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Messaggi del 05/04/2011
Post n°801 pubblicato il 05 Aprile 2011 da diegobaratono
Da:"http://public.web.cern.ch/public/
LHC Report: A new luminosity record After about one month of operation, the LHC has already accumulated an integrated luminosity of 28 pb-1, which corresponds to over 50% of the total delivered to the experiments in 2010. This impressive start to the LHC run in 2011 bodes well for the rest of year. Following careful collimator set-up and validation, the first phase of beam commissioning 2011 has come to an end. The first stable beams were declared on Sunday 13 March with a moderate 3 bunches per beam and an initial luminosity of 1.6 × 1030 cm-2s-1. Machine protection tests continued during the following week as the commissioning team made absolutely sure that all critical systems (beam dumps, beam interlock system, etc.) were functioning properly. When these tests had finished, the way was opened to increased intensity and the LHC quickly moved through the first part of its planned, staged intensity increase. Fills with increasing numbers of bunches were delivered to the experiments, culminating in a fill with 200 bunches per beam on the evening of Tuesday 22 March. With the reduced beam size at the interaction points in ATLAS and CMS this gave a peak luminosity of 2.5 × 1032 cm-2s-1, comfortably beating last year's record made with 368 bunches. On Thursday 24 March, the LHC switched to an energy of 1.38 TeV/beam to provide the experiments with some proton-proton collisions at the equivalent nucleon-nucleon centre of mass energy seen during the heavy ion run at the end of last year. These collisions are required to compare the behaviour of nucleon-nucleon collisions in the heavy ion environment with collisions free of the effects of the heavy ion medium. The data required should be delivered by the start of the weekend when the LHC will switch back to 3.5 TeV for some more physics running before the start of the 4 day technical stop planned for the end of March. by CERN Bulletin | | |
Post n°800 pubblicato il 05 Aprile 2011 da diegobaratono
Da:"Antikitera.net"
5 Aprile 2011 ARCHEOLOGIA
Wired Science
IL MECCANISMO DI ANTIKYTHERA SPIEGAVA I MOVIMENTI DEL SOLE Si sa che il più famoso calcolatore astronomico possedeva un complesso sistema di meccanismi a ruote dentate, secoli prima della meccanica moderna. Un nuovo studio rivela che il meccanismo di Antikythera usava la geometria pura e le ruote dentate per seguire il percorso apparente dei corpi celesti nei cieli. Lo strumento di duemila anni fa, che somiglia in modo impressionante ad un orologio del sec. XIX, per la sua precisione e la complessità, fu recuperato da un relitto nell'isola greca di Antikythera nel 1901. Il meccanismo indicava il giorno dell'anno, con le posizioni del sole e della luna e forse di altri pianeti. Esso prediceva le eclissi e indicava le scadenze dei Giochi Olimpici. La maggior parte dei calcoli si sviluppava grazie a 37 quadranti connessi tra loro, che potevano essere fatti ruotare con un sistema manuale. La faccia a vista del meccanismo doveva avere un quadrante simile a quello d'un orologio che conteneva le date del calendario in due ruote concentriche, l'una con i simboli dello Zodiaco greco, l'altra con quelli dei mesi egiziani. Tre lancette indicavano le date e le posizioni del sole e della luna. "Un pezzo ben elaborato" ha detto lo storico della scienza James Evans, della University of Puget Sound, in una presentazione all'Università di Washington a Seattle il 31 marzo scorso. "Non si poteva immaginare che esistessero meccanismi tanto complessi nel secondo secolo a.C." Le prime ricerche mostrarono che il meccanismo poteva seguire con precisione il movimento della luna. Poiché tale movimento è ellittico, non circolare, il moto apparente del satellite sembra accelerare e rallentare nel corso d'un mese. Nel 2006, Tony Freeth della Cardiff University mostrò con i suoi colleghi che un'abile configurazione di due ruote interconnesse, con una ruota eccentrica, poteva seguire il moto apparentemente irregolare della luna. A causa dell'orbita ellittica della terra intorno al sole, anche il moto apparente del sole ha una velocità variabile nel cielo, lungo l'anno. Tale effetto è però più sottile, rispetto alla luna. "Era molto difficile rendere un movimento tanto piccolo", ha detto Evans. Se c'era qualche ingranaggio destinato a rendere tale movimento, esso non è sopravvissuto al naufragio. Evans e i suoi colleghi pensavano a come poteva essere il meccanismo che rendesse I cambiamenti di velocità del moto apparente del sole. Se gli angoli dei vari mesi nel quadrante avessero avuto ampiezze diverse, pensava Evans, la lancetta del sole avrebbe potuto impiegare piò tempo nel segno del Toro che in quello della Bilancia. Ciò sarebbe stato equivalente a farlo andare più piano o più velocemente a seconda delle stagioni. Per provare quest'idea, I ricercatori hanno esaminato le immagini ai raggi X del meccanismo di Antikythera, che presenta alcune parti fortemente corrose. In uno studio pubblicato l'anno scorso sul Journal for the History of Astronomy (del quale Evans è co-editore), il gruppo ha analizzato 69 gradi del cerchio, conservati nel reperto abbastanza