Screaming with rage at your dying cell phone battery doesn't help much, but that could be about to change. Researchers have developed a postage stamp-sized microphone that can harvest acoustic energy to top up your charge on the go.
Zhong Wang of the Georgia Institute of Technology in Atlanta and his colleagues created their microphone from a thin sheet of paper just a few centimetres across. They used a laser to zap a grid of microscopic holes in the paper, then coated one side in copper and laid it on top of a thin sheet of Teflon, joining the two sheets at one edge.
Sound waves vibrate the two sheets in different ways, causing them to come in and out of contact. This generates an electric charge, similar to the one made when your rub a balloon on your hair, which can charge a phone slowly.
The paper microphone could also be used as a way to recycle sound energy from the environment, getting free electricity from the "waste" sounds all around us. The charge can also be converted into a range of sound frequencies, allowing the initial sounds to be amplified.
The amount of power the microphone provides depends on its size, but it's around 121 milliwatts per square metre. "It can be made into any size you like," says Wang, though he admits a stamp-sized microphone fitted to your phone would only provide a small amount of power rather than fully charging your phone.
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1. How quickly does eating too much cause new fat cells to form?
"Incredibly fast," says Matthew Rodeheffer, who studies obesity at Yale University, on the basis of recent research his team conducted on mice. After just five days on a high fat diet, new fat cells had appeared. In humans the process could be even faster, he says, potentially within a day. Once the cells are present, though, it takes them several weeks to actually fill up with fat.
But Giles Yeo at the University of Cambridge Metabolic Research Laboratories says having more fat cells isn't necessarily a bad thing. Being able to spread your fat over a larger number of cells means they are less likely to overfill, so you can store more fat while staying metabolically healthy. "Imagine each fat cell is like a balloon, but there is a safe limit to how much fat it ...
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Policy-makers the world over urgently need to address the growing divide between haves and have-nots. Science has much to tell them – if only they would listen
Bridging the money gap (Image: Lalo de Almeida/Contrasto/Eyevine)
WITH the UK general election campaign in full swing and candidates for the US presidency starting to declare themselves, it's becoming clear that one issue is central to debate on both sides of the Atlantic: inequality.
Not many politicos are talking about it directly. But the gulf between the haves and have-nots shows up in wrangling over everything from tax avoidance to benefit cuts, property ownership, corporate power and the erosion of the middle class.
The arguments tend to focus on economics and politics. But that overlooks the contribution that science can make. As we reported nearly three years ago, science has much to say about inequality's causes and effects, from patterns of income distribution to the health consequences of living in unequal societies (28 July 2012, p 37). But these insights have not made their way into mainstream political debate.
Now comes a further twist: a society's level of inequality appears to be driven by the kinds of energy at its disposal. Foraging societies tend to be very equal and agrarian ones very unequal; those powered by fossil fuels fall in between (see "Morality is rooted in the way societies get their energy").
This new way of looking at the problem is very broad-brush, and its implications are not yet clear. It could be used to defend the status quo: inequality in today's Western societies is actually quite low by historical standards. On the other hand, it is rising – and those historical standards are not necessarily desirable.
But the new analysis could be the start of a deeper debate that connects two of the key issues of our times. Just as with inequality, concern about our energy use is evident all over the political map, on issues ranging from defence to the environment.
The deep connection between the two has so far had little attention from academics, let alone politicians. Now that the fossil fuel economy is reaching the end of the road this needs to change. On both issues, science is speaking; politicians would do well to listen.
This article appeared in print under the headline "Bridging the divide"
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Robots armed with new radiation-sensing cameras are performing surveys in areas of the stricken plant where radiation levels are too high for humans to enter
IN THE dark abandoned shell of Fukushima Daiichi nuclear power plant, Rosemary and Sakura shoot what looks like a dystopian first-person shooter game. Rosemary scans her environment, while Sakura records every move.
But this is no traditional film crew. Rosemary and Sakura are robots operated by Tepco, the firm running the plant that went into meltdown following the March 2011 earthquake and tsunami. Using radiation-sensing cameras they perform surveys in areas where radiation levels are still too high for humans to safely enter. The data the robots collect will help plan how to decommission the plant.
