Plant has a bat beckoning beacon

29 July 2011 Last updated at 02:29 By Victoria Gill Science reporter, BBC Nature The dish-shaped leaves emit a powerful echo that helps the bat locate the plant A rainforest vine has evolved dish-shaped leaves to attract the bats that pollinate it, scientists have found.

Tests revealed that the leaves were supremely efficient at bouncing back the sound pulses the flying mammals used to navigate.

When the leaves were present the bats located the plant twice as quickly as when these echoing leaves were removed.

A team of scientists in the UK and Germany reported its findings in the journal Science.

The study is the first to find a plant with "specialised acoustic features" to help bat pollinators find them using sound.

Most bats send out pulses of sound to find their way around; the way they sense objects in their environment by sensing how these pulses bounce off them is known as echolocation.

"We already knew that plants used their brightly coloured petals to attract pollinators," explained Marc Holderied from the University of Bristol, one of the researchers involved in the study.

"What we've found is the echolocating equivalent to colourful flowers.

"We have a shape that produces an echo - an 'echoacoustic beacon'."

The scientists first notice the Caribbean plant, Marcgravia evenia, in a photograph in a Natural History magazine.

"We immediately recognised that this dish-shaped leaf could be a perfect bat attractor," he recalled.

He and his colleagues brought the plant into their laboratory and bounced to measure its acoustics - essentially firing sound pulses at it to see how they echoed.

The next step was to test how the bats responded to it.

The researchers set a test for a group of nectar-feeding bats (Glossophaga soricina) to measure how long it took them to locate a small feeder in a dark room.

They adorned the feeder either with the plants' dish-shaped leaf or with a normal (much flatter) foliage leaf from the same plant.

"Once we added the leaf, that really did the trick," said Dr Holderied. "The bats found the feeder in half the time."

"Now we know that the acoustic clues are important for pollination."

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Fragmented sleep 'harms memory'

25 July 2011 Last updated at 21:20 GMT Continuous sleep is important for memory formation Broken sleep affects the ability to build memories, a study of mice suggests.

The Proceedings of the National Academy of Science findings could help explain memory problems linked to conditions including Alzheimer's and sleep apnoea.

The Stanford University research found disrupting sleep made it harder for the animals to recognise familiar objects.

A UK sleep expert said the brain used deep sleep to evaluate the day's events and decide what to keep.

This study looked at sleep that was fragmented, but not shorter or less intense than normal for the mice.

It used a technique called optogenetics, where specific cells are genetically engineered so they can be controlled by light.

They targeted a type of brain cell that plays a key role in switching between the states of being asleep and being awake.

Mouse memory test

The researchers then sent light pulses directly into the brains of mice while they slept.

This meant they could disrupt their sleep without affecting total sleep time or the quality or composition of sleep.

The animals were then placed in a box with two objects, one of which they had encountered before.

Mice would naturally spend more time examining the newer object, and those who had been allowed uninterrupted sleep did just that.

But those whose sleep had been disrupted were equally interested in both objects, suggesting their memories had been affected.

Writing in the journal, the researchers, led by Dr Luis de Lecea, said: "Sleep continuity is one of the main factors affected in various pathological conditions that impact memory, including Alzheimer's and other age-related cognitive deficits."

Broken sleep also affects people addicted to alcohol, and those with sleep apnoea - a condition in which the throat repeatedly narrows or closes during sleep, restricting oxygen and causing the patient to wake up.

The researchers add there is no evidence of a causal link between sleep disruption and any of these conditions.

But they added: "We conclude that regardless of the total amount of sleep or sleep intensity, a minimal unit of uninterrupted sleep is crucial for memory consolidation."

Independent sleep expert Dr Neil Stanley, a former chairman of the British Sleep Society, said: "During the day, we accumulate all these memories.

"At some point we have to sort through what's happened during the day.

"There are some things that we need to 'lock down' as a permanent hard memory.

"That process occurs in deep sleep. So anything that affects sleep will have an effect on that process to a greater or a lesser extent."

Dr Stanley said there was particularly striking evidence that people with sleep apnoea had particular problems "locking down" memories.

