26 research outputs found

    Searching for massive pre--stellar cores through observations of N2H+ and N2D+

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    We have measured the deuterium fractionation (through the column density ratio N(N2D+)/N(N2H+)) and the CO depletion factor (ratio between expected and observed CO abundance) in a sample of 10 high-mass protostellar candidates, in order to understand whether the earliest evolutionary stages of high-mass stars have chemical characteristics similar to those of low-mass ones. The observations were carried out with the IRAM-30m telescope and the JCMT. We have detected N2D+ emission in 7 of the 10 sources of our sample, and found an average value N(N2D+)/N(N2H+)~0.015. This value is 3 orders of magnitude larger than the interstellar D/H ratio, indicating the presence of cold and dense gas, in which the physical-chemical conditions are similar to those observed in low-mass pre-stellar cores. Also, the integrated CO depletion factors show that in the majority of the sources the expected CO abundances are larger than the observed values, with a median ratio of 3.2. In principle, the cold gas that gives origin to the N2D+ emission can be the remnant of the massive molecular core in which the high-mass (proto-)star was born, not yet heated up by the central object. If so, our results indicate that the chemical properties of the clouds in which high-mass stars are born are similar to their low-mass counterparts. Alternatively, this cold gas can be located into one (or more) starless core (cores) near the protostellar object. Due to the poor angular resolution of our data, we cannot decide which is the correct scenario.Comment: 27 pages, 15 figures, accepted by Astronomy and Astrophysic

    Are Females More Responsive to Emotional Stimuli? A Neurophysiological Study Across Arousal and Valence Dimensions

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    Men and women seem to process emotions and react to them differently. Yet, few neurophysiological studies have systematically investigated gender differences in emotional processing. Here, we studied gender differences using Event Related Potentials (ERPs) and Skin Conductance Responses (SCR) recorded from participants who passively viewed emotional pictures selected from the International Affective Picture System (IAPS). The arousal and valence dimension of the stimuli were manipulated orthogonally. The peak amplitude and peak latency of ERP components and SCR were analyzed separately, and the scalp topographies of significant ERP differences were documented. Females responded with enhanced negative components (N100 and N200), in comparison to males, especially to the unpleasant visual stimuli, whereas both genders responded faster to high arousing or unpleasant stimuli. Scalp topographies revealed more pronounced gender differences on central and left hemisphere areas. Our results suggest a difference in the way emotional stimuli are processed by genders: unpleasant and high arousing stimuli evoke greater ERP amplitudes in women relatively to men. It also seems that unpleasant or high arousing stimuli are temporally prioritized during visual processing by both genders

    Pontas evocadas por estímulos somatossensitivos e atividade epileptiforme no eletrencefalograma em crianças "normais" Somatosensory evoked spikes and epileptiform activity in "normal" children

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    Estudamos a ocorrĂȘncia de potenciais de alta voltagem evocados por estĂ­mulos somatossensitivos - pontas evocadas (PE) - e de atividade epileptiforme espontĂąnea (AE) no EEG de 173 crianças normais de 7 a 11 anos de idade. Durante o EEG, dez percussĂ”es foram realizadas nas mĂŁos e pĂ©s. Foi avaliada a ocorrĂȘncia de PE acompanhando cada um dos estĂ­mulos e a presença de AE. AE foi observada em quatro crianças (2,3%): pontas centroparietais em duas, complexos de ponta-onda lenta generalizados em uma e pontas parietais e temporais mĂ©dias em uma. Uma menina de 10 anos de idade (0,58%) teve ao EEG pontas parietais medianas evocadas pela percussĂŁo do pĂ© esquerdo. Este EEG era normal quanto a outros aspectos. Nossos achados de AE em crianças normais sĂŁo similares aos encontrados em estudos de outros paĂ­ses. Constatamos que espĂ­culas somatossensitivas podem ser observadas em crianças normais o que sugere uma natureza funcional ligada Ă  idade.<br>Little is known about somatosensory evoked spikes (SES) in the EEG of normal children. We studied the occurrence of SES and spontaneous epileptiform activity (SEA) in 173 normal children ageg 7 to 11 years. During the EEG ten taps were applied to both hands and feet. The occurrence of high voltage potentials evoked by each stimulation of one or both heels or hands (SES) and the occurrence of SEA were evaluated. SEA was observed in four children (2.3 %): central/parietal spikes in two cases, generalized spike-and-wave in one, and parietal/midtemporal spikes in one case. A ten years old girl (0,58%) had SES on median parietal region by tapping the left foot. This EEG was otherwise normal. Our findings of SEA are similar to those obtained in other normal populations. SES can be observed in normal children. These SES suggest that we are dealing with an age-related functional phenomenon
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