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Uranyl fluoride is the inorganic compound with the formula UO 2 F 2 . It is most notable as a contaminant in the production of uranium tetrafluoride . [ 2 ]
As shown by X-ray crystallography , the uranyl centers UO 2+ 2 are surrounded by six fluoride ligands F − . [ 3 ]
This salt is very soluble in water as well as hygroscopic . It changes in color from brilliant orange to yellow after reacting with water. Uranyl fluoride is stable in air up to 300 °C, above which slow decomposition to U 3 O 8 occurs. When heated to decomposition, UO 2 F 2 emits toxic hydrofluoric acid fumes. [ citation needed ]
It is formed in the hydrolysis of uranium hexafluoride ( UF 6 ):
It can also be formed in the hydrofluorination of uranium trioxide ( UO 3 ):
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it .
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Uranium tetrafluoride is the inorganic compound with the formula UF 4 . It is a green solid with an insignificant vapor pressure and low solubility in water . Uranium in its tetravalent ( uranous ) state is important in various technological processes. In the uranium refining industry it is known as green salt . [ 1 ]
UF 4 is prepared from UO 2 in a fluidized bed by reaction with Hydrogen fluoride . The UO 2 is derived from mining operations. Around 60,000 tonnes are prepared in this way annually. A common impurity is UO 2 F 2 . UF4 is susceptible to hydrolysis as well. [ 1 ]
UF 4 is formed by the reaction of UF 6 with hydrogen gas in a vertical tube-type reactor.
The bulk density of UF 4 varies from about 2.0 g/cm 3 to about 4.5 g/cm 3 depending on the production process and the properties of the starting uranium compounds.
A molten salt reactor design, a type of nuclear reactor where the working fluid is a molten salt , would use UF 4 as the core material. UF 4 is generally chosen over related compounds because of the usefulness of the elements without isotope separation , better neutron economy and moderating efficiency, lower vapor pressure and better chemical stability.
Uranium tetrafluoride reacts stepwise with fluorine, first to give uranium pentafluoride and then volatile UF 6 :
UF 4 is reduced by magnesium to give the metal: [ 2 ]
UF 4 reacts slowly with moisture at ambient temperature, forming UO 2 and HF.
Like most binary metal fluorides , UF 4 is a dense highly crosslinked inorganic polymer . As established by X-ray crystallography , the U centres are eight-coordinate with square antiprismatic coordination spheres. The fluoride centres are doubly bridging . [ 2 ] [ 3 ]
Like all uranium salts, UF 4 is toxic and thus harmful by inhalation, ingestion, and through skin contact.
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Uranium pentafluoride is the inorganic compound with the chemical formula UF 5 . It is a pale yellow paramagnetic solid. The compound has attracted interest because it is related to uranium hexafluoride , which is widely used to produce uranium fuel. It crystallizes in two polymorphs , called α- and β-UF 5 .
Uranium pentafluoride is an intermediate in the conversion of uranium tetrafluoride to volatile UF 6 :
It can be produced by reduction of the hexafluoride with carbon monoxide at elevated temperatures. [ 1 ]
Other reducing agents have been examined. [ 2 ]
The α form is a linear coordination polymer consisting of chains of octahedral uranium centers in which one of the five fluoride anion forms a bridge to the next uranium atom. [ 3 ] The structure is reminiscent of that for vanadium pentafluoride .
In the β form, the uranium centers adopt a square antiprismatic structure . [ 4 ] The β polymorph gradually converts to α at 130 °C. [ 3 ]
Of theoretical interest, molecular UF 5 can be generated as a transient monomer by UV- photolysis of uranium hexafluoride . It is thought to adopt a square pyramidal geometry. [ 5 ]
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Uranium hexafluoride , sometimes called hex , is the inorganic compound with the formula U F 6 . Uranium hexafluoride is a volatile, white solid that is used in enriching uranium for nuclear reactors and nuclear weapons . [ 4 ]
Uranium dioxide is converted with hydrofluoric acid (HF) to uranium tetrafluoride : [ 4 ]
In samples contaminated with uranium trioxide , the oxyfluoride is produced in the HF step:
The resulting UF 4 is subsequently oxidized with fluorine to give the hexafluoride:
At atmospheric pressure , UF 6 sublimes at 56.5 °C. [ 5 ]
The solid-state structure was determined by neutron diffraction at 77 K and 293 K. [ 6 ] [ 7 ] [ 8 ]
UF 6 reacts with water , releasing hydrofluoric acid . The compound reacts with aluminium , forming a surface layer of AlF 3 that resists any further reaction from the compound.
Uranium hexafluoride is a mild oxidant . [ 10 ] It is a Lewis acid as evidenced by its binding to form heptafluorouranate(VI), [UF 7 ] − . [ 11 ]
Polymeric uranium(VI) fluorides containing organic cations have been isolated and characterized by X-ray diffraction. [ 12 ]
As one of the most volatile compounds of uranium, uranium hexafluoride is relatively convenient to process and is used in both of the main uranium enrichment methods, namely gaseous diffusion and the gas centrifuge method. Since the triple point of UF 6 ; 64 °C(147 °F; 337 K) and 152 kPa (22 psi; 1.5 atm); [ 13 ] is close to ambient conditions, phase transitions can be achieved with little thermodynamic work .
Fluorine has only a single naturally occurring stable isotope, so isotopologues of UF 6 differ in their molecular weight based solely on the uranium isotope present. [ 14 ] This difference is the basis for the physical separation of isotopes in enrichment.
All the other uranium fluorides are nonvolatile solids that are coordination polymers .
The conversion factor for the 238 U isotopologue of UF 6 ("hex") to "U mass" is 0.676. [ 15 ]
Gaseous diffusion requires about 60 times as much energy as the gas centrifuge process: gaseous diffusion-produced nuclear fuel produces 25 times more energy than is used in the diffusion process, while centrifuge-produced fuel produces 1,500 times more energy than is used in the centrifuge process.
In addition to its use in enrichment, uranium hexafluoride has been used in an advanced reprocessing method ( fluoride volatility ), which was developed in the Czech Republic . In this process, spent nuclear fuel is treated with fluorine gas to transform the oxides or elemental metals into a mixture of fluorides. This mixture is then distilled to separate the different classes of material. Some fission products form nonvolatile fluorides which remain as solids and can then either be prepared for storage as nuclear waste or further processed either by solvation -based methods or electrochemically .
Uranium enrichment produces large quantities of depleted uranium hexafluoride (D UF 6 or D- UF 6 ) as a waste product. The long-term storage of D- UF 6 presents environmental, health, and safety risks because of its chemical instability. When UF 6 is exposed to moist air, it reacts with the water in the air to produce UO 2 F 2 ( uranyl fluoride ) and HF ( hydrogen fluoride ) both of which are highly corrosive and toxic. In 2005, 686,500 tonnes of D- UF 6 was housed in 57,122 storage cylinders located near Portsmouth, Ohio ; Oak Ridge, Tennessee ; and Paducah, Kentucky . [ 16 ] [ 17 ] Storage cylinders must be regularly inspected for signs of corrosion and leaks. The estimated lifetime of the steel cylinders is measured in decades. [ 18 ]
There have been several accidents involving uranium hexafluoride in the US, including a cylinder-filling accident and material release at the Sequoyah Fuels Corporation in 1986 where an estimated 29 500 pounds of gaseous UF 6 escaped. [ 19 ] [ 20 ] The U.S. government has been converting D UF 6 to solid uranium oxides for disposal. [ 21 ] Such disposal of the entire D UF 6 stockpile could cost anywhere from $15 million to $450 million. [ 22 ]
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Some conspiracy theories argue that various governments and politicians globally, in particular the United States government , are suppressing evidence that unidentified flying objects (UFO) are controlled by an extraterrestrial or "non-human" intelligence, or built using alien technology. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] Since the 1980s, such conspiracy theories often argue that world governments are in communication or cooperation with extraterrestrials , and some claim that the governments are explicitly allowing cattle mutilation and alien abduction .
According to the Committee for Skeptical Inquiry little or no evidence exists to support them despite significant research on the subject by non-governmental scientific agencies. [ 8 ]
"The truth of what the strange disc ships really are will never be disclosed to the common people. We just don't count to the people who do know about such things."
Flying saucer conspiracy theories first began in the pages of pulp science-fiction, where they drew upon inspiration from the "lost continent" myths of Atlantis and Lemuria. [ 2 ] [ 1 ] : 4 [ 10 ] : 32 In 1947, during 'the first summer of the cold war', private pilot Kenneth Arnold reported witnessing supersonic 'flying discs'; historians would later chronicle at least 800 "copycat" reports in subsequent weeks, while other sources estimate the reports may have numbered in the thousands. [ 11 ] [ 12 ] : 53 Press speculated that the flying discs were secret American or Soviet technology. [ 13 ]
By December 1949, author Donald Keyhoe promoted the idea that the Air Force was withholding knowledge of interplanetary spaceships, culminating in his 1955 work The Flying Saucer Conspiracy . [ 1 ] : 111–113 Gulyas argues: "Keyhoe was instrumental in popularizing one of the most lasting memes in the long flying-saucer story: the government cover-up of 'the truth' about UFOs". [ 3 ] : 3 The following year, the book They Knew Too Much About Flying Saucers introduced the concept of the Men in Black. [ 2 ] : 302
Conspiracy theories became more prevalent after the Kennedy assassination. In 1967, controversial prosecutor Jim Garrison accused UFO hoaxer Fred Crisman of involvement in the assassination; Thereafter, UFO conspiracy theorists began to link Kennedy's death to aliens. [ 1 ] : 263, 323 An official debunking of a UFO sighting as "Swamp Gas" was met with ridicule, and by the 1970s, a supposed cover-up was termed a "Cosmic Watergate". [ 3 ] : 6 In 1977, blockbuster film Close Encounters of the Third Kind dramatized a government UFO cover-up. [ 3 ] : 44 By 1974, theories alleged the Air Force stored dead alien bodies at a mythical "Hangar 18", and in 1980, the book The Roswell Incident introduced the story of a UFO crash to a mass audience. [ 3 ] : 6 [ 14 ]
While earlier decades imagined a coverup of benevolent "space brothers", the 1980s saw the rise of what scholars called "ufology's dark side": theories that a government cabal was secretly involved with a race of malevolent aliens. [ 2 ] : 97 New theories linked a supposed UFO coverup to alien abductions, cattle mutilations, and even the JFK assassination. [ 2 ] : 87–99, 137–38, 147 At a 1989 Mutual UFO Network conference, author Bill Moore confessed that he had intentionally fed fake evidence of extraterrestrials to UFO researchers. [ 15 ] [ 3 ] : 8–9 [ 1 ] : 269
The 1990s saw the rise of UFO conspiracy theories in popular culture, with TV shows like The X-Files and films like Independence Day and Men in Black . [ 2 ] : 2 [ 6 ] : 179
In 2017, UFO conspiracy theories experienced renewed interest when Leslie Kean published stories of a 21st-century Pentagon UFO program . [ 16 ]
While unusual sightings have been reported in the sky throughout history, UFOs became culturally prominent after World War II , escalating during the Space Age . Studies and investigations into UFO reports conducted by governments (such as Project Blue Book in the United States and Project Condign in the United Kingdom ), as well as by organizations and individuals have occurred over the years without confirmation of the fantastical claims of small but vocal groups of ufologists who favour unconventional or pseudoscientific hypotheses, often claiming that UFOs are evidence of extraterrestrial intelligence , technologically advanced cryptids , demons , interdimensional contact or future time travelers . After decades of promotion of such ideas by believers and in popular media, the kind of evidence required to solidly support such claims has not been forthcoming. Scientists and skeptic organizations such as the Committee for Skeptical Inquiry have provided prosaic explanations for UFOs, namely that they are caused by natural phenomena, human technology, delusions, and hoaxes. Beliefs surrounding UFOs have inspired parts of new religions even as social scientists have identified the ongoing interest and storytelling surrounding UFOs as a modern example of folklore and mythology understandable with psychosocial explanations .
Benjamin Radford has pointed out how unlikely such suppression of evidence is given that "[t]he UFO coverup conspiracy would have to span decades, cross international borders, and transcend political administrations" and that "all of the world's governments, in perpetuity, regardless of which political party is in power and even among enemies, [would] have colluded to continue the coverup." [ 17 ]
A wide variety of people have publicly promoted the idea of a conspiracy to coverup UFOs.
A number of theorists achieved prominence for their claims. Donald Keyhoe was the most prominent proponent of UFO conspiracy theories during the 1950s. In the late 1960s and 1970s, Jacque Vallee and J. Allen Hynek were notable voices alleging a "Cosmic Watergate"; Both were involved in the blockbuster Close Encounters of the Third Kind . In the 1980s, Stanton Friedman rose to prominence after describing the Roswell incident as a conspiracy. In the 2010s, Luis Elizondo rose to prominence for his claims of a US government coverup.
Other proponents were less promiment. Richard Shaver, one early proponent, had been hospitalized for psychiatric problems, [ 2 ] : 115 while another, Paul Bennewitz, was hospitalized for paranoia after being deceived by Richard Doty. [ 1 ] : 258 Several proponents later confessed responsibility for hoaxes or lies, including Gray Barker, Carl Allen, Richard Doty, Bill Moore, and Ray Santelli. [ 4 ] Other proponents met violent ends—Morris Jessup and James E. McDonald died by suicide. John Lear helped promote both Bill Cooper and Bob Lazar -- Cooper broke with Lear and was years later shot and killed by law enforcement during an attempted arrest.
High-profile individuals who have suggested that UFO evidence is being suppressed include United States Senator Barry Goldwater , British Admiral Lord Hill-Norton (former NATO head and chief of the British Defence Staff), American Vice Admiral Roscoe H. Hillenkoetter (first CIA director), astronauts Gordon Cooper [ 1 ] : 155 [ 18 ] [ 19 ] and Edgar Mitchell . [ 20 ] [ 12 ] : 225 21st century proponents include former Canadian Defence Minister Paul Hellyer , Stanford University immunologist Garry Nolan , [ 21 ] and Israeli brigadier general Haim Eshed (former director of space programs for the Israel Ministry of Defense), [ 22 ] In 2017, To The Stars Inc. was founded by Jim Semivan, Harold E. Puthoff , and Tom DeLonge . [ 23 ] Luis Elizondo and David Grusch were notable proponents in the 2020s. Beyond their testimonies and reports they have presented no evidence to substantiate their statements and claims.
Works of popular fiction have included premises and scenes in which a government intentionally prevents disclosure to its populace of the discovery of extraterrestrial intelligence.
The 1960s saw conspiracy films like 2001: A Space Odyssey (as well as the novel),. [ 24 ] [ 25 ] The 1970s saw the UFO conspiracy discussed briefly in Jack Nicholson vehicle Easy Rider , [ 26 ] and in-depth in the Steven Spielberg films Close Encounters of the Third Kind . The 1980s saw Spielberg return to the topic with E.T. the Extra-Terrestrial while Disney's Flight of the Navigator introduced UFO conspiracy theories to a childhood audience. The 1990s saw UFO conspiracy theories in films like Total Recall , Independence Day , and Men in Black . [ 6 ] : 179 Television series and films including The X-Files , Dark Skies , and Stargate have also featured efforts by governments to conceal information about extraterrestrial beings. In March 2001, former astronaut and United States Senator John Glenn appeared on an episode of the TV series Frasier playing a fictional version of himself who confesses to a UFO coverup. [ 27 ]
The plot of the Sidney Sheldon novel The Doomsday Conspiracy involves a UFO conspiracy, as did the plot of the 2021 series American Horror Story: Double Feature . [ 28 ]
Scholars of religion have identified some new religious movements among the proponents of UFO conspiracy theories, most notably the Nation of Islam , Scientology , and Heaven's Gate . [ 7 ]
Mormon cosmology teaches that the Earth is not unique, but that it is one of many inhabited planets , with each planet created for the purpose of bringing about the "immortality and eternal life" (i.e., the exaltation) of humanity. [ 29 ] : 1595 One author observes "there has long been an association between UFOs and The Church of Jesus Christ of Latter-day Saints". [ 30 ]
Theosophists and occultists had long claimed knowledge of extraterrestrial beings. In 1946, Meade Layne achieved national notoriety when the wire service carried his claims to be in telepathic communication with people in a space ship. [ 1 ] : 102 Other "contactees" like George Adamski and George Hunt Williamson similarly had backgrounds in Theosophy. [ 2 ] : 150 Guy Warren Ballard , founder of the UFO religion "I AM" Activity , had a background in Theosophist.
In the years following the 1931 Japanese invasion of Manchuria , Nation of Islam founder W.D. Fard introduced the concept of The Mother Plane : an apocalyptic Japanese weapon of war. During the ensuing decades, the Mother Plane became identified with UFOs. [ 7 ]
1950s UFO religions included Unarius and the Aetherius Society . In the 1950s, L. Ron Hubbard , a pulp fiction author in Raymond Palmer's magazines and a practitioner of Aleister Crowley 's Thelema , founded the new religious movement Scientology . In the late 1960s, Hubbard began to secretly teach of Xenu , an extraterrestrial who conspired to turn ancient Earth into a prison for immortal souls. [ 7 ] In the 1970s, UFO religion Raëlism formed; In 2002 the group achieved notoriety for its unverified claims to have performed human cloning .
In 1997, rumors spread that a spaceship was trailing the Hale-Bopp comet. [ 15 ] : 132 On March 26, 1997, law enforcement discovered the bodies of the 39 active members of Heaven's Gate religious group. They had participated in a coordinated series of ritual suicides, coinciding with the closest approach of Comet Hale–Bopp. [ 15 ] From 1994 to 1997, UFO religion Order of the Solar Temple was responsible for 74 deaths in a series of mass murder-suicides.
UFO conspiracy theories began in 1940s pulp magazine edited by Raymond Palmer , known as "the man who invented flying saucers ". [ 1 ] : 3 [ 10 ] For years prior to the 1947 flying disc craze , Palmer had published reports of strange craft in his pulp sci-fi magazine Amazing Stories . [ 2 ] : 32 [ 10 ] During the 1947 flying disc craze, Palmer hired original saucer witness Kenneth Arnold to investigate a flying disc report near Maury Island, Washington. [ 1 ] : 13 [ 10 ] By October 1947, Palmer's magazine featured claims that the truth behind the discs was being covered up. [ 1 ] : 12 [ 10 ] Palmer would continue to promote UFO conspiracy theories for the rest of his life, eventually linking them to the JFK assassination and Watergate. [ 1 ] : 323 [ 10 ]
Beginning in 1945, Palmer began to print ostensibly-true stories based on the writings of Richard Shaver, a Pennsylvania welder who claimed to be in telepathic communication with a secret underground race. [ 2 ] : 32 In 1934, Shaver had been hospitalized for psychiatric problems; Barkun argues: "By most accounts Shaver himself believed with absolute conviction in the truthfulness of his stories. This, combined with their appearance in a pulp-fiction venue, served further to blur the already uncertain boundary between fact and fiction." [ 2 ] : 115 Shaver claimed that ancient civilizations had mastered space travel, spread civilization to other planets, and could travel to Earth. [ 2 ] : 116
In a July 1946 editorial, Palmer argued that "responsible parties in world governments" were aware "of the fact of spaceships visiting Earth". [ 31 ] : x [ 32 ] Peebles opines: "One would be hard pressed to find a more concise summary of the flying saucer myth. Yet this was a year before the first widely publicized sighting." [ 1 ] : 6 [ note 1 ]
The flying disc craze began on June 24, when media nationwide reported civilian pilot Kenneth Arnold's story of witnessing disc-shaped objects which headline writers dubbed " Flying Saucers ". [ 1 ] : ch.2 [ 33 ] Such reports quickly spread throughout the United States; historians would later chronicle at least 800 "copycat" reports in subsequent weeks, while other sources estimate the reports may have numbered in the thousands. [ 11 ] [ 12 ] : 53
On July 8, 1947, Roswell Army Air Field issued a press release stating that they had recovered a "flying disc". The Army quickly retracted the statement and clarified that the crashed object was a conventional weather balloon . [ 34 ] The Roswell incident did not surface again until 1978, when ufologist Stanton Friedman interviewed Jesse Marcel . [ 35 ] : 69
In late July, Palmer contacted Kenneth Arnold and asked him to investigate a "flying disc" report from Fred Crisman near Maury Island, Washington. [ 3 ] : 30–31 In June 1946 and again in May 1947, Palmer had published fantastical letters from Crisman, who claimed to have battled inhuman underground monsters in Burma. [ 3 ] : 30–31 Arnold agreed and Palmer wired him $200 to fund the investigation." [ 1 ] : 13 Arriving in Tacoma, Arnold interviewed Crisman, who told a tale of a flying disc that emitted rock-like debris and a visitation from mysterious black-clad stranger who gave ominous instructions not to speak of the disc. [ 1 ] : 13–15
Arnold summoned two Air Force investigators who took possession of the supposed debris, described as lava rocks, from Crisman. [ 1 ] : 13–15 As the investigators returned to base, their B-25 caught fire and crashed. A local paper ran a story suggesting the plane had been sabotaged or shot down to prevent the shipping of the flying disc fragments. Though Crisman later confessed to a hoax, Peebles argues the story was the "first to give a sinister air" or "conspiratorial atmosphere" to the flying saucer myth. [ 1 ] : 13–15
In the October 1947 issue of Amazing Stories, editor Raymond Palmer argued the flying disc flap was proof of Richard Sharpe Shaver's claims. [ 1 ] : 12 That same issue carried a letter from Shaver in which he argued the truth behind the discs would remain a secret. [ 4 ] [ note 2 ]
Wrote Shaver:
"The discs can be a space invasion, a secret new army plane — or a scouting trip by an enemy country...OR, they can be Shaver's space ships, taking off and landing regularly on earth for centuries past, and seen today as they have always been — as a mystery. They could be leaving earth with cargos of wonder-mech that to us would mean emancipation from a great many of our worst troubles— and we'll never see those cargos...I predict that nothing more will be seen, and the truth of what the strange disc ships really are will never be disclosed to the common people. We just don't count to the people who do know about such things. It isn't necessary to tell us anything." [ 4 ] [ 9 ] : 159 [ note 2 ]
During the last decades of his life, Shaver devoted himself to "rock books"—stones that he believed had been created by the advanced ancient races and embedded with legible pictures and texts. [ 9 ] : 206 After Shaver's death in 1975, his editor Raymond Palmer admitted that "Shaver had spent eight years not in the Cavern World, but in a mental institution" being treated for paranoid schizophrenia . [ 4 ] : ch. 3
"There is a definite link between flying saucers, The Shaver Mystery, The Kennedy’s assassinations, Watergate and Fred Crisman."
In 1952, Arnold and Palmer would author Coming of the Saucers . [ 1 ] : 13, 92 It detailed his 1947 investigation of Fred Crisman's claims, alleged he had been eavesdropped on during his investigation, and other strange behavior. [ 3 ] : 30 In 1968, Crisman would be subpoenaed by a New Orleans grand jury in the prosecution of a local man for the assassination of President John F. Kennedy—a prosecution that would later be dramatized in the 1991 Oliver Stone film JFK. [ 3 ] : 30–31 [ 1 ] : 323
The 1950s saw an increase in both governmental and civilian investigative efforts and reports of public disinformation and suppression of evidence.
On December 26, 1949, True magazine published an article by Donald Keyhoe titled " The Flying Saucers Are Real ". [ 1 ] : 40–41 [ 37 ] Keyhoe, a former Major in the US Marines, claimed that elements within the Air Force knew that saucers existed and had concluded they were likely 'inter-planetary'. [ 37 ]
The article examined the Mantell UFO incident and quoted an unnamed pilot who opined that the Air Force's explanation "looks like a cover up to me". The article claimed a "rocket authority at Wright field" had concluded saucers were interplanetary. Concern over a public panic, of the kind that supposedly occurred after the 1938 War of the Worlds broadcast , is cited in the article as a possible motive for the cover up.
The True article caused a sensation. [ 1 ] When Keyhoe expanded the article into a book, The Flying Saucers Are Real (1950), it sold over half a million copies in paperback. The Air Force denied "flying saucers" exist and further denied that they were US technology being covered-up. [ 1 ] [ 38 ]
In 1954, before Sputnik the first man-made satellite, Keyhoe told press that alien satellites had been detected in Earth orbit.
In 1955, Donald Keyhoe authored a new book that pointedly accused elements of the United States government of engaging in a conspiracy to cover up knowledge of flying saucers. [ 1 ] : 111–113 [ 39 ] Keyhoe claims the existence of a "silence group" orchestrating this conspiracy. [ 1 ] : 110–113 Historian of Folklore Curtis Peebles argues: " The Flying Saucer Conspiracy marked a shift in Keyhoe's belief system. No longer were flying saucers the central theme; that now belonged to the silence group and its coverup. For the next two decades Keyhoe's beliefs about this would dominate the flying saucer myth." [ 1 ] : 110–113
On January 22, 1958, Donald Keyhoe appeared on CBS's Armstrong Circle Theatre in an episode titled "UFO: Enigma of the Skies". During the live broadcast, Keyhoe deviated from the pre-approved script, announcing "now I’m going to reveal something that has never been disclosed before". At this point in the broadcast, Keyhoe's microphone was cut. According to Peebles, "Millions of people thought the Air Force had (literally) "silenced" Keyhoe. Keyhoe emerged as the winner of the Armstrong Theater battle. Believers would point to it as an example of 'silencing.' To the public at large, CBS's cutting off of the audio gave Keyhoe's appearance an impact much greater than anything he said." [ 1 ] : 129
The first "alien bodies" conspiracy theory emerged in October and November 1949, when journalist Frank Scully published two columns in Variety . [ 1 ] : 47–48 Scully claimed that dead extraterrestrial beings were recovered from a flying saucer crash, based on what he said was reported to him by a scientist involved. [ 41 ] [ 42 ] [ 43 ] His 1950 book Behind the Flying Saucers expanded on the theme, adding that there had been two such incidents in Arizona and one in New Mexico , a 1948 incident that involved a saucer that was nearly 100 feet (30 m) in diameter. [ note 3 ] [ 44 ] In January 1950, Time Magazine skeptically repeated stories of crashed saucers with humanoid occupants. [ 45 ]
It was later revealed that Scully had been the victim of "two veteran confidence artists ". [ 1 ] : 47–48 [ 46 ] In 1952 and 1956, True magazine published articles by San Francisco Chronicle reporter John Philip Cahn [ 47 ] [ 48 ] that exposed Newton and "Dr. Gee" (identified as Leo A. GeBauer) as oil con artists who had hoaxed Scully. [ 49 ]
In a 1997 Roswell report, Air Force investigator James McAndrew wrote that "even with the exposure of this obvious fraud, the Aztec story is still revered by UFO theorists. Elements of this story occasionally reemerge and are thought to be the catalyst for other crashed flying saucer stories, including the Roswell Incident." [ 50 ] : 84–85
On July 29, 1952, General John Samford , the director of Air Force intelligence, held a press conference on the recent UFO sightings over the nation's capital; The conference was the largest one held in the seven years since World War II. [ 1 ] : 65 Samford attributed the recent radar returns to temperature inversion . [ 1 ] : 65 While most reports were easily explainable, Samford acknowledged having received a number of reports from "credible observers of relatively incredible things." [ 1 ] : 65 Samford continued, saying: "our real interest in this project is not one of intellectual curiosity but is in trying to establish and appraise the possibility of a menace to the United States. And we can say, as of now, that there has been no pattern that reveals anything remotely like purpose or remotely like consistency that we can in any way associate with any menace to the United States." [ 1 ] : 65
While most accepted the official explanation, Peebles argues "many in the press and public got the impression that the Air Force was covering up, and this was reflected in some of the press coverage." [ 1 ] : 65 In 1952, the Robertson Panel recommended a campaign of public education. [ 51 ]
Al Chop , a civilian, had served as the Press Chief for Air Materiel Command in Dayton, Ohio until 1951 when he transferred to the Pentagon to serve as the press spokesman for Project Bluebook . [ 52 ] In 1956, a film titled Unidentified Flying Objects: The True Story of Flying Saucers dramatized the events of the early 1950s from the point of view of "Al Chop", an Air Force press officer played by reporter Tom Towers. [ 53 ] The film incorporates interviews with actual eyewitnesses and historic footage of unidentified objects, concluding with a dramatization of the 1952 UFO flap that featured repeated sightings over Washington D.C. [ 52 ]
Ruppelt was a captain in the US Air Force who served as director of official investigations into UFOs: Project Grudge and Project Bluebook. [ 1 ] : 110–113 [ 52 ] In 1956, Ruppelt authored The Report on Unidentified Flying Objects , a book that has been called the "most significant" of its era. [ 1 ] : 113 The book discussed the Twining memo which initiated UFO investigation and the rejected 1948 "Estimate of the Situation". Ruppelt
criticized the Air Force's handling of UFOs investigations. Historian Curtis Peebles concludes that the book "should have ended the speculation about an Air Force cover-up. In fact, Ruppelt's statements were converted into support for the cover-up idea." [ 1 ] : 110–113
In 1955, Morris K. Jessup achieved some notoriety with his book The Case for the UFO , in which he argued that UFOs represented a mysterious subject worthy of further study. [ 6 ] : 106 [ 1 ] : 112, 114 [ 54 ]
In January 1956, Jessup began receiving a series of letters from "Carlos Miguel Allende", later identified as Carl Meredith Allen . [ 6 ] : 106 [ 55 ] "Allende" warned Jessup not to investigate the levitation of UFOs and spun a tale of a dangerous experiment in which a navy ship was made invisible, only to inexplicably teleport from Philadelphia to Norfolk, Virginia, before reappearing back in Philadelphia. [ 6 ] : 106 The ship's crew was supposed to have suffered various side effects, including insanity, intangibility, and being "frozen" in place. [ 6 ] : 106
In 1957, Jessup was invited to the Office of Naval Research where he was shown an annotated copy of his book that was filled with handwritten notes in its margins, written with three different shades of blue ink, appearing to detail a debate among three individuals. [ 6 ] : 106 They discussed ideas about the propulsion for flying saucers , alien races , and express concern that Jessup was too close to discovering their technology. [ 6 ] : 106 Jessup noticed the handwriting of the annotations resembled the letters he received from Allen. Twelve years later, Allen would say that he authored all of the annotations in order "to scare the hell out of Jessup." [ 56 ]
Jessup died by suicide in 1959. [ 6 ] : 106 In 1963, Gray Barker authored a book alleging Jessup's death was suspicious. [ 57 ] [ note 4 ] By 1975, the Philadelphia Experiment was being promoted by paranormal author Charles Berlitz [ 58 ] and in 1984, the legend was adapted into a fictional film . In 1980, Berlitz co-authored The Roswell Incident . [ 6 ] : 106
1956 saw the publication of Gray Barker 's They Knew Too Much About Flying Saucers , the book which publicized the idea of Men in Black who appear to UFO witnesses and warn them to keep quiet. [ 2 ] : 82 There has been continued speculation that the men in black are government agents who harass and threaten UFO witnesses.
According to the Skeptical Inquirer article "Gray Barker: My Friend, the Myth-Maker", there may have been "a grain of truth" to Barker's writings on the Men in Black, in that government agencies did attempt to discourage public interest in UFOs during the 1950s. However, Barker is thought to have greatly embellished the facts of the situation. In the same Skeptical Inquirer article, Sherwood revealed that, in the late 1960s, he and Barker collaborated on a brief fictional notice alluding to the Men in Black, which was published as fact first in Raymond A. Palmer 's Flying Saucers magazine and some of Barker's own publications. In the story, Sherwood (writing as "Dr. Richard H. Pratt") claimed he was ordered to silence by the "blackmen" after learning that UFOs were time-travelling vehicles. Barker later wrote to Sherwood, "Evidently the fans swallowed this one with a gulp." [ 59 ]
The 1960s began an era of government skepticism. After the assassination of John F. Kennedy , the Pentagon Papers , and the Watergate scandal , trust in the US government declined and acceptance of conspiracy theories became widespread. [ 2 ] : 2 [ 3 ] : 6 [ 1 ] : 166, 205, 245
In 1966, amid a wave (or 'flap') of UFO reports throughout southern Michigan, there were two mass sightings reported. The first occurred around marshland near Dexter, while the second mass-sighting took place near the campus arboretum of Hillsdale College, about 50 miles away. [ 1 ] : 169–171
After the reports were attributed to swamp gas by Air Force civilian investigator J. Allen Hynek, the explanation was widely derided. [ 1 ] : 169–172 The Richmond News Leader accused the Air Force of attempting "to discredit the testimony of witnesses." and US congressman Gerald Ford called for a formal Congressional investigation into the sightings. [ 60 ] : 9 [ 1 ] : 171 Like "weather balloon" before it, the term "swamp gas" came to mean any unbelievable debunking.
On March 1, 1967, New Orleans District attorney Jim Garrison arrested and charged New Orleans businessman Clay Shaw with having conspired to assassinate President Kennedy . [ 3 ] : 30 [ 1 ] : 263 Fred Crisman was subpoenaed by Garrison and testified before the New Orleans grand jury in the case. [ 1 ] : 263 Garrison issued a press release accusing Crisman of being an undercover agent with knowledge of the Kennedy Assassination. [ 4 ]
The jury took less than an hour to find Shaw not guilty. [ 1 ] : 323 Garrison's prosecution of Shaw was highly criticized as "a fatally flawed case built on flimsy evidence that featured a chorus of dubious and even wacky witnesses" while others more pointedly accuse Garrison of "recklessness, cruelty, abuse of power, publicity mongering and dishonesty". [ 61 ] [ 62 ] [ 63 ]
Despite the near-universal condemnation of the prosecution, conspiracy theories continued to link Crisman to the Kennedy assassination and a supposed UFO cover-up. Crisman had been involved in the Shaver Mystery and the Maury Island Hoax in the 1940s. In the late 1970s, the United States House Select Committee on Assassinations considered the possibility that Crisman may have been one of the "three tramps" detained and photographed in the aftermath of the JFK assassination. [ 9 ] : 160 Pointing to Crisman's supposed involvement, later conspiracy authors like Kenn Thomas, Jim Marrs, and Bill Cooper alleged that Kennedy's assassination was tied to a UFO conspiracy. [ 3 ] : 30–31
In the novel and film 2001: A Space Odyssey by Arthur C. Clarke and Stanley Kubrick, American discovery of an extraterrestrial artifact prompts a cover up and disinformation campaign with fatal consequence for astronauts sent to investigate. [ 5 ] : ch. 12 [ 64 ] The film was prominent in Moon landing conspiracy theories , which variously argue that humans never went to the Moon, went there with the assistance of aliens, or even that NASA covered up lunar evidence of aliens. [ 65 ] One scholar opined that the 1968 film "seems to anticipate the post-Nixonian culture of governmental conspiracy". [ 66 ]
J. Allen Hynek was an American astronomer who served as scientific advisor to UFO studies undertaken by the U.S. Air Force. Hynek had drawn ridicule for his most famous debunking, in which he suggested a mass-sighting over Michigan may have been caused by "swamp gas" . [ 67 ] By 1974, the former skeptic was publicly charging that Bluebook was "a Cosmic Watergate". [ 3 ] : 6 Hynek claimed 20% of Bluebook cases were unexplained. Fellow Ufologist like Stanton Friedman echoed Hynek's "Cosmic Watergate" accusations. [ 68 ] In 1976, pulp publisher Ray Palmer argued "there is a definite link between flying saucers, The Shaver Mystery, The Kennedy’s assassinations, Watergate and Fred Crisman ." [ 69 ] [ 1 ] : 323
During the 1976 US presidential campaign, Jimmy Carter pledged that if elected, he would "make every piece of information this country has about UFOs available to the public and scientists". [ 6 ] : 124–125
In the mid-1970s, legends of alien bodies re-emerged in the popular lore. [ 1 ] : 242, 321 The idea of alien corpses from a crashed ship being stored in an Air Force morgue at the Wright-Patterson Air Force Base was mentioned in Scully's Behind the Flying Saucers , [ 70 ] expanded in the 1966 book Incident at Exeter , and became the basis for a 1968 science-fiction novel The Fortec Conspiracy . [ 71 ] : 87–88 [ 72 ] : 82 Fortec was about a fictional cover-up by the Air Force unit charged with reverse-engineering other nations' technical advancements. [ 72 ]
In 1974, science-fiction author and conspiracy theorist Robert Spencer Carr alleged that alien bodies recovered from the Aztec crash were stored in "Hangar 18" at Wright-Patterson. [ 1 ] : 242, 321 Carr claimed that his sources had witnessed the alien autopsy, [ 1 ] : 244 another idea later incorporated into the Roswell narrative. [ 73 ] : 53–54 [ 74 ] The Air Force explained that no "Hangar 18" existed at the base, noting a similarity between Carr's story and the fictional Fortec Conspiracy . [ 75 ] In the mid-1970s, author Leonard H. Stringfield promoted tales of UFO crash retrievals. [ 1 ] : 240–243 In 1977, recurring SNL characters The Coneheads were contacted by an Air Force investigator (Buck Henry) after an extraterrestrial artifact crashes in the Southwestern US. [ 76 ] The 1980 film Hangar 18 , which dramatized Carr's claims, was described as "a modern-day dramatization" of Roswell by the film's director James L. Conway , [ 77 ] : 287 and as "nascent Roswell mythology" by folklorist Thomas Bullard. [ 12 ] : 331
Decades later, Carr's son recalled that he had often "mortified my mother and me by spinning preposterous stories in front of strangers... [tales of] befriending a giant alligator in the Florida swamps, and sharing complex philosophical ideas with porpoises in the Gulf of Mexico." [ 78 ] : 32
In 1975, millions of Americans watched when NBC aired film The UFO Incident , a dramatization of the Betty and Barney Hill case, the first reported "alien abduction". [ 3 ] : 44 In 1961, the Hills reportedly witnessed an unidentified light in the night sky as they were driving from Montreal to Portsmouth. Under hypnosis, Barney told a story of being abducted and drew a picture of an alien with large, wrap-around eyes—the first report of a "gray" alien . [ 1 ] : 236 Recovered-memory therapy is not based on scientific evidence, and recovered memories are indistinguishable from false memories . [ 79 ] Psychologists and skeptics argued that "after viewing this movie, any person with a little imagination could now become an instant celebrity" by claiming an abduction, concluding that "one of those instant celebrities was Travis Walton." [ 80 ]
Two weeks after the film aired, an Arizona crew working on a Forestry contract reported that member Travis Walton had been abducted by a flying saucer. [ 1 ] : 227 [ 81 ] Science writers Philip J. Klass and Michael Shermer highlight a potential motive for the hoax was to provide an " Act of God " that would allow the crew to avoid a steep financial penalty from the Forestry Service for failing to complete their contract by the deadline. [ 82 ] [ 81 ] The Walton case is widely regarded as a hoax, even by believers of UFOs and alien abductions. [ 81 ] [ 80 ] [ 83 ]
By 1976, artist and amateur UFO researcher Budd Hopkins began focusing on abduction reports; Hopkins popularized the reports in his 1981 book Missing Time and its 1987 follow-up Intruders . [ 1 ] : 235–238 Also in 1987, established horror author Whitley Strieber released Communion , an ostensibly non-fiction autobiographical abduction tale; It topped the New York Times bestseller list. [ 1 ] : 235–238 Strieber's book popularized the idea of alien 'visitors' associated with anal probes. [ 84 ] : 215 In 1989, the book was adapted into a film of the same name , starring Christopher Walken.
