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Kazzinc selected the copper ISASMELT process for its Ust-Kamenogorsk metallurgical complex. It is designed to treat 290,000 t/y of copper concentrate and was commissioned in 2011. A projected capital cost for the smelter and refinery in 2006 was US$178 million. | 0 | Metallurgy |
Pressure oxidation is a process for extracting gold from refractory ore.
The most common refractory ores are pyrite and arsenopyrite, which are sulfide ores that trap the gold within them. Refractory ores require pre-treatment before the gold can be adequately extracted. The pressure oxidation process is used to prepare such ores for conventional gold extraction processes such as cyanidation. It is performed in an autoclave at high pressure and temperature, where high-purity oxygen mixes with a slurry of ore.
When the original sulfide minerals are oxidized at high temperature and pressure, it completely releases the trapped gold. Pressure oxidation has a very high gold recovery rate, normally at least 10% higher than roasting.
The oxidation of the iron sulfide minerals produces sulfuric acid, soluble compounds such as ferric sulfate, and solids such as iron sulfate or jarosite. The iron-based solids produced pose an environmental challenge, as they can release acid and heavy metals to the environment. They can also make later precious metal recovery more difficult. Arsenic in the ore is converted to solid scorodite inside the autoclave, allowing it to be easily disposed of. This is an advantage over processes such as roasting where these toxic products are released as gases.
A disadvantage of pressure oxidation is that any silver in the feed material will often react to form silver jarosite inside the autoclave, making it difficult and expensive to recover the silver.
An example of a mine utilizing this technology is the Pueblo Viejo mine in the Dominican Republic. At Pueblo Viejo, the process is performed by injecting high-purity oxygen into autoclaves operating at 230 degrees C and 40 bar of pressure. The resulting chemical reactions oxides the sulfide minerals the gold is trapped within. The oxidation of pyrite is highly exothermic, allowing the autoclave to operate at this temperature without an external heat source. | 0 | Metallurgy |
Elgiloy (Co-Cr-Ni Alloy) is a "super-alloy" consisting of 39-41% cobalt, 19-21% chromium, 14-16% nickel, 11.3-20.5% iron, 6-8% molybdenum, 1.5-2.5% manganese and 0.15% max. carbon.
It is used to make springs that are corrosion resistant and exhibit high strength, ductility, and good fatigue life. These same properties led to it being used for control cables in the Lockheed SR-71 Blackbird airplane, as they needed to cope with repeated stretching and contracting.
Elgiloy meets specifications AMS 5876, AMS 5833, and UNS R30003.
Due to its chemical composition, Elgiloy is highly resistant to sulfide stress corrosion cracking and pitting, and can operate at temperatures up to 454 °C.
Elgiloy is a trade name for this super alloy. Phynox is another trade name for the same super alloy. | 0 | Metallurgy |
In bacteria, the coding regions typically take up 88% of the genome. The remaining 12% does not encode proteins, but much of it still has biological function through genes where the RNA transcript is functional (non-coding genes) and regulatory sequences, which means that almost all of the bacterial genome has a function. The amount of coding DNA in eukaryotes is usually a much smaller fraction of the genome because eukaryotic genomes contain large amounts of repetitive DNA not found in prokaryotes. The human genome contains somewhere between 1–2% coding DNA. The exact number is not known because there are disputes over the number of functional coding exons and over the total size of the human genome. This means that 98–99% of the human genome consists of non-coding DNA and this includes many functional elements such as non-coding genes and regulatory sequences.
Genome size in eukaryotes can vary over a wide range, even between closely related species. This puzzling observation was originally known as the C-value Paradox where "C" refers to the haploid genome size. The paradox was resolved with the discovery that most of the differences were due to the expansion and contraction of repetitive DNA and not the number of genes. Some researchers speculated that this repetitive DNA was mostly junk DNA. The reasons for the changes in genome size are still being worked out and this problem is called the C-value Enigma.
This led to the observation that the number of genes does not seem to correlate with perceived notions of complexity because the number of genes seems to be relatively constant, an issue termed the G-value Paradox. For example, the genome of the unicellular Polychaos dubium (formerly known as Amoeba dubia) has been reported to contain more than 200 times the amount of DNA in humans (i.e. more than 600 billion pairs of bases vs a bit more than 3 billion in humans). The pufferfish Takifugu rubripes genome is only about one eighth the size of the human genome, yet seems to have a comparable number of genes. Genes take up about 30% of the pufferfish genome and the coding DNA is about 10%. (Non-coding DNA = 90%.) The reduced size of the pufferfish genome is due to a reduction in the length of introns and less repetitive DNA.
Utricularia gibba, a bladderwort plant, has a very small nuclear genome (100.7 Mb) compared to most plants. It likely evolved from an ancestral genome that was 1,500 Mb in size. The bladderwort genome has roughly the same number of genes as other plants but the total amount of coding DNA comes to about 30% of the genome.
The remainder of the genome (70% non-coding DNA) consists of promoters and regulatory sequences that are shorter than those in other plant species. The genes contain introns but there are fewer of them and they are smaller than the introns in other plant genomes. There are noncoding genes, including many copies of ribosomal RNA genes. The genome also contains telomere sequences and centromeres as expected. Much of the repetitive DNA seen in other eukaryotes has been deleted from the bladderwort genome since that lineage split from those of other plants. About 59% of the bladderwort genome consists of transposon-related sequences but since the genome is so much smaller than other genomes, this represents a considerable reduction in the amount of this DNA. The authors of the original 2013 article note that claims of additional functional elements in the non-coding DNA of animals do not seem to apply to plant genomes.
According to a New York Times article, during the evolution of this species, "... genetic junk that didn't serve a purpose was expunged, and the necessary stuff was kept." According to Victor Albert of the University of Buffalo, the plant is able to expunge its so-called junk DNA and "have a perfectly good multicellular plant with lots of different cells, organs, tissue types and flowers, and you can do it without the junk. Junk is not needed." | 1 | Gene expression + Signal Transduction |
Ataxia telangiectasia mutated (ATM) is a kinase that (similar to mTOR) can phosphorylate KAP1 resulting in the switch from viral latency to the lytic cycle. Chloroquine (an ATM) activator has been shown to result in increases in transcription of the HCMV genome. This effect is augmented by the use of tumor necrosis factor It has been proposed that this treatment (accompanied by antiretroviral treatment) has the potential to purge the virus from infected individuals. | 1 | Gene expression + Signal Transduction |
Canonical bases may have either a carbonyl or an amine group on the carbons surrounding the nitrogen atom furthest away from the glycosidic bond, which allows them to base pair (Watson-Crick base pairing) via hydrogen bonds (amine with ketone, purine with pyrimidine). Adenine and 2-aminoadenine have one/two amine group(s), whereas thymine has two carbonyl groups, and cytosine and guanine are mixed amine and carbonyl (inverted in respect to each other).
The precise reason why there are only four nucleotides is debated, but there are several unused possibilities.
Furthermore, adenine is not the most stable choice for base pairing: in Cyanophage S-2L, diaminopurine (DAP) is used instead of adenine. Diaminopurine basepairs perfectly with thymine as it is identical to adenine but has an amine group at position 2 forming 3 intramolecular hydrogen bonds, eliminating the major difference between the two types of basepairs (weak A-T vs strong C-G). This improved stability affects protein-binding interactions that rely on those differences.
Other combination include:
* Isoguanine and isocytosine, which have their amine and ketone inverted compared to standard guanine and cytosine. They are not used probably as tautomers are problematic for base pairing, but isoC and isoG can be amplified correctly with PCR even in the presence of the 4 canonical bases.
* Diaminopyrimidine and xanthine, which bind like 2-aminoadenine and thymine but with inverted structures. This pair is not used as xanthine is a deamination product.
However, correct DNA structure can form even when the bases are not paired via hydrogen bonding; that is, the bases pair thanks to hydrophobicity, as studies have shown with DNA isosteres (analogues with same number of atoms) such as the thymine analogue 2,4-difluorotoluene (F) or the adenine analogue 4-methylbenzimidazole (Z). An alternative hydrophobic pair could be isoquinoline and pyrrolo[2,3-b]pyridine
Other noteworthy basepairs:
* Several fluorescent bases have also been made, such as the 2-amino-6-(2-thienyl)purine and pyrrole-2-carbaldehyde base pair.
* Metal-coordinated bases, such as pairing between a pyridine-2,6-dicarboxylate (tridentate ligand) and a pyridine (monodentate ligand) through square planar coordination to a central copper ion.
* Universal bases may pair indiscriminately with any other base, but, in general, lower the melting temperature of the sequence considerably; examples include 2'-deoxyinosine (hypoxanthine deoxynucleotide) derivatives, nitroazole analogues, and hydrophobic aromatic non-hydrogen-bonding bases (strong stacking effects). These are used as proof of concept and, in general, are not utilized in degenerate primers (which are a mixture of primers).
* The numbers of possible base pairs is doubled when xDNA is considered. xDNA contains expanded bases, in which a benzene ring has been added, which may pair with canonical bases, resulting in four additional possible base-pairs (xA-T, xT-A, xC-G, xG-C) with eight bases (or 16 bases if the unused arrangements are used). Another form of benzene added bases is yDNA, in which the base is widened by the benzene. | 1 | Gene expression + Signal Transduction |
The efficiency of the blast furnace was improved by the change to hot blast, patented by James Beaumont Neilson in Scotland in 1828. This further reduced production costs. Within a few decades, the practice was to have a stove as large as the furnace next to it into which the waste gas (containing CO) from the furnace was directed and burnt. The resultant heat was used to preheat the air blown into the furnace. | 0 | Metallurgy |
Involved in the earliest step for the formation of the active cleavage complex, the CFIm complex is formed by three proteins of 25, 59 and 68 kDa, respectively:
*CFIm25 (or CPSF5/NUDT21)
*CFIm59 (or CPSF7)
*CFIm68 (or CPSF6)
CFIm25 and CFIm68 are sufficient for the activity of the complex, proving the expected redundancy of CFIm68 and CFIm59, which share great sequence similarity. | 1 | Gene expression + Signal Transduction |
There is significant overlap in function with regards to some of these proteins. In particular, the Rho-related genes are important in nuclear trafficking (i.e.: mitosis) as well as with mobility along the cytoskeleton in general. These genes of particular interest in cancer research.
*ARHGAP35
*ARHGAP5
*ARHGDIA
*ARHGEF10L Rho guanine nucleotide exchange factor 10L
*ARHGEF11 Rho guanine nucleotide exchange factor 11
*ARHGEF40 Rho guanine nucleotide exchange factor 40
*ARHGEF7 Rho guanine nucleotide exchange factor 7
*RAB10 NM_016131 The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes
*RAB11A NM_004663
*RAB11B NM_004218
*RAB14 NM_016322
*RAB18 NM_021252
*RAB1A NM_004161 Homo sapiens RAB1A, member RAS oncogene family (RAB1A), mRNA
*RAB1B NM_030981
*RAB21 NM_014999
*RAB22A NM_020673
*RAB2A NM_002858
*RAB2B NM_001163380
*RAB3GAP1 NM_012233
*RAB3GAP2 NM_012414
*RAB40C NM_021168
*RAB4A NM_004578
*RAB5A NM_004162
*RAB5B NM_002865
*RAB5C NM_004583
*RAB6A NM_002868
*RAB7A NM_004637
*RAB9A NM_004251
*RABEP1 NM_004703
*RABEPK NM_005833
*RABGEF1 NM_014504
*RABGGTA NM_004581
*RABGGTB NM_004582
*CENPB Centromere protein B
*CTBP1 Centromere protein T
*CCNB1IP1 NM_021178 E3 ubiquitin-protein ligase. Modulates cyclin B levels and participates in the regulation of cell cycle progression through the G2 phase
*CCNDBP1 NM_012142 May negatively regulate cell cycle progression
*CCNG1 NM_004060 May play a role in growth regulation
*CCNH NM_001239 Involved in cell cycle control and in RNA transcription by RNA polymerase II. Its expression and activity are constant throughout the cell cycle
*CCNK NM_001099402 Regulatory subunit of cyclin-dependent kinases that mediates phosphorylation of the large subunit of RNA polymerase II
*CCNL1 NM_020307 Transcriptional regulator which participates in regulating the pre-mRNA splicing process
*CCNL2 NM_030937 Transcriptional regulator which participates in regulating the pre-mRNA splicing process. Also modulates the expression of critical apoptotic factor, leading to cell apoptosis.
