PAMELA reasserts positron excess

Physics WorldJon Cartwright

Published in Physics World, 23 Aug 2013

The European collaboration PAMELA has published new data concerning a mysterious excess of positrons that permeate outer space. The data, which describe the collaboration’s first detection of absolute rather than relative positron numbers, could help refine theoretical models – including those that explain the excess as a footprint of dark matter.

PAMELA (Payload for Antimatter/Matter Exploration and Light-nuclei Astrophysics) is a satellite that was launched in 2006 by institutions in Germany, Italy, Russia and Sweden to examine the nature of antiparticles in cosmic rays. The first results, published in 2008, revealed a surprising feature: a steady rise in the ratio of positrons to electrons above an energy of about 10 GeV. This is contrary to basic theoretical calculations, which predict that the positron fraction should have decreased. […]

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Neutron study aims to improve HIV drugs

Physics WorldJon Cartwright

Published in Physics World, 21 Aug 2013

A neutron study of a common component of HIV drugs has revealed that the component is not as good at bonding as had been thought. The study, performed by an international group of researchers, highlights aspects of the drug component that could be improved to make it better at mitigating the effects of HIV.

HIV is a virus that replicates through use of a person’s immune system. HIV implants genetic information into the immune system’s T-cells, which then produce copies of the virus until they die. Once enough T-cells have died from churning out HIV, the person is unable to ward off other infections and they are said to be suffering from AIDS. […]

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US firm seeks funding for novel ‘slingatron’ prototype

Physics WorldJon Cartwright

Published in Physics World, 20 Aug 2013

A US company has launched a fund-raising campaign to build a prototype “slingatron” that could be used to propel a 100 g object to a speed of one kilometre per second. HyperV Technologies, based in Virginia in the US, is now attempting to raise $250,000 via the crowd-funding website Kickstarter to build the device, which it says will pave the way for a full scaled-up version that can launch much heavier cargo into space.

A slingatron is based upon an old-fashioned weapon known as a “sling” – it involves a heavy mass on the end of a rope, which a person whirls around their head with increasing frequency before letting go, sending the object flying. However, with the slingatron the rope is replaced by a spiral track spinning at a constant frequency. When an object is released from the middle, it follows the track round with an increasing radius, getting faster and faster as it does so. The larger the final radius – and the greater the spin frequency – the faster the object travels when it leaves. […]

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How does carbon fertilization affect crop yield?

Energy & EnvironmentJon Cartwright

Published in ERW, 16 Aug 2013

The carbon fertilization effect will cause changes in crop yields at least half as large as those due to alterations in climate, a US-based simulation has shown. Although the simulation is not comprehensive enough to provide definite estimates of the regions that will be most affected by the carbon fertilization effect, it does suggest that vegetation models ought to take the phenomenon into account on a regional level.

The carbon fertilization effect (CFE) is in principle simple: the larger amount of carbon dioxide in the atmosphere that has resulted from rising anthropogenic emissions should help the growth of plants, which use carbon dioxide during photosynthesis. The effect ought to increase crop yields – and that is some good news for farmers, amid the overwhelmingly gloomy forecasts for other aspects of climate change. […]

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Heatwaves will become more common

Chemistry WorldJon Cartwright

Published in ERW, 15 Aug 2013

Researchers in Germany and Spain predict that the world will suffer more extreme heat events thanks to climate change, regardless of the implementation of strong mitigation policies. The study suggests that societies must continue to adapt to heatwaves to prevent heat-related deaths, forest fires or harvest losses.

Scientists now widely accept that greenhouse-gas emissions have led to a rising number of heatwaves. Recent examples include the Russian heatwave of 2010, the US heatwave of 2012 and a European heatwave this year. Abnormally high temperatures can be a devastating repercussion of climate change: the European heatwave of 2003, for instance, is estimated to have caused some 70,000 deaths. […]

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A Doppler Effect for Distant Planets

ScienceJon Cartwright

Published in Science, 1 Aug 2013

An ambulance whizzes by, and suddenly its siren drops in pitch. We are all familiar with the Doppler effect, even if we don’t know it by name. Now, scientists have found an alternative version of the phenomenon, for when sound, or light, scatters off a rotating object. The discovery could enable astronomers to measure a distant planet’s rotation, or even improve the performance of wind turbines.

