81 research outputs found
Database activity in the Italian Astronet: DIRA 2
The development and utilization of informational archives and databases started, in the Italian Astronet Project, in the middle of 1983. In that year, a small group of astronomers and some more technical people met together in an Astronet working group, with a common, painful experience in managing astronomical catalogues and archives with computers. Nowadays, some years later, some software packages and the contents of both, a relative general database and several local databases represent the work and the effort of the group. The systems have been conceived and developed keeping in mind the original goal of the group: to allow the single atronomer to make a free use of original data. The main package (DIRA) was rewritten, after some years of use, to fully take advantage of the several suggestions of the astronomer that used it and gathered experiences in the astronomical catalog's management. A more technical goal was to install the whole system, born and developed in the vms environment, on unix and unix-like systems. This new version, DIRA2, has a new user interface, a query language with SQL style commands supporting numerical and character functions also and a set of commands to create new catalogues from existing data. The graphics commands are also more powerful with respect to the previous version. DIRA (and DIRA2 of course) philosophy and design are very simple and proved to be very appreciated by astronomers, namely, to normalize and homogenize, at minimum, astronomical catalogues, to collect satisfactory astronomical documentation on their contents and, finally, to allow an astronomical approach to the dialogue with the database. DIRA2 is currently used in most Italian astronomical institutes to retrieve data from a still growing database of about 140 well documented and controlled astronomical catalogues, for the identification of objects and the preparation of a 'medium size' survey, in astrometry and in the creation of new catalogues
Integrity Model Application: A Quality Support System for Decision-makers on Water Quality Assessment and Improvement
In this paper, a mathematical model has been applied to a river in North-East Italy to describe vulnerability scenarios due to environmental pollution phenomena. Such model, based on the influence diagrams theory, allowed identifying the extremely critical factors, such as wastewater discharges, drainage of diffuse pollution from agriculture and climate changes, which might affect the water quality of the river. The obtained results underlined how the water quality conditions have improved thanks to the continuous controls on the territory, following the application of Water Framework Directive 2000/60/EC. Nevertheless, some fluvial stretches did not reach the "good ecological status" by 2015, because of the increasing population in urban areas recorded in the last years and the high presence of tourists during the summer months, not balanced by a treatment plants upgrade
The intrinsic shape of galaxy bulges
The knowledge of the intrinsic three-dimensional (3D) structure of galaxy
components provides crucial information about the physical processes driving
their formation and evolution. In this paper I discuss the main developments
and results in the quest to better understand the 3D shape of galaxy bulges. I
start by establishing the basic geometrical description of the problem. Our
understanding of the intrinsic shape of elliptical galaxies and galaxy discs is
then presented in a historical context, in order to place the role that the 3D
structure of bulges play in the broader picture of galaxy evolution. Our
current view on the 3D shape of the Milky Way bulge and future prospects in the
field are also depicted.Comment: Invited Review to appear in "Galactic Bulges" Editors: Laurikainen
E., Peletier R., Gadotti D. Springer Publishing. 24 pages, 7 figure
Structural properties of disk galaxies. II. Intrinsic shape of bulges
(Abridged) The structural parameters of a magnitude-limited sample of 148
unbarred S0-Sb galaxies were analyzed to derive the intrinsic shape of their
bulges. We developed a new method to derive the intrinsic shape of bulges based
on the geometrical relationships between the apparent and intrinsic shapes of
bulges and disks. The equatorial ellipticity and intrinsic flattening of bulges
were obtained from the length of the apparent major and minor semi-axes of the
bulge, twist angle between the apparent major axis of the bulge and the galaxy
line of nodes, and galaxy inclination. We found that the intrinsic shape is
well constrained for a subsample of 115 bulges with favorable viewing angles. A
large fraction of them is characterized by an elliptical section (B/A<0.9).
