The O4f + O6V eclipsing binary system Sk−67°105 in the Large Magellanic Cloud     

Pablo G. Ostrov  Emilio Lapasset 《Monthly notices of the Royal Astronomical Society》2003,338(1):141-146

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Astronomical Site Testing in Northwest of Argentina     

Pablo Recabarren  Pablo Recabarren  Mirta Mosconi  Hernán Muriel  Hernán Muriel  Diego García Lambas  Diego García Lambas  Marc Sarazin  Riccardo Giovanelli 《Astrophysics and Space Science》2004,290(3-4):409-413

We present the preliminary results of the astronomical site testing, which the group IATE of the OAC is developing in northwest of Argentine in collaboration with ESO and the Department of Astronomy of Cornell University. We show the results, which we have obtained from the analysis of GOES 8 satellite images in the 10.7 μm band, which allowed us to configurate a map of clear sky regions in an area between 23° and 28° S, and 66° 30′ and 69° W. We also comment logistical and tectonic aspects, and discuss next steps to follow in the research.  相似文献   

Mechanical models of fracture reactivation and slip on bedding surfaces during folding of the asymmetric anticline at Sheep Mountain, Wyoming     

Pablo F. Sanz  David D. Pollard  Patricia F. Allwardt  Ronaldo I. Borja 《Journal of Structural Geology》2008,30(9):1177-1191

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First U–Pb SHRIMP age of the Hauterivian stage, Neuquén Basin, Argentina     

M. Beatriz Aguirre-Urreta  Pablo J. Pazos  Darío G. Lazo  C. Mark Fanning  Vanesa D. Litvak   《Journal of South American Earth Sciences》2008,26(1):91-99

A high-resolution ion-microprobe (SHRIMP) U–Pb zircon age from a tuff layer intercalated in the ammonoid bearing sedimentary succession of the Neuquén Basin in Argentina provides a robust geochronologic date to add to the absolute ages and to improve the relative chronology of the Early Cretaceous Hauterivian stage. The tuff layer appears interbedded between shales of the upper member (Agua de la Mula) of the Agrio Formation within the Spitidiscus riccardii ammonoid zone (base of the Late Hauterivian) yielding a date of 132.5 ± 1.3 Ma. This date confirms and supports an accurate correlation between the ammonoid biostratigraphy of the Neuquén Basin with the Western Mediterranean Province of the Tethys during the Early Cretaceous and matches with the most recently published time scale. It also casts doubts on the validity of K–Ar ages on glauconite-grains recently reported from the Lower Cretaceous of the Vocontian Basin of France.  相似文献   

The spatial implications of the functional proximity deriving from air passenger flows between European metropolitan urban regions     

Malcolm C. Burns  Josep Roca Cladera  Montserrat Moix Bergadà 《GeoJournal》2008,71(1):37-52

Until recently the traditional spatial configuration of the European geography was based upon the core-periphery model. The ‘pentagon’, broadly defined as lying between London, Paris, Milan, Munich and Hamburg, was seen as the core area characterised by having the highest concentration of economic development in the European Union (EU), with the remainder of the European territory viewed as peripheral, albeit to varying degrees. In a number of cases such peripheral areas equated with clear regional disparities. The elaboration of the European Spatial Development Perspective (ESDP) (CEC, European spatial development perspective, towards balanced and sustainable development in the territory of the European Union, 1999) challenged this core-periphery model. European spatial planning policies, aimed at encouraging social and economic, and with ever increasing importance, territorial cohesion, seek amongst other aspects to encourage the development of a balanced and polycentric urban system. This paper adopts a network analysis approach to the analysis of air passenger flows between some 28 principal European metropolitan urban regions. The evaluation of these flows contributes to an enhanced comprehension of the spatial dynamics of the European metropolitan territory which goes beyond that deriving from the more standard analyses of the individual components of the urban system. Several indicators are used, deriving from gravitational modelling techniques, to analyse the complexity of the air passenger flows. A multidimensional scaling (MDS) technique is introduced in order to interpret and visualise the resulting spatial configuration and positioning of the different metropolitan centres within the conceptual European ‘space of air passenger flows’, thereby contrasting with the more traditional map-based geographical image of Europe, based upon Cartesian coordinates.

