Plasma effects on harmonic spectra generated from moderately relativistic laser-plasma interactions.

When intense p-polarized laser light is incident on a plasma with an electron density many times the critical density, the flux of fast electrons created by Brunel absorption excites plasma oscillations. These oscillations may in turn affect the spectrum of high harmonics by modulating the spectrum at the plasma frequency, ω(p), and by coupling to the radiation field through the steep density gradient at the plasma-vacuum interface, so generating plasma line emission (PLE) at ω(p) and harmonics of ω(p). Both aspects depend sensitively on a range of plasma and laser pulse parameters, including the initial electron density, the density profile at the plasma-vacuum interface, and the intensity, pulse shape, and pulse length of the incident laser light. These various dependences have been characterised for moderately relativistic laser-plasma interactions by means of a series of particle-in-cell (PIC) simulations.

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 cutoff m=m*. The results presented in this Letter 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 the harmonic number in the ultrarelativistic range characterized by an index 5/3 < or approximately p < or approximately 7/3, significantly weaker than that predicted by the similarity model.

Plasma modulation of harmonic emission spectra from laser-plasma interactions.

We report results from particle-in-cell simulations of the interaction of intense laser light with overdense plasma designed to examine the effects of plasma waves generated by pulses of fast electrons on high-order harmonic emission from the plasma. We show that the emission spectrum is modulated at the plasma frequency and identify combinations of parameters and circumstances favorable for modulation. In particular, the observed modulation is shown to depend not only on the chosen plasma electron density and intensity of the incident light but on the density profile and pulse shape.

[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.

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

Introducción. El lóbulo temporal y la amígdala son estructuras que participan en el procesamiento emocional. La finalidad del presente estudio fue determinar el efecto diferencial de la lobectomía temporal izquierda (LTI) y derecha (LTD) en el reconocimiento y la experiencia emocional, así como en los estados afectivos en pacientes epilépticos refractarios al tratamiento evaluados pre y posquirúrgicamente. Pacientes y métodos. Participaron cinco pacientes con epilepsia del lóbulo temporal (dos del hemisferio derecho y tres del izquierdo) a los que se evaluó antes y después de tres meses de la cirugía. Se estudió el reconocimiento emocional facial y prosódico dentro y fuera de un contexto social, con y sin tiempo límite. Además, se valoró la experiencia emocional subjetiva ante fragmentos de películas y los estados emocionales positivos y negativos, la ansiedad y la depresión. Resultados. Posquirúrgicamente, los pacientes con LTD tuvieron menos aciertos en el reconocimiento de la expresión de miedo con tiempo límite y de la prosodia, mientras que los pacientes con LTI no mostraron deterioro o incluso mejoraron. No hubo diferencias en función del hemisferio intervenido ni en la intensidad con que percibieron las emociones en las escenas, ni en la experiencia emocional, aunque ambos grupos experimentaron una disminución de las emociones negativas y la ansiedad. Conclusiones. Los resultados sugieren que la LTD tuvo un mayor efecto sobre el reconocimiento emocional fuera de un contexto y con tiempo límite que la LTI, mientras que en la experiencia emocional no se observaron diferencias entre grupos. La lobectomía indujo una mejoría en los estados afectivos (AU)

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 inthe 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 (AU)

Lattice-parameter determination from the interaction of short femtosecond laser pulses with crystalline solids.

A novel method for determining the lattice parameter in a crystalline solid from the harmonic emission spectra reflected in laser-solid layers interactions is proposed. Radiated emission at high-order harmonic numbers is observed from thin crystalline layers illuminated by short femtosecond elliptically polarized laser light. The radiation mechanism presented here accounts for optical emission effects when free electrons in the material, ionized by the action of an applied external radiation field, are driven to large oscillation amplitudes and harmonics are generated by the electronic response to the periodic lattice potential. Perturbations in the electron motion inside the material due to the ion cores give rise to harmonic emission. In this work, the condition for radiation--the resonance condition--is found analytically through an exact expression for the electron displacement. The analytic prediction is supported by results obtained by solving numerically the electromagnetic force equations for electrons moving in the lattice potential.

Harmonic radiation emission from periodic lattices irradiated by short-pulse elliptically polarized laser light.

