Paleolimnological records reveal biotic homogenization driven by eutrophication in tropical reservoirs     

Simone Wengrat  Andre A. Padial  Erik Jeppesen  Thomas A. Davidson  Luciane Fontana  Sandra Costa-Böddeker  Denise C. Bicudo 《Journal of Paleolimnology》2018,60(2):299-309

Biodiversity changes in response to eutrophication, climate variability and species invasions. These pressures have been shown to reduce community heterogeneity at various scales; however, how productivity drives homogenization patterns in a community of primary producers, such as diatoms, has not been studied. Using a dataset with good temporal resolution, obtained from cores collected from seven tropical reservoirs, we evaluated patterns of spatial and temporal homogenization, i.e. the trends in temporal α-diversity and spatial β-diversity (change in community composition), of diatom assemblages over the past 60–100 years. The paleolimnological records allowed us to study biodiversity trends since the initial community (reservoir construction) in those systems with low anthropogenic impact and also those undergoing eutrophication. No clear trend of spatial β-diversity change over time was found when all reservoirs were analyzed together. However, when only eutrophic reservoirs were considered, a marked decrease in the spatial β-diversity occurred, suggesting that eutrophication leads to homogenization of the diatom assemblage. These findings were reinforced by the lack of change in β-diversity when the age of the reservoirs was standardized, indicating that the reservoirs’ ontogeny did not influence the spatial β-diversity trend and β-diversity did not increase even in the reservoirs with low anthropogenic impact. In addition, the results showed a decrease of α-diversity over time for almost all the eutrophic reservoirs, as well as a decrease in the total species pool for the reservoirs, although periphytic diatoms may be favored by the appearance and sometimes mass development of floating macrophytes in warm, shallow eutrophic reservoirs. This study supports the role of eutrophication as one of the main drivers of diatom assemblage homogenization in tropical reservoirs, with a significant loss of species over time.  相似文献   

A novel experimental procedure to investigate the biodegradation of NAPL under unsaturated conditions     

Laurent Andre  Monika A.M. Kedziorek  Alain C.M. Bourg  Frank Haeseler  Denis Blanchet   《Journal of Hydrology》2009,370(1-4):1-8

Soils need to be thoroughly investigated regarding their potential for the natural attenuation of non-aqueous phase liquids (NAPL). Laboratory investigations truly representative of degradation processes in field conditions are difficult to implement for porous media partially saturated with water, NAPL and air. We propose an innovative protocol to investigate degradation processes under steady-state vadose zone conditions. Experiments are carried out in glass columns filled with a sand and, as bacteria source, a soil from a diesel-fuel-polluted site. Water and NAPL (n-hexadecane diluted in heptamethylnonane (HMN)) are added to the porous medium in a two-step procedure using ceramic membranes placed at the bottom of the column. This procedure results, for appropriate experimental conditions, in a uniform distribution of the two fluids (water and NAPL) throughout the column. In a biodegradation experiment non-biodegradable HMN is used to provide NAPL mass, while keeping biodegradable n-hexadecane small enough to monitor its rapid degradation. Biodegradation is followed as a function of time by measuring oxygen consumption, using a respirometer. Degradative activity is controlled by diffusive transfers in the porous network, of oxygen from the gas phase to the water phase and of n-hexadecane from the NAPL phase to the water phase.  相似文献   

Incremental dynamic analysis of woodframe buildings     

Ioannis P. Christovasilis  Andre Filiatrault  Michael C. Constantinou  Assawin Wanitkorkul 《地震工程与结构动力学》2009,38(4):477-496

The collapse of wood buildings was one of the main contributors to the heavy death toll and economic losses during the 1995 Hyogo‐ken Nanbu (Kobe) earthquake in Japan. In California, half of the property loss from the 1994 Northridge earthquake was attributed to wood construction. Based on damage observed in recent earthquakes, the seismic vulnerability of existing wood buildings under maximum credible seismic events is uncertain. The main objective of this study is to quantify the seismic collapse fragilities and collapse mechanisms of a two‐story townhouse and three‐story woodframe apartment building through numerical analyses. Three construction quality variants (poor, typical and superior) were considered for each building in order to assess the effects of construction qualities on seismic collapse fragilities. The buildings were also re‐designed according to the 2006 edition of the International Building Code to quantify the seismic fragilities of modern woodframe construction. The results obtained suggest that the construction quality, excitation direction and wall finish materials can influence significantly the collapse fragilities of woodframe buildings. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

