Arctic ozone loss at record level

The Arctic ozone hole lay over over populated regions for parts of winter and spring

Ozone loss over the Arctic this year was so severe that for the first time it could be called an "ozone hole" like the Antarctic one, scientists report.

About 20km (13 miles) above the ground, 80% of the ozone was lost, they say.

The cause was an unusually long spell of cold weather at altitude. In cold conditions, the chlorine chemicals that destroy ozone are at their most active.

It is currently impossible to predict if such losses will occur again, the team writes in the journal Nature.

Early data on the scale of Arctic ozone destruction were released in April, but the Nature paper is the first that has fully analysed the data.

"Winter in the Arctic stratosphere is highly variable - some are warm, some are cold," said Michelle Santee from Nasa's Jet Propulsion Laboratory (JPL).

"But over the last few decades, the winters that are cold have been getting colder.

"So given that trend and the high variability, we'd anticipate that we'll have other cold ones, and if that happens while chlorine levels are high, we'd anticipate that we'd have severe ozone loss."

Ozone-destroying chemicals originate in substances such as chlorofluorocarbons (CFCs) that came into use late last century in appliances including refrigerators and fire extinguishers.

Their destructive effects were first documented in the Antarctic, which now sees severe ozone depletion in each of its winters.

Their use was progressively restricted and then eliminated by the 1987 Montreal Protocol and its successors.

The ozone layer blocks ultraviolet-B rays from the Sun, which can cause skin cancer and other medical conditions.

Longer, not colder

Winter temperatures in the Arctic stratosphere do not generally fall as low as at the southern end of the world.

No records for low temperature were set this year, but the air remained at its coldest for an unusually long period of time, and covered an unusually large area.

In addition, the polar vortex was stronger than usual. Here, winds circulate around the edge of the Arctic region, somewhat isolating it from the main world weather systems.

"Why [all this] occurred will take years of detailed study," said Dr Santee.

"It was continuously cold from December through April, and that has never happened before in the Arctic in the instrumental record."

The size and position of the ozone hole changed over time, as the vortex moved northwards or southwards over different regions.

Some monitoring stations in northern Europe and Russia recorded enhanced levels of ultraviolet-B penetration, though it is not clear that this posed any risk to human health.

While the Arctic was setting records, the Antarctic ozone hole is relatively stable from year to year.

This year has seen ozone-depleting conditions extending a little later into the southern hemisphere spring than usual - again, as a result of unusual weather conditions.

Chlorine compounds persist for decades in the upper atmosphere, meaning that it will probably be mid-century before the ozone layer is restored to its pre-industrial health.

Ozone destruction takes place within polar stratospheric clouds, with chlorine the main culprit

'Flying carpet' of conductive plastic takes flight

The sheet is lifted by the air packets, and propelled forwards

A miniature magic carpet made of plastic has taken flight in a laboratory at Princeton University.

The 10cm (4in) sheet of smart transparency is driven by "ripple power"; waves of electrical current driving thin pockets of air from front to rear underneath.

The prototype, described in Applied Physics Letters, moves at speeds of about a centimetre per second.

Improvements to the design could raise that to as much as a metre per second.

The device's creator, graduate student Noah Jafferis, says he was inspired by a mathematical paper he read shortly after starting his PhD studies at Princeton.

He abandoned what would have been a fashionable project printing electronic circuits with nano-inks for one that seemed to have more in common with 1001 Nights than 21st-Century engineering.

Prof James Sturm, who leads Mr Jafferis' research group, conceded that at times the project seemed foolhardy.

"What was difficult was controlling the precise behaviour of the sheet as it deformed at high frequencies," he told the BBC.

"Without the ability to predict the exact way it would flex, we couldn't feed in the right electrical currents to get the propulsion to work properly."

What followed was a two year digression attaching sensors to every part of the material so as to fine-tune its performance through a series of complex feedbacks.

But once that was mastered, the waveform of the undulating matched that prescribed by the theory, and the wafting motions gave life to the tiny carpet.

In the paper describing the design, Mr Jafferis and his co-authors are careful to keep the word "flying" in inverted commas, because the resulting machine has more in common with a hovercraft than an aeroplane.

