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Investors are trying to figure out which stocks they should buy, sell or avoid now that the government shutdown is two weeks old and the debt ceiling debate is stalling yet again. These investors often hear ideas for stocks to buy, but they often do not get told when to sell or avoid a stock. 24/7 Wall St. reviews many fresh research calls each and every day to find great ideas, and we have broken out the negative and cautious analyst calls today as the stocks to sell, according to those research reports. These are Wednesday’s top analyst downgrades and cautious research notes from Wall Street.

Achillion Pharmaceuticals Inc. (NASDAQ: ACHN) was downgraded to Neutral from Outperform at Credit Suisse.

Allegheny Technologies Inc. (NYSE: ATI) was started as Underperform with a $27 price target (versus a $32.03 close) at Sterne Agee.

AK Steel Holding Corp. (NYSE: AKS) was started as Underperform with a $3 price target (versus a $4.36 close) at Credit Suisse.

Cisco Systems Inc. (NASDAQ: CSCO) was downgraded to Neutral from Buy at MKM Partners.

CoreSite Realty Corp. (NYSE: COR) was downgraded to Neutral from Buy at Bank of America Merrill Lynch.

Exelon Corp. (NYSE: EXC) was downgraded to Underweight from Overweight with a $21 price target (versus a $29.52 close) at Morgan Keegan.

Invesco Ltd. (NYSE: IVZ) was downgraded to Neutral from Buy at Sterne Agee.

Schlumberger Ltd. (NYSE: SLB) was downgraded to Neutral at HSBC.

SPX Corp. (NYSE: SPW) was reinstated as Underperform with an $85 price target (versus a $84.29 close) at Bank of America Merrill Lynch.

Superior Energy Services Inc. (NYSE: SPN) was downgraded to Hold from Buy at Jefferies.