70,340 research outputs found
E3D, The Euro3D Visualization Tool I: Description of the program and its capabilities
We present the first version of E3D, the Euro3D visualization tool for data
from integral field spectroscopy. We describe its major characteristics, based
on the proposed requirements, the current state of the project, and some
planned future upgrades. We show examples of its use and capabilities.Comment: 4 pages, 6 figures, accepted for publishing in AN (ref.proc. of
Euro3D Science workshop, IoA Cambridge, May 2003
Spontaneous direct bonding of thick silicon nitride
Wafers with LPCVD silicon-rich nitride layers have been successfully direct bonded to silicon-rich nitride and boron-doped silicon surfaces. A chemical - mechanical polishing treatment was necessary to reduce the surface roughness of the nitride before bonding. The measured surface energies of the room-temperature bond were comparable to values found for Si - Si hydrophilic bonding. A mechanism similar to this bonding is suggested for silicon nitride bonding
The UV-upturn in brightest cluster galaxies
This paper is part of a series devoted to the investigation of a large sample
of brightest cluster galaxies (BCGs), their properties and the relationships
between these and the properties of the host clusters. In this paper, we
compare the stellar population properties derived from high signal-to-noise,
optical long-slit spectra with the GALEX ultraviolet (UV) colour measurements
for 36 nearby BCGs to understand the diversity in the most rapidly evolving
feature in old stellar systems, the UV-upturn. We investigate: (1) the possible
differences between the UV-upturn of BCGs and those of a control sample of
ordinary ellipticals in the same mass range, as well as possible correlations
between the UV-upturn and other general properties of the galaxies; (2)
possible correlations between the UV-upturn and the properties of the host
clusters; (3) recently proposed scenarios where helium-sedimentation in the
cluster centre can produce an enhanced UV-upturn. We find systematic
differences between the UV-colours of BCGs and ordinary ellipticals, but we do
not find correlations between these colours and the properties of the host
clusters. Furthermore, the observations do not support the predictions made by
the helium-sedimentation model as an enhancer of the UV-upturn.Comment: 12 pages, accepted for publication in MNRA
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
Cluster of galaxies around seven radio-loud QSOs at 1<z<1.6: K-band images
We have conducted a NIR study of the environments of seven radio-loud quasars
at redshifts 1<z<1.6. In present paper we describe deep band images
obtained for the fields of ~6X6 arcmin around the quasars with 3
limiting magnitudes of K~20.5. These fields were previously studied using deep
B and R band images (Sanchez & Gonzalez-Serrano 1999). Using together optical
and NIR data, it has been found a significant excess of galaxies which
optical-NIR colours, luminosity, spatial scale, and number of galaxies are
compatible with clusters at the redshift of the quasar.
We have selected a sample of cluster candidates analyzing the R-K vs. K
diagram. A ~25% of the candidates present red optical-NIR colours and an
ultraviolet excess. This population has been also found in clusters around
quasars at the same redshifts (Tanaka et al. 2000; Haines et al. 2001). These
galaxies seem to follow a mixed evolution: a main passive evolution plus late
starformation processes. The quasars do not inhabit the core of the clusters,
being found in the outer regions. This result agrees with the hypothesis that
the origin/feeding mechanism of the nuclear activity were merging processes.
The quasars inhabit the region were a collision is most probably to produce a
merger.Comment: 15 pages. A&A, accepted for publishin
Seeing the sky through Hubble's eye: The COSMOS SkyWalker
Large, high-resolution space-based imaging surveys produce a volume of data
that is difficult to present to the public in a comprehensible way. While
megapixel-sized images can still be printed out or downloaded via the World
Wide Web, this is no longer feasible for images with 10^9 pixels (e.g., the
Hubble Space Telescope Advanced Camera for Surveys [ACS] images of the Galaxy
Evolution from Morphology and SEDs [GEMS] project) or even 10^10 pixels (for
the ACS Cosmic Evolution Survey [COSMOS]). We present a Web-based utility
called the COSMOS SkyWalker that allows viewing of the huge ACS image data set,
even through slow Internet connections. Using standard HTML and JavaScript, the
application successively loads only those portions of the image at a time that
are currently being viewed on the screen. The user can move within the image by
using the mouse or interacting with an overview image. Using an astrometrically
registered image for the COSMOS SkyWalker allows the display of calibrated
world coordinates for use in science. The SkyWalker "technique" can be applied
to other data sets. This requires some customization, notably the slicing up of
a data set into small (e.g., 256^2 pixel) subimages. An advantage of the
SkyWalker is the use of standard Web browser components; thus, it requires no
installation of any software and can therefore be viewed by anyone across many
operating systems.Comment: 4 pages, 2 figures, accepted for publication in PAS
Note on the space group selection rule for closed strings on orbifolds
It is well-known that the space group selection rule constrains the
interactions of closed strings on orbifolds. For some examples, this rule has
been described by an effective Abelian symmetry that combines with a
permutation symmetry to a non-Abelian flavor symmetry like or
. However, the general case of the effective Abelian symmetries was
not yet fully understood. In this work, we formalize the computation of the
Abelian symmetry that results from the space group selection rule by imposing
two conditions only: (i) well-defined discrete charges and (ii) their
conservation. The resulting symmetry, which we call the space group flavor
symmetry , is uniquely specified by the Abelianization of the space group.
For all Abelian orbifolds with supersymmetry we compute and
identify new cases, for example, where contains a dark
matter-parity with charges 0 and 1 for massless and massive strings,
respectively.Comment: 28 pages, 1 tabl
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