In 1974, the film UFOs: Past, Present, and Future dramatized an ostensibly-historical meeting between humans and aliens who land after being summoned. [ 1 ] : 207 [ 4 ] : ch 12 The filmmakers reported being told by military officials that a UFO had landed at Holloman Air Force Base. [ 4 ] : ch 12 [ 85 ] The depiction of a landing in the blockbuster Close Encounters of the Third Kind has been called a "thinly veiled reference to the Holloman landing" story. [ 4 ] : ch 12 [ 86 ] [ 87 ] : 202 The Holloman story would be later promoted by hoaxer Richard Doty. [ 4 ] : ch 12
On December 14, 1977, the Spielberg blockbuster film Close Encounters of the Third Kind premiered and brought UFO conspiracy theories to a global market. [ 2 ] : 30 [ 3 ] : 44 [ 1 ] : 234 The film opens with a United Nations recovery of Flight 19 , lost in the Bermuda Triangle some 32 years prior, in Mexico's Sonora desert; Since Keyhoe's 1955 book The Flying Saucer Conspiracy , theorists had linked Flight 19's disappearance to flying saucers. [ 88 ] The film's subplot of an "exchange program" of humans visiting aliens would later resurface in conspiracy theory as Project Serpo . [ 4 ] : ch 12 : x
Legendary French filmmaker François Truffaut played a character inspired by French UFO investigator Jacques Vallee , an advisor to the film. [ 5 ] : x Real life debunker-turned-believer J. Allen Hynek made a cameo in the film. [ 4 ] In coming years, conspiracy figure John Lear and others would allege that powerful insiders had "subtly promoted" Close Encounters and other films to 'educate' the public. [ 2 ] : 30
In February 1978, UFO researcher Stanton Friedman interviewed Jesse Marcel , the only person known to have accompanied the Roswell debris from where it was recovered to Fort Worth where reporters saw material that was claimed to be part of the recovered object. [ 2 ] : 81 [ 3 ] : 92–93 [ 1 ] : 246–251 Marcel's statements contradicted those he made to the press in 1947. [ 89 ] Marcel revealed that the 1947 "weather balloon" had been a cover story, saying: "They wanted some comments from me, but I wasn't at liberty to do that. So, all I could do is keep my mouth shut. And General Ramey is the one who discussed – told the newspapers, I mean the newsman, what it was, and to forget about it. It is nothing more than a weather observation balloon. Of course, we both knew differently." [ 90 ] [ 91 ]
Uncertain of the material's origin, Marcel would speculate the debris might have been extraterrestrial. In all his statements, Marcel consistently denied the presence of bodies. [ 92 ] [ 93 ] On February 28, 1980, sensationalist tabloid the National Enquirer brought large-scale attention to the Roswell story. [ 94 ]
In the 1990s, the US military published two reports disclosing the true nature of the crashed aircraft: a surveillance balloon from Project Mogul. Nevertheless, the Roswell incident continues to be of interest to the media, and conspiracy theories surrounding the event persist. Roswell has been described as "the world's most famous, most exhaustively investigated and most thoroughly debunked UFO claim". [ 95 ]
In the 1980s, UFO conspiracy theories began to incorporate politics, alleging that the US Government was in league with an evil alien race. By way of contrast with prior UFO conspiracy theories about benevolent 'space brothers', author Jerome Clark named this new strain of thinking "ufology's dark side". [ 2 ] : 97
Richard Doty, who identified as a special agent with the Air Force Office of Special Investigations at Kirtland AFB , was a source for much of this new 'dark' mythology. [ 1 ] : 253 Another important figure during this era was John Lear , son of Learjet founder William Powell Lear. [ 1 ] : 258 Pilkington argues that in the second half of the 1980s, Lear was "probably the most influential source" of UFO conspiracy information. [ 4 ] : x
During the 1970s, the Colorado-New Mexico border region was a hotspot for cattle mutilation reports, especially the small town of Dulce, New Mexico on the Jicarilla Apache Indian Reservation . [ 2 ] Ranchers reported sightings of unusual lights, UFOs, and " quiet helicopters " associated with the mutilations. [ 2 ] : 69–70 Law enforcement recovered radar chaff, syringes, and a gas mask; Some of the corpses had rope marks and broken bones, as if they had been hoisted onto a helicopter and dropped onto he ground. [ 4 ] : x After ranchers took to firing on unidentified helicopters, the US Bureau of Land Management was forced to ground all helicopters in Eastern Colorado. [ 96 ] Writing in 2010, Pilkington reflects: "The silent helicopter has now been revealed as not only a reality, but one that was flying as long ago as 1972. This was the Hughes 500P , the P standing for Penetrator, an aircraft known by the few who flew it as ‘The Quiet One’." [ 4 ]
By 1976, some UFO conspiracy theorists argued that supposed cattle mutilations were caused by extra-terrestrial UFOs. [ 2 ] : 85 In 1979, the idea of aliens causing "mutiliations" was ridiculed when it was reported that a mutilated bull had been drugged with Thorazine ; Law enforcement told press: "We know this stuff is made here, and it isn't from outer space. Whoever is doing it is highly sophisticated, and they have a lot of resources. They're well organized". [ 97 ] [ 4 ]
Pilkington suggests the 'mutilations' may have been a covert epidemiological monitoring program, perhaps of radiation. In 1967, the United States Atomic Energy Commission had detonated an underground nuclear device near Dulce as part of Project Gasbuggy . [ 4 ] : x [ 1 ] : 217
The late 1970s also saw the beginning of controversy centered on Paul Bennewitz . [ 2 ] : 111 [ 4 ] On April 20, 1979, U.S. Attorney R. E. Thompson and US Senator Harrison Schmidt held a public meeting about cattle mutilations. The meeting was attended by about 80, one attendee was Paul Bennewitz, an amateur UFO investigator. [ 4 ] : 87–88 Bennewitz was befriended by Richard Doty, an Air Force Sergeant, who fed him false stories of a UFO conspiracy, government treaties with extraterrestrials, and alien harvesting of cattle. [ 4 ] This material inspired much of the post-1980 UFO mythology. [ 4 ] : x The earliest known reference to "MJ Twelve" comes from a 1981 document used in disinformation targeting Paul Bennewitz. [ 1 ] : 258–259
Paul Bennewitz was ultimately hospitalized for paranoia. [ 1 ] : 258 Doty would appear in the 2013 documentary Mirage Men to discuss his role in deceiving Bennewitz. While Doty claims Bennewitz was targeted for inadvertently recording classified technology at Kirtland Air Force Base, Pilkington argues that government agents likely targeted Bennewitz due to his participation in the 1979 meeting on cattle mutilations around Dulce. [ 4 ] : ch. 11 [ 98 ]
In 1979, Linda Moulton Howe was a documentarian exploring cattle mutilations. [ 2 ] : 86 [ 1 ] : 218 [ 4 ] In 1980, Moulton Howe's documentary "A Strange Harvest" alleged that cattle mutilations were connected to UFOs. [ 2 ] : 86 In April 1983, Moulton Howe travelled to visit Richard Doty and Kirtland Air Force Base. [ 4 ] : x
At Kirtland, Doty showed Moulton Howe fabricated documents purporting to be presidential briefing papers. The documents told of UFOs crashes at Roswell, surviving aliens, MJ-12, and a UFO coverup. For decades, Doty denied Moulton Howe's retelling of these events, but in the late 2000s, he would acknowledge the exchange took place, admitting "We gave Linda [...] some bad information." [ 4 ] : x Howe became a "staunch advocate" for these 'dark' conspiracy theories that the U.S. government is working with aliens. [ 99 ] [ 2 ] She would later be called one of "the gurus of American ufology". [ 100 ]
After the publication of The Roswell Incident , Richard C. Doty and other individuals presenting themselves as Air Force Intelligence Officers approached Moore. [ 101 ] : 213 They used the unfulfilled promise of hard evidence of extraterrestrial retrievals to recruit Moore, who kept notes on other ufologists and intentionally spread misinformation within the UFO community. [ 101 ]
On December 11, 1984, filmmaker Jaime Shandera received an anonymous parcel containing an undeveloped roll of film; When developed, the film was found to contain a copy of what is now known as the "Majestic 12 documents". Shandera received the package just after a phone call from Moore. [ 102 ] : 170 [ 103 ] : 240 The documents detailed the creation of a group, "Majestic 12", was formed to handle Roswell debris. [ 104 ] : 68–69
On October 14, 1988, actor Mike Farrell hosted UFO Cover Up? Live , a two-hour television special "focusing on the government's handling of information regarding UFOs" and "whether there has been any suppression of evidence supporting the existence of UFOs". [ 3 ] : 20 [ 1 ] : 268 The program interviewed shadow-clad informants Falcon (Richard Doty) and Condor about the Majestic 12 documents. [ 4 ] The program was noted for its claim of an alien being, held at Area 51, who liked to eat strawberry ice cream. [ 4 ]
The Majestic-12 materials have been heavily scrutinized and discredited. [ 15 ] Carl Sagan criticized the complete lack of provenance of documents "miraculously dropped on a doorstep like something out of a fairy story, perhaps ' The Elves and the Shoemaker '." [ 105 ] : 88 Researchers noted the idiosyncratic date format not found in government documents from the time they were purported to originate, but widely used in Moore's personal notes. [ 1 ] : 266 Some signatures appear to be photocopied from other documents. [ 106 ] For example, a signature from President Harry Truman is identical to one from an October 1, 1947 letter to Vannevar Bush. [ 107 ] [ 108 ] [ 109 ] After researchers noted many style and formatting errors, Moore admitted that he had typed and stamped the document as a facsimile. [ 1 ] : 259
At a 1989 Mutual UFO Network conference, Moore confessed that he had intentionally fed fake evidence of extraterrestrials to UFO researchers, including Bennewitz. [ 15 ] Roswell conspiracy proponents turned on Moore, but not the broader conspiracy theory. [ 110 ] Doty would later admit he had spread fabricated documents to UFO researchers in the 1980s. [ 111 ] : 53
In the Summer of 1988, Bill Cooper made his first public comments on the ParaNet Bulletin Board System , an early UFO message board, claiming that in 1966 he was serving aboard the USS Tiru when he and fellow Navy personnel witnessed a metal craft "larger than a football field" repeatedly enter and exit the water. [ 5 ] : 72–75 Cooper claimed he was instructed by superiors to never speak about the incident. [ 5 ] : 72–75
Biographer Mark Jacobson argues "the Tiru incident itself would not have done much to make Cooper's name in ufology. That opportunity came only a few days later" when he was contacted by fellow ParaNet poster John Lear . Lear, the son of Learjet founder Bill Lear , identified as a pilot who had flown missions for the CIA. [ 5 ] : ch 7 On August 25, 1988, Lear authored a post titled "The UFO Coverup" which incorporated elements of mythos from Paul Bennewitz , a ufologist who was later revealed to have been fed disinformation by American counter-intelligence agent Richard C. Doty . [ 5 ] : ch 7 [ 4 ] Cooper soon visited Lear, and the two spent much time together from 1988 to 1990. [ 5 ] : ch 7
Cooper's views were heavily influenced by Lear and his story of alien collusion with secret governmental forces. [ 112 ] In 1989, the two released an "indictment" against the US Government for "aiding and abetting and concealing this Alien Nation which exists in our borders". [ 112 ] In 2018, columnist Colin Dickey noted Lear and Cooper's influence, writing "in the early years [UFO writers] did not, by and large, embrace strong political positions. They were the tip of a spear asserting that the number one thing we had to fear was not little green men, but the government that colluded with them, appropriating their technology against us." [ 112 ]
Cooper and Lear's collaboration lasted until the 1989 MUFON conference where Bill Moore admitted to spreading lies to UFO researchers. In response, Cooper accused Lear of being a CIA plant. [ 112 ]
In 1991, Cooper published the influential conspiracy work Behold a Pale Horse which claimed that Kennedy was killed after he "informed Majestic 12 that he intended to reveal the presence of aliens to the American people". [ 113 ] [ 5 ] Behold a Pale Horse became 'wildly popular' with conspiracy theorists and went on to be one of the most-read books in the US prison system. [ 114 ] [ 5 ]
Cooper described the "Illuminati" as a secret international organization, controlled by the Bilderberg Group , that conspired with the Knights of Columbus , Masons , Skull and Bones , and other organizations. Its ultimate goal, he said, was the establishment of a New World Order . According to Cooper, the Illuminati conspirators not only invented alien threats for their own gain, but actively conspired with extraterrestrials to take over the world. [ 2 ] : 60 Cooper produced regular shortwave-radio broadcasts that were popular with conspiracy theorist and anti-government activists. Cooper reportedly met with Timothy McVeigh shortly before the Oklahoma City bombing . [ 2 ] : ix In November 2001, Cooper was shot and killed by law enforcement during an attempted arrest. [ 2 ] : 165
Lear introduced journalist George Knapp to UFO whistle-blower Bob Lazar and his tales of Area 51 . [ 115 ] In November 1989, Bob Lazar appeared in a special interview with Knapp on Las Vegas TV station KLAS to discuss his alleged employment at S-4. [ 1 ] : 274 [ 116 ]
Lazar's claims were widely discredited. Lazar never obtained the degrees he claims to hold from MIT and Caltech. [ 117 ] [ 118 ] In 1990, Lazar was arrested for aiding and abetting a prostitution ring. This was reduced to felony pandering , to which he pleaded guilty. [ 119 ] [ 120 ] [ 121 ] By 1991, Nevada press reported tourists traveling to the Groom Lake region in hopes of glimpsing UFOs. [ 122 ]
Lear remained a prominent voice in the UFO conspiracy theory community until his death in 2022, making multiple appearances on TV and online shows, including Coast to Coast AM . [ 123 ] Lazar continues to spread tales of Area 51 through media appearance. In 2018, he was featured in producer George Knapp and Jeremy Corbell 's documentary Bob Lazar: Area 51 & Flying Saucers [ 124 ] and Joe Rogan 's podcast . [ 125 ] [ 126 ] [ 127 ]
In 2005, UFO researcher Victor Martinez received an anonymous email about Project Serpo, a supposed "exchange program" where Americans were sent to live on an alien homeworld. [ 4 ] : x The anonymous informant and three other supposed-corroborating witnesses were revealed to be accounts operated by Rick Doty. [ 4 ] : x He participated in the 2013 documentary Mirage Men about his campaign against Bennewitz, Howe, and others.
Doty continues to spread UFO stories, appearing in conferences, films, and the 2021 TV series UFO . [ 128 ]
The 1990s saw as proliferation of conspiracy media along with the rise of internet culture. Images of a gray alien were called the " smiley face " of the 1990s. [ 129 ] The 1991 film JFK popularized Kennedy assassination conspiracy theories, specifically the writings of Jim Marrs . By 1997, Marrs was arguing that Kennedy's murder was connected to a UFO conspiracy. [ 2 ] : 147 In the 1992 comedy Sneakers , Dan Ackroyd plays a conspiracy theorist convinced that Eisenhower made a treaty with space aliens to permit cattle mutilations. [ 130 ] : x [ 131 ] : 805 [ 132 ]
In September 1993, The X-Files premiered focused on UFO conspiracy theories. Barkun observes that the show's oft-repeated mantra "Trust No One" serves to "neatly encapsulate the conspiracist's limitless suspicions", [ 2 ] : 2 while Gulyas describes the series as "an exemplar of paranoid television, embracing the
mounting paranoia and tensions of the 1990s". [ 3 ] : xii
The X-Files incorporated elements of UFO conspiracy theories, including a shadowy cabal of conspirators, a Roswell coverup, Men in Black, and a 'treaty' allowing alien abduction. In the episode “ Musings of a Cigarette Smoking Man ”, the series antagonist is revealed to have been responsible for assassinations of John F. Kennedy and Martin Luther King. [ 3 ] : 89–90 [ 4 ] : x The 1998 X-Files film explicitly homaged Bill Cooper, with on-screen characters talking about "Silent Weapons for Quiet Wars"—an influential chapter title from Cooper's book. [ 4 ] : x
The success of The X-Files inspired similar works. The 1994 made-for-TV movie Roswell , broadcast on the Showtime Network, dramatized tales of a UFO crash and coverup. The 1996 blockbuster Independence Day introduced a global audience to the idea of a recovered Roswell craft being secretly studied at Area 51. Episodes of the 1996 show Dark Skies featured the tagline "History as we know it is a lie". The show provided an alternative history that "wove nearly every significant historical event of the past fifty years into a paranoid vision of extraterrestrial infiltration." [ 3 ] : ch. 4
The following year, Men in Black re-cast the supposed secret agents as comic heroes rather than sinister villains. [ 6 ] : 179 While prior conspiracy films had taken the perspective of conspiracy theorists, Men in Black took the perspective of the conspirators. The film was the first time 'Men in Black" appeared in a major movie, cementing the men in black in popular culture. [ 133 ] The film 'poked fun' at government debunking, with one of the Men in Black telling a witness "The flash of light you saw was not a UFO, swamp gas from a weather balloon was trapped in a thermal pocket and reflected the light from Venus " -- a combination of 'official explanations' the Air Force has offered for UFO reports. [ 134 ]
Alien Autopsy: Fact or Fiction is a 1995 pseudo-documentary containing grainy black and white footage of a hoaxed alien autopsy . [ 3 ] : 93 [ 135 ] [ 136 ] In 1995, film purporting to show an alien autopsy conducted shortly after the Roswell incident was released by British entrepreneur Ray Santilli . [ 137 ] : 1101 The footage aired on television networks around the world. [ 138 ] The program was an overnight sensation, [ 139 ] : 32 with Time magazine declaring that the film had sparked a debate "with an intensity not lavished on any home movie since the Zapruder film ". [ 140 ]
The program was thoroughly debunked. The autopsy footage was filmed on an inexpensive set constructed in a London living room. Its alien bodies were hollow plaster casts filled with offal , sheep brains, and raspberry jam. [ 141 ] Multiple participants in Alien Autopsy stated that misleading editing had removed their opinions that the footage was a hoax. [ 140 ] [ 139 ] Santilli admitted in 2006 that the film was a fake. [ 139 ]
The Branton Files are a series of documents espousing various conspiracy theories circulated on the internet since at least the mid-1990s. They are most often attributed to Bruce Alan Walton who claims to have been a victim of alien abduction and had contact through "altered states of consciousness" with humans "living in the inner earth". The files have been characterized as "high fantasy" filled with "complex and convoluted conspiracism". [ 2 ] : 123 [ 15 ] The content influenced David Icke. [ 2 ] : 123–124
In the 1990s, author David Icke proposed that world elites are actually "reptilian" aliens. [ 2 ] : 68 Scholars note that the science-fiction franchise V had told a similar story from 1983 to 1984. [ 3 ] : 30
On March 13, 1997, there were widespread reports of unidentified lights over Nevada and Arizona. Days later, 39 members of UFO group Heaven's Gate were found dead in a mass suicide.
Arizona Governor Fife Symington III held a press conference , joking that "they found who was responsible" and revealing an aide dressed in an alien costume. Later, in 2007, Symington reportedly told a UFO investigator he'd had a personal close encounter with an alien spacecraft but remained silent "because he didn't want to panic the populace". According to Symington, "I'm a pilot and I know just about every machine that flies. It was bigger than anything that I've ever seen. It remains a great mystery. Other people saw it, responsible people... I don't know why people would ridicule it". [ 142 ] [ 143 ] [ 144 ] [ 145 ]
In the early 2000s, the concept of "disclosure" became increasingly popular in the UFO conspiracy community: that the government had classified and withheld information on alien contact and full disclosure was needed, and was pursued by activist lobbying groups. In 1993, Steven M. Greer founded the Disclosure Project to promote the concept. In May 2001, Greer held a press conference at the National Press Club in Washington, D.C. that demanded Congress hold hearings on "secret U.S. involvement with UFOs and extraterrestrials". [ 146 ] Disclosure Project's claims were met with by derision by skeptics and spokespeople for the United States Air Force . [ 147 ] According to religious scholar Joseph Laycock, the idea behind "disclosure" predates modern UFO culture: in 1946, the editor of Amazing Stories magazine wrote, “If you think responsible parties in world governments are ignorant of the fact of space ships visiting Earth, you just don’t think the way we do”. [ 32 ]
In December 2017, The New York Times published a story about the Advanced Aerospace Threat Identification Program , a Defense Intelligence Agency program to study "unidentified aerial phenomenon" [ 148 ] The program's director, Luis Elizondo claimed there is a government conspiracy to suppress evidence that UFOs are of "non-human" origin. [ 149 ] [ 150 ] [ 146 ]
U.S. news media and Congressional leadership were criticized for giving credibility to unverified stories of alien visitations and government cover ups. Some commentators expressed concerns about "UFO cults and cult-like behavior, violence and cyber-stalking by UFO zealots". [ 146 ] Astronomers, science writers and other experts observed that the increase in media publicity and government interest contrasted with "the widely held sentiment among scientists that, for decades, the media has lavished too much attention on sensational claims that vague lights in the sky are actually extraterrestrial spacecraft". Despite pressure by "disclosure" advocates fueled by anecdotes and hearsay of a government cover up, skeptical investigator Robert Sheaffer said "there is not going to be any "big reveal". [ 151 ]
In June 2020, Donald Trump , when asked if he would consider releasing more information about the Roswell incident, said, "I won't talk to you about what I know about it, but it's very interesting." [ 152 ] In December 2020, former president Obama joked with Stephen Colbert , "It used to be that UFOs and Roswell was the biggest conspiracy. And now that seems so tame, the idea that the government might have an alien spaceship." [ 153 ]
From 2019 to 2021, David Grusch was the representative of the National Reconnaissance Office to the Unidentified Aerial Phenomena Task Force ; Beginning in 2023, Grusch publicly claimed elements of the US government and its contractors were covering up evidence of UFOs and their reverse-engineering. [ 154 ] [ 155 ] [ 156 ] Within the UFO community, Grusch's claims were seen as an indication that long-awaited "disclosure" was imminent. [ 32 ] [ 157 ]
Grusch "became a hot new topic in the UFO world" and his claims "ignited a new wave of interest in extraterrestrial life", [ 158 ] but his story was criticized for its lack of verifiable evidence. According to science writer Mick West , "Grusch presented no documents (in public) and relied mostly on what he claimed to have been told by unnamed sources, things he could not share in detail". [ 157 ] Scholars note Grusch's claims of a government cover-up of alien visitation are "broadly considered untrue by the majority of the scientific community". [ 158 ]
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Uranium hydride may refer to the following chemical compounds:
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Uranium(IV) hydride is a chemical compound with the chemical formula U H 4 , a metal hydride .
In 1997, Souter et al. reported the production of UH 4 reacting laser ablated uranium atoms with di hydrogen and capturing the product on solid argon. The assignment of the structure was made using infrared spectroscopic evidence supported by DFT calculations. [ 1 ] Uranium(IV) hydride has a quasi-tetrahedral ( C s ) structure. UH 4 is formed by the successive insertion of uranium into two hydrogen molecules:
Further reaction with hydrogen, only produces dihydrogen complexes: UH 4 (H 2 ) n (1 ≤ n ≤ 6). [ 2 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it .
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Uranium triiodide is an inorganic compound with the chemical formula UI 3 . It is a black solid that is soluble in water.
Uranium triiodide can be obtained from the direct reaction of its constituent elements: [ 3 ]
When the reaction is conducted in tetrahydrofuran (THF), the product is the blue complex UI 3 (THF) 4 . [ 4 ]
It crystallizes in the orthorhombic crystal system ( plutonium tribromide -type) in the space group Ccmm with the lattice parameters a = 432.8 pm, b = 1401.1 pm, and c = 1000.5 pm and four formula units per unit cell . [ 1 ]
Uranium triiodide can be used as a Lewis acid catalyst for various Diels-Alder reactions carried out under mild conditions. [ 5 ]
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Uranium(IV) iodide , also known as uranium tetraiodide , is an inorganic chemical compound . It is a salt of uranium in oxidation state +4 and iodine.
Uranium tetraiodide can be prepared from the reaction between uranium and an excess of iodine. [ 2 ]
Uranium tetraiodide is a black solid and forms needle-like crystals. Upon heating, it dissociates into uranium triiodide and iodine gas. [ 2 ] It crystallizes in the monoclinic crystal system, space group C2/c. [ 1 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it .
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A UIMID (user identity module identifier) is a 32-bit Electronic Serial Number (ESN) stored in a R-UIM or CSIM ('smart card') used for TDMA or CDMA2000 phones (mainly the latter). It is given a different name to avoid confusion with the hardware ESN stored in the phone. In all known systems the UIMID displaces the ESN in signaling (based on setting bit 1 of the 'UsgInd' field to '1' in the card). Because the UIMID is allocated from the same numbering space as ESN its existence is transparent to the network. The reason the UIMID is transmitted instead of the ESN is because the card contains the MIN or IMSI and devices such as the HLR running the Asbi
mobility management protocol insist on a static association between these identifiers for subscription validation. The HLR will store the MIN or IMSI alongside the ESN in each record, and if an ANSI-41 message is received containing a different pair it will be rejected as invalid.
UIMID codes are allocated by the TIA using industry-defined guidelines and with codes that have been transferred from the ESN administrator (also the TIA). [ 1 ]
ESN and UIMID codes were exhausted by late 2008 at which point only reclaimed codes could be assigned to manufacturers including portions of blocks assigned to manufacturers but never used and portions used for technologies other than CDMA2000 . The TIA stopped accepting applications for UIMID blocks on June 30, 2010. Only one assignment has been made since 2010.
The replacement identifier for UIMID is EUIMID although for backwards compatibility a pseudo-UIMID (pUIMID) is still retained in cards. The pUIMID is composed of the prefix 0x80 to make it distinct from unique UIMID codes and a 24-bit SHA-1 hash of the EUIMID. pUIMID codes are not unique as there are only 2 24 of them and many times more EUIMID codes. The pUIMID can usually be used in place of a unique UIMID, except when uniqueness is important.
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The UKM Medical Molecular Biology Institute , usually referred to as UMBI, is a biomedicine and cancer research institute located in Bandar Tun Razak , Kuala Lumpur , Malaysia . The institute is one of research institute in National University of Malaysia (UKM). UMBI was established in 2003. [ 1 ] The institute has been recognized as a Center for Excellence in Higher Education (HICoE) in 2009 by the Prime Minister of Malaysia. [ 2 ]
The UKM Medical Molecular Biology Institute (UMBI) was founded as one of the Centre of Excellence in UKM after the approval from the National University of Malaysia senate meeting. UMBI was officially established in July 2003 with the operating budget allocated to this new institute of RM 25 thousand. [ 3 ] Professor Datuk Dr. A Rahman A Jamal has been appointed as a founding director of UMBI since 2003 until his tenure ends in 2017. [ 4 ]
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UKS 2323-326 is a very low mass and faint dwarf irregular galaxy located in the local group at a distance of 1.3 mpc from Earth . [ 2 ] The galaxy is a member of the Sculptor group . [ 3 ] The galaxy has a young stellar population that recently (~100 mya [ 3 ] ) formed defined red giant branch (RGB) stars but no significant amount of H ll emissions . It also has no detected hot dust or polycyclic aromatic hydrocarbons . [ 4 ] [ 5 ]
The galaxy shape is amorphous but surprisingly circular. The central region of UKS 2323-326 has a concentration of several tens of bright stars . Farther from the center of the galaxy are fewer bright stars and more faint stars. [ 3 ] There are a number of red giant branch (AGB) stars that exist in UKS 2323-326 and a lack of H II regions . [ 4 ]
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The UK Academy for Information Systems ( UKAIS ) is an active combination of a traditional learned society , communications channel and pressure group . It is a conduit for communication between industry and academia to ensure that relevant courses can be designed and research initiatives established throughout the UK . The UKAIS has attempted to create a 'uniform' definition of Information Systems: the means by which people and organisations, utilising technologies, gather, process, store, use and disseminate information.
By aiming to continually improve the quality and relevance of teaching through innovative and rigorous research the society contributes to both academic development and excellence in IS practice throughout the UK. Part of their role has been to establish links between commercial, government and academic organisations. Teaching, research and practice in the field are supported by UKAIS through its annual conference, PhD consortia, workshops, online events, research grants, teaching and learning awards, and membership benefits (e.g. supporting early career researchers through its mentoring scheme).
The UK Academy for Information Systems is a signatory of the San Francisco Declaration on Research Assessment (DORA).
The society arose from a meeting in 1993 of leading UK academics in information systems. Concerns were expressed at the meeting about the way IS teaching and research were funded which stemmed from a lack of recognition of IS as a growing and important academic discipline. The UKAIS was established in 1994 to remedy this situation as a charity, whose aims are to provide a better knowledge of IS within the UK and to provide a forum for discussing issues in IS teaching and research. It also aims to be influential in obtaining better understanding of the uniqueness of the subject by HEFCE , the UK Research Councils , professional bodies, UK business and Government. They have successfully achieved recognition that IS is not being dealt with sufficiently by such bodies and have suggested ways of improving the situation. [ 1 ]
Beyond this the work of the society is within the domain involving the study of theories and practices related to the social and technological phenomena, which determine the development, use and effects of information systems in organisations and society.
The UKAIS Annual Conference is one of the key academic events in the Information Systems calendar within the UK, and attracts leading scholars from the UK and overseas.
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The UK Battery Industrialisation Centre (UK BIC) is a research centre in the United Kingdom, to develop new electrical batteries , for the British automotive industry . UKBIC provides over £60 million worth of specialized manufacturing equipment, supporting manufacturers, entrepreneurs, researchers, and educators in battery technology development. It has accelerated low carbon R&D, contributing to the UK's Net Zero goal by 2050. [ 2 ]
Funding for the UK Battery Industrialisation Centre (UKBIC) is supplied by United Kingdom Research and Innovation (UKRI). This financial support was announced on 29 November 2017. The facility was officially inaugurated by the British Prime Minister, Boris Johnson , in July 2021, as documented on the UKBIC's official website.
The UKBIC facility is located outside Coventry , adjacent to Coventry airport and about half a mile east of the junction between the A46 and A45 . This is just outside the city boundary, in the extreme north of Warwick District , Warwickshire.
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The UK Centre for Astrobiology was set up at the University of Edinburgh in 2011 [ 1 ] [ 2 ] by Charles Cockell . It was set up as a UK node, formally affiliated as an international partner with the NASA Astrobiology Institute (NAI) alongside other national nodes until the NAI's dissolution in 2019. It was established as a virtual centre to sit at the interdisciplinary boundary of planetary sciences/astronomy and biological/earth sciences investigating numerous aspects of life in the universe, specifically 'how habitable worlds form in the Universe and how life emerges, proliferates and leaves traces on these worlds' as well as engaging in work on the robotic and human exploration of space and in space ethics, philosophy and governance.
In the ten years from 2011 to 2021, the UKCA led or was affiliated with over 150 scientific papers in this period. Its published scientific work encompassed life in extremes, exoplanet biosignatures, biosignatures of life on Mars and early Earth, analogue research and other areas encompassing the habitability of planetary bodies. For example, the Centre oversaw the launch and implementation of the first biological mining experiment in space on the International Space Station in support of long-term human space settlement, demonstrating the use of microorganisms to mine economically important elements in space. [ 3 ] The centre's members were involved in Mars analog missions, expeditions to numerous extreme environments, as well as space missions such as NASA's Curiosity rover mission. The centre was microbiology lead on the NASA BASALT project (Biologic Analog Science Associated with Lava Terrains) to develop NASA plans for the human exploration of Mars. [ 4 ] It was scientific coordinator of the EU Framework 7 project MASE (Mars Analogues for Space Exploration) investigating microbial life in numerous Mars-like environments. [ 5 ] It organised a number of conferences in this ten-year period, hosting UK and European-level astrobiology conferences.
The UKCA launched a number of scientific and technical initiatives. It set up the world's first underground astrobiology laboratory in the Boulby Underground Science Laboratory, running a program MINAR (MIne Analog Research) from 2013 which brought in international teams from NASA, ESA, India, and universities across the UK and internationally to study life in the deep subsurface and test planetary exploration equipment. [ 6 ] [ 7 ] [ 8 ] In particular, MINAR focuses on the synergies between planetary exploration and mining, using the active mine environment to test technologies that create synergies between these two areas, such as rovers to carry out 3D mapping and gas detection for safety and structural assessments in mines and the exploration of other planets. [ 9 ] The initiative hosted the NASA Spaceward Bound project and ESA astronaut training.
The centre also launched numerous education initiatives. For example, the Centre set up and hosted the astrobiology academy, an initiative to bring teachers together to develop curriculum and lesson plans that used astrobiology to teach science in schools. The initiative produced lesson plans that were used to launch astrobiology in Scottish primary and secondary schools in association with the Scottish government's RAISE programme (Raising Aspiration in Science Education). The material became part of the National Resource Guide and the National Education Portal. It has been used to teach astrobiology across India in collaboration with the A.P.J. Abdul Kalam Centre , reaching tens of thousands of students.
In 2016, the centre, in collaboration with the Scottish Prison Service , launched Life Beyond , which involved prisoners in the design of settlements beyond Earth. Scottish prisoners published two books on settlement designs for the Moon and Mars. [ 10 ] [ 11 ] This led to the development of a distance learning Life Beyond course, which can be undertaken by any prisoner around the world, [ 12 ] distributed to English and Welsh prisons in collaboration with the Prisoners' Education Trust . Given the similarities between prisons and planetary stations (confinement, interdependence), the project tapped into prisoners' experience of confinement to imagine life beyond Earth, involving them in literacy, science, governance and civic responsibility. [ 13 ] Life Beyond was cited by EuroPris as an example of best education practice in European prisons. [ 14 ]
The centre led initiatives in considering space governance and space philosophy. For example, between 2013 and 2015 it led three international workshops to consider the future of forms of liberty beyond Earth, investigating the political philosophy of extraterrestrial settlement and in particular the effects of the extraterrestrial environment on forms of freedom. This led to three multi-author books published with Springer on the political philosophy of liberty beyond Earth. [ 15 ] [ 16 ] [ 17 ]
The centre launched and led undergraduate and postgraduate astrobiology courses at the University of Edinburgh leading to a textbook published with Wiley-Blackwell on Astrobiology, which is in its second edition. [ 18 ] It led and offered the world's first massive open on-line course (MOOC) in astrobiology in 2012 with Coursera, which attracted over 150,000 students.
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The UK Centre for Materials Education (UKCME) was one of 24 subject centres within the Higher Education Academy (HEA). It supported teaching and learning in Materials Science and related disciplines. The Centre was established in 2000 as part of the Learning and Teaching Support Network (LTSN), later subsumed within the HEA. It was directed from its inception by Professor Peter Goodhew and ceased operating in 2010.
The Centre was based at the University of Liverpool and worked with individual academics, departments, professional bodies, employers and students to develop and share excellent practice that would enhance the learning experience.
The Centre funded and supported programmes to develop and evaluate innovative approaches to teaching Materials Science. The Centre also maintained an extensive database of resources relevant to materials education. Lecturers could find material to use in their teaching, whilst students would find items to help support their learning. The database also included resources on the processes of learning and teaching for those wishing to further develop their approach.
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The UK Molecular R-Matrix codes are a set of software routines used to calculate the effects of collision of electrons with atoms and molecules. The R-matrix method is used in computational quantum mechanics to study scattering of positrons and electrons by atomic and molecular targets. The fundamental idea was originally introduced by Eugene Wigner and Leonard Eisenbud in the 1940s. [ 1 ] [ 2 ] The method uses the fixed nuclei approximation , where the molecule's nuclei are considered fixed when collision occurs and the electronic part of the problem is solved. This information is then plugged into calculations which take into account nuclear motion. The UK Molecular R-Matrix codes were developed by the Collaborative Computational Project Q (CCPQ).
The CCPQ and CCP2 have supported various incarnations of the UK Molecular R-matrix project for almost 40 years. [ clarification needed ] The UK Molecular R-Matrix Group is actually a subgroup of CCP2, and their codes are maintained by Professor Jonathan Tennyson and his group of researchers. Advances in research have shown that the UK Molecular R-matrix codes can be used to explain scattering problems involving light molecular targets. [ 3 ]
Quantemol-N (QN) is software that allows the UK molecular R-matrix codes, which is used to model electron-polyatomic molecule interactions, to be employed quickly with reduced set-up times. QN is an interface that simplifies the process of using the sophisticated UK molecular R-Matrix codes. [ 4 ] [ 5 ]
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The UK Museum of Ordure ( UKMO ) was an online arts project initiated with the intention to explore the curatorial value of ordure , or human waste . It consisted of a website [ 1 ] which initially collected public submissions of ordure, as well as documenting various installations undertaken by the museum. It has since been renamed Museum of Ordure [ 2 ] in recognition that its remit is international in scope.
Founded by Stuart Brisley, Geoff Cox and Adrian Ward in 2001, it now consists of the members Rosse Yael Sirb as acting director, as well as Maya Balgioglu, Stuart Brisely, Geoff Cox, and Les Liens Invisibles. [ 3 ]
It currently defines itself as follows:
The Museum of Ordure explores the cultural value of ordure through its projects and ongoing public collections.
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The UK National Quantum Technologies Programme ( UKNQTP ) is a programme set up by the UK government [ 1 ] to translate academic work on quantum mechanics , and the effects of quantum superposition and quantum entanglement into new products and services. It brings UK physicists and engineers together with companies and entrepreneurs who have an interest in commercialising the technology.
The "second quantum revolution", or "quantum 2.0" is a term that is often used to describe quantum technologies based on superposition and entanglement. Originally described in a 1997 book by Gerard J. Milburn , [ 2 ] which was then followed by a 2003 article by Jonathan P. Dowling and Gerard J. Milburn , [ 3 ] [ 4 ] as well as a 2003 article by David Deutsch . [ 5 ] These technologies use equipment such as highly stabilised laser systems, magneto-optical traps , cryogenic cooled solid state devices, ion traps and vacuum systems to create, manipulate and then use quantum effects for a number of different purposes. These include: quantum information processing, such as quantum computing , quantum simulation , quantum secure communications , quantum sensing and metrology and quantum imaging , and are widely believed to offer capabilities that will out-perform existing and future classical technologies.
The programme has contributed to the vast number of quantum technologies start-ups within the UK. Examples include Orca Computing, Universal Quantum, Oxford Ionics, [ 6 ] Delta g and Cerca Magnetics.
The vision of the UK National Quantum Technologies programme is to "create a coherent government, industry and academic quantum technology community that gives the UK a world-leading position in the emerging multi-billion-pound new quantum technology markets, and to substantially enhance the value of some of the biggest UK-based industries." [ 7 ] [ 8 ]
In 2013, a group of key stakeholders were brought together by DSTL at Chicheley Hall . The UKNQTP was then initiated by a £270 million investment by the UK Chancellor of the exchequer, George Osborne in the Autumn Statement 2013. [ 9 ] In addition to this, the UK Defence Science and Technology Laboratory (Dstl) separately announced a £30 million investment into a programme to produce demonstrator devices.
The primary focus of the UKNQTP are five 'hubs' for quantum technologies: [ 10 ] [ 11 ]
Past hubs include:
The UKQTP is advised by the Quantum Technologies Strategic Advisory Board, which is chaired by Professor David Delpy , it also consists of Professor Sir Peter Knight , Baroness Neville-Jones , Professor Gerald Milburn, Professor Ian Walmsley and other leading individuals from industry, academia and public sector.
The programme is delivered by several UK public bodies: UK government Department for Science, Innovation and Technology , EPSRC , STFC , Innovate UK , Dstl , NPL , GCHQ and Innovate UK Business Connect.
The UKQTP has received some attention from the UK media, with an interview with Professor Miles Padgett on the BBC Radio 4 Today programme on 11 November 2015 and articles in New Scientist , [ 22 ] and Nature materials [ 23 ]
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In computing , UMA Acceleration Architecture (UXA) is the reimplementation of the EXA graphics acceleration architecture of the X.Org Server developed by Intel . Its major difference with EXA is the use of GEM , replacing Translation Table Maps . [ 1 ] In February 2009 it became clear that UXA would not be merged back into EXA. [ 2 ]
Intel is transitioning from UXA to SNA .
In May 2009 it was announced that Ubuntu would migrate their graphics acceleration for the Ubuntu 9.10 release to UXA. [ 3 ]
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UMS/UHD/UHX is a forklift truck in the Tergo series from the Swedish manufacturer Atlet AB . It differs from traditional forklift truck design philosophy in that it is entirely designed around the operator. By letting the forklift truck adjust to the operator's skills and body structure the UMS/UHD/UHX is an example of how ergonomics is an important part of machine efficiency.
Atlet, Henrik Moberger, Tärnan Reportage AB 2008. ISBN 978-91-633-1924-2
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The UNECE Environmental Performance Review ( EPR ) (French: Examen des performances environnementales – EPE) is an assessment process to evaluate the progress made by individual countries in improving their environmental policies. The EPRs are carried out under the auspices of the Committee on Environmental Policy of the United Nations Economic Commission for Europe ( UNECE ).
