NEW YORK -- Stocks that traded heavily or had substantial price changes Monday:

       Plantronics Inc., up $13.79 to $39.99.

       HP is buying the headset maker in a $3.3 billion deal.

       Staar Surgical Co., up $7.76 to $80.71.

       U.S. regulators approved the company's implantable lens product for nearsightedness.

       Neenah Inc., up $1.99 to $40.20.

       Schweitzer-Mauduit International is buying the paper producer.

       Huntsman Corp., up $1.91 to $37.89.

       The chemical company doubled its stock buyback program to $2 billion.

       Barclays Plc., down 96 cents to $8.09.

       The financial holding company warned investors of a loss due to its selling of more structured notes than it had registered for sale.

       ConocoPhillips, down $4 to $103.50.

       Energy stocks fell as oil prices slumped.

       Hasbro Inc., down $1.05 to $83.83.

       The maker of G.I. Joe and other toys reportedly rejected a settlement deal with Alta Fox over a potential proxy fight.

       Citigroup Inc., down 82 cents to $55.92.

       Bond yields fell and weighed down bank stocks, which rely on higher yields to charge more lucrative interest on loans.