Following “ongoing challenges” at Borders and the big stake taken in Barnes & Noble stock by activist investor Ron Burkle, genius Goldman Sachs Matthew Fassler has revised his rating on BN. He upgraded the stock to neutral from sell. At midday, Barnes & Noble (BKS) was up more than 10 percent on the stock market, while Borders (BGP) was up more than 13 percent on news of new management.AP