Shelley Ben Nathan has resigned from Bear Stearns, where she was a managing director and high-yield retail analyst, according to an e-mail message sent out to clients last Friday, which was her last day at the firm. "I have decided to change gears for a while and focus my energies full time on my family," she wrote. She has four children under five years old. Ben Nathan placed third in the high-yield retail sector for four consecutive years from 1997-2000 on the Institutional Investor All-America Fixed-Income Research Team. She did not return calls.