And he added that people with Alzheimer's often had trouble sleeping, but said: "There is something there. But whether it's the degeneration of the brain that causes poor sleep, or poor sleep that aids the degeneration of the brain has not been determined."

Miranda Watson, director of communications at the British Lung Foundation, said: "For patients with the dangerous sleep disorder, obstructive sleep apnoea, this study will come as no surprise.

"Patients regularly stop breathing during the night when their airways become blocked depriving them of a full night's rest.

"This interrupted sleep can cause extreme day time tiredness and memory loss."

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NZ penguin gets health clearance

29 July 2011 Last updated at 04:26 GMT "Happy Feet", the lost penguin, could get back to Antarctica early next month A young emperor penguin found washed up on a New Zealand beach is recovering well and could swim home next month.

Staff at Wellington zoo said results of an X-ray and blood test showed "Happy Feet", as it has been named, is fine after endoscopic surgery.

The penguin was found on Peka Peka beach, about 60km (37 miles) north of Wellington - some 3,000km from its home in Antarctica.

Experts had been reluctant to intervene as the bird appeared to be healthy.

However, it later grew lethargic and was operated on to remove sand from its stomach.

A Zoo spokeswoman, Kate Baker, said the penguin has gained about 4kg (9lb).

It was given a first swim at the zoo earlier this week, in salt water that was cooled to below 0C (32F).

Crowds have been flocking to the zoo to see the bird - the first such arrival of an Emperor penguin in New Zealand in at least 44 years.

The bird's plight has attracted worldwide attention.

Hundreds of people had gathered to watch a leading gastroenterologist from Wellington Hospital perform the endoscopy on the bird at the zoo in late June.

To help it feel more at home, the penguin is being kept in a room chilled to about 8C. There is a bed of ice for it to sleep on.

Zoo staff said the bird would probably be released offshore from the south end of the country early next month.

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Northern exposure

29 July 2011 Last updated at 10:29 GMT The latest image was acquired last Saturday, and was taken from a distance of about 5,200km Nasa's Dawn spacecraft has returned a view of the giant asteroid Vesta's northern hemisphere.

The spacecraft acquired the image after making its first pass over the dark side of the rock since going into orbit two weeks ago.

Vesta's northern polar region is currently in the deep shadow of winter.

Dawn's best look at some of the surface features hidden in the picture are unlikely to come until the probe departs the rock in a year's time.

By then, Vesta should have shifted on its axis sufficiently to allow the Sun's rays to fall across some of its high-latitude mountains, valleys and craters.

"The north pole is in shadow now and when Dawn leaves it will be slightly illuminated," explained Prof Ulrich Christensen, from the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany.

"We may get a glimpse of some features currently in darkness, but with the Sun still very low on the horizon lighting conditions may not be ideal," he told me.

In the meantime, there is plenty to occupy the Dawn team, which promises to deliver its first interpretation on Monday of some of the features seen in the earliest imagery.

Nasa has scheduled a media conference with the leading scientists at its Jet Propulsion Laboratory in California. A parallel conference will take place in Germany, reflecting that country's key participation in the mission. The framing camera system was developed by the Max Planck Institute.

It is hoped the researchers will show us not just more pictures on Monday, but some colour ones as well. The framing camera system has a number of colour filters.

The mission's chief scientist, Dr Chris Russell from the University of California Los Angeles, told the BBC last week that the team had seen quite deep colouration in places - strong oranges and blues.

Ever closer: Last week's image release highlighted the southern pole from a distance of about 10,500km

Dawn entered into orbit around 530km-wide Vesta on 17 July, and will spend 12 months studying the rock before moving on to the biggest object in the asteroid belt between Mars and Jupiter - the dwarf planet Ceres.

Both objects should have something to say about the earliest days of the Solar System. Scientists often describe asteroids as the rubble that was left over after the planets proper had formed.

I have to say, the Dawn mission has got me very excited. If you think about it, it's a while since we've seen a new world up close like this. Rosetta's pass of Lutetia last year was spectacular, but fleeting.

And even the major Saturnian moons encountered by Cassini this last decade had some half-decent imagery associated with them before the joint Nasa/Esa/Asi mission turned up.

