Landslides in Valles Marineris (Mars): A possible role of basal lubrication by sub-surface ice   总被引：1，自引：0，他引：1  

Fabio Vittorio De Blasio 《Planetary and Space Science》2011,59(13):1384-1392

There is much interest on the occurrence of water and ice in the past history of Mars. Because landslides on Mars are much better conserved than their terrestrial counterparts, a physical examination and morphological analysis can reveal significant details on the depositional environment at the instant of failure. A study of the landslides in Valles Marineris based on their physical aspect is presented and the velocity of the landslides is calculated with a stretching block model. The results show that the landslides were subject to strong basal lubrication that made them travel at high speed and to long distances. We use physical analysis to explore the four alternative possibilities that the natural lubricant of the landslides in Valles Marineris was either ice, deep water, a shallow carpet of water, or evaporites. Examination of the furrows present on the surface of the landslide deposits shows that either sub-surface ice or evaporites were likely present on the floor of Valles Marineris during the mass failures.  相似文献   

Use of ETM+ images to extend stem volume estimates obtained from LiDAR data     

Fabio Maselli  Marta ChiesiAlessandro Montaghi  Enzo Pranzini 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(5):662-671

Airborne LiDAR techniques can provide accurate measurements of tree height, from which estimates of stem volume and forest woody biomass can be obtained. These techniques, however, are still expensive to apply repeatedly over large areas. The current paper presents a methodology which first transforms mean stand heights obtained from LiDAR over small strips into relevant stem volume estimates. These are then extended over an entire forest by applying two estimation methods (k-NN and locally calibrated regression) to Landsat ETM+ images. The methodology is tested over a coastal area covered by pine forest in the Regional Park of San Rossore (Central Italy). The results are evaluated by comparison with the ground stem volumes of a recent forest inventory, taking into consideration the effect of stand size. In general, the accuracies of two estimation methods are dependent on the size of the forest stands and are satisfactory only when considering stands larger than 5-10 ha. The outputs of the parametric regression procedure are slightly more stable than those of k-NN and more faithfully reproduce the spatial patterns of the ground data.  相似文献   

Architecture,structural and tectonic significance of the Seagap fault (offshore Tanzania) in the framework of the East African Rift     

David Iacopini  Stefano Tavani  Sara Pentagallo  Vittorio Maselli  Marina Dottore Stagna  Cynthia Ebinger  David Reynolds  Arjan van Vliet 《Basin Research》2023,35(1):387-412

The Southeastern portion of the East African Rift System reactivates Mesozoic transform faults marking the separation of Madagascar from Africa in the Western Indian Ocean. Earlier studies noted the reactivation of the Davie Fracture Zone in oceanic lithosphere as a seismically active extensional fault, and new 3D seismic reflection data and exploration wells provide unprecedented detail on the kinematics of the sub-parallel Seagap fault zone in continental/transitional crust landward of the ocean-continent transition. We reconstruct the evolution of the seismically active Seagap fault zone, a 400-km-long crustal structure affecting the Tanzania margin, from the late Eocene to the present day. The Seagap fault zone is represented by large-scale localized structures affecting the seafloor and displaying growth geometries across most of the Miocene sediments. The continuous tectonic activity evident by our seismic mapping, as well as 2D deep seismic data from literature, suggests that from the Middle-Late Jurassic until 125 Ma, the Seagap fault acted as a regional structure parallel to, and coeval with, the dextral Davie Fracture Zone. The Seagap fault then remained active after the cessation of both seafloor spreading in the Somali basin and strike-slip activity on the Davie Fracture Zone, till nowaday. Its architecture is structurally expressed through the sequence of releasing and restraining bends dating back at least to the early Neogene. Seismic sections and horizon maps indicate that those restraining bends are generated by strike-slip reactivation of Cretaceous structures till the Miocene. Finally based on the interpretation of edge-enhanced reflection seismic surfaces and seafloor data, we shows that, by the late Neogene, the Seagap fault zone switched to normal fault behaviour. We discuss the Seagap fault's geological and kinematic significance through time and its current role within the microplate system in the framework of the East African rift, as well as implications for the evolution and re-activation of structures along sheared margins. The newly integrated datasets reveal the polyphase deformation of this margin, highlighting its complex evolution and the implications for depositional fairways and structural trap and seal changes through time, as well as potential hazards.  相似文献   

