February 24, 2012 9:51 pm

Bat colony faces cave new world

Zooarchaeology, which uses animal bones to study the history of biological diversity, reveals that bat populations have dwindled

The “changing of the guard” at the Great Cave of Niah in Malaysian Borneo is a wildlife wonder. Every evening at dusk two great black clouds intermingle, as up to half a million bats fly out for their nightly forage in the forest, while a similar number of swiftlets return to roost. At dawn the traffic is reversed.

The diurnal mass exchange of bats and birds has taken place for at least 50,000 years – and previously on an even larger scale than today – according to evidence collected by practitioners of zooarchaeology, an emerging scientific field that uses ancient animal bones to study the history of biological diversity.

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Chris Stimpson, a zooarchaeologist at Cambridge University, has studied 12,000 bat bones and 1,400 bird bones excavated from the Great Cave.

The results show that, in the broadest terms, the local ecology is the same as it was 50,000 years ago. The cave has been surrounded by closed-canopy rainforest throughout the period, Stimpson says, “in contrast to studies that have suggested the periodic replacement of lowland tropical forest by savannah-like habitats.” But more detailed examination of the bones shows significant changes, some of them brought about by humans, who started visiting the Great Cave more than 45,000 years ago.

People were eating cave-dwelling fruit bats and swiftlets about 40,000 years ago and hunting hornbills in the local forests 19,000 years ago, Stimpson discovered. He identified bones from four species of hornbill though only one lives in that part of Borneo today.

Give me some space

Nasa received 6,300 applicants to become astronauts during its latest recruitment period. A dozen will become Nasa’s 21st astronaut class, after a rigorous selection process.

Among the bat species, a colony of wrinkle-lipped bats, numbering three million at its peak, had disappeared by the 17th century. “This may be because the colony was disturbed when people began to visit the cave to collect the nests of cave swiftlets, which were much prized as the main ingredient of bird’s nest soup,” Stimpson says.

Although nest collecting and other human intrusion into the cave continue to this day, the biggest threat to its wildlife comes from destruction of the surrounding forest, whose area has been reduced by two-thirds over the past 40 years. As a result, numbers of cave bats and birds are declining rapidly, Stimpson says.

He is now working on a global project to assess changes over the past 50,000 years in the world’s three main regions of tropical forest – and in particular to examine the human impact on biodiversity.

“Essentially, what we regard as ‘pristine’ ecosystems are in fact ‘degraded’ ecosystems,” Stimpson says. “Zooarchaeology can help those involved in conservation efforts to understand how ecologically representative remnant stands of forest are.”

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Rare metal offers clues to cancer detection

A by-product of copper mining, usually used in lead-free petrol, may hold the key to early detection – and possibly even treatment – of cancer.

In laboratory tests at the Universidad Andrés Bello, Chile, scientists have discovered that a compound of the rare metal rhenium can highlight and destroy malignant cells, sparking hopes that a cancer detection kit could be developed within four years.

The team, led by Ramiro Arratia-Pérez, found that rhenium, combined with selenium and iodine, “stuck to cancerous cells and destroyed them without touching healthy cells”. The diseased cells also glowed red when in contact with the rhenium compound.

“It takes about 24 to 48 hours to detect [the cancerous cells]. A biopsy can take six to seven weeks. That’s why our idea is to develop an early detection kit. This is important because early detection often saves lives,” Arratia-Pérez says.

He reckoned such kits could take “four years at the most” to develop. Whether rhenium could be used to treat cancer, however, could take 10 to 20 years to establish.

Chile, which is already developing uses for the anti-bacterial properties of its vast copper riches, is the world’s biggest producer of the red metal and the third-biggest producer of molybdenum, the copper by-product from which rhenium is extracted.

The team tested the rhenium compound on skin cancer and hepatic cancer cells, and is currently testing different compounds on salmonella bacteria, with promising, although very preliminary, results. Whether rhenium used alone would be as effective has yet to be tested, Arratia-Pérez says.

The scientists used rhenium clusters supplied by the University of Arizona but Arratia-Pérez says the compound was initially discovered and could be produced in Chile. The study is published in the New Journal of Chemistry. Jude Webber

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And the weather? Rain and a solar storm

A computer technique called ensemble forecasting, which meteorologists use to predict weather, is being adapted to analyse activity on the sun that could have a damaging impact on Earth.

Nasa says ensemble forecasting will improve its ability to warn of an impending solar storm that could disrupt satellites, telecommunications, navigation and electrical power generation.

The chance of a mega-eruption of electrically charged particles from the sun’s surface, powerful enough to cause chaos when it reaches Earth, is increasing as the 11-year cycle of solar activity rises toward an expected maximum in 2013.

The ensemble technique runs a supercomputer model up to 100 times, each with slightly different starting conditions, so that forecasters can calculate the most likely outcomes.“Space weather alerts are available now, but we want to make them better,” says Michael Hesse, head of Nasa’s Space Weather Laboratory at Goddard Space Flight Centre.

The key event in space weather forecasting is a coronal mass ejection (CME) from the sun in Earth’s direction. A CME is a gigantic bubble of charged particles that can carry up to 10bn tonnes of matter at several million miles per hour through interplanetary space.

Predicting a solar storm’s terrestrial impact requires forecasting the CME, its travel time and the way it will interact with Earth’s atmosphere and magnetic field.

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Hard drives with a lot more byte

A team of European physicists has found a new way to record data on magnetic storage systems, such as computer hard drives, that is hundreds of times faster than current technology. The trick is to record information using only heat, in contrast to existing devices which use magnetic fields. The heat is delivered through ultra-short bursts of laser energy, each lasting less than one trillionth of a second.

“This revolutionary method allows the recording of terabytes (thousands of gigabytes) of information per second, hundreds of times faster than present hard drive technology,” says Thomas Ostler of York University, lead author of the research which is published in the journal Nature Communications. “As there is no need for a magnetic field, there is also less energy consumption.”

Researchers from Spain, Switzerland, Ukraine, Russia, Japan and the Netherlands also took part in the project, which was funded by their national research agencies and the European Union.

“For centuries it has been believed that heat can only destroy the magnetic order,” says Alexey Kimel of Radboud University Nijmegen. “Now we have successfully demonstrated that it can, in fact, be a sufficient stimulus for recording information on a magnetic medium.”

Modern technology records each bit of information by applying an external magnetic field to invert the north and south poles of tiny magnets within the recording medium. This new research shows that the poles can be inverted by a heat pulse.

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