Toroidal vortices as a solution to the dust migration problem

PublishedJournal Article© 2016 The Authors.In an earlier letter, we reported that dust settling in protoplanetary discs may lead to a dynamical dust-gas instability that produces global toroidal vortices. In this Letter, we investigate the evolution of a dusty protoplanetary disc with two different dust species (1 mm and 50 cm dust grains), under the presence of the instability. We show how toroidal vortices, triggered by the interaction of mm grains with the gas, stop the radial migration of metre-sized dust, potentially offering a natural and efficient solution to the dust migration problem.The figures were created using SPLASH (Price 2007), an SPH visualization tool publicly available at http://users.monash.edu.au/∼dprice/splash. This Letter was supported by the STFC consolidated grant ST/J001627/1, and by the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013 grant agreement no. 339248). This Letter used the DiRAC Complexity system, operated by the University of Leicester IT Services, which forms part of the STFC DiRAC HPC Facility (www.dirac.ac.uk). This equipment is funded by BIS National E-Infrastructure capital grant ST/K000373/1 and STFC DiRAC Operations grant ST/K0003259/1. DiRAC is part of the National E-Infrastructure. This Letter also used the University of Exeter Supercomputer, a DiRAC Facility jointly funded by STFC, the Large Facilities Capital Fund of BIS and the University of Exeter

Detonations in white dwarf dynamical interactions

In old, dense stellar systems collisions of white dwarfs are a rather frequent phenomenon. Here we present the results of a comprehensive set of Smoothed Particle Hydrodynamics simulations of close encounters of white dwarfs aimed to explore the outcome of the interaction and the nature of the final remnants for different initial conditions. Depending on the initial conditions and the white dwarf masses, three different outcomes are possible. Specifically, the outcome of the interaction can be either a direct or a lateral collision or the interaction can result in the formation of an eccentric binary system. In those cases in which a collision occurs, the infalling material is compressed and heated such that the physical conditions for a detonation may be reached during the most violent phases of the merger. While we find that detonations occur in a significant number of our simulations, in some of them the temperature increase in the shocked region rapidly lifts degeneracy, leading to the quenching of the burning. We thus characterize under which circumstances a detonation is likely to occur as a result of the impact of the disrupted star on the surface of the more massive white dwarf. Finally, we also study which interactions result in bound systems, and in which ones the more massive white dwarf is also disrupted as a consequence of the dynamical interaction. The sizable number of simulations performed in this work allows to find how the outcome of the interaction depends on the distance at closest approach, and on the masses of the colliding white dwarfs, and which is the chemical pattern of the nuclearly processed material. Finally, we also discuss the influence of the masses and core chemical compositions of the interacting white dwarfs and the different kinds of impact in the properties of the remnants.Comment: 18 pages, 6 figures. Accepted for publication in MNRA

Estudios del botánico aragonés Ignacio Jordán de Asso en la Universidad de Zaragoza (1760-1763)

Se hace un somero repaso biográfico de Ignacio Jordán de Asso, destacando la importancia de sus obras botánicas, precisando los años que cursó en la Universidad de Zaragoza sus estudios de Leyes y el ambiente académico de la época.Ignacio Jordán de Asso’s quick biographical review, emphasizing the importance of his botanical works, specifying the school years in the University of Zaragoza studing Laws and the study environment of the period

Miel y cera de las abejas europeas en las misiones franciscanas de nueva España y Méjico. Aproximación a un problema

Tras el feliz hallazgo de la Indias Occidentales, en las sucesivas expediciones que siguieron se enviaron desde la península toda suerte de animales domésticos con vistas a su aclimatación y explotación en los nuevos territorios. Sin embargo no existe constancia documental de la exportación de colmenas españolas con abejas, Apis mellifera, mucho más productoras de miel y cera que las colonias de Trigonas y Meliponas que allí explotaban algunas tribus indígenas. Los historiadores ingleses documentan envios de abejas desde su país en 1617, lo que hasta el presente era la prueba más temprana de estas exportaciones. En nuestro trabajo aportamos pruebas documentales, obtenidas en el Archivo de Indias, del interés de la Corona Española por llevar a la isla de Cuba colmenas de abejas ya en 1543. Como complemento analizamos también las referencias que sobre esta cuestión se toman de algunos cronistas de Indias, la opinión de los principales historiadores de la apicultura que han abordado la cuestión, así como la de entomólogos contemporáneos que han estudiado las colonias actuales de abejas silvestres en las inmediaciones de los principales puertos de arribo de los barcos europeos en el Nuevo.After the happy discovery of the “Indias”, in the following expeditions were sended every sort of domestic animals to become acclimatized and for the exploration of the news territories. However it doesn’t exist documental evidences of the export of spanish beehives wid bees, Apis mellifera, much more producers of honey and wax than the colonies of Trigona and Melipona that there exploited some indigenous tribes. The english historians vouch for consignments of bees from their country in 1617, this was still the present time the earlier proofs of these exports. In our work we contribute documental proofs, got in the “Indias” Archive, of the interest of the Spanish Kingdom to carry beehives to the Cuba island already in 1543. To complete we also analyse the eports taked bay some chroniciers of “Indias” about this question, the opinion of the main historians of the beekeeping they’re broached, as well as the contemporary entomologist opinion they’re studied the present colonies of wild bees in the environs of the main arrivals ports of the europeans ships in the New World

Modesto Salazar y la flora medicinal alicantina

Presentamos un estudio sobre la flora medicinal de la provincia de Alicante, publicado en 1866 por el farmacéutico militar Modesto Salazar y de San José, en la Revista de sanidad militar española y extranjera. A pesar de estar limitado a las plantas de uso farmacéutico, consideramos que la rareza del hallazgo merece ser hoy conocida por los estudiosos de la botánica española.Modesto Salazar and medicinal plants in the province of Alicante. We present a study about the medicinal flora in that region of Spain. It was published in 1866 by the military pharmacist Modesto Salazar y San José in the “Revista de Sanidad militar española y extranjera” (Journal of Spanish and foreign military health). Despite being limited to plants for pharmaceutical use, we consider this uncommon finding deserves to be known by the Spanish Botany researchers