Drugs-for-guns traffic bedevils Mass., Vt.

Law enforcement officials are watching with increasing alarm as narcotics from Mass. are ferried to Vermont and swapped for guns that are plentiful and cheap.

Lori Berseth (right) is consoled after seaching for her missing dog, Lucille, after a tornado destroyed the town of Mayflower, Arkansas.

Reuters

At least 16 dead as tornadoes strike central, southern US

A powerful storm system moving across the region spawned several deadly tornadoes.

Suffolk professors fear evaluations could erode tenure

Suffolk University will require all tenured faculty to undergo performance reviews that in some cases could lead to dismissal.

Diversity low in educator courses

The lack of racial diversity among teachers can be traced to not enough people of color enrolling in educator programs, according to a Globe review of state data.

Guide Kathy Eastman looks out a window at Buckman Tavern, where Lexington’s militiamen awaited the British in 1775.

Photos by John Tlumacki/Globe Staff

The Lexington-Concord debate: Which town fired first?

With the restoration of Buckman Tavern, the Lexington Historical Society is hosting an exhibit exploring the debate over whether the Revolutionary War began in Lexington or Concord.

Pope Francis leaves at the end of the Canonization Mass in which John Paul II and John XXIII were declared saints.

Analysis

Sainthood for two popes more Woodstock than World’s Fair

Was yesterday’s massive canonization ceremony just another big event, or a cultural “happening” destined to pass into history as a symbol of broader transformations?

As senators, Jeanne Shaheen, Scott Brown rarely interacted

The unusually cool relationship across the partisan divide helps explain why the N.H. Senate race has quickly turned bitter.

Los Angeles Clippers owner Donald Sterling with V. Stiviano, to whom racist remarks were allegedly directed.

Outcry rises over words linked to NBA owner

The NBA world continued to react to racially charged statments allegedly made by Los Angeles Clippers owner Donald Sterling.

Business

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Tom Webster, a chemical engineer at Northeastern, examined bone cancer cells at a school research center. Above, test tubes hold different concentrations of nanoparticles used to treat for antibiotic- resistant bacteria. Below, two pins used in diabetic patients; the one at right is coated with nanoparticles.

Nanomedicine could improve surgical implants

Northeastern University’s Tom Webster believes nanomaterials can be used to stave off infections triggered by conventional materials used in surgical implants.

Arts

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Opera Review

Tenor Fernando Guimarães and mezzo-soprano Jennifer Rivera in dress rehearsal for Boston Baroque’s “semi-staged” production of “Il ritorno d’Ulisse in patria.”

Boston Baroque makes a home for Monteverdi’s ‘Ulisse’

The singing throughout was excellent, and the orchestra impinged on it only rarely, but at times, particularly in the first half, the drama dragged.