Fukushima fallout fears over Japan farms

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New research has found that radioactive material in parts of north-eastern Japan exceeds levels considered safe for farming.

The findings provide the first comprehensive estimates of contamination across Japan following the nuclear accident in 2011.

Food production is likely to be affected, the researchers say.

The results are reported in the Proceedings of National Academy of Sciences(PNAS) journal.

In the wake of the accident at Japan’s Fukushima nuclear power plant, radioactive isotopes were blown over Japan and its coastal waters.

Fears that agricultural land would be contaminated prompted research into whether Japanese vegetables and meat were safe to eat.

An early study suggested that harvests contained levels of radiation well under the safety limit for human consumption.

Contaminated crops

Now, an international team of researchers suggests this result deserves a second look.

To estimate contamination levels, Teppei Yasunari, from the Universities Space Research Association in the US state of Maryland, and his colleagues, took measurements of the radioactive element caesium-137 in soil and grass from all but one of Japan’s 47 regions and combined these results with simulations based on weather patterns following the meltdown.

Caesium-137 lingers in the environment for decades, and so is more of a concern than other radioactive elements released in the cloud of steam when the reactors’ cooling systems failed, leading to explosions.

The team found that the area of eastern Fukushima had levels of the radioactive element that exceeded official government limits for arable land.Under Japanese Food Sanitation Law, 5,000 becquerel per kg (Bq/kg) of caesium is considered the safe limit in soil (caesium-137 makes up about half of total radioactive caesium, and therefore its safe limit is 2,500 Bq/kg).

The researchers estimate that caesium-137 levels close to the nuclear plant were eight times the safety limit, while neighbouring regions were just under this cut off; the rest of Japan was well below (averaging about 25 Bq/kg) the safety limit.

Relatively low contamination levels in western Japan could be explained by mountain ranges sheltering those regions from the dispersal of radioactive material, the authors said.

Food production in the most contaminated regions, the researchers write, is likely to be “severely impaired”, and that Fukishima’s neighbouring regions, such as, Iwate, Miyagi, Yamagata, Niigata, Tochigi, Ibaraki, and Chiba are likely to also be affected.

“Some neighbouring prefectures… are partially close to the limit under our upper bound estimate and, therefore, local-scale exceedance is likely given the strong spatial variability of [caesium-137] deposition,” the researchers explained in PNAS.

They urge the Japanese government to carry out a more thorough assessment of radioactive contamination across Japan before considering future decontamination plans.

A second study, published in the same edition of PNAS, collected over a hundred soil samples from within 70km of the Fukishima plant, and found similarly high caesium-137 levels across the Fukishima prefecture, and its neighbouring regions.

Radioecologist Nick Beresford from Centre of Ecology and Hydrology in Lancaster explained that once in soil, caesium will become bound to mineral components, which limits its uptake into plants.

However, this process depends on the soil type. “Caesium stays mobile for longer in organic soils, hence why England and Wales still have some post-Chernobyl restrictions in upland areas,” he told BBC News.

Ploughing, and some fertilisers can help farmers reduce plants’ uptake of the dangerous elements, and binding agents can be added to animal feed to reduce their uptake from the gut, he added.

Local recordings

New figures on background radiation levels recorded 60km northwest of the Daiichi power plant have also been released this week by Japanese physicist Tsuneo Konayashi from Fukushima Medical University.

Dr Konayashi saw an initial spike reaching over nine times the usual levels hours after the explosions at the plant; five months later levels have dropped to one and a half times those expected.

He continues to monitor radiation levels and distribute his data around campus.

Becquerels and Sieverts

  • A becquerel (Bq), named after French physicist Henri Becquerel, is a measure of radioactivity
  • A quantity of radioactive material has an activity of 1Bq if one nucleus decays per second – and 1kBq if 1,000 nuclei decay per second
  • A sievert (Sv) is a measure of radiation absorbed by a person, named after Swedish medical physicist Rolf Sievert
  • A milli-sievert (mSv) is 1,000th of a Sievert

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Primates leapt to social living

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Scientists may be a step closer to understanding the origins of human social behaviour.

An analysis of over 200 primate species by a University of Oxford team suggests that our ancestors gave up their solitary existence when they shifted from being nocturnal creatures to those that are active during the day.

