972 research outputs found
Gas and dust spectral analysis of galactic and extragalactic symbiotic stars
No full textSymbiotic stars are recognized as unique laboratories for studying a large variety of phenomena that are relevant to a number of important astro-physical problems. This PhD thesis deals with a spectral analysis of galactic and extragalactic symbiotic stars. The former are mainly D-type symbiotic stars for which a comprehensive study, from radio to X-ray spectral region, has been performed. With the latter, we refer to symbiotic stars in the Magellanic Clouds, to be analyzed mainly in the IR range. The common theoretical scenario that lies in the background of this work is the colliding-wind model, developed already during the 80’s, supported by first observational evidence at the beginning of 90’s (mainly thanks to Nussbaumer and collaborators), and finally completed with detailed and powerful hydrodynamical simulations by various authors in these recent years. In the light of this scenario, we have tried to interpret gas and dust spectra of our targets in a unique and self-consistent way. The spectral analysis has been performed by means of the numerical code SUMA, developed at the Instituto Astronomico e Geofisico of the University of Sao Paulo by Sueli M. Viegas (Al-
drovandi) and Marcella Contini from the School of Physics and Astronomy of the Tel-Aviv University.Le stelle simbiotiche sono riconosciute come unici laboratori per lo studio di una serie di importanti problemi astro-fisici. In questa tesi di dottorato si presenta un’analisi spettrale di un campione di stelle simbiotiche galattiche ed extragalattiche. Nel primo caso, si tratta principalmente di simbiotiche di tipo D per le quali e' stato effettuato uno studio comparativo con dati osservativi dal radio ai raggi X. Nel caso delle simbiotiche extragalattiche, ci si riferisce invece esclusivamente alle simbiotiche nelle Nubi di Magellano, per cui si stanno raccogliendo dati da satellite nel dominio InfraRosso. Il quadro teorico alla base di questo studio e da cui prende le mosse l’analisi spettrale, e' il colliding-wind model, sviluppato gi ́a nel corso degli anni ’80, sostenuto da prime evidenze osservative all’inizio degli anni ’90 (soprattutto grazie a Nussbaumer e collaboratori) e, infine, ulteriormente raffinato da vari autori per mezzo di nuove simulazioni idrodinamiche, in questi ultimi anni. Alla luce di questo scenario, si e' quindi tentata un’analisi degli spettri simbiotici che fosse coerente all’interno di un unico e consistente quadro interpretativo. L’analisi spettrale e' stata effettuata mediante il codice numerico SUMA, sviluppato presso l’Instituto Astronomico e Geofisico della Universita' di Sao Paulo da Sueli M. Viegas (Aldrovandi) e Marcella Contini della School of Physics and Astronomy della Tel-Aviv University
Shock fronts in the symbiotic system BI Crucis
No full textWe investigate the symbiotic star BI Crucis (BI Cru) through a comprehensive and self-consistent analysis of the spectra emitted in three different epochs: 1960s, 1970s and late 1980s. In particular, we would like to find out the physical conditions in the shocked nebula and in the dust shells, as well as their location within the symbiotic system, by exploiting both photometric and spectroscopic data from radio to UV. We suggest a model which, on the basis of optical imaging, emission-line ratios and spectral energy distribution profile, is able to account for collision of the winds, formation of lobes and jets by accretion onto the white dwarf (WD), as well as for the interaction of the blast wave from a past, unrecorded outburst with the interstellar medium (ISM). We have found that the spectra observed throughout the years show the marks of the different processes at work within BI Cru, perhaps signatures of a post-outburst evolution. We then call for new infrared and millimeter observations, potentially able to resolve the inner structure of the symbiotic nebula
The symbiotic star H1-36. A composite model of line and continuum spectra from radio to ultraviolet
No full textAims:In this paper, we analyse the spectra of D-type SS H1-36 within a colliding-wind scenario. We aim to analyse the properties of this object by taking the observational data along the whole electromagnetic spectrum into account, in order to derive a self-consistent picture able to interpret the nature of the system as a whole.
