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Phosphine ( IUPAC name: phosphane ) is a colorless, flammable, highly toxic compound with the chemical formula P H 3 , classed as a pnictogen hydride . Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting fish, due to the presence of substituted phosphine and diphosphane ( P 2 H 4 ). With traces of P 2 H 4 present, PH 3 is spontaneously flammable in air ( pyrophoric ), burning with a luminous flame. Phosphine is a highly toxic respiratory poison, and is immediately dangerous to life or health at 50 ppm. Phosphine has a trigonal pyramidal structure.
Phosphines are compounds that include PH 3 and the organophosphines , which are derived from PH 3 by substituting one or more hydrogen atoms with organic groups. [ 4 ] They have the general formula PH 3− n R n . Phosphanes are saturated phosphorus hydrides of the form P n H n +2 , such as triphosphane . [ 5 ] Phosphine ( PH 3 ) is the smallest of the phosphines and the smallest of the phosphanes.
Philippe Gengembre (1764–1838), a student of Lavoisier , first obtained phosphine in 1783 by heating white phosphorus in an aqueous solution of potash (potassium carbonate). [ 6 ] [ NB 1 ]
Perhaps because of its strong association with elemental phosphorus , phosphine was once regarded as a gaseous form of the element, but Lavoisier (1789) recognised it as a combination of phosphorus with hydrogen and described it as phosphure d'hydrogène (phosphide of hydrogen). [ NB 2 ]
In 1844, Paul Thénard, son of the French chemist Louis Jacques Thénard , used a cold trap to separate diphosphine from phosphine that had been generated from calcium phosphide , thereby demonstrating that P 2 H 4 is responsible for spontaneous flammability associated with PH 3 , and also for the characteristic orange/brown color that can form on surfaces, which is a polymerisation product. [ 7 ] He considered diphosphine's formula to be PH 2 , and thus an intermediate between elemental phosphorus, the higher polymers, and phosphine. Calcium phosphide (nominally Ca 3 P 2 ) produces more P 2 H 4 than other phosphides because of the preponderance of P-P bonds in the starting material.
The name "phosphine" was first used for organophosphorus compounds in 1857, being analogous to organic amines ( NR 3 ). [ NB 3 ] [ 8 ] The gas PH 3 was named "phosphine" by 1865 (or earlier). [ 9 ]
PH 3 is a trigonal pyramidal molecule with C 3 v molecular symmetry . The length of the P−H bond is 1.42 Å , the H−P−H bond angles are 93.5 ° . The dipole moment is 0.58 D, which increases with substitution of methyl groups in the series: CH 3 PH 2 , 1.10 D; (CH 3 ) 2 PH , 1.23 D; (CH 3 ) 3 P , 1.19 D. In contrast, the dipole moments of amines decrease with substitution, starting with ammonia , which has a dipole moment of 1.47 D. The low dipole moment and almost orthogonal bond angles lead to the conclusion that in PH 3 the P−H bonds are almost entirely pσ(P) – sσ(H) and phosphorus 3s orbital contributes little to the P-H bonding. For this reason, the lone pair on phosphorus is predominantly formed by the 3s orbital of phosphorus. The upfield chemical shift of it 31 P NMR signal accords with the conclusion that the lone pair electrons occupy the 3s orbital (Fluck, 1973). This electronic structure leads to a lack of nucleophilicity in general and lack of basicity in particular (p K aH = −14), [ 10 ] as well as an ability to form only weak hydrogen bonds . [ 11 ]
The aqueous solubility of PH 3 is slight: 0.22 cm 3 of gas dissolves in 1 cm 3 of water. Phosphine dissolves more readily in non-polar solvents than in water because of the non-polar P−H bonds. It is technically amphoteric in water, but acid and base activity is poor. Proton exchange proceeds via a phosphonium ( PH + 4 ) ion in acidic solutions and via phosphanide ( PH − 2 ) at high pH, with equilibrium constants K b = 4 × 10 −28 and K a = 41.6 × 10 −29 . Phosphine reacts with water only at high pressure and temperature, producing phosphoric acid and hydrogen: [ 12 ] [ 13 ]
Burning phosphine in the air produces phosphoric acid : [ 14 ] [ 12 ]
Phosphine may be prepared in a variety of ways. [ 15 ] Industrially it can be made by the reaction of white phosphorus with sodium or potassium hydroxide , producing potassium or sodium hypophosphite as a by-product.
Alternatively, the acid-catalyzed disproportionation of white phosphorus yields phosphoric acid and phosphine. Both routes have industrial significance; the acid route is the preferred method if further reaction of the phosphine to substituted phosphines is needed. The acid route requires purification and pressurizing.
It is prepared in the laboratory by disproportionation of phosphorous acid : [ 16 ]
Alternative methods are the hydrolysis zinc phosphide :
[ 17 ] Some other metal phosphides could be used including aluminium phosphide , or calcium phosphide . Pure samples of phosphine, free from P 2 H 4 , may be prepared using the action of potassium hydroxide on phosphonium iodide :
Phosphine is a worldwide constituent of the Earth's atmosphere at very low and highly variable concentrations. [ 18 ] It may contribute significantly to the global phosphorus biochemical cycle . The most likely source is reduction of phosphate in decaying organic matter, possibly via partial reductions and disproportionations , since environmental systems do not have known reducing agents of sufficient strength to directly convert phosphate to phosphine. [ 19 ]
It is also found in Jupiter 's atmosphere. [ 20 ]
In 2020 a spectroscopic analysis was reported to show signs of phosphine in the atmosphere of Venus in quantities that could not be explained by known abiotic processes . [ 21 ] [ 22 ] [ 23 ] Later re-analysis of this work showed interpolation errors had been made, and re-analysis of data with the fixed algorithm do not result in the detection of phosphine. [ 24 ] [ 25 ] The authors of the original study then claimed to detect it with a much lower concentration of 1 ppb. [ 26 ] [ disputed – discuss ]
Phosphine is a precursor to many organophosphorus compounds . It reacts with formaldehyde in the presence of hydrogen chloride to give tetrakis(hydroxymethyl)phosphonium chloride , which is used in textiles. The hydrophosphination of alkenes is versatile route to a variety of phosphines. For example, in the presence of basic catalysts PH 3 adds of Michael acceptors . Thus with acrylonitrile , it reacts to give tris(cyanoethyl)phosphine : [ 27 ]
Acid catalysis is applicable to hydrophosphination with isobutylene and related analogues:
where R is CH 3 , alkyl, etc.
Phosphine is used as a dopant in the semiconductor industry, and a precursor for the deposition of compound semiconductors . Commercially significant products include gallium phosphide and indium phosphide . [ 28 ]
Phosphine is an attractive fumigant because it is lethal to insects and rodents, but degrades to phosphoric acid, which is non-toxic. As sources of phosphine, for farm use , pellets of aluminium phosphide (AlP), calcium phosphide ( Ca 3 P 2 ), or zinc phosphide ( Zn 3 P 2 ) are used. These phosphides release phosphine upon contact with atmospheric water or rodents' stomach acid. These pellets also contain reagents to reduce the potential for ignition or explosion of the released phosphine.
An alternative is the use of phosphine gas itself which requires dilution with either CO 2 or N 2 or even air to bring it below the flammability point. Use of the gas avoids the issues related with the solid residues left by metal phosphide and results in faster, more efficient control of the target pests.
One problem with phosphine fumigants is the increased resistance by insects. [ 29 ]
Deaths have resulted from accidental exposure to fumigation materials containing aluminium phosphide or phosphine. [ 30 ] [ 31 ] [ 32 ] [ 33 ] It can be absorbed either by inhalation or transdermally . [ 30 ] As a respiratory poison, it affects the transport of oxygen or interferes with the utilization of oxygen by various cells in the body. [ 32 ] Exposure results in pulmonary edema (the lungs fill with fluid). [ 33 ] Phosphine gas is heavier than air so it stays near the floor. [ 34 ]
Phosphine appears to be mainly a redox toxin, causing cell damage by inducing oxidative stress and mitochondrial dysfunction. [ 35 ] Resistance in insects is caused by a mutation in a mitochondrial metabolic gene. [ 29 ]
Phosphine can be absorbed into the body by inhalation. The main target organ of phosphine gas is the respiratory tract. [ 36 ] According to the 2009 U.S. National Institute for Occupational Safety and Health (NIOSH) pocket guide, and U.S. Occupational Safety and Health Administration (OSHA) regulation, the 8 hour average respiratory exposure should not exceed 0.3 ppm. NIOSH recommends that the short term respiratory exposure to phosphine gas should not exceed 1 ppm. The Immediately Dangerous to Life or Health level is 50 ppm. Overexposure to phosphine gas causes nausea, vomiting, abdominal pain, diarrhea, thirst, chest tightness, dyspnea (breathing difficulty), muscle pain, chills, stupor or syncope, and pulmonary edema. [ 37 ] [ 38 ] Phosphine has been reported to have the odor of decaying fish or garlic at concentrations below 0.3 ppm. The smell is normally restricted to laboratory areas or phosphine processing since the smell comes from the way the phosphine is extracted from the environment. However, it may occur elsewhere, such as in industrial waste landfills. Exposure to higher concentrations may cause olfactory fatigue . [ 39 ]
Phosphine is used for pest control , but its usage is strictly regulated due to high toxicity. [ 40 ] [ 41 ] Gas from phosphine has high mortality rate [ 42 ] and has caused deaths in Sweden and other countries. [ 43 ] [ 44 ] [ 45 ]
Because the previously popular fumigant methyl bromide has been phased out in some countries under the Montreal Protocol , phosphine is the only widely used, cost-effective, rapidly acting fumigant that does not leave residues on the stored product. Pests with high levels of resistance toward phosphine have become common in Asia, Australia and Brazil. High level resistance is also likely to occur in other regions, but has not been as closely monitored. Genetic variants that contribute to high level resistance to phosphine have been identified in the dihydrolipoamide dehydrogenase gene. [ 29 ] Identification of this gene now allows rapid molecular identification of resistant insects.
Phosphine gas is denser than air and hence may collect in low-lying areas. It can form explosive mixtures with air, and may also self-ignite. [ 12 ]
Anne McCaffrey 's Dragonriders of Pern series features genetically engineered dragons that breathe fire by producing phosphine by extracting it from minerals of their native planet.
In the 2008 pilot of the crime drama television series Breaking Bad , Walter White poisons two rival gangsters by adding red phosphorus to boiling water to produce phosphine gas. However, this reaction in reality would require white phosphorus instead, and for the water to contain sodium hydroxide . [ 46 ] | https://en.wikipedia.org/wiki/PH3 |
Phosphonium iodide is a chemical compound with the formula PH 4 I . It is an example of a salt containing an unsubstituted phosphonium cation ( PH + 4 ). Phosphonium iodide is commonly used as storage for phosphine [ 2 ] and as a reagent for substituting phosphorus into organic molecules. [ 3 ]
Phosphonium iodide is prepared by mixing diphosphorus tetraiodide ( P 2 I 4 ) with elemental phosphorus and water at 80 °C and allowing the salt to sublime. [ 4 ] [ 5 ]
Its crystal structure has the tetragonal space group P4/nmm, which is a distorted version of the NH 4 Cl crystal structure; the unit cell has approximate dimensions 634×634×462 pm. [ 6 ] The hydrogen bonding in the system causes the PH + 4 cations to orient such that the hydrogen atoms point toward the I − anions. [ 7 ]
At 62 °C and atmospheric pressure, phosphonium iodide sublimates and dissociates reversibly into phosphine and hydrogen iodide (HI). [ 1 ] It oxidizes slowly in air to give iodine and phosphorus oxides ; it is hygroscopic [ 4 ] and is hydrolyzed into phosphine and HI: [ 8 ]
Phosphine gas may be devolved from phosphonium iodide by mixing an aqueous solution with potassium hydroxide : [ 9 ]
It reacts with elemental iodine and bromine in a nonpolar solution to give phosphorus halides; for example:
Phosphonium iodide is a powerful substitution reagent in organic chemistry; for example, it can convert a pyrilium into a phosphinine via substitution. [ 3 ] In 1951, Glenn Halstead Brown found that PH 4 I reacts with acetyl chloride to produce an unknown phosphine derivative, possibly CH 3 C(=PH)PH 2 ·HI . [ 4 ] | https://en.wikipedia.org/wiki/PH4I |
A phosphorane ( IUPAC name: λ 5 -phosphane ) is a functional group in organophosphorus chemistry with pentavalent phosphorus . Phosphoranes have the general formula PR 5 .
Phosphoranes of the type PX 5 adopt a trigonal bipyramidal molecular geometry with the two apical bonds longer than the three equatorial bonds. Hypervalent bonding is described by inclusion of non-bonding MOs, as also invoked for the closely related molecule phosphorus pentafluoride . [ 1 ]
The parent hydride compound is the hypothetical molecule PH 5 .
Pentaphenylphosphorane (Ph 5 P) is stable. [ 2 ]
Pentaalkoxyphosphoranes are more common with electronegative substituents. Examples of P(OR) 5 (R = alkyl), have however been prepared by reaction of phosphites with benzene alkyl sulfenates : [ 3 ]
Phosphoranes of the type R 3 P=CR 2 are more common and more important. Phosphoranes are also considered to be one of the resonance structures of ylides , these compounds feature a tetrahedral phosphorus center including a phosphorus–carbon double bond. These compounds are used as reagents in the Wittig reaction , for instance methylenetriphenylphosphorane or Ph 3 P=CH 2 . | https://en.wikipedia.org/wiki/PH5 |
Poly(3-hydroxybutyrate- co -3-hydroxyvalerate) , commonly known as PHBV , is a polyhydroxyalkanoate -type polymer. It is biodegradable , nontoxic , biocompatible plastic produced naturally by bacteria and a good alternative for many non-biodegradable synthetic polymers . It is a thermoplastic linear aliphatic polyester . It is obtained by the copolymerization of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid . PHBV is used in speciality packaging, orthopedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment.
PHBV was first manufactured in 1983 by Imperial Chemical Industries (ICI). It is commercialized under the trade name Biopol . ICI ( Zeneca ) sold it to Monsanto in 1996. This was then obtained by Metabolix in 2001. [ 2 ] [ 3 ] Biomer L is the trade name of PHBV from Biomer.
PHBV is synthesized by bacteria as storage compounds under growth limiting conditions. [ 4 ] It can be produced from glucose and propionate by the recombinant Escherichia coli strains. [ 2 ] Many other bacteria like Paracoccus denitrificans and Ralstonia eutropha are also capable of producing it.
It can also be synthesized from genetically engineered plants. [ 5 ]
PHBV is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid . [ 6 ] PHBV may also be synthesized from butyrolactone and valerolactone in the presence of oligomeric aluminoxane as catalyst . [ 7 ]
The monomers, 3-hydroxybutanoic acid and 3-hydroxypentanoic acid, are joined by ester bonds ; the back bone of the polymer is made up of carbon and oxygen atoms.
The property of the PHBV depends upon the ratio of these two monomers in it.
3-hydroxybutanoic acid provides stiffness while 3-hydroxypentanoic acid promotes flexibility. Thus PHBV can be made to resemble either polypropylene or polyethylene by changing the ratio of monomers. [ 8 ] Increase in the ratio of 3-hydroxybutanoic acid to 3-hydroxypentanoic acid results in an increase in melting point, water permeability , glass transition temperature (T g ) and tensile strength. However impact resistance is reduced. [ 3 ] [ 5 ] [ 7 ]
PHBV is a thermoplastic polymer. It is brittle, has low elongation at break and low impact resistance. [ 5 ]
PHBV find its application in controlled release of drugs, medical implants and repairs, specialty packaging , orthopedic devices and manufacturing bottles for consumer goods. It is also biodegradable which can be used as an alternative to non biodegradable plastics [ 9 ]
When disposed, PHBV degrades into carbon dioxide and water. PHBV undergo bacterial degradation. PHBV, just like fats to human, is an energy source to microorganisms. Enzymes produced by them degrade it and are consumed. [ 10 ]
PHBV has a low thermal stability and the cleavage occurs at the ester bond by β elimination reaction. [ 5 ]
Hydrolytic degradation occurs only slowly making it usable in medical applications.
PHBV, being biodegradable, biocompatible and renewable, is a good alternative for synthetic nonbiodegradable polymers made from petroleum. But it has the following drawbacks, [ 5 ] | https://en.wikipedia.org/wiki/PHBV |
PHIB-BLAST
The Pathogen-Host Interactions database ( PHI-base ) [ 1 ] is a biological database that contains manually curated information on genes experimentally proven to affect the outcome of pathogen-host interactions . The database has been maintained by researchers at Rothamsted Research and external collaborators since 2005. [ 2 ] [ 3 ] [ 4 ] [ 5 ] PHI-base has been part of the UK node of ELIXIR , the European life-science infrastructure for biological information, since 2016. [ 6 ]
The Pathogen - Host Interactions database was developed to utilise the growing number of verified genes that mediate an organism's ability to cause disease and/or trigger host responses. [ 7 ]
The web-accessible database catalogues experimentally verified pathogenicity, virulence, and effector genes from bacterial, fungal, and oomycete pathogens which infect animal, plant, and fungal hosts. PHI-base was the first online resource devoted to the identification and presentation of information on fungal and oomycete pathogenicity genes and their host interactions. PHI-base is a resource for the discovery of candidate targets in medically and agronomically important fungal and oomycete pathogens for intervention with synthetic chemistries and natural products ( fungicides ). [ 8 ] [ 9 ]
Each entry in PHI-base is curated by domain experts and supported by strong experimental evidence (gene disruption experiments) as well as literature references in which the experiments are described. Each gene in PHI-base is presented with its nucleotide and deduced amino acid sequence as well as a detailed structured description of the predicted protein's function during the host infection process. To facilitate data interoperability, genes are annotated using controlled vocabularies ( Gene Ontology terms, EC Numbers , etc.), and links to other external data sources such as UniProt , EMBL , and the NCBI taxonomy services.
Version 4.17 (May 2024) of PHI-base [ 1 ] provides information on 9973 genes from 296 pathogens and 249 hosts and their impact on 22415 interactions as well on efficacy information on ~20 drugs and the target sequences in the pathogen. PHI-base currently focuses on plant pathogenic and human pathogenic organisms including fungi, oomycetes, and bacteria. The entire contents of the database can be downloaded in a tab delimited format. Since the launch of version 4, the PHI-base is also searchable using the PHIB-BLAST search tool, which uses the BLAST algorithm to compare a user's sequence against the sequences available from PHI-base. [ 10 ] The database providers recently announced the launch of PHI-base 5 , a new gene-centric version of PHI-base, through a press release on the Rothamsted Research website. A summary of the improvements made is also available .
In 2016 the plant portion of PHI-base was used to establish a Semantic PHI-base search tool. [ 11 ]
PHI-base has been aligned with Ensembl Genomes since 2011, FungiDB since 2016, and Global Biotic Interactions (GloBI) since 2018. [ 12 ] All new PHI-base releases are integrated by these independent databases.
PHI-base is a resource for many applications including:
› The discovery of conserved genes in medically and agronomically important pathogens, which may be potential targets for chemical intervention
› Comparative genome analyses
› Annotation of newly sequenced pathogen genomes
› Functional interpretation of RNA sequencing and microarray experiments
› The rapid cross-checking of phenotypic differences between pathogenic species when writing articles for peer review
PHI-base use has been cited in over 900 peer-reviewed articles. [ 1 ]
Since 2015, the website has linked to an online literature curation tool called PHI-Canto , enabling community-driven literature curation for various pathogenic species. [ 13 ] PHI-Canto employs a community curation framework that not only offers a curation tool but also includes a phenotype ontology and controlled vocabularies using unified languages and rules used in biology experiments. The central concept of this framework is the introduction of a 'Metagenotype', which allows the annotation and assignment of phenotypes to specific pathogen mutant-host interactions. PHI-Canto extends the single species curation tool developed for PomBase [ 14 ] ( https://www.pombase.org ), the model organism database for fission yeast.
PHI-base is a National Capability funded by the Biotechnology and Biological Sciences Research Council (BBSRC), a UK research council. [ 7 ] | https://en.wikipedia.org/wiki/PHI-base |
The PHLPP isoforms ( PH domain and Leucine rich repeat Protein Phosphatases ) are a pair of protein phosphatases , PHLPP1 and PHLPP2 , that are important regulators of Akt serine-threonine kinases ( Akt1 , Akt2 , Akt3 ) and conventional/novel protein kinase C (PKC) isoforms. PHLPP may act as a tumor suppressor in several types of cancer due to its ability to block growth factor-induced signaling in cancer cells. [ 1 ]
PHLPP dephosphorylates Ser -473 (the hydrophobic motif) in Akt, thus partially inactivating the kinase. [ 2 ]
In addition, PHLPP dephosphorylates conventional and novel members of the protein kinase C family at their hydrophobic motifs, corresponding to Ser-660 in PKCβII. [ 3 ]
PHLPP is a member of the PPM family of phosphatases, which requires magnesium or manganese for their activity and are insensitive to most common phosphatase inhibitors, including [okadaic acid]. PHLPP1 and PHLPP2 have a similar domain structure, which includes a putative Ras association domain, a pleckstrin homology domain , a series of leucine-rich repeats , a PP2C phosphatase domain, and a C-terminal PDZ ligand. PHLPP1 has two splice variants, PHLPP1α and PHLPP1β, of which PHLPP1β is larger by approximately 1.5 kilobase pairs. PHLPP1α, which was the first PHLPP isoform to be characterized, lacks the N-terminal portion of the protein, including the Ras association domain. [ 1 ] PHLPP's domain structure influences its ability to dephosphorylate its substrates. A PHLPP construct lacking the PH domain is unable to decrease PKC phosphorylation, while PHLPP lacking the PDZ ligand is unable to decrease Akt phosphorylation. [ 2 ]
The phosphatases in the PHLPP family, PHLPP1 and PHLPP2 have been shown to directly dephosphorylate, and therefore inactivate, distinct Akt isoforms, at one of the two critical phosphorylation sites required for activation: Serine473. PHLPP2 dephosphorylates AKT1 and AKT3 , whereas PHLPP1 is specific for AKT2 and AKT3. Lack of PHLPP appears to have effects on growth factor-induced Akt phosphorylation. When both PHLPP1 and PHLPP2 are knocked down using siRNA and cells are stimulated using epidermal growth factor, peak Akt phosphorylation at both Serine473 and Threonine308 (the other site required for full Akt activation) is increased dramatically. [ 4 ]
In humans, there are three genes in the Akt family: AKT1 , AKT2 , and AKT3 . These enzymes are members of the serine/threonine-specific protein kinase family ( EC 2.7.11.1 ).
Akt1 is involved in cellular survival pathways and inhibition of apoptotic processes. Akt1 is also able to induce protein synthesis pathways, and is therefore a key signaling protein in the cellular pathways that lead to skeletal muscle hypertrophy, and general tissue growth. Since it can block apoptosis, and thereby promote cell survival, Akt1 has been implicated as a major factor in many types of cancer. Akt (now also called Akt1) was originally identified as the oncogene in the transforming retrovirus , AKT8.
Akt2 is important in the insulin signaling pathway. It is required to induce glucose transport. [ citation needed ]
These separate roles for Akt1 and Akt2 were demonstrated by studying mice in which either the Akt1 or the Akt2 gene was deleted, or "knocked out". In a mouse that is null for Akt1 but normal for Akt2, glucose homeostasis is unperturbed, but the animals are smaller, consistent with a role for Akt1 in growth. In contrast, mice that do not have Akt2 but have normal Akt1 have mild growth deficiency and display a diabetic phenotype ( insulin resistance ), again consistent with the idea that Akt2 is more specific for the insulin receptor signaling pathway. [ 5 ]
The role of Akt3 is less clear, though it appears to be expressed predominantly in brain. It has been reported that mice lacking Akt3 have small brains. [ 6 ]
Once correctly positioned in the membrane via binding of PIP3 , Akt can then be phosphorylated by its activating kinases, phosphoinositide-dependent kinase 1 ( PDK1 ) and PDK2. Serine473, the hydrophobic motif, is phosphorylated in an mTORC2-dependent manner, leading some investigators to hypothesize that mTORC2 is the long-sought PDK2 molecule. Threonine308, the activation loop , is phosphorylated by PDK1, allowing full Akt activation. Activated Akt can then go on to activate or deactivate its myriad substrates via its kinase activity. The PHLPPs therefore antagonize PDK1 and PDK2, since they dephosphorylate the site that PDK2 phosphorylates. [ 1 ]
PHLPP1 and 2 also dephosphorylate the hydrophobic motifs of two classes of the protein kinase C (PKC) family: the conventional PKCs and the novel PKCs. (The third class of PKCs, known as the atypicals, have a phospho-mimetic at the hydrophobic motif, rendering them insensitive to PHLPP.)
The PKC family of kinases consists of 10 isoforms, whose sensitivity to various second messengers is dictated by their domain structure. The conventional PKCs can be activated by calcium and diacylglycerol , two important mediators of G protein-coupled receptor signaling. The novel PKCs are activated by diacylglycerol but not calcium, while the atypical PKCs are activated by neither.
The PKC family, like Akt, plays roles in cell survival and motility. Most PKC isoforms are anti-apoptotic, although PKCδ (a novel PKC isoform) is pro-apoptotic in some systems.
Although PKC possesses the same phosphorylation sites as Akt, its regulation is quite different. PKC is constitutively phosphorylated, and its acute activity is regulated by binding of the enzyme to membranes. Dephosphorylation of PKC at the hydrophobic motif by PHLPP allows PKC to be dephosphorylated at two other sites (the activation loop and the turn motif). This in turn renders PKC sensitive to degradation. Thus, prolonged increases in PHLPP expression or activity inhibit PKC phosphorylation and stability, decreasing the total levels of PKC over time. [ 1 ]
Investigators have hypothesized that the PHLPP isoforms may play roles in cancer, for several reasons. First, the genetic loci coding for PHLPP1 and 2 are commonly lost in cancer. The region including PHLPP1, 18q21.33, commonly undergoes loss of heterozygosity ( LOH ) in colon cancers, while 16q22.3, which includes the PHLPP2 gene, undergoes LOH in breast and ovarian cancers, Wilms tumors, prostate cancer and hepatocellular carcinoma. [ 1 ] Second, experimental overexpression of PHLPP in cancer cell lines tends to decrease apoptosis and increase proliferation, and stable colon and glioblastoma cell lines overexpressing PHLPP1 show decreased tumor formation in xenograft models. [ 2 ] [ 7 ] Recent studies have also shown that Bcr-Abl , the fusion protein responsible for chronic myelogenous leukemia ( CML ), downregulates PHLPP1 and PHLPP2 levels, and that decreasing PHLPP levels interferes with the efficacy of Bcr-Abl inhibitors, including Gleevec , in CML cell lines. [ 8 ]
Finally, both Akt and PKC are known to be tumor promoters, suggesting that their negative regulator PHLPP may act as a tumor suppressor. | https://en.wikipedia.org/wiki/PHLPP |
PHOSFOS (Photonic Skins For Optical Sensing) is a research and technology development project co-funded by the European Commission .
The PHOSFOS project [ 1 ] is developing flexible and stretchable foils or skins that integrate optical sensing elements with optical and electrical devices, such as onboard signal processing and wireless communications, as seen in Figure 1. These flexible skins can be wrapped around, embedded in, and anchored to irregularly shaped or moving objects and allow quasi-distributed sensing of mechanical quantities such as deformation, pressure, stress, and strain. [ 2 ] This approach offers advantages over conventional sensing systems, such as increased portability and measurement range.
The sensing technology is based around sensing elements called Fiber Bragg Gratings (FBGs) that are fabricated in standard single core silica fibers, highly birefringent Microstructured fibers (MSF) and Plastic optical fibers (POF). The silica MSFs are designed to exhibit almost zero temperature sensitivity to cope with the traditional temperature cross-sensitivity issues of conventional fiber sensors. These specialty fibers are being modeled, designed, and fabricated within the programme. FBGs implemented in plastic optical fiber are also being studied because plastic fibers can be stretched up to 300% before breaking, permitting use under conditions that would result in catastrophic failure of other types of strain sensors.
Once optimized, the sensors are embedded into a flexible skin and interfaced with peripheral optoelectronics and electronics (see Figure 2).
The photonic skins developed by PHOSFOS have potential application in real-time remote monitoring of behavior and integrity of various structures such as in civil engineering (buildings, dams, bridges, roads, tunnels and mines), in aerospace (aircraft wings, helicopter blades), and in energy production (windmill blades). Applications in healthcare are also being investigated.
A summary of the key developments can be found on the PhoSFOS EU webpage and includes the demonstration of a fully flexible opto-electronic foil. [ 3 ]
Figure 3 shows the scattering of HeNe laser light from noise gratings recorded in PMMA using a 325 nm HeCd laser.
One of the early results from the project was in developing a repeatable method for joining polymer fiber to standard silica fiber — a major development that enabled using POF Bragg gratings in applications outside an optics lab. One of the first uses for these sensors was in monitoring strain in tapestries [ 4 ] shown in Figure 4. [ 5 ] In this case conventional electrical strain sensors and silica fiber sensors were shown to be strengthening the tapestries in areas where they were fixed. Because polymer fibre devices are much more flexible they did not distort the textiles as much, permitting more accurate measurement of strain.
Temperature and humidity sensing using a combined silica / POF fiber sensor has been demonstrated. [ 6 ] Combined strain, temperature and bend sensing has also been shown. [ 7 ] Using a fiber Bragg grating in an eccentric core polymer has been shown to yield a high sensitivity to bend. [ 8 ]
Other recent progress includes the demonstration of birefringent photonic crystal fibers with zero polarimetric sensitivity to temperature, [ 9 ] [ 10 ] and a successful demonstration of transversal load sensing with fibre Bragg gratings in microstructured optic fibers. [ 11 ]
The key areas where significant progress has been made are listed below: [ 12 ]
The 2nd "Benefits for Industry" Meeting of the EU FP7 Project PHOSFOS will take place on Sunday 22 May 2011 in Munich (Germany).
The meeting is co-located with the Industry Meets Academia Workshop organized by SPIE SPIE as part of the Optical Metrology Conference. It will be followed by the World of Photonics Congress and the Laser World of Photonics Trade Fair in Munich, in the week from 23 to 26 May 2011.
This Meeting is the second in its kind gathering all companies that have expressed their possible interest in the technology developed by the EU FP7 project PHOSFOS.
18 companies/institutes have registered for the Industrial User Club of PHOSFOS , new members are welcome. | https://en.wikipedia.org/wiki/PHOSFOS |
The PHO sphorylation SI te DA tabase PHOSIDA integrates thousands of high-confidence in vivo phosphosites identified in various species on the basis of mass spectrometry technology. For each phosphosite, PHOSIDA lists matching kinase motifs, predicted secondary structures, conservation patterns, and its dynamic regulation upon stimulus or other treatments such as kinase inhibition, for example. It includes phosphoproteomes of various organisms ranging from eukaryotes such as human and yeast to bacteria such as Escherichia coli and Lactococcus lactis . Even the phosphoproteome of an archaean organism, namely Halobacterium salinarium , is available. The integration of phosphoproteomes identified in organisms, which cover the phylogenetic tree representatively, enables to examine phosphorylation events from a global point of view including conservation and evolutionary preservation in time. [ 1 ]
Moreover, PHOSIDA also predicts phosphosites on the basis of support vector machines . | https://en.wikipedia.org/wiki/PHOSIDA |
A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH ( acidity or basicity ) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. [ 1 ] Hence, a pH indicator is a chemical detector for hydronium ions (H 3 O + ) or hydrogen ions (H + ) in the Arrhenius model .
Normally, the indicator causes the color of the solution to change depending on the pH. Indicators can also show change in other physical properties; for example, olfactory indicators show change in their odor . The pH value of a neutral solution is 7.0 at 25°C ( standard laboratory conditions ). Solutions with a pH value below 7.0 are considered acidic and solutions with pH value above 7.0 are basic. Since most naturally occurring organic compounds are weak electrolytes , such as carboxylic acids and amines , pH indicators find many applications in biology and analytical chemistry . Moreover, pH indicators form one of the three main types of indicator compounds used in chemical analysis. For the quantitative analysis of metal cations, the use of complexometric indicators is preferred, [ 2 ] [ 3 ] whereas the third compound class, the redox indicators , are used in redox titrations ( titrations involving one or more redox reactions as the basis of chemical analysis).
In and of themselves, pH indicators are usually weak acids or weak bases. The general reaction scheme of acidic pH indicators in aqueous solutions can be formulated as:
where, "HInd" is the acidic form and "Ind − " is the conjugate base of the indicator.
Vice versa for basic pH indicators in aqueous solutions:
where "IndOH" stands for the basic form and "Ind + " for the conjugate acid of the indicator.
The ratio of concentration of conjugate acid/base to concentration of the acidic/basic indicator determines the pH (or pOH) of the solution and connects the color to the pH (or pOH) value. For pH indicators that are weak electrolytes, the Henderson–Hasselbalch equation can be written as:
The equations, derived from the acidity constant and basicity constant, states that when pH equals the p K a or p K b value of the indicator, both species are present in a 1:1 ratio. If pH is above the p K a or p K b value, the concentration of the conjugate base is greater than the concentration of the acid, and the color associated with the conjugate base dominates. If pH is below the p K a or p K b value, the converse is true.
Usually, the color change is not instantaneous at the p K a or p K b value, but a pH range exists where a mixture of colors is present. This pH range varies between indicators, but as a rule of thumb, it falls between the p K a or p K b value plus or minus one. This assumes that solutions retain their color as long as at least 10% of the other species persists. For example, if the concentration of the conjugate base is 10 times greater than the concentration of the acid, their ratio is 10:1, and consequently the pH is p K a + 1 or p K b + 1. Conversely, if a 10-fold excess of the acid occurs with respect to the base, the ratio is 1:10 and the pH is p K a − 1 or p K b − 1.
For optimal accuracy, the color difference between the two species should be as clear as possible, and the narrower the pH range of the color change the better. In some indicators, such as phenolphthalein , one of the species is colorless, whereas in other indicators, such as methyl red , both species confer a color. While pH indicators work efficiently at their designated pH range, they are usually destroyed at the extreme ends of the pH scale due to undesired side reactions.
pH indicators are frequently employed in titrations in analytical chemistry and biology to determine the extent of a chemical reaction . [ 1 ] Because of the subjective choice (determination) of color, pH indicators are susceptible to imprecise readings. For applications requiring precise measurement of pH, a pH meter is frequently used. Sometimes, a blend of different indicators is used to achieve several smooth color changes over a wide range of pH values. These commercial indicators (e.g., universal indicator and Hydrion papers ) are used when only rough knowledge of pH is necessary. For a titration, the difference between the true endpoint and the indicated endpoint is called the indicator error. [ 1 ]
Tabulated below are several common laboratory pH indicators. Indicators usually exhibit intermediate colors at pH values inside the listed transition range. For example, phenol red exhibits an orange color between pH 6.8 and pH 8.4. The transition range may shift slightly depending on the concentration of the indicator in the solution and on the temperature at which it is used. The figure on the right shows indicators with their operation range and color changes.
An indicator may be used to obtain quite precise measurements of pH by measuring absorbance quantitatively at two or more wavelengths. The principle can be illustrated by taking the indicator to be a simple acid, HA, which dissociates into H + and A − .
The value of the acid dissociation constant , p K a , must be known. The molar absorbances , ε HA and ε A − of the two species HA and A − at wavelengths λ x and λ y must also have been determined by previous experiment. Assuming Beer's law to be obeyed, the measured absorbances A x and A y at the two wavelengths are simply the sum of the absorbances due to each species.
These are two equations in the two concentrations [HA] and [A − ]. Once solved, the pH is obtained as
If measurements are made at more than two wavelengths, the concentrations [HA] and [A − ] can be calculated by linear least squares . In fact, a whole spectrum may be used for this purpose. The process is illustrated for the indicator bromocresol green . The observed spectrum (green) is the sum of the spectra of HA (gold) and of A − (blue), weighted for the concentration of the two species.
When a single indicator is used, this method is limited to measurements in the pH range p K a ± 1, but this range can be extended by using mixtures of two or more indicators. Because indicators have intense absorption spectra, the indicator concentration is relatively low, and the indicator itself is assumed to have a negligible effect on pH.
In acid-base titrations, an unfitting pH indicator may induce a color change in the indicator-containing solution before or after the actual equivalence point. As a result, different equivalence points for a solution can be concluded based on the pH indicator used. This is because the slightest color change of the indicator-containing solution suggests the equivalence point has been reached. Therefore, the most suitable pH indicator has an effective pH range, where the change in color is apparent, that encompasses the pH of the equivalence point of the solution being titrated. [ 5 ]
Many plants or plant parts contain chemicals from the naturally colored anthocyanin family of compounds. They are red in acidic solutions and blue in basic. Anthocyanins can be extracted with water or other solvents from a multitude of colored plants and plant parts, including from leaves ( red cabbage ); flowers ( geranium , poppy , or rose petals); berries ( blueberries , blackcurrant ); and stems ( rhubarb ). Extracting anthocyanins from household plants, especially red cabbage , to form a crude pH indicator is a popular introductory chemistry demonstration.
Litmus , used by alchemists in the Middle Ages and still readily available, is a naturally occurring pH indicator made from a mixture of lichen species, particularly Roccella tinctoria . The word litmus is literally from 'colored moss' in Old Norse (see Litr ). The color changes between red in acid solutions and blue in alkalis. The term 'litmus test' has become a widely used metaphor for any test that purports to distinguish authoritatively between alternatives.
Hydrangea macrophylla flowers can change color depending on soil acidity. In acid soils, chemical reactions occur in the soil that make aluminium available to these plants, turning the flowers blue. In alkaline soils, these reactions cannot occur and therefore aluminium is not taken up by the plant. As a result, the flowers remain pink.
