High energy phenomena in eta carinae     

Roberto F. Viotti  Lucio Angelo Antonelli  Sonja Rebecchi  Corinne Rossi 《Journal of Astrophysics and Astronomy》2002,23(1-2):19-22

We have investigated with BeppoSAX the long term behaviour of the harder X-ray component of the supposed supermassive binary system η Car along its 5.52 year cycle. We have found that in March 1998 during egress from the last December 1997 eclipse, this component was the same as outside eclipse, but for a large (×3.5) increase of NH _h , that can be attributed to the presence or formation of opaque matter in front of the source near periastron. Unexpectedly, at that time the iron 6.7 keV emission line was 40% stronger. BeppoSAX has for the first time found ahard X-ray tail extending to at least 50 keV, that cannot be adequately fitted with an additional hotter thermal component. The 2–100 keV spectrum of η Car is instead well fitted with an absorbed powerlaw spectrum with photon index 2.53, suggesting non-thermal emission as an alternative model for the core source.  相似文献   

The soilmodels.info project   总被引：1，自引：0，他引：1  

Gerd Gudehus  Angelo Amorosi  Antonio Gens  Ivo Herle  Dimitrios Kolymbas  David Mašín  David Muir Wood  Andrzej Niemunis  Roberto Nova  Manuel Pastor  Claudio Tamagnini  Gioacchino Viggiani 《国际地质力学数值与分析法杂志》2008,32(12):1571-1572

  相似文献   

Gas hydrate and free gas distribution from inversion of seismic data on the South Shetland margin (Antarctica)   总被引：2，自引：0，他引：2  

Tinivella  Umberta  Accaino  Flavio  Camerlenghi  Angelo 《Marine Geophysical Researches》2002,23(2):109-123

Travel-time inversion is applied to seismic data to produce acoustic velocity images of the upper 800 m of the South Shetland margin (Antarctic Peninsula) in three different geological domains: (i) the continental shelf; (ii) the accretionary prism; (iii) the trench. The velocity in the continental shelf sediments is remarkably higher, up to 1000 m/s at 600–700 m below seafloor, than that of the other two geological domains, due to the sediment overcompaction and erosion induced by the wax and waning of a grounded ice sheet. Pre-stack depth migration was applied to the data in order to improve the seismic image and to test the quality of the velocity fields. Where the Bottom Simulating Reflector (BSR) is present, positive and negative velocity anomalies were found with respect to a reference empirical velocity profile. The 2D-velocity section was translated in gas hydrate and free gas distribution by using a theoretical approach. The analysis revealed that the BSR is mainly related to the presence of free gas below it. The free gas is distributed in the area with variable concentration and thickness, while the gas hydrate is quite uniformly distributed across the margin.  相似文献   

Heavy metals in marine sediments of Taranto Gulf (Ionian Sea, Southern Italy)   总被引：5，自引：0，他引：5  

Alessandro Buccolieri  Giovanni Buccolieri  Nicola Cardellicchio  Angelo Dell'Atti  Antonella Di Leo  Antonella Maci 《Marine Chemistry》2006,99(1-4):227

Al, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Ti and Zn concentrations have been determined in surface sediment samples collected in the Taranto Gulf (Ionian Sea, Southern Italy) in order to evaluate their levels and spatial distribution in this important area of the Mediterranean Sea. For various metals, the geoaccumulation index has been calculated as a criterion to assess if their concentrations represent contamination levels or can be considered as background levels. The results show that metals concentrations in sediments can be considered near the background levels found in the Mediterranean Sea.Analytical results have been elaborated by using a Geographical Information System (GIS) software to show metals accumulation areas. Using multivariate statistical analysis, we evaluate the possibility to distinguish the sampling stations, in relation to their geographical position. Results have showed metals distribution in the Taranto Gulf is principally influenced by industrial and urban wastes, located mostly in the northern coastal area of the Ionian Sea. Rivers in the Basilicata region and prevailing anticlockwise marine currents are further factors influencing metal accumulation in sediments.  相似文献   

