KIEV, Ukraine - Ukrainian security officers have arrested two Middle Eastern men whom they said possessed a substance that has been touted by sellers as an ingredient in nuclear weapons and dismissed by others as a hoax. Security agents in the southern city of Odessa seized 24 pounds of a substance they said was radioactive and identified as "red mercury," a State Security Service spokesman said Monday on condition of anonymity. He said they arrested two men from a Middle Eastern country, "Foreign citizens were looking for an opportunity to purchase a quantity of radioactive material in Ukraine and to...