Herbal Viagra actually contains the real thing

IF IT looks too good to be true, it probably is. Several "herbal remedies" for erectile dysfunction sold online actually contain the active ingredient from Viagra.

Michael Lamb at Arcadia University in Glenside, Pennsylvania, and colleagues purchased 10 popular "natural" uplifting remedies on the internet and tested them for the presence of sildenafil, the active ingredient in Viagra. They found the compound, or a similar synthetic drug, in seven of the 10 products – cause for concern because it can be dangerous for people with some medical conditions.

Lamb's work was presented last week at the American Academy of Forensic Sciences meeting in Washington DC.

This article appeared in print under the headline "Herbal Viagra gets a synthetic boost"

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Space gold rush should not be a free-for-all

We need a consensus on regulations surrounding space mining if it’s to enrich us all

EVER since we took our first steps out of Africa, human exploration has been driven by the desire to secure resources. Now our attention is turning to space.

The motivation for deep-space travel is shifting from discovery to economics. The past year has seen a flurry of proposals aimed at bringing celestial riches down to Earth. No doubt this will make a few billionaires even wealthier, but we all stand to gain: the mineral bounty and spin-off technologies could enrich us all.

But before the miners start firing up their rockets, we should pause for thought. At first glance, space mining seems to sidestep most environmental concerns: there is (probably!) no life on asteroids, and thus no habitats to trash. But its consequences – both here on Earth and in space – merit careful consideration.

Part of this is about principles. Some will argue that space's "magnificent desolation" is not ours to despoil, just as they argue that our own planet's poles should remain pristine. Others will suggest that glutting ourselves on space's riches is not an acceptable alternative to developing more sustainable ways of earthly life.

History suggests that those will be hard lines to hold, and it may be difficult to persuade the public that such barren environments are worth preserving. After all, they exist in vast abundance, and even fewer people will experience them than have walked through Antarctica's icy landscapes.

There's also the emerging off-world economy to consider. The resources that are valuable in orbit and beyond may be very different to those we prize on Earth (see "Space miners hope to build first off-Earth economy"). Questions of their stewardship have barely been broached – and the relevant legal and regulatory framework is fragmentary, to put it mildly.

Space miners, like their earthly counterparts, are often reluctant to engage with such questions. One speaker at last week's space-mining forum in Sydney, Australia, concluded with a plea that regulation should be avoided. But miners have much to gain from a broad agreement on the for-profit exploitation of space. Without consensus, claims will be disputed, investments risky, and the gains made insecure. It is in all of our long-term interests to seek one out.

This article appeared in print under the headline "Taming the final frontier"

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Bacteria defeat antibiotics they have never met before

BACTERIA that resist antibiotics are a growing problem worldwide, but one we thought we could limit or even reverse by better control of the drugs. This may be a forlorn hope: some bacteria that have never seen an antibiotic can evolve resistance, and even thrive on it.

Bacteria usually become resistant if they are exposed to drug levels too low to kill them off, but high enough to favour the survival of resistant mutants. Such resistance is growing and could make TB and other diseases untreatable again.

The prevailing notion was that bacteria acquire and maintain resistance genes at a cost. So by carefully controlling antibiotics, resistance should not emerge by itself – and should die out as soon as the antibiotic is withdrawn and resistance is no longer an advantage.

Maybe not. Olivier Tenaillon at Denis Diderot University, Paris, and colleagues were studying bacterial evolution by exposing Escherichia coli to high temperatures and little food. Unexpectedly, some bacteria spontaneously became resistant to the antibiotic rifampicin, even though they had never encountered it. The mutation that helped them deal with environmental stress just happened to confer resistance to the drug, used to treat TB and meningitis (BMC Evolutionary Biology, doi.org/kks).

"Our work suggests that selective pressure other than antibiotics may drive resistance," says Tenaillon.

Moreover, bacteria with the mutation grew 20 per cent faster than otherwise-identical bacteria – a first for a resistance mutation.

It only had this beneficial effect in the heat-adapted strain, says Arjan de Visser of Wageningen University in the Netherlands, who was not involved in the study. But, he adds, "these results are a cautionary tale for the use of antibiotics – resistance may come without costs [to bacteria]".

This article appeared in print under the headline "Bacteria defeat antibiotics they have never met"

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We need a piece of Mars to continue search for life

THERE'S no need to cry over spilt chemicals. Thanks to an accident inside one of its instruments, NASA's Curiosity rover has detected the presence of a substance called perchlorate in Martian soil (see "Curiosity's spills add thrills to the Mars life hunt").

Not exactly earth-shattering, you might think. But it adds a new twist to the most controversial chapter in Martian history: did the Viking landers detect life?

This is a question that has divided the Viking missions' researchers for almost three decades. One group has resolutely stuck to its guns that the landers detected signs of life. Equally adamant is a second group who say they absolutely did not – a view that has always been the official version of events.

