Posts Tagged ‘Physics World’

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First weak measurements made on optical polarization states

Published in Physics World, 11 Mar 2013

Physicists in Canada and the US claim to be the first to make a direct measurement of the polarization quantum state of light – a feat that at first glance appears to defy Heisenberg’s uncertainty principle. The technique, which relies on a process known as weak measurement, could help in fundamental studies on quantum mechanics or in the development of quantum computing.

In quantum mechanics, it is normally considered impossible to know everything about a system at one time. Measure the position of a particle accurately, for instance, and the particle’s momentum will suddenly become very ill defined. Physicists call pairs of variables such as position and momentum “conjugate”: they are innately connected, such that the measurement of one essentially destroys information about the other. […]

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Cumbria rejects hosting nuclear-waste repository

Published in Physics World, 1 Mar 2013

The UK government will have to look elsewhere to store its mounting nuclear waste after plans were rejected to assess sites in Cumbria for a £12bn underground nuclear-waste repository. On 30 January seven of the 10 members of Cumbria County Council cabinet voted against a proposal to build an underground laboratory in the region that would have acted as a testbed for a full-scale storage. District councils in west Cumbria are now hoping that the veto – the second in 14 years – will be overruled by the government.

The UK has been generating nuclear waste since its first nuclear power station fired up in 1956. Since then the country has accumulated some 470 000 m3 of waste, which could remain dangerously radioactive for up to a million years. Most of the high- and intermediate-level waste is currently in temporary above-ground storage at the Sellafield nuclear- reprocessing site in west Cumbria. The UK government, however, would like to find a permanent place to store the waste because of fears that the storage at Sellafield is deteriorating. Indeed, last year the UK’s National Audit Office reported that Sellafield’s storage posed an “intolerable risk” to people and the environment. […]

For the rest of this article, please contact Jon Cartwright for a pdf.

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Jail terms rock seismology

Published in Physics World, 1 Dec 2012

Seven earthquake experts have been jailed for making apparently misleading statements before a devastating earthquake hit the Italian city of L’Aquila in 2009. Jon Cartwright reports

The earthquake that struck L’Aquila in the early hours of 6 April 2009 left hundreds dead and the Italian city in ruins. Yet the jailing in October of six scientists and a government official for manslaughter, owing to their apparently misleading statements on the prospect of the catastrophe, could have an equally huge impact on the world of science.

The conviction, which concluded a trial that lasted over a year, has stunned seismologists worldwide. Last month the International Association of Seismology and Physics of the Earth Interior (IASPEI) expressed “deepest concern” about the outcome, which had condemned “some of IASPEI’s most brilliant scientists”. The trial, the association added, had set “a disturbing and unprecedented case” in linking earthquake casualties to “the free expression of scientific opinions”.

But while the scientific community has widely denounced the verdict, some believe those convicted were at least guilty of professional foolishness. “Many of my colleagues have had a knee-jerk reaction – that it’s crazy to bring science into the criminal arena,” says Tom Heaton, a seismologist at the California Institute of Technology and member of the California Earthquake Prediction Evaluation Council. “That may well be, but I saw some of the statements that were made, that everything was fine. And all I can say is, I would attempt not to make similar statements in California.” […]

For the rest of this article, please contact Jon Cartwright for a pdf.

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Physicists claim microwave-imaging ‘breakthrough’

Published in Physics World, 28 Nov 2012

Physicists in China say they have made a breakthrough in thermoacoustic imaging that could enable it to be used in hospitals within five years. The technique, which involves firing microwaves at tissue, had previously been considered too dangerous to use on humans, but the researchers have now employed what they say is a safer, nanosecond microwave source.

Thermoacoustic imaging was invented in the early 1980s. The idea is to expose tissue to a microwave pulse, which travels into the tissue until it is absorbed. Exactly how the pulse is absorbed depends on the type of tissue present. When the pulse is absorbed, it does not heat the tissue significantly because it is very short. The energy instead generates a moving deformation, which is an acoustic wave. The profile of this acoustic wave is detected using an array of transducers, and these data are used to create an image of the tissue through which the microwave pulse has passed. […]

The rest of this article is available here.

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Lapping it up

Published in Physics World, 1 Nov 2012

Cats are slow and elegant, dogs are quick and messy. But is the physics of their drinking all that different? Jon Cartwright reports

Cat and dog lovers, psychologists tell us, are a species apart. Those who like cats are sensitive yet open, while those who like dogs are bolder and more self-disciplined. But if there is one trait common to each, it is an endless fascination with their pets.

Roman Stocker is a case in point. “I love cats,” he says. “I just happened to be watching my cat over breakfast one morning, and then I started wondering: has anyone looked into how a cat laps?” To the average cat owner the question would have ended with idle musing, but to Stocker, an engineer at the Massachusetts Institute of Technology (MIT) in Cambridge, US, it was to spark a minor flurry of interest into our favourite animals’ drinking habits.

