Theoretical properties of radio-galaxies

A complete sample of symmetric double radio-galaxies has been investigated by inferring the propagation of a jet along the radio-axis and computing velocities with the aid of different models. A best linear fit between radio-luminosity and velocity is proposed in the range 10⁴⁰ ergs s^–145 ergs s^–1.     

Theoretical properties of radio-galaxies

We present optical photometric observations of the cataclysmic variables AO Psc and V 1223 Sgr, both of which are believed to contain slowly-rotating white-dwarf pulsars. These objectes belong to the new class of intermediate polars in which the magnetized-white-dwarf rotation period lies in between synchrous and extremely fast rotation periods. The observations reported here were carried out from the Kavalur Observatory using a 1 m reflector. High-time resolution light curves depicting a rich variety of flicker phenomena are presented. Results of a periodic analysis to search for coherent periodic modulations in the light curves are also presented. We have also derived the optical pulse profile of AO Psc and point out its similarities to the X-ray pulse profile.     

Time-dependent models for a decade of SN 1993J

A classical and a relativistic law of motion for a supernova remnant (SNR) are deduced assuming an inverse power law behavior for the density of the interstellar medium and applying the thin layer approximation. A third equation of motion is found in the framework of relativistic hydrodynamics with pressure, applying momentum conservation. These new formulas are calibrated against a decade of observations of SN 1993J. The existing knowledge of the diffusive processes of ultrarelativistic electrons is reviewed in order to explain the behavior of the ‘U’ shaped profile of intensity versus distance from the center of SN 1993J.     

On the Large-Scale Structure of the Universe as given by the Voronoi Diagrams

The size distributions of 2D and 3D Voronoi cells and of cells of Vp(2,3),-2D cut of 3D Voronoi diagram-are explored, with the single-parameter (re-scaled) gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp(2,3) map with galaxies lying on the cell boundaries is constructed to compare, as regards general appearance, with the observed CfA map of galaxies and voids, the parameters of the simulation being so chosen as to reproduce the largest observed void size.     

Revisiting the Cosmological Principle in a Cellular Framework

The cosmological principle in its various versions states that: (i) the galaxy does not occupy a particular position, (ii) the Universe is homogeneous and isotropic. This statement does not agree with the recent astronomical observations in the range z lower than 0.05 which are in agreement with a cellular structure of the Universe. Here we present a local analysis of the inhomogeneity of the Universe. When z is greater than 0.05 our analysis cannot be applied because the astronomical sample of galaxies here processed is not complete. The two tools of the Poisson Voronoi Tessellation (PVT) and the luminosity function for galaxies allow building a new version of the local cosmological principle.     

Scaling for the intensity of radiation in spherical and aspherical planetary nebulae

Planetary nebulae are imaged using three different physical processes. The first process is the expansion of the shell, which can be modelled by the canonical laws of motion in the spherical case and by momentum conservation when gradients of density are present in the interstellar medium. The second process is the diffusion of particles that radiate from the advancing layer. Three-dimensional diffusion from a sphere and one-dimensional diffusion with drift are analysed. The third process is the composition of an image through an integral operation along the line of sight. The framework developed is applied to A39, the Ring nebula and the etched hourglass nebula MyCn 18.     

Modelling intra-dependencies to assess road network resilience to natural hazards

Natural Hazards - Estimating the resilience of a road network (one of the essential critical infrastructures in times of crisis) to natural hazards is crucial in achieving the goals of disaster...     

The physics of turbulent and dynamically unstable Herbig–Haro jets

The overall properties of the Herbig–Haro objects such as centerline velocity, transversal profile of velocity, flow of mass, and flow of energy are explained adopting two models for the turbulent jet. The complex shapes of the Herbig–Haro objects, such as the arc in HH34, can be explained by introducing the combination of different kinematic effects such as velocity behavior along the main direction of the jet and the velocity of the star in the interstellar medium. The behavior of the intensity or brightness of the line of emission is explored in three different cases: transversal one-dimensional (1D) cut, longitudinal 1D cut, and 2D map. An analytical explanation for the enhancement in intensity or brightness such as usually modeled by the bow shock is given by a careful analysis of the geometrical properties of the torus.     

Révision stratigraphique de l’Ile de Timor (Indonésie orientale)

Resume. De nombreuses échelles stratigraphiques de l’?le de Timor ont vu le jour car les corrélations stratigraphiques étaient rendues difficiles par la complexité tectonique de l’?le et par la variété des faciès. Dès les premiers travaux, plusieurs séries ont été distinguées, regroupées en trois unités litho-structurales principales: unité allochtone, sub-autochtone et autochtone. Les données stratigraphiques et géodynamiques récentes montrent que l’?le de Timor est en fait constituée par six unités litho-structurales, chacune témoignant d’un épisode majeur de l’histoire géologique de l’Ile. Cette histoire consiste d’abord à la séparation, au Jurassique, d’un bloc issu du continent de Gondwana (unité para-allochtone) qui est entré en collision avec l’arc volcanique asiatique à l’Oligo-Miocène (unités allochtone et sub-allochtone). Cet ensemble a ensuite été séparé de l’Asie lors de l’ouverture de la mer de Banda sud, au Miocène supérieur (unité sub-autochtone) pour finalement entrer en collision avec la marge nord australienne au cours du Pliocène moyen (plateforme australienne et groupe de Kolbano). Timor est depuis incorporée à la marge nord australienne (unité autochtone). Ce travail présente les différentes échelles stratigraphiques de chaque nouvelle unité, des propositions de corrélations et une comparaison avec les ?les voisines de Sumba et de Sulawesi pour aboutir à une proposition d’évolution géodynamique. Manuscrit re?u le 13 février 2004 Révision acceptée le 14 février 2005     

Nouvelle hypothèse sur l'origine des formations géologiques de l'île de Timor (Sud-Est asiatique)

Similar lithological and tectonic features indicate that Timor and Sulawesi islands were part of the same continental block. Timor was in the southern part of Sulawesi, then separated during Late Miocene time during the opening of the South Banda Sea basin. At this time Timor evolved as a part of an Upper Miocene volcanic arc that collided the Australian plate at the end of the Lower Pliocene (3.5 Ma). To cite this article: M. Villeneuve et al., C. R. Geoscience 336 (2004).