A simple procedure for the assessment of hydropeaking flow alterations applied to several European streams     

Mauro Carolli  Davide Vanzo  Annunziato Siviglia  Guido Zolezzi  Maria Cristina Bruno  Knut Alfredsen 《Aquatic Sciences - Research Across Boundaries》2015,77(4):639-653

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A User-Oriented Methodology for DInSAR Time Series Analysis and Interpretation: Landslides and Subsidence Case Studies     

Davide Notti  Fabiana Calò  Francesca Cigna  Michele Manunta  Gerardo Herrera  Matteo Berti  Claudia Meisina  Deodato Tapete  Francesco Zucca 《Pure and Applied Geophysics》2015,172(11):3081-3105

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Deciphering the geologic memory of a Permian conglomerate of the Southern Alps by pebble <Emphasis Type="Italic">P</Emphasis>–<Emphasis Type="Italic">T</Emphasis> estimates     

M. Iole Spalla  Davide Zanoni  Guido Gosso  Michele Zucali 《International Journal of Earth Sciences》2009,98(1):203-226

The volcano–clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basement (TVB), comprises the Dosso dei Galli Conglomerate (DGC), the oldest deposit containing up to metre-sized metamorphic pebbles. This Lower Permian formation of the Trompia Basin was fed by the erosion products of the Variscan chain. We used microstructural and mineral chemical data on metamorphic pebbles of the DGC to infer a quantitative tectono-thermal evolution of the eroded pre-Permian basement and to compare them with those of TVB and the surrounding Southalpine basement units (tectono-metamorphic units = TMUs). Metapelitic and metaintrusive pebbles record a polyphase metamorphism with two metamorphic re-equilibrations: the first under epidote amphibolite facies (M1, ) and the second under greenschist facies (M2) conditions. Rock types and metamorphic data largely match those of TVB basement unit. The structural and metamorphic records in the pebbles are pre-Permian, and the conglomerate matrix is non-metamorphic. The DGC deposition age (283 ± 1–280.5 ± 2 Ma) constrains the minimal exhumation age of its basement source. The lack of staurolite bearing assemblages in metamorphic pebbles suggests that the DGC basement source was already exhumed to shallow structural levels (greenschist facies conditions) before the thermal equilibration consequent upon continental crust thickening induced by the Variscan collision.  相似文献   

Detrital Cr-spinel in the Šambron–Kamenica Zone (Slovakia): evidence for an ocean-spreading zone in the Northern Vardar suture?     

Davide Lenaz  Claudio Mazzoli  Jan Spišiak  Francesco Princivalle  Lara Maritan 《International Journal of Earth Sciences》2009,98(2):345-355

The Šambron–Kamenica Zone is situated on the northern margin of the Levočské vrchy mountains and Šarišskà vrchovina Highland, where the Central Carpathian Paleogene joins the Pieniny Klippen Belt. Sandstone outcrops in this area. From Cretaceous to Late Oligocene in age, these sediments suggest transport directions from S and SE. The heavy mineral assemblages of this sandstone include Cr-spinel grains, mainly displaying types II and III alpine-peridotite affinities, and are representative of Ocean Island Basalt volcanism. A sample from Upper Eocene sediments at Vit’az shows a clear change in Cr-spinel composition, which turns out to have types I and II peridotite affinities, and to derive from arc and Middle Ocean Ridge Basalt volcanism, with sediment transport directions from SW and WSW. These data indicate major variations in the Upper Eocene tectonic setting, giving constraints to paleogeographic reconstruction of the Slovak Central Carpathians.  相似文献   

Polarization light curves and position angle variation of beamed gamma-ray bursts     

Gabriele Ghisellini  Davide Lazzati 《Monthly notices of the Royal Astronomical Society》1999,309(1):L7-L11

The recently detected linear polarization in the optical light curve of GRB 990510 renewed interest in how polarization can be produced in gamma-ray burst fireballs. Here we present a model based on the assumption that we are seeing a collimated fireball, observed slightly off-axis. This introduces some degree of anisotropy, and makes it possible to observe a linearly polarized flux even if the magnetic field is completely tangled in the plane orthogonal to the line of sight. We construct the light curve of the polarization flux, showing that it is always characterized by two maxima, with the polarization position angle changing by 90° between the first and the second maximum. The very same geometry as assumed here implies that the total flux initially decays in time as a power law, but gradually steepens as the bulk Lorentz factor of the fireball decreases.  相似文献   

Seismic attenuation,normal moveout stretch,and low‐frequency shadows underlying bottom simulating reflector events          下载免费PDF全文

José M. Carcione  Ayman N. Qadrouh  Hervé Perroud  Davide Gei  Jing Ba  Stefano Picotti 《Geophysical Prospecting》2018,66(5):857-871

