The Near-Earth Objects Follow-up Program : IV. CCD Photometry in 1996-1999     

Yu.N. KruglyI.N. Belskaya  V.G. ShevchenkoV.G. Chiorny  F.P. VelichkoS. Mottola  A. EriksonG. Hahn  A. Nathues  G. NeukumN.M. Gaftonyuk  E. Dotto 《Icarus》2002,158(2):294-304

Lightcurve observations of 16 near-Earth objects (NEOs) and 2 Mars-crossers in 1996-1999 from three observational sites are presented. Eight objects were observed shortly after their discovery within the follow-up program of NEO observations. We were able to determine rotation periods for 14 asteroids. For 8 objects (5626, 5732, 1998 FM5, 1998 FX2, 1998 UT18, 1998 VO33, 1999 RQ36, 1999 US3) our determinations constitute new results while in the remaining 6 cases (3200, 4341, 7025, 7822, 11066, 1992 QN) we could improve or confirm previously published periods. We also put constraints on the spin vector of 3200 Phaethon.  相似文献   

The Valanginian carbon isotope event: a first episode of greenhouse climate conditions during the Cretaceous   总被引：1，自引：0，他引：1  

Andrea Lini  Helmut Weissert  Elisabetta Erba 《地学学报》1992,4(3):374-384

Lower Cretaceous pelagic carbonates outcropping along the Southern Alps of northern Italy provide a record of Tethyan palaeoceanography as well as of low frequency fluctuations in the global carbon cycle. The carbonate C-isotope stratigraphy established at five selected localities in the Southern Alps allows an accurate picture to be drawn of the duration and amplitude of the Valanginian C-isotope event. δ¹³C values near 1.25–1.50% determined in Berriasian and lower Valanginian sediments are replaced by more pdsitive δ¹³C values near 3% in the late Valanginian. The carbonate C-isotope excursion ends in the early Hauterivian with values fluctuating between 1.5% and 2%. The carbonate C-isotope excursion is accompanied by a positive excursion in the total organic carbon C-isotope curve. The Valanginian C-isotope excursion identified in Tethyan sediments correlates with a C-isotope excursion recorded in the western North Atlantic, in the Gulf of Mexico, and in the Central Pacific (DSDP Sites 534,391,535 and 167). By analogy with the Aptian stage, also marked by a significant positive C-isotope excursion, the time of positive δ¹³C values is regarded as a time of accelerated carbon cycling coupled with increased burial rates of organic carbon and detrital material in oceanic sediments. A warm and humid climate, possiblycoupled with a high atmospheric CO₂ content and a high global sea-level, may have triggered the acceleration of the global carbon cycling. In this case the Valanginian C-isotope event would reflect a first episode of Greenhouse Earth conditions during the Cretaceous.  相似文献   

Advanced numerical modeling of seismic response of a propped r.c. diaphragm wall     

Chiara Miriano  Elisabetta Cattoni  Claudio Tamagnini 《Acta Geotechnica》2016,11(1):161-175

The paper presents some results from a number of dynamic FE simulations carried out to investigate the seismic response of a propped flexible retaining wall in a dry coarse-grained soil, considering two bedrock acceleration time histories as seismic input. Two different soil plasticity models have been considered in this study: an anisotropic hardening, critical-state model for cyclic/dynamic loading of sands and the classical Mohr–Coulomb elastic-perfectly plastic model with nonassociative flow rule. The results obtained allow to highlight the main features of the seismic performance of such type of flexible retaining structures and to evaluate the effects of the constitutive assumptions made on soil behavior on the predicted wall displacements and structural loads.  相似文献   

