By Dan Weil The rules stipulate that Fed officials can’t purchase individual stocks, cryptocurrencies or commodities. Stung by the questionable trading activity of three former Federal Reserve officials, the Fed’s policymaking Federal Open Market Committee (FOMC) announced Friday that it’s adopting new rules for trading by senior central bank officials. The fresh regulations were first announced in October. They aim “to support public confidence in the impartiality and integrity of the [Federal Open Market] Committee’s work by guarding against even the appearance of any conflict of interest,” …