may the force be with you

Dark matter highlights extra dimensions

Philip Ball

In a spin: the twirling of galaxies reveals a mystery. Dark matter seems to be attracted to itself, and more so in smaller galaxies. © NASA/JPL-Caltech/SSC

# posted by dark master : 9/06/2005 09:29:00 AM  0 comments

Cellphones capable of transmitting data at blistering speeds have been demonstrated by NTT DoCoMo in Japan.

In experiments, prototype phones were used to view 32 high definition video streams, while travelling in an automobile at 20 kilometres per hour. Officials from NTT DoCoMo say the phones could receive data at 100 megabits per second on the move and at up to a gigabit per second while static. At this rate, an entire DVD could be downloaded within a minute. DoCoMo's current 3G (third generation) phone network offers download speeds of 384 kilobits per second and upload speeds of 129 kilobits per second.

The technology behind NTT DoCoMo's high-speed phone network remains experimental, but the 4G tests used a method called Variable-Spreading-Factor Spread Orthogonal Frequency Division Multiplexing (VSF-Spread OFDM), which increases downlink speeds by using multiple radio frequencies to send the same data stream.

Multiple routes

Another wireless networking trick, called multiple-input-multiple-output (MIMO) multiplexing, was used to send data via various routes across a network, in order to further increase data capacity. For example, MIMO could enable a cellphone to receive data from more than one base station in range.

The activities "are technically impressive," says Lajos Hanzo, a communications expert at Southampton University in the UK. But Hanzo told New Scientist NTT DoCoMo will need assistance from other phone companies if it is to kick-start 4G uptake. "In today's world nobody can go it alone," he says. "And hence any standard proposal must be internationally ratified, which has not as yet take place."

Some countries have already begun cooperating on such standards. Japan and China signed a memorandum on 24 August to work together on 4G. NTT DoCoMo hopes to launch a commercial 4G network by 2010.

# posted by dark master : 9/06/2005 09:27:00 AM  0 comments

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The parasitic hairworm persuades its grasshopper host to leave its forest home and plunge into water, so the worm can emerge and find a mate (Image: VB Films/CNRS/OPM)

A parasitic worm that makes the grasshopper it invades jump into water and commit suicide does so by chemically influencing its brain, a study of the insects’ proteins reveal.

The parasitic Nematomorph hairworm (Spinochordodes tellinii) develops inside land-dwelling grasshoppers and crickets until the time comes for the worm to transform into an aquatic adult. Somehow mature hairworms brainwash their hosts into behaving in way they never usually would – causing them to seek out and plunge into water.

Once in the water the mature hairworms – which are three to four times longer that their hosts when extended – emerge and swim away to find a mate, leaving their host dead or dying in the water. David Biron, one of the study team at IRD in Montpellier, France, notes that other parasites can also manipulate their hosts’ behaviour: “’Enslaver’ fungi make their insect hosts die perched in a position that favours the dispersal of spores by the wind, for example.”

But the “mechanisms underlying this intriguing parasitic strategy remain poorly understood, generally”, he says.

Now Biron and his colleagues have shown that the worm brainwashes the grasshopper by producing proteins which directly and indirectly affect the grasshopper’s central nervous system.

To view a video of the parasite and grasshopper in action, which includes a brief interview, in French, with lead researcher Frederic Thomas, visit the Canal IRD website.

Selective manipulation

“It’s a very novel study, because there are very, very few papers on how behaviour actually changes,” says Shelley Adamo at Dalhousie University in Halifax, Canada, an expert in insect behavioural physiology who is familiar with Biron’s work.

“One of the reasons they are interesting is that parasites are often able to get in there and selectively manipulate behaviour," she told New Scientist. She says the eventual hope is that understanding how parasites manipulate their hosts’ behaviour – by affecting the nervous and endocrine systems – might further the understanding of how human behaviour-systems link.

Biron and colleagues found that the adult worms – those ready to prime their hosts for a watery death – altered the central nervous system function of their hapless hosts by producing certain molecules mimicking the grasshoppers’ own proteins.

Gravity response

And grasshoppers housing the parasitic worm expressed different proteins in their brains than uninfected grasshoppers. Some of these proteins were linked to neurotransmitter activities. Others included those linked to geotactic behaviour – the oriented movement of an organism in response to gravity.

The team used an approach called “proteomics” to study the hijacking of the grasshopper’s behaviour. This technique analyses all the proteins expressed in a cell or tissue.

Biron and colleagues collected and analysed the proteins of grasshoppers (Meconema thalassinum) with and without parasitic hairworms before, during and after the grasshoppers’ suicidal plunges into a swimming pool at night-time.

“This is a unique approach and a very exciting one,” says Adamo. “This is the first time it’s been used to address this issue.”

Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2005.3213)

# posted by dark master : 9/06/2005 09:26:00 AM  0 comments

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Astronomers estimate the newly discovered pulsar has streaked across about a third of the night sky since it was created in a supernova 2.5 million years ago (Image: Bill Saxton/NRAO/AUI/NSF)

Astronomers have spotted the fastest moving stellar corpse to date – and it appears to be headed straight out of our galaxy.

A team from the US National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, US, clocked the dead star at 1100 kilometres per second.

The object, called B1508+55, is a rotating neutron star, or pulsar. It is the superdense core of a massive star that exploded as a supernova about 2.5 million years ago. The explosion seems to have ejected the pulsar with such force that it will eventually escape the Milky Way entirely, says team member Shami Chatterjee, an astronomer with NRAO and CfA.

However, current simulations of supernovae have never produced such breakneck speeds. In the models, the newly formed neutron star starts out fast but soon slows down when material from the outer layers of the exploded star crashes back onto it. In 2004, the first 3D model of a supernova found that the blast could send a neutron star flying at about 200 kilometres per second - nearly six times slower than the new record holder.

Kick velocities

"I think everyone believes that supernova explosions do in nature provide these [higher] kick velocities," Chatterjee told New Scientist. "It's just that our simulations are not quite there yet."

The researchers watched this pulsar for two years with the Very Long Baseline Array – a collection of 10 radio-telescopes scattered from Hawaii to the US Virgin Islands. They determined the pulsar lies 7700 light years away and gauged its speed by observing how its position on the sky changed in that time.

From this, they traced its route backwards to its likely birthplace 2.5 million years ago in a region full of huge stars in the constellation Cygnus. The stars are so massive that they will eventually blow up as supernovae, potentially spawning other speedy stellar corpses.

Journal reference: Astrophysical Journal Letters (vol 630, p L61)

# posted by dark master : 9/06/2005 09:22:00 AM  0 comments