Ars Technica: Nanowires are being experimented with for use in solar cells because they use less material and are potentially less expensive than conventional materials. Jesper Wallentin of Lund University in Sweden and his colleagues have found that two characteristics of nanowires are important for determining their efficiency—the diameter of the wire and the superconducting characteristics of the material. Their model showed that if the wire’s diameter was less than the sunlight’s wavelength, the wires resonated, which increased the amount of energy absorbed. They found the optimum diameter to be 180 nm. They also determined that layering doped and undoped material significantly increased the absorption of the wires. Wallentin’s team tested the models using indium phosphide (InP), also commonly used in conventional solar cells. They more than doubled previous nanowire-cell efficiency to 13.8%, still significantly less than the 22.1% of conventional InP cells. However, the new cells used only 12% of the surface area required by conventional cells. Although the nanowire cells didn’t match current capabilities, they represent a significant step forward and could be the key to reducing solar cell cost.
Science: Last week, an Italian judge explained his reasons for finding seven scientists guilty of manslaughter following the 2009 L’Aquila earthquake. Although Judge Marco Billi agrees that no one could have predicted the earthquake, he believes that the seven members of the Italian government’s National Commission for the Forecast and Prevention of Major Risks ignored the findings of a number of relevant studies and waged a “media operation” to reassure the public regarding a series of tremors that had struck the area just prior to the quake. Because they downplayed the potential threat, he says, many residents stayed indoors rather than seek shelter outside as they would have normally done. The result was a higher death toll than would otherwise have been expected. The seven have 45 days from the release of Billi’s statement to appeal the decision.
BBC: From the presence of radioactive carbon in ancient Japanese cedar trees and radioactive beryllium in Antarctic ice, scientists believe that a blast of radiation struck Earth around AD 774–775. Several theories have been put forth as the source, including a supernova or a solar flare. However, Ralph Neuhäuser of the University of Jena in Germany and colleagues have recently published a paper in the Monthly Notices of the Royal Astronomical Society in which they propose that the wave of radiation was produced by a gamma-ray burst (GRB) within the Milky Way. “We looked in the spectra of short gamma-ray bursts to estimate whether this would be consistent with the production rate of carbon-14 and beryllium-10 that we observed—and [we found] that is fully consistent,” said Neuhäuser. Because no extinction event was triggered, the GRB must have occurred sufficiently far away, some 3000 to 12 000 light-years. In galaxies like the Milky Way, GRBs are expected to occur just once every 100,000 to 1 million years. It is therefore “extremely unlikely” that Earth would experience another anytime soon, according to Neuhäuser.
Nature: South Korea, which is already developing a tokamak reactor and is participating in the ITER project, has announced another major fusion-facility project. The Korean Demonstration Fusion Power Plant (K-DEMO) is a joint project with the US Department of Energy’s Princeton Plasma Physics Laboratory. The goal is to use the technology developed in the South Korean tokamak project and by ITER to have a prototype commercial fusion plant operating by the 2030s. Korea plans to invest nearly 1 trillion won ($941 million) in the project, the first phase of which will be to develop the technology needed so that construction can begin in the early 2020s. With 300 million won already invested, the country hopes to employ 2400 workers in the initial phase. The final plan is a reactor that can produce 1 billion watts of power for several weeks, significantly higher than ITER’s goal of 500 million watts for just 500 seconds. Perhaps even more significant than the power goal is the plan for the reactor to be connected to the electrical grid, which would make it the first fusion reactor to produce commercial electricity.