Tuesday, March 14, 2006

Latest PhysicsWeb Summaries


Towards entangled-photon LEDs (Mar 6) http://physicsweb.org/article/news/10/3/4

Scientists in the UK have been able to generate pairs of entangled photons from a nanoscale crystal of semiconductor known as a "quantum dot" far more efficiently than was possible before. The breakthrough was made by Andrew Shields at Toshiba and colleagues at the University of
Cambridge, who produced entangled photons with an efficiency of 70% -- compared to a previous best figure of 49%. The improved performance approaches that required for useful applications, which means that devices emitting entangled light could one day be as common as lasers and light-emitting diodes (New J. Physics 8 29).

Antiproton co-discoverer dies (Mar 7) http://physicsweb.org/article/news/10/3/5

Owen Chamberlain, who co-discovered the antiproton with Emilio Segrè in 1955, has died at the age of 85. Chamberlain and Segrè shared the 1959 Nobel Prize for Physics for the discovery of the particle, which has the same mass as the proton, but opposite charge. Postulated by Paul Dirac in 1933, the antiproton is now routinely used in particle-physics experiments.

The oldest explosion in the universe (Mar 8) http://physicsweb.org/article/news/10/3/6

Astronomers have detected the most distant -- and therefore oldest -- gamma-ray burst ever. The burst, called GRB 050904, was observed last September and is thought to have come from an explosion that happened around 12.8 billion years ago, when the universe was just 7% of its
current age. The explosion released an intense flash of gamma rays that has been measured by three independent teams of astronomers from the US, Italy and Japan. The results -- reported in three papers in this week's Nature -- could help shed more light on the dynamics of the early

How to calculate hardness (Mar 9) http://physicsweb.org/article/news/10/3/7

When it comes to measuring the "hardness" of a material, most tests are distinctly low-tech and basically involve pressing a diamond tip into the surface and measuring the size of the dent produced. Now, however, physicists in the Czech Republic have developed a new way to predict the hardness of materials without going anywhere near a lab. The results, obtained from first-principles calculations alone, agree well with experimental data and could help scientists make harder materials (Phys. Rev. Lett. 96 085501).

Tiny motor turns giant rods (Mar 10) http://physicsweb.org/article/news/10/3/9

Researchers in the Netherlands have made a light-driven nano-scale motor that can rotate microscale objects that are 10,000 times bigger than itself. The motor consists of a molecule embedded in a liquid-crystalline film with a glass rod placed on top. As the molecule changes shape, it alters the structure of the film, which in turn makes the rod move (Nature 440 163).

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