Paleomagnetic analysis of curved thrust belts reproduced by physical models     

Elisabetta Costa  Fabio Speranza   《Journal of Geodynamics》2003,36(5):633-654

This paper presents a new methodology for studying the evolution of curved mountain belts by means of paleomagnetic analyses performed on analogue models. Eleven models were designed aimed at reproducing various tectonic settings in thin-skinned tectonics. Our models analyze in particular those features reported in the literature as possible causes for peculiar rotational patterns in the outermost as well as in the more internal fronts. In all the models the sedimentary cover was reproduced by frictional low-cohesion materials (sand and glass micro-beads), which detached either on frictional or on viscous layers. These latter were reproduced in the models by silicone. The sand forming the models has been previously mixed with magnetite-dominated powder. Before deformation, the models were magnetized by means of two permanent magnets generating within each model a quasi-linear magnetic field of intensity variable between 20 and 100 mT. After deformation, the models were cut into closely spaced vertical sections and sampled by means of 1×1-cm Plexiglas cylinders at several locations along curved fronts. Care was taken to collect paleomagnetic samples only within virtually undeformed thrust sheets, avoiding zones affected by pervasive shear. Afterwards, the natural remanent magnetization of these samples was measured, and alternating field demagnetization was used to isolate the principal components. The characteristic components of magnetization isolated were used to estimate the vertical-axis rotations occurring during model deformation. We find that indenters pushing into deforming belts from behind form non-rotational curved outer fronts. The more internal fronts show oroclinal-type rotations of a smaller magnitude than that expected for a perfect orocline. Lateral symmetrical obstacles in the foreland colliding with forward propagating belts produce non-rotational outer curved fronts as well, whereas in between and inside the obstacles a perfect orocline forms only when the ratio between obstacles' distance and thickness of the cover is greater than 10. Finally, when a belt collides with an obstacle in the foreland oblique to the shortening direction the outer front displays rotations opposite in sign to oroclinal-type rotations, whereas the internal fronts seem to assume an “oroclinal type” rotational pattern. Furthermore rotation is easier in laterally unconfined models, i.e. when the wedge can “escape” laterally. The results from our models may be useful when compared to paleomagnetic rotations detected in natural arcs. In these cases, our results may allow for better understanding the tectonic setting controlling the genesis of curved mountain fronts, as is the case of the Gela Nappe of Sicily we compare with some of our models.  相似文献   

Deep mid-water bacterial mats from anoxic basins of the Eastern Mediterranean     

Elisabetta Erba 《Marine Geology》1991,100(1-4):83-101

Peculiar pellicles have been recorded in the extant anoxic hypersaline basins of the Bannock area and the Western Strabo Trench (Eastern Mediterranean). Discrete layers of pellicles were found in 29 cores. They are oriented parallel to bedding planes or are folded within the sandy base of turbidites and within slumped sediments. In addition, similar pellicles occur at the surface of or interlocked within gypsum crystals recovered from the Bannock area.

The pellicles are 0.5–3 mm thick and dark greenish-grey in colour. They foliate into very small (<1 mm) undulating and anastomosing microlaminae entrapping abundant biogenic and inorganic particles. The amorphous organic matter of the pellicles is most probably produced by bacterial masses linked to mineralization processes of the organic debris. Anaerobic sulphate-reducing bacteria (Desulphovibrio) are abundant and the presence of methane bacteria is likely.

Detailed analyses with the light microscope and scanning electron microscope yielded differences and similarities concerning ultrastructure, content, abundance and morphotypes of the bacterial pellicles from the Bannock area and the Western Strabo Trench. A consistently well-developed ultrastructure comprising thin microlaminae characterizes the Bannock pellicles, whereas the ultrastructure of the Tyro and Poseidon pellicles is usually not organized. Siliceous microfossils are abundant in samples from both sites, but centrate diatoms prevail in the Bannock pellicles whereas pennate diatoms are overwhelmingly dominant in the Tyro and Poseidon pellicles. Calcareous micro- and nannofossils, together with pyrite framboids, are more abundant in samples from the Bannock area. Bacteria are extremely abundant in samples from the Bannock area and three different morphological types have been distinguished. Only one type of bacteria was commonly observed in pellicles from the Western Strabo Trench basins.

Pellicles form at the normal seawater/brine interface, as substantiated by transmittance profiles and bacteriological investigations. Therefore, the term “deep mid-water bacterial mats” is proposed herein for these peculiar layers.

After bacterial mats grow at the interface, they are included within the sediments by following one of two different paths: (a) when pelagic sedimentation prevails, pellicles sink to the basin floor due to the increasing load of biogenic and inorganic detritus, and (b) under a tectonically active regime, turbidity currents and slumps can disrupt the interface and destroy the floating mats. In the latter case, fragments of pellicles are transported to the bottom within the gravity flows.  相似文献   

Use of Chitosan with Different Deacetylation Degrees for the Adsorption of Food Dyes in a Binary System          下载免费PDF全文

Janaína O. Gonçalves  Diana A. Duarte  Guilherme L. Dotto  Luiz Antonio A. Pinto 《洁净——土壤、空气、水》2014,42(6):767-774

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A reappraisal of seismic Q evaluated at Mt. Etna volcano. Receipt for the application to risk analysis     

Edoardo Del Pezzo  Francesca Bianco  Elisabetta Giampiccolo  Giuseppina Tusa  Tiziana Tuvé 《Journal of Seismology》2015,19(1):105-119

