2,990 research outputs found

    idmTPreg: Regression Model for Progressive Illness Death Data

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    The progressive illness-death model is frequently used in medical applications. For example, the model may be used to describe the disease process in cancer studies. We have developed a new R package called idmTPreg to estimate regression coefficients in datasets that can be described by the progressive illness-death model. The motivation for the development of the package is a recent contribution that enables the estimation of possibly time-varying covariate effects on the transition probabilities for a progressive illness-death data. The main feature of the package is that it befits both non-Markov and Markov progressive illness-death data. The package implements the introduced estimators obtained using a direct binomial regression approach. Also, variance estimates and confidence bands are implemented in the package. This article presents guidelines for the use of the package.BERC 2014-2017 SEV-2013-0323 MTM2016-76969-P FP7/2011: Marie Curie Initial Training Network MEDIASRE

    Regeneración de un "aulagar" con Ulex europaeus después de un incendio en el norte de España

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    The recuperation of a shrubland characterized by the presence of Genista hispánica ssp. occidentalis, Ulex europaeus and Erica vagans after of a fire, near Oviedo (North Spain) is studied. The regeneration strategy of Erica vagans was by means of vegetative regrowth. The recolonization of Ulex europaeus and Genista hispánica ssp. occidentalis was both vegetative and from seed, although in the last species the establishment by seedlings was very infrequent. The post-fire vegetation development was affected by floristic composition of shrubland previous to the fire.[es] Se estudia la recuperación de un matorral caracterizado por la presencia de Genista hispánica ssp. occidentalis, Ulex europaeus y Erica vagans después de un incendio, en las proximidades de Oviedo. La estrategia regenerativa de Erica vagans es mediante rebrote vegetativo, mientras Ulex europaeus y Genista hispánica ssp. occidentalis tienen capacidad de regenerarse por rebrote vegetativo y por semilla, aunque en este último taxon, el mecanismo de regeneración a través de plántulas fue muy escaso. El desarrollo de la vegetación está muy marcado por la composición florística previa al fuego. [fr] On à étudié la récupération de broussailles caractérisées par la présence de Genista hispánica ssp. occidentalis, Ulex europaeus et Erica vagans, après un incendie prés d’Oviedo (Nord de Espagne). La stratégie de régénération d’Erica vagans se fait moyennant des pousses végétatives, tandis que la régénération d’Ulex europaeus et Genista hispánica ssp. occidentalis s'esf faite par pousses végétatives et par graines, bien que pour ce dernier taxon, le mécanisme de régénération au travers de plantules a été très rare. Le développement de la végétation est très marqué par la composition floristique existante durant l'incendie

    Detección de daño estructural de losas de hormigón armado de puentes sometidas a fatiga

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    The complex nature of structural phenomena still requires the comparison between numerical models and the real structural performance. Accordingly, many civil structures are monitored to detect structural damage and provide updated data for numerical models. Monitoring usually relies on the change of dynamic properties (experimental modal analysis). Regarding concrete structures, existing works have typically focused on the progressive decrease of natural frequencies under gradually increasing loads. In this paper, high-cycle fatigue effects are analyzed. An experimental campaign on specimens reproducing the top slab of concrete girders has been carried out, including fatigue tests and a reference static test. Impact-excitation tests were done at different stages to extract dynamic properties. Output-only models (only based on the structural response to an external excitation that is not measured) were used as identification techniques. The evolution of dynamic properties was correlated with damage development, with emphasis on the fatigue process stages: crack formation, cyclic reduction of tension-stiffening and brittle fracture of the reinforcement.La naturaleza compleja de muchos fenómenos estructurales requiere que los modelos numéricos necesiten ser verificados con el comportamiento estructural real. Por ello, muchas estructuras son monitorizadas, tanto para detectar posibles daños estructurales como para proporcionar datos a incluir en los modelos. A menudo, la monitorización se basa en el cambio de las propiedades dinámicas mediante técnicas de análisis modal experimental. Con respecto al hormigón estructural, la mayoría de los trabajos existentes se ha centrado en el cambio de las frecuencias propias con cargas monótonamente crecientes. En este artículo se analizan los efectos de la fatiga. Se ha llevado a cabo una campaña experimental sobre piezas que reproducen la losa superior de tableros de puentes, realizándose ensayos de fatiga y uno estático de referencia. Las propiedades dinámicas se han ido extrayendo mediante técnicas de output-only a partir de ensayos de excitación mediante impacto. El cambio de las propiedades dinámicas se ha correlacionado con las etapas del proceso de fatiga: formación de fisuras, reducción de tension-stiffening y rotura frágil de la armadura

    Predictions for Triple Stars with and without a Pulsar in Star Clusters

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    Though about 80 pulsar binaries have been detected in globular clusters so far, no pulsar has been found in a triple system in which all three objects are of comparable mass. Here we present predictions for the abundance of such triple systems, and for the most likely characteristics of these systems. Our predictions are based on an extensive set of more than 500 direct simulations of star clusters with primordial binaries, and a number of additional runs containing primordial triples. Our simulations employ a number N_{tot} of equal mass stars from N_{tot}=512 to N_{tot}=19661 and a primordial binary fraction from 0-50%. In addition, we validate our results against simulations with N=19661 that include a mass spectrum with a turn-off mass at 0.8 M_{sun}, appropriate to describe the old stellar populations of galactic globular clusters. Based on our simulations, we expect that typical triple abundances in the core of a dense cluster are two orders of magnitude lower than the binary abundances, which in itself already suggests that we don't have to wait too long for the first comparable-mass triple with a pulsar to be detected.Comment: 11 pages, minor changes to match MNRAS accepted versio

