9,778 research outputs found
A search for new hot subdwarf stars by means of Virtual Observatory tools
Hot subdwarf stars are faint, blue objects, and are the main contributors to
the far-UV excess observed in elliptical galaxies. They offer an excellent
laboratory to study close and wide binary systems, and to scrutinize their
interiors through asteroseismology, as some of them undergo stellar
oscillations. However, their origins are still uncertain, and increasing the
number of detections is crucial to undertake statistical studies. In this work,
we aim at defining a strategy to find new, uncatalogued hot subdwarfs. Making
use of Virtual Observatory tools we thoroughly search stellar catalogues to
retrieve multi-colour photometry and astrometric information of a known sample
of blue objects, including hot subdwarfs, white dwarfs, cataclysmic variables
and main sequence OB stars. We define a procedure to discriminate among these
spectral classes, particularly designed to obtain a hot subdwarf sample with a
low contamination factor. In order to check the validity of the method, this
procedure is then applied to two test sky regions: the Kepler FoV and to a test
region of around (RA:225, DEC:5) deg. As a result, we obtained 38 hot subdwarf
candidates, 23 of which had already a spectral classification. We have acquired
spectroscopy for three other targets, and four additional ones have an
available SDSS spectrum, which we used to determine their spectral type. A
temperature estimate is provided for the candidates based on their spectral
energy distribution, considering two-atmospheres fit for objects with clear
infrared excess. Eventually, out of 30 candidates with spectral classification,
26 objects were confirmed to be hot subdwarfs, yielding a contamination factor
of only 13%. The high rate of success demonstrates the validity of the proposed
strategy to find new uncatalogued hot subdwarfs. An application of this method
to the entire sky will be presented in a forthcoming work.Comment: 13 pages, 7 figure
Complicaciones a corto plazo de la artroplastia total primaria de cadera
Objetivos: Se pretende analizar las principales complicaciones a corto plazo (seis semanas) tras la Artroplastia total primaria de cadera. ;aterial y métodos: Se revisaron todos los pacientes a los que se realizó artroplastia total de cadera durante el año 2003. Las variables estudiadas fueron el índice de luxaciones, sangrado, infección, fracturas periprotésicas, complicaciones vásculo-nerviosas y mortalidad. Resultados: Obtuvimos una tasa del 4,4% de luxaciones; 1,7% de trombosis venosa profunda con un 0,87% de embolismo pulmonar, 1,7% de infecciones superficiales sin casos de infección profunda. El 14,9% de los casos necesitaron una transfusión postquirúrgica. Intraoperatoriamente observamos apertura del cálcar en el 3,5%, y fracturas periprotésicas postoperatorias en el 0,87%. No registramos complicaciones neurológicas ni mortalidad en estas primeras seis semanas del estudio. Conclusiones: La complicación más frecuente es la luxación, fundamentalmente en los casos secundarios a fractura. La trombosis venosa profunda, a èsar de la profilaxis, continúa siendo una complicación frecuente.Objectives: Our purpose was to analyze the main
early complications (six weeks) after primary total hip arthroplasty. Materials and Methods: All patients who had undergone primary total hip replacement during 2003 were reviewed. The studied outcomes were the rates of dislocation,
blood loss, infection, periprosthetic fractures, neural and
vascular complications, and mortality. Results: Our rates
were 4,4% for hip dislocation, 1,7% for deep vein thrombosis
with 0,87% for pulmonary embolism, 1,7% for wound infection
without cases of deep infection. 14,9% of the patients needed
postoperative transfusion. We reported 3,5% fractures of the
calcar during surgery and 0,87% of postoperative periprosthetic fractures. We didn ́t reported any neural complications
or mortality within six weeks postoperatively. Conclusions:
The most frequent complication is dislocation, mainly in
cases whose underlying diagnose was hip fracture. Although
prophylaxis is done, deep vein thrombosis goes on being a
frequent complication
Una aproximación práctica para el diseño de un proceso de reciclado de polímeros mediante disolución
La cantidad de residuos plásticos producidos en los últimos años se ha visto incrementada debido a la variedad de usos y las buenas propiedades que estos presentan. Por este motivo, es necesario ofrecer soluciones que permitan un reciclaje adecuado a cada tipo de residuo, siguiendo con las normativas vigentes. Entre las alternativas desarrolladas se encuentran el reciclado mecánico, químico y la incineración, sin embargo, estos metodos cuentan con determinados inconvenientes que dificultan su aplicación. Para solventar estos, se propone el tratamiento de los residuos mediante disolución, lo que implica la seleccion adecuada del mejor disolvente, con el objetivo de tratar la máxima cantidad de plástico posible. Esta selección se desarrolla siguiendo una serie de modelos teóricos que permiten el cálculo del parametro de solubilidad (d), y su interpretación a traves de distintos metodos gráficos que permiten seleccionar de manera sencilla los disolventes más adecuados. Por último, tambíen se muestran estrategias de cálculo para conocer las condiciones de operación que vienen definidas por una concentración y temperatura críticas, que limitan la región en la que la disolución permanece estable, y por tanto, es posible realizar el proceso de reciclado
La construcción mediática de la comunidad política: la prensa en la transición española a la democracia
El artículo analiza el comportamiento y las actitudes adoptadas por la prensa española durante el primer periodo de la transición a la democracia (noviembre de 1975-diciembre de 1978), momento en el que se realizaron los cambios políticos e institucionales más relevantes del proceso. Desde diversas perspectivas se explica el papel que jugaron los principales periódicos, así como las razones que les llevaron al consenso en los temas fundamentales de discusión pública. De esta forma, se constata cómo los medios de comunicación colaboraron de forma decisiva en la construcción de una nueva comunidad política democrática. A través de varios ejemplos de diarios, tomados uno por uno y en conjunto, se explican las especiales características de este interesante caso de colaboración entre poder político y periodismo, incluyendo algunas excepciones como la prensa de extrema derecha y los sectores nacionalistas vascos
The kinematics of the quadrupolar nebula M1-75 and the identification of its central star
The link between the shaping of bipolar planetary nebulae and their central
stars is still poorly understood. The kinematics and shaping of the multipolar
nebula M 1-75 are hereby investigated, and the location and nature of its
central star are briefly discussed. Fabry-Perot data from GHaFAS on the WHT
sampling the Doppler shift of the [N II] 658.3 nm line are used to study the
dynamics of the nebula, by means of a detailed 3-D spatio-kinematical model.