Another natural pH indicator is the spice turmeric . It turns yellow when exposed to acids and reddish brown when in presence of an alkalis . | https://en.wikipedia.org/wiki/PH_indicator |
A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions , indicating its acidity or alkalinity expressed as pH . [ 2 ] The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, and so the pH meter is sometimes referred to as a "potentiometric pH meter". The difference in electrical potential relates to the acidity or pH of the solution. [ 3 ] Testing of pH via pH meters ( pH-metry ) is used in many applications ranging from laboratory experimentation to quality control . [ 4 ]
The rate and outcome of chemical reactions taking place in water often depends on the acidity of the water, and it is therefore useful to know the acidity of the water, typically measured by means of a pH meter. [ 5 ] Knowledge of pH is useful or critical in many situations, including chemical laboratory analyses. pH meters are used for soil measurements in agriculture , water quality for municipal water supplies, swimming pools , environmental remediation ; brewing of wine or beer; manufacturing , healthcare and clinical applications such as blood chemistry ; and many other applications. [ 4 ]
Advances in the instrumentation and in detection have expanded the number of applications in which pH measurements can be conducted. The devices have been miniaturized , enabling direct measurement of pH inside of living cells . [ 6 ] In addition to measuring the pH of liquids, specially designed electrodes are available to measure the pH of semi-solid substances, such as foods. These have tips suitable for piercing semi-solids, have electrode materials compatible with ingredients in food, and are resistant to clogging. [ 7 ]
Potentiometric pH meters measure the voltage between two electrodes and display the result converted into the corresponding pH value. They comprise a simple electronic amplifier and a pair of electrodes, or alternatively a combination electrode, and some form of display calibrated in pH units. It usually has a glass electrode and a reference electrode , or a combination electrode. The electrodes, or probes, are inserted into the solution to be tested. [ 8 ] pH meters may also be based on the antimony electrode (typically used for rough conditions) or the quinhydrone electrode .
In order to accurately measure the potential difference between the two sides of the glass membrane reference electrode , typically a silver chloride electrode or calomel electrode are required on each side of the membrane. Their purpose is to measure changes in the potential on their respective side. One is built into the glass electrode. The other, which makes contact with the test solution through a porous plug, may be a separate reference electrode or may be built into a combination electrode. The resulting voltage will be the potential difference between the two sides of the glass membrane possibly offset by some difference between the two reference electrodes, that can be compensated for. The article on the glass electrode has a good description and figure.
The design of the electrodes is the key part: These are rod-like structures usually made of glass, with a bulb containing the sensor at the bottom. The glass electrode for measuring the pH has a glass bulb specifically designed to be selective to hydrogen-ion concentration. On immersion in the solution to be tested, hydrogen ions in the test solution exchange for other positively charged ions on the glass bulb, creating an electrochemical potential across the bulb. The electronic amplifier detects the difference in electrical potential between the two electrodes generated in the measurement and converts the potential difference to pH units. The magnitude of the electrochemical potential across the glass bulb is linearly related to the pH according to the Nernst equation .
The reference electrode is insensitive to the pH of the solution, being composed of a metallic conductor, which connects to the display. This conductor is immersed in an electrolyte solution, typically potassium chloride, which comes into contact with the test solution through a porous ceramic membrane. [ 9 ] The display consists of a voltmeter , which displays voltage in units of pH. [ 9 ]
On immersion of the glass electrode and the reference electrode in the test solution, an electrical circuit is completed, in which there is a potential difference created and detected by the voltmeter. The circuit can be thought of as going from the conductive element of the reference electrode to the surrounding potassium-chloride solution, through the ceramic membrane to the test solution, the hydrogen-ion-selective glass of the glass electrode, to the solution inside the glass electrode, to the silver of the glass electrode, and finally the voltmeter of the display device. [ 9 ] The voltage varies from test solution to test solution depending on the potential difference created by the difference in hydrogen-ion concentrations on each side of the glass membrane between the test solution and the solution inside the glass electrode. All other potential differences in the circuit do not vary with pH and are corrected for by means of the calibration. [ 9 ]
For simplicity, many pH meters use a combination probe, constructed with the glass electrode and the reference electrode contained within a single probe. A detailed description of combination electrodes is given in the article on glass electrodes . [ 10 ]
The pH meter is calibrated with solutions of known pH, typically before each use, to ensure accuracy of measurement. [ 11 ] To measure the pH of a solution, the electrodes are used as probes, which are dipped into the test solutions and held there sufficiently long for the hydrogen ions in the test solution to equilibrate with the ions on the surface of the bulb on the glass electrode. This equilibration provides a stable pH measurement. [ 12 ]
Details of the fabrication and resulting microstructure of the glass membrane of the pH electrode are maintained as trade secrets by the manufacturers. [ 13 ] : 125 However, certain aspects of design are published. Glass is a solid electrolyte, for which alkali-metal ions can carry current. The pH-sensitive glass membrane is generally spherical to simplify the manufacture of a uniform membrane. These membranes are up to 0.4 millimeters in thickness, thicker than original designs, so as to render the probes durable. The glass has silicate chemical functionality on its surface, which provides binding sites for alkali-metal ions and hydrogen ions from the solutions. This provides an ion-exchange capacity in the range of 10 −6 to 10 −8 mol/cm 2 . Selectivity for hydrogen ions (H + ) arises from a balance of ionic charge, volume requirements versus other ions, and the coordination number of other ions. Electrode manufacturers have developed compositions that suitably balance these factors, most notably lithium glass. [ 13 ] : 113–139
The silver chloride electrode is most commonly used as a reference electrode in pH meters, although some designs use the saturated calomel electrode . The silver chloride electrode is simple to manufacture and provides high reproducibility . The reference electrode usually consists of a platinum wire that has contact with a silver/silver chloride mixture, which is immersed in a potassium chloride solution. There is a ceramic plug, which serves as a contact to the test solution, providing low resistance while preventing mixing of the two solutions. [ 13 ] : 76–91
With these electrode designs, the voltmeter is detecting potential differences of ±1400 millivolts. [ 14 ] The electrodes are further designed to rapidly equilibrate with test solutions to facilitate ease of use . The equilibration times are typically less than one second, although equilibration times increase as the electrodes age. [ 13 ] : 164
Because of the sensitivity of the electrodes to contaminants, cleanliness of the probes is essential for accuracy and precision . Probes are generally kept moist when not in use with a medium appropriate for the particular probe, which is typically an aqueous solution available from probe manufacturers. [ 11 ] [ 15 ] Probe manufacturers provide instructions for cleaning and maintaining their probe designs. [ 11 ] For illustration, one maker of laboratory-grade pH gives cleaning instructions for specific contaminants: general cleaning (15-minute soak in a solution of bleach and detergent), salt ( hydrochloric acid solution followed by sodium hydroxide and water), grease (detergent or methanol), clogged reference junction (KCl solution), protein deposits (pepsin and HCl, 1% solution), and air bubbles. [ 15 ] [ 16 ]
The German Institute for Standardization publishes a standard for pH measurement using pH meters, DIN 19263. [ 17 ]
Very precise measurements necessitate that the pH meter is calibrated before each measurement. More typically calibration is performed once per day of operation. Calibration is needed because the glass electrode does not give reproducible electrostatic potentials over longer periods of time. [ 13 ] : 238–239
Consistent with principles of good laboratory practice , calibration is performed with at least two standard buffer solutions that span the range of pH values to be measured. For general purposes, buffers at pH 4.00 and pH 10.00 are suitable. The pH meter has one calibration control to set the meter reading equal to the value of the first standard buffer and a second control to adjust the meter reading to the value of the second buffer. A third control allows the temperature to be set. Standard buffer sachets, available from a variety of suppliers, usually document the temperature dependence of the buffer control. More precise measurements sometimes require calibration at three different pH values. Some pH meters provide built-in temperature-coefficient correction, with temperature thermocouples in the electrode probes. The calibration process correlates the voltage produced by the probe (approximately 0.06 volts per pH unit) with the pH scale. Good laboratory practice dictates that, after each measurement, the probes are rinsed with distilled water or deionized water to remove any traces of the solution being measured, blotted with a scientific wipe to absorb any remaining water, which could dilute the sample and thus alter the reading, and then immersed in a storage solution suitable for the particular probe type. [ 18 ]
In general there are three major categories of pH meters. Benchtop pH meters are often used in laboratories and are used to measure samples which are brought to the pH meter for analysis. Portable, or field pH meters, are handheld pH meters that are used to take the pH of a sample in a field or production site. [ 19 ] In-line or in situ pH meters, also called pH analyzers, are used to measure pH continuously in a process, and can stand-alone, or be connected to a higher level information system for process control. [ 20 ]
pH meters range from simple and inexpensive pen-like devices to complex and expensive laboratory instruments with computer interfaces and several inputs for indicator and temperature measurements to be entered to adjust for the variation in pH caused by temperature. The output can be digital or analog, and the devices can be battery-powered or rely on line power . Some versions use telemetry to connect the electrodes to the voltmeter display device. [ 13 ] : 197–215
Specialty meters and probes are available for use in special applications, such as harsh environments [ 21 ] and biological microenvironments. [ 6 ] There are also holographic pH sensors, which allow pH measurement colorimetrically , making use of the variety of pH indicators that are available. [ 22 ] Additionally, there are commercially available pH meters based on solid state electrodes , rather than conventional glass electrodes. [ 23 ]
The concept of pH was defined in 1909 by S. P. L. Sørensen , and electrodes were used for pH measurement in the 1920s. [ 24 ]
In October 1934, Arnold Orville Beckman registered the first patent for a complete chemical instrument for the measurement of pH, U.S. Patent No. 2,058,761, for his "acidimeter", later renamed the pH meter. Beckman developed the prototype as an assistant professor of chemistry at the California Institute of Technology , when asked to devise a quick and accurate method for measuring the acidity of lemon juice for the California Fruit Growers Exchange ( Sunkist ). [ 25 ] : 131–135
On April 8, 1935, Beckman's renamed National Technical Laboratories focused on the manufacture of scientific instruments, with the Arthur H. Thomas Company as a distributor for its pH meter. [ 25 ] : 131–135 In its first full year of sales, 1936, the company sold 444 pH meters for $60,000 in sales. [ 26 ] In years to come, the company sold millions of the units. [ 27 ] [ 28 ] In 2004 the Beckman pH meter was designated an ACS National Historic Chemical Landmark in recognition of its significance as the first commercially successful electronic pH meter. [ 26 ]
The Radiometer Corporation of Denmark was founded in 1935, and began marketing a pH meter for medical use around 1936, but "the development of automatic pH-meters for industrial purposes was neglected. Instead American instrument makers successfully developed industrial pH-meters with a wide variety of applications, such as in breweries, paper works, alum works, and water treatment systems." [ 24 ]
In the 1940s the electrodes for pH meters were often difficult to make, or unreliable due to brittle glass. Dr. Werner Ingold began to industrialize the production of single-rod measuring cells, a combination of measurement and reference electrode in one construction unit, [ 29 ] which led to broader acceptance in a wide range of industries including pharmaceutical production. [ 30 ]
Beckman marketed a portable "Pocket pH Meter" as early as 1956, but it did not have a digital read-out. [ 31 ] In the 1970s Jenco Electronics of Taiwan designed and manufactured the first portable digital pH meter. This meter was sold under the label of the Cole-Parmer Corporation . [ 32 ]
Specialized manufacturing is required for the electrodes, and details of their design and construction are typically trade secrets. [ 13 ] : 125 However, with purchase of suitable electrodes, a standard multimeter can be used to complete the construction of the pH meter. [ 33 ] However, commercial suppliers offer voltmeter displays that simplify use, including calibration and temperature compensation. [ 7 ] | https://en.wikipedia.org/wiki/PH_meter |
pH partition theory is a theory developed in the early 20th century as an attempt to explain drug bioavailability in humans. It describes the tendency for weak acids to accumulate in basic fluid compartments , and weak bases to accumulate in acidic compartments. The negative charge of deprotonated acids in basic solutions and, conversely, the positive charge state of weak bases in acidic solutions is used to explain this phenomenon as electric charge decreases membrane permeability. [ 1 ] pH partition theory is somewhat useful in explaining the accumulation of weak acids and bases; however, many other factors influence molecular transport in living systems, so it is not a general rule. [ 2 ] [ 1 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PH_partition_theory |
pHydrion is the trademarked name for a popular line of chemical test products, marketed by Micro Essential Laboratory, Inc. , the original manufacturer of Hydrion and pHydrion products. The trademarked pHydrion product line comprises chemical test papers, chemical indicators, chemical test kits, chemical indicator kits , pH indicator pencils , chemical buffers , buffer salts , buffer preservatives , dispensers , color charts, and testing products, for use in testing, detecting, identifying, measuring, and indicating levels of pH , of sanitizers, and of other substances. | https://en.wikipedia.org/wiki/PHydrion |
The PI3K/AKT/mTOR pathway is an intracellular signaling pathway important in regulating the cell cycle . Therefore, it is directly related to cellular quiescence , proliferation , cancer , and longevity. PI3K activation phosphorylates and activates AKT , localizing it in the plasma membrane . [ 1 ] AKT can have a number of downstream effects such as activating CREB , [ 2 ] inhibiting p27 , [ 3 ] localizing FOXO in the cytoplasm, [ 3 ] activating PtdIns -3ps, [ 4 ] and activating mTOR [ 3 ] which can affect transcription of p70 or 4EBP1. [ 3 ] There are many known factors that enhance the PI3K/AKT pathway including EGF , [ 5 ] shh , [ 2 ] IGF-1 , [ 2 ] insulin , [ 3 ] and calmodulin . [ 4 ] Both leptin and insulin recruit PI3K signalling for metabolic regulation. [ 6 ] The pathway is antagonized by various factors including PTEN , [ 7 ] GSK3B , [ 2 ] and HB9. [ 5 ]
In many cancers, this pathway is overactive, thus reducing apoptosis and allowing proliferation. This pathway is necessary, however, to promote growth and proliferation over differentiation of adult stem cells , neural stem cells specifically. [ 2 ] It is the difficulty in finding an appropriate amount of proliferation versus differentiation that researchers are trying to determine in order to utilize this balance in the development of various therapies. [ 2 ] Additionally, this pathway has been found to be a necessary component in neural long term potentiation . [ 4 ] [ 8 ]
Neural stem cells (NSCs) in the brain must find a balance between maintaining their multipotency by self renewing and proliferating as opposed to differentiating and becoming quiescent. The PI3K/AKT pathway is crucial in this decision making process. NSCs are able to sense and respond to changes in the brain or throughout the organism. When blood glucose levels are elevated acutely, insulin is released from the pancreas. Activation of insulin receptors activates the PI3K/AKT pathway, which promotes proliferation. [ 3 ] In this way, when there is high glucose and abundant energy in the organism, the PI3K/AKT pathway is activated and NSCs tend to proliferate. When there are low amounts of available energy, the PI3K/AKT pathway is less active and cells adopt a quiescent state.
This occurs, in part, when AKT phosphorylates FOXO, keeping FOXO in the cytoplasm. [ 3 ] FOXO, when dephosphorylated, can enter the nucleus and work as a transcription factor to promote the expression of various tumor suppressors such as p27 and p21 . [ 3 ] These tumor suppressors push the NSC to enter quiescence. FOXO knockouts lose the ability for cells to enter a quiescent state as well as cells losing their neural stem cell character, possibly entering a cancer like state. [ 3 ]
The PI3K/AKT pathway has a natural inhibitor called Phosphatase and tensin homolog ( PTEN ) whose function is to limit proliferation in cells, helping to prevent cancer. Knocking out PTEN has been shown to increase the mass of the brain because of the unregulated proliferation that occurs. [ 3 ] PTEN works by dephosphorylating PIP3 to PIP2 which limits AKTs ability to bind to the membrane, decreasing its activity. PTEN deficiencies can be compensated downstream to rescue differentiation or quiescence. Knocking out PTEN is not as serious as knocking out FOXO for this reason. [ 3 ]
The cAMP response element CREB is closely related to the cell decision to proliferate or not. Cells that are forced to overexpress AKT increase the amount of CREB and proliferation compared to wild type cells. These cells also express less glial and neural cell markers such as GFAP or β-tubulin . [ 2 ] This is because CREB is a transcription factor that influences the transcription of cyclin A which promotes proliferation. [ 2 ] For example, adult hippocampal neural progenitor cells need abeyance as stem cells to differentiate later. This is regulated by Shh . Shh works through a slow protein synthesis dependence, which stimulates other cascades that work synergistically with the PI3K/AKT pathway to induce proliferation. Then, the other pathway can be turned off and the effects of the PI3K/AKT pathway become insufficient in stopping differentiation. [ 2 ] The specifics of this pathway are unknown.
PI3K / AKT / mTOR pathway is a central regulator of ovarian cancer . PIM kinases are over expressed in many types of cancers and they also contribute to the regulation of ovarian cancer . PIM are directly and indirectly found to activate mTOR and its upstream effectors like AKT. Besides, PIM kinases can cause phosphorylation of IRS, which can alter PI3K. This indicates the close interaction of PIM with PI3K/ AKT/mTOR cascade and its components. Similarly, AKT has also been reported to perform the BAD phosphorylation in OC cells. PIM and the PI3K/AKT/mTOR network both can inhibit the P21 and P27 expressions in OC cells. These data suggest a strong possibility of interaction and relevance of PIM kinases and the PI3K/AKT/mTOR network in the regulation of ovarian cancer. [ 9 ] However, targeting this pathway in ovarian cancer has been challenging with several trials failing to achieve sufficient clinical benefit. [ 10 ] [ 11 ]
In many kinds of breast cancer, aberrations in the PI3K/AKT/mTOR pathway are the most common genomic abnormalities. The most common known aberrations include the PIK3CA gene mutation and the loss-of-function mutations or epigenetic silencing of PTEN. [ 12 ] The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway is activated in approximately 30–40% of BC cases. In triple-negative breast cancer (TNBC), oncogenic activation of the PI3K/AKT/mTOR pathway can happen as a function of overexpression of upstream regulators like EGFR , activating mutations of PIK3CA , loss of function or expression of phosphatase and tensin homolog (PTEN), and the proline-rich inositol polyphosphatase, which are downregulators of PI3K. [ 13 ] It is consistent with the hypothesis that PI3K inhibitors can overcome resistance to endocrine therapy when it is acquired [ citation needed ]
PIK3CA frequently have gain of function mutations in urothelial cancer. [ 14 ] Similar to PI3Ka, PI3Kb is expressed in many different cells, and it is mainly involved in the activation of platelets and development of thrombotic diseases. Studies have shown that PI3Kb contribute to tumor proliferation as well. Specifically, it has an important role in tumorigenesis in PTEN-negative cancers. [ 15 ] It's reported that interfering with the gene for PI3Kb might be a therapeutic approach for high-risk bladder cancers with mutant PTEN and E-cadherin loss. Specific isoform inhibitors to PI3Kb is a potential treatment for PTEN-deficient cancers. [ 16 ]
The PI3K pathway is a major source of drug resistance in prostate cancer . This is particularly true in castration-resistant prostate cancer, where tumours become resistant to androgen-deprivation therapy , which block the tumours ability to utilise the hormone androgen to grow. [ 17 ] This is due to a complex feedback mechanism which exists between the androgen receptor and the PI3K pathway. [ 18 ] As in other tumour types, mutations in key genes of this pathway can lead to hyperactivation of this pathway, for example in PIK3CA, [ 19 ] [ 20 ] Increases in the copy number of PIK3CA and increased mRNA expression also increases pathway activation in prostate cancers among others. [ 21 ] Gains in the nearby genetic region 3q26.31-32 have been shown to co-occur with a number of nearby PI3K family members including PIK3CA , PIK3CB and PIK3R4 , leading to transcriptional changes in PIK3C2G , PIK3CA, PIK3CB, PIK3R4 as well as pathways associated with cell proliferation . [ 22 ] These large spanning gains associate with Gleason grade , tumour stage , lymph node metastasis and other aggressive clinical features. [ 22 ] In patients treated with PI3K inhibitors, those with copy number gains in PIK3CB appear to have increased drug susceptibility. [ 23 ]
PI3K inhibitors may overcome drug resistance and improve advanced breast cancer (ABC) outcomes. [ 12 ] Different PI3K inhibitors exhibit different effect against various PI3K types. Class IA pan-PI3K inhibitors have been more extensively studied than isoform specific inhibitors; Pictilisib is another pan-PI3K inhibitor with greater subunitα-inhibitor activity than buparlisib. [ 13 ] Idelalisib is the first PI3K inhibitor approved by the US Food and Drug Administration and is utilized in the treatment of relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma and follicular lymphoma. Copanlisib is approved for relapsed follicular lymphoma in patients who have received at least two prior systemic therapies. [ 24 ] Duvelisib is approved for relapsed/refractory chronic lymphocytic leukemia /small lymphocytic lymphoma (CLL/SLL), and relapsed/refractory follicular lymphoma, both indications for patients who have received at least two prior therapies. [ 25 ]
AKT is downstream to PI3K and is inhibited by Ipatasertib. [ 13 ] Akt is an AGC-family kinase and a central, integral signaling node of the PAM pathway. There are three Akt isozymes, Akt1, Akt2 and Akt3. Small-molecule inhibitors of Akt1 could be especially useful to target tumors with a high prevalence of Akt1 E17K activating mutations, which is observed in 4–6% of breast cancers and 1–2% of colorectal cancer. [ 26 ] Research towards Akt inhibition has focused on inhibition of two distinct binding sites:
Allosteric Akt inhibitors, highlighted by MK-2206, have been extensively evaluated in a clinical setting; Recently, additional allosteric Akt inhibitors have been identified. ARQ-092, is a potent pan-Akt inhibitor which can inhibit tumor growth preclinically and is currently in Phase I clinical studies. [ 26 ]
There is significant correlation of phosphorylated mTOR with the survival rate for patients with stages I and II TNBC. A patient-derived xenograft TNBC model testing the mTOR inhibitor rapamycin showed 77–99% tumor-growth inhibition, which is significantly more than has been seen with doxorubicin; protein phosphorylation studies indicated that constitutive activation of the mTOR pathway decreased with treatment. [ 13 ]
It has been hypothesized that blockage of the PI3K/AKT/mTOR pathway can lead to increased antitumor activity in TNBC. Preclinical data have shown that the combination of compounds targeting different cognate molecules in the PI3K/AKT/mTOR pathway leads to synergistic activity. On the basis of these findings, new compounds targeting different components of the PI3K/AKT/mTOR pathway simultaneously continue to be developed. For example, gedatolisib inhibits mutant forms of PI3K-α with elevated kinase activity at concentrations equivalent to the IC50 for wild-type PI3K-α. PI3K-β, -δ and -γ isoforms were inhibited by gedatolisib at concentrations approximately 10-fold higher than those observed for PI3K-α. [ 13 ] Another advantage of simultaneously targeting PI3K and mTOR is the ensuing more robust inhibition of receptor tyrosine kinase-positive feedback loops seen with isolated PI3K inhibition. [ 27 ] Gedatolisib is currently under development for the treatment of TNBC, in combination with PTK7 antibody–drug conjugate. Apitolisib (GDC-0980) is a PI3K inhibitor (subunits α, δ, and γ) that also targets mTORC [ 28 ]
There are numerous cell signalling pathways that exhibit cross-talk with the PI3K pathway, potentially allowing cancer cells to escape inhibition of PI3K. [ 29 ] As such, inhibition of the PI3K pathway alongside other targets could offer a synergistic response, such as that seen with PI3K and MEK co-targeted inhibition in lung cancer cells. [ 30 ] More recently, co-targeting the PI3K pathway with PIM kinases has been suggested, with numerous pre-clinical studies suggesting the potential benefit of this approach. [ 31 ] [ 32 ] Development of panels of cell lines that are resistant to inhibition of the PI3K pathway may lead to the identification of future co-targets, and better understanding of which pathways may compensate for loss of PI3K signalling following drug treatment. [ 33 ] Combined PI3K inhibition with more traditional therapies such as chemotherapy may also offer improved response over inhibition of PI3K alone. [ 34 ]
The type of growth factor signaling can effect whether or not NSCs differentiate into motor neurons or not. Priming a media with FGF2 lowers the activity of the PI3K/AKT pathway, which activates GSK3β. This increases expression of HB9. [ 5 ] Directly inhibiting PI3K in NSCs leads to a population of cells that are purely HB9+ and differentiate at an elevated efficiency into motor neurons. Grafting these cells into different parts of rats generates motor neurons regardless of the transplanted cells' microenvironment. [ 5 ] Following injury, neural stem cells enter a repair phase and express high levels of PI3K to enhance proliferation. This is better for survival of the neurons as a whole but is at the expense of generating motor neurons. Therefore, it can be difficult for injured motor neurons to recover their ability. [ 5 ] It is the purpose of modern research to generate neural stem cells that can proliferate but still differentiate into motor neurons. Lowering the effect of the PI3K pathway and increasing the effect of GSK3β and HB9 in NSCs is a potential way of generating these cells. [ 5 ]
PTEN is a tumor suppressor that inhibits the PI3K/AKT pathway. PTEN inhibitors, such as bisperoxovanadium, [ 35 ] can enhance the PI3K/AKT pathway to promote cell migration, [ 36 ] survival [ 37 ] and proliferation. [ 7 ] While there are some concerns over possible cell cycle dysregulation and tumorigenesis, temporary and moderate PTEN inhibition may confer neuroprotection against traumatic brain injury [ 38 ] and improve CNS recovery by reestablishing lost connections by axonogenesis . [ 7 ] Medicinal value of PTEN inhibitors remains to be determined. [ citation needed ]
In order for long-term potentiation (LTP) to occur, there must be stimulation of NMDA receptors , which causes AMPA receptors to be inserted postsynaptically . PI3K binds to AMPA receptors in a conserved region to orient the receptors in the membrane, specifically at the GluR subunit. [ 4 ] PI3K activity increases in response to calcium ions and CaM . Additionally, AKT localizes PtdIns-3Ps in the post synapse, which recruits docking proteins such as tSNARE and Vam7. This directly leads to the docking of AMPA in the post synapse. [ 4 ] mTOR activated p70S6K and inactivated 4EBP1 which changes gene expression to allow LTP to occur. [ 8 ] Long-term fear conditioning training was affected in rats but there was no effect in short term conditioning. Specifically, amygdala fear conditioning was lost. This is a type of trace conditioning which is a form of learning that requires association of a conditioned stimulus with an unconditioned stimulus. This effect was lost in PI3K knockdowns and increased in PI3K overexpressions. [ 8 ]
In addition to its role in synaptic plasticity described above, PI3K-AKT signaling pathway also has an important role in brain growth, which is altered when PI3K signaling is disturbed. For example, intracranial volume is also associated with this pathway, in particular with AKT3 intronic variants. [ 39 ] Thyroid hormone was originally identified as the primary regulator of brain growth and cognition, and recent evidence has demonstrated that thyroid hormone produces some of its effects on the maturation and plasticity of synapses through PI3K. [ 40 ] | https://en.wikipedia.org/wiki/PI3K/AKT/mTOR_pathway |
Phosphorus pentaiodide is a hypothetical inorganic compound with formula P I 5 . The existence of this compound has been claimed intermittently since the early 1900s. [ 2 ] The claim is disputed: "The pentaiodide does not exist (except perhaps as PI 3 · I 2 , but certainly not as [PI 4 ] + I − ...)". [ 3 ]
Phosphorus pentaiodide was reported to be a brown-black crystalline solid melting at 41 °C produced by the reaction of lithium iodide and phosphorus pentachloride in methyl iodide , however, this claim is disputed and probably generated a mixture of phosphorus triiodide and iodine . [ 1 ] [ 4 ]
Although phosphorus pentaiodide has been claimed to exist in the form of [PI 4 ] + I − (tetraiodophosphonium iodide), experimental and theoretical data refutes this claim. [ 5 ] [ 1 ]
Unlike the elusive PI 5 , the [PI 4 ] + cation (tetraiodophosphonium cation) is widely known. This cation is known with the anions tetraiodoaluminate [AlI 4 ] − , hexafluoroarsenate [AsF 6 ] − , hexafluoroantimonate [SbF 6 ] − and tetraiodogallate [GaI 4 ] − . [ 4 ] [ 5 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it .
This article about theoretical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PI5 |
PICMG 1.1 is a PICMG specification that defines how PCI to PCI bridging is accomplished in PICMG 1.0 systems. [ 1 ]
Adopted : 5/25/1995
Current Revision : 1.1
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PICMG_1.1 |
PICMG 2.11 is a specification by PICMG that defines the electrical and mechanical requirements relating to plug-in power modules in CompactPCI systems. [ 1 ]
Adopted : 10/1/1999
Current Revision : 1.0
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PICMG_2.11 |
PICMG 2.2 is a specification by PICMG that standardizes pin assignments for PICMG 2.0 CompactPCI to include VME64 Extensions. [ 1 ]
Adopted : 9/9/1998
Current Revision : 1.0
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PICMG_2.2 |
PICMG 2.4 is a specification by PICMG that standardizes user IO pin mappings from ANSI / VITA standard IP sites to J3/P3, J4/P4, and J5/P5 on a CompactPCI backplane. [ 1 ]
Adopted: 9 September 1998
Current revision: 1.0
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PICMG_2.4 |
PICRUSt [ 1 ] is a bioinformatics software package. The name is an abbreviation for Phylogenetic Investigation of Communities by Reconstruction of Unobserved States.
The tool serves in the field of metagenomic analysis where it allows inference of the functional profile of a microbial community based on marker gene survey along one or more samples. In essence, PICRUSt takes a user supplied operational taxonomic unit table (typically referred to as an OTU table), representing the marker gene sequences (most commonly a 16S cluster ) accompanied with its relative abundance in each of the samples. The output of PICRUSt is a sample by functional-gene-count matrix, telling the count of each functional-gene in each of the samples surveyed. The ability of PICRUSt to estimate the functional-gene profile for a given sample relies on a set of known sequenced genomes . This could also be thought of as an automated alternative to manually researching the gene families likely to be present in organisms whose sequences are found in a 16S ribosomal RNA amplicon library . The below description corresponds to the original version of PICRUSt, but a major update to this tool is currently being developed. [ 2 ]
In an initial preprocessing phase, PICRUSt constructs confidence intervals and point predictions for the number of copies of each gene family in each bacterial and archaeal strain in a reference tree, using organisms with sequenced genomes as a reference. More specifically, for each gene family, PICRUSt maps known gene copy numbers (from complete sequenced genomes) onto a reference tree of life. These gene family copy numbers are treated as continuous traits , and an evolutionary model constructed under the assumption of Brownian Motion . These evolutionary models can be constructed with either Maximum Likelihood , Relaxed Maximum Likelihood or Wagner Parsimony This evolutionary model is then used to predict both a point estimate and a confidence interval for the copy number of microorganisms without sequenced genomes. This 'genome prediction' step produces a large table of bacterial types (specifically operational taxonomic unit or OTUs) vs. gene family copy numbers. This table is distributed to end users. It is important to note that this prediction method is not the same as a nearest neighbor approach (i.e. just looking up the nearest sequenced genome), and was shown to give a small but significant improvement in accuracy over that strategy. However, nearest neighbor prediction is available as an option in PICRUSt.
Notably, while this functionality is typically used for prediction of gene copy numbers in bacteria, it could, in principle, be used for prediction of any other continuous trait given trait data for diverse organisms and a reference phylogeny .
Langille et al. [ 1 ] tested the accuracy of this genome prediction step using leave-one-out cross validation on the input set of sequenced genomes. Additional tests examined sensitivity to errors in phylogenetic inference , lack of genomic data , and the accuracy of the confidence intervals on gene content.
A similar step predicts the copy number of 16S rRNA genes.
When applying PICRUSt to a 16S rRNA gene library, PICRUSt matches reference operational taxonomic units against the tables, and retrieves a predicted 16S rRNA copy number and gene copy number for each gene family. The abundance of each OTU is divided by its predicted copy number (if a bacterium has multiple 16S copies, its apparent abundance in 16S rRNA data will be inflated), and then multiplied by the copy number of the gene family. This gives a prediction for the contribution of each OTU to the overall gene content of the sample (the metagenome ). Finally, these individual contributions are summed together to produce an estimate of the genes present in the metagenome .
Langille et al., 2013 [ 1 ] tested the accuracy of this genome prediction step by using previously reported datasets in which the same biological sample was subjected to 16S rRNA gene amplification and shotgun metagenomics . In these cases, the shotgun metagenomic results were taken as a representation of the 'true' community, and the 16S rRNA gene amplicon libraries fed into PICRUSt to attempt to predict those data. Test datasets included human microbiome samples from the Human Microbiome Project , soil samples, diverse mammalian samples, and samples from the Guerrero Negro microbial mats
Because PICRUSt, and evolutionary comparative genomics in general, depends on sequenced genomes, biological samples from well-studied environments (many sequenced genomes) will be better predicted than poorly studied environments. In order to assess how many genomes are available, PICRUSt optionally allows users to calculate a Nearest Sequenced Taxon Index (NSTI) for their samples. This index reflects the average phylogenetic distance between each 16S rRNA gene sequence in their sample, and a 16S rRNA gene sequence from a fully sequenced genome . In general, the lower the NSTI score, the more accurate PICRUSt's predictions are expected to be. For example, [ 1 ] showed that PICRUSt was much more accurate on diverse soil samples and samples from the Human Microbiome Project than on microbial mat samples from Guerrero Negro , which contained many bacteria without any sequenced relatives.
Okuda et al., 2012 [ 3 ] published a similar method that used a bounded k-Nearest Neighbor approach to predict virtual metagenomes. They validated their approach using 16S rRNA gene sequences extracted from shotgun metagenomes , and compared the predictions of their method against the full metagenome.
CopyRighter, [ 4 ] like PICRUSt, uses evolutionary modeling and phylogenetic trait prediction to estimate 16S rRNA gene sequence copy numbers for each bacterial and archaeal type in a sample, and then uses these estimates to correct estimates of community composition.
PanFP [ 5 ] presented a similar method, but based on genome predictions for each taxonomic group. Benchmarking showed highly similar performance to PICRUSt when compared on the same datasets. One advantage is that all OTUs, not just those in a reference phylogeny table can be used. One disadvantage is that confidence intervals and evolutionary models are not constructed.
PAPRICA [ 6 ] is a metagenome prediction tool based on placing input 16S rRNA gene sequences into a known phylogenetic tree based corresponding to reference genomes. The main prediction output corresponds to Enzyme Commission numbers .
Piphillin [ 7 ] is a tool produced by the company Second Genome that produces metagenome predictions based on nearest-neighbour clustering of input 16S rRNA gene sequences with 16S rRNA gene sequences from reference genomes. There is a web portal for running this tool on the Second Genome website. This tool is under continual development and undergoing validation as summarized in a 2020 publication. [ 8 ]
Tax4Fun [ 9 ] is a similar tool based on linking the 16S ribosomal RNA genes from all KEGG organisms with 16S rRNA gene sequences found in the SILVA ribosomal RNA database . Originally this tool was restricted to 16S rRNA gene sequences found within the SILVA database. However, the latest version of this tool, Tax4Fun2, can be used with OTUs or amplicon sequence variants from any clustering pipeline. | https://en.wikipedia.org/wiki/PICRUSt |
PIPES ( piperazine- N , N ′ -bis(2-ethanesulfonic acid) ) is a frequently used buffering agent in biochemistry . It is an ethanesulfonic acid buffer developed by Good et al. in the 1960s. [ 1 ]
PIPES has two pKa values. One pKa (6.76 at 25 °C) is near the physiological pH which makes it useful in cell culture work. Its effective buffering range is 6.1-7.5 at 25 °C. The second pKa value is at 2.67 with a buffer range of from 1.5-3.5. PIPES has been documented minimizing lipid loss when buffering glutaraldehyde histology in plant and animal tissues . [ 2 ] [ 3 ] Fungal zoospore fixation for fluorescence microscopy and electron microscopy were optimized with a combination of glutaraldehyde and formaldehyde in PIPES buffer. [ 4 ] It has a negligible capacity to bind divalent ions. [ 5 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PIPES |
The PI (or photosynthesis-irradiance ) curve is a graphical representation of the empirical relationship between solar irradiance and photosynthesis . A derivation of the Michaelis–Menten curve, it shows the generally positive correlation between light intensity and photosynthetic rate. It is a plot of photosynthetic rate as a function of light intensity (irradiance).
The PI curve can be applied to terrestrial and marine reactions but is most commonly used to explain ocean-dwelling phytoplankton's photosynthetic response to changes in light intensity. Using this tool to approximate biological productivity is important because phytoplankton contribute ~50% [ 1 ] of total global carbon fixation and are important suppliers to the marine food web.
Within the scientific community, the curve can be referred to as the PI, PE or Light Response Curve. While individual researchers may have their own preferences, all are readily acceptable for use in the literature. Regardless of nomenclature, the photosynthetic rate in question can be described in terms of carbon (C) fixed per unit per time. Since individuals vary in size, it is also useful to normalise C concentration to Chlorophyll a (an important photosynthetic pigment) to account for specific biomass.
As far back as 1905, marine researchers attempted to develop an equation to be used as the standard in establishing the relationship between solar irradiance and photosynthetic production. Several groups had relative success, but in 1976 a comparison study conducted by Alan Jassby and Trevor Platt, researchers at the Bedford Institute of Oceanography in Dartmouth, Nova Scotia, reached a conclusion that solidified the way in which a PI curve is developed. After evaluating the eight most-used equations, Jassby and Platt argued that the PI curve can be best approximated by a hyperbolic tangent function, at least until photoinhibition is reached.
