Tidal Disruption Flares: The Accretion Disk Phase

The evolution of an accretion disk, formed as a consequence of the disruption of a star by a black hole, is followed by solving numerically the hydrodynamic equations. The present investigation aims to study the dependence of resulting light curves on dynamical and physical properties of such a transient disk during its existence. One of main results derived from our simulations is that black body fits of X-ray data tend to overestimate the true mean disk temperature. The temperature derived from black body fits should be identified with the color X-ray temperature rather than the average value derived from the true temperature distribution along the disk. The time interval between the beginning of the circularization of the bound debris and the beginning of the accretion process by the black hole is determined by the viscous timescale, which fixes also the raising part of the resulting light curve. The luminosity peak coincides with the beginning of matter accretion by the black hole and the late evolution of the light curve depends on the evolution of the debris fallback rate. Peak bolometric luminosities are in the range 10^45-10^46 erg s^-1 whereas peak luminosities in soft X-rays (0.2-2.0 keV) are typically one order of magnitude lower. The timescale derived from our preferred models for the flare luminosity to decay by two orders of magnitude is about 3-4 years. Predicted soft X-ray light curves were fitted to data on galaxies in which a variable X-ray emission, related to tidal events, was detected.Comment: 14 pages, 11 figures, Accepted for publication in Ap

Protoplanetary disks including radiative feedback from accreting planets

While recent observational progress is converging on the detection of compact regions of thermal emission due to embedded protoplanets, further theoretical predictions are needed to understand the response of a protoplanetary disk to the planet formation radiative feedback. This is particularly important to make predictions for the observability of circumplanetary regions. In this work we use 2D hydrodynamical simulations to examine the evolution of a viscous protoplanetary disk in which a luminous Jupiter-mass planet is embedded. We use an energy equation which includes the radiative heating of the planet as an additional mechanism for planet formation feedback. Several models are computed for planet luminosities ranging from $10^{-5}$ to $10^{-3}$ Solar luminosities. We find that the planet radiative feedback enhances the disk's accretion rate at the planet's orbital radius, producing a hotter and more luminous environement around the planet, independently of the prescription used to model the disk's turbulent viscosity. We also estimate the thermal signature of the planet feedback for our range of planet luminosities, finding that the emitted spectrum of a purely active disk, without passive heating, is appreciably modified in the infrared. We simulate the protoplanetary disk around HD 100546 where a planet companion is located at about 68 au from the star. Assuming the planet mass is 5 Jupiter masses and its luminosity is $\sim 2.5 \times 10^{-4} \, L_\odot$, we find that the radiative feedback of the planet increases the luminosity of its $\sim 5$ au circumplanetary disk from $10^{-5} \, \rm L_\odot$ (without feedback) to $10^{-3} \, \rm L_\odot$, corresponding to an emission of $\sim 1 \, \rm mJy$ in $L^\prime$ band after radiative transfer calculations, a value that is in good agreement with HD 100546b observations.Comment: 12 pages, 12 figures. Accepted for publication in The Astrophysical Journa

Spiral waves triggered by shadows in transition disks

Circumstellar asymmetries such as central warps have recently been shown to cast shadows on outer disks. We investigate the hydrodynamical consequences of such variable illumination on the outer regions of a transition disk, and the development of spiral arms. Using 2D simulations, we follow the evolution of a gaseous disk passively heated by the central star, under the periodic forcing of shadows with an opening angle of $\sim$28$^\circ$. With a lower pressure under the shadows, each crossing results in a variable azimuthal acceleration, which in time develops into spiral density waves. Their pitch angles evolve from $\Pi \sim 15^\circ-22^\circ$ at the onset, to $\sim$11$^\circ$-14$^\circ$, over $\sim$65~AU to 150~AU. Self-gravity enhances the density contrast of the spiral waves, as also reported previously for spirals launched by planets. Our control simulations with unshadowed irradiation do not develop structures, except for a different form of spiral waves seen at later times only in the gravitationally unstable control case. Scattered light predictions in the $H$-band show that such illumination spirals should be observable. We suggest that spiral arms in the case-study transition disk HD~142527 could be explained as a result of shadowing from the tilted inner disk.Comment: 6 pages, 4 figures, 1 table. Accepted for publication in ApJ

Relación entre variables de crecimiento y virulencia en aislados de Beauveria bassiana

