Sublethal effects of fipronil on the ability of honeybees (Apis mellifera L.) to orientate in a complex maze

contribution to session IVTest methodology Background: The recent fipronil-based pesticide is accused by bee-keepers of causing depopulations in hives of honeybees (Apis mellifera L.). Behavioural effects during the flight of foraging honeybees would have been evoked. To test whether the insecticide fipronil may disorientate foragers, its impact on orientation in a maze was examined. Bees had to fly through a sequence of boxes to reach the target, which was a feeder containing a reward of sugar solution. After being trained to associate a green mark with the reward, foragers received 1 μg kg-1 fipronil orally and their capacity to orientate through the maze following the colour mark was tested and compared to control. Results: The rate of foragers entering the maze, and so responding to the mark placed at the entrance, was reduced with fipronil-fed animals. Before and after treatment, 86-89% of bees equally flew through the whole path and arrived to the goal without mistakes. The rate of fipronil-treated bees finding path without mistakes decreased to 60%. Conversely, the rate of bees with unsuccessful searches for the goal notably increased with treatment (34% in treated bees versus 4% in control bees). Conclusion: Our results show that orientation capacities of foragers in a complex maze were affected by fipronil. Keywords: Apis mellifera L., pesticide, maze, conditioning, visual learning, flight

Scattering correction using continuously thickness-adapted kernels

International audienceQuantitative reconstruction values are often miscalculated in Cone Beam Computed Tomography (CBCT) due to the presence of secondary radiation originating from scattering of photons inside the object and detector under consideration. The effect becomes more prominent and challenging in case of X-ray source of high energy (over a few 100 keV) which is used in industrial Non-Destructive Testing (NDT), due to higher scatter to primary ratio (SPR). This paper describes a scatter correction algorithm for correcting the combined scattering due to the object and the detector based on variations in Scatter Kernel Superposition (SKS) method. Scatter correction is performed for homogeneous and heterogeneous objects in a robust iterative manner suitable for high SPR, using pencil beam kernels which are simulated in computed tomography (CT) module of the CIVA software for NDT simulations. Two methods for scatter correction using SKS approach are discussed and compared in the paper. In the first method, we use a discrete approach in which kernels for only few thicknesses are used. In the second method a continuous approach is proposed where the kernels are analytically parameterised for all thicknesses. The results obtained after scatter correction are well within the expected reconstruction values. The continuous method produces better edge enhanced corrected projections and the method results in improved reconstruction values than the discrete method

Separable scatter model of the detector and object contributions using continuously thickness-adapted kernels in CBCT

International audienceDue to the increased cone beam coverage and the introduction of flat panel detector, the size of X-ray illumination fields has grown dramatically in Cone Beam Computed Tomography (CBCT), causing an increase in scatter radiation. Existing reconstruction algorithms do not model the scatter radiation, so scatter artifacts appear in the reconstruction images. The contribution of scattering of photons inside the detector itself becomes prominent and challenging in case of X-ray source of high energy (over a few 100 keV) which is used in typical industrial Non Destructive Testing (NDT). In this paper, comprehensive evaluation of contribution of detector scatter is performed using continuously thickness-adapted kernels. A separation of scatter due to object and the detector is presented using a four-Gaussian model. The results obtained prove that the scatter correction only due to the object is not sufficient to obtain reconstruction image free from artifacts as the detector also scatters considerably. The obtained results are also validated experimentally using a collimator to remove the contribution of object scatter

Toxicité et risques liés à l'emploi de pesticides chez les pollinisateurs : cas de l'abeille domestique

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