Tepco has recently had problems with robots. On 10 April, it sent a robot inside the primary containment vessel of reactor 1 to measure radiation levels and investigate the condition of the melted fuel. But the robot stopped working on its first inspection and had to be abandoned. Radiation levels as high as 5150 millisieverts per hour have been detected in the basement of reactor 1.
Developed at the Chiba Institute of Technology, Rosemary and Sakura can climb 45 degree slopes and use gyroscopes and other sensors to navigate inside buildings without the need for GPS. But the standard radiation detector, gamma cameras weighing 150 kilograms, proved too cumbersome for them to use.
So the team has turned to a gamma camera that weighs just 17 kilograms and can rotate 360 degrees. This has been added to the robots as part of a system called N-Visage, which also includes a laser scanner that draws a 3D image of its environment.
The radiation measurements can be combined with a laser scan of the plant's exact layout, says Trevor Craig of UK start-up Createc, which developed N-Visage for Japan's International Research Institute for Nuclear Decommissioning, and reactor maker Hitachi. An earlier version was used in Sellafield in Cumbria.
Rosemary operates N-Visage, while Sakura acts as a wireless transmission station, feeding the data to human operators located in the plant's seismic-proof centre 200 metres away. They also get a fisheye view via cameras attached to the two robots.
In addition to creating real-time maps of radiation levels, the associated software can also predict how they will evolve as the facility is modified or taken apart. "Once we have a model like this we can play scenarios to find out what happens to dose rates if we decontaminate this wall, or put shielding next to highly contaminated fuel handling machinery," says Craig. "It helps work out what the decommissioning plan should be."
To date the N-Visage system has been used in the first three reactors at Fukushima. Createc is adapting the technology for use inside a snake-arm robot to delve even deeper into the reactors in an attempt to discover exactly where the fuel ended up.
This article appeared in print under the headline "Deep inside Fukushima"
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Mini drones with neural hardware that works like a brain could be in the skies within months – and carry out door-to-door deliveries or monitor crops
THAT drone buzzing round your head might be smarter than you think. Small drones with neural hardware resembling brains will soon share airspace with other aircraft, seeing and avoiding potential hazards autonomously. The ability will help drones take on a host of new roles.
Big firms like Amazon, DHL and Google are developing their own drone fleets for rapid delivery of consumer goods, fast food and pharmaceuticals. However, current rules restrict drones to flying within visual range of a human operator because of the risk of collision. Drones need an automatic "sense-and-avoid" capacity before they will be able to make deliveries on their own.
Computers capable of recognising objects in video and responding in real time are too big and too power-hungry for small drones. That means drones have to rely on short-range sensors like radar, which may not give enough warning to avoid a collision.
The key may be to mimic how animal brains work; our brains are poor at number-crunching but can process complex sensory input faster than digital systems.
Bio Inspired Technologies of Boise, Idaho, is doing just that. It is building a sense-and-avoid system using a memristor, a resistor with a memory. Like the synapse in a biological brain, the memristor changes when impulses pass through it. Crucially, it is able to remember the impulse after it has stopped.
This capability forms the basis of a learning system that mimics neurons and the connections between them. A chip-sized neural system linked to the drone's existing camera can be trained to recognise aircraft and other hazards at long range. Bio Inspired's drone should be ready for its first flight later this year.
The system can also recognise objects like clouds, birds, buildings and radio towers, and uses visual cues to estimate how far away the objects are.
"Objects like other aircraft can be catalogued in a vague sense, meaning 'I see an aircraft', or in an exact sense: 'I see another drone'," says Terry Gafron, CEO of Bio Inspired.
Equipped with this information, the drone plots a new flight path to avoid a hazard, updating it in real time as the threat moves.
"Nature seems to use this approach very effectively," says David Warne of Queensland University of Technology in Australia, who has worked with artificial neural networks that let drones recognise vegetation.
