Cambro-Ordovician Magmatism in SE Brazil: U-Pb and Rb-Sr Ages, Combined with Sr and Nd Isotopic Data of Charnockitic Rocks from the Varzea Alegre Complex     

Julio Cezar Mendes  Silvia Regina de Medeiros  Ian McReath  Cristina Maria Pinheiro de Campos   《Gondwana Research》2005,8(3):337-345

In the central-southern region of Espírito Santo State, southeastern Brazil, several granitoids with a variable composition intruded high-grade metamorphic rocks, in the northern segment of the Ribeira fold belt. A close relationship between hydrous and anhydrous facies is present in some of the plutons, including the Varzea Alegre Igneous Complex, which has an inner domain formed by gabbro, diorite and granite, and an irregular outer ring of charnockitic rocks. These green megaporphyritic charnockites have primary anhydrous mineral assemblage, I-type and metaluminous character, and high-K calc-alkaline signature. U-Pb zircon single crystal ages obtained by TIMS indicate crystallization at about 500 Ma, similar to other late tectonic plutons of this part of the Ribeira belt. Sr and Nd isotopic ratios ranging from 0.7078 to 0.7096 and 0.5114 to 0.5116 respectively, are interpreted to be indicative of a hybrid origin from crustal and mantle-derived magmas. A binary diagram using Sr isotope ratios also demonstrates that the genesis of the charnockites probably included both magma mixing and fractional crystallization processes.  相似文献   

Design,test and analysis of a light‐weight dissipative bracing system for seismic protection of structures     

Emanuele Renzi  Salvatore Perno  Silvia Pantanella  Vincenzo Ciampi 《地震工程与结构动力学》2007,36(4):519-539

The paper deals with the proposal and the experimental validation of a novel dissipative bracing system for the seismic protection of structures; compared with other similar systems, it is characterized by smaller size and weight, which makes it easier to move and to install, as well as particularly suitable to be inserted in light‐framed structures (e.g. steel structures of industrial plants). The proposed system consists of an articulated quadrilateral with steel dissipaters inserted, to be connected by tendons to frame joints; the prototypes have been designed and realized for the seismic protection of a two‐storey, large‐scale, steel frame, specially designed for shaking‐table tests. The paper, after an illustration of the system, and of its design and behaviour, presents the shaking‐table tests carried out. The experimental results have fully validated the proposed system, showing its good performance in controlling the seismic response of framed structures. A numerical non‐linear model, set up and validated on the basis of the physical tests, has been used to help interpreting the experimental results, but also to perform parametrical studies for investigating the influence of the design parameters on the performance of the control system. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Enrichment of redox-sensitive trace metals (U,V, Mo,As) associated with the late Hauterivian Faraoni oceanic anoxic event     

Stéphane Bodin  Alexis Godet  Virginie Matera  Philipp Steinmann  Jean Vermeulen  Silvia Gardin  Thierry Adatte  Rodolfo Coccioni  Karl B. Föllmi 《International Journal of Earth Sciences》2007,96(2):327-341

The Faraoni Level is a short-lived oxygen-deficient event that took place during the latest Hauterivian. In order to improve our understanding of the palaeoenvironmental conditions that occurred during this event, we have analysed the contents of several redox-sensitive trace elements (U, V, Mo, As, Co, Cd, Cu, Zn, Ni, Pb, Cr) from bulk limestone samples of late Hauterivian–early Barremian age from three reference sections. U, V, Mo and As show consistent and significant enrichments during the Faraoni event whereas the other redox-sensitive trace elements analysed here are not systematically enriched. In order to explain this discrepant behaviour, we propose that the Faraoni Level was deposited during a period of anoxic conditions near the sediment–water interface. The distinctive peaks in U, V, Mo and As contents are traceable throughout the three studied sections and represent a good correlation tool which helps to identify the Faraoni Level and its equivalents in the western Tethyan realm and outside of the Tethys. For example, a peak in U contents in upper Hauterivian sediments of the northwestern Pacific realm (ODP leg 185, site 1149) may well be an expression of the Faraoni event in this particular basin.  相似文献   