bene da mostrare i nomi dei segni dello Zodiaco e alter indicazioni. Poi il gruppo ha esteso lo studio a un'ampiezza di 88 gradi. Hanno così trovato che i due cerchi dello zodiaco e del calendario egiziano erano divisi in modo diverso, e proprio in modo da rendere i diversi tempi di percorrenza del sole. "E' stato più sensato percorrere questa via che non graduare la velocità dell'ingranaggio con l'uso di due ruote sovrapposte, come avevano fatto per l'orbita lunare", ha detto Evans. Nella sua conferenza di Seattle, Evans ha mostrato una ricostruzione di legno e ottone del meccanismo di Antikythera (si veda la foto) che include lo zodiaco modificato, così come le ruote di Mercurio, Venere, Marte, Giove e Saturno. L'esistenza delle ruote dei pianeti è ancora controversa, ha detto, e non tutti gli esperti sono d'accordo con questo modello, ma per Evans esso è attendibile. "Potreste scommettervi la vostra pensione sulla nostra ricostruzione dei diversi angoli dei mesi solari, almeno al 5. per cento" ha detto. Il meccanismo non serviva forse a misurare il passaggio del tempo, ha aggiunto. Ogni volta che trasporta il modello per una dimostrazione, le ruote girano e poi gli occorre un'ora buona per farlo funzionare di nuovo. Piuttosto, ha detto, la macchina serviva a suscitare meraviglia. "Era fatta per dimostrare, per spiegare, per insegnare, piuttosto che non servire per un uso pratico, come strumento di calcolo".
Post n°799 pubblicato il 05 Aprile 2011 da diegobaratono
Da:"ScienceDaily.com"
Science News
Sugar-Grain Sized Meteorites Rocked the Climates of Early Earth and Mars, According to New Study ScienceDaily (Apr. 1, 2011) — Bombardments of 'micro-meteorites' on Earth and Mars four billion years ago may have caused the planets' climates to cool dramatically, hampering their ability to support life, according to research published April 1 in the journal Geochimica et Cosmochimica Acta. Scientists from Imperial College London studied the effects of the Late Heavy Bombardment (LHB), a period of time in the early solar system when meteorite showers lasting around 100 million years barraged Earth and Mars. This bombardment discharged sulphur dioxide into the upper atmospheres of both planets and the researchers' analysis suggests that this may have had a catastrophic impact on their environments. Micro-meteorites come from the rocky asteroid belt between Mars and Jupiter. These space rocks, which are the size of sugar grains, get dragged by gravity towards Earth and Mars. As they enter the planets' upper atmospheres, they heat up to temperatures of approximately 1000 degrees Celsius, releasing gases including sulphur dioxide. Sulphur dioxide in the atmosphere forms aerosols, consisting of solid and liquid particles, which deflect sunlight away from the surface, making planets cooler. The authors of the new study have calculated that showers of micro-meteorites delivered approximately 20 million tonnes of sulphur dioxide each year into the upper atmosphere of Earth during the LHB. The team deduced that on Mars, these micro-meteorites delivered up to half a million tonnes of sulphur dioxide each year for the same period of time. Professor Mark Sephton, an author of the study from the Department of Earth Science and Engineering at Imperial College London, says: "Far less of the Sun's energy was reaching Earth 4 billion years ago, which would have made it hard for early life to emerge. Recently denied of its protective magnetic field and constantly subjected to large meteorite impacts, Mars was also starting to lose its greenhouse gases at this time, causing global cooling. The influx of sulphur dioxide into the Mars's atmosphere would have dealt a further blow to a planet already on the ropes, making conditions for life even more of a challenge." The team say that such a large influx of sulphur dioxide into early Earth's atmosphere had the same cooling effect on the climate as if there was an eruption of the size of the 1991 Mount Pinatubo eruption every year for 100 million years. The 1991 Mount Pinatubo eruption released 17 million tonnes of gases, including sulphur dioxide, into the atmosphere, preventing 10 percent of sunlight from reaching Earth and cooling the planet by half a degree Celsius. On Mars during the LHB, the scientists predict that the cooling effects of sulphur dioxide on the red planet's atmosphere would have been the equivalent of an eruption 1/34th the size of Mount Pinatubo occurring every year for 100 million years. The scientists say that the environmental consequences of sulphur dioxide in Earth's atmosphere could have been disastrous. At this time, the Sun's energy was 30 percent weaker than it is today, meaning less energy was reaching the surface. The team believe that a weaker Sun, combined with increasing levels of sulphur dioxide from micro-meteorites, could have plunged Earth into an Arctic winter, lasting millions of years and making conditions for primitive microbial life extremely difficult. On Mars, being further away from the Sun, the scientists suggest the environmental consequences would have been even more dramatic. High levels of sulphur dioxide would cause temperatures to plunge and water on the surface, in the form of lakes and rivers, to disappear, turning