Propagation failure of traveling waves in a discrete bistable medium

Propagation failure (pinning) of traveling waves is studied in a discrete scalar reaction-diffusion equation with a piecewise linear, bistable reaction function. The critical points of the pinning transition, and the wavefront profile at the onset of propagation are calculated exactly. The scaling of the wave speed near the transition, and the leading corrections to the front shape are also determined. We find that the speed vanishes logarithmically close to the critical point, thus the model belongs to a different universality class than the standard Nagumo model, defined with a smooth, polynomial reaction function.Comment: 8 pages, 6 eps figures, to appear in Physica

Asymptotic integral kernel for ensembles of random normal matrices with radial potentials

We use the steepest descents method to study the integral kernel of a family of normal random matrix ensembles with eigenvalue distribution P_{N}(z_{1},...,z_{N}) = Z_{N}^{-1} e^{-NSigma_{i=1}^{N}V_{alpha}(z_{i})} Pi_{1leqi<jleqN}|z_{i}-z_{j}|^{2} where V_{alpha}(z)=|z|^{alpha}, z in C and alpha in ]0,infty[. Asymptotic analysis with error estimates are obtained. A corollary of this expansion is a scaling limit for the n-point function in terms of the integral kernel for the classical Segal--Bargmann space

Social Class

Discussion of class structure in fifth-century Athens, historical constitution of theater audiences, and the changes in the comic representation of class antagonism from Aristophanes to Menander

Technical Change and Industrial Dynamics as Evolutionary Processes

Technical Change and Industrial Dynamics as Evolutionary Processes

9α,11β-PGF2 and its stereoisomer PGF 2α are novel agonists of the chemoattractant receptor, CRTH2

AbstractCRTH2 is a recently described chemoattractant receptor for the prostaglandin, PGD2, expressed by Th2 cells, eosinophils and basophils, and believed to play a role in allergic inflammation. Here we describe the potency of several PGD2 metabolites at the receptor to induce cell migration and activation. We report for the first time that the PGD2 metabolite, 9α,11β-PGF2, and its stereoisomer, PGF2α, are CRTH2 agonists. 9α,11β-PGF2 is a major metabolite produced in vivo following allergen challenge, whilst PGF2α is generated independently of PGD synthetase, with implications for CRTH2 signalling in the presence or absence of PGD2 production