Vesta seems very fresh, and Ceres should be even more remarkable.

Ceres, of course, will become the first dwarf planet to be visited by a spacecraft - before even Pluto can be passed by Nasa's New Horizons probe. That rendezvous is not due to occur until 2015.

Someone has just asked me in the office how long we can keep talking about new pictures from Dawn at Vesta. The inference being: it's just a big hunk of rock. A while yet, I'd say.

There's a certain fascination with asteroids. That's borne out by Thursday's news about an 200-300km-wide asteroid not far from Earth that is moving in the same orbit around the Sun. It proved to be the day's most read story on the BBC News website.

Dumb, dull rocks? I don't think so.

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Long winters 'led to bigger eyes'

27 July 2011 Last updated at 07:26 GMT By Judith Burns Science reporter, BBC News Researchers measured skulls from the 1800s Humans living at high latitude have bigger eyes and bigger brains to cope with poor light during long winters and cloudy days, UK scientists have said.

The Oxford University team said bigger brains did not make people smarter.

Larger vision processing areas fill the extra capacity, they write in the Royal Society's Biology Letters journal.

The scientists measured the eye sockets and brain volumes of 55 skulls from 12 populations across the world, and plotted the results against latitude.

Lead author Eiluned Pearce told BBC News: "We found a positive relationship between absolute latitude and both eye socket size and cranial capacity."

The team, from the Institute of Cognitive and Evolutionary Anthropology, used skulls dating from the 1800s kept at museums in Oxford and Cambridge.

The skulls were from indigenous populations ranging from Scandinavia to Australia, Micronesia and North America.

Largest brain cavities

The largest brain cavities came from Scandinavia, while the smallest were from Micronesia.

Eiluned Pearce said: "Both the amount of light hitting the Earth's surface and winter day-lengths get shorter as you go further north or south from the equator.

"We found that as light levels decrease, humans are getting bigger eye sockets, which suggests that their eyeballs are getting bigger.

Barn owls are nocturnal hunters

"They are also getting bigger brains, because we found this increase in cranial capacity as well.

"In the paper, we argue that having bigger brains doesn't mean that high-latitude humans are necessarily smarter. It's just they need bigger eyes and brains to be able to see well where they live."

The work indicates that humans are subject to the same evolutionary trends that give relatively large eyes to birds that sing first during the dawn chorus, or species such as owls that forage at night.

Co author Prof Robin Dunbar said: "Humans have only lived at high latitudes in Europe and Asia for a few tens of thousands of years, yet they seem to have adapted their visual systems surprisingly rapidly to the cloudy skies, dull weather and long winters we experience at these latitudes."

The team took into account the overall body size of each individual by measuring the foramen magnum - the hole in the base of the skull that attaches to the spinal column.

They also controlled for the possibility that the larger eye sockets were needed for extra fat around the eyeball to insulate them from freezing temperatures.

The team intends to do more work on establishing a firm link between eyeball size and enhanced visual processing areas in the brain, and to replicate the link found in the 55 original skulls with further study on specimens from other museums.

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Brain waves 'are the best brakes'

29 July 2011 Last updated at 08:44 GMT By Judith Burns Science reporter, BBC News Volunteers wearing EEG caps used a driving simulator Tapping into drivers' brain signals can cut braking distances and avoid car crashes, according to scientists.

Researchers at the Berlin Institute for Technology attached electrodes to the scalps of volunteers inside a driving simulator.

The system detected the intention to brake, and cut more than 3m (10ft) off stopping distances, the team report in the Journal of Neural Engineering.

The team's next aim is to check the system in a series of road tests.

The 18 volunteers were asked to keep 20m (66ft) behind the simulated car in front, which braked sharply at random intervals.

Scientists used a technique called electroencephalograhy (EEG) to analyse the drivers' brain signals.

The system was able to pinpoint the intention to brake 13 hundredths of a second before the driver applied pressure to the brakes.

The team reported that at a speed of 100km/h (65m/h) the braking distance was reduced by 3.66 meters (12 feet).

Computer scientist Stefan Haufe told BBC News: "We know that any intention is generated in the brain. So it's no wonder that such things are visible in the brain.

