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Stimulating Damaged Spines Rewires Rats for Recovery

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A promising new study shows that the nervous system can rewire itself—with a little help from neural engineers. 

For someone with a spinal cord injury, destroyed neurons act like a roadblock that prevents movement commands from traveling down the spinal cord and along the nerves. Although an injured person wills his fingers to grasp a cup, for example, the command never makes it to his hand.

But a study published today suggests that precisely controlled electrical stimulation can encourage the nervous system to create detours around that roadblock, allowing the command to get through. 

Neuroscientist Steve Perlmutter and his colleagues at the University of Washington devised a clever experiment using rats. The animals were first trained to perform a task in which they reached through narrow slots with their dominant forelimbs to grab food pellets. The rats were then given incomplete spinal cord injuries that almost totally paralyzed those limbs.

Next the rats were divided into three groups and, as if they were in physical therapy, trained again on the same task. The control group tried to perform the reach-and-grasp task unaided, the second group received random pulses of electrical stimulation in their spinal cords during the task, and the third group received stimulation pulses that were triggered by the rats’ attempts to move their immobilized limbs. 

Image: Perlmutter et al.
The head-mounted neurochip device recorded electrical signals from the muscles (called electromyographic or EMG activity) and triggered pulses of intraspinal microstimulation (ISMS).

The key advance here is that triggering technique. The researchers used a device called the neurochip-2, which recorded the weak electrical signal from the limb muscles and used that signal as the cue to initiate a pulse of electrical stimulation in the spinal cord. When the attempted muscle movement was synchronized with neural stimulation, the researchers believe that surviving neurons in the spinal cord formed new connections linking the muscles to the brain’s motor control region.  

What’s the underlying mechanism behind this remarkable repair work? I have just one word for you: neuroplasticity. Neural networks are malleable, and changing the patterns of connections between neurons can restore lost function. That’s why people who’ve suffered spinal cord injuries do rehab: They’re not trying to bring dead neurons back to life, but rather to teach the nervous system to work around them. However, people typically don’t recover much function with rehab alone. 

Perlmutter’s research suggests that adding electrical stimulation to rehab could provide a real boost. Over the course of the three-month study, the rats with neurochips showed dramatic improvement. The synchronized-stimulation rats ultimately performed the task 63 percent as well as they had before their injuries. Both the control group and the random-stimulation group performed about 30 percent as well as they did pre-injury.

Spectrum has covered “closed-loop” neurostimulation systems before, most notably in this feature article written by researchers from the companies Medronic, Cyberonics, and Neuropace. The authors described systems that used various bodily signals to trigger electrical pulses that countered epilepsy attacks and chronic pain. Such smart and responsive systems, which are now being used in humans, seem a clear step forward in electrical therapeutics

While the study from Perlmutter and his colleagues was conducted in rats, it points the way toward a new rehab strategy for people with spinal cord injuries. What’s more, it serves as a proof of principle for a strategy that may help people with other nervous system dysfunctions. By leveraging “the nervous system’s intrinsic capacity for reorganization and repair,” the authors write, electrical stimulation could help people regain lost motor abilities, perhaps, or bladder, bowel, or sexual function. 

"Tardis" Memory Could Enable Huge Multi-Core Computer Chips

Future generations of computer chips could become much more powerful, with processors containing hundreds or even thousands of cores. But these huge multi-core processors will also require loads of memory so their directories can keep track of data on each individual core and coordinate updates to shared data. A new MIT technique promises to greatly reduce the required memory for such coordination as multi-core processors scale up in the coming years.

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Mosquitos Have Brought a Nasty New Disease to the Americas. Can Computer Models Predict Its Spread?

So far in 2015, more than 565,000 people in the Americas and the Caribbean have come down with chikungunya, a viral disease spread by mosquitoes, according to estimates from the Pan American Health Organization. That’s pretty impressive work for a virus that made its first appearance in the western hemisphere in December 2013. 