In fact, the science of water consumption in the animal kingdom is a little more complex than you might think. Some animals, such as frogs, absorb water through their skin, while some, such as the desert-dwelling kangaroo rat, can extract enough moisture from their food. Unsurprisingly, drinking as a means of water consumption is the most popular, but even it has its variants. Vertebrates with big cheeks – pigs, sheep, horses and so on – can suck in water, whereas mammals with no cheeks, including most carnivores, cannot. Instead, carnivores must use their tongues; they must lap. […]

For the rest of this article, please contact Jon Cartwright for a pdf.

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How the Zebra got his stripes

Published in Physics World, 1 Nov 2012

Biophysicists are offering new clues to this age-old mystery, as Jon Cartwright reports

Rudyard Kipling’s Just So Stories told how various animals came to be. “How the rhinoceros got his skin”, “How the camel got his hump” and “How the whale got his throat” were some of the titles in the famous 1902 collection. The British writer never wrote a story entitled “How the zebra got his stripes” – although if you read his words closely, you’ll discover that, spooked by the leopard, the zebra fled into the forest and adopted stripes as a disguise.

That was just fiction, but a few decades earlier in 1867 the British naturalist Alfred Russel Wallace had put forward a similar idea – that the zebra evolved stripes as camouflage against predators in the tall grass. Wallace’s fellow naturalist Charles Darwin disagreed, pointing out that zebras prefer to hang out in open savannahs, where tall grass is rare. And so the scientific debate began: how did the zebra get his stripes?

Biologists haven’t been short of proposals. There are at least ten, including that stripes afford zebras a means to recognise one another, or that they provide an indication of fitness for potential mates. But none of these hypotheses has seen much supporting evidence, according to biophysicist Gábor Horváth at Eötvös University in Budapest, Hungary, and colleagues. […]

For the rest of this article, please contact Jon Cartwright for a pdf.

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Hitachi closes in on quartz data storage

Published in Physics World, 1 Nov 2012

They say the only safe way to preserve information is to set it in stone – but the next best option may be to set it in quartz. That is, according to researchers at Japanese electronics giant Hitachi, who have developed a “semi-perpetual” quartz-based data storage that could survive for millions of years.

Hitachi has been working on permanent methods of data storage for the last five years, driven by the concern that paper, CDs, hard disks and other storage media will not stand long-term physical disturbances and may not be easily readable with future technology. In 2009 Hitachi scientists found that they could store data optically in 3D in quartz, and showed that the medium had the potential to be highly durable and straightforward to read. […]

For the rest of this article, please contact Jon Cartwright for a pdf.

 

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Unexpected ‘ridge’ seen in CMS collision data again

Published in Physics World, 31 Oct 2012

The first data from proton–lead collisions at the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN include a “ridge” structure in correlations between newly generated particles. According to theorists in the US, the ridge may represent a new form of matter known as a “colour glass condensate”.

This is not the first time such correlations have been seen in collision remnants – in 2005, physicists working on the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory in New York found that the particles generated in collisions of gold nuclei had a tendency to spread transversely from the beam at very small relative angles, close to zero. A similar correlation was seen in 2010 at CMS in proton–proton collisions and then later that year in lead–lead collisions. (See image below, parts a and b.) […]

The rest of this article is available here.

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Moses Chan backtracks on search for supersolids

Published in Physics World, 16 Oct 2012

In 2004 Moses Chan and his graduate student Eun-Seong Kim thought that they had made one of the most exciting condensed-matter discoveries of the new century. It was the supersolid – a mysterious substance that could float through ordinary solids, like a ghost through walls. Now the Penn State University physicist has published a paper arguing that his initial interpretation was wrong – a mundane materials effect rather than supersolidity was the cause of their anomalous experimental results. “It would have been nice if the supersolid [interpretation] was correct,” he says, “but Mother Nature had her own way.”

The paper comes after Chan and others struggled for eight years to produce conclusive evidence for the effect. Although the experiments have been a disappointment, they were not done on a whim. The supersolid concept has a long history and theoretical physicists – including Nobel laureate Philip Anderson – have developed compelling arguments for its existence. […]

The rest of this story is available here.

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A phased approach

Published in Physics World, 1 Oct 2012

Now that the Square Kilometre Array will be split between sites in Australia and southern Africa, Jon Cartwright reports that some technological trickery will be needed to make the world’s biggest telescope work

While the discovery of the Higgs boson at CERN’s Large Hadron Collider (LHC) may have been taking all the headlines of late, there is some truth in claiming that the machine is already the “big science” of old. In just four years’ time, construction is slated to begin on a new project that will dwarf the Franco–Swiss particle accelerator by comparison. That project is the Square Kilometre Array (SKA) – the world’s biggest and most sensitive radio telescope.

Physically, SKA will be larger than the LHC, ultimately spreading over thousands of kilometres in Africa and Australasia. It will be made up of thousands of radio dishes and millions of radio antennas. To sort through the troves of data, it will need the fastest supercomputer on the planet. As Phil Diamond, who was appointed as the first director-general of SKA in September, points out: “It will be the largest science facility on Earth.” […]

For the rest of this article, please contact Jon Cartwright for a pdf.

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