"It has to keep close to the ground," Mr Jafferis explained to the BBC's Science in Action, "because the air is then trapped between the sheet and the ground. As the waves move along the sheet it basically pumps the air out the back." That is the source of the thrust.

Ray hope

Harvard University's Lakshminarayanan Mahadevan, who wrote the 2007 paper in Physical Review Letters that inspired the whole project, expressed a mixture of surprise and delight at the Princeton team's success.

"Noah has gone beyond our simple theory and actually built a device that works," he told the BBC "And what's more, it behaves, at least qualitatively, as we had predicted."

Mr Jafferis points out that the prototype is limited because tiny conducting threads anchor it to heavy batteries, so it's free to move only a few centimetres. But he is already working on a solar-powered upgrade that could freely fly over large distances.

The advantage of this kind of propulsion, he argues, is that unlike jets, propellers and hovercraft, there are no moving components like cogs and gears that rub against each other.

The propulsion is not completely unlike that of skates and rays

"The ideal use would be some kind of dusty, grimy environment where moving parts would get gummed up and stop," he explained.

The propulsion is not completely unlike that of skates and rays

That said, he laughingly admits that with the existing materials, a flying carpet powerful enough to carry a person would need a wingspan of 50 metres - not the best vehicle to take on the streets just yet.

On the other hand, preliminary calculations suggest that there is enough atmosphere on the planet Mars to send floating rovers scudding over its dusty surface.

Meanwhile, Prof Mahadevan looks forward to sophisticated improvements in the near future, suggesting the approach could progress to "mimicking the beautiful two-dimensional undulations of the skate or manta ray".

Rocket launches Chinese space lab

The Tiangong-1 space lab was launched in the Gobi deserts

A rocket carrying China's first space laboratory, Tiangong-1, has launched from the north of the country.

The Long March vehicle lifted clear from the Jiuquan spaceport in the Gobi Desert at 21:16 local time (13:16 GMT).

The rocket's ascent took the lab out over the Pacific, and on a path to an orbit some 350km above the Earth.

The 10.5m-long, cylindrical module will be unmanned for the time being, but the country's astronauts, or yuhangyuans, are expected to visit it next year.

Tiangong means "heavenly palace" in Chinese.


The immediate plan is for the module to operate in an autonomous mode, monitored from the ground. Then, in a few weeks' time, China will launch another unmanned spacecraft, Shenzhou 8, and try to link the pair together.

This rendezvous and docking capability is a prerequisite if larger structures are ever to be assembled in orbit.

"Rendezvous and docking is a sophisticated technology," said Yang Hong, Tiangong-1's chief designer. "It's also essential to building China's own space station," he told the state broadcaster China Central Television.

China has promised to build this station at the end of the decade.

Assuming the Shenzhou 8 venture goes well, two manned missions (Shenzhou 9 and 10) should follow in 2012. The yuhangyuans - two or three at a time - are expected to live aboard the conjoined vehicles for up to two weeks.

Tiangong-1 will launch on the latest version of a Long March 2F rocket
The lab will go into a 350km-high orbit and will be unattended initially
An unmanned Shenzhou vehicle will later try to dock with Tiangong
The orbiting lab will test key technologies such as life-support systems
China's stated aim is to build a 60-tonne space station by about 2020
The Tiangong project is the second step in what Beijing authorities describe as a three-step strategy.

The first step was the development of the Shenzhou capsule system which has so far permitted six nationals to go into orbit since 2003; then the technologies needed for spacewalking and docking, now in progress; and finally construction of the space station.

At about 60 tonnes in mass, this future station would be considerably smaller than the 400-tonne international platform operated by the US, Russia, Europe, Canada and Japan, but its mere presence in the sky would nonetheless represent a remarkable achievement.

Concept drawings describe a core module weighing some 20-22 tonnes, flanked by two slightly smaller laboratory vessels.

Officials say it would be supplied by freighters in exactly the same way that robotic cargo ships keep the International Space Station (ISS) today stocked with fuel, food, water, air, and spare parts.

China is investing billions of dollars in its space programme. It has a strong space science effort under way, with two orbiting satellites having already been launched to the Moon. A third mission is expected to put a rover on the lunar surface. The Asian country is also deploying its own satellite-navigation system known as BeiDou, or Compass.

