A new survey of cool supergiants in the Magellanic Clouds

In this study, we conduct a pilot program aimed at the red supergiant population of the Magellanic Clouds. We intend to extend the current known sample to the unexplored low end of the brightness distribution of these stars, building a more representative dataset with which to extrapolate their behaviour to other Galactic and extra-galactic environments. We select candidates using only near infrared photometry, and with medium resolution multi-object spectroscopy, we perform spectral classification and derive their line-of-sight velocities, confirming the nature of the candidates and their membership to the clouds. Around two hundred new RSGs have been detected, hinting at a yet to be observed large population. Using near and mid infrared photometry we study the brightness distribution of these stars, the onset of mass-loss and the effect of dust in their atmospheres. Based on this sample, new a priori classification criteria are investigated, combining mid and near infrared photometry to improve the observational efficiency of similar programs as this.Comment: 39 pages, 10 figures. Accepted for publication in A&

Spectral type, temperature and evolutionary stage in cool supergiants

In recent years, temperature scales in cool supergiants (CSGs) have been disputed, and the possibility that spectral types (SpTs) do not depend primarily on temperature has been raised. We explore the relations between different observed parameters and the capability of deriving accurate intrinsic stellar parameters from them through the analysis of the largest spectroscopic sample of CSGs to date from SMC and LMC. We explore possible correlations between different observational parameters, also making use of near- and mid-infrared colours and literature on photometric variability. Direct comparison between the behaviour of atomic lines (Fe I, Ti I, and Ca II) in the observed spectra and synthetic atmospheric models provides compelling evidence that effective temperature is the prime underlying variable driving the SpT sequence in CSGs. However, there is a clear correlation between SpT and luminosity, with later ones tending to correspond to more luminous stars with heavier mass loss. The population of CSGs in the SMC is characterised by a higher degree of spectral variability, early spectral types (centred on type K1) and low mass-loss rates (at least as measured by dust-sensitive mid-infrared colours). The population in the LMC displays less spectroscopic variability and later spectral types. The distribution of spectral types is not single-peaked. Instead, the brightest CSGs have a significantly different distribution from less luminous objects, presenting mostly M subtypes (centred on M2), and increasing mass-loss rates for later types. In conclusion, the observed properties of CSGs in the SMC and the LMC cannot be described correctly by standard evolutionary models. The very strong correlation between spectral type and bolometric luminosity, supported by all data from the Milky Way, cannot be reproduced at all by current evolutionary tracks.Comment: 25 pages, 24 figure

Visual Localisation of Mobile Devices in an Indoor Environment under Network Delay Conditions

Current progresses in home automation and service robotic environment have highlighted the need to develop interoperability mechanisms that allow a standard communication between the two systems. During the development of the DHCompliant protocol, the problem of locating mobile devices in an indoor environment has been investigated. The communication of the device with the location service has been carried out to study the time delay that web services offer in front of the sockets. The importance of obtaining data from real-time location systems portends that a basic tool for interoperability, such as web services, can be ineffective in this scenario because of the delays added in the invocation of services. This paper is focused on introducing a web service to resolve a coordinates request without any significant delay in comparison with the sockets

The population of M-type supergiants in the starburst cluster Stephenson 2

The open cluster Stephenson 2 contains the largest collection of red supergiants known in the Galaxy, and at present is the second most massive young cluster known in the Milky Way. We have obtained multi-epoch, intermediate-resolution spectra around the CaII triplet for more than 30 red supergiants in Stephenson~2 and its surroundings. We find a clear separation between a majority of RSGs having spectral types M0-M2 and the brightest members in the NIR, which have very late spectral types and show strong evidence for heavy mass loss. The distribution of spectral types is similar to that of RSGs in other clusters, such as NGC 7419, or associations, like Per OB1. The cluster data strongly support the idea that heavy mass loss and maser emission is preferentially associated with late-M spectral types, suggesting that they represent an evolutionary phase.Comment: Contribution to the Betelgeuse workshop, November 2012, Paris. To be published in the European Astronomical Society Publications Series, editors: Pierre Kervella, Thibaut Le Bertre & Guy Perri

Use of TimescaleDB as a database for ocean-meteorological data storage

The monitoring of the environment is essential to know and study the diferent phenomena that occur in the natural environment. [1]. Atmospheric and oceanographic data sets share many characteristics. They can be very large; many cover limited periods of time and have a limited spatial extent; gaps (lack of data) and outliers are common; The spatial distribution of several observation networks is uneven; and, often, the time series of data are not homogeneous. The data sets contain variables that, in general, are not independent in time or space; therefore, most of the variables must be seen within a multivariate context [2]. A time series database [3] (TSDB) is a database optimized for timestamp data. These databases have the ability to provide queries with subsamples, gap flling or aggregations throughout the time series, must be stored efciently to be inserted and retrieved quickly. TimescaleDB [4] is implemented as an extension on PostgreSQL, and exposes what look like singular tables, called hypertables, that are actually an abstraction or a virtual view of many individual tables holding the data, called chunks (created by partitioning the hypertable’s data into one or multiple dimensions). We will proceed to perform a series of tests to test the performance of TimeScale and compare it with other databases of the same style. Small comparisons will be made both in writing and reading data. Special emphasis will be placed on reading large datasets.Peer Reviewe

