The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
P Rafanelli - One of the best experts on this subject based on the ideXlab platform.
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unveiling the Submerged Part of the iceberg radio loud narrow line seyfert 1s with ska
Proceedings of The many facets of extragalactic radio surveys: towards new scientific challenges — PoS(EXTRA-RADSUR2015), 2016Co-Authors: M Berton, L Foschini, A Caccianiga, Jennifer Lee Richards, S Ciroi, E Congiu, V Cracco, Giovanni La Mura, Luca Marafatto, P RafanelliAbstract:M. Berton∗ , L. Foschini, A. Caccianiga, J. L. Richards, S. Ciroi, E. Congiu, V. Cracco, G. La Mura, L. Marafatto, P. Rafanelli 1 DiPartimento di Fisica e Astronomia "G. Galilei", Universita di Padova, Vicolo dell’osservatorio 3, 35122, Padova, Italy 2 INAF Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807, Merate (LC), Italy; 3 DePartment of Physics and AStronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USA; 4 INAF Osservatorio Astronomico di Padova, Vicolo dell’osservatorio 5, 35122, Padova, Italy. E-mail: marco.berton.1@studenti.unipd.it
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unveiling the Submerged Part of the iceberg radio loud narrow line seyfert 1s with ska
arXiv: Astrophysics of Galaxies, 2016Co-Authors: M Berton, L Foschini, A Caccianiga, Jennifer Lee Richards, S Ciroi, E Congiu, V Cracco, Giovanni La Mura, Luca Marafatto, P RafanelliAbstract:Narrow-line Seyfert 1 galaxies (NLS1) are active galactic nuclei (AGN) known to have small masses of the central black hole and high accretion rates. NLS1s are generally radio-quiet, but a small Part of them (about 7\%) are radio-loud. The recent discovery of powerful relativistic jets in radio-loud NLS1s (RLNLS1s), emitting at high-energy $\gamma$-rays, opened intriguing questions. The observed luminosity of the jet is generally weak, smaller than blazars, although when rescaled for the mass of the central black hole, it becomes of the same order of magnitude of the latter. The weak luminosity, and hence observed flux, resulted in a small number of known RLNLS1. From a recent survey of RLNLS1s, it was found that only 8 out of 42 sources had radio flux density at 1.4 GHz greater than 100 mJy, while 21 out of 42 had flux density smaller than 10 mJy. In addition, given the strong variability at all wavelengths, with present-day facilities RLNLS1s can often only be detected during high activity periods. The Square Kilometer Array (SKA), with its superior sensitivity, will break this limit, allowing us to unveil a relatively unknown population of jetted AGN. We present the results of a study aimed at evaluating the scenario that could emerge after the advent of SKA.
J C C Henriques - One of the best experts on this subject based on the ideXlab platform.
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model prototype similarity of oscillating water column wave energy converters
International Journal of Marine Energy, 2014Co-Authors: A.f. De O. Falcão, J C C HenriquesAbstract:Abstract Model testing in wave tanks or under sheltered sea conditions is an essential step in the development of wave energy converters. The paper focuses on the rules for geometric, hydrodynamic, thermodynamic and aerodynamic similarity in model testing of wave energy converters of oscillating-water-column (OWC) type, with emphasis on air compressibility effects in the air chamber and on air turbine aerodynamics. It is shown that the correct volume scale ratio for the air chamber is far from identical to the volume scale ratio for the Submerged Part of the converter, and should take into account the thermodynamics of the compressible flow through the air turbine or through the turbine simulator (orifice or other). For those cases when the model is large enough to be fitted with a scaled air turbine, dimensional analysis is applied to obtain ratios for turbine size and rotational speed, and also to establish relationships between rotational speed control algorithms. A numerical example is presented to illustrate the importance of appropriately simulating the air compressibility effects when testing at model scale.
M Berton - One of the best experts on this subject based on the ideXlab platform.
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unveiling the Submerged Part of the iceberg radio loud narrow line seyfert 1s with ska
Proceedings of The many facets of extragalactic radio surveys: towards new scientific challenges — PoS(EXTRA-RADSUR2015), 2016Co-Authors: M Berton, L Foschini, A Caccianiga, Jennifer Lee Richards, S Ciroi, E Congiu, V Cracco, Giovanni La Mura, Luca Marafatto, P RafanelliAbstract:M. Berton∗ , L. Foschini, A. Caccianiga, J. L. Richards, S. Ciroi, E. Congiu, V. Cracco, G. La Mura, L. Marafatto, P. Rafanelli 1 DiPartimento di Fisica e Astronomia "G. Galilei", Universita di Padova, Vicolo dell’osservatorio 3, 35122, Padova, Italy 2 INAF Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807, Merate (LC), Italy; 3 DePartment of Physics and AStronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USA; 4 INAF Osservatorio Astronomico di Padova, Vicolo dell’osservatorio 5, 35122, Padova, Italy. E-mail: marco.berton.1@studenti.unipd.it
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unveiling the Submerged Part of the iceberg radio loud narrow line seyfert 1s with ska
arXiv: Astrophysics of Galaxies, 2016Co-Authors: M Berton, L Foschini, A Caccianiga, Jennifer Lee Richards, S Ciroi, E Congiu, V Cracco, Giovanni La Mura, Luca Marafatto, P RafanelliAbstract:Narrow-line Seyfert 1 galaxies (NLS1) are active galactic nuclei (AGN) known to have small masses of the central black hole and high accretion rates. NLS1s are generally radio-quiet, but a small Part of them (about 7\%) are radio-loud. The recent discovery of powerful relativistic jets in radio-loud NLS1s (RLNLS1s), emitting at high-energy $\gamma$-rays, opened intriguing questions. The observed luminosity of the jet is generally weak, smaller than blazars, although when rescaled for the mass of the central black hole, it becomes of the same order of magnitude of the latter. The weak luminosity, and hence observed flux, resulted in a small number of known RLNLS1. From a recent survey of RLNLS1s, it was found that only 8 out of 42 sources had radio flux density at 1.4 GHz greater than 100 mJy, while 21 out of 42 had flux density smaller than 10 mJy. In addition, given the strong variability at all wavelengths, with present-day facilities RLNLS1s can often only be detected during high activity periods. The Square Kilometer Array (SKA), with its superior sensitivity, will break this limit, allowing us to unveil a relatively unknown population of jetted AGN. We present the results of a study aimed at evaluating the scenario that could emerge after the advent of SKA.