There are two simple derivations of the equation that are commonly used to generate the hyperbolic curve. The first assumes photosynthetic rate increases with increasing light intensity until Pmax is reached and continues to photosynthesize at the maximum rate thereafter.
Both Pmax and the initial slope of the curve, ΔP/ΔI, are species-specific, and are influenced by a variety of factors, such as nutrient concentration, temperature and the physiological capabilities of the individual. Light intensity is influenced by latitudinal position and undergo daily and seasonal fluxes which will also affect the overall photosynthetic capacity of the individual. These three parameters are predictable and can be used to predetermine the general PI curve a population should follow.
As can be seen in the graph, two species can have different responses to the same incremental changes in light intensity. Population A (in blue) has an initial rate higher than that of Population B (in red) and also exhibits a stronger rate change to increased light intensities at lower irradiance. Therefore, Population A will dominate in an environment with lower light availability. Although Population B has a slower photosynthetic response to increases in light intensity its Pmax is higher than that of Population A. This allows for eventual population dominance at greater light intensities. There are many determining factors influencing population success; using the PI curve to elicit predictions of rate flux to environmental changes is useful for monitoring phytoplankton bloom dynamics and ecosystem stability.
The second equation accounts for the phenomenon of photoinhibition . In the upper few meters of the ocean, phytoplankton may be subjected to irradiance levels that damage the chlorophyll-a pigment inside the cell, subsequently decreasing photosynthetic rate. The response curve depicts photoinhibition as a decrease in photosynthetic rate at light intensities stronger than those necessary for achievement of Pmax.
Terms not included in the above equation are:
The hyperbolic response between photosynthesis and irradiance, depicted by the PI curve, is important for assessing phytoplankton population dynamics, which influence many aspects of the marine environment. | https://en.wikipedia.org/wiki/PI_curve |
1T5A , 1ZJH , 3BJF , 3BJT , 3G2G , 3GQY , 3GR4 , 3H6O , 3ME3 , 3SRD , 3SRF , 3SRH , 3U2Z , 4B2D , 4FXF , 4FXJ , 4G1N , 4JPG , 4QG6 , 4QG8 , 4QG9 , 4QGC , 4RPP , 4WJ8 , 4YJ5
5315
18746
ENSG00000067225
ENSMUSG00000032294
P14618
P52480
NM_182470 NM_182471 NM_001316318
NM_001253883 NM_011099
NP_002645 NP_872270 NP_872271
NP_001365798 NP_001365799 NP_001365800 NP_001365801 NP_001392420
Pyruvate kinase isozymes M1/M2 (PKM1/M2), also known as pyruvate kinase muscle isozyme (PKM), pyruvate kinase type K , cytosolic thyroid hormone-binding protein (CTHBP), thyroid hormone-binding protein 1 (THBP1), or opa-interacting protein 3 (OIP3), is an enzyme that in humans is encoded by the PKM2 gene . [ 5 ] [ 6 ] [ 7 ] [ 8 ]
PKM2 is an isoenzyme of the glycolytic enzyme pyruvate kinase . Depending upon the different metabolic functions of the tissues, different isoenzymes of pyruvate kinase are expressed. PKM2 is expressed in some differentiated tissues, such as lung , fat tissue, retina , and pancreatic islets , as well as in all cells with a high rate of nucleic acid synthesis , such as normal proliferating cells, embryonic cells , and especially tumor cells. [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ] [ 15 ]
The discovery of PKM2 began with laboratory observations made by Otto Heinrich Warburg , a German physiologist and Nobel Laureate in Physiology or Medicine in 1931. [ 16 ] [ 17 ] Warburg's experiments show that the cells exhibit dependence on glucose and are capable of fermentation, even under aerobic conditions. These observations are known as the Warburg effect. Subsequent research on the metabolic demands of cancer cells, studies have been directed towards the investigation of specific subtypes of pyruvate kinase, notably M1 and M2.
Two isozymes are encoded by the PKM gene: PKM1 and PKM2. The M-gene consists of 12 exons and 11 introns . PKM1 and PKM2 are different splicing products of the M-gene (exon 9 for PKM1 and exon 10 for PKM2) and solely differ in 23 amino acids within a 56-amino acid stretch (aa 378–434) at their carboxy terminus . [ 18 ] [ 19 ]
Pyruvate kinase catalyzes the last step within glycolysis , the de phosphorylation of phosphoenolpyruvate to pyruvate , and is responsible for net ATP production within the glycolytic sequence. In contrast to mitochondrial respiration , energy regeneration by pyruvate kinase is independent from oxygen supply and allows survival of the organs under hypoxic conditions often found in solid tumors. [ 20 ]
The involvement of this enzyme in a variety of pathways , protein–protein interactions , and nuclear transport suggests its potential to perform multiple nonglycolytic functions with diverse implications, although multidimensional role of this protein is as yet not fully explored. However, a functional role in angiogenesis the so-called process of blood vessel formation by interaction and regulation of Jmjd8 has been shown. [ 21 ] [ 22 ]
The PKM1 isozyme is expressed in organs that are strongly dependent upon a high rate of energy regeneration, such as muscle and brain . [ 23 ] [ 24 ] [ 25 ]
PKM2 is enzyme pyruvate kinase M2 (PKM2) and a transcriptional coactivator of STAT1 responsible for the induction of the protein PDL-1 expression and its regulation in tumor and immune cells. [ 26 ] In the lactate production, the upregulated PKM2 is required and it leads to its contribution in inflammatory response, organ injury and septic death [ 27 ] [ 28 ] [ 29 ] As a consequence, the removal of PKM2 in myeloid cells, administration of anti-PD-L1 or supplementation with recombinant interleukin -1 (IL-7) eases the microbial clearance, inhibits T cell apoptosis, reduce multiple organ dysfunction and reduce septic death in Bmal1-deficient mice. [ 30 ]
PKM2 is a cytosolic enzyme that is associated with other glycolytic enzymes, i.e., hexokinase , glyceraldehyde 3-P dehydrogenase , phosphoglycerate kinase , phosphoglyceromutase , enolase , and lactate dehydrogenase within a so-called glycolytic enzyme complex. [ 25 ] [ 31 ] [ 32 ] [ 33 ]
However, PKM2 contains an inducible nuclear localization signal in its C-terminal domain. The role of PKM2 within the nucleus is complex, since pro-proliferative but also pro- apoptotic stimuli have been described. On the one hand, nuclear PKM2 was found to participate in the phosphorylation of histone 1 by direct phosphate transfer from PEP to histone 1. On the other hand, nuclear translocation of PKM2 induced by a somatostatin analogue, H 2 O 2 , or UV light has been linked with caspase -independent programmed cell death. [ 34 ] [ 35 ] [ 36 ]
PKM2 is expressed in most human tumors. [ 11 ] [ 14 ] [ 15 ] Initially, a switch from PKM1 to PKM2 expression during tumorigenesis was discussed. [ 37 ] These conclusions, however, were the result of misinterpretation of western blots that had used PKM1-expressing mouse muscle as the sole non-cancer tissue. In clinical cancer samples, solely an up-regulation of PKM2, but no cancer specificity, could be confirmed. [ 38 ]
In contrast to the closely homologous PKM1, which always occurs in a highly active tetrameric form and which is not allosterically regulated, PKM2 may occur in a tetrameric form but also in a dimeric form. The tetrameric form of PKM2 has a high affinity to its substrate phosphoenolpyruvate (PEP), and is highly active at physiological PEP concentrations. When PKM2 is mainly in the highly active tetrameric form, which is the case in differentiated tissues and most normal proliferating cells, glucose is converted to pyruvate under the production of energy. Meanwhile, the dimeric form of PKM2 is characterized by a low affinity to its substrate PEP and is nearly inactive at physiological PEP concentrations. Dimeric PKM2 produces little to no ATP in the conversion of PEP to pyruvate, making the net yield of ATP zero for glycolysis. [ 39 ] When PKM2 is mainly in the less active dimeric form, which is the case in tumor cells, all glycolytic intermediates above pyruvate kinase accumulate and are channelled into synthetic processes, which branch off from glycolytic intermediates such as nucleic acid-, phospholipid-, and amino acid synthesis. [ 23 ] [ 24 ] [ 25 ] Nucleic acids , phospholipids , and amino acids are important cell building-blocks, which are greatly needed by highly proliferating cells, such as tumor cells.
Due to the key position of pyruvate kinase within glycolysis, the tetramer:dimer ratio of PKM2 determines whether glucose carbons are converted to pyruvate and lactate under the production of energy (tetrameric form) or channelled into synthetic processes (dimeric form). [ 23 ] [ 24 ] [ 25 ] However, even if PKM2 activity is low leading to the diversion of upstream intermediates to synthetic processes, pyruvate and lactate will still be made using carbon atoms from glucose and other metabolites through 86 pathways bypassing pyruvate kinase . [ 40 ] These pyruvate kinase bypassing pathways are different from those participating in gluconeogenesis . Interestingly, many of the pyruvate kinase bypassing pathways use metabolites that transit through mitochondria , highlighting the importance of mitochondria in cancer metabolism irrespective of oxidative phosphorylation .
In tumor cells, PKM2 is mainly in the dimeric form and has, therefore, been termed Tumor M2-PK . The quantification of Tumor M2-PK in plasma and stool is a tool for early detection of tumors and follow-up studies during therapy. The dimerization of PKM2 in tumor cells is induced by direct interaction of PKM2 with different oncoproteins (pp60v-src, HPV-16 E7, and A-Raf). [ 31 ] [ 32 ] [ 41 ] [ 42 ] [ 43 ] The physiological function of the interaction between PKM2 and HERC1 as well as between PKM2 and PKCdelta is unknown). [ 44 ] [ 45 ] Due to the essential role of PKM2 in aerobic glycolysis (The Warburg effect) which is a dominant metabolic pathway used by cancer cells. [ 26 ] Its overcome in this pathway in macrophages may lead to better outcome in experimental sepsis. [ 46 ] [ 47 ] [ 48 ] Thus, PKM2 is a regulator of LPS- and tumor-induced PD-L1 expression on macrophages and dendritic cells as well as tumor cells. [ 26 ]
Studies involving the use of PKM2 activators have looked at promoting the conversion of dimeric PKM2 to its tetrameric form, hindering the growth of cancer cells. [ 49 ] Furthermore, concurrent research is centered on targeting the tetrameric form of PKM2 with small-molecule activators, such as TEPP-46 and DASA-58, to increase its resistance to inhibition. [ 50 ]
However, the tetramer:dimer ratio of PKM2 is not stationary value. High levels of the glycolytic intermediate fructose 1,6-bisphosphate induce the re-association of the dimeric form of PKM2 to the tetrameric form. As a consequence, glucose is converted to pyruvate and lactate with the production of energy until fructose 1,6-bisphosphate levels drop below a critical value to allow dissociation to the dimeric form. This regulation is termed metabolic budget system . [ 24 ] [ 25 ] [ 51 ] Another activator of PKM2 is the amino acid serine . [ 24 ] The thyroid hormone 3,3´,5-triiodi-L-thyronine ( T3 ) binds to the monomeric form of PKM2 and prevents its association to the tetrameric form. [ 52 ]
In tumor cells, the increased rate of lactate production in the presence of oxygen is termed the Warburg effect . Genetic manipulation of cancer cells so that they produce adult PKM1 instead of PKM2 reverses the Warburg effect and reduces the growth rate of these modified cancer cells. [ 37 ] Accordingly, cotransfection of NIH 3T3 cells with gag-A-Raf and a kinase dead mutant of PKM2 reduced colony whereas cotransfection with gag-A-Raf and wild type PKM2 led to a doubling of focus formation. [ 53 ]
The dimeric form of PKM2 has been observed to have protein kinase activity in tumor cells. It is able to bind to and phosphorylate the histone H3 of chromatin in cancer cells, thereby having a role in the regulation of gene expression. [ 54 ] This modification of histone H3 and the resulting involvement in gene expression regulation can be a cause of tumor cell proliferation. [ 54 ]
The pyruvate kinase activity of PKM2 can be promoted by SAICAR (succinylaminoimidazolecarboxamide ribose-5′-phosphate), an intermediate in purine biosynthesis. In cancer cells, glucose starvation leads to a rise in SAICAR levels and the subsequent stimulation of pyruvate kinase activity of PKM2. This allows for the completion of the glycolytic pathway to produce pyruvate and, therefore, survival under glucose deprivation. [ 55 ] In addition, an abundance of SAICAR can modify glucose absorption and lactate production in cancer cells. [ 55 ] However, it has been shown that SAICAR binding also sufficiently stimulates the protein kinase activity of PKM2 in tumor cells. [ 56 ] In turn, the SAICAR-PKM2 complex can potentially phosphorylate a number of other protein kinases using PEP as the phosphate donor. Many of these proteins contribute to the regulation of cancer cell proliferation. Specifically, PKM2 can be a component in mitogen-activated protein kinase (MAPK) signaling, which is associated with increased cell proliferation if functioning improperly. This provides a potential link between SAICAR-activated PKM2 and cancer cell growth. [ 56 ]
Two missense mutations , H391Y and K422R, of PKM2 were found in cells from Bloom syndrome patients prone to developing cancer. Results show that, despite the presence of mutations in the inter-subunit contact domain, the K422R and H391Y mutant proteins maintained their homotetrameric structure, similar to the wild-type protein, but showed a loss of activity of 75 and 20%, respectively. H391Y showed a 6-fold increase in affinity for its substrate phosphoenolpyruvate and behaved like a non-allosteric protein with compromised cooperative binding . However, the affinity for phosphoenolpyruvate was lost significantly in K422R. Unlike K422R, H391Y showed enhanced thermal stability, stability over a range of pH values, a lesser effect of the allosteric inhibitor Phe, and resistance toward structural alteration upon binding of the activator (fructose 1,6-bisphosphate) and inhibitor (Phe). Both mutants showed a slight shift in the pH optimum from 7.4 to 7.0. [ 57 ] The co-expression of homotetrameric wild type and mutant PKM2 in the cellular milieu resulting in the interaction between the two at the monomer level was substantiated further by in vitro experiments. The cross-monomer interaction significantly altered the oligomeric state of PKM2 by favoring dimerisation and heterotetramerization. In silico study provided an added support in showing that hetero-oligomerization was energetically favorable. The hetero-oligomeric populations of PKM2 showed altered activity and affinity, and their expression resulted in an increased growth rate of Escherichia coli as well as mammalian cells, along with an increased rate of polyploidy . These features are known to be essential to tumor progression. [ 58 ]
Further, cells stably expressing exogenous wild- or mutant-PKM2 (K422R or H391Y) or co-expressing both wild and mutant (PKM2-K422R or PKM2-H391Y), were assessed for cancer metabolism and tumorigenic potential. Cells co-expressing PKM2 and mutant (K422R or H391Y) showed significantly aggressive cancer metabolism, compared to cells expressing either wild or mutant PKM2 independently. A similar trend was observed for oxidative endurance, tumorigenic potential, cellular proliferation and tumor growth. These observations signify the dominant negative nature of these mutations. Remarkably, PKM2-H391Y co-expressed cells showed a maximal effect on all the studied parameters. Such a dominant negative impaired function of PKM2 in tumor development is not known; also evidencing for the first time the possible predisposition of BS patients with impaired PKM2 activity to cancer, and the importance of studying genetic variations in PKM2 in future to understand their relevance in cancer in general. [ 59 ]
Cancer cells are characterized by a reprogramming of energy metabolism. Over the last decade, understanding of the metabolic changes that occur in cancer has increased dramatically, and there is great interest in targeting metabolism for cancer therapy. PKM2 plays a key role in modulating glucose metabolism to support cell proliferation. PKM2, like other PK isoforms, catalyzes the last energy-generating step in glycolysis, but is unique in its capacity to be regulated. PKM2 is regulated on several cellular levels, including gene expression, alternative splicing and post-translational modification . In addition, PKM2 is regulated by key metabolic intermediates and interacts with more than twenty different proteins. Hence, this isoenzyme is an important regulator of glycolysis and additional functions in other novel roles that have recently emerged. Recent evidence indicates that intervening in the complex regulatory network of PKM2 has severe consequences on tumor cell proliferation, indicating the potential of this enzyme as a target for tumor therapy. [ 60 ]
With the yeast two-hybrid system, gonococcal Opa proteins were found to interact with PKM2. The results suggest that direct molecular interaction with the host metabolic enzyme PKM2 is required for the acquisition of pyruvate and for gonococcal growth and survival. [ 61 ]
Click on genes, proteins and metabolites below to link to respective articles. [ § 1 ] | https://en.wikipedia.org/wiki/PKM2 |
Proximity ligation-assisted chromatin immunoprecipitation sequencing (PLAC-seq) is a chromatin conformation capture (3C)-based technique to detect and quantify genomic chromatin structure from a protein-centric approach. [ 1 ] PLAC-seq combines in situ Hi-C and chromatin immunoprecipitation (ChIP) , which allows for the identification of long-range chromatin interactions at a high resolution with low sequencing costs. [ 1 ] Mapping long-range 3-dimensional(3D) chromatin interactions is important in identifying transcription enhancers and non-coding variants that can be linked to human diseases. [ 2 ]
Different 3C-based techniques have been used to study the higher-order 3D chromatin structure, and it has been combined with high-throughput sequencing to determine the chromatin structure on a genome-wide level. [ 3 ] Hi-C is one of the most widely used 3C-based techniques because it allows for high-resolution (kilobase-scale) genome-topology identification. However, it requires billions of sequencing reads which has limited its application. [ 2 ] Another commonly used 3C-based technique is chromatin interaction analysis by paired-end tag sequencing (ChiA-PET) . [ 2 ] ChiA-PET can identify long-range interactions of transcription promoters and enhancers at a high resolution but requires millions of cells. [ 2 ]
PLAC-seq alleviates these issues by using in situ Hi-C, which creates long-range DNA contacts in situ in the nucleus before lysis. [ 3 ] Unlike ChiA-PET which performs ChIP and proximity ligation after chromatin shearing, performing proximity ligation in the nuclei first prevents large disruptions of protein/DNA complexes. [ 2 ] This decreases false-positive interactions and improves DNA contact capture efficiency, meaning that PLAC-seq is more accurate and requires fewer cells. [ 1 ]
PLAC-seq was developed in 2016 [ 2 ] and an almost identical technique called HiChIP was also developed in the same year. [ 3 ] Both methods combine in situ Hi-C and ChIP but have different library preparation methods. [ 1 ] While PLAC-seq uses biotin pull-down followed by end-repair, adapter ligation, and PCR , HiChIP uses Tn5 tagmentation, biotin pull-down, and PCR. [ 1 ] However, both techniques can use the same quality control and data analysis techniques. [ 1 ]
Different computation software tools can be used to analyze the data from PLAC-seq, for example, Fit-Hi-C, [ 4 ] HiCCUPS, [ 5 ] Mango, [ 6 ] Hichipper, [ 7 ] MAPS, [ 8 ] and FitHiChIP. [ 9 ] Many of the earlier software tools were developed for other 3C-based technologies and were not optimized for PLAC-seq/HiChIP data. Fit-Hi-C and HiCCUPS, both developed in 2014, were mainly developed for Hi-C data, and utilize a matrix-balancing-based normalization approach. [ 4 ] [ 5 ] Mango was developed in 2015, and is mainly used for ChIA-PET data, but has high false-positive rates in analyzing PLAC-seq/HiChIP data due to the different biases. [ 6 ] [ 8 ] Hichipper was developed in 2018 to alleviate this issue and introduced a bias -correcting algorithm, but it still has difficulties identifying protein interactions between protein binding and non-protein binding regions on the chromosome. [ 7 ] [ 8 ] MAPS and FitHiChIP were developed in 2019 as a PLAC-seq/HiChIP-specific analysis pipeline, and are generally thought to be more effective than the existing models to analyze PLAC-seq/HiChIp data. [ 8 ] [ 9 ]
The general workflow of PLAC-seq involves cell harvesting and crosslinking , in situ digestion and proximity ligation, ChIP, library construction, sequencing, and data analysis. The first step of PLAC-seq includes the preparation and crosslinking of cell and tissue samples, which typically begins with cell collection through centrifugation . The next step involves the use of a DNA crosslinking agent such as formaldehyde (HCOH) followed by the addition of glycine to stop the crosslinking reaction. The cross-linked cells can then be pelleted by centrifugation and either stored at -80 or used in the next step of the procedure. In situ digestion involves cell lysis with the use of a lysis buffer followed by digestion with a restriction enzyme MboI. This step allows for uniform digestion of genetic material while keeping the crosslinked regions of the chromosome intact. After inactivation of the digestion reaction, dNTPs and biotin are added in order to repair overhangs and mark the DNA for pull down respectively. In situ proximity ligation occurs when the biotinylated ends of the crosslinked DNA are ligated with each other. Chromatin fragmentation by sonication allows for the shearing of non-crosslinked fragments of DNA. This is followed by immunoprecipitation of biotinylated DNA through the use of antibody -coated beads. The DNA is then reverse-crosslinked and purified using column-based DNA purification or phenol-chloroform extraction . The library construction step first involves the pull-down of biotinylated DNA and the addition of sequencing adapters. The cycle number for amplification needs to be determined prior to the final amplification and library purification. Data analysis of PLAC-seq sequencing data can be carried out in multiple ways, however, the common methods involve the use of Fit-Hi-C, [ 4 ] FitHiChIP, [ 9 ] and MAPS. [ 8 ] Data analysis involves mapping to a reference genome , using software tools such as Hichipper [ 7 ] to identify peaks, and downstream analysis involving peak comparison and functional enrichment analysis. [ 8 ] The resulting data can also be integrated with other genomic data such as Hi-C or RNA-seq in order to identify potential regulatory networks.
PLAC-seq was developed to map and analyze long-range chromatin interactions. These interactions have important implications when it comes to the transcriptional regulation of genes. [ 10 ]
One challenge for mammalian cells is fitting around two meters of genetic material into a nucleus that is around a few microns in diameter, and at the same time organizing the genetic material to be able to access and use the genetic and epigenetic information. To do this, DNA is compacted around histone octamers into 2D structures, and then further packaged into 3D compartments by various mechanisms such as cis -regulatory interactions and repressive interactions. Therefore, chromosomal regions distant in 2D may have intra- and interchromosomal long-range interactions in 3D. These 3D structures are involved in the induction and repression of genes that have biological implications on basic cell functions such as cell cycle , replication , and development. Aberrant 3D structures have roles in the development of diseases and abnormalities such as cancer . [ 11 ] This can involve interactions between promoters and terminators /enhancers through the formation of long-range chromatin loops. [ 12 ] [ 13 ]
PLAC-seq has been utilized to study H3K4me3 and H3K27ac PLACE (PLAC-Enriched) interactions. [ 2 ] It has also been used to call for significant H3K4me3-mediated chromatin interactions, thereby allowing for the identification of differential epigenetic modification in different cell types such as those found in the developing human cortex . [ 14 ]
Advantages: Compared to ChIA-PET, PLAC-seq requires significantly less amount of starting biological material. [ 1 ] With shearing being one of the first steps in ChIA-PET, this leads to the disruption of protein and DNA complexes. PLAC-seq avoids this by having the crosslinking reaction precede the shearing process. Furthermore, PLAC-seq requires fewer sequencing reads than Hi-C. [ 1 ] While ChIA-PET requires 100 million starting cells, PLAC-seq only requires 5 million cells. [ 2 ] Even with 20-fold fewer cells, PLAC-seq was able to produce more reads (175 million) with a fewer PCR duplication rate (33%) than ChIA-PET (16 million, and 44% respectively). [ 2 ] PLAC-seq was also nearly 100 times more cost-effective than ChIA-PET. [ 1 ]
Disadvantages: While many of the 3C-based techniques have different biases from the protocols, PLAC-seq (and HiChIP) data have biases from immunoprecipitation efficiencies that need to be corrected for in the computational step. [ 15 ] Effective ways of reducing and/or removing the different biases in 3C-based technologies is still being studied. [ 15 ] | https://en.wikipedia.org/wiki/PLAC-Seq |
PLATO ( P ackage for L inear-combination of AT omic O rbitals) is a suite of programs for electronic structure calculations. It receives its name from the choice of basis set (atomic orbitals) used to expand the electronic wavefunctions.
PLATO is a code, written in C, for the efficient modelling of materials. It is a tight binding code (both orthogonal and non-orthogonal), allowing for multipole charges and electron spin. It also contains Density Functional Theory programs for building tight binding models. The Density Functional Tight Binding program can be applied to systems with periodic boundary conditions in three dimension ( crystals ), as well as clusters and molecules . [ 1 ] [ 2 ] [ 3 ] [ 4 ]
How PLATO used to perform Density Functional Theory calculations (no longer available) is summarized in several papers: [ 5 ] [ 6 ] . [ 7 ] The way it performs tight binding is summarized in the following papers [ 8 ] [ 9 ]
Some examples of the way it has been used are listed below. | https://en.wikipedia.org/wiki/PLATO_(computational_chemistry) |
PLAnetary Transits and Oscillations of stars ( PLATO ) is a space telescope under development by the European Space Agency for launch in 2026. [ 4 ] It is the third medium-class mission in ESA's Cosmic Vision programme and is named after the influential Greek philosopher Plato .
The mission goals are to search for planetary transits across up to one million stars, and to discover and characterize rocky extrasolar planets around yellow dwarf stars (like the Sun ), subgiant stars, and red dwarf stars. The emphasis of the mission is on Earth-like planets in the habitable zone around Sun-like stars where water can exist in a liquid state. [ 5 ] A secondary objective of the mission is to study stellar oscillations or seismic activity in stars to measure stellar masses and evolution and enable the precise characterization of the planet host star, including its age. [ 6 ]
PLATO is an acronym, but also the name of a philosopher in Classical Greece ; Plato (428–348 BC ) was looking for a physical law accounting for the orbit of planets (errant stars) and able to satisfy the philosopher's needs for "uniformity" and "regularity". [ 7 ]
The PLATO Mission Consortium (PMC), led by Prof. Heike Rauer at the German Aerospace Center (DLR) Institute of Planetary Research, is responsible for part of the payload and major contributions to the science operations. The Cameras are built by an international team from Italy, Switzerland and Sweden and coordinated by Isabella Pagano at INAF ( Istituto Nazionale di Astrofisica ). The Telescope Optical Unit development is funded by the Italian Space Agency , the Swiss Space Office and the Swedish National Space Board . [ 3 ] The PMC Science Management (PSM), composed of more than 500 experts, is coordinated by Prof. Don Pollacco of the University of Warwick and provides expertise for:
The objective is the detection of terrestrial exoplanets up to the habitable zone of solar-type stars and the characterization of their bulk properties needed to determine their habitability . [ 1 ] [ 5 ] To achieve this objective, the mission has these goals:
PLATO will differ from the CoRoT , TESS , CHEOPS , and Kepler space telescopes in that it will study relatively bright stars (between magnitudes 4 and 11), enabling a more accurate determination of planetary parameters, and making it easier to confirm planets and measure their masses using follow-up radial velocity measurements on ground-based telescopes. Its dwell time will be longer than that of the TESS NASA mission, making it sensitive to longer-period planets.
The PLATO payload is based on a multi-telescope approach, involving 26 cameras in total: 24 "normal" cameras organized in 4 groups, and 2 "fast" cameras for bright stars. [ 1 ] The 24 "normal" cameras work at a readout cadence of 25 seconds and monitor stars fainter than apparent magnitude 8. The two "fast" cameras work at a cadence of 2.5 seconds to observe stars between magnitude 4 to 8. [ 1 ] [ 9 ] The cameras are refracting telescopes using six lenses; each camera has a 1,100 deg 2 field and a 120 mm lens diameter. Each camera is equipped with its own CCD staring array , consisting of four CCDs of 4510 x 4510 pixels . [ 1 ]
The 24 "normal cameras" will be arranged in four groups of six cameras with their lines of sight offset by a 9.2° angle from the +ZPLM axis. This particular configuration allows surveying an instantaneous field of view of about 2,250 deg 2 per pointing. [ 1 ] The space observatory will rotate around the mean line of sight once per year, delivering a continuous survey of the same region of the sky.
The space observatory is planned to launch at the end of 2026 on Ariane 6 [ 10 ] to the Sun-Earth L 2 Lagrange point . [ 1 ]
The public release of photometric data (including light curves) and high-level science products for each quarter will be made after six months and by one year after the end of their validation period. The data are processed by quarters because this is the duration between each 90-degree rotation of the spacecraft. For the first quarter of observations, six months are required for data validation and pipeline updates. For the next quarters, three months will be needed. [ 11 ]
A small number of stars (no more than 2,000 stars out of 250,000) will have proprietary status, meaning the data will only be accessible to the PLATO Mission Consortium members for a given time period. They will be selected using the first three months of PLATO observations for each field. The proprietary period is limited to 6 months after the completion of the ground-based observations or the end of the mission archival phase (Launch date + 7.5 years), whichever comes first. [ 11 ] | https://en.wikipedia.org/wiki/PLATO_(spacecraft) |
PLINK [ 1 ] is a free, commonly used, open-source whole-genome association analysis toolset designed by Shaun Purcell . The software is designed flexibly to perform a wide range of basic, large-scale genetic analyses.
PLINK currently supports following functionalities:
PLINK has its own format of text files ( .ped ) and binary text files ( .bed ) that serve as input files for most analyses. [ 2 ] A .map accompanies a .ped file and provides information about variants, while .bim and .fam files accompany .bed files as part of the binary dataset. Additionally, PLINK accepts inputs of VCF , BCF, Oxford, and 23andMe files, which are typically extracted into the binary .bed format prior to performing desired analyses. With certain formats such as VCF, some information such as phase and dosage will be discarded.
PLINK has a variety of output files depending on the analysis. PLINK has the ability to output files for BEAGLE and can recode a .bed file into a VCF for analyses in other programs. Additionally, PLINK is designed to work in conjunction with R , and can output files to be processed by certain R packages.
This free and open-source software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PLINK_(genetic_tool-set) |
A PLL multibit or multibit PLL is a phase-locked loop (PLL) which achieves improved performance compared to a unibit PLL by using more bits . Unibit PLLs use only the most significant bit (MSB) of each counter's output bus to measure the phase , while multibit PLLs use more bits. [ 1 ] PLLs are an essential component in telecommunications .
Multibit PLLs achieve improved efficiency and performance: better utilization of the frequency spectrum , to serve more users at a higher quality of service (QoS), reduced RF transmit power, and reduced power consumption in cellular phones and other wireless devices.
A phase-locked loop is an electronic component or system comprising a closed loop for controlling the phase of an oscillator while comparing it with the phase of an input or reference signal. An indirect frequency synthesizer uses a PLL. In an all-digital PLL, a voltage-controlled oscillator (VCO) is controlled using a digital , rather than analog , control signal. The phase detector gives a signal proportional to the phase difference between two signals; in a PLL, one signal is the reference, and the other is the output of the controlled oscillator (or a divider driven by the oscillator).
In a unibit phase-locked loop, the phase is measured using only one bit of the reference and output counters, the most significant bit (MSB). In a multibit phase-locked loop, the phase is measured using more than one bit of the reference and output counters, usually including the most significant bit.
In unibit PLLs, the output frequency is defined by the input frequency and the modulo count of the two counters. In each counter, only the most significant bit (MSB) is used. The other output lines of the counters are ignored; this is wasted information.
A PLL includes a phase detector, filter and oscillator connected in a closed loop, so the oscillator frequency follows (equals) the input frequency. Although the average output frequency equals the input frequency, the oscillator's frequency fluctuates or vibrates about that average value. The closed loop operates to correct such frequency deviations; higher performance PLL reduces these fluctuations to lower values, however these deviations can never be stopped. See Control theory . Phase noise , spurious emission , and jitter are results of the above phenomena.
Frequency settling time is the time it takes the PLL to hop to another frequency. Frequency hopping is used in GSM , and still more in modern systems.
In CDMA , frequency hopping achieves better performance than phase coding.
Fine frequency resolution is the capability of a PLL to generate closely spaced frequencies. For example, a cellular network may require a mobile phone to set its frequency at any of a plurality of values, spaced 30 kHz or 10 kHz.
The performance envelope of a PLL defines the interrelation between the above essential criteria of performance - for example improving the frequency resolution will result in a slower PLL and higher phase noise, etc.
The PLL Multibit expands the performance envelope of the PLL - it enables to achieve faster settling time together with fine frequency resolution and with lower phase noise.
As one progresses from the MSB toward the least significant bit (LSB), the frequency increases. For a binary counter, each next bit is at twice the frequency of the previous one. For modulo counters, the relationship is more complicated.
Only the MSB of the two counters are at the same frequency. The other bits in one counter have different frequencies from those in the other counter.
All the bits at the output of one counter, together, represent a digital bus . Thus, in a PLL frequency synthesizer there are two buses, one for the reference counter, the other for the output (or VCO) counter. In a uni-bit PLL, of the two digital buses, only one bit (line) of each is used. All the rest of the information is lost.
PLL design is an interdisciplinary task, difficult even for experts in PLLs. This - for the Unibit PLL, which is simpler than the Multibit PLL. The design should take into account: [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The above PLL uses more of the bits in the two counters. There is a difficult problem , of comparing signals at different frequencies, in two digital buses which count to a different final value.
Improved performance is possible by using the faster bits of the counters, taking into account the additional available information.
The operation of the PLL is further disrupted by overflow in the counters . This effect is only relevant in multibit PLLs; for Unibit PLL, there is only the one-bit signal MSB, therefore no overflow is possible.
The additional degree of freedom in Multibit PLLs allows to adapt each PLL to specific requirements. This can be effectively implemented with programmable logic devices (PLD), for example those manufactured by Altera Corp. [ 7 ] Altera provides both digital components and advanced design tools for using and programming the components.
Early multibit PLLs used a microprocessor , a microcontroller or DSP to close the loop in a smart implementation. [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ]
A multibit PLL offers fine frequency resolution and fast frequency hopping, together with lower phase noise and lower power consumption.
It thus enhances the overall performance envelope of the PLL.
The loop bandwidth can be optimized for phase noise performance and/or frequency settling speed; it depends less on the frequency resolution.
Improving the PLL performance can make better use of the frequency spectrum and reduce transmit power. And indeed, PLL performance is being constantly improved. [ 1 ] | https://en.wikipedia.org/wiki/PLL_multibit |
The term PLOKTA (sometimes rendered in lowercase, plokta ) /plok't*/ is an acronym for P ress L ots O f K eys T o A bort , and essentially means pressing random keys in an attempt to get some response from a ( computer ) system.
One might plokta when the abort procedure for a program is not known, or when trying to figure out if the system is just sluggish or really hung. Plokta can also be used while trying to figure out any unknown key sequence for a particular operation. Someone going into "plokta mode" usually places both hands flat on the keyboard and mashes them down, hoping for some useful response. This will sometimes eventually result in beeping sounds from an unresponding computer as its keyboard buffer fills up.
A slightly more directed form of plokta could often be seen in email messages or Usenet articles from new users with terminal -based clients - the text might end with
as the user vainly tries to find the right exit sequence, with the incorrect tries piling up at the end of the message.
This slang article is a stub . You can help Wikipedia by expanding it .
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PLOKTA |
PLUMED is an open-source library implementing enhanced-sampling algorithms, various free-energy methods , and analysis tools for molecular dynamics simulations. It is designed to be used together with ACEMD, AMBER , DL_POLY, GROMACS , LAMMPS , NAMD , OpenMM , ABIN, CP2K , i-PI, PINY-MD, and Quantum ESPRESSO , but it can also be used together with analysis and visualization tools VMD , HTMD, and OpenPathSampling. [ 1 ] [ 2 ]
In addition, PLUMED can be used as a standalone tool for analysis of molecular dynamics trajectories . A graphical user interface named METAGUI is available. [ 3 ]
PLUMED offers a large collection of collective variables that serve as descriptions of complex processes that occur during molecular dynamics simulations, for example angles, positions, distances, interaction energies, and total energy. [ 4 ]
This article about molecular modelling software is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PLUMED |
Poly (tetrahydropyran-2-yl N-(2 methacryloxyethyl) carbamate)-b-(methyl 4-(3-methacryloyloxypropoxy) cinnamate) ( PMCC ) is a synthetic polymer with thermally active groups, which upon heating, decomposes and exposes primary amines , providing a basis for surface modification. The structure of PMCC is based on a PMMA backbone with different functional groups on its sidechain. It is soluble in cyclohexanone or chloroform and has been used to create bone tissue replicas and to study protein immobilization in biological sciences. [ 1 ] [ 2 ] [ 3 ]
PMCC is a cinnamate - carbamate copolymer synthesized by a mixture of methacrylate monomers, a cinnamate monomer ("A", methyl 4-(3-methacryloyloxypropoxy) cinnamate ) and a carbamate monomer ("B", tetrahydropyran-2-yl N-(2-methacryloxyethyl) carbamate ). Polymerization of the two synthesized monomers is carried out through a radical polymerization using azobisisobutrylnitrile (ABIN) in tetrahydropyran (THP) with the temperature of 60 °C.
PMCC possesses two distinct decomposition/deprotection temperatures (T d ). One starts around 150 °C and accounts for 80% of the mass loss, and the second starts around 210 °C that accounts for the last 20%. When decomposition temperature is 150-180 °C, the carbamate monomer "B" of PMCC tends to decompose to carbon dioxide, 3,4-Dihydro-2H-pyran and polymer with primary amine groups.
