Very low temperature,natural deformation of fine grained limestone: a case study from the Lucania region,southern Apennines,Italy     

Stefano Mazzoli  Valentina Zampetti  Agostino Zuppetta 《Geodinamica Acta》2013,26(4):213-230

Abstract

The deformation behavior of fine grained limestones from the Monte Sirino area (Lucania region) of the southern Apennines has been analysed by constraining microstructural observations and crystallographic fabrics with data on the metamorphic conditions of deformation. X-ray and infrared analysis of clay minerals, together with illite ‘crystallinity’ data, suggest that the studied rocks underwent very low grade metamorphism in the deep diagenetic zone. The limestones consist of very fine grained (<10 μm) aggregates of micrite. Elliptically-shaped radiolarians, preserved as moulds with coarser (>20 μm) crystalline fillings, provide common strain markers. Optical microstructures and strain analysis indicate heterogeneous intracrystalline strain in the coarser (>50 μm) calcite. On the other hand, SEM and TEM observations, and crystallographic fabrics determined by X-ray texture goniometry, indicate a deformation involving not only intracrystalline slip, but also an important component of grain boundary sliding in the fine grained matrix. The inferred microscopic deformation mechanisms are compared with constitutive flow laws derived from experimental studies. For the maximum inferred temperature of deformation of 250 °C and geologic strain rates of 10^?13?10^?15 s^?1, deformation mechanism maps for calcite suggest twinning and other glide mechanisms to be active in grains larger than about 5?10 μm. Smaller grains would be mostly deformed by grain size sensitive creep mechanisms, which include both diffusion mass transfer processes and grain boundary sliding. Deformation features observed in the study limestones are compatible with the prediction of such temperature-dependent mechanism maps. © 2001 Éditions scientifiques et médicales Elsevier SAS  相似文献   

Polynomial chaos expansion for global sensitivity analysis applied to a model of radionuclide migration in a randomly heterogeneous aquifer     

Valentina Ciriello  Vittorio Di Federico  Monica Riva  Francesco Cadini  Jacopo De Sanctis  Enrico Zio  Alberto Guadagnini 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(4):945-954

We perform global sensitivity analysis (GSA) through polynomial chaos expansion (PCE) on a contaminant transport model for the assessment of radionuclide concentration at a given control location in a heterogeneous aquifer, following a release from a near surface repository of radioactive waste. The aquifer hydraulic conductivity is modeled as a stationary stochastic process in space. We examine the uncertainty in the first two (ensemble) moments of the peak concentration, as a consequence of incomplete knowledge of (a) the parameters characterizing the variogram of hydraulic conductivity, (b) the partition coefficient associated with the migrating radionuclide, and (c) dispersivity parameters at the scale of interest. These quantities are treated as random variables and a variance-based GSA is performed in a numerical Monte Carlo framework. This entails solving groundwater flow and transport processes within an ensemble of hydraulic conductivity realizations generated upon sampling the space of the considered random variables. The Sobol indices are adopted as sensitivity measures to provide an estimate of the role of uncertain parameters on the (ensemble) target moments. Calculation of the indices is performed by employing PCE as a surrogate model of the migration process to reduce the computational burden. We show that the proposed methodology (a) allows identifying the influence of uncertain parameters on key statistical moments of the peak concentration (b) enables extending the number of Monte Carlo iterations to attain convergence of the (ensemble) target moments, and (c) leads to considerable saving of computational time while keeping acceptable accuracy.  相似文献   

Evolution and instabilities of disks harboring super massive black holes     

Anna Curir  Valentina de Romeri  Giuseppe Murante 《Astrophysics and Space Science》2010,327(2):259-266

The bar formation is still an open problem in modern astrophysics. In this paper we present numerical simulations performed with the aim of analyzing the growth of the bar instability inside stellar-gaseous disks, where the star formation is triggered, and a central black hole is present. The aim of this paper is to point out the impact of such a central massive black hole on the growth of the bar. We use N-body-SPH simulations of the same isolated disk-to-halo mass systems harboring black holes with different initial masses and a different energy feedback on the surrounding gas. We compare the results of these simulations with the one of the same disk without a black hole in its center. We make the same comparison (disk with and without black hole) for a stellar disk in a fully cosmological scenario. A stellar bar, lasting 10 Gyrs, is present in all our simulations.  相似文献   

Ecological status in the Ligurian Sea: the effect of coastline urbanisation and the importance of proper reference sites     

Mangialajo L  Ruggieri N  Asnaghi V  Chiantore M  Povero P  Cattaneo-Vietti R 《Marine pollution bulletin》2007,55(1-6):30-41

The assessment of the ecological status, as required by the Water Framework Directive (WFD), plays an important role in coastal zone management, but only a small number of ecological indices are applicable on rocky bottoms. In this study, we apply a previously defined ecological quality index based on the cartography of littoral and upper-sublittoral rocky-shore communities (CARLIT), based on the sensitivity of algae dominated communities to anthropogenic impacts along a moderate urban gradient. We also apply this index in four Marine Protected Areas (MPAs), proposed as reference sites at a regional scale. After comparing the outputs with water variables and other quality indices, we can affirm that (1) the CARLIT index is suitable to detect different kinds of anthropogenic pressures, that (2) the choice of proper reference sites is a focal point in the fulfilment of the WFD (Water Framework Directive) and that (3) historical data are important to define reference conditions and the degradation of ecological status.  相似文献   

Impacts of changing climate on the hydrology and hydropower production of the Tagus River basin          下载免费PDF全文

