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Sebastian Heinz Andrea Merloni Tiziana Di Matteo Rashid Sunyaev 《Astrophysics and Space Science》2005,300(1-3):15-21
The scale invariance model (Heinz, S. and Sunyaev, R.A.: 2003, MNRAS 343, L59) can be used to derive robust scaling relations between the radio luminosity from accreting black holes and the black
hole mass and accretion rate. These relations agree well with the recently found “fundamental plane” of black hole activity
(Merloni, A., Heinz, S. and Di Matteo, T.: 2003, MNRAS 345, 1057). This relation provides a new, powerful tool for the comparison of jets from black holes of different masses and accretion
rates. The regression coefficients of this relation contain information about the nature of the X-ray emission mechanism driving
the correlation. We argue that X-ray synchrotron emission from the base of the jets is unlikely to be the dominant contribution
to the X-ray spectrum in most of the sources. 相似文献
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Dmytro M. Trots Alexander Kurnosov Leonid Vasylechko Marek Berkowski Tiziana Boffa Ballaran Daniel J. Frost 《Physics and Chemistry of Minerals》2011,38(7):561-567
A single crystal X-ray diffraction study on lithium tetraborate Li2B4O7 (diomignite, space group I41
cd) has been performed under pressure up to 8.3 GPa. No phase transitions were found in the pressure range investigated, and
hence the pressure evolution of the unit-cell volume of the I41
cd structure has been described using a third-order Birch–Murnaghan equation of state (BM-EoS) with the following parameters:
V
0
= 923.21(6) Å3, K
0
= 45.6(6) GPa, and K′ = 7.3(3). A linearized BM-EoS was fitted to the axial compressibilities resulting in the following parameters a
0
= 9.4747(3) Å, K
0a
= 73.3(9) GPa, K′
a
= 5.1(3) and c
0
= 10.2838(4) Å, K
0c
= 24.6(3) GPa, K′
c
= 7.5(2) for the a and c axes, respectively. The elastic anisotropy of Li2B4O7 is very large with the zero-pressure compressibility ratio β
0c
/β
0a
= 3.0(1). The large elastic anisotropy is consistent with the crystal structure: A three-dimensional arrangement of relatively
rigid tetraborate groups [B4O7]2− forms channels occupied by lithium along the polar c–axis, and hence compression along the c axis requires the shrinkage of the lithium channels, whereas compression in the a direction depends mainly on the contraction of the most rigid [B4O7]2− units. Finally, the isothermal bulk modulus obtained in this work is in general agreement with that derived from ultrasonic
(Adachi et al. in Proceedings-IEEE Ultrasonic Symposium, 228–232, 1985; Shorrocks et al. in Proceedings-IEEE Ultrasonic Symposium, 337–340, 1981) and Brillouin scattering measurements (Takagi et al. in Ferroelectrics, 137:337–342, 1992). 相似文献
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Jörg M. Colberg Tiziana Di Matteo 《Monthly notices of the Royal Astronomical Society》2008,387(3):1163-1178
We make use of the first high-resolution hydrodynamic simulations of structure formation which self-consistently follows the build-up of supermassive black holes (BHs) introduced in Di Matteo et al. to investigate the relation between BHs, host halo and large-scale environment. There are well-defined relations between halo and BH masses and between the activities of galactic nuclei and halo masses at low redshifts. A large fraction of BHs forms anti-hierarchically, with a higher ratio of BH to halo mass at high than at low redshifts. At z = 1 , we predict group environments (regions of enhanced local density) to contain the highest mass and most active (albeit with a large scatter) BHs while the rest of the BH population to be spread over all densities from groups to filaments and voids. Density dependencies are more pronounced at high rather than low redshift. These results are consistent with the idea that gas rich mergers are likely the main regulator of quasar activity. We find star formation to be a somewhat stronger and tighter function of local density than BH activity, indicating some difference in the triggering of the latter versus the former. There exist a large number of low-mass BHs, growing slowly predominantly through accretion, which extends all the way into the most underdense regions, that is, in voids. 相似文献
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The anisotropic modelling of intensity distribution, affected by the construction of macroseismic planes, allows an analysis of the influence of each point of observed intensity on the analytical determination of epicenter and of the principal attenuation directions. Such a procedure is a vital aid in the cases in which the observed intensity points, that, for location or joined intensity level, are not consistent with an anisotropic model of intensity attenuation. A suitable filtering on intensity levels associated with the points of the intensity map, for a better modelling of observed intensity distribution, is proposed with the aim of a better seismic hazard evaluation. 相似文献
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The taxonomic richness and geographic distribution of sponges stranded along Sardinian shores were investigated in the long term by means of a revisited ancient sampling method in order to support a comprehensive species inventory. Almost all stranded species were Keratosa (n = 20), plus 6 species of other Demospongiae taxa. Dictyoceratida were dominant, with 6 genera and 19 species of the families Irciniidae, Spongiidae and Thorectidae: 9 Mediterranean endemics, 7 Atlanto‐Mediterranean and 3 widespread species. Regarding Dendroceratida, only the genus Spongionella was found. Some species (n = 8) were recorded for the first time in circum‐Sardinian seas. A high percentage (54.3%; 19 out of the 35 species) of the total Mediterranean Dictyoceratida fauna was recorded, including the most endangered Mediterranean species, that is of the genera Spongia and Hippospongia. Hippospongia communis, Ircinia variabilis, Spongia zimocca and Spongia officinalis were the most common species. Morphotraits of rare and/or poorly known species were investigated by scanning electron microscopy (SEM). Comparison among Sardinian sectors, and between Sardinian and adjacent seas, revealed a high similarity of stranded Dictyoceratida, despite the fact that the data from Tyrrhenian and Balearic–Catalan seas were collected mainly from SCUBA records. The cost‐effective sampling method used in the present study seems appropriate to the gross qualitative monitoring of coastal areas (e.g. large unexplored Northern African coasts), in order to assess the conservation status of Mediterranean Keratosa species. The wide distribution of all Mediterranean bath sponge species indicates their good conservation status in circum‐Sardinian seas, a datum that could usefully support the future management of this bioresource, particularly in protected areas. 相似文献
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This paper reconstructs the use of space and defines activity areas within a single hut (Hut 8) at the Early Bronze Age village of Afragola (southern Italy). The village, consisting of a number of huts and other structures, was covered by approximately 1m of volcanic ash during the eruption of Vesuvius in 3550 ± 20BP. Thirteen samples were collected from inside the hut to analyze the spatial variability in sedimentary characteristics among three areas of Hut 8—the apsidal, central, and entrance areas. The micromorphological analysis revealed details about the occupation surface and its relationship to features and material remains in the hut not apparent in the field. The apsidal area was probably used for storage but not of solids, as no significant quantities of organic material were found. The central area contains a small oven, calcareous ash from fires, and organic material composed of charred remains and bone fragments and was likely used for small‐scale household tasks. A possible connection exists between the lithics and the microstratigraphic sequencing in the area west of the oven, suggesting that people congregated there to perform specific tasks. The entrance area contains highly compacted and heterogeneous sediments that were brought in from outside. Notable is the paucity of anthropogenic materials found inside the hut, especially given the remarkable preservation offered by the thick cover of volcanic ash. We hypothesize that Hut 8 was not occupied long enough to produce a large amount of debris or that it had limited indoor activities and was thoroughly cleaned. © 2010 Wiley Periodicals, Inc. 相似文献