Reassortment is an important source of genetic diversity in segmented viruses and is the main source of novel pathogenic influenza viruses. Despite this, studying the reassortment process has been ...constrained by the lack of a coherent, model-based inference framework. Here, we introduce a coalescent-based model that allows us to explicitly model the joint coalescent and reassortment process. In order to perform inference under this model, we present an efficient Markov chain Monte Carlo algorithm to sample rooted networks and the embedding of phylogenetic trees within networks. This algorithm provides the means to jointly infer coalescent and reassortment rates with the reassortment network and the embedding of segments in that network from full-genome sequence data. Studying reassortment patterns of different human influenza datasets, we find large differences in reassortment rates across different human influenza viruses. Additionally, we find that reassortment events predominantly occur on selectively fitter parts of reassortment networks showing that on a population level, reassortment positively contributes to the fitness of human influenza viruses.
A system consisting of a two-degree-of-freedom oscillator with sliding interfaces to two surfaces subjected to wear is investigated with respect to surface evolution and wear pattern dynamics. The ...system shows the usual possibility of wear pattern generation due to instabilities of the surface evolution equations. As a novel phenomenon in the context of wear pattern dynamics it is shown that, depending on initial conditions, transient growth of surface properties is possible even in the case of linear stability of the surface evolution. An explanation of the effect is given in terms of non-orthogonality of the surface evolution modes. The effect is to be expected in technical applications with multiple surfaces subjected to wear, like, e.g. friction brakes, and could be regarded as an additional mechanism leading to the generation of surface properties due to wear pattern dynamics.
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