24/7 Wall St.

The first quarter of 2014 has already ended. While stocks are within striking distance of new highs again, investors still remain concerned that they will buy the top or get inverted in the next market sell-off. 24/7 Wall St. reviews many analyst research reports from Wall Street each morning, hunting for new ideas for our readers. Some reports cover stocks to buy, while other reports cover stocks to sell or to avoid. These are this Tuesday’s top analyst upgrades, downgrades and initiations seen from Wall Street research firms.

Cancer Genetics Inc. (NASDAQ: CGIX) was started as Buy at Cantor Fitzgerald.

Clean Harbors Inc. (NYSE: CLH) was downgraded to Hold from Buy at KeyBanc Capital Markets.

Coupons.com Inc. (NYSE: COUP) was started as Buy at Bank of America Merrill Lynch, started as Neutral at Goldman Sachs and started as Sector Perform at RBC Capital Markets.

Cullen/Frost Bankers Inc. (NYSE: CFR) was raised to Neutral from Underperform at Sterne Agee.

Extreme Networks Inc. (NASDAQ: EXTR) was started as Buy at Wunderlich.

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Laboratory Corporation of America Holdings (NYSE: LH) was raised to Buy from Neutral at UBS.

Micron Technology Inc. (NASDAQ: MU) was reiterated as Outperform with a $30 price target at Credit Suisse, with an expectation that it will beat earnings estimates.

NVIDIA Corp. (NASDAQ: NVDA) was raised to Outperform from Market Perform at JMP Securities.

Potash Corp. of Saskatchewan Inc. (NYSE: POT) was downgraded to Hold from Buy at Cantor Fitzgerald.

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Splunk Inc. (NASDAQ: SPLK) was started as Outperform at Macquarie.

Stratasys Ltd. (NASDAQ: SSYS) was started with a Buy rating at UBS

3D Systems Corp. (NYSE: DDD) was started with a Neutral rating at UBS.

Tableau Software Inc. (NYSE: DATA) was raised to Outperform from Neutral at Baird; Macquarie started coverage as Neutral.

United Continental Holdings Inc. (NYSE: UAL) was raised to Buy from Neutral at UBS.

Waddell & Reed Financial Inc. (NYSE: WDR) was raised to Buy from Neutral by Goldman Sachs.