Surprisingly Little O VI Emission Arises in the Local Bubble

This paper reports the first study of the O VI resonance line emission (1032, 1038 Angstroms) originating in the Local Bubble (or Local Hot Bubble) surrounding the solar neighborhood. In spite of the fact that O VI absorption within the Local Bubble has been observed, no resonance line emission was detected during our 230 ksec Far Ultraviolet Spectroscopic Explorer observation toward a ``shadowing'' filament in the southern Galactic hemisphere. As a result, tight 2 sigma upper limits are set on the intensities in the 1032 and 1038 Angstrom emission lines: 500 and 530 photons cm^{-2} s^{-1} sr^{-1}, respectively. These values place strict constraints on models and simulations. They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside in distinct regions of the Local Bubble and are not mixed in a single plasma, whether in equilibrium with T ~ 10^6 K or highly overionized with T ~ 4 to 6 x 10^4 K. If the line of sight intersects multiple cool clouds within the Local Bubble, then the results also suggest that hot/cool transition zones differ from those in current simulations. With these intensity upper limits, we establish limits on the electron density, thermal pressure, pathlength, and cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore, the intensity of O VI resonance line doublet photons originating in the Galactic thick disk and halo is determined (3500 to 4300 photons cm^{-2} s^{-1} sr^{-1}), and the electron density, thermal pressure, pathlength, and cooling timescale of its O VI-bearing plasma are calculated. The pressure in the Galactic halo's O VI-bearing plasma (3100 to 3800 K cm^{-3}) agrees with model predictions for the total pressure in the thick disk/lower halo. We also report the results of searches for other emission lines.Comment: accepted by ApJ, scheduled for May 2003, replacement astro-ph submission corrects typos and grammatical errors in original versio

Low-temperature photocarrier dynamics in monolayer MoS2

The band structure of MoS$_2$ strongly depends on the number of layers, and a transition from indirect to direct-gap semiconductor has been observed recently for a single layer of MoS$_2$. Single-layer MoS$_2$ therefore becomes an efficient emitter of photoluminescence even at room temperature. Here, we report on scanning Raman and on temperature-dependent, as well as time-resolved photoluminescence measurements on single-layer MoS$_2$ flakes prepared by exfoliation. We observe the emergence of two distinct photoluminescence peaks at low temperatures. The photocarrier recombination at low temperatures occurs on the few-picosecond timescale, but with increasing temperatures, a biexponential photoluminescence decay with a longer-lived component is observed.Comment: 3 pages, 4 figure

Energy Distribution of Micro-events in the Quiet Solar Corona

Recent imaging observations of EUV line emissions have shown evidence for frequent flare-like events in a majority of the pixels in quiet regions of the solar corona. The changes in coronal emission measure indicate impulsive heating of new material to coronal temperatures. These heating or evaporation events are candidate signatures of "nanoflares" or "microflares" proposed to interpret the high temperature and the very existence of the corona. The energy distribution of these micro-events reported in the literature differ widely, and so do the estimates of their total energy input into the corona. Here we analyze the assumptions of the different methods, compare them by using the same data set and discuss their results. We also estimate the different forms of energy input and output, keeping in mind that the observed brightenings are most likely secondary phenomena. A rough estimate of the energy input observed by EIT on the SoHO satellite is of the order of 10% of the total radiative output in the same region. It is considerably smaller for the two reported TRACE observations. The discrepancy can be explained partially by different thresholds for flare detection. There is agreement on the slope and the absolute value of the distribution if the same method were used and a numerical error corrected. The extrapolation of the power law to unobserved energies that are many orders of magnitude smaller remains questionable. Nevertheless, these micro-events and unresolved smaller events are currently the best source of information on the heating process of the corona

Dor abdominal recorrente: quando suspeitar de crise epiléptica?

