Anomalies in Universal Intensity Scaling in Ultrarelativistic Laser-Plasma Interactions

Laser light incident on targets at intensities such that the electron dynamics is ultrarelativistic gives rise to a harmonic power spectrum extending to high orders and characterized by a relatively slow decay with the harmonic number m that follows a power law dependence, m^{-p}. Relativistic similarity theory predicts a universal value for p = 8/3 up to some cut-off m = m*. The results presented in this work suggest that under conditions in which plasma effects contribute to the emission spectrum, the extent of this contribution may invalidate the concept of universal decay. We report a decay with harmonic number in the ultrarelativistic range characterised by an index 5/3 < p < 7/3, significantly weaker than that predicted by the similarity model.Comment: 5 pages, 4 figure

Modulation of harmonic emission spectra from intense laser-plasma interactions

We report results from a series of PIC simulations carried out to investigate the interaction of intense laser light with overdense plasma and in particular, aspects of the harmonic emission spectrum generated in these interactions. Recent observations of emission in this range by Watts et al. [1] show emission above the 20th harmonic extending to the 37th with conversion efficiencies of order $10^{-6}$ with this spectrum showing distinct, if variable, modulation of between two and four harmonics. This spectral feature proved highly sensitive to the incident intensity, with more pronounced modulation at higher intensities. These authors also reported results from a set of model PIC simulations which showed a modulated emission spectrum across the entire harmonic range, but with a wider modulation bandwidth.
In the results to be presented we report on features of the emission spectrum across a wide parameter range and its dependence on the detailed structure of the plasma density profile. While we do see evidence of a modulated spectrum, this appears to be sensitive not only to the incident intensity but to the plasma density profile. In addition plasma emission present further complicates the harmonic emission spectrum. Our results lead us to conclude that attempts to interpret modulation in emission spectra in terms of one particular theoretical model and from this to infer the dynamics of the critical surface may be misguided

Differential effect of left and right temporal lobectomy on emotional recognition and experience in patients with epilepsy [Efecto diferencial de la lobectomía temporal izquierda y derecha sobre el reconocimiento y la experiencia emocional en pacientes con epilepsia]

Introduction. Temporal lobe and amygdala are structures that participate in emotional processing. The purpose of this study was to determine the differential effect of left (LTL) and right (RTL) temporal lobectomy on emotional recognition and experience as well as mood in treatment resistant epileptics who were evaluated pre and post-surgically. Patients and methods. Five temporal lobe epileptic patients participated in the study (two from the right and three from the left hemisphere) who were evaluated before and after three months of the surgery. Emotional and prosodic recognition were evaluated, inside and outside of a social context, with and without time limit. Besides, subjective emotional experience while seeing movie fragments was evaluated as well as positive and negative emotional states, anxiety and depression. Results. After the surgery, patients with RTL had lower number of correct responses in fear facial and prosodic recognition, while patients with LTL did not show deterioration or they even improved. There were not differences as a function of the intervened hemisphere neither in the intensity of emotions perceived in the scenes, nor in the emotional experience, however, both groups experienced a decrease of negative emotions and anxiety. Conclusions. The results suggest that RTL had a greater effect on emotional recognition outside of a context and with limited time than LTL, while in the emotional experience there were not differences between groups. Lobectomy induced an improvement on affective states. © 2006, Revista de Neurología