*CCNY NM_145012 Positive regulatory subunit of the cyclin-dependent kinases CDK14/PFTK1 and CDK16. Acts as a cell-cycle regulator of Wnt signaling pathway during G2/M phase
*PPP1CA NM_002708 Protein phosphatase that associates with over 200 regulatory proteins to form highly specific holoenzymes which dephosphorylate hundreds of biological targets
*PPP1CC NM_002710
*PPP1R10 NM_002714
*PPP1R11 NM_021959 Homo sapiens protein phosphatase 1, regulatory (inhibitor) subunit 11 (PPP1R11),
*PPP1R15B NM_032833
*PPP1R37 NM_019121
*PPP1R7 NM_002712
*PPP1R8 NM_002713
*PPP2CA NM_002715
*PPP2CB NM_001009552
*PPP2R1A NM_014225 Negative regulator of growth and cell divisionHomo sapiens protein phosphatase 2 (formerly 2A), regulatory subunit A (PR 65),
*PPP2R2A NM_002717
*PPP2R2D NM_018461
*PPP2R3C NM_017917
*PPP2R4 NM_021131
*PPP2R5A NM_006243
*PPP2R5B NM_006244
*PPP2R5C NM_002719
*PPP2R5D NM_006245
*PPP2R5E NM_006246
*PPP4C NM_002720
*PPP4R1 NM_005134
*PPP4R2 NM_174907
*PPP5C NM_006247
*PPP6C NM_002721
*PPP6R2 NM_014678
*PPP6R3 NM_018312
*RAD1Homo sapiens ribonuclease/angiogenin inhibitor (RNH), mRNA
*RAD17 NM_002869 Essential for sustained cell growth, maintenance of chromosomal stability, and ATR-dependent checkpoint activation upon DNA damage
*RAD23B NM_002873
*RAD50 NM_005732
*RAD51C NM_002874
*IST1 (locates to central dividing line of dividing cells) | 1 | Gene expression + Signal Transduction |
G proteins are important signal transducing molecules in cells. "Malfunction of GPCR [G Protein-Coupled Receptor] signaling pathways are involved in many diseases, such as diabetes, blindness, allergies, depression, cardiovascular defects, and certain forms of cancer. It is estimated that about 30% of the modern drugs' cellular targets are GPCRs." The human genome encodes roughly 800 G protein-coupled receptors, which detect photons of light, hormones, growth factors, drugs, and other endogenous ligands. Approximately 150 of the GPCRs found in the human genome still have unknown functions.
Whereas G proteins are activated by G protein-coupled receptors, they are inactivated by RGS proteins (for "Regulator of G protein signalling"). Receptors stimulate GTP binding (turning the G protein on). RGS proteins stimulate GTP hydrolysis (creating GDP, thus turning the G protein off). | 1 | Gene expression + Signal Transduction |
* Relatively low array size: Although it has the potential to use an increased amount of dyes to generate millions of different array elements, the current generation of commercially available microsphere arrays (from Luminex xMAP technology) only uses two sets of dyes and therefore can only detect ~100 targets per experiment.
* Hybridization between different sets of probes and target sequences requires a specific annealing temperature, which is affected by length and sequence of the oligonucleotide probe. Therefore, for every experiment, only one possible annealing temperature can be used. Thus, all probes used in given experiment must be designed to hybridize to the target at the same temperature. Although introducing base pair mismatch in some sets of the probes could minimize annealing temperature differences between each set of probes, the hybridization problem is still significant if more than 10-20 targets are tested in one reaction. | 1 | Gene expression + Signal Transduction |
The phenotype of each individual is modeled as the gene expression pattern at time . It is represented by a state vector in this model.
whose element denotes the expression state of gene i at time t. In the original Wagner model,
where 1 represents the gene is expressed while -1 implies the gene is not expressed. The expression pattern can only be ON or OFF. The continuous expression pattern between -1 (or 0) and 1 is also implemented in some other variants. | 1 | Gene expression + Signal Transduction |
Editing is differentially expressed in the cerebellum and cortex. This regulation is also present in mice suggesting conservation of editing regulation. No editing has been detected in human lung, heart, kidney or spleen tissue. | 1 | Gene expression + Signal Transduction |
The methods used for small parts and jewellery vary somewhat from those used for sculpture. A wax model is obtained either from injection into a rubber mould or by being custom-made by carving. The wax or waxes are sprued and fused onto a rubber base, called a "sprue base". Then a metal flask, which resembles a short length of steel pipe that ranges roughly from 3.5 to 15 centimeters tall and wide, is put over the sprue base and the waxes. Most sprue bases have a circular rim which grips the standard-sized flask, holding it in place. Investment (refractory plaster) is mixed and poured into the flask, filling it. It hardens, then is burned out as outlined above. Casting is usually done straight from the kiln either by centrifugal casting or vacuum casting.
The lost-wax process can be used with any material that can burn, melt, or evaporate to leave a mould cavity. Some automobile manufacturers use a lost-foam technique to make engine blocks. The model is made of polystyrene foam, which is placed into a casting flask, consisting of a cope and drag, which is then filled with casting sand. The foam supports the sand, allowing shapes that would be impossible if the process had to rely on the sand alone. The metal is poured in, vaporizing the foam with its heat.
In dentistry, gold crowns, inlays and onlays are made by the lost-wax technique. Application of Lost Wax technique for the fabrication of cast inlay was first reported by Taggart. A typical gold alloy is about 60% gold and 28% silver with copper and other metals making up the rest. Careful attention to tooth preparation, impression taking and laboratory technique are required to make this type of restoration a success. Dental laboratories make other items this way as well. | 0 | Metallurgy |
The galvanic series (or electropotential series) determines the nobility of metals and semi-metals. When two metals are submerged in an electrolyte, while also electrically connected by some external conductor, the less noble (base) will experience galvanic corrosion. The rate of corrosion is determined by the electrolyte, the difference in nobility, and the relative areas of the anode and cathode exposed to the electrolyte. The difference can be measured as a difference in voltage potential: the less noble metal is the one with a lower (that is, more negative) electrode potential than the nobler one, and will function as the anode (electron or anion attractor) within the electrolyte device functioning as described above (a galvanic cell). Galvanic reaction is the principle upon which batteries are based.
See the table of standard electrode potentials for more details. | 0 | Metallurgy |
The nuclear genetic code is flexible as illustrated by variant genetic codes that reassign standard stop codons to amino acids. | 1 | Gene expression + Signal Transduction |
Both TLR3 and TLR4 use the TRIF-dependent pathway, which is triggered by dsRNA and LPS, respectively. For TLR3, dsRNA leads to activation of the receptor, recruiting the adaptor TRIF. TRIF activates the kinases TBK1 and RIPK1, which creates a branch in the signaling pathway. The TRIF/TBK1 signaling complex phosphorylates IRF3 allowing its translocation into the nucleus and production of Interferon type I. Meanwhile, activation of RIPK1 causes the polyubiquitination and activation of TAK1 and NFκB transcription in the same manner as the MyD88-dependent pathway.
TLR signaling ultimately leads to the induction or suppression of genes that orchestrate the inflammatory response. In all, thousands of genes are activated by TLR signaling, and collectively, the TLRs constitute one of the most pleiotropic yet tightly regulated gateways for gene modulation.
TLR4 is the only TLR that uses all four adaptors. Complex consisting of TLR4, MD2 and LPS recruits TIR domain-containing adaptors TIRAP and MyD88 and thus initiates activation of NFκB (early phase) and MAPK. TLR4-MD2-LPS complex then undergoes endocytosis and in endosome it forms a signalling complex with TRAM and TRIF adaptors. This TRIF-dependent pathway again leads to IRF3 activation and production of type I interferons, but it also activates late-phase NFκB activation. Both late and early phase activation of NFκB is required for production of inflammatory cytokines. | 1 | Gene expression + Signal Transduction |
The brief existence of an mRNA molecule begins with transcription, and ultimately ends in degradation. During its life, an mRNA molecule may also be processed, edited, and transported prior to translation. Eukaryotic mRNA molecules often require extensive processing and transport, while prokaryotic mRNA molecules do not. A molecule of eukaryotic mRNA and the proteins surrounding it are together called a messenger RNP. | 1 | Gene expression + Signal Transduction |
Bulk metallic glasses have been modeled using atomic scale simulations (within the density functional theory framework) in a similar manner to high entropy alloys. This has allowed predictions to be made about their behavior, stability and many more properties. As such, new bulk metallic glass systems can be tested and tailored for a specific purpose (e.g. bone replacement or aero-engine component) without as much empirical searching of the phase space or experimental trial and error. Ab-initio molecular dynamics (MD) simulation confirmed that the atomic surface structure of a Ni-Nb metallic glass observed by scanning tunneling microscopy is a kind of spectroscopy. At negative applied bias it visualizes only one soft of atoms (Ni) owing to the structure of electronic density of states calculated using ab-initio MD simulation.
One common way to try and understand the electronic properties of amorphous metals is by comparing them to liquid metals, which are similarly disordered, and for which established theoretical frameworks exist. For simple amorphous metals, good estimations can be reached by semi-classical modelling of the movement of individual electrons using the Boltzmann equation and approximating the scattering potential as the superposition of the electronic potential of each nucleus in the surrounding metal. To simplify the calculations, the electronic potentials of the atomic nuclei can be truncated to give a muffin-tin pseudopotential. In this theory, there are two main effects that govern the change of resistivity with increasing temperatures. Both are based on the induction of vibrations of the atomic nuclei of the metal as temperatures increase. One is, that the atomic structure gets increasingly smeared out as the exact positions of the atomic nuclei get less and less well defined. The other is the introduction of phonons. While the smearing out generally decreases the resistivity of the metal, the introduction of phonons generally adds scattering sites and therefore increases resistivity. Together, they can explain the anomalous decrease of resistivity in amorphous metals, as the first part outweighs the second. In contrast to regular crystalline metals, the phonon contribution in an amorphous metal does not get frozen out at low temperatures. Due to the lack of a defined crystal structure, there are always some phonon wavelengths that can be excited. While this semi-classical approach holds well for many amorphous metals, it generally breaks down under more extreme conditions. At very low temperatures, the quantum nature of the electrons leads to long range interference effects of the electrons with each other in what is called "weak localization effects". In very strongly disordered metals, impurities in the atomic structure can induce bound electronic states in what is called "Anderson localization", effectively binding the electrons and inhibiting their movement. | 0 | Metallurgy |
Research on paracrine signaling through the JAK-STAT pathway revealed its potential in activating invasive behavior of ovarian epithelial cells. This epithelial to mesenchymal transition is highly evident in metastasis. Paracrine signaling through the JAK-STAT pathway is necessary in the transition from stationary epithelial cells to mobile mesenchymal cells, which are capable of invading surrounding tissue. Only the JAK-STAT pathway has been found to induce migratory cells. | 1 | Gene expression + Signal Transduction |
Non-metallic inclusions are chemical compounds and nonmetals that are present in steel and other alloys. They are the product of chemical reactions, physical effects, and contamination that occurs during the melting and pouring process. These inclusions are categorized by origin as either endogenous or exogenous. Endogenous inclusions, also known as indigenous, occur within the metal and are the result of chemical reactions. These products precipitate during cooling and are typically very small. Exogenous inclusions are caused by the entrapment of nonmetals. Their size varies greatly and their source can include slag, dross, flux residues, and pieces of the mold. | 0 | Metallurgy |
C/EBPβ levels are increased in cortical samples of Alzheimers and Parkinsons disease victims at autopsy. Cell culture studies in mice and human microglia lines also find increased C/EBPβ activity associated with pathogenic inflammation and cytokine responses. Downstream analysis of genes regulated by C/EBPβ have significance in immune response, mitochondrial health, and autophagy. Molecular interference of these cellular processes have been shown to play a role in neurodegenerative pathogenesis. Genetic and molecular pathways with degenerative implications involving C/EBPβ and its homologs are conserved across multiple model organisms including Mus musculus, Drosophila melanogaster, Caenorhabditis elegans, and Danio rerio'. Upstream regulators of C/EBPβ include genes known to be associated with neurodegenerative and neurodevelopmental disease when mutated or dysregulated. This includes a well characterized cellular stress response pathway involving p38 and JNK. | 1 | Gene expression + Signal Transduction |
This book describes how an official, the Bergmeister, is in charge of mining. He marks out the land into areas called meers when a vein is discovered. The rest of the book covers the laws of mining. There is a section on how the mine can be divided into shares. The roles of various other officials in regulating mines and taxing the production are stated. The shifts of the miners are fixed. The chief trades in the mine are listed and are regulated by both the Bergmeister and their foremen. | 0 | Metallurgy |
Transcriptome-wide analysis of alternative splicing is typically performed by high-throughput RNA-sequencing. Most commonly, by short-read sequencing, such as by Illumina instrumentation. But even more informative, by long-read sequencing, such as by Nanopore or PacBio instrumentation. Transcriptome-wide analyses can for example be used to measure the amount of deviating alternative splicing, such as in a cancer cohort.
