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101.
Frank M. Rieger Valentí Bosch-Ramon Peter Duffy 《Astrophysics and Space Science》2007,309(1-4):119-125
We consider the acceleration of energetic particles by Fermi processes (i.e., diffusive shock acceleration, second order Fermi
acceleration, and gradual shear acceleration) in relativistic astrophysical jets, with particular attention given to recent
progress in the field of viscous shear acceleration. We analyze the associated acceleration timescales and the resulting particle
distributions, and discuss the relevance of these processes for the acceleration of charged particles in the jets of AGN,
GRBs and microquasars, showing that multi-component powerlaw-type particle distributions are likely to occur. 相似文献
102.
103.
Delineating coastal groundwater discharge processes in a wetland area by means of electrical resistivity imaging, 224Ra and 222Rn 下载免费PDF全文
Mario Zarroca Rogelio Linares Valentí Rodellas Jordi Garcia‐Orellana Carles Roqué Joan Bach Pere Masqué 《水文研究》2014,28(4):2382-2395
Coastal groundwater discharge (CGD) plays an important role in coastal hydrogeological systems as they are a water resource that needs to be managed, particularly in wetland areas. Despite its importance, identifying and monitoring CGD often presents physical and logistical constraints, restraining the application of more traditional submarine groundwater discharge surveying techniques. Here we investigate the capability of electrical resistivity imaging (ERI) in the Peníscola wetland (Mediterranean coast, Spain). ERI surveying made it possible to identify and delineate an ascending regional groundwater flow of thermal and Ra‐enriched groundwater converging with local flows and seawater intrusion. The continuous inputs of Ra‐rich groundwater have induced high activities of Ra isotopes and 222Rn into the marsh area, becoming among the highest previously reported in wetlands and coastal lagoons. Geoelectrical imaging enabled inferring focused upward discharging areas, leaking from the aquifer roof through a confining unit and culminating as spring pools nourishing the wetland system. Forward modelling over idealized subsurface configurations, borehole datasets, potentiometric records from standpipe piezometers, petrophysical analysis, and four natural and independent tracers (224Ra, 222Rn, temperature and salinity) permitted assessing the geoelectrical model and a derived hydrogeological pattern. The research highlights the potential of ERI to improve hydrogeological characterization of subsurface processes in complex contexts, with different converging flows. Additionally, a hydrogeological conceptual model for a groundwater‐fed coastal wetland was proposed, based on the integration of surveying datasets. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
104.
105.
Occurrence of priority pollutants in WWTP effluents and Mediterranean coastal waters of Spain 总被引:1,自引:0,他引:1
A comprehensive study aimed at evaluating the occurrence, significance of concentrations and spatial distribution of priority pollutants (PPs) along the Comunidad Valenciana coastal waters (Spain) was carried out in order to fulfil the European Water Framework Directive (WFD). Additionally, PP concentrations were also analysed in the effluent of 28 WWTPs distributed along the studied area. In coastal waters 36 organic pollutants of the 71 analysed, including 26 PPs were detected although many of them with low frequency of occurrence. Only 13 compounds, which belong to four different classes (VOCs, organochlorinated pesticides, phthalates and tributyltin compounds (TBT)) showed a frequency of occurrence above 20% in coastal waters. In the results obtained until now, octylphenol, pentachlorobenzene, DEHP and TBT exceeded the annual average concentration (EQS-AAC), and only TBT surpassed the maximum allowable concentration (EQS-MAC). The most frequent contaminants determined in coastal waters were also present in WWTP effluents. 相似文献
106.
Jiří Borovička 《Earth, Moon, and Planets》2004,95(1-4):245-253
High dispersion photographic spectra of three Leonid and five Perseid meteors are used to derive relative abundances of nine
chemical elements in the radiating meteoric vapors and in the meteoroids. Al and Ca were found to be incompletely evaporated
in the main spectral component at 5000 K but completely evaporated in the second component at 10,000 K. Si lines are present
in both components which enhances the reliability of determination of the Si abundance. The composition of the meteoroids
was found to be more similar to comet Halley than to chondritic meteoroids. Fe, Cr, and Mn are depleted and Si, Na, and H
are enhanced relative to Mg in comparison with CI chondrites. 相似文献
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The frequency-dependent anisotropy of magnetic susceptibility (AMS) can be most easily determined through subtracting directional susceptibilities measured at two operating frequencies along each of the measuring directions and the differences subsequently processed using standard methods for AMS computation. The effect of the measurement precision on the accuracy of the determination of the frequency-dependent AMS is investigated through mathematical simulation of the measurement process using the statistical theory of measuring the AMS of rocks. The accuracy of the AMS determination is presented in terms of the errors in determining the principal susceptibilities and principal directions. By modelling the measuring errors, the limits are discovered for the investigation of the frequency-dependent AMS. The modelling shows extremely high requirements for measurement accuracy met by the most sensitive instruments, only. 相似文献
109.
Early geophysical maps dealing with seismology, geomagnetism, geothermics, and volcanology published by A. Petermann in his journal Geographische Mittheilungen between 1855 and 1878 are shown. Six maps of the highest cartographic standard are reproduced and commented. In Appendix an overview of geological maps edited by A. Petermann is added. 相似文献
110.