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superior.[5] == References == ^ F. Rösel, H.M. Fries, K. Alder, H.C. Pauli: At. Data Nucl. Data Tables 21 (1978) 91. ^ R.S. Hager and E.C. Seltzer, Nucl. Data Tables A4 (1968) 1. ^ I.M. Band, M.B. Trzhaskovskaya: Tables of the gamma–ray internal conversion coefficients for the K, L, M shells, 10<Z<104 (Leningrad: Nuclear Physics Institute, 1978). ^ T. Kibédi, T.W. Burrows, M.B. Trzhaskovskaya, P.M. Davidson, C.W. Nestor, Jr. Evaluation of theoretical conversion coefficients using BrIcc, Nucl. Instr. and Meth. A 589 (2008) 202-229. ^ http://www-nds.iaea.org/nsdd/presentations%202011/Wednesday/BrIcc_NSDD2011.pdf or see http://bricc.anu.edu.au/bricc-datatables.php == External links == Nuclear Structure and Decay Data - IAEA with query on Conversion Coefficients
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"title": "Internal conversion coefficient"
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A momordicine is any of several compounds found in the bitter melon vine, Momordica charantia. They are glycosides of cucurbitane derivatives. They include Momordicine II Momordicine IV, 7-O-D-glucopyranosyl-3,23-dihydroxycucurbita-5,24-dien-19-al Momordicine II and IV can be extracted from the leaves of M. charantia by methanol. They have been found to deter egg-laying of the leaf mining fly (Liriomyza trifolii) at a combined concentration of 96 μg/cm2. == See also == Momordicin (disambiguation) == References ==
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"page_id": 30344639,
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"title": "Momordicine"
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"The Monkey Suit" is the twenty-first and penultimate episode of the seventeenth season of the American animated television series The Simpsons. It originally aired on the Fox network in the United States on May 14, 2006. In the episode, Ned Flanders is shocked after seeing a new display at the museum about evolution. Together with Reverend Lovejoy, he spreads the religious belief of creationism in Springfield, and at a later town meeting, teaching evolution is made illegal. As a result, Lisa decides to hold secret classes for people interested in evolution. However, she is quickly arrested and a trial against her is initiated. J. Stewart Burns wrote "The Monkey Suit", for which he received inspiration from the 1925 Scopes Monkey Trial. The episode features a few references to this legal case, as well as several references to popular culture. Many analysts have commented on the episode's treatment of the creation–evolution controversy, a dispute about the origin of humanity between those who support a creationist view based upon their religious beliefs, versus those who accept evolution, as supported by scientific evidence. Critics have given the episode generally positive reviews, praising it for its satire of the creation-evolution debate. "The Monkey Suit" has won an award from the Independent Investigations Group (IIG) for being "one of those rare shows in the media that encourage science, critical thinking, and ridicule those shows that peddle pseudoscience and superstition." In 2007, a scene from the episode was highlighted in the scientific journal Nature. == Plot == After Bart hurriedly completes a series of summer vacation activities days before the start of the new academic year, Lisa decides to take the family to the museum to see a weaving exhibit. However, they soon discover that it has been replaced by a "History of Weapons" exhibit, sponsored
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by Kellogg's. Faced with an incredibly long line, Homer notices Ned Flanders and his sons at the front of the line and cuts in front of them. Everyone else starts taking advantage of Ned's kindness as well until the Flanders family is stuck at the end. At the end of the day, they are still waiting, and are denied entry, as it is closing time for the weapons exhibit. They decide to check out the human evolution exhibit next door. Ned is outraged to hear that humans actually evolved from apes and that the creation account in the Genesis is therefore a myth. Covering his sons' eyes, he forcefully drags them out of the exhibit. Ned meets up with the church council to suggest promotion of creationism. The next day, he and Reverend Lovejoy blackmail Principal Skinner into introducing creationism in the school. Lisa is perturbed by this, and at a town meeting asks everyone to make a choice between creationism and Darwinism, as there is only one truth. The townspeople vote for creationism, much to her chagrin, and the act of teaching or learning Darwinism and evolution is made illegal. Lisa therefore decides to start holding secret classes for people interested in evolution. However, just as the first lesson is about to begin, she is arrested by Chief Wiggum. She asks why she is being arrested when there are far worse crimes out there, and embarrassed he tells her they only have enough manpower to enforce the last three laws passed (as demonstrated by their non-response to Snake randomly shooting at people from atop the Kwik-E-Mart whilst yelling "you live, you die"). Lisa is brought to trial, which is dubbed Lisa Simpson v. God. Representing her is Clarice Drummond, an ACLU lawyer, while on Ned's side is Wallace Brady,
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an overweight, southern lawyer. The trial does not go smoothly for Lisa, as Professor Frink gives ambiguous answers regarding God's existence, while a creationist says that evolution cannot be real, as there is no proof of a "missing link" (depicted in a picture as a savage hominid, holding a rock over his head). After reading Charles Darwin's On the Origin of Species (incorrectly called The Origin of Species), Marge believes that he presents a convincing argument and decides to help Lisa (whilst Bart proposes sending Milhouse in disguise in her place to allow Lisa to flee the country). When the trial resumes, Marge tells Lisa that she now knows a way that she can help her. While Ned is being cross-examined by Drummond, she gives Homer a beer. Homer, ecstatic at getting the beer, tries to open it unsuccessfully. The more he tries, the more primitive he gets, hooting and banging the beer on the bench, disrupting the trial. Ned loses his temper and tells Homer to stop behaving like a monkey. Drummond then asks Ned to compare the picture of the "missing link" and Homer shaking the beer over his head, and asks if he truly believes Homer cannot be related to apes. Ned cannot and concedes victory to Lisa. After the trial, Lisa goes up to Ned and tells him that while she fully respects his religious beliefs, she just does not think it is proper for the church to dominate the school in the same way that he and Reverend Lovejoy do not want scientists taking over the church. Ned finally agrees with this, so he offers to take Lisa and his sons out for ice cream. However Todd (in a call back to an earlier joke) turns out to be Nelson instead after he insults Ned
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and pulls off his mask. == Production == "The Monkey Suit" was written by J. Stewart Burns and directed by Raymond S. Persi as part of the seventeenth season of The Simpsons (2005–2006). Burns received inspiration for the episode from the Scopes Monkey Trial, a 1925 legal case in which high school science teacher John Scopes was accused of violating Tennessee's Butler Act which made teaching evolution unlawful. Clarice Drummond, the ACLU lawyer who represents Lisa, is a reference to the ACLU lawyer Clarence Darrow who defended Scopes, while Wallace Brady is a reference to William Jennings Bryan, an attorney in the Scopes Monkey Trial. American actor and Dallas star Larry Hagman guest starred in the episode as Wallace Brady, while American actress Melanie Griffith played herself as the narrator of an audio tour at the museum. Burns did research for "The Monkey Suit" by reading Richard Dawkins' book The Selfish Gene and watching Inherit the Wind (a film loosely based on the Scopes Monkey Trial). He also visited a natural history museum. The opening of the episode, in which Bart rushes to do everything he planned on doing during summer vacation, was originally written and animated for the season fourteen episode "I'm Spelling as Fast as I Can" (2003) but was cut. This episode came in short, and to fill in time, the sequence was added. Burns has said commented the episode "ended up being incredibly short because when you do an episode where there's really just one good side of an argument [creation vs. evolution], you don't fill out as much time as you need to." The opening sequence features a large number of allusions to popular culture, including references to The Natural (1984 film), Happy Days (television sitcom), and Men in Black (1997 film). == Themes ==
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"The Monkey Suit" is an episode that tackles the creation–evolution controversy, and according to Theresa Sanders in her book Approaching Eden: Adam and Eve in Popular Culture, "skewered antievolution legislation." The authors of the book Chronology of the Evolution-Creationism Controversy commented that the episode "caricatures creationism as an intellectual joke." Burns has cited the episode as "a nice example of The Simpsons really taking one clear side". However, as pointed out by Sanders, it "should be pointed out that though the Simpsons episode clearly sides with Darwin, evolutionists come in for criticism as well. When Ned and his sons go into the museum's Hall of Man, one of the exhibits they see in support of evolution is a collection of dinosaur bones with the title 'Indisputable Fossil Records.' The cartoon's inclusion of the sign can be interpreted as mocking the pretension that science knows all and may not be questioned." Sanders cited another scene as an example of this; at the trial, Drummond asks Professor Frink if "this theory of evolution necessarily mean that there is no God?", to which he replies, "No, of course not. It just says that God is an impotent nothing from nowhere with less power than the undersecretary of Agriculture." Sanders wrote that "His arrogance is clear, and equally clear is the show's satirical presentation of science's hubris." Ted Gournelos analyzed "The Monkey Suit" in his 2009 book Popular Culture and the Future of Politics: Cultural Studies and the Tao of South Park, writing: "More than anything, the episode is used to critique the demonization of evolutionary theory by religious propaganda, by an instructional video used in the school (that shows a drunken Charles Darwin passionately kissing Satan) as well as by the prosecuting attorney. This allows for a somewhat leftist discussion of the issue,
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but ultimately is unable to address the rise of Christian fundamentalism in the United States [...]". Gournelos noted that the episode focuses on the old Scopes Monkey Trial and does not address contemporary creation–evolution debates, adding: "Interestingly, The Simpsons continues to place creationism at a higher popular plain than evolution, as the jury and trial audience are obviously biased towards the creationists (who, unlike in contemporary cases, are the prosecutors rather than the plaintiffs)." Gournelos concluded that the episode "pokes gentle fun at media rhetoric and the questioning of evolutionary theory [...], but is unable or unwilling to address the rise of intelligent design or contemporary court battles (in Pennsylvania [see Kitzmiller v. Dover Area School District], Kansas [see Kansas evolution hearings], and elsewhere) that might encourage debate in its audience." == Release == The episode originally aired on the Fox network in the United States on May 14, 2006. During this broadcast, it was seen by approximately 8.41 million viewers, finishing forty-sixth in the ratings for the week of May 8–14, 2006. Since airing, the episode has received generally positive reviews from critics. In a retrospective that was published on the twentieth anniversary of The Simpsons in 2010, writers for BBC News selected "The Monkey Suit" as one of the show's "10 classic episodes", one they said demonstrated that "the writers still have fire in their bellies." TV Squad critic Adam Finley wrote that "Last night's episode had some good moments, but it did feel like they were treading upon somewhat familiar ground and not saying anything especially new," referring to the fact the issue of science and religion has been dealt with before on the show, "most notably in the 'Lisa the Skeptic' episode in which the supposed skeleton of a dead angel is found." In 2007, "The
|
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"page_id": 4195776,
"source": null,
"title": "The Monkey Suit"
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Monkey Suit" won an award from the Independent Investigations Group (IIG) for being "one of those rare shows in the media that encourage science, critical thinking, and ridicule those shows that peddle pseudoscience and superstition." J. Stewart Burns, the writer of the episode, was present at the awards ceremony to accept the award. While reviewing the seventeenth season of The Simpsons, Jesse Hassenger of PopMatters noted that he thought the show had declined in quality compared to its earlier years, and added that the stronger episodes in the later seasons are that ones that "satirize topical issues", giving "The Monkey Suit" as an example. Similarly, Fort Worth Star-Telegram staff writer Robert Philpot commented that "Even in its weak seasons, this show has always been good for at least one belly laugh per episode. Not this year [season seventeen]. Aside from an installment that took on the evolution -vs.-creationism edge and a couple of other bits, the satirical edge has really dulled, making the announcement that it will have at least two more seasons a cause for concern rather than celebration." In the July 26, 2007 issue of Nature, the scientific journal's editorial staff listed among "The Top Ten science moments in The Simpsons" the scene from the episode in which "Flanders is flabbergasted that the science museum's exhibit on the origins of man both highlights evolution and makes light of creationism — and, to top it all, has a unisex bathroom." == See also == History of the creation–evolution controversy Creation and evolution in public education == References == == External links == "The Monkey Suit" at IMDb
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Thomas Robert Bolam FRSE MM (1893–1969) was a 20th century British chemist. == Life == He was born in Bristol on 7 September 1893. He was educated at the Fairfield Higher Grade school and the Merchant Venturers School in Bristol. He graduated BSc from Bristol University in 1914 and then at the start of the First World War he joined the Royal Engineers and served in France and Flanders winning the Military Medal. Returning to Bristol he gained an MSc in 1920 and began lecturing at the University of Edinburgh. He received a doctorate (DSc) from the university in 1930. In 1933 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were Sir James Walker, James Pickering Kendall, Ernest Bowman Ludlam and Leonard Dobbin. He served as Vice President of the Society 1959 to 1962. In the Second World War he served as an Air Raid Warden in Edinburgh. He died in Edinburgh on 8 July 1969. == Publications == The Donnan Equilibrium (1932) == Family == In 1926 he married Mary Russell Mackenzie (d.1954). They had no children. == References ==
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"title": "Thomas Robert Bolam"
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Blinatumomab, sold under the brand name Blincyto, is a biopharmaceutical medication used for the treatment of Philadelphia chromosome-negative relapsed or refractory acute lymphoblastic leukemia. It belongs to a class of constructed monoclonal antibodies, bi-specific T-cell engagers (BiTEs), that exert action selectively and direct the human immune system to act against tumor cells. Blinatumomab is a bispecific CD19-directed CD3 T-cell engager that specifically targets the CD19 antigen present on B cells. Blinatumomab is given via intravenous infusion. Blinatumomab was approved for medical use in the United States in December 2014, in Australia in November 2015, in Canada in March 2016, and in the European Union in November 2023. == Medical use == In the US, blinatumomab is indicated for the treatment of people one month and older with CD19-positive B-cell precursor acute lymphoblastic leukemia in first or second complete remission with minimal residual disease greater than or equal to 0.1%; relapsed or refractory CD19-positive B-cell precursor acute lymphoblastic leukemia; and CD19-positive Philadelphia chromosome-negative B-cell precursor acute lymphoblastic leukemia in the consolidation phase of multiphase chemotherapy. In the EU, blinatumomab is indicated for the treatment of adults with CD19 positive relapsed or refractory B‑cell precursor acute lymphoblastic leukemia; for the treatment of adults with Philadelphia chromosome-negative CD19 positive B-cell precursor acute lymphoblastic leukemia in first or second complete remission with minimal residual disease greater than or equal to 0.1%; for the treatment of children aged one month or older with Philadelphia chromosome-negative CD19 positive B‑cell precursor acute lymphoblastic leukemia which is refractory or in relapse after receiving at least two prior therapies or in relapse after receiving prior allogeneic hematopoietic stem cell transplantation; for the treatment of children aged one month or older with high-risk first relapsed Philadelphia chromosome-negative CD19 positive B-cell precursor acute lymphoblastic leukemia as part of the consolidation therapy;
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as part of consolidation therapy for the treatment of adults with newly diagnosed Philadelphia chromosome negative CD19 positive B-cell precursor acute lymphoblastic leukemia. == Mechanism of action == Blinatumomab is a bispecific T-cell engager (BiTE). It enables a patient's T cells to recognize malignant B cells. A molecule of blinatumomab combines two binding sites: a CD3 site for T cells and a CD19 site for the target B cells. CD3 is part of the T cell receptor. The drug works by linking these two cell types and activating the T cell to exert cytotoxic activity on the target cell. CD3 and CD19 are expressed in both pediatric and adult patients, making blinatumomab a potential therapeutic option for both pediatric and adult populations. == History == Blinatumomab (originally known as MT103) was developed by a German-American company Micromet, in cooperation with Lonza; In 2012, Micromet was purchased by Amgen, which furthered the drug's clinical trials. In July 2014, the FDA granted breakthrough therapy status to blinatumomab for the treatment of acute lymphoblastic leukemia. In October 2014, Amgen's Biologics License Application for blinatumomab was granted priority review designation by the US Food and Drug Administration (FDA). In December 2014, the blinatumomab was approved for use in the United States to treat Philadelphia chromosome-negative relapsed or refractory acute lymphoblastic leukemia under the FDA's accelerated approval program; marketing authorization depended on the outcome of clinical trials that were ongoing at the time of approval. == Society and culture == === Economics === Amgen announced that the price for blinatumomab would be US$178,000 per year, which made it the most expensive cancer drug on the market. Merck's pembrolizumab was priced at US$150,000 per year when it launched (in September 2014). At the time of initial approval, only about 1,000 patients in the US had an
|
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indication for blinatumomab. Memorial Sloan-Kettering Cancer Center calculated that according to "value-based pricing," assuming that the value of a year of life is US$121,000 with a 15% "toxicity discount," the market price of blinatumomab should be US$12,612 a month, compared to the market price of US$64,260 a month. A representative of Amgen said, "The price of Blincyto reflects the significant clinical, economic and humanistic value of the product to patients and the health-care system. The price also reflects the complexity of developing, manufacturing and reliably supplying innovative biologic medicines." == References ==
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"page_id": 18875843,
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"title": "Blinatumomab"
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== Thermal expansion == == Notes == All values refer to 25 °C unless noted. == References == === CRC === As quoted from this source in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 12, Properties of Solids; Thermal and Physical Properties of Pure Metals Touloukian, Y. S., Thermophysical Properties of Matter, Vol. 12, Thermal Expansion, IFI/Plenum, New York, 1975. === CR2 === As quoted in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 4, Properties of the Elements and Inorganic Compounds; Physical Properties of the Rare Earth Metals which further refers to: Beaudry, B. J. and Gschneidner, K.A. Jr., in Handbook on the Physics and Chemistry of Rare Earths, Vol. 1, Gschneidner, K.A. Jr. and Eyring, L., Eds., North-Holland Physics, Amsterdam, 1978, 173. McEwen, K.A., in Handbook on the Physics and Chemistry of Rare Earths, Vol. 1, Gschneidner, K.A. Jr. and Eyring, L., Eds., North-Holland Physics, Amsterdam, 1978, 411. === LNG === As quoted from this source in an online version of: J.A. Dean (ed), Lange's Handbook of Chemistry (15th Edition), McGraw-Hill, 1999; Section 4; Table 4.1, Electronic Configuration and Properties of the Elements Touloukian, Y. S., Thermophysical Properties of Matter, Vol. 12, Thermal Expansion, Plenum, New York, 1975. === WEL === As quoted at http://www.webelements.com/ from these sources: D.R. Lide, (Ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 79th edition, 1998. A.M. James and M.P. Lord in Macmillan's Chemical and Physical Data, Macmillan, London, UK, 1992. G.W.C. Kaye and T. H. Laby in Tables of physical and chemical constants, Longman, London, UK, 15th edition, 1993. J.A. Dean (ed) in
|
{
"page_id": 1967556,
"source": null,
"title": "Thermal expansivities of the elements"
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Lange's Handbook of Chemistry, McGraw-Hill, New York, USA, 14th edition, 1992.
