trials. Current RNA therapeutics in clinical trials range from a variety of target organs and diseases ranging from skin (potential treatment for disease such as keloid) to tumors (squamous cell lung cancer).
To date, for both the FDA and the EMA, ncRNAs are considered as "simple" medical products because of their production by chemical synthesis. When some of them, produced biologically (known as bioengineered ncRNA agents: BERAs), will be put on the market, the status of biological medical products will be applied, which could lead to inconsistencies in the legislation. | 1 | Gene expression + Signal Transduction |
*Metallurgical and Materials Transactions A – [https://link.springer.com/search?query=&search-within=Journal&facet-journal-id=11661&package=openaccessarticles open access articles]
*Metallurgical and Materials Transactions B – [https://link.springer.com/search?query=&search-within=Journal&facet-journal-id=11663&package=openaccessarticles open access articles]
*Advanced Engineering Materials – [http://www.aem-journal.de articles]
*Metals – [https://www.mdpi.com/journal/metals open access articles]
*Journal of Alloys and Compounds – [http://www.sciencedirect.com/science/journal/09258388/ open access articles]
*Acta Materialia – [http://www.sciencedirect.com/science/journal/13596454/open-access open access articles]
*International Journal of Materials Research – [https://www.degruyter.com/journal/key/ijmr/html articles] | 0 | Metallurgy |
Catenin beta-1, also known as β-catenin (beta-catenin), is a protein that in humans is encoded by the CTNNB1 gene.
β-Catenin is a dual function protein, involved in regulation and coordination of cell–cell adhesion and gene transcription. In humans, the CTNNB1 protein is encoded by the CTNNB1 gene. In Drosophila, the homologous protein is called armadillo. β-catenin is a subunit of the cadherin protein complex and acts as an intracellular signal transducer in the Wnt signaling pathway. It is a member of the catenin protein family and homologous to γ-catenin, also known as plakoglobin. β-Catenin is widely expressed in many tissues. In cardiac muscle, β-catenin localizes to adherens junctions in intercalated disc structures, which are critical for electrical and mechanical coupling between adjacent cardiomyocytes.
Mutations and overexpression of β-catenin are associated with many cancers, including hepatocellular carcinoma, colorectal carcinoma, lung cancer, malignant breast tumors, ovarian and endometrial cancer. Alterations in the localization and expression levels of β-catenin have been associated with various forms of heart disease, including dilated cardiomyopathy. β-Catenin is regulated and destroyed by the beta-catenin destruction complex, and in particular by the adenomatous polyposis coli (APC) protein, encoded by the tumour-suppressing APC gene. Therefore, genetic mutation of the APC gene is also strongly linked to cancers, and in particular colorectal cancer resulting from familial adenomatous polyposis (FAP). | 1 | Gene expression + Signal Transduction |
Prior to 1907, nearly all the copper mined in the US came from underground vein deposits, averaging 2.5 percent copper. By 1991, the average grade of copper ore mined in the US had fallen to only 0.6 percent. | 0 | Metallurgy |
Tin deposits exist in many parts of South America, with minor deposits in southern Peru, Colombia, Brazil, and northwestern Argentina, and major deposits of exploitable cassiterite in northern Bolivia. These deposits were exploited as early as 1000 AD in the manufacture of tin bronze by Andean cultures, including the later Inca Empire, which considered tin bronze the "imperial alloy". In North America, the only known exploitable source of tin during ancient times is located in the Zacatecas tin province of north central Mexico which supplied west Mexican cultures with enough tin for bronze production. | 0 | Metallurgy |
The susceptibility to crevice corrosion varies widely from one material-environment system to another. In general, crevice corrosion is of greatest concern for materials which are normally passive metals, like stainless steel or aluminum. Crevice corrosion tends to be of greatest significance to components built of highly corrosion-resistant superalloys and operating with the purest-available water chemistry. For example, steam generators in nuclear power plants degrade largely by crevice corrosion.
