[Clinical, radiographic, prognostic and therapeutic aspects of demelinating disease with tumefactive demyelinating lesions].

Background: Demyelinating diseases presenting with a tumefactive demyelinating lesion (TDL) raise questions about classification, diagnosis, prognosis, and treatment. Their long-term course is not well described in literature.

Patients/methods: In a retrospective study, we describe the main characteristics of 29 patients with TDLs.

Bound electronic and free carrier nonlinearities in Silicon nanocrystals at 1550nm.

We present a detailed investigation of the different processes responsible for the optical nonlinearities of silicon nanocrystals at 1550 nm. Through z-scan measurements, the bound-electronic and excited carrier contributions to the nonlinear refraction were measured in presence of two-photon absorption. A study of the nonlinear response at different excitation powers has permitted to determine the change in the refractive index per unit of photo-excited carrier density sigma(r) and the value of the real bound-electronic nonlinear refraction n(2be) as a function of the nanocrystals size.