The PowerShares QQQ, which tracks the top 100 stocks in the tech-heavy Nasdaq, was up almost 2 percent in a month that saw a slight drop for the Dow Jones industrial average and the S&P 500, and a bigger, 1.6 percent, decline for the small-stock Russell 2000. Some of the biggest gainers for the Nasdaq last month were Illumina, up 18.6 percent, Micron,...