Public health officials throughout the Americas have been scrambling to contain this unprecedented outbreak of chikungunya. To do so, it would certainly be helpful to be able to predict when and where the next hotspots will occur. But right now, public health officials simply don’t have the necessary tools, DARPA program manager Matthew Hepburn tells IEEE Spectrum

If we ask decision makers, whether they’re in the United States, or the ministry of health in one of these other countries, or the Pan American Health Organization, ‘What models or forecasts are you using today to make predictions?’ The answer is, ‘We’re not using any,’ ” Hepburn says.  

DARPA sought to correct this situation last year by issuing a challenge to computer modelers, asking them to predict the spread of chikungunya for the six-month period between September 2014 and March 2015. 

The results don’t seem very encouraging. “No one did a really good job of forecasting when a disease was going to spread to a new country, and when it would go into an exponential growth phase,” Hepburn told the crowd at a DARPA conference this summer.

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What's Next After 25 Years of Wi-Fi?

In 1997, the first version of Wi-Fi appeared. (The same year saw about half of U.S. homes using AOL as their Internet Service Provider, Netscape with the most web browser users, and Microsoft rescuing Apple from the verge of bankruptcy.) Today, the the Wi-Fi standard known as IEEE 802.11 celebrates its 25th anniversary in a world where many people take Wi-Fi access for granted while streaming high-definition video and checking in on social media through their smartphones and laptops.

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Experiments Show How Lasers Can Despin Asteroids by Turning Them Into Rockets

Sometime in the 2020s, NASA will launch the Asteroid Redirect Mission (ARM) towards a 30-meter space rock with the goal of picking a boulder up off of its surface and returning the rock to Earth for us to have a look at. NASA has to be very careful in deciding which asteroid to plunder for this mission, because the spacecraft the space agency plans to send won't have a good way of dealing with an asteroid that's spinning, which lots of asteroids are. And realistically, how the heck do you stop a giant space boulder from spinning, anyway? The answer is of course to use lasers, because, well, lasers solve everything.

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Metasurface Optics for Better Cellphone Cameras and 3-D Displays

Engineers at the California Institute of Technology have created a metasurface out of tiny pillars of silicon that act as waveguides for light. The way they arrange the pillars allows them to control the phase of light passing through the surface; this ability gives them control over how the light is focused, as well as its polarization, which is important for uses such as liquid crystal displays and 3-D glasses. Metasurfaces are structured planes so thin that they count as being two-dimensional; their periodic designs manipulate light in unusual ways.

“We're trying to create kind of a new platform for optics,” says Amir Arbabi, a postdoc in Andrei Faraon's Nanoscale and Quantum Optics Lab. The team described their work in the latest issue of Nature Nanotechnology.

The silicon pillars have to be somewhat shorter than the wavelength of light they're designed to manipulate. In the case of the metasurface described in the paper, the pillars are 715 nanometers tall, to handle infrared light with a wavelength of 915 nm. But they could easily be made shorter for visible light, Arbabi says. The pillars range in diameter from 65 to 455 nm, and they're elliptical in shape. The ellipses are not all oriented in the same direction; the pillars’ thickness and orientation determine how they focus and polarize the light passing through them.

Many of the same effects can be achieved with traditional optics, but that requires lining up multiple components such as lenses and prisms and beam splitters. The metasurface gets the job done with less bulk, allowing, among other things, thinner, lighter-weight cell phone camera lenses and better systems for directing the beams of industrial cutting lasers. It could also lead to novel applications. Using one of these devices, a display could switch between two polarizations and display two different holographic images. Or with an intermediate polarization, it could superimpose one image on the other. The metasruface could provide the optics for an LCD to create a 3-D display viewable from many angles without glasses.

What’s more, all of this can be done using the same lithography techniques used to build computer chips, doing away with individual fabrication and manual alignment of components. “We're trying to take these free-space components that are bulky and large and put them on a chip,” Arbabi says.

It shouldn't take much effort to move these metasurfaces from the lab to the marketplace, says Faraon. It's mainly a question of figuring out which optical system applications could benefit from the kind of mass production this technology makes possible. The array of potential applications is vast, Faraon says. “It gives you a unified framework, so you can design whatever optical component you would like.”