|
{
"page_id": 1967556,
"source": null,
"title": "Thermal expansivities of the elements"
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|
The mix of ammonium salts of phosphorylated glycerides can be either made synthetically or from mixture of glycerol and partially hardened plant (most often used: rapeseed oil) oils. == Applications == It is most often used in chocolate industry as an emulsifier, often as alternative to lecithin. == Properties == At room temperature it is liquid. == Synonyms == Ammonium phosphatide Emulsifier YN E number E442 == See also == Polyglycerol polyricinoleate (PGPR)
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{
"page_id": 11797961,
"source": null,
"title": "Mixed ammonium salts of phosphorylated glycerides"
}
|
A stabiliser or stabilizer is an additive to food which helps to preserve its structure. Typical uses include preventing oil-water emulsions from separating in products such as salad dressing; preventing ice crystals from forming in frozen food such as ice cream; and preventing fruit from settling in products such as jam, yogurt and jellies. Some of these food additives may promote the growth of specific microorganisms in the gastrointestinal tract that can ferment them. The following hydrocolloids are the most common ones used as stabilisers: alginate agar carrageen cellulose and cellulose derivatives gelatin guar gum gum Arabic locust bean gum pectin starch xanthan gum == See also == Gums and Stabilisers for the Food Industry, a conference series about title subject == References ==
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{
"page_id": 28771786,
"source": null,
"title": "Stabiliser (food)"
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|
Crotonyl-coenzyme A is an intermediate in the fermentation of butyric acid, and in the metabolism of lysine and tryptophan. It is important in the metabolism of fatty acids and amino acids. == Crotonyl-CoA and reductases == Before a 2007 report by Alber and coworkers, crotonyl-CoA carboxylases and reductases (CCRs) were known for reducing crotonyl-CoA to butyryl-CoA. A report by Alber and coworkers concluded that a specific CCR homolog was able to reduce crotonyl-CoA to (2S)-ethyl malonyl-CoA which was a favorable reaction. The specific CCR homolog came from the bacterium Rhodobacter sphaeroides. == Role of Crotonyl-CoA in Transcription == Post-translational modification of histones either by acetylation or crotonylation is important for the active transcription of genes. Histone crotonylation is regulated by the concentration of crotonyl-CoA which can change based on environmental cell conditions or genetic factors. == References == == See also == Crotonic acid Glutaryl-CoA dehydrogenase
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{
"page_id": 11470282,
"source": null,
"title": "Crotonyl-CoA"
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|
Callows (Irish: caladh) are a type of wetland found in Ireland. They are a seasonally flooded grassland ecosystem found on low-lying river floodplains. The callows are located at the center of Ireland. 5856 hectares of the callows are protected as a Special Area of Conservation (SAC). At the heart of the callows is the River Shannon: one of the only unregulated rivers left in western Europe. The River Shannon extends 360 kilometers. More than 20% of Ireland's landmass is drained by the River Shannon. Unlike many other parts of the world, the callows is relatively untouched by mankind. The area has not fallen victim to intensive agriculture or development by humans, making it a refuge for a wide range of flora and fauna. The callows are a wetland ecosystem full of rivers and creeks. Rolling hills and grassy meadows, which are full of cows, horses, flowers, birds, and more, extended for great distances in every direction. There are very few trees and tall plants as the grazers keep the plant life trimmed down. The region is also an ecotone that forms a gradient of dry to wet space controlled by flooding. Additionally the wetland area is mainly flat, which creates a flat river gradient and slows the movement of water. There are a few main characteristics that control the biodiversity of riparian ecosystems: hydrology, productivity, disturbance, and the heterogeneity of space. Fluctuations in water levels regulate plant distributions, species diversity, and the composition of the callows community. Factors, such as time, depth, and frequency, greatly affect the functioning of the ecosystem. The wetlands and meadows are home to a variety of organisms. The unique and well preserved habitat promotes a number of biological services. For example, spanning the vast meadows in this region are a range of insect-pollinated plant species.
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{
"page_id": 47580620,
"source": null,
"title": "Callows"
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Thus, pollination services are provided and the diversity of life in the callows will prevail. Even though the area is mainly free of human interaction, there are still some aspects of the callows that are regulated by people. First, since floodplains typically support hay meadows, there are farmers that still cut hay annually. This process has gone on for hundreds of years and actually promotes diversity of flora. There have also been a number of failed attempts to control the magnitude and duration of flooding in the wetland area. As with most places on Earth, climate change driven by humans is altering the callows ecosystem. Many aspects of seasonal flooding will begin to change with the drier summers and wetter winters that predicted in the future. Wetter winters mean longer flooding time and potentially deeper flood pools. As flood levels begin to rise, plant species that are not used to flooding will be affected. This will also change dynamics between flora and fauna by limiting food and habitat space. Also, increased agriculture and development are future threats. Protecting the callows and keeping it as a conservation area is vital to the survival of the unique array of organisms that call the callows home. == Examples == Shannon Callows River Suck Callows Little Brosna Callows Lough Eidin Callan, County Kilkenny Castletroy == Literary references == Patrick Deeley's novel The Lost Orchard deals with the protection of "The Callows", a marshy area. == References ==
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{
"page_id": 47580620,
"source": null,
"title": "Callows"
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|
The speed of sound in any chemical element in the fluid phase has one temperature-dependent value. In the solid phase, different types of sound wave may be propagated, each with its own speed: among these types of wave are longitudinal (as in fluids), transversal, and (along a surface or plate) extensional. == Speed of sound, solid phase == == Speed of sound, fluid phases == == See also == == Notes == Ref. CRC: Values are "at room temperature" unless noted, and "for normal atmospheric pressure" ("at 1 atm" for gases). Ref. WEL: Values refer to 293 K (20 °C; 68 °F) "where possible". Midpoint values are substituted if ranges were given in their original reference. Not specified further, it is assumed from the values that all (except fluids) are for the speed of sound in a thin rod. == References == == Sources == === WEL === As quoted at http://www.webelements.com/ from this source: G.V. Samsonov (Ed.) in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA, 1968. === CRC === As quoted from various sources in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 14, Geophysics, Astronomy, and Acoustics; Speed of Sound in Various Media === CR2 === As quoted from this source in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 6, Fluid Properties; Thermal Properties of Mercury Vukalovich, M. P., et al., Thermophysical Properties of Mercury, Moscow Standard Press, 1971. === APIH === Dwight E. Gray (ed), American Institute of Physics Handbook. McGraw-Hill. Boca Raton, Florida, New York, 1957. === Other === 88RAB: V.A. Rabinovich, et al. Thermophysical Properties of Neon, Argon, Krypton
|
{
"page_id": 1967563,
"source": null,
"title": "Speeds of sound of the elements"
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and Xenon. Selover (Eng. ed.) Hemisphere, Washington DC, 1988. Zuckerwar: A. J. Zuckerwar, Handbook of the Speed of Sound in Real Gases. Academic Press, 2002.
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{
"page_id": 1967563,
"source": null,
"title": "Speeds of sound of the elements"
}
|
Hal Whitehead is a biologist specializing in the study of the sperm whale (Physeter macrocephalus). Whitehead is professor at Dalhousie University. The primary field research vessel of his laboratory is the Balaena, a Valiant 40 ocean-going cruising boat, which normally does its work off the coast of Nova Scotia. Other marine mammals studied by Whitehead's laboratory include beluga whales, pilot whales, northern bottlenose whales, and bottlenose dolphins. Whitehead is a precursor in the field of cetacean research and specifically the acoustical abilities of sperm whales, which underlie a complex social organization. == Research findings == Whitehead's research is focused primarily upon the behavior, population biology, and ecology of the sperm whale. Topics include social structure, cultural transmission of behavior, as well as acoustic communicative behavior such as click trains. == Selected publications == Whitehead, H. (2003). Sperm Whales: Social Evolution in the Ocean. 456 p., 60 halftones, 84 line drawings, 41 tables. 6 x 9. Chicago: University of Chicago Press. Whitehead, H. and Luke Rendell. (2014). The Cultural Lives of Whales and Dolphins. 408 p., 15 color plates, 7 halftones, 4 line drawings, 5 tables. 6 x 9. Chicago: University of Chicago Press, ISBN 978-0-22632-592-7. == See also == Beaked whale Sperm whale == External links == Dalhousie University Whitehead Lab
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"page_id": 4392398,
"source": null,
"title": "Hal Whitehead"
}
|
Spiking neural networks (SNNs) are artificial neural networks (ANN) that mimic natural neural networks. These models leverage timing of discrete spikes as the main information carrier. In addition to neuronal and synaptic state, SNNs incorporate the concept of time into their operating model. The idea is that neurons in the SNN do not transmit information at each propagation cycle (as it happens with typical multi-layer perceptron networks), but rather transmit information only when a membrane potential—an intrinsic quality of the neuron related to its membrane electrical charge—reaches a specific value, called the threshold. When the membrane potential reaches the threshold, the neuron fires, and generates a signal that travels to other neurons which, in turn, increase or decrease their potentials in response to this signal. A neuron model that fires at the moment of threshold crossing is also called a spiking neuron model. While spike rates can be considered the analogue of the variable output of a traditional ANN, neurobiology research indicated that high speed processing cannot be performed solely through a rate-based scheme. For example humans can perform an image recognition task requiring no more than 10ms of processing time per neuron through the successive layers (going from the retina to the temporal lobe). This time window is too short for rate-based encoding. The precise spike timings in a small set of spiking neurons also has a higher information coding capacity compared with a rate-based approach. The most prominent spiking neuron model is the leaky integrate-and-fire model. In that model, the momentary activation level (modeled as a differential equation) is normally considered to be the neuron's state, with incoming spikes pushing this value higher or lower, until the state eventually either decays or—if the firing threshold is reached—the neuron fires. After firing, the state variable is reset to a
|
{
"page_id": 10159567,
"source": null,
"title": "Spiking neural network"
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lower value. Various decoding methods exist for interpreting the outgoing spike train as a real-value number, relying on either the frequency of spikes (rate-code), the time-to-first-spike after stimulation, or the interval between spikes. == History == Many multi-layer artificial neural networks are fully connected, receiving input from every neuron in the previous layer and signalling every neuron in the subsequent layer. Although these networks have achieved breakthroughs, they do not match biological networks and do not mimic neurons. The biology-inspired Hodgkin–Huxley model of a spiking neuron was proposed in 1952. This model described how action potentials are initiated and propagated. Communication between neurons, which requires the exchange of chemical neurotransmitters in the synaptic gap, is described in models such as the integrate-and-fire model, FitzHugh–Nagumo model (1961–1962), and Hindmarsh–Rose model (1984). The leaky integrate-and-fire model (or a derivative) is commonly used as it is easier to compute than Hodgkin–Huxley. While the notion of an artificial spiking neural network became popular only in the twenty-first century, studies between 1980 and 1995 supported the concept. The first models of this type of ANN appeared to simulate non-algorithmic intelligent information processing systems. However, the notion of the spiking neural network as a mathematical model was first worked on in the early 1970s. As of 2019 SNNs lagged behind ANNs in accuracy, but the gap is decreasing, and has vanished on some tasks. == Underpinnings == Information in the brain is represented as action potentials (neuron spikes), which may group into spike trains or coordinated waves. A fundamental question of neuroscience is to determine whether neurons communicate by a rate or temporal code. Temporal coding implies that a single spiking neuron can replace hundreds of hidden units on a conventional neural net. SNNs define a neuron's current state as its potential (possibly modeled as a
|
{
"page_id": 10159567,
"source": null,
"title": "Spiking neural network"
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differential equation). An input pulse causes the potential to rise and then gradually decline. Encoding schemes can interpret these pulse sequences as a number, considering pulse frequency and pulse interval. Using the precise time of pulse occurrence, a neural network can consider more information and offer better computing properties. SNNs compute in the continuous domain. Such neurons test for activation only when their potentials reach a certain value. When a neuron is activated, it produces a signal that is passed to connected neurons, accordingly raising or lowering their potentials. The SNN approach produces a continuous output instead of the binary output of traditional ANNs. Pulse trains are not easily interpretable, hence the need for encoding schemes. However, a pulse train representation may be more suited for processing spatiotemporal data (or real-world sensory data classification). SNNs connect neurons only to nearby neurons so that they process input blocks separately (similar to CNN using filters). They consider time by encoding information as pulse trains so as not to lose information. This avoids the complexity of a recurrent neural network (RNN). Impulse neurons are more powerful computational units than traditional artificial neurons. SNNs are theoretically more powerful than so called "second-generation networks" defined as ANNs "based on computational units that apply activation function with a continuous set of possible output values to a weighted sum (or polynomial) of the inputs"; however, SNN training issues and hardware requirements limit their use. Although unsupervised biologically inspired learning methods are available such as Hebbian learning and STDP, no effective supervised training method is suitable for SNNs that can provide better performance than second-generation networks. Spike-based activation of SNNs is not differentiable, thus gradient descent-based backpropagation (BP) is not available. SNNs have much larger computational costs for simulating realistic neural models than traditional ANNs. Pulse-coupled neural networks
|
{
"page_id": 10159567,
"source": null,
"title": "Spiking neural network"
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(PCNN) are often confused with SNNs. A PCNN can be seen as a kind of SNN. Researchers are actively working on various topics. The first concerns differentiability. The expressions for both the forward- and backward-learning methods contain the derivative of the neural activation function which is not differentiable because a neuron's output is either 1 when it spikes, and 0 otherwise. This all-or-nothing behavior disrupts gradients and makes these neurons unsuitable for gradient-based optimization. Approaches to resolving it include: resorting to entirely biologically inspired local learning rules for the hidden units translating conventionally trained “rate-based” NNs to SNNs smoothing the network model to be continuously differentiable defining an SG (Surrogate Gradient) as a continuous relaxation of the real gradients The second concerns the optimization algorithm. Standard BP can be expensive in terms of computation, memory, and communication and may be poorly suited to the hardware that implements it (e.g., a computer, brain, or neuromorphic device). Incorporating additional neuron dynamics such as Spike Frequency Adaptation (SFA) is a notable advance, enhancing efficiency and computational power. These neurons sit between biological complexity and computational complexity. Originating from biological insights, SFA offers significant computational benefits by reducing power usage, especially in cases of repetitive or intense stimuli. This adaptation improves signal/noise clarity and introduces an elementary short-term memory at the neuron level, which in turn, improves accuracy and efficiency. This was mostly achieved using compartmental neuron models. The simpler versions are of neuron models with adaptive thresholds, are an indirect way of achieving SFA. It equips SNNs with improved learning capabilities, even with constrained synaptic plasticity, and elevates computational efficiency. This feature lessens the demand on network layers by decreasing the need for spike processing, thus lowering computational load and memory access time—essential aspects of neural computation. Moreover, SNNs utilizing neurons capable of
|
{
"page_id": 10159567,
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"title": "Spiking neural network"
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SFA achieve levels of accuracy that rival those of conventional ANNs, while also requiring fewer neurons for comparable tasks. This efficiency streamlines the computational workflow and conserves space and energy, while maintaining technical integrity. High-performance deep spiking neural networks can operate with 0.3 spikes per neuron. == Applications == SNNs can in principle be applied to the same applications as traditional ANNs. In addition, SNNs can model the central nervous system of biological organisms, such as an insect seeking food without prior knowledge of the environment. Due to their relative realism, they can be used to study biological neural circuits. Starting with a hypothesis about the topology of a biological neuronal circuit and its function, recordings of this circuit can be compared to the output of a corresponding SNN, evaluating the plausibility of the hypothesis. SNNs lack effective training mechanisms, which can complicate some applications, including computer vision. When using SNNs for image based data, the images need to be converted into binary spike trains. Types of encodings include: Temporal coding; generating one spike per neuron, in which spike latency is inversely proportional to the pixel intensity. Rate coding: converting pixel intensity into a spike train, where the number of spikes is proportional to the pixel intensity. Direct coding; using a trainable layer to generate a floating-point value for each time step. The layer converts each pixel at a certain time step into a floating-point value, and then a threshold is used on the generated floating-point values to pick either zero or one. Phase coding; encoding temporal information into spike patterns based on a global oscillator. Burst coding; transmitting spikes in bursts, increasing communication reliability. == Software == A diverse range of application software can simulate SNNs. This software can be classified according to its uses: === SNN simulation ===
|
{
"page_id": 10159567,
"source": null,
"title": "Spiking neural network"
