Among the stock activity stories for Tuesday, Oct. 9, from AP Business News:
_ Shares of Baidu Inc. slid after a Credit Suisse analyst downgraded the Chinese Internet company, citing concerns over a weaker-than-expected advertising market and growing competition.
_ Shares of Optimer Pharmaceuticals Inc. fell as Wall Street weighed in on the company's marketing strategy and sales of its antibacterial drug Dificid.
_ Increased competition on several key routes led Hawaiian Airlines Inc. to cut its third-quarter revenue expectations. The stock of its parent company, Hawaiian Holdings Inc., fell on the news.