Science with the World Space Observatory - Ultraviolet

The World Space Observatory-Ultraviolet (WSO-UV) will provide access to the UV range during the next decade. The instrumentation on board will allow to carry out high resolution imaging, high sensitivity imaging, high resolution (R~55000) spectroscopy and low resolution (R~2500) long slit spectroscopy. In this contribution, we briefly outline some of the key science issues that WSO-UV will address during its lifetime. Among them, of special interest are: the study of galaxy formation and the intergalactic medium; the astronomical engines; the Milky Way formation and evol ution, and the formation of the Solar System and the atmospheres of extrasolar p lanets.Comment: Just one text file (aigomezdecastro.tex). To be published in the proceeding of the conference: "New Quest in Stellar Astrophysics II: UV properties of evolved stellar populations" held in Puerto Vallarta - Mexico, in april 200

Optimization of telescope scheduling - Algorithmic research and scientific policy

The use of very expensive facilities in Modern Astronomy has demonstrated the importance of automatic modes in the operation of large telescopes. As a consequence, several mathematical tools have been applied and developed to solve the (NP - hard) scheduling optimization problem: from simple heuristics to the more complex genetic algorithms or neural networks. In this work, the basic scheduling problem is translated into mathematical language and two main methods are used to solve it: neighborhood search methods and genetic algorithms; both of them are analysed. It is shown that the algorithms are sensitive to the scientific policy by means of the definition of the objective function ( F) and also by the assignment of scientific priorities to the projects. The definition of F is not trivial and requires a detailed discussion among the Astronomical Community

Dust growth in molecular cloud envelopes: a numerical approach

Variations in the grain size distribution are to be expected in the interstellar medium (ISM) due to grain growth and destruction. In this work, we present a dust collision model to be implemented inside a magnetohydrodynamical (MHD) code that takes into account grain growth and shattering of charged dust grains of a given composition (silicate or graphite). We integrate this model in the MHD code Athena, and builds on a previous implementation of the dynamics of charged dust grains in the same code. To demonstrate the performance of this coagulation model, we study the variations in the grain size distribution of a single-sized population of dust with radius 0.05 $\mu$m inside several dust filaments formed during a 2D MHD simulation. We also consider a realistic dust distribution with sizes ranging from 50 \AA~to 0.25 $\mu$m and analyze both the variations in the size distribution for graphite and silicates, as well as of the far ultraviolet extinction curve. From the obtained results, we conclude that the methodology here presented, based on the MHD evolution of the equation of motion for a charged particle, is optimal for studying the coagulation of charged dust grains in a diffuse regime such as a molecular cloud envelope. Observationally, these variations in the dust size distribution are translated into variations in the far ultraviolet extinction curve, and they are mainly caused by small graphite dust grains.Comment: Accepted for publication in Ap

Formation of X-ray emitting stationary shocks in magnetized protostellar jets

X-ray observations of protostellar jets show evidence of strong shocks heating the plasma up to temperatures of a few million degrees. In some cases, the shocked features appear to be stationary. They are interpreted as shock diamonds. We aim at investigating the physics that guides the formation of X-ray emitting stationary shocks in protostellar jets, the role of the magnetic field in determining the location, stability, and detectability in X-rays of these shocks, and the physical properties of the shocked plasma. We performed a set of 2.5-dimensional magnetohydrodynamic numerical simulations modelling supersonic jets ramming into a magnetized medium and explored different configurations of the magnetic field. The model takes into account the most relevant physical effects, namely thermal conduction and radiative losses. We compared the model results with observations, via the emission measure and the X-ray luminosity synthesized from the simulations. Our model explains the formation of X-ray emitting stationary shocks in a natural way. The magnetic field collimates the plasma at the base of the jet and forms there a magnetic nozzle. After an initial transient, the nozzle leads to the formation of a shock diamond at its exit which is stationary over the time covered by the simulations (~ 40 - 60 yr; comparable with time scales of the observations). The shock generates a point-like X-ray source located close to the base of the jet with luminosity comparable with that inferred from X-ray observations of protostellar jets. For the range of parameters explored, the evolution of the post-shock plasma is dominated by the radiative cooling, whereas the thermal conduction slightly affects the structure of the shock.Comment: Accepted for publication in Astronomy and Astrophysic

Caracterización ultraestructural y molecular de cepas de Tetraselmis (Chlorodendrophyceae, Chlorophyta) aisladas de Chile