PMCC is used mainly as a functional layer for grafting chemicals on substrates in nanoscale chemical patterning together with thermochemical nanolithography (tc-SPL) which involves the use of a heated nanoscale tip to thermally deprotect amine groups on the PMCC polymer surface. Patterning resolution with tc-SPL on PMCC as small as sub-10 nm, with depths as small as sub-2nm and at speeds up to millimeters per second have been reported. [ 3 ] [ 4 ] After the deprotection of the PMCC, the chemical function of the pattern is achieved by attaching various nano-objects to exposed amine groups. [ 5 ]
Liu et al. demonstrated the ability to create complex patterns with different functionalities by using PMCC and tc-SPL technology, including the electrostatic immobilization of negatively charged sulfonated enzymes at positively charged amine patterns. [ 6 ] These capabilities have significant implications for nanobiotechnology, as they could be used for the development of protein chips, and in studies of nanoelectronics fabrications. | https://en.wikipedia.org/wiki/PMCC_polymer |
PMHC cellular microarrays are a type of cellular microarray that has been spotted with pMHC complexes peptide- MHC class I or peptide- MHC class II .
These biochips can be used to interrogate immune cells, particularly antigen-specific T cells , from clinical samples for what they are capable of
recognizing. They can also be co-spotted with other molecules, such as antibodies that capture cytokines, allowing for high-throughput functional
analysis of the captured T cells. Molecules spotted on a pMHC cellular microarray can be classified as capture molecules, detector molecules and effector
molecules.
They were developed by Daniel Chen, Yoav Soen, Dan Kraft, Pat Brown and Mark Davis
at Stanford University Medical Center .
Chen DS, Davis MM (2006) Molecular and functional analysis using live cell microarrays. Curr Opin Chem Biol 10:28-34
Chen DS, Soen Y, Stuge TB, Lee PP, Weber JS, Brown PO, Davis MM (2005) Marked Differences in Human Melanoma Antigen-Specific T Cell Responsiveness after Vaccination Using a Functional Microarray. PLoS Med 2: 10: e265 ( [1] )
Soen Y., Chen D. S., Kraft D. L., Davis M. M. and Brown P.O. (2003) Detection and characterization of cellular immune responses using peptide-MHC microarrays. PLoS Biol. 1: E65 ( http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0000065 )
Chen DS, Davis MM (2005) Cellular immunotherapy: Antigen recognition is just the beginning. Springer Semin Immunopathol 27:119–127
Soen Y, Chen DS, Stuge TB, Weber JS, Lee PP, et al. (2004) A novel cellular microarray identifies functional deficiences in tumor-specific T cell responses. J Clin Oncol 22:2510 | https://en.wikipedia.org/wiki/PMHC_cellular_microarray |
PMM2 deficiency or PMM2-CDG , previously CDG-Ia , is a very rare genetic disorder caused by mutations in PMM2 . It is an autosomal recessive disease that is the most common type of congenital disorder of glycosylation or CDG. [ 2 ] PMM2-CDG is the most common of a growing family of more than 130 extremely rare inherited metabolic disorders. [ 3 ] Only about 800 children and adults have been reported worldwide. [ 4 ]
PMM2 deficiency is diagnosed through genetic sequencing. More than 115 mutations in the PMM2 gene have been found to cause this disease. [ 16 ]
Treatment with mannose powder 1 to 2 g / kg per day results in significant improvement in protein glycosylation after 1 year. [ 17 ] Other treatments involve management of the symptoms that are apparent in each individual, including physical therapy to improve core strength and mobility, occupational therapy for coordination, speech therapy for talking and eating. [ 13 ] | https://en.wikipedia.org/wiki/PMM2_deficiency |
PM Sayeed Marine Birds Conservation Reserve is the first protected area for marine birds in India . It is located in the Indian Union Territory of Lakshadweep . It was formed in 2020. It covers an area of 62 km 2 . [ 1 ]
The PM Sayeed Marine Birds Conservation Reserve will be home to four species of pelagic seabirds – the Greater crested tern , Lesser crested tern , Sooty tern , and the Brown noddy . [ 1 ] [ 2 ]
This article about protected areas of India is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PM_Sayeed_Marine_Birds_Conservation_Reserve |
10957
108767
ENSG00000146278
ENSMUSG00000040128
Q12796 Q49A59
Q3TWH3
NM_006813
NM_001033225
NP_006804
NP_001028397
Proline-rich nuclear receptor coactivator 1 is a protein that, in humans, is encoded by the PNRC1 gene . [ 5 ] [ 6 ]
PNRC1 functions as a coactivator for several nuclear receptors including AR , ERα , ERRα , ERRγ , GR , SF1 , PR , TR , RAR and RXR . [ 7 ] [ 8 ] The interaction between PNRC1 with nuclear receptors occurs through the SH3 domain of PNRC1. [ 8 ]
This article on a gene on human chromosome 6 is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PNRC1 |
4B6H
55629
52830
ENSG00000189266
ENSMUSG00000028675
Q9NPJ4
Q9CR73
NM_017761
NM_026383
NP_060231
NP_080659
Proline-rich nuclear receptor coactivator 2 is a protein that in humans is encoded by the PNRC2 gene . [ 5 ] [ 6 ]
This article on a gene on human chromosome 1 is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PNRC2 |
Phosphates are the naturally occurring form of the element phosphorus . [ 2 ]
In chemistry , a phosphate is an anion , salt , functional group or ester derived from a phosphoric acid . It most commonly means orthophosphate , a derivative of orthophosphoric acid, a.k.a. phosphoric acid H 3 PO 4 .
The phosphate or orthophosphate ion [PO 4 ] 3− is derived from phosphoric acid by the removal of three protons H + . Removal of one proton gives the dihydrogen phosphate ion [H 2 PO 4 ] − while removal of two protons gives the hydrogen phosphate ion [HPO 4 ] 2− . These names are also used for salts of those anions, such as ammonium dihydrogen phosphate and trisodium phosphate .
In organic chemistry , phosphate or orthophosphate is an organophosphate , an ester of orthophosphoric acid of the form PO 4 RR′R″ where one or more hydrogen atoms are replaced by organic groups. An example is trimethyl phosphate , (CH 3 ) 3 PO 4 . The term also refers to the trivalent functional group OP(O − ) 3 in such esters. Phosphates may contain sulfur in place of one or more oxygen atoms ( thiophosphates and organothiophosphates ).
Orthophosphates are especially important among the various phosphates because of their key roles in biochemistry , biogeochemistry , and ecology , and their economic importance for agriculture and industry. [ 2 ] The addition and removal of phosphate groups ( phosphorylation and dephosphorylation ) are key steps in cell metabolism .
Orthophosphates can condense to form pyrophosphates .
The phosphate ion has a molar mass of 94.97 g/mol, and consists of a central phosphorus atom surrounded by four oxygen atoms in a tetrahedral arrangement. It is the conjugate base of the hydrogen phosphate ion [HPO 4 ] 2− , which in turn is the conjugate base of the dihydrogen phosphate ion [H 2 PO 4 ] − , which in turn is the conjugate base of orthophosphoric acid , H 3 PO 4 .
Many phosphates are soluble in water at standard temperature and pressure . The sodium, potassium, rubidium , caesium , and ammonium phosphates are all water-soluble. Most other phosphates are only slightly soluble or are insoluble in water. As a rule, the hydrogen and dihydrogen phosphates are slightly more soluble than the corresponding phosphates.
In water solution, orthophosphoric acid and its three derived anions coexist according to the dissociation and recombination equilibria below [ 3 ]
Values are at 25 °C and 0 ionic strength.
The p K a values are the pH values where the concentration of each species is equal to that of its conjugate bases . At pH 1 or lower, the phosphoric acid is practically undissociated. Around pH 4.7 (mid-way between the first two p K a values) the dihydrogen phosphate ion, [H 2 PO 4 ] − , is practically the only species present. Around pH 9.8 (mid-way between the second and third p K a values) the monohydrogen phosphate ion, [HPO 4 ] 2− , is the only species present. At pH 13 or higher, the acid is completely dissociated as the phosphate ion, [PO 4 ] 3− .
This means that salts of the mono- and di-phosphate ions can be selectively crystallised from aqueous solution by setting the pH value to either 4.7 or 9.8.
In effect, H 3 PO 4 , [H 2 PO 4 ] − and [HPO 4 ] 2− behave as separate weak acids because the successive p K a differ by more than 4.
Phosphate can form many polymeric ions such as pyrophosphate , [P 2 O 7 ] 4− , and triphosphate , [P 3 O 10 ] 5− . The various metaphosphate ions (which are usually long linear polymers) have an empirical formula of [PO 3 ] − and are found in many compounds.
In biological systems , phosphorus can be found as free phosphate anions in solution ( inorganic phosphate ) or bound to organic molecules as various organophosphates . [ 5 ]
Inorganic phosphate is generally denoted P i and at physiological ( homeostatic ) pH primarily consists of a mixture of [HPO 4 ] 2− and [H 2 PO 4 ] − ions. At a neutral pH, as in the cytosol (pH = 7.0), the concentrations of the orthophoshoric acid and its three anions have the ratios [ H 2 PO 4 − ] [ H 3 PO 4 ] ≈ 7.5 × 10 4 [ HPO 4 2 − ] [ H 2 PO 4 − ] ≈ 0.62 [ PO 4 3 − ] [ HPO 4 2 − ] ≈ 2.14 × 10 − 6 {\displaystyle {\begin{aligned}{\frac {[{\ce {H2PO4-}}]}{[{\ce {H3PO4}}]}}&\approx 7.5\times 10^{4}\\[4pt]{\frac {[{\ce {HPO4^2-}}]}{[{\ce {H2PO4-}}]}}&\approx 0.62\\[4pt]{\frac {[{\ce {PO4^3-}}]}{[{\ce {HPO4^2-}}]}}&\approx 2.14\times 10^{-6}\end{aligned}}}
Thus, only the [H 2 PO 4 ] − and [HPO 4 ] 2− ions are present in significant amounts in the cytosol (62% [H 2 PO 4 ] − , 38% [HPO 4 ] 2− ). In extracellular fluid (pH = 7.4), this proportion is inverted (61% [HPO 4 ] 2− , 39% [H 2 PO 4 ] − ).
Inorganic phosphate can also be present as pyrophosphate anions [P 2 O 7 ] 4− , which give orthophosphate by hydrolysis :
Organic phosphates are commonly found in the form of esters as nucleotides (e.g. AMP , ADP , and ATP ) and in DNA and RNA . Free orthophosphate anions can be released by the hydrolysis of the phosphoanhydride bonds in ATP or ADP. These phosphorylation and dephosphorylation reactions are the immediate storage and source of energy for many metabolic processes. ATP and ADP are often referred to as high-energy phosphates , as are the phosphagens in muscle tissue. Similar reactions exist for the other nucleoside diphosphates and triphosphates .
An important occurrence of phosphates in biological systems is as the structural material of bone and teeth. These structures are made of crystalline calcium phosphate in the form of hydroxyapatite . The hard dense enamel of mammalian teeth may contain fluoroapatite , a hydroxy calcium phosphate where some of the hydroxyl groups have been replaced by fluoride ions.
Phosphates are medicinal salts of phosphorus. Some phosphates, which help cure many urinary tract infections , are used to make urine more acidic. To avoid the development of calcium stones in the urinary tract, some phosphates are used. [ 6 ] For patients who are unable to get enough phosphorus in their daily diet, phosphates are used as dietary supplements, usually because of certain disorders or diseases. [ 6 ] Injectable phosphates can only be handled by qualified health care providers. [ 6 ]
Plants take up phosphorus through several pathways: the arbuscular mycorrhizal pathway and the direct uptake pathway.
Hyperphosphatemia , or a high blood level of phosphates, is associated with elevated mortality in the general population. The most common cause of hyperphosphatemia in people, dogs, and cats is kidney failure. In cases of hyperphosphatemia, limiting consumption of phosphate-rich foods, such as some meats and dairy items and foods with a high phosphate-to-protein ratio, such as soft drinks, fast food, processed foods, condiments, and other products containing phosphate-salt additives is advised. [ 7 ]
Phosphates induce vascular calcification , and a high concentration of phosphates in blood was found to be a predictor of cardiovascular events . [ 8 ]
Phosphates are the naturally occurring form of the element phosphorus , found in many phosphate minerals . In mineralogy and geology, phosphate refers to a rock or ore containing phosphate ions. Inorganic phosphates are mined to obtain phosphorus for use in agriculture and industry. [ 2 ]
The largest global producer and exporter of phosphates is Morocco . Within North America, the largest deposits lie in the Bone Valley region of central Florida , the Soda Springs region of southeastern Idaho , and the coast of North Carolina . Smaller deposits are located in Montana , Tennessee , Georgia , and South Carolina . The small island nation of Nauru and its neighbor Banaba Island , which used to have massive phosphate deposits of the best quality, have been mined excessively. Rock phosphate can also be found in Egypt, Israel, Palestine, Western Sahara, Navassa Island , Tunisia, Togo, and Jordan, countries that have large phosphate-mining industries.
Phosphorite mines are primarily found in:
In 2007, at the current rate of consumption, the supply of phosphorus was estimated to run out in 345 years. [ 9 ] However, some scientists thought that a " peak phosphorus " would occur in 30 years and Dana Cordell from Institute for Sustainable Futures said that at "current rates, reserves will be depleted in the next 50 to 100 years". [ 10 ] Reserves refer to the amount assumed recoverable at current market prices. In 2012 the USGS estimated world reserves at 71 billion tons, while 0.19 billion tons were mined globally in 2011. [ 11 ] Phosphorus comprises 0.1% by mass of the average rock [ 12 ] (while, for perspective, its typical concentration in vegetation is 0.03% to 0.2%), [ 13 ] and consequently there are quadrillions of tons of phosphorus in Earth's 3×10 19 -ton crust, [ 14 ] albeit at predominantly lower concentration than the deposits counted as reserves, which are inventoried and cheaper to extract. If it is assumed that the phosphate minerals in phosphate rock are mainly hydroxyapatite and fluoroapatite, phosphate minerals contain roughly 18.5% phosphorus by weight. If phosphate rock contains around 20% of these minerals, the average phosphate rock has roughly 3.7% phosphorus by weight.
Some phosphate rock deposits, such as Mulberry in Florida, [ 15 ] are notable for their inclusion of significant quantities of radioactive uranium isotopes. This is a concern because radioactivity can be released into surface waters [ 16 ] from application of the resulting phosphate fertilizer .
In December 2012, Cominco Resources announced an updated JORC compliant resource of their Hinda project in Congo-Brazzaville of 531 million tons, making it the largest measured and indicated phosphate deposit in the world. [ 17 ]
Around 2018, Norway discovered phosphate deposits almost equal to those in the rest of Earth combined. [ 18 ] [ 19 ]
In July 2022 China announced quotas on phosphate exportation. [ 20 ]
The largest importers in millions of metric tons of phosphate are Brazil 3.2, India 2.9 and the USA 1.6. [ 21 ]
The three principal phosphate producer countries (China, Morocco and the United States) account for about 70% of world production.
In ecological terms, because of its important role in biological systems, phosphate is a highly sought after resource. Once used, it is often a limiting nutrient in environments , and its availability may govern the rate of growth of organisms. This is generally true of freshwater environments, whereas nitrogen is more often the limiting nutrient in marine (seawater) environments. Addition of high levels of phosphate to environments and to micro-environments in which it is typically rare can have significant ecological consequences. For example, blooms in the populations of some organisms at the expense of others, and the collapse of populations deprived of resources such as oxygen (see eutrophication ) can occur. In the context of pollution, phosphates are one component of total dissolved solids , a major indicator of water quality, but not all phosphorus is in a molecular form that algae can break down and consume. [ 23 ]
Calcium hydroxyapatite and calcite precipitates can be found around bacteria in alluvial topsoil. [ 24 ] As clay minerals promote biomineralization, the presence of bacteria and clay minerals resulted in calcium hydroxyapatite and calcite precipitates. [ 24 ]
Phosphate deposits can contain significant amounts of naturally occurring heavy metals. Mining operations processing phosphate rock can leave tailings piles containing elevated levels of cadmium , lead , nickel , copper , chromium , and uranium . Unless carefully managed, these waste products can leach heavy metals into groundwater or nearby estuaries. Uptake of these substances by plants and marine life can lead to concentration of toxic heavy metals in food products. [ 25 ] | https://en.wikipedia.org/wiki/PO4(3-) |
Silver phosphate or silver orthophosphate is a light sensitive, yellow, water-insoluble chemical compound composed of silver and phosphate ions of formula Ag 3 P O 4 .
Silver phosphate is formed as a yellow solid precipitate by the reaction between a soluble silver salt, such as silver nitrate , with a soluble orthophosphate . [ 3 ] Its solubility product is 8.89×10 −17 mol 4 ·dm −2 . [ 4 ] [ 5 ] The precipitation reaction is analytically significant [ 6 ] and can be used in qualitative or quantitative analysis. [ 7 ]
This compound dissolves in aqueous ammonia . [ 3 ] Large crystals of silver phosphate form upon gradual evaporation of such ammoniacal solutions.
Its structure has been confirmed by X-ray crystallography . [ 8 ]
The precipitation of silver phosphate is useful in traditional analytical chemistry . Precipitation of silver phosphate is also used in silver staining of biological materials (after reduction to silver metal) - as a magnifying agent for phosphate. [ 9 ]
Silver phosphate also found use in early photography as a light sensitive agent. [ 10 ]
Silver phosphate exhibits antibacterial properties. [ 11 ]
Silver phosphate is a high (90%) quantum yield photocatalyst for the visible light photochemical splitting of water and for production of activated oxygen by the same method. [ 12 ]
Silver pyrophosphate Ag 4 P 2 O 7 (CAS No. 13465-97-9) [ 13 ] can be prepared as a white precipitate from reaction of silver(I) and pyrophosphate ions. Like silver orthophosphate it is light sensitive. Silver orthophosphate turns red on exposure to light. [ 14 ] It has a density of 5.306 g/cm 3 and a melting point of 585 °C. [ 15 ] A hydrate also exists which decomposes at 110 °C. [ 15 ]
Silver metaphosphate (AgPO 3 ) (CAS No. 13465-96-8) [ 16 ] is a white solid with a density of 6.370 g/cm 3 and a melting point of 482 °C. A hydrate also exists which decomposes at 240 °C. [ 15 ] | https://en.wikipedia.org/wiki/PO4Ag3 |
POCUS ( point-of-care ultrasonography or point-of-care ultrasound ) is defined as the acquisition, interpretation, and immediate clinical integration of diagnostic medical ultrasound imaging performed by a treating clinician during a clinical interaction rather than by a radiologist, cardiologist, or other consulting physician. POCUS is utilized across various specialties, for a variety of clinical goals, and on a number of body systems to provide diagnostic information and guide procedures. [ 1 ]
POCUS has found utility in a number of clinical settings including Emergency Department , Critical Care, Obstetrics , general Inpatient Care, Orthopedics, Sports Medicine, Family Medicine, Pain Management, and Hospice and Palliative Care and is used in support of a variety of clinical goals including screening, diagnosis, monitoring care, and procedural interventions. It can be used to support management in a number of body systems including cardiovascular, pulmonary, abdominal (such as the FAST exam ), obstetrical, skin and soft tissue, and musculoskeletal.
POCUS is distinct from consultative ultrasonography, where a test is ordered by a clinician, performed by a technician, and interpreted by a consulting radiologist or other specialist separately from the clinical interaction. It is also distinct from therapeutic ultrasound , where ultrasound is used for treatment of a condition or for therapeutic benefit. POCUS is performed using portable ultrasound devices such as laptop based or handheld devices which can easily brought to the patient's bedside in a hospital or emergency department setting, or into an examination room in an office based outpatient setting. It allows for rapid collection of diagnostic information which can save both time and money and improve diagnostic accuracy and overall care. [ 2 ]
POCUS is also useful in improving performance in certain clinical procedures such as arthrocentesis, IV line placement, skin abscess drainage, nerve blocks, and many others.
While medical ultrasonography was developed in the mid 20th century, the approach to adoption varied from country to country. In some health care systems, for example in Germany, the technology became widely distributed and adopted by multiple specialties who incorporated ultrasound into clinical care. In those countries routine bedside ultrasonography was standard care by the 1990s. In other systems, for example in the US, ultrasonography was more limited in use and became the purview of consulting radiologists and a few other specialists, such as cardiologists and obstetricians. Probably because of the expense of the technology and barriers to learning and developing skills, adoption of bedside or point of care ultrasonography was much slower in these countries. One of the earliest expansions of point of care ultrasound occurred in the emergency department where protocols for rapid diagnosis of internal bleeding (such as the FAST exam) were developed. Other protocols emerged in the Emergency Department such as the BLUE protocol , and others. Diffusion of portable ultrasound technology to bedside hospital applications, critical care, and primary care has progressed at variable rates. [ 3 ] | https://en.wikipedia.org/wiki/POCUS |
Phosphoryl chloride (commonly called phosphorus oxychloride ) is a colourless liquid with the formula P O Cl 3 . It hydrolyses in moist air releasing phosphoric acid and fumes of hydrogen chloride . It is manufactured industrially on a large scale from phosphorus trichloride and oxygen or phosphorus pentoxide . [ 4 ] It is mainly used to make phosphate esters .
Like phosphate, POCl 3 is tetrahedral in shape. [ 6 ] It features three P−Cl bonds and one strong P–O bond, with an estimated bond dissociation energy of 533.5 kJ/mol. Unlike in the case of POF 3 , the Schomaker-Stevenson rule predicts appropriate bond length for the P–O bond only if the P–O bond is treated as a double bond, P=O. [ citation needed ] More modern treatments explain the tight P–O bond as a combination of lone pair transfer from the phosphorus to the oxygen atom and a dative π back-bond that produces an effective [P + ]-[O − ] configuration. [ 7 ]
Phosphoryl chloride exists as neutral POCl 3 molecules in the solid , liquid and gas states. This is unlike phosphorus pentachloride which exists as neutral PCl 5 molecules in the gas and liquid states but adopts the ionic form [PCl 4 ] + [PCl 6 ] − (tetrachlorophosphonium hexachlorophosphate(V)) in the solid state. The average bond lengths in the crystal structure of POCl 3 are 1.98 Å for P–Cl and 1.46 Å for P=O. [ 5 ]
It has a critical pressure of 3.4 atm . [ 8 ] With a freezing point of 1 °C and boiling point of 106 °C, the liquid range of POCl 3 is rather similar to water. Also like water, POCl 3 autoionizes , owing to the reversible formation of [POCl 2 ] + cations (dichlorooxophosphonium cations) and Cl − anions .
POCl 3 reacts with water to give hydrogen chloride and phosphoric acid :
Intermediates in the conversion have been isolated, including pyrophosphoryl chloride , O(−P(=O)Cl 2 ) 2 . [ 9 ]
Upon treatment with excess alcohols and phenols , POCl 3 gives phosphate esters :
Such reactions are often performed in the presence of an HCl acceptor such as pyridine or an amine .
POCl 3 can also act as a Lewis base , forming adducts with a variety of Lewis acids such as titanium tetrachloride :
The aluminium chloride adduct ( POCl 3 ·AlCl 3 ) is quite stable, and so POCl 3 can be used to remove AlCl 3 from reaction mixtures, for example at the end of a Friedel-Crafts reaction .
POCl 3 reacts with hydrogen bromide in the presence of Lewis-acidic catalysts to produce POBr 3 .
Phosphoryl chloride can be prepared by many methods. Phosphoryl chloride was first reported in 1847 by the French chemist Adolphe Wurtz by reacting phosphorus pentachloride with water. [ 10 ]
The commercial method involves oxidation of phosphorus trichloride with oxygen : [ 11 ]
An alternative method involves the oxidation of phosphorus trichloride with potassium chlorate : [ 12 ]
The reaction of phosphorus pentachloride ( PCl 5 ) with phosphorus pentoxide ( P 4 O 10 ).
The reaction can be simplified by chlorinating a mixture of PCl 3 and P 4 O 10 , generating the PCl 5 in situ .
The reaction of phosphorus pentachloride with boric acid or oxalic acid : [ 12 ]
Reduction of tricalcium phosphate with carbon in the presence of chlorine gas: [ 13 ]
The reaction of phosphorus pentoxide with sodium chloride is also reported: [ 13 ]
Phosphoryl chloride is used on an industrial scale for the manufacture of phosphate esters (organophosphates). These have a wide range of uses, including as flame retardants ( bisphenol A diphenyl phosphate , TCPP and tricresyl phosphate ), plasticisers for PVC and related polymers ( 2-ethylhexyl diphenyl phosphate ) and hydraulic fluids. [ 11 ] POCl 3 is also used in the production of organophosphate insecticides.
In the semiconductor industry, POCl 3 is used as a safe liquid phosphorus source in diffusion processes. The phosphorus acts as a dopant used to create n-type layers on a silicon wafer.
In the laboratory, POCl 3 is a reagent in dehydrations. One example involves conversion of formamides to isonitriles (isocyanides); [ 14 ] primary amides to nitriles : [ 15 ]
In a related reaction, certain aryl-substituted amides can be cyclized using the Bischler-Napieralski reaction .
Such reactions are believed to proceed via an imidoyl chloride . In certain cases, the imidoyl chloride is the final product. For example, pyridones and pyrimidones can be converted to chloro- derivatives such as 2-chloropyridines and 2-chloropyrimidines, which are intermediates in the pharmaceutical industry. [ 16 ]
In the Vilsmeier-Haack reaction , POCl 3 reacts with amides to produce a "Vilsmeier reagent", a chloro- iminium salt, which subsequently reacts with electron-rich aromatic compounds to produce aromatic aldehydes upon aqueous work-up. [ 17 ] | https://en.wikipedia.org/wiki/POCl3 |
PODi, the Digital Printing Initiative is an organization that helps set strategic direction in the digital print industry.
Membership – PODi members are industry leaders representing all facets of the digital printing ecosystem, including print and marketing service providers, enterprise marketers and manufacturers of software and hardware systems. PODi helps members integrate powerful digital technologies into their marketing, IT and management strategies.
Members companies include EFI , Canon , HP , Kodak , PageFlex, [ 1 ] Xerox , and XMPie. [ 2 ] These and many more members have cooperated in the development of the PPML variable data language, and more broadly, digital print standards development worldwide.
PODi hosts the world's largest collection (over 500) of digital print case studies. [ 3 ] Its annual conference, the AppForum, is the only independent thought leadership event expressly for the digital printing industry. Since the first event in 2002, AppForum has provided a unique platform for the digital printing community to come together, learn from people who are actually succeeding with variable data printing, print on demand, relevant marketing, cross media, web to print, QR Codes, augmented reality, and all the newest applications.
PODi also hosts educational webinars throughout the year, and has a growing toolbox of aids and training for [ 4 ] the process used for selling the new, more profitable, applications.
PODi is managed by Caslon in North America and internationally. Other affiliates manage communities in the United Kingdom and Europe. Membership is open to all businesses who own a digital printing press, use digital printing as an integral part of their marketing plans, provide support to the industry, or have a passion for the opportunities and applications that digital printing is adding to the future of relevant marketing.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PODi |
Phosphoric chloride difluoride POF 2 Cl is a colourless gas. At one atmosphere pressure the gas condenses to a liquid at 3.1 °C and freezes at −96.4. [ 3 ] Alternate names are difluorophosphoryl chloride [ 3 ] or phosphoryl chloride difluoride .
The critical temperature of POF 2 Cl is 150.6 at a critical pressure of 43.4 atmospheres. [ 4 ] The density of the liquid at 0 °C is 1.6555 g/cm 3 . [ 3 ]
The shape of the molecules in POF 2 Cl is tetrahedral. The P-O distance is 1.426 Å, Both P-F distances are 1.514 Å, and the P-Cl distance is 1.940 Å. The O–P–F angle is 114.09°, the F–P–F angle is 101.2°, the O–P–Cl angle is 118.85°, and the F–P-Cl angle 103.22°. [ 2 ] In the solid form, there are two inequivalent molecular positions. The O atom from one is close to the chlorine atom on the other position aligned roughly on the c-axis. Along the b-axis there is a zigzag of O atoms close to a P atom in the other position. [ 2 ]
The density of the solid is as calculated from crystal data is 2.177 g/cm 3 . [ 2 ]
In the 31 P-NMR spectrum (in H 3 PO 4 ), the phosphorus atom of POClF 2 is a triplet at 15 ppm. [ 4 ]
When mixed with HCl, exchange of halogen atoms between molecules is catalysed, and POCl 3 , POCl 2 F, and POF 3 end up in the mixture. HCl can end up in the product due to the starting materials, or contamination by water, and must be removed if POF 2 Cl is to be stored. [ 4 ]
Phosphoric chloride difluoride can be made by the reaction of liquid phosphorus pentachloride with phosphorodifluoridic acid HPO 2 F 2 or diphosphoridic tetrafluoride P 2 O 3 F 4 . This reaction takes place at room temperature up to 60 °C. The POF 2 Cl bubbles off as a gas, and can be condensed by cooling with dry ice-acetone mixture. [ 3 ]
Another starting point is from potassium difluorphosphate KPO 2 F 2 . [ 2 ]
Other less efficient methods involve fluorinating POCl 3 using fluoride salts like SbF 3 or NaF . But a mixture of fluorides results from these reactions. An even cheaper source is NaCl , CaF 2 and P 4 O 10 mixture heated to 500°. Industrial scale manufacture is possible with a HF reaction with POCl 3 . [ 2 ] | https://en.wikipedia.org/wiki/POF2Cl |
Phosphoryl fluoride (commonly called phosphorus oxyfluoride ) is a compound with the chemical formula P O F 3 . It is a colorless gas that hydrolyzes rapidly. It has a critical temperature of 73 °C and a critical pressure of 4.25 bars . [ 1 ]
Phosphorus oxyfluoride is prepared by partial hydrolysis of phosphorus pentafluoride .
Phosphorus oxyfluoride is the progenitor of the simple fluorophosphoric acids by hydrolysis. The sequence starts with difluorophosphoric acid :
The next steps give monofluorophosphoric acid and phosphoric acid :
Phosphoryl fluoride combines with dimethylamine to produce dimethylaminophosphoryl difluoride (H 3 C−) 2 N−P(=O)F 2 and difluorophosphate and hexafluorophosphate ions. [ 2 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/POF3 |
The PONA number is an index for oil components used to determine the paraffins (P), olefins (O), naphthenes (N) and aromatics (A) content [ 1 ] of FCC ( fluid catalytic cracking ) and coker ( visbreaker ) gasoline .
The PONA number plays a significant role in determining the quality of naphtha . Various grades of naphtha are produced depending on the PONA specifications, such as 60/15, 65/12, 70/10, etc. The first number represents the minimum allowable total parafins percentage and the second number specifies the maximum allowable aromatics percentage. It also determines the price of naphtha in international markets. | https://en.wikipedia.org/wiki/PONA_number |
POODLE (which stands for " Padding Oracle On Downgraded Legacy Encryption ") is a security vulnerability which takes advantage of the fallback to SSL 3.0 . [ 1 ] [ 2 ] [ 3 ] If attackers successfully exploit this vulnerability, on average, they only need to make 256 SSL 3.0 requests to reveal one byte of encrypted messages. Bodo Möller, Thai Duong and Krzysztof Kotowicz from the Google Security Team discovered this vulnerability; they disclosed the vulnerability publicly on October 14, 2014 (despite the paper being dated "September 2014" [ 1 ] ). [ 4 ] On December 8, 2014, a variation of the POODLE vulnerability that affected TLS was announced. [ 5 ]
The CVE-ID associated with the original POODLE attack is CVE - 2014-3566 .
F5 Networks filed for CVE - 2014-8730 as well, see POODLE attack against TLS section below.
To mitigate the POODLE attack, one approach is to completely disable SSL 3.0 on the client side and the server side. However, some old clients and servers do not support TLS 1.0 and above. Thus, the authors of the paper on POODLE attacks also encourage browser and server implementation of TLS_FALLBACK_SCSV, [ 6 ] which will make downgrade attacks impossible. [ 1 ] [ 7 ]
Another mitigation is to implement "anti-POODLE record splitting". It splits the records into several parts and ensures none of them can be attacked. However the problem of the splitting is that, though valid according to the specification, it may also cause compatibility issues due to problems in server-side implementations. [ 8 ]
A full list of browser versions and levels of vulnerability to different attacks (including POODLE) can be found in the article Transport Layer Security .
Opera 25 implemented this mitigation in addition to TLS_FALLBACK_SCSV. [ 9 ]
Google's Chrome browser and their servers had already supported TLS_FALLBACK_SCSV. Google stated in October 2014 it was planning to remove SSL 3.0 support from their products completely within a few months. [ 7 ] Fallback to SSL 3.0 has been disabled in Chrome 39, released in November 2014. [ 10 ] SSL 3.0 has been disabled by default in Chrome 40, released in January 2015. [ 11 ]
Mozilla disabled SSL 3.0 in Firefox 34 and ESR 31.3, which were released in December 2014, and added support of TLS_FALLBACK_SCSV in Firefox 35. [ 12 ]
Microsoft published a security advisory to explain how to disable SSL 3.0 in Internet Explorer and Windows OS, [ 13 ] and on October 29, 2014, Microsoft released a fix which disables SSL 3.0 in Internet Explorer on Windows Vista / Server 2003 and above and announced a plan to disable SSL 3.0 by default in their products and services within a few months. [ 14 ] Microsoft disabled fallback to SSL 3.0 in Internet Explorer 11 for Protect Mode sites on February 10, 2015, [ 15 ] and for other sites on April 14, 2015. [ 16 ]
Apple's Safari (on OS X 10.8, iOS 8.1 and later) mitigated against POODLE by removing support for all CBC protocols in SSL 3.0, [ 17 ] [ 18 ] however, this left RC4 which is also completely broken by the RC4 attacks in SSL 3.0. [ citation needed ] POODLE was completely mitigated in OS X 10.11 (El Capitan 2015) and iOS 9 (2015).
To prevent the POODLE attack, some web services dropped support of SSL 3.0. Examples include CloudFlare [ 19 ] and Wikimedia . [ 20 ]
Network Security Services version 3.17.1 (released on October 3, 2014) and 3.16.2.3 (released on October 27, 2014) introduced support for TLS_FALLBACK_SCSV, [ 21 ] [ 22 ] and NSS will disable SSL 3.0 by default in April 2015. [ 23 ] [ needs update ] OpenSSL versions 1.0.1j, 1.0.0o and 0.9.8zc, released on October 15, 2014, introduced support for TLS_FALLBACK_SCSV. [ 24 ] LibreSSL version 2.1.1, released on October 16, 2014, disabled SSL 3.0 by default. [ 25 ]
A new variant of the original POODLE attack was announced on December 8, 2014. This attack exploits implementation flaws of CBC encryption mode in the TLS 1.0 - 1.2 protocols. Even though TLS specifications require servers to check the padding, some implementations fail to validate it properly, which makes some servers vulnerable to POODLE even if they disable SSL 3.0. [ 5 ] SSL Pulse showed "about 10% of the servers are vulnerable to the POODLE attack against TLS" before this vulnerability was announced. [ 26 ] The CVE-ID for F5 Networks' implementation bug is CVE - 2014-8730 . The entry in NIST's NVD states that this CVE-ID is to be used only for F5 Networks' implementation of TLS, and that other vendors whose products have the same failure to validate the padding mistake in their implementations like A10 Networks and Cisco Systems need to issue their own CVE-IDs for their implementation errors because this is not a flaw in the protocol but in the implementation.
The POODLE attack against TLS was found to be easier to initiate than the initial POODLE attack against SSL. There is no need to downgrade clients to SSL 3.0, meaning fewer steps are needed to execute a successful attack. [ 27 ] | https://en.wikipedia.org/wiki/POODLE |
In programming language theory , the POPLmark challenge (from "Principles of Programming Languages benchmark", formerly Mechanized Metatheory for the Masses! ) (Aydemir, 2005) is a set of benchmarks designed to evaluate the state of automated reasoning (or mechanization) in the metatheory of programming languages, and to stimulate discussion and collaboration among a diverse cross section of the formal methods community. Very loosely speaking, the challenge is about measurement of how well programs may be proven to match a specification of how they are intended to behave (and the many complex issues that this involves). The challenge was initially proposed by the members of the PL club at the University of Pennsylvania , in association with collaborators around the world. The Workshop on Mechanized Metatheory is the main meeting of researchers participating in the challenge.
The design of the POPLmark benchmark is guided by features common to reasoning about programming languages. The challenge problems do not require the formalisation of large programming languages, but they do require sophistication in reasoning about:
As of 2007 [update] , the POPLmark challenge is composed of three parts. Part 1 concerns solely the types of System F <: ( System F with subtyping ), and has problems such as:
Part 2 concerns the syntax and semantics of System F <: . It concerns proofs of
Part 3 concerns the usability of the formalisation of System F <: . In particular, the challenge asks for:
Several solutions have been proposed for parts of the POPLmark challenge, using following tools: Isabelle/HOL , Twelf , Coq , αProlog , ATS , Abella and Matita . | https://en.wikipedia.org/wiki/POPLmark_challenge |
In functional analysis and quantum information science , a positive operator-valued measure ( POVM ) is a measure whose values are positive semi-definite operators on a Hilbert space . POVMs are a generalization of projection-valued measures (PVM) and, correspondingly, quantum measurements described by POVMs are a generalization of quantum measurement described by PVMs (called projective measurements).
In rough analogy, a POVM is to a PVM what a mixed state is to a pure state . Mixed states are needed to specify the state of a subsystem of a larger system (see purification of quantum state ); analogously, POVMs are necessary to describe the effect on a subsystem of a projective measurement performed on a larger system.
POVMs are the most general kind of measurement in quantum mechanics, and can also be used in quantum field theory . [ 1 ] They are extensively used in the field of quantum information .
