Tokyo stocks opened flat Tuesday as investors sat on the sidelines ahead of the release of the U.S. consumer price index later in the day. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 11.66 points, or 0.04 percent, from Monday to 28,553.77. The broader Topix index was down 2.10 points, or 0.11 percent, at 1,978.12. On the top-tier Prime Market, gainers were led by mining, land transportation, and air transportation issues, while precision instrument, transportation equipment, and insurance issues were among major decliners. At 9 a.m., the dollar fetched 142.55-60…