Wall Street falls as energy, materials stocks drag

U.S. stocks were lower on Thursday morning as materials and energy stocks sank due to lower commodity prices and investors weighed the prospect of an increase in interest rates next month. Fed Chair Janet Yellen said that the central bank must weigh the effects of post-crisis financial regulations and new channels through which policy affects markets as it prepares to raise interest rates. St. Louis Fed President James Bullard, who is ready to raise U.S. rates, said the United States and other c