euronal growth cones are guided by both attractive and repulsive signals during development. Until now, one part of the guidance signaling system appeared relatively straightforward: Rac GTPases stimulate attraction, while Rho GTPases stimulate repulsion. But on page 1117, Bashaw et al. describe the activity of a new Rho guanine nucleotide exchange factor in Drosophila melanogaster , GEF64C, th...

We study a class of attractive spin systems. We prove that for these processes, the system dies out when the parameters are on the critical surface. We also prove that the supercritical process survives with positive probability in a suuciently thick space-timèslab'.

hydrogen bonding is considered by many to be the ‘master key’ of molecular recognition — owing to its relatively predictable strength and directionality — and plays a major role in the assembly of diverse non-covalent assemblies1. Consequently, the study and exploitation of hydrogen bonds has been central to the development of modern supramolecular chemistry. In particular, numerous applied set...