Let H {\displaystyle {\mathcal {H}}} denote a Hilbert space and ( X , M ) {\displaystyle (X,M)} a measurable space with M {\displaystyle M} a Borel σ-algebra on X {\displaystyle X} . A POVM is a function F {\displaystyle F} defined on M {\displaystyle M} whose values are positive bounded self-adjoint operators on H {\displaystyle {\mathcal {H}}} such that for every ψ ∈ H {\displaystyle \psi \in {\mathcal {H}}}
is a non-negative countably additive measure on the σ-algebra M {\displaystyle M} and F ( X ) = I H {\displaystyle F(X)=\operatorname {I} _{\mathcal {H}}} is the identity operator . [ 2 ]
In quantum mechanics , the key property of a POVM is that it determines a probability measure on the outcome space, so that ⟨ F ( E ) ψ ∣ ψ ⟩ {\displaystyle \langle F(E)\psi \mid \psi \rangle } can be interpreted as the probability of the event E {\displaystyle E} when measuring a quantum state | ψ ⟩ {\displaystyle |\psi \rangle } .
In the simplest case, in which X {\displaystyle X} is a finite set, M {\displaystyle M} is the power set of X {\displaystyle X} and H {\displaystyle {\mathcal {H}}} is finite-dimensional, a POVM is equivalently a set of positive semi-definite Hermitian matrices { F i } {\displaystyle \{F_{i}\}} that sum to the identity matrix , [ 3 ] : 90
A POVM differs from a projection-valued measure in that, for projection-valued measures, the values of F {\displaystyle F} are required to be orthogonal projections .
In the discrete case, the POVM element F i {\displaystyle F_{i}} is associated with the measurement outcome i {\displaystyle i} , such that the probability of obtaining it when making a quantum measurement on the quantum state ρ {\displaystyle \rho } is given by
where tr {\displaystyle \operatorname {tr} } is the trace operator. When the quantum state being measured is a pure state | ψ ⟩ {\displaystyle |\psi \rangle } this formula reduces to
The discrete case of a POVM generalizes the simplest case of a PVM, which is a set of orthogonal projectors { Π i } {\displaystyle \{\Pi _{i}\}} that sum to the identity matrix :
The probability formulas for a PVM are the same as for the POVM. An important difference is that the elements of a POVM are not necessarily orthogonal. As a consequence, the number of elements n {\displaystyle n} of the POVM can be larger than the dimension of the Hilbert space they act in. On the other hand, the number of elements N {\displaystyle N} of the PVM is at most the dimension of the Hilbert space.
Naimark's dilation theorem [ 4 ] shows how POVMs can be obtained from PVMs acting on a larger space. This result is of critical importance in quantum mechanics, as it gives a way to physically realize POVM measurements. [ 5 ] : 285
In the simplest case, of a POVM with a finite number of elements acting on a finite-dimensional Hilbert space, Naimark's theorem says that if { F i } i = 1 n {\displaystyle \{F_{i}\}_{i=1}^{n}} is a POVM acting on a Hilbert space H A {\displaystyle {\mathcal {H}}_{A}} of dimension d A {\displaystyle d_{A}} , then there exists a PVM { Π i } i = 1 n {\displaystyle \{\Pi _{i}\}_{i=1}^{n}} acting on a Hilbert space H A ′ {\displaystyle {\mathcal {H}}_{A'}} of dimension d A ′ {\displaystyle d_{A'}} and an isometry V : H A → H A ′ {\displaystyle V:{\mathcal {H}}_{A}\to {\mathcal {H}}_{A'}} such that for all i {\displaystyle i} ,
For the particular case of a rank-1 POVM, i.e., when F i = | f i ⟩ ⟨ f i | {\displaystyle F_{i}=|f_{i}\rangle \langle f_{i}|} for some (unnormalized) vectors | f i ⟩ {\displaystyle |f_{i}\rangle } , this isometry can be constructed as [ 5 ] : 285
and the PVM is given simply by Π i = | i ⟩ ⟨ i | A ′ {\displaystyle \Pi _{i}=|i\rangle \langle i|_{A'}} . Note that here d A ′ = n {\displaystyle d_{A'}=n} .
In the general case, the isometry and PVM can be constructed by defining [ 6 ] [ 7 ] H A ′ = H A ⊗ H B {\displaystyle {\mathcal {H}}_{A'}={\mathcal {H}}_{A}\otimes {\mathcal {H}}_{B}} , Π i = I A ⊗ | i ⟩ ⟨ i | B {\displaystyle \Pi _{i}=\operatorname {I} _{A}\otimes |i\rangle \langle i|_{B}} , and
Note that here d A ′ = n d A {\displaystyle d_{A'}=nd_{A}} , so this is a more wasteful construction.
In either case, the probability of obtaining outcome i {\displaystyle i} with this PVM, and the state suitably transformed by the isometry, is the same as the probability of obtaining it with the original POVM:
This construction can be turned into a recipe for a physical realisation of the POVM by extending the isometry V {\displaystyle V} into a unitary U {\displaystyle U} , that is, finding U {\displaystyle U} such that
for i {\displaystyle i} from 1 to d A {\displaystyle d_{A}} . This can always be done.
The recipe for realizing the POVM described by { F i } i = 1 n {\displaystyle \{F_{i}\}_{i=1}^{n}} on a quantum state ρ {\displaystyle \rho } is then to embed the quantum state in the Hilbert space H A ′ {\displaystyle {\mathcal {H}}_{A'}} , evolve it with the unitary U {\displaystyle U} , and make the projective measurement described by the PVM { Π i } i = 1 n {\displaystyle \{\Pi _{i}\}_{i=1}^{n}} .
The post-measurement state is not determined by the POVM itself, but rather by the PVM that physically realizes it. Since there are infinitely many different PVMs that realize the same POVM, the operators { F i } i = 1 n {\displaystyle \{F_{i}\}_{i=1}^{n}} alone do not determine what the post-measurement state will be. To see that, note that for any unitary W {\displaystyle W} the operators
will also have the property that M i † M i = F i {\displaystyle M_{i}^{\dagger }M_{i}=F_{i}} , so that using the isometry
in the second construction above will also implement the same POVM. In the case where the state being measured is in a pure state | ψ ⟩ A {\displaystyle |\psi \rangle _{A}} , the resulting unitary U W {\displaystyle U_{W}} takes it together with the ancilla to state
and the projective measurement on the ancilla will collapse | ψ ⟩ A {\displaystyle |\psi \rangle _{A}} to the state [ 3 ] : 84
on obtaining result i 0 {\displaystyle i_{0}} . When the state being measured is described by a density matrix ρ A {\displaystyle \rho _{A}} , the corresponding post-measurement state is given by
We see therefore that the post-measurement state depends explicitly on the unitary W {\displaystyle W} . Note that while M i † M i = F i {\displaystyle M_{i}^{\dagger }M_{i}=F_{i}} is always Hermitian, generally, M i {\displaystyle M_{i}} does not have to be Hermitian.
Another difference from the projective measurements is that a POVM measurement is in general not repeatable. If on the first measurement result i 0 {\displaystyle i_{0}} was obtained, the probability of obtaining a different result i 1 {\displaystyle i_{1}} on a second measurement is
which can be nonzero if M i 0 {\displaystyle M_{i_{0}}} and M i 1 {\displaystyle M_{i_{1}}} are not orthogonal. In a projective measurement these operators are always orthogonal and therefore the measurement is always repeatable.
Suppose you have a quantum system with a 2-dimensional Hilbert space that you know is in either the state | ψ ⟩ {\displaystyle |\psi \rangle } or the state | φ ⟩ {\displaystyle |\varphi \rangle } , and you want to determine which one it is. If | ψ ⟩ {\displaystyle |\psi \rangle } and | φ ⟩ {\displaystyle |\varphi \rangle } are orthogonal, this task is easy: the set { | ψ ⟩ ⟨ ψ | , | φ ⟩ ⟨ φ | } {\displaystyle \{|\psi \rangle \langle \psi |,|\varphi \rangle \langle \varphi |\}} will form a PVM, and a projective measurement in this basis will determine the state with certainty. If, however, | ψ ⟩ {\displaystyle |\psi \rangle } and | φ ⟩ {\displaystyle |\varphi \rangle } are not orthogonal, this task is impossible , in the sense that there is no measurement, either PVM or POVM, that will distinguish them with certainty. [ 3 ] : 87 The impossibility of perfectly discriminating between non-orthogonal states is the basis for quantum information protocols such as quantum cryptography , quantum coin flipping , and quantum money .
The task of unambiguous quantum state discrimination (UQSD) is the next best thing: to never make a mistake about whether the state is | ψ ⟩ {\displaystyle |\psi \rangle } or | φ ⟩ {\displaystyle |\varphi \rangle } , at the cost of sometimes having an inconclusive result. It is possible to do this with projective measurements. [ 8 ] For example, if you measure the PVM { | ψ ⟩ ⟨ ψ | , | ψ ⊥ ⟩ ⟨ ψ ⊥ | } {\displaystyle \{|\psi \rangle \langle \psi |,|\psi ^{\perp }\rangle \langle \psi ^{\perp }|\}} , where | ψ ⊥ ⟩ {\displaystyle |\psi ^{\perp }\rangle } is the quantum state orthogonal to | ψ ⟩ {\displaystyle |\psi \rangle } , and obtain result | ψ ⊥ ⟩ ⟨ ψ ⊥ | {\displaystyle |\psi ^{\perp }\rangle \langle \psi ^{\perp }|} , then you know with certainty that the state was | φ ⟩ {\displaystyle |\varphi \rangle } . If the result was | ψ ⟩ ⟨ ψ | {\displaystyle |\psi \rangle \langle \psi |} , then it is inconclusive. The analogous reasoning holds for the PVM { | φ ⟩ ⟨ φ | , | φ ⊥ ⟩ ⟨ φ ⊥ | } {\displaystyle \{|\varphi \rangle \langle \varphi |,|\varphi ^{\perp }\rangle \langle \varphi ^{\perp }|\}} , where | φ ⊥ ⟩ {\displaystyle |\varphi ^{\perp }\rangle } is the state orthogonal to | φ ⟩ {\displaystyle |\varphi \rangle } .
This is unsatisfactory, though, as you can't detect both | ψ ⟩ {\displaystyle |\psi \rangle } and | φ ⟩ {\displaystyle |\varphi \rangle } with a single measurement, and the probability of getting a conclusive result is smaller than with POVMs. The POVM that gives the highest probability of a conclusive outcome in this task is given by [ 8 ] [ 9 ]
where
Note that tr ( | φ ⟩ ⟨ φ | F ψ ) = tr ( | ψ ⟩ ⟨ ψ | F φ ) = 0 {\displaystyle \operatorname {tr} (|\varphi \rangle \langle \varphi |F_{\psi })=\operatorname {tr} (|\psi \rangle \langle \psi |F_{\varphi })=0} , so when outcome ψ {\displaystyle \psi } is obtained we are certain that the quantum state is | ψ ⟩ {\displaystyle |\psi \rangle } , and when outcome φ {\displaystyle \varphi } is obtained we are certain that the quantum state is | φ ⟩ {\displaystyle |\varphi \rangle } .
The probability of having a conclusive outcome is given by
when the quantum system is in state | ψ ⟩ {\displaystyle |\psi \rangle } or | φ ⟩ {\displaystyle |\varphi \rangle } with the same probability. This result is known as the Ivanović-Dieks-Peres limit, named after the authors who pioneered UQSD research. [ 10 ] [ 11 ] [ 12 ]
Since the POVMs are rank-1, we can use the simple case of the construction above to obtain a projective measurement that physically realises this POVM. Labelling the three possible states of the enlarged Hilbert space as | result ψ ⟩ {\displaystyle |{\text{result ψ}}\rangle } , | result φ ⟩ {\displaystyle |{\text{result φ}}\rangle } , and | result ? ⟩ {\displaystyle |{\text{result ?}}\rangle } , we see that the resulting unitary U UQSD {\displaystyle U_{\text{UQSD}}} takes the state | ψ ⟩ {\displaystyle |\psi \rangle } to
and similarly it takes the state | φ ⟩ {\displaystyle |\varphi \rangle } to
A projective measurement then gives the desired results with the same probabilities as the POVM.
This POVM has been used to experimentally distinguish non-orthogonal polarisation states of a photon. The realisation of the POVM with a projective measurement was slightly different from the one described here. [ 13 ] [ 14 ] | https://en.wikipedia.org/wiki/POVM |
PP2 is a substance that has frequently been used in cancer research as a "selective" inhibitor for Src-family kinases . It strongly inhibits the kinases Lck ( IC 50 =4 nM ), Fyn (5 nM) and Hck (5 nM), shows weaker inhibition of epidermal growth factor receptor (480 nM) and practically no inhibition of ZAP-70 (100 μM) and JAK2 (50 μM). [ 1 ] [ 2 ] [ 3 ] [ 4 ] Despite its extensive use as a Src-selective inhibitor, recent research has shown that PP2 is non-selective and inhibits many other kinases with similar affinities. [ 5 ]
PP2A is a heterotrimeric enzyme composed of three types of subunits:
The diversity of the B subunit family allows PP2A to form multiple holoenzymes with distinct functions, enabling it to regulate numerous cellular processes with high specificity. [ 6 ]
The central mechanisms in the regulation of most cellular processes include protein phosphorylation and dephosphorylation. PP2 enzymes specifically target proteins that are phosphorylated on serine and threonine residues. [ 7 ] The dephosphorylation reaction typically requires water molecules and is catalyzed by a conserved active site in the PP2 enzyme.
The primary function of PP2 is to reverse the actions of kinases, which add phosphate groups to proteins. By removing phosphate groups, PP2 modulates the activity, location, and interaction of the target proteins, thereby controlling various aspects of cell behavior.
Due to its role in controlling phosphorylation status, PP2A is implicated in various physiological and pathological conditions:
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PP2_(kinase_inhibitor) |
PP3 is free software that produces sky charts , focussing on high quality graphics and typography. It is distributed a license based on the MIT License , but with this restriction added:
If you copy or distribute a modified version of this Software, the entire resulting derived work must be given a different name and distributed under the terms of a permission notice identical to this one.
Sky charts are produced as LaTeX files, so an installation of LaTeX and Ghostscript is required to obtain results in PostScript or PDF formats. Knowledge of command line syntax for these packages is however not required, as PP3 can run the conversions automatically.
Initially Wikipedia 's own star charts were produced by PP3. PP3 generates maps in the azimuthal equidistant projection . [ 1 ]
This scientific software article is a stub . You can help Wikipedia by expanding it .
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PP3 |
1XB7 , 3B1M , 3CS8 , 3D24 , 3U9Q , 3V9T , 3V9V , 4QJR , 4QK4
10891
19017
ENSG00000109819
ENSMUSG00000029167
Q9UBK2
O70343
NM_013261 NM_001330751 NM_001330752 NM_001330753
NM_008904
NP_001341755 NP_001341756 NP_001341757
NP_001389920
Peroxisome proliferator-activated receptor gamma coactivator 1-alpha ( PGC-1α ) is a protein that in humans is encoded by the PPARGC1A gene . [ 4 ] PPARGC1A is also known as human accelerated region 20 ( HAR20 ). It may, therefore, have played a key role in differentiating humans from apes. [ 5 ]
PGC-1α is the master regulator of mitochondrial biogenesis . [ 6 ] [ 7 ] [ 8 ] PGC-1α is also the primary regulator of liver gluconeogenesis , inducing increased gene expression for gluconeogenesis. [ 9 ]
PGC-1α is a gene that contains two promoters, and has 4 alternative splicings. PGC-1α is a transcriptional coactivator that regulates the genes involved in energy metabolism . It is the master regulator of mitochondrial biogenesis . [ 6 ] [ 7 ] [ 8 ] This protein interacts with the nuclear receptor PPAR-γ , which permits the interaction of this protein with multiple transcription factors . This protein can interact with, and regulate the activity of, cAMP response element-binding protein ( CREB ) and nuclear respiratory factors (NRFs) [ citation needed ] . PGC-1α provides a direct link between external physiological stimuli and the regulation of mitochondrial biogenesis, and is a major factor causing slow-twitch rather than fast-twitch muscle fiber types . [ 10 ]
Endurance exercise has been shown to activate the PGC-1α gene in human skeletal muscle. [ 11 ] Exercise-induced PGC-1α in skeletal muscle increases autophagy [ 12 ] [ 13 ] and unfolded protein response . [ 14 ]
PGC-1α protein may also be involved in controlling blood pressure , regulating cellular cholesterol homeostasis , and the development of obesity . [ 15 ]
PGC-1α is thought to be a master integrator of external signals. It is known to be activated by a host of factors, including:
PGC-1α has been shown to exert positive feedback circuits on some of its upstream regulators:
Akt and calcineurin are both activators of NF-kappa-B (p65). [ 23 ] [ 24 ] Through their activation, PGC-1α seems to activate NF-kappa-B. Increased activity of NF-kappa-B in muscle has recently been demonstrated following induction of PGC-1α. [ 25 ] The finding seems to be controversial. Other groups found that PGC-1s inhibit NF-kappa-B activity. [ 26 ] The effect was demonstrated for PGC-1 alpha and beta.
PGC-1α has also been shown to drive NAD biosynthesis to play a large role in renal protection in acute kidney injury . [ 27 ]
PPARGC1A has been implicated as a potential therapy for Parkinson's disease conferring protective effects on mitochondrial metabolism. [ 28 ]
Moreover, brain-specific isoforms of PGC-1alpha have recently been identified which are likely to play a role in other neurodegenerative disorders such as Huntington's disease and amyotrophic lateral sclerosis . [ 29 ] [ 30 ]
Massage therapy appears to increase the amount of PGC-1α, which leads to the production of new mitochondria. [ 31 ] [ 32 ] [ 33 ]
PGC-1α and beta has furthermore been implicated in polarization to anti-inflammatory M2 macrophages by interaction with PPAR-γ [ 34 ] with upstream activation of STAT6 . [ 35 ] An independent study confirmed the effect of PGC-1 on polarisation of macrophages towards M2 via STAT6/PPAR gamma and furthermore demonstrated that PGC-1 inhibits proinflammatory cytokine production. [ 36 ]
PGC-1α has been recently proposed to be responsible for β-aminoisobutyric acid secretion by exercising muscles. [ 37 ] The effect of β-aminoisobutyric acid in white fat includes the activation of thermogenic genes that prompt the browning of white adipose tissue and the consequent increase of background metabolism. Hence, the β-aminoisobutyric acid could act as a messenger molecule of PGC-1α and explain the effects of PGC-1α increase in other tissues such as white fat.
PGC-1α increases BNP expression by coactivating Estrogen-related receptor alpha (ERRα) and / or AP1. Subsequently, BNP induces a chemokine cocktail in muscle fibers and activates macrophages in a local paracrine manner, which can then contribute to enhancing the repair and regeneration potential of trained muscles.
Most studies reporting effects of PGC-1α on physiological functions have used mouse models in which the PGC-1α gene is either knocked out or overexpressed from conception. However, some of the proposed effects of PGC-1α have been questioned by studies using inducible knockout technology to remove the PGC-1α gene only in adult mice. For example, two independent studies have shown that adult expression of PGC-1α is not required for improved mitochondrial function after exercise training. [ 38 ] [ 39 ] This suggests that some of the reported effects of PGC-1α are likely to occur only in the developmental stage.
In the metabolic disorder of combined malonic and methylmalonic aciduria (CMAMMA) due to ACSF3 deficiency, there is a massively increased expression of PGC-1α, which is consistent with upregulated beta oxidation . [ 40 ]
PPARGC1A has been shown to interact with:
ERRα and PGC-1α are coactivators of both glucokinase (GK) and SIRT3 , binding to an ERRE element in the GK and SIRT3 promoters. [ citation needed ]
This article incorporates text from the United States National Library of Medicine , which is in the public domain . | https://en.wikipedia.org/wiki/PPARGC1A |
3SP6
133522
170826
ENSG00000155846
ENSMUSG00000033871
Q86YN6
Q8VHJ7
NM_001172698 NM_001172699 NM_133263
NM_133249 NM_001364996
NP_001166169 NP_001166170 NP_573570
NP_573512 NP_001351925
Peroxisome proliferator-activated receptor gamma coactivator 1-beta is a protein that in humans is encoded by the PPARGC1B gene . [ 5 ] [ 6 ] [ 7 ]
This article incorporates text from the United States National Library of Medicine , which is in the public domain .
This article on a gene on human chromosome 5 is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PPARGC1B |
A PPO inhibitor may inhibit two unrelated enzymes abbreviated "PPO". They are: | https://en.wikipedia.org/wiki/PPO_inhibitor |
PPT Petoletka ( Serbian : ППТ-Петолетка ) is a Serbian manufacturer of hydraulics and pneumatics, headquartered in Trstenik , Serbia.
"Prva Petoletka"-Trstenik was founded on 23 March 1949, by decision of the Government of People's Federal Republic of Yugoslavia , at the beginning of the first Five-year plan of development, after which it was named.
The factory entered its "golden era" during the 1980s. During this time the factory had nearly 20,000 employees. The design offices of Prva Petoletka designed hydraulic systems for many of the hydroelectric power plants in Yugoslavia , the hydraulic drive on a class of massive roto-excavators for surface mines, drive- and control-systems for the sets of the National Theatre in Belgrade , electro-hydraulic system for lifting of the main dome of the Temple of Saint Sava in Belgrade, hydraulics for a modern second-generation tank (the M-84 ), an inclined marine railway installed in the shipyard in Kladovo , landing gear for Boeing , as well as many large centralized lubrication systems in Yugoslavia.
Prva Petoletka was an important exporter, delivering its products to over 30 countries on several continents. At the height of production, PPT exported about 40% of its products. Petoletka cooperated with major world companies such as Boeing , Bugatti , Lucas , Bendix , Daimler , Martin Merkel, Pol-Mot, Orsta Hydraulik, Wabco Westinghouse, Linde Guldner, Ermeto, and Zahnradfabrik.
Prva Petoletka was contracted to lift the 4000 ton central dome of the Cathedral of Saint Sava in 1989. The height of the dome was 37 metres prior to its retrofit and together with the ten metre cross it weighed 40,000 kN. The dome was lifted to a height of 43 m. Arch carriers and pendentives occupy the rest of the space between the dome and the supporting construction. The lifting process was very slow and took forty days to complete.
In the 1990s Yugoslavia collapsed and war started in Croatia and Bosnia . International sanctions were imposed by the United Nations , which led to political isolation and economic decline for Serbia. This resulted in a crisis for the factory and its workers when PPT lost its ability to export products. Many high-profile engineers left Petoletka during the 1990s and started their own private companies. The state did not have funds to invest in factory machines and equipment and this resulted in most of factory's equipment becoming obsolete.
Since the 2000s, the PPT has sought privatization. The first tender for the sale of Prva Petoletka, held in June 2005, was unsuccessful. The second tender, opened in November 2007, also failed. The government decided to sell the factory in parts rather than as a whole because of the lack of interested parties to buy entire company. In 2009, an agreement was reached with the Russian company "Bummash" from Izhevsk , but deal failed once again. After that, restructuring of PPT has started and some members of the group have already found strategic partners.
During the 2010s, the company maintained production facilities in Trstenik , Vrnjacka Banja , Brus , Aleksandrovac , Novi Pazar , Leposavic , and Belgrade in Serbia and Bijelo Polje in Montenegro . Its headquarters and main production facilities were located in Trstenik. [ 3 ]
In January 2016, after two decades of insolvency, the company has declared bankruptcy . [ 4 ]
In January 2016, a new business entity under name “PPT Petoletka doo” was registered and took most of Prva Petoletka's former employees. [ 5 ] As of 2017, its main contractor is Russian Kamaz . [ 5 ] | https://en.wikipedia.org/wiki/PPT-Petoletka |
Pentaphenylphosphorus is an organic phosphorane containing five phenyl groups connected to a central phosphorus atom. The phosphorus atom is considered to be in the +5 oxidation state . The chemical formula could be written as P(C 6 H 5 ) 5 or Ph 5 P, where Ph represents the phenyl group. It was discovered and reported in 1949 by Georg Wittig . [ 2 ]
Pentaphenylphosphorus can be formed by the action of phenyllithium on tetraphenylphosphonium bromide or tetraphenylphosphonium iodide. [ 3 ] The compound was produced during the course of Wittig's Nobel-prize-winning investigations of organophosphorus compounds. [ 2 ]
Pentaphenylphosphorus is trigonal bipyramidal, according to several determinations by X-ray crystallography . The axial and equatorial P-C bond lengths are 199 and 185 picometers , respectively. [ 4 ]
The monoclinic crystal has dimensions a=10.03, b=17.22 c=14.17 Å and β=112.0°. [ 4 ] Pentaphenyl phosphorus can also crystallise with solvent, (to form a solvate ) with tetrahydrofuran and cyclohexane . [ 5 ] [ 6 ]
On heating, pentaphenylphosphorus decomposes to form biphenyl and triphenylphosphine . [ 2 ]
Pentaphenylphosphorus reacts with acidic hydrogen to yield the tetraphenylphosphonium ion and benzene. [ 2 ] For example pentaphenylphosphorus reacts with carboxylic acids and sulfonic acids to yield the tetraphenylphosphonium salt of the carboxylate or sulfonate, and benzene. [ 7 ]
Pentaphenylphosphorus transfers a phenyl group to organomercury, and tin halides. For example pentaphenylphosphorus reacts with phenylmercury chloride to yield diphenyl mercury and tetraphenylphosphonium chloride. With tributyltin chloride , tributylphenyltin is produced. However the pentaphenylphosphorus reaction with triphenylbismuth difluoride , chloride or bromide makes triphenylbismuth and fluorobenzene , chlorobenzene or bromobenzene . This is probably because tetraphenylbismuth halides (Ph 4 BiF, Ph 4 BiCl, Ph 4 BiBr) spontaneously decompose as the halogen reacts with one phenyl group. [ 8 ]
When heated with carbon dioxide or sulfur, bicyclic compounds are formed, where the reactant bridges between one of the phenyl groups and the phosphorus. [ 9 ] | https://en.wikipedia.org/wiki/PPh5 |
PQS is a general purpose quantum chemistry program. Its roots go back to the first ab initio gradient program developed in Professor Peter Pulay 's group but now it is developed and distributed commercially by Parallel Quantum Solutions. There is a reduction in cost for academic users and a site license. Its strong points are geometry optimization, NMR chemical shift calculations, and large MP2 calculations, and high parallel efficiency on computing clusters. It includes many other capabilities including Density functional theory , the semiempirical methods, MINDO /3, MNDO , AM1 and PM3 , Molecular mechanics using the SYBYL 5.0 Force Field , the quantum mechanics/molecular mechanics mixed method using the ONIOM method, natural bond orbital (NBO) analysis and COSMO solvation models . Recently, a highly efficient parallel CCSD(T) code for closed shell systems has been developed. This code includes many other post Hartree–Fock methods: MP2 , MP3 , MP4 , CISD , CEPA , QCISD and so on.
The origin of PQS program was developed by Meyer [ who? ] and Pulay in the late 1960s. They both were at the Max-Planck Institute for Physics and Astrophysics in Munich when they began to write a new ab initio program. [ 1 ] The main purpose was to establish new ab initio techniques. Pulay and Meyer had slightly different interests. [ 1 ] Pulay was interested in implementing gradient geometry optimization, analytical energy derivatives (force), and force constant calculations via the numerical differentiation of analytical forces, while Meyer enthused about the coupled-electron pair approximation (CEPA), spin density calculation, and extremely accurate correlation methods like pseudonatural orbital-configuration interaction (PNO-CI). [ 1 ] At that time, analytical gradients were limited to closed-shell Hartree-Fock wavefunctions. However, they were able to do it for unrestricted (UHF) and restricted open-shell (ROHF) methods in 1970. The first version of the code was completed in 1969 at Max-Planck institute and University of Stuttgart . Then, Meyer named it “ MOLPRO ” and used Gaussian lobe basis sets. [ 1 ] In the 1970s, the current version of MOLPRO added a number of advanced methods such as multiconfiguration self-consistent field (MC-SCF) and internally contracted multireference configuration interaction (MR-CI). Simultaneously, in the 1980s, MOLPRO was extended and mostly rewritten by Hans-Joachim Werner , Peter Knowles and Meyer's coworkers. [ 1 ]
Meanwhile, in 1976, Pulay was visiting Boggs at the University of Texas, Austin and Schaefer at the University of California . They wrote a new program called TEXAS based on the original MOLPRO and replaced Gaussian lobe functions with the standard Gaussian functions. [ 1 ] TEXAS emphasized large molecules, SCF convergence, geometry optimization techniques, and vibrational spectroscopy-related calculations. From 1982 onward, the program was further developed at the University of Arkansas. [ 1 ]
The primary significant expansion was the usage of a few new electron correlation methods by Saebo and a first- order MC-SCF program by Hamilton. A critical option was the implementation of the first practical gauge-invariant atomic orbital (GIAO) NMR program by Wolinski, who additionally included a highly efficient integral package. [ 1 ] Bofill executed an unhindered natural orbital-complete active space (UNO-CAS) program including analytical gradients; this is a minimal-cost alternative to MC-SCF and works just as well in most cases. TEXAS was initially parallelized in 1995–1996 on a cluster of 10 IBM RS6000 workstations. [ 1 ]
In 1996, Baker joined Pulay and, around the same time, Intel brought out the Pentium Pro , a processor for PC that was competitive with low-end workstations and less costly by around an order of magnitude. Understanding the capability of this improvement for computational chemistry , PQS was formed and a SBIR grant application was submitted in July 1997 for the commercial development of PC clusters for parallel ab initio calculations. [ 1 ] In the meantime, the Pulay group, financed by a National Science Foundation grant, set about constructing a Linux cluster using 300 MHz Pentium II processors. By a fortunate circumstance, a few capable and PC proficient graduate students were available, specifically Magyarfalvi and Shirel. [ 1 ] The PC cluster was a complete success, and significantly outperformed the IBM Workstation cluster that was the group's computational mainstay at a small amount of its expense. [ 1 ]
The PQS programming was demonstrated on the TEXAS code and parts of it, chiefly the NMR code, were authorized to PQS from the University of Arkansas. [ 1 ] Much of the code was widely changed to comply with the twin points of (a) having all major functionality fully parallel; and (b) having the capacity to routinely perform calculations on extensive systems. [ 1 ] They aimed primarily for a modest level of parallelism (from 8 to 32 CPUs), as this is the most widely recognized size for an individual or group resource. Indeed, even on very large clusters it is normal for any given user to be allocated only a percentage of the available processors. [ 1 ]
The basis capabilities in high-level correlated energies for PQS ab initio v. 4.0 include MP3 , MP4 , CID , CISD , CEPA-0 , CEPA-2 , QCISD , QCISD(T) , CCD , CCSD and CCSD(T) wavefunctions; enforced geometry optimization (used, among other things, to simulate the results of Atomic Force Microscopy (AFM) experiments); full-accuracy, canonical UMP2 energies and analytical polarizabilities and hyperpolarizabilities for HF and DFT wavefunctions. [ 2 ] | https://en.wikipedia.org/wiki/PQS_(software) |
PRIME ( probe incorporation mediated by enzymes ) is a molecular biology research tool developed by Alice Y. Ting and the Ting Lab at MIT for site-specific labeling of proteins in living cells with chemical probes. [ 1 ] [ 2 ] Probes often have useful biophysical properties, such as fluorescence , and allow imaging of proteins. [ 1 ] Ultimately, PRIME enables scientists to study functions of specific proteins of interest.
Protein labeling with fluorescent molecules allows the visualization of protein dynamics, localization, and protein-protein interactions , and therefore serves as an important technique to understand protein functions and networks in living cells. [ 3 ] The protein labeling should have a high selectivity towards the protein of interest, and should not interfere with the natural functions of the protein. Although genetic coding of fluorescent proteins, such as the green fluorescent protein (GFP), is the most popular technique due to its high specificity, fluorescent proteins are likely to interfere with the functions of the protein to which they are fused because of their large sizes. [ 3 ] There are multiple tagging tools, such as HaloTag, SNAP tag, and FlAsH, developed in order to overcome the weakness of traditional protein labeling with fluorescent proteins. However, they still have significant shortcomings either due to the large size of a tag or the low specificity of the labeling process. [ 4 ] PRIME has been developed in order to achieve a high labeling specificity comparable to fluorescent proteins with small molecules. [ 4 ]
In PRIME, a mutant enzyme LplA (lipoic acid ligase from Escherichia coli ) first catalyzes the conjugation of the "functional group handle" and LplA acceptor peptide (LAP), which is genetically fused to the protein of interest. [ 1 ] [ 4 ] [ 5 ] “Functional group handle” indicates a bridge molecule connecting a LAP tag to a fluorescent probe or fluorophore . Fluorescent probe reacts with the “functional group handle” connected to the tag, and ultimately labels the protein of interest. Different chemical reactions can be utilized to attach the fluorescent probe to a complex consisting of the protein, the LAP tag, and the bridge: Diels-Alder Reaction , [ 6 ] and chelation-assisted copper-catalyzed azide-alkyne cycloaddition (CuAAC) (refer to Azide-alkyne Huisgen cycloaddition ). [ 7 ] Two other versions of PRIME labeling technologies use mutant LplA proteins to directly incorporate a fluorophore to the LAP-tagged protein of interest. [ 8 ] [ 9 ]
Despite the advantages of PRIME over other tagging methods, PRIME still has some possible limitations. First of all, the LAP tag may interfere with the function of proteins to which it is fused. [ 1 ] It is recommended that the experimenters perform control experiments in order to make sure that the tagged recombinant protein functions properly. [ 1 ] Secondly, even at a low concentration, chemicals such as the fluorescent probe can be toxic to the cells. [ 1 ] Experimenters are also required to obtain the right balance between maximal signal of fluorescence and minimal disruption of cellular function. [ 1 ] | https://en.wikipedia.org/wiki/PRIME_(labeling_technique) |
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ENSG00000108946
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NM_212472 NM_001369389 NM_001369390
NM_001362677 NM_001373912 NM_001373913
NP_997637 NP_001356318 NP_001356319 NP_001263218.1 NP_001265362.1 NP_002725.1 NP_997636.1 NP_997637.1
NP_001349606 NP_001360841 NP_001360842
cAMP-dependent protein kinase type I-alpha regulatory subunit is an enzyme that in humans is encoded by the PRKAR1A gene . [ 5 ]
cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP-dependent protein kinase A ( PKA ), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of PKA is a tetramer composed of two regulatory and two catalytic subunits. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits of PKA have been identified in humans. The protein encoded by this gene is one of the regulatory subunits. This protein was found to be a tissue-specific extinguisher that downregulates the expression of seven liver genes in hepatoma x fibroblast hybrids Three alternatively spliced transcript variants encoding the same protein have been observed. [ 6 ]
Functional null mutations in this gene cause Carney complex (CNC), an autosomal dominant multiple neoplasia syndrome. This gene can fuse to the RET protooncogene by gene rearrangement and form the thyroid tumor-specific chimeric oncogene known as PTC2. [ 6 ]
Mutation of PRKAR1A leads to the Carney complex, associating multiple endocrine tumors. [ citation needed ]
PRKAR1A has been shown to interact with:
This article incorporates text from the United States National Library of Medicine , which is in the public domain . | https://en.wikipedia.org/wiki/PRKAR1A |
Protein arginine N- methyltransferase -4 (PRMT4/CARM1) [ 1 ] [ 2 ] [ 3 ] methylation of arginine residues within proteins plays a critical key role in transcriptional regulation (see the PRMT4 pathway on the left). PRMT4 binds to the classes of transcriptional activators known as p160 and CBP/p300. [ 4 ] The modified forms of these proteins are involved in stimulation of gene expression via steroid hormone receptors . Significantly, PRMT4 methylates core histones H3 and H4, which are also targets of the histone acetylase activity of CBP/p300 coactivators. PRMT4 recruitment of chromatin by binding to coactivators increases histone methylation and enhances the accessibility of promoter regions for transcription . Methylation of the transcriptional coactivator CBP by PRMT4 inhibits binding to CREB and thereby partitions the limited cellular pool of CBP for steroid hormone receptor interaction. | https://en.wikipedia.org/wiki/PRMT4_pathway |
389333
381148
ENSG00000228672
ENSMUSG00000073600
E7EW31
n/a
NM_001161546
NM_001270646
NP_001155018
n/a
Proline-rich basic protein 1 (PROB1) is a protein encoded by the PROB1 gene located on human chromosome 5 , open reading frame 65. PROB1 is also known as C5orf65 and weakly similar to basic proline-rich protein. [ 5 ] [ 6 ]
The PROB1 gene is 3251 bp long and contains a single exon. [ 6 ]
The PROB1 gene is located on human chromosome 5, cytogenetic band 5q31.2. [ 7 ]
PROB1 is expressed in 89 types of tissue in the human body, [ 8 ] with highest expression in the skeletal muscle of the leg and cardiac muscle of the heart. [ 9 ] While mRNA expression is somewhat ubiquitous and was also elevated in the spinal cord, cerebrum, and lymphocytes, measurable protein expression was only recorded in cardiac and skeletal muscle. [ 10 ]
PROB1 is composed of 1015 amino acids. It contains two proline-rich regions, which compose the majority of the protein, and a domain of unknown function ( DUF ). [ 7 ]
Predicted secondary structures for PROB1 reveal that the protein is mostly composed of random coils, with a small percentage of alpha helices and beta sheets present. [ 13 ] This is likely due to the properties of proline ; its large size, ring structure, and confined phi angle cause it to disrupt secondary structure formation. The DUF, which resides in the second proline-rich region of the protein, is also predicted to be completely composed of random coils. A tertiary structure prediction for PROB1 was generated using I-Tasser [ 11 ] and rendered in PyMOL; [ 12 ] overall, the protein displays an elongated structure.
