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Determining the relative roles of vicariance and selection in restricting gene flow between populations is of central importance to the evolutionary process of population divergence and speciation. Here we use molecular and morphological data to contrast the effect of isolation (by mountains and geographical distance) with that of ecological factors(More)
The spiral disk for type-J high-speed counter-current chromatography (HSCCC) has been improved by placing short segments of PTFE (tetrafluoroethylene) tubing into the channel at regular intervals. The best results were obtained with a four-channel spiral column using 600 spacers, which significantly improved stationary phase retention and partition(More)
A new catheter of dual lumen construction, suitable for clinical use, is capable of navigating acute vessel branches by selective retrojet fluid thrusts issuing from cowlings built into its distal sidewalls. Conventional radiopaque liquids can be used both to drive the system and to fluoroscopically locate its position relative to the vascular network. In(More)
With the help of a large number of monitoring sites, the behaviour of F in forested ecosystems of a formerly polluted area (Möhlin and Rheinfelden, Switzerland) could be studied over 30 years. An aluminium smelting plant originated the pollution of this area in the past: however, after the installation of a filtration plant in 1958 the F emissions were(More)
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