US markets today: Dow up 141 points as Wall Street eyes record week finish, UnitedHealth jumps on Buffett stake

US stocks are near record highs, fueled by hopes of a September Federal Reserve rate cut. The S&P 500 remains virtually unchanged, while the Dow rose. UnitedHealth Group surged after Berkshire Hathaway's investment. However, Applied Materials fell due to disappointing revenue guidance. China's economic slowdown prompts calls for policy support, impacting Asian markets.