The purpose of a mosquitoes whine is not to alert you before a bite, but to find mates. According to a study published in Current Biology, the mosquitoes responsible for most malaria deaths (a group known as Anopheles gambiae) find mates by using their wing beats to produce tones that harmonise with those of their partners. Although they look identical, they actually comprise seven species and several forms of chromosomes sets. The new findings explain how each species avoids mating with members of other species, even when they travel together in the same swarm. The researchers found that two mosquitoes don’t harmonise successfully if they are of the same sex or if they are not the same type of mosquito.
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16 January 2010
Birth of the Earth
A new model solves a key problem in the theory of the formation of planets around a star.
origins
If you read any acount of the formation of the solar system, you will learn that its planets were formed out of a disc of gas and dust that remained after the formation of the sun. In this disc, with the sun at its centre, dust particles became larger in size by ‘accreting’ other such particles. Over a period of time, lumps of matter formed in the disc collapsed inwards under their own gravity to eventually give rise to planets. The only problem with this hypothesis was that any attempt to computationally model the process ended up with the planet plunging into the sun. Going by these models, the planets and hence the earth had no business existing at all, but clearly since they do, scientists had concluded that there was something vital missing in their description of the process.
Now researchers at the University of Cambridge and American Museum of Natural History have run new simulations that do end up resulting in the formation of planets in stable orbits around the sun. The crucial difference in the new simulations is that the researchers assumed temperature variations in the gas and dust disc. Earlier models had assumed that the disc would radiate extra energy to surrounding space very quickly and it was possible to assume a uniform temperature in the disc. It turns out that the collection of gas and dust does not behave in this ideal manner, and that variations in temperature are crucial to the formation of stable planets.
The simulations give a vivid picture of the formation of planets. As the protoplanets accumulate more and more mass, their movement within the disk is constrained by the temperature differences in the disk. As a result, the planets get trapped into orbits that slowly move inwards as the disk dissipates. The planets are then eventually dropped into orbits whose radius depends on their mass.
Science Buzz
16 Jan 2010 - 22 Jan 2010
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The first vertebrates to walk earth emerged from the sea almost 20 million years earlier than was previously thought. Scientists have discovered footprints from an 8-ft-long prehistoric creature on a former lagoon in southeastern Poland, which could rewrite the history of when, where, and why fish evolved limbs and first walked onto land. “These are the oldest evidence of true tetrapods,” says co-author Grzegorz Niedbwiedzki, a palaeontologist at Warsaw University. The finding also suggests that fins-to-limbs evolution occurred in an intertidal environment rather than a seasonally flooded forest, as indicated by earlier finds.
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Some 4,000 years ago, ancient Egyptians used lead and lead salts to produce make-up to darken and adorn the eyes. It was no ordinary make-up, and sometimes took a month to concoct. “We knew ancient Greeks and Romans too had noted the make-up had medicinal properties, but wanted to determine exactly how,” said Philippe Walter, co-head of a team of scientists from the Louvre museum and the CNRS national research institute. The team, using analytical chemistry, determined that “in very low doses lead does not kill cells”. Instead, it produces a molecule—nitric oxide—that activates the immune defence system which beats back bacteria in case of eye infection.
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