45,427 research outputs found
SIDE, a fiber fed spectrograph for the 10.4 m Gran Telescopio Canarias (GTC)
SIDE (Super Ifu Deployable Experiment) will be a second-generation,
common-user instrument for the Grantecan (GTC) on La Palma (Canary Islands,
Spain). It is being proposed as a spectrograph of low and intermediate
resolution, highly efficient in multi-object spectroscopy and 3D spectroscopy.
SIDE features the unique possibility of performing simultaneous visible and NIR
observations for selected ranges. The SIDE project is leaded by the Instituto
de Astrofisica de Andalucia (IAA-CSIC) in Granada (Spain) and the SIDE
Consortium is formed by a total of 10 institutions from Spain, Mexico and USA.
The SIDE Feasibility Study has been completed and currently the project is
under revision by the GTC Project Office.Comment: 9 pages, 6 figures, to appear in "Ground-based and Airborne
Instrumentation for Astronomy II" SPIE conference Proc. 7014, Marseille,
23-28 June 200
The spherical collapse model with shell crossing
In this work, we study the formation and evolution of dark matter halos by
means of the spherical infall model with shell-crossing. We present a framework
to tackle this effect properly based on the numerical follow-up, with time, of
that individual shell of matter that contains always the same fraction of mass
with respect to the total mass. In this first step, we do not include angular
momentum, velocity dispersion or triaxiality. Within this framework - named as
the Spherical Shell Tracker (SST) - we investigate the dependence of the
evolution of the halo with virial mass, with the adopted mass fraction of the
shell, and for different cosmologies. We find that our results are very
sensitive to a variation of the halo virial mass or the mass fraction of the
shell that we consider. However, we obtain a negligible dependence on
cosmology. Furthermore, we show that the effect of shell-crossing plays a
crucial role in the way that the halo reaches the stabilization in radius and
the virial equilibrium. We find that the values currently adopted in the
literature for the actual density contrast at the moment of virialization,
delta_vir, may not be accurate enough. In this context, we stress the problems
related to the definition of a virial mass and a virial radius for the halo.
The question of whether the results found here may be obtained by tracking the
shells with an analytic approximation remains to be explored.Comment: 15 pages, 4 figures, 9 tables, replaced to match the published MNRAS
versio
Neutrino Energy Reconstruction and the Shape of the CCQE-like Total Cross Section
We show that because of the multinucleon mechanism effects, the algorithm
used to reconstruct the neutrino energy is not adequate when dealing with
quasielastic-like events, and a distortion of the total flux unfolded cross
section shape is produced. This amounts to a redistribution of strength from
high to low energies, which gives rise to a sizable excess (deficit) of low
(high) energy neutrinos. This distortion of the shape leads to a good
description of the MiniBooNE unfolded CCQE-like cross sections published in
Phys.Rev. D81 (2010) 092005. However, these changes in the shape are artifacts
of the unfolding process that ignores multinucleon mechanisms.Comment: 11 pages, 6 figures. Some references and comments adde
An investigation into the perspectives of providers and learners on MOOC accessibility
An effective open eLearning environment should consider the target learner’s abilities, learning goals, where learning takes place, and which specific device(s) the learner uses. MOOC platforms struggle to take these factors into account and typically are not accessible, inhibiting access to environments that are intended to be open to all. A series of research initiatives are described that are intended to benefit MOOC providers in achieving greater accessibility and disabled learners to improve their lifelong learning and re-skilling. In this paper, we first outline the rationale, the research questions, and the methodology. The research approach includes interviews, online surveys and a MOOC accessibility audit; we also include factors such the risk management of the research programme and ethical considerations when conducting research with vulnerable learners. Preliminary results are presented from interviews with providers and experts and from analysis of surveys of learners. Finally, we outline the future research opportunities. This paper is framed within the context of the Doctoral Consortium organised at the TEEM'17 conference
Mechanism for bipolar resistive switching in transition metal oxides
We introduce a model that accounts for the bipolar resistive switching
phenomenom observed in transition metal oxides. It qualitatively describes the
electric field-enhanced migration of oxygen vacancies at the nano-scale. The
numerical study of the model predicts that strong electric fields develop in
the highly resistive dielectric-electrode interfaces, leading to a spatially
inhomogeneous oxygen vacancies distribution and a concomitant resistive
switching effect. The theoretical results qualitatively reproduce non-trivial
resistance hysteresis experiments that we also report, providing key validation
to our model.Comment: Accepted for publication in Physical Review B, 6 twocolumn pages, 5
figure
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