a warm wet world into a cold arid one. Dr Richard Court, who is lead author of the study from the Department of Earth Science and Engineering at Imperial College London, adds: "These sugar-grain sized meteorites are left over material from the construction of our early Solar System, helping to build rocky planets such as Earth and Mars. Our study is helping us to see how these tiny space rocks could also bring environmental devastation on a global scale to early Earth and Mars." The researchers came to their conclusions by simulating what happens to micro-meteorites as they entered the atmosphere, using a technique called flash pyrolysis to heat rock fragments that were identical to micro-meteorites to 1000 degrees Celsius. They then used infrared spectroscopy to measure the amount of sulphur dioxide released from these rocks. The team then used their results and calculations of meteorite in-fall rates during the LHB to determine how much sulphur dioxide was delivered to Earth and Mars from micro-meteorites. This study is a continuation of earlier work by the team who have discovered that meteorites are not the source of the present-day methane in the atmosphere of Mars, raising hopes that the methane is being generated by life on the red planet. Their work has also shown that meteorites delivered other important gases to Earth during its early history that would have made it more habitable. In the future, the team will assess the contributions gases from meteorites on planets outside of the Solar System. The research was funded by the Science and Technology Facilities Council.
Post n°798 pubblicato il 05 Aprile 2011 da diegobaratono
Da:"ScienceDaily.com"
Why Ancient Mayan Communities Were 'Living on the Edge' of What Is Now a Massive Wetland ScienceDaily (Mar. 28, 2011) — University of Cincinnati research is investigating why a highly sophisticated civilization decided to build large, bustling cities next to what is essentially swampland. The research by UC Geography Professor Nicholas Dunning, a three-year, interdisciplinary project including David Lentz, professor of biological sciences, and Vern Scarborough, professor of anthropology, will be presented April 1 at the annual meeting of the Society for American Archaeology in Sacramento, Calif. Dunning's research zeroes in on why larger and successful Maya communities were located along the edges of the massive wetlands of Tikal. Supported by the National Science Foundation and the Wenner Gren Foundation, the UC researchers are exploring different aspects of the ancient Maya in one of the premier cities of the ancient Maya world, Tikal, located in northern Guatemala. It's a region where architecture -- pyramids, palaces and temples dating as far back as the fourth century B.C.- are still standing in tribute to this ancient, sophisticated, Native American society that largely disintegrated around 900 A.D. Their demise has remained a mystery for centuries. Located near the southwestern margin of the Bajo de Sante Fe, it's also a challenging region to conduct research. "It doesn't take a lot of rain to make it impossible to get in and out of the bajos. They're seasonal swamps. The mud gets deep very quickly," explains Dunning. But the researchers have found that when the Maya started building their cities adjacent to these wetlands, they were different environments than what exist now, Dunning says. Portions of the area where UC researchers are working once may have been a shallow lake and perennial wetlands from which early populations extracted organic, peat moss-like soil to help sustain nearby fields where the Maya were primarily farming maize. Over the years, the farming-on-the-edge practice on sloping land led to soil erosion that resulted in creating aprons of deep, rich soil along the interface between the uplands and the swamps. "We have good evidence from Tikal and other sites in this region that these areas became the focal point where agriculture occurred in the Classic Period, where these anthropogenic soils were created at the base of the slopes," Dunning says. In regard to the edge farming, the researchers studied the soil and found significant amounts of pollen, which would indicate a significant amount of maize was produced. In addition, the organic matter produced from the corn was reflected in the soil's composition. The UC research was a joint project with Instituto de Antropología e Historía (de Guatemala) -- IDEAH -- under the Guatemalan government. Lentz and Scarborough will also be presenting findings related to their fields -- regarding the Maya's advances in forestry and water management -- at the conference. Dunning has been conducting research related to the geography of Guatemala since 1991. "One of the fascinating aspects of archaeology is that in reconstructing entire civilizations, one can't understand how an ancient civilization worked from just one perspective, so it naturally lends itself to interdisciplinary work," he says. Additional authors and researchers on Dunning's presentation are Robert Griffin, Penn State University, John G. Jones, Washington State University, Christopher Carr, a UC doctoral student in the geography program and Kevin Magee, who recently completed his PhD in the UC geography program.