    System Orchestration Support for a Collaborative Blended Learning Flow

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    Portable and interactive technologies are changing the nature of collaborative learning practices and open up new possibilities for Computer Supported Collaborative Learning (CSCL). Now, activities occurring in and beyond the classroom can be combined and integrated leading to a new type of complex collaborative blended learning scenarios. However, to organize and structure these scenarios is challenging and represent a workload for practitioners, which hinder the adoption of these technology-enhanced practices. As an approach to alleviate this workload, this paper proposes a proof of concept of a technological solution to overcome the limitations detected in an analysis of an actual collaborative blended learning experiment carried out in a previous study. The solution consists on a Unit of Learning suitable to be instantiated with IMS Learning Design and complemented by a GenericService Integration system. This chapter also discusses to which extent the proposed solution covers the limitations detected in the previous study and how useful could be for reducing the orchestration effort in future experiences.This work has been partially funded by the Project Learn3 (TIN2008- 05163/TSI) from the Plan Nacional I+D+I and "Investigación y Desarrollo de Tecnologías para el e-Learning en la Comunidad de Madrid” funded by the Madrid Regional Government under grant No. S2009/TIC-1650

    Increased reservoir ages and poorly ventilated deep waters inferred in the glacial Eastern Equatorial Pacific.

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    Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates. Here we combine new radiocarbon data from the Eastern Equatorial Pacific (EEP) with chronostratigraphic calendar age constraints to estimate shallow sub-surface reservoir age variability, and thus provide estimates of deep-ocean ventilation ages. Both shallow- and deep-water ventilation ages drop across the last deglaciation, consistent with similar reconstructions from the South Pacific and Southern Ocean. The observed regional fingerprint linking the Southern Ocean and the EEP is consistent with a dominant southern source for EEP thermocline waters and suggests relatively invariant ocean interior transport pathways but significantly reduced air-sea gas exchange in the glacial southern high latitudes

    Octave bandwidth hybrid-coupled microstrip diplexer for a broadband radio astronomy receiver

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    A new octave bandwidth high selectivity compact microstrip diplexer working in the band from 10 to 20 GHz is presented, intended to be a part of an electro-optical interferometer covering the whole frequency band. The circuit is based on the combination of hybrid couplers and bandpass filters both on the microstrip technology. The diplexer provides two output frequency bands which cover the 10–14 GHz (relative bandwidth of 33%) and the 16–20 GHz (relative bandwidth of 22%) ranges, respectively, with a stop band in between from 14 to 16 GHz. Measured results show a insertion loss level of 3.3 dB for both output bands and high selectivity performance, exhibiting a rejection level between output bands higher than 20 dB and return loss better than 10 dB in all ports.This work has been funded by the Spanish Ministry of Economy, Industry and Competitiveness under Grant No. ESP2015-70646-C2-2-R

    Physical characterization of 2020 AV2, the first known asteroid orbiting inside Venus orbit

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    The first known asteroid with the orbit inside that of Venus is 2020~AV2_{2}. This may be the largest member of a new population of small bodies with the aphelion smaller than 0.718~au, called Vatiras. The surface of 2020~AV2_{2} is being constantly modified by the high temperature, by the strong solar wind irradiation that characterizes the innermost region of the Solar system, and by high-energy micrometeorite impacts. The study of its physical properties represents an extreme test-case for the science of near-Earth asteroids. Here, we report spectroscopic observations of 2020~AV2_{2} in the 0.5-1.5~μm\mu m wavelength interval. These were performed with the Nordic Optical Telescope and the William Herschel Telescope. Based on the obtained spectra, we classify 2020~AV2_{2} as a Sa-type asteroid. We estimate the diameter of this Vatira to be 1.500.65+1.101.50_{-0.65}^{+1.10} km by considering the average albedo of A-type and S-complex asteroids (pV=0.230.08+0.11p_V=0.23_{-0.08}^{+0.11}), and the absolute magnitude (H=16.40±0.7816.40\pm0.78 mag). The wide spectral band around 1~μm\mu m shows the signature of an olivine rich composition. The estimated band centre BIC=1.08±0.02 μmBIC = 1.08 \pm 0.02~\mu m corresponds to a ferroan olivine mineralogy similar to that of brachinite meteorites.Comment: Accepted for publication in MNRAS. 10 pages, 5 figures

    Improved copper–epoxy adhesion by laser micro- and nano-structuring of copper surface for thermal applications

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    The objective of this work is the enhancement of metal-to-metal bonding to provide high thermal conductivity together with electrical insulation, to be used as heat sinks at room and cryo-genic temperatures. High thermal conductive metal (copper) and epoxy resin (Stycast 2850FT) were used in this study, with the latter also providing the required electrical insulation. The copper surface was irradiated with laser to induce micro- and nano-patterned structures that result in an improvement of the adhesion between the epoxy and the copper. Thus, copper-to-copper bonding strength was characterized by means of mechanical tensile shear tests. The effect of the laser processing on the thermal conductivity properties of the Cu/epoxy/Cu joint at different temperatures, from 10 to 300 K, is also reported. Using adequate laser parameters, it is possible to obtain high bonding strength values limited by cohesive epoxy fracture, together with good thermal conductivity at ambient and cryogenic temperatures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
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