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421.
Francesca Zuccarello Lidia Contarino Paolo Romano Viviana Battiato Salvo L. Guglielmino 《Acta Geophysica》2009,57(1):24-30
In this paper we report some results obtained from multi-wavelength observations carried out to study the mechanisms operating
in flares and filament eruptions. Most of these studies have given indication of the presence of phenomena that might be considered
signatures of magnetic reconnection, while others have pointed out the important role played by magnetic helicity transport
in corona before the eruptive phase. 相似文献
422.
Francesca Zuccarello Salvatore L. Guglielmino Viviana Battiato Lidia Contarino Daniele Spadaro Pado Romano 《Acta Geophysica》2009,57(1):15-23
This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high
resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising
flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially
characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline
of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following
legs of the flux tubes. These results are briefly discussed in the light of most recent models. 相似文献
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We studied the seasonal variation of arthropod assemblages and the response to high discharge events in a subtropical Andean basin. Using abundance of common taxa and taxon richness of each sampled site, we examined the temporal variation of arthropods and related these changes with 12 environmental variables. Seasonal patterns of benthic arthropods were confirmed by uni- and multivariate techniques. Benthic abundance and taxon richness peaked on autumn-winter months, and declined abruptly on the month of peak discharge (summer season). Distinct taxonomic groups were dominant in each season influenced by discharge and seven chemical variables.Assemblage resistance to disturbance by spates was low. Rapid recovery of benthic arthropods after floods reflected high resilience of the system. The dominance of groups of short life cycles such as Ephemeroptera played an important role in this process. 相似文献
425.
J. F. Prieto P. J. González A. Seco G. Rodríguez-Velasco L. Tunini P. A. Perlock A. Arjona A. Aparicio A. G. Camacho J. B. Rundle K. F. Tiampo J. L. G. Pallero S. Pospiech J. Fernández 《Pure and Applied Geophysics》2009,166(8-9):1461-1484
We review the results of the geodetic and structural studies carried out on La Palma Island using geodetic and geophysical data during the period 1992–2007. InSAR and GPS observation techniques were applied to study the existence of deformation on the island and gravity observations were carried out for structural studies. Gravity data were inverted using a nonlinear three-dimensional gravity inversion approach to obtain the geometry of the anomalous bodies constructed in a random growth process with respect to an exponentially stratified background. The main structural feature is a large central body (under the Caldera de Taburiente) with high density, which was interpreted as the Pliocene-age uplifted seamount and a relatively dense intrusive plutonic complex/magma body. The Cumbre Vieja series is characterized by elongated minima distributed according to the rift structure. InSAR results show a clear subsidence located on the Teneguía volcano, where the last eruption took place in 1971. A thermal source is the most probable origin for this deformation. A GPS network composed of 26 stations covering the total island surface was set up. Vertical displacements determined comparing the GPS coordinates obtained in 2007 with coordinates determined in 1994 are consistent with the InSAR results obtained in the southern part of the island. This is not the case for the northern part. From the comparison of 2006 and 2007 coordinates it is clear that more time is needed to obtain significant displacements, but observed trends are also consistent with InSAR results. All the observed significant displacements are in stations located outside of the large high-density central body. 相似文献
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Assessment of heavy metal pollution in urban topsoils from the metropolitan area of Mexico City 总被引:2,自引:0,他引:2
O. Morton-Bermea E. Hernández-Álvarez G. González-Hernández F. Romero R. Lozano L.E. Beramendi-Orosco 《Journal of Geochemical Exploration》2009
This study reports the degree of heavy metal pollution (Cr, Cu, Ni, Pb, Zn and V) in 135 urban topsoil samples from the metropolitan area of Mexico City. Pollution indices (PI) were calculated to identify the metal accumulation with respect to the background values. The levels of heavy metals in the analyzed samples show a wide range of variation. Lead, Zn and Cu are the elements most enriched in the analyzed area, presenting pollution indexes of up to 23.8, 21.6 and 12.4, respectively. Geochemical maps were produced to assess the spatial distribution of pollution index. It is concluded that emissions from vehicles may be the major source of Pb urban contamination; furthermore, other small or large factories are possible sources for soil pollution (Cu, Zn). The concentration of Cr, Ni, and V in most of the analyzed samples do not appear to reach pollution levels. The assessment of the soil environmental quality in the metropolitan area Mexico City in terms of PI can be used as the basis for a regular monitoring program for implementing suitable pollution control measures. 相似文献
430.
Rabbia Osvaldo M. Correa Karen J. Hernández Laura B. Ulrich Thomas 《International Journal of Earth Sciences》2017,106(8):2687-2711
International Journal of Earth Sciences - The El Abra porphyry copper deposit belongs to the Late Eocene—Early Oligocene metallogenic belt of northern Chile, which host several world-class... 相似文献