22,299 research outputs found
Fermi detected blazars seen by INTEGRAL
Multiwavelength observations are essential to constrain physical parameters
of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected
in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were
detected. 15 of these sources allowed significant spectral extraction. They
show hard X-ray spectra with an average photon index of 2.1+-0.1 and a hard
X-ray luminosity of L(20-100 keV) = 1.3e46 erg/s. 15 of the INTEGRAL blazars
are also visible in the first 16 months of the Fermi/LAT data, thus allowing to
constrain the inverse Compton branch in these cases. Among others, we analyse
the LAT data of four blazars which were not included in the Fermi LAT Bright
AGN Sample based on the first 3 months of the mission: QSO B0836+710, H
1426+428, RX J1924.8-2914, and PKS 2149-306. Especially for blazars during
bright outbursts, as already observed simultaneously by INTEGRAL and Fermi
(e.g. 3C 454.3 and Mrk 421), INTEGRAL provides unique spectral coverage up to
several hundred keV. We present the spectral analysis of INTEGRAL and Fermi
data and demonstrate the potential of INTEGRAL observations of Fermi detected
blazars in outburst by analysing the combined data set of the persistent radio
galaxy Cen A.Comment: 5 pages, 5 figures, 2009 Fermi Symposium, eConf Proceedings C09112
Bounds on hep neutrinos
The excess of highest energy solar-neutrino events recently observed by
Superkamiokande can be in principle explained by anomalously high
-neutrino flux . Without using SSM calculations, from the
solar luminosity constraint we derive that cannot exceed
the SSM estimate by more than a factor three. If one makes the additional
hypothesis that neutrino production occurs where the He concentration
is at equilibrium, helioseismology gives an upper bound which is (less then)
two times the SSM prediction. We argue that the anomalous -neutrino flux
of order of that observed by Superkamiokande cannot be explained by
astrophysics, but rather by a large production cross-section.Comment: 7 pages, RevTeX fil
Wear rates in urban rail systems
A significant part of maintenance costs in urban rail systems (metro, tram, light rapid transit/light metro) is due to wheel-rail wear. Wear rates - measured for example as depth of wear per kilometre run (rolling stock) or per train passage (rails) - depend in a complex manner on several influence factors. Among
the most important are key design factors of the rolling stock (wheel profiles, suspension characteristics), of the track (distribution of curve radii, characteristics of switches and crossings, rail profiles), of the wheel-rail interface (lubrication, materials in contact, ambient characteristics), and of
operations (frequency of traction and braking, trainset inversion policy, maintenance policy etc.). When designing an urban rail system, all of these factors have to be under control in order to limit the costs due to wheel/rail reprofiling/grinding and replacement. The state of the art allows the calculation of
wear rates given quantitative input regarding the above factors. However, it is difficult to find in the literature experimental values for calibration of wear models and indications on what is a reasonable state-of-the-art wear rate for any given type of urban rail system. In this paper we present a structured
analysis of flange wear rates found in the literature and derived from the experience of the authors, for a variety of cases, including metros and mainline rail systems. We compare the wear rates and explain their relationship with the influence factors. We then relate the wear rates with the needs in terms of
wheel reprofiling/replacement. We estimate ranges for the calibration coefficients of wear models. We present the results in a way as to allow the designer of urban rail systems to derive values for target wear rates according to their specific conditions without the need for complex simulations
Novel calibrations of virial black hole mass estimators in active galaxies based on X-ray luminosity and optical/NIR emission lines
Accurately weigh the masses of SMBH in AGN is currently possible for only a
small group of local and bright broad-line AGN through reverberation mapping
(RM). Statistical demographic studies can be carried out considering the
empirical scaling relation between the size of the BLR and the AGN optical
continuum luminosity. However, there are still biases against low-luminosity or
reddened AGN, in which the rest-frame optical radiation can be severely
absorbed/diluted by the host and the BLR emission lines could be hard to
detect. Our purpose is to widen the applicability of virial-based SE relations
to reliably measure the BH masses also for low-luminosity or intermediate/type
2 AGN that are missed by current methodology. We achieve this goal by
calibrating virial relations based on unbiased quantities: the hard X-ray
luminosities, in the 2-10 keV and 14-195 keV bands, that are less sensitive to
galaxy contamination, and the FWHM of the most important rest-frame NIR and
optical BLR emission lines. We built a sample of RM AGN having both X-ray
luminosity and broad optical/NIR FWHM measurements available in order to
calibrate new virial BH mass estimators. We found that the FWHM of the
H, H and NIR lines (i.e. Pa, Pa and
HeI10830) all correlate each other having negligible or small offsets.
This result allowed us to derive virial BH mass estimators based on either the
2-10 keV or 14-195 keV luminosity. We took also into account the recent
determination of the different virial coefficients for pseudo and classical
bulges. By splitting the sample according to the bulge type and adopting
separate factors we found that our virial relations predict BH masses of
AGN hosted in pseudobulges 0.5 dex smaller than in classical bulges.
Assuming the same average factor for both populations, a difference of
0.2 dex is still found.Comment: 11 pages, 2 figures, 4 tables, accepted for publication on A&
Ten years of aero-servo-elastic tests at large POLIMI’s wind tunnel for active flutter control and loads alleviation
From car to bike. Marketing and dialogue as a driver of change
The Paris Climate Agreement has sent a key message to the international community regarding the need to increase efforts to move towards a low-carbon economy and help slow climate change, while underpinning global long-term economic growth and sustainable development. COP 21 recognizes the social, economic and environmental value of voluntary mitigation actions and their co-benefits for adaptation, health and sustainable development. In this framework, the PTP Cycle project, running from 2013 to 2016 and funded by the European Commission through the Intelligent Energy Europe program, introduces a non-market approach through voluntary participation in the adoption of sustainable transport modes such as cycling, based on marketing to potential customers through Personalized Travel Plans. The medium-sized city of Burgos (Spain) and the cities of Ljubljana, Riga, Antwerp and London
(boroughs of Haringey and Greenwich) developed a new policy instrument (Personalized Travel Plans) in order to increase bike patronage. Beyond potential savings of CO2, the results show that PTP as a form of Active Mobility Consultancy is a suitable instrument to influence modal shift to public transport, walking and cycling, and to address the challenges of climate change, while fostering sustainable transportation by changing mobility behaviour. These results, matching with the state-of-the-art of studies and pilot applications in other countries, allows deriving differentiated results for medium-size and large urban areas
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