EPRs provide countries with independent, external assessment of how they handle the pollution reduction process, manage their natural resources and protect nature and environment. EPRs also evaluate progress made by governments in meeting their international commitments on environment and sustainable development such as the Sustainable Development Goals . [ citation needed ]
The UNECE Programme on EPRs was inspired by a sister programme launched by the Organisation for Economic Co-operation and Development (OECD) for its member States in 1991. In 1993 at the second "Environment for Europe" Ministerial Conference in Lucerne, Switzerland, UNECE was asked to run an EPR Programme for its member States that were not covered by the OECD EPR Programme. [ 1 ] Therefore, the UNECE EPRs focus on the countries of Eastern Europe , Caucasus , Central Asia and South-Eastern Europe known as economies in transition . [ citation needed ]
The first EPR cycle established the baseline conditions regarding state of environment and national environmental policies. The second EPR cycle looked into the implementation and financing of environmental policies, integration of environmental concerns into economic sectors, and promotion of sustainable development. [ 2 ] By now, almost all eligible UNECE member countries have been reviewed twice. [ citation needed ]
The third review cycle was initiated at the seventh "Environment for Europe" Ministerial Conference ( Astana , Kazakhstan, 2011). [ 3 ] It focuses on environmental governance and green economy . It also analyses countries' cooperation with international community and environmental mainstreaming in priority sectors. [ citation needed ]
Topics for the EPR report are selected by the country which requests an EPR. EPRs cover horizontal issues such as legislation and policy development, compliance and enforcement, use of economic instruments for environmental protection, environmental information and education. They discuss in detail the issues of water management , air protection, waste management , biodiversity and protected areas , and integration of environmental considerations into selected sectors such as agriculture , energy , forestry , industry , transport , or health . Cross-cutting issues, such as environmental monitoring and climate change , are also addressed in the EPRs. [ citation needed ]
The EPR is a voluntary exercise undertaken only at the request of a country. Once the request is received, the UNECE secretariat organizes a preparatory mission to the country during which the structure of the review is agreed. [ citation needed ]
Upon completion of preparatory activities, international experts embark on a review mission to the country where they meet with national and local governmental representatives, international organizations, civil society groups and the private sector to gain an in-depth understanding of specific environmental issues. International experts are provided by governments and international organizations, such as OECD , United Nations Environment Programme (UNEP), United Nations Economic Commission for Africa (UNECA), United Nations Development Programme (UNDP), United Nations International Strategy for Disaster Reduction (UNISDR), United Nations Office for the Coordination of Humanitarian Affairs (OCHA), European Environment Agency (EEA), World Health Organization (WHO) and World Bank (WB). At the end of the review mission, the experts prepare chapters that are compiled into a draft EPR report. [ 4 ]
The draft EPR report is first reviewed by the EPR Expert Group, which consists of representatives from ten UNECE member countries elected for three years. During the review, the members of the Expert Group discuss the draft EPR report, with particular attention given to the conclusions and recommendations. Delegation from the reviewed country is invited to participate in the meeting and interact with the Expert Group. At the end of review, the report is amended and submitted to the Committee on Environmental Policy for peer review . [ 5 ]
At the annual session of the Committee on Environmental Policy, UNECE member States and a high-level delegation from the country discuss and review EPR recommendations. The Committee on Environmental Policy adopts the recommendations of the EPR report and the country commits to implement them. [ citation needed ]
The report is then finalized and published. An official launch event of the EPR publication usually takes place in the country under review. Typically, the launch event is accompanied by a press conference with high-level governmental representation. [ citation needed ]
When an EPR is conducted in the country for the second or the third time, governmental officials usually prepare a self-evaluation of implementation of recommendations of the previous review. The outcomes of self-evaluation are reviewed by the team of international experts and become part of the EPR report. [ citation needed ]
List of countries reviewed. [ 6 ]
In 2012–2013, the UNECE EPR Programme undertook a review of a non-UNECE country – Morocco . [ 7 ] The EPR of Morocco [ 8 ] was carried out in cooperation with UNECA to facilitate the transfer of the EPR methodology and know-how from UNECE to UNECA. [ 9 ] In 2017, the UNECE EPR Programme undertook a review of another non-UNECE country – Mongolia . The review was carried out in cooperation with ESCAP . [ citation needed ]
By providing concrete, tailor-made, recommendations, the EPR reports assist countries to reconcile their economic and social development with environmental protection. [ citation needed ]
Unlike for ratified international treaties, the countries do not have a formal legal obligation to implement EPR recommendations. However, governments do make serious efforts to implement the recommendations. The average rate of implementation of EPR recommendations is about 75 per cent. [ citation needed ]
The practical measures that have been implemented as a result of the EPRs include the strengthening of environmental institutions and governance, the adoption of new legislation and policy documents, introduction of economic instruments for environmental protection, better integration of environmental considerations into sectoral policies, increase of governmental expenditures for environmental protection and other measures. [ citation needed ]
Since 2017, EPRs include the review of relevant goals and targets of the 2030 Agenda for Sustainable Development and provide recommendations to the countries on the achievement of SDGs. [ 10 ]
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https://en.wikipedia.org/wiki/UNECE_Environmental_Performance_Reviews
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The UNESCO Science Prize is a biennial scientific prize awarded by the United Nations Educational, Scientific and Cultural Organization (UNESCO) to "a person or group of persons for an outstanding contribution they have made to the technological development of a developing member state or region through the application of scientific and technological research (particularly in the fields of education, engineering and industrial development)." [ 1 ]
The candidates for the Science Prize are proposed to the Director-General of UNESCO by the governments of member states or by non-governmental organizations . All proposals are judged by a panel of six scientists and engineers. The prize consists of US$ $15,000 , an Albert Einstein Silver Medal , and is awarded in odd years to coincide with UNESCO's General Conference. [ 1 ]
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https://en.wikipedia.org/wiki/UNESCO_Science_Prize
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uNETix is an early implementation of UNIX for IBM PC systems. It was not a "true" UNIX , but was written from scratch for the PC without using any code from System V .
uNETix only supported a single user. However, it maintained closer compatibility with standard versions of UNIX than early versions of QNX . uNETix' multiple windows capability was possibly the first implementation of windowing in a Unix-like operating system . [ 1 ] Up to 10 windows were supported, which could each run independent tasks and could have individual foreground and background colors set with a special color command.
Published by Lantech Systems, Inc, uNETix had a list price in 1984 of US$130, [ 1 ] but was discounted and advertised at US$99 (300 USD today). [ 2 ] The minimum RAM requirement was 256 KB, but a 256 KB machine would only be able to support single-tasking; multitasking required 512 KB. It had an emulation environment for MS-DOS that could run DOS 1.1 programs in one window while UNIX programs ran in other windows. [ 3 ] Its major weaknesses were slow speed and lack of hard disk support. uNETix came with a full assembly language programming environment, and a C compiler was optional. Lantech claimed that the C compiler was the first available for the x86 architecture .
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The UNIVAC 9000 series (9200, 9300, 9400, 9700) is a discontinued line of computers introduced by Sperry Rand in the mid-1960s to compete with the low end of the IBM System/360 series. The 9200 and 9300 (which differ only in CPU speed) implement the same restricted 16-bit subset of the System/360 instruction set as the IBM 360/20 , [ 1 ] while the UNIVAC 9400 implements a subset of the full 32-bit System/360 instruction set. [ 2 ] The 9400 was roughly equivalent to the IBM 360/30.
In 1972, UNIVAC stopped development of its 9000 series systems, in favor of hardware acquired from RCA , now called UNIVAC Series 90 .
The 9000 series uses monolithic integrated circuits for logic [ 3 ] [ 4 ] and plated-wire memory ; [ 3 ] the latter functions somewhat like core memory but uses a non-destructive read. Since the 9000 series was intended as direct competitors to IBM, they use 80-column cards and EBCDIC character encoding.
The family includes the 9200, 9300, 9400, and 9480 systems. The UNIVAC 9200 and 9300 were marketed as functional replacements for the UNIVAC 1004 and as direct competitors to the IBM 360/20. The printer-processor is one cabinet, the power supply and memory another and the card reader and optional card punch make an L-shaped configuration. Memory is 8 KB expandable to 32 KB. [ 1 ] The 9200 II and 9300 II models, introduced in 1969, are extensions of the original 9200 and 9300 systems. [ 3 ]
The printer differs from earlier UNIVAC printers, being similar to IBM's "bar printer" of the same era. It uses an oscillating-type bar instead of the drums that had been used until this point, and runs at speeds up to 300 lines per minute.
As Sperry moved into the 1970s, they expanded the 9000 family with the introduction of the 9700 system in 1971. [ 5 ] The 9700 was said to be three to five as powerful as the 9400, twice as powerful as the IBM System/360 Model 50 , and less costly than the IBM System/370 Model 145 . [ 6 ] A lower-cost replacement for the 9400, the 9480, was announced in 1973; it used MOS semiconductor memory rather than plated-wire memory. [ 7 ]
The 9200 and 9300 run the Minimum Operating System , previously known as NCOS - Non Concurrent Operating System. This system was loaded from cards , but thereafter also supported magnetic tape or magnetic disk for programs and data. [ 8 ] The 9400 and 9480 run a real-memory operating system called OS/4 . [ 9 ] A new operating system for the 9700, called OS/7 was under development, but was discontinued in 1975. [ 10 ] [ 11 ]
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An explosive (or explosive material ) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light , heat , sound , and pressure . An explosive charge is a measured quantity of explosive material, which may either be composed solely of one ingredient or be a mixture containing at least two substances.
The potential energy stored in an explosive material may, for example, be:
Explosive materials may be categorized by the speed at which they expand. Materials that detonate (the front of the chemical reaction moves faster through the material than the speed of sound ) are said to be "high explosives" and materials that deflagrate are said to be "low explosives". Explosives may also be categorized by their sensitivity . Sensitive materials that can be initiated by a relatively small amount of heat or pressure are primary explosives , and materials that are relatively insensitive are secondary or tertiary explosives .
A wide variety of chemicals can explode; a smaller number are manufactured specifically for the purpose of being used as explosives. The remainder are too dangerous, sensitive, toxic, expensive, unstable, or prone to decomposition or degradation over short time spans.
In contrast, some materials are merely combustible or flammable if they burn without exploding. The distinction, however, is not always clear. Certain materials—dusts, powders, gases, or volatile organic liquids—may be simply combustible or flammable under ordinary conditions, but become explosive in specific situations or forms, such as dispersed airborne clouds , or confinement or sudden release .
Early thermal weapons , such as Greek fire , have existed since ancient times. At its roots, the history of chemical explosives lies in the history of gunpowder . [ 1 ] [ 2 ] During the Tang dynasty in the 9th century, Taoist Chinese alchemists were eagerly trying to find the elixir of immortality. [ 3 ] In the process, they stumbled upon the explosive invention of black powder made from coal, saltpeter, and sulfur in 1044. Gunpowder was the first form of chemical explosives, and by 1161, the Chinese were using explosives for the first time in warfare. [ 4 ] [ 5 ] [ 6 ] The Chinese would incorporate explosives fired from bamboo or bronze tubes known as bamboo firecrackers. The Chinese also inserted live rats inside the bamboo firecrackers; when fired toward the enemy, the flaming rats created great psychological ramifications—scaring enemy soldiers away and causing cavalry units to go wild. [ 7 ]
The first useful explosive stronger than black powder was nitroglycerin , developed in 1847. Since nitroglycerin is a liquid and highly unstable, it was replaced by nitrocellulose , trinitrotoluene ( TNT ) in 1863, smokeless powder , dynamite in 1867 and gelignite (the latter two being sophisticated stabilized preparations of nitroglycerine rather than chemical alternatives, both invented by Alfred Nobel ). World War I saw the adoption of TNT in artillery shells. World War II saw extensive use of new explosives (see: List of explosives used during World War II ) .
In turn, these have largely been replaced by more powerful explosives such as C-4 and pentaerythritol tetranitrate (PETN) which are also waterproof and malleable though they may catch fire due to reactions with metals. [ 8 ]
The largest commercial application of explosives is mining . The detonation or deflagration of either a high or low explosive in a confined space can be used to liberate a fairly specific sub-volume of a brittle material (rock) in a much larger volume of the same or similar material. The mining industry tends to use nitrate-based explosives such as emulsions of fuel oil and ammonium nitrate solutions, [ 9 ] mixtures of ammonium nitrate prills (fertilizer pellets) and fuel oil ( ANFO ) and gelatinous suspensions or slurries [ 10 ] of ammonium nitrate and combustible fuels.
In materials science and engineering, explosives are used in cladding ( explosion welding ). A thin plate of some material is placed atop a thick layer of a different material, both layers typically of metal. Atop the thin layer is placed an explosive. At one end of the layer of explosive, the explosion is initiated. The two metallic layers are forced together at high speed and with great force. The explosion spreads from the initiation site throughout the explosive. Ideally, this produces a metallurgical bond between the two layers.
An explosion is a type of spontaneous chemical reaction that, once initiated, is driven by both a large exothermic change (great release of heat) and a large positive entropy change (great quantities of gases are released) in going from reactants to products, thereby constituting a thermodynamically favorable process in addition to one that propagates very rapidly. Thus, explosives are substances that contain a large amount of energy stored in chemical bonds . The energetic stability of the gaseous products and hence their generation comes from the formation of strongly bonded species like carbon monoxide, carbon dioxide, and nitrogen gas, which contain strong double and triple bonds having bond strengths of nearly 1 MJ/mole. Consequently, most commercial explosives are organic compounds containing –NO 2 , –ONO 2 and –NHNO 2 groups that, when detonated, release gases like the aforementioned (e.g., nitroglycerin , TNT , HMX , PETN , nitrocellulose ). [ 11 ]
An explosive is classified as a low or high explosive according to its rate of combustion : low explosives burn rapidly (or deflagrate ), while high explosives detonate . While these definitions are distinct, the problem of precisely measuring rapid decomposition makes practical classification of explosives difficult. For a reaction to be classified as a detonation as opposed to just a deflagration, the propagation of the reaction shockwave through the material being tested must be faster than the speed of sound through that material. The speed of sound through a liquid or solid material is usually orders of magnitude faster than the speed of sound through air or other gases.
Traditional explosives mechanics is based on the shock-sensitive rapid oxidation of carbon and hydrogen to carbon dioxide, carbon monoxide, and water in the form of steam. Nitrates typically provide the required oxygen to burn the carbon and hydrogen fuel. High explosives tend to have the oxygen, carbon, and hydrogen contained in one organic molecule, and less sensitive explosives like ANFO are combinations of fuel (carbon and hydrogen fuel oil) and ammonium nitrate . A sensitizer such as powdered aluminum may be added to an explosive to increase the energy of the detonation. Once detonated, the nitrogen portion of the explosive formulation emerges as nitrogen gas and toxic nitric oxides .
The chemical decomposition of an explosive may take years, days, hours, or a fraction of a second. The slower processes of decomposition take place in storage and are of interest only from a stability standpoint. Of more interest are the other two rapid forms besides decomposition: deflagration and detonation.
In deflagration, decomposition of the explosive material is propagated by a flame front which moves relatively slowly through the explosive material, i.e. at speeds less than the speed of sound within the substance (which is usually still higher than 340 m/s or 1,220 km/h in most liquid or solid materials) [ 12 ] in contrast to detonation, which occurs at speeds greater than the speed of sound. Deflagration is a characteristic of low explosive material.
This term is used to describe an explosive phenomenon whereby the decomposition is propagated by a shock wave traversing the explosive material at speeds greater than the speed of sound within the substance. [ 13 ] The shock front is capable of passing through the high explosive material at supersonic speeds — typically thousands of metres per second.
In addition to chemical explosives, there are a number of more exotic explosive materials and exotic methods of causing explosions. Examples include nuclear explosives , and abruptly heating a substance to a plasma state with a high-intensity laser or electric arc .
Laser- and arc-heating are used in laser detonators, exploding-bridgewire detonators , and exploding foil initiators , where a shock wave and then detonation in conventional chemical explosive material is created by laser- or electric-arc heating. Laser and electric energy are not currently used in practice to generate most of the required energy, but only to initiate reactions.
To determine the suitability of an explosive substance for a particular use, its physical properties must first be known. The usefulness of an explosive can only be appreciated when the properties and the factors affecting them are fully understood. Some of the more important characteristics are listed below:
Sensitivity refers to the ease with which an explosive can be ignited or detonated, i.e., the amount and intensity of shock , friction , or heat that is required. When the term sensitivity is used, care must be taken to clarify what kind of sensitivity is under discussion. The relative sensitivity of a given explosive to impact may vary greatly from its sensitivity to friction or heat. Some of the test methods used to determine sensitivity relate to:
Specific explosives (usually but not always highly sensitive on one or more of the three above axes) may be idiosyncratically sensitive to such factors as pressure drop, acceleration, the presence of sharp edges or rough surfaces, incompatible materials, or even — in rare cases — nuclear or electromagnetic radiation. These factors present special hazards that may rule out any practical utility.
Sensitivity is an important consideration in selecting an explosive for a particular purpose. The explosive in an armor-piercing projectile must be relatively insensitive, or the shock of impact would cause it to detonate before it penetrated to the point desired. The explosive lenses around nuclear charges are also designed to be highly insensitive, to minimize the risk of accidental detonation.
The index of the capacity of an explosive to be initiated into detonation in a sustained manner. It is defined by the power of the detonator, which is certain to prime the explosive to a sustained and continuous detonation. Reference is made to the Sellier-Bellot scale that consists of a series of 10 detonators, from n. 1 to n. 10 , each of which corresponds to an increasing charge weight. In practice, most of the explosives on the market today are sensitive to an n. 8 detonator, where the charge corresponds to 2 grams of mercury fulminate .
The velocity with which the reaction process propagates in the mass of the explosive. Most commercial mining explosives have detonation velocities ranging from 1,800 m/s to 8,000 m/s. Today, the velocity of detonation can be measured with accuracy. Together with density , it is an important element influencing the yield of the energy transmitted through both atmospheric over-pressure and ground acceleration. By definition, a "low explosive", such as black powder, or smokeless gunpowder has a burn rate of 171–631 m/s. [ 14 ] In contrast, a "high explosive", whether a primary, such as detonating cord , or a secondary, such as TNT or C-4, has a significantly higher burn rate about 6900–8092 m/s. [ 15 ]
Stability is the ability of an explosive to be stored without deterioration .
The following factors affect the stability of an explosive:
The term power or performance as applied to an explosive refers to its ability to do work. In practice it is defined as the explosive's ability to accomplish what is intended in the way of energy delivery (i.e., fragment projection, air blast, high-velocity jet, underwater shock and bubble energy, etc.). Explosive power or performance is evaluated by a tailored series of tests to assess the material for its intended use. Of the tests listed below, cylinder expansion and air-blast tests are common to most testing programs, and the others support specific applications.
In addition to strength, explosives display a second characteristic, which is their shattering effect or brisance (from the French meaning to "break"). Brisance is important in determining the effectiveness of an explosion in fragmenting shells, bomb casings, and grenades . The rapidity with which an explosive reaches its peak pressure ( power ) is a measure of its brisance. Brisance values are primarily employed in France and Russia.
The sand crush test is commonly employed to determine the relative brisance in comparison to TNT. No test is capable of directly comparing the explosive properties of two or more compounds; it is important to examine the data from several such tests (sand crush, trauzl , and so forth) in order to gauge relative brisance. True values for comparison require field experiments.
Density of loading refers to the mass of an explosive per unit volume. Several methods of loading are available, including pellet loading, cast loading, and press loading, the choice being determined by the characteristics of the explosive. Dependent upon the method employed, an average density of the loaded charge can be obtained that is within 80–99% of the theoretical maximum density of the explosive. High load density can reduce sensitivity by making the mass more resistant to internal friction . However, if density is increased to the extent that individual crystals are crushed, the explosive may become more sensitive. Increased load density also permits the use of more explosive, thereby increasing the power of the warhead . It is possible to compress an explosive beyond a point of sensitivity, known also as dead-pressing , in which the material is no longer capable of being reliably initiated, if at all. [ citation needed ]
Volatility is the readiness with which a substance vaporizes . Excessive volatility often results in the development of pressure within rounds of ammunition and separation of mixtures into their constituents. Volatility affects the chemical composition of the explosive such that a marked reduction in stability may occur, which results in an increase in the danger of handling.
The introduction of water into an explosive is highly undesirable since it reduces the sensitivity, strength, and velocity of detonation of the explosive. Hygroscopicity is a measure of a material's moisture-absorbing tendencies. Moisture affects explosives adversely by acting as an inert material that absorbs heat when vaporized, and by acting as a solvent medium that can cause undesired chemical reactions. Sensitivity, strength, and velocity of detonation are reduced by inert materials that reduce the continuity of the explosive mass. When the moisture content evaporates during detonation, cooling occurs, which reduces the temperature of reaction. Stability is also affected by the presence of moisture since moisture promotes decomposition of the explosive and, in addition, causes corrosion of the explosive's metal container.
Explosives considerably differ from one another as to their behavior in the presence of water. Gelatin dynamites containing nitroglycerine have a degree of water resistance. Explosives based on ammonium nitrate have little or no water resistance as ammonium nitrate is highly soluble in water and is hygroscopic.
Many explosives are toxic to some extent. Manufacturing inputs can also be organic compounds or hazardous materials that require special handling due to risks (such as carcinogens ). The decomposition products, residual solids, or gases of some explosives can be toxic, whereas others are harmless, such as carbon dioxide and water.
Examples of harmful by-products are:
"Green explosives" seek to reduce environment and health impacts. An example of such is the lead-free primary explosive copper(I) 5-nitrotetrazolate, an alternative to lead azide . [ 16 ]
Explosive material may be incorporated in the explosive train of a device or system. An example is a pyrotechnic lead igniting a booster, which causes the main charge to detonate.
The most widely used explosives are condensed liquids or solids converted to gaseous products by explosive chemical reactions and the energy released by those reactions. The gaseous products of complete reaction are typically carbon dioxide , steam , and nitrogen . [ 17 ] Gaseous volumes computed by the ideal gas law tend to be too large at high pressures characteristic of explosions. [ 18 ] Ultimate volume expansion may be estimated at three orders of magnitude, or one liter per gram of explosive. Explosives with an oxygen deficit will generate soot or gases like carbon monoxide and hydrogen , which may react with surrounding materials such as atmospheric oxygen . [ 17 ] Attempts to obtain more precise volume estimates must consider the possibility of such side reactions, condensation of steam, and aqueous solubility of gases like carbon dioxide. [ 19 ]
Oxygen balance is an expression that is used to indicate the degree to which an explosive can be oxidized. If an explosive molecule contains just enough oxygen to convert all of its carbon to carbon dioxide, all of its hydrogen to water, and all of its metal to metal oxide with no excess, the molecule is said to have a zero oxygen balance. The molecule is said to have a positive oxygen balance if it contains more oxygen than is needed, and a negative oxygen balance if it contains less oxygen than is needed. [ 20 ] The sensitivity, strength , and brisance of an explosive are all somewhat dependent upon oxygen balance and tend to approach their maxima as oxygen balance approaches zero.
A chemical explosive may consist of either a chemically pure compound, such as nitroglycerin , or a mixture of a fuel and an oxidizer , such as black powder or grain dust and air.
Some chemical compounds are unstable in that, when shocked, they react, possibly to the point of detonation. Each molecule of the compound dissociates into two or more new molecules (generally gases) with the release of energy.
The above compositions may describe most of the explosive material, but a practical explosive will often include small percentages of other substances. For example, dynamite is a mixture of highly sensitive nitroglycerin with sawdust , powdered silica , or most commonly diatomaceous earth , which act as stabilizers. Plastics and polymers may be added to bind powders of explosive compounds; waxes may be incorporated to make them safer to handle; aluminium powder may be introduced to increase total energy and blast effects. Explosive compounds are also often "alloyed": HMX or RDX powders may be mixed (typically by melt-casting) with TNT to form Octol or Cyclotol .
An oxidizer is a pure substance ( molecule ) that in a chemical reaction can contribute some atoms of one or more oxidizing elements, in which the fuel component of the explosive burns. On the simplest level, the oxidizer may itself be an oxidizing element , such as gaseous or liquid oxygen .
The availability and cost of explosives are determined by the availability of the raw materials and the cost, complexity, and safety of the manufacturing operations.
A primary explosive is an explosive that is extremely sensitive to stimuli such as impact , friction , heat , static electricity , or electromagnetic radiation . Some primary explosives are also known as contact explosives . A relatively small amount of energy is required for initiation . As a very general rule, primary explosives are considered to be those compounds that are more sensitive than PETN . As a practical measure, primary explosives are sufficiently sensitive that they can be reliably initiated with a blow from a hammer; however, PETN can also usually be initiated in this manner, so this is only a very broad guideline. Additionally, several compounds, such as nitrogen triiodide , are so sensitive that they cannot even be handled without detonating. Nitrogen triiodide is so sensitive that it can be reliably detonated by exposure to alpha radiation . [ 21 ] [ 22 ]
Primary explosives are often used in detonators or to trigger larger charges of less sensitive secondary explosives . Primary explosives are commonly used in blasting caps and percussion caps to translate a physical shock signal. In other situations, different signals such as electrical or physical shock, or, in the case of laser detonation systems, light, are used to initiate an action, i.e., an explosion. A small quantity, usually milligrams, is sufficient to initiate a larger charge of explosive that is usually safer to handle.
Examples of primary high explosives are:
A secondary explosive is less sensitive than a primary explosive and requires substantially more energy to be initiated. Because they are less sensitive, they are usable in a wider variety of applications and are safer to handle and store. Secondary explosives are used in larger quantities in an explosive train and are usually initiated by a smaller quantity of a primary explosive.
Examples of secondary explosives include TNT and RDX .
Tertiary explosives , also called blasting agents , are so insensitive to shock that they cannot be reliably detonated by practical quantities of primary explosive , and instead require an intermediate explosive booster of secondary explosive . These are often used for safety and the typically lower costs of material and handling. The largest consumers are large-scale mining and construction operations.
Most tertiaries include a fuel and an oxidizer. ANFO can be a tertiary explosive if its reaction rate is slow.
Low explosives (or low-order explosives) are compounds wherein the rate of decomposition proceeds through the material at less than the speed of sound . The decomposition is propagated by a flame front ( deflagration ) that travels much more slowly through the explosive material than the shock wave of a high explosive. Under normal conditions , low explosives undergo deflagration at rates that vary from a few centimetres per second to approximately 0.4 kilometres per second (1,300 ft/s). It is possible for them to deflagrate very quickly, producing an effect similar to a detonation . This can happen under higher pressure (such as when gunpowder deflagrates inside the confined space of a bullet casing, accelerating the bullet to well beyond the speed of sound) or temperature .
A low explosive is usually a mixture of a combustible substance and an oxidant that decomposes rapidly (deflagration); however, they burn more slowly than a high explosive, which has an extremely fast burn rate. [ 26 ]
Low explosives are normally employed as propellants . Included in this group are petroleum products such as propane and gasoline , gunpowder (including smokeless powder ), and light pyrotechnics such as flares and fireworks , but they can replace high explosives in certain applications, including gas pressure blasting. [ 27 ]
High explosives (HE, or high-order explosives) are explosive materials that detonate , meaning that the explosive shock front passes through the material at a supersonic speed. High explosives detonate with explosive velocity of about 3–9 kilometres per second (9,800–29,500 ft/s). For instance, TNT has a detonation (burn) rate of approximately 6.9 km/s (22,600 feet per second), detonating cord of 6.7 km/s (22,000 feet per second), and C-4 about 8.0 km/s (26,000 feet per second). They are normally employed in mining, demolition, and military applications. The term high explosive is in contrast with the term low explosive , which explodes ( deflagrates ) at a lower rate.
High explosives can be divided into two explosives classes differentiated by sensitivity : primary explosive and secondary explosive . Although tertiary explosives (such as ANFO at 3,200 m/s) can technically meet the explosive velocity definition, they are not considered high explosives in regulatory contexts.
Countless high-explosive compounds are chemically possible, but commercially and militarily important ones have included NG , TNT , TNP , TNX, RDX , HMX , PETN , TATP , TATB , and HNS .
Explosives are often characterized by the physical form that the explosives are produced or used in. These use forms are commonly categorized as: [ 28 ]
Shipping labels and tags may include both United Nations and national markings.
United Nations markings include numbered Hazard Class and Division (HC/D) codes and alphabetic Compatibility Group codes. Though the two are related, they are separate and distinct. Any Compatibility Group designator can be assigned to any Hazard Class and Division. An example of this hybrid marking would be a consumer firework , which is labeled as 1.4G or 1.4S.
Examples of national markings would include United States Department of Transportation (U.S. DOT) codes.
The UN GHS Hazard Class and Division (HC/D) is a numeric designator within a hazard class indicating the character, predominance of associated hazards, and potential for causing personnel casualties and property damage. It is an internationally accepted system that communicates using the minimum amount of markings the primary hazard associated with a substance. [ 29 ]
Listed below are the Divisions for Class 1 (Explosives):
To see an entire UNO Table, browse Paragraphs 3–8 and 3–9 of NAVSEA OP 5, Vol. 1, Chapter 3.
Compatibility Group codes are used to indicate storage compatibility for HC/D Class 1 (explosive) materials. Letters are used to designate 13 compatibility groups as follows.
The legality of possessing or using explosives varies by jurisdiction. Various countries around the world have enacted explosives law and require licenses to manufacture, distribute, store, use, possess explosives or ingredients.
In the Netherlands , the civil and commercial use of explosives is covered under the Wet explosieven voor civiel gebruik (explosives for civil use Act), in accordance with EU directive nr. 93/15/EEG [ 30 ] (Dutch). The illegal use of explosives is covered under the Wet Wapens en Munitie (Weapons and Munition Act) [ 31 ] (Dutch).
The new Explosives Regulations 2014 (ER 2014) [ 32 ] came into force on 1 October 2014 and defines "explosive" as:
"a) any explosive article or explosive substance which would —
(i) if packaged for transport, be classified in accordance with the United Nations Recommendations as falling within Class 1; or
(ii) be classified in accordance with the United Nations Recommendations as —
(aa) being unduly sensitive or so reactive as to be subject to spontaneous reaction and accordingly too dangerous to transport, and
(bb) falling within Class 1; or
(b) a desensitised explosive,
but it does not include an explosive substance produced as part of a manufacturing process which thereafter reprocesses it in order to produce a substance or preparation which is not an explosive substance" [ 32 ]
"Anyone who wishes to acquire and or keep relevant explosives needs to contact their local police explosives liaison officer. All explosives are relevant explosives apart from those listed under Schedule 2 of Explosives Regulations 2014." [ 33 ]
During World War I , numerous laws were created to regulate war related industries and increase security within the United States. In 1917, the 65th United States Congress created many laws , including the Espionage Act of 1917 and Explosives Act of 1917 .
The Explosives Act of 1917 (session 1, chapter 83, 40 Stat. 385 ) was signed on 6 October 1917 and went into effect on 16 November 1917. The legal summary is "An Act to prohibit the manufacture, distribution, storage, use, and possession in time of war of explosives, providing regulations for the safe manufacture, distribution, storage, use, and possession of the same, and for other purposes". This was the first federal regulation of licensing explosives purchases. The act was deactivated after World War I ended. [ 34 ]
After the United States entered World War II , the Explosives Act of 1917 was reactivated. In 1947, the act was deactivated by President Truman . [ 35 ]
The Organized Crime Control Act of 1970 ( Pub. L. 91–452 ) transferred many explosives regulations to the Bureau of Alcohol, Tobacco and Firearms (ATF) of the Department of Treasury . The bill became effective in 1971. [ 36 ]
Currently, regulations are governed by Title 18 of the United States Code and Title 27 of the Code of Federal Regulations :
Listed in alphabetical order:
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The UN Recommendations on the Transport of Dangerous Goods are contained in the UN Model Regulations prepared by the Subcommittee of Experts on the Transport of Dangerous Goods of the United Nations Economic and Social Council (ECOSOC). They cover the transport of dangerous goods by all modes of transport except by bulk tanker . They are not obligatory or legally binding on individual countries, but have gained a wide degree of international acceptance: they form the basis of several international agreements and many national laws.
"Dangerous goods" (also known as "hazardous materials" or "HAZMAT" in the United States) may be a pure chemical substance (e.g. TNT , nitroglycerin ), mixtures (e.g. dynamite , gunpowder ) or manufactured articles (e.g. ammunition , fireworks ). The transport hazards that they pose are grouped into nine classes, which may be subdivided into divisions and/or packing groups. The most common dangerous goods are assigned a UN number , a four digit code which identifies it internationally. Less common substances are transported under generic codes such as "UN1993: flammable liquid, not otherwise specified".
The UN Recommendations do not cover the manufacturing, use or disposal of dangerous goods.
The first version of the Recommendations on the Transport of Dangerous Goods was produced by the ECOSOC in 1956. [ 1 ] From 1996, the Recommendations were effectively split into two parts: the Model Regulations , which form a suggested drafting for laws and regulations on the transport of dangerous goods; and the Manual of Tests and Criteria , which contains technical information about methods of testing products to ascertain their hazards. The 23rd edition of the Recommendations was published in 2023.
The container requirements include some material and construction requirements but also performance testing [ 2 ] is required. The package testing is based on the packing group (hazard level) of the contents, the quantity of material, and the type of container.
The UN recommendations are implemented by regulatory bodies in each country: Transport Canada , United States Department of Transportation , [ 3 ] etc. Some carriers have additional requirements.
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The Report on the Alleged Use of Chemical Weapons in the Ghouta Area of Damascus on 21 August 2013 was a 2013 report produced by a team appointed by United Nations Secretary-General (UNSG) Ban Ki-moon to investigate alleged chemical weapon attacks during the Syrian civil war . [ 1 ] The report published on 16 September 2013 focused on the 21 August 2013 Ghouta chemical attack , which took place whilst the Mission was in Damascus to investigate prior alleged incidents, including the Khan al-Assal chemical attack in March 2013.
Two days before the attack, a UN team headed by Åke Sellström [ 1 ] arrived in Damascus with permission, from the Syrian government, to investigate earlier alleged chemical weapons use. [ 2 ] [ 3 ] On the day of the attack, UN Secretary General Ban Ki-moon expressed "the need to investigate [the Ghouta incident as] soon as possible," hoping for consent from the Syrian government. [ 2 ] The next day, UN High Commissioner for Human Rights Navi Pillay urged government and opposition forces to allow investigation, [ 4 ] and Ban requested the government provide immediate access. [ 5 ] [ 6 ] On 23 August, clashes between rebel and government forces continued in and around Ghouta, government shelling continued, and UN inspectors were denied access for a second day. [ 7 ] [ 8 ] United States officials told The Wall Street Journal that the White House "became convinced" that the Syrian government was trying to hide the evidence of chemical weapons use by shelling the sites and delaying their inspection. [ 5 ] Ban called for a ceasefire to allow the inspectors to visit the attack sites. [ 9 ] On 25 August the government agreed to cease hostilities with the presence of UN inspectors, [ 10 ] and agreements between the UN, government and rebel factions were reached for five hours of cease-fire each day from 26 to 29 August. [ 11 ]
Early in the morning of 26 August several mortars hit central Damascus, including one that fell near the Four Seasons hotel the UN inspectors were staying in. [ 12 ] Later in the day the UN team came under sniper fire en route to Moadamiyah in western Ghouta (in the south of Damascus), forcing them to return to their hotel and replace one of their vehicles before continuing their investigation four hours later. [ 13 ] [ 14 ] The attack prompted Ban to declare he would register a complaint to the Syrian government and opposition authorities. [ 15 ] [ 16 ] After returning to Moadamiyah the team visited clinics and makeshift field hospitals, collected samples and conducted interviews with witnesses, survivors and doctors. [ 13 ] The inspectors spoke with 20 victims of the attacks and took blood and hair samples, soil samples, and samples from domestic animals. [ 16 ] As a result of the delay caused by the sniper attack, the team's time in Moadamiyah was substantially shortened, with the scheduled expiry of the daily cease-fire leaving them around 90 minutes on the ground. [ 11 ] [ 16 ] [ 17 ]
On 28 and 29 August the UN team visited Zamalka and Ein Tarma in eastern Ghouta, in the east of Damascus, for a total time of five and a half hours. [ 1 ] On 30 August the team visited at a Syrian government military hospital in Mazzeh , and collected samples. [ 18 ] [ 19 ]
The UN investigation into the chemical attacks in Ghouta was published on 16 September. The report stated that "the environmental, chemical and medical samples, we have collected, provide clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used in Ein Tarma, Moadamiyah and Zamalka in the Ghouta area of Damascus." [ 1 ] The inspectors were able to identify several surface-to-surface rockets at the affected sites as 140mm BM-14 rockets originally manufactured in Russia and 330mm rockets probably manufactured in Syria. [ 20 ] U.N. Secretary General Ban Ki-moon called the findings "beyond doubt and beyond the pale," and clear evidence of a war crime. "The results are overwhelming and indisputable ... A majority of the rockets or rocket fragments recovered were found to be carrying sarin." [ 21 ] The report, which was "careful not to blame either side," said that during the mission's work in the rebel controlled Zamalka and Ein Tarma neighborhoods, "individuals arrived carrying other suspected munitions indicating that such potential evidence is being moved and possibly manipulated." [ 22 ] The areas were under rebel control, but the report did not elaborate on who the individuals were. [ 23 ] The UN investigators were accompanied by a rebel leader:
A leader of the local opposition forces [...] was identified and requested to take 'custody' of the Mission [...] to ensure the security and movement of the Mission, to facilitate the [ sic ] access to the most critical cases/witnesses to be interviewed and sampled by the Mission and to control patients and crowd in order for the Mission to focus on its main activities. [ 1 ]
An August Scientific American article had described difficulties that could arise when attempting to identify the manufacturer of sarin from soil or tissue samples. [ 24 ] UN lead investigator Sellström told the UN Security Council that the quality of the sarin was higher than that used by Iraq in the Iran–Iraq War and stating "In particular, the environmental, chemical and medical samples we have collected provide clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used," a conclusion omitted in the final report, [ 25 ] implying a purity higher than the Iraqi chemical weapons program 's 45–60%. [ 26 ] (By comparison, Aum Shinrikyo used nearly pure sarin in the 1994 Matsumoto incident . [ 27 ] ) According to Human Rights Watch , hundreds of kilograms of sarin were used in the attack, which it said suggested government responsibility, as opposition forces were not known to possess significant amounts of sarin. [ 28 ] The UN report states, "Chemical weapons use in such meteorological conditions maximizes their potential impact as the heavy gas can stay close to the ground and penetrate into lower levels of buildings and constructions where many people were seeking shelter." [ 29 ]
The Russian government dismissed the initial UN report after it was released, calling it "one-sided" and "distorted". [ 30 ] On 17 September, Russian Foreign Minister Sergei Lavrov reiterated his government's belief that the opposition carried out the attacks as a "provocation". [ 31 ] The United Nations high representative for disarmament affairs, Angela Kane , stated that the inspection team would review Russia's objections. [ 32 ]
A Russian defence expert Ruslan Pukhov, said that the code found by the UN investigators on the M-14 munition showed it had been produced in 1967 by the Sibselmash plant in Novosibirsk for a BM-14-17 multiple rocket launcher . He said that these weapons had been taken out of service by Syria and replaced with BM-21s . The second projectile identified by weapons inspectors, he thought, looked to be 'home-made'. [ 33 ] An Iranian chemical weapons expert, Abbas Foroutan, said in October 2013 that the UN should publish more details about the investigation than were provided in the report, including victims' pulse rates and blood pressure and their response to the atropine treatment, the victims' levels of acetylcholinesterase (sarin is an acetylcholinesterase inhibitor ), and more technical details on the lab testing process. [ 34 ]
The UN inspection team returned to the Damascus area to continue investigations into other alleged chemical attacks in late September 13. A final report on Ghouta and six other alleged attacks (including three alleged to have occurred after the Ghouta attack) was released on 13 December 2013. [ 35 ]
In the months immediately following the August attacks, and the situation they precipitated, "Syria declared to the OPCW 30 production, filling and storage facilities, eight mobile filling units and three chemical weapons-related facilities.They contained approximately 1,000 metric tons of chemical weapons, mostly in the form of raw precursors, 290 metric tons of loaded munitions and 1,230 unfilled munitions, OPCW documents showed." [ 36 ]
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A UN number ( United Nations number) is a four-digit number that identifies hazardous materials , and articles (such as explosives , flammable liquids , oxidizers , toxic liquids, etc.) in the framework of international trade and transport . Some hazardous substances have their own UN numbers (e.g. acrylamide has UN 2074), while sometimes groups of chemicals or products with similar properties receive a common UN number (e.g. flammable liquids, not otherwise specified, have UN 1993). A chemical in its solid state may receive a different UN number than the liquid phase if its hazardous properties differ significantly; substances with different levels of purity (or concentration in solution) may also receive different UN number
Associated with each UN number is a hazard identifier , which encodes the general hazard class and subdivision (and, in the case of explosives, their compatibility group). If a substance poses several dangers, then subsidiary risk identifiers may be specified. It is not possible to deduce the hazard class(es) of a substance from its UN number: they have to be looked up in a table.
UN numbers range from UN 0004 to about UN 3550 (UN 0001 – UN 0003 are no longer in use) and are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. They are published as part of their Recommendations on the Transport of Dangerous Goods , also known as the Orange Book . These recommendations are adopted by the regulatory organization responsible for the different modes of transport. There is no UN number allocated to non-hazardous substances.
An NA number ( North America number) is issued by the United States Department of Transportation and is identical to UN numbers, except that some substances without a UN number may have an NA number. These additional NA numbers use the range NA 9000 - NA 9279. There are some exceptions, for example, NA 2212 is all asbestos with UN 2212 limited to asbestos , amphibole amosite, tremolite , actinolite , anthophyllite , or crocidolite . Another exception, NA 3334, is self-defense spray, non-pressurized while UN 3334 is aviation -regulated liquid, not otherwise specified. For the complete list, see NA/UN exceptions .
An ID number is a third type of identification number used for hazardous substances being offered for air transport . Substances with an ID number are associated with proper shipping names recognized by the ICAO Technical Instructions. [ 1 ] ID 8000, Consumer commodity does not have a UN or NA number, and is classed as a Class 9 hazardous material.
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Uranium dioxide or uranium(IV) oxide ( UO 2 ) , also known as urania or uranous oxide , is an oxide of uranium , and is a black, radioactive , crystalline powder that naturally occurs in the mineral uraninite . It is used in nuclear fuel rods in nuclear reactors . A mixture of uranium and plutonium dioxides is used as MOX fuel . It has been used as an orange, yellow, green, and black color in ceramic glazes and glass .
Uranium dioxide is produced by reducing uranium trioxide with hydrogen . This reaction often creates triuranium octoxide as an intermediate. [ 3 ] [ 4 ] [ 5 ]
This reaction plays an important part in the creation of nuclear fuel through nuclear reprocessing and uranium enrichment . [ 5 ]
The solid is isostructural with (has the same structure as) fluorite ( calcium fluoride ), where each U is surrounded by eight O nearest neighbors in a cubic arrangement. In addition, the dioxides of cerium , thorium , and the transuranic elements from neptunium through californium have the same structures. [ 6 ] No other elemental dioxides have the fluorite structure. Upon melting, the measured average U-O coordination reduces from 8 in the crystalline solid (UO 8 cubes), down to 6.7±0.5 (at 3270 K) in the melt. [ 7 ] Models consistent with these measurements show the melt to consist mainly of UO 6 and UO 7 polyhedral units, where roughly 2 ⁄ 3 of the connections between polyhedra are corner sharing and 1 ⁄ 3 are edge sharing. [ 7 ]
Uranium dioxide is oxidized in contact with oxygen to form triuranium octoxide : [ 8 ]
The electrochemistry of uranium dioxide has been investigated in detail as the galvanic corrosion of uranium dioxide controls the rate at which used nuclear fuel dissolves. [ clarification needed ] See spent nuclear fuel for further details. Water increases the oxidation rate of plutonium and uranium metals. [ 9 ]
Uranium dioxide reacts with carbon at high temperatures, forming uranium carbide and carbon monoxide . [ 10 ]
This process must be done under an inert gas as uranium carbide is easily oxidized back into uranium oxide .