Anastasia Lobanova  Hagen Koch  Stefan Liersch  Fred F. Hattermann  Valentina Krysanova 《水文研究》2016,30(26):5039-5052

The Tagus River basin is an ultimately important water source for hydropower production, urban and agricultural water supply in Spain and Portugal. Growing electricity and water supply demands, over‐regulation of the river and construction of new dams, as well as large inter‐basin and intra‐basin water transfers aggravated by strong natural variability of climate in the catchment, have already imposed significant pressures on the river. The substantial reduction of discharge is observed already now, and projected climatic change is expected to alter the water budget of the catchment further.In this study, we address the effects of projected climate change on the water resources availability in the Tagus River basin and influence of potential changes on hydropower generation of the three important reservoirs in the basin. The catchment‐scale, process‐based eco‐hydrological model soil and water integrated model was set up, calibrated and validated for the entire Tagus River basin, taking into account 15 large reservoirs in the catchment. The future climate projections were selected from those generated within the Inter‐Sectoral Impact Model Intercomparison Project. They include five bias‐corrected climatic datasets for the region, obtained from global circulation model runs under two emissions scenario – moderate and extreme ones – and covered the whole century. The results show a strong agreement among model runs in projecting substantial decrease of discharge of the Tagus River discharge and, consequently, a strong decrease in hydropower production under both future climate scenarios. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Levels and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from Lenga Estuary, central Chile   总被引：1，自引：0，他引：1  

Pozo K  Perra G  Menchi V  Urrutia R  Parra O  Rudolph A  Focardi S 《Marine pollution bulletin》2011,62(7):1572-1576

The Lenga Estuary is a small brackish wetland located southwest of San Vicente Bay, Region VIII, Chile. Surface sediment from nine sites in the estuary were analysed for PAHs and compared to Sediment Quality Guidelines (SQG). Sediment samples were freeze dried and soxhlet extracted for 16 h using DCM. Identification and quantification was carried out by HPLC. Organic carbon was also determined. Results showed total PAH concentrations ranged from 290 to 6118 (2025 ± 1975) ng g⁻¹ d.w. (2025 ± 1975). Results for organic carbon percentages ranged from 1% to 7%. Statistical analysis showed a significant positive correlation (Pearson test) between organic carbon percentage PAHs. Comparison of contaminant levels and international Sediment Quality Guidelines (SQG) (ERL and ER) suggested that sediment of the Lenga estuary did not show any ecotoxicologial risk for benthic organisms where high levels of PAHs were detected. Monitoring of this and other contaminants is recommended in Chile.  相似文献   

Regional and global projections of twenty-first century glacier mass changes in response to climate scenarios from global climate models   总被引：1，自引：0，他引：1  

Valentina Radić  Andrew Bliss  A. Cody Beedlow  Regine Hock  Evan Miles  J. Graham Cogley 《Climate Dynamics》2014,42(1-2):37-58

A large component of present-day sea-level rise is due to the melt of glaciers other than the ice sheets. Recent projections of their contribution to global sea-level rise for the twenty-first century range between 70 and 180 mm, but bear significant uncertainty due to poor glacier inventory and lack of hypsometric data. Here, we aim to update the projections and improve quantification of their uncertainties by using a recently released global inventory containing outlines of almost every glacier in the world. We model volume change for each glacier in response to transient spatially-differentiated temperature and precipitation projections from 14 global climate models with two emission scenarios (RCP4.5 and RCP8.5) prepared for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The multi-model mean suggests sea-level rise of 155 ± 41 mm (RCP4.5) and 216 ± 44 mm (RCP8.5) over the period 2006–2100, reducing the current global glacier volume by 29 or 41 %. The largest contributors to projected global volume loss are the glaciers in the Canadian and Russian Arctic, Alaska, and glaciers peripheral to the Antarctic and Greenland ice sheets. Although small contributors to global volume loss, glaciers in Central Europe, low-latitude South America, Caucasus, North Asia, and Western Canada and US are projected to lose more than 80 % of their volume by 2100. However, large uncertainties in the projections remain due to the choice of global climate model and emission scenario. With a series of sensitivity tests we quantify additional uncertainties due to the calibration of our model with sparsely observed glacier mass changes. This gives an upper bound for the uncertainty range of ±84 mm sea-level rise by 2100 for each projection.  相似文献   

Can stellar winds account for temperature fluctuations?     

Valentina Luridiana  Miguel Cerviño  Luc Binette 《Astrophysics and Space Science》2002,281(1-2):323-324

  相似文献   

Confidence Limits of Evolutionary Synthesis Models     

Miguel Cerviño  Valentina Luridiana 《Astrophysics and Space Science》2002,281(1-2):207-210

The probabilistic nature of the IMF in stellar systems implies that clusters of the same mass and age do not present the same unique values of their observed parameters. Instead they follow a distribution. We address the study of such distributions in terms of their confidence limits that can be obtained by evolutionary synthesis models. These confidence limits can be understood as the inherent uncertainties of synthesis models. We will compare such confidence limits arising from the discreteness of the number of stars obtained with Monte Carlo simulations with the dispersion resulting from an analytical formalism. We give some examples of the effects on the kinetic energy, V–K, EW(Hβ) and multiwavelength continuum. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Erratum: Chemical abundances in QSO host galaxies and environments from narrow absorption line systems     

Valentina D'Odorico  Stefano Cristiani  Donatella Romano  Gian Luigi Granato  Luigi Danese 《Monthly notices of the Royal Astronomical Society》2004,355(4):1399-1399

  相似文献