Dioxin Like Compounds Bulk Deposition on Corn (Zea mais) and Alfa Alfa (Medicago sativa): Modelled Levels on Derived Silage and Hay and Their Relevance for Dairy Production     

Gianfranco Brambilla  Stefania Paola De Filippis  Vittorio Esposito  Gaetano Settimo 《洁净——土壤、空气、水》2013,41(2):113-118

Dioxin‐like compounds from regular, occasional or fugitive airborne sources of emission may fall out on fodders close to be harvested for silage and hay production. In this way, a prolonged long‐term intake of contaminated forages in dairy animals may be envisaged, able to determine a rise of the background contamination in milk. We simulated different risk scenarios taking into account the inventoried bulk dry depositions in rural areas of the aforesaid contaminants, silage and hay biomass production per hectare, forages regimen in dairy animals, and the congeners carry‐over rate (COR) from forages to milk. Considering atmospheric depositions >10 pg I‐TE m^?2 day^?1 and accounting for a 30% COR, dairy milk could rise up to the PCDD/F level of 3 pg WHO₁₉₉₈‐TE g^?1 fat. The modelling indicates that in rural areas bulk emissions should be selectively minimised, accounting for the calendar of the different agricultural practices, because of their potential impact on the fodders. Since environmental factors play a non‐negligible role in food production, a stronger harmonisation between I‐TE and WHO_1998–2005‐TE scales with respect to dioxin‐like polychlorobiphenyl congeners inclusion is envisaged. This will allow the prevention of the human indirect exposure to such contaminants when released in the air.  相似文献   

Seismic performance of R/C frames with overstrength discontinuities in elevation   总被引：2，自引：1，他引：1  

Gennaro Magliulo  Vittorio Capozzi  Roberto Ramasco 《Bulletin of Earthquake Engineering》2012,10(2):679-694

The paper presents the results of a research study concerning the seismic response and design of r/c frames with overstrength discontinuities in elevation. The discontinuities are obtained assigning overstrengths either to the beams or to the columns of a “regular frame” (assumed as reference). Two “regular frames” are designed: one according to the Eurocode 8 (EC8) medium ductility class (DCM) rules and the other one according to the EC8 high ductility class (DCH) rules. For all frames the criteria of vertical strength irregularity of many international seismic codes are applied. Non linear static and dynamic analyses are performed; mechanical non linearity is concentrated at the element ends. These analyses are carried out according to EC8 provisions: for non linear static analysis the N2 method is applied; in the case of non linear time-history analyses, seven real earthquakes, selected in order to fit on average the elastic design spectrum, are used as input. The seismic response of frames characterised by the assigned overstrength is not very different with respect to the “regular frame” one; furthermore all the frames satisfy the Ultimate Limit State, verified by the application of non linear static and dynamic analyses. This demonstrates that the sensitivity of frames, designed according to EC8 medium and high ductility classes, to overstrength vertical variations is low. Consequently, international code provisions on vertical strength regularity should be reviewed.  相似文献   

Long term monitoring of photosystem II herbicides--correlation with remotely sensed freshwater extent to monitor changes in the quality of water entering the Great Barrier Reef, Australia     

Kennedy K  Schroeder T  Shaw M  Haynes D  Lewis S  Bentley C  Paxman C  Carter S  Brando VE  Bartkow M  Hearn L  Mueller JF 《Marine pollution bulletin》2012,65(4-9):292-305

Photosystem II (PSII) herbicides are used in large quantities on agricultural lands adjoining the Great Barrier Reef (GBR). Routine monitoring at 14 sites in inshore waters of the GBR using passive sampling techniques detected diuron (32-94% of sampling periods) at maximum concentrations of 1.7-430ng L(-1) in the relatively pristine Cape York Region to the Mackay Whitsunday Region, respectively. A PSII herbicide equivalent (PSII-HEq) index developed as an indicator for reporting was dominated by diuron (average contribution 89%) and typically increased during the wet season. The maximum PSII-HEq indicates the potential for photosynthetic inhibition of diatoms, seagrass and coral-symbionts. PSII herbicides were significantly positively correlated with remotely sensed coloured dissolved organic matter, a proxy for freshwater extent. Combining these methods provides for the first time the potential to cost-effectively monitor improvements in water quality entering the GBR with respect to exposure to PSII herbicides.  相似文献   