The unexpected discovery of perchlorate supplies a legitimate reason to reopen the debate. Perchlorate is an oxidising agent that destroys organic molecules. Its presence could finally explain the disputed results.

The episode highlights another important issue. Curiosity is a sophisticated machine, but there is only so much soil chemistry we can do from millions of kilometres away. A sample return mission must be a priority.

This article appeared in print under the headline "We need a piece of Mars"

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Happy, snappy tweets gain the most Twitter followers

Want to be popular on Twitter? There are plenty of people who claim they can help, but their tips rarely work and many of them are scammers. Now scientists have joined in, boiling down half a million tweets to a few simple rules for gaining a following.

C.J. Hutto (@cjhutto on Twitter) and colleagues at the Georgia Institute of Technology in Atlanta examined the content and retweeting fate of tweets sent by 500 non-celebrities over a 15-month period. They looked for 2800 terms that convey positive and negative emotions, including slang and swear words, a set of emoticons and common acronyms, like LOL.

By giving each term a score on a sliding scale of positivity they were able to assess whether Twitter users who used each term gained or lost followers. The keys to success, they found, were to tweet positive messages, write clearly and retweet interesting titbits of news.

People who tweeted mostly about themselves didn't fare so well. "Twitter is used quite heavily as a news medium," Hutto says. "My weak connections on Twitter care less about what I had for breakfast than they do about this neat bit of news I discovered."

Know your audience

Previous studies had suggested that following "important" people like celebrities and getting them to follow you back, alongside the frequency and timing of tweets were key factors in upping your number of followers. But the team's study suggests it's what's in your tweets, rather than who you follow, that has the biggest impact on the size of your Twitter audience.

How engaged people are with their followers also matters. "Twitter users who engage with their existing followers via mentions, replies and favouriting had positive follower growth, while users who mostly broadcast to no one in particular had dramatically suppressed growth rates," says Hutto.

Readability was also key. The team constructed a "Tweet Reading Difficulty Index" to measure how understandable the tweets were. Those whose tweets scored higher on the index had more followers.

"When deciding whether or not to follow a virtual stranger, we found Twitter users seek out well-written over poorly written content," says Hutto. "People rely on linguistic cues like spelling and vocabulary to compensate for the lack of traditional contextual cues available in face-to-face settings."

The researchers will present their findings at the Conference on Human Factors in Computing Systems in Paris, France, in April.

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Take my taxi to the moon

Susmita Mohanty, the founder of India’s first private space company, Earth2Orbit, wants India to claim bigger piece of the space-launch pie

How active is India's space programme?
The Indian Space Research Organization (ISRO), which was founded in 1969, launches rockets, builds and uses satellites extensively for earthly applications and has recently started planetary exploration. It tested its first astronaut capsule for atmospheric re-entry in 2007, and is planning to build a residential astronaut training facility. ISRO is also planning a lunar lander mission for 2014 and will launch a mission to Mars this year.

How does your company, Earth2Orbit, fit in with this programme?
We want to commercialise India's space capabilities, in particular the Polar Satellite Launch Vehicle. It is one of the world's most reliable in its class. I want to make it the rocket of choice for international satellite-makers looking to get to low Earth or sun-synchronous orbits. India could build and launch up to six each year, but currently launches only two. We need to step up to full throttle. The same goes for satellites and ground equipment. Over the next decade or two, I think India should be aiming for at least a quarter of the multibillion-dollar global space market, if not more.

What do you think of the way spacecraft for carrying humans are currently designed?
The way the world aerospace industry is set up, it is closely linked to the defence sector – they share the technology, the tooling and the cumbersome contractual processes. Unlike commercial automobile or consumer-product companies, where the end user is the primary design driver, aerospace companies tend to please government customers. As a result, we often end up with over-engineered, under-designed crew craft with an exorbitant price tag.

How can we improve on these designs?
I want us to push the boundaries of technology and design and build intelligent spaceships – spaceships that think. Imagine if an international consortium of companies such as Apple, Samsung, Pininfarina, Space X and MIT Media Lab got together to design and build a spaceship! What would it look like? Could it think? Could it self-repair or self-clean? Would it challenge the crew?

The private sector is changing how we get into space. How has the X Prize contributed?
It created a tectonic shift in mindsets and showed how we can accelerate innovation in space exploration without having to spend taxpayer money. The first X Prize led to the first privately funded and designed spaceplane built by Burt Rutan. Then Richard Branson seized the opportunity: if all goes well, Virgin Galactic could fly more people to space in a year than the Russians or Americans have over the past 50 years!

What is next for space travel?
It barely takes 10 minutes to reach low Earth orbit. It probably takes longer for most urbanites to commute to work. I want to be able to "cab it" to low Earth orbit. I am dreaming of private astronaut taxis. The first generation will take paying passengers into orbit. The second generation will ferry us to the moon and Mars.