Crevice corrosion is extremely dangerous because it is localized and can lead to component failure while the overall material loss is minimal. The initiation and progress of crevice corrosion can be difficult to detect. | 0 | Metallurgy |
This method is mostly used for corrosion monitoring in water industry. These probes are suitable for monitoring fluctuations that may occur in a fluid inside the system. These probes are mostly used for conductive fluids such as water or any similar else. | 0 | Metallurgy |
In sporadic cancers, a DNA repair deficiency is occasionally found to be due to a mutation in a DNA repair gene. However, much more frequently, reduced or absent expression of a DNA repair gene in cancer is due to methylation of its promoter. For example, of 113 colorectal cancers examined, only four had a missense mutation in the DNA repair gene MGMT, while the majority had reduced MGMT expression due to methylation of the MGMT promoter region. Similarly, among 119 cases of mismatch repair-deficient colorectal cancers that lacked DNA repair gene PMS2 expression, 6 had a mutation in the PMS2 gene, while for 103 PMS2 was deficient because its pairing partner MLH1 was repressed due to promoter methylation (PMS2 protein is unstable in the absence of MLH1). In the remaining 10 cases, loss of PMS2 expression was likely due to epigenetic overexpression of the microRNA, miR-155, which down-regulates MLH1. | 1 | Gene expression + Signal Transduction |
Tripartite motif-containing 28 (TRIM28), also known as transcriptional intermediary factor 1β (TIF1β) and KAP1 (KRAB-associated protein-1), is a protein that in humans is encoded by the TRIM28 gene. | 1 | Gene expression + Signal Transduction |
When nascent hydrogen is produced by anaerobic corrosion of iron by the protons of water, the atomic hydrogen can diffuse into the metal crystal lattice because of the existing concentration gradient. After diffusion, hydrogen atoms can recombine into molecular hydrogen giving rise to the formation of high-pressure micro-bubbles of H in the metallic lattice. The trends to expansion of H bubbles and the resulting tensile stress can generate cracks in the metallic alloys sensitive to this effect also known as hydrogen embrittlement. Several recent studies (Turnbull, 2009; King, 2008; King and Kolar, 2009) address this question in the frame of the radioactive waste disposal in Switzerland and Canada. | 0 | Metallurgy |
Wootz steel has been reproduced and studied in depth by the Royal School of Mines. Dr. Pearson was the first to chemically examine wootz in 1795 and he published his contributions to the Philosophical Transactions of the Royal Society.
Russian metallurgist Pavel Petrovich Anosov (see Bulat steel) was almost able to reproduce ancient Wootz steel with nearly all of its properties and the steel he created was very similar to traditional Wootz. He documented four different methods of producing Wootz steel that exhibited traditional patterns. He died before he could fully document and publish his research. Oleg Sherby and Jeff Wadsworth and Lawrence Livermore National Laboratory have all done research, attempting to create steels with characteristics similar to Wootz, but without success. J.D Verhoeven and Alfred Pendray reconstructed methods of production, proved the role of impurities of ore in the pattern creation, and reproduced Wootz steel with patterns microscopically and visually identical to one of the ancient blade patterns. Reibold et al.'s analyses spoke of the presence of carbon nanotubes enclosing nanowires of cementite, with the trace elements/impurities of vanadium, molybdenum, chromium etc. contributing to their creation, in cycles of heating/cooling/forging. This resulted in a hard high carbon steel that remained malleable
There are smiths who are now consistently producing Wootz steel blades visually identical to the old patterns. Steel manufactured in Kutch particularly enjoyed a widespread reputation, similar to those manufactured at Glasgow and Sheffield.
Wootz was made over nearly a 2,000-year period (the oldest sword samples date to around 200 AD) and the methods of production of ingots, the ingredients, and the methods of forging varied from one area to the next. Some Wootz blades displayed a pattern, while some did not. Heat treating was quite different from forging, and there were many different patterns which were created by the various smiths who spanned from China to Scandinavia. | 0 | Metallurgy |
Sepro Mineral Systems Corp. is a Canadian company founded in 1987 and headquartered in British Columbia, Canada. The outcome of the acquisition of Sepro Mineral Processing International by Falcon Concentrators in 2008, the company's key focus is the production of mineral processing equipment for the mining and aggregate industries. Sepro Mineral Systems Corp. also provides engineering and process design services. Products sold by Sepro include grinding mills, ore scrubbers, vibrating screens, centrifugal gravity concentrators, agglomeration drums, and dense media separators. The company is also a supplier of single source modular pre-designed and custom designed plants and circuits.