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These simulate complex neural models. Large networks usually require lengthy processing. Candidates include: Brian – developed by Romain Brette and Dan Goodman at the École Normale Supérieure; GENESIS (the GEneral NEural SImulation System) – developed in James Bower's laboratory at Caltech; NEST – developed by the NEST Initiative; NEURON – mainly developed by Michael Hines, John W. Moore and Ted Carnevale in Yale University and Duke University; RAVSim (Runtime Tool) – mainly developed by Sanaullah in Bielefeld University of Applied Sciences and Arts; == Hardware == Sutton and Barton proposed that future neuromorphic architectures will comprise billions of nanosynapses, which require a clear understanding of the accompanying physical mechanisms. Experimental systems based on ferroelectric tunnel junctions have been used to show that STDP can be harnessed from heterogeneous polarization switching. Through combined scanning probe imaging, electrical transport and atomic-scale molecular dynamics, conductance variations can be modelled by nucleation-dominated domain reversal. Simulations showed that arrays of ferroelectric nanosynapses can autonomously learn to recognize patterns in a predictable way, opening the path towards unsupervised learning. == Benchmarks == Classification capabilities of spiking networks trained according to unsupervised learning methods have been tested on benchmark datasets such as Iris, Wisconsin Breast Cancer or Statlog Landsat dataset. Various approaches to information encoding and network design have been used such as a 2-layer feedforward network for data clustering and classification. Based on Hopfield (1995) the authors implemented models of local receptive fields combining the properties of radial basis functions and spiking neurons to convert input signals having a floating-point representation into a spiking representation. == See also == == References ==
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"page_id": 10159567,
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"title": "Spiking neural network"
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Magnesium transporters are proteins that transport magnesium across the cell membrane. All forms of life require magnesium, yet the molecular mechanisms of Mg2+ uptake from the environment and the distribution of this vital element within the organism are only slowly being elucidated. The ATPase function of MgtA is highly cardiolipin dependent and has been shown to detect free magnesium in the μM range In bacteria, Mg2+ is probably mainly supplied by the CorA protein and, where the CorA protein is absent, by the MgtE protein. In yeast the initial uptake is via the Alr1p and Alr2p proteins, but at this stage the only internal Mg2+ distributing protein identified is Mrs2p. Within the protozoa only one Mg2+ transporter (XntAp) has been identified. In metazoa, Mrs2p and MgtE homologues have been identified, along with two novel Mg2+ transport systems TRPM6/TRPM7 and PCLN-1. Finally, in plants, a family of Mrs2p homologues has been identified along with another novel protein, AtMHX. == Evolution == The evolution of Mg2+ transport appears to have been rather complicated. Proteins apparently based on MgtE are present in bacteria and metazoa, but are missing in fungi and plants, whilst proteins apparently related to CorA are present in all of these groups. The two active transport transporters present in bacteria, MgtA and MgtB, do not appear to have any homologies in higher organisms. There are also Mg2+ transport systems that are found only in the higher organisms. == Types == There are a large number of proteins yet to be identified that transport Mg2+. Even in the best studied eukaryote, yeast, Borrelly has reported a Mg2+/H+ exchanger without an associated protein, which is probably localised to the Golgi. At least one other major Mg2+ transporter in yeast is still unaccounted for, the one affecting Mg2+ transport in and out of
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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the yeast vacuole. In higher, multicellular organisms, it seems that many Mg2+ transporting proteins await discovery. The CorA-domain-containing Mg2+ transporters (CorA, Alr-like and Mrs2-like) have a similar but not identical array of affinities for divalent cations. In fact, this observation can be extended to all of the Mg2+ transporters identified so far. This similarity suggests that the basic properties of Mg2+ strongly influence the possible mechanisms of recognition and transport. However, this observation also suggests that using other metal ions as tracers for Mg2+ uptake will not necessarily produce results comparable to the transporter's ability to transport Mg2+. Ideally, Mg2+ should be measured directly. Since 28Mg2+ is practically unobtainable, much of the old data will need to be reinterpreted with new tools for measuring Mg2+ transport, if different transporters are to be compared directly. The pioneering work of Kolisek and Froschauer using mag-fura 2 has shown that free Mg2+ can be reliably measured in vivo in some systems. By returning to the analysis of CorA with this new tool, we have gained an important baseline for the analysis of new Mg2+ transport systems as they are discovered. However, it is important that the amount of transporter present in the membrane is accurately determined if comparisons of transport capability are to be made. This bacterial system might also be able to provide some utility for the analysis of eukaryotic Mg2+ transport proteins, but differences in biological systems of prokaryotes and eukaryotes will have to be considered in any experiment. == Function == Comparing the functions of the characterised Mg2+ transport proteins is currently almost impossible, even though the proteins have been investigated in different biological systems using different methodologies and technologies. Finding a system where all the proteins can be compared directly would be a major advance. If the proteins could
|
{
"page_id": 3474896,
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"title": "Magnesium transporter"
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be shown to be functional in bacteria (S. typhimurium), then a combination of the techniques of mag-fura 2, quantification of protein in the envelope membrane, and structure of the proteins (X-ray crystal or cryo-TEM) might allow the determination of the basic mechanisms involved in the recognition and transport of the Mg2+ ion. However, perhaps the best advance would be the development of methods allowing the measurement of the protein's function in the patch-clamp system using artificial membranes. == Bacteria == === Early research === In 1968, Lusk described the limitation of bacterial (Escherichia coli) growth on Mg2+-poor media, suggesting that bacteria required Mg2+ and were likely to actively take this ion from the environment. The following year, the same group and another group, Silver, independently described the uptake and efflux of Mg2+ in metabolically active E. coli cells using 28Mg2+. By the end of 1971, two papers had been published describing the interference of Co2+, Ni2+ and Mn2+ on the transport of Mg2+ in E. coli and in Aerobacter aerogenes and Bacillus megaterium. In the last major development before the cloning of the genes encoding the transporters, it was discovered that there was a second Mg2+ uptake system that showed similar affinity and transport kinetics to the first system, but had a different range of sensitivities to interfering cations. This system was also repressible by high extracellular concentrations of Mg2+ . === CorA === The CorA gene and its corresponding protein are the most exhaustively studied Mg2+ transport system in any organism. Most of the published literature on the CorA gene comes from the laboratory of M. E. Maguire. Recently the group of R. J. Schweyen made a significant impact on the understanding of Mg2+ transport by CorA. The gene was originally named after the cobalt-resistant phenotype in E. coli
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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that was caused by the gene's inactivation. The gene was genetically identified in E. coli by Park et al., but wasn't cloned until Hmiel et al. isolated the Salmonella enterica serovar Typhimurium (S. typhimurium) homologue. Later it would be shown by Smith and Maguire that the CorA gene was present in 17 gram-negative bacteria. With the large number of complete genome sequences now available for prokaryotes, CorA has been shown to be virtually ubiquitous among the Eubacteria, as well as being widely distributed among the Archaea. The CorA locus in E. coli contains a single open reading frame of 948 nucleotides, producing a protein of 316 amino acids. This protein is well conserved amongst the Eubacteria and Archaea. Between E. coli and S. typhimurium, the proteins are 98% identical, but in more distantly related species, the similarity falls to between 15 and 20%. In the more distantly related genes, the similarity is often restricted to the C-terminal part of the protein, and a short amino acid motif GMN within this region is very highly conserved. The CorA domain, also known as PF01544 in the pFAM conserved protein domain database (http://webarchive.loc.gov/all/20110506030957/http%3A//pfam.sanger.ac.uk/), is additionally present in a wide range of higher organisms, and these transporters will be reviewed below. The CorA gene is constitutively expressed in S. typhimurium under a wide range of external Mg2+ concentrations. However, recent evidence suggests that the activity of the protein may be regulated by the PhoPQ two-component regulatory system. This sensor responds to low external Mg2+ concentrations during the infection process of S. typhimurium in humans. In low external Mg2+ conditions, the PhoPQ system was reported to suppress the function of CorA and it has been previously shown that the transcription of the alternative Mg2+ transporters MgtA and MgtB is activated in these conditions. Chamnongpol and
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
Groisman suggest that this allows the bacteria to escape metal ion toxicity caused by the transport of other ions, particularly Fe(II), by CorA in the absence of Mg2+. Papp and Maguire offer a conflicting report on the source of the toxicity. The figure (not to scale) shows the originally published transmembrane (TM) domain topology of the S. typhimurium CorA protein, which was said to have three membrane-spanning regions in the C-terminal part of the protein (shown in blue), as determined by Smith et al.. Evidence for CorA acting as a homotetramer was published by Warren et al. in 2004. In December 2005 the crystal structure of the CorA channel was posted to the RSCB protein structure database. The results showed that the protein has two TM domains and exists as a homopentamer, in direct conflict with the earlier reports. Follow this link to see the structure in 3D. The soluble intracellular parts of the protein are highly charged, containing 31 positively charged and 53 negatively charged residues. Conversely, the TM domains contain only one charged amino acid, which has been shown to be unimportant in the activity of the transporter. From mutagenesis experiments, it appears that the chemistry of the Mg2+ transport relies on the hydroxyl groups lining the inside of the transport pore; there is also an absolute requirement for the GMN motif (shown in red). Before the activity of CorA could be studied in vivo, any other Mg2+ transport systems in the bacterial host had to be identified and inactivated or deleted (see below). A strain of S. typhimurium containing a functional CorA gene but lacking MgtA and MgtB was constructed(also see below), and the uptake kinetics of the transporter were analysed. This strain showed nearly normal growth rates on standard media (50 μM Mg2+), but the removal
|
{
"page_id": 3474896,
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"title": "Magnesium transporter"
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|
of all three genes created a bacterial strain requiring 100 mM external Mg2+ for normal growth. Mg2+ is transported into cells containing only the CorA transport system with similar kinetics and cation sensitivities as the Mg2+ uptake described in the earlier papers, and has additionally been quantified(see table). The uptake of Mg2+ was seen to plateau as in earlier studies, and although no actual mechanism for the decrease in transport has been determined, so it has been assumed that the protein is inactivated. Co2+ and Ni2+ are toxic to S. typhimurium cells containing a functional CorA protein and this toxicity stems from the blocking of Mg2+ uptake (competitive inhibition) and the accumulation of these ions inside the cell. Co2+ and Ni2+ have been shown to be transported by CorA by using radioactive tracer analysis, although with lower affinities (km) and velocities (Vmax) than for Mg2+ (see table). The km values for Co2+ and Ni2+ are significantly above those expected to be encountered by the cells in their normal environment, so it is unlikely that the CorA transport system mediates the uptake of these ions under natural conditions. To date, the evidence for Mn2+ transport by CorA is limited to E. coli. The table lists the transport kinetics of the CorA Mg2+ transport system. This table has been compiled from the publications of Snavely et al. (1989b), Gibson et al. (1991) and Smith et al. (1998a) and summarises the kinetic data for the CorA transport protein expressed from the wild type promoter in bacteria lacking MgtA and MgtB. km and Vmax were determined at 20 °C as the uptake of Mg2+ at 37 °C was too rapid to measure accurately. Recently the Mg2+-dependent fluorescence of mag-fura 2 was used to measure the free Mg2+ content of S. typhimurium cells in response
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
to external Mg2+, which showed that CorA is the major uptake system for Mg2+ in bacteria. The authors also showed for the first time that the changes in the electric potential (ΔΨ) across the plasma membrane of the cell affected both the rate of Mg2+ uptake and the free Mg2+ content of the cell; depolarisation suppressed transport, while hyperpolarisation increased transport. The kinetics of transport were defined only by the rate of change of free Mg2+ inside the cells (250 μM s−1). Because no quantification of the amount of CorA protein in the membrane was made, this value cannot be compared with other experiments on Mg2+ transporters. The efflux of Mg2+ from bacterial cells was first observed by Lusk and Kennedy (1969) and is mediated by the CorA Mg2+ transport system in the presence of high extracellular concentrations of Mg2+. The efflux can also be triggered by Co2+, Mn2+ and Ni2+, although not to the same degree as Mg2+. No Co2+ efflux through the CorA transport system was observed. The process of Mg2+ efflux additionally requires one of the CorB, CorC or CorD genes. The mutation of any single one of these genes leads to a Co2+ resistance a little less than half of that provided by a CorA mutant. This effect may be due to the inhibition of Mg2+ loss that would otherwise occur in the presence of high levels of Co2+. It is currently unknown whether Mg2+ is more toxic when the CorBCD genes are deleted. It has been speculated that the Mg2+ ion will initially interact with any transport protein through its hydration shell. Cobalt (III) hexaammine, Co(III)Hex, is a covalently bound (non-labile) analog for the first shell of hydration for several divalent cations, including Mg2+. The radius of the Co(III)Hex molecule is 244 pm, very similar
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
to the 250 pm radius of the first hydration shell of Mg2+. This analog is a potent inhibitor of the CorA transport system, more so than Mg2+, Co2+ or Ni2+. The additional strength of the Co(III)Hex inhibition might come from the blocking of the transport pore due to the inability of the protein to ‘dehydrate’ the substrate. It was also shown that Co(III)Hex was not transported into the cells, suggesting that at least partial dehydration would be required for the transport of the normal substrate (Mg2+). Nickel (II) hexaammine, with a radius of 255 pm, did not inhibit the CorA transport system, suggesting a maximum size limit exists for the binding of the CorA substrate ion. These results suggest that the important property involved in the recognition of Mg2+ by CorA is the size of the ion with its first shell of hydration. Hence, the volume change generally quoted for the bare to hydrated Mg2+ ion of greater than 500-fold, including the second sphere of hydration, may not be biologically relevant, and may be a reason for the first sphere volume change of 56-fold to be more commonly used. === MgtA and MgtB === The presence of these two genes was first suspected when Nelson and Kennedy (1972) showed that there were Mg2+-repressible and non-repressible Mg2+ uptake systems in E. coli. The non-repressible uptake of Mg2+ is mediated by the CorA protein. In S. typhimurium the repressible Mg2+ uptake was eventually shown to be via the MgtA and MgtB proteins. Both MgtA and MgtB are regulated by the PhoPQ system and are actively transcribed during the process of infection of human patients by S. typhimurium. Although neither gene is required for pathogenicity, the MgtB protein does enhance the long-term survival of the pathogen in the cell. The genes are also
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
upregulated in vitro when the Mg2+ concentration falls below 50 μM (Snavely et al., 1991a). Although the proteins have km values similar to CorA and transport rates approximately 10 times less, the genes may be part of a Mg2+ scavenging system. Chamnongpol and Groisman (2002) presents evidence that the role of these proteins may be to compensate for the inactivation of the CorA protein by the PhoPQ regulon. The authors suggest that the CorA protein is inactivated to allow the avoidance of metal toxicity via the protein in the low Mg2+ environments S. typhimurium is subjected to by cells after infection. The proteins are both P-type ATPases and neither gene shows any similarity to CorA. The MgtA and MgtB proteins are 75% similar (50% identical), although it seems that MgtB may have been acquired by horizontal gene transfer as part of Salmonella Pathogenicity Island 3. The TM topology of the MgtB protein has been experimentally determined, showing that the protein has ten TM-spanning helices with the termini of the protein in the cytoplasm (see figure ). MgtA is present in widely divergent bacteria, but is not nearly as common as CorA, while MgtB appears to have a quite restricted distribution. No hypotheses for the unusual distribution have been suggested. The figure, adapted from Smith et al. (1993b), shows the experimentally determined membrane topology of the MgtB protein in S. typhimurium. The TM domains are shown in light blue and the orientation in the membrane and the positions of the N- and C-termini are indicated. The figure is not drawn to scale. While the MgtA and MgtB proteins are very similar, they do show some minor differences in activity. MgtB is very sensitive to temperature, losing all activity (with regard to Mg2+ transport) at a temperature of 20 °C. Additionally, MgtB
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
and MgtA are inhibited by different ranges of cations (Table A10.1). The table lists cation transport characteristics of the MgtA and MgtB proteins in S. typhimurium as well as the kinetic data for the MgtA and MgtB transport proteins at 37 °C. The Vmax numbers listed in parentheses are those for uptake at 20 °C. The inhibition of Mg2+ transport by Mn2+ via MgtA showed unusual kinetics (see Figure 1 of Snavely et al., 1989b) The MgtA and MgtB proteins are ATPases, using one molecule of ATP per transport cycle, whereas the Mg2+ uptake via CorA is simply electrochemically favourable. Chamnongpol and Groisman (2002) have suggested that the MgtA and MgtB proteins form part of a metal toxicity avoidance system. Alternatively, as most P-type ATPases function as efflux mediating transporters, it has been suggested that the MgtA and MgtB proteins act as efflux proteins for a currently unidentified cation, and Mg2+ transport is either non-specific or exchanged to maintain the electro-neutrality of the transport process. Further experiments will be required to define the physiological function of these proteins. === MgtE === Two papers describe MgtE, a fourth Mg2+ uptake protein in bacteria unrelated to MgtA/B or CorA. This gene has been sequenced and the protein, 312 amino acids in size, is predicted to contain either four or five TM spanning domains that are closely arranged in the C-terminal part of the protein (see figure). This region of the protein has been identified in the Pfam database as a conserved protein domain (PF01769) and species containing proteins that have this protein domain are roughly equally distributed throughout the Eubacteria and Archaea, although it is quite rare in comparison with the distribution of CorA. However, the diversity of the proteins containing the domain is significantly larger than that of the CorA domain.