This article appeared in print under the headline "One minute with... Susmita Mohanty"

Profile

Susmita Mohanty is CEO of Earth2Orbit, which recently launched its first client satellite. She has worked at NASA and Boeing, and holds a PhD in aerospace architecture

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New blood test finds elusive fetal gene problem

A NEW non-invasive blood test for pregnant women could make it easier to catch abnormalities before their child is born.

Human cells should have two copies of each chromosome but sometimes the division is uneven. Existing tests count the fragments of placental DNA in the mother's blood. If the fragments from one chromosome are unusually abundant, it might be because the fetus has an extra copy of that chromosome. But triploidy, where there are three copies of every chromosome, is missed, since the proportion of fragments from each chromosome is the same.

California-based company Natera uses an algorithm to calculate the most likely genotype for the fetus. To do this it looks at single letter variations called SNPs in the parents and compares this to a database of the most common SNPs patterns in the population. This genotype is then compared with placental DNA.

This approach can catch triploidy since the whole fetal genotype is the reference rather than a single chromosome. The method was presented last week at the Society for Maternal-Fetal Medicine in San Francisco.

This article appeared in print under the headline "No hiding place for fetal gene errors"

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Amazon to open market in second-hand MP3s and e-books

A new market for second-hand digital downloads could let us hold virtual yard sales of our ever-growing piles of intangible possessions

WHY buy second-hand? For physical goods, the appeal is in the price – you don't mind the creases in a book or rust spots on a car if it's a bargain. Although digital objects never lose their good-as-new lustre, their very nature means there is still uncertainty about whether we actually own them in the first place, making it tricky to set up a second-hand market. Now an Amazon patent for a system to support reselling digital purchases could change that.

Amazon's move comes after last year's European Union ruling that software vendors cannot stop customers from reselling their products. But without technical support, the ruling has had no impact. In Amazon's system, customers will keep their digital purchases – such as e-books or music – in a personal data store in the cloud that only they can access, allowing them to stream or download the content.

This part is like any cloud-based digital locker except that the customer can resell previous purchases by passing the access rights to another person. Once the transaction is complete, the seller will lose access to the content. Any system for reselling an e-book, for example, would have to ensure that it is not duplicated in the transaction. That means deleting any copies the seller may have lying around on hard drives, e-book readers, and other cloud services, since that would violate copyright.

Amazon may be the biggest company to consider a second-hand market, but it is not the first. ReDigi, based in Boston, has been running a resale market for digital goods since 2011. After downloading an app, users can buy a song on ReDigi for as little as 49 cents that would costs 99 cents new on iTunes.

When users want to sell an item, they upload it to ReDigi's servers via a mechanism that ensures no copy is made during the transfer. Software checks that the seller does not retain a copy. Once transferred, the item can be bought and downloaded by another customer. ReDigi is set to launch in Europe in a few months.

Digital items on ReDigi are cheaper because they are one-offs. If your hard drive crashes and you lose your iTunes collection you can download it again. But you can only download an item from ReDigi once – there is no other copy. That is the trade-off that makes a second-hand digital market work: the risk justifies the price. The idea has ruffled a few feathers – last year EMI sued ReDigi for infringement of copyright. A judge denied the claim, but the case continues.

Used digital goods can also come with added charm. ReDigi tracks the history of the items traded so when you buy something, you can see who has owned it and when. ReDigi's second-hand marketplace has grown into a social network. According to ReDigi founder John Ossenmacher, customers like seeing who has previously listened to a song. "It's got soul like an old guitar," he says. "We've introduced this whole feeling of connectedness."

It could be good for business too if the original vendors, such as iTunes, were to support resale and take a cut of the resell price. Nevertheless, Amazon's move bucks the industry trend. Microsoft's new Xbox, for example, is expected not to work with second-hand games.

But the market could change rapidly now that Amazon's weight is behind this, says Ossenmacher. "The industry is waking up."

This article appeared in print under the headline "Old MP3, one careful owner"

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Spidey-sense suit tingles when someone gets too close

FOR Peter Parker, it was a tingling sensation that alerted him to an imminent threat. Now anyone can pretend to be Spider-Man by simply donning a suit that lets you feel how close you are to a nearby object. It can even let the wearer navigate with their eyes closed.

The suit, called SpiderSense and built by Victor Mateevitsi of the University of Illinois in Chicago has small robotic arms packaged in modules with microphones that send out and pick up ultrasonic reflections from objects. When the ultrasound detects someone moving closer to the microphone, the arms respond by exerting a growing pressure on the body. Seven of these modules are distributed across the suit to give the wearer as near to 360 degree ultrasound coverage as possible.

"When someone is punching Spider-Man, he feels the sensation and can avoid it. Our suit is the same concept," says Mateevitsi. SpiderSense could help blind people to find their way more easily, he says.

