The Nikkei stock index closed at an all-time high Monday for the second consecutive trading day, as buying momentum was supported by expectations for robust corporate performance. The 225-issue Nikkei Stock Average ended up 135.03 points, or 0.35 percent, from Thursday at 39,233.71. The broader Topix index finished 12.91 points, or 0.49 percent, higher at 2,673.62, its highest level since February 1990. Japanese markets were closed Friday for a public holiday. On the top-tier Prime Market, gainers were led by pharmaceutical, precision instrument and bank shares. The U.S. dollar remained mostly…