It is likely communal living was adopted to protect against day time predators, the researchers say.

The results are published in Nature.

From work on social insects and birds, some biologists have suggested that social groups begin to form when young do not leave their natal ground, but instead hang around and help raise their siblings.

Now, the latest evidence from primates suggests that this might not have been the case for our ancestors.

Leaping to sociality

By looking at whether closely related species share similar social structures, the Oxford team of evolutionary biologists shows that a common history is important in shaping the way animals behave in a group.

The team pinpointed the shift from non-social to social living to about 52 million years ago; a switch that appears to have happened in one step, and coincided with a move into daylight.

It did coincide with a change in family dynamics or female bonding, which emerged much later at about 16 million years ago.

“If you are a small animal active at night then your best strategy to avoid predation is to be difficult to detect,” explained Oxford’s Suzanne Shultz, who led the study.

“Once you switch to being active during the day, that strategy isn’t very effective, so an alternative strategy to reduce the risk of being eaten is to live in social groups,” she told BBC News.

Dr Shultz thinks that the move to day-time living in ancient primates allowed animals to find food more quickly, communicate better, and travel faster through the forest.

The link between sociality and a switch to daytime living might have been missed until now, she suspects, because biologists interested in this question have tended to work with Old World monkeys, like baboons, which are characterised by female bonded groups, which are not characteristic of many primate species.

Flexibly social

Human societies likely descended from similar large, loosely aggregated creatures, Dr Shultz explained, but the key difference, she pointed out, is that our closest cousins’ societies do not vary within a species, while humans’ do.

“In human societies we have polygyny… we have monogamy, and in some places we have females leaving the group they were born in, and in others males leave,” she said.

Why this difference exist is still unclear.

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Ancient horses’ spotted history reflected in cave art

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Scientists have found evidence that leopard-spotted horses roamed Europe 25,000 years ago alongside humans.

Until now, studies had only recovered the DNA of black and brown coloured coats from fossil specimens.

New genetic evidence suggests “dappled” horses depicted in European cave art were inspired by real life, and are less symbolic than previously thought.

The findings are published in the Proceedings of the National Academy of Sciences.

Horses, which were the most abundant large mammal roaming Eurasia 25,000 years ago, were a key component of early European diets.

So it is not surprising that the cave art of this time had a certain equestrian flair – horses make up 30% of the animals depicted in European cave paintings from this era.

Biologists, interested in the diversity of European animals before the last Ice Age, are interested in how accurately these early artistic impressions portrayed the colouring of the horses that lived alongside the ancient humans.

“It was critical to ensure that the horse depictions from the cave paintings were based on real-life experiences rather than products of the imagination,” explained lead author Arne Ludwig from The Leibniz Institute for Zoo and Wildlife Research in Berlin.

In previous work, Dr Ludwig, and his colleagues, recovered only the DNA of black and brown coat colours from the prehistoric horse bones.

But the dappled coats of the 25,000 year horses depicted at the Pech Merle cave complex in France convinced the team to take a second look.

Fur coats

By revisiting the fossil DNA of 31 horse specimens collected from across Europe, from Siberia to the Iberian Peninsula, the researchers found that six of the animals carried a mutation that causes modern horses to have white and black spots.

Of the remaining 25 specimens, 18 were brown coloured and six were black.

Dr Ludwig explained that all three of the horse colours – black, brown and spotted – depicted in the cave paintings have now been found to exist as real coat-colours in the ancient horse populations.

The researchers say that these three colours probably provided enough variation for humans to create the diversity of coat colours and patterns seen in modern horses.

The domestication of horses, which produced modern breeds, is thought to have begun about 4,600 years ago in the steppe between modern Ukraine and Kazakhstan.

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Pioneers boast high fertility, say scientists

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Scientists have shown that women who were first to settle in a new land had more children and grandchildren than those who followed.

Researchers analysed the family trees of French settlers who colonised Canada in the 17th and 18th centuries.

Their results could help to explain why some rare genetics diseases are common in communities established by migrations.

The findings have been published in the journal Science.

The team of researchers from Canada and Europe relied on data collected by the parish councils of Charlevoix and Saguenay Lac Saint-Jean, a region 170km north of Quebec, Canada.