B,V, and DDO photometric observations of red variable stars     

T. Storchi Bergmann  Silvia H. B. Livi  Roberto D. D. Costa 《Astrophysics and Space Science》1984,100(1-2):341-349

Light curves of the red variables L₂ Puppis, R Carinae, and S Carinae in the region of the spectrum covered by theB, V, and DDO photometry are presented. The behavior of the DDO color indices and their meaning for this type of star are discussed. S Carinae shows a different behavior from the other two stars that seems to be due to a population effect.  相似文献   

Le domaine Tariquide (arc de Gibraltar,Espagne et Maroc) : succession et hiatus de la sédimentation du Jurassique supérieur au Paléocène     

Michel Durand-Delga  Manuel Esteras  Silvia Gardin  Hélène Paquet 《Comptes Rendus Geoscience》2005,337(9):849-860

The originality of the Malm–Cretaceous series of the Tariquides (Gibraltar arc), as compared to those of the Rifian–Betic ‘Dorsale’ (Alboran domain), and especially with the Penibetic (Iberia) domain, is emphasized. In the Los Pastores Group, near Algeciras, Upper Tithonian nodular limestones directly lie on the Dogger and are followed by Aptychus-bearing limestones (Late Berriasian to Barremian). In the Musa Group, Rif, radiolarites are followed by siliceous limestones (Kimmeridgian–Tithonian), then by karst and massflow breccias connected to a Berriasian tectonics, by Aptychus-bearing marly limestones, then by karst filled by Turonian limestones, and finally by Maastrichtian–Palaeocene polychrome pelites, whose micropalaeontological and mineral compositions (clay minerals, FeMn nodules) refer to a deep-sea, probably infra-CCD, sedimentation. To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005).  相似文献   

Application of biomarkers for assessing the biological impact of dredged materials in the Mediterranean: the relationship between antioxidant responses and susceptibility to oxidative stress in the red mullet (Mullus barbatus)     

Regoli F  Pellegrini D  Winston GW  Gorbi S  Giuliani S  Virno-Lamberti C  Bompadre S 《Marine pollution bulletin》2002,44(9):912-922

In the period 1997-2000, approximately 1,800,000 m3 of material dredged from the Port of Leghorn was discharged into a sea dumping site located 14 miles from the coast. The red mullet (Mullus barbatus) was used as a bioindicator species for monitoring the biological impact of these discharges on a geographical and temporal scale. Organisms were sampled over three years (1998-2000) at different stations and several biomarkers, both of exposure and effect, were analyzed. Bioavailability of specific classes of pollutants was evaluated by analyzing levels of metallothioneins, the activity of cytochrome P450 1A (CYPIA) and of glutathione S-transferases. Among biomarkers of effect, special attention was paid to the balance between prooxidant challenge and antioxidant defenses, and to the appearance of damage caused by oxidative stress. The analyses of the main components of the antioxidant system included superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glyoxalase I and II, and total glutathione. These data were integrated with the measurement of total oxyradical scavenging capacity (TOSC) as an indication of the overall biological resistance to toxicity of different forms of oxyradicals (peroxyl radicals, hydroxyl radicals and peroxynitrite). Results indicated a biological impact in organisms sampled near the disposal site; the impact was particularly evident during 1999 and mainly related to organic chemicals such as PAH. Exposure to these pollutants also caused variations in the levels and activity of several antioxidants. The analysis of TOSC, however, revealed that the overall capacity of specific tissues of organisms to absorb various oxidants was not seriously compromised when challenged with increased prooxidant pressures. Variations of single antioxidants were useful in revealing early warning "biological responses", while integration with TOSC analyses indicated if such changes also reflect a more integrated and functional "biological effect" with possible consequences at the organisms level. The red mullet appears to be a useful sentinel species for a biomarker approach to monitoring impact caused by dredged materials.  相似文献   

XMM–Newton EPIC and Optical Monitor observations of Her X-1 over the 35-d beat period     

Silvia Zane  Gavin Ramsay  Mario A. Jimenez-Garate  Jan Willem den Herder  Charles J. Hailey 《Monthly notices of the Royal Astronomical Society》2004,350(2):506-516