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
The Pfam database lists seven distinct groups of MgtE domain containing proteins, of which six contain an archaic or eubacterial member. The expression of MgtE is frequently controlled by a conserved RNA structure, YkoK leader or M-box. The figure (right), adapted from Smith et al. (1995) and the PFAM database entry, shows the computer-predicted membrane topology of the MgtE protein in Bacillus firmus OF4. The TM domains are shown in light blue. The CBS domains, named for the protein they were identified in, cystathionine-beta synthase, shown in orange, are identified in the Pfam database as regulatory domains, but the mechanism of action has not yet been described. They are found in several voltage-gated chloride channels. The orientation in the membrane and the positions of the N- and C-termini are indicated. This figure is not drawn to scale. This transporter has recently had its structure solved by x-ray crystallography. The MgtE gene was first identified by Smith et al. (1995) during a screen for CorA-like proteins in bacteria and complements the Mg2+-uptake-deficient S. typhimurium strain MM281 (corA mgtA mgtB), restoring wild type growth on standard media. The kinetics of Mg2+ transport for the protein were not determined, as 28Mg2+ was unavailable. As a substitute, the uptake of 57Co2+ was measured and was shown to have a km of 82 μM and a Vmax of 354 pmol min−1 108 cells−1. Mg2+ was a competitive inhibitor with a Ki of 50 μM—the Ki of Mg2+ inhibition of 60Co2+ uptake via CorA is 10 μM. A comparison of the available kinetic data for MgtA and CorA is shown in the table. Clearly, MgtE does not transport Co2+ to the same degree as CorA, and the inhibition of transport by Mg2+ is also less efficient, which suggests that the affinity of MgtE for Mg2+ is
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
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|
lower than that of CorA. The strongest inhibitor of Co2+ uptake was Zn2+, with a Ki of 20 μM. The transport of Zn2+ by this protein may be as important as that of Mg2+. The table shows a comparison of the transport kinetics of MgtE and CorA, and key kinetic parameter values for them are listed. As shown, the data has been generated at differing incubation temperatures. km and Ki are not significantly altered by the differing incubation temperature. Conversely, Vmax shows a strong positive correlation with temperature, hence the value of Co2+ Vmax for MgtE is not directly comparable with the values for CorA. == Yeast == === Early research === The earliest research showing that yeast takes up Mg2+ appears to be done by Schmidt et al. (1949). However, these authors only showed altered yeast Mg2+ content in a table within the paper, and the report's conclusions dealt entirely with the metabolism of phosphate. A series of experiments by Rothstein shifted the focus more towards the uptake of the metal cations, showing that yeast take up cations with the following affinity series; Mg2+, Co2+, Zn2+ > Mn2+ > Ni2+ > Ca2+ > Sr2+. Additionally, it was suggested that the transport of the different cations is mediated by the same transport system — a situation very much like that in bacteria. In 1998, MacDiarmid and Gardner finally identified the proteins responsible for the observed cation transport phenotype in Saccharomyces cerevisiae. The genes involved in this system and a second mitochondrial Mg2+ transport system, functionally identified significantly after the gene was cloned, are described in the sections below. === ALR1 and ALR2 === Two genes, ALR1 and ALR2, were isolated in a screen for Al3+ tolerance (resistance) in yeast. Over-expression constructs containing yeast genomic DNA were introduced into wild type
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
yeast and the transformants were screened for growth on toxic levels of Al3+. ALR1 and ALR2 containing plasmids allowed the growth of yeast in these conditions. The Alr1p and Alr2p proteins consist of 859 and 858 amino acids respectively and are 70% identical. In a region in the C-terminal, half of these proteins are weakly similar to the full CorA protein. The computer-predicted TM topology of Alr1p is shown in the figure. The presence of a third TM domain was suggested by MacDiarmid and Gardner (1998), on the strength on sequence homology, and more recently by Lee and Gardner (2006), on the strength of mutagenesis studies, making the TM topology of these proteins more like that of CorA (see figure). Also, Alr1p contains the conserved GMN motif at the outside end of TM 2 (TM 2') and the mutation of the methionine (M) in this motif to a leucine (L) led to the loss of transport capability. The figure shows the two possible TM topologies of Alr1p. Part A of the figure shows the computer-predicted membrane topology of the Alr1p protein in yeast and part B shows the topology of Alr1p based on the experimental results of Lee and Gardner (2006). The GMN motif location is indicated in red and the TM domains in light blue. The orientation in the membrane and the positions of the N- and C-termini are indicated, the various sizes of the soluble domains are given in amino acids (AA), and TM domains are numbered by their similarity to CorA. Where any TM domain is missing, the remaining domains are numbered with primes. The figure is not drawn to scale. A third ALR-like gene is present in S. cerevisiae and there are two homologous genes in both Schizosaccharomyces pombe and Neurospora crassa. These proteins contain a
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
GMN motif like that of CorA, with the exception of the second N. crassa gene. No ALR-like genes have been identified in species outside of the fungi. Membrane fractionation and green fluorescent protein (GFP) fusion studies established that Alr1p is localised to the plasma membrane. The localisation of the Alr1p was observed to be internalised and degraded in the vacuole in response to extracellular cations. Mg2+, at very low extracellular concentrations (100 μM; < 10% of the standard media Mg2+ content), and Co2+ and Mn2+ at relatively high concentrations (> 20× standard media), induced the change in Alr1p protein localisation, and the effect was dependent on functional ubiquitination, endocytosis and vacuolar degradation. This mechanism was proposed to allow the regulation of Mg2+ uptake by yeast. However, a recent report indicates that several of the observations made by Stadler et al. were not reproducible. For example, regulation of ALR1 mRNA accumulation by Mg2+ supply was not observed, and the stability of the Alr1 protein was not reduced by exposure to excess Mg2+. The original observation of Mg-dependent accumulation of the Alr1 protein under steady-state low-Mg conditions was replicated, but this effect was shown to be an artifact caused by the addition of a small peptide (epitope) to the protein to allow its detection. Despite these problems, Alr1 activity was demonstrated to respond to Mg supply, suggesting that the activity of the protein is regulated directly, as was observed for some bacterial CorA proteins. A functional Alr1p (wild type) or Alr2p (overexpressed) is required for S. cerevisiae growth in standard conditions (4 mM Mg2+), and Alr1p can support normal growth at Mg2+ concentrations as low as 30 μM. 57Co2+ is taken up into yeast via the Alr1p protein with a km of 77 – 105 μM (; C. MacDiarmid and R. C.
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
Gardner, unpublished data), but the Ki for Mg2+ inhibition of this transport is currently unknown. The transport of other cations by the Alr1p protein was assayed by the inhibition of yeast growth. The overexpression of Alr1p led to increased sensitivity to Ca2+, Co2+, Cu2+, La3+, Mn2+, Ni2+ and Zn2+, an array of cations similar to those shown to be transported into yeast by a CorA-like transport system. The increased toxicity of the cations in the presence of the transporter is assumed to be due to the increased accumulation of the cation inside the cell. The evidence that Alr1p is primarily a Mg2+ transporter is that the loss of Alr1p leads to a decreased total cell content of Mg2+, but not of other cations. Additionally, two electrophysiological studies where Alr1p was produced in yeast or Xenopus oocytes showed a Mg2+-dependent current in the presence of the protein; Salih et al., in prep. The kinetics of Mg2+ uptake by Alr1p have been investigated by electrophysiology techniques on whole yeast cells. The results suggested that Alr1p is very likely to act as an ion-selective channel. In the same paper, the authors reported that Mg2+ transport by Alr1p varied from 200 pA to 1500 pA, with a mean current of 264 pA. No quantification of the amount of protein producing the current was presented, so the results lack comparability with the bacterial Mg2+ transport proteins. The alternative techniques of 28Mg2+ radiotracer analysis and mag-fura 2 to measure Mg2+ uptake have not yet been used with Alr1p. 28Mg2+ is currently not available and the mag-fura 2 system is unlikely to provide simple uptake data in yeast. The yeast cell maintains a heterogeneous distribution of Mg2+ suggesting that multiple systems inside the yeast are transporting Mg2+ into storage compartments. This internal transport will very likely mask
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
the uptake process. The expression of ALR1 in S. typhimurium without Mg2+ uptake genes may be an alternative, but, as stated earlier, the effects of a heterologous expression system would need to be taken into account. === MNR2 === The MNR2 gene encodes a protein closely related to the Alr proteins, but includes conserved features that define a distinct subgroup of CorA proteins in fungal genomes, suggesting a distinct role in Mg2+ homeostasis. Like an alr1 mutant, growth of an mnr2 mutant was sensitive to Mg2+-deficient conditions, but the mnr2 mutant was observed to accumulate more Mg2+ than a wild-type strain under these conditions. These phenotypes suggested that Mnr2 may regulate Mg2+ storage within an intracellular compartment. Consistent with this interpretation, the Mnr2 protein was localized to the membrane of the vacuole, an internal compartment implicated in the storage of excess mineral nutrients by yeast. A direct role of Mnr2 in Mg2+ transport was suggested by the observation that increased Mnr2 expression, which redirected some Mnr2 protein to the cell surface, also suppressed the Mg2+-requirement of an alr1 alr2 double mutant strain. The mnr2 mutation also altered accumulation of other divalent cations, suggesting this mutation may increase Alr gene expression or protein activity. Recent work supported this model, by showing that Alr1 activity was increased in an mnr2 mutant strain, and that the mutation was associated with induction of Alr1 activity at a higher external Mg concentration than was observed for an Mnr2 wild-type strain. These effects were observed without any change in Alr1 protein accumulation, again indicating that Alr1 activity may be regulated directly by the Mg concentration within the cell. === MRS2 and Lpe10 === Like the ALR genes, the MRS2 gene was cloned and sequenced before it was identified as a Mg2+ transporter. The MRS2 gene was
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
identified in the nuclear genome of yeast in a screen for suppressors of a mitochondrial gene RNA splicing mutation, and was cloned and sequenced by Wiesenberger et al. (1992). Mrs2p was not identified as a putative Mg2+ transporter until Bui et al. (1999). Gregan et al. (2001a) identified LPE10 by homology to MRS2 and showed that both LPE10 and MRS2 mutants altered the Mg2+ content of yeast mitochondria and affected RNA splicing activity in the organelle. Mg2+ transport has been shown to be directly mediated by Mrs2p, but not for Lpe10p. The Mrs2p and Lpe10p proteins are 470 and 413 amino acid residues in size, respectively, and a 250–300 amino acid region in the middle of the proteins shows a weak similarity to the full CorA protein. The TM topologies of the Mrs2p and Lpe10p proteins have been assessed using a protease protection assay and are shown in the figure. TM 1 and 2 correspond to TM 2 and 3 in the CorA protein. The conserved GMN motif is at the outside end of the first TM domain, and when the glycine (G) in this motif was mutated to a cysteine (C) in Mrs2p, Mg2+ transport was strongly reduced. The figure shows the experimentally determined topology of Mrs2p and Lpe10p as adapted from Bui et al. (1999) and Gregan et al. (2001a). The GMN motif location is indicated in red and the TM domains in light blue. The orientation in the membrane and the positions of the N- and C-termini are indicated. The various sizes of the soluble domains are given in amino acids (AA), TM domains are numbered, and the figure is not drawn to scale. Mrs2p has been localised to the mitochondrial inner membrane by subcellular fractionation and immunodetection and Lpe10p to the mitochondria. Mitochondria lacking Mrs2p do
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
not show a fast Mg2+ uptake, only a slow ‘leak’, and overaccumulation of Mrs2p leads to an increase in the initial rate of uptake. Additionally, CorA, when fused to the mitochondrial leader sequence of Mrs2p, can partially complement the mitochondrial defect conferred by the loss of either Mrs2p or Lpe10p. Hence, Mrs2p and/or Lpe10p may be the major Mg2+ uptake system for mitochondria. A possibility is that the proteins form heterodimers, as neither protein (when overexpressed) can fully complement the loss of the other. The characteristics of Mg2+ uptake in isolated mitochondria by Mrs2p were quantified using mag-fura 2. The uptake of Mg2+ by Mrs2p shared a number of attributes with CorA. First, Mg2+ uptake was directly dependent on the electric potential (ΔΨ) across the boundary membrane. Second, the uptake is saturated far below that which the ΔΨ theoretically permits, so the transport of Mg2+ by Mrs2p is likely to be regulated in a similar manner to CorA, possibly by the inactivation of the protein. Third, Mg2+ efflux was observed via Mrs2p upon the artificial depolarisation of the mitochondrial membrane by valinomycin. Finally, the Mg2+ fluxes through Mrs2p are inhibited by cobalt (III) hexaammine. The kinetics of Mg2+ uptake by Mrs2p were determined in the Froschauer et al. (2004) paper on CorA in bacteria. The initial change in free Mg2+ concentration was 150 μM s-1 for wild type and 750 μM s-1 for mitochondria from yeast overexpressing MRS2. No attempt was made to scale the observed transport to the amount of transporter present. == Protozoan (Paramecium) == The transport of Mg2+ into Paramecium has been characterised largely by R. R. Preston and his coworkers. Electrophysiological techniques on whole Paramecium were used to identify and characterise Mg2+ currents in a series of papers before the gene was cloned by Haynes et
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
al. (2002). The open reading frame for the XNTA gene is 1707 bp in size, contains two introns and produces a predicted protein of 550 amino acids. The protein has been predicted to contain 11 TM domains and also contains the α1 and α2 motifs (see figure) of the SLC8 (Na+/Ca2+ exchanger) and SLC24 (K+ dependent Na+/Ca2+ exchanger) human solute transport proteins. The XntAp is equally similar to the SLC8 and SLC24 protein families by amino acid sequence, but the predicted TM topology is more like that of SLC24, but the similarity is at best weak and the relationship is very distant. The AtMHX protein from plants also shares a distant relationship with the SLC8 proteins. The figure shows the predicted TM topology of XntAp. Adapted from Haynes et al. (2002), this figure shows the computer predicted membrane topology of XntAp in Paramecium. The orientation in the membrane was determined using HMMTOP. The TM domains are shown in light blue, the α1 and α2 domains are shown in green. The orientation in the membrane and the positions of the N- and C-termini are indicated and the figure is not drawn to scale. The Mg2+-dependent currents carried by XntAp are kinetically like that of a channel protein and have an ion selectivity order of Mg2+ > Co2+, Mn2+ > Ca2+ — a series again very similar to that of CorA. Unlike the other transport proteins reported so far, XntAp is dependent on intracellular Ca2+. The transport is also dependent on ΔΨ, but again Mg2+ is not transported to equilibrium, being limited to approximately 0.4 mM free Mg2+ in the cytoplasm. The existence of an intracellular compartment with a much higher free concentration of Mg2+ (8 mM) was supported by the results. == Animals == The investigation of Mg2+ in animals, including
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
humans, has lagged behind that in bacteria and yeast. This is largely because of the complexity of the systems involved, but also because of the impression within the field that Mg2+ was maintained at high levels in all cells and was unchanged by external influences. Only in the last 25 years has a series of reports begun to challenge this view, with new methodologies finding that free Mg2+ content is maintained at levels where changes might influence cellular metabolism. === MRS2 === A bioinformatic search of the sequence databases identified one homologue of the MRS2 gene of yeast in a range of metazoans. The protein has a very similar sequence and predicted TM topology to the yeast protein, and the GMN motif is intact at the end of the first TM domain. The human protein, hsaMrs2p, has been localised to the mitochondrial membrane in mouse cells using a GFP fusion protein. Very little is known about the Mg2+ transport characteristics of the protein in mammals, but Zsurka et al. (2001) has shown that the human Mrs2p complements the mrs2 mutants in the yeast mitochondrial Mg2+ uptake system. === SLC41 (MgtE) === The identification of this gene family in the metazoa began with a signal sequence trap method for isolating secreted and membrane proteins. Much of the identification has come from bioinformatic analyses. Three genes were eventually identified in humans, another three in mouse and three in Caenorhabditis elegans, with a single gene in Anopheles gambiae. The pFAM database lists the MgtE domain as pFAM01769 and additionally identifies a MgtE domain-containing protein in Drosophila melanogaster. The proteins containing the MgtE domain can be divided into seven classes, as defined by pFAM using the type and organisation of the identifiable domains in each protein. Metazoan proteins are present in three of the
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