The towns not only boast dairy farms, charming villages and sandy beaches but some of the best ever-kept marriage records – comprising more than a million people.

By building a picture of marriages and how many children the pairings produced, the researchers showed that woman who arrived as part of the first wave of immigration had 15% more children than those who arrived a generation later.

The pioneering woman married younger and benefited from scooping up the best local resources, they added.

But the study also found that the pioneering women’s children also had more children.

Lead author Laurent Excoffier, from the University of Bern in Switzerland, explained that the children of women at the front of the wave inherited their mother’s higher rate of fertility.

Yet, the researchers added, there was no such correlation between generations that arrived 30 years later behind the first wave.

Dr Excoffier drew parallels with cane toads. Scientists have observed that the toads at the edge of their range have bigger front legs and stronger back legs; all the better to invade new areas.

And when toads at the frontiers breed, their offspring inherit these longer, stronger limbs.

Such an effect is not unexpected, but until now no one has seen this phenomenon in humans.

“This was a rare chance to study a relatively recent human migration,” said co-author Damian Labuda, a geneticist from the University of Montreal, Canada.

Population geneticist Montgomery Slatkin from University of California, who was not involved in the work, called the study one of the “most interesting, detailed studies” he had seen.

“I think what happened [here] could easily have happened in other populations,” he added.

The findings suggest that families at the front of the wave of migration contributed more to the contemporary gene pool than those that were slower to arrive, explained Dr Labuda.

This could help explain why some rare genetic diseases are more common than expected in the Charlevoix and Saguenay Lac Saint-Jean regions.

That is because any disease causing mutations carried by people by the frontiers would be pass onto their descendents, who make up a large proportion of subsequent generations in the population.

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Icelandic rocks could have steered Vikings

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Vikings used rocks from Iceland to navigate the high seas, suggests a new study.

In Norse legends, sunstones are said to have guided seafarers to North America.

Now an international team of scientists report in the journal the Proceedings of the Royal Society Athat the Icelandic spars behave like mythical sunstones and polarise light.

By holding the stones aloft, voyaging Vikings could have used them to find the sun in the sky.

The Vikings were skilled navigators and travelled thousand of kilometres between Northern Europe and North America.

But without a magnetic compass, which was not invented until the 13th Century, they must have relied on other navigational aids.

Without the stars, which would have been out of sight during the constant daylight of the summer months, the sun would have been their best bet to set their course by.

But on cloudy or foggy days the seafarers would have been left with only the direction of the wind and swell to guide their way.

Through the fog

Norse legends tell of seafarers lifting stones to the sky to spy the direction of the sun when it was hidden by cloud cover.

Earlier this year, a study in the Philosophical Transactions of the Royal Society B reviewed the evidence that naturally forming crystals can selectively block light of one polarisation – how waves of light can be restricted to certain directions of oscillation.

The new result shows that Icelandic spars, which are formed from crystallised calcium carbonate, are good polarisers and could have been the raw material of the mythical sunstones.

The spars can be easily cleaved and crafted into a rhombus shape required for the polarising effect, and the discovery of one on the wreck of an Elizabethan ship that sunk in 1592 “looks very promising” the authors report.

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Rare white kiwi survives surgery

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The world’s only known white kiwi has survived surgery to remove stones from her gizzard, reports a New Zealand Wildlife Centre.

Over a week ago, rangers noted that Manukura, the six-month-old chick, was off her food.

X-rays revealed that two large stones were obstructing the chick’s guts.

In two separate operations, vets at Wellington Hospital in New Zealand used lasers to successfully break apart the rocks.

Pukaha Mount Bruce, New Zealand’s North Island wildlife centre, where Manukura lives, reported that the bird’s heart slowed suddenly during the surgery giving the operating team “a bit of a scare”.

But the little white bird pulled through and is recovering in isolation from other animals.

Kiwis, like other birds, swallow stones to help them digest their food. But Manukura, it seems, swallowed more than she could stomach.

Manukura, a North Island Brown Kiwi, is the 13th kiwi hatched in captivity at the centre this year.

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Dolphins ‘decompress like humans’

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Scientists have found tiny bubbles beneath the blubber of dolphins that have beached themselves.

The bubbles were discovered by taking ultrasound scans of the animals within minutes of stranding off Cape Cod, US.

