22 November 2014 | NewScientist | 25

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Climb walls like Spider-Man Who needs stairs? Regular humans can now scale vertical walls. Elliot Hawkes and his team at Stanford University, California, used a plastic called PDMS that forms large sheets  covered in fibres that work just like the hairs on geckos’ feet. These hairs produce intermolecular van der Waals forces, letting them stick to surfaces (Journal of the Royal Society Interface, DOI: 10.1098/rsif.2014.0675). Attached to handheld pads, the plastic lets human climbers shimmy up a vertical glass wall.

“the technology is moving faster than the international response”

Mary Wareham at Human Rights Watch on the danger of killer robots. On 14 November, 118 nations agreed to discuss the issue further at a UN meeting next April

Great wall of humanity goes on holidayThe greatest human migration on Earth isn’t the hajj – it is people in urban China going home for Chinese New Year. This year, the country’s internet giant Baidu gathered location data from more than 200 million smartphones as  their owners made journeys. Extrapolating from this, they estimate that 3.6 billion trips were made during the 34-day festival season. City dwellers accounted for most of the journeys, heading for the country and then returning, mainly to Beijing, Shanghai and bustling Guangdong province (arxiv.org/abs/1411.0983).

Film a finger, find your blood pressureSmartphones can peek inside your body. Researchers at India’s Tata Consultancy Services built a system that measures blood pressure from a close-up video of a fingertip, taken on a smartphone. Software counts the total number of red pixels in each frame, and how each pixel changes over time. It uses those numbers as a proxy for the rate of blood flow and pressure. The device can measure blood pressure to within 10 per cent of the accuracy of a clinical cuff.

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–It’s getting crowded round here–

THE tigers in India’s Panna National Park will soon live in a forest that watches out for them. A wireless network of low-power radars is being developed to track everything that moves in or out of the forest. This helps keep the tigers safe from poachers, and villagers’ cattle safe from the big cats.

Built by Anish Arora at Ohio State University in Columbus, the work was originally designed as a way for the US government to monitor the flow of people across the country’s borders. Had the US border patrol not opted to build a 1100-kilometre-long fence instead, the system could have alerted officers to people trying to cross the border with Mexico anywhere other than at official points.

Arora’s system is the first wildlife-tracking technology that detects and reports on a specific animal in real time. It works by looking for the patterns created as radar reflects off different objects, and then comparing these to recorded signatures. When the system spots a human entering the tiger’s reserve, or a tiger leaving, it alerts the wardens.

“It is as simple as that. The alarm goes off and poachers get caught,” says Arora. Or guards posted inside the 400-square-kilometre park can move to cut off a tiger that is advancing towards a farm. When the

system is fully up and running, Arora says, it will cover all the most tiger-trafficked parts of the forest.

It’s not the only technology on the lookout in Panna. P. Vijay Kumar of the Indian Institute of Science in Bangalore is working on an infrared system that ignores swaying trees and shrubs, and sounds the alarm only when it detects an intruder. M. Radhakrishna at the Indian Institute of Information Technology in Allahabad is burying fibre-optic cables that detect slight changes of pressure at the surface.

The step of a human or tiger makes the fibre bend slightly, changing the way light moves through it.

When it comes to imaging, Arora’s radar system has a big advantage over cameras. Gathering and processing radar data takes less computer power than visual images do, allowing the network to keep running day and night for long periods of time. “It can survive on very little power, a couple of AA batteries,” Arora says. He plans to put an updated version of the network live for several months starting in December (SenSys 2014, doi.org/w5b). hal hodson n

radar network makes tigers good neighbours

“ When the system spots a human entering the tiger’s reserve, or a tiger leaving, it alerts the wardens”

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