Tokyo stocks ended mixed Tuesday as investors locked in gains after the Nikkei index surpassed the 40,000 mark for the first time the previous day, although dip-buying in some chip-related issues helped limit losses. The 225-issue Nikkei Stock Average fell for the first time in three trading days, ending down 11.60 points, or 0.03 percent, from Monday at 40,097.63. The broader Topix index finished 13.65 points, or 0.50 percent, higher at 2,719.93. The U.S. dollar moved narrowly around the mid-150 yen zone, finding some support after a Federal Reserve official suggested Monday that the central …