Stability of the sponge assemblage of Mediterranean coralligenous concretions along a millennial time span     

Marco Bertolino  Barbara Calcinai  Riccardo Cattaneo‐Vietti  Carlo Cerrano  Anna Lafratta  Maurizio Pansini  Daniela Pica  Giorgio Bavestrello 《Marine Ecology》2014,35(2):149-158

The Mediterranean coralligenous substratum is a hard bottom of biogenic origin, mainly composed of calcareous algae, growing in dim light conditions. Sponges are among of the most representative taxa of the coralligenous assemblages, with more than 300 recorded species of different habits: massive, erect, boring and insinuating. When sponges die, their siliceous spicules remain trapped in the biogenic concretion, offering the opportunity to describe the coralligenous spongofauna over a very long span of time, virtually dating back to a large part of the Holocene period. The data reported here were obtained from core samples collected from four coralligenous concretions. Each block was collected in a different locality of the Ligurian Sea: Santo Stefano Shoals, Bogliasco, Punta del Faro (Portofino Promontory) and Punta Manara. Radiocarbon age determinations indicate for these conglomerates a maximal age between 1600 and 3100 years. The spicules trapped in the cores show deep dissolution marks in the form of circular holes on their surface or present an enlargement of the axial canal. However, their original shape, generally intact, suggests the absence of mechanical injuries and allows a tentative identification at the species level. The analysis of these old spicules reveals an ancient sponge assemblage composed of 30 recognisable species. This indicates that almost one half of the sponge community today settled on coralligenous substrata has been present in the conglomerates for their entire existence.  相似文献   

Multi-frame and multi-dimensional historical digital cities: the Como example     

Luana Valentini  Maria Antonia Brovelli  Giorgio Zamboni 《International Journal of Digital Earth》2014,7(4):336-350

In this article, we present the realisation of a multi-frame and multi-dimensional WebGIS that allows users to simultaneously analyse a specific portion of the Earth taking into account the historical information, too. Two graphical panels have been realised: one for the usual 2D view and one for a more realistic 3D view. Both panels display historical maps of the city, the current orthophoto and the digital topographical map. The 3D frame is based on NASA World Wind, an open source virtual globe from where 3D buildings are shown extruding the 2D shapes using their mean height. Thanks to a specifically designed graphical user interface, it is also possible to dynamically thematise the buildings on the globe according to different criteria (e.g. the construction time span) so that only the geometries fulfilling the request are turned on. Within the proposed application, a synchronisation between the two panels has been implemented, in order to maintain a constant alignment of the two viewers. The application is also open to the time dimension. In fact, assigning to each geometry two dates (e.g. ‘year of construction’ and ‘year of demolition’), it is possible to dynamically view how buildings have changed over time, both in their shape and height. Future developments of this work will concern the possibility of implementing a city model with a higher level of detail.  相似文献   

Analysis of fibrous zeolites in the volcanic deposits of the Viterbo Province,Italy     

Andrea Cattaneo  Andrea Rossotti  Giorgio Pasquarè  Anna Somigliana  Domenico M. Cavallo 《Environmental Earth Sciences》2011,63(4):861-871

Since Etrurian age, the Viterbo Province (Central Italy) is famous for its ancient towns carved out of local ignimbrite deposits which geologically represent the sedimentation of pumice-rich, volcano-related pyroclastic flows. Almost the entire study area is geologically characterized by a thick succession of ignimbrites, tephra fallouts and lava flow deposits locally subjected to zeolitization. Among zeolites, fibrous erionite represents a well-known health hazard and so this work aims at locating and quantifying the presence of fibrous zeolites in volcanic deposits of the Viterbo area, suggesting at the same time a standard operational procedure useful in other areas showing the same possible hazard. 41 samples collected in the Viterbo area were analyzed by X-ray powder diffraction, optical and electron microscopy. Fibrous zeolites were detected in five samples and quantified in amounts ranging from 0.35 to 1.66% vol. They generally occur in tetragonal or orthorhombic prismatic habit and showed chemical composition mainly consistent with K-phillipsite. Fibrous zeolites occurred with aspect ratios (mean = 6.3), comparable or lower than those of erionite fibers reported in previous studies and mean diameters >3 μm.  相似文献   

The iron Kα Compton shoulder in transmitted and reflected spectra     

Giorgio Matt 《Monthly notices of the Royal Astronomical Society》2002,337(1):147-150

We calculate the equivalent width of the core, and the centroid energy and relative flux of the first-order Compton shoulder of the iron Kα emission line from neutral matter. The calculations are performed with Monte Carlo simulations. We explore a large range of column densities for both transmitted and reflected spectra, and study the dependence on the iron abundance. The Compton shoulder is now becoming observable in many objects thanks to the improved sensitivity and/or energy resolution of the XMM – Newton and Chandra satellites, and the present work aims to provide a tool to derive information on the geometry and element abundances of the line-emitting matter from Compton shoulder measurements.  相似文献   

On the use of infinite elements in the analysis of two-dimensional layered elastic systems via discretized integral equations     

