Nonlinear kinetic estimate of Raman reflectivity in a hohlraum plasma with a radiation hydrodynamics code.

In this Letter, we introduce an inline model for stimulated Raman scattering (SRS), which runs on our radiation hydrodynamics code troll. This model accounts for nonlinear kinetic effects and for the SRS feedback on the plasma hydrodynamics. We dubbed it PIEM because it is a fully "PredIctivE Model," because no free parameter is to be adjusted a posteriori in order to match the experimental results. PIEM predictions are compared against experimental measurements performed at the Ligne d'Intégration Laser. From these comparisons, we discuss the PIEM ability to correctly catch the impact of nonlinear kinetic effects on SRS.

Early post-stroke physical conditioning in hemiplegic patients: A preliminary study.

OBJECTIVE: To establish the value of an early post-stroke evaluation of cardiorespiratory fitness in hemiparetic patients using a one-leg cycling exercise test and to analyze the impact of an adapted physical activity programme 12 weeks after the stroke. PROTOCOL: Eighteen hemiparetic stroke patients participated in the study. The subjects were randomly assigned to one of two groups: the control group (CG) underwent 4 weeks of conventional rehabilitation, whereas the training group (TG) performed additional physical exercises. The initial evaluation (T1) was carried out after 1 week of exercise and the final evaluation (T2) was performed after 28 days. Both evaluations consisted of maximal graded tests performed with the valid leg, followed by completion of a questionnaire on personal autonomy in activities of daily living (ADL). RESULTS: In the CG group, we recorded a 4 to 8% increase in peak oxygen uptake (VO2 peak). There was no significant increase in peak power output (Wpeak). However, the TG displayed significantly (P<0.05) greater peak values than those recorded on study entry (Wpeak: +30%, VO2 peak: +20%). The TG showed a statistically significant improvement in the Barthel and Katz ADL scale scores, whereas the pre- and post-rehabilitation values did not differ significantly in the CG. However, there was no correlation between the Barthel/Katz scale scores and Wpeak. CONCLUSION: Evaluation of cardiorespiratory fitness by using the valid leg seems to be feasible in hemiplegic patients 1 month post-stroke. Early post-stroke physical training appears to be needed to limit the negative effects of functional hypoactivity.

Laser-beam smoothing induced by stimulated brillouin scattering in an inhomogeneous plasma.

We present results of two-dimensional simulations of the stimulated Brillouin scattering (SBS) of an optically smoothed laser beam propagating in an expanding plasma. In the weak damping limit, both backscattered and transmitted light waves exhibit an additional spatiotemporal incoherence, which is shown to be induced by SBS taking place in an inhomogeneous plasma. This mechanism is not related to laser-beam self-focusing and is thus complementary to plasma-induced smoothing [A. J. Schmitt and B. B. Afeyan, Phys. Plasmas 5, 503 (1998)]. The incoherence induced by SBS in the entrance part of the plasma could reduce the growth of parametric instabilities developing further inside the plasma and is able to significantly enlarge the spreading angle of the transmitted light. The angular width of the backscattered light is also found to be significantly larger than the aperture angle of the incident beam.