Scale radii and aggregation histories of dark haloes     

Eduard Salvador-Solé  Alberto Manrique  José María Solanes 《Monthly notices of the Royal Astronomical Society》2005,358(3):901-912

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Imaging polarimetry of comet Hale-Bopp (C/1995 O1) around perihelion     

Paolo Tanga  Alberto Cellino  Mario Di Martino 《Earth, Moon, and Planets》1997,78(1-3):359-364

The polarization distribution of the inner coma of comet Hale-Bopp was measured by CCD imaging around perihelion. The dust shell positions correlate well with relative maxima of polarization. The images taken in the I-band identify different shell systems, each showing individual polarization properties. This could be related to differences in the dust properties of the associated jets. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Experimental and Numerical Studies on the Seismic Response of R.C. Hollow Bridge Piers   总被引：3，自引：2，他引：1  

Gian?Michele?CalviEmail author  Alberto?Pavese  Alessandro?Rasulo  Davide?Bolognini 《Bulletin of Earthquake Engineering》2005,3(3):267-297

Appropriate seismic assessment of reinforced concrete bridges is an important challenge in structural engineering in consideration of the number and relevance of bridges built without applying advanced codes of practice and of the strategic role of transportation networks in modern economy. This paper focuses on some relevant aspects of the damage development and collapse modes of hollow piers, as commonly designed in the past. The following aspects have been considered: absence of confinement, inadequate shear strength, shifting of the critical section, insufficient length of lap splices. A series of experimental tests has been designed and performed; the capacity of predicting appropriate results of formulations recommended in codes of practice or proposed in recent research documents has been checked comparing experimental and analytical results.  相似文献   

Extraterrestrial hydrogeology     

Victor?R.?BakerEmail author  James?M.?Dohm  Alberto?G.?Fairén  Ty?P.?A.?Ferré  Justin?C.?Ferris  Hideaki?Miyamoto  Dirk?Schulze-Makuch 《Hydrogeology Journal》2005,13(1):51-68

Subsurface water processes are common for planetary bodies in the solar system and are highly probable for exoplanets (planets outside the solar system). For many solar system objects, the subsurface water exists as ice. For Earth and Mars, subsurface saturated zones have occurred throughout their planetary histories. Earth is mostly clement with the recharge of most groundwater reservoirs from ample precipitation during transient ice- and hot-house conditions, as recorded through the geologic and fossilized records. On the other hand, Mars is mostly in an ice-house stage, which is interrupted by endogenic-driven activity. This activity catastrophically drives short-lived hydrological cycling and associated climatic perturbations. Regional aquifers in the Martian highlands that developed during past, more Earth-like conditions delivered water to the northern plains. Water was also cycled to the South Polar Region during changes in climate induced by endogenic activity and/or by changes in Mars orbital parameters. Venus very likely had a warm hydrosphere for hundreds of millions of years, before the development of its current extremely hot atmosphere and surface. Subsequently, Venus lost its hydrosphere as solar luminosity increased and a run-away moist greenhouse took effect. Subsurface oceans of water or ammonia-water composition, induced by tidal forces and radiogenic heating, probably occur on the larger satellites Europa, Ganymede, Callisto, Titan, and Triton. Tidal forces operating between some of the small bodies of the outer solar system could also promote the fusion of ice and the stability of inner liquid-water oceans.

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Resumen Los procesos hídricos subsuperficiales son comunes en cuerpos planetarios del sistema solar y son altamente probables para exoplanetas (planetas fuera del sistema solar). Para muchos cuerpos del sistema solar, el agua subsuperficial existe como hielo. Para la Tierra y Marte han ocurrido zonas saturadas subsuperficiales a través de sus historias planetarias. La Tierra es principalmente generosa con la recarga de la mayoría de reservorios de aguas subterráneas a partir de amplia precipitación reconocida en condiciones transitorias calientes y heladas, tal y como aparece en los registros fósiles y geológicos. Por otro lado, Marte se encuentra principalmente en una etapa de cámara de hielo la cual es interrumpida por actividad de tipo endogénico. Esta actividad pone en funcionamiento catastróficamente ciclos hidrológicos de vida corta y perturbaciones climáticas asociadas. Acuíferos regionales en las montañas de Marte que se desarrollaron en el pasado en condiciones similares a la Tierra distribuyen agua a las planicies del norte. El agua ha sido transportada hacia el sur de la región polar durante cambios en el clima inducidos por actividad endogénica y/o cambios en los parámetros orbitales de Marte. Venus muy probablemente tuvo una hidrósfera caliente durante cientos de millones de años, antes de que se desarrollara su atmósfera y superficie actual extremadamente caliente. Subsecuentemente, Venus perdió su hidrósfera a medida que la luminosidad solar aumentó y un efecto de invernadero húmedo escapatorio se llevó a cabo. Océanos subsuperficiales de composición agua o amoniaco-agua, inducidos por fuerzas de marea y calentamiento radiogénico, probablemente ocurren en los satélites más grandes como Europa, Ganimeda, Callisto, Titan y Triton. Las fuerzas de marea que operan entre los cuerpos pequeños del sistema solar externo podrían también promover la fusión de hielo y la estabilidad de líquido interno-aguas de los océanos.

