The Nasdaq rose 1.23% to 2,889.23 in midday trading, while the Dow Jones Industrial Average was up 1.61% to 12,880.47.

The S&P 500 was up 1.53% to 1,358.3.

The yield on a 10-year treasury bond rose 1.78% to 1.43%.

The price of gold was up 0.44% to $1,615.10 per ounce.

Trading among Orange County public companies was generally mixed.

Irvine-based drive maker Western Digital Corp.’s shares surged 18.48% to $38.47 a day after the disk drive maker reported better-than-expected results for the June quarter. Western Digital has a market value of about $10 billion.

Shares of Kaiser Aluminum Corp. were up 7% to $53 for a recent market cap of about $1 billion. The aluminum products maker reported strong results for the second quarter yesterday.

Shares of Irvine-based data management software company TigerLogic Corp. were up 7.83% to $1.90 for a market value of about $54 million.

Meantime, Irvine-based healthcare software maker Quality Systems Inc. shares fell 32.67% to $15.88 to a market value of about $950 million. Quality Systems reported weak sales of some of its software today, resulting in the company pulling away from previously stated guidance for the full year.

Shares of Santa Ana-based vocational school operator Corinthian Colleges Inc. were down 8.60% to $2.02 for a market value of about $174 million.