Traumatic eye injuries as a result of blunt impact: computational issues

The detachment or tearing of the retina in the human eye as a result of a collision is a phenomenon that occurs very often. Reliable numerical simulations of eye impact can be very useful tools to understand the physical mechanisms responsible for traumatic eye injuries accompanying blunt impact. The complexity and variability of the physical and mechanical properties of the biological materials, the lack of agreement on their related experimental data as well as the unsuitability of specific numerical codes and models are only some of the difficulties when dealing with this matter. All these challenging issues must be solved to obtain accurate numerical analyses involving dynamic behavior of biological soft tissues. To this purpose, a numerical and experimental investigation of the dynamic response of the eye during an impact event was performed. Numerical simulations were performed with IMPETUS-AFEA, a new general non-linear finite element (FE) software which offers non uniform rational B-splines (NURBS) FE technology for the simulation of large deformation and fracture in materials. IMPETUS code was selected in order to solve hourglass and locking problems typical of nearly incompressible materials like eye tissues. Computational results were compared with the experimental results on fresh enucleated porcine eyes impacted with airsoft pellets

MM2-thalamic Creutzfeldt-Jakob disease-Neuropathological, biochemical and transmission studies identify a distinctive prion strain

In Creutzfeldt-Jakob disease (CJD), molecular typing based on the size of the protease resistant core of the disease-associated prion protein (PrP(Sc) ) and the M/V polymorphism at codon 129 of the PRNP gene correlates with the clinico-pathologic subtypes. Approximately 95% of the sporadic 129MM CJD patients are characterized by cerebral deposition of type 1 PrP(Sc) and correspond to the classic clinical CJD phenotype. The rare 129MM CJD patients with type 2 PrP(Sc) are further subdivided in a cortical and a thalamic form also indicated as sporadic fatal insomnia. We observed two young patients with MM2-thalamic CJD. Main neuropathological features were diffuse, synaptic PrP immunoreactivity in the cerebral cortex and severe neuronal loss and gliosis in the thalamus and olivary nucleus. Western blot analysis showed the presence of type 2A PrP(Sc) . Challenge of transgenic mice expressing 129MM human PrP showed that MM2-thalamic sporadic CJD (sCJD) was able to transmit the disease, at variance with MM2-cortical sCJD. The affected mice showed deposition of type 2A PrP(Sc) , a scenario that is unprecedented in this mouse line. These data indicate that MM2-thalamic sCJD is caused by a prion strain distinct from the other sCJD subtypes including the MM2-cortical form

Combining a CDM model and a FE-Particle method to analyse the ruin modes of a composite structure during a crash

International audienceA continuum damage model inspired from the Matzenmiller-Lubliner-Taylor’s model, has been derived to predict damage induced in T800S/M21GC sample plates during low velocity impacts. It was found that for crashworthiness applications, it is necessary to couple the progressive ruin of the material to a representation of the matter openings. Element kill technique (erosion) is efficient but not predictive. A technique switching finite elements into particles at rupture is used to create cracks and accumulated mater during the crash of the structure. Switching criteria are defined using the contribution of the different ruin modes in the damage evolution

Combining a CDM model and a FE-Particle method to analyse the ruin modes of a composite structure during a crash

International audienceA continuum damage model inspired from the Matzenmiller-Lubliner-Taylor’s model, has been derived to predict damage induced in T800S/M21GC sample plates during low velocity impacts. It was found that for crashworthiness applications, it is necessary to couple the progressive ruin of the material to a representation of the matter openings. Element kill technique (erosion) is efficient but not predictive. A technique switching finite elements into particles at rupture is used to create cracks and accumulated mater during the crash of the structure. Switching criteria are defined using the contribution of the different ruin modes in the damage evolution