Today, Sepro Mineral Systems Corp. is represented by global agents in over 15 countries and has equipment operating in over 31 countries around the world. | 0 | Metallurgy |
A Morpholino, also known as a Morpholino oligomer and as a phosphorodiamidate Morpholino oligomer (PMO), is a type of oligomer molecule (colloquially, an oligo) used in molecular biology to modify gene expression. Its molecular structure contains DNA bases attached to a backbone of methylenemorpholine rings linked through phosphorodiamidate groups. Morpholinos block access of other molecules to small (~25 base) specific sequences of the base-pairing surfaces of ribonucleic acid (RNA). Morpholinos are used as research tools for reverse genetics by knocking down gene function.
This article discusses only the Morpholino antisense oligomers, which are nucleic acid analogs. The word "Morpholino" can occur in other chemical names, referring to chemicals containing a six-membered morpholine ring. To help avoid confusion with other morpholine-containing molecules, when describing oligos "Morpholino" is often capitalized as a trade name, but this usage is not consistent across scientific literature. Morpholino oligos are sometimes referred to as PMO (for phosphorodiamidate morpholino oligomer), especially in medical literature. Vivo-Morpholinos and PPMO are modified forms of Morpholinos with chemical groups covalently attached to facilitate entry into cells.
Gene knockdown is achieved by reducing the expression of a particular gene in a cell. In the case of protein-coding genes, this usually leads to a reduction in the quantity of the corresponding protein in the cell. Knocking down gene expression is a method for learning about the function of a particular protein; in a similar manner, causing a specific exon to be spliced out of the RNA transcript encoding a protein can help to determine the function of the protein moiety encoded by that exon or can sometimes knock down the protein activity altogether. These molecules have been applied to studies in several model organisms, including mice, zebrafish, frogs and sea urchins. Morpholinos can also modify the splicing of pre-mRNA or inhibit the maturation and activity of miRNA. Techniques for targeting Morpholinos to RNAs and delivering Morpholinos into cells have recently been reviewed in a journal article and in book form.
Morpholinos are in development as pharmaceutical therapeutics targeted against pathogenic organisms such as bacteria or viruses and genetic diseases. A Morpholino-based drug eteplirsen from Sarepta Therapeutics received accelerated approval from the US Food and Drug Administration in September 2016 for the treatment of some mutations causing Duchenne muscular dystrophy, although the approval process was mired in controversy. Other Morpholino-based drugs golodirsen, viltolarsen, and casimersen (also for Duchenne muscular dystrophy) were approved by the FDA in 2019–2021. | 1 | Gene expression + Signal Transduction |
The reaction happens with two metal cofactors (Mg or Mn) coordinated to the two aspartate residues on C1. They perform a nucleophilic attack of the 3'-OH group of the ribose on the α-phosphoryl group of ATP. The two lysine and aspartate residues on C2 selects ATP over GTP for the substrate, so that the enzyme is not a guanylyl cyclase. A pair of arginine and asparagine residues on C2 stabilizes the transition state. In many proteins, these residues are nevertheless mutated while retaining the adenylyl cyclase activity. | 1 | Gene expression + Signal Transduction |
The high-frequency impact treatment or HiFIT – Method is the treatment of welded steel constructions at the weld transition to increase the fatigue strength. | 0 | Metallurgy |
VMAT1 (SLC18A1) maps to a shared bipolar disorder(BPD)/schizophrenia locus, which is located on chromosome 8p21. It is thought that disruption in transport of monoamine neurotransmitters due to variation in the VMAT1 gene may be relevant to the etiology of these mental disorders. One study looked at a population of European descent, examining the genotypes of a bipolar group and a control group. The study confirmed expression of VMAT1 in the brain at a protein and mRNA level, and found a significant difference between the two groups, suggesting that, at least for people of European descent, variation in the VMAT1 gene may confer susceptibility. A second study examined a population of Japanese individuals, one group healthy and the other schizophrenic. This study resulted in mostly inconclusive findings, but some indications that variation in the VMAT1 gene would confer susceptibility to schizophrenia in Japanese women. While these studies provide some promising insight into the cause of some of the most prevalent mental disorders, it is clear that additional research will be necessary in order to gain a full understanding. | 1 | Gene expression + Signal Transduction |
The regulation of translation in eukaryotes is more complex than in prokaryotes. Initially, the eIF4F complex is recruited to the 5′ cap, which in turn recruits the ribosomal complex to the 5′ UTR. Both eIF4E and eIF4G bind the 5′ UTR, which limits the rate at which translational initiation can occur. However, this is not the only regulatory step of translation that involves the 5′ UTR.