Methods: After constraining the relative physical conditions by modelling more than 40 emission lines from radio to UV, we are able to explain the continuum spectral energy distribution by considering all the emitting contributions arising from both the stars, the dust shells, and the gaseous nebulæ.
Results: A comprehensive model of the radio spectra allows reproduction of the different slopes of the radio profile and the turnover frequency, as well as the different sizes of the observed shocked envelope at different frequencies in the light of the contributions from the expanding and reverse nebulæ. The IR continuum unveils the presence of two dust shells with different radii and temperatures, which might be a distinctive feature of D-type symbiotic systems as a class of objects. The broad profiles of IR lines direct us to investigate whether an X-ray jet may be present.
Conclusions: This insight leads us to indicate H1-36 as a promising X-ray target and to encourage observations and studies that consistently take the complex nature of symbiotic stars into account throughout the whole electromagnetic spectrum
Gas and dust spectra of the D' type symbiotic star HD 330036
No full textAims:We present a comprehensive and self-consistent modelling of the D' type symbiotic star (SS) HD 330036 from radio to UV.
Methods: Within a colliding-wind scenario, we analyse the continuum, line, and dust spectra by means of SUMA, a code that simulates the physical conditions of an emitting gaseous cloud under the coupled effect of ionisation from an external radiation source and shocks.
Results: We find that the UV lines are emitted from high-density gas between thestars downstream of the reverse shock, while the optical lines are emitted downstream of the shock propagating outwards from the system. As regards the continuum SED, three shells are identified in the IR, at 850 K, 320 K, and 200 K with radii r = 2.8 × 1013 cm, 4 × 1014 cm, and 1015 cm, respectively, after adopting a distance to Earth of d=2.3 kpc. Interestingly, all these shells appear to be circumbinary. Analysis of the unexploited ISO-SWS spectrum reveals that both PAHs and crystalline silicates coexist in HD 330036, with PAHs associated to the internal shell at 850 K, and crystalline silicates stored in the cool shells at 320 K and 200 K. Strong evidence that crystalline silicates are shaped in a disk-like structure is derived on the basis of the relative band strengths. Finally, we suggest that shocks can be a reliable mechanism for activating the annealing and the consequent crystallisation processes.
Conclusions: We show that a consistent interpretation of gas and dust spectra emitted by SS can be obtained by models that account for the coupled effect of the photoionising flux and of shocks. The VLTI/MIDI proposal recently accepted by ESO aims to verify and better constrain some of our results by means of IR interferometric observations
Free tissue transfert in high-grade bone and soft tissue sarcoma
No full textFree tissue transfert in high-grade bone and soft tissue sarcoma
Silicates in D-Type Symbiotic Stars: An Infrared Space Observatory Overview
No full textWe investigate the IR spectral features of a sample of D-type symbiotic stars in order to constrain the emitting properties of coupled dust-gas particles across the whole system. In particular, by analyzing unexploited ISO Short Wavelength Spectrometer data, deriving the basic observational parameters of dust bands, and comparing them with respect to those observed in other astronomical sources, we try to highlight the effect of environment on grain chemistry and physics. We find strong amorphous silicate emission bands at ~10 and ~18 μm in a large fraction of the sample. The analysis of the ~10 μm band, along with a direct comparison with several astronomical sources, reveals that silicate dust in symbiotic stars shows features between the characteristic circumstellar environments and the interstellar medium. This indicates an increasing reprocessing of grains in relation to specific symbiotic behavior of the objects. A correlation between the central wavelengths of the ~10 and ~18 μm dust bands is found. By modeling IR spectral lines we also investigate dust grain conditions within the shocked nebulae. Both the unusual depletion values and the high sputtering efficiency might be explained by the formation of SiO molecules, which are known to be a very reliable shock tracer. We conclude that the signature of dust chemical disturbance due to symbiotic activity should be looked for in the outer, circumbinary, expanding shells where the environmental conditions for grain processing might be achieved. Symbiotic stars are thus attractive targets for new mid-IR and millimeter observations