Like others in this area, much of Bio Inspired's research has been funded by the military. But it is likely that it will benefit the wider market. Sense-and-avoid will make it possible for fleets of small drones to criss-cross cities delivering packages. Like a bird or insect, a neural-enabled drone could fly to the trickiest landing place – even balconies.
Being able to recognise objects autonomously will enable a range of applications for small drones. Some of these are in the area of precision agriculture.
"The crop drone is on everyone's short list," says Gafron. Drones could survey a farm, recognise areas where crops aren't thriving and move in for a closer view to establish whether the field needs water, fertiliser or fungicide.
In the industrial field, neural drones could patrol pipelines looking for leaks, or identify electrical faults on power lines.
Closer to home, smart drones could clean windows, pick up litter, clear gutters or weed your garden, or send information to your car about which parking spaces are open. "It simply flies around town monitoring parking spaces," says Gafron.
Smart drones could even track animal populations, flying along livestock boundaries to track wolf populations for example. "Not only could the system fly autonomously, but it could conceivably tell the difference between a deer and a wolf from the air," Gafron says.
Memristor-inspired drones are not the only approach. Last year, US agency DARPA unveiled the TrueNorth neural chip developed in conjunction with IBM. This is a simulation of a neural network using digital hardware with enough neurons to match agile flyers like bees.
This article appeared in print under the headline "A drone that learns"
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GIVEN my predilection for peanut butter and ice cream, the offer of a scan to measure my body fat wouldn't normally fill me with excitement. But this is no ordinary fat map, and for once I'm hoping to have a lot of the stuff.
While normal white fat stubbornly stores excess calories on hips, bellies and thighs, over the last few years a picture has emerged of a different kind of fat – one which, paradoxically, might help us to lose weight. This is brown fat, which challenges all our assumptions about the fat in our bodies: it burns calories rather than storing them.
It was only six years ago we discovered that brown fat exists and is active in adults. Since then, it has become the focus of attention as a potential tool to help combat obesity and its related diseases. And the ...
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Does the sound of cracking knuckles make you flinch? What about a film of the joints in action? MRI scans have been used to capture the moment your joints go pop.
Gregory Kawchuk at the University of Alberta, Canada, and colleagues used a cable to slowly pull a man's fingers in an MRI scanner until the joints cracked. The sound was thought to come from the collapse of an air bubble, but in the scans the air cavity that formed in the fluid around the separating joints persisted after the noise.
A mysterious flash also appeared just before the crack. Kawchuk thinks it may be caused by cartilage releasing fluid as the tension on the joints rises.
"The scans don't allow us to explore the mechanism of sound production but like all sound, it has to come from a production of energy that causes vibrations to travel through the air," says Kawchuk. Higher resolution MRI scans might help solve the mystery, he says.
Knuckle cracking is thought to be harmless but the team want to image the parts of the joint not captured by their existing scans. This should enable them to find out where the air bubble ends up and investigate how the rest of the joint is affected by the cracking.
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Don't just flush it away. Just as one person's trash is another's treasure, hippo dung seems to be a valuable source of nutrition for the animals' aquatic neighbours.
By injecting millions of tons of faeces into African waters every year, hippos may be providing a vital link between terrestrial and aquatic ecosystems.
Douglas McCauley of the University of California in Santa Barbara and his colleagues compared fish and dragonfly larvae in two river pools in Kenya's Laikipia district, one inhabited by hippos (see picture above) and the other hippo-free.
They found components of hippo dung in the tissues of dragonfly larvae that lived alongside the animals year round. During the dry season, fish absorbed faecal nutrients as well, while levels in dragonfly larvae increased.
The team thinks that during the wet season, high rainfall dilutes the hippos' waste and faster-flowing rivers also wash away dung before animals can access it.
As climate change and development in east Africa continue to affect local rivers, it will be important to consider how the benefits of hippo excrement can be preserved.