Radiated emission at high-order harmonic numbers is observed from thin crystalline layers irradiated by short femtosecond elliptically polarized laser light. The applied external radiation field drives the free electrons in the material to large oscillation amplitudes and harmonics are generated by the electronic response to the periodic lattice potential. A model was modified by introducing a more general expression for the lattice force that by sharpening or by smoothing the potential in turn allows the strength of the electronic perturbation to be varied. The electron motion is computed numerically by solving the electromagnetic force equation and by regarding the lattice potential as a perturbative source. For linearly polarized laser light the radiation spectra are characterized by emission lines forming a flat plateau in the region of low harmonic orders with a sharp cutoff for higher numbers. For circular polarization strong emission is found for two harmonic numbers, the first in the low-harmonic region and the second around the cutoff. By solving analytically the electron motion in an elliptically polarized laser field, an exact expression for the electron displacement in all three spatial directions is found. The amplitude of the oscillations sets the analytic form for calculating the peak harmonic numbers emitted from the laser-lattice interaction. The radiation effect studied here, if detected, might hold some potential as a diagnostic and could be used, in principle, as a method for determining the lattice parameter in crystalline structures.

Plasma line emission from short pulse laser interactions with dense plasmas

Plasma line emission is observed in simulations of dense plasma irradiated by moderately intense light pulses of duration some tens of femtoseconds, and its scaling with density and with laser intensity is studied. Plasma emission is recorded both during the pulse where it is observed against the background spectrum of harmonics of the laser frequency as well as postpulse. Harmonics of the plasma line up to the fifth have been observed. An unexpected feature present in most of the reflected light spectra appears on the blue side of the plasma line with a central frequency omega approximately 1.5omega(p).

Biopsia estereotáctica guiada por computadora para lesiones intracraneales: evaluación de su seguridad y eficacia / Computer-guided stereotactic biopsy for intracranial lesions: evaluation of its safety and efficacy

La neurocirugía estereotáctica guiada por imágenes ha venido a mejorar las estrategias de manejo de las lesiones intracraneales. En el presente trabajo hacemos una evaluación de los resultados en una muestra de 64 pacientes operados con esta técnica en el Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez en México D.F.(INNN-MUS). Setenta y cuatro pacientes que fueron sometidos a neurocirugía esteretáctica guiada por imágenes entre 1994 y 1997 fueron revisados...

Gabapentin modifies extracellular opioid peptide content in amygdala: a microdialysis study.

Opioid peptide release was monitored in the amygdala and hippocampus of freely moving rats following a single oral administration of gabapentin using microdialysis. Extracellular opioid peptide levels were elevated above basal levels in the amygdala within the first 60 (54%) and 90 min (68%) after gabapentin administration. Levels returned to basal conditions 120 min following the treatment. No significant changes were detected in the hippocampus. The majority of immunoreactive material recovered from the amygdala following gabapentin administration was identified as Leu-enkephalin and Met-enkephalin by high performance liquid chromatography (HPLC) analysis. It is proposed that the enhanced opioid peptide release in the amygdala induced by gabapentin might be involved with the antiepileptic effects as well as with some adverse events produced by this drug.

Characterization of benzodiazepine receptor binding following kainic acid administration: an autoradiography study in rats.

Effects of status epilepticus and chronic temporal lobe epilepsy on benzodiazepine (BDZ) receptor binding in the rat brain were evaluated using in vitro autoradiography, 24 h and 40 days after kainic acid (KA) administration (10 mg/kg i.p). One day after KA-induced status epilepticus and in comparison to saline control group, significantly increased BDZ binding was detected in pyriform cortex (53%), whereas decreased binding was found in anterior amygdaloid nucleus (28%), fields CA1-3 of Ammon's horn (25%) and dentate gyrus (27%). Forty days after status epilepticus, significantly BDZ binding augmentation was noticed in dentate gyrus (65%) and in periaqueductal gray dorsolateral (52%), whereas decreased binding was found in medial thalamic nucleus (70%). Our data indicate different patterns of BDZ binding following KA administration, which may depend on the consequences of the status epilepticus (24 h after KA) and temporal lobe epilepsy (40 days after KA) per se.

[Traumatism of the posterior fossa in children]. / Traumatismos de la fosa posterior en niños.

Reported are 15 cases of children who suffered injuries to their posterior fossa and the subsequent formation of hematomas and their treatment by the physicians in the Neurosurgical Department of the Traumatology Hospital "Magdalena de las Salinas". Of the 15 cases, 11 had epidural hematomas (three of them with supratentorial extensions), one was subdural, two were cerebellar and another of the brainstem. Seven were considered acute, five were subacute and three were chronic. During their admittance to the hospital, five of the patients were in a state of coma, another five were sleepy or confused and the remaining five were conscious. Three of the patients were conservatively treated, two of which had sequelae or were moderately handicapped. Twelve of the patients were surgically intervened suboccipitally, eleven of which successfully recovered and one of which died. A history of brain injury, occipital fracture and signs of posterior fossa lesions lead to suspect the presence of posterior fossa hematoma.