Structural pattern of the western Las Cañadas caldera (Tenerife, Canary Islands) revealed by audiomagnetotellurics     

Nicolas Coppo  Pierre-André Schnegg  Pierik Falco  Roberto Costa  Martin Burkhard 《Swiss Journal of Geoscience》2008,101(2):409-413

The local and regional structural pattern of volcanic edifices strongly controls the space distribution of electrical resistivity. Here we report on the structural context of the western part of the Las Cañadas caldera of Tenerife (LCC) thought to have initiated the formation of the caldera. Using a new dataset of 11 audiomagnetotelluric tensors we emphasize the resistivity distribution of Ucanca caldera and propose a major revision of its extension. We find that Ucanca caldera has a limited westwards extent and that El Cedro sector is a depression margin of the caldera. According to the extent of hydrothermalized rocks at the base of the LCC wall and the distribution of Pico Teide – Pico Viejo vents, we constrain the location and size of Ucanca caldera. The interpretation of these results also constrains the extension of the Icod Valley and proposes a headwall located below the Pico Teide – Pico Viejo Complex.  相似文献   

A multibeam antenna for solar MM-wave burst observations with high spatial and temporal resolution     

R. Herrmann  A. Magun  J. E. R. Costa  E. Correia  P. Kaufmann 《Solar physics》1992,142(1):157-170

In this paper a new method for the determination of the position of microwave burst sources on the Sun, its implementation and first observational results, are presented. The 13.7 m antenna at Itapetinga with a five-channel receiver operating at 48 GHz and with a time resolution of 1 ms is used. Five horn antennas clustered around the focus of the Cassegrain reflector provide 5 beams diverging by about 2. This configuration allows the observation of different parts of an active region and the determination of the center of the burst position with an accuracy of 5 to 20 depending on the angular distance relative to the antenna axis. The field of view is 2 by 4. The time resolution of 1 ms is suitable to search for fast structures at 48 GHz. A total bandwidth of 400 MHz is used in order to achieve a sensitivity of 0.04 s.f.u. sufficient for the detection of weak bursts. First observational results of the flare on May 11, 1991 show a well-located source position during all stages.Paper presented at the 4th CESRA workshop in Ouranopolis (Greece) 1991.  相似文献   

Multiple energetic injections in a strong spike-like solar burst   总被引：1，自引：0，他引：1  

P. Kaufmann  E. Correia  J. E. R. Costa  B. R. Dennis  G. J. Hurford  J. C. Brown 《Solar physics》1984,91(2):359-376

An intense and fast spike-like solar burst was observed with high sensitivity in microwaves and hard X-rays, on December 18,1980, at 19^h21^m20^s UT. It is shown that the burst was built up of short time scale structures superimposed on an underlying gradual emission, the time evolution of which showed remarkable proportionality between hard X-ray and microwave fluxes. The finer time structures were best defined at mm-microwaves. At the peak of the event the finer structures repeat every 30–60 ms (displaying an equivalent repetition rate of 16–20 s^-1). The more slowly varying component with a time scale of about 1 s was identified in microwaves and hard X-rays throughout the burst duration. Similarly to what has been found for mm-microwave burst emission, we suggest that X-ray fluxes might also be proportional to the repetition rate of basic units of energy injection (quasi-quantized). We estimate that one such injection produces a pulse of hard X-ray photons with about 4 × 10²¹ erg, for 25 keV. We use this figure to estimate the relevant parameters of one primary energy release site both in the case where hard X-rays are produced primarily by thick-target bremsstrahlung, and when they are purely thermal, and also discuss the relation of this figure to global energy considerations. We find, in particular, that a thick-target interpretation only becomes possible if individual pulses have durations larger than 0.2 s.  相似文献   

Comparison of spatial interpolation methods for the estimation of precipitation distribution in Distrito Federal,Brazil     

Pablo de Amorim Borges  Johannes Franke  Yumiko Marina Tanaka da Anunciação  Holger Weiss  Christian Bernhofer 《Theoretical and Applied Climatology》2016,123(1-2):335-348

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Investigation of terrain illumination effects on vegetation indices and VI-derived phenological metrics in subtropical deciduous forests     

Lênio Soares Galvão  Fábio Marcelo Breunig  Thiago Sousa Teles  William Gaida  Rafaelo Balbinot 《地理信息系统科学与遥感》2016,53(3):360-381

We used RapidEye and Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra data to study terrain illumination effects on 3 vegetation indices (VIs) and 11 phenological metrics over seasonal deciduous forests in southern Brazil. We applied TIMESAT for the analysis of the Enhanced Vegetation Index (EVI) and the Normalized Difference Vegetation Index (NDVI) derived from the MOD13Q1 product to calculate phenological metrics. We related the VIs with the cosine of the incidence angle i (Cos i) and inspected percentage changes in VIs before and after topographic C-correction. The results showed that the EVI was more sensitive to seasonal changes in canopy biophysical attributes than the NDVI and Red-Edge NDVI, as indicated by analysis of non-topographically corrected RapidEye images from the summer and winter. On the other hand, the EVI was more sensitive to terrain illumination, presenting higher correlation coefficients with Cos i that decreased with reduction in the canopy background L factor. After C-correction, the RapidEye Red-Edge NDVI, NDVI, and EVI decreased 2%, 1%, and 13% over sunlit surfaces and increased up to 5%, 14%, and 89% over shaded surfaces, respectively. The EVI-related phenological metrics were also much more affected by topographic effects than the NDVI-derived metrics. From the set of 11 metrics, the 2 that described the period of lower photosynthetic activity and seasonal VI amplitude presented the largest correlation coefficients with Cos i. The results showed that terrain illumination is a factor of spectral variability in the seasonal analysis of phenological metrics, especially for VIs that are not spectrally normalized.  相似文献   

Cu(II) adsorption from aqueous solution using red mud activated by chemical and thermal treatment     

Fabiano T. da Conceição  Beatriz C. Pichinelli  Mariana S. G. Silva  Rodrigo Braga Moruzzi  Amauri Antonio Menegário  Maria Lucia Pereira Antunes 《Environmental Earth Sciences》2016,75(5):362

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Instrumental neutron activation analysis,gamma spectrometry and geographic information system techniques in the determination and mapping of rare earth element in phosphogypsum stacks     

Renata Coura Borges  Déborah Inês Teixeira Fávaro  Vanessa Godoy Caldas  Dejanira da Costa Lauria  Alfredo Victor Bellido Bernedo 《Environmental Earth Sciences》2016,75(8):705

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Variability of labile metals in estuarine sediments in areas under the influence of antifouling paints,southern Brazil     

Luiza Dy Fonseca Costa  Nicolai Mirlean  Julio Cesar Wasserman  Mônica Wallner-Kersanach 《Environmental Earth Sciences》2016,75(7):580

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Influence of different land uses on groundwater quality in southern Portugal     

Alexandra Marchã Penha  António Chambel  Martinho Murteira  Manuela Morais 《Environmental Earth Sciences》2016,75(7):622

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Integration of magnetic measurements,chemical and statistical analysis in characterizing agricultural soils (central Portugal)     

A. M. Lourenço  C. R. Gomes 《Environmental Earth Sciences》2016,75(11):968

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