UO 2 is used mainly as nuclear fuel , specifically as UO 2 or as a mixture of UO 2 and PuO 2 ( plutonium dioxide ) called a mixed oxide ( MOX fuel ), in the form of fuel rods in nuclear reactors . [ 11 ]
The thermal conductivity of uranium dioxide is very low when compared with elemental uranium , uranium nitride , uranium carbide and zircaloy cladding material as well as most uranium-based alloys. [ 12 ] [ 13 ] [ 14 ] This low thermal conductivity can result in localised overheating in the centres of fuel pellets. [ 15 ]
The graph below shows the different temperature gradients in different fuel compounds. For these fuels, the thermal power density is the same and the diameter of all the pellets are the same. [ citation needed ]
Uranium oxide (urania) was used to color glass and ceramics prior to World War II, and until the applications of radioactivity were discovered this was its main use. In 1958 the military in both the US and Europe allowed its commercial use again as depleted uranium, and its use began again on a more limited scale. Urania-based ceramic glazes are dark green or black when fired in a reduction or when UO 2 is used; more commonly it is used in oxidation to produce bright yellow, orange and red glazes. [ 16 ] Orange-colored Fiestaware is a well-known example of a product with a urania-colored glaze. [ 17 ] Uranium glass is pale green to yellow and often has strong fluorescent properties. [ 18 ] Urania has also been used in formulations of enamel and porcelain . [ 19 ] It is possible to determine with a Geiger counter if a glaze or glass produced before 1958 contains urania.
Prior to the realisation of the harmfulness of radiation, uranium was included in false teeth and dentures, as its slight fluorescence made the dentures appear more like real teeth in a variety of lighting conditions. [ 20 ]
Depleted UO 2 (DUO 2 ) can be used as a material for radiation shielding . For example, DUCRETE is a "heavy concrete " material where gravel is replaced with uranium dioxide aggregate; this material is investigated for use for casks for radioactive waste . [ 21 ] Casks can be also made of DUO 2 - steel cermet , a composite material made of an aggregate of uranium dioxide serving as radiation shielding, graphite and/or silicon carbide serving as neutron radiation absorber and moderator, and steel as the matrix, whose high thermal conductivity allows easy removal of decay heat. [ 22 ]
Depleted uranium dioxide can be also used as a catalyst , e.g. for degradation of volatile organic compounds in gaseous phase, oxidation of methane to methanol , and removal of sulfur from petroleum . It has high efficiency and long-term stability when used to destroy VOCs when compared with some of the commercial catalysts , such as precious metals , TiO 2 , and Co 3 O 4 catalysts. Much research is being done in this area, DU being favoured for the uranium component due to its low radioactivity. [ 23 ]
The use of uranium dioxide as a material for rechargeable batteries is being investigated. [ 24 ] The batteries could have a high power density and a reduction potential of -4.7 V per cell. [ 25 ] Another investigated application is in photoelectrochemical cells for solar-assisted hydrogen production where UO 2 is used as a photoanode . In earlier times, uranium dioxide was also used as heat conductor for current limitation (URDOX-resistor), which was the first use of its semiconductor properties. [ citation needed ]
Uranium dioxide displays strong piezomagnetism in the antiferromagnetic state, observed at cryogenic temperatures below 30 kelvins . Accordingly, the linear magnetostriction found in UO 2 changes sign with the applied magnetic field and exhibits magnetoelastic memory switching phenomena at record high switch-fields of 180,000 Oe. [ 26 ] The microscopic origin of the material magnetic properties lays in the face-centered-cubic crystal lattice symmetry of uranium atoms, and its response to applied magnetic fields. [ 27 ]
The band gap of uranium dioxide is comparable to those of silicon and gallium arsenide , near the optimum for efficiency vs band gap curve for absorption of solar radiation, suggesting its possible use for very efficient solar cells based on Schottky diode structure; it also absorbs at five different wavelengths, including infrared, further enhancing its efficiency. Its intrinsic conductivity at room temperature is about the same as of single crystal silicon. [ 28 ]
The dielectric constant of uranium dioxide is about 21.5, [ 29 ] which is almost twice as high as of silicon (11.7) [ 30 ] and GaAs (12.4). [ 31 ] This is an advantage over Si and GaAs in the construction of integrated circuits , as it may allow higher density integration with higher breakdown voltages and with lower susceptibility to the CMOS tunnelling breakdown. [ 32 ]
The Seebeck coefficient of uranium dioxide at room temperature is about -750 μV/K, a value significantly higher than the -270 μV/K of thallium tin telluride (Tl 2 SnTe 5 ) and thallium germanium telluride (Tl 2 GeTe 5 ) [ 32 ] and the −170 μV/K ( n-type ) / 160 μV/K ( p-type ) of bismuth telluride , [ 33 ] other materials promising for thermoelectric power generation applications [ 32 ] and Peltier elements . [ citation needed ]
The radioactive decay impact of the 235 U and 238 U on its semiconducting properties was not measured as of 2005 [update] . Due to the slow decay rate of these isotopes, it should not meaningfully influence the properties of uranium dioxide solar cells and thermoelectric devices, but it may become an important factor for high-performance integrated circuits . Use of depleted uranium oxide is necessary for this reason. The capture of alpha particles emitted during radioactive decay as helium atoms in the crystal lattice may also cause gradual long-term changes in its properties. [ 32 ]
The stoichiometry of the material dramatically influences its electrical properties. For example, the electrical conductivity of UO 1.994 is orders of magnitude lower at higher temperatures than the conductivity of UO 2.001 . [ 32 ]
Uranium dioxide, like U 3 O 8 , is a ceramic material capable of withstanding high temperatures (about 2300 °C, in comparison with at most 200 °C for silicon or GaAs), [ 32 ] making it suitable for high-temperature applications like thermophotovoltaic devices. [ citation needed ]
Uranium dioxide is also resistant to radiation damage, [ 32 ] making it useful for rad-hard devices [ citation needed ] for special military and aerospace applications. [ 32 ]
A Schottky diode of U 3 O 8 and a p-n-p transistor of UO 2 were successfully manufactured in a laboratory. [ 34 ]
Uranium dioxide is known to be absorbed by phagocytosis in the lungs. [ 35 ]
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Uranyl nitrate is a water-soluble yellow uranium salt with the formula UO 2 (NO 3 ) 2 · n H 2 O . The hexa-, tri-, and dihydrates are known. [ 3 ] The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels. In the nuclear industry, it is commonly referred to as yellow salt.
Uranyl nitrate can be prepared by reaction of uranium salts with nitric acid . It is soluble in water , ethanol , and acetone . As determined by neutron diffraction , the uranyl center is characteristically linear with short U=O distances. In the equatorial plane of the complex are six U-O bonds to bidentate nitrate and two water ligands. At 245 pm , these U-O bonds are much longer than the U=O bonds of the uranyl center. [ 1 ]
Uranyl nitrate is important for nuclear reprocessing . It is the compound of uranium that results from dissolving the decladded spent nuclear fuel rods or yellowcake in nitric acid, for further separation and preparation of uranium hexafluoride for isotope separation for preparing of enriched uranium . A special feature of uranyl nitrate is its solubility in tributyl phosphate ( PO(OC 4 H 9 ) 3 ), which allows uranium to be extracted from the nitric acid solution. Its high solubility is attributed to the formation of the lipophilic adduct UO 2 (NO 3 ) 2 (OP(OBu) 3 ) 2 . [ citation needed ]
During the first half of the 19th century, many photosensitive metal salts had been identified as candidates for photographic processes , among them uranyl nitrate. The prints thus produced were called uranium prints or uranotypes.
The first uranium printing processes were invented by Scotsman J. Charles Burnett between 1855 and 1857, and used this compound as the sensitive salt. Burnett authored a 1858 article comparing "Printing by the Salts of the Uranic and Ferric Oxides"
The process employs the ability of the uranyl ion to pick up two electrons and reduce to the lower oxidation state of uranium(IV) under ultraviolet light.
Uranotypes can vary from print to print from a more neutral, brown russet to strong Bartolozzi red, with a very long tone grade. Surviving prints are slightly radioactive , a property which serves as a means of non-destructively identifying them.
Several other more elaborate photographic processes employing the compound appeared and vanished during the second half of the 19th century with names like Wothlytype, Mercuro-Uranotype and the Auro-Uranium process. Uranium papers were manufactured commercially at least until the end of the 19th century, vanishing due to the superior sensitivity and practical advantages of silver halides . From the 1930s through the 1950s Kodak Books described a uranium toner (Kodak T-9) using uranium nitrate hexahydrate. [ citation needed ]
Along with uranyl acetate it is used as a negative stain for viruses in electron microscopy ; in tissue samples it stabilizes nucleic acids and cell membranes . [ citation needed ]
Uranyl nitrates are common starting materials for the synthesis of other uranyl compounds because the nitrate ligand is easily replaced by other anions. It reacts with oxalate to give uranyl oxalate . Treatment with hydrochloric acid gives uranyl chloride . [ 4 ]
Uranyl nitrate is an oxidizing and highly toxic compound. When ingested, it causes severe chronic kidney disease and acute tubular necrosis and is a lymphocyte mitogen . Target organs include the kidneys , liver , lungs and brain . It also represents a severe fire and explosion risk when heated or subjected to shock in contact with oxidizable substances. [ citation needed ]
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Uranyl hydroxide is a hydroxide of uranium with the chemical formula UO 2 (OH) 2 in the monomeric form and [(UO 2 ) 2 (OH) 4 ] 2- in the dimeric; both forms may exist in normal aqueous media. In aerobic conditions, up to 5 hydroxides can bind to uranyl ([(UO 2 ) 2 (OH) 5 ] 3- ). Uranyl hydroxide hydrate is precipitated as a colloidal yellowcake from oxidized uranium liquors near neutral pH.
Uranyl hydroxide was once used in glassmaking and ceramics in the colouring of the vitreous phases and the preparation of pigments for high temperature firing. The introduction of alkaline di uranates (like sodium diuranate ) into glasses leads to yellow by transmission, green by reflection; moreover these glasses become dichroic and fluorescent under ultraviolet rays.
Uranyl hydroxide is teratogenic and radioactive .
The formation of uranyl hydroxide hydrate can occur via hydrated uranyl fluoride [(UO 2 F 2 )(H 2 O)] 7 ·4H 2 O which is not stable at an elevated water vapor pressure. A complete loss of fluorine is undergone and the formation of uranyl hydroxide hydrate ([(UO 2 ) 4 O(OH) 6 ]·5H 2 O) occurs. This uranyl hydroxide species is structurally similar to the uranyl hydroxide hydrate minerals schoepite and metaschoepite. X-ray diffraction data was gathered and found that this species has expanded interlayer spacing suggesting there may be additional water molecules in between uranyl layers. Unlike metaschoepite, however, this species does not form UO 2 (OH) 2 upon dehydration. [ 1 ]
UO 2 (OH) 2 reacts with water in a hydration reaction to form [(UO 2 (OH) 2 )(H 2 O)] + and the monohydrate form also reacted with water to form dihydrates [(UO 2 OH)(H 2 O) 2 ] + and trihydrates [(UO 2 OH)(H 2 O) 3 ] + . The hydration reaction to form the monohydrate was significantly slower than if the hydroxide were replaced with acetate or nitrate. This could be due to the strongly basic (OH) − reducing the Lewis acidity of U or because the more complex acetate and nitrate anions provide more degrees of freedom. However, it was found that the formation of the dihydrate uranyl hydroxide hydrate (2) was nearly three times faster than the monohydrate (1). [ 2 ]
A mechanism for oxygen exchange between the UO 2 2+ cations in a highly alkaline solution was proposed and investigated by Shamov et al. in the Journal of the American Chemical Society . [ 3 ] An equilibrium between [UO 2 (OH) 4 ] 2- and [UO 2 (OH) 5 ] 3- was observed followed by the formation of the stable [UO 3 (OH) 3 ·H 2 O] 3- intermediate that formed from [UO 2 (OH) 5 ] 3- via intramolecular water elimination.
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Uranyl carbonate refers to the inorganic compound with the formula UO 2 CO 3 . Also known by its mineral name rutherfordine , this material consists of uranyl (UO 2 2+ ) and carbonate (CO 3 2- ). Like most uranyl salts, the compound is a polymeric, each uranium(VI) center being bonded to eight O atoms. [ 1 ] Hydrolysis products of rutherfordine are also found in both the mineral and organic fractions of coal and its fly ash and is the main component of uranium in mine tailing seepage water. [ 2 ]
Many uranyl carbonates exist, rutherfordine being the simplest stoichiometry. Most uranyl carbonates additional components including water and diverse anions and cations. [ 3 ]
A common method for concentrating uranium from a solution uses solutions of uranyl carbonates, which are passed through a resin bed where the complex ions are transferred to the resin by ion exchange with a negative ion like chloride. After build-up of the uranium complex on the resin, the uranium is eluted with a salt solution and the uranium is precipitated in another process. [ citation needed ]
Uranyl carbonates include: [ citation needed ]
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Uranyl chloride is a chemical compound with the chemical formula U O 2 Cl 2 . It consists of uranyl cations UO 2+ 2 and chloride anions Cl − . It is fluorescent . [ 1 ] Uranyl chloride also refers to inorganic compounds with the formula UO 2 Cl 2 (H 2 O) n where n = 0, 1, 2, or 3. These are yellow salts.
The hydrates are obtained by dissolving uranyl sulfate or uranyl acetate in hydrochloric acid followed by crystallization from concentrated solutions. Depending on the method of drying, one obtains the mono- or the trihydrate. The monohydrate is described as a yellow, sulfur-like powder. It is very hygroscopic. [ 3 ] The trihydrate is greenish-yellow. Both hydrates are fluorescent solids that are highly soluble in water. [ 4 ]
The anhydrous material can be obtained by the reaction of oxygen with uranium tetrachloride :
In terms of structures, all three of these compounds feature the uranyl center ( trans - UO 2+ 2 ) bound to five additional ligands, which can include (bridging) chloride, water, or another uranyl oxygen. [ 5 ] [ 6 ]
The aquo ligands can be replaced by a variety of donors, e.g. THF . [ 7 ] Uranyl chloride, and its two hydrates, ( UO 2 Cl 2 ·H 2 O and UO 2 Cl 2 ·3H 2 O ) decompose in the presence of light. This photosensitivity over the years, from time to time, has attracted scientific interest and there have been various unsuccessful attempts to develop applications in photography using these compounds. [ 1 ]
The company Indian Rare Earths Limited (IREL) has developed a process to extract uranium from the Western and Eastern coastal dune sands of India . After pre-processing with high-intensity magnetic separators and fine grinding, the mineral sands (known as monazite ), are digested with caustic soda at about 120 °C (248 °F) and water. The hydroxide concentrate is further digested with concentrated hydrochloric acid to solubilise all hydroxides to form a feed solution composed of chlorides of uranium and other rare earth elements including thorium . The solution is subjected to liquid–liquid extraction with dual solvent systems to produce uranyl chloride and thorium oxalate . The crude uranyl chloride solution is subsequently refined to nuclear grade ammonium diuranate by a purification process involving precipitation and solvent extraction in a nitrate media. [ citation needed ]
Uranyl chloride is highly toxic by ingestion and inhalation. Cumulative toxic effects are also probable, with the target organs being the liver and the kidneys. It is toxic to aquatic organisms, and may cause long-term catastrophic effects in the aquatic environment. As all uranium compounds, uranyl chloride is radioactive. [ 1 ]
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Uranyl fluoride is the inorganic compound with the formula UO 2 F 2 . It is most notable as a contaminant in the production of uranium tetrafluoride . [ 2 ]
As shown by X-ray crystallography , the uranyl centers UO 2+ 2 are surrounded by six fluoride ligands F − . [ 3 ]
This salt is very soluble in water as well as hygroscopic . It changes in color from brilliant orange to yellow after reacting with water. Uranyl fluoride is stable in air up to 300 °C, above which slow decomposition to U 3 O 8 occurs. When heated to decomposition, UO 2 F 2 emits toxic hydrofluoric acid fumes. [ citation needed ]
It is formed in the hydrolysis of uranium hexafluoride ( UF 6 ):
It can also be formed in the hydrofluorination of uranium trioxide ( UO 3 ):
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it .
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Uranyl sulfate describes a family of inorganic compounds with the formula UO 2 SO 4 (H 2 O) n . These salts consist of sulfate , the uranyl ion , and water. They are lemon-yellow solids. Uranyl sulfates are intermediates in some extraction methods used for uranium ores. [ 1 ] These compounds can also take the form of an anhydrous salt.
The structure of UO 2 (SO 4 )(H 2 O) 3.5 is illustrative of the uranyl sulfates. The trans -UO 2 2+ centers are encased in a pentagonal bipyramidal coordination sphere. In the pentagonal plane are five oxygen ligands derived from sulfate and aquo ligands. The compound is a coordination polymer. [ 2 ]
Aside from the large scale use in mining, uranyl sulfate finds some use as a negative stain in microscopy and tracer in biology . The Aqueous Homogeneous Reactor experiment, constructed in 1951, circulated a fuel composed of 565 grams of U-235 enriched to 14.7% in the form of uranyl sulfate. [ citation needed ]
The acid process of milling uranium ores involves precipitating uranyl sulfate from the pregnant leaching solution to produce the semi-refined product referred to as yellowcake . [ 3 ]
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Uranium trioxide (UO 3 ) , also called uranyl oxide , uranium(VI) oxide , and uranic oxide , is the hexavalent oxide of uranium . The solid may be obtained by heating uranyl nitrate to 400 °C. Its most commonly encountered polymorph is amorphous UO 3 .
There are three methods to generate uranium trioxide. As noted below, two are used industrially in the reprocessing of nuclear fuel and uranium enrichment.
Uranium trioxide is shipped between processing facilities in the form of a gel, most often from mines to conversion plants.
Cameco Corporation , which operates at the world's largest uranium refinery at Blind River, Ontario , produces high-purity uranium trioxide.
It has been reported that the corrosion of uranium in a silica rich aqueous solution forms uranium dioxide , uranium trioxide, [ 5 ] and coffinite . [ 6 ] In pure water, schoepite (UO 2 ) 8 O 2 (OH) 12 ·12(H 2 O) is formed [ 7 ] in the first week and then after four months studtite (UO 2 )O 2 ·4(H 2 O) was produced. This alteration of uranium oxide also leads to the formation of metastudtite , [ 8 ] [ 9 ] a more stable uranyl peroxide, often found in the surface of spent nuclear fuel exposed to water. Reports on the corrosion of uranium metal have been published by the Royal Society . [ 10 ] [ 11 ]
Like all hexavalent uranium compounds, UO 3 is hazardous by inhalation, ingestion, and through skin contact. It is a poisonous, slightly radioactive substance, which may cause shortness of breath, coughing, acute arterial lesions, and changes in the chromosomes of white blood cells and gonads leading to congenital malformations if inhaled. [ 12 ] [ 13 ] However, once ingested, uranium is mainly toxic for the kidneys and may severely affect their function.
The only well characterized binary trioxide of any actinide is UO 3 , of which several polymorphs are known. Solid UO 3 loses O 2 on heating to give green-colored U 3 O 8 : reports of the decomposition temperature in air vary from 200 to 650 °C. Heating at 700 °C under H 2 gives dark brown uranium dioxide (UO 2 ), which is used in MOX nuclear fuel rods.
There is a high-pressure solid form with U 2 O 2 and U 3 O 3 rings in it. [ 21 ] [ 22 ]
Several hydrates of uranium trioxide are known, e.g., UO 3 ·6H 2 O, which are commonly known as "uranic acid" in older literature due to their similarity in formula to various metal oxyacids , although they are not in fact particularly acidic. [ 3 ]
While uranium trioxide is encountered as a polymeric solid under ambient conditions, some work has been done on the molecular form in the gas phase, in matrix isolations studies, and computationally.
At elevated temperatures gaseous UO 3 is in equilibrium with solid U 3 O 8 and molecular oxygen .
With increasing temperature the equilibrium is shifted to the right. This system has been studied at temperatures between 900 °C and 2500 °C. The vapor pressure of monomeric UO 3 in equilibrium with air and solid U 3 O 8 at ambient pressure, about 10 −5 mbar (1 mPa) at 980 °C, rising to 0.1 mbar (10 Pa) at 1400 °C, 0.34 mbar (34 Pa) at 2100 °C, 1.9 mbar (193 Pa) at 2300 °C, and 8.1 mbar (809 Pa) at 2500 °C. [ 23 ] [ 24 ]
Infrared spectroscopy of molecular UO 3 isolated in an argon matrix indicates a T-shaped structure ( point group C 2v ) for the molecule. This is in contrast to the commonly encountered D 3h molecular symmetry exhibited by most trioxides. From the force constants the authors deduct the U-O bond lengths to be between 1.76 and 1.79 Å (176 to 179 pm ). [ 25 ]
Calculations predict that the point group of molecular UO 3 is C 2v , with an axial bond length of 1.75 Å, an equatorial bond length of 1.83 Å and an angle of 161° between the axial oxygens. The more symmetrical D 3h species is a saddle point, 49 kJ/mol above the C 2v minimum. The authors invoke a second-order Jahn–Teller effect as explanation. [ 26 ]
The crystal structure of a uranium trioxide phase of composition UO 2·82 has been determined by X-ray powder diffraction techniques using a Guinier-type focusing camera. The unit cell is cubic with a = 4·138 ± 0·005 kX. A uranium atom is located at (000) and oxygens at (View the MathML source), (View the MathML source), and (View the MathML source) with some anion vacancies. The compound is isostructural with ReO 3 . The U-O bond distance of 2·073 Å agrees with that predicted by Zachariasen for a bond strength S = 1. [ 27 ]
Uranium trioxide reacts at 400 °C with freon-12 to form chlorine , phosgene , carbon dioxide and uranium tetrafluoride . The freon-12 can be replaced with freon-11 which forms carbon tetrachloride instead of carbon dioxide. This is a case of a hard perhalogenated freon which is normally considered to be inert being converted chemically at a moderate temperature. [ 28 ]
Uranium trioxide can be dissolved in a mixture of tributyl phosphate and thenoyltrifluoroacetone in supercritical carbon dioxide , ultrasound was employed during the dissolution. [ 29 ]
The reversible insertion of magnesium cations into the lattice of uranium trioxide by cyclic voltammetry using a graphite electrode modified with microscopic particles of the uranium oxide has been investigated. This experiment has also been done for U 3 O 8 . This is an example of electrochemistry of a solid modified electrode , the experiment which used for uranium trioxide is related to a carbon paste electrode experiment. It is also possible to reduce uranium trioxide with sodium metal to form sodium uranium oxides. [ 30 ]
It has been the case that it is possible to insert lithium [ 31 ] [ 32 ] [ 33 ] into the uranium trioxide lattice by electrochemical means, this is similar to the way that some rechargeable lithium ion batteries work. In these rechargeable cells one of the electrodes is a metal oxide which contains a metal such as cobalt which can be reduced, to maintain the electroneutrality for each electron which is added to the electrode material a lithium ion enters the lattice of this oxide electrode.
Uranium oxide is amphoteric and reacts as acid and as a base , depending on the conditions.
Dissolving uranium oxide in a strong base like sodium hydroxide forms the doubly negatively charged uranate anion ( UO 2− 4 ). Uranates tend to concatenate, forming diuranate , U 2 O 2− 7 , or other poly-uranates.
Important diuranates include ammonium diuranate ((NH 4 ) 2 U 2 O 7 ), sodium diuranate (Na 2 U 2 O 7 ) and magnesium diuranate (MgU 2 O 7 ), which forms part of some yellowcakes . It is worth noting that uranates of the form M 2 UO 4 do not contain UO 2− 4 ions, but rather flattened UO 6 octahedra, containing a uranyl group and bridging oxygens. [ 34 ]
Dissolving uranium oxide in a strong acid like sulfuric or nitric acid forms the double positive charged uranyl cation . The uranyl nitrate formed (UO 2 (NO 3 ) 2 ·6H 2 O) is soluble in ethers , alcohols , ketones and esters ; for example, tributylphosphate . This solubility is used to separate uranium from other elements in nuclear reprocessing , which begins with the dissolution of nuclear fuel rods in nitric acid to form this salt. The uranyl nitrate is then converted to uranium trioxide by heating.
From nitric acid one obtains uranyl nitrate , trans -UO 2 (NO 3 ) 2 ·2H 2 O, consisting of eight-coordinated uranium with two bidentate nitrato ligands and two water ligands as well as the familiar O=U=O core.
UO 3 -based ceramics become green or black when fired in a reducing atmosphere and yellow to orange when fired with oxygen. Orange-coloured Fiestaware is a well-known example of a product with a uranium-based glaze. UO 3 -has also been used in formulations of enamel , uranium glass , and porcelain .
Prior to 1960, UO 3 was used as an agent of crystallization in crystalline coloured glazes. It is possible to determine with a Geiger counter if a glaze or glass was made from UO 3 .
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The UPRM College of Engineering is one of four colleges of the University of Puerto Rico at Mayaguez . This school is also the largest of its kind in Puerto Rico , with an enrollment of about 5,000 undergraduate students and about 400 graduates. It is the main producer of Hispanic engineers in the United States of America , according to the American Society of Engineering Education (ASEE). [ 1 ]
The School of Engineering currently consists of seven departments:
This Puerto Rico –related article is a stub . You can help Wikipedia by expanding it .
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The Department of Chemical Engineering (DChE) is an academic department operating under the College of Engineering of the University of the Philippines Diliman .
The department was established in 1956 and has an overall 90% passing rate in the licensure examinations held in the Philippines. It also contributes about 10% to 60% of the total number of new chemical engineers in the Philippines every year. [ 1 ]
The department offers undergraduate and graduate programs leading to the degree of chemical engineering:
The department consists of thirteen (13) research laboratories in different fields of chemical engineering and allied fields, and also hosts the Chemical Engineering Analytical Laboratory (CEAL), which offers analytical services to the university and industry.
CEAL houses a Scanning Electron Microscope (SEM), a Fourier-Transform Infrared (FTIR) Spectroscope, a Universal Testing Machine (UTM); gas chromatographs (FID, TCD, MS), Ion Chromatographs, and high-performance liquid chromatograph (HPLC); the Department also has a Kjeldahl apparatus, a Karl Fischer apparatus, and an atomic absorption spectrophotometer (AAS). There is a real-time PCR, and digital gradient electrophoresis, shaking incubators and refrigerated incubators for biological studies. [ 4 ]
The thirteen (13) research laboratories are the following:
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UPd 2 Al 3 is a heavy-fermion superconductor with a hexagonal crystal structure and critical temperature T c =2.0K that was discovered in 1991. [ 1 ] Furthermore, UPd 2 Al 3 orders antiferromagnetically at T N =14K, and UPd 2 Al 3 thus features the unusual behavior that this material, at temperatures below 2K, is simultaneously superconducting and magnetically ordered. [ 2 ] Later experiments demonstrated that superconductivity in UPd 2 Al 3 is magnetically mediated, [ 3 ] and UPd 2 Al 3 therefore serves as a prime example for non-phonon-mediated superconductors.
Heavy-fermion superconductivity was discovered already in the late 1970s (with CeCu 2 Si 2 being the first example), but the number of heavy-fermion compounds known to superconduct was still very small in the early 1990s, when Christoph Geibel in the group of Frank Steglich found two closely related heavy-fermion superconductors, UNi 2 Al 3 (T c =1K) and UPd 2 Al 3 (T c =2K), which were published in 1991. [ 4 ] [ 1 ] At that point, the T c =2.0K of UPd 2 Al 3 was the highest critical temperature amongst all known heavy-fermion superconductors, and this record would stand for 10 years until CeCoIn 5 was discovered in 2001. [ 5 ]
The overall metallic behavior of UPd 2 Al 3 , [ 1 ] e.g. as deduced from the dc resistivity, is typical for a heavy-fermion material and can be explained as follows: incoherent Kondo scattering above approximately 80 K and coherent heavy-fermion state (in a Kondo lattice ) at lower temperatures. Upon cooling below 14 K, UPd 2 Al 3 orders antiferromagnetically in a commensurate fashion (ordering wave vector (0,0,1/2)) and with a sizable ordered magnetic moment of approximately 0.85 μ B per uranium atom, as determined from neutron scattering . [ 6 ]
The metallic heavy-fermion state is characterized by a strongly enhanced effective mass, which is connected to a reduced Fermi velocity , which in turn brings about a strongly suppressed transport scattering rate. Indeed, for UPd 2 Al 3 optical Drude behavior with an extremely low scattering rate was observed at microwave frequencies. [ 7 ] This is the 'slowest Drude relaxation' observed for any three-dimensional metallic system so far.
Superconductivity in UPd 2 Al 3 has a critical temperature of 2.0K and a critical field around 3T. The critical field does not show anisotropy despite the hexagonal crystal structure. [ 8 ] For heavy-fermion superconductors it is generally believed that the coupling mechanism cannot be phononic in nature. In contrast to many other unconventional superconductors, for UPd 2 Al 3 there actually exists strong experimental evidence (namely from neutron scattering [ 3 ] and tunneling spectroscopy [ 9 ] ) that superconductivity is magnetically mediated.
In the first years after the discovery of UPd 2 Al 3 it was actively discussed whether its superconducting state can support a Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase , but this suggestion was later refuted. [ 2 ]
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UPt 3 is an inorganic binary intermetallic crystalline compound of platinum and uranium . [ 1 ]
It can be synthesised in the following ways: [ 3 ]
UPt 3 forms crystals of hexagonal symmetry (some studies hypothesize a trigonal structure instead [ 4 ] ), space group P6 3 /mmc, [ 5 ] cell parameters a = 0.5766 nm and c = 0.4898 nm ( c should be understood as distance from planes), with a structure similar to nisnite (Ni 3 Sn) and MgCd 3 . [ 6 ] [ 7 ]
The compound congruently melts at 1700 °C. [ 2 ] The enthalpy of formation of the compound is -111 kJ/mol. [ 3 ]
At temperatures below 1 K it becomes superconducting , thought to be due to the presence of heavy fermions (the uranium atoms). [ 8 ] [ 9 ]
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The U.S. Bureau of Mines (USBM) , developed by Donaldson et al. in 1969, is a method to measure wettability of petroleum reservoir rocks. In this method, the areas under the forced displacement Capillary pressure curves of oil and water drive processes are denoted as A 1 {\displaystyle A1} and A 2 {\displaystyle A2} to calculate the USBM index. [ 1 ] [ 2 ]
USBM index is positive for water-wet rocks, and negative for oil-wet systems.
The USBM index is theoretically unbounded and can vary from negative infinity to positive infinity. Since other wettability indices such as Amott-Harvey, Lak wettability index and modified Lak are bounded in the range of -1 to 1, Abouzar Mirzaei-Paiaman highlighted the bounded form of USBM (called USBM*) as a replacement of the traditional USBM as [ 3 ]
USBM* varies from -1 to 1 for strongly oil-wet and strongly water-wet rocks, respectively.
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https://en.wikipedia.org/wiki/USBM_wettability_index
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A USB image — is bootable image of Operating system (OS) or other software where the boot loader is located on a USB flash drive , or another USB device (with memory storage) instead of conventional CD or DVD discs. The operating system loads from the USB device either to load it much like a Live CD that runs OS or any other software from the storage or installs OS itself. USB image runs off of the USB device the whole time. A USB image is easier to carry, can be stored more safely than a conventional CD or DVD . Drawbacks are that some older devices may not support USB booting and that the USB storage devices lifespan might be shortened.
Ubuntu has included a utility for installing an operating system image file to a USB flash drive since version 9.10. [ 1 ] Windows support also has added a step by step on how to set up a USB device as a bootable drive. [ 2 ]
Both graphical applications and command line utilities are available for authoring bootable operating system images. dd is a utility commonly found in Unix operating systems that allow creation of bootable images. [ 3 ]
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https://en.wikipedia.org/wiki/USB_image
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USP26 is a peptidase enzyme. The USP26 gene is an X-linked gene exclusively expressed in the testis and it codes for the ubiquitin-specific protease 26. [ 1 ] The USP26 gene is found at Xq26.2 on the X-chromosome as a single exon. The enzyme that this gene encodes comprises 913 amino acid residues and it is 104 kilodalton in size, which is transcribed from a sequence of 2794 nucleotide base-pairs on the X-chromosome. [ 2 ] The USP26 enzyme is a deubiquitinating enzyme that places a very significant role in the regulation of protein turnover during spermatogenesis. It is a testis-specific enzyme that is solely express in spermatogonia and can prevent the degradation of ubiquitinated USP26 substrates. [ 3 ]
Recent research has suggested that defects in USP26 may be involved in some cases of male infertility , [ 1 ] [ 4 ] specifically Sertoli cell-only syndrome, and an absence of sperm in the ejaculate (azoospermia). [ 5 ]
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https://en.wikipedia.org/wiki/USP26
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The USP Controlled Room Temperature is a series of United States Pharmacopeia guidelines for the storage of pharmaceuticals; [ 1 ] the relevant omnibus standard is USP 797. [ 2 ] [ 3 ] Although 100% compliance remains challenging for any given facility, [ 4 ] the larger protocol may be regarded as constituting a form of clean room [ 5 ] which is included in a suite of best practices .
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https://en.wikipedia.org/wiki/USP_Controlled_Room_Temperature
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US Fleet Tracking is a privately owned company that specializes in manufacturing and distributing GPS Tracking products and accessories designed to enable businesses and individuals to monitor their mobile assets and vehicle fleets, tracking those vehicles live, in realtime, as they move.
The company manufactures a variety of GPS ( Global Positioning System ) trackers intended for use in vehicles and other mobile assets. It also offers an Internet-based subscription service that gives clients access to 5- or 10-second updates around the clock from each installed GPS tracker. The system collects and stores data from each unit on a 24/7 basis, and can generate reports showing the activity of each vehicle during a specified time frame. [ 1 ] The system can be configured to transmit alerts to the account owner if certain user-defined conditions are detected, such as a monitored vehicle exceeding acceptable speeds or entering/exiting a specific area. [ 2 ]
During his employment as IT Director at Metropolitan EMS (MEMS) in Little Rock, Arkansas (1997-1998), Jerry Hunter began working with 911 Emergency Dispatch systems and tablet-based data acquisition systems. His subsequent contract with Little Rock Police Department resulted in his development of 911 Emergency Dispatch system there, as well as in-car mobile data terminals with live GPS tracking, live camera system, messaging, and NCIC gateway and client products. These systems communicated primarily through proprietary dataradio systems from Motorola and Kenwood. Hunter founded predecessor company Pinnacle Labs Corp. in Arkansas in 2001, marketing his dispatch and in-car police systems throughout the US. This experience was critical in creating the foundation on which US Fleet Tracking's live tracking technology was built.
With the advent of Google Maps and the proliferation of wireless data services from Sprint and AT&T, Hunter founded US Fleet Tracking in 2005. Google Maps provided the ability to convert the dispatch platform into a web-based application without the need for specialized local maps and aerial imagery, and the proliferation of wireless data services eliminated the need for expensive private data radio towers. Relocating to Oklahoma City in 2006, Hunter brought this GPS tracking technology to the general marketplace, with the aim of providing affordable LIVE GPS tracking technology to mobile workforce businesses as well as private individuals. [ 3 ]
In 2007, US Fleet Tracking provided live GPS tracking to Gameday Management Group for use at the Super Bowl, tracking AFC and NFC Team buses, media buses, press buses, halftime entertainers, team owners and team family limousines, and other critical assets. US Fleet Tracking continues to provide these services for the Super Bowl each year, as it has each year since 2007 (through 2020). In 2013, US Fleet Tracking sponsored the FLS Microjet for its appearance at the EAA AirVenture Oshkosh airshow in Oshkosh, Wisconsin. The company demonstrated its live tracking technology at the event by installing its proprietary GPS equipment on the FLS Microjet and allowing the public to follow the course of the aircraft via a website in real time during the exhibition. [ 4 ]
In 2013 US Fleet Tracking announced the formation of a strategic partnership with AgTrax Technologies, developers of accounting software programs for agri-businesses. The partnership resulted in the integration of AgTrax’s software with US Fleet Tracking’s TotalView system to create an enhanced GPS tracking system that enables real-time monitoring of mobile agricultural equipment. [ 5 ]
In 2016 US Fleet Tracking established a partnership with Gorilla Safety, a Houston-based company specializing in software for the transportation sector, to create a fully integrated system that combines live GPS tracking with electronic logging features compliant with the Electronic Logging Device (ELD) mandate of the Federal Motor Carrier Safety Administration (FMCSA). [ 6 ]
US Fleet Tracking’s live GPS services have been used by organizers and logistics managers for countless high-profile events, including every Super Bowl (XLI through LIV) since 2007, the 2010 Winter Olympics , the 2010 Pro Bowl , the 2011 NHL All-Star Game , the 2012 Summer Olympics , the 2012 Republican National Convention , and the 2011 & 2012 Hoka Hey Motorcycle Challenge . [ 7 ] [ 8 ]
US Fleet Tracking has received the following honors:
• Silver, 2007 M2M Value Chain Awards, Enabler – M2M Magazine [ 9 ] • Bronze, 2008 M2M Value Chain Awards, Enabler – M2M Magazine [ 10 ] • 2010 Innovator of the Year – The Journal Record [ 11 ] • 2012 Rock Solid Award, Mobile Office – ProPickup [ 12 ]
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https://en.wikipedia.org/wiki/US_Fleet_Tracking
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UTRdb 2.0 is an updated version of the specialized database UTRdb , which focuses on the 5' and 3' untranslated regions (UTRs) of eukaryotic mRNAs . These UTRs play essential roles in the post-transcriptional regulation of gene expression by influencing various processes, including nucleo-cytoplasmic mRNA transport, translation efficiency, subcellular localization, and mRNA stability. Since its launch in 1996, UTRdb has been a valuable resource for researchers studying UTR sequences and their functional implications.
UTRdb 2.0 contains a comprehensive collection of over 26 million entries, derived from more than 6 million genes across 573 species. The database is enriched with a curated set of functional annotations to enhance the understanding of UTR function. These annotations include:
UTRdb 2.0 provides a flexible web interface that allows users to select and retrieve subsets of UTRs based on various criteria. This tool offers comprehensive download options to access the data for further analysis. [ 1 ] [ 2 ]
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https://en.wikipedia.org/wiki/UTRdb
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UTRome is a database of three-prime untranslated regions in C. elegans [ 1 ] developed by Marco Mangone
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https://en.wikipedia.org/wiki/UTRome
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Uranium ditelluride is an inorganic compound with the formula UTe 2 . It was discovered to be an unconventional superconductor in 2018. [ 1 ]
Superconductivity in UTe 2 appears to be a consequence of triplet electrons spin-pairing . [ 2 ] The material acts as a topological superconductor , stably conducting electricity without resistance even in high magnetic fields . [ 1 ] With recent crystal growth techniques a superconducting transition temperature of 2.10 K has been reached as of 2025. [ 3 ]
Charge density waves (CDW) [ 4 ] and pair density waves (PDW) [ 5 ] [ 6 ] [ 7 ] have been described in UTe 2 , with the latest case being the first time it has been described in a p-wave superconductor.
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https://en.wikipedia.org/wiki/UTe2
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UV-328 ( 2-(2 H -benzotriazol-2-yl)-4,6-di- tert -pentylphenol ) is a chemical compound that belongs to the phenolic benzotriazoles . It is a UV filter that is used as an UV-absorber for plastics. [ 3 ]
UV-328 has a melting point of 80-86 °C, a vapor pressure of 4,6·10 −5 Pa (20 °C) and a water solubility of 0,17±0,07 μg·l −1 (25 °C). [ 2 ]
The octanol-water partition coefficient (log K OW ) is 7,93. [ 2 ] [ 4 ]
UV-328 is a light stabilizer for a variety of plastics and other organic substrates. It has been used for the stabilization of styrene homopolymers and copolymers , acrylic polymers, unsaturated polyesters , polyvinyl chloride , polyolefins , polyurethanes , polyacetals , polyvinyl butyral , elastomers and adhesives . [ 5 ] It protects polymers and organic pigments from UV radiation and helps maintain the original appearance and physical integrity of moldings , films, sheets and fibers during outdoor weathering. The application concentration is 0.1-1 %. [ 5 ]
UV-328 has been used for applications such as automotive coatings, industrial coatings, commercial inks such as wood stains or do-it-yourself inks. [ 6 ]
UV-328 is persistent, bioaccumulative and toxic (PBT) as well as very persistent and very bioaccumulative (vPvB). Thus, it is in the list of substances of very high concern . [ 7 ] The 2023 Conference of the Parties of the United Nations Stockholm Convention on Persistent Organic Pollutants took the decision to eliminate the use of UV-328, by listing this chemical in Annex A to the Convention. [ 8 ]
A bioaccumulation factor (log BAF) of 2,6–3,4 was determined in fish from Canadian rivers. [ 9 ] It may cause long lasting harmful effects to aquatic life. [ 10 ]
UV-328 has been found to be associated with adverse health effects in mammals based on repeated-dose toxicity studies conducted in rats and dogs, with the primary health effect being liver toxicity. It is also associated with adverse effects on the kidney based on the study in rats. [ 11 ]
The finding of UV-328 in plastics sampled on remote beaches, [ 12 ] in stomachs of seabirds [ 13 ] and in preen gland oil [ 14 ] [ 15 ] show that it is also transported over long distances and is taken up by biota. [ 16 ] Detections in Arctic biota include eggs of common eider , kittiwake , European shag and glaucous gull as well as the livers of mink . [ 17 ]
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https://en.wikipedia.org/wiki/UV-328
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Ultraviolet-visible (UV-Vis) absorption spectroelectrochemistry (SEC) is a multiresponse technique that analyzes the evolution of the absorption spectra in UV-Vis regions during an electrode process. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] This technique provides information from an electrochemical and spectroscopic point of view. In this way, it enables a better perception about the chemical system of interest. [ 2 ] On one hand, molecular information related to the electronic levels of the molecules is obtained from the evolution of the spectra. On the other hand, kinetic and thermodynamic information of the processes is obtained from the electrochemical signal.
