1,490 research outputs found
Traveling with an invader: ectoparasitic mites of Hemidactylus frenatus (Squamata: Gekkonidae) in Colombia
Information about natural history of invasive species (such as parasitism) is a relevant issue in order to consider potential threats to native fauna. In this work we report two pterygosomatid mites for the first time in Colombia, Geckobia bataviensis and G. keegani, parasites of the invasive house gecko Hemidactylus frenatus. Although it has not been demonstrated that these mites may infest native gecko lizards, our study highlights the need to explore the prevalence of internal and external parasites in native and invasive geckos, to better evaluate the potential impact of invasive Hemidactylus lizards in Colombia.Asociación Herpetológica Argentin
Traveling with an invader: ectoparasitic mites of Hemidactylus frenatus (Squamata: Gekkonidae) in Colombia
Information about natural history of invasive species (such as parasitism) is a relevant issue in order to consider potential threats to native fauna. In this work we report two pterygosomatid mites for the first time in Colombia, Geckobia bataviensis and G. keegani, parasites of the invasive house gecko Hemidactylus frenatus. Although it has not been demonstrated that these mites may infest native gecko lizards, our study highlights the need to explore the prevalence of internal and external parasites in native and invasive geckos, to better evaluate the potential impact of invasive Hemidactylus lizards in Colombia.Asociación Herpetológica Argentin
Traveling with an invader: ectoparasitic mites of Hemidactylus frenatus (Squamata: Gekkonidae) in Colombia
Information about natural history of invasive species (such as parasitism) is a relevant issue in order to consider potential threats to native fauna. In this work we report two pterygosomatid mites for the first time in Colombia, Geckobia bataviensis and G. keegani, parasites of the invasive house gecko Hemidactylus frenatus. Although it has not been demonstrated that these mites may infest native gecko lizards, our study highlights the need to explore the prevalence of internal and external parasites in native and invasive geckos, to better evaluate the potential impact of invasive Hemidactylus lizards in Colombia.Asociación Herpetológica Argentin
A survey for water maser emission towards planetary nebulae. New detection in IRAS 17347-3139
We report on a water maser survey towards a sample of 27 planetary nebulae
(PNe) using the Robledo de Chavela and Medicina single-dish antennas, as well
as the Very Large Array (VLA). Two detections have been obtained: the already
known water maser emission in K 3-35, and a new cluster of masers in IRAS
17347-3139. This low rate of detections is compatible with the short life-time
of water molecules in PNe (~100 yr). The water maser cluster at IRAS 17347-3139
are distributed on a ellipse of size ~ 0.2" x 0.1", spatially associated with
compact 1.3 cm continuum emission (simultaneously observed with the VLA). From
archive VLA continuum data at 4.9, 8.4, and 14.9 GHz, a spectral index alpha =
0.76 +- 0.03 is derived for this radio source, which is consistent with either
a partially optically thick ionized region or with an ionized wind. However,
the latter scenario can be ruled out on mass-loss considerations, thus
indicating that this source is probably a young PN. The spatial distribution
and the radial velocities of the water masers are suggestive of a rotating and
expanding maser ring, tracing the innermost regions of a torus formed at the
end of the AGB phase. Given that the 1.3 cm continuum emission peak is located
near one of the tips of the major axis of the ellipse of masers, we speculate
on a possible binary nature of IRAS 17347-3139, where the radio continuum
emission could belong to one of the components and the water masers would be
associated with a companion.Comment: Accepted by The Astrophysical Journal. 25 pages, 6 figure
Evaluación de las necesidades hídricas de tres variedades de fresas y de su respuesta frente a un recorte hídrico moderado
Instituto Nacional de Investigaciones RTA2012-00001-00-00FEDER CC10-009-C02-0
Mz 3, a Multipolar Nebula in the Making
The nebula Mz 3 has arguably the most complex bipolar morphology, consisting
of three nested pairs of bipolar lobes and an equatorial ellipse. Its three
pairs of bipolar lobes share the same axis of symmetry, but have very different
opening angles and morphologies: the innermost pair of bipolar lobes shows
closed lobe morphology, while the other two have open lobes with cylindrical
and conical shapes, respectively. We have carried out high-dispersion
spectroscopic observations of Mz 3, and detected distinct kinematic properties
among the different morphological components. The expansion characteristics of
the two outer pairs of lobes suggest that they originated in an explosive
event, whereas the innermost pair of lobes resulted from the interaction of a
fast wind with the surrounding material. The equatorial ellipse is associated
with a fast equatorial outflow which is unique among bipolar nebulae. The
dynamical ages of the different structures in Mz 3 suggest episodic bipolar
ejections, and the distinct morphologies and kinematics among these different
structures reveal fundamental changes in the system between these episodic
ejections.Comment: To be published in the October issue of The Astronomical Journal. 16
pages, 10 figures. For full resolution figures, send requests to the Author
[email protected]
X-boson cumulant approach to the periodic Anderson model
The Periodic Anderson Model (PAM) can be studied in the infinite U limit by
employing the Hubbard X operators to project out the unwanted states. We have
already studied this problem employing the cumulant expansion with the
hybridization as perturbation, but the probability conservation of the local
states (completeness) is not usually satisfied when partial expansions like the
Chain Approximation (CHA) are employed. Here we treat the problem by a
technique inspired in the mean field approximation of Coleman's slave-bosons
method, and we obtain a description that avoids the unwanted phase transition
that appears in the mean-field slave-boson method both when the chemical
potential is greater than the localized level Ef at low temperatures (T) and
for all parameters at intermediate T.Comment: Submited to Physical Review B 14 pages, 17 eps figures inserted in
the tex
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