By Nick Mulvenney BEIJING (Reuters) - Usain Bolt secured a sweep of the sprint golds at a world championships for the third time on Saturday when, aided by a U.S. disqualification, he anchored Jamaica to the 4x100 meters relay title. The United States team featuring Justin Gatlin, who won silver behind Bolt in both individual sprints, botched their final handover between Tyson Gay and Mike Rodgers and were disqualified after crossing the line second. It was a record-extending 11th world gold for Bolt, who also won three sprint titles at the 2009 and 2013 world championships. More...