"We were surprised it is so predictive. That is the thing!"

Lead investigator Benjamin Blankertz added: "It's quite easily explained by the fact that we can tap the driver's intention at the source of the build up of intention in the brain.

"It's a longer process, from the very first upcoming cognitive processes and intention building, until finally the muscles start the movement."

The volunteers also had the muscle tension in their lower legs analysed to detect the first signs of leg motion before they released the accelerator and pushed the brake pedal.

This data enabled the scientists to analyse the EEG information to determine which parts of the brain are key to braking. They improved the detection system accordingly.

'Point of no return'

The Institute of Physics says this is the first time that EEG has been used to assist in braking.

The technique is, however, already used to help paralysed people control computers, prosthetic limbs and wheelchairs.

The researchers are planning to conduct road trials of their system to test its viability out of the lab.

But Benjamin Blankertz stressed that he suspects there may be some way to go before EEG can be used as a safety aid in real driving situations, not least because it requires the driver to wear a plastic cap with 64 electrodes covered in conductive gel.

The technology uses an EEG cap and 64 electrodes

This is uncomfortable, takes up to half an hour to fit, and the wearers have to wash the gel out of their hair afterwards. Smaller, more lightweight versions are in development.

The paper also mentions that wearers of EEG caps have to keep fairly still which is not always possible while driving, particularly when executing an emergency stop.

Dr Blankertz also said more work needs to be done on avoiding false alarms - to avoid the possibility that the machine could misread a drivers' brain signals and brake unnecessarily.

He said: "We need to investigate intention-building and decision-taking and self-initiated movement.

"Some recent research suggests that the outcome of free choices can be predicted from brain activity before the experimental subject is consciously aware of their intention.

"A technology that would make possible real time prediction of future decisions could be used to investigate how this relates to the so-called point of no return.

The team ultimately hopes to work with the automotive industry to combine their EEG technique with radar and laser systems that are used in some commercially available crash-avoidance systems, which detect obstacles such as walls, traffic signals and other vehicles.

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Light's speed curbs time travel

26 July 2011 Last updated at 09:46 GMT The speed of light in extremely cold gases of atoms can be varied widely Physicists have confirmed the ultimate speed limit for the packets of light called photons - making time travel even less likely than thought.

The speed of light in vacuum is the Universe's ultimate speed limit, but experiments in recent years suggested that single photons might beat it.

If they could, theory allows for the prospect of time travel.

Now, a paper in Physical Review Letters shows that individual photons too are limited to the vacuum speed limit.

That means that photons maintain the principle of causality laid out in Einstein's theory of special relativity - that is, an event's effect cannot precede its cause by travelling faster than light. It is violation of this causality that would, in principle, permit time travel.

While the limit in vacuum is a fixed number - some 300,000km per second - the speed of light can vary widely in different materials.

These differences explain everything from why a straw looks bent in a glass of water to experiments in cold gases of atoms in which light's speed is actively manipulated.

Some of those experiments showed "superluminal" behaviour, in which photons travelled faster than the speed of light in a given medium.

It remained, however, to determine whether or not individual photons could exceed the vacuum limit.

All relative

Now, Shengwang Du and colleagues at the Hong Kong University of Science and Technology have measured what is known as an optical precursor.

Like the wind that moves ahead of a speeding train, optical precursors are the waves that precede photons in a material; before now, such optical precursors have never been directly observed for single photons.

By passing pairs of photons through a vapour of atoms held at just 100 millionths of a degree above absolute zero - the Universe's ultimate low-temperature limit - the team showed that the optical precursor and the photon that caused it are indeed limited to the vacuum speed of light.

"By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon," said Professor Du.

Thus, photons cannot time travel, and moving information around at faster-than-light speeds is impossible.

But the work has more prosaic implications.

"Our findings will also likely have potential applications by giving scientists a better picture on the transmission of quantum information," said Professor Du.

Time travel by other means, however, is not entirely ruled out.

Einstein's theory of general relativity, in which space and time are two intertwined aspects of the same medium, would permit the bending of the medium to join two different times - a situation popularised as creating a "wormhole".

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