TOKYO, Aug 6 (Reuters) - Japan on Sunday marked the 78th anniversary of the U. About 50,000 participants in the outdoor memorial ceremony including ageing survivors observed a moment of silence, with the summer heat hitting 30 degrees Celsius (86 Fahrenheit)"Leaders around the world must confront the reality that nuclear threats now being voiced by certain policymakers reveal the folly of nuclear deterrence theory," Hiroshima Mayor Kazumi Matsui said at the ceremony, also attended by Kishida. See here for a complete list of exchanges and delays