Surfing versus science

Gene surfing

Spatially resolved genetic data is increasingly used to reconstruct the migrational history of species. To assist such inference, we study, by means of simulations and analytical methods, the dynamics of neutral gene frequencies in a population undergoing a continual range expansion in one dimension. During such a colonization period, lineages can fix at the wave front by means of a “surfing” m...

Science Versus Stigma

Science Versus Stigma Stigma is an enormous obstacle to more effective drug abuse treatment. Widespread perceptions that addiction strips individuals of basic human qualities lead to selffulfilling predictions that those who are addicted cannot recover or ever play positive and productive social roles. Two articles in this issue of Addiction Science & Clinical Practice illustrate a fundamental ...

Science versus the Mountain

Surfing on Calcium Waves

A key question in brain development is how migration of neuronal precursors is guided to establish the ordered laminar layers. In the April 20, 2007 issue of Cell, Guan et al. show that the leading process of migrating cerebellar granule neurons senses repulsive Slit molecules by generating a Ca(2+) wave that propagates to the soma to cause reversal of cell polarity and migration.

Energy Efficient Surfing

Surfing is a latchless pipelining technique where the propagation delays of gates and other logic functions are modulated to produce event attractors. We describe a test chip that demonstrates a surfing pipeline ring and then introduce new circuits that dramatically reduce the energy overhead for surfing. Our test chip implements a twelve-stage, surfing ring that supports two independent waves ...