Deep sequencing technologies have been used to conduct genome-wide analyses of both unprocessed and processed mRNAs; thus providing insights into alternative splicing. For example, results from use of deep sequencing indicate that, in humans, an estimated 95% of transcripts from multiexon genes undergo alternative splicing, with a number of pre-mRNA transcripts spliced in a tissue-specific manner. Functional genomics and computational approaches based on multiple instance learning have also been developed to integrate RNA-seq data to predict functions for alternatively spliced isoforms. Deep sequencing has also aided in the in vivo detection of the transient lariats that are released during splicing, the determination of branch site sequences, and the large-scale mapping of branchpoints in human pre-mRNA transcripts.
More historically, alternatively spliced transcripts have been found by comparing EST sequences, but this requires sequencing of very large numbers of ESTs. Most EST libraries come from a very limited number of tissues, so tissue-specific splice variants are likely to be missed in any case. High-throughput approaches to investigate splicing have, however, been developed, such as: DNA microarray-based analyses, RNA-binding assays, and deep sequencing. These methods can be used to screen for polymorphisms or mutations in or around splicing elements that affect protein binding. When combined with splicing assays, including in vivo reporter gene assays, the functional effects of polymorphisms or mutations on the splicing of pre-mRNA transcripts can then be analyzed.
In microarray analysis, arrays of DNA fragments representing individual exons (e.g. Affymetrix exon microarray) or exon/exon boundaries (e.g. arrays from ExonHit or Jivan) have been used. The array is then probed with labeled cDNA from tissues of interest. The probe cDNAs bind to DNA from the exons that are included in mRNAs in their tissue of origin, or to DNA from the boundary where two exons have been joined. This can reveal the presence of particular alternatively spliced mRNAs.
CLIP (Cross-linking and immunoprecipitation) uses UV radiation to link proteins to RNA molecules in a tissue during splicing. A trans-acting splicing regulatory protein of interest is then precipitated using specific antibodies. When the RNA attached to that protein is isolated and cloned, it reveals the target sequences for that protein. Another method for identifying RNA-binding proteins and mapping their binding to pre-mRNA transcripts is "Microarray Evaluation of Genomic Aptamers by shift (MEGAshift)".net This method involves an adaptation of the "Systematic Evolution of Ligands by Exponential Enrichment (SELEX)" method together with a microarray-based readout. Use of the MEGAshift method has provided insights into the regulation of alternative splicing by allowing for the identification of sequences in pre-mRNA transcripts surrounding alternatively spliced exons that mediate binding to different splicing factors, such as ASF/SF2 and PTB. This approach has also been used to aid in determining the relationship between RNA secondary structure and the binding of splicing factors.
Use of reporter assays makes it possible to find the splicing proteins involved in a specific alternative splicing event by constructing reporter genes that will express one of two different fluorescent proteins depending on the splicing reaction that occurs. This method has been used to isolate mutants affecting splicing and thus to identify novel splicing regulatory proteins inactivated in those mutants.
Recent advancements in protein structure prediction have facilitated the development of new tools for genome annotation and alternative splicing anlaysis. For instance, isoform.io, a platform guided by protein structure predictions, has evaluated hundreds of thousands of isoforms of human protein-coding genes assembled from numerous RNA sequencing experiments across a variety of human tissues. This comprehensive analysis has led to the identification of numerous isoforms with more confidently predicted structure and potentially superior function compared to canonical isoforms in the latest human gene database. By integrating structural predictions with expression and evolutionary evidence, this approach has demonstrated the potential of protein structure prediction as a tool for refining the annotation of the human genome. | 1 | Gene expression + Signal Transduction |
Ectopic is a word used with a prefix ecto-, meaning “out of”, and the suffix -topic, meaning "place." Ectopic expression is an abnormal gene expression in a cell type, tissue type, or developmental stage in which the gene is not usually expressed. The term ectopic expression is predominantly used in studies using metazoans, especially in Drosophila melanogaster for research purposes. | 1 | Gene expression + Signal Transduction |
Archaeological evidence indicates that the earliest metal objects in China were made in the late fourth millennium BCE. Copper was generally the earliest metal to be used by humanity, and was used in China since at least 3000 BCE.
Early metal-using communities have been found at the Qijia and Siba sites in Gansu. The metal knives and axes recovered in Qijia apparently point to some interactions with Siberian and Central Asian cultures, in particular with the Seima-Turbino complex, or the Afanasievo culture. Archeological evidence points to plausible early contact between the Qijia culture and Central Asia. Similar sites have been found in Xinjiang in the west and Shandong, Liaoning and Inner Mongolia in the east and north. The Central Plain sites associated with the Erlitou culture also contain early metalworks.
Copper manufacturing, more complex than jade working, gradually appeared in the Yangshao period (5000–3000 BCE). Jiangzhai is the only place where copper artifacts were found in the Banpo culture. Archaeologists have found remains of copper metallurgy in various cultures from the late fourth to the early third millennia BCE. These include the copper-smelting remains and copper artifacts of the Hongshan culture (4700–2900) and copper slag at the Yuanwozhen site. This indicates that inhabitants of the Yellow River valley had already learned how to make copper artifacts by the later Yangshao period.
The Qijia culture (c. 2500–1900) of Qinghai, Gansu, and western Shaanxi produced copper and bronze utilitarian items and gold, copper, and bronze ornaments. The earliest metalworks in this region are found at a Majiayao site at Linjia, Dongxiang, Gansu. "Their dates range from 2900 to 1600 BCE. These metal objects represent the Majiayao 馬家窯 type of the Majiayao culture (c. 3100–2700 BCE), Zongri 宗日 Culture (c. 3600–2050 BCE), Machang 馬廠 Type (c. 2300–2000 BCE), Qijia 齊家 Culture (c. 2050–1915 BCE), and Siba 四壩 Culture (c. 2000–1600 BCE)."
At Dengjiawan, in the Shijiahe site complex in Hubei, some pieces of copper were discovered; they are the earliest copper objects discovered in southern China. The Linjia site (林家遺址, Línjiā yízhǐ) has the earliest evidence for bronze in China, dating to c. 3000 BCE. | 0 | Metallurgy |
Material is put on a sinter machine in two layers. The bottom layer may vary in thickness from . A 12 to 20 mm sinter fraction is used, also referred to as the hearth layer. The second, covering layer consists of mixed materials, making for a total bed height of . The mixed materials are applied with drum feeders and roll feeders, which distributes the nodules in certain depth throughout the sinterring machine . The upper layer is smoothed using a leveler. The material, also known as a charge, enters the ignition furnace into rows of multi-slit burners. In the case of one plant, the first (ignition) zone has eleven burners. The next (soaking/annealing) zone typically offers 12 burners. Air is sucked from the bottom of the bed of mixed material throughout the sintering machine. Fire penetrates the mixed material gradually, until it reaches the hearth layer. This end point of burning is called burn through point (BTP). The hearth layer, which is nothing but sinter in smaller size, restricts sticking of hot sinter with pallets. BTP is achieved in a certain zone of sinter machine, to optimize the process, by means of several temperature measuring instrument placed throughout the sinter machine. After completion of burning, the mix converts into sinter, which then breaks into smaller size by sinter breaker. After breaking into small sizes, it cools down in cooler (linear or circular) by means of forced air. At discharge of sinter cooler, temperature of sinter is maintained as low, so that the hot sinter can be transported by a conveyor belt made of rubber. Necessary precautions are taken to trace any existence of fire in the belt and necessary extinguishing is done by spraying water. Then this product is being passed through a jaw-crusher, where the size of sinter is further reduced (~ 50 mm) into smaller size. Then the complete mixture is being passed through two screens. Smallest sinter fines (< 5 mm) are stored in proportioning bins and reused for preparing sinter again through mixing and nodulizing drum and fed to sinter machine for burning. A part of the smaller one ( 5 – 20 mm) is used for hearth layer in sinter machine and the rest is taken to the blast furnace along with the biggest sized sinters.
The temperature is typically maintained between in the ignition zone and between 900 and 1000 °C in the soaking zone to prevent sudden quenching of the sintered layer. The top 5 mm from screens goes to the conveyor carrying the sinter for the blast furnace and, along with blast furnace grade sinter, either goes to sinter storage bunkers or to BF bunkers. Blast furnace-grade sinter consists of particles sized 5 to 12 mm as well as 20 mm and above. | 0 | Metallurgy |
A number of proteins are known to be associated with TAD formation including the protein CTCF and the protein complex cohesin. It is also unknown what components are required at TAD boundaries; however, in mammalian cells, it has been shown that these boundary regions have comparatively high levels of CTCF binding. In addition, some types of genes (such as transfer RNA genes and housekeeping genes) appear near TAD boundaries more often than would be expected by chance.
Computer simulations have shown that chromatin loop extrusion driven by cohesin motors can generate TADs. In the loop extrusion model, cohesin binds chromatin, pulls it in, and extrudes chromatin to progressively grow a loop. Chromatin on both sides of the cohesin complex is extruded until cohesin encounters a chromatin-bound CTCF protein, typically located at the boundary of a TAD. In this way, TAD boundaries can be brought together as the anchors of a chromatin loop. Indeed, in vitro, cohesin has been observed to processively extrude DNA loops in an ATP-dependent manner and stall at CTCF. However, some in vitro data indicates that the observed loops may be artifacts. Importantly, since cohesins can dynamically unbind from chromatin, this model suggests that TADs (and associated chromatin loops) are dynamic, transient structures, in agreement with in vivo observations.
Other mechanisms for TAD formation have been suggested. For example, some simulations suggest that transcription-generated supercoiling can relocalize cohesin to TAD boundaries or that passively diffusing cohesin “slip links” can generate TADs. | 1 | Gene expression + Signal Transduction |
* Carbon steel is often divided into two main categories: low-carbon steel and high-carbon steel.
* Carbon steel may also contain other elements, such as manganese, phosphorus, sulfur, and silicon, which can affect its properties.
* Carbon steel can be easily machined and welded, making it versatile for various applications. It can also be heat treated to improve its strength, Hardness, and durability.
* Carbon steel is susceptible to rust and corrosion, especially in environments with high moisture levels and/or salt.
* Carbon steel can be shielded from corrosion by coating it with paint, varnish, or other protective material.
* Alternatively, it can be made from a stainless steel alloy that contains chromium, which provides excellent corrosion resistance.
* Carbon steel is sometimes alloyed with other elements to improve its properties, such as adding chromium and/or nickel to improve its resistance to corrosion and oxidation or adding molybdenum to improve its strength and toughness at high temperatures.
* Carbon steel is an environmentally friendly material, as it is easily recyclable and can be reused in various applications. It is also energy-efficient to produce, as it requires less energy than other metals such as aluminium and copper. | 0 | Metallurgy |
In metallurgy, selective leaching, also called dealloying, demetalification, parting and selective corrosion, is a corrosion type in some solid solution alloys, when in suitable conditions a component of the alloys is preferentially leached from the initially homogenous material. The less noble metal is removed from the alloy by a microscopic-scale galvanic corrosion mechanism. The most susceptible alloys are the ones containing metals with high distance between each other in the galvanic series, e.g. copper and zinc in brass. The elements most typically undergoing selective removal are zinc, aluminium, iron, cobalt, chromium, and others. | 0 | Metallurgy |
Microarray data sets are commonly very large, and analytical precision is influenced by a number of variables. Statistical challenges include taking into account effects of background noise and appropriate normalization of the data. Normalization methods may be suited to specific platforms and, in the case of commercial platforms, the analysis may be proprietary. Algorithms that affect statistical analysis include:
* Image analysis: gridding, spot recognition of the scanned image (segmentation algorithm), removal or marking of poor-quality and low-intensity features (called flagging).
* Data processing: background subtraction (based on global or local background), determination of spot intensities and intensity ratios, visualisation of data (e.g. see MA plot), and log-transformation of ratios, global or local normalization of intensity ratios, and segmentation into different copy number regions using step detection algorithms.
* Class discovery analysis: This analytic approach, sometimes called unsupervised classification or knowledge discovery, tries to identify whether microarrays (objects, patients, mice, etc.) or genes cluster together in groups. Identifying naturally existing groups of objects (microarrays or genes) which cluster together can enable the discovery of new groups that otherwise were not previously known to exist. During knowledge discovery analysis, various unsupervised classification techniques can be employed with DNA microarray data to identify novel clusters (classes) of arrays. This type of approach is not hypothesis-driven, but rather is based on iterative pattern recognition or statistical learning methods to find an "optimal" number of clusters in the data. Examples of unsupervised analyses methods include self-organizing maps, neural gas, k-means cluster analyses, hierarchical cluster analysis, Genomic Signal Processing based clustering and model-based cluster analysis. For some of these methods the user also has to define a distance measure between pairs of objects. Although the Pearson correlation coefficient is usually employed, several other measures have been proposed and evaluated in the literature. The input data used in class discovery analyses are commonly based on lists of genes having high informativeness (low noise) based on low values of the coefficient of variation or high values of Shannon entropy, etc. The determination of the most likely or optimal number of clusters obtained from an unsupervised analysis is called cluster validity. Some commonly used metrics for cluster validity are the silhouette index, Davies-Bouldin index, Dunns index, or Huberts statistic.