RNA-binding proteins sometimes serve to prevent the pre-initiation complex from forming. An example is regulation of the msl2 gene. The protein SXL attaches to an intron segment located within the 5′ UTR segment of the primary transcript, which leads to the inclusion of the intron after processing. This sequence allows the recruitment of proteins that bind simultaneously to both the 5′ and 3′ UTR, not allowing translation proteins to assemble. However, it has also been noted that SXL can also repress translation of RNAs that do not contain a poly(A) tail, or more generally, 3′ UTR. | 1 | Gene expression + Signal Transduction |
Post-translational regulation refers to the control of the levels of active protein.
There are several forms.
It is performed either by means of reversible events (posttranslational modifications, such as phosphorylation or sequestration) or by means of irreversible events (proteolysis). | 1 | Gene expression + Signal Transduction |
Tensioned screen cloth is typically 4 feet by the width or the length of the screening machine depending on whether the deck is side or end tensioned. Screen cloth for tensioned decks can be made with hooks and are attached with clamp rails bolted on both sides of the screen box. When the clamp rail bolts are tightened, the cloth is tensioned or even stretched in the case of some types of self-cleaning screen media. To ensure that the center of the cloth does not tap repeatedly on the deck due to the vibrating shaker and that the cloth stays tensioned, support bars are positioned at different heights on the deck to create a crown curve from hook to hook on the cloth. Tensioned screen cloth is available in various materials: stainless steel, high carbon steel and oil tempered steel wires, as well as moulded rubber or polyurethane and hybrid screens (a self-cleaning screen cloth made of rubber or polyurethane and metal wires).
Commonly, vibratory-type screening equipment employs rigid, circular sieve frames to which woven wire mesh is attached. Conventional methods of producing tensioned meshed screens has given way in recent years to bonding, whereby the mesh is no longer tensioned and trapped between a sieve frame body and clamping ring; instead, developments in modern adhesive technologies has allowed the industry to adopt high strength structural adhesives to bond tensioned mesh directly to frames. | 0 | Metallurgy |
CBP and p300 are large nuclear proteins that bind to many sequence-specific factors involved in cell growth and/or differentiation, including c-jun and the adenoviral oncoprotein E1A. The protein encoded by the PCAF gene associates with p300/CBP. It has in vitro and in vivo binding activity with CBP and p300, and competes with E1A for binding sites in p300/CBP. It has histone acetyl transferase activity with core histones and nucleosome core particles, indicating that this protein plays a direct role in transcriptional regulation. | 1 | Gene expression + Signal Transduction |
There are several different techniques to detect regulatory genes, but of the many there are a certain few that are used more frequently than others. One of these select few is called ChIP-chip. ChIP-chip is an in vivo technique used to determine genomic binding sites for transcription factors in two component system response regulators. In vitro microarray based assay (DAP-chip) can be used to determine gene targets and functions of two component signal transduction systems. This assay takes advantage of the fact that response regulators can be phosphorylated and thus activated in vitro using small molecule donors like acetyl phosphate. | 1 | Gene expression + Signal Transduction |
The Hedgehog protein family is involved in induction of cell types and the creation of tissue boundaries and patterning and are found in all bilateral organisms. Hedgehog proteins were first discovered and studied in Drosophila. Hedgehog proteins produce key signals for the establishment of limb and body plan of fruit flies as well as homeostasis of adult tissues, involved in late embryogenesis and metamorphosis. At least three "Drosophila" hedgehog homologs have been found in vertebrates: sonic hedgehog, desert hedgehog, and Indian hedgehog. Sonic hedgehog (SHH) has various roles in vertebrae development, mediating signaling and regulating the organization of central nervous system, limb, and somite polarity. Desert hedgehog (DHH) is expressed in the Sertoli cells involved in spermatogenesis. Indian hedgehog (IHH) is expressed in the gut and cartilage, important in postnatal bone growth. | 1 | Gene expression + Signal Transduction |
myo-Inositol trispyrophosphate (ITPP) is an inositol phosphate, a pyrophosphate, a drug candidate, and a putative performance-enhancing substance, which exerts its biological effects by increasing tissue oxygenation. | 1 | Gene expression + Signal Transduction |
Stainless steel forms a passivation layer of chromium(III) oxide. Similar passivation behavior occurs with magnesium, titanium, zinc, zinc oxides, aluminium, polyaniline, and other electroactive conductive polymers.
