(RECAP: Federal Reserve Chair Janet Yellen said Tuesday that the largest U.S. banks might need to hold additional capital to withstand periods of financial stress. Yellen told a banking conference in Atlanta that current rules on how much capital banks must hold to protect against losses don’t address all threats. She said the Fed’s staff is considering what further measures might be needed. Banks and their advocates have warned that further tightening bank regulation would lead to reduced lending to businesses and financial institutions and could slow economic growth.)