The Nikkei stock index plunged over 2 percent Tuesday morning on concern over the economic impact of surging oil prices amid the escalation of the conflict in the Middle East.The 225-issue Nikkei Stock Average fell 1,329.97 points, or 2.29 percent, from Monday to 56,727.27. The broader Topix index was down 87.28 points, or 2.24 percent, at 3,811.14.The U.S. dollar briefly strengthened to the mid-157 yen range in Tokyo in a flight to safety following the weekend launch of U.S. and Israeli strikes on Iran.At noon, the dollar fetched 157.23-24 yen compared with 157.28-38 yen in New York and 15…READ FULL ARTICLE