Analysis of Balmer Profiles of early type stars

The spectral energy distribution (SED) of recent star formation regions is dominated by the more massive and early stars (O and B types). These stars show large and very significant absorption features, the most prominent being the recombination lines of H, HeI and HeII. In particular, the shape of their profiles are very dependent on the luminosity of the star. We have explored the potential use of high resolution profiles to discriminate between different luminosity classes and spectral types, by using profiles of the He and Balmer lines. We have calculated growth curves for each of the lines and their dependence on gravity and effective temperature. We show some of these theoretical growth curves and our preliminary conclusions are analyzed and discussed.Comment: 1 pag, Contribution to the conference "Cosmic Evolution and Galaxy Formation: Structure, Interactions and Feedback", Nov. 1999 (Puebla, Mexico), to be published in ASP. Conf. Series, Eds. J. Franco, E. Terlevich. O. Lopez-Cruz, I. Aretxag

Evolutionary dynamics of insertion sequences in relation to the evolutionary histories of the chromosome and symbiotic plasmid genes of Rhizobium etli populations

Insertion sequences (IS) are mobile genetic elements that are distributed in many prokaryotes. In particular, in the genomes of the symbiotic nitrogen-fixing bacteria collectively known as rhizobia, IS are fairly abundant in plasmids or chromosomal islands that carry the genes needed for symbiosis. Here, we report an analysis of the distribution and genetic conservation of the IS found in the genome of Rhizobium etli CFN42 in a collection of 87 Rhizobium strains belonging to populations with different geographical origins. We used PCR to generate presence/absence profiles of the 39 IS found in R. etli CFN42 and evaluated whether the IS were located in consistent genomic contexts. We found that the IS from the symbiotic plasmid were frequently present in the analyzed strains, whereas the chromosomal IS were observed less frequently. We then examined the evolutionary dynamics of these strains based on a population genetic analysis of two chromosomal housekeeping genes (glyA and dnaB) and three symbiotic sequences (nodC and the two IS elements). Our results indicate that the IS contained within the symbiotic plasmid have a higher degree of genomic context conservation, lower nucleotide diversity and genetic differentiation, and fewer recombination events than the chromosomal housekeeping genes. These results suggest that the R. etli populations diverged recently in Mexico, that the symbiotic plasmid also had a recent origin, and that the IS elements have undergone a process of cyclic infection and expansion

Sub-au imaging of water vapour clouds around four Asymptotic Giant Branch stars

We present MERLIN maps of the 22-GHz H2O masers around four low-mass late-type stars (IK Tau U Ori, RT Vir and U Her), made with an angular resolution of ~ 15 milliarcsec and a velocity resolution of 0.1 km s-1. The H2O masers are found in thick expanding shells with inner radii ~ 6 to 16 au and outer radii four times larger. The expansion velocity increases radially through the H2O maser regions, with logarithmic velocity gradients of 0.5--0.9. IK Tau and RT Vir have well-filled H2O maser shells with a spatial offset between the near and far sides of the shell, which suggests that the masers are distributed in oblate spheroids inclined to the line of sight. U Ori and U Her have elongated poorly-filled shells with indications that the masers at the inner edge have been compressed by shocks; these stars also show OH maser flares. MERLIN resolves individual maser clouds, which have diameters of 2 -- 4 au and filling factors of only ~ 0.01 with respect to the whole H2O maser shells. The CSE velocity structure gives additional evidence the maser clouds are density bounded. Masing clouds can be identified over a similar timescale to their sound crossing time (~2 yr) but not longer. The sizes and observed lifetimes of these clouds are an order of magnitude smaller than those around red supergiants, similar to the ratio of low-mass:high-mass stellar masses and sizes. This suggests that cloud size is determined by stellar properties, not local physical phenomena in the wind.Comment: 21 pages, including 14 figures and 8 tables. Accepted for publication in MNRA

