10 March 2012 | NewScientist | 19

A SOUPED-UP metal detector could one day tell whether buried objects are unexploded bombs or just harmless junk.

The world is riddled with unexploded bombs left behind following munitions tests and warfare. Governments want to dig them up so the land they are in can be used again. The problem is, “it’s difficult to distinguish the unexploded bombs from man-

made clutter or junk”, says Eugene Lavely of BAE Systems in Burlington, Massachusetts.

Lavely and his colleagues have developed a technique, called time-domain electromagnetic induction, to tell risks from rubbish. Like “a fancy metal detector”, it uses a coil to send an electromagnetic pulse 15 metres into the ground, Lavely reported at the American Physical Society

Cancer chimeras complicate therapy

NO WONDER cancer is such a challenge to treat: a genetic analysis of advanced kidney cancer has shown that mutations can vary across the same tumour. This finding dashes hopes of tailoring treatment for an individual based on the mutations in a single biopsy.

Charles Swanton at Cancer Research UK in London and colleagues analysed kidney tumours from four people and found that around two-thirds of genetic mutations in the same tumour differed from one biopsy to the next.

The prognosis for each person was sometimes good and at other times bad depending on which part of the tumour was sampled.

It could explain why drugs that target specific mutations aren’t always successful, says Swanton, whose results appear this week in The New England Journal of Medicine, vol 366, p 883.

A good scratching tool is a definite bear necessity

AN ITCH can be maddening, so perhaps it’s no surprise this brown bear reached for a tool to help hit the spot. It was seen scratching its skin with rocks - making it the first bear definitively known to use a tool.

In July 2011, Volker Deecke of the University of Cumbria, UK, was on holiday in Alaska’s Glacier Bay national park when he spotted a brown bear in shallow water. The animal picked up a small, barnacle-covered rock, turned it around a few times then rubbed the rock over its face for a minute. It repeated this with another rock (Animal Cognition, DOI: 10.1007/s10071-012-0475-0).

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Listening for the hum of live bombs meeting in Boston last week. The pulse makes the things it hits reverberate like a struck drum, and the team have identified the reverberation signal of a torpedo-shaped metal object with a hollow core – where explosives may lie.

The researchers are now refining the method so that it is accurate enough to meet US standards, which require 99.9 per cent confidence that all bombs have been dug up before land can be used.

The bear was moulting, and had big patches of fur hanging off its skin. Moulting bears often scratch themselves with their claws, or rub their bodies against trees or rocks. “The barnacles may have given that exfoliating feeling,” Deecke says.

Brown bears may not be the only bears to use tools, says Euclid Smith of Emory University in Atlanta, Georgia. A 1972 report suggested that a polar bear might have clubbed a seal over the head with a chunk of ice. But the researchers did not see the event, and the behaviour has never been seen since.

Deecke points out that bears have large brains for their body size, suggesting they are clever, though too few tests of bear cognition have so far been carried out to say for sure.

WITH no limbs, how do snakes climb trees and slopes? It seems they can control each scale individually to grip surfaces.

Biologists have known for a while that the venetian-blind-like geometry of snakes’ scales help stop them sliding backwards.

Now Hamid Marvi of the Georgia Institute of Technology in Atlanta and colleagues have found that snakes are much less prone to slipping down a slope when they are awake than when sedated, suggesting they can actively improve their grip. Indeed, videos show that the snakes can control the angle of each scale to stick as firmly as possible to a surface. The work was presented at the American Physical Society meeting last week in Boston.

Snakes on a sloping plane

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