RESUMO
One of the main challenges in ultrafast material science is to trigger phase transitions with short pulses of light. Here we show how strain waves, launched by electronic and structural precursor phenomena, determine a coherent macroscopic transformation pathway for the semiconducting-to-metal transition in bistable Ti3O5 nanocrystals. Employing femtosecond powder X-ray diffraction, we measure the lattice deformation in the phase transition as a function of time. We monitor the early intra-cell distortion around the light absorbing metal dimer and the long range deformations governed by acoustic waves propagating from the laser-exposed Ti3O5 surface. We developed a simplified elastic model demonstrating that picosecond switching in nanocrystals happens concomitantly with the propagating acoustic wavefront, several decades faster than thermal processes governed by heat diffusion.
RESUMO
A typical case of fracture-separation of the cervical spine at the C6 articular level is described. The authors define the radiological signs of this rare but severe traumatic lesion, and emphasize that it is easy to diagnose this condition if one keeps it in mind.
Assuntos
Vértebras Cervicais/lesões , Fraturas Ósseas/diagnóstico por imagem , Adulto , Vértebras Cervicais/diagnóstico por imagem , Feminino , Fixação Interna de Fraturas , Humanos , RadiografiaRESUMO
One case of above acetabulum aneurismal cyst is presented and the authors insist on the main features of this benign tumor supplied with radiology, clinic and evolution. Location of such cyst are uncommon: 4 cases upon 137. Medical team has to resolve two problems: on one hand, positive diagnosis of this benign tumor, on the other hand, treatment of this particular location.