Species of the genus Tetraselmis (Chlorodendrophyceae, Chlorophyta) have traditionally been used in aquaculture facilities as food forlarval varieties of marine organisms. Recently, some strains with high lipid content have been considered as having potential for biofuelproduction. Although many Tetraselmis species are relatively well-characterized using light and electron microscopical methods,there are still taxonomic ambiguities among the species. DNA sequence analysis, which provides a reliable and more convenient toolfor species delimitation, has been poorly used in Tetraselmis. In this study, three strains of Tetraselmis, isolated from coastal Chileanwaters, have been characterized using an integrative approach (light and electron microscopy, molecular phylogeny of ITS, includingsecondary structure analysis). According to the pyrenoid ultrastructure of the strains investigated two of them (from Dichato andColiumo) belong to the subgenus Parviselmis, while the Caldera strain corresponds to the subgenus Tetrathele. Even though it was notpossible to identify the strains at species level, it was clearly demonstrated by phylogenetic analyses of ITS-1 and ITS-2 sequencesand by ITS-2 secondary structure that the Dichato and Coliumo strains are the same species, and could belong either to T. suecica or T.chui. However, the Caldera strain might correspond to an undescribed species. As our study has shown, the genus Tetraselmis needs tobe taxonomically revised using an integrative approach, which includes the investigations of authentic strains of this genus.Especies del género Tetraselmis (Chlorodendrophyceae, Chlorophyta) han sido tradicionalmente usadas en centros acuícolas comoalimento para larvas de una variedad de organismos marinos. Adicionalmente, algunas cepas con alto contenido de lípidos hansido recientemente consideradas como fuente potencial para la producción de biodiesel. Aunque muchas especies de Tetraselmis seencuentran morfológica y ultraestructuralmente bien caracterizadas, todavía hay ambigüedades taxonómicas al interior del género. Elanálisis de secuencias de ADN, una herramienta complementaria y conveniente para delimitar especies, ha sido pobremente utilizadoen Tetraselmis. En este estudio, se caracterizaron tres cepas de Tetraselmis, aisladas de aguas costeras chilenas, utilizando un enfoqueintegrativo (morfología, ultraestructura y filogenia molecular). Basado en la ultraestructura del pirenoide de las cepas estudiadas,dos de ellas (Dichato y Coliumo) pertenecen al subgénero Parviselmis, mientras que la cepa de Caldera corresponde al subgéneroTetrathele. Aunque no fue posible identificar las cepas a nivel específico, el análisis filogenético de las secuencias ITS-1 e ITS-2y la estructura secundaria del ITS-2 demostraron claramente que las cepas de Dichato y Coliumo son la misma especie, y podríanpertenecer a T. suecica o a T. chui, mientras que la cepa de Caldera podría corresponder a una especie no descrita aún para la ciencia.Los resultados obtenidos demuestran la necesidad de llevar a cabo una revisión taxonómica del género Tetraselmis, utilizando unenfoque integrativo, el cual incluya las cepas auténticas de las especies

Defining risk factors associated with difficult peripheral venous Cannulation: A systematic review and meta-analysis

Peripheral venous catheterization is a common technique in hospitals which is not always successful, resulting in multiple punctures and degradation of the vessels. This scenario, which we have termed 'difficult peripheral venous access', is associated to delays in care, obtention of samples or diagnosis, as well as a higher use of central catheters. This study intends to identify risk factors associated to the incidence of 'difficult peripheral venous access' in adults at hospital. We designed a systematic review of published studies (protocol PROSPERO 2018 CRD42018089160). We conducted structured electronic searches using key words and specific vocabulary, as well as directed searches in several databases. After validity analysis, we selected 7 studies with observational methodology. We found great variability in the definition of 'difficult peripheral venous access' and in the variables proposed as risk factors. Statistically significant factors through studies include demographic and anthropometric variables (gender, Body Mass Index), as well as medical and health conditions (diabetes, renal insufficiency, parenteral drug abuse, cancer chemotherapy), together with variables related to the vein or vascular access (vein visibility and palpability, vessel diameter, previous history of difficulty). Some studies have also considered variables related to the professional performing the technique. Meta-analyses were carried out for gender and obesity as potential risk factors. Only obesity appeared as a statistically significant risk factor with OR of 1.48; 95% CI (1.03 to 1.93; p = 0.016). Methodological heterogeneity prevented the development of further meta-analyses. It is essential to design future studies with diverse hospital populations, in which a wide selection of potential risk factors can be studied in a unique analysis. Our work identifies the most relevant variables that should be included in those studies

Evolución de los parámetros seminales, concentración y volumen y evaluación de futuros sementales en una población de machos cabríos de raza murciano granadina

Dentro del desarrollo del esquema nacional de mejora genética de la raza caprina Murciano Granadina en la Comunidad Valenciana, se ha establecido una población de machos para su evaluación a través de pruebas de progenie, siendo el primer paso su entrenamiento para la extracción de semen mediante vagina artificial. El entrenamiento comenzó a los 8 meses de edad