U.S. stock indexes made tentative gains Friday morning with investors encouraged by merger announcements. Computer company Dell, American Airlines and US Airways and food giant Heinz have all been involved in major deals this week. Even if these deals to not all survive to completion, mergers are viewed by many as a sign of corporate confidence and financial health. In midmorning trading, the Dow Jones industrial average added 24.64 points or 0.18 percent to 13,998.03. The Nasdaq composite index added 7.37 points or 0.23 percent to 3,206.02. The Standard & Poor\'s 100 gained 2.84 points or 0.19 percent to 1,524.22. The 10-year treasury note fell 7/32 to yield 2.025 percent. Against the dollar, the euro fell to $1.3351from Thursday\'s $1.3362. The dollar rose to 93.41 yen from 92.87 yen. The Nikkei 225 index in Tokyo lost 1.18 percent, 133.45 points, to 11,173.83.