Stocks were mixed on Tuesday morning amid continued concerns about 'higher for longer' interest rates, as Treasury yields rose to a 15-year high, and recent bank credit downgrades by S&P. Housing market data was weaker than expected. The National Association of Realtors said that U.S. existing home sales fell to a seasonally adjusted annual rate of 4.07 million units in July. The reading was the lowest since January and below the Reuters consensus forecast of 4.15