Manejo postoperatorio de la hepatectomía mayor

La resección hepática se ha convertido en el pilar del tratamiento de las neoplasias malignas. Los resultados después de la resección han mejorado significativamente con los avances de las técnicas quirúrgicas, anestésicas y cuidados perioperatorios. El hígado se compone de 2 lóbulos anatómicos de diferente tamaño, derecho e izquierdo, separados por la cisura hepática mayor. Cada lóbulo está formado por segmentos que constituyen unidades independientes en cuanto a vascularización y a drenaje biliar. El lóbulo derecho integra del IV al VIII segmento. Y el izquierdo del I a III segmento. El hígado recibe sangre arterial y venosa. La arteria hepática provee un 30% del flujo sanguíneo hepático. El resto proviene de la porta. Los vasos hepáticos, la vía biliar y los nervios del sistema autónomo forman el pedículo hepático. Según la nomenclatura internacional, una hepatectomía mayor es cualquier resección de al menos 3 segmentos

Homotopy continuation for vector space interference alignment in MIMO X networks

In this paper we propose an algorithm to design interference alignment (IA) precoding and decoding matrices for MIMO X networks (XN). The proposed algorithm is rooted in the homotopy continuation techniques commonly used to solve systems of nonlinear equations. Homotopy methods find the solution of a target system by smoothly deforming the known solutions of a start system which can be trivially solved. The key observation leading to a simple start system is realizing that the inverse IA problem, i.e., finding the channels that satisfy the IA conditions given a set of precoders and decoders, is linear and, therefore, a convenient trivial system. Once the start system has been solved, standard prediction and correction techniques are applied to track the solution all the way to the target system. Our results show that the proposed algorithm is able to consistently find solutions achieving the maximum number of degrees of freedom (DoF) whereas alternating minimization techniques, which typically work well for the interference channel (IC), repeatedly fail for the XN. Further, the algorithm provides insights into the feasibility of alignment in MIMO X networks for which theoretical results are scarce.This work was supported by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under project COSIMA (TEC2010-19545-C04-03), project COMONSENS (CSD2008-00010, CONSOLIDER-INGENIO 2010 Program) and FPU grant AP2009-1105

Frustration free gapless Hamiltonians for Matrix Product States

For every Matrix Product State (MPS) one can always construct a so-called parent Hamiltonian. This is a local, frustration free, Hamiltonian which has the MPS as ground state and is gapped. Whenever that parent Hamiltonian has a degenerate ground state (the so-called non-injective case), we construct another 'uncle' Hamiltonian which is local and frustration free but gapless, and its spectrum is $\R^+$. The construction is obtained by linearly perturbing the matrices building up the state in a random direction, and then taking the limit where the perturbation goes to zero. For MPS where the parent Hamiltonian has a unique ground state (the so-called injective case) we also build such uncle Hamiltonian with the same properties in the thermodynamic limit.Comment: 36 pages, new version with some contents rearranged, and a correction in the injective cas

How is star formation fed and quenched in massive galaxies at high redshift?

Observations of the location and kinematics of the atomic gas (HI) and the continuum radio emission from high redshift galaxies would mean a huge step forward in our understanding of galaxy evolution. We now have a secure global picture of the stellar content of massive galaxies and their precursors up to z~4. But we still have to understand why star formation in these systems started early and quenched some time after, a scenario known as downsizing which, at face value, conflicts with the predictions from the current hierarchical galaxy formation paradigm. SKA will provide the missing piece to solve the puzzle: information about the amounts of gas falling into galaxies to form stars, as well as data to measure when and how the star formation turns off as the gas stops cooling due to still to be understood feedback mechanisms, such as (radio mode) obscured nuclear activity.PGP-G acknowledges support from Spanish Government MINECO AYA2012-31277 Grant. JIGS acknowledges support from the Spanish Ministry for Economy and Competitiveness AYA2011-29517-C03-02. AFS acknowledges support from the Spanish Ministry for Economy and Competitiveness and FEDER funds through grants AYA2010-22111-C03-02 and AYA2013-48623-C2-2, and Generalitat Valenciana project PROMETEOII/2014/060.Peer reviewe