4,101 research outputs found
Centro de recuperação de animais selvagens de Castelo Branco - resultados 1999 a 2001.
O CERAS (Centro de Estudos e Recuperação de Animais Selvagens de Castelo Branco) está localizado na Escola Superior Agrária de Castelo Branco e tem como principais objectivos a recuperação e o estudo da fauna selvagem, através da recuperação, programas de reprodução em cativeiro, estudos para a protecção da fauna e dos seus habitats. Com este artigo pretendemos mostrar os primeiros resultados obtidos no centro de recuperação de fauna durante os 3 primeiros anos de funcionamento, 1999 a 2001, no qual deram entrada 157 animais, e destes 50% foram devolvidos à natureza. As principais causas de ingresso dos animais são a pilhagem/cativeiro ilegal, seguido de órfãos, atropelamentos e tiro. Existe uma variação anual na entrada de animais no centro que está relacionada com o final da época de nidificação e o começo da actividade cinegética.info:eu-repo/semantics/publishedVersio
Positive solutions of BVPs on the half-line involving functional BCs
We study the existence of positive solutions on the half-line of a second
order ordinary differential equation subject to functional boundary conditions.
Our approach relies on a combination between the fixed point index for
operators on compact intervals, a fixed point result for operators on
noncompact sets, and some comparison results for principal and nonprincipal
solutions of suitable auxiliary linear equations.Comment: 13 page
A flat faint end of the Fornax cluster galaxy luminosity function
We analyse the photometric properties of the early-type Fornax cluster dwarf
galaxy population (M_V>-17 mag), based on a wide field imaging study of the
central cluster area in V and I band-passes with IMACS/Magellan at Las Campanas
Observatory. We create a fiducial sample of ~100 Fornax cluster dwarf
ellipticals (dEs) with -16.6<M_V<-8.8 mag in the following three steps: (1) To
verify cluster membership, we measured I-band surface brightness fluctuations
(SBF) distances to candidate dEs known from previous surveys; (2) We
re-assessed morphological classifications for those candidate dEs that are too
faint for SBF detection; and (3) We searched for new candidate dEs in the
size-luminosity regime close to the resolution limit of previous surveys. The
resulting fiducial dE sample follows a well-defined surface brightness -
magnitude relation, showing that Fornax dEs are about 40% larger than Local
Group dEs. The sample also defines a colour-magnitude relation similar to that
of Local Group dEs. The early-type dwarf galaxy luminosity function in Fornax
has a very flat faint end slope alpha = -1.1 +/- 0.1. We compare the number of
dwarfs per unit mass with those in other environments and find that the Fornax
cluster fits well into a general trend of a lack of high-mass dwarfs in more
massive environments.Comment: 5 pages, 4 figures, to appear in the proceedings of IAU Symposium 244
'Dark galaxies and lost baryons', Cambridge University Press, editors J. I.
Davies & M. D. Disne
The Dwarf Galaxy Population of the Dorado group down to Mv=-11
We present V and I CCD photometry of suspected low-surface brightness dwarf
galaxies detected in a survey covering ~2.4 deg^2 around the central region of
the Dorado group of galaxies. The low-surface brightness galaxies were chosen
based on their sizes and magnitudes at the limiting isophote of 26.0V\mu. The
selected galaxies have magnitudes brighter than V=20 (Mv=-11 for an assumed
distance to the group of 17.2 Mpc), with central surface brightnesses \mu0>22.5
V mag/arcsec^2, scale lengths h>2'', and diameters > 14'' at the limiting
isophote. Using these criteria, we identified 69 dwarf galaxy candidates. Four
of them are large very low-surface brightness galaxies that were detected on a
smoothed image, after masking high surface brightness objects. Monte Carlo
simulations performed to estimate completeness, photometric uncertainties and
to evaluate our ability to detect extended low-surface brightness galaxies show
that the completeness fraction is, on average, > 80% for dwarf galaxies with
and 22.5<\mu0<25.5 V mag/arcsec^2, for the range of sizes
considered by us (D>14''). The V-I colors of the dwarf candidates vary from
-0.3 to 2.3 with a peak on V-I=0.98, suggesting a range of different stellar
populations in these galaxies. The projected surface density of the dwarf
galaxies shows a concentration towards the group center similar in extent to
that found around five X-ray groups and the elliptical galaxy NGC1132 studied
by Mulchaey and Zabludoff (1999), suggesting that the dwarf galaxies in Dorado
are probably physically associated with the overall potential well of the
group.Comment: 32 pages, 16 postscript figures and 3 figures in GIF format, aastex
v5.0. To appear in The Astronomical Journal, January 200
The counterparts of Local Group dwarf spheroidals in nearby clusters
In this contribution, we report on the discovery of dwarf spheroidals (dSphs)
in the core of the Fornax cluster. Their photometric properties -- like
magnitude, colour, surface brightness -- are very similar to those of Local
Group dSphs. However, at a given total magnitude, dSphs in Fornax seem to be
more extended than their Local Group counterparts. The membership of several
dwarf galaxy candidates in Fornax has been confirmed by surface brightness
fluctuation measurements on deep wide-field images taken with the Magellan
telescope. The analysis of these images also confirms the flat faint end slope
of the luminosity function for dSphs in Fornax which contradicts the expected
large number of small dark matter halos connected to dwarf galaxies in
LambdaCDM theory. Dwarf spheroidals have also been detected in the Hydra I and
Centaurus cluster. A preliminary analysis of their photometric properties shows
that they obey similar scaling relations as their counterparts in Fornax and
the Local Group.Comment: 4 pages, 4 figures, to appear in the proceedings of the IAUC198
"Near-Field Cosmology with Dwarf Elliptical Galaxies", H. Jerjen & B.
Binggeli (eds.
Spin and lattice excitations of a BiFeO3 thin film and ceramics
We present a comprehensive study of polar and magnetic excitations in BiFeO3
ceramics and a thin film epitaxially grown on an orthorhombic (110) TbScO3
substrate. Infrared reflectivity spectroscopy was performed at temperatures
from 5 to 900 K for the ceramics and below room temperature for the thin film.
All 13 polar phonons allowed by the factor-group analysis were observed in
theceramic samples. The thin-film spectra revealed 12 phonon modes only and an
additional weak excitation, probably of spin origin. On heating towards the
ferroelectric phase transition near 1100 K, some phonons soften, leading to an
increase in the static permittivity. In the ceramics, terahertz transmission
spectra show five low-energy magnetic excitations including two which were not
previously known to be infrared active; at 5 K, their frequencies are 53 and 56
cm-1. Heating induces softening of all magnetic modes. At a temperature of 5 K,
applying an external magnetic field of up to 7 T irreversibly alters the
intensities of some of these modes. The frequencies of the observed spin
excitations provide support for the recently developed complex model of
magnetic interactions in BiFeO3 (R.S. Fishman, Phys. Rev. B 87, 224419 (2013)).
The simultaneous infrared and Raman activity of the spin excitations is
consistent with their assignment to electromagnons
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