Mary Jo White and Gary Gensler, chairmen of the Securities and Exchange Commission and the Commodity Futures Trading Commission, respectively, are scheduled to appear today before the Senate banking committee. Sen. Sherrod Brown, D-Ohio, says he intends to hold the regulators' feet to the fire regarding banks' commodity trading. "Banks should focus on core banking activities," Brown wrote in an e-mail. "Our economy is strengthened when financial conflict of interest and financial risk are reduced." The committee also is expected to question White and Gensler about implementation of derivatives rules under the Dodd-Frank Act.