  相似文献   

What criticality in cellular automata models of earthquakes?   总被引：1，自引：0，他引：1  

Silvia Castellaro  Francesco Mulargia 《Geophysical Journal International》2002,150(2):483-493

  相似文献   

Flood Events of Selected European Rivers in the Sixteenth Century     

Rudolf Brázdil  Rüdiger Glaser  Christian Pfister  Petr Dobrovolný  Jean-Marc Antoine  Mariano Barriendos  Dario Camuffo  Mathias Deutsch  Silvia Enzi  Emanuela Guidoboni  Oldřich Kotyza  Fernando Sanchez Rodrigo 《Climatic change》1999,43(1):239-285

The severity and frequency of sixteenth-century floods of the Rhine, the Main, the middle and upper Elbe with its tributaries, rivers of northern and central Italy, the Garonne and rivers in Catalonia and Andalusia are analyzed using documentary evidence. The basic topographical and hydrological characteristics of the rivers investigated as well as the synoptic causes of their flooding during the instrumental period are presented. Different examples of modifications of the run-off process due to anthropogenic activity are discussed. Prevalence in flood occurrence during the second half of the sixteenth century in comparison to the first half is typical for central European and Andalusian rivers (mainly in the 1560s and 1590s) and agrees with the evolution of precipitation patterns. On the other hand, Italian and Catalonian rivers, in part, had a higher occurrence of floods during the first half of the century. Changes in the flooding seasons in both halves of the century are not unambiguous. Results of an analysis on a broader European scale show floods to be a random natural phenomena with limited areal extent defined by the spatial influence of forcing meteorological factors (continuous heavy rains, sudden melting of thick snow cover, etc.). Despite some limitations of documentary evidence, series of reconstructed historical floods are valuable sources of proxy data which can be utilized for the study of the flooding fluctuations in the pre-instrumental period.  相似文献   

Impact of the clouds of volcanic aerosols in Italy during the last 7 centuries     

Dario Camuffo  Silvia Enzi 《Natural Hazards》1995,11(2):135-161

Intense natural pollution has occurred in the past in Italy corresponding to intense volcanic activity, which appears to have diminished somewhat in recent times. Between 1500 and 1900, Etna, Vesuvius, Vulcano and Stromboli, plus volcanoes outside Italy were very active and there are numerous, well documented episodes of atmospheric acidification which caused widespread damage, especially to the vegetation. Other than the acid rains, volcanic emissions also caused so calleddry fogs which consist of a more or less dense mist composed of foul smelling gases and aerosols, characterized by a reddish color, that could appear and persist when the relative humidity was low as shown by measurements taken on such occasions. This phenomenon appeared most frequently at the beginning of the hot season. In fact, volcanic clouds of gases and aerosols formed especially when the Tyrrhenian sea water was relatively cold giving rise to very stable atmospheric conditions locally and the summer anticyclone meant that the winds were calm. Under such conditions the emissions of Stromboli and Vulcano, especially those emitted at low levels, remained entrapped in the stable layer, which were then transported towards the land reaching Northern Italy at a distance on the order of 10³ km. Thedry fogs could persist for days or weeks. Harvests were seriously damaged and frequently the crops were subsequently attacked by parasites. The leaves of the vegetation became discoloured with numerous punctiform lesions or gangrene at the edges of the leaves. The phenomenon was so frequent that, in texts on agricultural meteorology of the 1800s, a distinction was made between the causticdry fogs which damaged the vegetation anddamp fogs which instead were good for it. The most important episode occurred in 1783 due to the activity of Laki Grímsvötn (Iceland) with the contribution of Italian volcanoes. This dry fog lasted many months and affected the greater part of the northern hemisphere including Europe and Asia, harming people, animals and vegetation. Apart from paroxysmal cases, from the 1300s up to today, some tens ofdry fogs have been noted, all of which have been sufficiently well documented. The frequency of these events culminated between the middle of the 1700s and the middle of the 1800s. There is reason to believe that this well documented phenomenon of the past, with sufficient volcanic activity, could recur on the meso and large scale; with present day activity the emissions continue to cause damage to vegetation, both in the Aspromonte mountains (Calabria, Southem Italy) as well as in other parts of Italy.  相似文献