Take a look at some of Tuesday's midday movers:
Lockheed Martin - The defense contractor fell after projecting 2015 earnings short of estimates. Rivals Northrop Grumman, Raytheon and General Dynamics also dropped..
Plantronics - The headset maker fell after it posted weaker-than-expected third-quarter results.
CIT Group - The commercial lender edged lower after releasing quarterly results.
Twitter - The social-media supplier tumbled on user-growth concerns ahead of its earnings.
CommScope Holding Company - The company surged on a Wall Street Journal report it was nearing a deal to buy TE Connectivity's network-equipment unit for about $3 billion.
Newmont Mining - The commodity producer and competitors including Barrick Gold, Goldcorp and Yamana Gold rose with gold.
AK Steel - The steel supplier gained after better-than-expected fourth-quarter profits.
Peabody Energy - The coal miner declined as it posted disappointing fourth-quarter earnings.
Nucor - The he steel manufacturer rose after reporting a rise in quarterly profit.
Family Dollar Stores - The discount retailer edged higher. Investor Nelson Peltz cut his stake by 72 percent, according to a regulatory filing.
Bristol-Myers Squibb - The pharmaceutical company slid after saying the strong dollar will drag on its 2015 outlook.
Novartis - The Swiss drug maker gained after projecting increased sales and profits.
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