Physics Today’s online staff summarize the most important and interesting news about science from the world's top media outlets.
Wired: Last month, Google revealed that it had partnered with Aclima, an environmental monitoring startup, to map pollution levels for a month in Denver, Colorado. Now it is expanding to do the same in San Francisco. For several years, the two companies had been testing Aclima's air-quality sensors at Google's facilities around the world. Putting the sensors in Google Street View vehicles is the next step in developing the system. Devices for measuring pollutants have to account for a wide range of atmospheric variables, which makes them complex and potentially expensive. One of Aclima's goals is to reduce the sensors' cost significantly so that public networks of the sensors can be established. The companies are sharing the collected data with the host cities in order to help them make more informed choices about how to handle local air quality.
Ars Technica: A p–n junction, essential to most electronic devices, is a boundary between two types of semiconducting materials and is usually created through chemical doping. Creating those junctions on the scale of a single atom has proven difficult. Now, an international team of researchers has succeeded in creating a single-atom-thick p–n junction by using vapor deposition to layer two different two-dimensional semiconductor materials. Because the two materials vaporize at significantly different temperatures, one layer can be set in place before the second material, which vaporizes at the lower temperature, is deposited on top. Testing revealed that the resulting material behaved like a p–n junction, but the team has not yet demonstrated its use in any actual circuits.
Nature: Today, President Obama is announcing a set of regulations to limit greenhouse gas emissions from power plants over the next 15 years. The primary goal will be a 32% reduction from 2005 emissions levels by 2030 for the entire electricity-generating industry. The regulations set targets for each state and require each state to submit, by 2016, plans to reach those targets. However, the states can request a 2-year extension and participate in emissions trading. The regulations will not go into effect until 2017. Even though they don't require congressional approval, the regulations are expected to be challenged by Republicans in Congress and the coal industry.