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maxman木虫 (正式写手)
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physics news update(12.7)
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PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 757 December 7, 2005 by Phillip F. Schewe, Ben Stein THE TOP PHYSICS STORIES FOR 2005. At the Relativistic Heavy Ion Collider (RHIC) on Long Island, the four large detector groups agreed, for the first time, on a consensus interpretation of several year's worth of high-energy ion collisions: the fireball made in these collisions---a sort of stand-in for the primordial universe only a few microseconds after the big bang---was not a gas of weakly interacting quarks and gluons as earlier expected, but something more like a liquid of strongly interacting quarks and gluons (www.aip.org/pnu/2005/split/728-1.html ). Other top physics stories for 2005 include, in general chronological order of their appearance throughout the year, the following: the arrival of the Cassini spacecraft at Saturn and the successful landing of the Huygens probe on the moon Titan (http://www.aip.org/pnu/2005/split/716-1.html); the development of lasing in silicon (Nature, 17 February); the biggest burst of light ever recorded from outside the solar system, from a soft gamma repeater (http://www.aip.org/pnu/2005/split/721-1.html); further evidence for superfluid behavior in a solid (http://www.aip.org/pnu/2005/split/724-2.html); detection of infrared radiation directly from an exoplanet (http://www.aip.org/pnu/2005/split/724-1.html); zeptogram mass sensitivity in a cantilever sensor (http://www.aip.org/pnu/2005/split/725-1.html); spashless impact of droplets at low pressures (http://www.aip.org/pnu/2005/split/725-3.html); the demonstration of pyrofusion, fusion reactions created with a pyroelectric crystal (http://www.aip.org/pnu/2005/split/729-1.html); the best yet prediction of hadron masses using lattice QCD (http://www.aip.org/pnu/2005/split/731-1.html); the best measurement yet of the weak nuclear force (http://www.aip.org/pnu/2005/split/736-1.html); superfluidity directly observed in a sample of ultracold fermi atoms (http://www.aip.org/pnu/2005/split/734-1.html); extension of the "comb" technique for measuring frequency (a topic pertaining to the 2005 Nobel prize in physics) into the ultraviolet (http://www.aip.org/pnu/2005/split/735-2.html); geoneutrinos observed (http://www.aip.org/pnu/2005/split/739-3.html); hybrid atom-molecule dark states (http://www.aip.org/pnu/2005/split/744-1.html); using statistical mechanics to predict the effectiveness of flu vaccines (http://www.aip.org/pnu/2005/split/724-3.html); hydrophobic water (http://www.aip.org/pnu/2005/split/747-2.html); 2005 Nobel Prize (http://www.aip.org/pnu/2005/split/748-1.html); molecules that walk (http://www.aip.org/pnu/2005/split/751-2.html); phonon Hall effect (http://www.aip.org/pnu/2005/split/750-1.html); short gamma ray bursts identified as coming from in-spiraling neutron stars (Nature 6 October); hyperentangled states (http://www.aip.org/pnu/2005/split/754-1.html); further progress in research concerning left-handed or negative-refraction materials, including perfect lensing (Science 22 April), almost perfect lensing in the mid-infrared (http://www.aip.org/pnu/2005/split/750-3.html), and extension of negative-index behavior into the near-infrared region (http://www.aip.org/pnu/2005/split/756-1.html. FRACTAL-DOMINATED CHEMISTRY. Why does cream poured into coffee swirl the way it does? A new study of how chemical reactions proceed establishes new equations for reaction rates by taking mixing abnormalities more into account. Many existing equations assume efficient mixing of ingredients, but this is far from the case. Before reactions can take place, proper mixing has to occur, and as two Hungarian physicists now discover in their simulations of mixing under more realistic fluid flow conditions, reactions often occur along a fractal frontier. Indeed, much real-world fluid chemistry is chaotic in nature and takes place not in general solution but along a many-filamented fractal surface. Some previous studies of the steady time-independent fracticality of chemical reactions occurring in open flows, those in which fluid continuously flows into and out of a container. According to Gyorgy Karolyi (Budapest University of Technology and Economics) and Tamas Tel (Eotvos University), their new study is the first to address the tougher problem of a closed flow, one in which the fluid remains in the container; in this case, the resultant filamentary fractal is not steady but instead evolves through time, gradually filling up more and more of the container volume. They derive the relation between reaction rate and fractal dimensionality (the extent to which surface of the filaments lies between that of a two dimensional and three dimensional object). Fractal mixing is suspected in the disposition of several natural systems, such as plankton in the ocean, sea ice floating in the ocean, and cloud patterns (http://earthasart.gsfc.nasa.gov/vortices.html. Karolyi (karolyi@tas.me.bme.hu) suggests that the new equations might provide new insights for those who design microfluidic devices such as micromixers used in printing and medical equipment. (Karolyi and Tel, Physical Review Letters, upcoming article) [ Last edited by maxman on 2005-12-11 at 10:20 ] |
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