UV-Vis absorption SEC allows qualitative analysis, through the characterization of the different present compounds, and quantitative analysis, by determining the concentration of the analytes of interest. Furthermore, it helps to determine different electrochemical parameters such as absorptivity coefficients, standard potentials , diffusion coefficients, electronic transfer rate constants, etc. [ 7 ] [ 8 ] Throughout history, reversible processes have been studied with colored reagents or electrolysis products. [ 9 ] Nowadays, it is possible to study all kinds of electrochemical processes in the entire UV-Vis spectral range, [ 2 ] even in the near infrared (NIR). [ 10 ]
In UV-Vis absorption SEC , depending on the configuration of the light beam respect to the electrode/solution interface, two types of optical arrangements can be distinguished: normal and parallel configuration. [ 2 ] [ 11 ]
In normal configuration , the light beam samples perpendicularly the electrode surface. Normal configuration provides optical information related to the changes that take place in the solution adjacent to the electrode and on the electrode surface. [ 11 ] The optical path length coincides with the diffusion layer thickness, which is usually in the order of micrometers . This arrangement is the most suitable when the compound of interest is deposited or adsorbed on the working electrode , because it provides information about all processes occurring on the electrode surface. [ 7 ]
UV-Vis absorption SEC in normal arrangement can be performed using both transmission and reflection phenomena. [ 11 ]
In normal transmission , the light beam passes through a optically transparent working electrode, collecting information about the phenomena that take place on the surface of the electrode and on the solution adjacent to it. [ 11 ] Electrodes in this configuration must be composed of materials that have great electrical conductivity and adequate optical transparency in the spectral region of interest. [ 7 ]
The external reflection mode was proposed to improve the sensitivity and to use non-transparent electrodes. [ 2 ]
In normal reflection , the light beam travels in a perpendicular direction to the working electrode surface on which the reflection occurs. The reflected beam is collected to be analyzed in the spectrometer . It is also possible to work with other incidence and collection angles. This configuration is an alternative when the working electrode is non-transparent. [ 11 ] In this configuration, the optical path-length in solution is on the order of twice the diffusion layer thickness. It should be noticed that growth of films on the electrode surface could cause optical interference phenomena. As it is based on reflection phenomenon, in many cases reflectance is used as unit of measurement instead of absorbance. [ 6 ]
The parallel configuration or long optical path-length arrangement only provides information about the spectral changes that occur in the solution adjacent to the working electrode surface, improving the sensitivity to soluble compounds because the length of the optical pathway can be as longer as the length of the electrode . [ 2 ] [ 11 ]
The light beam travels parallel to the working electrode surface, sampling the first micrometers of the solution adjacent to the working electrode surface, and collecting the information on the spectrometer . [ 6 ] [ 11 ]
Usually, aligning light beams has been a difficult task. However, simple alternatives have been developed to perform measurements in parallel configuration. [ 2 ] There are several advantages in this configuration respect to the normal one: better sensitivity, lower detection limits; optically transparent electrodes are not required; and the spectral changes are related only to the diffusion layer. [ 2 ] [ 7 ] [ 11 ]
The experimental set-up used to carry out UV-Vis absorption SEC measurements depends on the chosen configuration and the characteristics of the analyte . The experimental set-up is composed of a light source, a spectrometer , a potentiostat / galvanostat , a SEC cell, a three-electrode system, optical elements to conduct the light beam, and a computer for data collection and analysis. [ 7 ] Currently, there are commercial devices that integrate all these elements in a single instrument, simplifying significantly the SEC experiments. [ 12 ]
UV-Vis absorption SEC is a recent technique that is continuously evolving. However, many advantages have been observed over other techniques. The most outstanding advantages are: [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ]
UV-Vis absorption SEC has been used mainly in different research fields such as: [ 2 ] [ 14 ]
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https://en.wikipedia.org/wiki/UV-Vis_absorption_spectroelectrochemistry
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UV-sensitive syndrome is a cutaneous condition inherited in an autosomal recessive fashion, characterized by photosensitivity and solar lentigines . [ 1 ] Recent research identified that mutations of the KIAA1530 (UVSSA) gene as cause for the development of UV-sensitive syndrome. [ 2 ] Furthermore, this protein was identified as a new player in the Transcription-coupled repair (TC-NER). [ 2 ]
This cutaneous condition article is a stub . You can help Wikipedia by expanding it .
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https://en.wikipedia.org/wiki/UV-sensitive_syndrome
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The Ultraviolet Explorer ( UVEX ) is an upcoming wide-field ultraviolet space telescope from NASA scheduled to launch in 2030. [ 1 ] UVEX will build off of previous ultraviolet space telescopes, specifically GALEX , conducting surveys of the entire sky in both near- and far-ultraviolet light. UVEX will study the evolution of low-metallicity stars and how they affect the evolution of low-metallicity and low-mass galaxies. The probe can also be used for quick-turnaround observation of cosmic events, such as merging stars. UVEX's data will be able to complement other all-sky survey programs in different wavelengths of light, notably those by the Vera C. Rubin Observatory , the Nancy Grace Roman Space Telescope , and Euclid . Compared to earlier ultraviolet space telescopes, UVEX will feature more capable instrumentation and a larger mirror, enabling it to obtain higher-resolution data and observe fainter objects. [ 2 ] [ page needed ]
UVEX will contain one instrument, consisting of the UV-optimized optical telescope array (OTA) and the UV Instrument Module (UVIM). The OTA consists of a 75 cm (30 in)-diameter primary mirror in a three-mirror anastigmat configuration which will capture and redirect light to three different sensors.
UVEX is classified as a Medium-Class Explorer (MIDEX) in NASA's Explorers Program and is planned to launch in 2030. After a period of orbit corrections and instrument commissioning, the probe will begin a two-year series of full-sky surveys. Because of its larger primary mirror, which can capture more light at once than the smaller mirrors of its predecessors, UVEX will observe dimmer and further objects. The probe will reach AB magnitudes greater than 25.8, comparable to the ground-based Vera C. Rubin Observatory . [ 1 ] UVEX will also perform weekly surveys of the Magellanic Clouds , something its predecessors struggled with because of their brightness. [ 2 ] : 4
UVEX's science goals are divided into three "pillars:" [ 2 ] : 4
UVEX will operate in a highly elliptical lunar resonance orbit called P/2. This type of orbit is currently in use by the TESS spacecraft, which is also performing whole-sky surveys, although TESS is primarily searching for exoplanets. The P/2 orbit is in a 2:1 resonance with the Moon , meaning that the spacecraft completes two orbits of Earth for every one orbit of the Moon. Because of this resonance, which enables occasional gravitational interactions with the Moon, the orbit is extremely stable. In addition, the orbit avoids the Van Allen belts entirely, drastically reducing wear on spacecraft components. Because of its high altitude and eccentricity, UVEX will take 13.7 days to complete one orbit. [ 2 ] : 4 [ 3 ]
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https://en.wikipedia.org/wiki/UVEX
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A UV coating (or more generally a radiation cured coating) is a surface treatment which either is cured by ultraviolet radiation, or which protects the underlying material from such radiation's harmful effects. [ 1 ] They have come to the fore because they are considered environmentally friendly and do not use solvents or produce volatile organic compounds (VOCs) , or Hazardous Air Pollutant (HAPs) , [ 2 ] although some materials used for UV coating, such as PVDF [ 3 ] in smart phones and tablets, are known to contain substances harmful to both humans and the environment. [ 4 ]
UV coatings have been applied to mechanical tubing, safety/water suppression pipe and OCTG/line pipe for many years. UV coatings advantages in this application can be summarized as faster , smaller , and cleaner with no thermal ovens required. The coating and curing (almost instantly) at speeds ranging from 100 feet per minute to over 800 feet per minute so the faster production speeds provide greater opportunity for return on investment for the customer (ROI). The resulting smaller floor footprint for UV coatings line is 20–32 feet (6.1–9.8 m) in total length, while running 100–800 feet (30–244 m) feet per minute is also considered desirable. The process is cleaner because no Volatile organic compound|volatile organic compounds (VOCs), or Air pollution|Hazardous Air Pollutant (HAPs) are produced. [ 5 ]
Ultraviolet cured coatings can be applied over ink printed on paper and dried by exposure to UV radiation. [ 6 ] UV coatings can be formulated up to 100% solids so that they have no volatile component that contributes to pollution. [ 7 ] This high solids level also allows for the coating to be applied in very thin films. UV coatings can be formulated to a wide variety of gloss ranges. UV coating can be applied via most conventional industrial coating applications as well as by silkscreen and 3D printing. [ 8 ]
Due to the normally high solids content of UV coating/varnish the surface of the cured film can be extremely reflective and glossy. 80 lb text and heavier weights of paper can be UV coated, however, cover weights are preferred.
UV can be applied on spot locations of the paper or by flooding the page. This coating application can deepen the color of the printed area. Drying is virtually instantaneous when exposed to the correct level of UV light so projects can move quickly into the bindery .
A printed page with UV coating applied can be very shiny or flattened to a matte finish. A good example of UV coated paper is photo paper sold for home printing projects. UV coatings that are not fully cured can have a slightly sticky/tacky feel.
Glass and plastic can be coated to diminish the amount of ultraviolet radiation that passes through. Common uses of such coating include eyeglasses and automotive windows. Photographic filters remove ultraviolet to prevent exposure of the film or sensor by invisible light. UV curable coatings can be used to impart a variety of properties to polymeric surfaces, including glare reduction, wear or scratch resistance, anti-fogging, microbial resistance, chemical resistance. Computer screens, keyboards, and most other personal electronic devices are treated with some type of UV-curable coating. Coatings are usually applied to plastic substrates via spray, dip, roll, flow and other processes. UV-curable coatings are often specified for plastic parts because the process does not require heat, which can distort the plastic shape. [ 9 ]
The industrial wood finisher has essentially three options in types of UV-curable coatings to use—100% UV, water-reduced UV and solvent reduced UV. Each type of UV-curable coating can be applied by virtually any method of application. The selected method of application is dependent on the surface structure/property to be finished, the finish quality desired on that surface, and the production rate that finishing must achieve. [ 10 ] Another consideration is recovery, typically UV-curable coatings are more expensive than conventional cure coatings and as such any material that does not get applied to the part would need to be recovered as efficiently as possible.
The selection of the UV-curable coating type applied by any method is really a matter of finish build or thickness, the ease to achieve certain finish subtleties (gloss, leveling, etc.), and the ease of use of the coating system. In general, if 100% UV-curable coatings can be used to produce the desired finish quality, it is best to set a course of action to use them.
Costs, operation expenses and reporting requirements will be most advantageous with 100% UV-curable coatings. [ 11 ] If very thin film builds are desired, less than 100% actives may be necessary and the use of water-reduced UV-curable coatings is most preferential. [ 12 ]
When the aluminum cans are formed, they are washed and cleaned. A special coating also is applied on the inside of the can. On the printing press up to 6 different ink rollers supply the colors that coat the printing plates. (Similar process compared to offset lithography). After making contact with the rubber blanket, the can has a complete negative image per color. The process is considered wet on wet ink. After going through each color on the rotary belt, the final image is formed and a special coating is applied to each can to protect the can/colors from wear and tear. The completed cans are sent to the UV oven, that operate over 100 F and contains between six and eight 300 watt/inch UV lamps. Both inside and outside of the can are exposed to the light to ensure proper ink curing.
In recent years, manufacturers have formulated ultraviolet curable coatings for applications outside of a factory or laboratory environment. This technology was first developed and commercialized by Professional Coatings Inc, (Cabot Ar) for substrates such as wood, concrete, vinyl tile and LVT. Other companies such as Arboritec/UVElite and UVGreenCure have continued in the development of new technologies around coating formulation and floor curing machines. Site Applied UV Coatings are available in both 100% solid and water-based formulations. They offer the advantage of quick return to service in the case of substrates such as wood, where polyurethanes can take several days before achieving full cure, and longevity in applications such as VCT, where an acrylic finish can be reapplied several times per year and buffed routinely. The coatings are applied as traditional coatings and then cured with an ultraviolet light (Generally either a mercury discharge lamp or LED-based system) mounted to a rolling chassis or by a handheld unit.
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https://en.wikipedia.org/wiki/UV_coating
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UV curing ( ultraviolet curing ) is the process by which ultraviolet light initiates a photochemical reaction that generates a crosslinked network of polymers through radical polymerization or cationic polymerization . [ 1 ] UV curing is adaptable to printing , coating , decorating, stereolithography , and in the assembly of a variety of products and materials. UV curing is a low-temperature, high speed, and solventless process as curing occurs via polymerization . [ 2 ] Originally introduced in the 1960s, this technology has streamlined and increased automation in many industries in the manufacturing sector. [ 3 ]
UV curing is used for converting or curing inks , adhesives , and coatings . [ 4 ] UV-cured adhesive has become a high speed replacement for two-part adhesives, eliminating the need for solvent removal, ratio mixing, and potential life concern. [ 5 ] It is used in flexographic , offset , pad , and screen printing processes; where UV curing systems are used to polymerize images on screen-printed products, ranging from T-shirts to 3D and cylindrical parts. It is used in fine instrument finishing (guitars, violins, ukuleles, etc.), pool cue manufacturing and other wood craft industries. [ 6 ] Printing with UV curable inks provides the ability to print on a very wide variety of substrates such as plastics, [ 6 ] paper, canvas, glass, metal, [ 7 ] foam boards, tile, films, and many other materials. [ 8 ]
Industries that use UV curing include medicine, automobiles, cosmetics (for example artificial fingernails and gel nail polish ), food, science, education, and art. [ 9 ] UV curable inks have successfully met the demands of the publication sector in terms of print quality, durability, and compatibility with different substrates, making them a suitable choice for printing applications in this industry. [ 10 ]
A primary advantage of curing with ultraviolet light is the speed at which a material can be processed. Speeding up the curing, or drying step, [ 11 ] in a process can reduce flaws and errors by decreasing time that an ink or coating spends as wet. This can increase the quality of a finished item, and potentially allow for greater consistency. Another benefit to decreasing manufacturing time is that less space needs to be devoted to storing items which can not be used until the drying step is finished.
Because UV energy has unique interactions with many different materials, UV curing allows for the creation of products with characteristics not achievable via other means. This has led to UV curing becoming fundamental in many fields of manufacturing and technology, where changes in strength, hardness, durability, chemical resistance, and many other properties are required.
The main components of a UV curing solution includes resins, monomers, and photoinitiators. Resin is an oligomer that imparts specific properties to the final polymer . A monomer is used as a cross-linking agent and regulates the viscosity of the mixture to suit the application. The photoinitiator is responsible for absorbing the light and kickstarting the reaction, which helps control the cure rate and depth of cure. Each of these elements has a role to play in the crosslinking process and is linked to the composition of the final polymer . [ 12 ]
Medium-pressure mercury-vapor lamps have historically been the industry standard for curing products with ultraviolet light. [ 13 ] The bulbs work by sending an electric discharge to excite a mixture of mercury and noble gases , generating a plasma. Once the mercury reaches a plasma state, it irradiates a high spectral output in the UV region of the electromagnetic spectrum . Major peaks in light intensity occur in the 240-270 nm and 350-380 nm regions. These intense peaks, when matched with the absorption profile of a photoinitiator , cause the rapid curing of materials. By modifying the bulb mixture with different gases and metal halides , the distribution of wavelength peaks can be altered, and material interactions are changed.
Medium-pressure lamps can either be standard gas-discharge lamps or electrodeless lamps , and typically use an elongated bulb to emit energy. By incorporating optical designs such an elliptical or even aconic reflector , light can either be focused or projected over a far distance. These lamps can often operate at over 900 degrees Celsius and produce UV energy levels over 10 W/cm 2 .
Low-pressure mercury-vapor lamps generate primarily 254 nm 'UVC' energy, and are most commonly used in disinfection applications. Operated at lower temperatures and with less voltage than medium-pressure lamps, they, like all UV sources , require shielding when operated to prevent excess exposure of skin and eyes.
Since development of the aluminium gallium nitride LED in the early 2000s, UV LED technology has seen sustained growth in the UV curing marketplace. Generating energy most efficiently in the 365-405 nm 'UVA' wavelengths, continued technological advances, [ 14 ] have allowed for improved electrical efficiency of UV LEDs as well as significant increases in output. Benefiting from lower-temperature operation and the lack of hazardous mercury, [ 15 ] UV LEDs have replaced medium-pressure lamps in many applications. Major limitations include difficulties in designing optics for curing on complex three-dimensional objects, and poor efficiency at generating lower-wavelength energy, though development work continues.
Radical Polymerization is used in the curing of acrylic resins in the presence of UV in the industry. [ 16 ] Light energy from UV breaks apart photoinitiaters, forming radicals. The radical then react with the polymers, forming polymers with radical groups that then react with additional monomers. The monomer chain extends until it reaches another polymer and reacts with the polymer. Polymers will form with monomer bridges between them, thus leading to a cross-linked network.
Cationic polymerization is used in the curing of epoxy resins in the presence of UV in the industry. [ 16 ] Light energy from UV breaks apart photoinitiaters, forming an acidic solution which then donates a proton to the polymer. The monomers then attach themselves to the polymer, forming longer and longer chains leading to a cross-linked network.
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https://en.wikipedia.org/wiki/UV_curing
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An ultraviolet detector (also known as UV detector or UV-Vis detector ) [ 1 ] [ 2 ] is a type of non-destructive chromatography detector which measures the amount of ultraviolet or visible light absorbed by components of the mixture being eluted off the chromatography column. They are often used as detectors for high-performance liquid chromatography . [ 3 ]
The vast majority of liquid chromatographic systems are equipped with ultraviolet (UV) absorption detectors. The most common UV-Vis detectors used are variable wavelength detectors (VWD), photo diode array detectors (PDA), and diode array detectors (DAD). [ 4 ] Variable wavelength detectors decide in advance which wavelength is needed for the detection. Its absorbance as function of time is collected in a graphic format called a chromatogram. [ 5 ]
As can be seen in Figure 1, these detectors have a light source , a dispersion element that is a diffraction grating or prism , a flow cell, to where the sample arrives directly from the chromatographic column , an optical bench of lenses and mirrors, and a diode that receives the light coming from the optical system and translates it into a signal proportional to light intensity. When the user selects a wavelength for the detector, the optical system rotates the grating or prism in the space, so that the desired wavelength passes through optical system, then the flow cell and reaches the diode. The UV/Vis detector then produces a chromatogram as a two-dimensional (2D) output. This output plots time on the x-axis and response in absorbance units (AU) on the y-axis. The chromatogram is then analyzed by integrating the peaks curves to get their area, then getting their retention time (RT) from the peak maximum to identify them, and then perform quantitative analysis, by comparing their area to those of samples whose concentrations are known, i.e, standards.
In recent years, diode array UV-Vis detectors have been increasingly used to collect entire spectra at any given moment of data collection. Diode array detectors (DADs) collect entire UV spectra at every point of the eluting peaks while operating as a multi-wavelength UV-Vis detector. This way they give additional information, which help understand more about the nature of the substances appearing in the chromatogram and allow their identification. [ 6 ] DADs are the preferred detectors for HPLC method development because they facilitate better peak identification.
A schematic of the optical systems is shown in Figure 1. The variable UV-Vis absorbance detector's optical bench is showing how the flow cell is positioned after the optical system, including the monochromator, which typically has a physical slit and a moving grating, so it is illuminated by a selected wavelength, reaching a photo-diode. The bench of the diode array detector, however, is configured so that the flow cell is positioned before the optical parts, so that the beam containing the entire spectrum is passing through it. The optical parts consist also with a monochromator and a slit, but with a fixed grating, which disperses the light onto a diode array imaging element.
This article related to chromatography is a stub . You can help Wikipedia by expanding it .
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UV pinning is the process of applying a dose of low intensity ultraviolet (UV) light to a UV curable ink (UV ink). The light's wavelengths must be correctly matched to the ink's photochemical properties. As a result, the ink droplets move to a higher viscosity state, but stop short of full cure . This is also referred to as the " gelling " of the ink.
UV pinning is typically used in UV ink jet applications (e.g. the printing of labels , the printing of electronics , and the fabrication of 3-D microstructures ).
UV pinning enhances the management of drop size and image integrity, minimizing the unwanted mixing of drops and providing the highest possible image quality and the sharpest colour rendering.
Challenge:
Overcome the wetting problems that were causing UV-Curable inks to spread and cause ink droplets to bleed into each other before full curing single-pass digital printing of narrow web labels.
Solution:
A UV pinning system that uses high power UV light emitting diodes ( LEDs ) installed next to the inkjet array (print head). The UV light from the pinning system, typically lower than that of the full cure UV system, causes the UV ink to thicken, also known as gelling, but not fully cure. This ink thickening stops dot gain and holds the ink droplet pattern in place until it reaches the full cure UV system.
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The UWA telerobot is a teleoperable robot belonging to the school of mechanical and civil engineering at the University of Western Australia .
The UWA telerobot is a historic landmark for the Internet and The University of Western Australia. It was the first telerobot device made available for general use on the Internet in 1994. The UWA telerobot was originally developed as part of a PhD thesis by Kenneth Taylor [ 1 ] and was the subject of a later PhD by Barney Dalton. [ 2 ]
The first robot on the Internet, a plastic toy robot with only 2 degrees of freedom , was placed online by a team under Ken Goldberg at the University of Southern California [ 3 ] only three weeks before the UWA team released their website. The USC robot only lasted for seven months. The UWA robot is still online today, although the original robot was replaced in 1996 [ 1 ] and the robot is no longer available for unrestricted public access, though interested parties can request permission. [ 4 ]
The current UWA telerobot is an ABB IRB1400 model 6 DOF serial chain robot fitted with a pneumatic gripper attachment. The robot runs on a standard ABB S4 Robot Controller linked to a Linux server and which in turn communicates with a second server running ABB 's RobComm software and a National Instruments Labview application that was custom written for the task by James Trevelyan with assistance from Perth -based Icon Technologies and students. [ 5 ] The robot forms part of the UWA telelabs project. [ 6 ]
The Telerobot has undergone many changes to its control structure over time. Originally controlled via static HTML web pages using CGI , work by Dalton saw the introduction of an augmented reality Java -based interface that met with limited success. [ 2 ] Control is currently by way of a downloadable LabVIEW client application that incorporates real-time video streaming, with access control provided by the Telelabs system. [ 5 ]
The robot continues to be the basis for research and group projects undertaken by Mechatronics Engineering students and staff at UWA , Primarily involving the addition of new features or capabilities to the system. The robot is also used as a teaching aid for a course in mechanisms and multibody systems run by Karol Miller . [ 7 ] [ 8 ]
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Ubiquitin-AMC is a fluorogenic substrate for a wide range of deubiquitinating enzymes (DUBs), including ubiquitin C-terminal hydrolases (UCHs) and ubiquitin specific proteases (USPs). It is a particularly useful reagent for the study of deubiquitinating activity where detection sensitivity or continuous monitoring of activity is essential. [ 1 ]
Ubiquitin-AMC is prepared by the C-terminal derivatization of ubiquitin with 7-amino-4-methylcoumarin and has been shown to be a useful and sensitive fluorogenic substrate for wide range of deubiquitinylating enzymes (DUBs), including ubiquitin C-terminal hydrolases (UCHs) and ubiquitin specific proteases (USPs).
Ubiquitin-AMC has been shown to be a sensitive substrate for UCH-L3 (Km = 0.039 μM) and for Isopeptidase-T (Km = 0.17-1.4 μM), [ 2 ] and is particularly useful for studying deubiquitinylating activity where detection sensitivity or continuous monitoring of activity is essential. [ 3 ]
Typical assay set-up: Assay substrate concentration: 0.01-1.0 μM. Enzyme concentrations, UCH-L3: 10-100pM, isopeptidase-T: 10-100nM. Release of AMC fluorescence by DUB enzymes can be monitored using 380 nm excitation and 460 nm emission wavelengths.
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An Ubbelohde type viscometer or suspended-level viscometer is a measuring instrument which uses a capillary based method of measuring viscosity . [ 2 ] [ 3 ] It is recommended for higher viscosity cellulosic polymer solutions. The advantage of this instrument is that the values obtained are independent of the total volume. The device was developed by the German chemist Leo Ubbelohde (1877-1964).
ASTM and other test methods are: ISO 3104, ISO 3105, ASTM D445, ASTM D446, ASTM D4020, IP 71, BS 188. [ 4 ] [ citation needed ]
The Ubbelohde viscometer is closely related to the Ostwald viscometer . Both are u-shaped pieces of glassware with a reservoir on one side and a measuring bulb with a capillary on the other. A liquid is introduced into the reservoir then sucked through the capillary and measuring bulb. The liquid is allowed to travel back through the measuring bulb and the time it takes for the liquid to pass through two calibrated marks is a measure for viscosity. The Ubbelohde device has a third arm extending from the end of the capillary and open to the atmosphere. In this way the pressure head only depends on a fixed height and no longer on the total volume of liquid.
The determination of viscosity is based on Poiseuille's law :
where t is the time it takes for a volume V to elute. The ratio d v d t {\displaystyle {\frac {dv}{dt}}} depends on R as the capillary radius , on the average applied pressure P, on its length L and on the dynamic viscosity η .
The average pressure head is given by:
with ρ the density of the liquid, g the Standard gravity and H the average head of the liquid. In this way the viscosity of a fluid can be determined.
Usually the viscosity of a liquid is compared to a liquid with an analyte for example a polymer dissolved in it. The relative viscosity is given by:
where t 0 and ρ 0 are the elution time and density of the pure liquid. When the solution is very diluted
the so-called specific viscosity becomes:
This specific viscosity is related to the concentration of the analyte through the Intrinsic viscosity [η] by the power series :
or
where η s p c {\displaystyle {\frac {\eta _{sp}}{c}}} is called the viscosity number .
The intrinsic viscosity can be determined experimentally by measuring the viscosity number as function of concentration as the Y-axis intercept.
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Ubenimex ( INN ), also known more commonly as bestatin , is a competitive, reversible protease inhibitor . It is an inhibitor of arginyl aminopeptidase (aminopeptidase B), [ 3 ] leukotriene A 4 hydrolase (a zinc metalloprotease that displays both epoxide hydrolase and aminopeptidase activities), [ 4 ] alanyl aminopeptidase (aminopeptidase M/N), [ 5 ] leucyl/cystinyl aminopeptidase (oxytocinase/vasopressinase), [ 6 ] [ 7 ] and membrane dipeptidase (leukotriene D 4 hydrolase). It is being studied for use in the treatment of acute myelocytic leukemia [ 8 ] and lymphedema . [ 9 ] It is derived from Streptomyces olivoreticuli . [ 10 ] Ubenimex has been found to inhibit the enzymatic degradation of oxytocin , vasopressin , enkephalins , and various other peptides and compounds. [ citation needed ]
This pharmacology -related article is a stub . You can help Wikipedia by expanding it .
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The Ubersketch is a moniker for a collection of sketches created in The Geometer's Sketchpad by the PRISM-NEO project which mimic ( virtual ) manipulatives , such as the ones found at The National Library of Virtual Manipulatives. The editor of the collection is Greg Clarke of the Simcoe-Muskoka Catholic District School Board .
There is a related set of Adobe Flash objects called the UberFlash collection which are being implemented as part of the Ontario Ministry of Education 's CLIPS project.
The CLIPS calculator, nicknamed the uberCalc, is another collection of tools compiled by Greg Clarke.
This geometry-related article is a stub . You can help Wikipedia by expanding it .
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Ubique was an Israeli software company that produced social-networking and messaging software. Founded in 1994, Ubique is notable for launching the first social-networking software, which included features such as instant messaging, voice over IP ( VoIP ), chat rooms, web-based events, and collaborative browsing.
The company is best known for its most prominent product, Virtual Places, a presence-based chat program that allowed users to explore websites together. This software required both server and client components, enabling users to overlay avatars onto their web browsers and collaborate in real-time as they visited websites. Virtual Places was utilized by providers such as VPChat and Digital Space and eventually evolved into Lotus Sametime. Despite advancements and changes, some consumer-oriented communities still use older versions of Virtual Places.
The company's technology laid the foundation for the development of a sophisticated instant messaging and presence platform, which culminated in the creation of Lotus Sametime. Ubique's mission from its inception was "to add people to the web," transforming the early static web into a dynamic, interactive environment.
In 1995, America Online (AOL) acquired Ubique with the aim of enhancing its online interactive communication services. However, after the discontinuation of GNN in 1996, Ubique shifted its focus from consumer markets to corporate presence technology and instant messaging. In 1998, Ubique was acquired by Lotus /IBM to integrate its technology into Lotus products. By 2006, elements of Ubique were incorporated into IBM Haifa Labs , which continued to develop real-time collaboration technologies. [ 1 ]
Ubique Ltd was founded in 1994 in Israel by Ehud Shapiro and a group of scientists from
the Weizmann Institute to develop real-time , distributed computing products. The
company developed a presence-based chat system known as Virtual Places along with real-time instant messaging and presence technology software. These were the very early days of the web, which at the time had only static data. Ubique's mission was "to add people to the web".
In 1995, America Online Inc. purchased Ubique for $14.5 million with the intention to use Ubique's Virtual
Places technology to enhance and expand its existing live online interactive communication for both the AOL consumer online service and the new Global Network Navigator (GNN) brand service. Only the GNN-branded Virtual Places product was ever released. [ 2 ]
In 1996, GNN was discontinued in 1996. Ubique's management, with the support of AOL, decided to look for other markets for Virtual Places technology. The outcome was that Ubique shifted Virtual Places from the consumer market to focus on presence technology and instant messaging for the corporate market. AOL divested Ubique but remained as a principal investor while Ubique sought a new owner.
In 1998, Ubique was acquired by Lotus / IBM to integrate the core
technology of instant messaging and presence functions into a software product integrated with Lotus / IBM . [ 3 ]
In 2000, Lotus announced Lotus Sametime using Ubique's technology.
In 2006, Elements of Ubique along with other Israeli-based companies were integrated into the
newly created IBM Haifa Labs . The Lab develops Session Initiation Protocol (SIP) infrastructure and features of real-time collaboration, including session management, presence awareness, subscriptions and notifications, text messaging, developer toolkits, and mobile real-time messaging infrastructure. [ 4 ]
Ubique's best-known product is Virtual Places, a presence-based chat program in which users explore web sites together. It is used by providers such as VPChat and Digital Space and eventually evolved into Lotus Sametime .
Virtual Places requires a server and client software. Users start Virtual Places along with a web
browser and sign into the Virtual Places server. Avatars are overlaid onto the web browser and
users are able to collaborate with each other while they all visit web sites in real time.
Some Virtual Places consumer-oriented communities are still alive on the Web and are using the old version of it.
With the technology developed for Virtual Places, Ubique created an instant messaging and presence technology platform which evolved into Lotus Sametime.
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Ubiquinol oxidases ( EC 1.10.3.11 ) are enzymes in the bacterial electron transport chain that oxidise ubiquinol into ubiquinone and reduce oxygen to water. These enzymes are one set of the many alternative terminal oxidases in the branched prokaryotic electron transport chain. [ 1 ] The overall structure of the E. coli ubiquinol oxidase is similar to that of the mammalian Cytochrome c oxidase , with the addition of a polar ubiquinol-binding site embedded in the membrane. [ 2 ]
This EC 1.10 enzyme -related article is a stub . You can help Wikipedia by expanding it .
This article about metabolism is a stub . You can help Wikipedia by expanding it .
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Ubiquitin-conjugating enzymes , also known as E2 enzymes and more rarely as ubiquitin-carrier enzymes , perform the second step in the ubiquitination reaction that targets a protein for degradation via the proteasome . The ubiquitination process covalently attaches ubiquitin , a short protein of 76 amino acids , to a lysine residue on the target protein. Once a protein has been tagged with one ubiquitin molecule, additional rounds of ubiquitination form a polyubiquitin chain that is recognized by the proteasome's 19S regulatory particle, triggering the ATP -dependent unfolding of the target protein that allows passage into the proteasome's 20S core particle, where proteases degrade the target into short peptide fragments for recycling by the cell . [ 1 ]
A ubiquitin-activating enzyme , or E1, first activates the ubiquitin by covalently attaching the molecule to its active site cysteine residue. The activated ubiquitin is then transferred to an E2 cysteine. Once conjugated to ubiquitin, the E2 molecule binds one of several ubiquitin ligases or E3s via a structurally conserved binding region. The E3 molecule is responsible for binding the target protein substrate and transferring the ubiquitin from the E2 cysteine to a lysine residue on the target protein. [ 1 ]
A particular cell usually contains only a few types of E1 molecule, a greater diversity of E2s, and a very large variety of E3s. In humans, there are about 30 E2s which can bind with one of the 600+ E3s. [ 2 ] The E3 molecules responsible for substrate identification and binding are thus the mechanisms of substrate specificity in proteasomal degradation. Each type of E2 can associate with many E3s. [ 3 ]
E2s can also be used to study protein folding mechanisms. Since the ubiquitylation system is shared across all organisms, studies can use modified E2 proteins in order to understand the overall system for how all organisms process proteins. [ 4 ] There are also some proteins which can act as both and E2 and an E3 containing domains which cover both E2 and E3 functionality. [ 5 ]
The following human genes encode ubiquitin-conjugating enzymes:
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Ubiquitous computing (or " ubicomp ") is a concept in software engineering , hardware engineering and computer science where computing is made to appear seamlessly anytime and everywhere. In contrast to desktop computing , ubiquitous computing implies use on any device, in any location, and in any format. A user interacts with the computer, which can exist in many different forms, including laptop computers , tablets , smart phones and terminals in everyday objects such as a refrigerator or a pair of glasses . The underlying technologies to support ubiquitous computing include the Internet , advanced middleware , kernels , operating systems , mobile codes , sensors , microprocessors , new I/Os and user interfaces , computer networks , mobile protocols, global navigational systems , and new materials.
This paradigm is also described as pervasive computing , [ 1 ] ambient intelligence , [ 2 ] or "everyware". [ 3 ] Each term emphasizes slightly different aspects. When primarily concerning the objects involved, it is also known as physical computing , the Internet of Things , haptic computing , [ 4 ] and "things that think".
Rather than propose a single definition for ubiquitous computing and for these related terms, a taxonomy of properties for ubiquitous computing has been proposed, from which different kinds or flavors of ubiquitous systems and applications can be described. [ 5 ]
Ubiquitous computing themes include: distributed computing , mobile computing , location computing, mobile networking, sensor networks , human–computer interaction , context-aware smart home technologies, and artificial intelligence .
Ubiquitous computing is the concept of using small internet connected and inexpensive computers to help with everyday functions in an automated fashion. [ 6 ]
Mark Weiser proposed three basic forms for ubiquitous computing devices : [ 7 ]
Ubiquitous computing devices proposed by Mark Weiser are all based around flat devices of different sizes with a visual display. [ 8 ] Expanding beyond those concepts there is a large array of other ubiquitous computing devices that could exist. [ 5 ]
Mark Weiser coined the phrase "ubiquitous computing" around 1988, during his tenure as Chief Technologist of the Xerox Palo Alto Research Center (PARC) . Both alone and with PARC Director and Chief Scientist John Seely Brown , Weiser wrote some of the earliest papers on the subject, largely defining it and sketching out its major concerns. [ 7 ] [ 9 ] [ 10 ]
Recognizing that the extension of processing power into everyday scenarios would necessitate understandings of social, cultural and psychological phenomena beyond its proper ambit, Weiser was influenced by many fields outside computer science, including " philosophy , phenomenology , anthropology , psychology , post-Modernism , sociology of science and feminist criticism ". He was explicit about "the humanistic origins of the 'invisible ideal in post-modernist thought'", [ 10 ] referencing as well the ironically dystopian Philip K. Dick novel Ubik .
Andy Hopper from Cambridge University UK proposed and demonstrated the concept of "Teleporting" – where applications follow the user wherever he/she moves.
Roy Want, while a researcher and student working under Andy Hopper at Cambridge University, worked on the "Active Badge System", which is an advanced location computing system where personal mobility that is merged with computing.
Bill Schilit (now at Google) also did some earlier work in this topic, and participated in the early Mobile Computing workshop held in Santa Cruz in 1996.
Ken Sakamura of the University of Tokyo , Japan leads the Ubiquitous Networking Laboratory (UNL), Tokyo as well as the T-Engine Forum . The joint goal of Sakamura's Ubiquitous Networking specification and the T-Engine forum, is to enable any everyday device to broadcast and receive information. [ 11 ] [ 12 ]
MIT has also contributed significant research in this field, notably Things That Think consortium (directed by Hiroshi Ishii , Joseph A. Paradiso and Rosalind Picard ) at the Media Lab [ 13 ] and the CSAIL effort known as Project Oxygen . [ 14 ] Other major contributors include University of Washington 's Ubicomp Lab (directed by Shwetak Patel ), Dartmouth College 's DartNets Lab, Georgia Tech 's College of Computing , Cornell University 's People Aware Computing Lab, NYU 's Interactive Telecommunications Program , UC Irvine 's Department of Informatics, Microsoft Research , Intel Research and Equator, [ 15 ] Ajou University UCRi & CUS. [ 16 ]
One of the earliest ubiquitous systems was artist Natalie Jeremijenko 's "Live Wire", also known as "Dangling String", installed at Xerox PARC during Mark Weiser's time there. [ 17 ] This was a piece of string attached to a stepper motor and controlled by a LAN connection; network activity caused the string to twitch, yielding a peripherally noticeable indication of traffic. Weiser called this an example of calm technology . [ 18 ]
A present manifestation of this trend is the widespread diffusion of mobile phones. Many mobile phones support high speed data transmission, video services, and other services with powerful computational ability. Although these mobile devices are not necessarily manifestations of ubiquitous computing, there are examples, such as Japan's Yaoyorozu ("Eight Million Gods") Project in which mobile devices, coupled with radio frequency identification tags demonstrate that ubiquitous computing is already present in some form. [ 19 ]
Ambient Devices has produced an "orb", a "dashboard", and a " weather beacon ": these decorative devices receive data from a wireless network and report current events, such as stock prices and the weather, like the Nabaztag , which was invented by Rafi Haladjian and Olivier Mével , and manufactured by the company Violet.
The Australian futurist Mark Pesce has produced a highly configurable 52- LED LAMP enabled lamp which uses Wi-Fi named MooresCloud after Gordon Moore . [ 20 ]
The Unified Computer Intelligence Corporation launched a device called Ubi – The Ubiquitous Computer designed to allow voice interaction with the home and provide constant access to information. [ 21 ]
Ubiquitous computing research has focused on building an environment in which computers allow humans to focus attention on select aspects of the environment and operate in supervisory and policy-making roles. Ubiquitous computing emphasizes the creation of a human computer interface that can interpret and support a user's intentions. For example, MIT's Project Oxygen seeks to create a system in which computation is as pervasive as air:
In the future, computation will be human centered. It will be freely available everywhere, like batteries and power sockets, or oxygen in the air we breathe...We will not need to carry our own devices around with us. Instead, configurable generic devices, either handheld or embedded in the environment, will bring computation to us, whenever we need it and wherever we might be. As we interact with these "anonymous" devices, they will adopt our information personalities. They will respect our desires for privacy and security. We won't have to type, click, or learn new computer jargon. Instead, we'll communicate naturally, using speech and gestures that describe our intent... [ 22 ]
This is a fundamental transition that does not seek to escape the physical world and "enter some metallic, gigabyte-infested cyberspace" but rather brings computers and communications to us, making them "synonymous with the useful tasks they perform". [ 19 ]
Network robots link ubiquitous networks with robots , contributing to the creation of new lifestyles and solutions to address a variety of social problems including the aging of population and nursing care. [ 23 ]
The "Continuity" set of features, introduced by Apple in OS X Yosemite , can be seen as an example of ubiquitous computing. [ 24 ]
Privacy is easily the most often-cited criticism of ubiquitous computing (ubicomp), and may be the greatest barrier to its long-term success. [ 25 ]
This is a list of notable institutions who claim to have a focus on Ubiquitous computing sorted by country:
Topological Media Lab , Concordia University, Canada
Community Imaging Group, University of Oulu , Finland
Telecooperation Office (TECO), Karlsruhe Institute of Technology , Germany
Ubiquitous Computing Research Resource Centre (UCRC), Centre for Development of Advanced Computing [ 26 ]
Centre for Research in Ubiquitous Computing (CRUC), Karachi, Pakistan
Mobile Life Centre , Stockholm University
Mixed Reality Lab, University of Nottingham
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The Ubuntu Forums is the official forum for the Ubuntu operating system. [ 1 ]
As of May 2022, The Ubuntu Forums has 2.1 million registered members and more than 2.2 million threads. [ 2 ] The Ubuntu Forums currently runs on the forum software vBulletin . [ 3 ]
On July 20, 2013 the site was compromised, with attacker(s) both defacing the site and gaining access to "all user email addresses and hashed passwords" [ 4 ]
The site was compromised once again on July 15, 2016. "Usernames, email addresses and IPs for 2 million users" were compromised but 'no active passwords' were accessed. [ 5 ]
The Ubuntu Forums were created by Ryan Troy in October 2004. [ 6 ] The forums became a popular resource for Ubuntu and were deemed the Official Ubuntu Forums in November 2004. [ 7 ] The forums hosting continued to be paid for by Ryan and the occasional donations of forum members until March 2006, when Canonical offered to host the forums on its own servers. In June 2007, the forums' domain name, license, and assets were all transferred to Canonical, which now has sole ownership. [ 8 ]
The primary function of The Ubuntu Forums is for Ubuntu support, but it also has a popular community area where other topics may be discussed. [ 9 ]
The Ubuntu Forums are governed by a moderation team made up of volunteers, often referred to as The Forum Staff. [ 10 ] The Forum Staff have three ranks: Administrators, Super Moderators and Moderators. The Administrators serve on the Forum Council. [ 11 ]
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The ucode system (written in lower case " ucode ") is an identification number system that can be used to identify things in the real world uniquely. Digital information can be associated with objects and places, and the associated information can be retrieved by using ucode.
