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Why walking on beach sand can be an electric experience
In brief–
KEVIN SPREEK MEESTER/JUPITER
IT’S not only the breeze that whips sand in your face on a windy beach, electric fields also play their part. Sand grains blown by the wind will often bounce along over a surface. This process – known as saltation – erodes rocks and is one of the ways that grains are carried along, creating ripples and sand dunes. Researchers used to think that wind and gravity alone influenced saltation, but their models failed to explain what happened to the sand in real life, for example, why it often clings to a surface despite high winds. Now Jasper Kok and Nilton Renno of the University of Michigan in Ann Arbor suggest that electrical fields are also involved. In the past, surprisingly strong fields have been measured pointing upwards in clouds of sand. Kok and Renno wondered whether the grains might be picking up some electrons when bouncing off the ground so that they become negatively charged. This is known to occur in the processing of industrial powders. Using a computer model, they found that electrical charges would create extra forces on the grains, in addition to wind and gravity, and lead to the curious effects seen in the real world. For example, the electrical attraction between grains helps the wind to pick up more grains from the surface, Kok says, but also keeps them close to the ground.
20 | NewScientist | 24 November 2007
‘Happy’ worms live longer on antidepressants IT SEEMS antidepressants don’t just help humans. Roundworms given a particular antidepressant lived longer – possibly because they were fooled into behaving as though they’d run short of food. A low-calorie lifestyle is known to boost the lifespan of worms and some mammals, so it might be possible to use the drug as an aid to longevity in humans. Michael Petrascheck and his colleagues at the Fred Hutchinson Cancer Research Center in Seattle, Washington, exposed the worm Caenorhabditis elegans to 88,000
chemicals to see which, if any, caused them to live longer. Petrascheck noticed that one of the successful compounds resembled a class of antidepressants that work by blocking the action of the neurotransmitter serotonin. When he tested these drugs, he found that some of them, too, extended the worm’s lifespan. The best, mianserin, made the worms live 31 per cent longer than untreated worms (Nature, DOI: 10.1038/nature05991). Further tests showed that mianserin blocks two specific
receptors, SER-4 and SER-3, that are involved in keeping the balance between hunger and satiety. When the researchers repeated the test using worms on calorie-restricted diets – known to make them live longer – they found that mianserin did not extend their lifespans any further. This suggests that the drug works by mimicking the sensation of starvation. “The animal perceives that it’s starving, and that’s enough to increase lifespan,” says Petrascheck. Tests in mice are under way. BRYAN REYNOLDS/OSF
Lie on the beach and feel the field
Hang on to your menstrual blood THE “monthly curse” may be anything but: menstrual blood appears to be a rich and accessible source of adult stem cells. The uterine lining is already known to contain adult stem cells, but harvesting them would be as invasive as getting them from other adult sources, such as bone marrow. Now two separate groups led by Xiaolong Meng of the Bio-Communications Research Institute in Witchita, Kansas, and Julie Allickson at Cryo-Cell International in Oldsmar, Florida, say they have found these cells in menstrual blood. Both groups say the cells show all the hallmarks of stem cells: they replicate without differentiating, they can be made to differentiate into many different cell types, and they show characteristic markers of stem cells on their surface. Meng’s work was published in the Journal of Translational Medicine last week (DOI: 10.1186/1479-5876-5-57). Cryo-Cell has now patented a collection and storage technique called “C’Elle”, enabling women to preserve their own menstrual stem cells in case they could be used to treat heart disease, diabetes, and spinal cord injury in the future.
It takes teamwork to chew up wood WITH their prodigious appetite for wood, termites ought to have simple enough digestive systems: wood goes in, is turned to food, and the remnants are excreted. But the devil is in the detail. The bacteria found in the guts of Nasutitermes termites from Costa Rica use hundreds, perhaps thousands, of enzymes to break down tough plant matter into sugar. For those trying to use similar processes to make biofuel out of woodchips, termites have some lessons to offer. “We’re laying out the tools termites use to digest wood,” says Jared Leadbetter of the California
Institute of Technology in Pasadena. Atrificial cocktails of enzymes have so far had only limited success in converting woodchips to ethanol biofuel, and the new finding suggests why. Leadbetter and colleagues sampled the hindgut contents of 165 termites and sequenced the genomes of everything inside. They found several hundred species of symbiotic bacteria which contained genes involved in digesting cellulose, lignin and xylan – the three major components of wood (Nature, DOI: 10.1038/nature06269). To break down just one of these components takes at least a dozen enzymes , Leadbetter says. Bound together in wood they are far tougher, requiring enzymes to work in concert.