* Class prediction analysis: This approach, called supervised classification, establishes the basis for developing a predictive model into which future unknown test objects can be input in order to predict the most likely class membership of the test objects. Supervised analysis for class prediction involves use of techniques such as linear regression, k-nearest neighbor, learning vector quantization, decision tree analysis, random forests, naive Bayes, logistic regression, kernel regression, artificial neural networks, support vector machines, mixture of experts, and supervised neural gas. In addition, various metaheuristic methods are employed, such as genetic algorithms, covariance matrix self-adaptation, particle swarm optimization, and ant colony optimization. Input data for class prediction are usually based on filtered lists of genes which are predictive of class, determined using classical hypothesis tests (next section), Gini diversity index, or information gain (entropy).
* Hypothesis-driven statistical analysis: Identification of statistically significant changes in gene expression are commonly identified using the t-test, ANOVA, Bayesian methodMann–Whitney test methods tailored to microarray data sets, which take into account multiple comparisons or cluster analysis. These methods assess statistical power based on the variation present in the data and the number of experimental replicates, and can help minimize Type I and type II errors in the analyses.
* Dimensional reduction: Analysts often reduce the number of dimensions (genes) prior to data analysis. This may involve linear approaches such as principal components analysis (PCA), or non-linear manifold learning (distance metric learning) using kernel PCA, diffusion maps, Laplacian eigenmaps, local linear embedding, locally preserving projections, and Sammon's mapping.
* Network-based methods: Statistical methods that take the underlying structure of gene networks into account, representing either associative or causative interactions or dependencies among gene products. Weighted gene co-expression network analysis is widely used for identifying co-expression modules and intramodular hub genes. Modules may corresponds to cell types or pathways. Highly connected intramodular hubs best represent their respective modules.
Microarray data may require further processing aimed at reducing the dimensionality of the data to aid comprehension and more focused analysis. Other methods permit analysis of data consisting of a low number of biological or technical replicates; for example, the Local Pooled Error (LPE) test pools standard deviations of genes with similar expression levels in an effort to compensate for insufficient replication. | 1 | Gene expression + Signal Transduction |
Although the possibility of function in gene deserts was predicted as early as the 1960s, genetic identification tools were unable to uncover any specific characteristics of the long noncoding regions, other than that no coding occurred in those regions. Before the completion of the human genome in 2001 through the Human Genome Project, most of the early associative gene comparisons relied on the belief that essential housekeeping genes were clustered in the same areas of the genome for ease of access and tight regulation. This belief later constructed a hypothesis that gene deserts are therefore previous regulatory sequences that are highly linked (and hence do not undergo recombination), but have had substitutions between them over time. These substitutions could cause tightly conserved genes to separate over time, thus forming regions of nonsense codes with a few essential genes. However, uncertainty due to differential gene conservation rates in different portions of chromosomes prevented accurate identification.
Later associations were remodeled when regulatory sequences were associated with transcription factors, leading to the birth of large-scale genome-wide mapping. Thus began the hunt for the contents and functions of gene deserts. Recent advancements in the screening of chromatin signatures on chromosomes (for instance, chromosome conformation capture, also known as 3C) have allowed the confirmation of the long-range gene activation model, which postulates that there are indeed physical links between regulatory enhancers and their target promoters. Research on gene deserts, although centralized on human genetics, has also been applied to mice, various birds, and Drosophila melanogaster. Although conservation is variable among selected species’ genomes, orthologous gene deserts function similarly. Thus, the prevailing the contention of gene deserts is that these noncoding sequences harbor active and important regulatory elements. | 1 | Gene expression + Signal Transduction |
Flotation processes are described in ancient Greek and Persian literature. During the late 19th century, the process basics were discovered through a slow evolutionary phase. During the first decade of the 20th century, a more rapid investigation of oils, froths, and agitation led to proven workplace applications, especially in Broken Hill, Australia, that brought the technological innovation known as “froth flotation.” During the early 20th century, froth flotation revolutionized mineral processing.
Initially, naturally occurring chemicals such as fatty acids and oils were used as flotation reagents in large quantities to increase the hydrophobicity of the valuable minerals. Since then, the process has been adapted and applied to a wide variety of materials to be separated, and additional collector agents, including surfactants and synthetic compounds have been adopted for various applications. | 0 | Metallurgy |
The Antique Gas & Steam Engine Museum (AGSEM) is a living history museum founded in 1969. It is located on of county-owned land at 2040 N Santa Fe Ave. on the outskirts of Vista, California. The museum is a non-profit 501c(3) organization, run by several paid employees along with volunteer help.
The museum is open almost every day of the year and has two bi-annual shows, on the 3rd and 4th weekends of June and October. The museum also has other public and private events throughout the year.
Exhibits at the museum include: | 0 | Metallurgy |
Small activating Ribonucleic acids (saRNAs) are small double-stranded RNAs (dsRNAs) that target gene promoters to induce transcriptional gene activation in a process known as RNA activation (RNAa).
Small dsRNAs, such as small interfering RNAs (siRNAs) and microRNAs (miRNAs), are known to be the trigger of an evolutionarily conserved mechanism known as RNA interference (RNAi). RNAi invariably leads to gene silencing via remodeling of chromatin to thereby suppress transcription, degrading complementary mRNA, or blocking protein translation. Later it was found that dsRNAs can also act to activate transcription and was thus designated saRNA. By targeting selected sequences in gene promoters, saRNAs induce target gene expression at the transcriptional/epigenetic level.
saRNAs are typically 21 nucleotides in length with a 2 nucleotide overhang at the 3 end of each strand, the same structure as a typical siRNA. To identify an saRNA that can activate a gene of interest, several saRNAs need to be designed within a 1- to 2-kb promoter region by following a set of rules and tested in cultured cells. In some reports, saRNAs are designed in such a way to target non-coding transcripts that overlap the promoter sequence of a protein coding gene. Both chemically synthesized saRNAs and saRNAs expressed as short hairpin RNA (shRNA) have been used in in vitro and in vivo' experiments.
An online resource for saRNAs has been developed ([https://bioinfo.imtech.res.in/manojk/sarna/ https://bioinfo.imtech.res.in/manojk/sarna/]) and published.
Therapeutic use of saRNAs have been suggested. They have been tested in animal models to treat bladder tumors,
liver carcinogenesis,
pancreatic cancer,
and erectile dysfunction.
In 2016, a phase I clinical trial involving advanced liver cancer patients was launched for the saRNA drug MTL-CEBPA. It aimed to complete in 2021. | 1 | Gene expression + Signal Transduction |
In vertebrates, calcium ions, like many other ions, are of such vital importance to many physiological processes that its concentration is maintained within specific limits to ensure adequate homeostasis. This is evidenced by human plasma calcium, which is one of the most closely regulated physiological variables in the human body. Normal plasma levels vary between 1 and 2% over any given time. Approximately half of all ionized calcium circulates in its unbound form, with the other half being complexed with plasma proteins such as albumin, as well as anions including bicarbonate, citrate, phosphate, and sulfate.
Different tissues contain calcium in different concentrations. For instance, Ca (mostly calcium phosphate and some calcium sulfate) is the most important (and specific) element of bone and calcified cartilage. In humans, the total body content of calcium is present mostly in the form of bone mineral (roughly 99%). In this state, it is largely unavailable for exchange/bioavailability. The way to overcome this is through the process of bone resorption, in which calcium is liberated into the bloodstream through the action of bone osteoclasts. The remainder of calcium is present within the extracellular and intracellular fluids.
Within a typical cell, the intracellular concentration of ionized calcium is roughly 100 nM, but is subject to increases of 10- to 100-fold during various cellular functions. The intracellular calcium level is kept relatively low with respect to the extracellular fluid, by an approximate magnitude of 12,000-fold. This gradient is maintained through various plasma membrane calcium pumps that utilize ATP for energy, as well as a sizable storage within intracellular compartments. In electrically excitable cells, such as skeletal and cardiac muscles and neurons, membrane depolarization leads to a Ca transient with cytosolic Ca concentration reaching around 1 µM. Mitochondria are capable of sequestering and storing some of that Ca. It has been estimated that mitochondrial matrix free calcium concentration rises to the tens of micromolar levels in situ during neuronal activity. | 1 | Gene expression + Signal Transduction |
The ambush hypothesis is a hypothesis in the field of molecular genetics that suggests that the prevalence of “hidden” or off-frame stop codons in DNA selectively deters off-frame translation of mRNA to save energy, molecular resources, and to reduce strain on biosynthetic machinery by truncating the production of non-functional, potentially cytotoxic protein products. Typical coding sequences of DNA lack in-frame internal stop codons to avoid the premature reduction of protein products when translation proceeds normally. The ambush hypothesis suggests that kinetic, cis-acting mechanisms are responsible for the productive frameshifting of translational units so that the degeneracy of the genetic code can be used to prevent deleterious translation. Ribosomal slippage is the most well described mechanism of translational frameshifting where the ribosome moves one codon position either forward (+1) or backward (-1) to translate the mRNA sequence in a different reading frame and thus produce different protein products.
In respect to codon usage, the ambush hypothesis theorizes that there is a positive correlation between the use of a codon and the amount a codon contributes to hidden stops. Phylogenetic analyses of both the nuclear and mitochondrial genomes of all major taxonomic kingdoms suggests ubiquitous off-frame stop codon existence and a positive correlation between the usage frequency of a codon and the number of ways a codon can contribute to hidden stop codons in different translational reading frames.
Combinatorics have been used across genetic codes to determine how each in-frame codon can potentially contribute to stop codons in off-frame contexts. The standard genetic code only contains 20 codons that cannot become stop codons in a frameshifted ribosomal environment (-1 frameshift: 42, +1 frameshift: 28) and 127 out of the 400 (31.75%) possible adjacent amino acid combinations in the vertebrate mitochondrial code creates an off-frame stop codon. This suggests that substitutions and synonymous codon usage are not neutral and that selective pressures might have readjusted codon assignments to increase the frequencies of those that can be used as hidden stops.
Observations that the number of off-frame stop codons is positively correlated with the expression level of a gene support the ambush hypothesis by increasing translational regulation (hidden stop frequency) to discourage off-frame reading in genes that are expressed at a high level. The positive correlation indicates that the off-frame translation of larger genes with higher expression levels likely costs a cell more energy, resources, and pathway efficiency than translating smaller, more rare genes in a shifted reading frame. Off-frame stop codon frequency is negatively correlated with gestation time in primates and though there are many factors that link molecular translational efficiency to the rate of morphogenesis, these findings suggests that not only individual cells but entire organisms may benefit from the development of hidden stop codons to effectively halt off-frame synthesis.
The ambush hypothesis is challenged by recent observations that off-frame stop codons are directly correlated with the GC content in the genome because stop codons are GC-poor. [http://www.biomedcentral.com/1471-2164/14/418 Morgens et al. 2013] argues that previous research concerning the ambush hypothesis has relied on codon usage data which is representative of the GC content of an organism and thus not appropriate to evaluate the selective effect of off-frame stop codons. | 1 | Gene expression + Signal Transduction |
Up-regulated expression of genes in mammals is initiated when signals are transmitted to the promoters associated with the genes. Promoter DNA sequences may include different elements such as CpG islands (present in about 70% of promoters), a TATA box (present in about 24% of promoters), initiator (Inr) (present in about 49% of promoters), upstream and downstream TFIIB recognition elements (BREu and BREd) (present in about 22% of promoters), and downstream core promoter element (DPE) (present in about 12% of promoters). The presence of multiple methylated CpG sites in CpG islands of promoters causes stable silencing of genes. However, the presence or absence of the other elements have relatively small effects on gene expression in experiments. Two sequences, the TATA box and Inr, caused small but significant increases in expression (45% and 28% increases, respectively). The BREu and the BREd elements significantly decreased expression by 35% and 20%, respectively, and the DPE element had no detected effect on expression.
Cis-regulatory modules that are localized in DNA regions distant from the promoters of genes can have very large effects on gene expression, with some genes undergoing up to 100-fold increased expression due to such a cis-regulatory module. These cis-regulatory modules include enhancers, silencers, insulators and tethering elements. Among this constellation of elements, enhancers and their associated transcription factors have a leading role in the regulation of gene expression.
Enhancers are regions of the genome that are major gene-regulatory elements. Enhancers control cell-type-specific gene expression programs, most often by looping through long distances to come in physical proximity with the promoters of their target genes. In a study of brain cortical neurons, 24,937 loops were found, bringing enhancers to promoters. Multiple enhancers, each often at tens or hundred of thousands of nucleotides distant from their target genes, loop to their target gene promoters and coordinate with each other to control expression of their common target gene.