Unique identification system for real world objects is considered [ 1 ] an essential enabler for the realisation of Internet of Things and therefore ucode system is seen as a building block for Internet of Things. [ 2 ]
The ucode system uses 128 bit code for unique naming of things, so there are 340282366920938463463374607431768211455 or 3.4 x 10^38 different codes. If more codes are needed, they can be added in chunks of 128 bits. Ucode is application and technology-agnostic. Uniqueness means that each ucode is unique, there can – or at least should - not be another ucode with exactly the same number. Ucode is not tied to any specific application or business domain, neither is it committed to any specific technology for containing the ucode number, e.g. RFID, barcode or matrix code. ucode is supported by the uID center, which is a non-profit organisation based in Tokyo , Japan . The Chairman of the uID Center is Professor Ken Sakamura who is also the person behind ucode.
Ubiquitous ID system consists of five components: (1) ucode, (2) ucode tag, (3) ubiquitous communicator, (4) ucode resolution server and (5) ucode information server. [ 3 ] The resolution process goes as follows. First, the ucode from an ucode tag using e.g. a mobile phone is read. The camera of the phone can be used to read a matrix code containing the ucode. Then, the mobile phone inquires the ucode resolution server – via internet connection - about the code. The ucode resolution server returns the source of the provided ucode information based on the ucode read. Finally, the ubiquitous communicator connects to the information provision source and acquires contents and services.
The ucode server architecture is similar to the familiar Internet DNS resolution service. Like DNS, the ucode resolution mechanism consists of hierarchical levels. The ucode resolution mechanism is three tiered as follows:
The root server is maintained by uID Center in Tokyo. TLD servers are in place in Japan, other Asian countries and in Europe (Oulu, Finland). The number of TLD and SLD servers is not limited.
Ucode tags can take various forms. [ 3 ] They can be
Print tags can be matrix codes, e.g. QR codes or barcodes. A special sub-section of RFID tags are NFC tags, which can contain ucode. UID Center has certified a 46 differenrf ucode tags, the first ones in 2003 were barcodes made by Sato corporation, Toppan Forms Inc. and Dai Nippon Printing Co., later on two dimensional matrix codes were introduced, followed by hologram implementation and several RFID tags, often compliant with ISO/IEC15693 standard and using frequency band 13.56 MHz.
The ucode solution has been used in a number of trial cases related to tourist guides, geospatial information applications, housing and real estate as well as food and drug traceability.
Japanese organisation Center for Better Living is using ucode for labelling construction material and components in a unique and traceable manner. The label is a sign of approved quality and entitles the buyer into a two to ten year repair warranty, depending on the nature of the material or component.
EPCGlobal is an identification system aimed for supply chain information management. The EPC (Electronic Product Code) relies on RFID tags for object identification. EPCGlobal is a successor of MIT Auto ID Center which developed the technology used by EPCGlobal.
[EAN] International Article Numbering system and its sister system UPC Universal Product Code are the familiar barcodes seen in all retail merchandise. ucode differs from them in identifying individual objects, not just the product type.
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In classical mechanics , the Udwadia–Kalaba formulation is a method for deriving the equations of motion of a constrained mechanical system . [ 1 ] [ 2 ] The method was first described by Anatolii Fedorovich Vereshchagin [ 3 ] [ 4 ] for the particular case of robotic arms , and later generalized to all mechanical systems by Firdaus E. Udwadia and Robert E. Kalaba in 1992. [ 5 ] The approach is based on Gauss's principle of least constraint . The Udwadia–Kalaba method applies to both holonomic constraints and nonholonomic constraints, as long as they are linear with respect to the accelerations. The method generalizes to constraint forces that do not obey D'Alembert's principle . [ 6 ] [ 7 ] [ 8 ]
The Udwadia–Kalaba equation was developed in 1992 and describes the motion of a constrained mechanical system that is subjected to equality constraints. [ 5 ]
This differs from the Lagrangian formalism, which uses the Lagrange multipliers to describe the motion of constrained mechanical systems, and other similar approaches such as the Gibbs–Appell approach . The physical interpretation of the equation has applications in areas beyond theoretical physics, such as the control of highly nonlinear general dynamical systems. [ 9 ]
In the study of the dynamics of mechanical systems, the configuration of a given system S is, in general, completely described by n generalized coordinates so that its generalized coordinate n -vector is given by
where T denotes matrix transpose . Using Newtonian or Lagrangian dynamics , the unconstrained equations of motion of the system S under study can be derived as a matrix equation (see matrix multiplication ):
M ( q , t ) q ¨ ( t ) = Q ( q , q ˙ , t ) , {\displaystyle \mathbf {M} (q,t){\ddot {\mathbf {q} }}(t)=\mathbf {Q} (q,{\dot {q}},t)\,,}
where the dots represent derivatives with respect to time :
It is assumed that the initial conditions q (0) and q ˙ ( 0 ) {\displaystyle {\dot {\mathbf {q} }}(0)} are known. We call the system S unconstrained because q ˙ ( 0 ) {\displaystyle {\dot {\mathbf {q} }}(0)} may be arbitrarily assigned.
The n -vector Q denotes the total generalized force acted on the system by some external influence; it can be expressed as the sum of all the conservative forces as well as non -conservative forces.
The n -by- n matrix M is symmetric , and it can be positive definite ( M > 0 ) {\displaystyle (\mathbf {M} >0)} or semi-positive definite ( M ≥ 0 ) {\displaystyle (\mathbf {M} \geq 0)} . Typically, it is assumed that M is positive definite; however, it is not uncommon to derive the unconstrained equations of motion of the system S such that M is only semi-positive definite; i.e., the mass matrix may be singular (it has no inverse matrix ). [ 10 ] [ 11 ]
We now assume that the unconstrained system S is subjected to a set of m consistent equality constraints given by
where A is a known m -by- n matrix of rank r and b is a known m -vector. We note that this set of constraint equations encompass a very general variety of holonomic and non-holonomic equality constraints. For example, holonomic constraints of the form
can be differentiated twice with respect to time while non-holonomic constraints of the form
can be differentiated once with respect to time to obtain the m -by- n matrix A and the m -vector b . In short, constraints may be specified that are
As a consequence of subjecting these constraints to the unconstrained system S , an additional force is conceptualized to arise, namely, the force of constraint. Therefore, the constrained system S c becomes
M q ¨ = Q + Q c ( q , q ˙ , t ) , {\displaystyle \mathbf {M} {\ddot {\mathbf {q} }}=\mathbf {Q} +\mathbf {Q} _{c}(q,{\dot {q}},t),}
where Q c —the constraint force—is the additional force needed to satisfy the imposed constraints. The central problem of constrained motion is now stated as follows:
find the equations of motion for the constrained system—the acceleration—at time t , which is in accordance with the agreed upon principles of analytical dynamics.
Below, for positive definite M {\displaystyle \mathbf {M} } , M − 1 / 2 {\displaystyle \mathbf {M} ^{-1/2}} denotes the inverse of its square root , defined as
where W {\displaystyle \mathbf {W} } is the orthogonal matrix arising from eigendecomposition (whose rows consist of suitably selected eigenvectors of M {\displaystyle \mathbf {M} } ), and Λ − 1 / 2 {\displaystyle \mathbf {\Lambda } ^{-1/2}} is the diagonal matrix whose diagonal elements are the inverse square roots of the eigenvalues corresponding to the eigenvectors in W {\displaystyle \mathbf {W} } . [ 1 ]
The solution to this central problem is given by the Udwadia–Kalaba equation. When the matrix M is positive definite, the equation of motion of the constrained system S c , at each instant of time, is [ 5 ] [ 12 ]
where the '+' symbol denotes the pseudoinverse of the matrix A M − 1 / 2 {\displaystyle \mathbf {A} \mathbf {M} ^{-1/2}} . The force of constraint is thus given explicitly as
and since the matrix M is positive definite the generalized acceleration of the constrained system S c is determined explicitly by
In the case that the matrix M is semi-positive definite ( M ≥ 0 ) {\displaystyle (\mathbf {M} \geq 0)} , the above equation cannot be used directly because M may be singular. Furthermore, the generalized accelerations may not be unique unless the ( n + m )-by- n matrix
has full rank (rank = n ). [ 10 ] [ 11 ] But since the observed accelerations of mechanical systems in nature are always unique, this rank condition is a necessary and sufficient condition for obtaining the uniquely defined generalized accelerations of the constrained system S c at each instant of time. Thus, when M ^ {\displaystyle {\hat {\mathbf {M} }}} has full rank, the equations of motion of the constrained system S c at each instant of time are uniquely determined by (1) creating the auxiliary unconstrained system [ 11 ]
and by (2) applying the fundamental equation of constrained motion to this auxiliary unconstrained system so that the auxiliary constrained equations of motion are explicitly given by [ 11 ]
Moreover, when the matrix M ^ {\displaystyle {\hat {\mathbf {M} }}} has full rank, the matrix M A {\displaystyle \mathbf {M} _{\mathbf {A} }} is always positive definite. This yields, explicitly, the generalized accelerations of the constrained system S c as
This equation is valid when the matrix M is either positive definite or positive semi-definite. Additionally, the force of constraint that causes the constrained system S c —a system that may have a singular mass matrix M —to satisfy the imposed constraints is explicitly given by
At any time during the motion we may consider perturbing the system by a virtual displacement δ r consistent with the constraints of the system. The displacement is allowed to be either reversible or irreversible. If the displacement is irreversible, then it performs virtual work . We may write the virtual work of the displacement as
The vector C ( q , q ˙ , t ) {\displaystyle \mathbf {C} (q,{\dot {q}},t)} describes the non-ideality of the virtual work and may be related, for example, to friction or drag forces (such forces have velocity dependence). This is a generalized D'Alembert's principle , where the usual form of the principle has vanishing virtual work with C ( q , q ˙ , t ) = 0 {\displaystyle \mathbf {C} (q,{\dot {q}},t)=0} .
The Udwadia–Kalaba equation is modified by an additional non-ideal constraint term to
The method can solve the inverse Kepler problem of determining the force law that corresponds to the orbits that are conic sections . [ 13 ] We take there to be no external forces (not even gravity) and instead constrain the particle motion to follow orbits of the form
where r = x 2 + y 2 {\displaystyle r={\sqrt {x^{2}+y^{2}}}} , ε {\displaystyle \varepsilon } is the eccentricity, and ℓ {\textstyle \ell } is the semi-latus rectum. Differentiating twice with respect to time and rearranging slightly gives a constraint
We assume the body has a simple, constant mass. We also assume that angular momentum about the focus is conserved as
with time derivative
We can combine these two constraints into the matrix equation
The constraint matrix has inverse
The force of constraint is therefore the expected, central inverse square law
Consider a small block of constant mass on an inclined plane at an angle α {\displaystyle \alpha } above horizontal. The constraint that the block lie on the plane can be written as
After taking two time derivatives, we can put this into a standard constraint matrix equation form
The constraint matrix has pseudoinverse
We allow there to be sliding friction between the block and the inclined plane. We parameterize this force by a standard coefficient of friction multiplied by the normal force
Whereas the force of gravity is reversible, the force of friction is not. Therefore, the virtual work associated with a virtual displacement will depend on C . We may summarize the three forces (external, ideal constraint, and non-ideal constraint) as follows:
Combining the above, we find that the equations of motion are
This is like a constant downward acceleration due to gravity with a slight modification. If the block is moving up the inclined plane, then the friction increases the downward acceleration. If the block is moving down the inclined plane, then the friction reduces the downward acceleration.
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In organic chemistry , the Ugi reaction is a multi-component reaction involving a ketone or aldehyde , an amine , an isocyanide and a carboxylic acid to form a bis- amide . [ 1 ] [ 2 ] [ 3 ] [ 4 ] The reaction is named after Ivar Karl Ugi , who first reported this reaction in 1959.
The Ugi reaction is exothermic and usually complete within minutes of adding the isocyanide. High concentration (0.5M - 2.0M) of reactants give the highest yields. Polar, aprotic solvents , like DMF , work well. However, methanol and ethanol have also been used successfully. This uncatalyzed reaction has an inherent high atom economy as only a molecule of water is lost, and the chemical yield in general is high. Several reviews have been published. [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ excessive citations ]
Due to the reaction products being potential protein mimetics there have been many attempts to development an enantioselective Ugi reaction, [ 13 ] the first successful report of which was in 2018. [ 14 ]
One plausible reaction mechanism is depicted below: [ 15 ]
Amine 1 and ketone 2 form the imine 3 with loss of one equivalent of water. Proton exchange with carboxylic acid 4 activates the iminium ion 5 for nucleophilic addition of the isocyanide 6 with its terminal carbon atom to nitrilium ion 7 . A second nucleophilic addition takes place at this intermediate with the carboxylic acid anion to 8 . The final step is a Mumm rearrangement with transfer of the R4 acyl group from oxygen to nitrogen. All reaction steps are reversible except for the Mumm rearrangement, which drives the whole reaction sequence.
In the related Passerini reaction (lacking the amine), the isocyanide reacts directly with the carbonyl group, but other aspects of the reaction are the same. This reaction can take place concurrently with the Ugi reaction, acting as a source of impurities.
The usage of bifunctional reaction components greatly increases the diversity of possible reaction products. Likewise, several combinations lead to structurally interesting products. The Ugi reaction has been applied in combination with an intramolecular Diels-Alder reaction [ 16 ] in an extended multistep reaction.
A reaction in its own right is the Ugi–Smiles reaction with the carboxylic acid component replaced by a phenol . In this reaction the Mumm rearrangement in the final step is replaced by the Smiles rearrangement . [ 17 ]
Another combination (with separate workup of the Ugi intermediate) is one with the Buchwald–Hartwig reaction . [ 18 ] In the Ugi–Heck reaction a Heck aryl-aryl coupling takes place in a second step. [ 19 ]
Several groups have used β-amino acids in the Ugi reaction to prepare β-lactams. [ 22 ] This approach relies on acyl transfer in the Mumm rearrangement to form the four-membered ring. The reaction proceeds in moderate yield at room temperature in methanol with formaldehyde or a variety of aryl aldehydes. For example, p -nitrobenzaldehyde reacts to form the β-lactam shown in 71% yield as a 4:1 diastereomeric mixture :
Zhang et al. [ 23 ] have combined aldehydes with carboxylic acids and used the Ugi reaction to create lactams of various sizes. Short et al. [ 24 ] have prepared γ-lactams from keto-acids on solid-support.
The Ugi reaction is one of the first reactions to be exploited explicitly to develop chemical libraries. These chemical libraries are sets of compounds that can be tested repeatedly. Using the principles of combinatorial chemistry , the Ugi reaction offers the possibility to synthesize a great number of compounds in one reaction, by the reaction of various ketones (or aldehydes), amines, isocyanides and carboxylic acids. These libraries can then be tested with enzymes or living organisms to find new active pharmaceutical substances. One drawback is the lack of chemical diversity of the products. Using the Ugi reaction in combination with other reactions enlarges the chemical diversity of possible products.
Examples of Ugi reaction combinations:
Crixivan can be prepared using the Ugi reaction. [ 26 ]
Additionally, many of the caine -type anesthetics are synthesized using this reaction. Examples include lidocaine and bupivacaine .
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The ugly duckling theorem is an argument showing that classification is not really possible without some sort of bias . More particularly, it assumes finitely many properties combinable by logical connectives , and finitely many objects; it asserts that any two different objects share the same number of ( extensional ) properties. The theorem is named after Hans Christian Andersen 's 1843 story " The Ugly Duckling ", because it shows that a duckling is just as similar to a swan as two swans are to each other. It was derived by Satosi Watanabe in 1969. [ 1 ] : 376–377
Suppose there are n things in the universe, and one wants to put them into classes or categories. One has no preconceived ideas or biases about what sorts of categories are "natural" or "normal" and what are not. So one has to consider all the possible classes that could be, all the possible ways of making a set out of the n objects. There are 2 n {\displaystyle 2^{n}} such ways, the size of the power set of n objects. One can use that to measure the similarity between two objects, and one would see how many sets they have in common. However, one cannot. Any two objects have exactly the same number of classes in common if we can form any possible class, namely 2 n − 1 {\displaystyle 2^{n-1}} (half the total number of classes there are). To see this is so, one may imagine each class is represented by an n -bit string (or binary encoded integer), with a zero for each element not in the class and a one for each element in the class. As one finds, there are 2 n {\displaystyle 2^{n}} such strings.
As all possible choices of zeros and ones are there, any two bit-positions will agree exactly half the time. One may pick two elements and reorder the bits so they are the first two, and imagine the numbers sorted lexicographically. The first 2 n / 2 {\displaystyle 2^{n}/2} numbers will have bit #1 set to zero, and the second 2 n / 2 {\displaystyle 2^{n}/2} will have it set to one. Within each of those blocks, the top 2 n / 4 {\displaystyle 2^{n}/4} will have bit #2 set to zero and the other 2 n / 4 {\displaystyle 2^{n}/4} will have it as one, so they agree on two blocks of 2 n / 4 {\displaystyle 2^{n}/4} or on half of all the cases, no matter which two elements one picks. So if we have no preconceived bias about which categories are better, everything is then equally similar (or equally dissimilar). The number of predicates simultaneously satisfied by two non-identical elements is constant over all such pairs. Thus, some kind of inductive [ citation needed ] bias is needed to make judgements to prefer certain categories over others.
Let x 1 , x 2 , … , x n {\displaystyle x_{1},x_{2},\dots ,x_{n}} be a set of vectors of k {\displaystyle k} booleans each. The ugly duckling is the vector which is least like the others. Given the booleans, this can be computed using Hamming distance .
However, the choice of boolean features to consider could have been somewhat arbitrary. Perhaps there were features derivable from the original features that were important for identifying the ugly duckling. The set of booleans in the vector can be extended with new features computed as boolean functions of the k {\displaystyle k} original features. The only canonical way to do this is to extend it with all possible Boolean functions. The resulting completed vectors have 2 k {\displaystyle 2^{k}} features. The ugly duckling theorem states that there is no ugly duckling because any two completed vectors will either be equal or differ in exactly half of the features.
Proof. Let x and y be two vectors. If they are the same, then their completed vectors must also be the same because any Boolean function of x will agree with the same Boolean function of y. If x and y are different, then there exists a coordinate i {\displaystyle i} where the i {\displaystyle i} -th coordinate of x {\displaystyle x} differs from the i {\displaystyle i} -th coordinate of y {\displaystyle y} . Now the completed features contain every Boolean function on k {\displaystyle k} Boolean variables, with each one exactly once. Viewing these Boolean functions as polynomials in k {\displaystyle k} variables over GF(2), segregate the functions into pairs ( f , g ) {\displaystyle (f,g)} where f {\displaystyle f} contains the i {\displaystyle i} -th coordinate as a linear term and g {\displaystyle g} is f {\displaystyle f} without that linear term. Now, for every such pair ( f , g ) {\displaystyle (f,g)} , x {\displaystyle x} and y {\displaystyle y} will agree on exactly one of the two functions.
If they agree on one, they must disagree on the other and vice versa. (This proof is believed to be due to Watanabe.)
A possible way around the ugly duckling theorem would be to introduce a constraint on how similarity is measured by limiting the properties involved in classification, for instance, between A and B. However Medin et al. (1993) point out that this does not actually resolve the arbitrariness or bias problem since in what respects A is similar to B: "varies with the stimulus context and task, so that there is no unique answer, to the question of how similar is one object to another". [ 3 ] [ 5 ] For example, "a barberpole and a zebra would be more similar than a horse and a zebra if the feature striped had sufficient weight. Of course, if these feature weights were fixed, then these similarity relations would be constrained". Yet the property "striped" as a weight 'fix' or constraint is arbitrary itself, meaning: "unless one can specify such criteria, then the claim that categorization is based on attribute matching is almost entirely vacuous".
Stamos (2003) remarked that some judgments of overall similarity are non-arbitrary in the sense they are useful:
"Presumably, people's perceptual and conceptual processes have evolved that information that matters to human needs and goals can be roughly approximated by a similarity heuristic... If you are in the jungle and you see a tiger but you decide not to stereotype (perhaps because you believe that similarity is a false friend), then you will probably be eaten. In other words, in the biological world stereotyping based on veridical judgments of overall similarity statistically results in greater survival and reproductive success." [ 6 ]
Unless some properties are considered more salient, or 'weighted' more important than others, everything will appear equally similar, hence Watanabe (1986) wrote: "any objects, in so far as they are distinguishable, are equally similar". [ 7 ]
In a weaker setting that assumes infinitely many properties, Murphy and Medin (1985) give an example of two putative classified things, plums and lawnmowers:
"Suppose that one is to list the attributes that plums and lawnmowers have in common in order to judge their similarity. It is easy to see that the list could be infinite: Both weigh less than 10,000 kg (and less than 10,001 kg), both did not exist 10,000,000 years ago (and 10,000,001 years ago), both cannot hear well, both can be dropped, both take up space, and so on. Likewise, the list of differences could be infinite… any two entities can be arbitrarily similar or dissimilar by changing the criterion of what counts as a relevant attribute." [ 8 ]
According to Woodward, [ 9 ] the ugly duckling theorem is related to Schaffer's Conservation Law for Generalization Performance , which states that all algorithms for learning of boolean functions from input/output examples have the same overall generalization performance as random guessing. [ 10 ] The latter result is generalized by Woodward to functions on countably infinite domains. [ 11 ]
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Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy . It was also known as the X-ray Explorer Satellite , SAS-A (for Small Astronomy Satellite A , the first of the three-spacecraft SAS series), SAS 1 , or Explorer 42 . The NASA observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee , 520 km perigee , 3 degrees inclination, with a period of 96 minutes. The mission ended in March 1973. Uhuru was a scanning mission, with a spin period of ~12 minutes. It performed the first comprehensive survey of the entire sky for X-ray sources, with a sensitivity of about 0.001 times the intensity of the Crab nebula .
The main objectives of the mission were: [ 2 ]
The payload consisted of two sets of proportional counters , each with ~0.084 m 2 effective area.
The counters were sensitive with more than 10% efficiency to X-ray photons in the ~2–20 keV range.
The lower energy limit was determined by the attenuation of the beryllium windows of the counter plus a thin thermal shroud that was needed to maintain temperature stability of the spacecraft.
The upper energy limit was determined by the transmission properties of the counter filling gas.
Pulse-shape discrimination and anticoincidence techniques were used to filter out emissions of particles and undesirable high-energy photons in the background.
Pulse-height analysis in eight energy channels was used to obtain information on the energy spectrum of the incident photons.
The two sets of counters were placed back to back and were collimated to 0.52° × 0.52° and 5.2° × 5.2° (full width at half maximum) respectively.
While the 0.52° detector gave finer angular resolution, the 5.2° detector had higher sensitivity for isolated sources. [ 2 ]
Uhuru achieved several outstanding scientific advances, including the discovery and detailed study of the pulsing accretion-powered binary X-Ray sources such as Cen X-3 , Vela X-1 , and Her X-1 , the identification of Cygnus X-1 , the first strong candidate for an astrophysical black hole , and many important extragalactic sources.
The Uhuru Catalog, issued in four successive versions, the last being the 4U catalog, was the first comprehensive X-ray catalog, contains 339 objects and covers the whole sky in the 2–6 keV band. [ 3 ] The final version of the source catalog is known as the 4U Catalog; [ 4 ] earlier versions were the 2U and 3U catalogs. Sources are referenced as, e.g., " 4U 1700-37 ".
The satellite's name, "Uhuru", is the Swahili word for "freedom". It was named in recognition of the hospitality of Kenya from where it was launched, using the Italian San Marco launch platform near Mombasa. [ citation needed ]
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In Section 203(a) of the Central Utah Project Completion Act , the United States Congress authorized a federally authorized and funded replacement project to replace the Uinta and Upalco Units of the Central Utah Project (CUP) which were not constructed. The replacement project is the Uinta Basin Replacement Project (UBRP). The UBRP will provide: 2,500 acre-feet (3,100,000 m 3 ) of irrigation water; 3,000 acre-feet (3,700,000 m 3 ) of municipal and industrial water; reduced wilderness impacts; increased instream flows; and improved recreation. Design work began in 2002. Construction began in 2004 and is anticipated to be completed in 2011. The Central Utah Water Conservancy District is responsible for construction. The United States Department of the Interior oversees funding and compliance with law and environmental regulation.
The Uinta Mountains are the only major mountain range running east to west in North America . The Uinta Basin lies to the south of the Uinta Mountains and is fed by creeks and rivers flowing south from those mountains. Many of the principal rivers (Strawberry River, Currant Creek, Rock Creek, Lake Fork River, and Uinta River) flow into the Duchesne River which feeds the Green River —a tributary of the Colorado River .
The basin is the location of the Ute Tribe of the Uinta and Ouray Reservation (Tribe) which is commonly referred to as the Northern Ute Tribe, as well as the cities of Duchesne, Roosevelt, and Vernal. When oil prices are sufficiently high to overcome the cost of transportation to areas outside the basin, the area's oil industry roars to life (as it has in the past two years). Ordinarily, agriculture (chiefly cattle operations) is the lifeblood of the basin economy; and, in the basin, irrigation is the lifeblood of agriculture. Wilderness designation protects much of the Uinta Mountains. The mountains and associated streams are an important ecological resource.
At the sabres game the fan in the section 203 seat 4 said the above
Interests competing for Uinta Basin water include: non-Indian irrigators, the Tribe, the cities, the oil industry, and the natural environment. All water development in the basin has been intended to serve one or more of these interests.
The UBRP is founded on and entwined with other water development in the basin. Key stages in that development are the establishment of the Northern Ute Reservation, homesteading and early water development, the Uinta Indian Irrigation Project, the Moon Lake Project, the CUP as originally planned (with the Uinta and Upalco Units), and the current UBRP.
In 1956, congress created the Colorado River Storage Project , authorizing the CUP (as well as other Reclamation projects). The CUP provided for the trans-basin diversion of Uinta Basin water to the Wasatch Front . The Wasatch Front is the most populous area of Utah and includes Provo and Salt Lake City . The project mitigated for the trans-basin diversion by creating the Uinta and Upalco Units. These units would have provided new storage in the Uinta Basin—on the Uinta and Lake Fork Rivers respectively.
For a variety of reasons, the Uinta and Upalco Units were never constructed. Section 203 (a) of the Central Utah Project Completion Act authorized funding for UBRP—a project intended to provide similar benefits, in some measure, to those that were promised by the units that were not constructed. Originally, the UBRP project planned under the authority of Section 203 (a) was to serve both Indian and non-Indian needs using Indian and non-Indian water. Although planning continued for several years, the Tribe withdrew its support at the eleventh hour—as contracts were being executed. The departure of the Tribe made a reformulation of the plan necessary. Eventually, a scaled-down version was developed. The scaled-down project intentionally avoided interference with tribal water rights, lands, and interests.
The Central Utah Water Conservancy District (District) is the sponsor and entity responsible for repayment of the federal obligation associated with the Bonneville Unit of the CUP and UBRP.
Each stage in the Uinta Basin water development brought with it new water facilities. Each stage served a different bundle of water right interests and a different set of constituents. The result is a complex layering of economic interests, water rights, land ownership, management objectives, and politics.
Perhaps nowhere in the Basin is this layering and the accompanying actual and potential conflict more focused than the Lake Fork River. The river begins in the High Uintas Wilderness area and feeds thirteen small, high-elevation lakes-turned-reservoirs (High Mountain Lakes). It then provides early-priority Tribe flow rights though a portion of the UIIP, feeds Reclamation's Moon Lake Project (serving non-Indian irrigators), and provides additional irrigation water by exchange with Starvation Reservoir (a CUP feature). Because it diverts Lake Fork River water, integrating UBRP into this already complex and contentious water environment was difficult and problematic.
The Feasibility Study and Environmental Assessment for UBRP were published in 2001. As a partial replacement for the Uinta and Upalco Units, UBRP is intended to serve the following purposes: stabilizing the aging and unsafe High Mountain Lakes on the Lake Fork River drainage and restoring ecological values compatible with the High Uintas Wilderness; providing replacement water for the late season irrigation water stored in the High Mountain Lakes; providing 3,000 acre-feet (3,700,000 m 3 ) of water per year to Roosevelt City for municipal and industrial (M&I) purposes; providing 2,500 acre-feet (3,100,000 m 3 ) of water per year to Lake Fork River irrigators; facilitating improved water resources management and water conservation in the Uinta Basin by increasing water efficiency, enhancing beneficial use, and developing water storage; and enhancing environmental, fish, wildlife, and recreation resources.
The project purposes are to be accomplished by construction (or upgrade) of the following facilities.
Media related to Uintah Basin at Wikimedia Commons
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The Uintah Indian Irrigation Project is the principal Indian irrigation project in the Uintah Basin . The United States Bureau of Indian Affairs designed and constructed this project. The project was authorized in 1906, soon after the US Indian Irrigation Service was established as part of the Bureau of Indian Affairs. However, non-Indian irrigators largely controlled the infrastructure, generally benefiting more from the project than Ute Indians in the Uinta Basin. [ 1 ]
By 1935, the Uintah Indian Irrigation Project was irrigating over 77,000 acres (310 km 2 ) of Indian land. Today, it continues to serve Indian and non-Indian irrigators in the drainage of the Lake Fork River and elsewhere in the Basin. It continues to be owned by the Bureau of Indian Affairs, which has responsibility for its operation; however, operation has been turned over to a quasi-private operation and maintenance company organized in accordance with provisions of the Central Utah Project Completion Act .
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The Ukrainian Engineers' Society of America is an organization of Ukrainian engineers and students based in New York City . The society was founded in New York City on September 18, 1948, by a group of Ukrainian immigrants of the engineering profession. Their first annual meeting was held on November 20, 1948. Their goal is to "...unite engineers and scientists for their mutual professional enrichment and exchange of knowledge; and also to study the current status of technology , industry and the economy in Ukraine; and for the development of a social/professional network". [ 1 ] The society publishes the periodicals Ukrainian Engineering News and Bulletin TYIA . They also have published books.
According to their website, their functions include:
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Ulam's game , or the Rényi–Ulam game , is a mathematical game similar to the popular game of twenty questions . In Ulam's game, a player attempts to guess an unnamed object or number by asking yes–no questions of another, but one of the answers given may be a lie. [ 1 ]
Alfréd Rényi ( 1961 ) introduced the game in a 1961 paper, based on Hungary's Bar Kokhba game , but the paper was overlooked for many years.
Stanisław Ulam rediscovered the game, presenting the idea that there are a million objects and the answer to one question can be wrong, and considered the minimum number of questions required, and the strategy that should be adopted. [ 2 ] [ 3 ] Pelc gave a survey of similar games and their relation to information theory . [ 4 ]
This mathematics -related article is a stub . You can help Wikipedia by expanding it .
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Ullmann's Encyclopedia of Industrial Chemistry is a major reference work related to industrial chemistry by chemist Fritz Ullmann , first published in 1914, and exclusively in German as "Enzyklopädie der Technischen Chemie" until 1984.
Ullmann's Encyclopedia of Industrial Chemistry is a major reference work related to industrial chemistry by chemist Fritz Ullmann . [ 1 ] [ 2 ] Its first edition was published in German by Fritz Ullmann in 1914. [ 3 ] [ 4 ] The fourth edition, published 1972 to 1984, already contained 25 volumes. [ 4 ] The fifth edition, published 1985 to 1996, was the first version available in English. [ 4 ] In 1997, the first online version was published. [ 4 ] The year 2014 marked its centenary . [ 3 ]
As of 2016, [update] Ullmann's Encyclopedia was in its seventh edition, in 40 volumes, including one index volume and more than 1,050 articles (200 more than the sixth edition), approximately 30,000 pages, 22,000 images, 8,000 tables, 19,000 references and 85,000 indices. [ 5 ]
Barbara Elvers (Wiley-VCH) is currently Senior Editorial Advisor and Claudia Ley is Editor-in-Chief, both Wiley-VCH. The Editorial Board has around 20 members from different nations. [ 8 ]
The encyclopedia is a multi-author work. Around 3,000 international authors from universities and industry contributed to it. [ 3 ]
Note: The "topics" are a selection of related articles provided by Wiley Online Library. The number (#) indicates that, for example, 15 articles relate to the main branch of agrochemicals . The numbers do not exactly sum up to the total number of articles (1,050), but its sole purpose is for organizing and categorizing the large number of articles where possible. [ 7 ]
In the 1940s, American Chemists Donald F. Othmer and Raymond E. Kirk [ 9 ] from New York University began to create an English counterpart to Ullmann, named the Kirk-Othmer Encyclopedia of Chemical Technology . [ 3 ] It was originally published by Wiley , which in 1996 took over the German Wiley-VCH publishing house and thus has combined the two encyclopedias ever since. The German chemistry magazine CHEManager wrote, quote: "In a double pack, the two companion works are simply unbeatable, because the knowledge gathered in both offers answers (almost) all questions that can arise in connection with chemical products and processes". [ 3 ] These two encyclopedias were compared in Reference Reviews in 2007. [ 10 ]
As of 2004, [update] Kirk-Othmer was in its 5th edition with more than 1,300 articles in 27 volumes with over 22,950 pages. [ 11 ] [ 12 ]
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The Ullmann condensation or Ullmann-type reaction is the copper-promoted conversion of aryl halides to aryl ethers, aryl thioethers, aryl nitriles, and aryl amines. These reactions are examples of cross-coupling reactions . [ 1 ]
Ullmann-type reactions are comparable to Buchwald–Hartwig reactions but usually require higher temperatures. Traditionally, these reactions require high-boiling, polar solvents such as N -methylpyrrolidone , nitrobenzene , or dimethylformamide and high temperatures (often in excess of 210 °C) with stoichiometric amounts of copper. Aryl halides are required to be activated by electron-withdrawing groups . Traditional Ullmann style reactions used "activated" copper powder, e.g. prepared in situ by the reduction of copper sulfate by zinc metal in hot water. The methodology improved with the introduction of soluble copper catalysts supported by diamines and acetylacetonate ligands. [ 1 ]
Illustrative of the traditional Ullmann ether synthesis is the preparation of p-nitrophenyl phenyl ether from 4-chloronitrobenzene and phenol . [ 2 ]
Copper is used as a catalyst, either in the form of the metal or copper salts. Modern arylations use soluble copper catalysts. [ 3 ]
A traditional Goldberg reaction involves reaction of an aniline with an aryl halide. The coupling of 2-chlorobenzoic acid and aniline is illustrative: [ 4 ]
A typical catalyst is formed from copper(I) iodide and phenanthroline . The reaction is an alternative to the Buchwald–Hartwig amination reaction.
Aryl iodides are more reactive arylating agents than are aryl chlorides, following the usual pattern. Electron-withdrawing groups on the aryl halide also accelerate the coupling. [ 5 ]
The nucleophile can also be carbon including carbanions as well as cyanide . In the traditional Hurtley reaction , the carbon nucleophiles were derived from malonic ester and other dicarbonyl compounds: [ 6 ]
More modern Cu-catalyzed C-C cross-couplings utilize soluble copper complexes containing phenanthroline ligands. [ 7 ]
The arylation of alkylthiolates proceeds by the intermediacy of cuprous thiolates. [ 8 ]
In the case of Ullmann- type reactions (aminations, etherifications, etc. of aryl halides), the conversions involve copper(I) alkoxide, copper(I) amides, copper(I) thiolates. The copper(I) reagent can be generated in situ from the aryl halide and copper metal. Even copper(II) sources are effective under some circumstances. A number of innovations have been developed with regards to copper reagents. [ 1 ]
These copper(I) compounds subsequently react with the aryl halide in a net metathesis reaction:
In the case of C-N coupling, kinetic studies implicate oxidative addition reaction followed by reductive elimination from Cu(III) intermediates ( L n = one or more spectator ligands ): [ 9 ]
The Ullmann ether synthesis is named after its inventor, Fritz Ullmann . [ 10 ] The corresponding Goldberg reaction, is named after Irma Goldberg . [ 11 ] The Hurtley reaction, which involves C-C bond formation, is similarly named after its inventor. [ 6 ]
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The Ullmann reaction or Ullmann coupling , named after Fritz Ullmann , couples two aryl or alkyl groups with the help of copper. The reaction was first reported by Ullmann and his student Bielecki in 1901. It has been later shown that palladium and nickel can also be effectively used. [ 1 ] [ 2 ]
Aryl-Aryl bond formation is a fundamental tool in modern organic synthesis, with applications spanning natural product synthesis, pharmaceuticals , agrochemicals , and the development of commercial dyes and polyaromatics . With over a century of history, the Ullmann reaction has been one of the first to use a transition metal, primarily copper, in its higher oxidation states. Despite the significant implications of biaryl coupling in industries, the Ullmann reaction was plagued by a number of problems in its early development. However, in modern times the Ullmann reaction has revived interest due to several advantages of copper over other catalytic metals.
The reaction mechanism of the Ullmann reaction has been extensively studied. Electron spin resonance rules out a radical intermediate. This was confirmed in a set of experiments performed in 2008 by Hartwig and co-workers. [ 3 ] The oxidative addition / reductive elimination sequence observed with palladium catalysts is unlikely for copper because copper(III) is rarely observed. The reaction likely involves the formation of an organocopper compound (RCuX) which reacts with the other aryl reactant in a nucleophilic aromatic substitution . Alternative mechanisms have been proposed such as σ-bond metathesis . [ 4 ] [ 5 ] [ 6 ] The simplified mechanism shown below is generally accepted. [ 7 ]
Fritz Ullmann and his student Bielecki were the first to report the reaction. [ 8 ] This groundbreaking result was the first to show that a transition metal could help perform an aryl carbon-carbon bond formation.
A typical example of classic Ullmann biaryl coupling is the conversion of ortho -chloro nitrobenzene into 2,2'-dinitro biphenyl with a copper - bronze alloy . [ 9 ] [ 10 ]
The reaction has been applied to fairly elaborate substrates.
The traditional version of the Ullmann reaction requires stoichimoetric equivalents of copper, harsh reaction conditions, and the reaction has a reputation for erratic yields. The traditional Ullmann reaction thus had poor atom economy and produced toxic CuI . Because of these problems many improvements and alternative procedures have been introduced. [ 11 ] [ 12 ] [ 13 ]
The classical Ullmann reaction is limited to electron deficient aryl halides (hence the example of 2-nitrophenyl chloride above) and requires harsh reaction conditions. Modern variants of the Ullman reaction employing palladium and nickel have widened the substrate scope of the reaction and rendered reaction conditions more mild. Yields are generally still moderate, however. [ 14 ] In organic synthesis this reaction is often replaced by palladium coupling reactions such as the Heck reaction , the Hiyama coupling , and the Sonogashira coupling .
Biphenylenes had been obtained before with reasonable yields using 2,2-diiodobiphenyl or 2,2-diiodobiphenylonium ion as starting material.
Closure of 5-membered rings is more facile, but larger rings have also been made using this approach.
Around the year 2000, various bidentate ligands were found to improve the efficieny of the Ullmann reaction. Bidentate ligands allow for milder reaction conditions and higher functional group tolerance. They included amino acids, oxines , Schiff bases , and many other O-O or N-N bidentates. [ 16 ] [ 17 ] [ 18 ] These initial bidentate systems elevated the practicality of Ullmann reactions but it still had drawbacks. High loadings of copper and ligand were required and activation of the notoriously difficult aryl-chloride was still not possible. These problems were solved in 2015 with the design of special oxalic diamine ligands, making the Ullmann reaction viable for industrial application. [ 19 ]
Ullmann synthesis of biaryl compounds can be used to generate chiral products from chiral reactants. [ 20 ] Nelson and collaborators worked on the synthesis of asymmetric biaryl compounds and obtained the thermodynamically controlled product. [ 20 ]
The diastereomeric ratio of the products is enhanced with bulkier R groups in the auxiliary oxazoline group.
Unsymmetrical Ullmann reactions are rarely pursued but have been achieved when one of the two coupling components is in excess. [ 12 ]
The Ullmann reaction is limited to electron-deficient aryl halides and requires harsh reaction conditions. In organic synthesis this reaction is often replaced by palladium coupling reactions such as the Heck reaction , the Hiyama coupling , and the Sonogashira coupling
In a variation of the Ullmann reaction, β- bromo styrene is reacted with imidazole in an ionic liquid such as 1-butyl-3-methylimidazolium tetrafluoroborate to give an N -styrylimidazole. [ 21 ] The reaction requires L proline in addition to copper iodide as catalyst.
Aqueous Ullmann reactions have been used on the pilot plant scale. [ 22 ]
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Ulrich Hofmann (January 22, 1903 – July 5, 1986) was a German chemist known for his study of clay minerals and the pioneering use of electron microscopes in the study of carbonaceous materials . [ 1 ] [ 2 ] [ 3 ]
Hofmann was born in Munich in 1903 and the son of the German chemist Karl Andreas Hofmann . He studied chemistry at Technische Universität Berlin and obtained a diploma in 1925. He went on to receive his doctorate in 1926 from his father with the work Glanzkohlenstoff und die Reihe des schwarzen kristallinen Kohlenstoffs (Lustrous carbon and the series of black crystalline carbon). In 1931 he received habilitation on graphite oxide [ 4 ] [ 5 ] and then worked as a lecturer at Technische Universität Berlin .