Here’s how the Doppler effect works: When a noisy object is moving toward you, its sound waves bunch up, producing a higher frequency, or pitch. Conversely, as soon as the object is moving away from you, the sound waves stretch out, and the pitch lowers. The faster the object, the greater the pitch change. […]

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Harnessing the force from nothing

Physics WorldJon Cartwright

Published in Physics World, 1 Aug 2013

A vacuum is abuzz with quantum fluctuations of particles that constantly pop into and out of existence. The particles are deemed “virtual” because they can only exist by borrowing energy from the vacuum for a fleeting period dictated by the uncertainty principle, but their effects are very real. In 1948 the Dutch physicist Hendrik Casimir predicted that the jostling of virtual particles would generate an imbalanced force on two parallel mirrors held in a vacuum. Since a virtual photon can appear only in regions that are large enough to contain its wavelength, the density of photons between the mirrors will be less than that than on the outside. As a result, Casimir showed, the mirrors will be drawn closer together.

It took 50 years to observe this subtle effect. Since then researchers have begun to recognize it as a potential nuisance for microelectromechanical systems (MEMS), such as pressure sensors and accelerometers. As manufacturing scales shrink from hundreds of microns down to the nanoscale, there is a concern that the Casimir force will generate friction between MEMS components. Yet physicists have also started to wonder whether this force from nothing could be turned into a force for good. “There is no reason why not,” says George Palasantzas at the University of Groningen in the Netherlands. […]

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Maxwell’s demon gets scribbling

Chemistry WorldJon Cartwright

Published in Chemistry World, 30 Jul 2013

Maxwell’s demon is a famous thought experiment designed to show how, in an isolated system, disorder or ‘entropy’ can decrease in apparent violation of the second law of thermodynamics. Now researchers in the US have put a new twist on the idea, claiming to show theoretically how the second law can remain intact if the demon is allowed to scribble down random information.

In the original thought experiment, proposed by the UK physicist James Clerk Maxwell in 1867, a demon sits between two isolated chambers. By carefully timing the opening of a hatch between the chambers, the demon can let only slower, ‘cold’ particles through to one side, and only faster, ‘hot’ particles through to the other. Without expending energy then, the demon makes the system more ordered, lowering entropy and apparently violating the second law. […]

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B-mode polarization spotted in cosmic microwave background

Physics WorldJon Cartwright

Published in Physics World, 25 Jul 2013

The South Pole Telescope (SPT) has made the first detection of a subtle twist in light from the cosmic microwave background (CMB), known as B-mode polarization. The signal, the existence of which has been long predicted, paves the way for a definitive test of inflation – a key theory in the Big Bang model of the universe.

“While this effect was fully expected, its detection is a milestone event in the use of the CMB to probe our universe,” says Chuck Bennett, a leading expert in CMB observation based at Johns Hopkins University in Maryland, US, who was not involved with the study. “It is solid research and I believe the result.” […]

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How to survive earthquakes and noisy neighbours

Physics WorldJon Cartwright

Published in Physics World, 25 Jul 2013

The past few years has seen a steady stream of proposals for cloaking objects, whether it’s from light, heat, water waves, magnetic fields or even time. Now, physicist Sang-Hoon Kim at the Mokpo National Maritime University in Korea is adding to this list, first off with a cloak that could protect buildings from earthquakes.

An earthquake cloak has been proposed before using – as is common in invisibility cloaks – elaborately structured “metamaterials” to guide seismic waves safely around a building. However, Kim, together with Mukunda Das at the Australian National University in Canberra, has put forward a different approach: a metamaterial barrier that dissipates seismic energy as sound and heat. The idea is that many buildings could hide in the “shadow zone” of the barrier. This could be a boon for city planners, who would not have to make cloaks for individual buildings. Kim and Das’s paper has been accepted for publication in Modern Physics Letters B and is available as a preprint entitled “Artificial seismic shadow zone by acoustic metamaterials“. […]

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