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With a decline exceeding 30% over three generations, the once-common European Turtle-dove is now considered globally threatened by IUCN. As a legal game species in 10 European countries, the recent International Single Species Action Plan for this species highlighted the need to carry out an assessment of the sustainability of current levels of hunting. In 2013–2014, the Western European population was estimated at 1.3–2.1 million pairs, and the hunting bag in the same region to be 1.1 million birds. Using the Demographic Invariant Method, we assessed whether current levels of hunting harvest within Europe constitute overexploitation of the western flyway European Turtle-dove population. We calculated the maximum growth rate λmax that a population might achieve in the absence of any additive mortality. Then we estimated the potential maximum harvestable population fraction (P) allowed by excess population growth. We explored a wide range of plausible scenarios relating to assumed demographic rates, geographic scope of the flyway and management objectives. λmax was estimated to lie between 1.551 and 1.869. Current levels of hunting along the western flyway are more than double the sustainable fraction (P) under all suitably conservative scenarios, and only fall below this threshold under the most restrictive assumptions. We conclude that current levels of legal hunting along the western flyway are unlikely to be sustainable. Reducing uncertainty associated with assessments of the sustainability of turtle dove hunting will require improved information on (in order of decreasing importance) current levels of hunting, adult survival, age structure and population size.
In this work, we present a study of epitaxial Aluminium Nitride (AlN) for thin film bulk acoustic wave (BAW) applications. Molecular beam epitaxy (MBE) was used to perform high crystalline quality AlN thin films growth on different silicon substrate preparations. A morphological study was performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), while structural properties and acoustic wave speed were respectively assessed by X-ray diffraction and acoustic picoseconds.
During the last ten years, we have developed an efficient growth process of nitrides on silicon substrates by molecular beam epitaxy. In collaboration with partners AlGaN/GaN HEMTs on Si having promising performances have been fabricated. Focusing on the growth aspect and underlying some of the key issues, we present in this paper an overview of our contribution in the field of AlGaN/GaN HEMTs on Si substrates.
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