The schematic illustration in this section shows an enhancer looping around to come into close physical proximity with the promoter of a target gene. The loop is stabilized by a dimer of a connector protein (e.g. dimer of CTCF or YY1), with one member of the dimer anchored to its binding motif on the enhancer and the other member anchored to its binding motif on the promoter (represented by the red zigzags in the illustration). Several cell function specific transcription factors (there are about 1,600 transcription factors in a human cell) generally bind to specific motifs on an enhancer and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern the level of transcription of the target gene. Mediator (coactivator) (a complex usually consisting of about 26 proteins in an interacting structure) communicates regulatory signals from enhancer DNA-bound transcription factors directly to the RNA polymerase II (pol II) enzyme bound to the promoter.
Enhancers, when active, are generally transcribed from both strands of DNA with RNA polymerases acting in two different directions, producing two eRNAs as illustrated in the Figure. An inactive enhancer may be bound by an inactive transcription factor. Phosphorylation of the transcription factor may activate it and that activated transcription factor may then activate the enhancer to which it is bound (see small red star representing phosphorylation of transcription factor bound to enhancer in the illustration). An activated enhancer begins transcription of its RNA before activating a promoter to initiate transcription of messenger RNA from its target gene. | 1 | Gene expression + Signal Transduction |
In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product. The result of this is that the genes contained in the operon are either expressed together or not at all. Several genes must be co-transcribed to define an operon.
Originally, operons were thought to exist solely in prokaryotes (which includes organelles like plastids that are derived from bacteria), but their discovery in eukaryotes was shown in the early 1990s, and are considered to be rare. In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNAs.
Operons are also found in viruses such as bacteriophages. For example, T7 phages have two operons. The first operon codes for various products, including a special T7 RNA polymerase which can bind to and transcribe the second operon. The second operon includes a lysis gene meant to cause the host cell to burst. | 1 | Gene expression + Signal Transduction |
The local solidification time can be calculated using Chvorinov's rule, which is:
Where t is the solidification time, V is the volume of the casting, A is the surface area of the casting that contacts the mold, n is a constant, and B is the mold constant. It is most useful in determining if a riser will solidify before the casting, because if the riser does solidify first then it is worthless. | 0 | Metallurgy |
As other species of sulfur at intermediate oxidation state, such as thiosulfate, tetrathionate can be responsible for the pitting corrosion of carbon steel and stainless steel.
Tetrathionate has also been found to serve as a terminal electron acceptor for Salmonella enterica serotype Typhimurium, whereas existing thiosulfate in the small intestines of mammals is oxidized by reactive oxygen species released by the immune system (mainly NADPH oxidase produced superoxide) to form tetrathionate. This aids in the growth of the bacterium, helped by the inflammatory response. | 0 | Metallurgy |
The metals of antiquity are the seven metals which humans had identified and found use for in prehistoric times in Africa, Europe and throughout Asia: gold, silver, copper, tin, lead, iron, and mercury. These seven are the metals from which the classical world was forged.
Zinc, arsenic, and antimony were also known during antiquity, but they were not recognised as distinct metals until later. A special case is platinum; it was known to native South Americans around the time Europe was going through classical antiquity, but was unknown to Europeans until the 18th century. Thus, at most eleven elemental metals and metalloids were known by the end of antiquity; this contrasts greatly with the situation today, with over 90 elemental metals known. Bismuth only began to be recognised as distinct around 1500 by the European and Incan civilisations. The first elemental metal with a clearly identifiable discoverer is cobalt, discovered in 1735 by Georg Brandt, by which time the Scientific Revolution was in full swing. (Even then, cobalt might have been prepared before the 13th century by alchemists roasting and reducing its ore, but in any case its distinct nature was not recognised.) | 0 | Metallurgy |
Since the outer conductor layer is low-impedance copper, and only the center is higher impedance steel, the skin effect gives RF transmission lines with heavy copper-cladding a low impedance at high frequencies, equivalent to that of a solid copper wire.
Tensile strength of copper-clad steel conductors is greater than that of ordinary copper conductors permitting greater span lengths than with copper.
Another advantage is that smaller diameter copper-clad steel conductors may be used in coaxial cables, permitting higher impedance and smaller cable diameter than with copper conductors of similar strength.
Due to the inseparable union of the two metals and the low amount of the more costly one, it deters theft since copper recovery is impractical and thus has very little scrap value.
Installations with copper-clad steel conductors are generally accepted as fulfilling the legal specifications for a good electrical ground. For this reason its use is preferred by industrial companies and utilities when cost is a concern. | 0 | Metallurgy |
Amalgamation with mercury can be used to recover very small gold particles, and mercury is still widely used in small-scale artisanal mining across the world. Mercury forms a mercury-gold amalgam with smaller gold particles, and then the gold is concentrated by boiling away the mercury from the amalgam. This is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour. Large-scale use of mercury stopped in the 1960s. However, mercury is still used in artisanal and small-scale gold mining (ASGM). One mechanism by which mercury is employed in hydraulic mining is as an "undercurrent", in which the flow of smaller grains is diverted over mercury-coated copper plates. High flow velocities associated with hydraulic mining cause flouring of mercury, the wearing down of mercury particles that contributes to mercury loss into the environment.
Over of mercury contaminated the environment in California as a result of placer mining in the late nineteenth and early twentieth centuries. Stamp mill mining contributed an additional of mercury contamination. Mercury contamination in California waterways is a major contemporary environmental issue, as is groundwater pollution, mostly by inorganic mercury. | 0 | Metallurgy |
Copper does not require complex ventilation measures. It is suitable for both unventilated warm and ventilated cold roof constructions. | 0 | Metallurgy |
For cases where a very strong mechanical bond is required (such as for components that are going to be used to machine with) the components surface is often machined to create grooves for the coating to bond to. Dovetail grooves offer strong positive bonding but can be laboursome and costly. A cheaper method is to cut simple partially open grooves, yet this method produces an inferior final bond strength. The edges and corners of a component present possible weak points in the coating structure, as they can break off from the component. To increase the bond strength at these points the corners and edges of the component should be rounded off. If the coating does not need to reach the edges of a component, then an undercut can be used (as shown in the diagram to the right) to secure the coating to the substrate. Although undercuts can also be used in other scenarios.
Coatings often have a tendency to shrink after being applied due to the cooling process. This means steps need to be taken in order to minimise the negative effects of shrinking. If not, the coating can suffer from stress due to tension which will weaken the coating and in some cases may cause it to peel off. The fact coatings shrink can be used to increase the bond strength if applied wisely. Coating over the entire external surface of a component means that the coating will shrink around the component when cooled providing a sort of gripping force that will increase the mechanical bond strength. This is also the case if a flat component is sprayed over the edges, the coating will grip the surface like a clamp; again increasing bond strength. Internal coatings suffer from the effect of shrinking in that they will be pulled away from the surface of the component. To counter this the component can be heated to reduce the relative shrinking effects on cooling.
Components should be dry machined (without oils) to avoid oils being deposited on the component before spraying. If this is unavoidable then the substrate will need to be cleaned again prior to detonation spraying. | 0 | Metallurgy |
This is a class of casting processes that use pattern materials that evaporate during the pour, which means there is no need to remove the pattern material from the mold before casting. The two main processes are lost-foam casting and full-mold casting. | 0 | Metallurgy |
From the start Fulmer was a commercial enterprise aiming to make a surplus for investment in its own development. It received no grant or membership fees. Its income was solely from projects, each with defined objectives and time and cost limits agreed with individual sponsors from Government or Industry. Normally, the project contract would provide that all results would belong in confidence to the sponsor, who would also own any patents arising from the investigation. | 0 | Metallurgy |
The three prime untranslated regions (3UTRs) of messenger RNAs (mRNAs) often contain regulatory sequences that post-transcriptionally cause gene silencing. Such 3-UTRs often contain both binding sites for microRNAs (miRNAs) as well as for regulatory proteins. By binding to specific sites within the 3-UTR, a large number of specific miRNAs decrease gene expression of their particular target mRNAs by either inhibiting translation or directly causing degradation of the transcript, using a mechanism similar to RNA interference (see MicroRNA). The 3-UTR also may have silencer regions that bind repressor proteins that inhibit the expression of an mRNA.
The 3-UTR often contains microRNA response elements (MREs). MREs are sequences to which miRNAs bind and cause gene silencing. These are prevalent motifs within 3-UTRs. Among all regulatory motifs within the 3'-UTRs (e.g. including silencer regions), MREs make up about half of the motifs.
As of 2014, the miRBase web site, an archive of miRNA sequences and annotations, listed 28,645 entries in 233 biologic species. Of these, 1,881 miRNAs were in annotated human miRNA loci. miRNAs were predicted to each have an average of about four hundred target mRNAs (causing gene silencing of several hundred genes). Freidman et al. estimate that >45,000 miRNA target sites within human mRNA 3'UTRs are conserved above background levels, and >60% of human protein-coding genes have been under selective pressure to maintain pairing to miRNAs.
Direct experiments show that a single miRNA can reduce the stability of hundreds of unique mRNAs. Other experiments show that a single miRNA may repress the production of hundreds of proteins, but that this repression often is relatively mild (less than 2-fold).
The effects of miRNA dysregulation of gene expression seem to be important in cancer. For instance, in gastrointestinal cancers, nine miRNAs have been identified as epigenetically altered and effective in down regulating DNA repair enzymes.
The effects of miRNA dysregulation of gene expression also seem to be important in neuropsychiatric disorders, such as schizophrenia, bipolar disorder, major depression, Parkinsons disease, Alzheimers disease and autism spectrum disorders. | 1 | Gene expression + Signal Transduction |
The regulation of transcription by enhancers has been studied since the 1980s. Large or multi-component transcription regulators with a range of mechanistic properties, including locus control regions, clustered open regulatory elements, and transcription initiation platforms, were observed shortly thereafter. More recent research has suggested that these different categories of regulatory elements may represent subtypes of super-enhancer.
In 2013, two labs identified large enhancers near several genes especially important for establishing cell identities. While Richard A. Young and colleagues identified super-enhancers, Francis Collins and colleagues identified stretch enhancers. Both super-enhancers and stretch enhancers are clusters of enhancers that control cell-specific genes and may be largely synonymous.
As currently defined, the term “super-enhancer” was introduced by Young’s lab to describe regions identified in mouse embryonic stem cells (ESCs). These particularly large, potent enhancer regions were found to control the genes that establish the embryonic stem cell identity, including Oct-4, Sox2, Nanog, Klf4, and Esrrb. Perturbation of the super-enhancers associated with these genes showed a range of effects on their target genes’ expression. Super-enhancers have been since identified near cell identity-regulators in a range of mouse and human tissues. | 1 | Gene expression + Signal Transduction |
Cancer is not just one disease but a group of diseases involving abnormal cell growth and metastasis of such cells to other body parts. There are also several types of cancers, each with its own distinctive characteristics and stages that may require different treatment or targeted drug delivery approaches. Yet, even these treatments have their own advantages and disadvantages. Thus, since the discovery of cancer, researchers have constantly been developing new and innovative cancer treatments, including chemotactic drug delivery. For example, and as mentioned earlier in this article, researchers have sought to use microdroplets, protocells, and biological and bio-hybrid drug carriers to deliver drugs to cancer cells in a more effective manner, while reducing unwanted side effects. In fact, the justification for using such systems, guided by chemotaxis, is that the environment inside a tumor has a higher resting temperature, higher peroxide concentration, lower pH, and a lower oxygen concentration than its surrounding tissue. With these unique conditions, researchers can exploit chemotactic drug delivery to target tumor cells directly, avoiding healthy tissues, reducing toxicity, improving drug efficacy, and decreasing drug dosage. | 1 | Gene expression + Signal Transduction |
Silicon carbide is an important material in TRISO-coated fuel particles, the type of nuclear fuel found in high temperature gas cooled reactors such as the Pebble Bed Reactor. A layer of silicon carbide gives coated fuel particles structural support and is the main diffusion barrier to the release of fission products.
