Updated from 1:31 p.m. EST with new stock prices

Small-cap stocks ended a volatile week with another tumble Friday, joining the broader market for a downhill ride. The Russell 2000 lost 0.5% at 702.02, and the S&P SmallCap 600 was down 0.5% to 370.08.

Among the day's biggest losers was Aspen Technology ( AZPN). Shares of the Burlington, Mass.-based maker of industrial-process optimization software fell 5.7% to $12.71 after it announced it would be delisted from the Nasdaq and begin trading on Pink Sheets effective Feb. 19.

Also losing ground, Ultralife Batteries ( ULBI) shares dropped 16.9% to $14.04 after forecasting a fourth-quarter operating loss of about $2.5 million on revenue of $36.5 million. The Newark, N.Y.-based company had previously guided for a profit in the range of $2.7 million to $3.5 million on $41 million to $44 million in revenue. Analysts polled by Thomson Financial are looking for an operating profit of $3 million.

Shares of Emcore ( EMKR), a semiconductor company based in Abuquerque, N.M., got knocked down 10.2% to $12.32 after the company announced it would be selling $94 million in stock so it could buy telecom assets of Intel's ( INTC) Optical Platform division. The sale takes the form of 7.5 million shares of common stock for $12.50 and five-year warrants for 1.3 million shares with an exercise price of $15.06 a share.

Several stocks, including Cognex ( CGNX) managed to rise on the down day. Shares rocketed 26.3% to $19.43 on last night's fourth-quarter earnings. The Natick, Mass., maker of vision systems for manufacturing-process automation, or machines that can see what they're doing, posted income of $11.1 million, or a quarter a share, vs. $9.5 million, or 21 cents a share, in 2006. The Street was expecting 20 cents a share. Needham & Co. upgraded the stock to strong buy from buy.

eHealth ( EHTH) shares likewise climbed on last night's fourth-quarter results. The Mountain View, Calif., online health insurance services company posted a profit of $3.7 million, or 14 cents a share, vs. $3.8 million, or 15 cents a share, a year ago. The EPS results beat analysts' forecasts by a penny. Shares rose 18.7% to $26.14.

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