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91.
XMM-Newton is a major X-ray observatory of the European Space Agency (ESA). Its observing time is open to astronomers from the whole scientific community on a peer reviewed competitive basis. The Science Operations Centre, located at ESA’s premises in Villafranca del Castillo, Spain, is responsible for the instrument operations, as well as for all the tasks related to facilitating the scientific exploitation of the data which the mission has been producing since its launch in December 1999. Among them, one may list:
Everyone can be an XMM-Newton observer. So far, astronomers from 36 countries submitted observing programs. Public data can be accessed by every scientist in the world through the XMM-Newton Science Archive (XSA).Despite all these efforts, one can’t help noticing an asymmetric level of scientific exploitation in the realm of X-ray astronomy between developing and developed countries. The latter have traditionally enjoyed the comparative advantage of deeper know-how, deriving from direct experience in hardware and mission development. The XMM-Newton Science Operations Centre’s efforts act to alleviate this situation through, for example, increasing the usage of the web for data and information dissemination, as well as by supporting actively such initiatives as the COSPAR Capacity-Building Workshops, specifically designed to create long-lasting bridges between researchers in developing and developed countries. 相似文献
• | distribution of scientific data in different formats, from raw telemetry, up to processed and calibrated high-level science products, such as images, spectra, source lists, etc; |
• | development and distribution of dedicated science analysis software, as well as of continuously updated instrument calibration; |
• | regular organisation of training workshops (free of cost), for potential users of XMM-Newton data, where the procedures and techniques to successfully reduce and analyze XMM-Newton data are introduced; |
• | access to the data through state-of-the-art, in-house-developed archival facilities, either through the Internet or via CD-ROM; |
• | continuously updated documentation on all aspects of spacecraft and instrument operations, data reduction and analysis; |
• | maintenance of a comprehensive set of project web pages; |
• | a competent and responsive HelpDesk, providing dedicated support to individual XMM-Newton users. |
92.
A. Di Matteo M. Milli Ph.D. 《International Journal of Environmental Science and Technology》2008,5(3):415-424
This paper outlines the results of a study recently carried out on the western coast of the Sestri Levante peninsula (Eastern Liguria-Italy), aiming to assess the effects of newly accomplished defensive measures against coastal erosion: the accretion of the beach with natural sand and its protection with artificial structures orthogonal and parallel to the shoreline. Through conventional and more innovative methodologies (respectively single beam echo sounders and global positioning system) the research work has resulted in a new evaluation of the morphological, bathymetric and sedimentological features that make up this shoreline and its volumetrical change over the century. The survey and the research carried out on the studied area have enabled us to give a more detailed picture of the evolution of the littoral, to assess the possible use of “non-traditional” techniques of beach development monitoring, to evaluate the volumetric variations of the emerged and submerged beaches, to establish the sedimentological activity of the beach after the latest nourishment measures, and finally, to verify the effectiveness of the protection measures implemented on this coastline. The acquired data have been stored in the database and a geographic information system has been used to process, analyze, and evaluate the results. The main findings show that the latest intervention has brought about a new phase in the evolution of the coastline, giving rise to a new pseudo-balanced condition. The re-distribution of materials used for the beach nourishment, leads us to believe that the defence underwater barrier has only partially worked. The main conclusion for a correct coastal zone management underline the necessity to plan local and more wide monitoring during at least 8–10 consecutive years. 相似文献
93.
This paper presents results from research on the hydraulic loadings of exposed (unsheltered) jetties (open pile piers with decks and beams). The work presented here focuses on results from physical model tests on wave-induced loads on deck and beam elements of exposed jetties and similar structures. These tests investigated the physics of the loading process, and provided new guidance on wave-in-deck loads to be used in design. Wave forces and pressures were measured on a 1:25 scale model of a jetty head with projecting elements. Structure geometry and wave conditions tested were selected after an extensive literature review (summarised in the paper) and consultation with the project steering group. Different configurations were tested to separate 2-d and 3-d effects, and to identify the effects of inundation and of down-standing beams. 相似文献
94.
Elisa Cenci Matteo PizzolonNicole Chimento Carlotta Mazzoldi 《Estuarine, Coastal and Shelf Science》2011
Deployed for diverse purposes, artificial substrata can, theoretically, act as fish attractors or as fish producers. We tested these hypotheses by comparing fish assemblages on two artificial hard substrata, the Ca’ Roman and Sottomarina jetties, before (1994 and 2003) and after (2005 and 2006) the deployment of a new breakwater in the area. Our results support the fish production hypothesis. A remarkable increase in richness and abundance of sedentary species was observed on the extant substrata with the presence of the new barrier. More mobile species showed less definite trends. The net result has been a total increase in abundance and richness in the area. While fish assemblage showed important temporal variation in composition before deployment (Ca’ Roman, comparison between 1994 and 2003), clear trends of increasing abundance were concurrent with the presence of the new barrier. This increase in abundance, particularly of sedentary species, may be attributed to enhanced connectivity and/or an improvement in larval retention due to the changes in water circulation connected with the new breakwater, or to an increase in juveniles and/or adults promoted by changes in environmental conditions. Indeed, changes in benthic cover were recorded, with an increase of uncovered rock and the appearance of previously unrecorded algae after breakwater deployment. 相似文献
95.