The team’s findings help confirm what many researchers have long suspected: dolphins avoid the bends by taking long, shallow decompression dives after feeding at depth.

The study is reported in Proceedings of the Royal Society B.

Many biologists believe that marine mammals do not struggle, as human divers do, with decompression sickness – “the bends” – when ascending from great depths.

In humans, breathing air at the comparatively high pressures delivered by scuba equipment causes more nitrogen to be absorbed into the blood and the body’s tissues, and this nitrogen comes back out as divers ascend.

If divers ascend too quickly, the dissolved nitrogen forms bubbles in the body, causing decompression sickness.

But marine mammals such as whales, dolphins, and seals are highly adept at dealing with the pressures of the deep.

They slow their hearts, collapse the tiny air-filled chambers in their lungs, and channel blood to essential organs – like the brain – to conserve oxygen, and limit the build-up of nitrogen bubbles in the blood that happens at depth.

However, veterinary scientist Michael Moore from Woods Hole Oceanographic Institute in the US, thinks that it is “naive” to think that diving mammals do not also struggle with these laws of chemistry.

Even marine mammals ascending from the deep must rid themselves of the gas that has built up in their tissues, or risk developing the bends.

If dolphins, he explained, come up too quickly then there is evidence that they “grab another gulp of air and go back down again,” in much the same way a human diver would “re-tank and re-ascend” to try to prevent the bends.

“But there’s one place you can’t do that [if you are a dolphin] and that’s sitting on the beach,” Dr Moore told BBC News.

And so when he and his team scanned eight Atlantic white-sided dolphins and 14 short-beaked common stranded dolphins using ultrasound, they were not surprised to find tiny bubbles below the blubber of the animals.

Because three of the dolphins were scanned within minutes of their stranding, the team ruled out the possibility that the air pockets were a result of beaching, and instead think that they formed while the animals were still in the water.

Bends over

Sascha Hooker, a marine mammal ecologist with the Sea Mammal Research Unit in St Andrews, UK, commented: “This study is much less about why animals strand, and much more about using stranded animals to give us a bit more insight [into] what is going on inside live marine mammals.

“[What’s] particularly interesting from this is that the animals that were released… survived.

“So it looks like these animals are able to deal with some bubbles.”

She explained that studying the behaviour and physiology of diving animals is incredibly difficult because researchers cannot follow them down to the deep.

Stranded animals, therefore, offer researchers rare access to these expert divers to measure what changes they undergo to avoid the bends.

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Nobel win for crystal discovery

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The Nobel prize for chemistry has gone to a single researcher for his discovery of the structure of quasicrystals.

The new structural form was previously thought to be impossible and provoked controversy.

Daniel Shechtman, from Technion – Israel Institute of Technology in Haifa, will receive the entire 10m Swedish krona (£940,000) prize.

The Nobel prize in chemistry caps this year’s science awards.

Professor David Phillips, president of the Royal Society of Chemistry, called quasicrystals “quite beautiful”.

He added: “Quasicrystals are a fascinating aspect of chemical and material science – crystals that break all the rules of being a crystal at all.”

Dr Shechtman had to fight a fierce battle against established science to convince others of what he had first seen in his lab at the National Institute of Standards and Technology in Washington – formerly called the National Bureau of Standards – on an April morning in 1982.

For years, the researcher was “ridiculed” and “treated badly” by his peers, he recounts.

The Nobel laureate first created quasicrystals by rapidly cooling molten metals, such as aluminium and manganese, by squirting the mixture onto a cool surface.

By sending an electron wave through a molten metal “grate”, the Israeli researcher was able to see how the wave was diffracted by the metals’ atoms.

Under the microscope he observed that the new crystal was made up of perfectly ordered, but never repeating, units – a structure that is at odds with all other crystals that are regular and precisely repeating.

Dr Shechtman himself is said to have cried “Eyn chaya kazo”, which translates from the Hebrew as “there can be no such creature”.

Against the grain

“The head of my lab came to me smiling sheepishly, and put a book on my desk and said: ‘Danny, why don’t you read this and see that it is impossible what you are saying,'” Dr Shechtman recounted in an interview with Technion.

The Israeli researcher was later told that he was a disgrace to the group and asked to leave.

On returning to Israel, Dr Shechtman published the results.

