On the Influence of Magnetic Fields on the Structure of Protostellar Jets

We here present the first results of fully three-dimensional (3-D) MHD simulations of radiative cooling pulsed (time-variable) jets for a set of parameters which are suitable for protostellar outflows. Considering different initial magnetic field topologies in approximate $equipartition$ with the thermal gas, i.e., (i) a longitudinal, and (ii) a helical field, both of which permeating the jet and the ambient medium; and (iii) a purely toroidal field permeating only the jet, we find that the overall morphology of the pulsed jet is not very much affected by the presence of the different magnetic field geometries in comparison to a nonmagnetic calculation. Instead, the magnetic fields tend to affect essentially the detailed structure and emission properties behind the shocks at the head and at the pulse-induced internal knots, particularly for the helical and toroidal geometries. In these cases, we find, for example, that the $H_\alpha$ emissivity behind the internal knots can be about three to four times larger than that of the purely hydrodynamical jet. We also find that some features, like the nose cones that often develop at the jet head in 2-D calculations involving toroidal magnetic fields, are smoothed out or absent in the 3-D calculations.Comment: 13 pages, 3 figures, Accepted by ApJ Letters after minor corrections (for high resolution figures, see http://www.iagusp.usp.br/~adriano/h.tar

Multidimensional Hydrodynamical Simulations of radiative cooling SNRs-clouds interactions: an application to Starburst Environments

In this work we are interested to study the by-products of SNR-clouds in a starburst (SB) system. These interactions can have an important role in the recycling of matter from the clouds to the ISM and vice-versa. In the present work, we have focused our attention on the global effects of the interactions between clouds and SN shock waves in the ISM of SB environments, and performed 3-D radiative cooling hydrodynamical simulations with the adaptive YGUAZU grid code. We have also considered the effects of the photo-evaporation due to the presence of a high number of UV photons from hot stars and supernovae (SNe). The results have shown that, in the presence of radiative cooling, instead of an efficient gas mixing with the diffuse ISM, the interactions cause the fragmentation of the clouds into smaller ones. The results have also revealed that the SNR-clouds interactions are less efficient at producing substantial mass loss from the clouds to the diffuse ISM than mechanisms such as the photo-evaporation caused by the UV flux from the hot stars.Comment: 15 pages, 25 figures. Figures with higher resolution at the page: http://www.astro.iag.usp.br/~dalpino/ Astronomy & Astrophysics accepte

Predictive maintenance for monitoring performance decay of plaster converings according to the criteria of ISO 16686-7 code

The aim of the present work is the construction of the performance/time curve that characterizes and defines the aging of plaster coverings on tuff masonry, a widely used technical solution in the building stock of the city of Naples. 53 sample building were tested; these were selected according to a criteria of homogeneity of the technological characteristics of the support and covering material (tuff masonry + lime-cement plaster + acrylic paint). The year of construction of the buildings, as well as any problem occurred during the work realization, was acknowledged. The described objective represents a result of indubitable utility and practical consequence, as it allows: - the evaluation of the residual service life at the moment of the execution of field tests with fixed methodologies; - the definition of the time thresholds for the execution of the most appropriate interventions, determined in a maintenance plan, in which predictive maintenance of course plays a fundamental role. The chosen methodology for the evaluation of performances, considering the indications of ISO 15686-7, is the infrared thermographic camera test, combined with close-up visual inspections and percussion tests. The activities were carried out through the following main phases: - defining the task; - planning; - examination; - evaluation; - reporting. The results showed the possibility to create curves like the one represented in the annex B of the already quoted ISO 15686-7 and hence to define the decay with 5 performance degrees (no symptoms – slight symptoms – medium – strong symptoms – totally unacceptable, including collapse and malfunction), corresponding to an accurate quantification of the conditions of conservation, and that is mainly possible thanks to the output of the thermographic camera. In relation to the results, different scenarios of planned maintenance for a period of 30 years have been hypothesized