Silicon carbide composite material has been investigated for use as a replacement for Zircaloy cladding in light water reactors. One of the reasons for this investigation is that, Zircaloy experiences hydrogen embrittlement as a consequence of the corrosion reaction with water. This produces a reduction in fracture toughness with increasing volumetric fraction of radial hydrides. This phenomenon increases drastically with increasing temperature to the detriment of the material. Silicon carbide cladding does not experience this same mechanical degradation, but instead retains strength properties with increasing temperature. The composite consists of SiC fibers wrapped around a SiC inner layer and surrounded by an SiC outer layer. Problems have been reported with the ability to join the pieces of the SiC composite. | 0 | Metallurgy |
In order to terminate the integrated stress response, dephosphorylation of eIF2α is required. The protein phosphatase 1 complex (PP1) aids in the dephosphorylation of eIF2α. This complex contains a PP1 catalytic subunit as well as two regulatory subunits. This complex is negatively regulated by two proteins: growth arrest and DNA damage‐inducible protein (GADD34), also known as PPP1R15A, or constitutive repressor of eIF2α phosphorylation (CReP), also known as PPP1R15B. CReP acts to keep levels of eIF2α phosphorylation low in cells under normal conditions. GADD34 is produced in response to ATF4 and works to increase dephosphorylation of eIF2α. The dephosphorylation of eIF2α results in the return of normal protein synthesis and cellular function. However, dephosphorylation of eIF2α can also facilitate the production of death-inducing proteins in cases where the cell is so severely damaged that normal functioning cannot be restored. | 1 | Gene expression + Signal Transduction |
The noncanonical Wnt/Ca pathway regulates intracellular calcium levels. Again Wnt binds and activates to Frizzled. In this case however activated Frizzled causes a coupled G-protein to activate a phospholipase (PLC), which interacts with and splits PIP into DAG and IP. IP can then bind to a receptor on the endoplasmic reticulum to release intracellular calcium stores, to induce calcium-dependent gene expression. | 1 | Gene expression + Signal Transduction |
Because of the way ESTs are sequenced, many distinct expressed sequence tags are often partial sequences that correspond to the same mRNA of an organism. In an effort to reduce the number of expressed sequence tags for downstream gene discovery analyses, several groups assembled expressed sequence tags into EST contigs. Example of resources that provide EST contigs include: TIGR gene indices, Unigene, and STACK
Constructing EST contigs is not trivial and may yield artifacts (contigs that contain two distinct gene products). When the complete genome sequence of an organism is available and transcripts are annotated, it is possible to bypass contig assembly and directly match transcripts with ESTs. This approach is used in the TissueInfo system (see below) and makes it easy to link annotations in the genomic database to tissue information provided by EST data. | 1 | Gene expression + Signal Transduction |
Members of the signal transducer and activator of transcription (STAT) protein family are intracellular transcription factors that mediate many aspects of cellular immunity, proliferation, apoptosis and differentiation. They are primarily activated by membrane receptor-associated Janus kinases (JAK). Dysregulation of this pathway is frequently observed in primary tumors and leads to increased angiogenesis which enhances the survival of tumors and immunosuppression. Gene knockout studies have provided evidence that STAT proteins are involved in the development and function of the immune system and play a role in maintaining immune tolerance and tumor surveillance. | 1 | Gene expression + Signal Transduction |
In the solvent extraction a mixture of an extractant in a diluent is used to extract a metal from one phase to another. In solvent extraction this mixture is often referred to as the "organic" because the main constituent (diluent) is some type of oil.
The PLS (pregnant leach solution) is mixed to emulsification with the stripped organic and allowed to separate. The metal will be exchanged from the PLS to the organic they are modified. The resulting streams will be a loaded organic and a raffinate. When dealing with electrowinning, the loaded organic is then mixed to emulsification with a lean electrolyte and allowed to separate. The metal will be exchanged from the organic to the electrolyte. The resulting streams will be a stripped organic and a rich electrolyte. The organic stream is recycled through the solvent extraction process while the aqueous streams cycle through leaching and electrowinning processes respectively. | 0 | Metallurgy |
The CC chemokine (or β-chemokine) proteins have two adjacent cysteines (amino acids), near their amino terminus.
There have been at least 27 distinct members of this subgroup reported for mammals, called CC chemokine ligands (CCL)-1 to -28; CCL10 is the same as CCL9. Chemokines of this subfamily usually contain four cysteines (C4-CC chemokines), but a small number of CC chemokines possess six cysteines (C6-CC chemokines). C6-CC chemokines include CCL1, CCL15, CCL21, CCL23 and CCL28. CC chemokines induce the migration of monocytes and other cell types such as NK cells and dendritic cells.
Examples of CC chemokine include monocyte chemoattractant protein-1 (MCP-1 or CCL2) which induces monocytes to leave the bloodstream and enter the surrounding tissue to become tissue macrophages.
CCL5 (or RANTES) attracts cells such as T cells, eosinophils and basophils that express the receptor CCR5.
Increased CCL11 levels in blood plasma are associated with aging (and reduced neurogenesis) in mice and humans. | 1 | Gene expression + Signal Transduction |
In the Old World, the first metals smelted were tin and lead. The earliest known cast lead beads were found in the Çatalhöyük site in Anatolia (Turkey), and dated from about 6500 BC, but the metal may have been known earlier.
Since the discovery happened several millennia before the invention of writing, there is no written record of how it was made. However, tin and lead can be smelted by placing the ores in a wood fire, leaving the possibility that the discovery may have occurred by accident. Recent scholarship however has called this find into question.
Lead is a common metal, but its discovery had relatively little impact in the ancient world. It is too soft to use for structural elements or weapons, though its high density relative to other metals makes it ideal for sling projectiles. However, since it was easy to cast and shape, workers in the classical world of Ancient Greece and Ancient Rome used it extensively to pipe and store water. They also used it as a mortar in stone buildings.
Tin was much less common than lead, is only marginally harder, and had even less impact by itself. | 0 | Metallurgy |
Mechanical spalling occurs at high-stress contact points, for example, in a ball bearing. Spalling occurs in preference to brinelling, where the maximal shear stress occurs not at the surface, but just below, shearing the spall off.
One of the simplest forms of mechanical spalling is plate impact, in which two waves of compression are reflected on the free-surfaces of the plates and then interact to generate a region of high tensile stress inside one of the plates.
Spalling can also occur as an effect of cavitation, where fluids are subjected to localized low pressures that cause vapour bubbles to form, typically in pumps, water turbines, vessel propellers, and even piping under some conditions. When such bubbles collapse, a localized high pressure can cause spalling on adjacent surfaces. | 0 | Metallurgy |
The Bolzano process is a means to reduce magnesium to metallic form. "Dolomite-ferrosilicon briquettes are stacked on a special charge support system through which internal electric heating is conducted to the charge. A complete reaction takes 20 to 24 hours at 1,200 °C."
In 2014, Brazilian operations produced 10-15 kilotons of Mg by this process.
Also in 2014, Nevada Clean Magnesium announced its Tami-Mosi plan to create a ASTM B-92 pilot plant. The mineral resource is estimated at 412 billion tons of 12.3% grade Mg. The company produced its first ingot from a pilot plant in December 2018. | 0 | Metallurgy |
Different mRNAs within the same cell have distinct lifetimes (stabilities). In bacterial cells, individual mRNAs can survive from seconds to more than an hour. However, the lifetime averages between 1 and 3 minutes, making bacterial mRNA much less stable than eukaryotic mRNA. In mammalian cells, mRNA lifetimes range from several minutes to days. The greater the stability of an mRNA the more protein may be produced from that mRNA. The limited lifetime of mRNA enables a cell to alter protein synthesis rapidly in response to its changing needs. There are many mechanisms that lead to the destruction of an mRNA, some of which are described below. | 1 | Gene expression + Signal Transduction |
Thermal Integrity Profiling (TIP) is a non-destructive testing method used to evaluate the integrity of concrete foundations. It is standardized by [http://www.astm.org/Standards/D7949.htm?A ASTM D7949 - Standard Test Methods for Thermal Integrity Profiling of Concrete Deep Foundations].
The testing method was first developed in the mid 1990s at the University of South Florida. It relates the heat generated by curing of cement to the integrity and quality of drilled shafts, augered cast in place (ACIP) piles and other concrete foundations. In general, a shortage of competent concrete (necks or inclusions) is registered by relative cool regions; the presence of extra concrete (over-pour bulging into soft soil strata) is registered by relative warm regions.
Concrete temperatures along the length of the foundation element are sampled throughout the concrete hydration process. TIP analysis is performed at the point of peak temperature, generally 18 to 24hrs post-concreting. Measurements are available relatively soon after pouring (6 to 72 hours),generally before other integrity testing methods such as cross hole sonic logging and low strain integrity testing can be performed.
TIP can be performed using a probe lowered down standard access tubes or by installing embedded thermal wires along the length of the reinforcement cage. Four thermal wires are commonly installed along the steel cage, each 90 degrees from one another, forming a north-east-south-west configuration. If records at a certain depth show regions with cooler temperatures (when compared to the average temperature at that depth), a concrete deficiency or defect may be present. An average temperature at a certain depth that is significantly lower than the average temperatures at other depths may also be indication of a potential problem. It is also possible to estimate the effective area of the foundation, and to assess if the reinforcing cage is properly aligned and centered. | 0 | Metallurgy |
While only one oxhide ingot fragment has been recovered from Egypt (in the context of a LBA smelting workshop), there is a wide array of painted scenes in Egypt that show oxhide ingots. The earliest scene dates to the 15th century BC and the latest scene to the 12th century BC. The ingots display their typical four protrusions, and red paint (which suggests they are copper) is preserved on them. The captions accompanying the scenes explain that the men who bring the ingots come from the north, specifically Retnu (Syria) and Keftiu (unidentified). They are shown being carried on the shoulders of men, sitting with other goods in storage, or as part of scenes in smelting workshops. In a relief from Karnak, the pharaoh Amenhotep II is seen riding a chariot and spearing an oxhide ingot with five arrows. A laudatory caption emphasizing the pharaoh’s strength accompanies the scene.
Several of the “Amarna letters” dating to the mid-14th century BC refer to hundreds of copper talents—in addition to goods such as elephant tusks and glass ingots—sent from the kingdom of Alashiya to Egypt. Some scholars identify Cyprus with Alashiya. In particular, the Uluburun cargo is similar to the goods that, according to the letters, Alashiya sent to Egypt. | 0 | Metallurgy |
Block kriging is the most common geostatistical method used for interpolating metallurgical index parameters and it is often applied on a domain basis. Classical geostatistics require that the estimation variable be additive, and there is currently some debate on the additive nature of the metallurgical index parameters measured by the above tests. The Bond ball mill work index test is thought to be additive because of its units of energy; nevertheless, experimental blending results show a non-additive behavior. The SPI(R) value is known not to be an additive parameter, however errors introduced by block kriging are not thought to be significant . These issues, among others, are being investigated as part of the Amira P843 research program on Geometallurgical mapping and mine modelling. | 0 | Metallurgy |
Bacteria themselves do not have noticeable effect on concrete. However, sulfate-reducing bacteria (SRB) in untreated sewage water tend to produce hydrogen sulfide (HS), which is then oxidized in sulfuric acid (HSO) by atmospheric oxygen (abiotic reaction) and by aerobic bacteria present in biofilm (biotic reaction) on the concrete surface above the water level. The sulfuric acid dissolves the carbonates in the hardened cement paste (HCP), and also calcium hydroxide (portlandite: Ca(OH)) and calcium silicate hydrate (CaO·SiO·nHO), and causes strength loss, as well as producing sulfates which are harmful to concrete.
:HSO + Ca(OH) → CaSO + 2 HO
:HSO + CaO·SiO·n HO → CaSO + HSiO + n HO
In each case the soft expansive and water-soluble corrosion product of gypsum (CaSO) is formed. Gypsum is easily washed away in wastewater causing a loss of concrete aggregate and exposing fresh material to acid attack.
Concrete floors lying on ground that contains pyrite (iron(II) disulfide) are also at risk.
As a preventive measure sewage may be pretreated to increase pH or oxidize or precipitate the sulfides in order to minimize the activity of sulfide-reducing bacteria.
As bacteria often prefer to adhere to the surfaces of solids than to remain into suspension in water (planktonic bacteria), the biofilms formed by sessile (i.e., fixed) bacteria are often the place where they are the most active. Biofilms made of multiple layers (like an onion) of dead and living bacteria protect the living ones from the harsh conditions often prevailing in water outside biofilm. Biofilms developing on the already exposed surface of metallic elements encased in concrete can also contribute to accelerate their corrosion (differential aeration and formation of anodic zones at the surface of the metal). Sulfides produced by the SRB bacteria can also induce stress corrosion cracking in steel and other metals. | 0 | Metallurgy |
The Kirkendall effect is the motion of the interface between two metals that occurs as a consequence of the difference in diffusion rates of the metal atoms. The effect can be observed for example by placing insoluble markers at the interface between a pure metal and an alloy containing that metal, and heating to a temperature where atomic diffusion is reasonable for the given timescale; the boundary will move relative to the markers.
This process was named after Ernest Kirkendall (1914–2005), assistant professor of chemical engineering at Wayne State University from 1941 to 1946. The paper describing the discovery of the effect was published in 1947.