1999 Andrei Borisovich Vistelius Research Award     

Andre G. Journel 《Mathematical Geology》1999,31(8):1019-1021

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Geostatistics and Petroleum Geology     

Andre G. Journel 《Mathematical Geology》2000,32(1):139-141

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Consistent floor response spectra for performance-based seismic design of nonstructural elements     

Roberto J. Merino  Daniele Perrone  Andre Filiatrault 《地震工程与结构动力学》2020,49(3):261-284

The achievement of adequate performance objectives for buildings under increasing seismic intensities is not only related to the performance of structural members but also to the behavior of nonstructural elements. The need to properly design nonstructural elements for earthquakes has been largely demonstrated in the last few years and has become an important objective within the earthquake engineering community. A crucial aspect in the proper design of nonstructural elements is the definition of the seismic demand in terms of both absolute acceleration and relative displacement floor response spectra. In the first part of this study, relative displacement and absolute acceleration floor response spectra were computed for four reinforced concrete moment-resisting archetype frames via dynamic time-history analyses and were compared with floor response spectra predicted by means of two recent simplified methodologies available in the literature. It was observed that one of the existing methodologies is generally unable to predict consistent absolute acceleration and relative displacement floor response spectra. An improved procedure is developed for estimating consistent floor response spectra for building structures subjected to low and medium-high seismic intensities. This new procedure improves the predictions of a relative displacement floor response spectrum by constraining its ordinates at long nonstructural periods to the expected peak absolute displacement of the floor. The resulting acceleration and relative displacement response spectra are then consistently related by the well-known pseudo-spectral relationship over the entire nonstructural period range. The effectiveness of the proposed methodology was appraised against floor response spectra computed from nonlinear time-history analyses.  相似文献   

SMSM: a similarity measure for trajectory stops and moves     

Andre L. Lehmann  Luis Otavio Alvares 《International journal of geographical information science》2019,33(9):1847-1872

For many years trajectory similarity research has focused on raw trajectories, considering only space and time information. With the trajectory semantic enrichment, emerged the need for similarity measures that support space, time, and semantics. Although some trajectory similarity measures deal with all these dimensions, they consider only stops, ignoring the moves. We claim that, for some applications, the movement between stops is as important as the stops, and they must be considered in the similarity analysis. In this article, we propose SMSM, a novel similarity measure for semantic trajectories that considers both stops and moves. We evaluate SMSM with three trajectory datasets: (i) a synthetic trajectory dataset generated with the Hermoupolis semantic trajectory generator, (ii) a real trajectory dataset from the CRAWDAD project, and (iii) the Geolife dataset. The results show that SMSM overcomes state-of-the-art measures developed either for raw or semantic trajectories.  相似文献   

Evaluating the accuracy and uncertainty of atmospheric and wave model hindcasts during severe events using model ensembles     

Abdolali  Ali  van der Westhuysen  Andre  Ma  Zaizhong  Mehra  Avichal  Roland  Aron  Moghimi  Saeed 《Ocean Dynamics》2021,71(2):217-235

Ocean Dynamics - Various uncertainties exist in a hindcast due to the inabilities of numerical models to resolve all the complicated atmosphere-sea interactions, and the lack of certain ground...  相似文献   

Automated Detection of Coronal Loops Using a Wavelet Transform Modulus Maxima Method     

R. T. James McAteer  Pierre Kestener  Alain Arneodo  Andre Khalil 《Solar physics》2010,262(2):387-397

We propose and test a wavelet transform modulus maxima method for the automated detection and extraction of coronal loops in extreme ultraviolet images of the solar corona. This method decomposes an image into a number of size scales and tracks enhanced power along each ridge corresponding to a coronal loop at each scale. We compare the results across scales and suggest the optimum set of parameters to maximize completeness, while minimizing detection of noise. For a test coronal image, we compare the global statistics (e.g. number of loops at each length) to previous automated coronal-loop detection algorithms.  相似文献   

Factors driving the biogeochemical budget of the Amazon River and its statistical modelling     

Vincent Bustillo  Reynaldo Luiz Victoria  Jose Mauro Sousa de Moura  Daniel de Castro Victoria  Andre Marcondes Andrade Toledo  Erich Collicchio 《Comptes Rendus Geoscience》2011,343(4):261-277

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