U.S. stocks slightly positive, led by Alcoa By: MarketWatch February 02, 2010 at 09:49 AM EST U.S. stocks opened slightly positive on Tuesday, as strong earnings and analyst rating upgrades helped lift sentiment. Read More >> Related Stocks: Alcoa American Express Barnes & Noble D.R.Horton Dow Chemical DuPont USA Standard & Poors 500 United Parcel Service