The Wine Attributes with the Greatest Influence in the Process of Consumer Choice in Spain
No full textThe commercialisation of wine in Spain is problematic due to two concrete circumstances: the decrease in wine consumption because of a consumer shift toward substitute drinks and the greater presence of national and foreign wine in the interior market, which involves an increase in business competitiveness. The increase in competitiveness of quality Spanish wine depends on producing enterprises’ knowledge of wine consumer preferences so they can offer consumers what they demand. In order to respond to this matter and better adapt supply, 421 wine consumers were surveyed using the Best-Worst Scaling methodology. Various segmentations were also made by consumer income and age groups. The results indicate that the two main attributes which condition consumers in choosing wine are the region of origin and having tasted it previously. The region of origin attribute is valued in general by consumers over 34 years old who have a monthly family income above 1,500 €. The attribute of having tasted it before, which on many occasions is associated with the price attribute, is valued particularly by younger consumers and those with lower incomes.Consumer behaviour, Wine attributes, Food Marketing, Consumer/Household Economics,
Dr. Rodolfo D. Torres talk at University of Washington Tacoma: After Latino Metropolis
No full textThe role of class and spatial politics in Latino Los Angeles will be the subject of this timely talk. Professor Rodolfo D. Torres is co-author of the highly acclaimed book, Latino Metropolis (University of Minnesota Press, 2000). He will revisit this important book
How corporate governance and globalization can run afoul of the law and good practices in business: The Enron's disgraceful affair.
No full textThe purpose of this paper is to set out the Enron’s demise into the perspective of Corporate and Global Governance. To accomplish this target, the incremental cash flow model is expanded to give room for governance issues, while a functional introduction to information sets is developed, including bounded rationality, asymmetric information, opportunistic behavior, transaction costs and agency problems. Then, corporate governance is linked to globalization by means of some recent approaches that go beyond a narrow economic mindset to encompass a far-reaching dynamics. Taking advantage of such background, the Enron’s story is tracked down over a span of fifteen years since its starting day to its bankruptcy filing. Leading events are explained from corporate and global governance viewpoints, while an in-depth analysis is worked out on Enron’s complex game of deception and breach of contracts: the outrageous affiliated limited partnerships, the lavish pay package to its executives, the involvement with global governance through the Indian affair and the Taliban connection. It is for the incremental cash flow model to explain malfeasance with cash flows from assets, and how cash flows to creditors were actually contrived. Furthermore, to highlight how cash flows were swindled from stockholders and, finally, how Enron made wheeling and dealing with cash flows on behalf of its managers.corporate governance, global governance, incremental cash flow model, globalization, information sets, good practices.
Rodolfo Lenz
No full textIn this article the author intends to offer an overall profile of Dr. Rodolfo
Lenz’ versatile personality, portraying him as the man, the phonetician, the
expert scholar in Araucanian, the orthographer, the methodologist, the
compulsive scientist. All these personality traits contributed to renovate in
Chile the interest in language, in foreign language methodology and the
institutionalization of folklore as a science, which earned him the Chilean
nationalityEn este trabajo el autor se propone dar una visión de conjunto de la polifacética
personalidad del Dr. Rodolfo Lenz: el hombre, el fonetista, el araucanista, el
lexicógrafo, el gramático, el ortógrafo, el metodólogo, el científico compulsivo.
Aspectos todos que contribuyeron a renovar profundamente en Chile el
estudio de las ciencias del lenguaje, la metodología de la enseñanza de las
lenguas extranjeras y la fundación del folclor como ciencia, por todo lo cual
el Gobierno le confirió nuestra nacionalida
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