363 research outputs found
Glory revealed in disk-integrated photometry of Venus
Context. Reflected light from a spatially unresolved planet yields unique
insight into the overall optical properties of the planet cover. Glories are
optical phenomena caused by light that is backscattered within spherical
droplets following a narrow distribution of sizes; they are well known on Earth
as localised features above liquid clouds. Aims. Here we report the first
evidence for a glory in the disk-integrated photometry of Venus and, in turn,
of any planet. Methods. We used previously published phase curves of the planet
that were reproduced over the full range of phase angles with model predictions
based on a realistic description of the Venus atmosphere. We assumed that the
optical properties of the planet as a whole can be described by a uniform and
stable cloud cover, an assumption that agrees well with observational evidence.
Results. We specifically show that the measured phase curves mimic the
scattering properties of the Venus upper-cloud micron-sized aerosols, also at
the small phase angles at which the glory occurs, and that the glory contrast
is consistent with what is expected after multiple scattering of photons. In
the optical, the planet appears to be brighter at phase angles of 11-13 deg
than at full illumination; it undergoes a maximum dimming of up to 10 percent
at phases in between. Conclusions. Glories might potentially indicate spherical
droplets and, thus, extant liquid clouds in the atmospheres of exoplanets. A
prospective detection will require exquisite photometry at the small
planet-star separations of the glory phase angles.Comment: In press. Astronomy & Astrophysics. Letter to the Editor; 201
Multilayer hazes over Saturn’s hexagon from Cassini ISS limb images
Producción CientíficaVer abstract
Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 m with PlanetCam-UPV/EHU
We provide measurements of the absolute reflectivity of Jupiter and Saturn
along their central meridians in filters covering a wide range of visible and
near-infrared wavelengths (from 0.38 to 1.7 m) that are not often
presented in the literature. We also give measurements of the geometric albedo
of both planets and discuss the limb-darkening behavior and temporal
variability of their reflectivity values for a period of four years
(2012-2016). This work is based on observations with the PlanetCam-UPV/EHU
instrument at the 1.23 m and 2.2 m telescopes in Calar Alto Observatory
(Spain). The instrument simultaneously observes in two channels: visible (VIS;
0.38-1.0 m) and short-wave infrared (SWIR; 1.0--1.7 m). We obtained
high-resolution observations via the lucky-imaging method. We show that our
calibration is consistent with previous independent determinations of
reflectivity values of these planets and, for future reference, provide new
data extended in the wavelength range and in the time. Our results have an
uncertainty in absolute calibration of 10--20\%. We show that under the
hypothesis of constant geometric albedo, we are able to detect absolute
reflectivity changes related to planetary temporal evolution of about 5-10\%.Comment: 13 pages, 18 figures, (in press
Magneto--thermal evolution of neutron stars
We study the mutual influence of thermal and magnetic evolution in a neutron
star's crust in axial symmetry. Taking into account realistic microphysical
inputs, we find the heat released by Joule effect consistent with the
circulation of currents in the crust, and we incorporate its effects in 2D
cooling calculations. We solve the induction equation numerically using a
hybrid method (spectral in angles, but a finite--differences scheme in the
radial direction), coupled to the thermal diffusion equation. We present the
first long term 2D simulations of the coupled magneto-thermal evolution of
neutron stars. This substantially improves previous works in which a very crude
approximation in at least one of the parts (thermal or magnetic diffusion) has
been adopted. Our results show that the feedback between Joule heating and
magnetic diffusion is strong, resulting in a faster dissipation of the stronger
fields during the first million years of a NS's life. As a consequence, all
neutron stars born with fields larger than a critical value (about 5 10^13 G)
reach similar field strengths (approximately 2-3 10^{13} G) at late times.
