537 research outputs found
Models of cuspy triaxial stellar systems. II. Regular orbits
In the first paper of this series we used the N--body method to build a dozen
cuspy (gamma ~ 1) triaxial models of stellar systems, and we showed that they
were highly stable over time intervals of the order of a Hubble time, even
though they had very large fractions of chaotic orbits (more than 85 per cent
in some cases). The models were grouped in four sets, each one comprising
models morphologically resembling E2, E3, E4 and E5 galaxies, respectively. The
three models within each set, although different, had the same global
properties and were statistically equivalent. In the present paper we use
frequency analysis to classify the regular orbits of those models. The bulk of
those orbits are short axis tubes (SATs), with a significant fraction of long
axis tubes (LATs) in the E2 models that decreases in the E3 and E4 models to
become negligibly small in the E5 models. Most of the LATs in the E2 and E3
models are outer LATs, but the situation reverses in the E4 and E5 models where
the few LATs are mainly inner LATs. As could be expected for cuspy models, most
of the boxes are resonant orbits, i.e., boxlets. Nevertheless, only the (x, y)
fishes of models E3 and E4 amount to about 10 per cent of the regular orbits,
with most of the fractions of the other boxlets being of the order of 1 per
cent or less.Comment: Accepted for publication in the Monthly Notices of the Royal
Astronomical Societ
Educación ambiental, vida en la naturaleza y ciencia escolar : Estado de situación y posibles estrategias de integración
La construcción de relaciones entre Vida en la Naturaleza, Educación Ambiental y Ciencia Escolar da lugar a un campo de trabajo educativo sobre el cual es posible trazar diversas configuraciones didácticas. Desde esta perspectiva, en el presente estudio se analiza el estado de situación de este campo relacional a partir de los resultados obtenidos de encuestas realizadas a estudiantes de Institutos Superiores de Formación Docente en Educación Física, para luego proponer posibles estrategias de intersección didáctica, siempre desde el marco referencial que brinda la tríada conceptual: motricidad, ambiente próximo y planetariedad. Las propuestas están dirigidas a enriquecer la formación inicial de futuros educadores así como también a contribuir en la formación permanente de docentes de diversos profesorados, pudiendo ser extendidas a facilitadores del ámbito educativo no forma
Positivismo crimininológico, racismo y holocausto
Fil: Navone, Karina A. Universidad de Buenos Aires. Facultad de Derecho. Buenos Aires, Argentin
Characterization and evaluation of a marine protected area: 'Tavolara - Punta Coda Cavallo' (Sardinia, NW Mediterranean)
Habitat mapping plays a key role in the management and conservation of natural systems. In protected areas, where sustainable development is always subordinate to conservation efforts, maps are largely used to represent habitats, development pressures, tourist facilities or legal restrictions such as the zoning of a protected area. Some authors have recently developed a methodology that allows the production of a set of maps for the management of marine protected areas. In this paper, we present the application of this methodology to the case study of the marine protected area 'Tavolara Punta Coda Cavallo'. © 2013 Copyright A. Rovere
An analysis of the most distant catalogued open clusters -- Re-assessing fundamental parameters with Gaia EDR3 and
Several studies have been presented in the last few years applying some kind
of automatic processing of data to estimate the fundamental parameters of open
clusters. These parameters are later on employed in larger scale analyses, for
example the structure of the Galaxy's spiral arms. The distance is one of the
more straightforward parameters to estimate, yet enormous differences can still
be found among published data. This is particularly true for open clusters
located more than a few kpc away. We cross-matched several published catalogues
and selected the twenty-five most distant open clusters (9000 pc). We then
performed a detailed analysis of their fundamental parameters, with emphasis on
their distances, to determine the agreement between catalogues and our
estimates.} Photometric and astrometric data from the Gaia EDR3 survey was
employed. The data was processed with our own membership analysis code
(pyUPMASK), and our package for automatic fundamental cluster's parameters
estimation (). We find differences in the estimated distances
of up to several kpc between our results and those catalogued, even for the
catalogues that show the best matches with values. Large
differences are also found for the age estimates. As a by-product of the
analysis we find that vd Bergh-Hagen 176 could be the open cluster with the
largest heliocentric distance catalogued to date. Caution is thus strongly
recommended when using catalogued parameters of open clusters to infer
large-scale properties of the Galaxy, particularly for those located more than
a few kpc away.Comment: Accepted for publication in A&
Niveles de infección de helmintos de Rattus rattus (Rodentia: Muridae) en la ciudad de Corrientes, Argentina
The aim of this study was to describe the infection levels of helminths of Rattus rattus in Corrientes city, Corrientes Province, Argentina. In order to determine the role of rodents as potential reservoirs for zoonotic parasites, different indices of helminth infection were assessed with respect to sex, age, season and urban landscapes. A total of 107 individuals of R. rattus were examined. Seven species of helminths were found. The values of total prevalence, mean intensity and mean abundance were 68%, 20 and 13, respectively.
Nippostrongylus brasiliensis was the species more prevalent and abundant. The results showed that the age of the rodents and the season of capture had effects on the helminth infection.El objetivo del trabajo fue describir los niveles de infección de Rattus rattus en la ciudad de Corrientes, provincia de Corrientes, Argentina. Con el objetivo de determinar el rol de los roedores como reservorios potenciales de parásitos zoonóticos, se analizó la distribución de helmintos respecto al sexo, edad, estación del año y ambientes urbanos. Un total de 107 individuos de R. rattus fueron examinados. Se identificaron siete especies de helmintos. Los valores de prevalencia total, intensidad media y abundancia media fueron 68%, 20 y 13, respectivamente. Nippostrongylus brasiliensis fue la especie más prevalente y abundante. Los resultados demostraron que la edad de los roedores y la estación del año tuvieron efectos en la infección con helmintos.Facultad de Ciencias Naturales y Muse
First record of the acanthurid fish Zebrasoma xanthurum (Blyth, 1852) in the Mediterranean Sea, with some considerations on the risk associated with aquarium trade
The occurrence of a single individual of yellowtail tang Zebrasoma xanthurum (Acanthuridae) from Sardinia island (Italy), probably released from an aquarium, is here reported. This represents the first record of this species in the Mediterranean Sea. The overall information available on Acanthurid fishes and other exotic species in the Mediterranean is discussed in the light of the ongoing ecological changes taking place in rocky reef ecosystems
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