Current problems on asymptotic branch stars     

Vittorio Castellani  Francesca A. D'antona 《Astrophysics and Space Science》1972,15(2):340-347

An effort is made to select, from the available observational data, information concerning the asymptotic branch stars. Particular care is devoted to derive luminosity functions for these stars in clusters representative of selected classes. Some theoretical predictions are briefly made. It is stressed that, from a theoretical point of view, the comparison between the one-shell H-burning evolutionary characteristics and the corresponding ones for the A.B. phase could be expected to provide a powerful means of investigation.

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Sommario Sulla base dei dati osservativi disponibili sono raccolte ed esaminate le possibili informazioni riguardanti la fase di braccio asintotico. In particolare vengono investigate le funzioni di luminosità relative a questa fase evolutiva, e ne viene tentato un inquadramento nella classificazione multidimensionale degli ammassi globulari recentemente proposta. Sono fornite alcune valutazioni teoriche, ed è messo in evidenza come il confronto delle caratteristiche evolutive delle fasi di bruciamento ad una (H) e due (H, He) shell potrebbe rivelarsi come un potente mezzo di investigazione.

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Sicilian serpentinite xenoliths containing abiotic organics with nanodiamond clusters as key model for prebiotic processes     

Sergei K.Simakov  Vittorio Scribano  Nikolai N.Mel’Nik  Germana Barone 《地学前缘(英文版)》2021,12(1):255-263

Rock fragments from the deepest parts of a buried hydrothermal system belonging to the Mesozoic Tethys Ocean entered as xenoliths in a Miocenic diatreme,hence brought to the surface,in the Hyblean Plateau(Sicily).Some xenoliths consist of strongly serpentinized ultramafic rocks bearing blebs of abiotic organic matter,where clusters of amorphous carbon nanoparticles,including nanodiamonds,are immersed.Such an occurrence conjures up established hypotheses that diamond surfaces are suitable catalytic platforms stimulating the assemblage of complex bio-organic molecules relevant to the emergence of life on Earth.The appearance of bio-organic molecules under primitive Earth conditions is one of the major unsolved questions on the origin of life.Here we report new micro-Raman spectra on blebs of abiotic organic matter from a selected xenolith.Diamond bands were related to hydrogenated nanocrystalline diamonds,with size of nearly 1-1.6 nm,formed from organics at low pressures and temperatures.In particular,diamond surfaces can give rise to crystalline interfacial water layers that may have played a fundamental role in the early biosphere evolution as a good medium for rapidly transporting positive charges in the form of hydrated protons.Nowadays,proton gradients in alkaline hydrothermal vents along oceanic ridges are generally viewed as key pre-biotic factors.In general,serpentinites span the entire geological record,including prebiotic times.These hydrous ultramafic rocks often display evidence of abiotic carbon species,both organic and inorganic,including nanodiamonds,being also capable to give rise to chemiosmotic processes and proton gradients necessary to the organisms,such as the"Last Universal Common Ancestor"(LUCA),in the prebiotic Earth.  相似文献   

Barnacle Larvae and their Settlement in Genoa Harbour (North Tyrrhenian Sea)   总被引：1，自引：0，他引：1  

Sebastiano Geraci  Vittorio Romairone 《Marine Ecology》1982,3(3):225-232

Abstract. Density of barnacle larvae in plankton and settlement on atoxic plane surfaces have been compared at one station of Genoa harbour over sixteen months.
There were two periods of larval emission, during summer and autumn, with a slight one during winter. Barnacle settlement varied according to sea temperature, the amount of larvae and competition for the substratum.  相似文献   

Photostability and photolability of dissolved organic matter upon irradiation of natural water samples under simulated sunlight   总被引：2，自引：0，他引：2  

Davide Vione  Vittorio Lauri  Claudio Minero  Valter Maurino  Mery Malandrino  Maria Eugenia Carlotti  Romeo-Iulian Olariu  Cecilia Arsene 《Aquatic Sciences - Research Across Boundaries》2009,71(1):34-45

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