Rodent selection by Geoffroy’s cats in a semi-arid scrubland of central Argentina     

S.B.C. Bisceglia  J.A. Pereira  P. TetaR.D. Quintana 《Journal of Arid Environments》2011,75(11):1024-1028

Small mammals usually constitute the main prey for Leopardus geoffroyi throughout its distribution. We studied the patterns of small rodent selection by this felid in a semi-arid scrubland of central Argentina, addressing whether prey choice may be related to the availability, morphology, and distribution of the different rodent species. Cat’s diet was studied during 2005-2006 through the analysis of 182 scats, along with field estimates of rodent abundances from trapping. The cricetine rodents Akodon molinae and Calomys musculinus were predated according to the availability expected by trapping, indicating that their use was opportunistic. Akodon azarae and Graomys griseoflavus, on one hand, and Eligmodontia typus, on the other hand, were consumed in lower and higher proportion than their availabilities, respectively. Our results suggest that some cricetine rodent characteristics such as abundance, escape ability, microhabitat use, and activity period, appear to be potential factors contributing to differential vulnerability to predation by Geoffroy’s cat in central Argentina.  相似文献   

Stochastic computational modelling of highly heterogeneous poroelastic media with long‐range correlations     

Diego G. Frias  Mrcio A. Murad  Felipe Pereira 《国际地质力学数值与分析法杂志》2004,28(1):1-32

The compaction of highly heterogeneous poroelastic reservoirs with the geology characterized by long‐range correlations displaying fractal character is investigated within the framework of the stochastic computational modelling. The influence of reservoir heterogeneity upon the magnitude of the stresses induced in the porous matrix during fluid withdrawal and rock consolidation is analysed by performing ensemble averages over realizations of a log‐normally distributed stationary random hydraulic conductivity field. Considering the statistical distribution of this parameter characterized by a coefficient of variation governing the magnitude of heterogeneity and a correlation function which decays with a power‐law scaling behaviour we show that the combination of these two effects result in an increase in the magnitude of effective stresses of the rock during reservoir depletion. Further, within the framework of a perturbation analysis we show that the randomness in the hydraulic conductivity gives rise to non‐linear corrections in the upscaled poroelastic equations. These corrections are illustrated by a self‐consistent recursive hierarchy of solutions of the stochastic poroelastic equations parametrized by a scale parameter representing the fluctuating log‐conductivity standard deviation. A classical example of land subsidence caused by fluid extraction of a weak reservoir is numerically simulated by performing Monte Carlo simulations in conjunction with finite elements discretizations of the poroelastic equations associated with an ensemble of geologies. Numerical results illustrate the effects of the spatial variability and fractal character of the permeability distribution upon the evolution of the Mohr–Coulomb function of the rock. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Genesis of the mafic impact melt rock in the northwest sector of the Vredefort Dome,South Africa     

Wolf Uwe Reimold  Natalia Hauser  Alisson Lopes Oliveira  Ana Rita Pereira Maciel  Steven Goderis  Lidia Pittarello  Wencke Wegner  Mario Fischer-Goedde  Christian Koeberl  Vinciane Debaille  Carolinna Silva Maia de Souza 《Meteoritics & planetary science》2023,58(7):907-944

Genesis and emplacement of Vredefort Granophyre, the impact melt rock exposed on the Vredefort Dome, the erosional remnant of the central uplift of the Vredefort impact structure, South Africa, have long been debated. This debate was recently reinvigorated by the discovery that besides the previously known felsic variety of >66 wt% SiO₂, a second, somewhat more mafic phase of <66 wt% SiO₂ occurs along a Granophyre dike on farms Kopjeskraal and Eldorado in the northwest sector of the dome. Two hypotheses have been put forward to explain the genesis and emplacement of this second phase: (1) successive injections of impact melt into extensional fractures opened in the course of central uplift formation/crater modification, with melts of distinct compositions derived from a differentiating impact melt body in the crater, and (2) generation of the more mafic phase as a product of admixture/assimilation of a mafic country rock component, either the so-called epidiorite of possible Ventersdorp Supergroup affiliation or the Dominion Group meta-lava (DGL), to Felsic Granophyre. In the latter model, contamination with mafic country rock would have occurred during downward intrusion and stoping into and below the crater floor. The so-called Mafic Granophyre has previously only ever been sampled on a single site (Farm Kopjeskraal). In this study, samples of Granophyre occurring along the southerly extension of this dike on farm Rensburgdrif, and from a second dike on the Rietkuil property further southwest were investigated by field work, and petrographic, geochemical, and isotopic analysis. The mafic phase indeed occurs in the interior of the dike at Rensburgdrif, and also on Rietkuil. New geochemical and Sr-Nd isotope data support the hypothesis that the Mafic Granophyre composition represents a mixture between Felsic Granophyre and a mafic country rock. A 20% admixture of epidiorite or DGL to Felsic Granophyre provides an excellent match for the chemical composition of the Mafic Granophyre. The Sr-Nd isotope data indicate that this admixture likely involved the epidiorite component rather than DGL. Together with earlier Sr-Nd-Os-Se isotopic data, and other geochemical data, these results further support formation of the Mafic Granophyre by local assimilation/admixture of epidiorite to Felsic Granophyre.  相似文献   

The turbulent dispersion of surface drifters by water waves: experimental study     

Violante-Carvalho  Nelson  Skvortsov  Alexei  Babanin  Alexander  Pereira  Henrique  Pinho  Uggo  Esperança  Paulo T. T. 《Ocean Dynamics》2021,71(3):379-389

