Alcoa, one of the world’s largest aluminum producers, has reported a 52-percent drop in third quarter profits and said it would conserve cash by suspending its stock buyback program and all non-critical capital projects. Alcoa, the first component of the Dow Jones industrial average to report earnings, said results were hurt by sharply lower aluminum prices, weaker demand and a charge from curtailing production at a Texas smelter. The company reported earnings of $268 million, or 33 cents per share, for the three months ended Sept. 30. That compared with $555 million, or 63 cents per share, during the same period last year.