“Then all hell broke loose,” he said.

Many scientists from around the world started telling him that they too had seen the same crystal structure.

Not everyone was convinced, however. To his dying day, Linus Pauling, the head of the American Chemical Society, said that Dr Shechtman was “talking nonsense”.

But Bassam Shakhashiri, president-elect of the American Chemical Society, told BBC News: “This is how we make progress in science.

“[If] someone comes up with a discovery that we are sceptical about…we [have to] take time to verify the observations and discuss the conclusions among ourselves.”

He added: “This is a really great example of the triumph of science.

“And an opportunity for all of us… who are curious about nature, to be vigilant, to be careful, and to engage in respectful debate about the interpretation of results.”

‘Quite beautiful’

Irregular shapes, similar to what Dr Shechtman was seeing, are found in the medieval Islamic mosaics of the Alhambra Palace in Spain. The tiles that line the walls and floors of the palace are regular, and follow mathematical rules, but also never repeat themselves.

Following Dr Shechtman’s discovery, scientists have formed other kinds of quasicrystals in the lab, and a naturally forming example has been found among mineral samples from a Russian river.

Quasicrystal structures tend to be hard, non-sticky and are poor conductors of heat and electricity. These properties make them useful as coatings for frying pans and as insulating material for electrical wires.

They are also found in the world’s most durable steel, used in razor blades and ultra-fine needles in eye surgery.

“It’s a great work of discovery, with potential applications that range from light-emitting diodes to improved diesel engines,” said the president of the American Chemical Society, Nancy Jackson.

Dr Andrew Goodwin, from the department of chemistry at Oxford University, added: “Shechtman’s quasicrystals are now widely used to improve the mechanical properties of engineering materials and are the basis of an entirely new branch of structural science.

“If there is one particular lesson we are taking from his research, it is not to underestimate the imagination of nature herself.”

The Nobel prizes have been given out annually since 1901, covering the fields of medicine, physics, chemistry, literature and peace.

Monday’s award of the 2011 prize for physiology or medicine went to Bruce Beutler of the US, Jules Hoffmann from France and Ralph Steinman from Canada for their work on immunology.

And Tuesday’s award for physics went to Saul Perlmutter and Adam Riess of the US and Brian Schmidt of Australia, who will divide the prize for their discovery that our Universe’s expansion is accelerating.

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Venus springs ozone layer surprise

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Scientists have discovered that Venus has an ozone layer.

The thin layer, hundreds of times less dense than the Earth’s, was discovered by the European Space Agency’s (Esa) Venus Express craft, researchers report in the journal Icarus.

Until now, ozone layers have only been detected in the atmospheres of Earth and Mars, and the discovery on Venus came as a surprise.

The find could help astronomers refine their hunt for life on other planets.

The European spacecraft spied the ozone layer when focusing on stars through Venus’ atmosphere.

The distant stars appeared fainter than expected, because the ozone layer absorbed some of their ultraviolet light.

The paper’s lead author Franck Montmessin, of the LATMOS atmospheric research centre in France, explained that Venus’ ozone layer sits 100km up; about three times the height of our own.

The ozone – a molecule containing three oxygen atoms – formed when sunlight broke down carbon dioxide in the Venusian atmosphere to form oxygen molecules.

On Earth, ozone, which absorbs much of the Sun’s harmful UV-rays preventing them reaching the surface, is formed in a similar way.

However, this process is supplemented by oxygen released by carbon dioxide-munching microbes.

Ozoning in

Speaking of the international team’s find, Hakan Svedhem, ESA project scientist for the Venus Express mission, said: “This ozone detection tells us a lot about the circulation and the chemistry of Venus’s atmosphere.

“Beyond that, it is yet more evidence of the fundamental similarity between the rocky planets, and shows the importance of studying Venus to understand them all.”

Some astrobiologists assume that the presence of oxygen, carbon, and ozone in an atmosphere indicates that life exists on a planet’s surface.

The new results negate that assumption – the mere presence of oxygen in an atmosphere is now not enough evidence to start looking for life.

However, the presence of large quantities of these gases, as in the Earth’s atmosphere, is probably still a good lead, the scientists said.

“We can use these new observations to test and refine the scenarios for the detection of life on other worlds,” said Dr Montmessin.

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