Stocks opened lower Monday amid concerns over debt problems in the United States and Europe, causing investors to move into safe haven assets like gold, which hit another record high.

The Dow Jones Industrial Average tumbled after ending higher on Friday, but finishing lower for the week.

Here are six stocks that are on the move:

Nike
The footwear company's price target was increased to $103 from $90 at UBS while also raising earnings estimates for next year.

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Greenhill
The investment bank reported better than expected second quarter earnings. The firm released results over the weekend, after the departure of a third managing director since early June sent shares down 12 percent Friday.

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St. Jude Medical
The medical device manufacturer was upgraded to overweight from equal-weight at Barclays Capital.

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US Airways
The airline was downgraded to neutral from buy at Bank of America Merrill Lynch.

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Exelon
The energy company was upgraded to buy from neutral at Ticonderoga Securities with a price target of $49.

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Dollar Tree
The discount retailer was downgraded to neutral from buy at Goldman Sachs.

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