U.S. stock markets opened with modest losses Monday morning as central bank asset purchase announcements have run their course with investors. In recent weeks, the European Central Bank, the U.S. Federal Reserve and the Bank of Japan have announced bond-buying programs, which each gave markets a lift. In China, the government announced major infrastructure projects to provide stimulus to the economy. At a new level, stocks now have to rely on their own merits again and investors are correcting their positions after a wave of optimism. In midmorning trading, the Dow Jones industrial average shed 37.86 points, or 0.28 percent, to 13,541.61. The tech-dominated Nasdaq Composite index lost 18.37 points, or 0.58 percent, to 3,161.60. The Standard and Poor\'s 500 gave up 5.01 points, 0.34 percent, to 1,455.14. The benchmark 10-year treasury rose 10/32 to yield 1.723 percent. The euro fell to $1.2912 from Friday\'s $1.2981. The U.S. dollar fell to 78.02 yen from 78.15 yen. In Tokyo, the Nikkei 225 index shed 0.45 percent, 40.71 points, to 9,069.29.