The Kirkendall effect has important practical consequences. One of these is the prevention or suppression of voids formed at the boundary interface in various kinds of alloy to metal bonding. These are referred to as Kirkendall voids. | 0 | Metallurgy |
Direct reduction processes were developed to overcome the difficulties of conventional blast furnaces. DRI plants need not be part of an integrated steel plant, as is characteristic of blast furnaces. The initial capital investment and operating costs of direct reduction plants are lower than integrated steel plants and are more suitable for developing countries where supplies of high grade coking coal are limited, but where steel scrap is generally available for recycling. Many other countries use variants of the process.
Factors that help make DRI economical:
* Direct-reduced iron has about the same iron content as pig iron, typically 90–94% total iron (depending on the quality of the raw ore) so it is an excellent feedstock for the electric furnaces used by mini mills, allowing them to use lower grades of scrap for the rest of the charge or to produce higher grades of steel.
* Hot-briquetted iron (HBI) is a compacted form of DRI designed for ease of shipping, handling, and storage.
* Hot direct reduced iron (HDRI) is DRI that is transported hot, directly from the reduction furnace, into an electric arc furnace, thereby saving energy.
* The direct reduction process uses pelletized iron ore or natural "lump" ore. One exception is the fluidized bed process which requires sized iron ore particles.
* The direct reduction process can use natural gas contaminated with inert gases, avoiding the need to remove these gases for other use. However, any inert gas contamination of the reducing gas lowers the effect (quality) of that gas stream and the thermal efficiency of the process. The use of natural gas also produces greenhouse gases.
* Supplies of powdered ore and raw natural gas are both available in areas such as Northern Australia, avoiding transport costs for the gas. In most cases the DRI plant is located near a natural gas source as it is more cost effective to ship the ore rather than the gas.
* To eliminate fossil fuel use in iron and steel making, renewable hydrogen gas can be used in place of syngas to produce DRI and eliminate production of greenhouse gases. | 0 | Metallurgy |
The PELP1 protein encodes a protein of 1130 amino acids, and exhibits both cytoplasmic and nuclear localization depending on the tissue. PELP1 lacks known enzymatic activity and functions as a scaffolding protein. It contains 10 NR-interacting boxes (LXXLL motifs) and functions as a coregulator of several nuclear receptors via its LXXLL motifs including ESR1, ESR2, ERR-alpha, PR, GR, AR, and RXR. PELP1 also functions as a coregulator of several other transcription factors, including AP1, SP1, NFkB, STAT3, and FHL2.
PELP1 has a histone binding domain and interacts with chromatin-modifying complexes, including CBP/p300, histone deacetylase 2, histones, SUMO2, lysine-specific demethylase 1 (KDM1), PRMT6, and CARM1. PELP1 also interacts with cell cycle regulators such as pRb. E2F1, and p53.
PELP1 is phosphorylated by hormonal and growth factor signals. PELP1 phosphorylation status is also influenced by cell cycle progression, and it is a substrate of CDKs. Further, PELP1 is phosphorylated by DNA damage induced kinases (ATM, ATR, DNA-PKcs). | 1 | Gene expression + Signal Transduction |
Baculovirus-infected insect cells (Sf9, Sf21, High Five strains) or mammalian cells (HeLa, HEK 293) allow production of glycosylated or membrane proteins that cannot be produced using fungal or bacterial systems. It is useful for production of proteins in high quantity. Genes are not expressed continuously because infected host cells eventually lyse and die during each infection cycle. | 1 | Gene expression + Signal Transduction |
The strength of a synapse has been defined by Bernard Katz as the product of (presynaptic) release probability pr, quantal size q (the postsynaptic response to the release of a single neurotransmitter vesicle, a quantum), and n, the number of release sites. "Unitary connection" usually refers to an unknown number of individual synapses connecting a presynaptic neuron to a postsynaptic neuron.
The amplitude of postsynaptic potentials (PSPs) can be as low as 0.4 mV to as high as 20 mV. The amplitude of a PSP can be modulated by neuromodulators or can change as a result of previous activity. Changes in the synaptic strength can be short-term, lasting seconds to minutes, or long-term (long-term potentiation, or LTP), lasting hours. Learning and memory are believed to result from long-term changes in synaptic strength, via a mechanism known as synaptic plasticity. | 1 | Gene expression + Signal Transduction |
During extraction of the oil from oil sand, tailings consisting of water, silt, clays and other solvents are also created. This solid will become mature fine tailings by gravity. Foght et al (1985) estimated that there are 10 anaerobic heterotrophs and 10 sulfate-reducing prokaryotes per milliliter in the tailings pond, based on conventional most probable number methods. Foght set up an experiment with two tailings ponds and an analysis of the archaea, bacteria, and the gas released from tailings ponds showed that those were methanogens. As the depth increased, the moles of CH released actually decreased.
Siddique (2006, 2007) states that methanogens in the tailings pond live and reproduce by anaerobic degradation, which will lower the molecular weight from naphtha to aliphatic, aromatic hydrocarbons, carbon dioxide and methane. Those archaea and bacteria can degrade the naphtha, which was considered as waste during the procedure of refining oil. Both of those degraded products are useful. Aliphatic, aromatic hydrocarbons and methane can be used as fuel in the humans' daily lives. In other words, these methanogens improve the coefficient of utilization. Moreover, these methanogens change the structure of the tailings pond and help the pore water efflux to be reused for processing oil sands. Because the archaea and bacteria metabolize and release bubbles within the tailings, the pore water can go through the soil easily. Since they accelerate the densification of mature fine tailings, the tailings ponds are enabled to settle the solids more quickly so that the tailings can be reclaimed earlier. Moreover, the water released from the tailings can be used in the procedure of refining oil. Reducing the demand of water can also protect the environment from drought. | 0 | Metallurgy |
Leaching involves the use of aqueous solutions to extract metal from metal-bearing materials which are brought into contact with them. In China in the 11th and 12th centuries, this technique was used to extract copper; this was used for much of the total copper production. In the 17th century it was used for the same purposes in Germany and Spain.
The lixiviant solution conditions vary in terms of pH, oxidation-reduction potential, presence of chelating agents and temperature, to optimize the rate, extent and selectivity of dissolution of the desired metal component into the aqueous phase. By using chelating agents, one can selectively extract certain metals. These agents are typically amines of Schiff bases.
The five basic leaching reactor configurations are in-situ, heap, vat, tank and autoclave. | 0 | Metallurgy |
Mechanical clock mechanisms are sensitive to temperature changes as each part has tiny tolerance and it leads to errors in time keeping. A bimetallic strip is used to compensate this phenomenon in the mechanism of some timepieces. The most common method is to use a bimetallic construction for the circular rim of the balance wheel. What it does is move a weight in a radial way looking at the circular plane down by the balance wheel, varying then, the momentum of inertia of the balance wheel. As the spring controlling the balance becomes weaker with the increasing temperature, the balance becomes smaller in diameter to decrease the momentum of inertia and keep the period of oscillation (and hence timekeeping) constant.
Nowadays this system is not used anymore since the appearance of low temperature coefficient alloys like nivarox, parachrom and many others depending on each brand. | 0 | Metallurgy |
While the cytosolic fermentation pathway of lactate is well established, a novel feature of the lactate shuttle hypothesis is the oxidation of lactate in the mitochondria. Baba and Sherma (1971) were the first to identify the enzyme lactate dehydrogenase (LDH) in the mitochondrial inner membrane and matrix of rat skeletal and cardiac muscle. Subsequently, LDH was found in the rat liver, kidney, and heart mitochondria. It was also found that lactate could be oxidized as quickly as pyruvate in rat liver mitochondria. Because lactate can either be oxidized in the mitochondria (back to pyruvate for entry into the Krebs’ cycle, generating NADH in the process), or serve as a gluconeogenic precursor, the intracellular lactate shuttle has been proposed to account for the majority of lactate turnover in the human body (as evidenced by the slight increases in arterial lactate concentration). Brooks et al. confirmed this in 1999, when they found that lactate oxidation exceeded that of pyruvate by 10-40% in rat liver, skeletal, and cardiac muscle.
In 1990, Roth and Brooks found evidence for the facilitated transporter of lactate, monocarboxylate transport protein (MCT), in the sarcolemma vesicles of rat skeletal muscle. Later, MCT1 was the first of the MCT super family to be identified. The first four MCT isoforms are responsible for pyruvate/lactate transport. MCT1 was found to be the predominant isoform in many tissues including skeletal muscle, neurons, erythrocytes, and sperm. In skeletal muscle, MCT1 is found in the membranes of the sarcolemma, peroxisome, and mitochondria. Because of the mitochondrial localization of MCT (to transport lactate into the mitochondria), LDH (to oxidize the lactate back to pyruvate), and COX (cytochrome c oxidase, the terminal element of the electron transport chain), Brooks et al. proposed the possibility of a mitochondrial lactate oxidation complex in 2006. This is supported by the observation that the ability of muscle cells to oxidize lactate was related to the density of mitochondria. Furthermore, it was shown that training increases MCT1 protein levels in skeletal muscle mitochondria, and that corresponded with an increase in the ability of muscle to clear lactate from the body during exercise. The affinity of MCT for pyruvate is greater than lactate, however two reactions will ensure that lactate will be present in concentrations that are orders of magnitude greater than pyruvate: first, the equilibrium constant of LDH(3.6 x 104) greatly favors the formation of lactate. Secondly, the immediate removal of pyruvate from the mitochondria (either via the Krebs’ cycle or gluconeogenesis) ensures that pyruvate is not present in great concentrations within the cell.
LDH isoenzyme expression is tissue-dependent. It was found that in rats, LDH-1 was the predominant form in the mitochondria of myocardium, but LDH-5 was predominant in the liver mitochondria. It is suspected that this difference in isoenzyme is due to the predominant pathway the lactate will take - in liver it is more likely to be gluconeogenesis, whereas in the myocardium it is more likely to be oxidation. Despite these differences, it is thought that the redox state of the mitochondria dictates the ability of the tissues to oxidize lactate, not the particular LDH isoform. | 1 | Gene expression + Signal Transduction |
Ca ions are an essential component of plant cell walls and cell membranes, and are used as cations to balance organic anions in the plant vacuole. The Ca concentration of the vacuole may reach millimolar levels. The most striking use of Ca ions as a structural element in algae occurs in the marine coccolithophores, which use Ca to form the calcium carbonate plates, with which they are covered.
Calcium is needed to form the pectin in the middle lamella of newly formed cells.
Calcium is needed to stabilize the permeability of cell membranes. Without calcium, the cell walls are unable to stabilize and hold their contents. This is particularly important in developing fruits. Without calcium, the cell walls are weak and unable to hold the contents of the fruit.
Some plants accumulate Ca in their tissues, thus making them more firm. Calcium is stored as Ca-oxalate crystals in plastids. | 1 | Gene expression + Signal Transduction |
Superconductivity in UPdAl has a critical temperature of 2.0K and a critical field around 3T. The critical field does not show anisotropy despite the hexagonal crystal structure.
For heavy-fermion superconductors it is generally believed that the coupling mechanism cannot be phononic in nature. In contrast to many other unconventional superconductors, for UPdAl there actually exists strong experimental evidence (namely from neutron scattering and tunneling spectroscopy ) that superconductivity is magnetically mediated.
In the first years after the discovery of UPdAl it was actively discussed whether its superconducting state can support a Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase, but this suggestion was later refuted. | 0 | Metallurgy |
In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electroformable metal onto a conductive surface of a model (mandrel). Once the deposited material has been built up to the desired thickness, the electroform is parted from the substrate. This process allows precise replication of the mandrel surface texture and geometry at low unit cost with high repeatability and excellent process control.
If the mandrel is made of a non-conductive material it can be coated with a thin conductive layer. | 0 | Metallurgy |
Unlike the proofreading mechanisms of DNA polymerase those of RNAP have only recently been investigated. Proofreading begins with separation of the mis-incorporated nucleotide from the DNA template. This pauses transcription. The polymerase then backtracks by one position and cleaves the dinucleotide that contains the mismatched nucleotide. In the RNA polymerase this occurs at the same active site used for polymerization and is therefore markedly different from the DNA polymerase where proofreading occurs at a distinct nuclease active site.
The overall error rate is around 10 to 10. | 1 | Gene expression + Signal Transduction |
In humans, DNA methylation occurs at the 5′ position of the pyrimidine ring of the cytosine residues within CpG sites to form 5-methylcytosines. The presence of multiple methylated CpG sites in CpG islands of promoters causes stable inhibition (silencing) of genes. Silencing of transcription of a gene may be initiated by other mechanisms, but this is often followed by methylation of CpG sites in the promoter CpG island to cause the stable silencing of the gene. | 1 | Gene expression + Signal Transduction |
A transcript is an RNA molecule that is copied or transcribed from a DNA template. A transcript can be further processed by alternative splicing, which is the retention of different combinations of exons. These unique combinations of exons are termed RNA transcript isoforms. The transcriptome is a set of all RNA, including rRNA, mRNA, tRNA, and non-coding RNA. Specifically mRNA transcripts can be used to investigate differences in gene expression patterns. Transcriptome profiling is determining the composition of transcripts and their relative expression levels in a given reference set of cells. This analysis involves characterization of all functional genomic elements, coding and non-coding.