Mateevitsi tested the suit out on students, getting them to stand outside on campus, blindfolded, and "feel" for approaching attackers. Each wearer had ninja cardboard throwing stars to use whenever they sensed someone approaching them. "Ninety five per cent of the time they were able to sense someone approaching and throw the star at them," says Mateevitsi.

"I'm very excited about this," says Gershon Dublon of the Massachusetts Institute of Technology, who also works on augmenting parts of the human body. Mateevitsi's work is a step on the road to giving humans truly integrated extrasensory perception, says Dublon.

Mateevitsi wants to use the suit, or just a few sensors on the arms and back, to boost cyclists' awareness of other traffic on the road. SpiderSense is due to be presented at the Augmented Human conference in Stuttgart, Germany, in March. The team now plans to add more sensors to the suit to increase its resolution.

"We humans have the senses that we are born with and we can't extend them," Mateevisti says. "But there are some threats which are very deadly, but we can't sense them, like radiation. Electronic sensors can feel those threats."

The team also plans to begin trials of SpiderSense with visually impaired people.

This article appeared in print under the headline "Back off, my Spidey senses tell me you're too close"

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3D-printed cyborg muscle produces artificial heartbeat

Sandrine Ceurstemont, editor, New Scientist TV

You might expect a robot's heartbeat to be a metallic ticking. But the pulsing in this video isn't completely artificial: it's powered by living material.

Created by Peter Walters from the University of the West of England in Bristol, UK, and colleagues, the pump uses the gas released by live yeast to generate pressure and distend a membrane, turning it into an artificial muscle. A valve - activated by electricity produced by a microbial fuel cell - controls the movement of the membrane. It opens to release pressure when the muscle is fully expanded, allowing it to shrink back to its resting state again to begin another cycle.

Walters says that using yeast allows a lot of pressure to be generated quickly. The downside is the pong: "With the live yeast, the laboratory smells like a brewery," he says. 

Getting rid of the waste that the yeast produces is also a challenge. The team is developing the system in conjunction with Ecobot, a robot that can digest food and sewage to power itself, which could potentially feed off the pump's waste.  A new version of the muscle will be able to pump liquid, circulating liquid food and water for Ecobot's microbial fuel cell, which could in turn power the muscle.

A 3D printer created the rigid components of the system as well as the moulds for the flexible silicone parts. This allowed the pieces to be fabricated easily, using liquid resin cured by ultraviolet light.

In the future, the robotic pulsing could be used in art and design. "It could serve as an artificial heartbeat for a cyborg-like machine," write the team.

If you enjoyed this post, watch an artificial heart that uses a shape-shifting ferrofluid to pump blood or see how to make your own drugs with a 3D printer.

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Today on New Scientist: 19 February 2013

Doctors would tax sugary drinks to combat obesity

Hiking the price of fizzy drinks would cut consumption and so help fight obesity, urges the British Academy of Medical Royal Colleges

Space station's dark matter hunter coy about findings

Researchers on the Alpha Magnetic Spectrometer, which sits above the International Space Station, have collected their first results - but won't reveal them for two weeks

Huge telescopes could spy alien oxygen

Hunting for oxygen in the atmospheres of distant exoplanets is a tough job, but a new wave of giant telescopes should be up to the task

Evolution's detectives: Closing in on missing links

Technology is taking the guesswork out of finding evolution's turning points, from the first fish with legs to our own recent forebears, says Jeff Hecht

Moody Mercury shows its hidden colours

False-colour pictures let us see the chemical and physical landscape of the normally beige planet closest to the sun

LHC shuts down to prepare for peak energy in 2015

Over the next two years, engineers will be giving the Large Hadron Collider the makeover it needs to reach its maximum design energy

Insert real news events into your mobile game

From meteor airbursts to footballing fracas, mobile games could soon be brimming with news events that lend them more currency

3D-printing pen turns doodles into sculptures

The 3Doodle, which launched on Kickstarter today, lets users draw 3D structures in the air which solidify almost instantly

We need to rethink how we name exoplanets

Fed up with dull names for exoplanets, Alan Stern and his company Uwingu have asked the public for help. Will it be so long 2M 0746+20b, hello Obama?

A shocking cure: Plug in for the ultimate recharge

An electrical cure for ageing attracted the ire of the medical establishment. But could the jazz-age inventor have stumbled upon a genuine therapy?

Biofuel rush is wiping out unique American grasslands

Planting more crops to meet the biofuel demand is destroying grasslands and pastures in the central US, threatening wildlife

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Insert real news events into your mobile game

Paul Marks, chief technology correspondent

(Image: MultiPlay.io)

Seen it in the news? Now play it: a mobile-game programming system allows 3D depictions of news events to be introduced into the action. It's been developed by MultiPlay.io, a British start-up that says the technology could make gameplay more current and provide new ways for designers and coders to make cash - perhaps selling "news injection" rights to news agencies, TV stations or newspapers.