Ocean Dynamics - Dispersion of a passive tracer by water waves is of significant importance for many scientific and technological problems including bio-diversity of marine life, ecological impact...  相似文献   

Polymerisation versus degradation of sunflower oil spilled in the marine environments     

Pereira MG  Mudge SM  Latchford J 《Marine pollution bulletin》2003,46(9):1078-1081

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Decrease of Zn, Cd and Pb concentrations in marine fish species over a decade as response to reduction of anthropogenic inputs: the example of Tagus estuary     

Raimundo J  Pereira P  Caetano M  Cabrita MT  Vale C 《Marine pollution bulletin》2011,62(12):2854-2858

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A full non-metallic trailer for GPR road surveys     

H. Lorenzo  F.I. RialM. Pereira  M. Solla 《Journal of Applied Geophysics》2011,75(3):490-497

In this work, the design and construction of a special trailer designed to evaluate traffic infrastructure with GPR is presented. This trailer is adapted to the requirements of a multipurpose GPR system and different ground-coupled antennas to allow for multi-frequency surveys of roads without obstructing traffic. The prototype presented in this work is completely non-metallic, allowing massive data acquisition at a cruising speed up to 80 km/h. It provides the possibility of carrying two bowtie antennas simultaneously with a simple mechanism that allows for changing the elevation from the roadbed to the antenna/s for adequate and safe operation. The work includes the results of tests conducted to evaluate the performance of the system under different field work conditions.  相似文献   

Fish consumption and risk of contamination by mercury---considerations on the definition of edible parts based on the case study of European sea bass     

Mieiro CL  Pacheco M  Duarte AC  Pereira ME 《Marine pollution bulletin》2011,62(12):2850-2853

In the present study, the risk to humans by consuming European sea bass (Dicentrarchus labrax), captured at three sites along a Hg contamination gradient, was evaluated by comparing muscle and kidney total Hg (T-Hg) levels with the European regulations for marketed fish. Moreover, T-Hg and organic Hg (O-Hg) levels in muscle were compared with the Provisional Tolerable Weekly Intake (PTWI) and the Reference Dose (RfD). Although T-Hg levels in muscle were below the European value allowable for marketed fish, kidney’s levels were higher than the set value, stressing the importance of redefining the concept of edible tissue and which tissues should be considered. Mercury weekly ingestion in the contaminated areas was higher than the PTWI, and O-Hg daily ingestion rates were higher than the RfD in all sampling sites. Thus, populations consuming sea bass from the contaminated sites may be at risk, with particular relevance for children and pregnant women.  相似文献   

The pyrogeography of sub-Saharan Africa: a study of the spatial non-stationarity of fire–environment relationships using GWR     

Ana?C.?L.?SáEmail author  José?M.?C.?Pereira  Martin?E.?Charlton  Bernardo?Mota  Paulo?M.?Barbosa  A.?Stewart Fotheringham 《Journal of Geographical Systems》2011,13(3):227-248

This study analyses the relationship between fire incidence and some environmental factors, exploring the spatial non-stationarity of the phenomenon in sub-Saharan Africa. Geographically weighted regression (GWR) was used to study the above relationship. Environment covariates comprise land cover, anthropogenic and climatic variables. GWR was compared to ordinary least squares, and the hypothesis that GWR represents no improvement over the global model was tested. Local regression coefficients were mapped, interpreted and related with fire incidence. GWR revealed local patterns in parameter estimates and also reduced the spatial autocorrelation of model residuals. All the covariates were non-stationary and in terms of goodness of fit, the model replicates the data very well (R ² = 87%). Vegetation has the most significant relationship with fire incidence, with climate variables being more important than anthropogenic variables in explaining variability of the response. Some coefficient estimates exhibit locally different signs, which would have gone undetected by a global approach. This study provides an improved understanding of spatial fire–environment relationships and shows that GWR is a valuable complement to global spatial analysis methods. When studying fire regimes, effects of spatial non-stationarity need to be incorporated in vegetation-fire modules to have better estimates of burned areas and to improve continental estimates of biomass burning and atmospheric emissions derived from vegetation fires.  相似文献   

Pleistocene mammals from the southern Brazilian continental shelf     

Renato Pereira Lopes  Francisco Sekiguchi Buchmann 《Journal of South American Earth Sciences》2011,31(1):17-27

Fossils of terrestrial mammals preserved in submarine environment have been recorded in several places around the world. In Brazil such fossils are rather abundant in the southernmost portion of the coast, associated to fossiliferous concentrations at depths up to 10 m. Here is presented a review of such occurrences and the first record of fossils in deeper areas of the continental shelf. The fossils encompass several groups of both extinct and extant mammals, and exhibit several distinct taphonomic features, related to the marine environment. Those from the inner continental shelf are removed and transported from the submarine deposits to the coast during storm events, thus forming large konzentrat-lagerstätte on the beach, called “Concheiros”. The only fossils from deeper zones of the shelf known so far are a portion of a skull, a left humerus and of a femur of Toxodon sp. and a lower right molar of a Stegomastodon waringi, all collected by fishermen at depths around 20 m. The presence of fossils at great depths and distances from the present coastline, without signs of abrasion and far from areas of fluvial discharges does indicate that these remains have not been transported from the continent to the shelf, but have been preserved directly on the area that today correspond to the continental shelf. These remains indicate the existence of large fossiliferous deposits that have developed during periods of sea-level lowstand (glacial maxima) and have been submerged and reworked by the sea-level rise at the end of the last glaciation.  相似文献