The first frost in the Pipe Nebula

Spectroscopic studies of ices in nearby star-forming regions indicate that ice mantles form on dust grains in two distinct steps, starting with polar ice formation (H2O rich) and switching to apolar ice (CO rich). We test how well the picture applies to more diffuse and quiescent clouds where the formation of the first layers of ice mantles can be witnessed. Medium-resolution near-infrared spectra are obtained toward background field stars behind the Pipe Nebula. The water ice absorption is positively detected at 3.0 micron in seven lines of sight out of 21 sources for which observed spectra are successfully reduced. The peak optical depth of the water ice is significantly lower than those in Taurus with the same visual extinction. The source with the highest water-ice optical depth shows CO ice absorption at 4.7 micron as well. The fractional abundance of CO ice with respect to water ice is 16+7-6 %, and about half as much as the values typically seen in low-mass star-forming regions. A small fractional abundance of CO ice is consistent with some of the existing simulations. Observations of CO2 ice in the early diffuse phase of a cloud play a decisive role in understanding the switching mechanism between polar and apolar ice formation.Comment: 17 pages, 8 figures, accepted by A&

Porosity measurements of interstellar ice mixtures using optical laser interference and extended effective medium approximations

Aims. This article aims to provide an alternative method of measuring the porosity of multi-phase composite ices from their refractive indices and of characterising how the abundance of a premixed contaminant (e.g., CO2) affects the porosity of water-rich ice mixtures during omni-directional deposition. Methods. We combine optical laser interference and extended effective medium approximations (EMAs) to measure the porosity of three astrophysically relevant ice mixtures: H2O:CO2=10:1, 4:1, and 2:1. Infrared spectroscopy is used as a benchmarking test of this new laboratory-based method. Results. By independently monitoring the O-H dangling modes of the different water-rich ice mixtures, we confirm the porosities predicted by the extended EMAs. We also demonstrate that CO2 premixed with water in the gas phase does not significantly affect the ice morphology during omni-directional deposition, as long as the physical conditions favourable to segregation are not reached. We propose a mechanism in which CO2 molecules diffuse on the surface of the growing ice sample prior to being incorporated into the bulk and then fill the pores partly or completely, depending on the relative abundance and the growth temperature.Comment: 9 pages, 6 figures, 1 table. Accepted for publication in A&

A Unified Monte Carlo Treatment of Gas-Grain Chemistry for Large Reaction Networks. I. Testing Validity of Rate Equations in Molecular Clouds

In this study we demonstrate for the first time that the unified Monte Carlo approach can be applied to model gas-grain chemistry in large reaction networks. Specifically, we build a time-dependent gas-grain chemical model of the interstellar medium, involving about 6000 gas-phase and 200 grain surface reactions. This model is used to test the validity of the standard and modified rate equation methods in models of dense and translucent molecular clouds and to specify under which conditions the use of the stochastic approach is desirable. We found that at temperatures 25--30 K gas-phase abundances of H$_2$O, NH$_3$, CO and many other gas-phase and surface species in the stochastic model differ from those in the deterministic models by more than an order of magnitude, at least, when tunneling is accounted for and/or diffusion energies are 3x lower than the binding energies. In this case, surface reactions, involving light species, proceed faster than accretion of the same species. In contrast, in the model without tunneling and with high binding energies, when the typical timescale of a surface recombination is greater than the timescale of accretion onto the grain, we obtain almost perfect agreement between results of Monte Carlo and deterministic calculations in the same temperature range. At lower temperatures ($\sim10$ K) gaseous and, in particular, surface abundances of most important molecules are not much affected by stochastic processes.Comment: 33 pages, 9 figures, 1 table. Accepted for publication in Ap

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Introduction: The chronic obstructive pulmonary disease (COPD) is an inflammatory lung disease characterized by the presence of respiratory symptoms and persistent airflow limitation associated with a systemic inflammatory condition. It is a major cause of morbidity and mortality worldwide. The disease’s clinical course is associated with the individuals’ lung function decline, a reduction of their capacity to perform activities of daily living, and with its impact on the health-related quality of life (HRQL) which is not always taken into consideration. Objectives: Describe the HRQL in a group of patients with COPD and establish COPD severity and relationship between HRQL and COPD severity. Methods: This is a prospective, transversal, observational, and analytical study. The sample was drawn from patients with COPD from the Hospital Rawson and Clínica Caraffa. Data on demography, smoking, comorbidities and aspects inherent to COPD were collected. The mMRC scale and the COPD assessment Test (CAT) were used. To evaluate the HRQL the European Quality of Life-5 Dimensions (EQ5D) and the St. George Respiratory Questionnaire (SGRQ) were used. Results: 50 patients (28 women) were included in the study. Median age: 62.6 years old. 70% of the patients presented at least one comorbidity, being high blood pressure the most frequent one. SGRQ score was on average 42.9 points and the most affected dimension was “activity”. 80% of the individuals measured by the EQ5D had problems at least in one of the dimensions comprised in the questionnaire. Conclusion: In this sample, COPD affected the HRQL. HRQL is deteriorated in COPD patients and it is significantly correlated with dyspnea (p=0.0001). The HRQL is worse in symptomatic patients and active smokers (p= 0.001 and p=0.01).Introducción: La enfermedad pulmonar obstructiva crónica (EPOC) es una enfermedad inflamatoria pulmonar caracterizada por la presencia de síntomas respiratorios y limitación persistente al flujo aéreo asociado a un estado inflamatorio sistémico. Es una de las principales causas de morbimortalidad a nivel mundial. Su evolución conlleva reducción de la función pulmonar y de la capacidad de los sujetos para realizar actividades de la vida cotidiana y su impacto en la calidad de vida relacionada con la salud (CVRS) no siempre es tenida en cuenta. Objetivos: Describir la CVRS en un grupo de pacientes con EPOC y establecer en ellos: gravedad de la EPOC; asociación entre CVRS y gravedad de la EPOC. MM: Estudio prospectivo, transversal, observacional y analítico. La muestra estuvo constituida por pacientes con EPOC del Hospital Rawson y Clínica Caraffa. Se recolectaron datos demográficos, consumo de tabaco, comorbilidades y aspectos inherentes a la EPOC. Se aplicaron la escala mMRC y el COPD assessment Test(CAT). Para evaluar la CVRS se utilizaron el European Quality of Life-5 Dimensions(EQ5D) y el Cuestionario Respiratorio de Saint George(SGRQ). El proyecto fue aprobado por el Comité de Ética. Resultados: n=50 pacientes, 28 mujeres. Edad media: 62,6 años. El 70% presentó al menos una comorbilidad, siendo más frecuente la hipertensión arterial. El puntaje SGRQ promedio fue 42,9; la dimensión más afectada fue “actividad”. En relación al EQ5D, el 80% de los sujetos padecía al menos uno de los parámetros contemplados en el cuestionario. La dimensión más afectada fue ansiedad/depresión, así como también fue la que presentó el mayor porcentaje de problemas graves o extremos. El valor medio de la escala visual analógica del EQ5D-VAS fue 64,4. Conclusiones: En esta muestra, la EPOC provocó alteración en la CVRS. La CVRS está deteriorada en pacientes con EPOC y correlaciona significativamente con la disnea (p=0,0001). La CVRS es peor en pacientes sintomáticos y tabaquistas activos (p= 0,001 y p=0,01).

The IC1396N proto-cluster at a scale of 250 AU

We investigate the mm-morphology of IC1396N with unprecedented spatial resolution to analyze its dust and molecular gas properties, and draw comparisons with objects of similar mass. We have carried out sensitive observations in the most extended configurations of the IRAM Plateau de Bure interferometer, to map the thermal dust emission at 3.3 and 1.3mm, and the emission from the $J$=13$_k\to12_k$ hyperfine transitions of methyl cyanide (CH$_3$CN). We unveil the existence of a sub-cluster of hot cores in IC1396N, distributed in a direction perpendicular to the emanating outflow. The cores are embedded in a common envelope of extended and diffuse dust emission. We find striking differences in the dust properties of the cores ($\beta\simeq$ 0) and the surrounding envelope ($\beta\simeq$ 1), very likely testifying to differences in the formation and processing of dust material. The CH$_3$CN emission peaks towards the most massive hot core and is marginally extended in the outflow direction

A low background Micromegas detector for the CAST experiment

A low background Micromegas detector has been operating on the CAST experiment at CERN for the search of solar axions during the first phase of the experiment (2002-2004). The detector operated efficiently and achieved a very low level of background rejection ($5\times 10^{-5}$ counts keV$^{-1}$cm$^{-2}$s$^{-1}$) thanks to its good spatial and energy resolution as well as the low radioactivity materials used in the construction of the detector. For the second phase of the experiment (2005-2007), the detector will be upgraded by adding a shielding and including focusing optics. These improvements should allow for a background rejection better than two orders of magnitude.Comment: 6 pages, 3 figures To appear on the proceedings of the 9th ICATPP Conference on AStroparticle, Particle, Space Physics, Detectors and Medical Physics Application

Detection of 6.7 GHz methanol absorption towards hot corinos

Methanol masers at 6.7 GHz have been found exclusively towards high-mass star forming regions. Recently, some Class 0 protostars have been found to display conditions similar to what are found in hot cores that are associated with massive star formation. These hot corino sources have densities, gas temperatures, and methanol abundances that are adequate for exciting strong 6.7 GHz maser emission. This raises the question of whether 6.7 GHz methanol masers can be found in both hot corinos and massive star forming regions, and if not, whether thermal methanol emission can be detected. We searched for the 6.7 GHz methanol line towards five hot corino sources in the Perseus region using the Arecibo radio telescope. To constrain the excitation conditions of methanol, we observed thermal submillimeter lines of methanol in the NGC1333-IRAS 4 region with the APEX telescope. We did not detect 6.7 GHz emission in any of the sources, but found absorption against the cosmic microwave background in NGC1333-IRAS 4A and NGC1333-IRAS 4B. Using a large velocity gradient analysis, we modeled the excitation of methanol over a wide range of physical parameters, and verify that the 6.7 GHz line is indeed strongly anti-inverted for densities lower than 10^6 cm^-3. We used the submillimeter observations of methanol to verify the predictions of our model for IRAS 4A by comparison with other CH3OH transitions. Our results indicate that the methanol observations from the APEX and Arecibo telescopes are consistent with dense (n ~ 10^6 cm^-3), cold (T ~ 15-30 K) gas. The lack of maser emission in hot corinos and low-mass protostellar objects in general may be due to densities that are much higher than the quenching density in the region where the radiation field is conducive to maser pumping.Comment: Accepted by A&