Child hallucinations not just a bad dream

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    BLACK holes can be secretive about their past, but now there may be an easy way to tell if a monster black hole was once a pair that got cosy and fused together.

    Computer simulations suggest that when two black holes spiral towards each other on a collision course , much of the gas and dust in the spinning accretion disc surrounding each of them is ripped away by the gravity of the other. Some of this material fuses into a larger third disc that surrounds both.

    According to a model created by Kimitake Hayasaki at Kyoto University in Japan and colleagues, this third disc should periodically return material to the depleted original accretion discs, which survive for a time. Hayasakis model , details of which will appear in The Astrophysical Journal, shows this shuffling of gas and dust should create spikes in the ultraviolet emissions from the system, which existing spaceborne telescopes could spot.

    By contrast, gravity waves, the only other telltale signalfrom black hole mergers, are notoriously difficult to detect and have yet to be observed.

    Secrets out on black hole trysts

    FUNGI found in peoples back gardens could help clean up the depleted uranium dust left on battlefields in Iraq and the Balkans. At present, the only way to decontaminate sites is to collect and dispose of munitions fragments by hand, which fails to deal with uranium dust.

    Depleted uranium has twice the density of lead and is added to bullets and shells to give them extra momentum to penetrate and destroy targets. These weapons spread the uranium across the battlefield, where it can persist

    in the environment for decades. Residual uranium-235 in the material can damage kidneys, and has been linked to nerve damage and lung cancer.

    Now a team led by Geoffrey Gadd at the University of Dundee, UK, says that several common types of fungi can grow on the uranium and chemically assimilate it.

    The team grew these fungi in the lab using a medium containing fragments of depleted uranium. They found that parts of the fungi in contact with the

    metal became coated with a yellow substance (Current Biology, vol 18, p R375).

    This, it turned out, comprised several forms of uranyl phosphate, a substance which Gadd says is capable of long-term uranium retention in that it does not break down naturally . This will help prevent uptake by plants, animals and microbes, he says.

    Whats more, uranyl phosphate is insoluble in water, which Gadd says might prevent the spent uranium from leaching out into the soil.

    Uranium-eating fungi could clean up battlefields

    ITS not just humans who succumb to peer pressure rats do too. Brown rats have a tendency to disregard personal experiences and copy the behaviour of their peers. Whats more, the urge to conform appears to be so strong that they will choose to eat food they know to be unpalatable when interacting with other rats that have done the same.

    Bennett Galef and Elaine Whiskin at McMaster University in Hamilton, Ontaria, Canada, put rats off cinnamon-flavoured food pellets by injecting the animals with a nausea-inducing chemical after their meals. Given a choice, these trained animals preferred to eat cocoa-flavoured food pellets.

    However, when those rats then spent time with demonstrator rats that had just eaten and smelt of cinnamon, they regained their liking for it (Animal Behaviour, DOI: 10.1016/j.anbehav.2007.11.012).

    Until now, humans and chimps were the only other animals known to conform in this way. Andrew Whiten from the University of St Andrews, UK, says that the discovery emphasises the importance of social learning in the animal kingdom.

    The big question now, he says, is why they conform. Its not immediately obvious why a rat or chimp or human would cast aside what it knows from its own experience and adopt an inferior course of action just because everybody else is doing it.

    Rats fall victim to peer pressure

    HALLUCINATIONS caused by sedatives and opiates given to children in intensive care are not just a bad dream. They may cause more stress than real memories.

    When Gillian Colville and colleaguesat St Georges Hospital in London screened 102 children in the intensive care unit (ICU) at Great Ormond Street Hospital for Children in London, they found that nearly a third suffered from post-traumatic stress disorder.

    Being able to remember facts aboutwhat had happened to them didnt make PTSD more likely, but crucially, children who experienced delusions

    while in the ICU tended to have higher PTSD scores than those that didnt (American Journal of Respiratory and Critical Care Medicine, vol 177, p 976). Children who received medication for longer were also more likely to have delusions, which included feeling bugs crawling on them and seeing people who looked like their parents.

    Sedatives and opiates relieve pain and reduce anxiety, enabling children to tolerate lifesaving procedures like having a breathing tube inserted, so they cant be avoided. But if medical staff understand this is a risk, they might take measures that could help, says Colville, such as having drug holidays in which doses are skipped, or weaning them off the drugs more slowly.

    Realitys easier to take than sedation

    18 | NewScientist | 10 May 2008

    In brief