The frequency-dependent Wright-Fisher model: diffusive and non-diffusive approximations

We study a class of processes that are akin to the Wright-Fisher model, with transition probabilities weighted in terms of the frequency-dependent fitness of the population types. By considering an approximate weak formulation of the discrete problem, we are able to derive a corresponding continuous weak formulation for the probability density. Therefore, we obtain a family of partial differential equations (PDE) for the evolution of the probability density, and which will be an approximation of the discrete process in the joint large population, small time-steps and weak selection limit. If the fitness functions are sufficiently regular, we can recast the weak formulation in a more standard formulation, without any boundary conditions, but supplemented by a number of conservation laws. The equations in this family can be purely diffusive, purely hyperbolic or of convection-diffusion type, with frequency dependent convection. The particular outcome will depend on the assumed scalings. The diffusive equations are of the degenerate type; using a duality approach, we also obtain a frequency dependent version of the Kimura equation without any further assumptions. We also show that the convective approximation is related to the replicator dynamics and provide some estimate of how accurate is the convective approximation, with respect to the convective-diffusion approximation. In particular, we show that the mode, but not the expected value, of the probability distribution is modelled by the replicator dynamics. Some numerical simulations that illustrate the results are also presented

Progress in silicon solar cell characterization with infrared imaging methods

This paper reviews the latest results in application and development of infrared imaging methods for fast and spatially resolved silicon solar cell characterization. Infrared imaging methods comprise electroluminescence (EL) imaging, photoluminescence (PL) imaging, and lock-in thermography (LIT). We report on new insights into the nature of local series resistances and important observations on local junction breakdown in industrial multicrystalline silicon solar cells. Significant improvements have been achieved in the applicability of infrared imaging methods for in-line application in silicon solar cell production. It was demonstrated that quantitative values for local reverse currents in hot-spots can be easily obtained in 10 milliseconds. Quantitative series resistance images were obtained in 800 milliseconds with a good potential to reduce the measurement time to below 500 milliseconds

Polymer Surface Treatment and Coating Technologies

An overview of surface modification and coating techniques for plastics is presented for changing the surface properties to meet the performance requirements in a variety of applications. Surface modification and coatings are utilized for purposes of adhesion, wettability, biocompatibility, scratch and abrasion resistance, chemical resistance, barrier properties, and more. Methods for modification include physical processes, such as surface roughening and abrading; liquid chemical processes, such as acid etching; and reactive gas chemical processes. The reactive gas chemical processes covered include corona, flame, and low-temperature plasma. Surface degradation from reactive gas exposure is presented with respect to the sources, chemical mechanisms, and methods for characterization. Coatings for plastics, including paints, functional coatings, and metallization, are summarized