The firm's HTML5 games creator, also called MultiPlay.io, lets users import 3D animations during gameplay, allowing, for instance, last week's meteor explosion over Russia to be pasted in above the game action, says one of the company's founders, Ashraf Samy Hegab. Similarly, he says, if a millionaire footballer hits the news in, say, a fight with a nightclub bouncer, lookalike avatars could engage in just such a fracas as you motor by in a driving game.

The system creates games for Apple iOS, Google Android and Windows Phone devices. Changes to games need to be made in a browser on a PC or Mac, but can be made in real time without you having to download an app update.

"We're using a clever way of splitting the game logic that lets you change the game on the fly, as easy as a drag-and-drop task in a browser," says Hegab. "You don't need to know anything about servers or 3D programming using our engine." The idea also lets you extend the game's virtual playing area by expanding the game map, or add 3D vehicles you've designed yourself, such as glitzy spacecraft or cars. You could even add a model of yourself.

But news injection is MultiPlay.io's main aim - and its founders are hoping to interest news agencies when Mobile World Congress kicks off in Barcelona, Spain, later this month. They are not alone: adding news to make games more relevant is becoming popular, with some websites beginning to offer games with news-related activities built in, such as the fascinating Game The News, which "creates its own twists on news events in a playable form".

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Nuclear waste: too hot to handle?

Cumbria's decision to veto an underground repository for the UK shows how hard it is to find a long-term solution

THERE are 437 nuclear power reactors in 31 countries around the world. The number of repositories for high-level radioactive waste? Zero. The typical lifespan of a nuclear power plant is 60 years. The waste from nuclear power is dangerous for up to one million years. Clearly, the waste problem is not going to go away any time soon.

In fact, it is going to get a lot worse. The World Nuclear Association says that http://www.world-nuclear.org/info/inf102.html 45 countries without nuclear power are giving it serious consideration. Several others, including China, South Korea and India, are planning to massively expand their existing programmes. Meanwhile, dealing with the waste from nuclear energy can be put off for another day, decade or century.

It's not that we haven't tried. By the 1970s, countries that produced nuclear power were promising that repositories would be built hundreds of metres underground to permanently isolate the waste. Small groups of technical experts and government officials laboured behind closed doors to identify potential sites. The results - produced with almost no public consultation - were disastrous.

In 1976, West German politicians unilaterally selected a site near the village of Gorleben on the East German border for a repository, fuelling a boisterous anti-nuclear movement that seems to have no end in sight.

In the UK, the practice of choosing candidate sites with little public input was lampooned as "decide, announce, defend". In the US, backroom political manoeuvring led to the 1987 selection of Yucca Mountain in Nevada, at the time an under-populated gambling Mecca with no political muscle. Nevadans have been fighting what they call the "Screw Nevada Bill" ever since. The Obama administration pulled funding from Yucca Mountain to appease Senate majority leader Harry Reid, who is from Nevada, but the decision is still being battled in the courts and Congress, and the site is not completely off the table.

It took a while, but governments began to catch on that the top-down approach wasn't working. Time for a new strategy: look for a community willing to host a repository, using lots of touchy-feely language such as consent-based, transparent, adaptive, phased and terminable. On paper, it is win-win. Sweden and Finland, those paragons of Nordic cooperation and efficiency, are now in the home stretch for opening the world's first nuclear waste repositories, and are held up as proof-positive that the new policy can work.

Yet finding a volunteer community is the relatively easy part, because nuclear waste repositories bring jobs and money. But this doesn't mean their neighbours, or the regional powers that be, are going to go along with it.

This unfortunate aspect of policymaking became readily apparent in the UK last month. Everything seemed a sure shot for taking the next exploratory steps toward a nuclear waste repository in west Cumbria. Located next door to Sellafield, the granddaddy of the UK's nuclear facilities, two local communities comfortable with nuclear matters were in favour. The bugles and bunting were practically being unfurled when Cumbria County Council, concerned about tourism in the Lake District and possible future leaks, vetoed the plan. No other volunteers are in line as a backup.

The US recently announced its own volunteer-based policy, including promises to have an interim storage site up and running within eight years and a repository by 2048. It should know better. Is it forgetting its own track record, even with interim storage facilities?

In the 1980s, the community of Oak Ridge, Tennessee, agreed to host an interim facility. Statewide opposition shut it down. In the 1990s, the Skull Valley Band Of The Goshute Nation, a recognised Native American sovereign nation, volunteered to host an interim facility on its reservation in Utah. Last December, after more than 15 years of legal sparring with the state, the utilities working with the Goshute finally gave up.

The most recent volunteer community to be snubbed is Nye County, where Yucca Mountain is situated. After a commission chartered by the Obama administration recommended a new "consent-based" approach to break the deadlock over the site, Nye County officials wrote to US energy secretary Steven Chu giving their consent to host the repository at Yucca Mountain. Nevada Governor Brian Sandoval subsequently informed Chu that the state of Nevada will never consent to a repository.

