SECURITIES

PaineWebber Replaces Head of Mutual Fund Unit: Joyce Fensterstock, president of Mitchell Hutchins Asset Management Inc., PaineWebber Group Inc.’s mutual fund group, confirmed that she has been relieved of her duties. Paul Guenther, PaineWebber’s president, has taken over the post pending a permanent replacement, a company spokeswoman said. The move is the brokerage firm’s latest attempt to contain the damage from its $268-million bailout of the short-term government bond fund, according to Lipper Analytical Services Inc. Fensterstock was the latest casualty from the costly and embarrassing rescue of the fund, which dabbled in risky securities.