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Researchers have developed a new immunization strategy that requires up to 50% fewer immunization doses compared with the current most efficient strategy. The new strategy could be used to prevent the spread of human epidemics and computer viruses, and it applies to a wide variety of networks. The new method, called the “equal graph partitioning” (EGP) immunization strategy, is being proposed by a team of scientists from Boston University, Bar-Ilan University in Ramat-Gan, Israel, and Stockholm University. Their study is published in a recent issue of Physical Review Letters. In real life, the number of immunization doses is often limited or very expensive, so a strategy that requires the fewest doses could be very useful. As the researchers explain, the question of how to immunize a network with a minimum number of doses is mathematically equivalent to asking how to fragment a network with a minimum number of node removals. In this sense, the new EGP strategy works differently than t...

In 2006, Andrew Jordan, professor of physics and astronomy at the University of Rochester, together with Alexander Korotkov at the University of California, Riverside, spelled out how to exploit a quantum quirk to accomplish a feat long thought impossible, and this week a research team at the University of California at Santa Barbara has tested the

The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes". Light is composed of photons so we could ask if the photon has mass. The answer is then definitely "no": The photon is a massless particle. According to theory it has energy and momentum but no mass and this is confirmed by experiment to within strict limits. Even before it was known that light is composed of photons it was known that light carries momentum and will exert a pressure on a surface. This is not evidence that it has mass since momentum can exist without mass. [ For details see the Physics FAQ article What is the mass of the photon? ]. Sometimes people like to say that the photon does have mass because a photon has energy E = hf where h is Planck's constant and f is the frequency of the photon. Energy, they say, is equivalent to mass according to Einstein's famous formula E = m...

The early days of 3D acceleration were a confusing time. Rather than the simpler world of today, back then we had PowerVR, Glide, OpenGL, and a number of less-popular APIs. Microsoft finally grabbed the reins and stepped in with Direct3D/DirectX, fixing the convoluted mess. OpenGL and Direct3D are now the standard, with Direct3D enjoying a much wider adoption. These early days of physics acceleration are entirely reminiscent of the beginnings of 3D acceleration, and Microsoft is once again stepping in to sort out the mess that is starting to develop. We, of course, have AGEIA and their PhysX API, we have NVIDIA/Havok in bed with each other, and even ATI is brewing something up. It's getting ugly before it even starts. The consumers don't want another format/API war, and Microsoft knows that. There are no concrete details as of yet, but we can probably expect Microsoft's physics SDK to become a part of DirectX 10 late in the game, though most likely it will be a standard fea...

Physicists have made water run uphill quite literally under its own steam. The droplets propel themselves over metal sheets scored with a carefully designed array of grooves. The US scientists did the experiment to demonstrate how the random motion of water molecules in hot steam could be channelled into a directed force. But the team, writing in Physical Review Letters, believes the effect may be useful in driving coolants through overheating computer microchips. The physics at work here has been witnessed by all of us in the kitchen. Leave an empty pan on the stove for too long, and water, when you drip it over the scorching pan bottom, will hover over the surface on a bed of steam. The effect was described in the 18th Century by a German scientist Johann Gottlob Leidenfrost. What happens is that the heat is so intense, it boils the underside of the water droplet without any physical contact with the pan. "We were interested in whether it would be possible to use this phenomeno...

A Silicon Valley start-up hopes to introduce a lot of bounce, rattle and roll into the video game industry with a new microchip that makes virtual worlds behave as realistically as they look. For years, video games have been getting prettier thanks to increasingly sophisticated graphics processors. But crates that don't budge, planks that don't splinter and windows that don't break are a constant complaint of gamers who crave more than just skin-deep realism. Ageia Technologies Inc. wants to change that with its new PhysX processor, which simulates the physical properties of everything from smoke to rocks. "What we are offering to the game industry is the ability to make physics and interactivity reach the same level of importance that graphics has," said Manju Hegde, AgeHia's chief executive. "Physics makes games feel real the way graphics makes games look real," Hegde told Reuters in a recent interview. Ageia faces a number of obstacles, however, ...

Researchers at the University of Cambridge have discovered a material that gives a whole new complexion to the term 'fridge magnet'. When this alloy is placed in a magnetic field, it gets colder. Karl Sandeman and his co-workers think that their material - a blend of cobalt, manganese, silicon and germanium - could help to usher in a new type of refrigerator that is up to 40 percent more energy-efficient than conventional models. Given how much energy is consumed by domestic and industrial refrigeration, that could have a significant environmental payoff. Sandeman will describe the work at the Institute of Physics Condensed Matter and Materials Physics conference at the University of Exeter, on Friday 21 April. The 'magnetic fridge' envisaged by the Cambridge team would use a phenomenon called the magnetocaloric effect (MCE), whereby a magnetic field causes certain materials to get warmer (a positive MCE) or cooler (a negative MCE). Although the effect was discovered...

It seems that nothing stays the same: not even the 'constants' of physics. An experiment suggests that the mass of ratio of proton compared to an electron has decreased over the past 12 billion years, for no apparent reason. read more | digg story