Say Hello to MIAOW, the First Open Source Graphics Processor

While open-source hardware is already available for CPUs, researchers from the Vertical Research Group at the University of Wisconsin-Madison have announced at the Hot Chips Event in Cupertino, Calif., that they have created the first open source general-purpose graphics processor (GPGPU). 

Called MIAOW, which stands for Many-core Integrated Accelerator Of the Waterdeep, the processor is a resistor-transistor logic implementation of AMD's open source Southern Islands instruction set architecture. The researchers published a white paper on the device. 

The creation of MIAOW is the latest in a series of steps meant to keep processor development in step with Moore's Law, explains computer scientist Karu Sankaralingham, who leads the Wisconsin research group. 

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Europe Mismanages 10 Times the Amount of E-Waste It Exports

Broken electronics shipped off to foreign shores can lead to environmental damage and health risks for scavenging workers. But a European Union-funded report has found that mismanagement and illegal trading of electronic waste within Europe itself can involve 10 times the amount of e-waste that ends up as undocumented exports to other countries.

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New Sensor Predicts Which Lung Transplants Will Fail

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With a tiny chip-based sensor and 30 minutes of time, surgeons could evaluate a lung destined for transplantation and predict whether that donated organ is likely to fail or whether it will save a life. 

In lung transplant surgery, the clock is ticking. Once surgeons remove the donor lung they have about 7 hours before it’s too damaged to be used, and transplant teams often rush the organ via helicopter to the hospital where a desperate recipient is waiting. People who need lung transplants are typically in the final stages of a lung disease such as emphysema or cystic fibrosis, and have exhausted all other treatment options. 

Sometimes, despite the doctors’ best efforts, the transplanted lung begins to malfunction in the recipient’s body. This disorder, called primary graft dysfunction, is the leading cause of death for patients in the immediate aftermath of surgery. 

The new sensor can predict, before transplantation, which donated lungs will malfunction. Biomedical engineer Shana Kelley and her colleagues at the University of Toronto created a tiny electrochemical device that detects several biomarkers associated with graft dysfunction, and can do so within half an hour. The researchers describe the experimental device in the journal Science


Their technical advance is the creation of a “fractal circuit sensor,” on which nanoscale gold particles form spiky lines along a glass chip. These protrusions increase the sensor’s surface area, and produce more accurate readings. On these gold electrodes are genetic “probes,” strands of DNA that register the presense of genetic biomarkers associated with graft dysfunction. For example, one probe indicates that the lung cells are producing interleukin-6, a molecule linked to the body’s inflammatory response. When the genetic probes detect and bind to their targets, the electrodes register a tiny change in voltage. 

This new tech is still far from real clinical use, but Kelley and her colleagues think it could offer a big improvement over current procedures. Today, transplant teams do basic checks of a donated lung’s viability, but they don’t have time to do sophisticated tests. Genetic tests of the lung tissue currently require “6 to 12 hours in a typical hospital workflow,” the researchers write, and they require highly trained personnel and contamination-free laboratories—which may not be available at the critical transplant moment.

The new sensor can do the same genetic testing in less than 30 minutes. In addition to preventing graft dyfunction by recognizing problematic lungs, the sensor could also be used to evaluate questionable lungs that are currently discarded out of an abundance of caution. “It is estimated that 40 percent of the discarded lungs may actually be suitable for clinical transplantation,” the researchers write. Salvaging those organs would be a great benefit, because a lung is a terrible thing to waste. 

How to Build a Space Elevator From Scratch

Even with innovations like SpaceX’s reusable robotic boosters, chemical rockets remain an expensive, dangerous and unreliable way to reach orbit. How much easier it would be if astronauts could simply step into an elevator, press O for Orbit, and ascend gracefully to outer space.

This is the dream of the collection of scientists, engineers, and entrepreneurs in the International Space Elevator Consortium (ISEC) who got together for its annual conference last week in Seattle.

