PCDD and PCDF intake through consumption of locally produced seafood by Venice lagoon residents: elements for risk management     

Miniero R  Ceretti G  Cherin E  Dellatte E  De Luca S  Ferri F  Fulgenzi AR  Grim F  Iacovella N  Iamiceli AL  Ingelido AM  Vio P  di Domenico A 《Marine pollution bulletin》2005,50(12):1727-1732

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Variable self‐similar sinuosity properties within simulated river networks     

Cédric Gaucherel  Ludovic Salomon  Jacques Labonne 《地球表面变化过程与地形》2011,36(10):1313-1320

River networks have been shown to obey power scaling laws and to follow self‐organization principles. Their self‐similar (fractal) properties open a path to relate small scale and large scale hydrological processes, such as erosion, deposition or geological movements. However, the existence of a self‐similar dimension has only been checked using either the whole channel network or, on the contrary, a single channel link. No study has explicitly addressed the possible spatial variation of the self‐similar properties between these two extreme geomorphologic objects. Here, a new method based on self‐similarity maps (SSM) is proposed to spatially explore the stream length self‐similar dimension D_l within a river network. The mapping principle consists in computing local self‐similar dimensions deduced from a fit of stream length estimations using increasing divider sizes. A local uncertainty related to the fit quality is also computed and localized on every stream. To assess the efficiency of the approach, contrasted river networks are simulated using optimal channel networks (OCN), where each network is characterized by an exponent γ conditioning its overall topology. By building SSM of these networks, it is shown that deviations from uniform self‐similarity across space occur. Depending on the type of network (γ parameter), these deviations are or are not related to Strahler's order structure. Finally, it is found numerically that the structural averaged stream length self‐similar dimension D_l is closely related to the more functional γ parameter. Results form a bridge between the studies on river sinuosity (single channel) and growth of channel networks (watershed). As for every method providing spatial information where they were lacking before, the SSM may soon help to accurately interpret natural networks and help to simulate more realistic channel networks. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Impact controversies: Impact recognition criteria and related issues     

Wolf Uwe Reimold  Ludovic Ferrière  Alex Deutsch  Christian Koeberl 《Meteoritics & planetary science》2014,49(5):723-731

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Revisiting the Rochechouart impact structure,France     

Haley M. Sapers  Gordon R. Osinski  Neil R. Banerjee  Ludovic Ferrière  Philippe Lambert  Matthew R. M. Izawa 《Meteoritics & planetary science》2014,49(12):2152-2168

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Potential sources of contamination to weak lensing measurements: constraints from N-body simulations     

Catherine Heymans  Martin White  Alan Heavens  Chris Vale  Ludovic Van Waerbeke 《Monthly notices of the Royal Astronomical Society》2006,371(2):750-760

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WIP: A Web‐based program for indexing planar features in quartz grains and its usage          下载免费PDF全文

Anna Losiak  Izabela Golebiowska  Ludovic Ferrière  Jacek Wojciechowski  Matthew S. Huber  Christian Koeberl 《Meteoritics & planetary science》2016,51(4):647-662

Planar deformation features (PDFs) in quartz are the most important diagnostic features that allow the unambiguous identification of impact structures on Earth. In order to confirm that these features (that are characterized by planar character and form along specific crystallographic planes) are indeed PDFs, they need to be properly investigated and indexed. Following universal‐stage measurements, the process of indexing is usually performed manually, using a Wulff stereonet and following a strict procedure, which is time consuming and error prone. In this article, we present WIP, a new Web‐based program for indexing planar deformation features in quartz. The correctness of our program is shown by its application to measurements that had previously been indexed manually. The observed minor differences, especially in the absolute frequency percentage of PDFs, are negligible and not significant enough to influence the estimation of shock pressure that could be calculated from the indexed results. Usability of this program is shown using the spatial relationships between a statistically significant number of 278 quartz grains with 409 sets of PDFs analyzed within the area (~35 mm²) of a single thin section of a meta‐greywacke from the Bosumtwi impact structure. Our program is not only more accurate and faster than the manual (graphical) method but also removes the human error from the plotting process and allows control of several parameters, such as the value of estimated measurement error used in the indexing calculation or method of aggregated error handling. The program also provides information about the angles between the planes of the measured PDF sets present in a grain, which allows determination of the angles between (for example) indexed {} and {} sets.  相似文献   

Estimating potential evapotranspiration without continuous daily data: possible errors and impact on water balance simulations     

Ludovic Oudin  Lætitia Moulin  Hocine Bendjoudi  Pierre Ribstein 《水文科学杂志》2013,58(2):209-222

Abstract

Alternative approaches to estimating monthly and annual potential evapotranspiration (PE) are explored in cases where daily climate data are not routinely recorded. A database consisting of data from 222 weather stations, representing a wide variety of climatic conditions, is used to draw general conclusions. In addition, two PE formulae with different data requirements are used: the standard FAO-56 Penman-Monteith equation, and a simple temperature-based equation. First, we tested the degree of bias introduced by using climate data averaged over long time periods instead of daily data. Second, we explored the sensitivity of PE estimation with respect to variations in sampling frequency of climate variables. The results show that using mean weather data has only a limited effect on monthly and annual PE estimates. Conversely, imperfect sampling of weather data may bias monthly and to a lesser extent annual PE estimates if the sampling period exceeds 5 and 10 days, respectively. Finally, we tested the impact of erroneous weather data on the simulations of annual actual evapotranspiration obtained with the Budyko model. The impact on the Budyko model outputs depends more on the dryness index of a given location than on annual PE; for regions under water stress, the errors in estimation of actual evapotranspiration are very limited, compared to humid regions where available energy is the dominating factor and the propagation of PE errors is important.

