The Nikkei stock index closed Wednesday at its highest level in two and a half months, as investors snapped up technology stocks and recently battered shares on expectations of improved earnings due to a weaker yen. The 225-issue Nikkei Stock Average ended up 493.92 points, or 1.26 percent, from Tuesday at 39,667.07, the highest closing since April 9. The broader Topix index finished 15.58 points, or 0.56 percent, higher at 2,802.95. On the top-tier Prime Market, gainers were led by electric appliance, service and pharmaceutical issues. The U.S. dollar was firmer in the upper 159 yen range fol…