Special "weathering steel" alloys such as Cor-Ten rust at a much slower rate than normal, because the rust adheres to the surface of the metal in a protective layer. Designs using this material must include measures that avoid worst-case exposures since the material still continues to rust slowly even under near-ideal conditions. | 0 | Metallurgy |
The blast furnaces used in the Imperial Smelting Process ("ISP") were developed from the standard lead blast furnace, but are fully sealed. This is because the zinc produced by these furnaces is recovered as metal from the vapor phase, and the presence of oxygen in the off-gas would result in the formation of zinc oxide.
Blast furnaces used in the ISP have a more intense operation than standard lead blast furnaces, with higher air blast rates per m of hearth area and a higher coke consumption.
Zinc production with the ISP is more expensive than with electrolytic zinc plants, so several smelters operating this technology have closed in recent years. However, ISP furnaces have the advantage of being able to treat zinc concentrates containing higher levels of lead than can electrolytic zinc plants. | 0 | Metallurgy |
The low-density lipoprotein receptor gene family codes for a class of structurally related cell surface receptors that fulfill diverse biological functions in different organs, tissues, and cell types. The role that is most commonly associated with this evolutionarily ancient family is cholesterol homeostasis (maintenance of appropriate concentration of cholesterol). In humans, excess cholesterol in the blood is captured by low-density lipoprotein (LDL) and removed by the liver via endocytosis of the LDL receptor. Recent evidence indicates that the members of the LDL receptor gene family are active in the cell signalling pathways between specialized cells in many, if not all, multicellular organisms.
There are seven members of the LDLR family in mammals, namely:
* LDLR
* VLDL receptor (VLDLR)
* ApoER2, or LRP8
* Low density lipoprotein receptor-related protein 4
** also known as multiple epidermal growth factor (EGF) repeat-containing protein (MEGF7)
* LDLR-related protein 1
* LDLR-related protein 1b
* Megalin. | 1 | Gene expression + Signal Transduction |
In molecular biology, ribosomal s6 kinase (rsk) is a family of protein kinases involved in signal transduction. There are two subfamilies of rsk, p90, also known as MAPK-activated protein kinase-1 (MAPKAP-K1), and p70, also known as S6-H1 Kinase or simply S6 Kinase. There are three variants of p90 in humans, rsk 1-3. Rsks are serine/threonine kinases and are activated by the MAPK/ERK pathway. There are two known mammalian homologues of S6 Kinase: S6K1 and S6K2. | 1 | Gene expression + Signal Transduction |
In eukaryotes, a corepressor is a protein that binds to transcription factors. In the absence of corepressors and in the presence of coactivators, transcription factors upregulate gene expression. Coactivators and corepressors compete for the same binding sites on transcription factors. A second mechanism by which corepressors may repress transcriptional initiation when bound to transcription factor/DNA complexes is by recruiting histone deacetylases which catalyze the removal of acetyl groups from lysine residues. This increases the positive charge on histones which strengthens the electrostatic attraction between the positively charged histones and negatively charged DNA, making the DNA less accessible for transcription.
In humans several dozen to several hundred corepressors are known, depending on the level of confidence with which the characterisation of a protein as a corepressors can be made. | 1 | Gene expression + Signal Transduction |
Native silver is a rare element. Although it exists as such, it is usually found in nature combined with other metals, or in minerals that contain silver compounds, generally in the form of sulfides such as galena (lead sulfide) or cerussite (lead carbonate). So the primary production of silver requires the smelting and then cupellation of argentiferous lead ores.