Recurrent episodes of abdominal pain are common in childhood. Among the diagnostic possibilities are migraine and abdominal epilepsy (AE). AE is an infrequent syndrome with paroxystic episodes of abdominal pain, awareness disturbance, EEG abnormalities and positive results with the introduction of antiepileptic drugs. We present one 6 year-old girl who had short episodes of abdominal pain since the age of 4. The pain was followed by cry, fear and occasionally secondary generalization. MRI showed tumor in the left temporal region. As a differential diagnosis, we report a 10 year-old boy who had long episodes of abdominal pain accompanied by blurring of vision, vertigo, gait ataxia, dysarthria, acroparesthesias and vomiting. He received the diagnosis of basilar migraine. In our opinion, AE is part of a large group (partial epilepsies) and does not require a special classification. Pediatric neurologists must be aware of these two entities that may cause abdominal pain.Episódios recorrentes de dor abdominal são freqüentes na infância e entre as causas neurológicas há migrânea e epilepsia abdominal (EA). EA é uma síndrome que consiste de episódios paroxísticos de dor abdominal associada à alteração de consciência, anormalidades eletrencefalográficas e boa resposta à terapia anticonvulsivante. Apresentamos uma menina de 6 anos que tinha desde os 4 anos episódios de curta duração de dor abdominal, seguidos por choro, medo e ocasional generalização secundária. A RM mostrou a presença de um tumor em região temporal esquerda. Como diagnóstico diferencial, apresentamos um menino de 10 anos que há 12 meses referia episódios de dor abdominal de longa duração acompanhados por turvação visual, vertigem, marcha atáxica, disartria, acroparestesia e vômito, recebendo posteriormente o diagnóstico de migrânia basilar. Em nossa opinião, EA faz parte de um grande grupo (epilepsias parciais) e não requer uma classificação especial. O neuropediatra deve estar alerta para essas duas entidades que podem cursar com dor abdominal.62863

Lupus erítematoso sistêmico juvenil: comprometimento neurológico

With the purpose of analyzing the neurological involvement due to systemic lupus erythematosus (SLE), we evaluated 17 female patients who were seen regularly at the hospital and had been diagnosed as having SLE according to classification criteria proposed by the American College of Rheumatology revised in 1982, before the age of 16. Neurological involvement was detected in 12 patients (71%): headache (35%), extrapyramidal syndrome (35%), epileptic syndrome (24%) pyramidal syndrome (24%), peripheral neuropathy (12%) and optic neuritis (6%). The findings of CT scan (58%) and cerebrospinal fluid (50%) were most closely correlated to clinical neurological involvement.Com o objetivo de analisar o comprometimento neurológico secundário ao lupus eritematoso sistêmico (LES), avaliamos pacientes que estavam em acompanhamento ambulatorial. Foram selecionadas 17 pacientes do sexo feminino cujo diagnóstico do LES foi até a idade de 16 anos, e preencheu os critérios para a classificação propostos pelo Colégio Americano de Reumatologia revisados em 1982. O comprometimento neurológico foi observado em 12 pacientes (71%): cefaléia (35%), síndrome extrapiramidal (35%), síndrome epiléptica (24%), síndrome piramidal (24%), neuropatia periférica (12%) e neurite óptica (6%). Dos exames complementares a tomografia coputadorizada de crânio (58%) e o líquido cefalorraquidiano (50%) mostraram maior correlação com a presença de comprometimento neurológico.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Setor de Reumatologia PediátricaUNIFESP, EPM, Setor de Reumatologia PediátricaSciEL

Quality Of Life And Epilepsy Surgery In Childhood And Adolescence.

Epilepsy can affect the quality of life (QOL) of patients. The temporal lobe epilepsy (TLE) is often refractory to medication, which has an adverse impact on QOL. The surgery can be a form to control the seizures and to improve the QOL of the patients. The aim of this study was to verify the QOL of children and adolescents with TLE who underwent surgery for epilepsy, comparing QOL before and after surgery and investigating which parameters showed improvement. We used semi-structured questionnaire in the pre-and post-surgery in 13 patients. The data were analyzed using the Wilcoxon test. The analysis showed that there was general improvement in the QOL postoperatively. There was improvement in general health issues, adverse effects of antiepileptic drugs and the relationship with parents. When properly indicated, epilepsy surgery improves quality of life of patients with TLE.6923-