Bigger rockets are coming, too. The Long March 5 will be capable of putting more than 20 tonnes in a low-Earth orbit. This lifting muscle, again, will be necessary for the construction of a space station.

"There are loads of ideas floating around, and they're serious about implementing them," said UK space scientist John Zarnecki, who is a visiting professor at Beihang University, the new name for the Beijing University of Aeronautics and Astronautics.

"There's a sense of great optimism. It's not driven so much by science, but by the desire to develop new technologies. The money is there, although it's not limitless. And they're taking it step by step," he told BBC News.

Tiangong-1 has a two-year lifetime. It is likely to be followed by a second lab and possibly a third. China says that at the end of their missions, the modules will be driven into the atmosphere for a destructive descent into a remote part of the Pacific Ocean.

Frog killer immune genes revealed

The lowland leopard frog may have answered the question of why some die and others live

Scientists have taken a big step toward understanding why some frogs survive the fungal disease chytridiomycosis while others quickly die.

A group from Cornell University, US, identified genetic factors that seem to make some individual frogs immune.

This could improve captive breeding schemes, the team writes in Proceedings of the National Academy of Sciences.

Chytridiomycosis is slowly spreading across the world, and has already sent a number of species extinct.

Just two years ago, researchers discovered how it kills - by damaging the skin so that key nutrients cannot pass through, resulting eventually in cardiac arrest.

Frogs and other amphibians that have no resistance succumb quickly, with some populations being extirpated in just a few weeks.

Yet some populations and some entire species survive intact, which has long perplexed researchers; and salamanders and caecilians (limbless amphibians bearing a superficial resemblance to earthworms or snakes) appear more resistant as groups than frogs - another mystery.

Complex made simple
The Cornell group collected lowland leopard frogs (Lithobates yavapaiensis) from five places in Arizona.
In the lab, they infected the animals with the chytrid fungus (Batratochytrium dendrobatidis, or Bd).

All the frogs collected from three of the locations died; but from the other two locations, some survived, and fought off the infection completely within two weeks, remaining healthy.

The researchers traced the difference back to regions of DNA that form part of the immune system called the major histocompatibility complex (MHC).

Its role - in humans and other animals, just as in amphibians - is to "present" bits of invaders such as fungi or bacteria to other immune cells, identifying them as things that must be tackled.

"All amphibians (and for that matter, all vertebrate animals) have MHC genes that play the same 'gatekeeper' role in initiating immune responses," said lead researcher Anna Savage.
"So our finding that MHC genotypes contribute to chytridiomycosis outcomes has potential ramifications for all amphibian species currently threatened by Bd."

It appears likely that the two populations whose members survived infection in the lab are the ones that had been most strongly exposed to the fungus in the wild since it was detected in Arizona in the 1970s.

In this case, they probably carry the "resistant genes" because there has already been quite a lot of selection - only the strong have survived.

"It means frogs may have the evolutionary potential to adapt [to Bd]," Ms Savage told BBC News.

"Natural selection can only result in disease adaptation if genetic variation for that trait exists, and we have shown that it does."

The next step along this avenue of research is to find out whether the same thing provides immunity in other species - and whether it can
explain why entire species such as the infamous cane toad survive Bd.

Then, conservationists will have to work out how the information can be used.

Breeding success
Ms Savage suggests a role in captive breeding programmes - the last resort for species that cannot remain in their native habitat because it is infested with chytrid.
The idea would be to screen amphibians' MHC genes before breeding, to increase the odds of producing Bd-resistant tadpoles.

Prof Reid Harris, an amphibian specialist at James Madison University in Virginia who is trying to develop new treatments for chytrid, described the latest news as "very exciting".

"The study goes a long way toward understanding the genetic basis of resistance to the amphibian chytrid, and it opens up the possibility of selecting for resistance to the disease," he told BBC News.

"However, amphibian defences are multidimensional and include innate immune components and microbial defences.

"It is likely that a successful mitigation strategy will be multidimensional as well."

However, chytrid is only one of the many threats that amphibians face today.

The most profound is loss of habitat, as marshes are drained, forests cleared, and wild areas tamed for human use.

"Although our study provides a new hope that amphibians may bounce back from chytridiomycosis, it does not eliminate the need for human conservation efforts," Ms Savage stressed.

