Take a look at some of Thursday's midday movers:
Apple rose after Canaccord Genuity raised its fiscal 2014 and 2015 earnings and revenue estimates based on strong iPhone 5s sales, and strong initial iPad Air sales.
Compuware gained after Starboard Value asked the business-software maker to consider an immediate sale or restructuring plan. The activist investor is one of Compuware's largest shareholders with a stake of just under 5%.
Hewlett-Packard fell after it halted sales of its Chromebook 11 computers on reports the device's charger has been overheating.
Solar City rose after RW Baird upgraded the stock to outperform and raised its price target to $71 from $50.
Tandem Diabetes Care soared in its market debut after being priced at $15, the high end of the expected range. Tandem makes insulin pumps for diabetes patients.
Houghton Mifflin Harcourt rose in its market debut after being priced at $12, below the projected range of $14 to $16. Houghton Mifflin is a textbook publisher that emerged from bankruptcy last year.
Google climbed on news it won the dismissal of a lawsuit by authors who accused it of digitally copying millions of books for an online library without permission.
Viacom declined after forecasting weaker ad performance in its current quarter.
Sony climbed after Morgan Stanley upgraded the stock to overweight from equal weight.
Lockheed Martin rose after the defense contractor said it would cut 4,000 jobs, or more than 3 percent of its workforce.
Lululemon fell after Sterne Agee downgraded the stock to underperform from neutral, dropping its price target to $56 from $75.
Under Armour fell after saying it would acquire social-network and app-maker MapMyFitness for $150 million.
Sanofi held near neutral after an FDA panel said safety issues don't preclude approval of its multiple sclerosis drug Lemtrada.
Eli Lilly rose after the company said it will invest more than $700 million to boost its insulin-manufacturing capacity.
The Carlyle Group moved up after Goldman Sachs upgraded the stock to buy from neutral with a price target of $36.
Suburban Propane Partners dropped after posting a wider-than-expected fourth-quarter loss on lower revenue.
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—By CNBC's Rich Fisherman.
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