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31.
The ‘algarrobo’Prosopis flexuosais an important food resource in the Monte Desert of Argentina. Native, domestic, and exotic mammals consume the fruit of this legume and disperse the seed through faeces. In the present study we analyse the effect that different dispersal agents (cattle, horse, European wild boar, rodents, gray fox) have on seed damage, viability, and germination. Cattle increase germination at the expense of reduced viability, whereas horses maintain viability but do not contribute to a prompt germination response. Among native mammals, the gray fox maintains seed viability without increasing germination, whereas rodents affect seed viability but enhance germination rates. The European wild boar, however, damages all of the seeds it consumes. 相似文献
32.
This paper presents the structural response of a fast and relatively small, composite materials catamaran to slamming loads. Finite element method is used to provide valuable information in order to optimise the design of the catamaran. The analysis is carried out using ANSYS 6.0 finite element software.The response of the structure to quasi-static slamming loads according to Det Norske Veritas High Speed and Light Craft crest landing and hollow landing rules [DNV, 1999] has been implemented and studied. An optimisation study for the structural response is carried out by changing the ply orientation in the vessel and suitable recommendations are made. 相似文献
33.
Germán Bayona Camilo Montes Agustín Cardona Carlos Jaramillo Germán Ojeda Victor Valencia Carolina Ayala‐Calvo 《Basin Research》2011,23(4):403-422
The upper Campanian–Lower Eocene synorogenic sedimentary wedge of the Ranchería Basin was deposited in an intraplate basin resting on a tilted continental crustal block that was deformed by collision and subsequent subduction of the Caribbean Plate. Upper Cretaceous–Lower Eocene strata rest unconformably upon Jurassic igneous rocks of the Santa Marta Massif, with no major thrust faults separating the Santa Marta Massif from the Ranchería Basin. The upper Campanian–Lower Eocene succession includes, from base to top: foraminifera‐rich calcareous mudstone, mixed carbonate–siliciclastic strata and mudstone, coal and immature fluvial sandstone beds. Diachronous collision and eastward tilting of the plate margin (Santa Marta Massif and Central Cordillera) favoured the generation of accommodation space in a continuous intraplate basin (Ranchería, Cesar and western Maracaibo) during the Maastrichtian to Late Palaeocene. Terrigenous detritus from the distal colliding margin filled the western segments of the continuous intraplate basin (Ranchería and Cesar Basins); in the Late Paleocene, continental depositional systems migrated eastwards as far as the western Maracaibo Basin. In Early Eocene time, reactivation of former extensional structures fragmented the intraplate basin into the Ranchería‐Cesar Basins to the west, and the western Maracaibo Basin and Palmar High to the East. This scenario of continent–oceanic arc collision, crustal‐scale tilting, intraplate basin generation and fault reactivation may apply for Upper Cretaceous–Palaeogene syntectonic basins in western Colombia and Ecuador, and should be considered in other settings where arc–continent collision is followed by subduction. 相似文献
34.
Using P-wave travel time data from local seismicity, the crustal structure ofthe central and southern part of Colombia was determined. A very stableand narrow range of possible velocity models for the region was obtainedusing travel time inversion. This range of models was tested with earthquakelocations to select the best velocity model. The 1D velocity modelproposed has five layers over a halfspace, with interfaces at depths of 4,25, 32, 40 and 100 km and P-wave velocities of 4.8, 6.6, 7.0, 8.0, 8.1and 8.2 km/sec, respectively. According to this model the Moho lies at32 km depth on average. For P-waves, the station corrections range from–0.62 to 0.44 sec and for S-wave they range from –1.17 to 0.62 sec.These low variations in station residuals indicate small lateral velocitychanges and therefore the velocity model found should be well suited forearthquake locations and future starting model for 3D tomography studies.Using this new velocity model, the local earthquakes were relocated. Theshallow seismicity, < 30 km, clearly shows the borders betweentectonic plates and also the main fault systems in the region. The deepseismicity, > 80 km, shows two subduction zones in the country: theCauca subduction zone with a strike of N120°E, dip of 35°and thickness of 35 km, and the Bucaramanga subduction zone which has,for the northern part, a strike of N103°E, dip of 27° andthickness undetermined and, for the southern part, a strike ofN115°E, dip of 40° and thickness of 20 km. Based ondifferences of thickness of brittle crust in the subducted slab and spatialdistribution of the seismicity, the Cauca and Bucaramanga subduction zonesseem to represent independent processes. The Cauca subduction seems tobe connected to the process of the Nazca plate being subducted under theNorth Andes Block. In the Bucaramanga subduction zone, the transitionbetween southern and northern parts and changes in geometry of the slabseem to be gradual and there is no evidence of a tear in the slab, howeverthe local seismicity does not allow us to determine which plate or plates arebeing subducted. The Bucaramanga nest appears to be included into thesubducted slab. 相似文献
35.
María del Carmen Scapini Víctor Hugo Conzonno Vilma Teresa Balzaretti Alicia Fernández Cirelli 《Aquatic Sciences - Research Across Boundaries》2010,72(1):1-12
Structural aspects of humic substances (HSs) in marine waters of Engaño Bay (Atlantic Ocean) and water from the Chubut River (Patagonia, Argentina) were compared. The HSs were isolated, purified, and analyzed using a multiple-method approach for structural characterization: elemental analysis, nuclear magnetic resonance (13C and 1H NMR), infrared spectroscopy (FTIR), UV-visible absorption and fluorescence. Similarities between the marine and freshwater components were evaluated on the basis of N and O contents, H/C and C/N atomic ratios, infrared bands from nitrogen-containing and carboxylic groups, percentage of functional groups obtained from NMR spectra, spectral slope coefficient of absorption spectra, absorbance ratios at 250 and 365 nm (E 2/E 3), aromaticity, excitation–emission matrices and fluorescence quantum yield. Both the Engaño Bay and Chubut River waters have HSs that are mainly composed of fulvic acids (FAs); although they are very similar, they may be distinguished from one another. Similarities include the predominance of aliphatic carbon content (low aromatic content); however, the water bodies differed in their content of proteins and carboxylic acids. The Engaño Bay FAs have mainly an aquatic origin; although the Chubut River FAs suggest a similar aquagenic origin, there is also evidence of contributions from pedogenic FAs. 相似文献
36.
Subsidence involves sinking of the ground surface. The movement generally is localised and may or may not involve some amount of horizontal movement. It may be rapid or take place gradually over a period of time. Subsidence may be brought about by natural causes as, for example, when the roof of a cavern in limestone is weakened to the extent that it is no longer self-supporting and so collapses. Other more exotic examples are associated with volcanism and earthquakes. Perhaps, however, subsidence is more frequently associated with movements caused by mining activities, that is, the removal of mineral deposits, be they in solid, liquid or gaseous form, from within the ground. Mining is one of the earliest activities of man and has taken place in every continent. Subsidence also can result from subsurface excavations such as tunnels, caverns, cellars and sewers. One of the added problems of some forms of subsidence is that it is impossible to predict. This, coupled with the fact that the presence of potentially collapsible voids may be unknown, unrecorded or simply forgotten about further complicates the problem. The objectives of this paper are to document and draw attention to a number of unusual examples of subsidence. These have been generated due to the mining of chalk in southern England, the collapse of slate mines and caverns in Germany, the underground extraction of evaporites in Northern Ireland, fault reactivation in Wales and northern England and the extensive extraction of pumice on the flanks of Galeras volcano in Colombia. 相似文献