1,436 research outputs found
Toward a third generation of gravitational wave observatories
Large gravitational wave interferometric detectors, like Virgo and LIGO, demonstrated the capability to reach their design sensitivity, but to transform these machines into an effective observational instrument for gravitational wave astronomy a large improvement in sensitivity is required. Advanced detectors in the near future and third generation observatories in slightly more than one decade will open the possibility to perform gravitational wave astronomical observations from the Earth. An overview of the technological progress needed to realize a third generation observatory, like the Einstein Telescope (ET), and a possible evolution scenario are discussed in this paper
Poloidal-Field Instability in Magnetized Relativistic Stars
We investigate the instability of purely poloidal magnetic fields in
nonrotating neutron stars by means of three-dimensional general-relativistic
magnetohydrodynamics simulations, extending the work presented in Ciolfi et al.
(2011). Our aim is to draw a clear picture of the dynamics associated with the
instability and to study the final configuration reached by the system, thus
obtaining indications on possible equilibria in a magnetized neutron star.
Furthermore, since the internal rearrangement of magnetic fields is a highly
dynamical process, which has been suggested to be behind magnetar giant flares,
our simulations can provide a realistic estimate of the electromagnetic and
gravitational-wave emission which should accompany the flare event. Our main
findings are the following: (i) the initial development of the instability
meets all the expectations of perturbative studies in terms of the location of
the seed of the instability, the timescale for its growth and the generation of
a toroidal component; (ii) in the subsequent nonlinear reorganization of the
system, ~90% of magnetic energy is lost in few Alfven timescales mainly through
electromagnetic emission, and further decreases on a much longer timescale;
(iii) all stellar models tend to achieve a significant amount of magnetic
helicity and the equipartition of energy between poloidal and toroidal magnetic
fields, and evolve to a new configuration which does not show a subsequent
instability on dynamical or Alfven timescales; (iv) the electromagnetic
emission matches the duration of the initial burst in luminosity observed in
giant flares, giving support to the internal rearrangement scenario; (v) only a
small fraction of the energy released during the process is converted into
f-mode oscillations and in the consequent gravitational-wave emission, thus
resulting in very low chances of detecting this signal with present and..Comment: 13 pages, 11 figures, updated to match the published versio
Mineral Fibres
In the last decades, there has been increasing interest in Naturally Occurring Asbestos (NOA) and asbestos containing materials (ACMs) as a source of possible environmental risk. A crucial theme of interest related to environmental pollution is the enhanced mobilization of asbestos minerals affecting soils and rocks due to human activities (e.g., road construction, mining activity) in comparison with natural weathering processes. The volume has aimed to gather contributions and to compare results derived from various experiences of research groups regarding NOA minerals as a source of possible environmental risks for population. Case studies from various geological contexts are presented. Moreover, contributions presenting novel and classical approaches for ACM inertization and recycling, together with possible solutions for reducing asbestos exposure, has been also presented
Petrography, Geochemistry and Mineralogy of Serpentinite Rocks Exploited in the Ophiolite Units at the Calabria-Basilicata Boundary, Southern Apennine (Italy)
Il telescopio Einstein: l'osservatorio di onde gravitazionali di 3a generazione. Einstein Telescope: the 3rd generation gravitational wave observatory
Potentially toxic elements (PTEs) associated with asbestos chrysotile, tremolite and actinolite in the Calabria region (Italy)
[EN]Potentially toxic elements (PTEs) hosted in asbestos elongate mineral particles is one of the factors that determines their toxic/pathogenic effects.
This study quantifies and compares these elements in terms of major, minor and trace element concentrations (Si, Mg, Ca, Al, Fe, Mn, Cr, Co, Ni, Cu, Zn, Be, V, As, Rb, Sb, Ba, Pb, Sr) in various types of asbestos using micro X-ray fluorescence (μ-XRF) and inductively coupled plasma mass spectrometry (ICP-MS), in order to understand how they contribute to asbestos-related diseases. Chrysotile, tremolite asbestos and actinolite asbestos extracted from the Gimigliano-Mount Reventino Unit (Calabria Region, Southern Italy) were used for this study.
In the minerals analysed, high concentrations of Cr (171 ppm) and Be (2.9 ppm) were found in tremolite asbestos and chrysotile respectively. When calculating the pseudo-total concentrations of trace elements in the samples, the largest amounts were detected in tremolite asbestos, followed by actinolite asbestos and chrysotile. However, since other metals such as Mn and Fe (minor elements) are known to induce toxicity, and considering their input to the overall balance, actinolite contained the largest amount of PTEs and in this case chrysotile proved to be more toxic than tremolite asbestos. Furthermore, the potential leaching of PTEs, released by chrysotile, tremolite and actinolite asbestos-containing rocks, into the soil and water supply is also discussed. Since asbestos elongate mineral particles can be widespread in the environment (i.e. air, rocks, soil, water), it is essential to quantify the toxic elements present in asbestos elongate mineral particles in order to prevent asbestos-related diseases. The knowledge obtained from this study will provide us with a better understanding of asbestos-related lung cancer.GIR CHARROC
Investigation of mechanical losses of thin silicon flexures at low temperatures
The investigation of the mechanical loss of different silicon flexures in a
temperature region from 5 to 300 K is presented. The flexures have been
prepared by different fabrication techniques. A lowest mechanical loss of
was observed for a 130 m thick flexure at around 10 K.
While the mechanical loss follows the thermoelastic predictions down to 50 K a
difference can be observed at lower temperatures for different surface
treatments. This surface loss will be limiting for all applications using
silicon based oscillators at low temperatures. The extraction of a surface loss
parameter using different results from our measurements and other references is
presented. We focused on structures that are relevant for gravitational wave
detectors. The surface loss parameter = 0.5 pm was obtained. This
reveals that the surface loss of silicon is significantly lower than the
surface loss of fused silica.Comment: 16 pages, 7 figure
Probing mass-radius relation of protoneutron stars from gravitational-wave asteroseismology
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