"Habitat loss, invasive species and habitat degradation are other major factors leading to amphibian declines; and if we can work to provide good habitats so that amphibian population sizes and genetic diversity can increase, they will be much more likely to have the genetic capacity to adapt to Bd."

Chytridiomycosis can kill amphibians in less than a week - depending on their genes

New study says birds learn how to build nests

Footage of southern masked weaver birds formed the basis of the study

A new study has found birds learn the art of nest-building, rather than it being just an instinctive skill.

Researchers from Edinburgh, Glasgow and St Andrews Universities studied film of southern masked weavers recorded by scientists in Botswana.

This colourful species was chosen because individual birds build many complex nests in a season.

Dr Patrick Walsh of Edinburgh University said the study revealed "a clear role for experience".

The research has been published in the Behavioural Processes journal.

Individual birds varied their technique from one nest to the next and there were instances of birds building nests from left to right as well as from right to left.
As birds gained more experience, they dropped blades of grass less often.

"If birds built their nests according to a genetic template, you would expect all birds to build their nests the same way each time. However this was not the case," added Dr Walsh.

"Southern Masked Weaver birds displayed strong variations in their approach, revealing a clear role for experience.

"Even for birds, practise makes perfect."

'Antimagnet' joins list of invisibility approaches

The design may lead to shields that protect pacemaker wearers during MRI scans


Researchers have designed a "cloak" that is invisible to magnetic fields both coming in and coming out.

The idea of blocking magnetic fields has been proposed before, but the new design, in the New Journal of Physics, could even hide magnetic materials.

It could thus find application in security or medical contexts, such as those surrounding MRI scans.

The approach uses superconductor layers and the "metamaterials" familiar from recent invisibility cloak research.

Metamaterials are artificially designed materials designed to guide electromagnetic waves - like light or magnetic fields - in a way that natural materials do not.

Much research in recent years has attempted to put metamaterials to work in Harry Potter-style invisibility cloaks that guide light waves around a cloak's wearer - although experiments have only demonstrated such effects on tiny items, or for a limited range of colours.

But because light and magnetism are two facets of the same physical force, many of the same principles apply for demonstrating a magnetic cloak, as the report's lead author Alvaro Sanchez explained.

"Magnetism has been very important in technology for the last 150 years," Prof Sanchez told BBC News. "We know very well how to create magnetic fields, but we don't know how to cancel them in a given space region."

Metal undetector
Prof Sir John Pendry, widely regarded as a founding theorist in the metamaterial field, demonstrated in a 2008 paper in Nature Materials that the ideas behind making objects invisible to light could be put to use hiding magnetic fields as well.

"We realised that these ideas were very interesting but a final device was not there - only the general concept," Prof Sanchez explained.

He and his colleagues at the Autonomous University of Barcelona in Spain thus set about coming up with a design for such an antimagnet.
Their idea is to use an inner cloak of superconducting material, surrounded by layers of metamaterials whose response to the magnetic field varies in a prescribed way through the thickness of the cloak.

Ortwin Hess, professor of metamaterials at Imperial College London, called the work "a refreshing extension" of the theoretical ideas laid out in previous work.

"Its emphasis lies on presenting a way how to make the scheme more practical by increasing its simplicity," he told BBC News, though both he and Prof Sanchez agree that some challenges remain in the production of the actual materials.

"What it offers in addition to the previous scheme is the fact that it also cancels, by adding a simple superconducting layer, possible magnetic fields that may be emitted from a magnet inside the magnetic cloak," he added, which means that such an antimagnet could hide any objects, even magnetic ones.
It may prove to be comparatively simple to use the same ideas to trick metal detectors
The team is now working to produce a working model of such an antimagnet, which Prof Sanchez said may eventually find application in allowing pacemaker or implant wearers to undergo MRI scans, or in a number of energy generation scenarios in which magnetic fields play a large part.

What is more, the idea could be put to use in hiding the "magnetic signatures" of submarines to evade detection or underwater mines, or even to trick metal detectors.

"We now know how to make an antimagnet that exactly cloaks a magnetic field - it's something difficult that can be done in some high-tech labs, but to reduce the magnetic signature of something that you want to pass through a metal detector such that it becomes undetectable is much less demanding," Prof Sanchez said.

"We have so much security based simply on metal detectors, based on magnetic signals, I think this is something officials may start thinking about."