It's now over half a century since the dawn of nuclear energy and dangerous and long-lived waste continues to pile up all over the globe. Something needs to be done. Although touted as the solution, finding a consenting community is merely the first step. The harder part is getting everyone else to sign on.

And then comes the real challenge - to determine if the ground beneath a volunteer community is geologically suitable for a repository. This daunting endeavour requires a decades-long process that is both politically sensitive and technically complex. Inevitably, surprises occur as studies go underground. Here, the public needs an independent, technically savvy group whom they trust to address their concerns and interpret the scientific results.

The difficulties of finding a happily-ever-after triad of volunteer community, consenting neighbours and geologically suitable site cannot be lightly dismissed. Replacing a top-down approach with a consent-based one is a step in the right direction, but it doesn't fundamentally solve the problem.

This article appeared in print under the headline "Down in the dumps"

William M. Alley oversaw the US Geological Survey's Yucca Mountain project from 2002 to 2010

Rosemarie Alley and William M. Alley are authors of Too Hot To Touch: The problem of high-level nuclear waste (Cambridge University Press)

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False memories prime immune system for future attacks

IN A police line-up, a falsely remembered face is a big problem. But for the body's police force – the immune system – false memories could be a crucial weapon.

When a new bacterium or virus invades the body, the immune system mounts an attack by sending in white blood cells called T-cells that are tailored to the molecular structure of that invader. Defeating the infection can take several weeks. However, once victorious, some T-cells stick around, turning into memory cells that remember the invader, reducing the time taken to kill it the next time it turns up.

Conventional thinking has it that memory cells for a particular microbe only form in response to an infection. "The dogma is that you need to be exposed," says Mark Davis of Stanford University in California, but now he and his colleagues have shown that this is not always the case.

The team took 26 samples from the Stanford Blood Center. All 26 people had been screened for diseases and had never been infected with HIV, herpes simplex virus or cytomegalovirus. Despite this, Davis's team found that all the samples contained T-cells tailored to these viruses, and an average of 50 per cent of these cells were memory cells.

The idea that T-cells don't need to be exposed to the pathogen "is paradigm shifting," says Philip Ashton-Rickardt of Imperial College London, who was not involved in the study. "Not only do they have capacity to remember, they seem to have seen a virus when they haven't."

So how are these false memories created? To a T-cell, each virus is "just a collection of peptides", says Davis. And so different microbes could have structures that are similar enough to confuse the T-cells.

To test this idea, the researchers vaccinated two people with an H1N1 strain of influenza and found that this also stimulated the T-cells to react to two bacteria with a similar peptide structure. Exposing the samples from the blood bank to peptide sequences from certain gut and soil bacteria and a species of ocean algae resulted in an immune response to HIV (Immunology, doi.org/kgg).

The finding could explain why vaccinating children against measles seems to improve mortality rates from other diseases. It also raises the possibility of creating a database of cross-reactive microbes to find new vaccination strategies. "We need to start exploring case by case," says Davis.

"You could find innocuous pathogens that are good at vaccinating against nasty ones," says Ashton-Rickardt. The idea of cross-reactivity is as old as immunology, he says. But he is excited about the potential for finding unexpected correlations. "Who could have predicted that HIV was related to an ocean algae?" he says. "No one's going to make that up!"

This article appeared in print under the headline "False memories prime our defences"

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False memories prime immune system for future attacks

IN A police line-up, a falsely remembered face is a big problem. But for the body's police force – the immune system – false memories could be a crucial weapon.

When a new bacterium or virus invades the body, the immune system mounts an attack by sending in white blood cells called T-cells that are tailored to the molecular structure of that invader. Defeating the infection can take several weeks. However, once victorious, some T-cells stick around, turning into memory cells that remember the invader, reducing the time taken to kill it the next time it turns up.

Conventional thinking has it that memory cells for a particular microbe only form in response to an infection. "The dogma is that you need to be exposed," says Mark Davis of Stanford University in California, but now he and his colleagues have shown that this is not always the case.

The team took 26 samples from the Stanford Blood Center. All 26 people had been screened for diseases and had never been infected with HIV, herpes simplex virus or cytomegalovirus. Despite this, Davis's team found that all the samples contained T-cells tailored to these viruses, and an average of 50 per cent of these cells were memory cells.

The idea that T-cells don't need to be exposed to the pathogen "is paradigm shifting," says Philip Ashton-Rickardt of Imperial College London, who was not involved in the study. "Not only do they have capacity to remember, they seem to have seen a virus when they haven't."

So how are these false memories created? To a T-cell, each virus is "just a collection of peptides", says Davis. And so different microbes could have structures that are similar enough to confuse the T-cells.

To test this idea, the researchers vaccinated two people with an H1N1 strain of influenza and found that this also stimulated the T-cells to react to two bacteria with a similar peptide structure. Exposing the samples from the blood bank to peptide sequences from certain gut and soil bacteria and a species of ocean algae resulted in an immune response to HIV (Immunology, doi.org/kgg).

