Companies whose shares are expected to trade actively in today’s session are Nuance Communications Inc. (NASDAQ:NUAN), Vodafone Group Plc (NASDAQ:VOD) (LON:VOD), Hewlett-Packard Company (NYSE:HPQ), BGC Partners, Inc. (NASDAQ:BGCP), Obagi Medical Products, Inc. (NASDAQ:OMPI) and Humana Inc (NYSE:HUM).

stocks to watch

Nuance Communications Inc. (NASDAQ:NUAN): Shares of the voice and language solutions provider surged 8.72 percent to $21.94 after activist investor Carl Icahn acquired 9.27 percent stake in the company. The speech recognition technology of Nuance is used in iPhones. Carl Icahn purchased 29.33 million shares of the company.

Vodafone Group Plc (NASDAQ:VOD) (LON:VOD): AT&T and Verizon Communications are working to put a joint buyout offer for the British mobile operator. The bid is expected to be pitched at about 40 percent premium over Vodafone’s current price, reports Financial Times’ Alphaville column. American shares of Vodafone surged 4.80 percent to $29.70 in the early session.

Hewlett-Packard Company (NYSE:HPQ): Goldman Sachs said in its latest research report that EPS expectations of the computer maker would see downward revisions in coming quarters, and any recovery will be muted through 2014. The investment firm downgraded the stock from neutral to sell. The company’s restructuring efforts will be countered by weakness in enterprise software, PC, services and printing businesses. Shares tanked 4.33 percent to $22.30 in early trading.

BGC Partners, Inc. (NASDAQ:BGCP): NASDAQ OMX Group announced to purchase the electronic trading platform from BGC in a $1.23 billion cash and stock deal. The stock exchange company plans to foray into electronic fixed-income business. BGC shares surged 45.45 percent to $5.60 in early market trading.

Obagi Medical Products, Inc. (NASDAQ:OMPI): Merz Pharma Group offered to acquire Obagi  for $385 million cash. The specialty pharmaceutical company had earlier received a $345 million offer from Valeant Pharmaceuticals in March. Merz Pharma values Obagi at $22 per share. Shares surged 15.07 percent to $22.68 as investors expect a bidding war to ensue.

Humana Inc (NYSE:HUM): Shares of the health insurer rose 8.96 percent to $81.68 after the announcement of the new government rates late Monday. Humana and other health insurers will get much more money than expected for running the Medicare Advantage plans from next year.