seven groups. All of the metazoa proteins contain two MgtE domains, but some of these have been predicted only by context recognition (Coin, Bateman and Durbin, unpublished. See the pFAM website for further details). The human SLC41A1 protein contains two MgtE domains with 52% and 46% respective similarity to the PF01769 consensus sequence and is predicted to contain ten TM domains, five in each MgtE domain (see figure), which suggests that the MgtE protein of bacteria may work as a dimer. Adapted from Wabakken et al. (2003) and the pFAM database, the figure shows the computer predicted membrane topology of MgtE in H. sapiens. The TM domains are shown in light blue, the orientation in the membrane and the positions of the N- and C-termini are indicated, and the figure is not drawn to scale. Wabakken et al. (2003) found that the transcript of the SLC41A1 gene was expressed in all human tissues tested, but at varying levels, with the heart and testis having the highest expression of the gene. No explanation of the expression pattern has been suggested with regard to Mg2+-related physiology. It has not been shown whether the SLC41 proteins transport Mg2+ or complement a Mg2+ transport mutation in any experimental system. However, it has been suggested that as MgtE proteins have no other known function, they are likely to be Mg2+ transporters in the metazoa as they are in the bacteria. This will need to be verified using one of the now standard experiment systems for examining Mg2+ transport. === TRPM6/ TRPM7 === The investigation of the TRPM genes and proteins in human cells is an area of intense recent study and, at times, debate. Montell et al. (2002) have reviewed the research into the TRP genes, and a second review by Montell (2003) has reviewed
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
the research into the TRPM genes. The TRPM family of ion channels has members throughout the metazoa. The TRPM6 and TRPM7 proteins are highly unusual, containing both an ion channel domain and a kinase domain (Figure 1.7), the role of which brings about the most heated debate. The activity of these two proteins has been very difficult to quantify. TRPM7 by itself appears to be a Ca2+ channel but in the presence of TRPM6 the affinity series of transported cations places Mg2+ above Ca2+. The differences in reported conductance were caused by the expression patterns of these genes. TRPM7 is expressed in all cell types tested so far, while TRPM6 shows a more restricted pattern of expression. An unfortunate choice of experimental system by Voets et al., (2004) led to the conclusion that TRPM6 is a functional Mg2+ transporter. However, later work by Chubanov et al. (2004) clearly showed that TRPM7 is required for TRPM6 activity and that the results of Voets et al. are explained by the expression of TRPM7 in the experimental cell line used by Voets et al. in their experiments. Whether TRPM6 is functional by itself is yet to be determined. The predicted TM topology of the TPRM6 and TRPM7 proteins has been adapted from Nadler et al. (2001), Runnels et al. (2001) and Montell et al. (2002), this figure shows the computer predicted membrane topology of the TRPM6 and TRPM7 proteins in Homo sapiens. At this time, the topology shown should be considered a tentative hypothesis. The TM domains are shown in light blue, the pore loop in purple, the TRP motif in red and the kinase domain in green. The orientation in the membrane and the positions of the N- and C-termini are indicated and the figure is not drawn to scale. The conclusions
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
of the Voets et al. (2004) paper are probably incorrect in attributing the Mg2+ dependent currents to TRPM7 alone, and their kinetic data are likely to reflect the combined TRPM7/ TRPM6 channel. The report presents a robust collection of data consistent with a channel-like activity passing Mg2+, based on both electrophysiological techniques and also mag-fura 2 to determine changes in cytoplasmic free Mg2+. === Paracellular transport === Claudins allow for Mg2+ transport via the paracellular pathway; that is, it mediates the transport of the ion through the tight junctions between cells that form an epithelial cell layer. In particular, Claudin-16 allows the selective reuptake of Mg2+ in the human kidney. Some patients with mutations in the CLDN19 gene also have altered magnesium transport. The gene Claudin-16 was cloned by Simon et al. (1999), but only after a series of reports described the Mg2+ flux itself with no gene or protein. The expression pattern of the gene was determined by RT-PCR, and was shown to be very tightly confined to a continuous region of the kidney tubule running from the medullary thick descending limb to the distal convoluted tubule. This localisation was consistent with the earlier reports for the location of Mg2+ re-uptake by the kidney. Following the cloning, mutations in the gene were identified in patients with familial hypomagnesaemia with hypercalciuria and nephrocalcinosis, strengthening the links between the gene and the uptake of Mg2+. == Plants == The current knowledge of the molecular mechanisms for Mg2+ transport in plants is very limited, with only three publications reporting a molecular basis for Mg2+ transport in plants. However, the importance of Mg2+ to plants has been well described, and physiological and ecophysiological studies about the effects of Mg2+ are numerous. This section will summarise the knowledge of a gene family identified in
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
plants that is distantly related to CorA. Another gene, a Mg2+/H+ exchanger (AtMHX), unrelated to this gene family and to CorA has also been identified, is localised to the vacuolar membrane, and will be described last. === The AtMRS2 gene family === Schock et al. (2000) identified and named the family AtMRS2 based on the similarity of the genes to the MRS2 gene of yeast. The authors also showed that the AtMRS2-1 gene could complement a Δmrs2 yeast mutant phenotype. Independently, Li et al. (2001) published a report identifying the family and showing that two additional members could complement Mg2+ transport deficient mutants, one in S. typhimurium and the other in S. cerevisiae. The three genes that have been shown to transport Mg2+ are AtMRS2-1, AtMRS2-10 and AtMRS2-11, and these genes produce proteins 442, 443 and 459 amino acids in size, respectively. Each of the proteins shows significant similarity to Mrs2p of yeast and a weak similarity to CorA of bacteria, contains the conserved GMN amino acid motif at the outside end of the first TM domain, and is predicted to have two TM domains. The AtMRS2-1 gene, when expressed in yeast from the MRS2 promoter and being fused C-terminally to the first 95 amino acids of the Mrs2p protein, was directed to the mitochondria, where it complemented a Δmrs2 mutant both phenotypically (mitochondrial RNA splicing was restored) and with respect to the Mg2+ content of the organelle. No data on the kinetics of the transport was presented. The AtMRS2-11 gene was analysed in yeast (in the alr1 alr2 strain), where it was shown that expression of the gene significantly increased the rate of Mg2+ uptake into starved cells over the control, as measured using flame atomic absorption spectroscopy of total cellular Mg2+ content. However, Alr1p was shown to be
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
significantly more effective at transporting Mg2+ at low extracellular concentrations, suggesting that the affinity of AtMRS2-11 for Mg2+ is lower than that of Alr1p. An electrophysiological (voltage clamp) analysis of the AtMRS2-11 protein in Xenopus oocytes also showed a Mg2+-dependent current at membrane potentials (ΔΨ) of –100 – –150 mV inside. These values are physiologically significant, as several membranes in plants maintain ΔΨ in this range. However, the author had difficulty reproducing these results due to an apparent "death" of oocytes containing the AtMRS2-11 protein, and therefore these results should be viewed with caution. The AtMRS2-10 transporter has been analysed using radioactive tracer uptake analysis. 63Ni2+ was used as the substitute ion and Mg2+ was shown to inhibit the uptake of 63Ni2+ with a Ki of 20 μM. Uptake was also inhibited by Co(III)Hex and by other divalent cations. Only Co2+ and Cu2+ inhibited transport with Ki values less than 1 mM. The AtMRS2-10 protein was fused to GFP, and was shown to be localised to the plasma membrane. A similar experiment was attempted in the Schock et al. (2000) paper, but the observed localisation was not significantly different from that seen with unfused GFP. The most likely reason for the lack of a definitive localisation of AtMRS2-1 in the Schock et al. paper is that the authors removed the TM domains from the protein, thereby precluding its insertion into a membrane. The exact physiological significance of the AtMRS2-1 and AtMRS2-10 proteins in plants has yet to be clarified. The AtMRS2-11 gene has been overexpressed (from the CaMV 35S promoter) in A. thaliana. The transgenic line has been shown to accumulate high levels of the AtMRS2-11 transcript. A strong Mg2+ deficiency phenotype (necrotic spots on the leaves, see Chapter 1.5 below) was recorded during the screening process (in both the
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
T1 and T2 generations) for a homozygote line, but this phenotype was lost in the T3 generation and could not be reproduced when the earlier generations were screened a second time. The author suggested that environmental effects were the most likely cause of the inconsistent phenotype. === AtMHX === The first magnesium transporter isolated in any multicellular organism, AtMHX shows no similarity to any previously isolated Mg2+ transport protein. The gene was initially identified in the A. thaliana genomic DNA sequence database, by its similarity to the SLC8 family of Na+/Ca2+ exchanger genes in humans. The cDNA sequence of 1990 bp is predicted to produce a 539-amino acid protein. AtMHX is quite closely related to the SLC8 family at the amino acid level and shares a topology with eleven predicted TM domains (Figure A10.5). There is one major difference in the sequence, in that the long non-membranal loop (see Figure A10.5) is 148 amino acids in the AtMHX protein but 500 amino acids in the SLC8 proteins. However, this loop is not well conserved and is not required for transport function in the SLC8 family. The AtMHX gene is expressed throughout the plant but most strongly in the vascular tissue. The authors suggest that the physiological role of the protein is to store Mg2+ in these tissues for later release when needed. The protein localisation to the vacuolar membrane supports this suggestion (see also Chapter 1.5). The protein transports Mg2+ into the vacuolar space and H+ out, as demonstrated by electrophysiological techniques. The transport is driven by the ΔpH maintained between the vacuolar space (pH 4.5 – 5.9) and the cytoplasm (pH 7.3 – 7.6) by an H+-ATPase. How the transport of Mg2+ by the protein is regulated was not determined. Currents were observed to pass through the protein in
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
both directions, but the Mg2+ out current required a ‘cytoplasmic’ pH of 5.5, a condition not found in plant cells under normal circumstances. In addition to the transport of Mg2+, Shaul et al. (1999) also showed that the protein could transport Zn2+ and Fe2+, but did not report on the capacity of the protein to transport other divalent cations (e.g. Co2+ and Ni2+) or its susceptibility to inhibition by cobalt (III) hexaammine. The detailed kinetics of Mg2+ transport have not been determined for AtMHX. However, physiological effects have been demonstrated. When A. thaliana plants were transformed with overexpression constructs of the AtMHX gene driven by the CaMV 35S promoter, the plants over-accumulated the protein and showed a phenotype of necrotic lesions in the leaves, which the authors suggest is caused by a disruption in the normal function of the vacuole, given their observation that the total Mg2+ (or Zn2+) content of the plants was not altered in the transgenic plants. The image has been adapted from Shaul et al. (1999) and Quednau et al. (2004), and combined with an analysis using HMMTOP, this figure shows the computer predicted membrane topology of the AtMHX protein in Arabidopsis thaliana. At this time the topology shown should be considered a tentative hypothesis. The TM domains are shown in light blue, the orientation in the membrane and the positions of the N- and C-termini are indicated, and the figure is not drawn to scale. The α1 and α2 domains, shown in green, are both quite hydrophobic and may both be inserted into the membrane. == References ==
|
{
"page_id": 3474896,
"source": null,
"title": "Magnesium transporter"
}
|
In chemistry, an unpaired electron is an electron that occupies an orbital of an atom singly, rather than as part of an electron pair. Each atomic orbital of an atom (specified by the three quantum numbers n, l and m) has a capacity to contain two electrons (electron pair) with opposite spins. As the formation of electron pairs is often energetically favourable, either in the form of a chemical bond or as a lone pair, unpaired electrons are relatively uncommon in chemistry, because an entity that carries an unpaired electron is usually rather reactive. In organic chemistry they typically only occur briefly during a reaction on an entity called a radical; however, they play an important role in explaining reaction pathways. Radicals are uncommon in s- and p-block chemistry, since the unpaired electron occupies a valence p orbital or an sp, sp2 or sp3 hybrid orbital. These orbitals are strongly directional and therefore overlap to form strong covalent bonds, favouring dimerisation of radicals. Radicals can be stable if dimerisation would result in a weak bond or the unpaired electrons are stabilised by delocalisation. In contrast, radicals in d- and f-block chemistry are very common. The less directional, more diffuse d and f orbitals, in which unpaired electrons reside, overlap less effectively, form weaker bonds and thus dimerisation is generally disfavoured. These d and f orbitals also have comparatively smaller radial extension, disfavouring overlap to form dimers. Relatively more stable entities with unpaired electrons do exist, e.g. the nitric oxide molecule has one. According to Hund's rule, the spins of unpaired electrons are aligned parallel and this gives these molecules paramagnetic properties. The most stable examples of unpaired electrons are found on the atoms and ions of lanthanides and actinides. The incomplete f-shell of these entities does not interact very strongly
|
{
"page_id": 18679245,
"source": null,
"title": "Unpaired electron"
}
|
with the environment they are in and this prevents them from being paired. The ions with the largest number of unpaired electrons are Gd3+ and Cm3+ with seven unpaired electrons. An unpaired electron has a magnetic dipole moment, while an electron pair has no dipole moment because the two electrons have opposite spins so their magnetic dipole fields are in opposite directions and cancel. Thus an atom with unpaired electrons acts as a magnetic dipole and interacts with a magnetic field. Only elements with unpaired electrons exhibit paramagnetism, ferromagnetism, and antiferromagnetism. == References ==
|
{
"page_id": 18679245,
"source": null,
"title": "Unpaired electron"
}
|
TaqMan probes are hydrolysis probes that are designed to increase the specificity of quantitative PCR. The method was first reported in 1991 by researcher David Gefland at Cetus Corporation, and the technology was subsequently developed by Hoffmann-La Roche for diagnostic assays and by Applied Biosystems (now part of Thermo Fisher Scientific) for research applications. The TaqMan probe principle relies on the 5´–3´ exonuclease activity of Taq polymerase to cleave a dual-labeled probe during hybridization to the complementary target sequence and fluorophore-based detection. As in other quantitative PCR methods, the resulting fluorescence signal permits quantitative measurements of the accumulation of the product during the exponential stages of the PCR; however, the TaqMan probe significantly increases the specificity of the detection. TaqMan probes were named after the videogame Pac-Man (Taq Polymerase + PacMan = TaqMan) as its mechanism is based on the Pac-Man principle. == Principle == TaqMan probes consist of a fluorophore covalently attached to the 5’-end of the oligonucleotide probe and a quencher at the 3’-end. Several different fluorophores (e.g. 6-carboxyfluorescein, acronym: FAM, or tetrachlorofluorescein, acronym: TET) and quenchers (e.g. tetramethylrhodamine, acronym: TAMRA) are available. The quencher molecule quenches the fluorescence emitted by the fluorophore when excited by the cycler’s light source via Förster resonance energy transfer (FRET). As long as the fluorophore and the quencher are in proximity, quenching inhibits any fluorescence signals. TaqMan probes are designed such that they anneal within a DNA region amplified by a specific set of primers. (Unlike the diagram, the probe binds to single stranded DNA.) TaqMan probes can be conjugated to a minor groove binder (MGB) moiety, dihydrocyclopyrroloindole tripeptide (DPI3), in order to increase its binding affinity to the target sequence; MGB-conjugated probes have a higher melting temperature (Tm) due to increased stabilization of van der Waals forces. As the Taq polymerase
|
{
"page_id": 8979919,
"source": null,
"title": "TaqMan"
}
|
extends the primer and synthesizes the nascent strand (from the single-stranded template), the 5' to 3' exonuclease activity of the Taq polymerase degrades the probe that has annealed to the template. Degradation of the probe releases the fluorophore from it and breaks the proximity to the quencher, thus relieving the quenching effect and allowing fluorescence of the fluorophore. Hence, fluorescence detected in the quantitative PCR thermal cycler is directly proportional to the fluorophore released and the amount of DNA template present in the PCR. == Applications == TaqMan probe-based assays are widely used in quantitative PCR in research and medical laboratories: Gene expression assays Pharmacogenomics Human Leukocyte Antigen (HLA) genotyping Determination of viral load in clinical specimens (HIV, Hepatitis) Bacterial Identification assays DNA quantification SNP genotyping Verification of microarray results == See also == Quantitative PCR SYBR Green Reverse transcription polymerase chain reaction Molecular beacon Gene Expression == Notes and references == == External links == 1. TaqMan RT-PCR resources- primer databases, software, protocols Archived 2010-11-25 at the Wayback Machine 2. Beacon Designer - Software to design real time PCR primers and probes including SYBR Green primers, TaqMan Probes, Molecular Beacons.