Analysis of protein structure, post-translational modifications, and localization signals reveals that PROB1 has no transmembrane domains and is an intracellular protein. Immunohistochemistry indicates its localization to the nucleoplasm of the cell. [ 14 ]
An array of post-translational modifications were found for PROB1, including an S-palmitolyation site [ 15 ] and a multitude of overlapping O-GlcNAcylation [ 16 ] and phosphorylation sites. [ 17 ] A representation containing a subset of the predicted modifications was generated using Dog 2.0 [ 18 ] and is shown below.
PROB1 has been found to be coexpressed with proteins SPATA24 and JADE2, but no notable functional protein interactions with PROB1 are known at this time. [ 19 ]
There are no known human paralogs of PROB1 to date. [ 20 ] [ 21 ]
PROB1 has only mammalian orthologs. Its most distant ortholog is the marsupial Vombatus ursinus (common wombat), which is estimated to have diverged about 159 million years ago as dated by TimeTree. [ 22 ] A subset of the multitude of orthologs produced by BLAST [ 20 ] is shown in the accompanying table.
PROB1 is implicated in keratoconus, which causes collagen-related degeneration of the cornea. Variants of PROB1 in the 5q31.1-q35.3 linkage region completely segregated with the keratoconus phenotype in a study utilizing segregation analysis methodology. [ 23 ] Additionally, PROB1 expression is shown to be significantly elevated in several disease states, including head and neck cancer [ 24 ] and prostate inflammation. [ 25 ] | https://en.wikipedia.org/wiki/PROB1 |
PROBA-2 is the second satellite in the European Space Agency 's series of PROBA low-cost satellites that are being used to validate new spacecraft technologies while also carrying scientific instruments. [ 3 ] PROBA-2 is a small satellite (130 kg) developed under an ESA General Support Technology Program (GSTP) contract by a Belgian consortium led by Verhaert (now QinetiQ Space ) of Kruibeke, Belgium. The nominal mission duration was two years. [ 1 ] As of 2022,
the mission continues. [ 4 ]
It was launched on 2 November 2009, with the Rockot launch system together with ESA 's SMOS mission. [ 5 ] The platform was launched in a Sun-synchronous orbit low Earth orbit (altitude of 725 km). [ 1 ]
PROBA-2 contains five scientific instruments. Two of them are designated to observe the Sun : "The Sun Watcher using APS and Image Processing" ( SWAP , an EUV imager) and the "Large Yield Radiometer" ( LYRA ), a radiometer made of diamond photodiodes. The Principal investigator teams of both instruments are hosted at the Royal Observatory of Belgium . This institute will also host the PROBA-2 Science Center from which the SWAP and LYRA instruments will be operated and their data distributed. There are three other instruments to measure basic space plasma properties: the Dual segmented Langmuir probe (DSLP) [ 1 ] (developed by the Astronomical Institute and Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic), the Thermal Plasma Measurement Unit (TPMU), and the Science Grade Vector Magnetometer (SGVM) developed by the Technical University of Denmark . [ 1 ]
This article related to the European Space Agency is a stub . You can help Wikipedia by expanding it .
This article about one or more spacecraft of a European multinational organisation is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PROBA-2 |
PRODIGAL ( proactive discovery of insider threats using graph analysis and learning) is a computer system for predicting anomalous behavior among humans, by data mining network traffic such as emails, text messages and server log entries. [ 1 ] It is part of DARPA 's Anomaly Detection at Multiple Scales (ADAMS) project. [ 2 ] The initial schedule is for two years and the budget $9 million. [ 3 ]
It uses graph theory , machine learning , statistical anomaly detection , and high-performance computing to scan larger sets of data more quickly than in past systems. The amount of data analyzed is in the range of terabytes per day. [ 3 ] The targets of the analysis are employees within the government or defense contracting organizations; specific examples of behavior the system is intended to detect include the actions of Nidal Malik Hasan and WikiLeaks source Chelsea Manning . [ 1 ] Commercial applications may include finance. [ 1 ] The results of the analysis, the five most serious threats per day, go to agents, analysts, and operators working in counterintelligence . [ 1 ] [ 3 ] [ 4 ]
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PRODIGAL |
PROX is an acronym for PReferential OXidation , that refers to the preferential oxidation of carbon monoxide in a gas mixture by a catalyst . It is intended to remove trace amounts of CO from H 2 /CO/CO 2 mixtures produced by steam reforming and water-gas shift . An ideal PROX catalyst preferentially oxidizes carbon monoxide (CO) using a heterogeneous catalys t placed upon a ceramic support. Catalysts include metals such as platinum , platinum/iron, platinum/ruthenium, gold nanoparticles as well as novel copper oxide/ceramic conglomerate catalysts. [ 1 ]
This reaction is a considerable subject area of research with implications for fuel cell design.
Its main utility lies in the removal of carbon monoxide (CO) from the fuel cell's feed gas. CO poisons the catalyst of most low-temperature fuel cells.
Carbon monoxide is often produced as a by-product from steam reforming of hydrocarbons, which produces hydrogen and CO.
It is possible to consume most of the CO by reacting it with steam in the water-gas shift reaction :
The water-gas shift reaction can reduce CO to 1% of the feed, with the added benefit of producing more hydrogen, but not eliminate it completely.
To be used in a fuel cell, feed gas must have CO below 10 ppm .
The PROX process allows for the reaction of CO with oxygen, reducing CO concentration from approximately 0.5–1.5% in the feed gas to less than 10 ppm.
Due to the prevalent presence of hydrogen in the feed gas, the competing, undesired combustion of hydrogen will also occur to some degree:
The selectivity of the process is a measure of the quality of the reactor, and is defined as the ratio of consumed carbon monoxide to the total of consumed hydrogen and carbon monoxide.
The disadvantage of this technology is its very strong exothermic nature, coupled with a very narrow optimal operation temperature window, and is best operated between 353 and 450 K, [ citation needed ] yielding a hydrogen loss of around one percent. Effective cooling is therefore required. In order to minimize steam generation, excessive dilution with nitrogen is used. Additionally the reaction is interrupted with an intermediary cooler before proceeding to a second stage.
In the first reaction an excess of oxygen is provided, at around a factor of two, and about 90% of the CO is transformed. In the second step a substantially higher oxygen excess is used, at approximately a factor of 4, which is then processed with the remaining CO, in order to reduce the CO concentration to less than 10 ppm. To also avoid excess CO-fraction loading, the transient operation of a CO adsorber may be important.
The instrumentation and process control complexity requirements are relatively high. The advantage of this technique over selective methanation is the higher space velocity, which reduces the required reactor size. For the case of strong temperature rises, the feed of air can simply be broken.
The technical origins for CO-PROX lies in the synthesis of ammonia ( Haber process ). Ammonia synthesis also has a strict requirement of CO-free hydrogen, as CO is a strong catalyst poison for the usual catalysts used in this process. | https://en.wikipedia.org/wiki/PROX |
pSC101 is a DNA plasmid that is used as a cloning vector in genetic cloning experiments. pSC101 was the first cloning vector, used in 1973 by Herbert Boyer and Stanley Norman Cohen . Using this plasmid they have demonstrated that a gene from a frog could be transferred into bacterial cells and then expressed by the bacterial cells. The plasmid is a natural plasmid from Salmonella panama . [ 1 ]
In the early 1970s, [ 2 ] Herbert Boyer and Stanley Norman Cohen produced pSC101, the first plasmid vector for cloning purposes. Soon after successfully cloning two pSC101 plasmids together to create one large plasmid, they published the results describing the experiment, in 1973. [ 2 ] The cloning of genes into plasmids occurred soon after.
In 1980, [ 2 ] pSC101 became the first patented commercial DNA cloning vector when patents were awarded to Boyer and Cohen. The "SC" stands for Stanley Cohen. Although the original pSC101 only contained tetracycline resistance and a restriction site for EcoRI, the commercially available pSC101 gained restriction sites for several enzymes, including HindIII, in addition to the EcoRI site.
Certain mutants of the pSC101 replication protein RepA are heat sensitive and can not stably maintain the plasmid in bacteria when grown at temperatures above 37C. [ 3 ] This property can be used to "cure" bacteria transformed with plasmids using the pSC101 origin of replication by growing them at an elevated temperature, typically 42C. [ 4 ]
This genetics article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PSC101 |
Thiophosphoryl chloride is an inorganic compound with the chemical formula P S Cl 3 . [ 5 ] It is a colorless pungent smelling liquid that fumes in air. It is synthesized from phosphorus chloride and used to thiophosphorylate organic compounds, such as to produce insecticides .
Thiophosphoryl chloride can be generated by several reactions starting from phosphorus trichloride . The most common and practical synthesis, hence used in industrial manufacturing, is directly reacting phosphorus trichloride with excess sulfur at 180 °C. [ 6 ]
Using this method, yields can be very high after purification by distillation. Catalysts facilitate the reaction at lower temperatures, but are not usually necessary.
Alternatively, it is obtained by combining phosphorus pentasulfide and phosphorus pentachloride. [ 7 ]
Thiophosphoryl chloride has tetrahedral molecular geometry and C 3v molecular symmetry , with the structure S=PCl 3 . According to gas electron diffraction , the phosphorus–sulfur bond length is 189 pm and the phosphorus–chlorine bond length is 201 pm, while the Cl−P−Cl bond angle is 102°. [ 8 ]
PSCl 3 is soluble in benzene , carbon tetrachloride , chloroform , and carbon disulfide . [ 5 ] However, it hydrolyzes rapidly in basic or hydroxylic solutions, such as alcohols and amines , to produce thiophosphates . [ 6 ] In water PSCl 3 reacts, and contingent on the reaction conditions, produces either phosphoric acid , hydrogen sulfide , and hydrochloric acid or dichlorothiophosphoric acid and hydrochloric acid. [ 9 ]
An intermediate in this process appears to be tetraphosphorus nonasulfide . [ 10 ]
PSCl 3 is used to thiophosphorylate organic compounds (to add thiophosphoryl group, P=S, with three free valences at the P atom, to organic compounds ). [ 6 ] This conversion is widely applicable for amines and alcohols, as well as aminoalcohols , diols , and diamines . [ 5 ] Industrially, PSCl 3 is used to produce insecticides , like parathion . [ 9 ]
PSCl 3 reacts with tertiary amides to generate thioamides . [ 5 ] For example:
When treated with methylmagnesium iodide , it give tetramethyldiphosphine disulfide (H 3 C−) 2 P(=S)−P(=S)(−CH 3 ) 2 . [ 11 ] | https://en.wikipedia.org/wiki/PSCl3 |
Phosphorothioic chloride difluoride or thiophosphoryl chloride difluoride is a chemical compound with formula P S Cl F 2 . It is normally found as a gas boiling at 6.3 °C and melting at −155.2 °C. The density of the gas at standard conditions is 5.579 g/L. [ 1 ] Critical pressure is 41.4 bars , and critical temperature is 439.2 K. [ 2 ]
Phosphorothioic chloride difluoride was made in 1940 by reacting PSCl 3 with SbF 3 and SbCl 5 at 75 °C. [ 3 ]
In another reaction PSCl 3 reacts with KSO 2 F to make PSF 3 , KCl and SO 2 , but also partly yields PSClF 2 . [ 4 ]
A small percentage of is formed when F 2 P(=S)−S−P(−CF 3 ) 2 or (F 3 C−) 2 P(=S)−S−PF 2 reacts with chlorine. [ 5 ]
It can be formed from difluoro(germylthio)phosphine:
Although phosphorothioic chloride difluoride does not spontaneously ignite in air, mixtures with air are explosive. The gas is hydrolysed slowly by water vapour. It also reacts with potassium hydroxide solution. [ 3 ]
Heat of vaporization is 5703 cal /mol. [ 3 ]
Infrared bands in the gas are at 946, 920, 738, 541, 395, 361, 317, missed, and 198 cm −1 . In liquid, a Raman spectroscopy has bands at 939, 913, 727, 536, 394, 359, 314, 251, 207. These are for PF 2 symmetric stretch in a' and a'' symmetry, PS stretch, PCl stretch, PCl bend, PF 2 scissor, PF 2 rock, PS op-bend, and PS ip-bend. [ 7 ] [ 8 ]
The nuclear magnetic resonance coupling constants for 31 P are 1220. It is a triplet line with intensities 1:2:1. The chemical shift from orthophosphoric acid is −50×10 −6 . For 19 F the coupling constant is 1218. It is a doublet line in ratio 1:1. The chemical shift from CCl 3 F is −15.9×10 −6 . [ 9 ] | https://en.wikipedia.org/wiki/PSClF2 |
Thiophosphoryl fluoride is an inorganic molecular gas with formula P S F 3 containing phosphorus , sulfur and fluorine . It spontaneously ignites in air and burns with a cool flame . The discoverers were able to have flames around their hands without discomfort, [ 5 ] and called it "probably one of the coldest flames known". [ 5 ] The gas was discovered in 1888. [ 5 ]
It is useless for chemical warfare as it burns immediately and is not toxic enough. [ 6 ]
Thiophosphoryl fluoride was discovered and named by J. W. Rodger and T. E. Thorpe in 1888. [ 5 ] [ 7 ]
They prepared it by heating arsenic trifluoride and thiophosphoryl chloride together in a sealed glass tube to 150 °C. Also produced in this reaction was silicon tetrafluoride and phosphorus fluorides. By increasing the PSCl 3 the proportion of PSF 3 was increased. They observed the spontaneous inflammability. They also used this method:
at 170 °C, and also substituting a mixture of red phosphorus and sulfur, and substituting bismuth trifluoride . [ 5 ]
Another way to prepare PSF 3 is to add fluoride to PSCl 3 using sodium fluoride in acetonitrile. [ 8 ]
A high yield reaction can be used to produce the gas: [ citation needed ]
Under high pressure phosphorus trifluoride can react with hydrogen sulfide to yield: [ 9 ]
Another high pressure production uses phosphorus trifluoride with sulfur . [ 9 ]
PSF 3 is unstable against moisture or heat. The pure gas is completely absorbed by alkali solutions, producing the fluoride and a thiophosphate ( PSO 3− 3 ), but stable against CaO. The latter can be used to remove SiF 4 or PF 3 impurities. [ 5 ]
Reaction with neutral water is slow:
Nevertheless, dissociation constants for related acids suggest that the phosphorus atom is at least as electrophilic as in phosphoryl fluoride . [ 10 ]
Autodecomposition from heat gives phosphorus fluorides, sulfur, and phosphorus:
Hot PSF 3 reacts with glass, producing SF 4 , sulfur and elemental phosphorus. If water is present and the glass is leaded , then the hydrofluoric acid and hydrogen sulfide combination produces a black plumbous sulfide deposit on the inner surface. [ 5 ]
In air, PSF 3 burns spontaneously with a greyish green flame, producing solid white fumes containing SO 2 and P 2 O 5 . The flame is one of the coldest known. With dry oxygen, combustion may not be spontaneous and the flame is yellow. [ 5 ]
Thiophosphoryl fluoride reduces oxygenated compounds to give phosphoryl fluoride and sulfur : [ 9 ] [ 11 ]
The latter reaction also indicates why PSF 3 is not formed from PF 3 and SO 2 . [ 9 ]
Various oxidants can convert thiophosphoryl fluoride to phosphorus dichloride trifluoride , e.g.: [ 12 ]
Thiophosphoryl difluoride isocyanate can be formed by reacting PSF 3 with silicon tetraisocyanate at 200 °C in an autoclave. [ 13 ]
In general, nucleophilic substitution onto thiophosphoryl fluoride is complex, because free fluoride ions tend to induce disproportionation to hexafluorophosphate and dithiodifluorophosphate ( PS 2 F − 2 ). [ 10 ] [ 14 ] For example, with cesium fluoride : [ 15 ]
Thus PSF 3 combines with dimethylamine in solution to produce dimethylaminothiophosphoryl difluoride (H 3 C−) 2 N−P(=S)F 2 and difluorophosphate and hexafluorophosphate ions: [ 10 ] [ 16 ]
PSF 3 reacts with four times its volume of ammonia gas producing ammonium fluoride and a mystery product, possibly P(NH 2 ) 2 SF . [ 5 ]
PSF 3 does not react with ether , benzene , carbon disulfide , or pure sulfuric acid . [ 5 ] It initiates tetrahydrofuran polymerization. [ 17 ]
PSF 3 reacts with [SF 6 ] − in a mass spectrometer to form [PSF 4 ] − . [ 18 ]
One fluorine can be substituted by iodine to give thiophosphoryl difluoride iodide, PSIF 2 . [ 19 ] PSIF 2 can be converted to hydrothiophosphoryldifluoride, S=PHF 2 , by reducing it with hydrogen iodide . [ 20 ] In F 2 P(=S)−S−PF 2 , one sulfur forms a bridge between two phosphorus atoms. [ 19 ]
Dimethylaminothiophosphoryl difluoride ( (H 3 C−) 2 N−P(=S)F 2 ) is a foul smelling liquid with a boiling point of 117 °C. It has a Trouton constant (entropy of vaporization at the boiling point of the liquid) of 24.4, and a heat of evaporation of 9530 cal/mole. Alternately it can be produced by fluorination of dimethylaminothiophosphoryl dichloride ( (H 3 C−) 2 N−P(=S)Cl 2 ).
The thiophosphoryl trifluoride molecule shape has been determined using electron diffraction. The interatomic distances are P=S 0.187±0.003 nm, P−F 0.153±0.002 nm and bond angles of F−P−F bonding is 100.3±2°, The microwave rotational spectrum has been measured for several different isotopologues . [ 21 ]
The critical point is at 346 K at 3.82 MPa. [ 22 ] The liquid refractive index is 1.353. [ 4 ]
The enthalpy of vaporisation 19.6 kJ/mol at boiling point. [ 23 ] The enthalpy of vaporisation at other temperatures is a function of temperature T: H(T)=28.85011(346-T) 0.38 kJ/mol. [ 24 ]
The molecule is polar. It has a non-uniform distribution of positive and negative charge which gives it a dipole moment . When an electric field is applied more energy is stored than if the molecules did not respond by rotating. This increases the dielectric constant . The dipole moment of one molecule of thiophosphoryl trifluoride is 0.640 Debye . [ 25 ]
The infrared spectrum includes vibrations at 275, 404, 442, 698, 951 and 983 cm −1 . [ 26 ] These can be used to identify the molecule. | https://en.wikipedia.org/wiki/PSF3 |
Psi is an ab initio computational chemistry package originally written by the research group of Henry F. Schaefer, III ( University of Georgia ). Utilizing Psi, one can perform a calculation on a molecular system with various kinds of methods such as Hartree-Fock , Post-Hartree–Fock electron correlation methods, and density functional theory . [ 2 ] [ 3 ] The program can compute energies, optimize molecular geometries, and compute vibrational frequencies. [ 2 ] [ 3 ] The major part of the program is written in C++ , while Python API is also available, which allows users to perform complex computations or automate tasks easily. [ 2 ] [ 4 ] [ 5 ] [ 6 ]
Psi4 is the latest release of the program package - it is open source , released as free under the LGPL3 through GitHub . Primary development of Psi4 is currently performed by the research groups of David Sherrill ( Georgia Tech ), T. Daniel Crawford ( Virginia Tech ), Francesco Evangelista ( Emory University ), and Henry F. Schaefer, III ( University of Georgia ), with substantial contributions by Justin Turney ( University of Georgia ), Andy Simmonett ( NIH ), and Rollin King ( Bethel University ). [ 2 ] [ 4 ] [ 5 ] [ 6 ] Psi4 is available on Linux releases such as Fedora and Ubuntu.
The basic capabilities of Psi are concentrated around the following methods [ 2 ] of quantum chemistry :
Several methods are available for computing excited electronic states, including configuration interaction singles (CIS), the random phase approximation (RPA), time-dependent density functional theory (TD-DFT), and equation-of-motion coupled cluster (EOM-CCSD). [ 2 ]
Psi4 has introduced the density-fitting approximation in many portions of the code, leading to faster computations and reduced I/O requirements. [ 2 ] [ 4 ] [ 5 ]
Psi4 is the preferred quantum chemistry backend for the OpenFermion project, which seeks to perform quantum chemistry computations on quantum computers. [ 7 ]
In Psi4 1.4, [ 6 ] the program was adapted to facilitate high-throughput workflows and can be connected to BrianQC to speed up calculations for Hartree-Fock and Density functional theory methods. | https://en.wikipedia.org/wiki/PSI_(computational_chemistry) |
VMware ESXi (formerly ESX ) is an enterprise-class , type-1 hypervisor developed by VMware , a subsidiary of Broadcom , for deploying and serving virtual computers . As a type-1 hypervisor, ESXi is not a software application that is installed on an operating system (OS); instead, it includes and integrates vital OS components, such as a kernel . [ 5 ]
After version 4.1 (released in 2010), VMware renamed ESX to ESXi . ESXi replaces Service Console (a rudimentary operating system) with a more closely integrated OS. ESX/ESXi is the primary component in the VMware Infrastructure software suite . [ 6 ]
The name ESX originated as an abbreviation of Elastic Sky X . [ 7 ] [ 8 ] In September 2004, the replacement for ESX was internally called VMvisor , but later changed to ESXi (as the "i" in ESXi stood for "integrated"). [ 9 ] [ 10 ]
ESX runs on bare metal (without running an operating system) [ 11 ] unlike other VMware products. [ 12 ] It includes its own kernel. In the historic VMware ESX, a Linux kernel was started first [ 13 ] and then used to load a variety of specialized virtualization components, including ESX, which is otherwise known as the vmkernel component. [ 14 ] The Linux kernel was the primary virtual machine; it was invoked by the service console. At normal run-time, the vmkernel was running on the bare computer, and the Linux-based service console ran as the first virtual machine. VMware dropped development of ESX at version 4.1, and now uses ESXi, which does not include a Linux kernel at all. [ 15 ]
The vmkernel is a microkernel [ 16 ] with three interfaces: hardware, guest systems, and the service console (Console OS).
The vmkernel handles CPU and memory directly, using scan-before-execution (SBE) to handle special or privileged CPU instructions [ 17 ] [ 18 ] and the SRAT (system resource allocation table) to track allocated memory. [ 19 ]
Access to other hardware (such as network or storage devices) takes place using modules. At least some of the modules derive from modules used in the Linux kernel . To access these modules, an additional module called vmklinux implements the Linux module interface. According to the README file, "This module contains the Linux emulation layer used by the vmkernel." [ 20 ]
The vmkernel uses the device drivers: [ 20 ]
These drivers mostly equate to those described in VMware's hardware compatibility list . [ 21 ] All these modules fall under the GPL . Programmers have adapted them to run with the vmkernel: VMware Inc. has changed the module-loading and some other minor things. [ 20 ]
In ESX (and not ESXi), the Service Console is a vestigial general purpose operating system most significantly used as bootstrap for the VMware kernel, vmkernel, and secondarily used as a management interface. Both of these Console Operating System functions are being deprecated from version 5.0, as VMware migrates exclusively to the ESXi model. [ 22 ] The Service Console, for all intents and purposes, is the operating system used to interact with VMware ESX and the virtual machines that run on the server.
In the event of a hardware error, the vmkernel can catch a Machine Check Exception. [ 23 ] This results in an error message displayed on a purple diagnostic screen. This is colloquially known as a purple diagnostic screen, or purple screen of death (PSoD, cf. blue screen of death (BSoD)).
Upon displaying a purple diagnostic screen, the vmkernel writes debug information to the core dump partition. This information, together with the error codes displayed on the purple diagnostic screen can be used by VMware support to determine the cause of the problem.
VMware ESX used to be available in two main types: ESX and ESXi, but as of version 5, the original ESX has been discontinued in favor of ESXi.
ESX and ESXi before version 5.0 do not support Windows 8/Windows 2012. These Microsoft operating systems can only run on ESXi 5.x or later. [ 24 ]
VMware ESXi, a smaller-footprint version of ESX, does not include the ESX Service Console. Before Broadcom acquired VMware, it was available - without the need to purchase a vCenter license - as a free download from VMware, with some features disabled. [ 25 ] [ 26 ] [ 27 ]
ESXi stands for "ESX integrated". [ 28 ]
VMware ESXi originated as a compact version of VMware ESX that allowed for a smaller 32 MB disk footprint on the host. With a simple configuration console for mostly network configuration and remote based VMware Infrastructure Client Interface, this allows for more resources to be dedicated to the guest environments.
Two variations of ESXi exist:
The same media can be used to install either of these variations depending on the size of the target media. [ 29 ] One can upgrade ESXi to VMware Infrastructure 3 [ 30 ] or to VMware vSphere 4.0 ESXi.
Originally named VMware ESX Server ESXi edition, through several revisions the ESXi product finally became VMware ESXi 3. New editions then followed: ESXi 3.5, ESXi 4, ESXi 5 and (as of 2024 [update] ) ESXi 8.
VMware has been sued by Christoph Hellwig, a Linux kernel developer. The lawsuit began on March 5, 2015. It was alleged that VMware had misappropriated portions of the Linux kernel, [ 31 ] [ 32 ] and, following a dismissal by the court in 2016, Hellwig announced he would file an appeal. [ 33 ]
The appeal was decided February 2019 and again dismissed by the German court, on the basis of not meeting "procedural requirements for the burden of proof of the plaintiff". [ 34 ]
In the last stage of the lawsuit in March 2019, the Hamburg Higher Regional Court also rejected the claim on procedural grounds. Following this, VMware officially announced that they would remove the code in question. [ 35 ] This followed with Hellwig withdrawing his case, and withholding further legal action. [ 36 ]
The following products operate in conjunction with ESX:
Network-connectivity between ESX hosts and the VMs running on it relies on virtual NICs (inside the VM) and virtual switches. The latter exists in two versions: the 'standard' vSwitch allowing several VMs on a single ESX host to share a physical NIC and the 'distributed vSwitch' where the vSwitches on different ESX hosts together form one logical switch. Cisco offers in their Cisco Nexus product-line the Nexus 1000v , an advanced version of the standard distributed vSwitch. A Nexus 1000v consists of two parts: a supervisor module (VSM) and on each ESX host a virtual Ethernet module (VEM). The VSM runs as a virtual appliance within the ESX cluster or on dedicated hardware (Nexus 1010 series) and the VEM runs as a module on each host and replaces a standard dvS (distributed virtual switch) from VMware.
Configuration of the switch is done on the VSM using the standard NX-OS CLI . It offers capabilities to create standard port-profiles which can then be assigned to virtual machines using vCenter.
There are several differences between the standard dvS and the N1000v; one is that the Cisco switch generally has full support for network technologies such as LACP link aggregation or that the VMware switch supports new features such as routing based on physical NIC load. However, the main difference lies in the architecture: Nexus 1000v is working in the same way as a physical Ethernet switch does while dvS is relying on information from ESX. This has consequences for example in scalability where the Kappa limit for a N1000v is 2048 virtual ports against 60000 for a dvS.
The Nexus1000v is developed in co-operation between Cisco and VMware and uses the API of the dvS. [ 41 ]
Because VMware ESX is a leader in the server-virtualization market, [ 42 ] software and hardware vendors offer a range of tools to integrate their products or services with ESX. Examples are the products from Veeam Software with backup and management applications [ 43 ] and a plugin to monitor and manage ESX using HP OpenView , [ 44 ] Quest Software with a range of management and backup-applications and most major backup-solution providers have plugins or modules for ESX. Using Microsoft Operations Manager (SCOM) 2007/2012 with a Bridgeways ESX management pack gives the user a realtime ESX datacenter health view.
Hardware vendors such as Hewlett Packard Enterprise and Dell include tools to support the use of ESX(i) on their hardware platforms. An example is the ESX module for Dell's OpenManage management platform. [ 45 ]
VMware has added a Web Client [ 46 ] since v5 but it will work on vCenter only and does not contain all features. [ 47 ]
As of September 2020, these are the known limitations of VMware ESXi 7.0 U1.
Some maximums in ESXi Server 7.0 may influence the design of data centers: [ 48 ] [ 49 ]
In terms of performance, virtualization imposes a cost in the additional work the CPU has to perform to virtualize the underlying hardware. Instructions that perform this extra work, and other activities that require virtualization, tend to lie in operating system calls. In an unmodified operating system, OS calls introduce the greatest portion of virtualization "overhead". [ citation needed ]
Paravirtualization or other virtualization techniques may help with these issues. VMware developed the Virtual Machine Interface for this purpose, and selected operating systems currently [update] support this. A comparison between full virtualization and paravirtualization for the ESX Server [ 50 ] shows that in some cases paravirtualization is much faster.
When using the advanced and extended network capabilities by using the Cisco Nexus 1000v distributed virtual switch the following network-related limitations apply: [ 41 ]
Regardless of the type of virtual SCSI adapter used, there are these limitations: [ 51 ] | https://en.wikipedia.org/wiki/PSOD |
PSO J172.3556+18.7734 is an astrophysical jet that was discovered in May 2011. It was originally thought to be a quasar by astronomers; as of March 8, 2021, it is now classified as a cosmic jet (astrophysical jet). [ 1 ] [ 2 ] As of 2021 [update] , it is the farthest jet discovered with a redshift of 6.82. [ 3 ] [ 4 ] [ 5 ]
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PSO_J172.3556+18.7734 |
PTC rubber [ 1 ] is a silicone rubber which conducts electricity with a resistivity that increases exponentially with increasing temperature for all temperatures up to a temperature where the resistivity grows to infinity. Above this temperature the PTC rubber is an electrical insulator . PTC rubber is made from polydimethylsiloxane (PDMS) loaded with carbon nanoparticles . PTC stands for Positive temperature coefficient .
If the electric field strength inside the material is large enough (typically larger than 30 V/mm), the carbon nanoparticles trigger a quantum mechanical tunneling effect current to flow through the material. The contribution from a large number of small tunneling effect currents can add up to macroscopic currents in the range of amperes .
The quantum mechanical tunneling effect inside the material is highly temperature dependent. The current decreases exponentially with increasing temperature. This means that the resistivity of the material grows exponentially with increasing temperature. At a specific temperature the quantum mechanical tunneling effect current ceases. At temperatures higher than this the PTC rubber is an electrical insulator and no electrical current can flow through it. This temperature can be adjusted between 0 and +80 °C during the production of the PTC rubber. Hence, PTC rubber is a PTC material with very strong PTC characteristics. In fact, PTC rubber has the strongest PTC effect of all known materials, and over a wide temperature range. It has PTC properties for all temperatures.
The PTC rubber can be rolled into thin sheets and laminated with copper . The copper is in turn connected to a voltage to provide the electrical field inside the material necessary to trigger the tunneling effect . The sheets can be formed into any shape and size.
PTC rubber sheets can be used as thin flexible PTC heaters . These heaters will provide high power when they are cold and rapidly heat up themselves to a constant temperature and remain there virtually unaffected by changes in the ambient conditions. They can be powered with any voltage between 5 and 230 V, AC or DC.
The PTC rubber material is a self-regulating heater . It produces the same amount of heat in each point of the heater as is conducted and radiated away from the heater to the object it is attached to, and its surroundings. It is in constant thermal equilibrium with the environment, point by point. A measure of the power produced by the heater is actually a measurement of the heat transfer between the heater and the object. Hence, it can be used as a heat transfer sensor. | https://en.wikipedia.org/wiki/PTC_rubber |
The Photothermoelectric (PTE) effect is based on the Seebeck effect , where the heating is achieved by absorbing light on a thermoelectric (TE) material . Synonymous to PPE technique for thermal characterization of materials, PTE can be used to thermally characterize both thermoelectrics (acts as sensor and sample) and other sample materials (while acting as a sensor). [ 1 ] An advantage of such sensors stems from their wide temperature range of applicability since pyromaterials are limited to its curie temperature . On the other hand, in order to obtain a useful signal from TE material, depends on its Seebeck coefficient , comparatively large amount of heat (light excitation) has to be deposited on the material. As far as now, Frequency domain PTE technique is in its preliminary stage for the thermal characterization of materials. Advances were done in liquid thermoelectrics as well on PTE. [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/PTE_technique |
PTFE fiber is a chemically resistant material. It is used in woven form in certain pump packings [ 1 ] as well as in nonwoven form in hot gas bag filters for industries with corrosive exhausts. [ 2 ] [ 3 ]
Because PTFE is relatively insoluble and has a very high melting point, PTFE fibers can not be fashioned from conventional melt or solution spinning . Instead they are made by combining particles of PTFE with cellulose, forming fibers of the cellulose and then sintering the PTFE particles (and charring the cellulose). The remnant char gives the fiber a brown color. It can be bleached white, although this reduces the strength. [ 4 ]
This article about materials science is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PTFE_fiber |
pUC19 is one of a series of plasmid cloning vectors designed by Joachim Messing and co-workers. [ 1 ] The designation "pUC" is derived from the classical "p" prefix (denoting " plasmid ") and the abbreviation for the University of California , where early work on the plasmid series had been conducted. [ 2 ] The pUC plasmids are all circular double stranded DNA about 2700 base pairs in length. [ 3 ] The pUC plasmids are some of the most widely used cloning vectors. [ 3 ] This is in part because cells that have successfully been transformed can be easily distinguished from those that have not based on color differences of colonies. [ 3 ] pUC18 is similar to pUC19, but the MCS region is reversed.
pUC19 encodes of the N-terminal fragment of β-galactosidase ( lacZ ) gene of E. coli , also referred to as the α-peptide. [ 4 ] [ 3 ] The multiple cloning site (MCS), which contains many restriction sites , is split into codons 6-7 of the lacZ gene. [ 4 ] This allows for blue–white screening when using host strains such as E. coli JM109, which produces only the C-terminal portion of lacZ , also known as the β-polypeptide. [ 3 ] If pUC19 is inserted into E. coli JM109 and grown on agar media supplemented with IPTG and X-gal , then colonies will appear blue, as the plasmid encodes for the α-peptide required to make a functional form of β-galactosidase. If a fragment of DNA is inserted into the MCS of pUC19, however, colonies were appear white, as the plasmid will not be able to produce the α-peptide. [ 3 ]
In addition to β-galactosidase, pUC19 also encodes for an ampicillin resistance gene ( amp R ), via a β-lactamase enzyme that functions by degrading ampicillin and reducing its toxicity to the host. [ 5 ] Cells which have been successfully transformed with pUC19 can be differentiated from cells which have not by growing them on media with ampicillin. Only the cells with the plasmid containing amp R will survive.
The origin of replication ( ori ), is derived from the plasmid pMB1. [ 6 ] [ 1 ] pUC19 is a high copy number plasmid. [ 3 ] The high copy number is a result of the lack of the rop gene and a single point mutation in the ori of pMB1. [ 7 ] [ 8 ]
The lacZ fragment, whose synthesis can be induced by IPTG, is capable of intra-allelic complementation with a defective form of β-galactosidase enzyme encoded by host chromosome (mutation lacZDM15 in E. coli JM109, DH5α and XL1-Blue strains). [ 4 ] In the presence of IPTG in growth medium, bacteria synthesise both fragments of the enzyme. Both the fragments can together hydrolyse X-gal (5-bromo-4-chloro-3-indolyl- beta-D-galactopyranoside) and form blue colonies when grown on media where it is supplemented.
Insertion of foreign DNA into the MCS located within lacZ causes insertional inactivation of this gene at the N-terminal fragment of beta-galactosidase and abolishes intra-allelic complementation. Thus bacteria carrying recombinant plasmids in the MCS cannot hydrolyse X-gal, giving rise to white colonies, which can be distinguished on culture media from non-recombinant cells, which are blue. [ 9 ]
Due to its extensive use as a cloning vector in research and industry, pUC19 is frequently used in research as a model plasmid. [ 10 ] For example, biophysical studies on its naturally supercoiled state have determined its radius of gyration to be 65.6 nm and its Stokes radius to be 43.6 nm. | https://en.wikipedia.org/wiki/PUC19 |
PUREX ( plutonium uranium reduction extraction ) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons . [ 7 ] It is based on liquid–liquid extraction ion-exchange . [ 8 ] PUREX is the de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel ( spent nuclear fuel , or irradiated nuclear fuel). It is also the standard process used in industrial scale operations. [ 9 ]
PUREX is applied to spent nuclear fuel , which consists primarily of very high atomic-weight ( actinoid or "actinide") elements (e.g. uranium , plutonium , americium ) along with smaller amounts of material composed of lighter atoms, notably the fission products produced by reactor operation.
The actinoid elements in this case consist primarily of the unconsumed remains of the original fuel (typically U-235 , U-238 , and/or Pu-239 ).
The fuel is first dissolved in nitric acid at a concentration around 7 M . Solids are removed by filtration to avoid the formation of emulsions , referred to as third phases in the solvent extraction community.
The organic solvent consists of 30% tributyl phosphate (TBP) in a hydrocarbon such as kerosene . Uranyl(VI) UO 2+ 2 ions are extracted in the organic phase as UO 2 (NO 3 ) 2 ·2TBP complexes; plutonium is extracted as similar complexes . The heavier actinides, primarily americium and curium , and the fission products remain in the aqueous phase. The nature of uranyl nitrate complexes with trialkyl phosphates has been characterized. [ 11 ]
Plutonium is separated from uranium by treating the TBP-kerosene solution with reducing agents to convert the plutonium to its +3 oxidation state, which will pass into the aqueous phase. Typical reducing agents include N,N-diethyl- hydroxylamine , ferrous sulphamate , and hydrazine . Uranium is then stripped from the kerosene solution by back-extraction into nitric acid at a concentration around 0.2 M. [ 12 ]
The term PUREX raffinate describes the mixture of metals in nitric acid which are left behind when the uranium and plutonium have been removed by the PUREX process from a nuclear fuel dissolution liquor. This mixture is often known as high level nuclear waste .
Two PUREX raffinates exist. The most highly active raffinate from the first cycle is the one which is most commonly known as PUREX raffinate. The other is from the medium-active cycle in which the uranium and plutonium are refined by a second extraction with tributyl phosphate .
