Downtown vegans have a new reason to rejoice, as Blog Downtown announces the pending arrival of Dr. J’s Vibrant Cafe, the second iteration of the meat-free restaurant which is due for Main and 4th Streets. First, the bad news: Although there may be only one Dr. J in our books, the restaurant has nothing to do with the great Julius Erving. Instead, the titular heroine here is Taiwanese health food guru Dr. Juliet Tien, a holistic nutritionist behind her own “Vibrant Academy,” cookbook scribe, and maker of a frozen foods line, who previously had a location in Westwood. The good doc’s Downtown space will hold about 100 seats, offering a tea and smoothie bar, organic, “macrobiotic Ayurvedic and gluten free” fusion dishes, and a grocery section. The 2,700-square-foot space, designed by Kevin Tsai, is just starting construction and will include al fresco dining on a patio.