Synthetic spectra of H Balmer and HeI absorption lines. I: Stellar library

We present a grid of synthetic profiles of stellar H Balmer and HeI lines at optical wavelengths with a sampling of 0.3 A. The grid spans a range of effective temperature 4000 K < Teff < 50000 K, and gravity 0.0 < log g < 5.0 at solar metallicity. For Teff > 25000 K, NLTE stellar atmosphere models are computed using the code TLUSTY (Hubeny 1988). For cooler stars, Kurucz (1993) LTE models are used to compute thesynthetic spectra. The grid includes the profiles of the high-order hydrogen Balmer series and HeI lines for effective temperatures and gravities that have not been previously synthesized. The behavior of H8 to H13 and HeI 3819 with effective temperature and gravity is very similar to that of the lower terms of the series (e.g. Hb) and the other HeI lines at longer wavelengths; therefore, they are suited for the determination of the atmospheric parameters of stars. These lines are potentially important to make predictions for these stellar absorption features in galaxies with active star formation. Evolutionary synthesis models of these lines for starburst and post-starburst galaxies are presented in a companion paper. The full set of the synthetic stellar spectra is available for retrieval at our website http://www.iaa.es/ae/e2.html and http://www.stsci.edu/science/starburst/ or on request from the authors at [email protected]: To be published in ApJS. 28 pages and 12 figure

The Nuclear and Circum-nuclear Stellar Population in Seyfert 2 Galaxies: Implications for the Starburst-AGN Connection

We report the results of a spectroscopic investigation of a sample of 20 of the brightest type 2 Seyfert nuclei. Our goal is to search for the direct spectroscopic signature of massive stars, and thereby probe the role of circumnuclear starbursts in the Seyfert phenomenon. The method used is based on the detection of the higher order Balmer lines and HeI lines in absorption and the Wolf-Rayet feature at $\sim$4680 \AA in emission. These lines are strong indicators of the presence of young (a few Myrs) and intermediate-age (a few 100 Myrs) stellar populations. In over half the sample, we have detected HeI and/or strong stellar absorption features in the high-order (near-UV) Balmer series together with relatively weak lines from an old stellar population. In three others we detect a broad emission feature near 4680 \AA that is most plausibly ascribed to a population of Wolf-Rayet stars (the evolved descendants of the most massive stars). We therefore conclude that the blue and near-UV light of over half of the sample is dominated by young and/or intermediate age stars. The ``young'' Seyfert 2's have have larger far-IR luminosities, cooler mid/far-IR colors, and smaller [OIII]/H$\beta$ flux ratios than the ``old'' ones. These differences are consistent with a starburst playing a significant energetic role in the former class. We consider the possibility that there may be two distinct sub-classes of Seyfert 2 nuclei (``starbursts'' and ``hidden BLR''). However, the fact that hidden BLRs have been found in three of the ``young'' nuclei argues against this, and suggests that nuclear starbursts may be a more general part of the Seyfert phenomenon.Comment: To be published in ApJ, 546, Jan 10, 200

Activitats formadores programades i competències adquirides

projecte: 2014PID-UB/073El present projecte se centra en analitzar amb profunditat el funcionament, organització i resultats, en termes de rendiment i de adquisició de competències transversals, de les activitats formadores programades en 5 grups de l’assignatura de Política Econòmica d’Espanya i la Unió Europea. Les activitats són quatre: a) l’elaboració de mapes conceptuals (individual i/o en equip en funció de la grandària del grup) de documents i articles bàsics de la bibliografia recomanada; b) la redacció individual d’un document de reflexió curt; c) la confecció d’un treball en equip i d) la prova final de síntesi. En la primera i segona fases del procés cadascuna de les activitats ha estat configurada en el campus com una tasca, i s’han modificat i re-definit els instruments plantejats per realitzar-la i avaluar-la amb el corresponent feedback, amb la participació dels estudiants en el disseny de les rubriques per l’avaluació i la identificació i puntuació de les competències transversals adquirides. En la tercera i quarta fases la intervenció s’ha centrat en la remodelació de la activitat “elaboració del mapa conceptual” utilizant la metodologia de l’aprenentatge per indagació (IBL), tot introduint les innovacions més complexes en dos grups concrets, als quals, per les seves dimensions, ha estat possible implicar més als estudiants en el procediment de co-disseny. Els resultats previstos són molt semblants als assolits, excepte el d’aconseguir el co-disseny de la rubrica final per l’avaluació, ja que degut a manca material de temps no ha estat viable la participació dels estudiants en aquest darrer instrument.Codi del projecte: 2014PID-UB/07

Uptake of 99mTc-MIBI by Sclerosing Pneumocytoma Raising a False Suspicion of Metastasis From Medullary Thyroid Carcinoma.

