The S&P 500 was down 0.2% in midday trading to 2,254.61.
The Dow Jones Industrial Average was flat at 19,772.69.
The NASDAQ was down 0.8% to 5,401.46.
The yield on a 10-year Treasury bond rose 0.1% to 2.47%.
The price of gold rose 0.3% to $1,166.
Newport Beach-based Alliance Healthcare Services Inc. was up 13.8% to $9.05 and a $97 million market cap. The provider of radiology and oncology services said investor Tahoe Investment Group, Co. Ltd., sent a letter proposing to an all cash deal to purchase the company for $9.60 per share.
Irvine-based Western Digital Corp. was down 2.9% to $65.78 and an $18.8 billion market cap on moderate volume. The company makes computer memory and storage products.