New Activity of Chiron: Results from 5 Years of Photometric Monitoring     

René DuffardDaniela Lazzaro  Sandro PintoJorge Carvano  Claudia AngeliAlvaro Alvarez Candal  Silvia Fernández 《Icarus》2002,160(1):44-51

The results of photometric observations of Centaur object Chiron carried out at the Observatório do Pico dos Dias (OPD, Brazil), the Estación Astrof?́sica de Bosque Alegre (EABA, Argentina), and Complejo Astronómico El Leoncito (CASLEO, Argentina) from 1997 to 2001 are presented here. The analysis of the photometric data shows that the brightness of Chiron reached a minimum value in 1999 and began increasing again in 2000. The absolute magnitude, H_V, varied from 7.26 in June 1999 to 5.78 in April 2001. The data tend to indicate that Chiron is starting a new outburst of activity which is compatible with a sporadic cometary behavior not related to heliocentric distance.  相似文献   

Microdeformation of lacustrine laminite sequences from Late Miocene formations of SE Spain: an interpretation of loop bedding   总被引：2，自引：0，他引：2  

Jose P. Calvo  Miguel Rodriguez-Pascua  Silvia Martin-Velazquez  Sergio Jimenez  & Gerardo De Vicente 《Sedimentology》1998,45(2):279-292

Lacustrine laminated sediments (laminites) present in Late Miocene formations of the Híjar Basin, SE Spain, display well developed loop bedding, a structure consisting of bundles of laminae that are sharply constricted at intervals, giving a morphology of loops or links of a chain. The laminite sequences, which are interbedded with turbidite marlstones, were accumulated on the bottom of a permanently stratified lake developed in a rapidly subsiding basin limited by 010° and 105° normal faults. As deduced from both macro- and microdeformational analyses, the basin evolved under an extensional stress field throughout the Late Miocene. Four main types of loops, simple and complex loops with subcategories, have been recognized within the laminite sequence. Simple loops of type 1 show the best definite pattern, quite similar to ' pinch and swell structures ', a type of boudinage typical of stretching of alternating beds where the competence contrast is not strongly marked. The remaining loop types display contortion and occasional breakage of laminae (microfaulted edges) indicative of microdeformation near the boundary between the ductile-brittle deformational fields. The distribution of the various loop types across the laminite sequence reflects an interplay between progressive lithification of the laminites as sedimentation progressed and tectonic stresses which affected the sediment sequence. Accordingly, a mechanism of deformation under an extensional stress field, ultimately related to the creep movement of the main basin faults which resulted in successive seismic shocks of low magnitude, is proposed to explain the formation of loop bedding in the laminites.  相似文献   

The future of global oil demand and the growing role of the transport sector     

Silvia Pariente-David 《Natural Resources Research》1998,7(2):129-135

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The historical temperature series of Bologna (Italy): 1716–1774     

Silvia Comani 《Climatic change》1987,11(3):375-390

The Bologna meteorological record is one of the oldest and most complete among the series already collected for Europe. Data from the regions south of the Alps being extremely sparse, this station is of great importance for all climatic reconstructions dating as far back as the beginning of the 18th century. The focus here is on the temperature series, because it presents some a priori problems with respect to the series analysis itself. These problems relate to the homogeneity of the temperature record, which is affected by the use of different thermometers within the record, the statistical reconstruction of the thermometric scales, and the drift in calibration of one of these instruments. After correcting for these heterogeneities, the temperature series indicate a thermal behaviour in agreement with other historical European sources. The Bologna series is characterised by a warm period during the first decades of the 18th century, with large decreases in temperature in 1740 and 1742, and a positive trend from 1742 to the end of the record. The behaviour of the Bologna temperature series is in good agreement with the series for Central England, De Bilt (Netherlands) and Padua (Italy).  相似文献   

The Geochemistry of Lake Joyce, McMurdo Dry Valleys, Antarctica     

Joseph A. Shacat  William J. Green  Eric H. Decarlo  Silvia Newell 《Aquatic Geochemistry》2004,10(3):325-352

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Seismic Design of Symmetric Structures for Accidental Torsion   总被引：5，自引：0，他引：5  

Silvia L. Dimova  Ilia Alashki 《Bulletin of Earthquake Engineering》2003,1(2):303-320

The paper presents an analytical estimation of the dynamic effects, caused by the shifting of the centre of mass with accidental eccentricity in symmetric structures. The approximate analytical solution proves, that even under small accidental eccentricities the symmetric structures exhibit “irregular behaviour” and the accidental torsional effects cannot be described properly by static application of torsional moments. The prescribed application rule by Eurocode 8 for multimodal analysis underestimates the accidental torsional effects up to 21% for 5% eccentricity for the structures considered in the paper. An expression for the correction of member responses is derived. It is proved by numerical simulations of the dynamic response of three-dimensional models of symmetric structures, that the proposed correction coefficient gives accurate results in cases of single-storey and multi-storey structures. It gives a convenient way for the design practice to estimate accurately the accidental torsional effects on planar and 3-D models of symmetric structures. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Large Scale Rockfall Reach Susceptibility Maps in La Cabrera Sierra (Madrid) performed with GIS and Dynamic Analysis at 1:5,000   总被引：1，自引：0，他引：1  