El control microbiano se considera como método básico en las estrategias del Manejo Integrado de Plagas para el control de las plagas agrícolas. Los hongos entomopatógenos (HE) como Beauveria bassiana invaden al insecto de manera directa a través del tegumento, eliminando la necesidad de que los conidios deban ser ingeridos. Los criterios para seleccionar un microorganismo entomopatógeno y desarrollarlo para el control microbiano son muy complejos, pero en general se deben tomar en cuenta las características del insecto, del ecosistema, y del microorganismo entomopatógeno. A causa de la gran diferencia en la especificidad y virulencia hacia el hospedero entre aislados, la identificación de características que puedan tener una función importante en el ataque del insecto resulta valioso para entender la virulencia en la selección y desarrollo de HE como agentes biocontrol. El objetivo de este estudio fue evaluar algunas variables de crecimiento como viabilidad (V), velocidad de crecimiento radial (Vr) y densidad superficial de conidios en caja Petri (ρ) y determinar su correlación con el grado de virulencia (TL50 y porcentaje de mortalidad máxima [M]) para cada aislado evaluado. Además, se evaluó la hidrofobicidad de los conidios (Hf) empleados en el bioensayo para determinar si esta característica está relacionada con el grado de virulencia de los aislados. La producción de conidios por larvas muertas (Φ) se midió al final del bioensayo. Se demostró que la V de los conidios, variable de crecimiento que se midió previo al bioensayo, fue el de mayor correlación positiva (r = 0.588) con la virulencia, las demás variables de crecimiento Φ (0.425), ρ (r = 0.236) y Vr (r = 0.221) mostraron una menor correlación. En cuanto a la Hf no se encontró una correlación positiva con la mayor virulencia, para ambos parámetros M (r = -0.355) y TL50 (- 0.492). La afirmación previa fue corroborada mediante un Análisis de Componentes Principales y coeficientes de regresión simple que se utilizó para indagar correlaciones entre variables de estudio

Community structure informs species geographic distributions

This is the author accepted manuscript. The final version is available from Public Library of Science via the DOI in this recordUnderstanding what determines species’ geographic distributions is crucial for assessing global change threats to biodiversity. Measuring limits on distributions is usually, and necessarily, done with data at large geographic extents and coarse spatial resolution. However, survival of individuals is determined by processes that happen at small spatial assembly processes occurring at small scales, and are often available for relatively extensive areas, so could be useful for explaining species distributions. We demonstrate that Bayesian Network Inference (BNI) can overcome several challenges to including community structure into studies of species distributions, despite having been little used to date. We hypothesized that the relative abundance of coexisting species can improve predictions of species distributions. In 1570 assemblages of 68 Mediterranean woody plant species we used BNI to incorporate community structure into Species Distribution Models (SDMs), alongside environmental information. Information on species associations improved SDM predictions of community structure and species distributions moderately, though for some habitat specialists the deviance explained increased by up to 15%. We demonstrate that most species associations (95%) were positive and occurred between species with ecologically similar traits. This suggests that SDM improvement could be because species co-occurrences are a proxy for local ecological processes. Our study shows that Bayesian Networks, when interpreted carefully, can be used to include local conditions into measurements of species’ large-scale distributions, and this information can improve the predictions of species distributionsThis work was funded by FCT Project “QuerCom” (EXPL/AAG-GLO/2488/2013) and the ERA-Net BiodivERsA project “EC21C” (BIODIVERSA/0003/2011). A.M.N. was supported by a Bolsa de Investigacao de Pos-doutoramento (BI_Pos-Doc_UEvora_Catedra Rui Nabeiro_EXPL_AAG-GLO_2488_2013) and postdoctoral fellowships from the Ministry of Economy and Competitivity (FPDI-2013-16266 and IJCI‐2015‐23498). MGM acknowledges support by a Marie Curie Intra-European Fellowship within the 7th European Community Framework Programme (FORECOMM). J. Vicente is supported by POPH/FSE funds and by National Funds through FCT - Foundation for Science and Technology under the Portuguese Science Foundation (FCT) through Post-doctoral grant SFRH/BPD/84044/2012. AE has a postdoctoral contract funded by the project CN-17-022 (Principado de Asturias, Spain). We are grateful to OneGeology for providing the geological data

Análisis cultural de los ítems de dos listas de verificación quirúrgica de España y Argentina

Objetivo: Comparar la concordancia entre dos listas de verificación quirúrgica implantadas en dos hospitales en España y Argentina utilizando como marco de referencia la Clasificación Internacional para la Seguridad de Pacientes.Método: Estudio basado en el juicio de expertos realizado con un cuestionario ad hoc en soporte electrónico que abarca 7 de las 13 categorías de la Clasificación Internacional para la Seguridad de Pacientes. Participaron 15 expertos en seguridad quirúrgica de cada país, asociando cada ítem de las listas de verificación con las dimensiones seleccionadas. Los datos se analizaron con el programa SPSS V20.Resultados: Se evidencia un mayor porcentaje de coincidencias con campos relacionados con prevención de eventos críticos. La dimensión Procesos clínicos y procedimientos obtuvo una mayor frecuencia de asignación en ambas listas.Conclusión: Existe variabilidad en la implantación de las listas de verificación quirúrgica. Los expertos consideran la lista argentina más clara en cada dimensión.Palabras clave: Enfermería de quirófano. Seguridad del paciente. Quirófanos. Calidad de la atención de salud