www.newscientist.com
KEVIN SPREEK MEESTER/JUPITER
IT’S not only the breeze that whips sand in your face on a windy beach, electric fields also play their part. Sand grains blown by the wind will often bounce along over a surface. This process – known as saltation – erodes rocks and is one of the ways that grains are carried along, creating ripples and sand dunes. Researchers used to think that wind and gravity alone influenced saltation, but their models failed to explain what happened to the sand in real life, for example, why it often clings to a surface despite high winds. Now Jasper Kok and Nilton Renno of the University of Michigan in Ann Arbor suggest that electrical fields are also involved. In the past, surprisingly strong fields have been measured pointing upwards in clouds of sand. Kok and Renno wondered whether the grains might be picking up some electrons when bouncing off the ground so that they become negatively charged. This is known to occur in the processing of industrial powders. Using a computer model, they found that electrical charges would create extra forces on the grains, in addition to wind and gravity, and lead to the curious effects seen in the real world. For example, the electrical attraction between grains helps the wind to pick up more grains from the surface, Kok says, but also keeps them close to the ground.
20 | NewScientist | 24 November 2007
‘Happy’ worms live longer on antidepressants IT SEEMS antidepressants don’t just help humans. Roundworms given a particular antidepressant lived longer – possibly because they were fooled into behaving as though they’d run short of food. A low-calorie lifestyle is known to boost the lifespan of worms and some mammals, so it might be possible to use the drug as an aid to longevity in humans. Michael Petrascheck and his colleagues at the Fred Hutchinson Cancer Research Center in Seattle, Washington, exposed the worm Caenorhabditis elegans to 88,000
chemicals to see which, if any, caused them to live longer. Petrascheck noticed that one of the successful compounds resembled a class of antidepressants that work by blocking the action of the neurotransmitter serotonin. When he tested these drugs, he found that some of them, too, extended the worm’s lifespan. The best, mianserin, made the worms live 31 per cent longer than untreated worms (Nature, DOI: 10.1038/nature05991). Further tests showed that mianserin blocks two specific
receptors, SER-4 and SER-3, that are involved in keeping the balance between hunger and satiety. When the researchers repeated the test using worms on calorie-restricted diets – known to make them live longer – they found that mianserin did not extend their lifespans any further. This suggests that the drug works by mimicking the sensation of starvation. “The animal perceives that it’s starving, and that’s enough to increase lifespan,” says Petrascheck. Tests in mice are under way. BRYAN REYNOLDS/OSF
Lie on the beach and feel the field
Hang on to your menstrual blood THE “monthly curse” may be anything but: menstrual blood appears to be a rich and accessible source of adult stem cells. The uterine lining is already known to contain adult stem cells, but harvesting them would be as invasive as getting them from other adult sources, such as bone marrow. Now two separate groups led by Xiaolong Meng of the Bio-Communications Research Institute in Witchita, Kansas, and Julie Allickson at Cryo-Cell International in Oldsmar, Florida, say they have found these cells in menstrual blood. Both groups say the cells show all the hallmarks of stem cells: they replicate without differentiating, they can be made to differentiate into many different cell types, and they show characteristic markers of stem cells on their surface. Meng’s work was published in the Journal of Translational Medicine last week (DOI: 10.1186/1479-5876-5-57). Cryo-Cell has now patented a collection and storage technique called “C’Elle”, enabling women to preserve their own menstrual stem cells in case they could be used to treat heart disease, diabetes, and spinal cord injury in the future.
It takes teamwork to chew up wood WITH their prodigious appetite for wood, termites ought to have simple enough digestive systems: wood goes in, is turned to food, and the remnants are excreted. But the devil is in the detail. The bacteria found in the guts of Nasutitermes termites from Costa Rica use hundreds, perhaps thousands, of enzymes to break down tough plant matter into sugar. For those trying to use similar processes to make biofuel out of woodchips, termites have some lessons to offer. “We’re laying out the tools termites use to digest wood,” says Jared Leadbetter of the California
Institute of Technology in Pasadena. Atrificial cocktails of enzymes have so far had only limited success in converting woodchips to ethanol biofuel, and the new finding suggests why. Leadbetter and colleagues sampled the hindgut contents of 165 termites and sequenced the genomes of everything inside. They found several hundred species of symbiotic bacteria which contained genes involved in digesting cellulose, lignin and xylan – the three major components of wood (Nature, DOI: 10.1038/nature06269). To break down just one of these components takes at least a dozen enzymes , Leadbetter says. Bound together in wood they are far tougher, requiring enzymes to work in concert.
www.newscientist.com