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Visible–near infrared spectral indices for mapping mineralogy and chemistry with OSIRIS‐REx     

Hannah H. Kaplan  Victoria E. Hamilton  Ellen S. Howell  F. Scott Anderson  M. Antonella Barrucci  John Brucato  Thomas H. Burbine  Beth E. Clark  Ed A. Cloutis  Harold C. Connolly  Elisabetta Dotto  Joshua P. Emery  Sonia Fornasier  Cateline Lantz  Lucy F. Lim  Frederic Merlin  Alice Praet  Dennis C. Reuter  Scott A. Sandford  Amy A. Simon  Driss Takir  Dante S. Lauretta 《Meteoritics & planetary science》2020,55(4):744-765

The primary objective of the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS‐REx) mission is to return to Earth a pristine sample of carbonaceous material from the primitive asteroid (101955) Bennu. To support compositional mapping of Bennu as part of sample site selection and characterization, we tested 95 spectral indices on visible to near infrared laboratory reflectance data from minerals and carbonaceous meteorites. Our aim was to determine which indices reliably identify spectral features of interest. Most spectral indices had high positive detection rates when applied to spectra of pure, single‐component materials. The meteorite spectra have fewer and weaker absorption features and, as a result, fewer detections with the spectral indices. Indices targeting absorptions at 0.7 and 2.7–3 μm, which are attributable to hydrated minerals, were most successful for the meteorites. Based on these results, we identified a set of 17 indices that are most likely to be useful at Bennu. These indices detect olivines, pyroxenes, carbonates, water/OH‐bearing minerals, serpentines, ferric minerals, and organics. Particle size and albedo are known to affect band depth but had a negligible impact on interpretive success with spectral indices. Preliminary analysis of the disk‐integrated Bennu spectrum with these indices is consistent with expectations given the observed absorption near 3 μm. Our study prioritizes spectral indices to be used for OSIRIS‐REx spectral analysis and mapping and informs the reliability of all index‐derived data products, including a science value map for sample site selection.  相似文献   

Seismological constraints on the 2018 Mt. Etna (Italy) flank eruption and implications for the flank dynamics of the volcano     

Salvatore Alparone  Graziella Barberi  Elisabetta Giampiccolo  Vincenza Maiolino  Antonino Mostaccio  Carla Musumeci  Antonio Scaltrito  Luciano Scarfì  Tiziana Tuv  Andrea Ursino 《地学学报》2020,32(5):334-344

3D earthquake locations, focal mechanisms and stress tensor distribution in a 16‐month interval covering the 2018 Mt. Etna flank eruption, enabled us to investigate the relationship between magma intrusion and structural response of the volcano and shed light on the dynamic processes affecting the instability of Mt. Etna. The magma intrusion likely caused tension in the flanks of the volcano, leading to significant ground deformation and redistribution of stress on the neighbouring faults at the edge of Mt. Etna's unstable sector, encouraging the ESE sliding of the eastern flank of the volcano. Accordingly, FPSs of the post‐eruptive events show strike slip faulting mechanisms, under a stress regime characterized by a maximum compressive σ₁, NE‐SW oriented. In this perspective, any flank eruption could temporarily enhance the sliding process of both the southern and eastern flanks of the volcano.  相似文献   

A peculiar family of Jupiter Trojans: The Eurybates     

F. De Luise  E. Dotto  M.A. Barucci  D. Perna  F. Marzari 《Icarus》2010,209(2):586-590

The Eurybates family is a compact core inside the Menelaus clan, located in the L₄ swarm of Jupiter Trojans. Fornasier et al. (Fornasier, S., Dotto, E., Hainaut, O., Marzari, F., Boehnhardt, H., De Luise, F., Barucci, M.A. [2007]. Icarus 190, 622-642) found that this family exhibits a peculiar abundance of spectrally flat objects, similar to Chiron-like Centaurs and C-type main belt asteroids. On the basis of the visible spectra available in literature, Eurybates family’s members seemed to be good candidates for having on their surfaces water/water ice or aqueous altered materials.To improve our knowledge of the surface composition of this peculiar family, we carried out an observational campaign at the Telescopio Nazionale Galileo (TNG), obtaining near-infrared spectra of 7 members. Our data show a surprisingly absence of any spectral feature referable to the presence of water, ices or aqueous altered materials on the surface of the observed objects. Models of the surface composition are attempted, evidencing that amorphous carbon seems to dominate the surface composition of the observed bodies and some amount of silicates (olivine) could be present.  相似文献