THE OPEN Nov beans:  2 1/2 higher Dec meal:  .40 lower Dec soyoil:  41 higher Dec corn:  1/4 higher Sep wheat:  3 1/2 higher The markets opened as called with prices trading mixed.  Grains turned lower after the start of the trading session, but short-covering was noted in corn.  There was noted unwinding of recent buy bean/sell corn trade.  Wheat futures, which had stabilized into the morning session, took a turn for lower prices.  Good export sales in beans gave prices a momentary lift, but bulls took that strength as an opportunity to sell something.  Beans seem to find resistance as we draw closer to high level talks scheduled between China/US for August 15.  Buy corn/sell whe...