Stocks continued to trade in moderately positive territory at midafternoon Wednesday, after showing mixed action earlier in the session. The Dow Jones industrial average rose 0.5%, helped by IBM's (IBM) 5% rise on its upbeat quarterly report. The Nasdaq added 0.4%, while the S&P 500 edged up 0.2%. Volume remains down slightly from Tuesday's levels. It had been up slightly in morning action. Among IBD 50 stocks, SodaStream International (SODA)