The finding could explain why vaccinating children against measles seems to improve mortality rates from other diseases. It also raises the possibility of creating a database of cross-reactive microbes to find new vaccination strategies. "We need to start exploring case by case," says Davis.

"You could find innocuous pathogens that are good at vaccinating against nasty ones," says Ashton-Rickardt. The idea of cross-reactivity is as old as immunology, he says. But he is excited about the potential for finding unexpected correlations. "Who could have predicted that HIV was related to an ocean algae?" he says. "No one's going to make that up!"

This article appeared in print under the headline "False memories prime our defences"

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Comet rain took life's ingredients to Jupiter's moons

Dust made from pulverised comets may have seeded Jupiter's moons with the raw ingredients for life. That includes Europa, which is thought to harbour a liquid ocean beneath its icy crust.

Jupiter has two kinds of natural satellites: large spherical moons and smaller lumpy bodies that follow elongated orbits. Chemical analysis of the irregular bodies suggests they are made of the same stuff as asteroids and comets. This means they are probably rich in the carbon-containing compounds that are key to life on Earth.

It is thought that a gravitational reshuffling of the planets some 4 billion years ago shook up distant belts of space rocks and sent many of them hurtling towards the sun. Some got caught in Jupiter's orbit and became the irregular satellites. The objects frequently collided as they settled into their new orbits, creating dust as fine as coffee grounds.

Blanketed moons

Models say that Jupiter should have captured about 70 million gigatonnes of rocky material, but less than half that amount remains as irregular moons. "So what happened to all the stuff?" asks William Bottke of the Southwest Research Institute in Boulder, Colorado.

His team ran simulations of the irregular moons' evolution and found that their ground-up material would have fallen towards Jupiter, dragged by gravity and blown by the solar wind. About 40 per cent of it would have hit Jupiter's four largest moons. Most of this landed on Callisto (Icarus, doi.org/kff). The rest hit Ganymede and then Europa.

That's roughly consistent with images from the Galileo spacecraft, which show dark material on Ganymede and Callisto. "Callisto literally looks like it's buried in dark debris," says Bottke, while Ganymede has a lot of similarities but less dark stuff on its surface.

Sinking carbon

But the surface of Europa is relatively clean. Cracks cover the moon's crust, which suggests it has cycled material from deeper inside, so the carbon-rich debris may have been incorporated into the ice and even made it into the ocean, says Bottke. "Would it be important in Europa's ocean? It's hard to say," he says. "But it is kind of interesting to think about."

Bottke's calculations only set a lower limit on the amount of carbon-rich material that could have ended up in Europa's ocean, says Cynthia Phillips of the SETI Institute in Mountain View, California, who studies Europa.

"This could potentially be an even larger source of astrobiologically interesting material for the ocean layer than the authors of this paper estimate," she says.

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Mosh pit physics could aid disaster planning

Metalheads in mosh pits act like atoms in a gas. That's the conclusion of the first study of the collective motion of people at a rock concert.

The finding could add to the realism of computer-generated crowd scenes in films and games.; More importantly, it could help architects design buildings that ease the flow of chaotic crowds in an emergency.

Research into how humans behave in crowds had mostly been limited to fairly organised situations, like pedestrians forming lanes when walking on the street. But when Jesse Silverberg, a graduate student at Cornell University in Ithaca, New York, took his girlfriend to her first heavy metal concert a few years ago, he witnessed a different and surprising form of crowd behaviour.

"I didn't want to put her in harm's way, so we stood off to the side," he says. "I'm usually in the mosh pit, but for the first time I was off to the side and watching. I was amazed at what I saw."

Metal fans' favoured dance style is called moshing and mostly involves bodies slamming into each other. Silverberg wondered if the mathematical laws that describe group behaviour in flocks of birds or schools of fish could apply to moshers as well.

Like a random gas

Together with another grad student and two physics professors at Cornell, he pulled videos of mosh pits off YouTube and used software developed for analysing particles in a fluid to track the moshers' motions. They found that the dancers' speeds had the same statistical distribution as the speeds of particles in a gas. Such particles move around freely, interacting only when they bounce off one another.

"This presented a bit of a mystery," Silverberg says. What makes a crowd of people with independent decision-making powers behave like a random gas?

To investigate, the team simulated a mosh pit with a few basic rules: the virtual moshers bounce off each other when they collide (instead of sticking or sliding through each other); they can move independently; and they can flock, or follow each other, to varying degrees. Finally, the team added a certain amount of statistical noise to the simulated moshers' movements – "to mimic the effects of the inebriants that the participants typically use", says co-author Matthew Bierbaum.

They found that by tweaking their model parameters – decreasing noise or increasing the tendency to flock, for instance – they could make the pit shift between the random-gas-like moshing and a circular vortex called a circle pit, which is exactly what they saw in the YouTube videos of real mosh pits. Their simulation is available online.

