A perfect little show in the lobby of the Traffic Zone studio building, in Minneapolis' Warehouse District, proves once again how savvy artists can be about their work. "Ephemera" features just seven pieces, most by Traffic Zone artists and each an exquisite exercise in minimalist elegance. Jantje Visscher's ribbons of crumpled Lucite refract light into shimmering patterns; Harriet Bart's Roman-style glass vials and heap of crushed glass seem to defy time; and Laura Crosby's fog-shrouded landscape and beach photos exude serenity. Bruce Shapiro's ever-evolving sand sculpture is a poetic marvel: In a tray of sand about 10 feet square, a steel ball rolls constantly, rhythmically pushing up low, overlapping ridges and circles of sand in a serene, conceptual mandala. Moved as if by an invisible hand or a will of its own, the steel ball brings an inexorable destruction and reordering to this miniature landscape. Fascinating.