6,767 research outputs found
THE THABINA IRRIGATION SCHEME IN A CONTEXT OF REHABILITATION AND MANAGEMENT TRANSFER: PROSPECTIVE ANALYSIS AND LOCAL EMPOWERMENT
Resource /Energy Economics and Policy,
Simultaneous multi-band detection of Low Surface Brightness galaxies with Markovian modelling
We present an algorithm for the detection of Low Surface Brightness (LSB)
galaxies in images, called MARSIAA (MARkovian Software for Image Analysis in
Astronomy), which is based on multi-scale Markovian modeling. MARSIAA can be
applied simultaneously to different bands. It segments an image into a
user-defined number of classes, according to their surface brightness and
surroundings - typically, one or two classes contain the LSB structures. We
have developed an algorithm, called DetectLSB, which allows the efficient
identification of LSB galaxies from among the candidate sources selected by
MARSIAA. To assess the robustness of our method, the method was applied to a
set of 18 B and I band images (covering 1.3 square degrees in total) of the
Virgo cluster. To further assess the completeness of the results of our method,
both MARSIAA, SExtractor, and DetectLSB were applied to search for (i) mock
Virgo LSB galaxies inserted into a set of deep Next Generation Virgo Survey
(NGVS) gri-band subimages and (ii) Virgo LSB galaxies identified by eye in a
full set of NGVS square degree gri images. MARSIAA/DetectLSB recovered ~20%
more mock LSB galaxies and ~40% more LSB galaxies identified by eye than
SExtractor/DetectLSB. With a 90% fraction of false positives from an entirely
unsupervised pipeline, a completeness of 90% is reached for sources with r_e >
3" at a mean surface brightness level of mu_g=27.7 mag/arcsec^2 and a central
surface brightness of mu^0 g=26.7 mag/arcsec^2. About 10% of the false
positives are artifacts, the rest being background galaxies. We have found our
method to be complementary to the application of matched filters and an
optimized use of SExtractor, and to have the following advantages: it is
scale-free, can be applied simultaneously to several bands, and is well adapted
for crowded regions on the sky.Comment: 39 pages, 18 figures, accepted for publication in A
Lovely Came Back
https://digitalcommons.library.umaine.edu/mmb-vp/2047/thumbnail.jp
Hydro-institutional mapping in the Steelpoort River Basin, South Africa
River basins / Institutions / Organizations / Private sector / Public sector / Local government / Mapping / Water resource management / Water policy / Legislation / Rural women / Constraints / Groundwater / Surface water / Water quality / Water use / Water users / Dams / Reservoirs / Large-scale systems / Irrigation management / Industrialization / Case studies / Operations / Maintenance / Canals / Conflict / Farmer-agency interactions / Policy / Water supply / Rural development
Dual formulation of classical W-algebras
By extending the concept of \mc, I introduce a dual formulation of
(classical) nonlinear extensions of the \vir\ algebra. This dual formulation is
closely related to three dimensional actions which are analogous to a \cs\
action. I present an explicit construction in terms of superfields of the
super \wfour.Comment: (only change is an added reference), 9 pages, USC--92/01
Superconductivity and charge carrier localization in ultrathin bilayers
/ (LSCO15/LCO) bilayers
with a precisely controlled thickness of N unit cells (UCs) of the former and M
UCs of the latter ([LSCO15\_N/LCO\_M]) were grown on (001)-oriented {\slao}
(SLAO) substrates with pulsed laser deposition (PLD). X-ray diffraction and
reciprocal space map (RSM) studies confirmed the epitaxial growth of the
bilayers and showed that a [LSCO15\_2/LCO\_2] bilayer is fully strained,
whereas a [LSCO15\_2/LCO\_7] bilayer is already partially relaxed. The
\textit{in situ} monitoring of the growth with reflection high energy electron
diffraction (RHEED) revealed that the gas environment during deposition has a
surprisingly strong effect on the growth mode and thus on the amount of
disorder in the first UC of LSCO15 (or the first two monolayers of LSCO15
containing one plane each). For samples grown in pure
gas (growth type-B), the first LSCO15 UC next to the SLAO
substrate is strongly disordered. This disorder is strongly reduced if the
growth is performed in a mixture of and gas
(growth type-A). Electric transport measurements confirmed that the first UC of
LSCO15 next to the SLAO substrate is highly resistive and shows no sign of
superconductivity for growth type-B, whereas it is superconducting for growth
type-A. Furthermore, we found, rather surprisingly, that the conductivity of
the LSCO15 UC next to the LCO capping layer strongly depends on the thickness
of the latter. A LCO capping layer with 7~UCs leads to a strong localization of
the charge carriers in the adjacent LSCO15 UC and suppresses superconductivity.
The magneto-transport data suggest a similarity with the case of weakly hole
doped LSCO single crystals that are in a so-called {"{cluster-spin-glass
state}"
GHASP: an H kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc-band
We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP,
Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which
high-resolution Fabry-Perot H{\alpha} maps have previously been obtained. Our
data set is constructed by new Rc-band observations taken at the Observatoire
de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS)
archival data, obtained with the purpose of deriving homogeneous photometric
profiles and parameters. Our results include Rc-band surface brightness
profiles for 170 galaxies and profiles for 108 of these objects. We
catalogue several parameters of general interest for further reference, such as
total magnitude, effective radius and isophotal parameters -- magnitude,
position angle, ellipticity and inclination. We also perform a structural
decomposition of the surface brightness profiles using a multi-component method
in order to separate disks from bulges and bars, and to observe the main
scaling relations involving luminosities, sizes and maximum velocities.
We determine the Rc-band Tully Fisher relation using maximum velocities
derived solely from H rotation curves for a sample of 80 galaxies,
resulting in a slope of , zero point of and an
estimated intrinsic scatter of . We note that, different from
the TF-relation in the near-infrared derived for the same sample, no change in
the slope of the relation is seen at the low-mass end (for galaxies with
km/s). We suggest that this different behaviour of the Tully
Fisher relation (with the optical relation being described by a single
power-law while the near-infrared by two) may be caused by differences in the
stellar mass to light ratio for galaxies with km/s.Comment: 17 pages, 11 figure
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