Point Spread Function Estimation Using Speckle Reconstructions of Solar Surface Images     

T. A. Waldmann  O. von der Lühe 《Solar physics》2010,267(1):217-231

We present a method for retrieving the wavefront phase and estimating the point spread function using data from a single imaging channel. The method involves a set of short exposures and its speckle reconstruction of the observed object, and a parameterized point spread function model which is used in order to estimate the wavefront phase and the point spread function from the data. Estimates of the wavefront phase and the point spread function are computed by minimizing an error function with the method of simulated annealing. Results of tests with simulated data and with real data are shown. We conclude that the proposed technique provides reliable estimates of the instantaneous point spread function and is robust against noise.  相似文献   

Localized zones of denitrification in a floodplain aquifer in southern Wisconsin, USA   总被引：1，自引：0，他引：1  

Laura Craig  Jean M. Bahr  Eric E. Roden 《Hydrogeology Journal》2010,18(8):1867-1879

A floodplain aquifer within an agricultural watershed near Madison, Wisconsin (USA), was studied to determine whether denitrification was occurring below the surface organic layer. Groundwater levels and concentrations of O₂, Cl^?, NO ₃ ^? , SO ₄ ^2? , dissolved organic carbon (DOC), and major cations were monitored over a 1-year period along a 230-m transect between an agricultural field and a stream discharge point. Seventeen groundwater samples were analyzed for δ¹⁵N_NO3 and δ¹⁸O_NO3 composition. Samples in which NO ₃ ^? was too low for stable isotope analysis were analyzed for excess dissolved N₂. Groundwater NO ₃ ^? concentrations declined between the agricultural field and the discharge point. Chloride and δ¹⁵N_NO3/δ¹⁸O_NO3 data indicated that the drop in NO ₃ ^? was caused primarily by dilution of shallow NO ₃ ^? -rich water with deeper, NO ₃ ^? -depleted groundwater. Two localized zones of denitrification were identified in the upland-wetland transition by their δ¹⁵N_NO3 and δ¹⁸O_NO3 signatures, and two in the stream hyporheic zone by the presence of excess dissolved N₂. The combined stratigraphic, hydrologic, and geochemical data in these locations correspond to groundwater mixing zones where NO ₃ ^? is delivered to subsurface layers that support denitrification fueled by dissolved (e.g. DOC or dissolved Fe(II)) and/or solid-phase (e.g. particulate organic carbon, solid-associated Fe(II), or pyrite) electron donors.  相似文献   

Analyses of precipitation,temperature and evapotranspiration in a French Mediterranean region in the context of climate change     

Keltoum Chaouche  Luc Neppel  Claudine Dieulin  Nicolas Pujol  Bernard Ladouche  Eric Martin  Dallas Salas  Yvan Caballero 《Comptes Rendus Geoscience》2010,342(3):234-243

This study is focused on the western part of the French Mediterranean area, namely the Pyrénées-Orientales and Aude administrative departments. The water resources (surface and groundwater) in the region are sensitive to climate change. The study addresses the question of whether any trend in the annual and monthly series of temperature, rainfall and potential evapotranspiration (PET) already appears at the scale of this region. Two data sources have been used: (a) direct local measurements using the meteorological network; and (b) spatially interpolated data from the French weather service model SAFRAN for the period 1970–2006. The non-parametric Mann–Kendall test was applied to identify significant trends at the local scale and, because of the natural spatial variability of the Mediterranean climate, regional interpretation was also performed. The trends observed in the 13 catchments of interest are consistent with those observed at a larger scale. An increase in annual mean temperature and annual PET was observed throughout the study area, whereas annual precipitation has not exhibited any trend. The monthly scale has revealed strong seasonal variability in trend. The trend for an increase in monthly PET has been observed mainly in the spring, and has not been seen in the coastal areas. A trend for an increase in monthly temperature has been observed in June and in the spring throughout the entire area. Monthly rainfall has been found to decrease in June and increase in November throughout the area. The significant trends observed in rainfall and temperature seem to be consistent between the different data sources.  相似文献   

