Memory-induced acceleration and slowdown of barrier crossing.

We study the mean first-passage time τ for the barrier crossing of a single massive particle with non-Markovian memory by Langevin simulations in one dimension. In the Markovian limit of short memory time τ, the expected Kramers turnover between the overdamped (high-friction) and the inertial (low-friction) limits is recovered. Compared to the Markovian case, we find barrier crossing to be accelerated for intermediate memory time, while for long memory time, barrier crossing is slowed down and τ increases with τ as a power law τ∼τ.

A genome-wide search for linkage to asthma. German Asthma Genetics Group.

Asthma is among the most frequent chronic diseases in childhood. Although numerous environmental risk factors have already been identified, the basis for familial occurrence of asthma remains unclear. Previous genome screens for atopy in British/Australian families and for asthma in different American populations showed inconsistent results.