| DARPA Gets Social for Latest Challenge How good are you at spotting balloons...and connecting with other people while doing it? That's what the latest challenge from the Defense Advanced Research Projects Agency seems set to test. They're prepared to award $40,000 to the first person who can accurately tell them the latitudes and longitudes of 10 red weather balloons set up in various positions across the skies of the continental United States. The balloons will lift off at 7 AM on Saturday and remain in place until sunset. The contest will be open until December 14, giving contestants a week to collect the data. The key point is, since no one can be everywhere at once, competitors will need to rely on other people scattered throughout the states. DARPA expects people to team up, using their social networking skills to pinpoint the weather balloons. DARPA's goal isn't so much to see if contestants can answer the question, but rather to learn how we use social networks to solve a problem. After all, they know where the weather balloons are. Norman Whitaker, DARPA's deputy director of transformational convergence technology, said that "It's the techniques people use to solve the challenge we're focused on. We have people who are going to be actively watching from the sidelines to see how this plays out." DARPA hopes that what they learn from this challenge can be applied to using social networks to help build teams to solve real-world challenges. Read more about this Making Solar Cells Absorb More Power If you've ever noticed how some solar cells reflect light, you know their biggest weakness: they don't absorb as much power as they could, so they yield less electricity. Indeed, much of the focus of solar cell research has been on making them more efficient. Now Yi Cui of Stanford University in California has come up with a way to get more light to a solar cell's silicon layers, increasing its efficiency by up to 25 percent. Cui's team deposits a silver reflector layer onto a quartz base. The quartz base is studded with an array of nanoscale cones. The quartz and the reflector layer make sure that photons which would otherwise be wasted instead bounce up toward the active layer. This active layer features both transparent electrodes and ones made from active semiconductors. The result: a solar cell which appears black rather than reflective. Lab tests confirmed that the new solar cells are nearly 6 per cent efficient, compared with 4.7 percent for traditional flat film amorphous solar cells. Cui thinks he can push that efficiency much higher. He also notes an important extra benefit to the layer of cones: it should cause water to roll right off the cells, taking any light-blocking dust with it. Cui thinks his technique can also be used to improve the efficiency of solar panels using polycrystalline silicon, which is more widely used than the flat film cells because it is more efficient. Read more about this | 
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