Pre-Paid Legal Services ( PPD) gained after the Ada, Okla., marketer of legal plans said its second-quarter income nearly doubled. The company earned $12.1 million, or 81 cents a share, compared with $6.9 million, or 44 cents a share, a year ago.

Commissions totaled $32.7 million, down from $38.8 million last year. Revenue totaled $112 million, up from $105.6 million a year ago. Shares of Pre-Paid climbed $1.77, or 5.2%, to $35.85.

Metretek Technologies ( MEK) advanced after the Denver-based oil and gas services company said its PowerSecure unit received contracts worth about $5 million. The contracts cover the installation of interactive distributed generation systems.

The contracts range in value from $200,000 to more than $3 million. Shares of Metretek gained 89 cents, or 5.7%, to $16.40.

NovaGold Resources ( NG) surged after Barrick Gold ( ABX) made an offer to buy the Canadian mining company for about $1.53 billion. The all-cash offer of $14.50 a share represents a premium of 24% over the July 21 closing price of NovaGold's stock. NovaGold was climbing $3.82, or 32.7%, to $15.49.

Partners Trust Financial Group ( PRTR) slipped after the Utica, N.Y., company was downgraded by Ryan Beck to underperform from market perform.

Last week, the company reported second-quarter earnings of $6.8 million, or 15 cents a share, compared with $6.9 million, or 14 cents a share, a year ago. Partners Trust shares fell 52 cents, or 4.8%, to $10.43.

China BAK Battery ( CBAK) plummeted after the China-based battery company said it expected third-quarter revenue to come in about 15% below the second quarter. The company cited lower-than-expected sales of steel-case battery cells and aluminum-case battery cells.

The company said the decline was primarily attributable to seasonal variations that are more accentuated than prior periods because of its increased production. "We expect sales of battery cells for cellular phones to increase in the fourth quarter in line with seasonal trends," the company said. "In addition, we expect sales of new products, such as battery cells for notebook computers and cordless power tools to increase."

As a result, China BAK forecast full-year earnings of around $24 million. Shares sank $1.99, or 29.3%, to $4.80.

Medical-device maker Nephros ( NEP) dropped after the company said Friday that it received notice from the American Stock Exchange that it isn't in compliance with continued listing standards.

The company is considering what actions it can take to regain compliance with the listing standards and intends to submit a plan to the Amex staff in a timely manner. Shares of New York-based Nephros were losing 18 cents, or 13%, to $1.20.