|
{
"page_id": 8979919,
"source": null,
"title": "TaqMan"
}
|
Craniosynostosis, a condition in which the sutures of the head (joints between the bones of the skull) prematurely fuse and subsequently alter the shape of the head, is seen in multiple conditions, as listed below. The level of involvement varies by condition and can range from minor, single-suture craniosynostosis to major, multisutural craniosynostosis. == 0-9 == == A == == B == == C == == D == == E == == F == == G == == H == == I == == J == == L == == M == == N == == O == == P == == R == == S == == T == == V == == Z == == References ==
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{
"page_id": 74384851,
"source": null,
"title": "List of conditions with craniosynostosis"
}
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Peter John Dornan FRS (born 1939) is a British physicist, and professor at Imperial College London where he advised his PhD student Ann Heinson. On 18 September 2009, a festschrift was held in his honor. Dornan was awarded the Rutherford Medal and Prize in 2002. == References == == External links == Google Scholar
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"page_id": 34014669,
"source": null,
"title": "Peter Dornan"
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For detection systems that record discrete events, such as particle and nuclear detectors, the dead time is the time after each event during which the system is not able to record another event. An everyday life example of this is what happens when someone takes a photo using a flash – another picture cannot be taken immediately afterward because the flash needs a few seconds to recharge. In addition to lowering the detection efficiency, dead times can have other effects, such as creating possible exploits in quantum cryptography. == Overview == The total dead time of a detection system is usually due to the contributions of the intrinsic dead time of the detector (for example the ion drift time in a gaseous ionization detector), of the analog front end (for example the shaping time of a spectroscopy amplifier) and of the data acquisition (the conversion time of the analog-to-digital converters and the readout and storage times). The intrinsic dead time of a detector is often due to its physical characteristics; for example a spark chamber is "dead" until the potential between the plates recovers above a high enough value. In other cases the detector, after a first event, is still "live" and does produce a signal for the successive event, but the signal is such that the detector readout is unable to discriminate and separate them, resulting in an event loss or in a so-called "pile-up" event where, for example, a (possibly partial) sum of the deposited energies from the two events is recorded instead. In some cases this can be minimised by an appropriate design, but often only at the expense of other properties like energy resolution. The analog electronics can also introduce dead time; in particular a shaping spectroscopy amplifier needs to integrate a fast rise, slow fall
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{
"page_id": 1246675,
"source": null,
"title": "Dead time"
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signal over the longest possible time (usually 0.5–10 microseconds) to attain the best possible resolution, such that the user needs to choose a compromise between event rate and resolution. Trigger logic is another possible source of dead time; beyond the proper time of the signal processing, spurious triggers caused by noise need to be taken into account. Finally, digitisation, readout and storage of the event, especially in detection systems with large number of channels like those used in modern High Energy Physics experiments, also contribute to the total dead time. To alleviate the issue, medium and large experiments use sophisticated pipelining and multi-level trigger logic to reduce the readout rates. From the total time a detection system is running, the dead time must be subtracted to obtain the live time. == Paralyzable and non-paralyzable behaviour == A detector, or detection system, can be characterized by a paralyzable or non-paralyzable behaviour. In a non-paralyzable detector, an event happening during the dead time is simply lost, so that with an increasing event rate the detector will reach a saturation rate equal to the inverse of the dead time. In a paralyzable detector, an event happening during the dead time will not just be missed, but will restart the dead time, so that with increasing rate the detector will reach a saturation point where it will be incapable of recording any event at all. A semi-paralyzable detector exhibits an intermediate behaviour, in which the event arriving during dead time does extend it, but not by the full amount, resulting in a detection rate that decreases when the event rate approaches saturation. == Analysis == It will be assumed that the events are occurring randomly with an average frequency of f. That is, they constitute a Poisson process. The probability that an event will
|
{
"page_id": 1246675,
"source": null,
"title": "Dead time"
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|
occur in an infinitesimal time interval dt is then f dt. It follows that the probability P(t) that an event will occur at time t to t+dt with no events occurring between t=0 and time t is given by the exponential distribution (Lucke 1974, Meeks 2008): P ( t ) d t = f e − f t d t {\displaystyle P(t)dt=fe^{-ft}dt\,} The expected time between events is then ⟨ t ⟩ = ∫ 0 ∞ t P ( t ) d t = 1 / f {\displaystyle \langle t\rangle =\int _{0}^{\infty }tP(t)dt=1/f} === Non-paralyzable analysis === For the non-paralyzable case, with a dead time of τ {\displaystyle \tau } , the probability of measuring an event between t = 0 {\displaystyle t=0} and t = τ {\displaystyle t=\tau } is zero. Otherwise the probabilities of measurement are the same as the event probabilities. The probability of measuring an event at time t with no intervening measurements is then given by an exponential distribution shifted by τ {\displaystyle \tau } : P m ( t ) d t = 0 {\displaystyle P_{m}(t)dt=0\,} for t ≤ τ {\displaystyle t\leq \tau \,} P m ( t ) d t = f e − f t d t ∫ τ ∞ f e − f t d t = f e − f ( t − τ ) d t {\displaystyle P_{m}(t)dt={\frac {fe^{-ft}dt}{\int _{\tau }^{\infty }fe^{-ft}dt}}=fe^{-f(t-\tau )}dt} for t > τ {\displaystyle t>\tau \,} The expected time between measurements is then ⟨ t m ⟩ = ∫ τ ∞ t P m ( t ) d t = ⟨ t ⟩ + τ {\displaystyle \langle t_{m}\rangle =\int _{\tau }^{\infty }tP_{m}(t)dt=\langle t\rangle +\tau } In other words, if N m {\displaystyle N_{m}} counts are recorded during a particular time interval T {\displaystyle T} and
|
{
"page_id": 1246675,
"source": null,
"title": "Dead time"
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the dead time is known, the actual number of events (N) may be estimated by N ≈ N m 1 − N m τ T {\displaystyle N\approx {\frac {N_{m}}{1-N_{m}{\frac {\tau }{T}}}}} If the dead time is not known, a statistical analysis can yield the correct count. For example, (Meeks 2008), if t i {\displaystyle t_{i}} are a set of intervals between measurements, then the t i {\displaystyle t_{i}} will have a shifted exponential distribution, but if a fixed value D is subtracted from each interval, with negative values discarded, the distribution will be exponential as long as D is greater than the dead time τ {\displaystyle \tau } . For an exponential distribution, the following relationship holds: ⟨ t n ⟩ ⟨ t ⟩ n = n ! {\displaystyle {\frac {\langle t^{n}\rangle }{\langle t\rangle ^{n}}}=n!} where n is any integer. If the above function is estimated for many measured intervals with various values of D subtracted (and for various values of n) it should be found that for values of D above a certain threshold, the above equation will be nearly true, and the count rate derived from these modified intervals will be equal to the true count rate. == Time-To-Count == With a modern microprocessor based ratemeter one technique for measuring field strength with detectors (e.g., Geiger–Müller tubes) with a recovery time is Time-To-Count. In this technique, the detector is armed at the same time a counter is started. When a strike occurs, the counter is stopped. If this happens many times in a certain time period (e.g., two seconds), then the mean time between strikes can be determined, and thus the count rate. Live time, dead time, and total time are thus measured, not estimated. This technique is used quite widely in radiation monitoring systems used in nuclear
|
{
"page_id": 1246675,
"source": null,
"title": "Dead time"
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|
power generating stations. == See also == Data acquisition (DAQ) Allan variance Photomultiplier Positron emission tomography Class-D amplifier == References == == Further reading == Lucke, Robert L. (June 1976). "Counting Statistics for Nonnegligible Dead Time Corrections". Rev. Sci. Instrum. 47 (6): 766. Bibcode:1976RScI...47..766L. doi:10.1063/1.1134733. Meeks, Craig; Siegel, P.B. (June 2008). "Dead time correction via the time series". Am. J. Phys. 76 (6): 589. Bibcode:2008AmJPh..76..589M. doi:10.1119/1.2870432. Morris, S.L. and Naftilan, S.A., "Determining Photometric Dead Time by Using Hydrogen Filters", Astron. Astrophys. Suppl. Ser. 107, 71-75, Oct. 1994
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{
"page_id": 1246675,
"source": null,
"title": "Dead time"
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Leticia del Rosario or Leticia R. del Rosario Mejía (June 4, 1914 – October 9, 2009) was the first Puerto Rican woman with a PhD in Physics and a professor and researcher in nuclear physics at the University of Puerto Rico (UPR). == Early years == Leticia del Rosario (full name: Leticia Rafaela del Rosario Mejía) was born in Yauco, Puerto Rico on June 4, 1914. Her parents were Carlos Antonio del Rosario Rodríguez, a pharmacist, and Juana Josefa Mejía Rodríguez. She was the youngest of eight children. When she was 3 years old, the family moved to San Juan, Puerto Rico, where she completed her primary and secondary studies at Colegio Puertorriqueño de Niñas, a secular private school for women. == Education == Del Rosario attended the University of Puerto Rico (UPR), Río Piedras campus, from 1931 until 1935, where she earned a bachelor’s degree in physical sciences. After teaching high school for two years, she traveled to the University of Chicago in 1940 to continue graduate studies. There she worked with Arthur J. Dempster in a thesis titled “The Relative Abundance of Lithium Isotopes”. After obtaining a master’s degree, she returned to Puerto Rico and continued teaching in high school before joining the University of Puerto Rico as a professor of physics in 1943. In 1944, she went back to Chicago to continue doctoral studies under the guidance of Samuel K. Allison, at that time Director of the Institute for Nuclear Studies (renamed as Enrico Fermi Institute for Nuclear Studies in 1955). While in Chicago, she was also a student of Arthur H. Compton, and Enrico Fermi. In 1948 she graduated with the thesis “Use of electron multiplier tube as a new technique in disintegration experiment”. == Academic career at UPR == In 1943, Leticia del Rosario was
|
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"page_id": 74843608,
"source": null,
"title": "Leticia del Rosario"
}
|
hired as an Assistant Professor in the Department of Physics of the University of Puerto Rico, Río Piedras campus. At the time, Jaime Benítez Rexach was the chancellor, physicist Facundo Bueso Sanllehí was dean of natural sciences, and Amador Cobas was chair of the physics department. After one year, she took a leave of absence to continue her doctoral studies. In 1948, after obtaining her PhD, she went back to UPR. Soon after that, in 1949, she was designated chair of the physics department. She held that position until 1954. In the summer of 1949, she traveled to Oak Ridge National Laboratory (ORNL), sponsored by the Rockefeller Foundation, to participate in a training course on the use of radioisotopes for research in nuclear physics, medicine, and agriculture. At UPR she was member of the Cosmic Rays Laboratory and the director in 1953–1954. In this period, her research focused on cosmic radiation measurements. With funding from the Research Corporation and the Office of Naval Research, she and physicist Jesús Dávila Aponte investigated the range distribution of μ-mesons at sea level. Later they conducted a study to measure underground cosmic radiation. She also collaborated in a study, led by Amador Cobas, to measure the variation of cosmic rays at higher altitudes. The experiments were conducted using globes that contained photographic plates sensitive to protons and beta rays. In 1957, Del Rosario led the organizing committee of the symposium Atomic Energy and the University of Puerto Rico ("Energía Atómica y la Universidad de Puerto Rico"). The symposium sponsored by ORNL and UPR, was celebrated on January 24–28. Important scientists including Lewis I. Strauss, director of the US Atomic Commission and Alvin M. Weinberg, director of ORNL, participated in the meeting. The topics discussed included plans to install nuclear reactors in Puerto Rico, for
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{
"page_id": 74843608,
"source": null,
"title": "Leticia del Rosario"
}
|
scientific research and power generation. In 1959, she transferred from the School of Natural Sciences to the Department of Physical Sciences in the School of General Studies at UPR. In 1961, she was director of a training program for physics high school teachers funded by the National Science Foundation. She was chair of the physical sciences department from 1964 until 1966 when she returned to her position in the School of Natural Sciences. In 1970, Del Rosario was designated Dean of Studies, a position she held until her retirement in 1973. == Affiliations == Leticia Del Rosario was member of the American Physical Society and represented Puerto Rico in the Latin American Council for Cosmic Radiation ("Consejo Latinoamericano para Radiación Cósmica" (CLARC)). At UPR she was member of the Academic Senate and founder and president of the University Faculty Organization ("Organización de Profesores Universitarios"). In 1977, she was elected member of the Puerto Rico Academy of Arts and Sciences. == Late years == Del Rosario retired from UPR in 1973. In 1974 she was named Emeritus Professor. In 1980, she was designated by the governor of Puerto Rico as director of Institute of Puerto Rican Culture (Instituto de Cultura Puertorriqueña). She was in the position until 1983. She died in San Juan on October 9, 2009. == References ==
|
{
"page_id": 74843608,
"source": null,
"title": "Leticia del Rosario"
}
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George Streisinger (December 27, 1927 – August 11, 1984) was an American molecular biologist and co-founder of the Institute of Molecular Biology at the University of Oregon. He was the first person to clone a vertebrate, cloning zebrafish in his University of Oregon laboratory. He also pioneered work in the genetics of the T-even bacterial viruses. In 1972, along with William Franklin Dove he was awarded a Guggenheim Fellowship award, and in 1975 he was selected as a member of the National Academy of Sciences, making him the second Oregonian to receive the distinction. The University of Oregon's Institute of Molecular Biology named their main building "Streisinger Hall" in his honor. == Personal History == George Streisinger was born in Budapest, Hungary, on December 27, 1927. Because they were Jewish, in 1937, his family left Budapest for New York to escape Nazi persecution. Streisinger attended New York public schools and graduated from the Bronx High School of Science in 1944. He obtained a B.S. degree from Cornell University in 1950, and a Ph.D. from the University of Illinois in 1953. He completed postdoctoral studies at the California Institute of Technology from 1953 to 1956. He married Lotte Sielman in 1949. Streisinger accepted a post at the University of Oregon Institute of Molecular Biology in Eugene in 1960. Streisinger was well known as an innovative professor in and out of the classroom, conscripting a dance class to illustrate protein synthesis, and often requested beginning and non-major biology students. He was very politically active, organizing grass-roots resistance to the Vietnam war and legislative opposition to John Kennedy's civil defense program. He testified to successfully ban mutagenic herbicides in Douglas fir reforestation, and led and won a battle to exclude secret war department research from the University of Oregon campus. His wife, Lotte,
|
{
"page_id": 20776409,
"source": null,
"title": "George Streisinger"
}
|
was a noted artist and community activist, and the founder of the Eugene Saturday Market, the inspiration for the Portland Oregon Saturday Market. == Research == Following his graduation from Cornell, George under- took graduate studies in the genetics of T-even coliphage with Salvador Luria in the Bacteriology Department of the University of Illinois. His studies revealed phenotypic mixing, in which a phage with a host-range genotype of one phage type was found in a particle who was phenotypically dissimilar. When published in 1956, these studies had profound impact on the study of viral biology. During his postdoc at Caltech, with Jean Weigle, he undertook further studies on T2 × T4 hybrids, which led to the discovery of DNA modification (by glucosylation). At the University of Oregon, Streisinger pioneered the study of zebrafish in his lab. Zebrafish can be genetically modified easily, and researchers can modify them to mimic the traits of certain diseases. In analyzing these created diseases, scientists seek solutions to diseases which affect humans. Over 9,000 researchers in 1,551 labs throughout 31 countries study zebrafish, and many of them received their initial training at the University of Oregon. == References ==
|
{
"page_id": 20776409,
"source": null,
"title": "George Streisinger"
}
|
Blue raspberry is a manufactured flavoring and food coloring for candy, snack foods, syrups, and soft drinks. The flavor does not derive from any species of raspberry, but rather was developed using esters that are part of the flavor profile of pineapple, banana and cherry. Sugar is commonly added to create taste appeal for the blue raspberry flavor. Food products labeled as blue raspberry flavor are commonly dyed with a bright blue synthetic food coloring, such as brilliant blue FCF (also called FD&C Blue No. 1) or European food coloring number E133. The blue color was used to differentiate raspberry-flavored foods from cherry-, watermelon-, and strawberry-flavored foods, each of which is typically red. The use of blue dye also partially is due to the FDA's 1976 banning of amaranth-based Red Dye No. 2, which had previously been heavily used in raspberry-flavored products. == History == Blue raspberry flavoring debuted commercially in the United States in 1958 with Gold Medal's snow cone syrup. Its wider adoption followed the U.S. Food and Drug Administration's (FDA) 1969 approval of FD&C Blue No. 1. This regulatory change encouraged other companies, including The Icee Company and Otter Pops, to introduce blue raspberry products in the early 1970s. == See also == Rubus leucodermis - a fruit-bearing plant that is sometimes called the "blue raspberry" == References == == External links == Media related to Blue raspberry at Wikimedia Commons
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{
"page_id": 28181980,
"source": null,
"title": "Blue raspberry flavor"
}
