The young stellar population of IC 1613. III. New O-type stars unveiled by GTC-OSIRIS

Recent findings hint that the winds of massive stars with poorer metallicity than the SMC may be stronger than predicted by theory. Besides calling the paradigm of radiation driven winds into question, this result would impact the predicted evolutionary paths of massive stars, their calculated ionizing radiation and mechanical feedback and the role these objects play at different stages of the Universe. The field needs a systematic study of the winds of a large set of very metal poor massive stars, but the sampling of spectral types is particularly poor in the very early types. This paper's goal is to increase the list of known O-type stars in the dwarf irregular galaxy IC1613, whose metallicity is smaller than the SMC's by roughly a factor 2. Using the reddening-free Q-parameter, evolutionary masses and GALEX photometry, we built a list of very likely O-type stars. We obtained low-resolution R~1000 GTC-OSIRIS spectra for a fraction of them and performed spectral classification, the only way to unequivocally confirm candidate OB-stars. We have discovered 8 new O-type stars in IC1613, increasing the list of 7 known O-type stars in this galaxy by a factor of 2. The best quality spectra were analyzed with the model atmosphere code FASTWIND to derive stellar parameters. We present the first spectral type -- effective temperature scale for O-stars beyond the SMC. The derived effective temperature calibration for IC1613 is about 1000K hotter than the scale at the SMC. The analysis of an increased list of O-type stars will be crucial for the studies of the winds and feedback of massive stars at all ages of the Universe.Comment: A&A accepted. 13 pages, including appendix. 15 figures tota

Programas bilingües en la provincia de Zaragoza: implementación, metodología y evaluación

En el presente trabajo realizamos un estudio de los programas de educación biblingües en la provincia de Zaragoza. En 1º lugar realizamos un análisis estadístico de los ecntros bilingües. A continuación describimos los programas bilingües que se imparten en la provincia de Zaragoza (CILE 1, currículo integrado español-inglés) y por último realizamos una comparativa de la implementación de los citados programas en dos centros de ZaragozaGrado en Educación Primari

The IACOB spectroscopic database of Galactic OB stars

We present the IACOB spectroscopic database, the largest homogeneous database of high-resolution, high signal-to-noise ratio spectra of Northern Galactic OB-type stars compiled up to date. The spectra were obtained with the FIES spectrograph attached to the Nordic Optical Telescope. We briefly summarize the main characeristics and present status of the IACOB, first scientific results, and some future plans for its extension and scientific exploitation.Comment: 2 pages. Poster contribution to the proceedings of the IAU272 "Active OB stars: structure, evolution, mass loss and critical limits

An upper bound for the magnetic force gradient in graphite

Cervenka et al. have recently reported ferromagnetism along graphite steps. We present Magnetic Force microscopy (MFM) data showing that the signal along the steps is independent of an external magnetic field. Moreover, by combining Kelvin Probe Force Microscopy (KPFM) and MFM, we are able to separate the electrostatic and magnetic interactions along the steps obtaining an upper bound for the magnetic force gradient of about16 microN/m, a figure six times lower than the lowest theoretical bound reported by Cervenka et al. Our experiments suggest absence of MFM signal in graphite at room temperature.Comment: 14 pages, including supplemetary informatio

Improved graphene blisters by ultrahigh pressure sealing

Graphene is a very attractive material for nanomechanical devices and membrane applications. Graphene blisters based on silicon oxide micro-cavities are a simple but relevant example of nanoactuators. A drawback of this experimental set up is that gas leakage through the graphene-SiO2 interface contributes significantly to the total leak rate. Here we study the diffusion of air from pressurized graphene drumheads on SiO2 micro-cavities and propose a straightforward method to improve the already strong adhesion between graphene and the underlying SiO2 substrate, resulting in reduced leak rates. This is carried out by applying controlled and localized ultrahigh pressure (> 10 GPa) with an Atomic Force Microscopy diamond tip. With this procedure, we are able to significantly approach the graphene layer to the SiO2 surface around the drumheads, thus enhancing the interaction between them allowing us to better seal the graphene-SiO2 interface, which is reflected in up to ~ 4 times lower leakage rates. Our work opens an easy way to improve the performance of graphene as a gas membrane on a technological relevant substrate such as SiO2.Comment: pages 19, 4 figures + supplementary informatio

Estudio teórico y experimental de la eliminación de Nitrógeno Amoniacal en aguas residuales sanitarias

A les aigües residuals de les empreses o indústries, el nitrogen amoniacal suposa a l’actualitat un greu problema, degut a que el seu origen resideix a les aigües residuals sanitàries, y per tant, aigües que les empreses no tracten prèviament al seu abocament. La problemàtica de les elevades concentracions de nitrogen amoniacal als abocaments, es veu afavorit per les condicions a les que es troben les aigües residuals a les arquetes de toma de mostres on hi trobem foscor, anaerobiosi y turbulències, donat que són arquetes de tipus sifónica. El conjunt de totes aquestes condicions són a les que s’han sotmès les diferents mostres, a l’efecte d’estudiar quin seria el possible tractament que es podria donar per l’eliminació o estabilització de la concentració de nitrogen amoniacal sota el límits de la normativa. Al realitzar l’estudi experimental s’ha observat, que la formació de nitrogen amoniacal a partir d’urea, es veu afavorit per l’agitació a la qual es veuen sotmeses les aigües a l’arqueta de toma de mostres