RESUMO
Quasicrystals are long-range-ordered materials that lack translational invariance, so the study of their physical properties remains a challenging problem. Here, we have carried out inelastic-X-ray- and neutron-scattering experiments on single-grain samples of the Zn-Mg-Sc icosahedral quasicrystal and of the Zn-Sc periodic cubic 1/1 approximant, with the aim of studying the respective influence of the local order and of the long-range order (periodic or quasiperiodic) on lattice dynamics. Besides the overall similarities and the existence of a pseudo-gap in the transverse dispersion relation, marked differences are observed, the pseudo-gap being larger and better defined in the approximant than in the quasicrystal. This can be qualitatively explained using the concept of a pseudo-Brillouin-zone in the quasicrystal. These results are compared with simulations on atomic models and using oscillating pair potentials, and the simulations reproduce in detail the experimental results. This paves the way for a detailed understanding of the physics of quasicrystals.
RESUMO
Having a haptic virtual environment for tele-echography will enable the medical expert with faster adaptation and especially facilitated immersion in what we could call a "virtual echographic examination cabinet". The innovation of this haptic control is to preserve medical expert proprioception and gesture feelings, which provide the users with indications that are synchronized with the echographic images. In this paper, we will focus on the telegesture module: we will detail several issues and solutions related to this particular problem of tele-robotic scan examination.
Assuntos
Consulta Remota/instrumentação , Robótica/instrumentação , Tato , Ultrassonografia Pré-Natal/instrumentação , Interface Usuário-Computador , Comunicação , Sistemas Computacionais , Retroalimentação , Feminino , Gestos , Humanos , Gravidez , Gravação em Vídeo/instrumentaçãoRESUMO
A case of acute pericarditis in a 2 1/2 year-old girl is reported. It appeared 3 days after the onset of a meningococcal meningitis which was favourably influenced by antibiotherapy. This pericarditis was immunologic in origin and disappeared within a few days with corticosteroid therapy. Differential diagnosis between purulent versus non suppurative acute pericarditis in patients with meningococcal bacteriemia is discussed.
