Lawyers say China’s government intervened and helped get charges dropped against three Chinese scientists at the University of Michigan. The three men were accused of helping a colleague smuggle biological materials into the U.S. The materials turned out to be mostly tiny transparent worms — nothing dangerous. But U.S. officials last year hailed the arrests as a victory for national security. Xu Bai and Fengfan Zhang were charged with conspiring to help another scientist who shipped packages to them from China. A third man, Zhiyong Zhang, was charged with making false statements. U.S. prosecutors won't comment.