Meanwhile, top losers in the sector included Tesco Corporation ( USA ) (NASDAQ: TESO ), down 7 percent, and Northern Oil & Gas, Inc. (NYSE: NOG ), down 8 percent. Top Headline Dean Foods Co (NYSE: DF ) posted weaker-than-expected earnings for its first quarter on Tuesday. Shares of CPI Aerostructures, Inc. (NYSE: CVU ) got a boost, shooting up 25 percent to $7.10 after the company posted upbeat Q1 results.