332 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
Cloning and expression of a human kinesin heavy chain gene: interaction of the COOH-terminal domain with cytoplasmic microtubules in transfected CV-1 cells.
To understand the interactions between the microtubule-based motor protein kinesin and intracellular components, we have expressed the kinesin heavy chain and its different domains in CV-1 monkey kidney epithelial cells and examined their distributions by immunofluorescence microscopy. For this study, we cloned and sequenced cDNAs encoding a kinesin heavy chain from a human placental library. The human kinesin heavy chain exhibits a high level of sequence identity to the previously cloned invertebrate kinesin heavy chains; homologies between the COOH-terminal domain of human and invertebrate kinesins and the nonmotor domain of the Aspergillus kinesin-like protein bimC were also found. The gene encoding the human kinesin heavy chain also contains a small upstream open reading frame in a G-C rich 5' untranslated region, features that are associated with translational regulation in certain mRNAs. After transient expression in CV-1 cells, the kinesin heavy chain showed both a diffuse distribution and a filamentous staining pattern that coaligned with microtubules but not vimentin intermediate filaments. Altering the number and distribution of microtubules with taxol or nocodazole produced corresponding changes in the localization of the expressed kinesin heavy chain. The expressed NH2-terminal motor and the COOH-terminal tail domains, but not the alpha-helical coiled coil rod domain, also colocalized with microtubules. The finding that both the kinesin motor and tail domains can interact with cytoplasmic microtubules raises the possibility that kinesin could crossbridge and induce sliding between microtubules under certain circumstances
A New Species of Cyclobulura (Nematoda: Subuluridae) from Zaedyus pichiy and Chaetophractus vellerosus (Xenarthra: Dasypodidae) in Argentina
Cyclobulura superinae n. sp. collected from Zaedyus pichiy and Chaetophractus vellerosus is herein described as the second species in Cyclobulura Quentin, 1977, and the first subulurid in armadillos. The species is unique in the spur-like structures present at the tip of both spicules, yet they conform to the description of Cyclobulura in the structure of the buccal parts. Specimens of the new species show longer chordal lobes and more conspicuous radial lobes and are smaller than specimens of C. lainsoni. In addition, males of C. superinae exhibit a spur-like process in the distal end of the spicules and a shorter tail (170 vs. 300 µm) with no spine. Finally, the eggs of C. superinae are smaller (60-89 × 45-71 vs. 95-100 × 80-85). To our knowledge, the new species is the first subulurid nematode found in an armadillo
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
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’
Dados, palitos, pixels y bits: alternativas didácticas para explorar la metodología de Monte Carlo en un tono lúdico
This paper presents didactic strategies in a ludic tone to explore the methodology of Monte Carlo and analizes the implementations that have been performed in several educational scenarios. These proposals allow us to put into action concepts of probability and statistics in an amusing and attractive way by conducting cooperative “experiments-games” that are based on the use of real and virtual objects. Each strategy is aimed to teachers of high school and teacher training institutes, and also for early stages at University level, in order to be modified, recreated, and enhanced according to the specific areas of application.En este artículo se presentan estrategias didácticas en tono lúdico para explorar la metodología de Monte Carlo y se analizan las puestas en práctica realizadas en diversos escenarios educativos. Las propuestas elaboradas permiten poner en acción conceptos de probabilidad y estadística de un modo divertido y atrayente mediante la realización de “experimentos-juegos” cooperativos con objetos reales y virtuales. Cada estrategia está dirigida a profesores de escuelas secundarias y de institutos de formación docente, y también al ciclo básico de la Universidad, para que sea modificada, recreada y profundizada de acuerdo a las áreas específicas de aplicación
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