Ayala-Carcedo  Francisco J.  Cubillo-Nielsen  Silvia  Alvarez  Ana  Domínguez  María J.  Laín  Luis  Laín  Ricardo  Ortiz  Guillermo 《Natural Hazards》2003,29(3):325-340

For the testing of the effect on the tsunami prevention facilities, a simplified methodfor tsunami risk assessment was suggested without wave run-up analysis. This methodis proposed using calculated offshore tsunami waveform and field reconnaissance suchas the seawall height, time necessary for residents' evacuation and tsunami warninginsurance. Then, two normalized values are evaluated; one is the ratio of calculatedmaximum tsunami height to seawall height, the other is the ratio of time betweentsunami over-topping and evacuation completion to total time required for evacuation.These two values are used to qualitatively estimate the safety of residents and the effectof tsunami prevention facilities, eliminating the necessity to compute complicatedtsunami run-up onshore.  相似文献   

Late Permian–Middle Jurassic lithospheric thinning in Peru and Bolivia, and its bearing on Andean-age tectonics     

Thierry Sempere  Gabriel Carlier  Pierre Soler  Michel Fornari  Víctor Carlotto  Javier Jacay  Oscar Arispe  Didier Nraudeau  Jos Crdenas  Silvia Rosas  Nstor Jimnez 《Tectonophysics》2002,345(1-4)

Integrated studies and revisions of sedimentary basins and associated magmatism in Peru and Bolivia (8–22°S) show that this part of western Gondwana underwent rifting during the Late Permian–Middle Jurassic interval. Rifting started in central Peru in the Late Permian and propagated southwards into Bolivia until the Liassic/Dogger, along an axis that coincides with the present Eastern Cordillera. Southwest of this region, lithospheric thinning developed in the Early Jurassic and culminated in the Middle Jurassic, producing considerable subsidence in the Arequipa basin of southern Peru. This 110-Ma-long interval of lithospheric thinning ended 160 Ma with the onset of Malm–earliest Cretaceous partial rift inversion in the Eastern Cordillera area.The lithospheric heterogeneities inherited from these processes are likely to have largely influenced the distribution and features of younger compressional and/or transpressional deformations. In particular, the Altiplano plateau corresponds to a paleotectonic domain of “normal” lithospheric thickness that was bounded by two elongated areas underlain by thinned lithosphere. The high Eastern Cordillera of Peru and Bolivia results from Late Oligocene–Neogene intense inversion of the easternmost thinned area.  相似文献   

The diffuse clouds towards Cyg OB2 No. 5 and No. 12     

Silvia Casu  Flavio Scappini  Cesare Cecchi-Pestellini  Michael Olberg 《Monthly notices of the Royal Astronomical Society》2005,359(1):73-78

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Size fractionation and optical properties of colloids in an organic-rich estuary (Thurso, UK)   总被引：2，自引：0，他引：2  

Silvia Batchelli  Franois L.L. Muller  Mohamed Baalousha  Jamie R. Lead 《Marine Chemistry》2009,113(3-4):227-237

The optical characteristics of a black water river estuary from the north coast of Scotland were examined in the filtered (0.4 µm), ultrafiltered (5 kDa) and colloid-enriched fractions of estuarine samples. The samples were collected over the full salinity range during a period when the pH was relatively constant (8.2–8.5) throughout the estuary, allowing the influence of salinity on estuarine colloidal processes to be distinguished. The properties examined in the bulk, the low molecular weight (LMW) and the colloidal fraction (HMW) were UV–visible absorption, 3-D fluorescence excitation–emission matrix (EEM) spectrum, inorganic and organic carbon, mean size (by dynamic light scattering), and size distribution by flow field-flow fractionation analysis (FlFFF). The combined results of these analyses support the view that river-borne, humic-rich colloids underwent two types of transformation upon mixing with the seawater end member. The first one resulted in an apparent increase in the abundance of LMW constituents and may be explained by coiling of the individual humic macromolecules. The second one resulted in an increase in the mean size measured in both the lower and higher colloidal size ranges, and may be explained by aggregation of colloids to form entities that were still mostly colloidal i.e., smaller than 0.4 µm. The LMW contribution to the bulk optical properties increased with increasing salinity. Very similar findings were obtained from simulated mixing experiments using a Nordic Reference NOM extract as a source of freshwater colloids. This indicates that changes in the molecular architecture and molar mass of river-borne colloids—not changes in their chemical nature—were responsible for the observed variations in the spectral characteristics of CDOM in this estuary.  相似文献