The current RNA capture methods involve sorting cells in suspension from acutely dissociated tissue, and thus can lose information about cell morphology and microenvironment. Transcript abundance and isoforms are significantly different across tissues and are continually changing throughout an individual’s life. Gene expression is highly tissue specific, therefore with traditional RNA capture methods one must be cautious in the interpretation of gene expression patterns, as they often reflect expression of a heterogeneous mix of cell populations. Even in the same cell type, tissue measurements, where a population of cells is obtained, mask both low-level mRNA expression in single cells and variation in expression between cells. The photoactivatable TIVA tag is engineered to capture the mRNA of a single cell in complex tissues. | 1 | Gene expression + Signal Transduction |
The LHCGR consists of 674 amino acids and has a molecular mass of about 85–95 kDA based on the extent of glycosylation.
Like other GPCRs, the LHCG receptor possess seven membrane-spanning domains or transmembrane helices. The extracellular domain of the receptor is heavily glycosylated. These transmembrane domains contain two highly conserved cysteine residues, which build disulfide bonds to stabilize the receptor structure. The transmembrane part is highly homologous with other members of the rhodopsin family of GPCRs. The C-terminal domain is intracellular and brief, rich in serine and threonine residues for possible phosphorylation. | 1 | Gene expression + Signal Transduction |
The Human-transcriptome DataBase for Alternative Splicing (H-DBAS) is a database of alternatively spliced human transcripts based on H-Invitational. | 1 | Gene expression + Signal Transduction |
Studies have reported that: 1) the levels of CMTM5-v1 in the malignant tissues of patients with prostate cancer are lower than the levels in their nearby normal prostate gland tissues as well as in the tissues of patients with benign prostate hyperplasia; 2) patients with lower prostate cancer tissue levels of CMTM5-v1 have higher prostate cancer Gleason scores and therefore poorer prognoses than patients with higher prostate cancer tissue levels of CMTM5-v1; and 3) the forced overexpression of CMTM5-v1 in cultured DU145 cells (a human prostate cancer cell line) reduces, while the forced higher expression of the CMTM5-v1 levels increases, their proliferation and migration. Similar findings for an unspecified CMTM5 isoform are reported in ovarian cancer, hepatocellular carcinoma, pancreatic cancer, non-small-cell lung carcinoma, renal cell carcinoma, and breast cancer. The forced over expression of CMTM5-v1 in Huh7 human hepatic cells also inhibited the ability of these cells to grow in a mouse model of cancer. Finally, various cancer human cell lines including those of the liver, breast, prostate, colon, stomach, nasopharynx, laryngopharynx, esophagus, lung, and cervix express low levels of, or no, CMTM5-v1 and concurrently have highly methylated CpG sites near to the CMTM5 gene. These findings suggest that the CMTM5 gene may act as a tumor suppressor gene, i.e. a normal gene whose product(s) inhibit the development and/or progression of various cancers. The findings also support further studies to confirm and expand these relationships and determine if the expression of CMTM5 isoforms can be used as tumor markers for these cancers severities/prognoses and/or targets as for treating them. | 1 | Gene expression + Signal Transduction |
Sibelektroterm () is a manufacturing company in Kirovsky District of Novosibirsk, Russia. It was founded in 1945. The enterprise is a developer and manufacturer of electrometallurgical equipment. | 0 | Metallurgy |
Current research related to VMAT uses VMAT2 knockout mice to explore the behavioral genetics of this transporter in an animal model. VMAT2 knockouts are known to be lethal as homozygotes, but heterozygote knockouts are not lethal and are used in many studies as a durable animal model.
From knockout and knockdown mice, researchers have discovered that it is good to have over-expression or under-expression of the VMAT genes in some circumstances. Mice are also used in drug studies, particularity studies involving the effect cocaine and methamphetamine have on VMATs. Studies involving animals have prompted scientists to work on developing drugs that inhibit or enhance the function of VMATs. Drugs that inhibit VMATs may have use in addiction but further studies are needed. Enhancing the function of VMATs may also have therapeutic value. | 1 | Gene expression + Signal Transduction |
Micro RNAs are involved in regulating the expression of many proteins. Med1 is targeted by miR-1, which is important in gene regulation in cancers. The tumor suppressor miR-137 also regulates MED1. | 1 | Gene expression + Signal Transduction |
Historically, the reduction of iron ore without smelting is the oldest process for obtaining steel. Low-temperature furnaces, unable to reach the melting temperatures of iron alloys, produce a burr, a heterogeneous agglomerate of metallic iron more or less impregnated with carbon, gangue, and charcoal. This process was gradually succeeded, from the 1st century in China and the 13th century in Europe, by the blast furnace, which simultaneously reduces and melts iron.
Elaborate low furnaces, such as the tatara or the Catalan forge, survived until the early 19th century. Compared with the indirect process (reduction-melting in the blast furnace, followed by cast-iron refining), these processes only survived when they enjoyed at least one of the following two advantages:
* ability to process ores that are incompatible with blast furnaces (such as iron sands that clog blast furnaces, or ores that generate slag that is too pasty to be drained);
* a more "reasonable" size than that of giant plants and their constraints (ore and capital requirements, production to sell off, etc.). | 0 | Metallurgy |
Gag/pol translational readthrough site (or Retroviral readthrough element) is a cis-regulatory element found in retroviruses. The readthrough site facilitates the mechanism of translation readthrough of the stop codon at the gag-pol junction producing the gag and pol fusion protein in certain retroviruses.
Retroviruses whose gag and pol genes are in the same reading frame often depend upon approximately 5% read-through of the gag UAG termination codon to form the gag-pol polyprotein. This readthrough is usually dependent on a pseudoknot located eight nucleotides downstream of the stop codon (UAG). Sequence conservation is found in the second pseudoknot loop. | 1 | Gene expression + Signal Transduction |
Certain combinations of alloys have become popular as industry standards. Selection of the combination is driven by cost, availability, convenience, melting point, chemical properties, stability, and output. Different types are best suited for different applications. They are usually selected on the basis of the temperature range and sensitivity needed. Thermocouples with low sensitivities (B, R, and S types) have correspondingly lower resolutions. Other selection criteria include the chemical inertness of the thermocouple material and whether it is magnetic or not. Standard thermocouple types are listed below with the positive electrode (assuming ) first, followed by the negative electrode. | 0 | Metallurgy |
Ferrosilicon is an alloy of iron and silicon with a typical silicon content by weight of 15–90%. It contains a high proportion of iron silicides. | 0 | Metallurgy |
The hardness of a material can be measured in many ways. The Knoop hardness test, a method of microindentation hardness, is the most reproducible for dense ceramics. The Vickers hardness test and superficial Rockwell scales (e.g., 45N) can also be used, but tend to cause more surface damage than Knoop. The Brinell test is suitable for ductile metals, but not ceramics. In the Knoop test, a diamond indenter in the shape of an elongated pyramid is forced into a polished (but not etched) surface under a predetermined load, typically 500 or 1000 g. The load is held for some amount of time, say 10 s, and the indenter is retracted. The indention long diagonal (d, μm, in Fig. 4) is measured under a microscope, and the Knoop hardness (HK) is calculated from the load (P, g) and the square of the diagonal length in the equations below. The constants account for the projected area of the indenter and unit conversion factors. Most oxide ceramics have a Knoop hardness in the range of 1000–1500 kg/mm (10 – 15 GPa), and many carbides are over 2000 (20 GPa). The method is specified in ASTM C849, C1326 & E384. Microindentation hardness is also called microindentation hardness or simply microhardness. The hardness of very small particles and thin films of ceramics, on the order of 100 nm, can be measured by nanoindentation methods that use a Berkovich indenter.
: (kg/mm) and (GPa)
The toughness of ceramics can be determined from a Vickers test under a load of 10 – 20 kg. Toughness is the ability of a material to resist crack propagation. Several calculations have been formulated from the load (P), elastic modulus (E), microindentation hardness (H), crack length (c in Fig. 5) and flexural strength (σ). Modulus of rupture (MOR) bars with a rectangular cross-section are indented in three places on a polished surface. The bars are loaded in 4-point bending with the polished, indented surface in tension, until fracture. The fracture normally originates at one of the indentions. The crack lengths are measured under a microscope. The toughness of most ceramics is 2–4 MPa, but toughened zirconia is as much as 13, and cemented carbides are often over 20. The toughness-by-indention methods have been discredited recently and are being replaced by more rigorous methods that measure crack growth in a notched beam in bending.
: initial crack length
: indention strength in bending | 0 | Metallurgy |
The synapse contains at least two clusters of synaptic vesicles, the readily releasable pool and the reserve pool. The readily releasable pool is located within the active zone and connected directly to the presynaptic membrane while the reserve pool is clustered by cytoskeletal and is not directly connected to the active zone. | 1 | Gene expression + Signal Transduction |
Oxhide ingots are heavy (20–30 kg) metal slabs, usually of copper but sometimes of tin, produced and widely distributed during the Mediterranean Late Bronze Age (LBA). Their shape resembles the hide of an ox with a protruding handle in each of the ingot’s four corners. Early thought was that each ingot was equivalent to the value of one ox. However, the similarity in shape is simply a coincidence. The ingots' producers probably designed these protrusions to make the ingots easily transportable overland on the backs of pack animals. Complete or partial oxhide ingots have been discovered in Sardinia, Crete, Peloponnese, Cyprus, Cannatello in Sicily, Boğazköy in Turkey (ancient Hattusa, the Hittite capital), Qantir in Egypt (ancient Pi-Ramesses), and Sozopol in Bulgaria. Archaeologists have recovered many oxhide ingots from two shipwrecks off the coast of Turkey (one off Uluburun and one in Cape Gelidonya). | 0 | Metallurgy |
Pregnant leach solution or pregnant liquor solution (PLS) is acidic metal-laden water generated from stockpile leaching and heap leaching. Pregnant leach solution is used in the solvent extraction and electrowinning (SX/EW) process.
The portion of an original liquid that remains after other components have been dissolved by a solvent is called raffinate. | 0 | Metallurgy |
Using a thin coat of polish can prevent tarnish from forming over these metals. Tarnish can be removed by using steel wool, sandpaper, emery paper, baking soda or a file to rub or polish the metal's dull surface. Fine objects (such as silverware) may have the tarnish electrochemically reversed (non-destructively) by resting the objects on a piece of aluminium foil in a pot of boiling water with a small amount of salt or baking soda, or it may be removed with a special polishing compound and a soft cloth. Gentler abrasives, like calcium carbonate, are often used by museums to clean tarnished silver as they cannot damage or scratch the silver and will not leave unwanted residues. | 0 | Metallurgy |
It is sometimes desirable to chemically alter the surface of copper or copper alloys to create a different color. The most common colors produced are brown or statuary finishes for brass or bronze and green or patina finishes for copper. Mechanical surface treatments, chemical coloring, and coatings are described elsewhere in this article at: Finishes. | 0 | Metallurgy |
Some coactivators indirectly regulate gene expression by binding to an activator and inducing a conformational change that then allows the activator to bind to the DNA enhancer or promoter sequence. Once the activator-coactivator complex binds to the enhancer, RNA polymerase II and other general transcription machinery are recruited to the DNA and transcription begins. | 1 | Gene expression + Signal Transduction |
The acronym prefix "R.A." is sometimes pronounced as the one syllable word "ray" because of the plot's strong resemblance to a geometric ray. This characteristic arrow-like shape derives from two key features: on the right at the vector origin, a long asymptotic tail, and on the left (forming the arrow head) two (often dense) patches of condition-unique points. | 1 | Gene expression + Signal Transduction |
Stresses higher than anticipated can also accelerate rolling contact fatigue, which is a known precursor to WECs. WECs commence at subsurface during the initial phases of their formation, particularly at non-metallic inclusions. As the sliding contact period extended, these cracks extended from the subsurface region to the contact surface, ultimately leading to flaking. Furthermore, there was an observable rise in the extent of microstructural modifications near the cracks, suggesting that the presence of the crack is a precursor to these alterations.
The direction of sliding on the bearing surface played a significant role in WEC formation. When the traction force opposed the direction of over-rolling (referred to as negative sliding), it consistently led to the development of WECs. Conversely, when the traction force aligned with the over-rolling direction (positive sliding), WECs did not manifest. The magnitude of sliding exerted a dominant influence on WEC formation. Tests conducted at a sliding-to-rolling ratio (SRR) of -30% consistently resulted in the generation of WECs, while no WECs were observed in tests at -5% SRR. Furthermore, the number of WECs appeared to correlate with variations in contact severity, including changes in surface roughness, rolling speed, and lubricant temperature. | 0 | Metallurgy |