It’s time again for the MacArthur Foundation to begin handing out its so-called “genius grants” – $500,000 gifts with no strings attached, awarded to the “most promising creative thinkers” in America – and this year, the city of Boston is home to no fewer than six of the recipients. “It is not surprising that Boston, with its top-tier universities and hospitals, would attract geniuses. But the Boston winners also represent something else: the triumph of synergy as people cross the traditional boundaries that divide one field from another.” The Boston winners include composer Osvaldo Golijov, female circumcision activist Dr. Nawal Nour, and Xiaowei Zhuang, a Harvard physics professor.