In many cases, the seismic response of bottom‐simulating reflectors is characterised by low frequencies called “low‐frequency shadow”. Generally, this phenomenon is interpreted as attenuation due to partial saturation with free gas. Actually, this frequency loss may have multiple causes, with a normal moveout stretch as a possible candidate. To analyse this phenomenon, we compute synthetic seismograms by assuming a lossy bottom‐simulating layer, with varying quality factor and thickness, bounded by the upper hydrate‐brine/gas‐brine and lower gas‐brine/brine interfaces. First, we estimate the shift of the centroid frequency of the power spectrum as a function of the travelled distance of the seismic pulse. Then, we perform one‐dimensional numerical experiments to quantify the loss of frequency of the seismic event below the bottom‐simulating reflector as a function of the quality factor of the bottom‐simulating layer and its thickness (due to wave interference). Then, we compute shot gathers to obtain the stacked section, with and without the normal moveout stretch correction and with and without the presence of wave attenuation in the bottom‐simulating layer. The results indicate that the low‐frequency shadow due to the normal moveout stretch is stronger than that due to attenuation and may constitute a false indicator of the presence of gas. In fact, often, the low‐frequency shadow overlies events with higher frequencies, in contradiction with the physics of wave propagation. This is particularly evident when the low‐frequency shadow is so extensive that the presence of high frequencies below cannot be justified by the acquisition geometry.  相似文献   

Recent progress in study on calcareous algae and algal sediments          下载免费PDF全文

Yasufumi Iryu  Davide Bassi 《Island Arc》2017,26(3)

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A Bayesian hierarchical approach for spatial analysis of climate model bias in multi-model ensembles     

Maeregu?Woldeyes?ArisidoEmail author  Carlo?Gaetan  Davide?Zanchettin  Angelo?Rubino 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(10):2645-2657

Coupled atmosphere–ocean general circulation models are key tools to investigate climate dynamics and the climatic response to external forcings, to predict climate evolution and to generate future climate projections. Current general circulation models are, however, undisputedly affected by substantial systematic errors in their outputs compared to observations. The assessment of these so-called biases, both individually and collectively, is crucial for the models’ evaluation prior to their predictive use. We present a Bayesian hierarchical model for a unified assessment of spatially referenced climate model biases in a multi-model framework. A key feature of our approach is that the model quantifies an overall common bias that is obtained by synthesizing bias across the different climate models in the ensemble, further determining the contribution of each model to the overall bias. Moreover, we determine model-specific individual bias components by characterizing them as non-stationary spatial fields. The approach is illustrated based on the case of near-surface air temperature bias in the tropical Atlantic and bordering regions from a multi-model ensemble of historical simulations from the fifth phase of the Coupled Model Intercomparison Project. The results demonstrate the improved quantification of the bias and interpretative advantages allowed by the posterior distributions derived from the proposed Bayesian hierarchical framework, whose generality favors its broader application within climate model assessment.  相似文献   

Characterization of sub‐daily thermal regime in alpine rivers: quantification of alterations induced by hydropeaking          下载免费PDF全文

Davide Vanzo  Annunziato Siviglia  Mauro Carolli  Guido Zolezzi 《水文研究》2016,30(7):1052-1070

The thermal regime of rivers is threatened by anthropogenic stresses at a large variety of timescales. We focus on sub‐daily thermal alterations induced by the release of hypolimnetic water for hydropower production (thermopeaking). We analyse the thermal signal focusing on the following characteristics that are potentially affected by hypolimnetic releases: (i) sub‐daily thermal rate of change and (ii) oscillation frequencies contained in the thermal signal. Through a proper scaling, we derive two dimensionless at‐a‐station indicators to compare alterations among stations with different locations and physiographic characteristics of the basins. Then we analyse the data from two different thermal datasets (Italy/Switzerland) for a total of 48 stations with 10 min time resolution of temperature data. The stations are grouped according to the absence of upstream hydropeaking releases (29 stations, reference group) and the existence of upstream hydropeaking, hence potentially impacted by thermopeaking (19 stations, altered group). Using a simple statistical approach, based on a non‐parametric definition of outliers, we identify the range of variability of the two indicators for the reference, unaltered group. This range measures the ‘natural’ sub‐daily thermal variability of the proposed indicators. Finally, we investigate the seasonality effects on the two proposed indicators and it results, that sub‐daily alterations mostly occur during summer. The two indicators represent a novel tool for the assessment of river thermal regime alterations and can be easily included in existing methodologies to assess river quality. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

MgAl2O4 spinels from Allende and NWA 763 carbonaceous chondrites: Structural refinement,cooling history,and trace element contents     

Davide Lenaz  Vanni Lughi  Diego Perugini  Maurizio Petrelli  Gianluca Turco  Birger Schmitz 《Meteoritics & planetary science》2019,54(12):3089-3100

MgAl₂O₄ spinels from Allende and NWA 763 carbonaceous chondrites were studied by X‐ray single crystal diffraction, SEM, electron microprobe, LA‐ICP‐MS, and Raman spectroscopy. Those from Allende are almost pure, but, in one case, we found a strong FeO_tot zonation. Spinels from NWA 763 show Mg‐Fe²⁺ substitutions. Almost pure MgAl₂O₄ spinels from both meteorites underwent slow cooling and reached their intracrystalline closure temperature (T_c) in the range 460–520 °C. The NWA 763 spinel with higher FeO content shows a T_c of about 720 °C. X‐ray single crystal diffraction and Raman spectroscopy suggest a slow cooling and an ordered structure with trivalent cations in M site and divalent in T site. Among the trace elements, Ti and Co are enriched with respect to the terrestrial analogs, while Mn, Ni, and Sn show intermediate values between different terrestrial occurrences. Vanadium cannot be used as a tracer of extraterrestrial origin as for Cr‐spinels, because its content is similar in extraterrestrial and terrestrial spinels. In the zoned crystal from Allende, Co show a strong zonation similar to that of FeO.  相似文献