Lead melts at 327 °C, lead oxide at 888 °C, and silver melts at 960 °C. To separate the silver, the alloy is melted again at the high temperature of 960 °C to 1000 °C in an oxidizing environment. The lead oxidises to lead monoxide, then known as litharge, which captures the oxygen from the other metals present. The liquid lead oxide is removed or absorbed by capillary action into the hearth linings. This chemical reaction may be viewed as
: (s) + 2 (s) + (g) → 2 (absorbed) + Ag(l)
The base of the hearth was dug in the form of a saucepan and covered with an inert and porous material rich in calcium or magnesium such as shells, lime, or bone ash. The lining had to be calcareous because lead reacts with silica (clay compounds) to form viscous lead silicate that prevents the needed absorption of litharge, whereas calcareous materials do not react with lead. Some of the litharge evaporates, and the rest is absorbed by the porous earth lining to form "litharge cakes".
Litharge cakes are usually circular or concavo-convex, about 15 cm in diameter. They are the most common archaeological evidence of cupellation in the Early Bronze Age. By analyzing their chemical composition, archaeologists can discern what kind of ore was treated, its main components, and the chemical conditions used in the process. This permits insights about production process, trade, social needs or economic situations. | 0 | Metallurgy |
Microarrays can be fabricated using a variety of technologies, including printing with fine-pointed pins onto glass slides, photolithography using pre-made masks, photolithography using dynamic micromirror devices, ink-jet printing, or electrochemistry on microelectrode arrays.
In spotted microarrays, the probes are oligonucleotides, cDNA or small fragments of PCR products that correspond to mRNAs. The probes are synthesized prior to deposition on the array surface and are then "spotted" onto glass. A common approach utilizes an array of fine pins or needles controlled by a robotic arm that is dipped into wells containing DNA probes and then depositing each probe at designated locations on the array surface. The resulting "grid" of probes represents the nucleic acid profiles of the prepared probes and is ready to receive complementary cDNA or cRNA "targets" derived from experimental or clinical samples.
This technique is used by research scientists around the world to produce "in-house" printed microarrays in their own labs. These arrays may be easily customized for each experiment, because researchers can choose the probes and printing locations on the arrays, synthesize the probes in their own lab (or collaborating facility), and spot the arrays. They can then generate their own labeled samples for hybridization, hybridize the samples to the array, and finally scan the arrays with their own equipment. This provides a relatively low-cost microarray that may be customized for each study, and avoids the costs of purchasing often more expensive commercial arrays that may represent vast numbers of genes that are not of interest to the investigator.
Publications exist which indicate in-house spotted microarrays may not provide the same level of sensitivity compared to commercial oligonucleotide arrays, possibly owing to the small batch sizes and reduced printing efficiencies when compared to industrial manufactures of oligo arrays.
In oligonucleotide microarrays, the probes are short sequences designed to match parts of the sequence of known or predicted open reading frames. Although oligonucleotide probes are often used in "spotted" microarrays, the term "oligonucleotide array" most often refers to a specific technique of manufacturing. Oligonucleotide arrays are produced by printing short oligonucleotide sequences designed to represent a single gene or family of gene splice-variants by synthesizing this sequence directly onto the array surface instead of depositing intact sequences. Sequences may be longer (60-mer probes such as the Agilent design) or shorter (25-mer probes produced by Affymetrix) depending on the desired purpose; longer probes are more specific to individual target genes, shorter probes may be spotted in higher density across the array and are cheaper to manufacture.
One technique used to produce oligonucleotide arrays include photolithographic synthesis (Affymetrix) on a silica substrate where light and light-sensitive masking agents are used to "build" a sequence one nucleotide at a time across the entire array. Each applicable probe is selectively "unmasked" prior to bathing the array in a solution of a single nucleotide, then a masking reaction takes place and the next set of probes are unmasked in preparation for a different nucleotide exposure. After many repetitions, the sequences of every probe become fully constructed. More recently, Maskless Array Synthesis from NimbleGen Systems has combined flexibility with large numbers of probes. | 1 | Gene expression + Signal Transduction |
In wire and fiber, all crystals tend to have nearly identical orientation in the axial direction, but nearly random radial orientation. The most familiar exceptions to this rule are fiberglass, which has no crystal structure, and carbon fiber, in which the crystalline anisotropy is so great that a good-quality filament will be a distorted single crystal with approximately cylindrical symmetry (often compared to a jelly roll). Single-crystal fibers are also not uncommon.