Deep blue is the bulk ions, light blue is the fission products (group I is Rb/Cs; group II is Sr/Ba; group III is Y and the lanthanides ), orange is the corrosion products (from stainless steel pipework), green are the major actinides, violet are the minor actinides and magenta is the neutron poison )
Currently PUREX raffinate is stored in stainless steel tanks before being converted into glass . The first cycle PUREX raffinate is very radioactive . It has almost all of the fission products , corrosion products such as iron / nickel , traces of uranium, plutonium and the minor actinides .
Waste from the commercial PUREX process include acidic aqueous raffinate with high levels of radioactive materials (HLLW) as well as high volumes of lower-level waste streams and degraded organic solvents. [ 13 ] The PUREX plant at the Hanford Site was responsible for producing 'copious volumes of liquid wastes', resulting in the radioactive contamination of groundwater. [ 14 ]
Greenpeace measurements in La Hague and Sellafield indicated that radioactive pollutants are steadily released into the sea, and the air. Therefore, people living near these processing plants are exposed to higher radiation levels than the naturally occurring background radiation . According to Greenpeace , this additional radiation is small but not negligible. [ 15 ]
The PUREX process was invented by Herbert H. Anderson and Larned B. Asprey at the Metallurgical Laboratory at the University of Chicago , as part of the Manhattan Project under Glenn T. Seaborg ; their patent "Solvent Extraction Process for Plutonium" filed in 1947, [ 16 ] mentions tributyl phosphate as the major reactant which accomplishes the bulk of the chemical extraction. [ 17 ] | https://en.wikipedia.org/wiki/PUREX |
PUVA ( psoralen and UVA) is an ultraviolet light therapy treatment for skin diseases: vitiligo , eczema , psoriasis , graft-versus-host disease , mycosis fungoides , large plaque parapsoriasis , and cutaneous T-cell lymphoma , using the sensitizing effects of the drug psoralen . [ 1 ] : 686 [ 2 ] [ 3 ] The psoralen is applied or taken orally to sensitize the skin, then the skin is exposed to UVA.
Photodynamic therapy is the general use of nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells. Still, PUVA therapy is often classified as a separate technique from photodynamic therapy. [ 4 ] [ 5 ]
Psoralens are materials that make the skin more sensitive to UV light. They are photosensitizing agents found in plants naturally and manufactured synthetically. Psoralens are taken as pills (systemically) or can be applied directly to the skin, by soaking the skin in a solution that contains the psoralens. They allow UVA energy to be effective at lower doses. When combined with exposure to the UVA in PUVA, psoralens are highly effective at clearing psoriasis and vitiligo . In the case of vitiligo, they work by increasing the sensitivity of melanocytes, the cells that manufacture skin color, to UVA light. Melanocytes have sensors that detect UV light and trigger the manufacture of brown skin color. This color protects the body from the harmful effects of UV light. It can also be connected to the skin's immune response.
LED PUVA lamps give much more intense light compared to fluorescent type lamps. This reduces the treatment time, makes the treatment more effective, and enables the use of a weaker psoralen.
The physician and physiotherapists can choose a starting dose of UV based on the patient's skin type. The UV dose will be increased in every treatment until the skin starts to respond, normally when it becomes a little bit pink.
Normally the UVA dose is increased slowly, starting from 10 seconds and increased by 10 seconds a day, until the skin becomes a little bit pink. When the skin is little bit pink the time should be steady.
To reduce the number of treatments, some clinics test the skin before the treatments, by exposing a small area of the patient's skin to UVA, after ingestion of psoralen. The dose of UVA that produces redness 12 hours later, called the minimum phototoxic dose (MPD), or minimal erythema dose (MED) becomes the starting dose for treatment.
At least for vitiligo, narrowband ultraviolet B (UVB) nanometer phototherapy is now used more commonly than PUVA since it does not require the use of the psoralen and is easier to use with larger involved areas. As with PUVA, treatment is carried out twice per week in a clinic or every day at home, and there is no need to use psoralen. [ 6 ]
Narrowband UVB therapy is less effective for the legs and hands, compared to the face and neck. To the hands and legs PUVA may be more effective. The reason can be because UVA penetrates deeper in the skin, and the melanocytes in the skin of the hands and legs are positioned deeper in the skin. Narrowband UVB 311 nanometer is blocked by the topmost skin layer, and UVA 365 nanometer reaches the melanocytes that are in the bottom skin layer.
Melanin is a dark pigment of the skin and the melanocytes produce it. The melanocytes produce melanin when their receptors detect UV light. The purpose of the melanin is to block UV light so that it will not cause damage to the body cells under the skin.
For small spots of vitiligo, it is possible to use psoralen as drops, applied only on the spots. This method does not have side effects since the amount is very low.
For larger area, the psoralen is taken as a pill, and the amount is high (10 mg); some patients experience nausea and itching after ingesting the psoralen compound. For these patients PUVA bath therapy may be a good option.
Long term use of PUVA therapy with a pill has been associated with higher rates of skin cancer. [ 7 ]
The most significant complication of PUVA therapy for psoriasis is squamous cell skin cancer . Two carcinogenic components of the therapy include the nonionizing radiation of UVA light as well as the psoralen intercalation with DNA. Both processes negatively contribute to genome instability . [ citation needed ]
In Egypt around 2000 BC, the juice of Ammi majus was rubbed on patches of vitiligo after which patients were encouraged to lie in the sun. [ 8 ] In the 13th century, vitiligo was treated with a tincture of honey and the powdered seeds of a plant called "aatrillal", which was abundant in the Nile Valley. The plant has since been identified as A. majus , [ 9 ] which contains significant amounts of both bergapten and methoxsalen , two psoralen derivatives well known for their photosensitizing effects.
In the 1890s Niels Ryberg Finsen of Copenhagen developed a bulky phototherapy machine to treat skin diseases using UV light. In 1900, the French electrical engineer Gustave Trouvé miniaturized Finsen's machine with a series of portable light radiators to heal skin diseases such as lupus and epithelioma. Such machines have only been available in a chemically synthesized form [ clarification needed ] since the 1970s. [ 10 ]
In the 1940s, Abdel Monem El Mofty from Cairo University Medical School used crystalline methoxsalen (8-methoxypsoralen, also called xanthotoxin) followed by sunlight exposure to treat vitiligo. This began the development of modern PUVA therapy for the treatment of vitiligo, psoriasis, and other diseases of the skin. | https://en.wikipedia.org/wiki/PUVA_therapy |
PVSRIPO , or PVS-RIPO , is the name of a modified polio virus that has recently shown promise for treating cancer . It is the focus of clinical trials being conducted at Duke University . [ 1 ]
PVS-RIPO consists of a genetically modified nonpathogenic version of the oral poliovirus Sabin type 1. The internal ribosome entry site (IRES) on the poliovirus was replaced with the IRES from human rhinovirus type 2 (HRV2), to avoid neurovirulence. Once administered, the virus enters and begins replicating within cells that express CD155 /Necl5, which is an onco-fetal cell adhesion molecule that is common across solid tumors . [ 2 ]
A website at Duke University describes many of properties of PVSRIPO, and historical background about using viruses to oppose cancer. [ 3 ] According to that website,
The FDA approved clinical trials with PVS-RIPO in brain tumor patients recently. Since May 2012, five brain tumor patients have been treated. Remarkably, there have been no toxic side effects with PVS-RIPO whatsoever, even at the highest possible dose (10 billion infectious virus particles).
The potential value of PVSRIPO was the focus of a 2015 story on 60 Minutes . [ 4 ]
In May 2016, the US Food and Drug Administration granted it breakthrough therapy designation for glioblastoma . [ 2 ] | https://en.wikipedia.org/wiki/PVSRIPO |
In 2001, the IETF set up the Pseudowire Emulation Edge to Edge working group , and this group was given the initialism PWE3 (the 3 standing for the third power of E , i.e. EEE ). The working group was chartered to develop an architecture for service provider edge-to-edge pseudowires and service-specific documents detailing the encapsulation techniques.
In computer networking and telecommunications , a pseudowire (PW) is an emulation of a native service over a packet-switched network (PSN). The native service may be ATM , Frame Relay , Ethernet , low-rate TDM , or SONET/SDH , while the PSN may be MPLS , IP (either IPv4 or IPv6), or L2TPv3 .
The working group chairs were originally Danny McPherson and Luca Martini,
but following Martini's resignation Stewart Bryant became co-chair.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PWE3 |
The PX4 autopilot is an open-source system for autonomous aircraft. The project was started in 2009.
PX4 supports the following features:
PX4 is capable of integrating with other autopilot software, such as the QGroundControl ground control station software, via the MAVLink protocol.
PX4 is open-source and available under a BSD-3-Clause license .
This article about aircraft components is a stub . You can help Wikipedia by expanding it .
This free and open-source software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PX4_autopilot |
P elements are transposable elements that were discovered in Drosophila as the causative agents of genetic traits called hybrid dysgenesis . The transposon is responsible for the P trait of the P element and it is found only in wild flies. They are also found in many other eukaryotes. [ 1 ]
The name was first suggested by evolutionary biologist Margaret Kidwell , who, together with James Kidwell and John Sved, researched hybrid dysgenesis in Drosophila . They referred to strains as P of paternal and M of maternal if they contributed to hybrid dysgenesis in this reproductive role. [ 2 ]
The P element encodes for an enzyme known as P transposase . Unlike laboratory-bred females, wild-type females are thought also to express an inhibitor to P transposase function, produced by the very same element. This inhibitor reduces the disruption to the genome caused by the movement of P elements, allowing fertile progeny. Evidence for this comes from crosses of laboratory females (which lack the P transposase inhibitor) with wild-type males (which have P elements). In the absence of the inhibitor, the P elements can proliferate throughout the genome, disrupting many genes and often proving lethal to progeny or rendering them sterile.
P elements are commonly used as mutagenic agents in genetic experiments with Drosophila . One advantage of this approach is that the mutations are easy to locate. In hybrid dysgenesis, one strain of Drosophila mates with another strain of Drosophila , producing hybrid offspring and causing chromosomal damage known to be dysgenic. Hybrid dysgenesis requires a contribution from both parents. For example, in the P-M system, where the P strain contributes paternally and M strain contributes maternally, dysgenesis can occur. The reverse cross, with an M cytotype father and a P mother, produces normal offspring, as it crosses in a P x P or M x M manner. P male chromosomes can cause dysgenesis when crossed with an M female.
The P element is a class II transposon , and moves by a DNA-based "cut and paste" mechanism. The recognition sequence comprises four exons separated by three introns . [ 3 ] Complete splicing of the introns produces the transposase enzyme, while alternative partial splicing of introns 1 and 2, leaving only intron 3 in the mRNA transcript, encodes the P element repressor . The complete, autonomous P element encodes a transposase enzyme, which recognizes the 31- bp terminal inverted repeats at either end of the P element and catalyzes P element excision and re-insertion. The complete element is 2,907 bp in length; non-autonomous P elements contain an internal deletion of varying length which abolishes transposase production, but such elements can still be mobilized if a functional transposase is encoded elsewhere in the genome. P element insertion and subsequent excision necessarily leaves behind 8-bp direct repeats at the excision site; thus the presence of such repeats is indicative of previous P element activity.
All P elements have a canonical structure containing 31-bp terminal inverted repeats and 11-bp internal inverted repeats located at the THAP domain of the transposase. The shortest and longest P elements are non-autonomous elements. The longest P elements encode transposase needed for transposition. The same sequence that encodes the transposase also encodes a suppressor of transposition, which accumulates in the cytoplasm during the development of cells. Thus, in a cross of a P or M male with a P female, the female cytoplasm contains the suppressor, which binds to any P elements and prevents their transposition.
Hybrid dysgenesis refers to the high rate of mutation in germ line cells of Drosophila strains resulting from a cross of males with autonomous P elements ( P Strain/ P cytotype) and females that lack P elements ( M Strain/ M cytotype). The hybrid dysgenesis syndrome is marked by temperature-dependent sterility, elevated mutation rates, and increased chromosomal rearrangement and recombination.
The hybrid dysgenesis phenotype is affected by the transposition of P elements within the germ-line cells of offspring of P strain males with M strain females. Transposition only occurs in germ-line cells, because a splicing event needed to make transposase mRNA does not occur in somatic cells.
Hybrid dysgenesis manifests when crossing P strain males with M strain females and not when crossing P strain females (females with autonomous P elements) with M strain males. The eggs of P strain females contain high amounts of a repressor protein that prevents transcription of the transposase gene. The eggs of M strain mothers, which do not contain the repressor protein, allow for transposition of P elements from the sperm of fathers. In P strain females, the repressors are found in the cytoplasm. Hence, when P strain males fertilize M strain females (whose cytoplasm contain no repressor), the male contributes its genome with the P element but not the male cytoplasm leading to P strain progeny. [ 3 ]
This effect contributes to piRNAs being inherited only in the maternal line, which provides a defense mechanism against P elements. [ 4 ]
The P element has found wide use in Drosophila research as a mutagen. The mutagenesis system typically uses an autonomous but immobile element, and a mobile nonautonomous element. Flies from subsequent generations can then be screened by phenotype or PCR . Naturally-occurring P elements contain coding sequence for the enzyme transposase and recognition sequences for transposase action. Transposase regulates and catalyzes the excision of a P element from the host DNA, cutting at the two recognition sites, and then reinserting randomly. It is the random insertion that may interfere with existing genes, or carry an additional gene, that can be used for genetic research.
To use this as a useful and controllable genetic tool, the two parts of the P element must be separated to prevent uncontrolled transposition. The normal genetic tools are DNA coding for transposase with no transposase recognition sequences so it cannot insert and a " P Plasmid". P Plasmids always contain a Drosophila reporter gene, often a red-eye marker (the product of the white gene), and transposase recognition sequences. They may contain a gene of interest, an E. coli selectable marker gene, often some kind of antibiotic resistance , an origin of replication or other associated plasmid "housekeeping" sequences.
There are two main ways to utilise these tools:
The inserted gene may have damaged the function of one of the host's genes. Several lines of flies are required so comparison can take place and ensure that no additional genes have been knocked out.
Possible mutations:
The hijack of an enhancer from another gene allows the analysis of the function of that enhancer. This, especially if the reporter gene is for a fluorescent protein, can be used to help map expression of the mutated gene through the organism, and is a very powerful tool. It is a useful tool for looking at gene expression patterns (temporally and spatially).
These methods are referred to as reverse genetics. Reverse genetics is an approach to discover the function of a gene by analyzing the phenotypic effects of specific gene sequences obtained by DNA sequencing
Once the function of the mutated protein has been determined it is possible to sequence/purify/clone the regions flanking the insertion by the following methods:
The process of cutting, self ligation and re cutting allows the amplification of the flanking regions of DNA without knowing the sequence. The point at which the ligation occurred can be seen by identifying the cut site of [enzyme 1]. | https://en.wikipedia.org/wiki/P_element |
The P ring forms part of the basal body of the bacterial appendage known as the flagellum . It is known to be embedded in the peptidoglycan cell wall . [ 1 ] Together with the L ring , it has the function of anchoring the flagellum to the cell surface. [ 2 ]
This bacteria -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/P_ring |
A P wave ( primary wave or pressure wave ) is one of the two main types of elastic body waves , called seismic waves in seismology. P waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph . P waves may be transmitted through gases, liquids, or solids.
The name P wave can stand for either pressure wave (as it is formed from alternating compressions and rarefactions ) or primary wave (as it has high velocity and is therefore the first wave to be recorded by a seismograph). [ 1 ] The name S wave represents another seismic wave propagation mode, standing for secondary or shear wave, a usually more destructive wave than the primary wave.
Primary and secondary waves are body waves that travel within the Earth. The motion and behavior of both P and S waves in the Earth are monitored to probe the interior structure of the Earth . Discontinuities in velocity as a function of depth are indicative of changes in phase or composition. Differences in arrival times of waves originating in a seismic event like an earthquake as a result of waves taking different paths allow mapping of the Earth's inner structure. [ 3 ] [ 4 ]
Almost all the information available on the structure of the Earth's deep interior is derived from observations of the travel times, reflections , refractions and phase transitions of seismic body waves, or normal modes . P waves travel through the fluid layers of the Earth's interior , and yet they are refracted slightly when they pass through the transition between the semisolid mantle and the liquid outer core . As a result, there is a P wave " shadow zone " between 103° and 142° [ 5 ] from the earthquake's focus, where the initial P waves are not registered on seismometers. In contrast, S waves do not travel through liquids.
Advance earthquake warning is possible by detecting the nondestructive primary waves that travel more quickly through the Earth's crust than do the destructive secondary and Rayleigh waves .
The amount of warning depends on the delay between the arrival of the P wave and other destructive waves, generally on the order of seconds up to about 60 to 90 seconds for deep, distant, large quakes such as the 2011 Tohoku earthquake . The effectiveness of a warning depends on accurate detection of the P waves and rejection of ground vibrations caused by local activity (such as trucks or construction). Earthquake early warning systems can be automated to allow for immediate safety actions, such as issuing alerts, stopping elevators at the nearest floors, and switching off utilities.
In isotropic and homogeneous solids, a P wave travels in a straight line longitudinally ; thus, the particles in the solid vibrate along the axis of propagation (the direction of motion) of the wave energy. The velocity of P waves in that kind of medium is given by v p = K + 4 3 μ ρ = λ + 2 μ ρ {\displaystyle v_{\mathrm {p} }\;=\;{\sqrt {\frac {\,K+{\tfrac {4}{3}}\mu \;}{\rho }}}\;=\;{\sqrt {\frac {\,\lambda +2\mu \;}{\rho }}}} where K is the bulk modulus (the modulus of incompressibility), μ is the shear modulus (modulus of rigidity, sometimes denoted as G and also called the second Lamé parameter ), ρ is the density of the material through which the wave propagates, and λ is the first Lamé parameter .
In typical situations in the interior of the Earth, the density ρ usually varies much less than K or μ , so the velocity is mostly "controlled" by these two parameters.
The elastic moduli P wave modulus , M {\displaystyle M} , is defined so that M = K + 4 3 μ {\textstyle \,M=K+{\tfrac {4}{3}}\mu \,} and thereby v p = M ρ {\displaystyle v_{\mathrm {p} }={\sqrt {\frac {\,M\;}{\rho }}}}
Typical values for P wave velocity in earthquakes are in the range 5 to 8 km/s. The precise speed varies according to the region of the Earth's interior, from less than 6 km/s in the Earth's crust to 13.5 km/s in the lower mantle, and 11 km/s through the inner core. [ 6 ]
Geologist Francis Birch discovered a relationship between the velocity of P waves and the density of the material the waves are traveling in: v p = a ( M ¯ ) + b ρ {\displaystyle v_{\mathrm {p} }=a({\bar {M}})+b\,\rho } which later became known as Birch's law . (The symbol a () is an empirically tabulated function, and b is a constant.) | https://en.wikipedia.org/wiki/P_wave |
Protactinium(V) oxide is a chemical compound with the formula Pa 2 O 5 . When it is reduced with hydrogen , it forms PaO 2 . Aristid V. Grosse was first to prepare 2 mg of Pa 2 O 5 in 1927. [ 1 ] Pa 2 O 5 does not dissolve in concentrated HNO 3 , but dissolves in HF and in a HF + H 2 SO 4 mixture and reacts at high temperatures with solid oxides of alkali metal and alkaline earth metals . [ 2 ] [ 3 ] : 195
As protactinium(V) oxide, like other protactinium compounds, is radioactive , toxic and very rare, it has very limited technological use. Mixed oxides of Nb, Mg, Ga and Mn, doped with 0.005–0.52% Pa 2 O 5 , have been
used as high temperature dielectrics (up to 1300 °C) for ceramic capacitors . [ 3 ] : 189
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pa2O5 |
PaNie is a 25 kDa protein produced by the root rot disease-causing pathogen Pythium aphanidermatum . It stands for Pythium aphanidermatum Necrosis inducing elicitor . PaNie (aka NLP Pya ) belongs to a family of elicitors named the Nep1 -like proteins (NLPs), which cause necrosis when injected into the leaves of dicotyledonous plants. [ 1 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PaNie |
The Paal–Knorr synthesis is a reaction used to synthesize substituted furans , pyrroles , or thiophenes from 1,4-diketones . It is a synthetically valuable method for obtaining substituted furans and pyrroles, which are common structural components of many natural products. It was initially reported independently by German chemists Carl Paal and Ludwig Knorr in 1884 as a method for the preparation of furans, and has been adapted for pyrroles and thiophenes. [ 1 ] [ 2 ] Although the Paal–Knorr synthesis has seen widespread use, the mechanism wasn't fully understood until it was elucidated by V. Amarnath et al. in the 1990s. [ 3 ] [ 4 ]
The furan synthesis requires an acid catalyst: [ 5 ]
In the pyrrole synthesis a primary amine participates:
and in that of thiophene for instance the compound phosphorus pentasulfide :
The acid catalyzed furan synthesis proceeds by protonation of one carbonyl which is attacked by the forming enol of the other carbonyl. Dehydration of the hemiacetal gives the resultant furan. [ 6 ]
The mechanism of the Paal–Knorr furan synthesis was elucidated in 1995 by V. Amarnath et al . [ 3 ] Amarnath's work showed that the diastereomers of 3,4-disubstituted-2,5-hexane diones react at different rates. In the commonly accepted mechanism, these diones would go through a common enol intermediate, meaning that the meso and d,l -racemic isomers would cyclize at the same rate as they form from a common intermediate. The implication of different reaction is that cyclization needs to occur in a concerted step with enol formation. Thus the mechanism was proposed to occur via attack of the protonated carbonyl with the forming enol. Amarnath also found that the unreacted dione had not undergone conformational isomerization, which also indicated that an enol was not an intermediate.
The mechanism for the synthesis of the pyrrole was investigated by V. Amarnath et al. in 1991. [ 4 ] His work suggests that the protonated carbonyl is attacked by the amine to form the hemiaminal. The amine attacks the other carbonyl to form a 2,5-dihydroxytetrahydropyrrole derivative which undergoes dehydration to give the corresponding substituted pyrrole. [ 7 ]
The reaction is typically run under protic or Lewis acidic conditions, with a primary amine. Use of ammonium hydroxide or ammonium acetate (as reported by Paal) gives the N-unsubstituted pyrrole.
Thiophene synthesis is achieved via a mechanism very similar to the furan synthesis. The initial diketone is converted to a thioketone with a sulfurizing agent, which then undergoes the same mechanism as the furan synthesis. [ 8 ]
Most sulfurization agents are strong dehydrators and drive completion of the reaction. Early postulates toward the mechanism of the Paal-Knorr furan synthesis suggested that the thiophene was achieved by sulfurization of the furan product. Campaigne and Foye showed that treatment of isolated furans from the Paal-Knorr furan synthesis with phosphorus pentasulfide gave inconsistent results with the treatment of 1,4-dicarbonyls with phosphorus pentasulfide, which ruled out the sulfurization of a furan mechanism and suggests that the reaction proceeds via sulfurization of a dicarbonyl, producing a thioketone . [ 8 ]
The Paal–Knorr reaction is quite versatile. In all syntheses almost all dicarbonyls can be converted to their corresponding heterocycle. R2 and R5 can be H, aryl or alkyl. R3 and R4 can be H, aryl, alkyl, or an ester. In the pyrrole synthesis (X = N), R1 can be H, aryl, alkyl, amino, or hydroxyl. [ 9 ]
A variety of conditions can be used to carry out these reactions, most of which are mild. The Paal–Knorr Furan synthesis is normally carried out under aqueous acidic conditions with protic acids such as aqueous sulfuric or hydrochloric acid , or anhydrous conditions with a Lewis acid or dehydrating agent. Common dehydrating agents include phosphorus pentoxide , anhydrides , or zinc chloride. The pyrrole synthesis requires a primary amine under similar conditions, or ammonia (or ammonia precursors) can be used. Synthesis of a thiophene requires a sulfurizing agent which is typically a sufficient dehydrator, such as phosphorus pentasulfide , Lawesson's reagent , or hydrogen sulfide .
Traditionally, the Paal–Knorr reaction has been limited in scope by the availability of 1,4-diketones as synthetic precursors. Current chemical methods have greatly expanded the accessibility of these reagents, and variations of the Paal-Knorr now allow for different precursors to be used. The Paal–Knorr was also considered limited by harsh reaction conditions, such as prolonged heating in acid, which may degrade sensitive functionalities in many potential furan precursors. Current methods allow for milder conditions that can avoid heat altogether, including microwave catalyzed cyclizations.
Several 1,4-dicarbonyl surrogates can be used in place of a 1,4-dicarbonyl. While these substitutes have different structures from a 1,4-dicarbonyl, their reactions proceed via mechanisms very similar to that of the Paal-Knorr.
β,γ-Epoxy carbonyls have been known to cyclize to furans. This procedure can use the β-unsaturated carbonyls as starting materials, which can be epoxidized. The resulting epoxycarbonyl can be cyclized to a furan under acidic or basic conditions. [ 10 ]
2-Yn-1,4-diols systems have also been used to do Paal–Knorr chemistry. Using palladium, a 2-yn-1,4-diol can be isomerized to the corresponding 1,4-diketone in situ and then dehydrated to the corresponding furan using a dehydration agent. [ 11 ]
The significance of this variation is in the fact that it increases the scope of the Paal–Knorr by taking advantage of the wealth of acetylene chemistry that exists, specifically that for the generation of propargyl alcohols.
Acetals have also proven useful starting materials for the Paal-Knorr. A ketone with an acetal 3 bonds away from it can be converted under exactly the same conditions as a 1,4-diketone to the corresponding heterocycle.
Another variation has been the introduction of microwave radiation to enhance the Paal–Knorr. Traditional Paal–Knorr conditions involved prolonged heating of strong acids to drive dehydration which occurred over a period of several hours. Microwave-assisted Paal–Knorr reactions have been demonstrated to occur on time scales measured in minutes and in open flasks at room temperature. [ 12 ]
The Knorr pyrrole synthesis , reported by Knorr in 1884 is the synthesis of a substituted pyrrole from an amino-ketone and a ketone. [ 13 ]
Also reported by Knorr is a synthesis of pyrazoles from 1,3-dicarbonyls and hydrazines , hydrazides, or semibicarbazides. This synthesis occurs via a condensation mechanism similar to the Paal-Knorr, however if a substituted hydrazine is used, it results in a mixture of regioisomers where the substituted heteroatom is either next to the R1 substituent or the R3 substituent. [ 14 ]
In 2000, B. M. Trost et al. reported a formal synthesis of the antibiotic roseophilin. Trost's route to the macrocyclic core of roseophilin, like others, relied on a Paal–Knorr Pyrrole synthesis to obtain the fused pyrrole. [ 15 ] Heating the 1,4-diketone with ammonium acetate in methanol with camphor sulfonic acid and 4 angstrom molecular sieves gave the pyrrole with no N-substitution. This pyrrole was found to be unstable, and as such was treated with trimethylsilyl ethoxy methoxy chloride (SEM-Cl) to protect the pyrrole prior to isolation.
In 1982, H. Hart et al. reported a synthesis of a macrocycle containing fused furan rings using a Paal–Knorr furan synthesis. [ 16 ] Refluxing para -toluene sulfonic acid in benzene was found to dehydrate the 1,4-diketones to their respective furans to achieve the challenging macrocyclic fused furans. | https://en.wikipedia.org/wiki/Paal–Knorr_synthesis |
Pace count beads , pacer beads or ranger beads are a manual counting tool used to keep track of distance traveled through a pace count . It is used in military land navigation or orienteering . [ 1 ] Stringed beads found at stoneage sites in Africa may have been used for pace counting, and modified Japamala have been used to keep pace. [ 2 ] [ 3 ] A typical example for military use is keeping track of distance traveled during a foot patrol . [ 4 ]
The tool is usually constructed using a set of about 13 beads on a length of cord. The beads are divided into two sections, separated by a knot. Nine beads are used in the lower section, and four (or in some cases more) beads are used in the upper section. There is often a loop in the upper end, making it possible to attach the tool to the user's gear with a simple Larks head hitch. [ 5 ]
The beads can be used to count paces or a distance calculated from the number of paces. Both methods require the user to know the relationship between the paces walked, and the distance traveled. [ 6 ] There are two main ways to use the beads. One is to represent the distance a person has walked, and the other is to represent the distance they need to walk. In the latter, beads may be used to count down the distance to a destination.
As users walk, they typically slide one bead on the cord for every ten paces taken. On the tenth pace, the user slides a bead in the lower section towards the knot. After the 90th pace, all nine beads are against the knot. On the 100th pace, all nine beads in the lower section are returned away from the knot, and a bead from the upper section is slid upwards, away from the knot.
In this manner, the user calculates the distance traveled by keeping track of the paces taken. To use this method, the user must know the length of their pace to calculate the distance accurately traveled. Also, the number of paces to be walked must be precalculated (example: 2,112 paces= one mile, based on a 30-inch pace), and then the distance traveled has to be calculated from the walked paces.
For every 100 meters the user walks, one of the lower beads is pulled down. When the ninth of the lower beads is pulled, the user has walked 900 meters. When the user has walked 1000 meters, one of the upper beads is pulled down, and all the lower beads are pulled back up.
Using this method, the user must know the number of paces walked in 100 meters. An experienced user can also adapt the pace count for each hundred meter depending on the terrain. When using this method, the user does not have to calculate distance from the number of paces.
This method can be used for non-metric distances as well, though with the beads arranged in a different manner.
The United States Army stated in its field manual on Map Reading and Land Navigation that, "there are many methods to keep track of distance traveled", including placing pebbles in your pockets or tying knots on a string. [ 7 ] Pace count beads are generally not issued in the United States Military, thus soldiers and Marines typically make their own or purchase them from an equipment supply company. | https://en.wikipedia.org/wiki/Pace_count_beads |
In topology , a branch of mathematics, Pachner moves , named after Udo Pachner, are ways of replacing a triangulation of a piecewise linear manifold by a different triangulation of a homeomorphic manifold. Pachner moves are also called bistellar flips . Any two triangulations of a piecewise linear manifold are related by a finite sequence of Pachner moves.
Let Δ n + 1 {\displaystyle \Delta _{n+1}} be the ( n + 1 ) {\displaystyle (n+1)} - simplex . ∂ Δ n + 1 {\displaystyle \partial \Delta _{n+1}} is a combinatorial n -sphere with its triangulation as the boundary of the n+1 -simplex.
Given a triangulated piecewise linear (PL) n -manifold N {\displaystyle N} , and a co-dimension 0 subcomplex C ⊂ N {\displaystyle C\subset N} together with a simplicial isomorphism ϕ : C → C ′ ⊂ ∂ Δ n + 1 {\displaystyle \phi :C\to C'\subset \partial \Delta _{n+1}} , the Pachner move on N associated to C is the triangulated manifold ( N ∖ C ) ∪ ϕ ( ∂ Δ n + 1 ∖ C ′ ) {\displaystyle (N\setminus C)\cup _{\phi }(\partial \Delta _{n+1}\setminus C')} . By design, this manifold is PL-isomorphic to N {\displaystyle N} but the isomorphism does not preserve the triangulation. | https://en.wikipedia.org/wiki/Pachner_moves |
The pachysolen tannophilus nuclear code (translation table 26) is a genetic code found in the ascomycete fungus Pachysolen tannophilus . [ 1 ]
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V)
This code uses the initiation codons AUG, GUG and UUG.
This article incorporates text from the United States National Library of Medicine , which is in the public domain . [ 2 ] | https://en.wikipedia.org/wiki/Pachysolen_tannophilus_nuclear_code |
The pachytene stage ( /ˈpækɪtiːn/ PAK-i-teen ; from Greek words meaning "thick threads". [ 1 ] : 27 ), also known as pachynema , is the third stage of prophase I during meiosis, the specialized cell division that reduces chromosome number by half to produce haploid gametes . It follows the zygotene stage and is followed by the stage Diplotene
During pachytene, the homologous chromosomes are fully synapsed along their lengths by the completed synaptonemal complex protein structure formed in the previous stages. This holds the homologous closely paired, allowing intimate DNA interactions. [ 2 ]
The chromosomes reach their highest level of condensation during pachytene. Each chromosome consists of two closely associated sister chromatids along their entire length. The chromosomes appear as distinct, well-defined threadlike structures under the microscope. [ 3 ] [ 4 ] Sex chromosomes , however, are not wholly identical, and only exchange information over a small region of homology called the pseudoautosomal region . [ 5 ]
Multiple recombination nodules are distinctly visible along the paired homologous chromosomes. These proteinaceous structures mark the sites of genetic crossover events between the non-sister chromatids that were initiated during zygotene. [ 6 ]
Proteins like MLH1 and MLH3 stabilize the crossover events, ensuring at least one obligatory crossover per chromosome arm. [ 7 ] This gives each chromosome a minimum of two crossover sites. Additional crossovers are also possible but regulated. [ 8 ] [ 9 ]
During pachytene, any unresolved DNA double-strand breaks from previous recombination events are repaired. Mismatch repair proteins help correct any errors in base pairing between the homologs. [ 10 ]
Treatment of male mice during meiosis with gamma radiation causes DNA damage . [ 11 ] Homologous recombination is the principal mechanism of DNA repair acting during meiosis. From the leptotene to early pachytene stages of meiosis exogenous damage triggered the massive presence of gamma H2AX (which forms when DNA double-strand breaks appear), H2AX was present throughout the nucleus, and this was associated with DNA repair mediated by homologous recombination components DMC1 and RAD51 proteins. [ 11 ]
Pachytene is also a stage where a critical checkpoint operates to monitor proper chromosome synapsis and recombination. Errors detected at this stage can arrest the meiotic cell cycle and trigger apoptosis (programmed cell death) of the defective cell. [ 12 ]
Once crossover events are stabilized, the synaptonemal complex disassembles and chromosomes begin to gradually desynapse as the cell transitions into the diplotene stage.
The pachytene stage is essential for the extensive genetic recombination and accurate chromosome segregation in meiosis. Defects at this stage can lead to aneuploidy and nondisjunction. [ 13 ] | https://en.wikipedia.org/wiki/Pachytene |
The Pacific Ocean Shelf Tracking Project ( POST ) is a field project of the Census of Marine Life that researches the behavior of marine animals through the use of ocean telemetry and data management systems. [ 1 ] This system of telemetry consists of highly efficient lines of acoustic receivers that create sections of the continental shelf along the coast of the Pacific Northwest . The acoustic receivers pick up signals from the tagged animals as they pass along the lines, allowing for the documentation of movement patterns. The receivers also allow for the estimation of parameters such as swimming speed and mortality. [ 2 ] The trackers sit on the seabed of the continental shelf and in the major rivers of the world. This method can be used to improve fishing skills and management. [ 3 ]
The program started in 2002 and was initially limited to the study of the movement and ocean-survival of both hatchery-raised and wild salmon in the Pacific Northwest . After the successful pilot period, the program has now moved into the tracking of trout, [ 4 ] sharks, [ 5 ] rockfish, and lingcod. [ 6 ]
This biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pacific_Ocean_Shelf_Tracking_Project |
Pacific Research Laboratories, Inc. (PRL) is a design, research and development (R&D) and prototype manufacturing company. It is the leading producer of Sawbones, designed to simulate bone architecture and a bone's physical properties. [ 1 ] It was founded in 1978. [ 2 ] The company had 135 employees as of April 2016 [ 3 ] and is the largest manufacturer in Vashon, Washington . It is locally referred to as "The Bone Factory." [ 4 ]
PRL has capabilities in (R&D) prototypes, short run production, and rapid prototyping . It is the manufacturer for Seaglider fairings, wings and rudders; [ 5 ] Seaglider is an underwater glider autonomous underwater vehicle (AUV) developed by the University of Washington . [ 6 ] PRL also manufactures Super Shroud cell tower concealment shrouds.
The company also works in product development and design, including quick-turnaround projects using urethanes, silicones, glass/carbon fibers, braided fiberglass, thermoplastics, electronics, hydraulics, and pneumatics; the creation of prototypes, master patterns, and tooling; reverse engineering ; laser scanning ; and manufacturing using 3D printing , 3-axis CNC router , 4-axis CNC machining, and a triaxial fiberglass braider.
In December 2010, Pacific Research Laboratories became employee owned under an employee stock ownership plan (ESOP). [ 3 ] | https://en.wikipedia.org/wiki/Pacific_Research_Laboratories |
The Pacific Symposium on Biocomputing ( PSB ) is an annual multidisciplinary scientific meeting co-founded in 1996 by Dr. Teri Klein , Dr. Lawrence Hunter and Sharon Surles. [ 2 ] The conference is to presentation and discuss research in the theory and application of computational methods for biology. Papers and presentations are peer reviewed and published. [ 3 ] PSB brings together researchers from the US and the Asian Pacific nations, to exchange research results and address open issues in all aspects of computational biology . PSB is a forum for the presentation of work in databases, algorithms, interfaces, visualization, modeling, and other computational methods, as applied to biological problems, with emphasis on applications in data-rich areas of molecular biology .
The PSB aims for " critical mass " in sub-disciplines within biocomputing . For that reason, it is the only meeting whose sessions are defined dynamically each year in response to specific proposals. PSB sessions are organized by leaders in the emerging areas and targeted to provide a forum for publication and discussion of research in biocomputing's topics.
Since 2017 the Research Parasite Award [ 4 ] has been announced and presented annually at the Symposium to recognize scientists who study previously-published data in ways not anticipated by the researchers who first generated it. [ 5 ] Since the 2019 award year, the Research Parasite Award has been supported in part by an endowment housed at the University of Pennsylvania. Research Symbiont Award [ 6 ] is another award presented annually at the Symposium to recognize exemplars in the practice of data sharing. | https://en.wikipedia.org/wiki/Pacific_Symposium_on_Biocomputing |
The Pacific Tsunami Warning Center ( PTWC ), located on Ford Island , Hawaii , is one of two tsunami warning centers in the United States, covering Hawaii, Guam , American Samoa and the Northern Mariana Islands in the Pacific, as well as Puerto Rico , the U.S. Virgin Islands and the British Virgin Islands in the Caribbean Sea. Other parts of the United States are covered by the National Tsunami Warning Center .
