Mizuho downgraded Thermo Fisher Scientific Inc (NYSE:

) from “buy” to “neutral.” TMO's shares closed at $52.54 yesterday. Thermo Fisher Scientific's trailing-twelve-month ROE is 6.87%. Needham downgraded Ultra Clean Holdings Inc (NASDAQ:

) from “buy” to “hold.” UCTT's stock closed at $6.11 yesterday. Ultra Clean Holdings' trailing-twelve-month operating margin is 4.96%. Citigroup downgraded Quality Systems Inc (NASDAQ:

) from “neutral” to “sell.” QSII's shares closed at $29.90 yesterday. Quality Systems' trailing-twelve-month ROA is 19.07%. Deutsche Bank downgraded Aon Corporation (NYSE:

) from “buy” to “hold.” Aon's shares closed at $47.83 yesterday. Aon's trailing-twelve-month profit margin is 8.54%.