A time-dependent atomistic reconstruction of severe irradiation damage and associated property changes in nuclear graphite

Detailed knowledge regarding the nature of and mechanisms causing neutron irradiation damage in graphite remains a scientific and technological challenge, particularly at high irradiation doses. Using electrons as a surrogate for neutron irradiation, we develop a time-dependent atomistic reconstruction strategy fed by a time series of high-resolution transmission electron microscopy (HRTEM) images, to monitor damage propagation in a graphite grain up to a dose of about one displacement per atom (i.e. well beyond the conventional irradiation simulations based on molecular dynamics). The reduction in crystalline order and the development of interlayer bonding observed in the models with increasing irradiation time induce significant modifications of the elastic constants and thermal conductivity. Homogenizing these properties to the case of isotropic polycrystalline graphite we are able to reproduce the increase in Young’s modulus and decrease in thermal conductivity observed experimentally for reactor graphites with increasing dose. Further validation of the models is provided via a comparison of simulated and experimental data from irradiated material such as: HRTEM images, carbon K-edge electron energy loss spectra, dose rate and stored energies

The detection and quantification of a digenean infection in the snail host with special emphasis on Fasciola sp.

In this review, ten methods used to study digenean infections in their intermediate hosts were compared to determine which one should be used either in the field or in the lab to establish the prevalence and intensity of infections in snails. Snail crushing and snail dissection allow quick establishing of prevalence in natural or experimental infections, whereas histology is considered as the most accurate approach to assess the intensity of infection. The follow-up of cercarial shedding only gave an idea on cercarial production. Among recently developed techniques, polymerase chain reaction (PCR) brings the most accurate information and shows high sensitivity and specificity levels when compared to blotting techniques. The easiness and relatively low cost of the basic PCR protocol make it interesting to investigate the epidemiology of the liver fluke in a lab with limited financial resources. Nevertheless, if this technique allows a relatively good estimation of the prevalence, information concerning the intensity of infection is best obtained through real time PCR. However, at the time being this technique is too expensive to be used routinely in the field. The choice between classical or new techniques is usually based on a compromise, as each technique has its advantages and drawbacks