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The main goal of this paper is to show that the elliptic restricted three-body problem has ejection-collision orbits when the mass parameter µ is small enough. We make use of the blow up techniques. Moreover, we describe the global flow of the elliptic problem when µ = 0 taking into account the singularities due to collision and to infinity. 相似文献
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Celestite formation, bacterial sulphate reduction and carbonate cementation of Eocene reefs and basinal sediments (Igualada, NE Spain) 总被引：5，自引：0，他引：5
Conxita Taberner James D. Marshall† James P. Hendry‡ Catherine Pierre§ & M. F. Thirlwall¶ 《Sedimentology》2002,49(1):171-190
Petrographic and geochemical studies of an Upper Eocene reef and associated basinal sediments from the mixed carbonate–siliciclastic fill of the south‐eastern Pyrenean foreland basin near Igualada (NE Spain) provide new insights into the evolution of subsurface hydrology during the restriction of a marine basin. The reef deposits are located on delta‐lobe sandstones and prodelta marls, which are overlain by hypersaline carbonates and Upper Eocene evaporites. Authigenic celestite (SrSO4) is an important component in the observed diagenetic sequences. Celestite is a significant palaeohydrological indicator because its low solubility constrains transportation of Sr2+ and SO42? in the same diagenetic fluid. Stable isotopic analyses of carbonates in the reef indicate that meteoric recharge was responsible for aragonite stabilization and calcite cementation. Sulphur and oxygen isotope geochemistry of the celestite demonstrates that it formed from residual sulphate after bacterial sulphate reduction, but also requires that there was a prior episode of sulphate recycling. Meteoric water reaching the reef and basinal areas was most probably charged with SO42? from the dissolution of younger Upper Eocene marine evaporites. This sulphate, combined with organic matter present in the sediments, fuelled bacterial sulphate reduction in the meteoric palaeoaquifer. Strontium for celestite precipitation was partly derived in situ from dissolution of aragonite corals in the reef and basinal counterparts. However, 87Sr/86Sr data also suggest that Sr2+ was partly derived from dissolution of overlying evaporites. Mixing of these two fluids promoted celestite formation. The carbonate stable isotopic data suggest that the local meteoric water was enriched in 18O compared with that responsible for stabilization of other reefs along the basin margin. Furthermore, meteoric recharge at Igualada post‐dated evaporite deposition in the basin, whereas other parts of the same reef complex were stabilized before evaporite formation. This discrepancy resulted from the spatial distribution of continental siliciclastic units that acted as groundwater conduits. 相似文献
3.
Life after death: shallow‐water Mediterranean invertebrate communities associated with mammal bones 
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下载免费PDF全文 Sergi Taboada Maria Bas Carlos Leiva Mariona Garriga Rafael Sardá Conxita Avila 《Marine Ecology》2016,37(1):164-178
Invertebrate and microbial marine communities associated with mammal bones are interesting and poorly understood habitats, mainly known from studies on deep‐water whale remains. In order to characterize these communities in the shallow‐water Mediterranean, we present here the results of a pioneering experiment using mammal bones. Minke whale, pig and cow bones were experimentally deployed on three different background communities: rocky substrate, soft‐bottom and a Posidonia oceanica meadow. Bones were deployed for a year at about 20 m depth and collected every 3 months, and the invertebrate fauna colonizing the bones was identified to the lowest possible taxonomic level. As expected, mammal bones showed remarkable differences when compared with background communities. Within bones, four different clusters could be identified, primarily on the basis of the polychaete fauna, the most abundant and diverse group in the survey. Clusters A1–A3 corresponded to high to moderately altered successional stages composed by a fauna closer to that of anthropogenically enriched shallow‐water environments. These clusters were characterized by the occurrence of the opportunist polychaetes Ophryotrocha puerilis, Neanthes caudata (Cluster A1), Protodorvillea kefersteini (Cluster A2) and Ophryotrocha alborana (Cluster A3). Cluster B was characterized by the presence of the polychaete Oxydromus pallidus together with typical invertebrate background fauna, which suggests that this community, after a year of deployment, was closer to that found in natural conditions. As opposed to similar shallow‐water studies in other geographic areas, no occurrence of the polychaete Osedax (commonly known as bone‐eating worms) was reported from our experiments. Apart from the study on the invertebrate communities, insights about the population dynamics of three of the most abundant species (O. puerilis, O. alborana, N. caudata) are given as well as remarks on a hypothetical trophic network based on fecal pellet analysis. 相似文献
4.
