Each weekday, TheStreet.com Ratings updates its ratings on the stocks we cover. Our model projects a stock's total return potential over a 12-month period including both price appreciation and dividends. Our buy, hold or sell ratings designate how we expect these stocks to perform against a general benchmark of the equities market and interest rates.

While our model is quantitative, it uses both subjective and objective elements. For instance, subjective elements include expected equities market returns, future interest rates, implied industry outlook and forecasted company earnings. Objective elements include volatility of past operating revenue, financial strength and company cash flows.

Some recent rating changes are highlighted below.

Software company

Adobe

(ADBE) - Get Report

has been upgraded to a buy from a hold. The company reported a 36.9% year-over-year profit increase in the first quarter of fiscal 2007. During the quarter, the company benefited from investment gains, higher interest income and a lower tax rate. Adobe is also about to upgrade its popular Creative Suite 3 product. The company had been rated a hold since July 2006.

Radio and television broadcaster

Westwood One

( WON) has been downgraded to a sell from a hold. The company's revenues, net income and earnings per share have all declined over the past fiscal year. The current debt-to-equity ratio is 1.81, which TheStreet.com Ratings feels is quite high. Westwood One had been rated a hold since January 2007.

Orbotech

(ORBK) - Get Report

has been downgraded to a hold from a buy. The company makes high-tech equipment for inspecting circuit boards and display panels. Although Orbotech's revenues have grown over the past fiscal year, earnings per share have declined. The stock price has also fallen 11% over the past 12 months. Orbotech had been rated a buy since May 2005.

Health Management

(HMA)

has been downgraded to a hold from a sell. The company owns and operates acute care hospitals in non-urban areas of the southern United States. The company lost 17 cents per share in the fourth quarter of fiscal 2006, a major reversal from the same quarter a year ago, when Health Management earned 35 cents per share. The company's stock price has tumbled 47% over the past year, but remains expensive compared to other health care providers. TheStreet.com Ratings believes this will make it difficult for investors to achieve positive results with this company in the future. Health Management had been rated a hold since January 2007.

Cabot Microelectronics

(CCMO)

has been upgraded to a buy from a hold. The company makes high-performance polishing slurries for advanced circuit devices. Gross profit margins are currently rather high for this company, coming in at 55.5% in the first quarter of fiscal 2007. TheStreet.com Ratings feels CCMP has also been very successful managing its debt. The company had been rated a hold since May 2006.

Additional ratings changes are listed in the table below.