62 research outputs found
Gravitational Mesoscopic Constraints in Cosmological Dark Matter Halos
We present an analysis of the behaviour of the `coarse-grained'
(`mesoscopic') rank partitioning of the mean energy of collections of particles
composing virialized dark matter halos in a Lambda-CDM cosmological simulation.
We find evidence that rank preservation depends on halo mass, in the sense that
more massive halos show more rank preservation than less massive ones. We find
that the most massive halos obey Arnold's theorem (on the ordering of the
characteristic frequencies of the system) more frequently than less massive
halos. This method may be useful to evaluate the coarse-graining level (minimum
number of particles per energy cell) necessary to reasonably measure signatures
of `mesoscopic' rank orderings in a gravitational system.Comment: LaTeX, 15 pages, 3 figures. Accepted for publication in Celestial
Mechanics and Dynamical Astronomy Journa
Galactic cannibalism in the galaxy cluster C0337-2522 at z=0.59
According to the galactic cannibalism model, cD galaxies are formed in the
center of galaxy clusters by merging of massive galaxies and accretion of
smaller stellar systems: however, observational examples of the initial phases
of this process are lacking. We have identified a strong candidate for this
early stage of cD galaxy formation: a group of five elliptical galaxies in the
core of the X-ray cluster C0337-2522 at redshift z=0.59. With the aid of
numerical simulations, in which the galaxies are represented by N-body systems,
we study their dynamical evolution up to z=0; the cluster dark matter
distribution is also described as a N-body system. We find that a multiple
merging event in the considered group of galaxies will take place before z=0
and that the merger remnant preserves the Fundamental Plane and the
Faber-Jackson relations, while its behavior with respect to the Mbh-sigma
relation is quite sensitive to the details of black hole merging [abridged].Comment: 30 pages, 7 figures, MNRAS (accepted
SobrevivĂȘncia e ocorrĂȘncia de muda em Triatoma infestans Klug (Hemiptera, Reduviidae) apĂłs choque de temperatura
Survival and molting occurrence were studied in specimens of Triatoma infestans over 30 days after temperature shocks. Hyperthermal and hypotermal shocks could be found to affect both survival and molting incidence as a function of temperature and period of the developement phase and sex of the specimens. Considering the various test conditions, the shock at 0°C for 12 h was found to elicit the most deleterious effect, whereas shocks at 40°C and 0°C even for 1 h are interpreted as affecting the hormonal balance which controls molting. Cases of a rise in post-shock survival are suggested to have been favored by heat-shock protein action.A sobrevivĂȘncia e a ocorrĂȘncia de mudas em espĂ©cimes de Triatoma infestans foram estudados num perĂodo de 30 dias apĂłs choques de temperatura. Foi demonstrado que choques hipertĂ©rmico e hipotĂ©rmico interferem nesses processos, na dependĂȘncia da temperatura do choque, tempo de sua duração, fase de desenvolvimento e sexo dos espĂ©cimes. Dentre as situaçÔes experimentais utilizadas, o choque a 0°C por 12 h pareceu produzir a ação mais deletĂ©ria, porĂ©m choques a 40°C e 0°C mesmo por uma hora sĂŁo admitidos como afetando o desenvolvimento hormonal que controla a muda. Casos de aumento de sobrevivĂȘncia pĂłs-choque sĂŁo sugeridos como tendo sido favorecidos por ação de proteĂnas de choque tĂ©rmico
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