Shinzo Abe, Japan's prime minister, left, waits to begin an opening plenary entitled &quot;National Actions to Enhance Nuclear Security&quot;at the Nuclear Security Summit in Washington, D.C., U.S., on Friday, April 1, 2016. After a spate of terrorist attacks from Europe to Africa, U.S. President Barack  Obama is rallying international support during the summit for an effort to keep Islamic State and similar groups from obtaining nuclear material and other weapons of mass destruction. <br /> Credit: Andrew Harrer / Pool via CNP/MediaPunch
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