U.S. President Barack Obama (L) shows the way to China's President Hu Jintao at the Nuclear Security Summit in Washington, April 12, 2010. [Photo/Agencies] 

An MD-500 helicopter hovers near an ultra-high 500-kilovolt live wire, as an engineer, buckled to a safety belt, conducts a power line overhaul in Caidian District of Wuhan, capital of Central China's Hubei province, April 12, 2010. [Photo/Xinhua]