The infall of a satellite galaxy onto a galactic disk generally brings in angular momentum that is not aligned with the axis of the disk. The main dynamical issues addressed are what fraction of the orbital angular momentum of the satellite and the associated energy is added to the disk, as opposed to being left in the halo, and whether the absorbed fraction is added coherently or thermalized i...

sciurids: results from golden mantled ground squirrels and comparisons for five species. Anim. Behav. 26, 409–421. 3. Hunt, D.M., Wilkie, S.E., Bowmaker, J.K., and Poopalasundaram, S. (2001). Vision in the ultraviolet. Cell. Mol. Life Sci. 58, 1583–1598. 4. Cowing, J.A., Poopalasundaram, S., Wilkie, S.E., Robinson, P.R., Bowmaker, J.K., and Hunt, D.M. (2002). The molecular mechanism for the spe...

How chemoattractant gradients form and persist in complex tissues is a key question in cell migration. Two studies now show that CXCR7 acts as a sink in the migrating zebrafish lateral line primordium to generate SDF1 gradients.