Editor's Note: In this feature from Stockpickr, we highlight lists of stocks that have been upgraded by analysts or are experiencing activist investor situations or some other market-moving events. Rumors of the Day: Shares of Tellabs ( TLAB) are climbing on heavy volume Monday due to reinvigorated buyout rumors, according the StreetInsider.com. Shares of the telecom-equipment maker were rising 64 cents, or 7.1%, to $9.54. Today's Hot List: Danaher ( DHR) has inked a $2.8 billion deal to acquire Tektronix ( TEK) for $38 a share in cash. Tektronix will become part of Danaher's Electronic Test platform, joining Danaher's Fluke and Fluke Networks businesses, and nearly doubling the platform's revenue. Tektronix shares soared 33%, or $9.31, to $37.65, while Danaher fell $1.18, or 1.4%, to $81.29. Citigroup ( C) slumped after the bank reported disappointing third-quarter earnings of 47 cents a share, down 57% from a year ago. Citi shares plunged $1.83, or 3.8%, to $46.04. Analyst Downgrades: Bernstein downgraded Boeing ( BA) from outperform to market perform and lowered its price target to $107. Bernstein said 787 delays could continue, limiting upside potential. Shares of the aerospace and defense company dropped $1.72 to $94.98. Analyst Upgrades: UBS upgraded Novellus Systems ( NVLS) to neutral from sell and raised its price target to $30 from $28 while holding full-year EPS estimates at $1.65. Shares of the chip-equipment maker added 4 cents to $27.99.