This fraction is 33%, 55%, and 43% if using their maximum, mean, or median
equatorial ellipticity, respectively. Most are flattened along their polar axis
(C<(A+B)/2). The distribution of triaxiality is strongly bimodal. This
bimodality is driven by bulges with Sersic index n>2, or equivalently, by the
bulges of galaxies with a bulge-to-total ratio B/T>0.3. In particular, bulges
with n\leq2 and with B/T\leq0.3 show a larger fraction of oblate axisymmetric
(or nearly axisymmetric) bulges, a smaller fraction of triaxial bulges, and
fewer prolate axisymmetric (or nearly axisymmetric) bulges with respect to
bulges with n>2 and with B/T>0.3, respectively. According to predictions of the
numerical simulations of bulge formation, bulges with n\leq2, which show a high
fraction of oblate axisymmetric (or nearly axisymmetric) shapes and have
B/T\leq0.3, could be the result of dissipational minor mergers. Both major
dissipational and dissipationless mergers seem to be required to explain the
variety of shapes found for bulges with n>2 and B/T>0.3.Comment: 16 pages, 12 figures; accepted for publication in A&
A mixed finite-element, finite-volume, semi-implicit discretisation for atmospheric dynamics: Spherical geometry
This is the author accepted manuscriptThe reformulation of the Met Officeâs dynamical core for weather and climate prediction previously described by the authors is extended to spherical domains using a cubed- sphere mesh. This paper updates the semi-implicit mixed finite-element formulation to be suitable for spherical do- mains. In particular the finite-volume transport scheme is extended to take account of non-uniform, non-orthogonal meshes and uses an advective-then-flux formulation so that increment from the transport scheme is linear in the diver- gence. The resulting model is then applied to a standard set of dry dynamical core tests and compared to the exist- ing semi-implicit semi-Lagrangian dynamical core currently used in the Met Officeâs operational model.Natural Environment Research Council (NERC)Natural Environment Research Council (NERC)Engineering and Physical Sciences Research Council (EPSRC)Engineering and Physical Sciences Research Council (EPSRC
Intrinsic Shapes of Elliptical Galaxies
Tests for the intrinsic shape of the luminosity distribution in elliptical
galaxies are discussed, with an emphasis on the uncertainties. Recent
determinations of the ellipticity frequency function imply a paucity of nearly
spherical galaxies, and may be inconsistent with the oblate hypothesis.
Statistical tests based on the correlation of surface brightness, isophotal
twisting, and minor axis rotation with ellipticity have so far not provided
strong evidence in favor of the nearly oblate or nearly prolate hypothesis, but
are at least qualitatively consistent with triaxiality. The possibility that
the observed deviations of elliptical galaxy isophotes form ellipses are due to
projection effects is evaluated. Dynamical instabilities may explain the
absence of elliptical galaxies flatter than about E6, and my also play a role
in the lack of nearly-spherical galaxies
Evidence for the formation of nanoprecipitates with magnetically disordered regions in bulk Ni50Mn45In5 Heusler alloys
Shell ferromagnetism is a new functional property of certain Heusler alloys
which has been recently observed in
. We report the results of a
comparative study of the magnetic microstructure of bulk
Heusler alloys using
magnetometry, synchrotron x-ray diffraction, and magnetic small-angle neutron
scattering (SANS). By combining unpolarized and spin-polarized SANS (POLARIS)
we demonstrate that a number of important conclusions regarding the mesoscopic
spin structure can be made. In particular, the analysis of the magnetic neutron
data suggests that nanoprecipitates with an effective ferromagnetic component
form in an antiferromagnetic matrix on field annealing at .
These particles represent sources of perturbation, which seem to give rise to
magnetically disordered regions in the vicinity of the particle-matrix
interface. Analysis of the spin-flip SANS cross section via the computation of
the correlation function yields a value of for the
particle size and for the size of the spin-canted
region.Comment: 11 pages, 8 figure
The natural wood regime in rivers
International audienc
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