Techs clung to the upside as stocks opened on mixed footing Thursday. The Nasdaq inched up 0.1% on an 8% increase in volume. The Dow Jones industrial average and the S&P 500 were down 0.1% each, with NYSE volume up 3%. The stock market today worked its way through a host of mixed signals in early trade from earnings reports and economics news. April layoffs and weekly jobless claims were higher than expected.