The list features Indian-origin engineer Arati Prabhakar, 55 who heads the United States Defense Advanced Research Projects Agency (DARPA). "Running the military's technology innovation lab in the middle of the austerity era is no easy task. But Prabhakar, who first led a major federal office when she was only 34 and later spent time as a venture capitalist, is meeting the challenge with an outsider's enthusiasm," Fortune said of Prabhakar, who is ranked 45th.