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Résumé Les processus de subsurface impliquant leau sont communs pour les corps planétaires du système solaire et sont très probables sur les exoplanètes (planètes en dehors du système solaire). Pour plusieurs objets du systèmes solaire, leau de subsurface est présente sous forme de glace. Pour la Terre et Mars, les zones saturées de subsurface apparaissent à travers toute leur histoire planétaire. La Terre est particulièrement clémente avec la recharge des réservoirs, avec de amples précipitations, des conditions glaciaires et de fortes chaleurs, comme latteste les enregistrements géologiques et paléontologiques. Dun autre côté, Mars se trouve dans une phase essentiellement glaciaire, qui est interrompue par des activités contraintes par les phénomènes endogéniques. Cette activité conduit de manière catastrophique à des cycles hydrologiques et à des perturbations climatiques brutaux. Les aquifères régionaux dans les haute terres martiennes qui se sont formés dans des conditions similaires aux conditions terrestres, alimentent les plaines du Nord. Leau a également été déplacée vers le Pôle Sud martien durant des changements marqués par une forte activité endogénique et une modification des paramètres de lorbite de Mars. Venus possèdait vraisemblablement une hydrosphère chaude durant des millions dannée, avant le développement de son atmosphère et sa surface particulièrement chaude. Par après Venus a perdit son hydrosphère alors que la luminosité solaire augmentait et quune humidité liée à un effet de serre sinstallait. Les océans de subsurface deau ou deau ammoniacale, induits par les forces de marée et le chauffage radiogénique, apparaissent probablement sur les satellites les plus importants (Europa, Ganymede, Callisto, Titan, Triton). Les forces de marée entre les petits corps externes du système solaire peuvent également occasionner la fusion de glace et la stabilité des océans internes deau liquide.

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Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean?   总被引：1，自引：0，他引：1  

Alberto V. Borges 《Estuaries and Coasts》2005,28(1):3-27

Annually integrated air-water CO₂ flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate air-water CO₂ fluxes over the coastal ocean (26×10⁶ km²), taking into account its geographical and ecological diversity. Air-water CO₂ fluxes were then up-scaled in global ocean (362×10⁶ km²) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×10⁶ km²). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO₂(−1.17 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr⁻¹). The inclusion of the coastal ocean increases the estimates of CO₂ uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr⁻¹) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr⁻¹) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO₂ emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr⁻¹). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for atmospheric CO₂ (0.38 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr⁻¹) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO₂ but at temperate latitudes, it still behaves as a moderate CO₂ sink. A rigorous up-scaling of air-water CO₂ fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global CO₂ cycle.  相似文献   

Cultural heritage and geological hazards: the case of the Calomini hermitage in Tuscany (Italy)   总被引：1，自引：0，他引：1  

Giacomo D’Amato Avanzi  Daria Marchetti  Alberto Puccinelli 《Landslides》2006,3(4):331-340

The Calomini hermitage is located on a steep slope, below an 80- to 130-m-high hanging rock wall. The hermitage, a significant example of religious architecture, has been a pilgrimage place since the Middle Ages. The monastery, completed by the tenth century, is built into the rock mass for more than half of its length. The stability and safety of the complex are threatened by stability problems in the rock slope. Structural and geotechnical investigations were carried out, showing the potential for rock blocks slides, particularly under dynamic conditions, with the fall of middle size blocks. Recently, some remedial works have been carried out, and wire meshes have been hung on the rock wall. Nevertheless, a significant portion of the Calomini hermitage area may be still dangerous and exposed to severe landslide hazard. Therefore, further research and countermeasures are necessary to protect a very important item of Italian cultural and architectural heritage.  相似文献   

A physical analogue model to analyse interactions between tensile stresses and dissolution in carbonate slopes     

Stefano Casini  Salvatore Martino  Marco Petitta  Alberto Prestininzi 《Hydrogeology Journal》2006,14(8):1387-1402

A physical analogue model was developed to analyse the relationship between tensional states in rock masses, seepage and karst processes. Use was made of an experimental apparatus consisting of two hydraulic circuits realized by drilling two holes into each of two blocks of sampled limestone from the central Apennines (Italy). A static load (208.85 kg) was applied to one of the blocks in order to elicit tensile stresses within it. Physical and chemical monitoring data showed that the main process involved was temperature-dependent CaCO₃ dissolution. This process was more marked in the loaded block circuit, as Ca⁺⁺ concentration in circulated water reached 54 mg/L, whereas only 28 mg/L was reached in the unloaded one. The interaction between load and dissolution caused the observed opening of microcracks, as confirmed by further increase of water loss and by dilution in the loaded block circuit, resulting in a decrease of Ca⁺⁺ concentration. These findings were confirmed by recording additional water losses after increasing the load up to 445.05 kg. A finite difference numerical model showed that tensile stresses (max 20 kPa) within the loaded block were clustered at the intersection of the main joints with the flowpaths, thus representing points of preferential and accelerated dissolution.This study is part of a research project on analogical and numerical modelling for geological risk mitigation being conducted at CERI, Research Centre for Geological Risks of the University of Rome “La Sapienza” (Valmontone, Roma, Italy; http://www.ceri@uniroma1.it).  相似文献   

