Quantifying year-round nocturnal bird migration with a fluid dynamics model

To understand the influence of biomass flows on ecosystems, we need to characterize and quantify migrations at various spatial and temporal scales. Representing the movements of migrating birds as a fluid, we applied a flow model to bird density and velocity maps retrieved from the European weather radar network, covering almost a year. We quantified how many birds take-off, fly, and land across Western Europe to (1) track bird migration waves between nights, (2) cumulate the number of birds on the ground and (3) quantify the seasonal flow into and out of the study area through several regional transects. Our results identified several migration waves that crossed the study area in 4 days only and included up to 188 million (M) birds that took-off in a single night. In spring, we estimated that 494 M birds entered the study area, 251 M left it, and 243 M birds remained within the study area. In autumn, 314 M birds entered the study area while 858 M left it. In addition to identifying fundamental quantities, our study highlights the potential of combining interdisciplinary data and methods to elucidate the dynamics of avian migration from nightly to yearly time scales and from regional to continental spatial scales.     

Open loop and closed loop spectral frequency active filtering

This paper proposes two frequency based methods for parallel active filtering of current harmonics in utility grids. Active filter (AF) reference prediction and AF current control are the two key-points to obtain high performances. This paper deals with the AF reference prediction. The two proposed methods are based on the Fourier series and its implementation on DSP. They belong to two prediction structures: (1) the open-loop structure which predicts the reference currents from the load currents; and (2) the closed-loop structure which predicts the reference currents from the grid currents. Fourier series based methods are very flexible and have several interesting properties. These two methods have been successfully implemented and tested. The latter method cancels permanent errors and results in better performances. Both methods are very flexible     

The imaginary carrot: no correlation between raising funds and research productivity in geosciences

Scientometrics - The ability of researchers to raise funding is central to academic achievement. However, whether success in obtaining research funds correlates with the productivity, quality or...     

A comparison of gap-filling approaches for Landsat-7 satellite data

The purpose of this study is to assess the relative performance of four different gap-filling approaches across a range of land-surface conditions, including both homogeneous and heterogeneous areas as well as in scenes with abrupt changes in landscape elements. The techniques considered in this study include: (1) Kriging and co-Kriging; (2) geostatistical neighbourhood similar pixel interpolator (GNSPI); (3) a weighted linear regression (WLR) algorithm; and (4) the direct sampling (DS) method. To examine the impact of image availability and the influence of temporal distance on the selection of input training data (i.e. time separating the training data from the gap-filled target image), input images acquired within the same season (temporally close) as well as in different seasons (temporally far) to the target image were examined, as was the case of using information only within the target image itself. Root mean square error (RMSE), mean spectral angle (MSA), and coefficient of determination (R²) were used as the evaluation metrics to assess the prediction results. In addition, the overall accuracy (OA) and kappa coefficient (kappa) were used to assess a land-cover classification based on the gap-filled images. Results show that all of the gap-filling approaches provide satisfactory results for the homogeneous case, with R² > 0.93 for bands 1 and 2 in all cases and R² > 0.80 for bands 3 and 4 in most cases. For the heterogeneous example, GNSPI performs the best, with R² > 0.85 for all tested cases. WLR and GNSPI exhibit equivalent accuracy when a temporally close input image is used (i.e. WLR and GNSPI both have an R² equal to 0.89 for band 1). For the case of abrupt changes in scene elements or in the absence of ancillary data, the DS approach outperforms the other tested methods.     

Splenic vein thrombosis and chronic pancreatitis: therapeutic approach

10% of chronic pancreatitis (CP) cases are complicated by splenic vein thrombosis (SVT) which is responsible for upper digestive haemorrhages. To improve our approach to treatment we reviewed 30 cases of SVT associated with CP treated in our centre from 1985 to 1995. 14 patients were treated conservatively. Six of them were refused for surgery due to extension of splenic vein thrombosis into the portal vein. Two patients without extrinsic compression of the vein were treated with anticoagulants. 16 patients were treated by surgery with low morbidity and without mortality. The standard treatment in fourteen cases was splenopancreatectomy. The average follow-up of seven years shows that these patients have preserved their body mass index (BMI). The results suggest that early surgical intervention is beneficial in preventing progression of SVT to the portomesenteric vein.