323 research outputs found
La calidad de vida urbana media a través del tipo de acceso al agua potable : el caso de Cochabamba, Bolivia
Tesis--Universitat Jaume IBibliografÃa: p. 569-58
Spin-up of low mass classical bulges in barred galaxies
Secular evolution is one of the key routes through which galaxies evolve
along the Hubble sequence. Not only the disk undergoes morphological and
kinematic changes, but also a preexisting classical bulge may be dynamically
changed by the secular processes driven primarily by the bar. We study the
influence of a growing bar on the dynamical evolution of a low mass classical
bulge such as might be present in galaxies like the Milky Way. Using
self-consistent high resolution {\it N}-body simulations, we study how an
initially isotropic non-rotating small classical bulge absorbs angular momentum
emitted by the bar. The basic mechanism of this angular momentum exchange is
through resonances and a considerable fraction of the angular momentum is
channeled through Lagrange point (-1:1) and ILR (2:1) orbits. In the phase of
rapid dynamical growth, also retrograde non-resonant orbits absorb significant
angular momentum. As a result of this angular momentum gain, the initially
non-rotating classical bulge transforms into a fast rotating, radially
anisotropic and triaxial object, embedded in the similarly fast rotating boxy
bulge formed from the disk. Towards the end of the evolution, the classical
bulge develops cylindrical rotation. By that time, its inner regions host a
"classical bulge-bar" whose distinct kinematics could serve as direct
observational evidence for the secular evolution in the galaxy. Some
implications of these results are discussed briefly.Comment: 15 pages, 16 figures, accepted for publication by MNRA
España. Historia. Edad Antigua. (19--)
Copia Digital. Real Academia de la Historia : 2010Forma de ingreso: Legado. Fuente de ingreso: Gonzalo Menéndez-Pidal y Goyri (Madrid). Fecha de ingreso: 29 de febrero de 2003Nota: "Los nombres subrayados son cabeza de convento jurÃdico". Signos convencionales indicando los lÃmites de provincia, conventos jurÃdicos y tribus, y las colonias y municipiosMapa diseñado por Gonzalo Menéndez-Pidal y Goyri para ilustrar sus librosManuscrito sobre papel grueso en tinta china. Rotulación con plantilla. Notas a lápiz fuera de la lÃnea de enmarque para corregir en el original definitiv
Non invasive ventilation after extubation in paediatric patients: a preliminary study
<p>Abstract</p> <p>Background</p> <p>Non-invasive ventilation (NIV) may be useful after extubation in children. Our objective was to determine postextubation NIV characteristics and to identify risk factors of postextubation NIV failure.</p> <p>Methods</p> <p>A prospective observational study was conducted in an 8-bed pediatric intensive care unit (PICU). Following PICU protocol, NIV was applied to patients who had been mechanically ventilated for over 12 hours considered at high-risk of extubation failure -elective NIV (eNIV), immediately after extubation- or those who developed respiratory failure within 48 hours after extubation -rescue NIV (rNIV)-. Patients were categorized in subgroups according to their main underlying conditions. NIV was deemed successful when reintubation was avoided. Logistic regression analysis was performed in order to identify predictors of NIV failure.</p> <p>Results</p> <p>There were 41 episodes (rNIV in 20 episodes). Success rate was 50% in rNIV and 81% in eNIV (p = 0.037). We found significant differences in univariate analysis between success and failure groups in respiratory rate (RR) decrease at 6 hours, FiO<sub>2 </sub>at 1 hour and PO<sub>2</sub>/FiO<sub>2 </sub>ratio at 6 hours. Neurologic condition was found to be associated with NIV failure. Multiple logistic regression analysis identified no variable as independent NIV outcome predictor.</p> <p>Conclusions</p> <p>Our data suggest that postextubation NIV seems to be useful in avoiding reintubation in high-risk children when applied immediately after extubation. NIV was more likely to fail when ARF has already developed (rNIV), when RR at 6 hours did not decrease and if oxygen requirements increased. Neurologic patients seem to be at higher risk of reintubation despite NIV use.</p
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