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An exoskeleton that enables movement and provides tactile feedback has helped eight paralysed people regain sensation and move previously paralysed muscles
"I FELT the ball!" yelled Juliano Pinto as he kicked off the Football World Cup in Brazil last year. Pinto, aged 29 at the time, lost the use of his lower body after a car accident in 2006. "It was the most moving moment," says Miguel Nicolelis at Duke University in North Carolina, head of the Walk Again Project, which developed the thought-controlled exoskeleton that enabled Pinto to make his kick.
Since November 2013, Nicolelis and his team have been training Pinto and seven other people with similar injuries to use the exoskeleton – a robotic device that encases the limbs and converts brain signals into movement.
The device also feeds sensory information to its wearer, which seems to have partially reawakened their nervous system. When Nicolelis reassessed his volunteers after a year of training, he found that all eight people had regained sensations and the ability to move muscles in their once-paralysed limbs.
"Nobody expected it at all," says Nicolelis, who presented the results at the Brain Forum in Lausanne, Switzerland, on 31 March. "When we first saw the level of recovery, there was not a single person in the room with a dry eye."
When a person's spinal cord is injured, the connection between body and brain can be damaged, leaving them unable to feel or move parts of their body. If a few spinal nerves remain, people can sometimes regain control over their limbs, although this can involve years of rehabilitation.
The Walk Again Project's results suggest that rehabilitation with an exoskeleton might offer a better future. Developed by a team of 156 people spanning the globe, the device reads the wearer's brain activity using an electrode cap. Activity patterns associated with the wearer's intention to move are translated into an electrical signal that moves the legs of the exoskeleton, allowing the person to walk.
The exoskeleton has another important feature: it provides tactile feedback to the wearer. A flexible bed of temperature, pressure and proximity sensors – what the team calls an artificial skin – lines the sole of each foot. When the wearer takes a step, a signal is relayed to their forearm, which is still able to feel sensations. "You are driving the exoskeleton by thinking about what you want to do, and you are getting instantaneous feedback from the surface on how you're walking and how you're moving in space," says Nicolelis.
Seven of Nicolelis's eight volunteers have complete spinal cord injuries. At the start of the training, all eight said they felt disconnected from their lower body, and were unable to even imagine moving their paralysed body parts. But after 1100 hours of training, everyone said they felt a sense of ownership over their limbs. "They felt that they had legs again," says Nicolelis. "They can actually feel that they are touching the ground and moving their legs."
But what really startled the team was that everyone showed signs of functional recovery. "In every patient we saw an improvement in tactile sensation," says Nicolelis. Some people could feel regions of their body seven vertebrae below their spinal cord injury, and everyone could voluntarily move muscles in their lower limbs.
Reactivated nerves
The greatest improvement was in a woman who had received a complete spinal cord injury 13 years ago. After a year of training, she could feel sensations below her injury, and, when supported in a harness, could make leg movements associated with walking.
While the individuals are still some way from being able to support their own weight and walk unaided, their level of improvement is "dumbfounding", says Sukhvinder Kalsi-Ryan, a physiotherapist at the University Health Network in Toronto, Canada, who trials therapies for people with spinal cord injuries. "This is the most extreme recovery I've ever seen," says Kalsi-Ryan. "What Nicolelis has done is phenomenal – the patients are much closer to normal human movement." The results are more impressive because they were seen in all eight people, she adds.
"These are important observations," says Lee Miller, who is developing thought-controlled prostheses in monkeys at Northwestern University in Chicago. "But it's important to temper the excitement with the recognition that it will be a long road before patients could begin to think of being able to walk independently again."
No one is sure how tactile feedback is triggering recovery. "One of the most important factors in rehabilitation is mimicking normal stimulation," says Kalsi-Ryan. When nerves and other cells aren't used, they shrink and atrophy. "Things just stop working," she says. The feedback from the exoskeleton's artificial skin may trick nerve cells into reactivating and regrowing. "They have created the closest thing to a human experience," she says.
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THE image of a Stone-Age man grasping the bony end of a bloody mammoth leg and chomping down on it with powerful gnashers is taking a bit of a battering. We already know that Neanderthals were partial to delicacies such as fish and small birds, with a healthy helping of plants. Now some are saying they might have flavoured their meaty feasts with wild herbs, too.
