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The coastal plain of the Río de la Plata constitutes a large wetland which develops on the right margin of the river estuary. Anthropic activities such as intensive exploitation of groundwater carried out in the vicinity of the wetland can modify the natural hydrological regime. The aim of this work is to asses the effects of intensive aquifer exploitation in coastal wetlands using hydrogeological models. Such models allow to evaluate changes in the environmental conditions of wetland at regional level. The hydrogeological model exposed in this work shows how the intensive groundwater exploitation affects the wetland area, generating important variations both in the groundwater flows and in the salinity of the groundwater. Identification of these modifications to the environment is important to generate guidelines leading to minimize these affectations. 相似文献
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We have analysed the 1978 UBV photoelectric observations of the short-period (RS CVn type) binary system RT And, using the rectifiable methods of Russell and Merrill (1952) and Kitamura (1965). The primary minimum is a transit. The solutions allow us to classify the system as a detached one, but a certain disagreement results with respect to solutions of previous epochs. A graphical test of the reliability of the solution is given. 相似文献
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We report on the analysis of a fast (>2,000 km/s) CME-driven shock event observed with the UVCS telescope operating aboard SoHO on 23 July 2002. The same shock was also detected in the metric band by several ground-based radiospectrographs. The peculiarity of this event is the presence in the radio spectra of two intense metric type II bursts features drifting at different rates, together with clear shock/related broadenings of the O VI doublet lines observed by UVCS that were found to be temporally associated with the above radio features. The nature of these multiple radio lanes in the metric band is still under debate. One possible explanation is that they are produced by multiple shock waves generated by different ejections or, alternatively, by the flare and the associated CME. Also, emission from the upstream and downstream shock regions can produce split bands. By adopting a plausible CME model, together with a detailed analysis of the white-light, UV, and radio data associated with this event, we are able to conclude that both the radio and the UV shock signatures were produced by a single shock wave surface generated by the expanding CME. 相似文献
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C.S. Hassler E. Alasonati C.A. Mancuso Nichols V.I. Slaveykova 《Marine Chemistry》2011,123(1-4):88-98
As a result of ubiquitous excretion by micro-organisms, extracellular polymeric substances are reported in high concentrations in marine systems. The majority of this material is exopolysaccharide (EPS). Despite previous studies showing that EPS can affect carbon as well as trace metal cycling, little is known about the effect on Fe – a critical nutrient limiting primary productivity in up to 40% of the ocean. Here, we have characterised an EPS purified from bacteria isolated from the pelagic Southern Ocean (Pseudoalteromonas sp.) and investigated its role in Fe chemical speciation, solubility, as well as bioavailability for two keystone Southern Ocean phytoplankton strains. This EPS has an average molecular weight of 4.6 MDa, exhibiting mainly –OH, COO– and –NH2 functional groups. An asymmetrical flow field-flow fractionation coupled online with UV-spectrophotometer, differential refractive index, and multiangle laser light scattering (aFlFFF-UV-DRI-MALS) demonstrates that this EPS is polydisperse with three, not well resolved, size populations having molar masses in the range from 0.57 to 15.8 MDa. Fe was exclusively associated with the medium size fraction of this EPS and was the most abundant trace metal with 2.2 nM Fe per nM EPS. Only a third of this Fe was chemically labile, and the strength of Fe-EPS complexes increased with equilibration time. 1 nM EPS is efficient to retain Fe in solution, mainly in the colloidal phase (0.02–0.2 μm). Fe bound to the EPS was highly bioavailable (25% as much as for inorganic Fe). Due to combined effect of EPS on Fe solubility and bioavailability, it can increase the residence time of bioavailable Fe in the euphotic zone, therefore possibly sustaining and controlling primary productivity in sensitive oceanic regions, such as the Southern Ocean. 相似文献
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In this work, we apply multichannel singular spectrum analysis (MSSA), a data-adaptive, multivariate, non-parametric technique that simultaneously exploits the spatial and temporal correlations of the input data to extract common modes of variability, to investigate the intermediate quasi-periodicities of the Fe xiv green coronal emission line at 530.3 nm for the period between 1944 and 2008. Our analysis reveals several significant mid-term periodicities in a range from about one to four years that are consistent with the so-called quasi-biennial oscillations (QBOs), which have been detected by several authors using different data sets and analysis methods. These QBOs display amplitudes varying significantly with time and latitude over the six solar cycles (18 to 23) covered by this study. A clear North–South asymmetry is detected both in their intensity and period distribution, with a net predominance of spectral power in the active-region belt of the northern hemisphere. On the other hand, while the QBOs with periods \(\gtrsim1.7\) years are particularly intense around the polar regions and therefore related to the global magnetic field, the ones with shorter periods are mainly generated at mid-latitudes, in correspondence with the emergence of active regions. Our findings indicate that the North–South asymmetry manifested in the uneven latitudinal distribution of QBOs is a fundamental, albeit puzzling, characteristic of solar activity. 相似文献
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In recent years much effort has been devoted to constructing systems for sharing resources within the solar physics community. Several advanced archives and data analysis systems do exist, but there is low availability of data visualization tools for displaying simultaneous multi instruments/wavelengths solar data. Meanwhile map server technology has received great attention by the IT researcher and geophysical community. In this paper we discuss a possible use of an open source environment for building spatially enabled Internet applications for the visualization and analysis of solar physics data sets. We present the preliminary status of the MINVIT (Multi Instrumental Visualization Tool) project, which shall be able to merge images and information produced by different instruments in a single/synoptic image available on-line. Moreover, the tool is designed in order to allow the visualization of the temporal evolution of data. We further discuss the possible integration into the grid framework, focusing on a middleware able to query EGSO resources such us UOC and SEC in order to include data from several space and ground-based solar observatories. 相似文献
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L. Milano S. Mancuso A. Vittone A. D'Orsi S. Marcozzi 《Astrophysics and Space Science》1986,124(1):83-100
From the observed light curves of six eclipsing binaries with solar-type activity and from the analysis of their period variations some problems in the interpretation of the observations came out: Are these binaries similar to classical RS CVn stars? Is the stellar surface spot coverage the unique interpretation of the observed light curves? Are these systems really linked with W UMa's? In a further study some models will be tempted to try to solve these problems. 相似文献
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R. Burchi D. Chochol A. Dipaolantonio S. Mancuso L. Milano A. Vittone 《Astrophysics and Space Science》1983,89(2):387-393
We present three colour photoelectric observations of CI Cyg during the 1980 eclipse. Some interesting photometric peculiarities are shown that must be taken into account for a theoretical model of this eclipsing symbiotic star. 相似文献