Technetium-99m methoxy isobutyl isonitrile ( &lt;sup&gt;99m&lt;/sup&gt; Tc-MIBI; sestamibi) single-photon emission computed tomography (SPECT)/computed tomography (CT) performed for preoperative localization of parathyroid adenomas or for other indications can reveal incidentalomas. Interpretation of such findings can be challenging, particularly when thyroid or other endocrine tumors are also present. Preoperative staging of a 59-year-old female patient with medullary thyroid carcinoma (MTC) showing moderate hypermetabolism on &lt;sup&gt;18&lt;/sup&gt; F-fluorodeoxyglucose positron emission tomography/CT also detected a slightly hypermetabolic pulmonary nodule (standardized uptake value normalized by body weight max = 2.0 g/mL). A sestamibi SPECT/CT performed because of concomitant primary hyperparathyroidism showed increased uptake by both the MTC and the pulmonary nodule, raising suspicion of MTC metastasis. Lung wedge resection biopsy revealed a sclerosing pneumocytoma (SPC), a rare benign pulmonary tumor not previously known to retain sestamibi. In contrast to classical knowledge that sestamibi uptake by tumors is associated with its retention by mitochondria, immunohistochemical analyses showed that the mitochondrial content of the patient's SPC was low. This case illustrates the behavior of SPC in sestamibi scintigraphy and indicates that SPC is a potential cancer mimicker in this setting

Kinetic and morphometric evaluation of fucoidan‐degrading fungal strains

Fucoidan is a sulfated fucose hetero‐polysaccharide found in brown algae. This compound has a wide variety of biological activities including anticoagulant, antithrombotic, antitumoral and antiviral (Alexeeva et al. 2002; Ellouali et al. 1993; McClure et al. 1992). Specific enzymes able to degrade fucoidan matrix are important tools to establish structural characteristics and biological functions of this polysaccharide. Such enzymes, called fucoidanases, have been only isolated from marine organisms (Sakai et al. 2004; Giordano et al. 2006). Reports of fungal microorganisms with enzymatic activity over this sulfated‐polysaccharide are scarce. Mycelial growth and morphology of filamentous fungi can be mathematically described by kinetic models, through the estimation of specific growth rate of molds on plates containing target polysaccharide as sole carbon source, using image processing techniques (Loera and Viniegra 1998). In this sense, the aim of this work was to identify fungal strains able to growth over fucoidan media as sources of active fucoidanases, by quantification of kinetic and morphology features, to establish the influence of media composition on growth patterns. Aspergillus niger PSH, Penicillium purpurogenum GH2 and Mucor sp. 3P were the screened strains. Different culture media with and without mineral salts were tested for microbial growth. Fucoidan of Laminaria japonica and urea were used as carbon and nitrogen source. Radial growth rate (Ur) was kinetically monitored measuring colony diameters. Hyphal length (Lav) and diameter (Dh) were quantified by image analyses measurements. All the evaluated strains were able to growth on different fucoidan‐urea media, and their plate invasion capacity and radial growth rate were directly proportional to measured morphometric parameters. The three fungi strains synthesize acting metabolites toward fucoidan matrix, and are important tools for the synthesis of sulfated fucan‐degrading enzymes. These results are, until now, the first report of enzymes able to growth and degrade fucoidan obtained by terrestrial fungus

Microwave-assisted extraction of sulfated polysaccharides(fucoidan)from brown seaweed

Sulfated polysaccharides (fucoidan) were recovered from brown seaweed Fucus vesiculosus by microwave-assisted extraction (MAE). Different conditions of pressure (30 to 120 psi), extraction time (1 to 31 min), and alga/water ratio (1/25 to 5/25 g ml-1) were evaluated during this process aiming to establish a condition to maximize the extraction results. The alga degradation (%), total sugar yield (%), and SO3 content (%) were also determined to each experimental condition. All the studied variables presented significant (p<0.05) influence on fucoidan yield. MAE at 120 psi, 1 min, using 1 g alga/25 ml water was the best condition for the fucoidan recovery. L-fucose was the main constituent of this polysaccharide, which also contained xylose and galactose. MAE under optimum reaction conditions was an effective method to recover fucoidan from Fucus vesiculosus. This method required short extraction times, and non corrosive solvents, resulting in reduced costs and being an environmentally friend technique.The financial support from Mexican Science and Technology Council (CONACYT, grant number: 2066071230415) and the Portuguese Foundation for Science and Technology (FCT) are gratefully acknowledged. The authors also thank Bruna Fonseca and Professor Teresa Tavares for the accessibility to the microwave assisted equipment; and Professor Isabel Sousa Pinto and Rita Araujo from CIIMAR - Interdisciplinary Centre of Marine and Environmental Research for facilitate the algae selection