Major U.S. indexes were higher at midday Tuesday as tech stocks surged and oil prices eased. The Nasdaq jumped 1%, while the S&P 500 climbed about 0.6% and the Dow was little changed.

Nvidia (NVDA) shares rose as partner Foxconn touted strong demand for its servers and Nvidia’s artificial intelligence (AI) chips.

Shares of DocuSign (DOCU) and MDU Resources Group (MDU) gained after S&P Global announced they were part of changes in its indexes. DocuSign is set to replace MDU in the S&P MidCap 400 index, while MDU is moving to the S&P SmallCap 600 index, bumping Chuy Holdings (CHUY).

Beaten down Humana (HUM) shares got a lift as Bernstein analysts upgraded the stock, saying the recent drop made the shares attractive.

The decline in oil prices sent shares of Marathon Petroleum (MPC) and others in the oil industry lower. Prices for gold and other key metals declined, sending shares of Freeport-McMoRan (FCX) and rival miners down. 

Roblox (RBLX) shares sank after short seller Hindenburg Research claimed the online gaming platform overstated its user data and was a dangerous site for kids. 

The yield on the 10-year Treasury note advanced. The dollar was up on the euro and yen, but lost ground to the pound. Most major cryptocurrencies traded lower.