In 1937, Hofmann joined the NSDAP . In the same year, he also became a professor of chemistry and the head of the Institute of Chemistry at the University of Rostock . He only served briefly in World War II since he was released for war-related work. In 1942, he became head of the Institute for Inorganic and Analytical Chemistry at the Vienna University of Technology , where he also installed an electron microscope by Manfred von Ardenne . In 1945, Hofmann left Vienna and, from 1948, taught chemistry and set up his laboratory at the Philosophical-Theological University of Regensburg (now University of Regensburg ), where no chemistry had previously been taught. In 1951, he became professor of inorganic and physical chemistry at Technische Universität Darmstadt . [ 6 ] In 1960, Hofmann became head of the Institute for Inorganic Chemistry at the University of Heidelberg , where he later retired in 1971. [ 1 ]
Hofmann's research dealt in particular with the chemistry of clay minerals , as well as with pigments and ancient ceramics. In the 1930s, he and Kurd Endell examined the structure of clay minerals using X-ray structure analysis, among other things. Among other things, they published in 1933 on the structure of the clay mineral montmorillonite. Together with Kurd Endell, he also found the reason why German bentonites, in contrast to those from Wyoming in the USA, were not suitable for the construction industry - the cation between the silicate layers was sodium in American bentonite , and calcium or magnesium in German deposits. However, German bentonite could also be used by adding sodium carbonate, which they patented in 1934/35. Hofmann also examined other clays (such as kaolin ) to see how the properties (e.g., swelling behavior) changed with the cations between the silicate layers when absorbing water. [ 7 ]
Continuing the work of Peter Debye and Paul Scherrer , who analyzed the structure of graphite and diamond with X-rays, he studied lustrous carbon and graphite oxide , among other things. He studied, for example, the absorptivity and catalytic activity of graphite and graphite growth at high temperatures. This also brought him into contact with industries such as Siemens-Plania in Berlin before World War II . In 1941, together with Manfred von Ardenne , he examined carbon black particles using an electron microscope and found them to be made up of chains of spherical carbon structures. [ 7 ]
In 1952 he became the first president of the German Society for Electron Microscopy . In 1955 he received the Alfred Stock Memorial Prize , in 1964 the Seger Plaque , and in 1965 the Wolfgang Ostwald Prize . He was a member of the Heidelberg Academy of Sciences (1961) and the Leopoldina (1962). In 1968 he received an honorary doctorate from the University of Munich . [ 7 ]
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Ulrich Müller (born 6 July 1940 in Bogotá ) is a German chemist who is known for his works on solid-state chemistry and the application of crystallographic group theory to crystal chemistry . [ 1 ] [ 2 ] He is the author of several textbooks on chemistry, solid-state chemistry , and crystallography. [ 1 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ]
Müller studied chemistry at the University of Stuttgart from 1959 to 1963. [ 1 ] [ 9 ] He worked on his dissertation at the Purdue University and the University of Stuttgart . [ 1 ] He finished it in 1966 in the group of Kurt Dehnicke . [ 1 ] [ 10 ] From 1967 to 1970, he worked in the group of Hartmut Bärnighausen at the University of Marburg . [ 1 ] In 1972, he finished his habilitation . [ 1 ] From 1972 to 1975, Müller was a professor for inorganic chemistry at the University of Marburg . From 1975 to 1977, he was a guest professor at the University of Costa Rica . [ 1 ] Then, several professorships for inorganic chemistry followed: University of Marburg from 1977 to 1992, University of Kassel from 1992 to 1999, and University of Marburg from 2000 to 2005. Since 2005, he has been an emeritus professor. [ 1 ]
His research focused on the following topics: [ 1 ]
He was awarded the Literaturpreis des Fonds der chemischen Industrie for his textbook "Anorganische Strukturchemie" (engl. Inorganic Structural Chemistry). [ 11 ]
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Ulrike Diebold (born 12 December 1961, in Kapfenberg, Austria ) [ 1 ] is an Austrian physicist and materials scientist who is a professor of surface science at TU Vienna . [ 2 ] She is known for her groundbreaking research on the atomic scale geometry and electronic structure of metal-oxide surfaces. [ 3 ]
Diebold was born on 12 December 1961 in Kapfenberg , Austria. She spent much of her high school years reading, skiing, and agonizing over what to major in at the university. She ultimately settled on engineering physics , an area with good job prospects that was also general enough to accommodate a variety of future directions. After completing her diploma in engineering physics ( TU Vienna , 1986), she became increasingly enthusiastic about experimental physics while working on her master's thesis, and ultimately completed a Doctor of Technology (Dr. techn.) in this area with Prof. Peter Varga [ 4 ] ( TU Vienna , 1990). [ 5 ]
Diebold's first appointment after graduation was as a post-doctoral research associate in the group of Theodore E. Madey in the department of physics at Rutgers University (1990–1993). It was there that she was first introduced to oxide surfaces, an area that she would later come to refer to as "the love of her scientific life". [ 5 ] Her first faculty appointment followed, at Tulane University, New Orleans, USA , where she was an assistant professor (1993–1999), associate professor (1999–2001), and professor of physics (2001–2009), and also an adjunct professor of chemistry (1993–2009). During this time period, she also completed her habilitation in experimental physics ( TU Vienna , 1998), held the Yahoo! Founder Chair in Science and Engineering (2006–2009), and was the associate department chair (2002–2009).
In 2005, Diebold and her group were forced to temporarily evacuate from New Orleans , which experienced massive flooding and power outages from the impact of Hurricane Katrina . [ 6 ] They were hosted by the group of Theodore E. Madey at Rutgers University during this challenging period. [ 7 ] In 2010 she moved to the Institute of Applied Physics at TU Wien where she is currently a professor of surface science and deputy department head, [ 8 ] and retains the title of research professor at Tulane University. [ 9 ] [ 5 ] Since 2022 she also serves as Vice President of the Austrian Academy of Sciences . [ 10 ]
Ulrike Diebold is well known for her influential work in the fields of surface science , materials and physical chemistry , and condensed matter physics . In particular, she has contributed greatly to the understanding of atomic-scale surface structure and electronic surface structure of metal oxides. For her work, she mainly employs Ultra-high vacuum technology and Scanning Tunneling Microscopy .
In 2013, Diebold was the sole recipient of Austria's highest research award across all disciplines, the Wittgenstein Award . [ 11 ] The award, which comes with substantial unrestricted research funds, is bestowed in support of the notion that scientists should be guaranteed the greatest possible freedom and flexibility in the performance of their research. It enabled Diebold's research activities to flourish without restriction. Other honors include:
Diebold has served in a number of editorial roles and on a number of advisory boards for scientific journals. These include:
Diebold holds dual citizenship of both Austria and the US. She is married to Gerhard Piringer [ 37 ] with whom she has two sons, Thomas (born 1996) and Niklas (born 1999). [ citation needed ]
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In mechanical engineering , ultimate failure describes the breaking of a material. In general there are two types of failure: fracture and buckling . Fracture of a material occurs when either an internal or external crack elongates the width or length of the material. In ultimate failure this will result in one or more breaks in the material. Buckling occurs when compressive loads are applied to the material instead of cracking the material bows. This is undesirable because most tools that are designed to be straight will be inadequate if curved. If the buckling continues, it will create tension on the outer side of the bend and compression on the inner side, potentially fracturing the material.
In engineering there are multiple types of failures based on the application of the material. In many machine applications any change in the part due to yielding will result in the machine piece needing to be replaced. Although this deformation or weakening of the material is not the technical definition of ultimate failure, the piece has failed. In most technical applications, pieces are rarely allowed to reach their ultimate failure or breakage point, instead for safety factors they are removed at the first signs of significant wear.
There are two different types of fracture: brittle and ductile. Each of these types of failure occur based on the material's ductility . Brittle failure occurs with little to no plastic deformation before fracture. An example of this would be stretching a clay pot or rod, when it is stretched it will not neck or elongate, but merely break into two or more pieces. While applying a tensile stress to a ductile material, instead of immediately breaking the material will instead elongate. The material will begin by elongating uniformly until it reaches the yield point, then the material will begin to neck. When necking occurs the material will begin to stretch more in the middle and the radius will decrease. Once this begins the material has entered a stage called plastic deformation. Once the material has reached its ultimate tensile strength it will elongate more easily until it reaches ultimate failure and breaks.
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In engineering , the ultimate load [ 1 ] is a statistical figure used in calculations, and should (hopefully) never actually occur.
Strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate loads (limit loads multiplied by prescribed factors of safety).
It in used in bridge and tunnel construction.
With respect to aircraft structure and design, ultimate load is the amount of load applied to a component beyond which the component will fail. The chance that it will occur is, however, not zero, and, if it were to occur, then the relevant structure in the aircraft would stand a large chance of fracture.
During the testing for determination of the loads, no fracture must occur at the ultimate load for a period of 3 seconds.
This is also commonly used in knowing the properties of metal beams. For example, it is used in experiments such as T.T.M. (tensile testing machine) and U.T.M. (universal testing machine)
The ultimate load B u is related to the limit load B n , using the concept of safety factor , j. The relation is as follows
B u >= B n × j
This engineering-related article is a stub . You can help Wikipedia by expanding it .
This aviation -related article is a stub . You can help Wikipedia by expanding it .
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Ultimate reality is "the supreme, final, and fundamental power in all reality". [ 1 ] It refers to the most fundamental fact about reality, especially when it is seen as also being the most valuable fact. This may overlap with the concept of the Absolute in certain philosophies.
Anaximander ( c. 610 – c. 546 BCE ) believed that the ultimate substance of the universe, generally known as arche , was apeiron , an infinite and eternal substance that is the origin of all things.
Aristotle (384–322 BCE) held that the unmoved mover "must be an immortal, unchanging being, ultimately responsible for all wholeness and orderliness in the sensible world" [ 2 ] and that its existence is necessary to support everyday change.
Democritus (c. 460–370 BCE) and Epicureanism (c. 307 BCE) rejected the idea of ultimate reality, saying that only atoms and void exist, but they do have the eternal, unbounded, and self-caused nature of non- materialistic views of the concept.
In Neoplatonism (3rd century CE), the first principle of reality is "the One" which is a perfectly simple and ineffable principle which is the source of the universe, and exists without multiplicity and beyond being and non-being.
Stoic physics (c. 300 BCE – 3rd century CE) called the primitive substance of the universe pneuma or God, which is everything that exists and is a creative force that develops and shapes the cosmos. [ 3 ]
In Theravada Buddhism, Nirvana is ultimate reality. [ 4 ] Nirvana is described in negative terms; it is unconstructed and unconditioned. [ 5 ]
Mahayana Buddhism has different conceptions of ultimate reality, which is framed within the context of the two truths , the relative truth of everyday things and the ultimate truth. Some traditions, specifically those who rely on the Madhyamaka philosophy, reject the notion of a truly existing or essential ultimate reality, regarding any existent as empty ( sunyata ) of inherent existence ( svabhava ). [ 6 ]
Other strands of Mahayana thought have a more positive or cataphatic view of the ultimate reality. The Yogacara school tends to follow an idealistic metaphysics. Other examples include those traditions which rely more heavily on Buddha-nature thought, such as East Asian Mahayana schools like Huayan and Tibetan traditions like shentong . [ 7 ]
In Hinduism, Brahman connotes the highest universal principle, the ultimate reality in the universe . [ 8 ] [ 9 ] [ 10 ] In major schools of Hindu philosophy , it is the material, efficient, formal and final cause of all that exists. [ 9 ] [ 11 ] [ 12 ] It is the pervasive, genderless, infinite, eternal truth and bliss which does not change, yet is the cause of all changes. [ 8 ] [ 10 ] [ 13 ] Brahman as a metaphysical concept is the single binding unity behind diversity in all that exists in the universe. [ 8 ] [ 14 ]
In Taoism , the Tao is the impersonal principle that underlies reality . It is a metaphysical principle and process that refers to how nature develops, being an enigmatic process of transformation. It is described as the source of existence , an ineffable mystery, and something that can be individually harnessed for the good. [ 15 ] It is thought of as being "the flow of the universe" and the source of its order and its qi , but it is not considered a deity to be worshipped , even if some interpretations believed it had the power to bless or illuminate.
Abrahamic conceptions of ultimate reality show diversity, in which some perspectives consider God to be a personal deity, while others have taken more abstract views. John Scotus Eriugena held that God's essence is uncaused and incomprehensible. Similarly, Maimonides believed that God is a perfect unity and is indescribable with positive attributes , and that anthropomorphic imagery in the Bible is metaphorical. [ 16 ]
Baruch Spinoza believed that God is the natural world , existing eternally and necessarily, and that everything is an effect of God's nature. He defined God as a metaphysical substance rather than a personal being, and wrote in Ethics that "blessedness" comes from the love of God, meaning knowledge of reality as it is.
Contemporary philosophy notes the possibility that reality has no fundamental explanation and should be seen as a brute fact . Adherents of the principle of sufficient reason reject this, holding that everything must have a reason.
According to Dadosky, the concept of "ultimate reality" is difficult to express in words, poetry, mythology , and art. Paradox or contradiction is often used as a medium of expression because of the "contradictory aspect of the ultimate reality". [ 17 ]
According to Mircea Eliade , ultimate reality can be mediated or revealed through symbols . [ 18 ] For Eliade the " archaic " mind is constantly aware of the presence of the Sacred , and for this mind all symbols are religious (relinking to the Origin). Through symbols human beings can get an immediate " intuition " of certain features of the inexhaustible Sacred. The mind makes use of images to grasp the ultimate reality of things because reality manifests itself in contradictory ways and therefore can't be described in concepts . It is therefore the image as such, as a whole bundle of meaning, that is "true" (faithful, trustworthy). [ 18 ] Eliade says: [ 19 ]
the sacred is equivalent to a power , and, in the last analysis, to reality . The sacred is saturated with being . Sacred power means reality and at the same time enduringness and efficacy. The polarity sacred-profane is often expressed as opposition between real and unreal or pseudoreal . [...] Thus it is easy to understand that religious man deeply desires to be , to participate in reality , to be saturated with power.
Common symbols of ultimate reality include world trees , the tree of life , microcosm , fire , children. [ 20 ]
Paul Tillich held that God is the ground of being and is something that precedes the subject and object (philosophy) dichotomy . He considered God to be what people are ultimately concerned with, existentially , and that religious symbols can be recovered as meaningful even without faith in the personal God of traditional Christianity. [ 21 ]
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Ultimate tensile strength (also called UTS , tensile strength , TS , ultimate strength or F tu {\displaystyle F_{\text{tu}}} in notation) [ 1 ] is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate tensile strength is close to the yield point , whereas in ductile materials, the ultimate tensile strength can be higher.
The ultimate tensile strength is usually found by performing a tensile test and recording the engineering stress versus strain . The highest point of the stress–strain curve is the ultimate tensile strength and has units of stress. The equivalent point for the case of compression, instead of tension, is called the compressive strength .
Tensile strengths are rarely of any consequence in the design of ductile members, but they are important with brittle members. They are tabulated for common materials such as alloys , composite materials , ceramics , plastics, and wood.
The ultimate tensile strength of a material is an intensive property ; therefore its value does not depend on the size of the test specimen. However, depending on the material, it may be dependent on other factors, such as the preparation of the specimen, the presence or otherwise of surface defects, and the temperature of the test environment and material.
Some materials break very sharply, without plastic deformation , in what is called a brittle failure. Others, which are more ductile, including most metals, experience some plastic deformation and possibly necking before fracture.
Tensile strength is defined as a stress, which is measured as force per unit area. For some non-homogeneous materials (or for assembled components) it can be reported just as a force or as a force per unit width. In the International System of Units (SI), the unit is the pascal (Pa) (or a multiple thereof, often megapascals (MPa), using the SI prefix mega ); or, equivalently to pascals, newtons per square metre (N/m 2 ). A United States customary unit is pounds per square inch (lb/in 2 or psi). Kilopounds per square inch (ksi, or sometimes kpsi) is equal to 1000 psi, and is commonly used in the United States, when measuring tensile strengths.
Many materials can display linear elastic behavior , defined by a linear stress–strain relationship , as shown in figure 1 up to point 3. The elastic behavior of materials often extends into a non-linear region, represented in figure 1 by point 2 (the "yield strength"), up to which deformations are completely recoverable upon removal of the load; that is, a specimen loaded elastically in tension will elongate, but will return to its original shape and size when unloaded. Beyond this elastic region, for ductile materials, such as steel, deformations are plastic . A plastically deformed specimen does not completely return to its original size and shape when unloaded. For many applications, plastic deformation is unacceptable, and is used as the design limitation.
After the yield point, ductile metals undergo a period of strain hardening, in which the stress increases again with increasing strain, and they begin to neck , as the cross-sectional area of the specimen decreases due to plastic flow. In a sufficiently ductile material, when necking becomes substantial, it causes a reversal of the engineering stress–strain curve (curve A, figure 2); this is because the engineering stress is calculated assuming the original cross-sectional area before necking. The reversal point is the maximum stress on the engineering stress–strain curve, and the engineering stress coordinate of this point is the ultimate tensile strength, given by point 1.
Ultimate tensile strength is not used in the design of ductile static members because design practices dictate the use of the yield stress . It is, however, used for quality control, because of the ease of testing. It is also used to roughly determine material types for unknown samples. [ 2 ]
The ultimate tensile strength is a common engineering parameter to design members made of brittle material because such materials have no yield point . [ 2 ]
Typically, the testing involves taking a small sample with a fixed cross-sectional area, and then pulling it with a tensometer at a constant strain (change in gauge length divided by initial gauge length) rate until the sample breaks.
When testing some metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers. [ 3 ] This practical correlation helps quality assurance in metalworking industries to extend well beyond the laboratory and universal testing machines .
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The Ultra-Fast Flash Observatory ( UFFO ) Pathfinder is a space observatory measuring prompt emission of gamma-ray bursts (GRB) both in optical/UV and in X-ray range down to sub-second timescales for the first time. [ 1 ] Instead of turning the whole satellite towards GRB location like the Swift Gamma-Ray Burst Mission (that takes about 100 seconds), UFFO employs a slewing mirror telescope approach – the optical path of the telescope is changed by rotation of motorized mirror within ~1 second after burst was detected.
UFFO was launched April 28, 2016 on board the Mikhailo Lomonosov satellite [ 2 ] during the first [ 3 ] launch from the new Russian Vostochny Cosmodrome .
UBAT is a wide-field coded mask X-ray camera. It has a 191 cm 2 detecting area, 90.2°×90.2° field of view and is sensitive in the 15-150 keV photon energy range. UBAT is able to localize bursts with an accuracy of 7σ to a region 10 arcmin across in less than one second time and is used as a trigger source for the SMT.
The SMT is a key component of the UFFO - a telescope designed for fast observation of prompt optical/UV emissions of GRB. SMT consist of the slewing mirror stage, the Ritchey–Chrétien telescope and image processing / motor controlling electronics. The SMT has 100 mm diameter aperture [ 4 ] [ 5 ] (although it is often mistakenly reported to have 20 cm aperture on various web pages [ 6 ] ) , 17×17 arcmin field of view, 4 arcsec angular resolution and is able to register single photons in the 200 nm - 650 nm wavelength range due to using an ICCD as a detector.
The UDAQ is in charge of UFFO control by execution of an on-board command list. It may also implement commands from the ground. UDAQ collects data both from UBAT and SMT, storing it in several NOR flash memories and transferring to the spacecraft. It is also in charge of temperature / power / light control (the last one is especially important, because the sensitive detectors of the SMT and UBAT must be powered off on the day side of the orbit). As in the UBAT and SMT, the UDAQ's electronics is based on a FPGA rather than on a CPU like most other satellites.
The objective of the UFFO is probing the early optical rise of GRBs for the first time. The first 100 seconds of a GRB optical/UV emission, which has hardly been studied up to now. It takes a long time for ground telescopes to focus on the relevant part of the sky after a GRB is registered. In particular, this may help to understand the evolution of the universe at a high redshift z >10.
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In astroparticle physics , an ultra-high-energy cosmic ray ( UHECR ) is a cosmic ray with an energy greater than 1 EeV (10 18 electronvolts , approximately 0.16 joules ), [ 1 ] far beyond both the rest mass and energies typical of other cosmic ray particles. The origin of these highest energy cosmic rays is not known. [ 2 ]
These particles are extremely rare; between 2004 and 2007, the initial runs of the Pierre Auger Observatory (PAO) detected 27 events with estimated arrival energies above 5.7 × 10 19 eV , that is, about one such event every four weeks in the 3,000 km 2 (1,200 sq mi) area surveyed by the observatory. [ 3 ]
The first observation of a cosmic ray particle with an energy exceeding 1.0 × 10 20 eV (16 J) was made by John Linsley and Livio Scarsi at the Volcano Ranch experiment in New Mexico in 1962. [ 4 ] [ 5 ]
Cosmic ray particles with even higher energies have since been observed. Among them was the Oh-My-God particle observed by the University of Utah's Fly's Eye experiment on the evening of 15 October 1991 over Dugway Proving Ground , Utah. Its observation was shocking to astrophysicists , who estimated its energy at approximately 3.2 × 10 20 eV (50 J) [ 6 ] —essentially an atomic nucleus with kinetic energy equal to a baseball (5 ounces or 142 grams) traveling at about 100 kilometers per hour (60 mph).
The energy of this particle is some 40 million times that of the highest energy protons that have been produced in any terrestrial particle accelerator . However, only a small fraction of this energy would be available for an interaction with a proton or neutron on Earth, with most of the energy remaining in the form of kinetic energy of the products of the interaction (see Collider § Explanation ). The effective energy available for such a collision is the square root of double the product of the particle's energy and the mass energy of the proton, which for this particle gives 7.5 × 10 14 eV , roughly 50 times the collision energy of the Large Hadron Collider .
Since the first observation, by the University of Utah 's Fly's Eye Cosmic Ray Detector , at least fifteen similar events have been recorded, confirming the phenomenon. These very high energy cosmic ray particles are very rare; the energy of most cosmic ray particles is between 10 MeV and 10 GeV.
Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra-high-energy cosmic ray particles (with energies beyond 10 20 eV). These high-energy particles have an estimated arrival rate of just 1 per square kilometer per century, therefore, in order to record a large number of these events, the Auger Observatory has created a detection area of 3,000 km 2 (the size of Rhode Island ) in Mendoza Province , western Argentina . The Pierre Auger Observatory, in addition to obtaining directional information from the cluster of water-Cherenkov tanks used to observe the cosmic-ray-shower components, also has four telescopes trained on the night sky to observe fluorescence of the nitrogen molecules as the shower particles traverse the sky, giving further directional information on the original cosmic ray particle.
In September 2017, data from 12 years of observations from PAO supported an extragalactic source (outside of Earth's galaxy) for the origin of extremely high energy cosmic rays. [ 7 ]
The origin of these rare highest energy cosmic rays is not known. Since observations find no correlation with the Galactic plane and Galactic magnetic fields are not strong enough to accelerate particles to these energies, these cosmic rays are believed to have extra-galactic origin. [ 2 ]
One suggested source of UHECR particles is their origination from neutron stars . In young neutron stars with spin periods of <10 ms, the magnetohydrodynamic (MHD) forces from the quasi-neutral fluid of superconducting protons and electrons existing in a neutron superfluid accelerate iron nuclei to UHECR velocities. The neutron superfluid in rapidly rotating stars creates a magnetic field of 10 8 to 10 11 teslas, at which point the neutron star is classified as a magnetar . This magnetic field is the strongest stable field in the observed universe and creates the relativistic MHD wind believed to accelerate iron nuclei remaining from the supernova to the necessary energy.
Another hypothesized source of UHECRs from neutron stars is during neutron star to strange star combustion. This hypothesis relies on the assumption that strange matter is the ground state of matter which has no experimental or observational data to support it. Due to the immense gravitational pressures from the neutron star, it is believed that small pockets of matter consisting of up , down , and strange quarks in equilibrium acting as a single hadron (as opposed to a number of Σ 0 baryons ). This will then combust the entire star to strange matter, at which point the neutron star becomes a strange star and its magnetic field breaks down, which occurs because the protons and neutrons in the quasi-neutral fluid have become strangelets . This magnetic field breakdown releases large amplitude electromagnetic waves (LAEMWs). The LAEMWs accelerate light ion remnants from the supernova to UHECR energies.
"Ultra-high-energy cosmic ray electrons " (defined as electrons with energies of ≥10 14 eV ) might be explained by the Centrifugal mechanism of acceleration in the magnetospheres of the Crab -like Pulsars . [ 8 ] The feasibility of electron acceleration to this energy scale in the Crab pulsar magnetosphere is supported by the 2019 observation of ultra-high-energy gamma rays coming from the Crab Nebula , a young pulsar with a spin period of 33 ms. [ 9 ]
Interactions with blue-shifted cosmic microwave background radiation limit the distance that these particles can travel before losing energy; this is known as the Greisen–Zatsepin–Kuzmin limit or GZK limit.
The source of such high energy particles has been a mystery for many years. Recent results from the Pierre Auger Observatory show that ultra-high-energy cosmic ray arrival directions appear to be correlated with extragalactic supermassive black holes at the center of nearby galaxies called active galactic nuclei (AGN) . [ 10 ] However, since the angular correlation scale used is fairly large (3.1°) these results do not unambiguously identify the origins of such cosmic ray particles. The AGN could merely be closely associated with the actual sources, for example in galaxies or other astrophysical objects that are clumped with matter on large scales within 100 megaparsecs . [ 11 ]
Some of the supermassive black holes in AGN are known to be rotating, as in the Seyfert galaxy MCG 6-30-15 [ 12 ] with time-variability in their inner accretion disks. [ 13 ] Black hole spin is a potentially effective agent to drive UHECR production, [ 14 ] provided ions are suitably launched to circumvent limiting factors deep within the galactic nucleus, notably curvature radiation [ 15 ] and inelastic scattering with radiation from the inner disk. Low-luminosity, intermittent Seyfert galaxies may meet the requirements with the formation of a linear accelerator several light years away from the nucleus, yet within their extended ion tori whose UV radiation ensures a supply of ionic contaminants. [ 16 ] The corresponding electric fields are small, on the order of 10 V/cm, whereby the observed UHECRs are indicative for the astronomical size of the source. Improved statistics by the Pierre Auger Observatory will be instrumental in identifying the presently tentative association of UHECRs (from the Local Universe) with Seyferts and LINERs . [ 17 ]
In addition to neutron stars and active galactic nuclei, the best candidate sources of the UHECR are: [ 2 ]
It is hypothesized that active galactic nuclei are capable of converting dark matter into high energy protons. Yuri Pavlov and Andrey Grib at the Alexander Friedmann Laboratory for Theoretical Physics in Saint Petersburg hypothesize that dark matter particles are about 15 times heavier than protons, and that they can decay into pairs of heavier virtual particles of a type that interacts with ordinary matter. [ 21 ] Near an active galactic nucleus, one of these particles can fall into the black hole, while the other escapes, as described by the Penrose process . Some of those particles will collide with incoming particles; these are very high energy collisions which, according to Pavlov, can form ordinary visible protons with very high energy. Pavlov then claims that evidence of such processes are ultra-high-energy cosmic ray particles. [ 22 ]
Ultra-high-energy particles can interact with the photons in the cosmic microwave background while traveling over cosmic distances. [ 23 ] This lead to a predicted high energy cutoff for those cosmic rays known as the Greisen–Zatsepin–Kuzmin limit (GZK limit) which matches observed cosmic ray spectra. [ 2 ] : 6
The propagation of particles can also be affected by cosmic magnetic fields. While there is some studies of galactic magnetic fields, the origin and scale of
extragalactic magnetic fields are poorly understood. [ 2 ] : 15
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Ultra-high vacuum (often spelled ultrahigh in American English, UHV ) is the vacuum regime characterised by pressures lower than about 1 × 10 −6 pascals (1.0 × 10 −8 mbar ; 7.5 × 10 −9 Torr ). UHV conditions are created by pumping the gas out of a UHV chamber. At these low pressures the mean free path of a gas molecule is greater than approximately 40 km, so the gas is in free molecular flow , and gas molecules will collide with the chamber walls many times before colliding with each other. Almost all molecular interactions therefore take place on various surfaces in the chamber.
UHV conditions are integral to scientific research. Surface science experiments often require a chemically clean sample surface with the absence of any unwanted adsorbates . Surface analysis tools such as X-ray photoelectron spectroscopy and low energy ion scattering require UHV conditions for the transmission of electron or ion beams. For the same reason, beam pipes in particle accelerators such as the Large Hadron Collider are kept at UHV. [ 1 ]
Maintaining UHV conditions requires the use of unusual materials for equipment. Useful concepts for UHV include:
Typically, UHV requires:
Hydrogen and carbon monoxide are the most common background gases in a well-designed, well-baked UHV system. Both Hydrogen and CO diffuse out from the grain boundaries in stainless steel. Helium could diffuse through the steel and glass from the outside air, but this effect is usually negligible due to the low abundance of He in the atmosphere.
Measurement of high vacuum is done using a nonabsolute gauge that measures a pressure-related property of the vacuum. See, for example, Pacey. [ 2 ] These gauges must be calibrated. [ 3 ] The gauges capable of measuring the lowest pressures are magnetic gauges based upon the pressure dependence of the current in a spontaneous gas discharge in intersecting electric and magnetic fields. [ 4 ]
UHV pressures are measured with an ion gauge , either of the hot filament or inverted magnetron type.
In any vacuum system, some gas will continue to escape into the chamber over time and slowly increase the pressure if it is not pumped out. [ 5 ] This leak rate is usually measured in mbar L/s or torr L/s. While some gas release is inevitable, if the leak rate is too high, it can slow down or even prevent the system from reaching low pressure.
There are a variety of possible reasons for an increase in pressure. These include simple air leaks, virtual leaks , and desorption (either from surfaces or volume). A variety of methods for leak detection exist. Large leaks can be found by pressurizing the chamber, and looking for bubbles in soapy water, while tiny leaks can require more sensitive methods, up to using a tracer gas and specialized Helium mass spectrometer .
Outgassing is a problem for UHV systems. Outgassing can occur from two sources: surfaces and bulk materials. Outgassing from bulk materials is minimized by selection of materials with low vapor pressures (such as glass, stainless steel , and ceramics ) for everything inside the system. Materials which are not generally considered absorbent can outgas, including most plastics and some metals. For example, vessels lined with a highly gas-permeable material such as palladium (which is a high-capacity hydrogen sponge) create special outgassing problems.
Outgassing from surfaces is a subtler problem. At extremely low pressures, more gas molecules are adsorbed on the walls than are floating in the chamber, so the total surface area inside a chamber is more important than its volume for reaching UHV. Water is a significant source of outgassing because a thin layer of water vapor rapidly adsorbs to everything whenever the chamber is opened to air. Water evaporates from surfaces too slowly to be fully removed at room temperature, but just fast enough to present a continuous level of background contamination. Removal of water and similar gases generally requires baking the UHV system at 200 to 400 °C (392 to 752 °F) while vacuum pumps are running. During chamber use, the walls of the chamber may be chilled using liquid nitrogen to reduce outgassing further.
In order to reach low pressures, it is often useful to heat the entire system above 100 °C (212 °F) for many hours (a process known as bake-out ) to remove water and other trace gases which adsorb on the surfaces of the chamber. This may also be required upon "cycling" the equipment to atmosphere. This process significantly speeds up the process of outgassing, allowing low pressures to be reached much faster. After baking, to prevent humidity from getting back into the system after it is exposed to atmospheric pressure, a nitrogen gas flow that creates a small positive pressure can be maintained to keep the system dry.
There is no single vacuum pump that can operate all the way from atmospheric pressure to ultra-high vacuum. Instead, a series of different pumps is used, according to the appropriate pressure range for each pump. In the first stage, a roughing pump clears most of the gas from the chamber. This is followed by one or more vacuum pumps that operate at low pressures. Pumps commonly used in this second stage to achieve UHV include:
Turbo pumps and diffusion pumps rely on supersonic attack upon system molecules by the blades and high speed vapor stream, respectively.
To save time, energy, and integrity of the UHV volume an airlock or load-lock vacuum system [ 6 ] is often used. The airlock volume has one door or valve, such as a gate valve or UHV angle valve, [ 7 ] facing the UHV side of the volume, and another door against atmospheric pressure through which samples or workpieces are initially introduced. After sample introduction and assuring that the door against atmosphere is closed, the airlock volume is typically pumped down to a medium-high vacuum. In some cases the workpiece itself is baked out or otherwise pre-cleaned under this medium-high vacuum. The gateway to the UHV chamber is then opened, the workpiece transferred to the UHV by robotic means or by other contrivance if necessary, and the UHV valve re-closed. While the initial workpiece is being processed under UHV, a subsequent sample can be introduced into the airlock volume, pre-cleaned, and so-on and so-forth, saving much time. Although a "puff" of gas is generally released into the UHV system when the valve to the airlock volume is opened, the UHV system pumps can generally snatch this gas away before it has time to adsorb onto the UHV surfaces. In a system well designed with suitable airlocks, the UHV components seldom need bakeout and the UHV may improve over time even as workpieces are introduced and removed.
Metal seals, with knife edges on both sides cutting into a soft, copper gasket are employed. This metal-to-metal seal can maintain pressures down to 100 pPa (7.5 × 10 −13 Torr). Although generally considered single use, the skilled operator can obtain several uses through the use of feeler gauges of decreasing size with each iteration, as long as the knife edges are in perfect condition. For SRF cavities, indium seals are more commonly used in sealing two flat surfaces together using clamps to bring the surfaces together. The clamps need to be tightened slowly to ensure the indium seals compress uniformly all around.
Many common materials are used sparingly if at all due to high vapor pressure, high adsorptivity or absorptivity resulting in subsequent troublesome outgassing, or high permeability in the face of differential pressure (i.e.: "through-gassing"):
Technical limitations:
A UHV manipulator allows an object which is inside a vacuum chamber and under vacuum to be mechanically positioned. It may provide rotary
motion, linear motion, or a combination of both. The most complex devices give motion in three axes and rotations around two of those axes. To generate the mechanical movement inside the chamber, three basic mechanisms are commonly employed: a mechanical coupling through the vacuum wall (using a vacuum-tight seal around the coupling: a welded metal bellows for example), a magnetic coupling that transfers motion from air-side to vacuum-side: or a sliding seal using special greases of very low vapor pressure or ferromagnetic fluid. Such special greases can exceed USD $400 per kilogram. [ citation needed ] Various forms of motion control are available for manipulators, such as knobs, handwheels, motors, stepping motors , piezoelectric motors , and pneumatics . The use of motors in a vacuum environment often requires special design or other special considerations, as the convective cooling taken for granted under atmospheric conditions is not available in a UHV environment.
The manipulator or sample holder may include features that allow additional control and testing of a sample, such as the ability to apply heat, cooling, voltage, or a magnetic field. Sample heating can be accomplished by electron bombardment or thermal radiation. For electron bombardment, the sample holder is equipped with a filament which emits electrons when biased at a high negative potential. The impact of the
electrons bombarding the sample at high energy causes it to heat. For thermal radiation, a filament is mounted close to the sample and resistively heated to high temperature. The infrared energy from the filament heats the sample.
Ultra-high vacuum is necessary for many surface analytic techniques such as:
UHV is necessary for these applications to reduce surface contamination, by reducing the number of molecules reaching the sample over a given time period. At 0.1 millipascals (7.5 × 10 −7 Torr), it only takes 1 second to cover a surface with a contaminant, so much lower pressures are needed for long experiments.
UHV is also required for:
While not compulsory, it can prove beneficial in applications such as:
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Ultra-large-scale system ( ULSS ) is a term used in fields including Computer Science , Software Engineering and Systems Engineering to refer to software intensive systems with unprecedented amounts of hardware , lines of source code , numbers of users , and volumes of data . The scale of these systems gives rise to many problems: they will be developed and used by many stakeholders across multiple organizations, often with conflicting purposes and needs; they will be constructed from heterogeneous parts with complex dependencies and emergent properties; they will be continuously evolving; and software, hardware and human failures will be the norm, not the exception. The term 'ultra-large-scale system' was introduced by Northrop and others [ 1 ] to describe challenges facing the United States Department of Defense . The term has subsequently been used to discuss challenges in many areas, including the computerization of financial markets . [ 2 ] The term "ultra-large-scale system" (ULSS) is sometimes used interchangeably with the term "large-scale complex IT system" (LSCITS). These two terms were introduced at similar times to describe similar problems, the former being coined in the United States and the latter in the United Kingdom.
The term ultra-large-scale system was introduced in a 2006 report from the Software Engineering Institute at Carnegie Mellon University authored by Linda Northrop and colleagues. [ 1 ] The report explained that software intensive systems are reaching unprecedented scales (by measures including lines of code; numbers of users and stakeholders; purposes the system is put to; amounts of data stored, accessed, manipulated, and refined; numbers of connections and interdependencies among components; and numbers of hardware elements). When systems become ultra-large-scale, traditional approaches to engineering and management will no longer be adequate. The report argues that the problem is no longer of engineering systems or system of systems , but of engineering " socio-technical ecosystems ".
In 2013, Linda Northrop and her team conducted a talk to review outcome of the 2006 study and the reality of 2013. In summary, the talk concluded that (a) ULS systems are in the midst of society and the changes to current social fabric and institutions are significant; (b) The 2006 original research team was probably too conservative in their report; (c) Recent technologies have exacerbated the pace of scale growth; and (d) There are great opportunities. [ 3 ]
At a similar time to the publication of the report by Northrop and others, a research and training initiative was being initiated in the UK on Large-scale Complex IT Systems . Many of the challenges recognized in this initiative were the same as, or were similar to those recognized as the challenges of ultra-large-scale systems. [ 4 ] Greg Goth [ 5 ] quotes Dave Cliff , director of the UK initiative as saying "The ULSS proposal and the LSCITS proposal were written entirely independently, yet we came to very similar conclusions about what needs to be done and about how to do it". A difference pointed out by Ian Sommerville [ 4 ] is that the UK initiative began with a five to ten year vision, while that of Northrop and her co-authors was much longer term. This seems to have led to there being two slightly different perspectives on ultra-large-scale systems. For example, Richard Gabriel's perspective is that ultra-large-scale systems are desirable but currently impossible to build due to limitations in the fields of software design and systems engineering. [ 6 ] On the other hand, Sommerville 's perspective is that ultra-large-scale systems are already emerging (for example in air traffic control ), the key problem being not how to achieve them but how to ensure they are adequately engineered. [ 4 ]
Ultra-large-scale systems hold the characteristics of systems of systems (systems that have: operationally independent sub-systems; managerially independent components and sub-systems; evolutionary development; emergent behavior; and geographic distribution). In addition to these, the Northrop report [ 1 ] argues that a ULSS will:
The Northrop report [ 1 ] states that "the sheer scale of ULS systems will change everything. ULS systems will necessarily be decentralized in a variety of ways, developed and used by a wide variety of stakeholders with conflicting needs, evolving continuously, and constructed from heterogeneous parts. People will not just be users of a ULS system; they will be elements of the system. The realities of software and hardware failures will be fundamentally integrated into the design and operation of ULS systems. The acquisition of a ULS system will be simultaneous with its operation and will require new methods for control. In ULS systems, these characteristics will dominate. Consequently, ULS systems will place unprecedented demands on software acquisition, production, deployment, management, documentation, usage, and evolution practices."
The term ultra-large-scale system was introduced by Northrop and others [ 1 ] to discuss challenges faced by the United States Department of Defense in engineering software intensive systems. In 2008 Greg Goth wrote that although Northrop's report focused on the US military's future requirements, "its description of how the fundamental principles of software design will change in a global economy ... is finding wide appeal". [ 5 ] The term is now used to discuss problems in several domains.
The Northrop report argued that "the U.S. Department of Defense (DoD) has a goal of information dominance ... this goal depends on increasingly complex systems characterized by thousands of platforms, sensors, decision nodes, weapons, and warfighters connected through heterogeneous wired and wireless networks. ...These systems will push far beyond the size of today's systems by every measure ... They will be ultra-large-scale systems." [ 1 ]
Following the 2010 Flash Crash , Cliff and Northrop [ 2 ] have argued "The very high degree of interconnectedness in the global markets means that entire trading systems, implemented and managed separately by independent organizations, can rightfully be considered as significant constituent entities in the larger global super-system. ... The sheer number of human agents and computer systems connected within the global financial-markets system-of-systems is so large that it is an instance of an ultra-large-scale system, and that largeness-of-scale has significant effects on the nature of the system". [ 2 ]
Kevin Sullivan has stated that the US healthcare system is "clearly an ultra-large-scale system" [ 7 ] and that building national scale cyberinfrastructure for healthcare "demands not just a rigorous, modern software and systems engineering effort, but an approach at the cutting edge of our understanding of information processing systems and their development and deployment in complex socio-technical environments". [ 7 ]
Other domains said to be seeing the rise of ultra-large-scale systems include government, transport systems (for example air traffic control systems), energy distribution systems (for example smart grids) and large enterprises.
