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11 May 2013 | NewScientist | 17 Silver solution to clean, cheap water SOMETIMES the solution to an enormous problem is tiny. Silver nanoparticles may be the key to supplying clean, affordable drinking water worldwide. Thalappil Pradeep at the Indian Institute of Technology in Chennai and colleagues have developed a filter based on an aluminium composite, embedded with silver nanoparticles. As water flows through the filter, the nanoparticles are oxidised and release ions, which kill viruses and bacteria, and neutralise toxic chemicals such as lead and arsenic. Some nanoparticles leach into the water but at concentrations that pose no threat to health. Pradeep describes the process of making the filter as “water positive”: 1 litre of water spent on making nanoparticles gives 500 litres of clean water. In tests, a 50-gram composite filtered 1500 litres of water without needing reactivation, so they estimate that a 120g-filter that costs just $2 would provide safe drinking water for a family of five for one year (PNAS, DOI: 10.1073/pnas.1220222110). The filters are undergoing field trials in India with the aim of preventing waterborne diseases. Cosmic winds blew up galactic bubbles SUPERSONIC winds stopped in their tracks – that’s what dunnit. This is the latest explanation for the giant bubbles that stick out above and below our galaxy. In 2010, NASA’s FERMI gamma- ray telescope unveiled a stunning image of two bubbles – each 25,000 light years high – that emerge from the centre of the Milky Way, on either side of the galactic plane. One suggestion i s that cosmic winds, made of gases and particles produced during intense episodes of star formation, blow out these Fermi bubbles, but the exact mechanism is unclear. Now, Brian Lacki of the Institute for Advanced Study in Princeton, New Jersey, says the bubbles’ defined borders are the result of the cosmic winds coming to an abrupt stop. These winds move at well over 1000 kilometres per second. Lacki suggests that they come to a sudden halt when their pressure equals the pressure of the gas around them. The abrupt transition from supersonic to subsonic speeds creates a DO YOU find it easy to recognise a face? Some people find it impossible – they have prosopagnosia, or face blindness. Now the first treatment could be on the cards following the identification of specific brain areas that allow us to recognise our friends. Zaira Cattaneo at the University of Milano-Bicocca in Italy and colleagues used transcranial magnetic stimulation to block areas of the brain while 16 volunteers without the condition identified whether two images of a face were the same or different. “When we interfered with the left prefrontal cortex we affected featural processing,” says Cattaneo. Interfering with the right prefrontal cortex, meanwhile, impaired the ability to distinguish the relationship between features, such as the distance between the nose and the eyes (NeuroImage, doi.org/mff). This is the first time that a causal relationship has been shown between these areas and different aspects of facial processing. Now the team is trying to activate these areas of the brain. “The aim is to enhance face recognition abilities by directly modulating excitability in the prefrontal cortices,” says Cattaneo. I’ll never forget whatsherface ELENA KULIKOVA/GETTY termination shock wave, giving the Fermi bubbles their sharply defined boundaries (arxiv.org/ abs/1304.6137). The theory could solve another mystery: the source of the highest-energy cosmic rays that hit Earth. Lacki says that charged particles, accelerated by the shock wave, get trapped by magnetic fields in the bubble. They go around and around the fields until they become so energetic that they are ejected from the bubbles. Some arrive on Earth as high-energy cosmic rays. Looks cute, but has strange habits THEY may look adorable, but lemurs are weird. The fat-tailed dwarf lemurs of western Madagascar caused a stir when they were found to hibernate. It looked as if they were the only primates to do so, but now it turns out that two more lemur species do too – only in a completely different way. Unlike other hibernators, fat-tailed lemurs do not drastically reduce their body temperature as they slumber. Instead, they allow it to fluctuate by as much as 20 °C, matching the temperature of their tree-hole nest. Now Anne Yoder of Duke University in Durham, North Carolina, and colleagues have discovered that the little-known Crossley’s and Sibree’s dwarf lemurs hibernate in underground burrows. But these lemurs, living in eastern Madagascar, keep their body temperature constant (Scientific Reports, doi.org/mfk). Yoder says that was unexpected. “Rather than being typical tropical hibernators, it’s the fat-tailed dwarf lemurs that are the oddballs. The eastern dwarf lemurs show physiological patterns much more similar to temperate hibernators.” The eastern lemurs are pretty strange in their own right. “They’re primates who spend several months of the year underground. That’s pretty crazy, I think,” says Yoder. GEOFF TRINDER/ARDEA.COM For new stories every day, visit newscientist.com/news