Fractional crystallization models and B–Be–Li systematics at Mt Somma-Vesuvius volcano (Southern Italy)     

Angelo Paone 《International Journal of Earth Sciences》2008,97(3):635-650

A compilation of B–Be–Li data on rocks that cover the entire eruptive history of Somma-Vesuvius is presented and interpreted in the light of evolution models for the Somma-Vesuvius rocks. Using major and trace element data, fractional crystalllization models are presented for different geochemical units. These data were used to constrain the source mineralogy of the Somma-Vesuvius rocks (ol-opx-cpx-gar-amp of 0.4-0.3-0.1-0.1-0.1), the amount of sediment added (5–10%) and the melt fraction from batch partial melting computations (0.05–0.1). From the B–Li data it is inferred that the main process responsible for the B isotopic signature is sediment recycling. However, the B–Li data show a major variation in Li abundances respect to B which is explained with Li dehydration before the fluid enriched the mantle wedge that produced the arc magmas. The Somma-Vesuvius B isotope composition is intermediate between that of the Campi Flegrei and the broad field of the Eolian Island arc. A low Be isotopes in the recent volcanic rocks can be explained as: (a) the top 1–22 m of the incoming sediment is accreted, (b) large amounts of sediment erosion, (c) a slow rate of subduction which have provoked a long magmatic history for the Vesuvius magma, (d) the sediment component takes several Myr longer than the subducting plate to reach the magma source region beneath Italy.  相似文献   

Verification of the dualism ordering method by the canonical correspondence analysis: fish community samples     

Tadeusz Penczak  Francisco Godinho  Angelo A. Agostinho 《Limnologica》2002,32(1)

Two ordination techniques (Romaniszyn diagram, RD, and Canonical correspondence analysis, CCA) were applied to the same data set (fish assemblage composition along two Paraná river tributaries and associated environmental variables), to identify spatial community patterns and further to evaluate the performance of RD. The major patterns in these Brazilian streams were successfully revealed by both methods (i.e. clear separation of both tributaries on the basis of fish assemblage composition and environmental factors), but more complex situations may limit the application of RD in comparison with CCA.  相似文献   

An approach for quantifying geomorphological impacts for EIA of transportation infrastructures: a case study in northern Spain   总被引：2，自引：0，他引：2  

Jaime Bonachea  Viola Maria Bruschi  Juan Remondo  Alberto Gonzlez-Díez  Luis Salas  Jurjen Bertens  Antonio Cendrero  Csar Otero  Cecilia Giusti  Andrea Fabbri  Jos Ramn Gonzlez-Lastra  Jos María Aramburu 《Geomorphology》2005,66(1-4):95

A methodological proposal for the assessment of impacts due to linear infrastructures such as motorways, railways, etc. is presented. The approach proposed includes a series of specific issues to be addressed for each geomorphological feature analysed—both ‘static’ and ‘dynamic’—as well as a series of steps to be followed in the process.Geomorphic characteristics potentially affected were initially identified on the basis of a conceptual activities/impacts model that helps to single out geomorphic impacts related to environmental concerns for the area. The following issues were addressed for each individual impact: nature of potential effects; indicators that can be used to measure impacts; criteria of ‘geomorphologic performance’; procedure for measurement/prediction of changes; translation of geomorphologic impacts into significant terms from the viewpoint of human concerns; possible mitigation and/or compensation measures.The procedure has been applied to a case study corresponding to a new motorway in the Basque Country, northern Spain. Geomorphological impacts considered in this analysis included: (1) consumable resources; (2) sites of geomorphological interest; (3) land units with high potential for use, high productivity or value for conservation; (4) visual landscape; (5) slope instability processes. The procedure has been designed for implementation in a Geographic Information System (GIS) environment. Details are given on the application of the method to each individual impact analysed and results are presented in both numerical and map form.Impacts assessed were initially expressed by means of heterogeneous magnitudes, depending on the geomorphological feature considered. Those geomorphological impacts were then translated into significant terms and homogeneous magnitudes. Integration was carried out on the basis of impact values thus obtained. Final integrated results were also expressed in numerical and map form.The method proposed enables comparison of alternatives as well as ‘prediction’ and assessment of impacts in terms directly related to geomorphic characteristics. It also facilitates the expression of those impacts in terms that allow integration with other types of environmental impacts.  相似文献   