Cristina Jommi  Giorgio Novati 《Computers and Geotechnics》1989,8(4):269-288

A boundary integral equation approach is presented for the two-dimensional plane strain analysis of horizontally layered elastic systems resting on a rough and rigid base. The validity of Somigliana identity for unbounded layers is discussed and an Infinite Boundary Element is proposed in order to take into account the lateral unboundedness of the physical problem in the discretized equations. This element is implemented in a computer code based on a successive stiffness solution procedure. A series of numerical tests concerning single- and multi-layered problems is illustrated, and the performance of the proposed solution method is compared with that of more traditional boundary element and finite element techniques.  相似文献   

High Energy Astrophysics with INTEGRAL     

Giorgio G.C. Palumbo 《Astrophysics and Space Science》2001,276(1):325-331

INTEGRAL is an ESA mission scheduled to be launched in 2001. Its fourcoaligned instruments will allow observations of cosmic sources from afraction of a keV to several MeV plus source monitoring in the opticalband. INTEGRAL will be operated as a space observatory and an Announcementof Opportunity to the astronomical community at large will be issued byESA in the spring of the year 2000. Purpose of this paper is to illustrateINTEGRAL capabilities of the three X and Gamma Ray detectors plus opticalmonitor in order to help potential users to write observing proposals.  相似文献   

    

Giuseppe Gambolati  Giorgio Galeati 《Mathematical Geology》1987,19(3):249-257

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Direct,partitioned and projected solution to finite element consolidation models     

Giuseppe Gambolati  Giorgio Pini  Massimiliano Ferronato 《国际地质力学数值与分析法杂志》2002,26(14):1371-1383

Direct, partitioned, and projected (conjugate gradient‐like) solution approaches are compared on unsymmetric indefinite systems arising from the finite element integration of coupled consolidation equations. The direct method is used in its most recent and computationally efficient implementations of the Harwell Software Library. The partitioned approach designed for coupled problems is especially attractive as it addresses two separate positive definite problems of a smaller size that can be solved by symmetric conjugate gradients. However, it may stagnate and when converging it does not prove competitive with a global projection method such as Bi‐CGSTAB, which may take full advantage of its flexibility in working on scaled and reordered equations, and thus may greatly improve its computational performance in terms of both robustness and convergence rate. The Bi‐CGSTAB superiority to the other approaches is discussed and demonstrated with a few representative examples in two‐dimensional (2‐D) and three‐dimensional (3‐D) coupled consolidation problems. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Integrated approach to choosing suitable areas for the realization of productive wells in rural areas of sub-Saharan Africa     

Giorgio Ghiglieri  Alberto Carletti 《水文科学杂志》2013,58(8):1357-1370

Abstract

Comprehensive geological, hydrogeological and hydrogeochemical investigations were carried out in the south of Hodh El Chargui (southeast Mauritania). Obtaining a hydrogeological conceptual model is crucial for groundwater resources development and management. This is especially true in developing countries and in the rural areas of sub-Saharan Africa. The chosen areas are represented by lithologies referring to a long geological time frame, dating from the Upper Neoproterozoic to the Quaternary age. We developed a methodology in order to identify sites that were suitable for the realization of productive, protected and correct wells to supply safe water to the rural community. A multicriteria approach to studying hydrogeology was used in the project area. In order to identify some main areas in which to carry out pilot interventions, criteria relating to water accessibility and availability, and to hydrogeological and water quality, were considered. Moreover, during the project, it was possible to transfer know-how and hand over responsibilities to the local population and bodies.

Citation Ghiglieri, G. & Carletti, A. (2010 Ghiglieri, G., Balia, R., Oggiano, G. and Pittalis, D. 2010. Prospecting for safe (low fluoride) groundwater in the Eastern African Rift: the Arumeru District (Northern Tanzania). Hydrol. Earth System Sci., 14: 1081–1091.  [Google Scholar]) Integrated approach to choosing suitable areas for the realization of productive wells in rural areas of sub-Saharan Africa. Hydrol. Sci. J. 55(8), 1357–1370.  相似文献   

Multi-methodological investigation of kunzite, hiddenite, alexandrite, elbaite and topaz, based on laser-induced breakdown spectroscopy and conventional analytical techniques for supporting mineralogical characterization     

Manuela Rossi  Marcella Dell’Aglio  Alessandro De Giacomo  Rosalba Gaudiuso  Giorgio Saverio Senesi  Olga De Pascale  Francesco Capitelli  Fabrizio Nestola  Maria Rosaria Ghiara 《Physics and Chemistry of Minerals》2014,41(2):127-140

Gem-quality alexandrite, hiddenite and kunzite, elbaite and topaz minerals were characterized through a multi-methodological investigation based on EMPA-WDS, LA-ICP-MS, and laser-induced breakdown spectroscopy (LIBS). With respect to the others, the latter technique enables a simultaneous multi-elemental composition without any sample preparation and the detection of light elements, such as Li, Be and B. The criteria for the choice of minerals were: (a) the presence of chromophore elements in minor contents and/or as traces; (b) the presence of light lithophile elements (Li, Be and B); (c) different crystal chemistry complexity. The results show that LIBS can be employed in mineralogical studies for the identification and characterization of minerals, and as a fast screening method to determine the chemical composition, including the chromophore and light lithophile elements.  相似文献