Piezometric levels as possible indicator of aquifer structure: analysis of the data from Maknassy basin aquifer system (Central Tunisia)     

Ismail Chenini  Abdallah Ben Mammou  Mohamed Moncef Turki  Eric Mercier 《Arabian Journal of Geosciences》2010,3(1):41-47

The knowledge of piezometric data is of vast interest in many applications, such as assessing groundwater flow direction and identifying recharge zone of the aquifer. In this paper, a methodology is presented as a complementary approach to characterize multilayered aquifer system structure and functioning using piezometric data and the cartography of the hydraulic charge difference. The methodology is presented to gradually discriminate the aquifer system levels and to evaluate the spatial distribution of hydraulic heads. The hydraulic charge difference mapping permits to track spatial evolution of the impermeable levels. The methodology has been applied over the Maknassy basin aquifer system, located in central Tunisia. The obtained results, showing the multilayered aquifer structure, are validated using hydrochemical approach and piezometric data not considered in the reasoning.  相似文献   

The SAURON project – VII. Integral-field absorption and emission-line kinematics of 24 spiral galaxy bulges     

Jesús Falcón-Barroso  Roland Bacon  Martin Bureau  Michele Cappellari  Roger L. Davies  P. T. de Zeeuw  Eric Emsellem  Kambiz Fathi  Davor Krajnovi&#;  Harald Kuntschner  Richard M. McDermid  Reynier F. Peletier  Marc Sarzi 《Monthly notices of the Royal Astronomical Society》2006,369(2):529-566

We present observations of the stellar and gas kinematics for a representative sample of 24 Sa galaxies obtained with our custom-built integral-field spectrograph SAURON operating on the William Herschel Telescope. The data have been homogeneously reduced and analysed by means of a dedicated pipeline. All resulting data cubes were spatially binned to a minimum mean signal-to-noise ratio of 60 per spatial and spectral resolution element. Our maps typically cover the bulge-dominated region. We find a significant fraction of kinematically decoupled components (12/24), many of them displaying central velocity dispersion minima. They are mostly aligned and co-rotating with the main body of the galaxies, and are usually associated with dust discs and rings detected in unsharp-masked images. Almost all the galaxies in the sample (22/24) contain significant amounts of ionized gas which, in general, is accompanied by the presence of dust. The kinematics of the ionized gas are consistent with circular rotation in a disc co-rotating with respect to the stars. The distribution of mean misalignments between the stellar and gaseous angular momenta in the sample suggests that the gas has an internal origin. The [O  iii ]/Hβ ratio is usually very low, indicative of current star formation, and shows various morphologies (ring-like structures, alignments with dust lanes or amorphous shapes). The star formation rates (SFRs) in the sample are comparable with that of normal disc galaxies. Low gas velocity dispersion values appear to be linked to regions of intense star formation activity. We interpret this result as stars being formed from dynamically cold gas in those regions. In the case of NGC 5953, the data suggest that we are witnessing the formation of a kinematically decoupled component from cold gas being acquired during the ongoing interaction with NGC 5954.  相似文献   

The INTEGRAL spectrometer SPI: performance of point-source data analysis     

P. Dubath  J. Knödlseder  G. K. Skinner  P. Connell  I. Kreykenbohm  A. Strong  P. Sizun  D. Attié  S. Schanne  B. Cordier  L. Bouchet  A. von Kienlin 《Monthly notices of the Royal Astronomical Society》2005,357(2):420-428

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Terrestrische Reptilien der Karroo- und Gondwanafauna     

Friedrich von Huene 《International Journal of Earth Sciences》1939,30(3):359

Ohne Zusammenfassung  相似文献   

Erdbeben und Gebirgsbau in Südwestdeutschland     

W. von Seidlitz 《International Journal of Earth Sciences》1913,4(4):262-273

Ohne Zusammenfassung  相似文献   

RIGS: where do we stand?     

Eric Robinson 《Geology Today》1999,15(1):38-39

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Tertiary consent     

Eric Robinson 《Geology Today》1999,15(1):40-40

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