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Cellomics is the discipline of quantitative cell analysis using bioimaging methods and informatics with a workflow involving three major components: image acquisition, image analysis, and data visualization and management. These processes are generally automated. All three of these components depend on sophisticated software to acquire qualitative data, quantitative data, and the management of both images and data, respectively. Cellomics is also a trademarked term, which is often used interchangeably with high-content analysis (HCA) or high-content screening (HCS), but cellomics extends beyond HCA/HCS by incorporating sophisticated informatics tools. == History == HCS and the discipline of cellomics was pioneered by a once privately held company named Cellomics Inc., which commercialized instruments, software, and reagents to facilitate the study of cells in culture, and more specifically, their responses to potentially therapeutic drug-like molecules. In 2005, Cellomics was acquired by Fisher Scientific International, Inc., now Thermo Fisher Scientific, which develops cellomics-related products under its high content analysis product line. == Applications == Like many of the -omics, e.g., genomics and proteomics, applications have grown in depth and breadth over time. Currently there are over 40 different application areas that cellomics is used in, including the analysis of 3-D cell models, angiogenesis, and cell-signalling. Originally a tool used by the pharmaceutical industry for screening, cellomics has now expanded into academia to better understand cell function in the context of the cell. Cellomics is used in both academic and industrial life-science research in areas, such as cancer research, neuroscience research, drug discovery, consumer products safety, and toxicology; however, there are many more areas for which cellomics could provide a much deeper understanding of cellular function. == Image analysis == With HCA at its core, cellomics incorporates the flexibility of fluorescence microscopy, the automation and capacity of the plate reader, and flow cytometry’s multi-parametric analysis in
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{
"page_id": 2164190,
"source": null,
"title": "Cellomics"
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order to extract data from single-cells or from a population of cells. Once an image is acquired using high content technology hardware, cell data is extracted from that image using image analysis software. Single cell data or population data may be of interest, but for both, a series of steps is followed with varying degrees of user interaction depending on the application and the software being used. The first step is segmenting the cells in the image which provides the software algorithms with the information it needs for downstream processing of individual cell measurements. Next, a user must define the area(s) of interest based on a multitude of parameters, i.e., the area a user wants to measure. After the area of interest has been defined, measurements are collected. The measurements, oftentimes referred to as features, are dictated by the type of data desired from the sample. There are many mathematical algorithms powering all of these steps, and each image analysis software package provides its own level of openness to the mathematical algorithms being used. == Data management == Large numbers of images and amounts of data need to be managed when doing cellomics research. Data and image volumes can quickly range from 11MB to 1TB in less than a year, which is why cellomics uses the power of informatics to collect, organize, and archive all of this information. Secure and effective data mining requires the associated metadata to be captured and integrated into the data management model. Due to the critical nature of cellomics data management, implementing cellomics studies often requires inter-departmental cooperation between information technology and the life science research group leading the study. == References ==
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{
"page_id": 2164190,
"source": null,
"title": "Cellomics"
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The Journal of Luminescence is a monthly peer-reviewed scientific journal published by Elsevier. The editor-in-chief is Xueyuan Chen (Chinese Academy of Sciences). According to the Journal Citation Reports, the journal has a 2023 impact factor of 3.3. The journal covers all aspects related to the emission of light (luminescence). == References == == External links == Official website
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{
"page_id": 10028510,
"source": null,
"title": "Journal of Luminescence"
}
|
Dr. Johan N. Lundström (born 1973) is a Swedish biologist and psychologist. He was awarded his Ph.D. in 2005 from Uppsala University and is most notable for his chemosensory work, and currently works at the Monell Chemical Senses Center. His experiments involve the use of neuroimaging and testing of human behaviour. Johan Lundström's Group of the department of clinical neuroscience currently conduct basic research into the understanding of the neural and behavioural function of the olfactory system and how it interacts with other senses to understand our environment in health and disease. == References == == External links == Dr. Lundström's page on the Monell website Dr Lundström's research group
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"page_id": 18744801,
"source": null,
"title": "Johan Lundström"
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A Bjerrum plot (named after Niels Bjerrum), sometimes also known as a Sillén diagram (after Lars Gunnar Sillén), or a Hägg diagram (after Gunnar Hägg) is a graph of the concentrations of the different species of a polyprotic acid in a solution, as a function of pH, when the solution is at equilibrium. Due to the many orders of magnitude spanned by the concentrations, they are commonly plotted on a logarithmic scale. Sometimes the ratios of the concentrations are plotted rather than the actual concentrations. Occasionally H+ and OH− are also plotted. Most often, the carbonate system is plotted, where the polyprotic acid is carbonic acid (a diprotic acid), and the different species are dissolved carbon dioxide, carbonic acid, bicarbonate, and carbonate. In acidic conditions, the dominant form is CO2; in basic (alkaline) conditions, the dominant form is CO2−3; and in between, the dominant form is HCO−3. At every pH, the concentration of carbonic acid is assumed to be negligible compared to the concentration of dissolved CO2, and so is often omitted from Bjerrum plots. These plots are very helpful in solution chemistry and natural water chemistry. In the example given here, it illustrates the response of seawater pH and carbonate speciation due to the input of man-made CO2 emission by the fossil fuel combustion. The Bjerrum plots for other polyprotic acids, including silicic, boric, sulfuric and phosphoric acids, are other commonly used examples. == Bjerrum plot equations for carbonate system == If carbon dioxide, carbonic acid, hydrogen ions, bicarbonate and carbonate are all dissolved in water, and at chemical equilibrium, their equilibrium concentrations are often assumed to be given by: [ CO 2 ] eq = [ H + ] eq 2 [ H + ] eq 2 + K 1 [ H + ] eq + K 1
|
{
"page_id": 27395553,
"source": null,
"title": "Bjerrum plot"
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K 2 × DIC , [ HCO 3 − ] eq = K 1 [ H + ] eq [ H + ] eq 2 + K 1 [ H + ] eq + K 1 K 2 × DIC , [ CO 3 2 − ] eq = K 1 K 2 [ H + ] eq 2 + K 1 [ H + ] eq + K 1 K 2 × DIC , {\displaystyle {\begin{aligned}[]\left[{\textrm {CO}}_{2}\right]_{\text{eq}}&={\frac {\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}+K_{1}\left[{\textrm {H}}^{+}\right]_{\text{eq}}+K_{1}K_{2}}}\times {\textrm {DIC}},\\[3pt]\left[{\textrm {HCO}}_{3}^{-}\right]_{\text{eq}}&={\frac {K_{1}\left[{\textrm {H}}^{+}\right]_{\text{eq}}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}+K_{1}\left[{\textrm {H}}^{+}\right]_{\text{eq}}+K_{1}K_{2}}}\times {\textrm {DIC}},\\[3pt]\left[{\textrm {CO}}_{3}^{2-}\right]_{\text{eq}}&={\frac {K_{1}K_{2}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}+K_{1}\left[{\textrm {H}}^{+}\right]_{\text{eq}}+K_{1}K_{2}}}\times {\textrm {DIC}},\end{aligned}}} where the subscript 'eq' denotes that these are equilibrium concentrations, K1 is the equilibrium constant for the reaction CO2 + H2O ⇌ H+ + HCO−3 (i.e. the first acid dissociation constant for carbonic acid), K2 is the equilibrium constant for the reaction HCO−3 ⇌ H+ + CO2−3 (i.e. the second acid dissociation constant for carbonic acid), and DIC is the (unchanging) total concentration of dissolved inorganic carbon in the system, i.e. [CO2] + [HCO−3] + [CO2−3]. K1, K2 and DIC each have units of a concentration, e.g. mol/L. A Bjerrum plot is obtained by using these three equations to plot these three species against pH = −log10 [H+]eq, for given K1, K2 and DIC. The fractions in these equations give the three species' relative proportions, and so if DIC is unknown, or the actual concentrations are unimportant, these proportions may be plotted instead. These three equations show that the curves for CO2 and HCO−3 intersect at [H+]eq = K1, and the curves for HCO−3 and CO2−3 intersect at [H+]eq = K2. Therefore, the values of K1 and K2 that were used to create a given Bjerrum plot can easily be found from that plot, by reading off the concentrations at these points of
|
{
"page_id": 27395553,
"source": null,
"title": "Bjerrum plot"
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|
intersection. An example with linear Y axis is shown in the accompanying graph. The values of K1 and K2, and therefore the curves in the Bjerrum plot, vary substantially with temperature and salinity. == Chemical and mathematical derivation of Bjerrum plot equations for carbonate system == Suppose that the reactions between carbon dioxide, hydrogen ions, bicarbonate and carbonate ions, all dissolved in water, are as follows: Note that reaction 1 is actually the combination of two elementary reactions: CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO−3 Assuming the mass action law applies to these two reactions, that water is abundant, and that the different chemical species are always well-mixed, their rate equations are d [ CO 2 ] d t = − k 1 [ CO 2 ] + k − 1 [ H + ] [ HCO 3 − ] , d [ H + ] d t = k 1 [ CO 2 ] − k − 1 [ H + ] [ HCO 3 − ] + k 2 [ HCO 3 − ] − k − 2 [ H + ] [ CO 3 2 − ] , d [ HCO 3 − ] d t = k 1 [ CO 2 ] − k − 1 [ H + ] [ HCO 3 − ] − k 2 [ HCO 3 − ] + k − 2 [ H + ] [ CO 3 2 − ] , d [ CO 3 2 − ] d t = k 2 [ HCO 3 − ] − k − 2 [ H + ] [ CO 3 2 − ] {\displaystyle {\begin{aligned}{\frac {{\textrm {d}}\left[{\textrm {CO}}_{2}\right]}{{\textrm {d}}t}}&=-k_{1}\left[{\textrm {CO}}_{2}\right]+k_{-1}\left[{\textrm {H}}^{+}\right]\left[{\textrm {HCO}}_{3}^{-}\right],\\{\frac {{\textrm {d}}\left[{\textrm {H}}^{+}\right]}{{\textrm {d}}t}}&=k_{1}\left[{\textrm {CO}}_{2}\right]-k_{-1}\left[{\textrm {H}}^{+}\right]\left[{\textrm {HCO}}_{3}^{-}\right]+k_{2}\left[{\textrm {HCO}}_{3}^{-}\right]-k_{-2}\left[{\textrm {H}}^{+}\right]\left[{\textrm {CO}}_{3}^{2-}\right],\\{\frac {{\textrm {d}}\left[{\textrm {HCO}}_{3}^{-}\right]}{{\textrm {d}}t}}&=k_{1}\left[{\textrm {CO}}_{2}\right]-k_{-1}\left[{\textrm {H}}^{+}\right]\left[{\textrm
|
{
"page_id": 27395553,
"source": null,
"title": "Bjerrum plot"
}
|
{HCO}}_{3}^{-}\right]-k_{2}\left[{\textrm {HCO}}_{3}^{-}\right]+k_{-2}\left[{\textrm {H}}^{+}\right]\left[{\textrm {CO}}_{3}^{2-}\right],\\{\frac {{\textrm {d}}\left[{\textrm {CO}}_{3}^{2-}\right]}{{\textrm {d}}t}}&=k_{2}\left[{\textrm {HCO}}_{3}^{-}\right]-k_{-2}\left[{\textrm {H}}^{+}\right]\left[{\textrm {CO}}_{3}^{2-}\right]\end{aligned}}} where [ ] denotes concentration, t is time, and K1 and k−1 are appropriate proportionality constants for reaction 1, called respectively the forwards and reverse rate constants for this reaction. (Similarly K2 and k−2 for reaction 2.) At any equilibrium, the concentrations are unchanging, hence the left hand sides of these equations are zero. Then, from the first of these four equations, the ratio of reaction 1's rate constants equals the ratio of its equilibrium concentrations, and this ratio, called K1, is called the equilibrium constant for reaction 1, i.e. where the subscript 'eq' denotes that these are equilibrium concentrations. Similarly, from the fourth equation for the equilibrium constant K2 for reaction 2, Rearranging 3 gives and rearranging 4, then substituting in 5, gives The total concentration of dissolved inorganic carbon in the system is given by substituting in 5 and 6: DIC = [ CO 2 ] + [ HCO 3 − ] + [ CO 3 2 − ] = [ CO 2 ] eq ( 1 + K 1 [ H + ] eq + K 1 K 2 [ H + ] eq 2 ) = [ CO 2 ] eq ( [ H + ] eq 2 + K 1 [ H + ] eq + K 1 K 2 [ H + ] eq 2 ) {\displaystyle {\begin{aligned}{\textrm {DIC}}&=\left[{\textrm {CO}}_{2}\right]+\left[{\textrm {HCO}}_{3}^{-}\right]+\left[{\textrm {CO}}_{3}^{2-}\right]\\&=\left[{\textrm {CO}}_{2}\right]_{\text{eq}}\left(1+{\frac {K_{1}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}}}+{\frac {K_{1}K_{2}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}}}\right)\\&=\left[{\textrm {CO}}_{2}\right]_{\text{eq}}\left({\frac {\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}+K_{1}\left[{\textrm {H}}^{+}\right]_{\text{eq}}+K_{1}K_{2}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}}}\right)\end{aligned}}} Re-arranging this gives the equation for CO2: [ CO 2 ] eq = [ H + ] eq 2 [ H + ] eq 2 + K 1 [ H + ] eq + K 1 K 2 × DIC {\displaystyle \left[{\textrm {CO}}_{2}\right]_{\text{eq}}={\frac {\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}}{\left[{\textrm {H}}^{+}\right]_{\text{eq}}^{2}+K_{1}\left[{\textrm {H}}^{+}\right]_{\text{eq}}+K_{1}K_{2}}}\times {\textrm {DIC}}} The equations
|
{
"page_id": 27395553,
"source": null,
"title": "Bjerrum plot"
}
|
for HCO−3 and CO2−3 are obtained by substituting this into 5 and 6. == See also == Charlot equation Gran plot (also known as Gran titration or the Gran method) Henderson–Hasselbalch equation Hill equation (biochemistry) Ion speciation Fresh water Seawater Thermohaline circulation == References ==
|
{
"page_id": 27395553,
"source": null,
"title": "Bjerrum plot"
}
|
Acetylpropionyl, also known as acetyl propionyl or 2,3-pentanedione, is an organic compound, specifically a diketone. Uses for acetylpropionyl include as a: Solvent for cellulose acetate, paints, inks, and lacquers Starting material for dyes, pesticides, and drugs Flavor, with an odor described as "buttery, cheesy, sweet, nutty, fruity, creamy, caramel" Food production facilities use acetylpropionyl in foods such as cookies, coffee, cereal, and chocolate. It is also found in nicotine containing liquids for vaping, and in flavored cigarettes. It is often used as a flavoring substitute for diacetyl, but may share similar human pulmonary toxicity. == Safety == As a flavoring agent, it is an ingredient in some e-liquid products for use with electronic cigarettes to give a buttery or caramel flavor. There is substantial evidence of the pulmonary toxicity of acetylpropionyl in animals. Rats exposed to acetylpropionyl develop both fibrosis and necrosis of the respiratory tract. Mice exposed to acetylpropionyl demonstrate more bronchial constriction in response to methacholine challenge. It is also known to cause genetic changes in animal brains. Acetylpropionyl has been used as a substitute for the toxic flavoring chemical diacetyl. However, in one flavoring manufacturing facility that substituted diacetyl for acetylpropionyl, abnormal lung function values were associated with total time spent in production areas. An investigation by NIOSH in 2009 at a facility that used buttermilk flavoring containing acetylpropionyl demonstrated that workers had higher than average reports of shortness of breath, asthma, and restrictive type spirometry defects. Another investigation by NIOSH in 2013 at a flavoring manufacturer that used acetylpropionyl revealed that those workers who spent the most time working with flavoring chemicals, including acetylpropionyl, were more likely to have abnormal lung function as detected by pulmonary function tests. == See also == Diacetyl, a similar diketone Acetoin == References ==
|
{
"page_id": 46335459,
"source": null,
"title": "Acetylpropionyl"
}
|
Since the first printing of Carl Linnaeus's Species Plantarum in 1753, plants have been assigned one epithet or name for their species and one name for their genus, a grouping of related species. Thousands of plants have been named for people, including botanists and their colleagues, plant collectors, horticulturists, explorers, rulers, politicians, clerics, doctors, philosophers and scientists. Even before Linnaeus, botanists such as Joseph Pitton de Tournefort, Charles Plumier and Pier Antonio Micheli were naming plants for people, sometimes in gratitude for the financial support of their patrons. Early works researching the naming of plant genera include an 1810 glossary by Alexandre de Théis and an etymological dictionary in two editions (1853 and 1856) by Georg Christian Wittstein. Modern works include The Gardener's Botanical by Ross Bayton, Index of Eponymic Plant Names and Encyclopedia of Eponymic Plant Names by Lotte Burkhardt, Plants of the World by Maarten J. M. Christenhusz (lead author), Michael F. Fay and Mark W. Chase, The A to Z of Plant Names by Allan J. Coombes, the four-volume CRC World Dictionary of Plant Names by Umberto Quattrocchi, and Stearn's Dictionary of Plant Names for Gardeners by William T. Stearn; these supply the seed-bearing genera listed in the first column below. Excluded from this list are genus names not accepted (as of January 2021) at Plants of the World Online, which includes updates to Plants of the World (2017). == Key == Ba = listed in Bayton's The Gardener's Botanical Bt = listed in Burkhardt's Encyclopedia of Eponymic Plant Names Bu = listed in Burkhardt's Index of Eponymic Plant Names Ch = listed in Christenhusz's Plants of the World Co = listed in Coombes's The A to Z of Plant Names Qu = listed in Quattrocchi's CRC World Dictionary of Plant Names St = listed in Stearn's
|
{
"page_id": 66258404,
"source": null,
"title": "List of plant genera named for people (A–C)"
}
|
Dictionary of Plant Names for Gardeners In addition, Burkhardt's Index is used as a reference for every row in the table not cited to Stearn. == Genera == == See also == List of plant genus names with etymologies: A–C, D–K, L–P, Q–Z List of plant family names with etymologies == Notes == == Citations == == References == Bayton, Ross (2020). The Gardener's Botanical: An Encyclopedia of Latin Plant Names. Princeton, New Jersey: Princeton University Press. ISBN 978-0-691-20017-0. Burkhardt, Lotte (2018). Verzeichnis eponymischer Pflanzennamen – Erweiterte Edition [Index of Eponymic Plant Names – Extended Edition] (pdf) (in German). Berlin: Botanic Garden and Botanical Museum, Freie Universität Berlin. doi:10.3372/epolist2018. ISBN 978-3-946292-26-5. S2CID 187926901. Retrieved January 1, 2021. See http://creativecommons.org/licenses/by/4.0/ for license. Burkhardt, Lotte (2022). Eine Enzyklopädie zu eponymischen Pflanzennamen [Encyclopedia of eponymic plant names] (pdf) (in German). Berlin: Botanic Garden and Botanical Museum, Freie Universität Berlin. doi:10.3372/epolist2022. ISBN 978-3-946292-41-8. S2CID 246307410. Retrieved January 27, 2022. See http://creativecommons.org/licenses/by/4.0/ for license. Christenhusz, Maarten; Fay, Michael Francis; Chase, Mark Wayne (2017). Plants of the World: An Illustrated Encyclopedia of Vascular Plants. Chicago, Illinois: Kew Publishing and The University of Chicago Press. ISBN 978-0-226-52292-0. Coombes, Allen (2012). The A to Z of Plant Names: A Quick Reference Guide to 4000 Garden Plants. Portland, Oregon: Timber Press. ISBN 978-1-60469-196-2. Cullen, Katherine E. (2006). Biology: The People Behind the Science. New York, New York: Infobase Publishing. ISBN 978-0-8160-7221-7. POWO (2019). "Plants of the World Online". London: Royal Botanic Gardens, Kew. Archived from the original on March 22, 2017. Retrieved January 1, 2021. See terms of use. Quattrocchi, Umberto (2000). CRC World Dictionary of Plant Names, Volume I, A–C. Boca Raton, Florida: CRC Press. pp. 1–700. ISBN 978-0-8493-2675-2. Stearn, William (2002). Stearn's Dictionary of Plant Names for Gardeners. London: Cassell. ISBN 978-0-304-36469-5. == Further reading == Gledhill,
|
{
"page_id": 66258404,
"source": null,
"title": "List of plant genera named for people (A–C)"
}
|
David (2008). The Names of Plants. New York, New York: Cambridge University Press. ISBN 978-0-521-86645-3.
