We study femtosecond-laser-pulse-induced electron emission from W(100), Al(110), and Ag(111) in the subdamage regime (1-44 mJ/cm 2 fluence) by simultaneously measuring the incident-light reflectivity, total electron yield, and electron-energy distribution curves of the emitted electrons. The total-yield results are compared with a space-charge-limited extension of the Richardson-Dushman equation for short-time-scale thermionic emission and with particle-in-a-cell computer simulations of femtosecond-pulsed-induced thermionic emission. Quantitative agreement between the experimental results and two calculated temperaturedependent yields is obtained and shows that the yield varies linearly with temperature beginning at a threshold electron temperature of -0.25 eV The particle-in-a-cell simulations also reproduce the experimental electronenergy distribution curves. Taken together, the experimental results, the theoretical calculations, and the results of the simulations indicate that thermionic emission from nonequilibrium electron heating provides the dominant source of the emitted electrons. Furthermore, the results demonstrate that a quantitative theory of space-charge-limited femtosecond-pulse-induced electron emission is possible.
Plasma density oscillations (Langmuir waves) in the wake of an intense (Ipeak-3 x 1017W/cm2) laser pulse (100 fs) are measured with ultrafast time resolution using a longitudinal interferometric technique. Phase shifts consistent with large amplitude (Sne/ne-1) density waves at the electron plasma frequency were observed in a fully tunnel-ionized He plasma, corresponding to longitudinal electric fields of-10 GV/m. Strong radial ponderomotive forces enhance the density oscillations. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, , manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the *
Encephalitis is the most frequent neurological complication of measles virus infection. This review examines the pathophysiology of measles infection and the presentations, diagnosis and treatment of the four types of measles-induced encephalitis including primary measles encephalitis, acute post-measles encephalitis, measles inclusion body encephalitis and subacute sclerosing panencephalitis. The early symptoms of encephalitis may be non-specific and can be mistakenly attributed to a systemic infection leading to a delay in diagnosis. This review provides a summary of the symptoms that should cause health care workers to suspect measles-induced encephalitis.
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