Geological mapping reveals the role of Early Jurassic rift architecture in the dispersal of calciturbidites: New insights from the Central and Northern Apennines     

Angelo Cipriani  Martina Caratelli  Massimo Santantonio 《Basin Research》2020,32(6):1485-1509

  相似文献   

Salinity and periodic inundation controls on the soil‐plant‐atmosphere continuum of gray mangroves          下载免费PDF全文

Saverio Perri  Francesco Viola  Leonardo Valerio Noto  Annalisa Molini 《水文研究》2017,31(6):1271-1282

Salinity and periodic inundation are both known to have a major role in shaping the ecohydrology of mangroves through their controls on water uptake, photosynthesis, stomatal conductance, gas exchanges, and nutrient availability. Salinity, in particular, can be considered one of the main abiotic regulating factors for halophytes and salt‐tolerant species, due to its influence on water use patterns and growth rate. Ecohydrological literature has rarely focused on the effects of salinity on plant transpiration, based on the fact that the terrestrial plants mostly thrive in low‐saline, unsaturated soils where the role of osmotic potential can be considered negligible. However, the effect of salinity cannot be neglected in the case of tidal species like mangroves, which have to cope with hyperosmotic conditions and waterlogging. We introduce here a first‐order ecohydrological model of the soil/plant‐atmosphere continuum of Avicennia marina—also known as gray mangrove—a highly salt‐tolerant pioneer species able to adapt to hyperarid intertidal zones and characterized by unique morphological and ecophysiological traits. The A. marina's soil‐plant‐atmosphere continuum takes explicitly into account the role of water head, osmotic water potential, and water salinity in governing plant water fluxes. A. marina's transpiration is thus modeled as a function of salinity based on a simple parameterization of salt exclusion mechanisms at the root level and a modified Jarvis' expression accounting for the effects of salinity on stomatal conductance. Consistently with previous studies investigating the physiology of mangroves in response to different environmental drivers, our results highlight the major influence of salinity on mangrove transpiration when contrasted with other potential stressors such as waterlogging and water stress.  相似文献   

High-P (P = 1.5–1.8 GPa) blueschist from Elba: Implications for underthrusting and exhumation of continental units in the Northern Apennines     

Samuele Papeschi  Giovanni Musumeci  Hans-Joachim Massonne  Francesco Mazzarini  Eric James Ryan  Giulio Viola 《Journal of Metamorphic Geology》2020,38(5):495-525

The Acquadolce Subunit on the Island of Elba, Italy, records blueschist facies metamorphism related to the Oligocene–early Miocene stages of continental collision in the Northern Apennines. The blueschist facies metamorphism is represented by glaucophane- and lawsonite-bearing metabasite associated with marble and calcschist. These rock types occur as lenses in a schistose complex representing foredeep deposits of early Oligocene age. Detailed petrological analyses on metabasic and metapelitic protoliths, involving mineral and bulk-rock chemistry coupled with P–T and P–T–X(Fe₂O₃) pseudosection modelling using PERPLE_X, show that the Acquadolce Subunit recorded nearly isothermal exhumation from peak pressure–temperature conditions of 1.5–1.8 GPa and 320–370°C. During exhumation, peak lawsonite- and possibly carpholite- or stilpnomelane-bearing assemblages were overprinted and partially obliterated by epidote-blueschist and, subsequently, albite-greenschist facies metamorphic assemblages. This study sheds new light on the tectonic evolution of Adria-derived metamorphic units in the Northern Apennines, by showing (a) the deep underthrusting of continental crust during continental collision and (b) rapid exhumation along ‘cold’ and nearly isothermal paths, compatible with syn-orogenic extrusion.  相似文献