Organic carbon metabolism and carbonate dynamics in a Mediterranean seagrass (Posidonia oceanica), meadow     

Cristina Barrón  Carlos M. Duarte  Michel Frankignoulle  Alberto Vieira Borges 《Estuaries and Coasts》2006,29(3):417-426

We measured monthly dissolved oxygen (DO) changes in situ benthic incubations from March 2001 to October 2002 in aPosidonia oceanica meadow and unvegetated sediments of Magalluf Bay (Mallorca Island, Spain) to determine gross primary production (GPP), community respiration (R), and net community production (NCP). From June 2001 to October 2002, we also measured fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TAlk). The yearly integrated metabolic rates based on DO changes show that theP. oceanica communities are net autotrophic while the metabolic rates in the unvegetated benthic communities are nearly balanced. Higher calcium carbonate (CaCO₃) cycling, both in terms of production and dissolution, was observed inP. oceanica communities than in unvegetated benthic communities. In theP. oceanica meadow, the annual release of CO₂ from net CaCO₃ production corresponds to almost half of the CO₂ uptake by NCP based on DIC incubations. In unvegetated benthic communities, the annual uptake of CO₂ from net CaCO₃ dissolution almost fully compensates the CO₂ release by NCP based on DIC incubations. CaCO₃ dynamics is potentially a major factor in CO₂ benthic fluxes in seagrass and carbonate-rich temperate coastal ecosystems.  相似文献   

Structure of the lithosphere beneath the Eastern Alps (southern sector of the TRANSALP transect)   总被引：1，自引：0，他引：1  

Alberto Castellarin  Rinaldo Nicolich  Roberto Fantoni  Luigi Cantelli  Mattia Sella  Luigi Selli 《Tectonophysics》2006,414(1-4):259

The interpretation of the seismic Vibroseis and explosive TRANSALP profiles has examined the upper crustal structures according to the near-surface geological evidences and reconstructions which were extrapolated to depth. Only the southern sector of the TRANSALP transect has been discussed in details, but its relationship with the whole explored chain has been considered as well. The seismic images indicate that pre-collision and deep collision structures of the Alps are not easily recognizable. Conversely, good records of the Neo-Alpine to present architecture were provided by the seismic sections.Two general interpretation models (“Crocodile” and “Extrusion”) have been sketched by the TRANSALP Working Group [2002]. Both illustrate the continental collision producing strong mechanical interaction of the facing European and African margins, as documented by giant lithosphere wedging processes. Arguments consistent with the “Extrusion” model and with the indentation of Adriatic (Southalpine) lithosphere underneath the Tauern Window (TW) are:

– According to the previous DSS reconstructions, the Bouguer anomalies and the Receiver Functions seismological data, the European Moho descends regularly attaining a zone south of the Periadriatic Lineament (PL). The Moho boundary and its geometry appear to be rather convincing from images of the seismic profile;

– the Tauern Window intense uplift and exhumation is coherent with the strong compression regime, which acted at depth, thus originating the upward and lateral displacement of the mobile and ductile Penninic masses according to the “Extrusion” model;

– the indentation of the Penninic mobile masses within the colder and more rigid Adriatic crust cannot be easily sustained. Wedging of the Adriatic stiffened lower crust, under high stresses and into the weaker Penninic domain, can be a more suitable hypothesis. Furthermore, the intrusion of the European Penninic crustal wedge underneath the Dolomites upper crust is not supported by any significant uplifting of the Dolomites. The total average uplift of the Dolomites during the Neogene appears to be 6−7 times smaller than that recognized in the TW. Markedly the northward dip of the PL, reaching a depth of approximately 20 km, is proposed in our interpretation;

– finally, the Adriatic upper crustal evolution points to the late post-collision change in the tectonic grow-up of the Eastern Alps orogenic chain. The tectonic accretion of the northern frontal zone of the Eastern and Central Alps was interrupted from the Late Miocene (Serravallian–Tortonian) onward, as documented by the Molasse basin evolution. On the contrary, the structural nucleation along the S-vergent tectonic belt of the eastern Southern Alps (Montello–Friuli thrust belt) severely continued during the Messinian and the Plio–Pleistocene. This structural evolution can be considered to be consistent with the deep under-thrusting and wedge indentation of the Adriatic lithosphere underneath the southern side of the Eastern Alps thrust-and-fold belt.

Similarly, the significance of the magmatic activity for the construction of the Southern Alps crust and for its mechanical and geological differentiation, which qualified the evolution of the thrust-and-fold belt, is highlighted, starting with the Permian–Triassic magmatism and progressing with the Paleogene occurrences along the Periadriatic Lineament and in the Venetian Magmatic Province (Lessini–Euganei Hills).  相似文献   

Lawsonite-bearing omphacitites from Alpine Corsica (France)     

Alberto Vitale Brovarone 《International Journal of Earth Sciences》2013,102(5):1377-1379

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