Convergent extension is the cell-rearrangement process by which a developing embryo elongates to establish the head-to-tail body axis. In the early Drosophila embryo, this process occurs within a one-cell-thick epithelial layer. Using confocal microscopy, images were collected of the two-dimensional cell pattern at four stages during convergent extension in wild-type embryos and at one stage in...

A topological group G is sequentially h-complete if all the continuous homomorphic images of G are sequentially complete. In this paper we give necessary and sufficient conditions on a complete group for being compact, using the language of sequential h-completeness. In the process of obtaining such conditions, we establish a structure theorem for ω-precompact sequentially h-complete groups. As...