Galaxy clusters back general relativity

Physics WorldJon Cartwright

Published in Physics World, 28 Sep 2011

A study of light coming from galaxy clusters has yet again given the thumbs up to the general theory of relativity, Albert Einstein’s famous theory of gravity. Done by physicists in Denmark who measured gravitational redshift, the research appears to rule out some alternative models of gravity – particularly those that deny the existence of dark matter.

Since its publication in 1916, the general theory of relativity has defied all experimental attempts to prove it wrong. In the currently favoured “cosmological constant and cold dark matter” model (?CDM) of cosmology, general relativity has successfully explained many aspects of the universe, including the cosmic-microwave background, gravitational lensing and large-scale structure. […]

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Space Storms to Pose Greater Risk to Flyers and Astronauts

ScienceJon Cartwright

Published in ScienceNOW, 23 Sep 2011

If you thought the outlook for Earth’s climate looked bleak, don’t look up. A new study suggests that space weather—the hail of energetic particles above our atmosphere—is set to worsen in coming decades. The grim forecast suggests that astronauts and frequent flyers will face greater radiation hazards and could rule out a crewed mission to Mars before 2050.

Space weather is a general term for the environmental conditions above Earth’s atmosphere. When space weather is bad, dangerous particles abound. These include protons and ions, known as galactic cosmic rays (GRCs), raining down at near-light speed from space, and similar particles coming in bursts from the sun, called solar energetic particles (SEPs). […]

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Iran Reschedules Espionage Trial for Texas Graduate Student

ScienceJon Cartwright

Published in ScienceInsider, 22 Sep 2011

A doctoral student at the University of Texas (UT), Austin, who has been detained for months in his native Iran on espionage charges will go on trial on 4 October, according to sources close to the student.

Omid Kokabee, who was working toward a Ph.D. in optics, was arrested at a Tehran airport while on vacation in Iran in late January or early February. He had been due to appear in court on 16 July on charges of “illegal earnings” and “communicating with a hostile government,” but officials cancelled his trial at the last minute. […]

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Catalytic polyoxometalate plays hide and seek in MOF

Chemistry WorldJon Cartwright

Published in Chemistry World, 20 Sep 2011

Chemists in the US have managed to enhance a catalyst that can be used to destroy toxic or smelly chemicals in the air. The researchers introduced the catalyst, a polyoxometalate, into the pores of a crystalline metal-organic framework (MOF). The enhanced catalyst could be used to remove airborne contaminants, including industrial chemicals and chemical warfare agents.

Oxidation is one of the best ways of removing airborne contaminants. To make the process easy, scientists are keen to use the oxygen from air in ambient conditions, but few catalysts  manage to do this at a fast enough rate. […]

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‘Tug-of-war’ prompts chemical reaction

Physics WorldJon Cartwright

Published in Physics World, 15 Sep 2011

Researchers in the US have shown that mechanical force can bring about unique chemical reactions. Their experiment involved pulling on molecules in solution using ultrasound and suggests that mechanics could open up other new reaction pathways in chemistry. The discovery could also lead to the development of new technologies such as force-activated sensors or reversible adhesives.

Chemists have several ways to help chemical reactions along, such as adding heat or light. But broad additions of energy such as these can bring about unwanted by-products and waste valuable reactants. In other cases, heat and light simply do not work. […]

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Wonder material not so wonderful

Chemistry WorldJon Cartwright

Published in Chemistry World, 8 Sep 2011

Graphene – a sheet of graphite just one atom thick – is often claimed to be a wonder material, thanks to its superlative mechanical, thermal and electrical properties. But now a group of UK chemists is claiming that, in an electrochemical setting, graphene is not such a wonder material after all. Contrary to the widely held view, the chemists think graphene electrodes are mostly ineffective at transferring electrons, implying that graphene is a poor choice for sensing applications.

Craig Banks and others at Manchester Metropolitan University came to the conclusion after having performed electrochemical experiments with various electrodes. Some of these electrodes were coated in a single graphene layer, some were coated in a graphene multi-layer, and some were left uncovered. Carefully measuring the current passing through the electrodes while changing the applied voltage, Banks’s group discovered that electron transfer in graphene occurs mostly around its edges and at any defects. ‘Given its geometric size, this means that it is largely unreactive,’ says Banks. […]

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CRESST uncovers hint of dark matter

Physics WorldJon Cartwright

Published in Physics World, 8 Sep 2011

Physicists are finally closing in on dark matter, the elusive substance thought to make up most of the matter in the universe. Either that, or they’re being misled by some unknown source of error.

That seemed to be the general idea, after the team behind the CRESST (or the Cryogenic Rare Event Search with Superconducting Thermometers) experiment in Italy announced on Tuesday that it had uncovered signals that could be interpreted as dark matter. These signals join possible traces of dark matter seen by two other direct-detection experiments in recent years, which suggests that evidence is mounting. The trouble is, physicists cannot agree whether the different signals match up or not. […]

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Microscopy reveals why ketchup squirts

Chemistry WorldJon Cartwright

Published in Chemistry World, 2 Sep 2011

Researchers in the US claim to have uncovered the single-particle dynamics that leads to so-called non-Newtonian behaviour, which is exhibited in tomato ketchup, paints and many other liquids. The results of the study, which used a combination of confocal microscopy and force measurements, could help in the development of industrial machinery.

For normal, Newtonian fluids, the viscosity stays the same no matter how much shear stress is applied – water is a common example. But non-Newtonian fluids get thinner or thicker with shear stress. Tomato ketchup, for instance, stays almost solid in the bottom of a plastic bottle until it is squeezed, at which point it squirts out easily: it is ‘shear thinning’. Meanwhile, a mixture of cornstarch and water turns from being fluid-like to near-solid when shear is applied: it is ‘shear thickening’. […]

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Limestone is efficient energy distributor

Chemistry WorldJon Cartwright

Published in Chemistry World, 1 Sep 2011

Limestone batteries could be the key to transporting energy across huge distances, according to chemists in Germany. The idea, which would be used to take solar energy harnessed in the African desert to cities in Europe, might be more efficient than power lines, and could even sequester carbon dioxide emitted by fossil fuel plants.

Researchers exploring greener ways to generate electricity have often looked to the deserts, where enough sunlight falls in six hours to power the world for an entire year. DESERTEC, developed by European scientists, economists and politicians, offers one way to tap this resource. In this concept, power plants would be located in northern Africa that concentrate the sun’s rays onto oil, which would boil water into steam to drive turbines. The electricity generated by these turbines would then be transported thousands of kilometres to cities in Europe via high-voltage, direct-current (HVDC) power lines. […]

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Zigzag nanowire regulates Brownian motion

Physics WorldJon Cartwright

Published in Physics World, 29 Aug 2011

Physicists in the US have created a magnetic trap that can contain microscopic particles despite their Brownian motion. The trap, which is based on a magnetized, zigzag-shaped nanowire, could help researchers to perform chemical or biological experiments in a microfluidic environment, where fluids are geometrically constrained to a submillimetre scale.

Microfluidics is a nascent field that involves shifting picolitre quantities of liquids through micron-width channels. The ability to perform measurements on tiny quantities is useful to many researchers in chemistry, biology and medicine who have to work with materials that are expensive or difficult to synthesize, such as new drugs. Moreover, several microfluidic systems can be incorporated together, allowing the creation of “lab on a chip” platforms for the study of many chemical processes at once. […]

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