The stock market turned down during the two-week period ended March 19 as the weakening Chinese economy, continuing tensions between Russia and Ukraine and anticipation over the next moves by the Federal Reserve dimmed investor confidence. The Dow Jones ended with a 0.8 percent decrease. The Valley 50 fared worse, down 1.4 percent. Capstone Turbine Corp. in Chatsworth led as the top gainer at 32 percent after announcing new orders in the U.S. and U.K. Vitesse Semiconductor Corp. increased 29 percent after analysts raised earnings estimates for the Camarillo company. Agricultural biotech firm Ceres Inc. had the biggest drop with 11 percent.