Stability of volcanic conduits: Critical mechanical parameters

Several geological evidences support the occurrence of volcanic conduit enlargement during explosive events (e.g. presence of lithic fragments in most pyroclastic deposits), with significant effects on the eruptive dynamics, particularly on the mass discharge rate. Conduit wall collapse is supposed to be a relevant enlargement process, being more intense near and above the fragmentation level. Nonetheless, the influence of country rock conditions has never been addressed, and its implications on the eruptive dynamics are still unclear. This work focuses on the effects of the country rock mechanical parameters and the presence of unconfined aquifers on conduit stability, using a 1D steady-state model and the application of two collapse criteria. For given magma properties and conduit dimensions, it emerges that conduit stability is mainly controlled by the friction angle of the country rocks and, to a lesser extent, by the cohesion. The horizontal stress gradients are only significant when the Mohr-Coulomb criterion is employed, whereas the variability in the vertical stress gradient has a minor effect on conduit stability. Moreover, the presence of unconfined aquifers is an important destabilizing factor, which is consistent with the ejection of significant amounts of lithic fragments in many phreatomagmatic eruptions

CO(1-0) line imaging of massive star-forming disc galaxies at z=1.5-2.2

We present detections of the CO(J= 1-0) emission line in a sample of four massive star-forming galaxies at z~1.5-2.2 obtained with the Karl G. Jansky Very Large Array (VLA). Combining these observations with previous CO(2-1) and CO(3-2) detections of these galaxies, we study the excitation properties of the molecular gas in our sample sources. We find an average line brightness temperature ratios of R_{21}=0.70+\-0.16 and R_{31}=0.50+\-0.29, based on measurements for three and two galaxies, respectively. These results provide additional support to previous indications of sub-thermal gas excitation for the CO(3-2) line with a typically assumed line ratio R_{31}~0.5. For one of our targets, BzK-21000, we present spatially resolved CO line maps. At the resolution of 0.18'' (1.5 kpc), most of the emission is resolved out except for some clumpy structure. From this, we attempt to identify molecular gas clumps in the data cube, finding 4 possible candidates. We estimate that <40 % of the molecular gas is confined to giant clumps (~1.5 kpc in size), and thus most of the gas could be distributed in small fainter clouds or in fairly diffuse extended regions of lower brightness temperatures than our sensitivity limit

Oferta turistica internacional para el mercado chileno

132 p.Esta investigación, se centra en una revista, la cual es un instrumento de difusión- especializada- del turismo mundial. A través de sus páginas se dan a conocer innumerables destinos y lugares, tanto nacionales como internacionales, para los chilenos. De esta perspectiva el presente estudio pretende avanzar en el conocimiento de las ofertas turísticas internacionales para el mercado chileno, realizando un análisis de la oferta extranjera con las respectivas características que cada país posee para atraer a los potenciales turistas de nuestro país, que lugares poseen, ya sean: monumentos, playas, lagos, ríos, montañas, hoteles, islas, etc. El estudio se llevo a cabo mediante revisiones bibliográficas para identificar ciertos aspectos relacionados con el tema y tener una visión mas actualizada de lo que hoy es la oferta de turismo internacional para el mercado chileno. Los pasos de la investigación consisten en analizar la principal fuente de información, reunir la información necesaria que permita resolver los objetivos planteados, apoyados por el software estadístico SPSS para procesar y realizar los respectivos análisis de los datos y además, complementarlo con el software Excel. En términos generales la oferta turística internacional para el mercado chileno es variada, pero existe una marcada tendencia hacia lugares cálidos y ciudades cercanas a nuestro país, entre los que destacan playas y costas de Brasil, Uruguay, México y ciudades de Argentina (como las más divulgadas)

Topological and flat bands states induced by hybridized interactions in one-dimensional photonic lattices

We report on a study of a one-dimensional linear photonic lattice hosting, simultaneously, fundamental and dipolar modes at every site. We show how, thanks to the interaction between the different orbital modes, this minimal model exhibits rich transport and topological properties. By varying the detuning coefficient we find a regime where bands become flatter (with reduced transport) and, a second regime, where both bands connect on at a gap-closing transition (with enhanced transport). We detect an asymmetric transport due to the asymmetric inter-mode coupling and a linear energy exchange mechanism between modes. Further analysis show that the bands have a topological transition with a non-trivial Zak phase which leads to the appeareance of edge states in a finite system. Finally, for zero detuning, we found a symmetric condition for coupling constants, where the linear spectrum becomes completely flat, with states fully localized in space occupying only two lattice sites.Comment: 8 pages, 5 figure

Environments of a sample of AzTEC submillimetre galaxies in the COSMOS field

Aims. Submillimetre galaxies (SMGs) are bright sources at submillimetre wavelengths (F-850 mu m>2-5 mJy). Made up of mostly of high-z galaxies (z>1), SMGs are amongst the most luminous dusty galaxies in the Universe. These galaxies are thought to be the progenitors of the massive elliptical galaxies in the local Universe and to reside in massive haloes at early epochs. Studying their environments and clustering strength is thus important to put these galaxies in a cosmological context.Methods. We present an environmental study of a sample of 116 SMGs in 96 ALMA observation fields, which were initially discovered with the AzTEC camera on ASTE and identified with high-resolution 1.25 mm ALMA imaging within the COSMOS survey field, having either spectroscopic or unambiguous photometric redshift. We analysed their environments making use of the latest release of the COSMOS photometric catalogue, COSMOS2015, a catalogue that contains precise photometric redshifts for more than half a million objects over the 2 deg(2) COSMOS field. We searched for dense galaxy environments computing the so-called overdensity parameter as a function of distance within a radius of 5 from the SMG. We validated this approach spectroscopically for those SMGs for which spectroscopic redshift is available. As an additional test, we searched for extended X-ray emission as a proxy for the hot intracluster medium, performing an X-ray stacking analysis in the 0.5-2 keV band with a 32 '' aperture and our SMG position using all available XMM-Newton and Chandra X-ray observations of the COSMOS field.Results. We find that 27% (31 out of 116) of the SMGs in our sample are located in a galactic dense environment; a fraction that is similar to previous studies. The spectroscopic redshift is known for 15 of these 31 sources, thus this photometric approach is tested using spectroscopy. We are able to confirm that 7 out of 15 SMGs lie in high-density peaks. However, the search for associated extended X-ray emission via an X-ray stacking analysis leads to a detection that is not statistically significant.Peer reviewe