Andrea Squartini - One of the best experts on this subject based on the ideXlab platform.
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rapid peat accumulation favours the occurrence of both fen and bog microbial communities within a mediterranean free floating peat island
Scientific Reports, 2017Co-Authors: Giuseppe Concheri, Piergiorgio Stevanato, Claudio Zaccone, William Shotyk, Valeria Dorazio, Teodoro Miano, Pietro Piffanelli, Valeria Rizzi, Chiara Ferrandi, Andrea SquartiniAbstract:The unique environment of a 4m-thick, free-floating peat island within the Posta Fibreno lake (Central Italy) was analyzed using DNA-based techniques to assess bacterial and fungal community members identity and abundance. Two depths were sampled at 41 and 279 cm from the surface, the former corresponding to an emerged portion of Sphagnum residues accumulated less than 30 yrs ago, and the latter mainly consisting of silty peat belonging to the deeply Submerged Part of the island, dating back to 1520-1660 AD. The corresponding communities were very diverse, each of them dominated by a different member of the Delta-proteobacteria class for prokaryotes. Among Eukaryotes, Ascomycota prevailed in the shallow layer while Basidiomycota were abundant in the deep sample. The identity of taxa Partitioning between acidic surface layer and neutral core is very reminiscent of the differences reported between bogs and fens respectively, supporting the view of Posta Fibreno as a relic transitional floating mire. Moreover, some microbial taxa show an unusual concurrent species convergence between this sub-Mediterranean site and far Nordic or circumpolar environments. This study represents the first report describing the biotic assemblages of such a peculiar environment, and provides some insights into the possible mechanisms of its evolution.
Catherine Pierre - One of the best experts on this subject based on the ideXlab platform.
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Paleo-environmental controls on cold seep carbonate authigenesis in the Sea of Marmara
Earth and Planetary Science Letters, 2013Co-Authors: Antoine Crémière, Germain Bayon, Emmanuel Ponzevera, Catherine PierreAbstract:The factors controlling fluid emission dynamics at ocean margins are poorly understood. In Particular, there are significant uncertainties on how fluid seepage at cold seeps may have responded to abrupt environmental changes in the geological past. This study reports on a detailed geochemical investigation of seafloor carbonate crusts sampled at cold seeps along the Submerged Part of the North Anatolian Fault system in the Sea of Marmara - an inland sea, which has experienced major paleo-environmental changes over the last deglaciation period. We also analyzed a series of authigenic carbonate concretions recovered from two sediment cores at the Western-High ridge, an active fluid venting area. The ages of seafloor carbonate crusts derived from isochron U-Th dating cover the last 7 kyr, suggesting that fluid activity along the fault system remained continuous over that time interval. In the sediment cores, carbonate concretions are concentrated at the lacustrine-to-marine transition, which corresponds to the period when Mediterranean waters flowed into the Marmara Basin about 12-14 kyr ago. U-Th isotopic data indicate that most of these concretions formed later during the Holocene, around 9-10 kyr ago, a period coinciding with an important anoxic event that led to the deposition of a sapropel layer in the Sea of Marmara. Based upon these results, we suggest that the absence of carbonate concretions in the lacustrine sediment unit indicates that dissolved sulfate concentrations in the Marmara lake pore waters during glacial time were too low to promote significant anaerobic methane oxidation, thereby preventing sedimentary carbonate authigenesis. In contrast, the progressive inflow of Mediterranean waters into the glacial Marmara lake after 15 ka provided a source of dissolved sulfate that allowed anaerobic oxidation of methane to proceed within the anoxic sediment. Importantly, the synchronism between the main phase of authigenic carbonate precipitation at the studied sites (average 9.4±1.8 ka, n=16) and the regional anoxic sapropel event support the idea that the drop in bottom water dissolved oxygen content was probably a key factor to enhance microbial activity and associated carbonate precipitation at that time. Overall, these results provide straightforward evidence that fluid emission dynamics and hydrocarbon oxidation at cold seeps can be directly related to changing environmental conditions through time.
