After six years, three arena designs, two arena architects, a scaling back, a new development partnership and many protests, it appears the 22-acre Atlantic Yards megadevelopment over rail yards in Brooklyn, N.Y., is moving ahead. Developer Forest City Ratner Cos. says all the parties involved, including the Empire State Development Corp., have executed “all necessary documents and officially closed on the project.” Ratner also has announced the formation of a new partnership to develop the mixed-use project. The partnership deal, which calls for the sale by Ratner of 80% of basketball’s Nets to Onexim Sports and Entertainment Holdings, also includes Nets Sports and Entertainment, as well as Ratner and Onexim. Ratner says $511 million of bonds have been sold to finance the arena, which will be named Barclays Center. Roughly 35 buildings on the site have been demolished and a temporary rail yard completed.