Without a time machine to take us back 40,000 to 50,000 years, the suggestion remains highly speculative. But our long-lost cousins were clearly not the carnivorous beasts we once assumed them to be.
The idea that they were partial to a handful of herbs comes from the hardened plaque – or dental calculus – chipped off the teeth of a 50,000-year-old Neanderthal from El Sidrón in Spain. A few years ago, Karen Hardy of the University of Barcelona and colleagues found traces of camomile and yarrow in the calculus – both plants with strong flavours but no nutritional value (Naturwissenschaften, doi.org/h33). They argued that the plants were eaten for medicinal purposes. Self-medication is common in the animal world, says Hardy, and it's very likely Neanderthals did the same.
Sabrina Krief of the French natural history museum in Paris, thinks differently, based on her observations of wild chimpanzees in Kibale National Park in Uganda. After a hunt, these chimps can eat up to three different types of leaf with their prey (Antiquity, doi.org/3mk). Chimps are thought toself-medicate with leaves, but Krief says some scoff leaves to spice up their food. Her rationale is that all the chimps in a group ate them at the same time, and it's unlikely that every chimp needed the same remedy. Also, different chimp tribes opt for different leaves.
If chimps flavour their food, why not Neanderthals? The palaeontologists contacted by New Scientist say this is possible but highly theoretical. What is clear is that Neanderthals were not simple carnivores. All hominins must eat carbohydrates to survive, says Hardy. Meat just doesn't provide enough energy.
There's also a limit to the amount of animal protein we should have in our diet – too much meat is not good for us, says Hardy. So at the very least, we know that Neanderthals liked some veg with their steak – though what kind of veg is still up for debate. Remains at a site in Gibraltar suggest they also liked nuts and wild olives.
And they clearly liked a variety of meats. Geoff Smith of the Monrepos archaeological research centre in Germany says they were more likely to eat bovids, horses and deer than larger game – mammoth and rhino were occasional treats. Signs that they broke up the bones of their game suggest that they sucked out the rich, fatty marrow, says Smith, who presented evidence for this at the Paleoanthropology Society meeting in San Francisco this week.
And what of their cooking techniques? Some Neanderthal sites have hearths, and Hardy's study showed signs of smoke from a wood fire and desiccated starches. They were probably well versed in the art of roasting.
Perhaps Neanderthals even boiled their food, boiling bones to extract the juices and nutrients, a bit like making a stew. "They may have done," says Wil Roebroeks of Leiden University in the Netherlands."Who knows?" The trouble, says Hardy, is we've never found a Neanderthal pot.
This article appeared in print under the headline "Neanderthals may have used spices in their diet"
Palaeo toothpicks and grassy floss
CANDY floss it's not, but the Neanderthals' starchy, vegetable-rich diet was not quite what the palaeo dentist ordered. It came with a healthy helping of glucose – a fabulous source of energy to power both your brain and the bacteria that live in your mouth. Dental plaque has always been a nuisance for hominins, says Karen Hardy of the University of Barcelona in Spain.
That plaque is now allowing Hardy and other researchers to study the diets of early humans in some detail. What might Neanderthal dental hygiene have been like?
It turns out early humans were probably no strangers to the toothpick. Chimps, bonobos, orangutans, long-tailed macaques and Japanese macaques have all been seen using twigs for this purpose. And in 2013, a team wrote that grooves in the teeth of a 1.77 million year old hominin found in Georgia were probably made by a lifetime of wielding toothpicks (PNAS, doi.org/3mm).
Hardy says early humans are thought to have used bits of wood, bone, sinew and grass to pick and even floss between their teeth.
Their risk of tooth decay might also have been offset by a diet of wild plants. Farmed cereal grains tend to stick to the teeth more easily than wild foods, which can be very abrasive, says Amanda Henry of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. This suggests the palaeo diet came with its very own in-built toothbrush.
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Bridging the money gap (Image: Lalo de Almeida/Contrasto/Eyevine) 
(Image: Andre da Loba) 
(Image: Jen Guyton) 