PTWC is also the operational center of the Pacific Tsunami Warning System and issued tsunami warnings for dozens of countries from 1965 to 2014. In October 2014, the authority to issue tsunami warnings was delegated to individual member states. As a result, the center now issues advice rather than official warnings for non-U.S. coastlines, with the exception of the British Virgin Islands.
The PTWC uses seismic data as its starting point, but then takes into account oceanographic data when calculating possible threats. Tide gauges in the area of the earthquake are checked to establish if a tsunami has formed. The center then forecasts the future of the tsunami.
Up until the late 1940s, the United States had no way to warn the public about tsunami threats. After the 1946 Aleutian Islands earthquake , which generated a tsunami and killed more than 170 people in Hawaii , a plan was devised to warn the public of possible tsunami inundation. The facility became operational in 1948 and was called the Seismic Sea Wave Warning System (SSWWS), headquartered at the Coast and Geodetic Survey 's seismological observatory in Honolulu , Hawaii. [ 1 ]
Initially, the Seismic Sea Wave Warning System covered only the Hawaiian Islands and was limited to teletsunamis (distant events), using data from 4 seismic stations and 9 tide gages. [ 2 ] The 1960 Valdivia earthquake and tsunami , which killed thousands of people, led to the establishment of the Pacific Tsunami Warning System under the auspices of UNESCO's Intergovernmental Oceanographic Commission , with the Seismic Sea Wave Warning System as its operational center. As a result, the name of the facility was changed to the Pacific Tsunami Warning Center. [ 2 ]
The expanded system became operational in April 1965 but, like its local predecessor, was limited to teletsunamis – tsunamis which are capable of causing damage far away from their source. [ 3 ] The system covered all countries of the Pacific Ocean with data from 20 seismic stations around the world and 40 tide stations. [ 2 ] [ 1 ]
In the aftermath of the 1964 Alaska earthquake and tsunami , which killed 131 people, it was decided to create another warning system to provide timely warnings about local events for coastal areas of Alaska. After Congress approved funding in 1965, the Alaska Regional Tsunami Warning System was launched in September 1967 with observatories in Palmer, Adak and Sitka. At that time, PTWC ended its coverage of Alaska. [ 4 ]
The 1975 Hawaii earthquake and tsunami , which killed several people, highlighted the threat of tsunamis caused by nearby events. As a result, PTWC began issuing tsunami warnings for local events near Hawaii. [ 4 ]
In 1982, the Alaska Tsunami Warning Center's area of responsibility was enlarged to include California, Oregon and Washington, as well as British Columbia in Canada, but only for earthquakes in the vicinity of the West Coast. PTWC continued to provide coverage of teletsunamis. The Alaska center's responsibilities were expanded in 1996 to include all Pacific-wide sources, after which it became known as the West Coast/Alaska Tsunami Warning Center (WCATWC). As a result, PTWC's area of responsibility was further reduced. [ 4 ]
On December 1, 2001, the PTWC was re-dedicated as the Richard H. Hagemeyer Pacific Tsunami Warning Center, in honor of the former U.S. Tsunami Program Manager and National Weather Service Pacific Region Director who managed the center for many years. [ 4 ]
In 2005, in the aftermath of the 2004 Indian Ocean earthquake and tsunami , the Pacific Tsunami Warning Center's responsibilities were expanded to include tsunami guidance for the Indian Ocean, the South China Sea and the Caribbean Sea, though its authority to issue warnings was limited to Puerto Rico and the U.S. Virgin Islands . For all other areas, the decision to issue tsunami warnings was left to individual countries.
The responsibility for Puerto Rico and the U.S. Virgin Islands was passed to the West Coast/Alaska Tsunami Warning Center in June 2007, while PTWC continued to issue advice for other parts of the Caribbean Sea. In 2013, the West Coast/Alaska Tsunami Warning Center became known as the National Tsunami Warning Center. [ 4 ]
PTWC discontinued its messages for the Indian Ocean in 2013 after regional tsunami warning centers were opened in Australia, India and Indonesia. [ 5 ]
In October 2014, the authority to issue official tsunami warnings for coastlines in the Pacific was delegated to individual member states. This happened because warnings and watches issued by PTWC caused confusion when they conflicted with a country's independently derived level of alert. As a result, the center now issues advice rather than official warnings for all non-U.S. coastlines, with the exception of the British Virgin Islands. [ 6 ]
In 2015, the annual operating cost of the Pacific Tsunami Warning System was estimated to be between 50 and 80 million U.S. dollars. [ 2 ]
In April 2017, the responsibility for Puerto Rico and the U.S. Virgin Islands returned to PTWC, along with the British Virgin Islands, to consolidate Caribbean responsibilities under one warning center. [ 7 ]
As of 2023, the Pacific Tsunami Warning System has access to about 600 high-quality seismic stations around the world and about 500 coastal and deep-ocean sea level stations. It has 46 member states: Brunei , Cambodia , Canada , Chile (including Easter Island and the Juan Fernández Islands ), China (which is considered to include Hong Kong and Macau ), Colombia , Costa Rica , East Timor , North Korea , Ecuador (including the Galapagos Islands ), El Salvador , Guatemala , Honduras , Indonesia , Japan , Malaysia , Mexico , Nicaragua , Panama , Peru , Philippines , South Korea , Russia , Singapore , Thailand , United States (including Guam , Northern Mariana Islands , and the Minor Outlying Islands ), Vietnam , Australia (including Norfolk Island ), Cook Islands , Fiji , France (including French Polynesia , New Caledonia and Wallis and Futuna ), Kiribati (including the Gilbert Islands , the Phoenix Islands and Kiritimati ), the Marshall Islands (including Kwajalein Atoll and Majuro ), the Federated States of Micronesia , Nauru , New Zealand (including the Kermadec Islands ), Niue , Palau , Papua New Guinea , Samoa , the Solomon Islands , Tokelau , Tonga , Tuvalu , the United Kingdom (including the Pitcairn Islands ), and Vanuatu . [ 8 ]
Official tsunami warnings and watches are limited to U.S. coastlines, with the exception of the British Virgin Islands. PTWC messages for other regions do not include alerts, but rather advice, as the authority to issue tsunami warnings was delegated to member states in 2014 to avoid confusion among the public. [ 6 ]
The alert levels below were retired on October 1, 2014.
Local populations in the United States of America receive tsunami information through radio and television receivers connected to the Emergency Alert System , and in some places (such as Hawaii) civil defense sirens and roving loudspeaker broadcasts from police vehicles. The public can subscribe to the RSS feed or email alerts from the PTWC web site, [ 13 ] and the UNESCO site. [ 14 ] Email and text messages are also available from the USGS Earthquake Notification Service [ 15 ] which includes tsunami alerts.
In 1995, NOAA began developing the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. By 2001, an array of six stations had been deployed in the Pacific Ocean . [ 16 ]
Beginning in 2005, as a result of the tsunami caused by the 2004 Indian Ocean earthquake , plans were announced to add 32 more DART buoys to be operational by mid-2007. [ 17 ]
These stations give detailed information about tsunamis while they are still far off shore. Each station consists of a sea-bed bottom pressure recorder (at a depth of 1000–6000 m) which detects the passage of a tsunami and transmits the data to a surface buoy via acoustic modem. The surface buoy then radios the information to the PTWC via the GOES satellite system. The bottom pressure recorder lasts for two years while the surface buoy is replaced every year. The system has considerably improved the forecasting and warning of tsunamis in the Pacific Ocean. | https://en.wikipedia.org/wiki/Pacific_Tsunami_Warning_Center |
Pack200 , specified in JSR 200 [ 1 ] (J2SE 1.5), deprecated in JEP 336 [ 2 ] (Java SE 11) and removed in JEP 367 (Java SE 14), [ 3 ] is a compacting archive format developed by Sun , capable of reducing JAR file sizes by up to a factor of 9, [ 4 ] with a factor of 3 to 4 seen in practice. [ 5 ] [ 6 ] Pack200 is optimized for compressing JAR archive files, specifically the Java bytecode portion of the JAR files. Applications of this technology include faster Java application deployment over Java Web Start .
After Pack200, gzip compression is usually applied. In HTTP compression, such content is specified by the Content-Encoding type pack200-gzip . When stored as a file, the extension .pack.gz is used. [ 7 ]
Pack200 may also refer to the Pack200 compression tools ( pack200 and unpack200 ) provided in the Java Development Kit from Java 5 until Java 14.
Pack200 modifies the contents of the Java class files in the JAR archive undergoing compression. Transformations to the class files include merging constant pools and removing duplicated attributes. [ 8 ] The format is not lossless; it is possible for a JAR file after unpacking to not be identical to how it was before packing. [ 9 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pack200 |
The package-merge algorithm is an O (nL) -time algorithm for finding an optimal length-limited Huffman code for a given distribution on a given alphabet of size n , where no code word is longer than L . It is a greedy algorithm , and a generalization of Huffman's original algorithm . Package-merge works by reducing the code construction problem to the binary coin collector's problem . [ 1 ]
Suppose a coin collector has a number of coins of various denominations, each of which has a numismatic value unrelated to its denomination. The coin collector has run out of money and needs to use some of his coin collection to buy something of cost N . He wishes to select a subset of coins from his collection of minimum numismatic value whose denominations total N .
The binary version of this problem is that all denominations are powers of 2, that is, 1, 1/2, 1/4, etc. dollars.
Assume that the largest denomination is 1 dollar, and that N is an integer. (The algorithm works even if these assumptions do not hold, by trivial modifications.) The coin collector first separates his coins into lists, one for each denomination, sorted by numismatic value. He then packages the smallest denomination coins in pairs, starting from the pair of smallest total numismatic value. If there is one coin left over, it will be the coin of highest numismatic value of that denomination, and it is set aside and ignored henceforth. These packages are then merged into the list of coins of the next smallest denomination, again in order of numismatic value. The items in that list are then packaged in pairs, and merged into the next smallest list, and so forth.
Finally, there is a list of items, each of which is a 1 dollar coin or a package consisting of two or more smaller coins whose denominations total 1 dollar. They are also sorted in order of numismatic value. The coin collector then selects the least value N of them.
Note that the time of the algorithm is linear in the number of coins.
Let L be the maximum length any code word is permitted to have.
Let p 1 , …, p n be the frequencies of the
symbols of the alphabet to be encoded. We first sort the symbols so that p i ≤ p i +1 . Create L coins for each symbol, of denominations 2 −1 , …, 2 − L , each of numismatic value p i . Use the package-merge algorithm to select the set of coins of minimum numismatic value whose denominations total n − 1. Let h i be the number of coins of numismatic value p i selected.
The optimal length-limited Huffman code will encode symbol i with a bit string of length h i . The canonical Huffman code can easily be constructed by a simple bottom-up greedy method, given that the h i are known, and this can be the basis for fast data compression . [ 2 ]
With this reduction, the algorithm is O(nL) -time and O(nL) -space. However, the original paper, " A fast algorithm for optimal length-limited Huffman codes ", shows how this can be improved to O(nL) -time and O(n) -space. The idea is to run the algorithm a first time, only keeping enough data to be able to determine two equivalent subproblems that sum to half the size of the original problem. This is done recursively, resulting in an algorithm that takes about twice as long but requires only linear space. [ 1 ]
Many other improvements have been made to the package-merge algorithm to reduce the multiplicative constant and to make it faster in special cases, such as those problems having repeated p i s. [ 3 ] The package-merge approach has also been adapted to related problems such as alphabetic coding . [ 4 ]
Methods involving graph theory have been shown to have better asymptotic space complexity than the package-merge algorithm, but these have not seen as much practical application. | https://en.wikipedia.org/wiki/Package-merge_algorithm |
Package testing or packaging testing involves the measurement of a characteristic or property involved with packaging . This includes packaging materials, packaging components, [ 1 ] primary packages, shipping containers , and unit loads , as well as the associated processes.
Testing measures the effects and interactions of the levels of packaging, the package contents, external forces, and end-use.
It can involve controlled laboratory experiments , subjective evaluations by people, or field testing. Documentation is important: formal test method , test report, photographs, video, etc.
Testing can be a qualitative or quantitative procedure. Package testing is often a physical test . With some types of packaging such as food and pharmaceuticals, chemical tests are conducted to determine suitability of food contact materials . Testing programs range from simple tests with little replication to more thorough experimental designs .
Package testing can extend for the full life cycle. Packages can be tested for their ability to be recycled and their ability to degrade as surface litter , in a sealed landfill or under composting conditions. [ 2 ]
Packaging testing might have a variety of purposes, such as:
Packaging tests can be used for:
For some types of products, package testing is mandated by regulations: food . pharmaceuticals , medical devices , dangerous goods , etc. This may cover both the design qualification, periodic retesting, and control of the packaging processes. Processes may be controlled by a variety of quality management systems such as HACCP , statistical process control , validation protocols, ISO 9000, etc.
For unregulated products, testing can be required by a contract or governing specification. The degree of package testing can often be a business decision. Risk management may involve factors such as
With distribution packaging, one vital packaging development consideration is to determine if a packaged-product is likely to be damaged in the process of getting to the final customer. A primary purpose of a package is to ensure the safety of a product during transportation and storage. If a product is damaged during this process, then the package has failed to accomplish a primary objective and the customer will either return the product or be unlikely to purchase the product altogether. [ 6 ]
Package testing is often a formal part of Project management programs. Packages are usually tested when there is a new packaging design, a revision to a current design, a change in packaging material, and various other reasons. Testing a new packaging design before full scale manufacturing can save time and money. [ 7 ]
Many suppliers or vendors offer limited material and package testing as a free service to customers. It is common for packagers to partner with reputable suppliers: Many suppliers have certified quality management systems such as ISO 9000 or allow customers to conduct technical and quality audits. Data from testing is commonly shared. There is sometimes a risk that supplier testing may tend to be self-serving and not completely impartial.
Large companies often have their own packaging staff and a package testing and development laboratory . Corporate engineers know their products, manufacturing capabilities, logistics system, and their customers best. Cost reduction of existing products and cost avoidance for new products have been documented. [ 8 ]
Another option is to use a paid consultant , Independent contractor , and third-party independent testing laboratory . They are commonly chosen for specialized expertise, for access to certain test equipment, for surge projects, or where independent testing is otherwise required. Many have certifications and accreditations: ISO 9000, ISO/IEC 17025 , and various governing agencies.
Several standards organizations publish test methods for package testing. Included are:
Governments and regulators publish some packaging test methods. There are also many corporate test standards in use. A review of technical literature and patents provides good options to consider for test procedures.
Researchers are not restricted to the use of published standards but can modify existing test methods or develop procedures specific to their particular needs. If a test is conducted with a deviation from a published test method or if a new method is employed, the test report must fully disclose the procedure.
The basis of packaging design and performance is the component materials. The physical properties , and sometimes chemical properties , of the materials need to be communicated to packaging engineers to aid in the design process. Suppliers publish data sheets and other technical communications that include the typical or average relevant physical properties and the test method these are based upon. Sometimes these are adequate. Other times, additional material and component testing is required by the packager or supplier to better define certain characteristics.
When a final package design is complete, the specifications for the component materials needs to be communicated to suppliers. Packaging materials testing is often needed to identify the critical material characteristics and engineering tolerances . These are used to prepare and enforce specifications.
For example, shrink film data might include: tensile strength (MD and CD), elongation , Elastic modulus , surface energy , thickness, Moisture vapor transmission rate , Oxygen transmission rate , heat seal strength, heat sealing conditions, heat shrinking conditions, etc. Average and process capability are often provided. The chemical properties related for use as Food contact materials may be necessary.
Some types of package testing do not use scientific instruments but use people for the evaluation.
The regulations for child-resistant packaging require a test protocol that involves children. Samples of the test packages are given to a prescribed population of children. With specified 50-child panels, a high percentage must be unable to open a test package within 5 minutes. [ 11 ] Adults are also tested for their ability to open a child-resistant package.
Consumer packages are often evaluated by focus groups . People evaluate the package features in a room monitored by video cameras. The consumer responses are treated qualitatively for feedback into the new packaging process.
Some food packagers use organoleptic evaluations. People use their senses (taste, smell, etc.) to determine if a package component has tainted the food in the package.
A new package may be evaluated in a test market that uses people to try the packages at home. Consumers have the opportunity to buy a product, perhaps with a coupon or discount. Return postcards or Internet sites provide feedback to package developers. Perhaps the most critical feedback is repeated sales items in the new package. Packaging evaluations are an important part of marketing research .
Legibility of text on packaging and labels is always subjective due to the inherent variations of people. Efforts have been made to help better quantify this by people in a laboratory: still using people for the evaluation but also employing a test apparatus to help reduce variability. [ 12 ] [ 13 ]
Some laboratory tests are conducted but still result in an observation by people. Some test procedures call for a judgment by test engineers whether or not pre-established acceptance criteria have been met.
The environmental conditions of testing are critical. The measured performance of many packages is affected by the conditioning and testing atmospheres. For example, paper based products are strongly affected by their moisture content: Relative humidity needs to be controlled. Plastic products are often strongly affected by temperature . [ 14 ]
Conditions of 23 °C (73.4 °F) and 50% relative humidity are common but other standard testing conditions are also published in material and package test standards. Engineering tolerances for the conditions are also specified. Often the package is conditioned to the specified environment and tested under those conditions. This can be in a conditioned room or in a chamber enclosing the test. With some testing, the package is conditioned to a specified environment, then is removed to ambient conditions and quickly tested. The test report needs to state the actual conditions used.
Engineers have found it important to know the effects of the full range of expected conditions on package performance. This can be through investigating published technical literature, obtaining supplier documentation, or by conducting controlled tests at diverse conditions.
Laboratory tests can help determine the shelf life of a package and its contents under a variety of conditions. This is particularly important for foods, pharmaceuticals, some chemicals, and a variety of products. The testing is usually product specific: the mechanisms of degradation are often different. Exposures to expected and elevated temperatures and humidities are commonly used for shelf life testing. The ability of packaging to control product degradation is frequently a subject of laboratory and field evaluations.
Many products degrade with exposure to the atmosphere: foods, pharmaceuticals, chemicals, etc. The ability of a package to control the permeation and penetration of gasses is vital for many types of products. Tests are often conducted on the packaging materials but also on the completed packages, sometimes after being subjected to flexing, handling, vibration, or temperature.
Packages can degrade with exposure to temperature, humidity, time, sterilization (steam, radiation, gas, etc.), sunlight, and other environmental factors. For some types of packaging, it is common to test for possible corrosion of metals, polymer degradation , and weather testing of polymers . Several types of accelerated aging of packaging and materials can be accomplished in a laboratory.
Exposure to elevated temperatures accelerates some degradation mechanisms. An Arrhenius equation is often used to correlate certain chemical reactions at different temperatures, based on the proper choice of Q 10 coefficients.
As with any laboratory testing, validating field trials are important.
Vacuum chambers are used to test the ability of a package to withstand low pressures. This can be to:
Both primary (consumer) packages and shipping containers have a risk of being dropped or being impacted by other items. Package integrity and product protection are important packaging functions. Tests are conducted to measure the resistance of packages and products to controlled laboratory shock and impact.
Testing also determines the effectiveness of package cushioning to isolate fragile products from shock . Instrumentation is used to measure the shock transmitted to a cushioned product. Simple drop tests can be used for evaluations. [ 16 ]
Many packages are used for products that are sensitive to temperature. The ability of insulated shipping containers to protect their contents from exposure to temperature fluctuations can be measured in a laboratory. The testing can be of empty containers or of full containers with appropriate jell or ice packs , contents, etc. Ovens, freezers, and environmental chambers are commonly used for this and other types of packaging. Effects of shock and vibration on thermal performance may also be studied.
Digital temperature data loggers are used to measure temperatures experienced in different distribution systems. This data is sometimes used to develop unique laboratory test methods for that distribution system.
Some packages, particularly glass, can be sensitive to sudden changes in temperature: Thermal shock . One method of testing involves rapid movement from cold to hot water baths, and back.
Package handles (and hand holes in packages) assist carrying and handling packages. Objective laboratory procedures are frequently used to help determine performance. Fixtured "hands" of various designs are used to hold a handle (sometimes two handles for a box). Most common are "jerk testing" by modified drop test procedures or use of the constant pull rates of a universal testing machine . Other procedures use a static force by hanging a heavily loaded package for an extended time or even using a centrifuge .
Vibration is encountered during shipping (vehicle vibration, rough roads, etc.) and movement on conveyors . Potential vibration damage may include:
The ability of a package to withstand these vibrations and to protect the contents can be measured by several laboratory test procedures. Some allow searching for the particular frequencies of vibration that have potential for damage. Modal testing methodologies are sometimes employed. Others use specified bands of random vibration to better represent complex vibrations measured in field studies of distribution environments.
Abrasion can affect several levels of packaging. Items being shipped may rub against each other or against package surfaces during shipment. Inner packages can abrade against each other, damaging graphics and bar codes. Shipping containers such as corrugated boxes can have tape and labels damaged.
Several types of package vibration tests are used to help determine effects of transport vibration. [ 18 ] Corrective action can then be taken.
Separate material tests are also useful. [ 19 ]
Compression testing relates to stacking or crushing of packages, particularly shipping containers. It usually measures of the force required to crush a package, stack of packages, or a unit load. Packages can be empty or filled as for shipment. A force-deflection curve used to obtain the peak load or other desired points. Other tests use a constant load and measure the time to failure or to a critical deflection.
Dynamic compression is sometimes tested by shock or impact testing with an additional load to crush the test package. Dynamic compression also takes place in stacked vibration testing.
Large pallet loads, bulk boxes , wooden boxes , and crates can be evaluated by many of the other test procedures previously listed. In addition, some special test methods are available for these larger loads.
Package bar codes are evaluated for several aspects of legibility by bar code verifiers as part of a continuing quality program. More thorough validation may include evaluations after use (and abuse) testing such as sunlight, abrasion, impact, moisture, etc.
Shipping containers are often subjected to sequential tests involving a combination of individual test methods. A variety of standard test schedules or protocols are available for evaluating transport packaging. They are used to help determine the ability of complete and filled shipping containers to various types of logistics systems. Some test the general ruggedness of the shipping container while others have been shown to reproduce the types of damage encountered in distribution. Some base the type and severity of testing on formal studies of the distribution environment: instrumentation , data loggers, and observation. Test cycles with these documented elements better simulate parts of certain logistics shipping environments.
In addition, package testing often relates to the specific product inside the package. Some broad categories of products and special package testing considerations follow:
Foods categories such as fresh produce , frozen foods , irradiated foods , fresh fish, canned foods , etc. have regulatory requirements and special packaging needs. Package testing often relates to:
Packaging for drugs and pharmaceuticals is highly regulated. Special testing needs include:
Packaging for medical materials, medical devices , health care supplies, etc., have special user requirements and is highly regulated. Barrier properties, durability, visibility, sterility and strength need to be controlled; usually with documented test results for initial designs and for production.
Assurance of sterility and suitability for use are critical. For example, medical devices and products are often sterilized in the package. The sterility must be maintained throughout distribution to allow immediate use by physicians. A series of special packaging tests is used to measure the ability of the package to maintain sterility. Verification and validation protocols are rigidly maintained.
Packaging of hazardous materials, or dangerous goods, are highly regulated. There are some material and construction requirements but also performance testing is required. The testing is based on the packing group (hazard level) of the contents, the quantity of material, and the type of container. [ 20 ] Research into improvements is continuing. [ 21 ] | https://en.wikipedia.org/wiki/Package_testing |
The Association for Packaging and Processing Technologies (formerly Packaging Machinery Manufacturers Institute) is a trade association representing more than 900 North American manufacturers and suppliers of equipment, components and materials as well as providers of related equipment and services to the packaging and processing industry. [ 1 ]
In 1933, President Franklin D. Roosevelt enacted the National Industrial Recovery Act (Ch. 90, 48 Stat. 195), which set stringent regulations on industry. Boyd Redner writes in A History of The Packaging Machinery Manufacturers Institute: “The National Industrial Recovery Act spelled out provisions to businessmen … every industry was to come under a code, and the code had two sets of regulations … [1.] regulations spelled out maximum hours that could be worked and the minimum hourly pay … and [2.] they were also to include a stipulation of Fair Trade Practices, so that one employer was required to join some code group.” [ 2 ] Thirty five packaging machinery businessmen met in Buffalo, New York , in 1933, to decide whether to form an association that would act as the advocate for the packaging machinery industry to the Department of Labor . Subsequently, PMMI was incorporated in Aug. 21, 1933.
In 1935, after the National Recovery Act was declared unconstitutional by the U.S. Supreme Court, PMMI veered from their mission as a defender of packaging practices against the regulation of the NRA, to a role of homogenizing the packaging processes. Packaging machine designs of that period were the result of individual requirements from the company to the inventor-entrepreneur.
PMMI implicitly brought the inventors together in a forum where they could discuss with each other the business and the industry. “The code proved to us not only that we could work together but that we could also trust one another. It proved further that we were an industry. It gave us a sense of importance of packaging machinery manufacturing that we have never lost.”
By 1938, all PMMI members had catalogs on file at the PMMI office at 342 Madison Avenue, New York City, NY, so the office could be a clearinghouse for inquiries. During World War II most PMMI member plants were converted to war work. [ 3 ] In 1956, PMMI began producing the PMMI Packaging Machinery Show due to a rising need for packaging machinery by consumer product goods companies. In 1995, PMMI added a second trade show PACK EXPO West, that is now PACK EXPO Las Vegas. [ 4 ]
PMMI offers five membership categories: general, associate, components supplier , materials supplier and affiliated supplier membership. [ 5 ]
As the owner and producer of the PACK EXPO portfolio of trade shows, PMMI is responsible for the following industry-wide events in the US, PACK EXPO Las Vegas, PACK EXPO International (Chicago), Healthcare Packaging EXPO (co-located with PACK EXPO Las Vegas and PACK EXPO International), PACK EXPO East and ProFood Tech. In Mexico PMMI organizes EXPO PACK México and EXPO PACK Guadalajara.
In 2013 PMMI formed a strategic partnership with Cologne Trade Fair (Koelnmesse), the organizer of Anuga FoodTec , ProSweets Cologne, International FoodTec India and International FoodTec Brazil. [ 6 ]
PMMI U is the education section of the Institute.
In 1966, PMMI initiated its first Education Committee to expand the packaging education program nationwide. Today, PMMI U annually donates $100,000 to packaging students, member employees, and packaging schools. [ 7 ] PMMI U has partnered with 28 institutions in the United States and Canada that offer packaging and processing curriculum. PMMI U has also partnered with the Mid Atlantic Mechantronic Advisory Council and several packaging and technical schools to develop a series of Certificate Programs focused on Mechatronics. [ 8 ]
In response to the National Product Liability Act of 1977, [ 9 ] PMMI Product Safety Committee and the American National Standards Institute created ANSI B155.1-1973 – Safety Requirements for the Construction, Care, and Use of Packaging and Packaging-Related Converting Machinery for use in future litigation. [ 10 ] | https://en.wikipedia.org/wiki/Packaging_Machinery_Manufacturers_Institute |
Packaging Machinery Technology [ 1 ] ( ISSN -1556-1658) was a trade publication and web site owned by PMMI for packaging and packaging machinery manufacturers and packaging engineers in the United States and Canada.
Circulation was about 35,000 copies per issue. The editorial director was Sean Riley, with the editorial offices located in Paoli, Pennsylvania . In 2014, PMMI purchased Summit Media Group and all of its publications. [ 2 ] PMT Magazine was rebranded as Packaging + Processing OEM Magazine in 2015. [ 3 ] In 2017, it was rebranded again as OEM Magazine . [ 4 ] [ 5 ]
This trade magazine–related article is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about magazines . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Packaging_Machinery_Technology |
Packaging engineering , also package engineering , packaging technology and packaging science , is a broad topic ranging from design conceptualization to product placement. All steps along the manufacturing process, and more, must be taken into account in the design of the package for any given product. Package engineering is an interdisciplinary field integrating science, engineering, technology and management to protect and identify products for distribution, storage, sale, and use. It encompasses the process of design, evaluation, and production of packages. It is a system integral to the value chain that impacts product quality, user satisfaction, distribution efficiencies, and safety. Package engineering includes industry-specific aspects of industrial engineering , marketing , materials science , industrial design and logistics . Packaging engineers must interact with research and development, manufacturing, marketing, graphic design, regulatory, purchasing, planning and so on. The package must sell and protect the product, while maintaining an efficient, cost-effective process cycle. [ 2 ]
Engineers develop packages from a wide variety of rigid and flexible materials. Some materials have scores or creases to allow controlled folding into package shapes (sometimes resembling origami [ 3 ] ). Packaging involves extrusion , thermoforming , molding and other processing technologies. Packages are often developed for high speed fabrication, filling, processing, and shipment. Packaging engineers use principles of structural analysis and thermal analysis in their evaluations.
Some packaging engineers have backgrounds in other science , engineering , or design disciplines while some have college degrees specializing in this field. [ 4 ]
Formal packaging programs might be listed as package engineering, packaging science, packaging technology, etc. BE, BS, MS, M.Tech and PhD programs are available. Students in a packaging program typically begin with generalized science, business, and engineering classes before progressing into industry-specific topics such as shelf life stability, corrugated box design , cushioning , engineering design , labeling regulations, project management , food safety , [ 5 ] robotics , RFID tags, quality management , package testing , packaging machinery, [ 6 ] [ 7 ] tamper-evident methods, [ 8 ] recycling , computer-aided design , [ 9 ] etc.
Artificial intelligence is becoming useful in several aspects of packaging development. [ 10 ] [ 11 ] Packaging engineers are using AI systems in their operations; AI can also design novel packages. For example, the DABUS system designed containers for food and beverages with fractal patterns for gripping and for optical impact. Patent law is developing in this area. A World Patent has been issued with the inventor listed as DABUS [ 12 ] but several jurisdictions indicate that a living person must be the inventor. [ 13 ] [ 14 ] | https://en.wikipedia.org/wiki/Packaging_engineering |
A packaging gas is used to pack sensitive materials such as food into a modified atmosphere environment. The gas used is usually inert , or of a nature that protects the integrity of the packaged goods, inhibiting unwanted chemical reactions such as food spoilage or oxidation . Some may also serve as a propellant for aerosol sprays like cans of whipped cream . For packaging food, the use of various gases is approved by regulatory organisations. [ 1 ]
Their E numbers are included in the following lists in parentheses. [ 2 ]
These gas types do not cause a chemical change to the substance that they protect.
Specific kinds of packaging gases are aerosol propellants . These process and assist the ejection of the product from its container.
These must be used with caution as they may have adverse effects when exposed to certain chemicals. They will cause oxidisation or contamination to certain types of materials.
Hydrocarbon gases approved for use with food need to be used with extreme caution as they are highly combustible, when combined with oxygen they burn very rapidly and may cause explosions in confined spaces. Special precautions must be taken when transporting these gases. [ 4 ]
This food ingredient article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Packaging_gas |
Packaging machinery is used throughout all packaging operations, involving primary packages to distribution packs. This includes many packaging processes: fabrication, cleaning, filling, sealing, combining, labeling, overwrapping, palletizing .
Some packaging operations cannot be accomplished without packaging equipment. For example many packages include heat seals to prepare or seal a package. Heat sealers are needed, even in slow labor-intensive operations.
With many industries, the effectiveness of the heat seal is critical to product safety so the heat sealing operation must closely controlled with documented Verification and validation protocols. Food, drug, and medical regulations require consistent seals on packages. Proper equipment is needed.
Packaging operations can be designed for variable package sizes and forms or for handling only uniform packages, where the machinery or packaging line is adjustable between production runs. Certainly slow manual operations allow workers to be flexible to package variation but also some automated lines can handle significant random variation. [ 1 ]
Moving from manual operations, through semi-automatic operations to fully automated packaging lines offers advantages to some packagers. [ 2 ] Other than the obvious control of labor costs, quality can be more consistent, and throughput can be optimized. [ 3 ]
Efforts at packaging line automation increasingly use programmable logic controllers [ 4 ] and robotics . [ 5 ]
Large fully automatic packaging lines can involve several pieces of major equipment from different manufactures as well as conveyors and ancillary equipment. Integrating such systems can be a challenge. Often consultants or external engineering firms are used to coordinate large projects.
Choosing packaging machinery includes an assessment of technical capabilities, labor requirements, worker safety, maintainability , serviceability, reliability , ability to integrate into the packaging line, capital cost, floorspace, flexibility (change-over, materials, multiple products, etc.), energy requirements, quality of outgoing packages, qualifications (for food, pharmaceuticals, etc.), throughput, efficiency, productivity, ergonomics , return on investment , etc.
Packaging machinery can be:
In addition to purchasing equipment, leasing options are often attractive. [ 6 ]
Machinery must be compatible with the expected operating conditions. For example, cold temperature operations require special considerations. [ 7 ] Some industries must perform periodic washdowns of all equipment. This high pressure chemical washing puts special demands on machinery and control systems. [ 8 ] [ 9 ] Condensation within closed portions of machinery can also be problematic.
Machinery needs to keep control of the product being packaged. For example, powders need to be stable, liquids cannot slosh out, [ 10 ] etc.
Some manufacturers decide not to do their own packaging but to employ contract packagers to perform all or some operations. Capital, labor, and other costs are outsourced .
Packaging machines may be of the following general types:
Packaging is necessary to protect products, and is now done mainly through the use of packaging machinery. Machinery plays increasingly important roles such as: | https://en.wikipedia.org/wiki/Packaging_machinery |
In chemical processing , a packed bed is a hollow tube , pipe, or other vessel that is filled with a packing material. The packed bed can be randomly filled with small objects like Raschig rings or else it can be a specifically designed structured packing . Packed beds may also contain catalyst particles or adsorbents such as zeolite pellets, granular activated carbon, etc.
The purpose of a packed bed is typically to improve contact between two phases in a chemical or similar process. Packed beds can be used in a chemical reactor , a distillation process, or a scrubber , but packed beds have also been used to store heat in chemical plants. In this case, hot gases are allowed to escape through a vessel that is packed with a refractory material until the packing is hot. Air or other cool gas is then fed back to the plant through the hot bed, thereby pre-heating the air or gas feed.
A packed bed used to perform separation processes , such as absorption , stripping , and distillation is known as a packed column. [ 1 ] Columns used in certain types of chromatography consisting of a tube filled with packing material can also be called packed columns and their structure has similarities to packed beds.
The column bed can be filled with randomly dumped packing material (creating a random packed bed) or with structured packing sections, which are arranged in a way that force fluids to take complicated paths through the bed (creating a structured packed bed). In the column, liquids tend to wet the surface of the packing material and the vapors pass across this wetted surface, where mass transfer takes place. Packing materials can be used instead of trays to improve separation in distillation columns. Packing offers the advantage of a lower pressure drop across the column (when compared to plates or trays ), which is beneficial while operating under vacuum. Differently shaped packing materials have different surface areas and void space between the packing. Both of these factors affect packing performance.
Another factor in performance, in addition to the packing shape and surface area, is the liquid and vapor distribution that enters the packed bed. The number of theoretical stages required to make a given separation is calculated using a specific vapor to liquid ratio. If the liquid and vapor are not evenly distributed across the superficial tower area as it enters the packed bed, the liquid to vapor ratio will not be correct and the required separation will not be achieved. The packing will appear to not be working properly. The height equivalent to a theoretical plate (HETP) will be greater than expected. The problem is not the packing itself but the mal-distribution of the fluids entering the packed bed. These columns can contain liquid distributors and redistributors which help to distribute the liquid evenly over a section of packing, increasing the efficiency of the mass transfer. [ 1 ] The design of the liquid distributors used to introduce the feed and reflux to a packed bed is critical to making the packing perform at maximum efficiency.
Packed columns have a continuous vapor-equilibrium curve, unlike conventional tray distillation in which every tray represents a separate point of vapor-liquid equilibrium. However, when modeling packed columns, it is useful to compute a number of theoretical plates to denote the separation efficiency of the packed column with respect to more traditional trays. In design, the number of necessary theoretical equilibrium stages is first determined and then the packing height equivalent to a theoretical equilibrium stage , known as the height equivalent to a theoretical plate (HETP), is also determined. The total packing height required is the number theoretical stages multiplied by the HETP.
Packed bed reactors are reactor vessels containing a fixed bed of catalytic material; they are widely used in the chemical process industry and find primary use in heterogeneous , gas-phase, catalytic reactions. The advantages of using a packed bed reactor include the high conversion of reactants per unit mass of catalyst, relatively low operating costs, and continuous operation. Disadvantages include the presence of thermal gradients throughout the bed, poor temperature control, and difficult servicing of the reactor. [ 2 ]
The Ergun equation can be used to predict the pressure drop along the length of a packed bed given the fluid velocity , the packing size, and the viscosity and density of the fluid.
The Ergun equation, while reliable for systems on the surface of the earth, is unreliable for predicting the behavior of systems in microgravity. Experiments are currently underway aboard the International Space Station to collect data and develop reliable models for in-orbit packed-bed reactors. [ 3 ]
The performance of a packed bed is highly dependent on the flow of material through it, which in turn is dependent on the packing and how the flow is managed. Tomographic techniques such as near-infrared , x-ray , gamma ray , electrical capacitance , electrical resistance tomography are used to quantify liquid distribution patterns in packed columns; choice of tomographic technique depends on the primary measurement of interest, randomness of packing, safety requirements, desired data acquisition rate, and budget. [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] | https://en.wikipedia.org/wiki/Packed_bed |
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