We are completing the construction of GIANO, a high resolution near-infrared cryogenic spectrograph for the Telescopio Nazionale Galileo (TNG). Most of the optics are made of aluminium and operate at ...cryogenic temperature. We evaluated the optical degradation due to mis-matches between the thermal expansion coefficients of the different aluminium parts of the instrument. We performed accurate measurements of the relative thermal expansion coefficients (CTE) of Al-6061 and Al-6082 over the 300–77 K temperatures range. We find that the two alloys have identical thermal expansion coefficient within a maximum (3
σ
) uncertainty of Δ
α
/
α
< 0.28%. Our results show that it is possible to overcome the problem of the alignment of a cryogenic instrument, manufacturing the curved optics, the optics’ holders and the optical bench with different metallic alloys with small CTE mismatch (Al-6061 and Al-6082). This conclusion has also been confirmed by the results of the optical tests with the instrument cooled in the laboratory, showing no significant image quality degradation.
The Risk Map of Italian Cultural Heritage Accardo, G.; Giani, E.; Giovagnoli, A.
Journal of architectural conservation,
07/2003, Volume:
9, Issue:
2
Journal Article
Peer reviewed
The Risk Map of Italian Cultural Heritage is a current research project of the Istituto Centrale del Restauro (ICR), with the aim of developing a more rational and economical means of undertaking the ...maintenance, conservation, and restoration of the architectural and archaeological monuments of Italy.
The first step of the project has been to create a geographical information system (GIS), which collects, processes, and manages both cartographic and alphanumerical data coming from peripheral units based in many Italian towns by the 'Soprintendenze', being the territorial departments of the Ministry of Culture. The connection between environmental danger and risk to the monuments is highlighted through a mapping process, by overlapping computerized maps having a thematic content (such as air pollution, climate, and earthquakes) and the distribution of cultural assets. The second step has ensured that the above data were homogeneous through defining standardized schedules at different levels of detail. These schedules contain information both on the environment of the territory and the conservation status of the monuments.
Future development, according to the methodological approach adopted by the Risk Map project, foresees the census area as a smaller territorial unit. Moreover, it is the opinion of the authors that an improvement in documentation and recording of all formal and constituent elements of the monuments is essential in order to obtain a true reconstruction (either real or virtual) of damaged cultural property.
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Pulsar Searches with the SKA Levin, L.; Armour, W.; Baffa, C. ...
Proceedings of the International Astronomical Union,
09/2017, Volume:
13, Issue:
S337
Journal Article
Peer reviewed
Open access
The Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, ...pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.
The young stellar object MWC 297 is an embedded B1.5Ve star exhibiting strong hydrogen emission lines and a strong near-infrared continuum excess. This object has been observed with the VLT ...interferometer equipped with the AMBER instrument during its first commissioning run. AMBER/VLTI is currently the only near infrared interferometer that can observe spectrally dispersed visibilities. MWC 297 has been spatially resolved in the continuum with a visibility of $0.50^{+0.08}_{-0.10}$ as well as in the Brγ emission line where the visibility decreases to $0.33\pm0.06$. This change in the visibility with wavelength can be interpreted by the presence of an optically thick disk responsible for the visibility in the continuum and of a stellar wind traced by the Brγ emission line and whose apparent size is 40% larger. We validate this interpretation by building a model of the stellar environment that combines a geometrically thin, optically thick accretion disk model consisting of gas and dust, and a latitude-dependent stellar wind outflowing above the disk surface. The continuum emission and visibilities obtained from this model are fully consistent with the interferometric AMBER data. They agree also with existing optical, near-infrared spectra and other broad-band near-infrared interferometric visibilities. We also reproduce the shape of the visibilities in the Brγ line as well as the profile of this line obtained at an higher spectral resolution with the VLT/ISAAC spectrograph, and those of the Hα and Hβ lines. The disk and wind models yield a consistent inclination of the system of approximately 20°. A picture emerges in which MWC 297 is surrounded by an equatorial flat disk that is possibly still accreting and an outflowing wind that has a much higher velocity in the polar region than at the equator. The AMBER/VLTI unique capability of measuring spectral visibilities therefore allows us for the first time to compare the apparent geometry of a wind with the disk structure in a young stellar system.
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