A large landslide (40 × 106 m3) was reactivated on the left bank of Canelles reservoir, Spain. The instability was made evident after a considerable reduction
of the reservoir level. The drawdown took place during the summer of 2006 after several years of high water levels. The drawdown
velocity reached values between 0.5 and 1.2 m/day (registered at low elevations). The paper reports the geological and geotechnical
investigations performed to define the movement. The geometry of the slip surface was established from the detailed analysis
of the continuous cores recovered in deep borings and from limited information provided by inclinometers. Deep piezometric
records provided also valuable information on the pore water pressure in the vicinity of the failure surface. These data allowed
validating a flow–deformation coupled calculation model, which takes into account the changes in water level that occurred
4 years previous to the failure as well as the average rainfall. The analysis indicates that the most likely reason for the
instability is the rapid drawdown that took place during the summer of 2006. The potential sudden acceleration of the slide
is also analysed in the paper introducing coupled thermal hydraulic and mechanical effects that may develop at the basal shearing
surface of the sliding mass. The results indicate that the slide velocity may reach values around 16 m/s when displacement
reaches 250 m. 相似文献
5.
Conxita Pinyol 《Celestial Mechanics and Dynamical Astronomy》1995,61(4):315-331
The main goal of this paper is to give an approximation to initial conditions for ejection-collision orbits with the more massive primary, in the planar elliptic restricted three body problem when the mass parameter µ and the eccentricity e are small enough. The proof is based on a regularization of variables and a perturbation of the two body problem.This work was partially supported by DGICYT grant number PB90-0695. 相似文献
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Heat‐induced excess pore pressures on the failure surface of a planar slide have been calculated by solving the mass and heat balance equations on the shear band. The set of differential equations and the equation of motion of the slide have been solved in closed form for the case of incompressible fluid and incompressible soil skeleton. The solution describes the accelerated motion of the slide. It has been compared with the numerical solution when soil and water stiffness terms are not disregarded. A case study, based on a well‐known translational slide (Cortes slide) has been solved. Numerical and analytical solutions are compared. Results of a sensitivity analysis indicate that the permeability of the shear band is the key parameter to control the onset of a rapid motion. For a band permeability above a threshold value, in the vicinity of 10?15m2 (10?8m/s), fast accelerated motions are very unlikely. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Esther Barrabés Josep Maria Cors Conxita Pinyol Jaume Soler 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):55-66
Hip-hop solutions of the 2N-body problem with equal masses are shown to exist using an analytic continuation argument. These solutions are close to planar regular 2N-gon relative equilibria with small vertical oscillations. For fixed N, an infinity of these solutions are three-dimensional choreographies, with all the bodies moving along the same closed curve in the inertial frame. 相似文献
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Santiago Giralt Ana Moreno Roberto Bao Alberto Sáez Ricardo Prego Blas L. Valero-Garcés Juan José Pueyo Penélope González-Sampériz Conxita Taberner 《Journal of Paleolimnology》2008,40(1):195-215
A high resolution multiproxy study (magnetic susceptibility, X-ray diffraction, XRF scanner, gray-colour values, Total Organic
Carbon, Total Inorganic Carbon, Total Carbon and Total Biogenic Silica) of the sedimentary infill of Lago Chungará (northern
Chilean Altiplano) was undertaken to unravel the environmental forcings controlling its evolution using a number of different
multivariate statistical techniques. Redundancy analyses enabled us to identify the main provenance of the studied proxies
whereas stratigraphically unconstrained cluster analyses allowed us to distinguish the “outsiders” as result of anomalous
XRF scanner acquisitions. Principal Component Analysis (PCA) was employed to identify and isolate the main underlying environmental
gradients that characterize the sedimentary infill of Lago Chungará. The first eigenvector of the PCA could be interpreted
as an indicator of changes in the input of volcaniclastic material, whereas the second one would indicate changes in water
availability. The chronological model of this sedimentary sequence was constructed using 17 AMS 14C and 1 238U/230Th dates in order to characterize the volcaniclastic input and the changes in water availability in the last 12,300 cal years
BP.
Comparison of the reconstructed volcaniclastic input of Lago Chungará with the dust particle record from the Nevado Sajama
ice core suggested that the Parinacota volcano eruptions were the main source of dust during the mid and Late Holocene rather
than the dry out lakes as has previously been pointed out. The comparison of the water availability reconstruction of Lago
Chungará with three of the most detailed paleoenvironmental records of the region (Paco Cocha, Lake Titicaca and Salar Uyuni)
showed an heterogeneous (and sometimes contradictory) temporal and spatial pattern distribution of moisture. Although the
four reconstructions showed a good correlation, each lacustrine ecosystem responded differently to the moisture oscillations
that affected this region. The variations in the paleoenvironmental records could be attributed to the dating uncertainities,
lake size, lake morphology, catchment size and lacustrine ecosystem responses to the abrupt arid events. 相似文献