Post n°797 pubblicato il 05 Aprile 2011 da diegobaratono
Da:"ANSA.it"
Shuttle: rinvio lancio per traffico (ANSA) - ROMA, 4 APR - E' stato rinviato di 10 giorni 'per motivi di traffico' il lancio dello shuttle Endeavour con il quale voleranno l'astronauta italiano dell'Agenzia Spaziale Europea (Esa) Roberto Vittori e lo strumento Ams (Alpha Magnetic Spectrometer).
Lo shuttle partira' il 29 aprile, rende noto la Nasa, perche' nei giorni intorno al 19 aprile non ci sara' la possibilita' di garantire l'attracco della shuttle a causa dell'arrivo alla Stazione Spaziale Internazionale (Iss) del cargo russo Progress M-10M.
Post n°796 pubblicato il 05 Aprile 2011 da diegobaratono
Da:"Reuters.com"
U.S.-Russian crew blast off for space station The Russian Soyuz TMA-21 spacecraft, named after the first cosmonaut Yuri Gagarin, carrying the International Space Station (ISS) crew of U.S. astronaut Ronald Garan and Russian cosmonauts Alexandr Samokutyaev and Andrey Borisenko, leaves a trail across sky on this long exposure picture, as it blasts off at the Baikonur cosmodrome April 5, 2011. Credit: Reuters/Shamil Zhumatov
By Alissa de Carbonnel KOROLYOV, Russia | Mon Apr 4, 2011 7:19pm EDT KOROLYOV, Russia (Reuters) - A Russian Soyuz spacecraft, carrying two cosmonauts and a U.S. astronaut to the International Space Station, blasted off early on Tuesday from Russia's launchpad in Kazakhstan, blazing a fiery trail across the night sky. Russian Soyuz Commander Alexander Samokutyayev, NASA Flight Engineer Ron Garan and cosmonaut Andrey Borisenko are to join three other crew members aboard the orbital station after a two-day trip from Earth aboard the cramped spacecraft, an upgraded model of a Soviet-designed standby. Russian Mission Control said the three men lifted off on schedule from the Baikonur cosmodrome at 0418 local time (2218 GMT on Monday). "The Soyuz-TMA 21 spacecraft has reached orbit," Samokutyayev, strapped in with his two crewmates, reported to Russian Mission Control a few minutes into the flight after the rocket stages dropped off. The crew in white space suits flashed thumbs up to onboard cameras and a stuffed toy mascot began floating above their heads as they entered weightlessness. Once it was safely in orbit, applause broke out at the cavernous Mission Control center in a northern Moscow suburb, named after Gagarin's mentor, the legendary chief designer of the Soviet space programme Sergei Korolyov. It is the first flight for Russians Samokutyayev and Borisenko, while Garan has logged 13 days in space during a 2008 shuttle mission. The launch comes less than a week before the 50th anniversary of Yuri Gagarin's historic flight from the same, once-secret Baikonur launch facility to become the first human in orbit. Tuesday's successful launch of the Soyuz -- which was named after Gagarin and his portrait daubed across its hull -- will likely assuage concerns over reliance on the single-use Russian spacecraft as NASA mothballs its shuttle fleet later this year. Lift off had been postponed from March 30 due to a glitch in the upgraded Soyuz's communication system. Garan, an avid twitter user and blogger, has promised to keep up the information flow from orbit. On Sunday, he tweeted pictures of himself getting a last haircut on Earth and called Gagarin's flight "a giant leap in our evolution as a species." He and his crewmates will spend six months aboard the station, a $100 billion project of 16 nations that has been under construction about 220 miles above Earth since 1998. The growing orbital complex, a mix of mostly Russian and American-built modules, can now accommodate a six-member crew at all times. Russian cosmonaut Dmitry Kondratyev, U.S. astronaut Cady Coleman and European Space Agency's Paolo Nespoli of Italy have been aboard the station since mid-December. (Editing by Philippa Fletcher)
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