Irrespectively of the initial magnetic field strength, after years the
temperature becomes so low that the magnetic diffusion timescale becomes longer
than the typical ages of radio--pulsars, thus resulting in apparently no
dissipation of the field in old NS. We also confirm the strong correlation
between the magnetic field and the surface temperature of relatively young NSs
discussed in preliminary works. The effective temperature of models with strong
internal toroidal components are systematically higher than those of models
with purely poloidal fields, due to the additional energy reservoir stored in
the toroidal field that is gradually released as the field dissipates.Comment: 10 pages, 5 figures, accepted for publication in A&
Reanalyzing Jupiter ISO/SWS Data through a More Recent Atmospheric Model
The study of isotopic ratios in planetary atmospheres gives an insight into the formation history and evolution of these objects. The more we can constrain these ratios, the better we can understand the history and future of our solar system. To help in this endeavour, we used Infrared Space Observatory Short Wavelength Spectrometer (ISO/SWS) Jupiter observations in the 793–1500 cm−1 region together with the Nonlinear Optimal Estimator for MultivariatE Spectral analySIS (NEMESIS) radiative transfer suite to retrieve the temperature–pressure profile and the chemical abundances for various chemical species. We also used the 1500–2499 cm−1 region to determine the cloud and aerosol structure of the upper troposphere. We obtained a best-fit simulated spectrum with 2/=0.47 for the 793–1500 cm−1 region and 2/=0.71 for the 1500–2499 cm−1 region. From the retrieved methane abundances, we obtained, within a 1 uncertainty, a 12C/13C ratio of 84 ± 27 and a D/H ratio of (3.5 ± 0.6) × 10−5, and these ratios are consistent with other published results from the literature.This research was funded by the Portuguese Fundação Para a Ciência e Tecnologia through the research grants UIDB/04434/2020 and UIDP/04434/2020 as well as a fellowship grants 2021.04584.BD and 2022.09859.BD
Low temperature catalytic adsorption of NO over activated carbon honeycomb (ACH) monoliths
ABSTRACT: An activated carbon honeycomb (ACH) monolith was developed for the adsorption of NO at 30ºC. For ACH monoliths preparation carboxymethylcellulose (CMC) and coal tar pitch were used as binder and co-binder, respectively. The effects of the addition of O2 and the presence of copper as catalyst were studied. For the Cu-impregnated activated carbon monolith samples, the presence of O2 favored NO adsorption by increasing the breakthrough time and the adsorption capacity.RESUMEN: Se desarrolló un monolito tipo celular de carbón activado (ACH) para la adsorción de NO a 30ºC. Para la preparación de los monolitos celulares se usó como aglomerante la carboximetilcelulosa (CMC) y como coaglomerante brea de alquitranes de carbón (BAC). Se estudiaron los efectos de la adición de O2 y la presencia de cobre como catalizador. Para las muestras de monolito de carbón activado impregnado con Cu, la presencia de O2 favoreció la adsorción de NO incrementando el tiempo del punto de quiebre (breakthrough) y la capacidad de adsorción
Validación por la Comunidad Docente de una Metodología de Aprendizaje Activo para Cursos de Programación
Actas de: III Jornadas de Innovación Educativa en Ingeniería Telemática (JIE). Granada, 28-30 Octubre 2013.En este artículo se presenta y evalúa una metodología para cursos de programación, basada en el aprendizaje activo y el aprendizaje basado en proyectos. Esta metodología se centra en el trabajo continuo, día a día, del alumno. Por un lado, ofrece pautas para que los alumnos organicen su tiempo, promoviendo el autoaprendizaje y el trabajo individual. Por otro, durante el proyecto los alumnos desarrollan sus capacidades de trabajo en equipo, fomentando el desarrollo de competencias transversales como el aprendizaje colaborativo. La metodología descrita se ha aplicado durante varios cursos en una asignatura de programación en C de segundo curso de los cuatro grados de Ingeniería de Telecomunicaciones. Para poder evaluar, ajustar y mejorar el proceso de enseñanzaaprendizaje propuesto, se utilizan mecanismos de realimentación y seguimiento del alumnado y del profesorado. En este artículo, la implantación de la metodología es evaluada por 40 profesores de distintas universidades españolas que imparten asignaturas en cursos de ingeniería, con objeto de validar su aplicabilidad en otros contextos.Este trabajo ha sido financiado parcialmente por el proyecto nacional del Ministerio de Economía y Competitividad, “Espacios Educativos Especulares” - EEE (TIN2011-28308-C03-01), por el proyecto regional de la Comunidad de Madrid, “eMadrid” (S2009/TIC-1650) y por el programa de estancias postdoctorales Alianza 4 Universidades.Publicad
A Review of Advances in the Identification and Characterization of Groundwater Dependent Ecosystems Using Geospatial Technologies
Groundwater Dependent Ecosystem (GDE) protection is increasingly being recognized as essential for the sustainable management and allocation of water resources. GDE services are crucial for human well-being and for a variety of flora and fauna. However, the conservation of GDEs is only possible if knowledge about their location and extent is available. Several studies have focused on the identification of GDEs at specific locations using ground-based measurements. However, recent progress in remote sensing technologies and their integration with Geographic Information Systems (GIS) has provided alternative ways to map GDEs at a much larger spatial extent. This paper presents a review of the geospatial methods that have been used to map and delineate GDEs at spatial different extents. Additionally, a summary of the satellite sensors useful for identification of GDEs and the integration of remote sensing data with ground-based measurements in the process of mapping GDEs is presented
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