26 research outputs found
Searching for massive pre--stellar cores through observations of N2H+ and N2D+
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
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 estĂmulos somatossensitivos e atividade epileptiforme no eletrencefalograma em crianças "normais" Somatosensory evoked spikes and epileptiform activity in "normal" children
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