Among the stock activity stories for Thursday, Nov. 12, from AP Financial News:

VANCOUVER, Wash. (AP) -- Northwest Pipe Co. shares tumbled after the maker of welded steel pipes said it has delayed the release of its third-quarter financial results, but that it expects to post a $1 million loss.

SAN FRANCISCO (AP) -- Shares of teen apparel retailer The Buckle Inc. dropped after Goldman Sachs initiated coverage of the stock with a "Sell" rating and warned that it sees red flags that indicate the retailer's performance could soon decline.

SAN FRANCISCO (AP) -- Shares of Sotheby's climbed to a new year-high after the auction house exceeded expectations at its contemporary sale Wednesday evening in New York.