The idea of a space elevator has been around for over a century. The basic concept is simple: a tether descends from a spacecraft in geostationary orbit to a floating platform at the equator, probably in the eastern Pacific Ocean. Because of a counterweight that would extend far into space, the space elevator’s tether would be gravitationally stable, allowing electric elevator cars to make the week-long climb to orbit powered by solar panels and ground-based lasers.

Such a system, ISEC researchers believe, could eventually slash the cost of raising a kilogram of payload into geosynchronous orbit from roughly US $25,000 to $300 or less. The key word, of course, is “eventually.” Technical challenges are legion, including building the aircraft carrier–size floating platform, designing safe, speedy climbers, and avoiding space debris and other satellites. But the truly fundamental obstacle is the lack of a material strong and resilient enough to form the elevator’s tether.

In current designs, the space elevator’s tether is not a thick round cable as originally proposed, but a paper-thin ribbon, a meter wide and 100,000 kilometers long. Even with such a slimmed-down approach, the strain of simply keeping its own mass aloft would instantly shred any tether made from steel, Kevlar, carbon composites, or even the best carbon nanotubes we can currently make.

In the ISEC conference’s keynote address, Mark Haase, a materials engineer from the University of Cincinnati, talked about how a tether at least ten times stronger than anything existing today might be made. His idea started with carbon nanotubes, which still hold tremendous promise for the manufacturing of superstrong materials. Discovered in 1991, carbon nanotubes are cylindrical structures formed by sheets of single carbon atoms. They are already being manufactured in bulk, mostly as an additive to other materials in order to boost their strength and thermal or electrical conductivity.

But while individual carbon nanotubes can be immensely strong, they are awkward to tease into macroscopic-scale objects. They can’t be melted and extruded like Kevlar, nor sorted and aligned like natural fibers. The longest carbon nanotube made so far, if stood on its end, would barely reach a child’s knee, let alone one-quarter of the way to the Moon. Haase believes that the way forward is to cross-link nanotube molecules using minuscule amounts of polymer glue.

ISEC is not putting all of its eggs in a basket made from carbon nanotubes, however. Graphene, a single-atom-thick sheet of carbon, is also a promising material, although it does not respond as well as nanotubes to the kind of twisting and bending that a 100,000-km-long tether moving back and forth through the atmosphere would certainly experience.

More exotic still are boron nitride nanotubes. Similar in form to carbon nanotubes but made up of alternating boron and nitrogen atoms, this ceramic is incredibly chemically stable. That quality should help it survive long periods situated high in Earth’s atmosphere where highly reactive atomic oxygen would likely degrade a carbon nanotube tether. (Engineers on the nanotube track say they have devised a solution to this cosmic erosion: a gold coating for vulnerable sections of the tether.) Boron nitride nanotubes could also cope well with solar and cosmic radiation beyond the magnetosphere.

“As we gain more knowledge about these materials, we have a real chance to improve strengths,” says Haase. He predicts that the most promising candidates, nanotube-polymer composites, will reach the minimum strength needed for a space elevator tether “in about 20 years.”

Bryan Laubscher, a director at ISEC, believes that the search for a tether material will have an impact long before then. Laubscher, who left his job as an engineer at Lockheed Martin in 2010 to form a company developing high strength materials for use in aviation and space applications, says, “Imagine a Boeing 797 made from carbon nanotubes. It would have one-tenth of the mass of today’s aircraft, and an airframe that won’t come apart in a crash.” 

In fact, ISEC is relying on the private sector for every dime of the space elevator’s estimated $18 billion price-tag. In a position paper published earlier this year, ISEC noted, “To this point, we have found no needed capability within the government that must be incorporated in the space elevator architecture.”

That might be a swipe at NASA, which in 2012 abandoned a $2 million competition aimed at creating ultra-strong tether materials. But when even the world’s richest and most visionary space agency can’t help with your moonshot, you might want to at least consider that your lofty ambitions for a space elevator seem destined to stay firmly on the ground floor.


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