Author Archives: John Timmer

Imaging a supernova with neutrinos

There are lots of ways to describe how rarely neutrinos interact with normal matter. Duke’s Kate Scholberg, who works on them, provided yet another. A 10 Mega-electron Volt gamma ray will, on average, go through 20 centimeters of carbon before it’s absorbed; a 10 MeV neutrino will go a light year. “It’s called the weak interaction for a reason,” she quipped, referring to the weak-force-generated processes that produce and absorb these particles.

But there’s one type of event that produces so many of these elusive particles that we can’t miss it: a core-collapse supernova, which occurs when a star can no longer produce enough energy to counteract the pull of gravity. We typically spot these through the copious amounts of light they produce, but in energetic terms, that’s just a rounding error: Scholberg said that 99 percent of the gravitational energy of the supernova goes into producing neutrinos.

Within instants of the start of the collapse, gravity forces electrons and protons to fuse, producing neutrons and releasing neutrinos. While the energy that goes into producing light gets held up by complicated interactions with the outer shells of the collapsing star, neutrinos pass right through any intervening matter. Most of them do, at least; there are so many produced that their rare interactions collectively matter, though our supernova models haven’t quite settled on how yet.

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SpaceX: Launch Successful, Landing Not So Much

This morning’s SpaceX launch went off without a hitch, sending a Dragon capsule into orbit for a rendezvous with the International Space Station. It marks the latest in a string of successful launches for Elon Musk’s company. However, the experimental portion of the launch—an attempt to land the Falcon 9 launch vehicle on a barge—did not work out so well.

Musk went on to say that this was hard enough to trash some of the support equipment on the barge, though the barge itself will be back for the next attempt. No video is currently available, as the landing attempt took place in the dark and fog. Musk joked that they’ll “piece it together from telemetry and … actual pieces.”

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Researchers Craft Molecule that Works as Flash Storage

As features on chips get smaller, we’re edging closer to where we bump up against basic physics, which dictates that the behavior of wiring will become unpredictable once the number of atoms involved gets small enough. As a result, there’s been some preliminary work done on producing processor components out of single molecules, like carbon nanotubes.

But it’s not just processors we care about. As features of flash memory shrink, we’ll eventually run up against a similar problem: the locations where electrons are stored will be too small to hold sufficient charge for the device to actually work. Fortunately, it looks like molecules may be able to help us out here, as well. Researchers are reporting that they’ve designed a combination of two molecules that can hold electrons for use as flash memory.

This isn’t the first advance in single-molecule flash memory. Last year, researchers reported building a flash device that included layers of graphene and molybdenum disulfide, both of which form molecular sheets a single atom thick. But these devices required several layers of these materials to work, so the charge ended up stored in several stacked sheets of graphene.

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Researchers Craft A Battery That Can Be Recharged with Waste Heat

Pretty much anything we do that involves energy, from generating electricity to using it in a laptop, produces energy in the form of heat that ultimately goes to waste. The problem is that all of the means we have of converting heat into useful energy require large temperature differences. The waste heat, by contrast, is a low-grade energy source, usually involving temperature differences of less than 100 degrees Celsius.

So far, attempts to find ways of producing useful energy from waste heat have largely focused on thermoelectric devices, which directly convert temperature gradients to electricity. But these devices generally cost a lot to produce, so the economics of using them to capture waste heat are pretty questionable. But now researchers have produced a demonstration of a device that acts more like a battery that can be charged or discharged based on temperature differences. Although it’s not especially efficient, the ability to store charges may add significantly to its utility.

The research team involved in the work (a collaboration between people at MIT and Stanford) had previously demonstrated an actual battery that took advantage of temperature differences. In that example, which relied on a copper-based chemical reaction, charging and discharging took place at two different temperatures. At an elevated temperature (perhaps one provided by waste heat), the voltage difference needed for charging was lower than it would have been otherwise. By dropping the battery to room temperature during discharge, their battery produced a higher voltage. In essence, the temperature difference was used to get more useful current out of the battery.

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After Biosafety Lapses, US Halts Funding for Work Modifying Virus Targets

Today, the White House announced a pause in a specific type of research on viruses. Rather than being a response to the recent Ebola infections, this dates back to events that began in 2011. Back then, researchers who were studying the bird flu put it through a series of lab procedures that ended with a flu virus that could readily infect mammals. Some members of the scientific community considered this work irresponsible, as the resulting virus could, again, potentially infect humans.

Similar research and a debate over its value and threat have continued. Now, however, the Obama administration decided to put it on hold. Prompted by several recent biosafety lapses (including the discovery of old smallpox samples at the National Institutes of Health), the government will temporarily stop funding for these projects. During the pause, the government will organize a “deliberative process” that will consider the value of the research and the appropriate safety precautions that will need to be followed if it’s done. The review will be run by a combination of the National Science Advisory Board for Biosecurity and the National Academies of Science.

The funding pause will apply to any projects that can allow viruses like the flu, MERS, and SARS to either add mammals to the list of species they can infect, or to increase their virulence following infection. The government also hopes that any lab pursuing this research using private funding will voluntarily join in the pause. Researchers who are simply studying naturally occurring viruses without modifying them will not be affected by this pause.

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