Bomb Details Emerge in Boston Case  —  BOSTON — The explosives used to kill three people and injure 176 at the Boston Marathon on Monday were likely some kind of “pressure-cooker” devices that sent sharp bits of shrapnel flying into victims in the vicinity of the blast, several law enforcement officials said Tuesday.

Why Boston Bombings Might Be Scarier Than 9/11  —  Killing Americans at play resonates differently than attacks on economic and military targets.  —  Call it “terrorism” if a label helps you make sense of this madness.  Find who did it and squash him—or them—with what President Obama called “the full weight of justice.”

Is The Reinhart-Rogoff Result Based on a Simple Spreadsheet Error?  —  So this is huge.  Or, rather, it won't matter even a tiny little bit but it ought to be a big deal anyway.  You've probably heard that countries with a high debt:GDP ratio suffer from slow economic growth.

Envelope tests positive for ricin at Washington mail facility  —  Washington (CNN) — An envelope that tested positive for the deadly poison ricin was intercepted Tuesday afternoon at the U.S. Capitol's off-site mail facility in Washington, congressional and law enforcement sources tell CNN.

Letter Sent To U.S. Senator Tests Positive For Poison  —  Officials at the U.S. Capitol's offsite mail facility on Tuesday discovered an envelope that tested positive for the deadly substance ricin.  Its intended recipient was U.S. Sen. Roger Wicker (R-MS).

An Al-Shabaab Link to Boston Marathon Bombings?  —  A series of Twitter gloats today raised questions about the possible involvement of Somali terror group Al-Shabaab in the Boston Marathon bombing.  —  No person or group has yet directly taken responsibility for the attack that killed three and wounded 176, 17 of those critically.

Militia Groups Denounce Boston Marathon Attack  —  Early speculation that militias were behind the bombings are “totally off-base,” says one leader.  “This was a target of civilians, which is reprehensible by every measure of what we hold to our values.”  —  Via: Adrees Latif / Reuters