Multi-wavelength images and spectra from the WFC and IDS on the INT, and from
ACAM on the WHT, allowed us to constrain the parameters of the central star.
The two pairs of lobes, angularly separated by ~22 degrees, were ejected
simultaneously approx. ~3500-5000 years ago, at the adopted distance range from
3.5 to 5.0 kpc. The larger lobes show evidence of a slight degree of point
symmetry. The shaping of the nebula could be explained by wind interaction in a
system consisting of a post-AGB star surrounded by a disc warped by radiative
instabilities. This requires the system to be a close binary or a single star
which engulfed a planet as it died. On the other hand, we present broad- and
narrow-band images and a low S/N optical spectrum of the highly-reddened,
previously unnoticed star which is likely the nebular progenitor. Its estimated
V-I colour allows us to derive a rough estimate of the parameters and nature of
the central star.Comment: 8 pages, 6 figures, accepted for publication in Astronomy &
Astrophysic
Analysis of self--averaging properties in the transport of particles through random media
We investigate self-averaging properties in the transport of particles
through random media. We show rigorously that in the subdiffusive anomalous
regime transport coefficients are not self--averaging quantities. These
quantities are exactly calculated in the case of directed random walks. In the
case of general symmetric random walks a perturbative analysis around the
Effective Medium Approximation (EMA) is performed.Comment: 4 pages, RevTeX , No figures, submitted to Physical Review E (Rapid
Communication
The chromatin remodeling factor CHD8 interacts with elongating RNA polymerase II and controls expression of the cyclin E2 gene
CHD8 is a chromatin remodeling ATPase of the SNF2 family. We found that depletion of CHD8 impairs cell proliferation. In order to identify CHD8 target genes, we performed a transcriptomic analysis of CHD8-depleted cells, finding out that CHD8 controls the expression of cyclin E2 (CCNE2) and thymidylate synthetase (TYMS), two genes expressed in the G1/S transition of the cell cycle. CHD8 was also able to co-activate the CCNE2 promoter in transient transfection experiments. Chromatin immunoprecipitation experiments demonstrated that CHD8 binds directly to the 5′ region of both CCNE2 and TYMS genes. Interestingly, both RNA polymerase II (RNAPII) and CHD8 bind constitutively to the 5′ promoter-proximal region of CCNE2, regardless of the cell-cycle phase and, therefore, of the expression of CCNE2. The tandem chromodomains of CHD8 bind in vitro specifically to histone H3 di-methylated at lysine 4. However, CHD8 depletion does not affect the methylation levels of this residue. We also show that CHD8 associates with the elongating form of RNAPII, which is phosphorylated in its carboxy-terminal domain (CTD). Furthermore, CHD8-depleted cells are hypersensitive to drugs that inhibit RNAPII phosphorylation at serine 2, suggesting that CHD8 is required for an early step of the RNAPII transcription cycle
Conceptual design of the ITER fast-ion loss detector
et al.A conceptual design of a reciprocating fast-ion loss detector for ITER has been developed and is presented here. Fast-ion orbit simulations in a 3D magnetic equilibrium and up-to-date first wall have been carried out to revise the measurement requirements for the lost alpha monitor in ITER. In agreement with recent observations, the simulations presented here suggest that a pitch-angle resolution of ∼5° might be necessary to identify the loss mechanisms. Synthetic measurements including realistic lost alpha-particle as well as neutron and gamma fluxes predict scintillator signal-to-noise levels measurable with standard light acquisition systems with the detector aperture at ∼11 cm outside of the diagnostic first wall. At measurement position, heat load on detector head is comparable to that in present devices.This research was supported in part by the Spanish Ministry of Economy and Competitiveness (Grant Nos. RYC2011-09152, FIS2015-69362-P, and ENE2012- 31087) and the Marie Curie FP7 Integration Grant (No. PCIG11-GA2012-321455).Peer Reviewe
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