Search

The purpose of the experiment described herein is the study of material deformation (here a cylinder) induced by explosives. During its expansion, the cylinder (initially 3 mm thick) is thinning until fracture appears. Some tens of microseconds before destruction, strain localizations occur and induce mechanical necking. To characterize the time of first localizations, 25 stereoscopic acquisitions at about 500,000 frames per second are used by resorting to a single ultra-high speed camera. The 3D reconstruction from stereoscopic movies is described. A special calibration procedure is followed, namely, the calibration target is imaged during the experiment itself. To characterize the performance of the present procedure, resolution and optical distortions are estimated. The principle of stereoscopic reconstruction of an object subjected to a high-speed experiment is then developed. This reconstruction is achieved by using a global image correlation code that exploits random markings on the object outer surface. The spatial resolution of the estimated surface is evaluated thanks to a realistic image pair synthesis. Last, the time evolution of surface roughness is estimated. It gives access to the onset of necking.

Environmental features impacting the spread of invasive species after introduction can be assessed using population genetic structure as a quantitative estimation of effective dispersal at the landscape scale. However, in the case of an ongoing biological invasion, deciphering whether genetic structure represents landscape connectivity or founder effects is particularly challenging.We examined the modes of dispersal (natural and human‐aided) and the factors (landscape or founders history) shaping genetic structure in range edge invasive populations of the Asian tiger mosquito, Aedes albopictus, in the region of Grenoble (Southeast France).Based on detailed occupancy–detection data and environmental variables (climatic, topographic and land‐cover), we modelled A. albopictus potential suitable area and its expansion history since first introduction. The relative role of dispersal modes was estimated using biological dispersal capabilities and landscape genetics approaches using genome‐wide SNP dataset.We demonstrate that both natural and human‐aided dispersal have promoted the expansion of populations. Populations in diffuse urban areas, representing highly suitable habitat for A. albopictus, tend to disperse less, while roads facilitate long‐distance dispersal. Yet, demographic bottlenecks during introduction played a major role in shaping the genetic variability of these range edge populations.The present study is one of the few investigating the role of founder effects and ongoing expansion processes in shaping spatial patterns of genetic variation in an invasive species at the landscape scale. The combination of several dispersal modes and large proportions of continuous suitable habitats for A. albopictus promoted range filling of almost its entire potential distribution in the region of Grenoble only few years after introduction. [ABSTRACT FROM AUTHOR]

Invasion of new territories by insect vector species that can transmit pathogens is one of the most important threats for human health. The spread of the mosquito Aedes albopictus in Europe is emblematic, because of its major role in the emergence and transmission of arboviruses such as dengue or chikungunya. Here, we modeled the spread of this mosquito species in France through a statistical framework taking advantage of a long-term surveillance dataset going back to the first observation of Ae. albopictus in the Metropolitan area. After validating the model, we show that human activities are especially important for mosquito dispersion while land use is a major factor for mosquito establishment. More importantly, we show that Ae. albopictus invasion is accelerating through time in this area, resulting in a geographic range extending further and further year after year. We also show that sporadic “jump” of Ae. albopictus in a new location far from the colonized area did not succeed in starting a new invasion front so far. Finally, we discuss on a potential adaptation to cooler climate and the risk of invasion into Northern latitudes. [ABSTRACT FROM AUTHOR]

Most often, digital image correlation is used to analyse a sequence of images. Exploitation of an expected temporal regularity in the displacement fields can be used to enhance the performances of a digital image correlation analysis, either in terms of spatial resolution, or in terms of uncertainty. A general theoretical framework is presented, tested on artificial and experimental image series. [ABSTRACT FROM PUBLISHER]