Giorgio Perrotta M. Stipa D. Silvi S. Coltellacci G. Curti G. Colonna T. Formica V. Casali T. Fossati F. Di Matteo M. Zelli M. Rinaldi L. Ansalone A. Di Salvo 《Experimental Astronomy》2011,32(1):63-82
The Mission MAGIA (Missione Altimetrica Geofisica GeochImica lunAre) was proposed in the framework of the ??Bando per Piccole Missioni?? of ASI (Italian Space Agency) in 2007. The mission was selected for a phase A study by ASI on February 7th 2008. The tight budget allocation, combined with quite ambitious scientific objectives, set challenging requirements for the satellite design. The paper gives a fast overview of the payloads complement and of the mission-constrained design drivers, including cost minimization, risk reduction, and AIT flexibility. The spacecraft architecture is then outlined, along with an overview of the key subsystems and trade-offs. Some details are given of a Moon gravitometric experiment based on a mother?Cdaughter satellite configuration with the daughter being a subsatellite released from the MAGIA satellite and intended to circle the Moon at a very low altitude. Budgets are appended at the end of the paper showing the key study results. 相似文献
96.
Giovanni De Giudici Riccardo Biddau Matteo Leoni 《Geochimica et cosmochimica acta》2005,69(16):4073-4083
The effect of lattice disorder and mineral surface area on the reactivity of finely ground fluorite was studied on ball-milled powders. Structural information was provided by X-ray whole powder pattern modeling (WPPM). The mean size of coherent scattering domains decreases with milling time from 70 nm to ∼20 nm, whereas the density of lattice defects increases with both time and intensity of milling treatment, from 4 × 1015 m-2 to 24 × 1015 m-2. High resolution transmission electron microscopy (HRTEM) of ground fluorite grains shows several line defects and a general tendency of nanometric crystalline domains to agglomerate in larger grains.Solution chemistry was investigated using batch reactors with free drift of solution saturation state with respect to fluorite. Total surface area was measured by the Brunaver, Emmet and Teller (BET) method, and dissolution rates were measured at pH = 2 (HCl) and T = 295 K. In far from equilibrium conditions, dissolution rates normalized by BET area do not increase with the dislocation density. In near-equilibrium condition, however, measured stationary ionic product clearly increases with both time and intensity of milling treatment. Thermodynamic predictions of the solubility constant indicate negligible or little effect of total surface area. Consequently, the observed increase in the stationary ionic product can be related to the increasing lattice defect content. This confirms the significant role of dislocation outcrops on mineral dissolution in close to equilibrium conditions. 相似文献
97.
T. Di Matteo 《Monthly notices of the Royal Astronomical Society》1998,299(1):L15-L20
A magnetically structured accretion disc corona, generated by buoyancy instability in the disc, can account for observations of flare-like events in active galactic nuclei. We examine how Petschek magnetic reconnection, associated with MHD turbulence, can result in a violent release of energy and heat the magnetically closed regions of the corona up to canonical X-ray emitting temperatures. X-ray magnetic flares, the after effect of the energy released in slow shocks, can account for the bulk of the X-ray luminosity from Seyfert galaxies and consistently explain the observed short-time-scale variability. 相似文献
98.
Matteo Guainazzi 《Monthly notices of the Royal Astronomical Society》2002,329(1):L13-L17
In this paper, a BeppoSAX observation of the bright Seyfert 2 galaxy NGC 6300 is presented. The rapidly variable emission from the active nucleus is seen through a Compton-thin absorber. A Compton-reflection component with an unusually high reflection fraction , and the comparison with a reflection-dominated spectrum measured by RXTE two and half years earlier suggest that NGC 6300 belongs to the class of 'transient' active galactic nucleus, undergoing long and repeated periods of low activity. The spectral transition provides support to the idea that Compton-thick and Compton-thin X-ray absorbers in Seyfert 2 galaxies are decoupled, the former being most likely associated with the 'torus', whereas the latter is probably located at much larger distances. 相似文献
99.
Paolo Padovani Eric Perlman Hermine Landt Paolo Giommi Matteo Perri 《Astrophysics and Space Science》2004,294(1-2):71-78
We present a new population of radio quasars whose X-ray band, unlike previously known sources which have (flat) inverse Compton
radiation, is characterized by (steep) synchrotron emission, with a broad-band spectral energy distribution similar to that
of BL Lacs with high energy synchrotron peaks. We discuss how this new class was discovered, the class properties, and the
implications of its existence for our understanding of jets and active galactic nuclei in general. 相似文献
100.