The making of metal sheet often involves compression in one direction and, in efficient rolling operations, tension in another, which can orient crystallites in both axes by a process known as grain flow. However, cold work destroys much of the crystalline order, and the new crystallites that arise with annealing usually have a different texture. Control of texture is extremely important in the making of silicon steel sheet for transformer cores (to reduce magnetic hysteresis) and of aluminium cans (since deep drawing requires extreme and relatively uniform plasticity).
Texture in ceramics usually arises because the crystallites in a slurry have shapes that depend on crystalline orientation, often needle- or plate-shaped. These particles align themselves as water leaves the slurry, or as clay is formed.
Casting or other fluid-to-solid transitions (i.e., thin-film deposition) produce textured solids when there is enough time and activation energy for atoms to find places in existing crystals, rather than condensing as an amorphous solid or starting new crystals of random orientation. Some facets of a crystal (often the close-packed planes) grow more rapidly than others, and the crystallites for which one of these planes faces in the direction of growth will usually out-compete crystals in other orientations. In the extreme, only one crystal will survive after a certain length: this is exploited in the Czochralski process (unless a seed crystal is used) and in the casting of turbine blades and other creep-sensitive parts. | 0 | Metallurgy |
MAPK pathways of fungi are also well studied. In yeast, the Fus3 MAPK is responsible for cell cycle arrest and mating in response to pheromone stimulation. The pheromone alpha-factor is sensed by a seven transmembrane receptor. The recruitment and activation of Fus3 pathway components are strictly dependent on heterotrimeric G-protein activation. The mating MAPK pathway consist of three tiers (Ste11-Ste7-Fus3), but the MAP2 and MAP3 kinases are shared with another pathway, the Kss1 or filamentous growth pathway. While Fus3 and Kss1 are closely related ERK-type kinases, yeast cells can still activate them separately, with the help of a scaffold protein Ste5 that is selectively recruited by the G-proteins of the mating pathway. The trick is that Ste5 can associate with and "unlock" Fus3 for Ste7 as a substrate in a tertiary complex, while it does not do the same for Kss1, leaving the filamentous growth pathway to be activated only in the absence of Ste5 recruitment.
Fungi also have a pathway reminiscent of mammalian JNK/p38 signaling. This is the Hog1 pathway: activated by high osmolarity (in Saccharomyces cerevisiae) or a number of other abiotic stresses (in Schizosaccharomyces pombe). The MAP2 kinase of this pathway is called Pbs2 (related to mammalian MKK3/4/6/7), the dedicated MAP3 kinases involved in activation are Ssk2 and SSk22. The system in S. cerevisiae is activated by a sophisticated osmosensing module consisting of the Sho1 and Sln1 proteins, but it is yet unclear how other stimuli can elicit activation of Hog1. Yeast also displays a number of other MAPK pathways without close homologs in animals, such as the cell wall integrity pathway (Mpk1/Slt2) or the sporulation pathway (Smk1). | 1 | Gene expression + Signal Transduction |
Carbon steel consists of two components: pure iron, in the form of ferrite, and cementite or iron carbide, a compound of iron and carbon. Cementite is very hard and brittle; its hardness is about 640 by the Brinell hardness test, whereas ferrite is only 200. The amount of the carbon and the cooling regimen determine the crystalline and chemical composition of the final steel. In bulat, the slow cooling process allowed the cementite to precipitate as micro particles in between ferrite crystals and arrange in random patterns. The color of the carbide is dark while steel is grey. This mixture is what leads to the famous patterning of Damascus steel.
Cementite is essentially a ceramic, which accounts for the sharpness of the Damascus (and bulat) steel. Cementite is unstable and breaks down between 600 and 1100 °C into ferrite and carbon, so working the hot metal must be done very carefully. | 0 | Metallurgy |
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