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Why the sun's corona is hotter than the surface
Research news and discovery
EYE OF SCIENCE/SPL
In brief– Painkiller gene
Keep-’em-keen gene stops insects starting a family MATING is all very well, but if an insect doesn’t stop courting and start laying eggs afterwards, its population won’t grow. Now researchers have found the gene that is crucial to this behavioural switch, suggesting a possible way to control insect populations. Female mosquitoes and fruit flies spend a lot of time enticing males to mate with them. But once they have succeeded, their behaviour changes and they start laying eggs. The trigger for this is a small protein called sex peptide (SP) in the male’s semen.
Barry Dickson and colleagues at the Institute of Molecular Pathology in Vienna, Austria, were searching for genes that controlled the reproductive process, and found that when they turned one off, females kept on courting and didn’t lay many eggs. This was the gene for the SP receptor, expressed in the reproductive tract and in brain areas involved in mating. The team has discovered the same receptor in several insect species, including Aedes aegypti, a mosquito that carries dengue, yellow fever and chikungunya. Blocking it might be an “attractive target” for insect control, says Dickson, because affected females would remain in the mating pool, keeping males occupied – and away from females that fancied settling down and laying eggs.
Why it’s cooler close to the sun IF YOU could fly to the sun’s surface like the characters in Danny Boyle’s movie Sunshine, you might expect it to get gradually hotter the closer you flew. Curiously though, the temperature would peak in the sun’s wispy outer atmosphere, the corona. Now, views from Japan’s Hinode spacecraft may explain why. In the past, researchers have 14 | NewScientist | 15 December 2007
suggested that the jostling of atmospheric magnetic fields by processes such as convection creates magnetic ripples called Alfvén waves, which might carry energy up along field lines into the corona to heat it to millions of degrees. But nobody was sure if these waves carried enough energy. A team led by Bart De Pontieu of the Lockheed Martin Solar and
Astrophysics Laboratory in Palo Alto, California, who had an instrument on Hinode, observed the swaying of jets of gas called spicules, which emerge like whiskers from the sun’s surface. They argue that their back-andforth motion can only be explained by powerful Alfvén waves moving upwards into the corona, carrying at least 120 watts per square metre. This is more than enough to maintain the corona’s tremendous heat, they say (Science, vol 318, p 1574).
WE EXPERIENCE chilli peppers as hot because they activate an enzyme called c-Kit. It now seems that getting rid of c-Kit increases pain tolerance in mice, while stimulating it lowers the level at which heat becomes painful. This could lead to the development of a new class of painkillers that work by blocking the enzyme. The skin contains more than a million “nociceptors”, or bare nerve endings, around half of which fire in response to pain. Gary Lewin and colleagues at the Max Delbrück Centre for Molecular Medicine in Berlin, Germany, found that mice which cannot make c-Kit took 40 per cent longer to jerk their paw away from a hot infrared beam. Also, the beam had to be 6 °C hotter to make the nociceptors fire. Conversely, in normal mice c-Kit seems to be what makes inflamed skin feel pain more easily, for example after sunburn (Neuron, DOI: 10.1016/j.neuron.2007.10.040).
How Saturn got its flying saucers IF A scientist claimed they’d discovered how the UFOs around Saturn got there, you might question their credentials. Unless, of course, they were talking about two of the planet’s moons, which are shaped like flying saucers. Two of Saturn’s small moons, Pan and Atlas, have a ridge several kilometres high running along their equators, making them much wider than they are tall. Now researchers led by Sébastien Charnoz of Denis Diderot University in Paris, France, have run simulations suggesting that these ridges are made of material swept up from Saturn’s rings. Particles would have gradually accumulated on the ridges as the moons travelled across the plane of the rings, says the team (Science, vol 318, p 1622). www.newscientist.com
EYE OF SCIENCE/SPL
In brief– Painkiller gene
Keep-’em-keen gene stops insects starting a family MATING is all very well, but if an insect doesn’t stop courting and start laying eggs afterwards, its population won’t grow. Now researchers have found the gene that is crucial to this behavioural switch, suggesting a possible way to control insect populations. Female mosquitoes and fruit flies spend a lot of time enticing males to mate with them. But once they have succeeded, their behaviour changes and they start laying eggs. The trigger for this is a small protein called sex peptide (SP) in the male’s semen.
Barry Dickson and colleagues at the Institute of Molecular Pathology in Vienna, Austria, were searching for genes that controlled the reproductive process, and found that when they turned one off, females kept on courting and didn’t lay many eggs. This was the gene for the SP receptor, expressed in the reproductive tract and in brain areas involved in mating. The team has discovered the same receptor in several insect species, including Aedes aegypti, a mosquito that carries dengue, yellow fever and chikungunya. Blocking it might be an “attractive target” for insect control, says Dickson, because affected females would remain in the mating pool, keeping males occupied – and away from females that fancied settling down and laying eggs.
Why it’s cooler close to the sun IF YOU could fly to the sun’s surface like the characters in Danny Boyle’s movie Sunshine, you might expect it to get gradually hotter the closer you flew. Curiously though, the temperature would peak in the sun’s wispy outer atmosphere, the corona. Now, views from Japan’s Hinode spacecraft may explain why. In the past, researchers have 14 | NewScientist | 15 December 2007
suggested that the jostling of atmospheric magnetic fields by processes such as convection creates magnetic ripples called Alfvén waves, which might carry energy up along field lines into the corona to heat it to millions of degrees. But nobody was sure if these waves carried enough energy. A team led by Bart De Pontieu of the Lockheed Martin Solar and
Astrophysics Laboratory in Palo Alto, California, who had an instrument on Hinode, observed the swaying of jets of gas called spicules, which emerge like whiskers from the sun’s surface. They argue that their back-andforth motion can only be explained by powerful Alfvén waves moving upwards into the corona, carrying at least 120 watts per square metre. This is more than enough to maintain the corona’s tremendous heat, they say (Science, vol 318, p 1574).
WE EXPERIENCE chilli peppers as hot because they activate an enzyme called c-Kit. It now seems that getting rid of c-Kit increases pain tolerance in mice, while stimulating it lowers the level at which heat becomes painful. This could lead to the development of a new class of painkillers that work by blocking the enzyme. The skin contains more than a million “nociceptors”, or bare nerve endings, around half of which fire in response to pain. Gary Lewin and colleagues at the Max Delbrück Centre for Molecular Medicine in Berlin, Germany, found that mice which cannot make c-Kit took 40 per cent longer to jerk their paw away from a hot infrared beam. Also, the beam had to be 6 °C hotter to make the nociceptors fire. Conversely, in normal mice c-Kit seems to be what makes inflamed skin feel pain more easily, for example after sunburn (Neuron, DOI: 10.1016/j.neuron.2007.10.040).
How Saturn got its flying saucers IF A scientist claimed they’d discovered how the UFOs around Saturn got there, you might question their credentials. Unless, of course, they were talking about two of the planet’s moons, which are shaped like flying saucers. Two of Saturn’s small moons, Pan and Atlas, have a ridge several kilometres high running along their equators, making them much wider than they are tall. Now researchers led by Sébastien Charnoz of Denis Diderot University in Paris, France, have run simulations suggesting that these ridges are made of material swept up from Saturn’s rings. Particles would have gradually accumulated on the ridges as the moons travelled across the plane of the rings, says the team (Science, vol 318, p 1622). www.newscientist.com