Science News omnibus

n1vux on 2005-08-19T21:34:06

«Room-temperature ice is possible if the water molecules you’re freezing are submitted to a high enough electric field. » -- Physics News Update

Light that travels… faster than light!

«A team of researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) has successfully demonstrated, for the first time, that it is possible to control the speed of light – both slowing it down and speeding it up – in an optical fiber, using off-the-shelf instrumentation in normal environmental conditions. ... They were also able to create extreme conditions in which the light signal travelled faster than 300 million meters a second. And even though this seems to violate all sorts of cherished physical assumptions, Einstein needn't move over – relativity isn't called into question, because only a portion of the signal is affected. » [emphasis supplied ]

- The Brillouin phenomena apparently involve group velocity, not actual FTL propagation of waves, just of group crests? One of the 3 Google News hits for this story says it's embargoed until Monday 2AM, but two others are out with it, and it's on the university website;... apparently the press release also travelled faster than the speed of light?  

- Ecole Polytechnique Fédérale de Lausanne (Français; Deutsch Presskommunique; English press release ) & Applied Physics Letters

via EurekAlert
Their previous work.

New method for trapping light may improve communications technologies

« A discovery by Princeton researchers may lead to an efficient method for controlling the transmission of light and improve new generations of communications technologies powered by light rather than electricity. [...] [They] tested whether quasicrystals -- an unusual form of solid -- would be useful for controlling the path of light by constructing a three-dimensional, softball-sized model of such a structure with 4,000 [count of one ] centimeter-long polymer rods.  [...] A quasicrystal is an unusual form of solid composed of two building blocks, or groups of atoms, that repeat regularly throughout the structure with two different spacings. [...] They observed how microwaves were blocked at certain angles in order to gauge how well the structure would control light passing through it. Building the physical model was a breakthrough that proved more valuable than using complex mathematical calculations, which had been a hurdle in previous efforts to evaluate the effectiveness of photonic quasicrystals in blocking light.»  (PR; photo on PU site. )

« [O]ur quasicrystal is far from optimized because it consists solely of thin rods connecting lattice points. A [...] more equal filled/void ratio would reduce polarization effects and enhance the gap overlap while maintaining the nearly spherical Brillouin zone. Laser tweezers used for particle trapping or two-photon polymerization would allow the construction of a quasicrystalline matrix of dielectric components with a photonic bandgap in the visible spectrum.» [Conclusion of preprint]

- Initially this sounds deceptively similar to the above Swiss fiber-optic experiment, and both involve Brillouin Scattering phenomena, but this actually quite different. 
(1) Quasicrystals (*) are 3-dimensional analogs of the Penrose tiling  (*), both of which seemingly violate the impossibility of 5-fold rotational symmetry -- counter-intuitively, 5-fold symmetry of a sort is possible in an aperiodic tiling. (Thus providing a simpler counter-example to Wang's conjecture, which held all tilings could be periodic.)  
(2) This is a scaled experiment performed with macroscopic stereolithographic model(s) inspected with microwaves and RF network analyzers, instead of an actual light experiment in light media as with the Swiss study above.
(3) This study is identifying candidates for photonic band-gap nanomaterials, and thus is similar to the negative index of refraction materials. 

- Princeton University PR and Website with preprint from Nature 436 p993ff,  18 August 2005, Letters; via EurekAlert

Saturn's rings have own atmosphere

« Data from the NASA/ESA/ASI Cassini spacecraft indicate that Saturn's majestic ring system has its own atmosphere - separate from that of the planet itself. During its close fly-bys of the ring system, instruments on Cassini have been able to determine that the environment around the rings is like an atmosphere, composed principally of molecular oxygen. This atmosphere is very similar to that of Jupiter's moons Europa and Ganymede.»

- This again reminds me of Larry Niven 's novels The Integral Trees and The Smoke Ring novels, set in a physically plausible torus of atmosphere around a double star  (the physics are quite similar to those for space-tethers in use on modern satellites ) . 
  Note that phrase similar to Europa's -- whose atmospheric pressure is estimated at one-hundred-billionth of Earth's (*) and thus not breathable; what little there is would also be rather cold.

- European Space Agency, Src, via EurekAlert (and also SpaceRef, SciScoop, ...)

Galactic survey reveals a new look for the Milky Way

«With the help of NASA's Spitzer Space Telescope, astronomers have conducted the most comprehensive structural analysis of our galaxy and have found tantalizing new evidence that the Milky Way is much different from your ordinary spiral galaxy. »

- Ordinary? Ordinary may be the wrong word for un-barred in this case. The typical spiral galaxy is barred. The non-barred spirals are less typical, possibly older.  E.g.,
  Ã‚«Barred spiral galaxies are relatively common, with surveys showing that up to two-thirds of all spiral galaxies contain a bar.»    - Wikipedia

- University of Wisconsin-Madison, Src, via EurekAlert

Too Many Roads Lead to Traffic Congestion

« In all networks, like road or airline traffic networks, the Internet, cancer tumors or industry supply chains, you need to pass packets from node to node, such as cars, information or data. But which are the most efficient, decentralized networks or hub-like centralized ones? According to Technology Research News (TRN), researchers from Oxford University, U.K., have designed a model which maps traffic congestion. This model combines roads going through the center of a city and other ones avoiding it. And they found that, from a cost point of view, it would be sometimes better to close roads going through cities than adding more. They also think that these conclusions can be applied to almost all kinds of networks, biological ones or created by humans. » [RP]

«Researchers from Oxford University in England have tackled the problem [of network optimization] by examining the congestion costs within a network model that combines paths that go around the perimeter of the network and central hubs that provide shorter paths through the network. Real-world networks are too complicated to describe exactly mathematically. The researchers' model is simple enough to solve exactly, yet realistic enough to provide insights into real networks.
The research is aimed at finding ways to ease bottlenecks in networks involving manufacturing, the Internet and traffic, and ways to disrupt networks like tumor blood flow and terrorist supply chains. The findings could also help design better networks. » [OU]

-  That adding a road may increase congestion is not a new result: traffic modellers were aware of this in 1980 if not before. 

- Oxford University, via Technology Research News  and Roland Piquepaille's Technology Trends