Molecular genetic markers may reveal informative patterns of population processes such as historical migration, which may substantiate inference on postglacial re-colonization inferred, e.g., from fossil records. Palynological records of Swiss stone pine (Pinus cembra) suggest that the species has re-colonized the central Alps from a southeastern Alpine refugium after the last glacial maximum. Such a migration pathway likely resulted in a gradual decrease in genetic diversity with increasing distance to the glacial refugium, owing to founder events at the leading range edge. The present distribution of P. cembra in Switzerland consists of two rather distinct ranges, namely the inner-alpine parts of the Grisons and Valais, respectively, and additional disjunct occurrences in the northern and southern periphery of the Alps as well as between the two main ranges. We screened chloroplast microsatellite loci on 39 Swiss P. cembra populations and show that the genetic structure detected was congruent with a common ancestry from a single glacial refugium, likely located at the (south-)eastern periphery of the Alps. In contrast, our data rejected the alternative hypothesis of a distinct genetic separation of the two main ranges of Swiss stone pine in Switzerland. We further show that low genetic diversity within and high differentiation among peripheral populations in the northern Alps as well as the genetic differentiation between core and peripheral populations reflect genetic drift as a consequence of colonization history and limited gene flow by pollen and seed.
This paper presents in detail numerical methods and techniques for lightning impulse (LI) modeling and simulation of power and distribution transformers. The modeling methods are based on equivalent circuits of transformer winding entities resulting from the initial winding discretization determined by the required accuracy. The parameters of the equivalent circuit such as resistances and self- and mutual capacitances and inductances are obtained from field simulations (FEM). The circuit equations of the transformer’s equivalent circuit written in the state space form yield a large system of differential equations that is solved in time-domain by using the standard Runge-Kutta numerical integration technique. The obtained solution represents the voltage distribution over the winding in each moment of the LI-time (50μs). The results verification by comparison against measurements is presented in detail.
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