Fundamental gaps in our current understanding of software and software development at the scale of ULS systems present profound impediments to the technically and economically effective achievement of significant gains in core system functionality. These gaps are strategic, not tactical. They are unlikely to be addressed adequately by incremental research within established categories. Rather, we require a broad new conception of both the nature of such systems and new ideas for how to develop them. We will need to look at them differently, not just as systems or systems of systems, but as socio-technical ecosystems. We will face fundamental challenges in the design and evolution, orchestration and control, and monitoring and assessment of ULS systems. These challenges require breakthrough research. [ 1 ]
The Northrop report proposed that a portfolio of interdisciplinary research be developed, following a ULS systems research agenda that highlights the following areas: [ 1 ] Human interaction – People are key participants in ULS systems. Many problems in complex systems today stem from failures at the individual and organizational level. Understanding ULS system behavior will depend on the view that humans are elements of a socially constituted computational process. This research involves anthropologists , sociologists , and social scientists conducting detailed socio-technical analyses of user interactions in the field, with the goal of understanding how to construct and evolve such socio-technical systems effectively. [ 8 ]
Computational emergence – ULS systems must satisfy the needs of participants at multiple levels of an organization. These participants will often behave opportunistically to meet their own objectives. Some aspects of ULS systems will be "programmed" by properly incentivizing and constraining behavior rather than by explicitly prescribing. This research area explores the use of methods and tools based on economics and game theory (for example, mechanism design) to ensure globally optimal ULS system behavior by exploiting the strategic self-interests of the system's constituencies. This research area also includes exploring metaheuristics and digital evolution to augment the cognitive limits of human designers, so they can manage ongoing ULS system adaptation more effectively. [ 9 ]
Design – Current design theory, methods, notations, tools, and practices and the acquisition methods that support them are inadequate to design ULS systems effectively. This research area broadens the traditional technology-centric definition of design to include people and organizations; social, cognitive, and economic considerations; and design structures such as design rules and government policies. It involves research in support of designing ULS systems from all of these points of view and at many levels of abstraction, from the hardware to the software to the people and organizations in which they work. [ 10 ]
Computational engineering – New approaches will be required to enable intellectual control at an entirely new level of scope and scale for system analysis, design, and operation. ULS systems will be defined in many languages, each with its own abstractions and semantic structures. This research area focuses on evolving the expressiveness of representations to accommodate this semantic diversity. Because the complexity of ULS systems will challenge human comprehension, this area also focuses on providing automated support for computing the behavior of components and their compositions in systems and for maintaining desired properties as ULS systems evolve. [ 11 ]
Adaptive system infrastructure – ULS systems require an infrastructure that permits organizations in distributed locations to work in parallel to develop, select, deploy, and evolve system components. This research area investigates integrated development environments and runtime platforms that support the decentralized nature of ULS systems. This research also focuses on technologies, methods, and theories that will enable ULS systems to be developed in their deployment environments. [ 12 ]
Adaptable and predictable system quality – ULS systems will be long-running and must operate robustly in environments fraught with failures, overloads, and cyberattacks . These systems must maintain robustness in the presence of adaptations that are not centrally controlled or authorized. [ 13 ]
Managing traditional qualities such as security , performance, reliability, and usability is necessary but not sufficient to meet the challenges of ULS systems. This research area focuses on how to maintain quality in a ULS system in the face of continuous change, ongoing failures, and attacks. It also includes identifying, predicting, and controlling new indicators of system health (akin to the U. S. gross domestic product ) that are needed because of the scale of ULS systems.
Policy, acquisition, and management – Policy and management frameworks for ULS systems must address organizational, technical, and operational policies at all levels. Rules and policies must be developed and automated to enable fast and effective local action while preserving global capabilities. This research area focuses on transforming acquisition policies and processes to accommodate the rapid and continuous evolution of ULS systems by treating suppliers and supply chains as intrinsic and essential components of a ULS system. [ 14 ]
The proposed research does not supplant current, important software research but rather significantly expands its horizons. Moreover, because it is focused on systems of the future, the SEI team purposely avoided couching descriptions in terms of today's technology. The envisioned outcome of the proposed research is a spectrum of technologies and methods for developing these systems of the future, with national-security, economic, and societal benefits that extend far beyond ULS systems themselves.
The UK's research programme in Large-scale Complex IT Systems [ 15 ] [ 16 ] has been concerned with issues around ULSS development and considers that an LSCITS (Large-scale complex IT system) shares many of the characteristics of a ULSS.
The National Natural Science Foundation of China has outlined a five-year project for researchers to study the assembly of ultra-large spacecraft. [ 17 ] Although vague, the project would have applications for potential megaprojects , including colossal space-based solar power stations. Work on an Ultra-Large Aperture On-Orbit Assembly Project under the Chinese Academy of Sciences (CAS) and with support from the Chinese Ministry of Science and Technology is already underway.
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Ultra-low-sulfur diesel ( ULSD ) is diesel fuel with substantially lowered sulfur content. Since 2006, almost all of the petroleum-based diesel fuel available in Europe and North America has been of a ULSD type.
The move to lower sulfur content allows for the application of advanced emissions control technologies that substantially lower the harmful emissions from diesel combustion. [ 1 ] Testing by engine manufacturers and regulatory bodies have found the use of emissions control devices in conjunction with ULSD can reduce the exhaust output of ozone precursors and particulate matter to near-zero levels. [ 2 ]
In 1993 the European Union began mandating the reduction of diesel sulfur content and implementing modern ULSD specifications in 1999. [ 3 ] [ 4 ] The United States started phasing in ULSD requirements for highway vehicles in 2006, with implementation for off-highway applications, such as locomotive and marine fuel, beginning in 2007. [ 5 ]
Sulfur is not a lubricant in and of itself, but it can combine with the nickel content in many metal alloys to form a low-melting eutectic alloy that can increase lubricity. The process used to reduce the sulfur also reduces the fuel's lubricating properties. Lubricity is a measure of the fuel's ability to lubricate and protect the various parts of the engine's fuel injection system from wear. The processing required to reduce sulfur to 15 ppm also removes naturally occurring lubricity agents in diesel fuel. To manage this change ASTM International (formerly the American Society for Testing and Materials) adopted the lubricity specification defined in ASTM D975 [ 6 ] for all diesel fuels and this standard went into effect January 1, 2005. [ 7 ] The D975 standard defines two ULSD standards, Grade No. 2-D S15 (regular ULSD) and Grade No. 1-D S15 (a higher volatility fuel with a lower gelling temperature than regular ULSD).
The refining process that removes the sulfur also reduces the aromatic content and density of the fuel, resulting in a minor decrease in the energy content, by about 1%. [ citation needed ] This decrease in energy content may result in slightly reduced peak power and fuel economy.
The transition to ULSD is not without substantial costs. The US government estimated that pump prices for diesel fuel increased between 5 and 25 cents per US gallon (1.3 and 6.6 ¢/L) as a result of the transition [ citation needed ] and, according to the American Petroleum Institute , the domestic refining industry has invested over $8 billion to comply with the new regulations.
ULSD runs in any engine designed for the ASTM D975 diesel fuel, however, it is known to cause some seals to shrink, [ 8 ] and may cause fuel pump failures in Volkswagen TDI engines used in 2006 to pre-2009 models. [ citation needed ] TDI engines from 2009 and on are designed to use ULSD exclusively; biodiesel blends are reported to prevent that failure. [ 1 ] [ 9 ]
Some filling stations in Kenya started offering 50 ppm diesel as of December 2010. As of 2018, Kenya has not fully implemented emission control systems.
As of June 2012, 50 ppm diesel is now standard across all filling stations, in a bid to reduce pollution. [ 10 ]
Morocco has started to introduce 50 ppm diesel to filling stations as of 2009. [ 11 ]
Since 2011, the 10 ppm diesel has been available in some filling stations. [ 12 ] A generalization to all filling stations with the 10 ppm diesel is available since December 2015. [ 13 ]
50 ppm sulfur content was first legislated by the South African Department of Minerals and Energy in early 2006, and has been widely available since then.
South Africa's Clean Fuels 2 standard, expected to have begun in 2017, reducing the allowable sulfur content to 1 ppm. As of 2013, Sasol launched 10 ppm diesel at selected filling stations. [ 14 ]
Euro-II gasoline and diesel standards. In 27th February 2024, the Saudi Ministry of Energy announced the successful introduction of Euro 5 standard diesel fuel and gasoline across the Kingdom of Saudi Arabia.
China has limited sulfur in diesel fuel to 150 ppm (equivalent to the Euro III standard). The limits of 10 ppm (equivalent to the Euro V standard), only apply in certain cities such as Beijing. [ 15 ]
From 2014 to 2017, China will limit sulfur in diesel fuel to 50 ppm. After 2017, the sulfur content in diesel fuel will be limited to 10ppm. [ 16 ]
In July 2000, Hong Kong became the first city in Asia to introduce ULSD, with sulfur content of 50 parts per million (ppm). In addition, new petrol private cars were asked to meet Euro III standards from 2001.
Since the introduction of the law, all fuel station started supplying ULSD since August 2000.
Sulfur content of regular diesel fuel was lowered from 500 ppm to 350 ppm on 1 January 2001.
As part of the ULSD package, Hong Kong government lowered the tax for ULSD from HK$2.89 to $2.00 per liter in June 1998. The temporary concession was extended to 31 March 2000, then to 31 December 2000.
On 19 June 2000, under Report of the Subcommittee on resolution under section 4(2) of the Dutiable Commodities Ordinance (Cap. 109) , ULSD fuel tax was lowered to HK$1.11 per liter between 7 July 2000 and 31 December 2000, then increased to $2 in 2001, then $2.89 per liter on 1 January 2002. This resolution was passed on 27 June 2000.
Castle Peak Power Station was designed to burn heavy fuel oil for boiler startup, flame stabilization and occasionally as a secondary fuel. Since the early 2010s, all boilers were converted to burn ULSD to cut down sulfur dioxide emission. On the other hand, Black Point Power Station and Penny's Bay Power Station were designed to burn ULSD as a secondary and primary fuel respectively. So all power stations under CLP Power burn ULSD instead of higher sulfur alternatives now.
Pakistan began importing Euro-V standard fuel in mid 2020. The import of Euro-V petrol was started on August 10, 2020, while all diesel imports of the country will conform to Euro-V standard by January 2021. [ 17 ] [ 18 ] The shift was carried out directly from Euro-II to Euro-V. [ 19 ]
Delhi first introduced 50 ppm sulfur diesel on 1 April 2010 as a step aimed at curbing vehicular pollution in the capital. This was done in 12 other cities at the same time. The sulfur content in the diesel being used was 350 ppm. [ 20 ]
There are two types of diesel available in India from year 2010. Bharat Stage IV (equivalent to Euro IV) specification having Sulfur level below 50 ppm is available all over the country and the Bharat Stage VI with ultra low sulfur was slowly introduced in New Delhi in April 2018.
The Bharat Stage VI with ultra low sulfur content of less than 10 ppm will be standard across the country from April 2020.
The National Environment Agency (NEA) defines ultra low sulfur diesel (ULSD) as diesel fuel with less than 50ppm, or 0.005 per cent, by July 2017 the limit will be 10 ppm.
On 16 June 2005, NEA announced that the use of ULSD would be mandatory beginning 1 December 2005. The regulation also offered tax incentives for Euro IV diesel taxis, buses and commercial vehicles between 1 June 2004 and 3 September 2006, pending a mandatory conversion to Euro IV-compliant vehicles in 2007.
Beginning on 1 July 2007, Taiwan has limited sulfur in diesel fuel to 10 ppm. [ 21 ]
In the European Union , the "Euro IV" standard has applied since 2005, which specifies a maximum of 50 ppm of sulfur in diesel fuel for most highway vehicles; [ 22 ] ultra-low-sulfur diesel with a maximum of 10 ppm of sulfur must “be available” from 2005 and was widely available as of 2008. In 2009, the Euro V fuel standard came into effect [ 23 ] which reduced maximum sulfur to 10 ppm. In 2009, diesel fuel for most non-highway applications is also expected to conform to the Euro V standard for fuel. Various exceptions exist for certain uses and applications, most of which are being phased out over a period of several years. In particular, the so-called EU accession countries (primarily in Eastern Europe ), have been granted certain temporary exemptions to allow for transition.
Certain EU countries may apply higher standards or require faster transition. [ 24 ] For example, Germany implemented a tax incentive of per liter of "sulfur free" fuel (both gasoline and diesel) containing less than 10 ppm beginning in January 2003 and average sulfur content was estimated in 2006 to be 3-5 ppm. Similar measures have been enacted in most of the Nordic countries , Benelux , Ireland and the United Kingdom to encourage early adoption of the 50 ppm and 10 ppm fuel standards. [ 24 ]
Since 1990, diesel fuel with a sulfur content of 50 ppm has been available on the Swedish market. From the year 1992, production started of a diesel fuel with 2 to 5 ppm of sulfur and a maximum of 5% by volume aromatics. There are certain tax incentives for using this fuel and from about year 2000, this low aromatic, low sulfur fuel has achieved 98-99% penetration of the Swedish diesel fuel market. Now RME (rapeseed methyl ester, also known as FAME (Fatty Acid Methyl Ester)) is a biofuel additive.
Since 2003, a "zero" sulfur with very low aromatic content (less than 1% by volume) diesel fuel has been made available on the Swedish market under the name EcoPar . It is used wherever the working environment is highly polluted, an example being where diesel trucks are used in confined spaces such as in harbors, inside storage houses, during construction of road and rail tunnels & in vehicles that are predominantly run in city centers.
As of 2008, most accession countries are expected to have made the transition to diesel fuel with 10 ppm sulfur or less. Slightly different times for transition have applied to each of the countries, but most have been required to reduce the maximum sulfur content to less than 50 ppm since 2005. [ 25 ] Certain exemptions are expected for certain industries and applications, which will also be phased out over time. Compared to other EU countries, ULSD may be less widely available.
In Serbia , an EU candidate country, all diesel fuel has been of the ultra-low-sulfur ( "evrodizel" ) type since August 2013. [ 26 ] Before that, there were two types of diesel fuel: D2 with 500 ppm sulfur or more, and low-sulfur "evrodizel" .
Under Sulfur in Diesel Fuel Regulations (SOR/2002-254), the sulfur content of diesel fuel produced or imported was reduced to 15 ppm after 31 May 2006. This was followed by the reduction of sulfur in diesel fuel sold for use in on-road vehicles after 31 August 2006. For the designated Northern Supply Area , the deadline for reducing the sulfur content of diesel fuel for use in on-road vehicles was 31 August 2007.
An amendment titled Regulations Amending the Sulfur in Diesel Fuel Regulations (SOR/2005-305) added following deadlines:
An amendment titled Regulations Amending the Sulfur in Diesel Fuel Regulations (SOR/SOR/2006-163) allowed diesel with sulfur content up to 22 ppm to be sold for onroad vehicles between 1 September 2006 and 15 October 2006, then 15 ppm after that date. This amendment facilitated the introduction of 15 ppm sulfur diesel fuel for on-road use in 2006, by lengthening the period between the dates that the production/import limit and the sales limit come into effect. It provided additional time to fully turn over the higher-sulfur diesel fuel inventory for on-road use in the distribution system. The requirements of the Regulations were aligned, in level and timing, with those of the U.S. EPA.
Mexico began introduction of ULSD throughout the country in 2006. [ 27 ]
Ultra-low-sulfur diesel fuel was proposed by EPA as a new standard for the sulfur content in on-road diesel fuel sold in the United States since October 15, 2006, except for rural Alaska which transferred in 2010. California has required it since September 1, 2006. This new regulation applies to all diesel fuel, diesel fuel additives and distillate fuels blended with diesel for on-road use, such as kerosene. Since December 1, 2010, all highway diesel fuel nationwide has been ULSD. Non-road diesel engine fuel moved to 500 ppm sulfur in 2007, and further to ULSD in 2010. Railroad locomotive and marine diesel fuel moved to 500 ppm sulfur in 2007, and changed to ULSD in 2012. There were exemptions for small refiners of non-road, locomotive and marine diesel fuel that allowed for 500 ppm diesel to remain in the system until 2014. After December 1, 2014 all highway, non-road, locomotive and marine diesel fuel is ULSD.
The EPA mandated the use of ULSD fuel in model year 2007 and newer highway diesel fuel engines equipped with advanced emission control systems that required the new fuel. These advanced emission control technologies were required for marine diesel engines in 2014 and for locomotives in 2015.
The allowable sulfur content for ULSD (15 ppm) is much lower than the previous U.S. on-highway standard for low sulfur diesel (LSD, 500 ppm) which allowed advanced emission control systems to be fitted that would otherwise be damaged and or rendered ineffective by these compounds. These systems can greatly reduce emissions of oxides of nitrogen and particulate matter . [ 1 ]
Because this grade of fuel is comparable to European grades, European engines will no longer have to be redesigned to cope with higher sulfur content in the U.S. These engines may use advanced emissions control systems which would otherwise be damaged by sulfur. It was hoped that the ULSD standard would increase the availability of diesel-fueled passenger cars in the U.S. In Europe, diesel-engine automobiles have been much more popular with buyers than has been the case in the U.S.
Additionally, the EPA has assisted manufacturers with the transition to tougher emissions regulations by loosening them for model year 2007 to 2010 light-duty diesel engines. [ 28 ]
According to EPA estimates, with the implementation of the new fuel standards for diesel, nitrogen oxide emissions will be reduced by 2.6 million tons each year and soot or particulate matter will be reduced by 110,000 tons a year.
On June 1, 2006, U.S. refiners were required to produce 80% of their annual output as ULSD (15 ppm), and petroleum marketers and retailers were required to label [ 29 ] diesel fuel, diesel fuel additives and kerosene pumps with EPA-authorized language disclosing fuel type and sulfur content. Other requirements effective June 1, 2006, including EPA-authorized language on Product Transfer Documents and sulfur-content testing standards, are designed to prevent misfueling, contamination by higher-sulfur fuels and liability issues. The EPA deadline for industry compliance to a 15 ppm sulfur content was originally set for July 15, 2006 for distribution terminals, and by September 1, 2006 for retail. But on November 8, 2005, the deadline was extended by 1.5 months to September 1, 2006 for terminals and October 15, 2006 for retail. In California, the extension was not granted and followed the original schedule. As of December, 2006, the ULSD standard has been in effect according to the amended schedule, and compliance at retail locations was reported to be in place.
Source: [ 30 ]
Argentina has three grades of diesel fuel, as follows:
Grade 1, also known as AGRODIESEL or GASOIL AGRO, is intended mainly for agricultural equipment. Sale of Grade 1 diesel is optional at retail outlets.
Grade 2, also known as GASOLINE COMMUNITY (common diesel fuel), is intended for the bulk of diesel fuelled vehicles. Grade 2 diesel fuel is available with 2 different sulfur levels depending on the population density of the location where it is retailed.
Grade 3 diesel fuel, also known as GASOLINE ULTRA, is the highest quality diesel fuel and is supposed to be available starting February 1, 2006. Sale of Grade 3 diesel at retail outlets is optional until 2008.
At the time the regulation was published, the sulfur limits amounted to 3000 ppm for Grade 1, 1500/2500 ppm (depending on the area) for Grade 2, and 500 ppm for Grade 3. Sulfur limit reductions occur in 2008, 2009, 2011, and 2016. After the last reduction, in June 2016, the sulfur limits become 1000 ppm, 30 ppm, and 10 ppm for the three respective grades.
Law 26.093 requires 5% biodiesel to be blended with diesel fuel starting January 1, 2010.
Since January 2012, Brazilian service stations started offering two types of Diesel, 50 ppm and 500 ppm on most areas and 1800 ppm in remote areas. Since January 2013, the 10 ppm or EURO V Diesel replaced the 50 ppm Diesel, which is now widely used and can be found in the majority of service stations, and the 1800 ppm was discontinued. All vehicles produced or sold in Brazil since January 2012 must be able to use only 50 ppm or lower sulfur Diesel.
Also, all Diesel available for purchase in Brazil contains 10% of biodiesel. [ 31 ]
Chile requires <15 ppm [ 32 ] in Santiago, for diesel since 2011, and the rest of the country requires <50 ppm. [ 33 ]
Since January 1, 2013, Colombia's diesel has <50 ppm for public and private transport. [ 34 ]
Uruguay is expected to impose a 50 ppm ULSD limit by 2009. 70% of the fuel used in Uruguay is diesel. [ citation needed ]
Australia has had a limit of 10 ppm since 1 January 2009. [ 35 ] The limit had been 50ppm.
New Zealand has had a limit of 10 ppm since 1 January 2009. [ 36 ] Prior to that, the limit was 50 ppm.
As of 2002, much of the former Soviet Union still applied limits on sulfur in diesel fuel substantially higher than in Western Europe. Maximum levels of 2,000 and 5,000 ppm were applied for different uses. In Russia, lower maximum levels of 350 ppm and 500 ppm sulfur in automotive fuel were enforced in certain areas, and Euro IV and Euro V fuel with a concentration of 50 ppm or less was available at certain fueling stations, at least in part to comply with emissions control equipment on foreign-manufactured cars and trucks, the number of which is increased every year, especially in big cities such as Moscow and Saint Petersburg. According to the technical regulation, selling a fuel with sulfur content over 50 ppm was allowed until 31 December 2011. Euro IV diesel in particular may be available at fueling stations selling to long-distance truck fleets servicing import and export flows between Russia and the EU. [ 37 ]
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https://en.wikipedia.org/wiki/Ultra-low-sulfur_diesel
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Ultra-low particulate air ( ULPA ) is a type of air filter . A ULPA filter can remove from the air at least 99.999% of dust , pollen , mold , bacteria and any airborne particles with a minimum particle penetration size of 120 nanometres (0.12 μm , ultrafine particles ). A ULPA filter can remove—to a large extent but not 100%—oil smoke, tobacco smoke , rosin smoke, smog , and insecticide dust. [ 1 ] It can also remove carbon black to some extent. Some fan filter units incorporate ULPA filters. The EN 1822 and ISO 29463 standards may be used to rate ULPA filters. [ 2 ] [ 3 ]
Both high-efficiency particulate air ( HEPA ) and ULPA filter media have similar designs.
The filter media is like an enormous web of randomly arranged fibres. When air passes through this dense web, the solid particles get attached to the fibres and thus eliminated from the air.
Porosity is one of the key considerations of these fibres. Lower porosity, while decreasing the speed of filtration, increases the quality of filtered air. This parameter is measured in pores per linear inch.
Physically blocking particles with a filter, called sieving, cannot remove smaller-sized particles. The cleaning process, based on the particle size of the pollutant, is based on four techniques: [ 1 ]
A number of recommended practices have been written on testing these filters, including: [ 4 ]
ISO 60 U
≥ 99.9999%
≥ 99.9995%
ISO 70 U
≥ 99.99999%
≥ 99.9999%
See also the different classes for air filters for comparison
This technology-related article is a stub . You can help Wikipedia by expanding it .
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https://en.wikipedia.org/wiki/Ultra-low_particulate_air
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An ultracentrifuge is a centrifuge optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as 1 000 000 g (approx. 9 800 km/s² ). [ 1 ] There are two kinds of ultracentrifuges, the preparative and the analytical ultracentrifuge . Both classes of instruments find important uses in molecular biology , biochemistry , and polymer science. [ 2 ]
In 1924 Theodor Svedberg built a centrifuge capable of generating 7,000 g (at 12,000 rpm), and called it the ultracentrifuge, to juxtapose it with the Ultramicroscope that had been developed previously. In 1925-1926 Svedberg constructed a new ultracentrifuge that permitted fields up to 100,000 g (42,000 rpm). [ 3 ] Modern ultracentrifuges are typically classified as allowing greater than 100,000 g. [ 4 ] Svedberg won the Nobel Prize in Chemistry in 1926 for his research on colloids and proteins using the ultracentrifuge. [ 5 ] [ 6 ] [ 3 ]
In early 1930s, Émile Henriot found that suitably placed jets of compressed air can spin a bearingless top to very high speeds and developed an ultracentrifuge on that principle. Jesse Beams from the Physics Department at the University of Virginia first adapted that principle to a high-speed camera , and then started improving Henriot's ultracentrifuge, but his rotors consistently overheated. [ 7 ]
Beam's student Edward Greydon Pickels solved the problem in 1935 by vacuumizing the system, which allowed a reduction in friction generated at high speeds. Vacuum systems also enabled the maintenance of constant temperature across the sample, eliminating convection currents that interfered with the interpretation of sedimentation results. [ 8 ]
In 1946, Pickels cofounded Spinco (Specialized Instruments Corp.) to market analytical and preparative ultracentrifuges based on his design. Pickels considered his design to be too complicated for commercial use and developed a more easily operated, “foolproof” version. But even with the enhanced design, sales of analytical centrifuges remained low, and Spinco almost went bankrupt. The company survived by concentrating on sales of preparative ultracentrifuge models, which were becoming popular as workhorses in biomedical laboratories. [ 8 ] In 1949, Spinco introduced the Model L, the first preparative ultracentrifuge to reach a maximum speed of 40,000 rpm . In 1954, Beckman Instruments (later Beckman Coulter ) purchased the company, forming the basis of its Spinco centrifuge division. [ 9 ]
Ultracentrifuges are available with a wide variety of rotors suitable for a great range of experiments. Most rotors are designed to hold tubes that contain the samples. Swinging bucket rotors allow the tubes to hang on hinges so the tubes reorient to the horizontal as the rotor initially accelerate. [ 10 ] Fixed angle rotors are made of a single block of material and hold the tubes in cavities bored at a predetermined angle. Zonal rotors are designed to contain a large volume of sample in a single central cavity rather than in tubes. Some zonal rotors are capable of dynamic loading and unloading of samples while the rotor is spinning at high speed.
Preparative rotors are used in biology for pelleting of fine particulate fractions, such as cellular organelles ( mitochondria , microsomes , ribosomes ) and viruses . They can also be used for gradient separations, in which the tubes are filled from top to bottom with an increasing concentration of a dense substance in solution. Sucrose gradients are typically used for separation of cellular organelles. Gradients of caesium salts are used for separation of nucleic acids. After the sample has spun at high speed for sufficient time to produce the separation, the rotor is allowed to come to a smooth stop and the gradient is gently pumped out of each tube to isolate the separated components.
The tremendous rotational kinetic energy of the rotor in an operating ultracentrifuge makes the catastrophic failure of a spinning rotor a serious concern, as it can explode spectacularly. Rotors conventionally have been made from high strength-to-weight metals such as aluminum or titanium. The stresses of routine use and harsh chemical solutions eventually cause rotors to deteriorate. Proper use of the instrument and rotors within recommended limits and careful maintenance of rotors to prevent corrosion and to detect deterioration is necessary to mitigate this risk. [ 11 ] [ 12 ]
More recently some rotors have been made of lightweight carbon fiber composite material, which are up to 60% lighter, resulting in faster acceleration/deceleration rates. Carbon fiber composite rotors also are corrosion-resistant, eliminating a major cause of rotor failure. [ 13 ]
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https://en.wikipedia.org/wiki/Ultracentrifugation
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An ultracentrifuge is a centrifuge optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as 1 000 000 g (approx. 9 800 km/s² ). [ 1 ] There are two kinds of ultracentrifuges, the preparative and the analytical ultracentrifuge . Both classes of instruments find important uses in molecular biology , biochemistry , and polymer science. [ 2 ]
In 1924 Theodor Svedberg built a centrifuge capable of generating 7,000 g (at 12,000 rpm), and called it the ultracentrifuge, to juxtapose it with the Ultramicroscope that had been developed previously. In 1925-1926 Svedberg constructed a new ultracentrifuge that permitted fields up to 100,000 g (42,000 rpm). [ 3 ] Modern ultracentrifuges are typically classified as allowing greater than 100,000 g. [ 4 ] Svedberg won the Nobel Prize in Chemistry in 1926 for his research on colloids and proteins using the ultracentrifuge. [ 5 ] [ 6 ] [ 3 ]
In early 1930s, Émile Henriot found that suitably placed jets of compressed air can spin a bearingless top to very high speeds and developed an ultracentrifuge on that principle. Jesse Beams from the Physics Department at the University of Virginia first adapted that principle to a high-speed camera , and then started improving Henriot's ultracentrifuge, but his rotors consistently overheated. [ 7 ]
Beam's student Edward Greydon Pickels solved the problem in 1935 by vacuumizing the system, which allowed a reduction in friction generated at high speeds. Vacuum systems also enabled the maintenance of constant temperature across the sample, eliminating convection currents that interfered with the interpretation of sedimentation results. [ 8 ]
In 1946, Pickels cofounded Spinco (Specialized Instruments Corp.) to market analytical and preparative ultracentrifuges based on his design. Pickels considered his design to be too complicated for commercial use and developed a more easily operated, “foolproof” version. But even with the enhanced design, sales of analytical centrifuges remained low, and Spinco almost went bankrupt. The company survived by concentrating on sales of preparative ultracentrifuge models, which were becoming popular as workhorses in biomedical laboratories. [ 8 ] In 1949, Spinco introduced the Model L, the first preparative ultracentrifuge to reach a maximum speed of 40,000 rpm . In 1954, Beckman Instruments (later Beckman Coulter ) purchased the company, forming the basis of its Spinco centrifuge division. [ 9 ]
Ultracentrifuges are available with a wide variety of rotors suitable for a great range of experiments. Most rotors are designed to hold tubes that contain the samples. Swinging bucket rotors allow the tubes to hang on hinges so the tubes reorient to the horizontal as the rotor initially accelerate. [ 10 ] Fixed angle rotors are made of a single block of material and hold the tubes in cavities bored at a predetermined angle. Zonal rotors are designed to contain a large volume of sample in a single central cavity rather than in tubes. Some zonal rotors are capable of dynamic loading and unloading of samples while the rotor is spinning at high speed.
Preparative rotors are used in biology for pelleting of fine particulate fractions, such as cellular organelles ( mitochondria , microsomes , ribosomes ) and viruses . They can also be used for gradient separations, in which the tubes are filled from top to bottom with an increasing concentration of a dense substance in solution. Sucrose gradients are typically used for separation of cellular organelles. Gradients of caesium salts are used for separation of nucleic acids. After the sample has spun at high speed for sufficient time to produce the separation, the rotor is allowed to come to a smooth stop and the gradient is gently pumped out of each tube to isolate the separated components.
The tremendous rotational kinetic energy of the rotor in an operating ultracentrifuge makes the catastrophic failure of a spinning rotor a serious concern, as it can explode spectacularly. Rotors conventionally have been made from high strength-to-weight metals such as aluminum or titanium. The stresses of routine use and harsh chemical solutions eventually cause rotors to deteriorate. Proper use of the instrument and rotors within recommended limits and careful maintenance of rotors to prevent corrosion and to detect deterioration is necessary to mitigate this risk. [ 11 ] [ 12 ]
More recently some rotors have been made of lightweight carbon fiber composite material, which are up to 60% lighter, resulting in faster acceleration/deceleration rates. Carbon fiber composite rotors also are corrosion-resistant, eliminating a major cause of rotor failure. [ 13 ]
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https://en.wikipedia.org/wiki/Ultracentrifuge
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In condensed matter physics , an ultracold atom is an atom with a temperature near absolute zero . At such temperatures, an atom's quantum-mechanical properties become important, especially through what's known as a "superfluid" , such as Superfluid Helium 4 .
To reach such low temperatures, a combination of several techniques typically has to be used. [ 1 ] First, atoms are trapped and pre-cooled via laser cooling in a magneto-optical trap . To reach the lowest possible temperature, further cooling is performed using evaporative cooling in a magnetic or optical trap . Several Nobel prizes in physics are related to the development of the techniques to manipulate quantum properties of individual atoms (e.g. 1989, 1996, 1997, 2001, 2005, 2012, 2018).
Experiments with ultracold atoms study a variety of phenomena, including quantum phase transitions , Bose–Einstein condensation (BEC), bosonic superfluidity , quantum magnetism , many-body spin dynamics, Efimov states , Bardeen–Cooper–Schrieffer (BCS) superfluidity and the BEC–BCS crossover . [ 2 ] Some of these research directions utilize ultracold atom systems as quantum simulators to study the physics of other systems, including the unitary Fermi gas and the Ising and Hubbard models. [ 3 ] Ultracold atoms could also be used for realization of quantum computers. [ 4 ] [ 5 ]
Samples of ultracold atoms are typically prepared through the interactions of a dilute gas with a laser field. Evidence for radiation pressure, force due to light on atoms, was demonstrated independently by Lebedev, and Nichols and Hull in 1901. In 1933, Otto Frisch demonstrated the deflection of individual sodium particles by light generated from a sodium lamp.
The invention of the laser spurred the development of additional techniques to manipulate atoms with light. Using laser light to cool atoms was first proposed in 1975 by taking advantage of the Doppler effect to make the radiation force on an atom dependent on its velocity, a technique known as Doppler cooling . Similar ideas were also proposed to cool samples of trapped ions. Applying Doppler cooling in three dimensions will slow atoms to velocities that are typically a few cm/s and produce what is known as an optical molasses . [ 6 ]
Typically, the source of neutral atoms for these experiments were thermal ovens which produced atoms at temperatures of a few hundred kelvins. The atoms from these oven sources are moving at hundred of meters per second. One of the major technical challenges in Doppler cooling was increasing the amount of time an atom can interact with the laser light. This challenge was overcome by the introduction of a Zeeman Slower . A Zeeman Slower uses a spatially varying magnetic field to maintain the relative energy spacing of the atomic transitions involved in Doppler cooling. This increases the amount of time the atom spends interacting with the laser light. Experiments can also use metal dispensers, which are pure metal (typically alkali metals ) rods that can emit when heated up (the vapor pressure is higher) with electrical current.
The development of the first magneto-optical trap (MOT) by Raab et al. in 1987 was an important step towards the creation of samples of ultracold atoms. Typical temperatures achieved with a MOT are tens to hundreds of microkelvins. In essence, a magneto optical trap confines atoms in space by applying a magnetic field so that lasers not only provide a velocity dependent force but also a spatially varying force. The 1997 Nobel prize [ 6 ] in physics was awarded for development of methods to cool and trap atoms with laser light and was shared by Steven Chu , Claude Cohen-Tannoudji and William D. Phillips .
Evaporative cooling was used in experimental efforts to reach lower temperatures in an effort to discover a new state of matter predicted by Satyendra Nath Bose and Albert Einstein known as a Bose–Einstein condensate (BEC). In evaporative cooling, the hottest atoms in a sample are allowed to escape which reduces the average temperature of the sample. The Nobel Prize in 2001 [ 1 ] was awarded to Eric A. Cornell , Wolfgang Ketterle and Carl E. Wieman for the achievement of Bose–Einstein condensate in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates.
In recent years a variety of sub-Doppler cooling techniques, including polarization gradient cooling , gray molasses cooling , and Raman sideband cooling , have enabled the cooling and trapping of single atoms in optical tweezers . [ 7 ] [ 8 ] [ 9 ] Experimental platforms leveraging ultracold neutral atoms in optical tweezers and optical lattices have become an increasingly popular setting for studying quantum computing, quantum simulation, and precision metrology . Atoms with closed cycling transitions, capable of scattering many photons with a low probability of decay into other states, are common choices of species for ultracold neutral atom experiments. The lowest-energy fine structure transitions in alkali atoms enable fluorescence imaging, while a combination of hyperfine and Zeeman sublevels can be used for implementing sub-Doppler cooling. Alkaline earth atoms have also gained popularity owing to narrow-linewidth cooling transitions and ultra-narrow optical clock transitions.
Ultracold atoms have a variety of applications owing to their unique quantum properties and the great experimental control available in such systems. For instance, ultracold atoms have been proposed as a platform for quantum computation and quantum simulation, [ 10 ] accompanied by very active experimental research to achieve these goals.
Quantum simulation is of great interest in the context of condensed matter physics, where it may provide valuable insights into the properties of interacting quantum systems. The ultracold atoms are used to implement an analogue of the condensed matter system of interest, which can then be explored using the tools available in the particular implementation. Since these tools may differ greatly from those available in the actual condensed matter system, one can thus experimentally probe otherwise inaccessible quantities. Furthermore, ultracold atoms may even allow to create exotic states of matter, which cannot otherwise be observed in nature.
All atoms are identical, making ensembles of atoms ideal for universal timekeeping. In 1967, the SI definition of the second was changed to reference a hyperfine transition frequency in Cesium atoms. Atomic clocks based on alkaline earth atoms or alkaline earth like ions (such as Al + ) have now been developed making use of narrow-line optical transitions. To achieve high numbers of non-interacting atoms, which assists in the precision of these clocks, neutral atoms can be trapped in optical lattices. On the other hand, ion traps permit long interrogation times.
Ultracold atoms are also used in experiments for precision measurements enabled by the low thermal noise and, in some cases, by exploiting quantum mechanics to exceed the standard quantum limit. In addition to potential technical applications, such precision measurements may serve as tests of our current understanding of physics.
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https://en.wikipedia.org/wiki/Ultracold_atom
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In chronobiology , an ultradian rhythm is a recurrent period or cycle repeated throughout a 24-hour day. In contrast, circadian rhythms complete one cycle daily, while infradian rhythms such as the menstrual cycle have periods longer than a day. The Oxford English Dictionary 's definition of Ultradian specifies that it refers to cycles with a period shorter than a day but longer than an hour. [ 1 ]
The descriptive term ultradian is used in sleep research in reference to the 90–120 minute cycling of the sleep stages during human sleep. [ 2 ]
There is a circasemidian rhythm in body temperature and cognitive function which is technically ultradian. However, this appears to be the first harmonic of the circadian rhythm of each and not an endogenous rhythm with its own rhythm generator.
Other ultradian rhythms include blood circulation , blinking , pulse , hormonal secretions such as growth hormone , [ 3 ] heart rate , thermoregulation , micturition , bowel activity, nostril dilation , appetite , and arousal . Ultradian rhythms of appetite require antiphasic release of neuropeptide Y (NPY) and corticotropin-releasing hormone (CRH), stimulating and inhibiting appetite ultradian rhythms. [ 4 ] Recently, ultradian rhythms of arousal lasting approximately 4 hours were attributed to the dopaminergic system in mammals. [ 5 ] When the dopaminergic system is perturbed either by use of drugs or by genetic disruption, these 4-hour rhythms can lengthen significantly into the infradian (> 24 h) range, sometimes even lasting for days (> 110 h) when methamphetamine are provided. [ 5 ]
According to a study published in 1996: Ultradian mood states in bipolar disorder cycle much faster than rapid cycling ; the latter is defined as four or more mood episodes in one year, sometimes occurring within a few weeks. Ultradian mood cycling is characterized by cycles shorter than 24 hours. [ 6 ]
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https://en.wikipedia.org/wiki/Ultradian_rhythm
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In functional analysis , an ultradistribution (also called an ultra-distribution [ 1 ] ) is a generalized function that extends the concept of a distributions by allowing test functions whose Fourier transforms have compact support . [ 2 ] They form an element of the dual space 𝒵′, where 𝒵 is the space of test functions whose Fourier transforms belong to 𝒟, the space of infinitely differentiable functions with compact support. [ 3 ]
This mathematical analysis –related article is a stub . You can help Wikipedia by expanding it .
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https://en.wikipedia.org/wiki/Ultradistribution
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In physics , ultradivided matter is a family of states of matter characterised by a heterogeneous mixture of two or more different materials, where the interaction energy between the suspended phase is larger than kT. The term 'ultradivided matter' encapsulates several types of substance including: soap micelles , emulsions , and suspensions of solids such as colloids .). [ 1 ]
An ultradivided state differs from a solution. In a steady-state solution, all interactions between a solution's constituent molecules are on the order of the thermal energy kT . Thus any otherwise aggregative force between similar molecules in a solution is subordinate to thermal fluctuations , and the solution does allow flocculation of one of the constituent components. Ultradivided matter, however, is characterised by large interfacial energies where the intermolecular interactions of one or more constituents of the substance are stronger than kT. This leads to different behaviour. An intuitive example of this can be seen in the tendency of a biphasic mixture of water (a polar liquid) and oil (a non-polar liquid) to spontaneously separate into two phases. This may seem to imply a change from a state with higher disorder or higher entropy (a suspension of oil droplets in water) to a lower-entropy arrangement (a neat separation into two regions of different material). Such a transition would seem to violate the second law of thermodynamics , which is impossible. The resolution to this apparent paradox is that the interface between oil and water necessitates an ordered alignment of oil and water molecules at the interface. Minimisation of the surface area between the two phases thus correlates with an increase of the entropy of the system. The highest entropy state thus has a minimum interfacial surface area between the two phases and thus a neat separation is created, into two regions of different material.
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https://en.wikipedia.org/wiki/Ultradivided_matter
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Ultrafast X-rays or ultrashort X-ray pulses are femtosecond x-ray pulses with wavelengths occurring at interatomic distances . This beam uses the X-ray's inherent abilities to interact at the level of atomic nuclei and core electrons . This ability combined with the shorter pulses at 30 femtosecond could capture the change in position of atoms, or molecules during phase transitions , chemical reactions , and other transient processes in physics , chemistry , and biology . [ 1 ] [ 2 ]
Ultrafast X-ray diffraction (time-resolved X-ray diffraction) can surpass ultrashortpulse visible techniques , which are limited to detecting structures on the level of valence and free electrons . Ultrashort pulse X-ray techniques are able to resolve atomic scales , where dynamic structural changes and reactions occur in the interior of a material. [ 3 ] [ 4 ] [ 5 ] [ 6 ]
Rose-Petruck, Christoph; et al. (March 25, 1999). "Figure 1". Nature . 398 (6725): 310– 312. Bibcode : 1999Natur.398..310R . doi : 10.1038/18631 . S2CID 4399550 .
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https://en.wikipedia.org/wiki/Ultrafast_X-ray
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An ultrafast molecular process is any technology that relies on properties of molecules that are only extant for a very short period of time (less than 1e-9 seconds). Such processes are very important in areas such as combustion chemistry and in the study of proteins .
This chemical process -related article is a stub . You can help Wikipedia by expanding it .
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https://en.wikipedia.org/wiki/Ultrafast_molecular_process
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