52 research outputs found
Biomagnifcation and body distribution of ivermectin in dung beetles
We thank the staf of Doñana Biological Reserve (DBR-ICTS), Doñana National Park, and Los Alcornocales
Natural Park, especially D. Paz, F. Ibáñez, P. Bayón, M. Malla and D. Ruiz for logistic facilities for the field
work and permissions (2019107300000904/IRM/MDCG/mes) to collect cattle dung and dung beetles. We
are grateful to J. Castro and A. Rascón for technical assistance. We also thank A. V. Giménez-Gómez for her
technical assistance in the laboratory work. We thank also F.-T Krell and the two anonymous reviewers for their
constructive comments. Financial support was provided by the project CGL2015-68207-R of the SecretarÃa de
Estado de Investigación–Ministerio de EconomÃa y Competitividad.A terrestrial test system to investigate the biomagnifcation potential and tissue-specifc distribution
of ivermectin, a widely used parasiticide, in the non-target dung beetle Thorectes lusitanicus (Jekel)
was developed and validated. Biomagnifcation kinetics of ivermectin in T. lusitanicus was investigated
by following uptake, elimination, and distribution of the compound in dung beetles feeding on
contaminated faeces. Results showed that ivermectin was biomagnifed in adults of T. lusitanicus
when exposed to non-lethal doses via food uptake. Ivermectin was quickly transferred from the gut to
the haemolymph, generating a biomagnifcation factor (BMFk) three times higher in the haemolymph
than in the gut after an uptake period of 12 days. The fat body appeared to exert a major role on
the biomagnifcation of ivermectin in the insect body, showing a BMFk 1.6 times higher than in the
haemolymph. The results of this study highlight that the biomagnifcation of ivermectin should be
investigated from a global dung-based food web perspective and that the use of these antiparasitic
substances should be monitored and controlled on a precautionary basis. Thus, we suggest that an
additional efort be made in the development of standardised regulatory recommendations to guide
biomagnifcation studies in terrestrial organisms, but also that it is necessary to adapt existing methods
to assess the efects of such veterinary medical products
Evolution of thermo-physical properties and annealing of fast neutron irradiated boron carbide
International audienceBoron carbide is widely used as a neutron absorber in most nuclear reactors, in particular in fast neutron ones. The irradiation leads to a large helium production (up to 1022-cm3) together with a strong decrease of the thermal conductivity. In this paper, we have performed thermal diffusivity measurements and X-ray diffraction analyses on boron carbide samples coming from control rods of the French Phenix LMFBR reactor. The burnups range from 1021 to 8.1021-cm3. We first confirm the strong decrease of the thermal conductivity at the low burnup, together with high microstructural modifications swelling, large micro-strains, high defects density, and disordered-like material conductivity. We observe the microstructural parameters are highly anisotropic, with high micro-strains and flattened coherent diffracting domains along the (00l) direction of the hexagonal structure. Performing heat treatments up to high temperature (2200DC) allows us to observe the material thermal conductivity and microstructure restoration. It then appears the thermal conductivity healing is correlated to the micro-strain relaxation. We then assume the defects responsible for most of the damage are the helium bubbles and the associated stress fields
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