* Researchers explore mixed vaccine shots as COVID-19 variants surge
* House GOP keeps Liz Cheney in leadership, rebuking Trump loyalists
* Treasury yield curve at steepest level since 2017
* Biden pushes ahead on his proposed $1,400 stimulus checks
* Survey: nearly 70% of Americans support Biden’s $1.9 trillion relief plan
* Global economic rebound slowed for a third month in January
* Is tighter liquidity in China a new global headwind?
* Sen. Klobuchar (D-Minn.) unveils sweeping antitrust reform bill
* Lazy investing strategy has been a winning strategy
* US Services PMI indicates “sharp upturn in business activity” in January
* US private payrolls rebounded modestly in January after December decline: