Vacuum ultraviolet photolysis of hydrogenated amorphous carbons. III. Diffusion of photo-produced H2 as a function of temperature

Hydrogenated amorphous carbon (a-C:H) has been proposed as one of the carbonaceous solids detected in the interstellar medium. Energetic processing of the a-C:H particles leads to the dissociation of the C-H bonds and the formation of hydrogen molecules and small hydrocarbons. Photo-produced H2 molecules in the bulk of the dust particles can diffuse out to the gas phase and contribute to the total H2 abundance. We have simulated this process in the laboratory with plasma-produced a-C:H and a-C:D analogs under astrophysically relevant conditions to investigate the dependence of the diffusion as a function of temperature. Plasma-produced a-C:H analogs were UV-irradiated using a microwave-discharged hydrogen flow lamp. Molecules diffusing to the gas-phase were detected by a quadrupole mass spectrometer, providing a measurement of the outgoing H2 or D2 flux. By comparing the experimental measurements with the expected flux from a one-dimensional diffusion model, a diffusion coefficient D could be derived for experiments carried out at different temperatures. Dependance on the diffusion coefficient D with the temperature followed an Arrhenius-type equation. The activation energy for the diffusion process was estimated (ED(H2)=1660+-110 K, ED(D2)=2090+-90 K), as well as the pre-exponential factor (D0(H2)=0.0007+0.0013-0.0004 cm2 s-1, D0(D2)=0.0045+0.005-0.0023 cm2 s-1) The strong decrease of the diffusion coefficient at low dust particle temperatures exponentially increases the diffusion times in astrophysical environments. Therefore, transient dust heating by cosmic rays needs to be invoked for the release of the photo- produced H2 molecules in cold PDR regions, where destruction of the aliphatic component in hydrogenated amorphous carbons most probably takes place

Una aplicación del analisis de la supervivencia en ciencias de la salud

Este trabajo presenta las técnicas estadísticas mas utilizadas en ciencias de la salud para analizar datos de supervivencia con tiempos incompletos. A partir de un sencillo estudio, para valorar el efecto de diferentes variables pronósticas sobre el riesgo de recaída de heroinómanos recién deshabituados, se describe la estimación Kaplan-Meier y actuarial de las funciones de supervivencia y de riesgo, la comparación de curvas de supervivencia con la prueba de Mantel-Haenszel, el ajuste de un modelo de regresión de Cox y su uso predictivo. Se explica cómo interpretar practicamente los difeentes resultados obtenidos con [os programas 1L y 2L del Sistema BMDEThis paper describes the most used statistical methods for survival analysis of censored data in Health Sciences: the Kaplan-Meier and the actuarial estimation of the survival and hazard functions, the Mantel- Haenszel (Logrank) test for comparing survival distributions, the Cox regression model and how to fit the model to a set of data from a study for assessing the effects of prognostic covariates on the risk of recidive. The paper explains the predictive use of the model and how to interpret the results of the several analyses performed with 1L and 2L BMDP program

Extending the applicability of an open-ring trap to perform experiments with a single laser-cooled ion

An open-ring ion trap, also referred to as transparent trap was initially built up to perform $\beta$-$\nu$ correlation experiments with radioactive ions. This trap geometry is also well suited to perform experiments with laser-cooled ions, serving for the development of a new type of Penning trap, in the framework of the project TRAPSENSOR at the University of Granada. The goal of this project is to use a single $^{40}$Ca$^+$ ion as detector for single-ion mass spectrometry. Within this project and without any modification to the initial electrode configuration, it was possible to perform Doppler cooling on $^{40}$Ca$^+$ ions, starting from large clouds and reaching single ion sensitivity. This new feature of the trap might be important also for other experiments with ions produced at Radioactive Ion Beam (RIB) facilities. In this publication, the trap and the laser system will be described, together with their performance with respect to laser cooling applied to large ion clouds down to a single ion.Comment: 9 pages, 13 figure

Improved determination of the 1(0)-0(0) rotational frequency of NH3D+ from the high resolution spectrum of the v4 infrared band

The high resolution spectrum of the v4 band of NH3D+ has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of molecular constants obtained from the analysis of the spectrum, a value of 262817(6) MHz (3sigma) has been derived for the frequency of the 1(0)-0(0) rotational transition. This value supports the assignment to NH3D+ of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.Comment: Accepted for publication in the Astrophysical Journal Letters 04 June 201

Cinematic representations of medical technologies in the Spanish official newsreel, 1943–1970

NO-DO, the Spanish official newsreel produced by Franco's dictatorship (1939–1975), held a 30-year monopoly over audio-visual information in Spain from 1943 to 1975. This paper reports on an analysis of the coverage of medical technologies by the Spanish Cinematic Newsreel Service, NO-DO, from 1943 to 1970. The study focuses on the changing roles played by cultural representations of medical technologies deployed in NO-DO. Our analysis shows how these representations offered a new space for the legitimization of the regime and, more importantly, played a key role in the attempts to construct and enforce a hegemonic national identity after the Spanish Civil War (1936–1939). During the period of isolationist autocracy that ended in the mid-1950s, the images of medical technologies reinforced the idea of a self-sufficient “national space” and deepened the break with the historical past. Once the international isolation of the regime was overcome in the late 1950s and the 1960s, the representation of medical technologies contributed to establishing a Spanish national identity that mirrored the outside world, the foreign space. Finally, gender representations in NO-DO are also explored