Citation Oudin, L., Moulin, L., Bendjoudi, H. & Ribstein, P. (2010) Estimating potential evapotranspiration without continuous daily data: possible errors and impact on water balance simulations. Hydrol. Sci. J. 55(2), 209–222.  相似文献   

Assessment of immune parameters of manila clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> in different physiological conditions using flow cytometry     

Kyung-Il Park  Ludovic Donaghy  Hyun-Sil Kang  Hyun-Ki Hong  Young-Ok Kim  Kwang-Sik Choi 《Ocean Science Journal》2012,47(1):19-26

Cellular and humoral immune parameters are often used as biomarkers to trace environmental and physiological stresses in marine bivalves. In this study, we compared various immune parameters of Manila clams (Ruditapes philippinarum) under normal conditions and under a high level of desiccation, using flow cytometry. The immune parameters analyzed included, total hemocyte count, hemocyte mortality, hemocyte DNA damage, reactive oxygen species (ROS) production, and phagocytosis activity. Total hemocyte count, hemocyte DNA damage, and hemocyte mortality were significantly elevated among clams under high desiccation stress, while phagocytosis activity and spontaneous ROS production were significantly lower compared to those parameters of the control clams (p<0.05). These data suggest that the immune parameters analyzed in this study well reflect the physiological status of clams.  相似文献   

Sources of contamination to weak lensing three-point statistics: constraints from N-body simulations     

Elisabetta Semboloni  Catherine Heymans  Ludovic van Waerbeke  Peter Schneider 《Monthly notices of the Royal Astronomical Society》2008,388(3):991-1000

We investigate the impact of the observed correlation between a galaxy's shape and its surrounding density field on the measurement of third-order weak lensing shear statistics. Using numerical simulations, we estimate the systematic error contribution to a measurement of the third-order moment of the aperture mass statistic (GGG) from three-point intrinsic ellipticity correlations (III), and the three-point coupling between the weak lensing shear experienced by distant galaxies and the shape of foreground galaxies (GGI and GII). We find that third-order weak lensing statistics are typically more strongly contaminated by these physical systematics compared to second-order shear measurements, contaminating the measured three-point signal for moderately deep surveys with a median redshift   z _m∼ 0.7  by ∼15 per cent. It has been shown that accurate photometric redshifts will be crucial to correct for this effect, once a model and the redshift dependence of the effect can be accurately constrained. To this end we provide redshift-dependent fitting functions to our results and propose a new tool for the observational study of intrinsic galaxy alignments. For a shallow survey with   z _m∼ 0.4  we find III to be an order of magnitude larger than the expected cosmological GGG shear signal. Compared to the two-point intrinsic ellipticity correlation which is similar in amplitude to the two-point shear signal at these survey depths, third-order statistics therefore offer a promising new way to constrain models of intrinsic galaxy alignments. Early shallow data from the next generation of very wide weak lensing surveys will be optimal for this type of study.  相似文献   

Influence of Random Inclusion of Synthetic Wicks Fibers of Hair on the Behavior of Clayey Soils     

Armand Sylvain Ludovic Wouatong  Wamba Danny Love Djukem  François Ngapgue  Valentine Katte  Véronique Kamgang Kabeyene Beyala 《Geotechnical and Geological Engineering》2017,35(6):2637-2646

Several soil improvement methods are used to enhance the engineering properties of soil, among which, reinforcement by fibers is considered as an effective ground improvement method because of its cost effectiveness, and easy adaptability. The present investigation chooses synthetic wick and vinifera raphia fibers as reinforcement. The synthetic wick fiber was randomly included into the soil at four different percentages i.e. 0, 2, 4, 6% by volume of raw soil. Vinifera raphia fiber was used at one percentage (4%) as control. The main objective of this research is to focus on the strength behavior of clayey soil reinforced with randomly included synthetic wick fiber. The physical and mineralogical characterization was carried out on ten soil samples. The compression, flexion, abrasion, water absorption and capillarity tests were performed on synthetic wick reinforced specimens with various fiber contents. The results of these tests have clearly shown an improvement in the compression strength values from 1.65 to 2.84 MPa for the wicks fibers, and the flexural strength values which varied between 1.08 and 1.96 MPa. Hence, the waste of synthetic wick fibers is therefore an efficient reinforcement for compressed earth blocks, which are very significant for construction of durable and economic infrastructures.  相似文献