|
{
"page_id": 66258404,
"source": null,
"title": "List of plant genera named for people (A–C)"
}
|
ISO 16610: Geometrical product specifications (GPS) – Filtration is a standard series on filters for surface texture, and provides guidance on the use of these filters in various applications. Filters are used in surface texture in order reduce the bandwidth of analysis in order to obtain functional correlation with physical phenomena such as friction, wear, adhesion, etc. For example, filters are used to separate roughness and waviness from the primary profile, or to create a multiscale decomposition in order to identify the scale at which a phenomenon occurs. Historically, the first roughness measuring instruments - stylus profilometer - used to have electronic filters made of capacitors and resistors that filtered out low frequencies in order to retain frequencies that represent roughness. Later, digital filters replaced analog filters and international standards such as ISO 11562 for the Gaussian filter were published. == Filter toolbox for surface texture == Today, a full set of filters is described in the ISO 16610 standard series. This standard is part of the GPS standards on Geometrical Product Specification and Verification, developed by ISO TC 213. == Filter matrix == ISO 16610 is composed of two families of documents, one for profiles (open and closed) and one for surfaces. A general introduction is provided in: ISO 16610-1: Overview and basic concepts (published in 2015) === Profile filters === Profile filters are defined for open profiles, measured along a line by profilometers and expressed as z=f(x), as well as for closed profiles, measured around a circular component by roundness instruments and expressed as radius=f(angle). Most of these standards were first published as a Technical Specification (TS) and later converted to International Standards or withdrawn. Parts related to profile filters are: ISO 16610-20: Linear profile filters: Basic concepts (published in 2015) ISO 16610-21: Linear profile filters: Gaussian filters
|
{
"page_id": 47908321,
"source": null,
"title": "ISO 16610"
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(published in 2011) ISO 16610-22: Linear profile filters: Spline filters (published in 2015) ISO 16610-28: Linear profile filters: End effects (published in 2016) ISO 16610-29: Linear profile filters: Spline wavelets (published in 2015) ISO 16610-30: Robust profile filters: Basic concepts (published in 2015) ISO 16610-31: Robust profile filters: Gaussian regression filters (published in 2016) ISO 16610-32: Robust profile filters: Spline filters (published as a TS in 2009) ISO 16610-40: Morphological profile filters: Basic concepts (published in 2015) ISO 16610-41: Morphological profile filters: Disc and horizontal line-segment filters (published in 2015) ISO 16610-45: Morphological profile filters: Segmentation filters (planned for the future) ISO 16610-49: Morphological profile filters: Scale space techniques (published in 2015) Note: ISO/TS 16610-32 on robust spline filters was published as a technical specification in 2009 but was withdrawn in 2015. === Areal filters === Areal filters are defined for surfaces measured either by lateral scanning instruments or optical profilometers. Parts related to areal filters are: ISO 16610-60: Linear areal filter: Basic concepts (published in 2015) ISO 16610-61: Linear areal filter: Gaussian filters (published in 2015) ISO 16610-62: Linear areal filter: Spline filters ISO 16610-68: Linear areal filter: End-effects (planned for the future) ISO 16610-69: Linear areal filter: Spline wavelets ISO 16610-70: Robust areal filter: Basic concepts ISO 16610-71: Robust areal filter: Gaussian regression filters (published in 2014) ISO 16610-80: Morphological areal filter: Basic concepts ISO 16610-81: Morphological areal filter: Sphere and horizontal planar segment filters ISO 16610-85: Morphological areal filter: Segmentation (published in 2013) ISO 16610-89: Morphological areal filter: Scale space techniques == Guide for the use of filters in surface texture == The following section describes which application is suitable for each filter. References to published papers or books are provided when available. Readers are encouraged to add below proven applications related to surface texture and tribology
|
{
"page_id": 47908321,
"source": null,
"title": "ISO 16610"
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where a particular filter can be used alone or in conjunction with other treatments or analyses to provide significant results. Part 21 - Profile Gaussian filter Microroughness filtering (lambda S) Separation of roughness and waviness profiles (lambda C) Band-pass filtering Part 22 - Profile Spline filter Part 29 - Profile Spline wavelets Part 31 - Profile Robust Gaussian filter Part 41 - Profile Morphological filter Part 45 - Profile Segmentation filter Part 49 - Profile Scale space technique Part 61 - Areal Gaussian filter Microroughness S-Filter L-Filter for the generation of the roughness S-L surface Part 62 - Areal Spline filter Part 71 - Areal Robust regression Gaussian filter Microroughness S-Filter on stratified and structured surfaces L-Filter for the generation of the roughness S-L surface on stratified and structured surfaces F-Filter for the generation of S-F surface Outlier detection Part 81 - Areal Morphological filter F-Filter used to flatten a surface with the upper or lower envelope Tip deconvolution of AFM instrument Part 85 - Areal Segmentation filter Identification of structures (grains, pores, cells, ...) Automatic leveling of MEMS Part 89 - Areal Scale space technique == See also == Outline of metrology and measurement ISO 25178: areal surface texture standard Surface roughness Gaussian filter == References ==
|
{
"page_id": 47908321,
"source": null,
"title": "ISO 16610"
}
|
Weatherization (American English) or weatherproofing (British English) is the practice of protecting a building and its interior from the elements, particularly from sunlight, precipitation, and wind, and of modifying a building to reduce energy consumption and optimize energy efficiency. Weatherization is distinct from building insulation, although building insulation requires weatherization for proper functioning. Many types of insulation can be thought of as weatherization, because they block drafts or protect from cold winds. Whereas insulation primarily reduces conductive heat flow, weatherization primarily reduces convective heat flow. In the United States, buildings use one third of all energy consumed and two thirds of all electricity. Due to the high energy usage, they are a major source of the pollution that causes urban air quality problems and pollutants that contribute to climate change. Building energy usage accounts for 49 percent of sulfur dioxide emissions, 25 percent of nitrous oxide emissions, and 10 percent of particulate emissions. == Procedures == Typical weatherization procedures include: Sealing bypasses (cracks, gaps, holes), especially around doors, windows, pipes and wiring that penetrate the ceiling and floor, and other areas with high potential for heat loss, using caulk, foam sealant, weather-stripping, window film, door sweeps, electrical receptacle gaskets, and so on to reduce infiltration. Sealing recessed lighting fixtures ('can lights' or 'high-hats'), which leak large amounts of air into unconditioned attic space. Sealing air ducts, which can account for 20% of heat loss, using fiber-reinforced mastic (not duck/duct tape, which is not suitable for this purpose) Installing/replacing dampers in exhaust ducts, to prevent outside air from entering the house when the exhaust fan or clothes dryer is not in use. Protecting pipes from corrosion and freezing. Installing footing drains, foundation damp proofing/ waterproofing membranes, interior perimeter drains, sump pump, gutters, downspout extensions, downward-sloping grading, French drains, swales, and other
|
{
"page_id": 67042,
"source": null,
"title": "Weatherization"
}
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techniques to protect a building from both surface water and ground water. Providing proper ventilation to unconditioned spaces to protect a building from the effects of condensation. See Ventilation issues in houses Installing roofing, building wrap, siding, flashing, skylights or solar tubes and making sure they are in good condition on an existing building. Installing insulation in walls, floors, and ceilings, around ducts and pipes, around water heaters, and near the foundation and sill. Installing storm doors and storm windows. Replacing old drafty doors with tightly sealing, foam-core doors. Retrofitting older windows with a stop or parting bead across the sill where it meets the sash. Replacing older windows with low-energy, double-glazed windows. The phrase "whole-house weatherization" extends the traditional definition of weatherization to include installation of modern, energy-saving heating and cooling equipment, or repair of old, inefficient equipment (furnaces, boilers, water heaters, programmable thermostats, air conditioners, and so on). The "Whole-House" approach also looks at how the house performs as a system. == Air quality == Weatherization generally does not cause indoor air quality problems by adding new pollutants to the air. (There are a few exceptions, such as caulking, that can sometimes emit pollutants.) However, measures such as installing storm windows, weather stripping, caulking, and blown-in wall insulation can reduce the amount of outdoor air infiltrating into a home. Consequently, after weatherization, concentrations of indoor air pollutants from sources inside the home can increase. Weatherization may have a negative impact on indoor air quality, if done improperly, exacerbating respiratory conditions especially among occupants with pre-existing respiratory illnesses. This may occur because of a drastic decrease in air exchange rate in the home, introduction of new chemicals, and poor management of indoor moisture due to a poorly performed weatherization work. Low air exchange rates may lead to higher concentrations
|
{
"page_id": 67042,
"source": null,
"title": "Weatherization"
}
|
of pollutants in the air when ventilation is not sufficiently addressed during weatherization work. However, the situation may be different in case of a house situated in an area with high outdoor air pollution levels such as in close proximity (<200 m) from a busy major road. In such a scenario, a more airtight building envelope can actually offer protection against infiltration of outdoor air pollution. The same is true for the protection offered by tighter building envelopes during wildfire events that cause elevated levels of outdoor air pollution. == US Weatherization Assistance Program == Weatherization is a set of measures and practices aimed at improving the energy efficiency of a building or home, primarily to reduce energy consumption and lower utility bills. The main goal of weatherization is to make a structure more comfortable and cost-effective to live in, especially during extreme weather conditions. It involves making various improvements to a building's insulation, air sealing, and overall energy systems. The American Council for an Energy-Efficient Economy estimates that up to February 2018 over 7 million homes have been weatherized, giving yearly savings of 2.6 TWh of electricity, 7.9 TWh (27×10^12 Btu) of fossil gas and 3.2 million metric tons (3.5 million short tons) of reduced carbon dioxide emissions. The US Department of Energy estimates weatherization returns $2.69 for each dollar spent on the program, realized in energy and non-energy benefits. Families whose homes are weatherized are expected to save $358 on their first year's utility bills. Low Income Home Energy Assistance Programs in many states work side by side with WAP to provide both immediate and long-term solutions to energy poverty. == See also == Building envelope Building indoor environment Building performance Central heating Heating, ventilation and air conditioning (HVAC) Low-energy house Vapor barrier WikiBooks How-to guide to Weatherization
|
{
"page_id": 67042,
"source": null,
"title": "Weatherization"
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|
== References == == External links == Houston Advanced Research Center The Weatherization Assistance Program (WAP) Technical Assistance Center (WAPTAC) The WAP System for Identifying and Reviewing New Technologies and Techniques Weatherization Information Portal Home Energy Weatherization Articles https://www.rhinoshieldwis.com/ http://rhinoshieldjax.com/
|
{
"page_id": 67042,
"source": null,
"title": "Weatherization"
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|
In quantum field theory, a Slavnov–Taylor identity is the non-Abelian generalisation of a Ward–Takahashi identity, which in turn is an identity between correlation functions that follows from the global or gauged symmetries of a theory, and which remains valid after renormalization. The identity was originally discovered by Gerard 't Hooft, and it is named after Andrei Slavnov and John C. Taylor who rephrased the identity to hold off the mass shell. == References == == External links == Slavnov-Taylor identities
|
{
"page_id": 27002337,
"source": null,
"title": "Slavnov–Taylor identities"
}
|
The Ehrenfest paradox concerns the rotation of a "rigid" disc in the theory of relativity. In its original 1909 formulation as presented by Paul Ehrenfest in relation to the concept of Born rigidity within special relativity, it discusses an ideally rigid cylinder that is made to rotate about its axis of symmetry. The radius R as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R0 when stationary. However, the circumference (2πR) should appear Lorentz-contracted to a smaller value than at rest, by the usual factor γ. This leads to the contradiction that R = R0 and R < R0. The paradox has been deepened further by Albert Einstein, who showed that since measuring rods aligned along the periphery and moving with it should appear contracted, more would fit around the circumference, which would thus measure greater than 2πR. This indicates that geometry is non-Euclidean for rotating observers, and was important for Einstein's development of general relativity. Any rigid object made from real material that is rotating with a transverse velocity close to that material's speed of sound must exceed the point of rupture due to centrifugal force, because centrifugal pressure can not exceed the shear modulus of material. F S = m v 2 r S < m c s 2 r S ≈ m G r S ρ ≈ G {\displaystyle {\frac {F}{S}}={\frac {mv^{2}}{rS}}<{\frac {mc_{s}^{2}}{rS}}\approx {\frac {mG}{rS\rho }}\approx G} where c s {\displaystyle c_{s}} is speed of sound, ρ {\displaystyle \rho } is density and G {\displaystyle G} is shear modulus. Therefore, when considering relativistic speeds, it is only a thought experiment. Neutron-degenerate matter may allow velocities close to the speed of light, since the speed of a neutron-star oscillation is relativistic (though these bodies cannot strictly be
|
{
"page_id": 2819556,
"source": null,
"title": "Ehrenfest paradox"
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|
said to be "rigid"). == Essence of the paradox == Imagine a disk of radius R rotating with constant angular velocity ω {\displaystyle \omega } . The reference frame is fixed to the stationary center of the disk. Then the magnitude of the relative velocity of any point in the circumference of the disk is ω R {\displaystyle \omega R} . So the circumference will undergo Lorentz contraction by a factor of 1 − ( ω R ) 2 / c 2 {\displaystyle {\sqrt {1-(\omega R)^{2}/c^{2}}}} . However, since the radius is perpendicular to the direction of motion, it will not undergo any contraction. So c i r c u m f e r e n c e d i a m e t e r = 2 π R 1 − ( ω R ) 2 / c 2 2 R = π 1 − ( ω R ) 2 / c 2 . {\displaystyle {\frac {\mathrm {circumference} }{\mathrm {diameter} }}={\frac {2\pi R{\sqrt {1-(\omega R)^{2}/c^{2}}}}{2R}}=\pi {\sqrt {1-(\omega R)^{2}/c^{2}}}.} This is paradoxical, since in accordance with Euclidean geometry, it should be exactly equal to π. == Ehrenfest's argument == Ehrenfest considered an ideal Born-rigid cylinder that is made to rotate. Assuming that the cylinder does not expand or contract, its radius stays the same. But measuring rods laid out along the circumference 2 π R {\displaystyle 2\pi R} should be Lorentz-contracted to a smaller value than at rest, by the usual factor γ. This leads to the paradox that the rigid measuring rods would have to separate from one another due to Lorentz contraction; the discrepancy noted by Ehrenfest seems to suggest that a rotated Born rigid disk should shatter. Thus Ehrenfest argued by reductio ad absurdum that Born rigidity is not generally compatible with special relativity. According to special
|
{
"page_id": 2819556,
"source": null,
"title": "Ehrenfest paradox"
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relativity an object cannot be spun up from a non-rotating state while maintaining Born rigidity, but once it has achieved a constant nonzero angular velocity it does maintain Born rigidity without violating special relativity, and then (as Einstein later showed) a disk-riding observer will measure a circumference: C ′ = 2 π R 1 − v 2 / c 2 . {\displaystyle C^{\prime }={\frac {2\pi R}{\sqrt {1-v^{2}/c^{2}}}}.} == Einstein and general relativity == The rotating disc and its connection with rigidity was also an important thought experiment for Albert Einstein in developing general relativity. He referred to it in several publications in 1912, 1916, 1917, 1922 and drew the insight from it, that the geometry of the disc becomes non-Euclidean for a co-rotating observer. Einstein wrote (1922): 66ff: Imagine a circle drawn about the origin in the x'y' plane of K' and a diameter of this circle. Imagine, further, that we have given a large number of rigid rods, all equal to each other. We suppose these laid in series along the periphery and the diameter of the circle, at rest relatively to K'. If U is the number of these rods along the periphery, D the number along the diameter, then, if K' does not rotate relatively to K, we shall have U / D = π {\displaystyle U/D=\pi } . But if K' rotates we get a different result. Suppose that at a definite time t of K we determine the ends of all the rods. With respect to K all the rods upon the periphery experience the Lorentz contraction, but the rods upon the diameter do not experience this contraction (along their lengths!). It therefore follows that U / D > π {\displaystyle U/D>\pi } . It therefore follows that the laws of configuration of rigid bodies
|
{
"page_id": 2819556,
"source": null,
"title": "Ehrenfest paradox"
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|
with respect to K' do not agree with the laws of configuration of rigid bodies that are in accordance with Euclidean geometry. If, further, we place two similar clocks (rotating with K'), one upon the periphery, and the other at the centre of the circle, then, judged from K, the clock on the periphery will go slower than the clock at the centre. The same thing must take place, judged from K' if we define time with respect to K' in a not wholly unnatural way, that is, in such a way that the laws with respect to K' depend explicitly upon the time. Space and time, therefore, cannot be defined with respect to K' as they were in the special theory of relativity with respect to inertial systems. But, according to the principle of equivalence, K' is also to be considered as a system at rest, with respect to which there is a gravitational field (field of centrifugal force, and force of Coriolis). We therefore arrive at the result: the gravitational field influences and even determines the metrical laws of the space-time continuum. If the laws of configuration of ideal rigid bodies are to be expressed geometrically, then in the presence of a gravitational field the geometry is not Euclidean. == Brief history == Citations to the papers mentioned below (and many which are not) can be found in a paper by Øyvind Grøn which is available on-line. 1909: Max Born introduces a notion of rigid motion in special relativity. 1909: After studying Born's notion of rigidity, Paul Ehrenfest demonstrated by means of a paradox about a cylinder that goes from rest to rotation, that most motions of extended bodies cannot be Born rigid. 1910: Gustav Herglotz and Fritz Noether independently elaborated on Born's model and showed (Herglotz–Noether theorem)
|
{
"page_id": 2819556,
"source": null,
"title": "Ehrenfest paradox"
}
|
that Born rigidity only allows three degrees of freedom for bodies in motion. For instance, it's possible that a rigid body is executing uniform rotation, yet accelerated rotation is impossible. So a Born rigid body cannot be brought from a state of rest into rotation, confirming Ehrenfest's result. 1910: Max Planck calls attention to the fact that one should not confuse the problem of the contraction of a disc due to spinning it up, with that of what disk-riding observers will measure as compared to stationary observers. He suggests that resolving the first problem will require introducing some material model and employing the theory of elasticity. 1910: Theodor Kaluza points out that there is nothing inherently paradoxical about the static and disk-riding observers obtaining different results for the circumference. This does however imply, Kaluza argues, that "the geometry of the rotating disk" is non-euclidean. He asserts without proof that this geometry is in fact essentially just the geometry of the hyperbolic plane. 1911: Vladimir Varićak argued that the paradox only occurs in the Lorentz standpoint, where rigid bodies contract, but not if the contraction is "caused by the manner of our clock-regulation and length-measurement". Einstein published a rebuttal, denying that his viewpoint was different from Lorentz's. 1911: Max von Laue shows, that an accelerated body has an infinite number of degrees of freedom, thus no rigid bodies can exist in special relativity. 1916: While writing up his new general theory of relativity, Albert Einstein notices that disk-riding observers measure a longer circumference, C′ = 2πr/√1−v2. That is, because rulers moving parallel to their length axis appear shorter as measured by static observers, the disk-riding observers can fit more smaller rulers of a given length around the circumference than stationary observers could. 1922: A. S. Eddington, in The Mathematical Theory of
|
{
"page_id": 2819556,
"source": null,
"title": "Ehrenfest paradox"
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|
Relativity (p. 113), calculates a contraction of the radius of the rotating disc (compared to stationary scales) of one quarter of the 'Lorentz contraction' factor applied to the circumference. 1935: Paul Langevin essentially introduces a moving frame (or frame field in modern language) corresponding to the family of disk-riding observers, now called Langevin observers. (See the figure.) He also shows that distances measured by nearby Langevin observers correspond to a certain Riemannian metric, now called the Langevin-Landau-Lifschitz metric. 1937: Jan Weyssenhoff (now perhaps best known for his work on Cartan connections with zero curvature and nonzero torsion) notices that the Langevin observers are not hypersurface orthogonal. Therefore, the Langevin-Landau-Lifschitz metric is defined, not on some hyperslice of Minkowski spacetime, but on the quotient space obtained by replacing each world line with a point. This gives a three-dimensional smooth manifold which becomes a Riemannian manifold when we add the metric structure. 1946: Nathan Rosen shows that inertial observers instantaneously comoving with Langevin observers also measure small distances given by Langevin-Landau-Lifschitz metric. 1946: E. L. Hill analyzes relativistic stresses in a material in which (roughly speaking) the speed of sound equals the speed of light and shows these just cancel the radial expansion due to centrifugal force (in any physically realistic material, the relativistic effects lessen but do not cancel the radial expansion). Hill explains errors in earlier analyses by Arthur Eddington and others. 1952: C. Møller attempts to study null geodesics from the point of view of rotating observers (but incorrectly tries to use slices rather than the appropriate quotient space) 1968: V. Cantoni provides a straightforward, purely kinematical explanation of the paradox by showing that "one of the assumptions implicitly contained in the statement of Ehrenfest's paradox is not correct, the assumption being that the geometry of Minkowski space-time allows
|
{
"page_id": 2819556,
"source": null,
"title": "Ehrenfest paradox"
}
|
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