Malcolm C. BurnsEmail:

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Gas hydrate disturbance fabrics of southern Hydrate Ridge sediments (ODP Leg 204): Relationship with texture and physical properties   总被引：1，自引：0，他引：1  

Elena Piñero  Eulàlia Gràcia  Francisca Martínez-Ruiz  Juan Cruz Larrasoaña  Alexis Vizcaino  Gemma Ercilla 《Geo-Marine Letters》2007,27(2-4):279-288

Soupy and mousse-like fabrics are disturbance sedimentary features that result from the dissociation of gas hydrate, a process that releases water. During the core retrieval process, soupy and mousse-like fabrics are produced in the gas hydrate-bearing sediments due to changes in pressure and temperature conditions. Therefore, the identification of soupy and mousse-like fabrics can be used as a proxy for the presence of gas hydrate in addition to other evidence, such as pore water freshening or anomalously cool temperature. We present here grain-size results, mineralogical composition and magnetic susceptibility data of soupy and mousse-like samples from the southern Hydrate Ridge (Cascadia accretionary complex) acquired during Leg 204 of the Ocean Drilling Program. In order to study the relationship between sedimentary texture and the presence of gas hydrates, we have compared these results with the main textural and compositional data available from the same area. Most of the disturbed analyzed samples from the summit and the western flank of southern Hydrate Ridge show a mean grain size coarser than the average mean grain size of the hemipelagic samples from the same area. The depositional features of the sediments are not recognised due to disturbance. However, their granulometric statistical parameters and distribution curves, and magnetic susceptibility logs indicate that they correspond to a turbidite facies. These results suggest that gas hydrates in the southern Hydrate Ridge could form preferentially in coarser grain-size layers that could act as conduits feeding gas from below the BSR. Two samples from the uppermost metres near the seafloor at the summit of the southern Hydrate Ridge show a finer mean grain-size value than the average of hemipelagic samples. They were located where the highest amount of gas hydrates was detected, suggesting that in this area the availability of methane gas was high enough to generate gas hydrates, even within low-permeability layers. The mineralogical composition of the soupy and mousse-like sediments does not show any specific characteristic with respect to the other samples from the southern Hydrate Ridge.  相似文献   

A Functional Analysis of the Benthic Macrofauna of the São Sebastião Channel (Southeastern Brazil)     

Emilia Arasaki  Pablo Muniz  & Ana Maria S. Pires-Vanin 《Marine Ecology》2004,25(4):249-263

Abstract.  The major problem in coastal areas of developing countries is disturbance caused by anthropogenic influence. This disturbance can be quantified by analysing the distribution and composition of marine communities using uni- and multivariate techniques and the biotic index. A study of benthic macrofauna was carried out along the São Sebastião Channel, northern coast of São Paulo State, Brazil, in an area with a submarine outfall, a petroleum terminal and a commercial harbour. Sampling was undertaken seasonally, by means of a van Veen grab (0.1 m²) at 15 oceanographic stations, from November 1993 to August 1994. A total of 392 species were identified (129 Polychaeta, 127 Mollusca, 98 Crustacea, 28 Echinodermata and 10 other phyla). The sedimentary pattern recorded for the São Sebastião Channel is very heterogeneous, influenced mainly by strong wind-driven currents, and differs from nearby shelf areas. The study area could be divided into three regions based on sediment texture and fauna: one region dominated by medium and coarse sand with low values of organic carbon; a second area where pelitic fractions were dominant with high values of organic carbon and nitrogen; and a third region characterised by fine and very fine sand, presenting intermediate organic carbon values. No temporal significant variation in abundance and species composition was found, except in autumn. The use of the 'marine Biotic Coefficient' showed the same ecological trend as the faunal abundance and demonstrated that the central continental region of the channel is affected by human activities.  相似文献   

The pelagic foodweb in the upwelling ecosystem of Galicia (NW Spain) during spring: natural abundance of stable carbon and nitrogen isotopes   总被引：6，自引：1，他引：6  

Bode  Antonio; Carrera  Pablo; Lens  Santiago 《ICES Journal of Marine Science》2003,60(1):11-22

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Asteroid “clans”: Super-families or multiple events?     

Alberto Cellino  Vincenzo Zappalà 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):37-47

Among the recently determined asteroid families (Zappala' et al., 1992) a number of very large clusterings are recognized. Some of them agglomerate few families previously identified as single groupings. In most cases, the new big families (called clans) seem to be composed by different sub-clusterings connected each other by very narrow bridges. In the present paper we analyze their possible origin and evolution: a primordial single event followed by subsequent collisions of the fragments, a super-catastrophic original impact or different collisional events overlapping by chance.  相似文献   

The rotations of 128 Nemesis and 393 Lampetia: The longest known periods to date     

F. Scaltriti  V. Zappalà  H.J. Schober 《Icarus》1979,37(1):133-141

Extensive photoelectric lightcurves of the asteroids 128 Nemesis and 393 Lampetia show for both objects extremely long rotational periods, the longest known to date for minor planets. For 393 Lampetia the combined results suggest with high probability a period of 38.7 hr with a maximal amplitude of 0.14 mag; a double-wave characteristic of the lightcurve must be assumed. For 128 Nemesis the complete double-wave lightcurve was observed and a period of 39.0 hr with a total amplitude of only 0.10 mag was deduced. Observations of 128 Nemesis confirm without doubt the presence of small-scale features of amplitude 0.01 to 0.02 mag, corresponding to small topographic features of about 15 km in height and width on the surface.  相似文献