"These are collective behaviours that you wouldn't have predicted based on the previous literature on collective motion in humans," Silverberg says. "That work was geared at pedestrians, but what we're seeing is fundamentally different."

"The fact that human beings are very complex creatures, and yet we can develop a lifeless computer simulation that mimics their behaviour, really tells us that we're understanding something new about the behaviour of crowds that we didn't understand before," says co-author James Sethna.

Lane formation

The team also found a third mosh-pit mode that they hadn't seen on YouTube, which they call lane formation. "If you increase the flocking or decrease the density of the simulated moshers, the active participants can break down the circle and just stream through the crowd," Bierbaum says. "I'd be excited to see this, but it would have to be at a very large venue, so that the ends didn't collide with each other to form a circle pit."

Although the project was mostly for fun, the researchers think it could have real-world implications for crowd animators and architects.

"When you have earthquakes or buildings on fire, people tend to panic when they escape. We don't have a good way of experimentally seeing what's going on," Silverberg says. "By going to these heavy-metal concerts, we're able to ethically and safely observe how humans behave in these unusual excited states."

"That's how we justify it after the fact, by talking about safety," Sethna adds.

The correlation between moshers and random gases "seems very fitting to me", says Jon Freund, drummer in Ithaca-based metal band Thirteen South. "It's kind of the same thing – a pure expression of energy that's just random."

But he says knowing the physics behind it won't change how he moshes – mostly because these days he stays out of the pit. "I'm a hide-on-the-stage-and-play-my-drums mosher," he admits. "I don't want to get hit in the head."

Silverberg notes that the study's main limitation was the quality of the data. "YouTube videos are typically shaky and taken from a poor viewing angle," he says. What's more, staff at venues "tend to baulk when you walk in with a camera". He hopes to convince at least one venue to let him film with a camera suspended over the crowd. "There really is so much to do and so much we don't know yet. It's really just beginning."

Journal reference: arxiv.org/abs/1302.1886

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Night-vision rat becomes first animal with sixth sense

Douglas Heaven, reporter

The latest bionic superhero is a rat: its brain hooked up to an infrared detector, it's become the first animal to be given a sixth sense.

Developed by Miguel Nicolelis and colleagues at Duke University in Durham, North Carolina, the system connects a head-mounted sensor to a brain region that normally processes touch sensations from whiskers. As shown in this video, the rat's brain is tricked when infrared light is detected, giving it a new sense organ. "Instead of seeing, the rats learned how to touch the light," says Nicolelis.

Even though the touch-processing brain area acquires a new role, the team found that it continues to process touch sensations from whiskers, somehow dividing its time between both types of signal. "The adult brain is a lot more plastic than we thought," says Nicolelis.

The finding could lead to new brain prostheses that restore sight in humans with a damaged visual cortex. By bypassing the damaged part of the brain altogether, it might be possible to wire up a video camera to a part of the brain that processes touch, letting people "touch" what the camera sees.

According to Nicolelis, it could also lead to superhero powers for humans. "It could be X-rays, radio waves, anything," he says. "Superman probably had a prosthetic device that nobody knew of."

If you enjoyed this post,watch a robot and human swap brains to learn teamwork or see a body-sharing robot that lets you experience another place.

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Algorithm learns how to revive lost languages

Like living things, languages evolve. Words mutate, sounds shift, and new tongues arise from old.

Charting this landscape is usually done through manual research. But now a computer has been taught to reconstruct lost languages using the sounds uttered by those who speak their modern successors.

Alexandre Bouchard-Côté at the University of British Columbia in Vancouver, Canada, and colleagues have developed a machine-learning algorithm that uses rules about how the sounds of words can vary to infer the most likely phonetic changes behind a language's divergence.

For example, in a recent change known as the Canadian Shift, many Canadians now say "aboot" instead of "about". "It happens in all words with a similar sound," says Bouchard-Côté.

The team applied the technique to thousands of word pairings used across 637 Austronesian languages – the family that includes Fijian, Hawaiian and Tongan.

Tracking human history

The system was able to suggest how ancestor languages might have sounded and also identify which sounds were most likely to change. When the team compared the results with work done by human specialists, they found that over 85 per cent of suggestions were within a single character of the actual words.

For example, the modern word for "wind" in Fijiian is cagi . Using this and the same word in other modern Austronesian languages, the automatic system reconstructed the ancestor word beliu and the human experts reconstructed bali.

Reconstructing ancient languages can reveal details of our ancient history. Looking at when the word for "wheel" diverges in the family tree of European languages helps us date the human settlement of different parts of the continent, for instance.

The technique could improve machine translation of phonetically similar languages, such as Portuguese and French.

Endangered languages could also be preserved if they are phonetically related to more widely spoken tongues, says Bouchard-Côté. He is now working on an online version of the tool for linguists to use.

Journal: PNAS, 10.1073/pnas.1204678110

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