Practicalities of BVID detection on aerospace-grade CFRP materials with optical fibre sensors

Several reports have recently shown the capability of optical fibre sensors for the detection of barely visible impact damage (BVID) on CFRP laminates, based on changes in the optical signal before and after impact. Although this approach was shown to work well in lab conditions, little attention has been paid so far to its practicality when considering realistic ambient conditions or to the detection range. In this work we attempt to derive BVID detection thresholds for fibre Bragg grating-based sensors, by considering standardized temperature and vibration levels for aerospace applications. To the best of our knowledge this is the first practical threshold assessment for BVID detection on aerospace-grade CFRP for such sensors. We have put our detection thresholds to the test by analysing a total of 24 BVIDs on 12 panels made from 4 different CFRP material systems and derived commendable sizes for the detection range on the different material systems

Range-wide patterns of human-mediated hybridisation in European wildcats

Hybridisation between wild taxa and their domestic congeners is a significant conservation issue. Domestic species frequently outnumber their wild relatives in population size and distribution and may therefore genetically swamp the native species. The European wildcat (Felis silvestris) has been shown to hybridise with domestic cats (Felis catus). Previously suggested spatially divergent introgression levels have not been confirmed on a European scale due to significant differences in the applied methods to assess hybridisation of the European wildcat. We analysed 926 Felis spp. samples from 13 European countries, using a set of 86 selected ancestry-informative SNPs, 14 microsatellites, and ten mitochondrial and Y-chromosome markers to study regional hybridisation and introgression patterns and population differentiation. We detected 51 hybrids (four F1 and 47 F2 or backcrosses) and 521 pure wildcats throughout Europe. The abundance of hybrids varied considerably among studied populations. All samples from Scotland were identified as F2 hybrids or backcrosses, supporting previous findings that the genetic integrity of that wildcat population has been seriously compromised. In other European populations, low to moderate levels of hybridisation were found, with the lowest levels being in Central and Southeast Europe. The occurrence of distinct maternal and paternal markers between wildcat and domestic cat suggests that there were no severe hybridisation episodes in the past. The overall low (< 1%) prevalence of F1 hybrids suggests a low risk of hybridisation for the long-term genetic integrity of the wildcat in most of Europe. However, regionally elevated introgression rates confirm that hybridisation poses a potential threat. We propose regional in-depth monitoring of hybridisation rates to identify factors driving hybridisation so as to develop effective strategies for conservation. © 2020, The Author(s)