The Heavy Element Enrichment of Lyman alpha Clouds in the Virgo Supercluster

Using high S/N STIS echelle spectra (FWHM=7 km/s) of 3C 273, we constrain the metallicities of two Lya clouds in the vicinity of the Virgo cluster. We detect C II, Si II, and Si III absorption lines in the Lya absorber at z = 0.00530. Previous observations with FUSE have revealed Ly beta - Ly theta lines at this redshift, thereby accurately constraining N(H I). We model the ionization of the gas and derive [C/H] = -1.2^{+0.3}_{-0.2}, [Si/C] = 0.2+/-0.1, and log n_{H} = -2.8+/-0.3. The model implies a small absorber thickness, ~70 pc, and thermal pressure p/k ~ 40 cm^{-3} K. It is most likely that the absorber is pressure confined by an external medium because gravitational confinement would require a very high ratio of dark matter to baryonic matter. Based on Milky Way sight lines in which carbon and silicon abundances have been reliably measured in the same interstellar cloud (including new measurements presented herein), we argue that the overabundance of Si relative to C is not due to dust depletion. Instead, this probably indicates that the gas has been predominately enriched by Type II supernovae. Such enrichment is most plausibly provided by an unbound galactic wind, given the absence of galaxies within a projected distance of 100 kpc and the presence of galaxies capable of driving a wind at larger distances. We also constrain the metallicity and physical conditions of the Virgo absorber at z = 0.00337 based on detections of O VI and H I and an upper limit on C IV. If this absorber is collisionally ionized, the O VI/C IV limit requires T > 10^{5.3} K. For either collisional ionization or photoionization, we find that [O/H] > -2.0 at z = 0.00337.Comment: Final Ap.J. versio

Infrared Spectroscopy of Molecular Supernova Remnants

We present Infrared Space Observatory spectroscopy of sites in the supernova remnants W28, W44, and 3C391, where blast waves are impacting molecular clouds. Atomic fine-structure lines were detected from C, N, O, Si, P, and Fe. The S(3) and S(9) lines of H2 were detected for all three remnants. The observations require both shocks into gas with moderate (~ 100 /cm3) and high (~10,000 /cm3) pre-shock densities, with the moderate density shocks producing the ionic lines and the high density shock producing the molecular lines. No single shock model can account for all of the observed lines, even at the order of magnitude level. We find that the principal coolants of radiative supernova shocks in moderate-density gas are the far-infrared continuum from dust grains surviving the shock, followed by collisionally-excited [O I] 63.2 and [Si II] 34.8 micron lines. The principal coolant of the high-density shocks is collisionally-excited H2 rotational and ro-vibrational line emission. We systematically examine the ground-state fine structure of all cosmically abundant elements, to explain the presence or lack of all atomic fine lines in our spectra in terms of the atomic structure, interstellar abundances, and a moderate-density, partially-ionized plasma. The [P II] line at 60.6 microns is the first known astronomical detection. There is one bright unidentified line in our spectra, at 74.26 microns. The presence of bright [Si II] and [Fe II] lines requires partial destruction of the dust. The required gas-phase abundance of Fe suggests 15-30% of the Fe-bearing grains were destroyed. The infrared continuum brightness requires ~1 Msun of dust survives the shock, suggesting about 1/3 of the dust mass was destroyed, in agreement with the depletion estimate and with theoretical models for dust destruction.Comment: 40 pages; 10 figures; accepted by ApJ July 11, 200

Intermediate- and High-Velocity Ionized Gas toward zeta Orionis

We combine UV spectra obtained with the HST/GHRS echelle, IMAPS, and Copernicus to study the abundances and physical conditions in the predominantly ionized gas seen at high (-105 to -65 km/s) and intermediate velocities (-60 to -10 km/s) toward zeta Ori. We have high resolution (FWHM ~ 3.3-4.5 km/s) and/or high S/N spectra for at least two significant ions of C, N, Al, Si, S, and Fe -- enabling accurate estimates for both the total N(H II) and the elemental depletions. C, N, and S have essentially solar relative abundances; Al, Si, and Fe appear to be depleted by about 0.8, 0.3-0.4, and 0.95 dex, respectively. While various ion ratios would be consistent with collisional ionization equilibrium (CIE) for T ~ 25,000-80,000 K, the widths of individual high-velocity absorption components indicate that T ~ 9000 K -- so the gas is not in CIE. Analysis of the C II fine-structure excitation equilibrium yields estimated densities (n_e ~ n_H ~ 0.1-0.2 cm^{-3}), thermal pressures (2 n_H T ~ 2000-4000 cm^{-3}K), and thicknesses (0.5-2.7 pc) for the individual clouds. We compare the abundances and physical properties derived for these clouds with those found for gas at similar velocities toward 23 Ori and tau CMa, and also with several models for shocked gas. While the shock models can reproduce some features of the observed line profiles and some of the observed ion ratios, there are also significant differences. The measured depletions suggest that \~10% of the Al, Si, and Fe originally locked in dust in the pre-shock medium may have been returned to the gas phase, consistent with predictions for the destruction of silicate dust in a 100 km/s shock. The near-solar gas phase abundance of carbon, however, seems inconsistent with the predicted longer time scales for the destruction of graphite grains.Comment: 50 pages, 9 figures; aastex; accepted by Ap