Klimaatwijziging en biodiversiteit in de jaren 1950, anachronisme of early warning?

Edgar Kesteloot, former chairman of Belgische Natuur- en Vogelreservaten (BNVR) and head of department at the Royal Belgian Institute of Natural Sciences (KBIN) gave lectures in 1954 and 1955 about changes in the fl ora and fauna of the previous 100 years. He also published a few articles on the subject. The author sought explanations for the changes in the emergence of new, man-made or altered habitats, as well as in climate change! He was also concerned about the rise in sea level. Some present-day natural and environmental themes seem to have a longer history than we commonly think

Small-scale clinal variation, genetic diversity and environmental heterogeneity in the marine gobies <i>Pomatoschistus minutus</i> and <i>P. lozanoi</i> (Gobiidae, Teleostei)

Genetic variation was assayed at 14 allozyme loci in estuarine, coastal and offshore samples of Lozano's goby, Pomatoschistus lozanoi and the sand goby, P. minutus. Samples were taken from locations on the Belgian Continental Shelf and in the Schelde estuary with a range of environmental heterogeneity. We evaluate whether any differences in (1) the degree of genetic variation and (2) allele frequencies at the various loci exist within samples occurring in various habitats on the BCS and in the Schelde estuary. No significant differences in levels of genetic diversity were recorded between estuarine, coastal and offshore samples in either species. A temporally stable clinal gradient in allele frequencies at the two-allele locus GPI-A* was observed in P. lozanoi, differentiating the samples in an estuarine, coastal and offshore group. We suggest that these differences might be maintained by balancing selection at locus GPI-A*

Phase synchronization for classification of spontaneous EEG signals in brain-computer interfaces

By directly analyzing brain activity, Brain-Computer Interfaces (BCIs) allow for communication that does not rely on any muscular control and therefore constitute a possible communication channel for the completely paralyzed. Typically, the user performs different mental tasks, that correspond to different output commands as recognized by the system. From the recorded brain signals (Electroencephalogram, EEG), features that characterize the mental tasks and allow their discrimination by a classifier have to be extracted. This dissertation addresses the extraction of features in the framework of BCIs. On the one hand, new features are proposed. On the other hand, feature selection algorithms are investigated in order to select relevant features. Currently existing BCIs mostly use power estimates in some pre-defined frequency bands, which are single-channel features. Some authors report on the use of multichannel features, but interactions between specific brain regions have not yet been studied. We propose to use the synchronization feature Phase Locking Value (PLV) for the classification of spontaneous EEG recorded during different mental tasks. It is fast to compute and can be applied to relatively short time windows, two important assets for BCI applications. In a first instance, average synchronization values are considered. Tests on offline data show that significant classification accuracies can be obtained by the sole use of PLV. This demonstrates the relevance of synchronization features for the classification of EEG in this context. We found that PLV and power features do not clearly outperform each other, but their combination often leads to significantly improved results and never significantly deteriorates the classification accuracies obtained by the separate subsets. In the next step, feature selection algorithms are investigated in order to select the most interesting features. We show that Genetic Algorithms (GAs) as well as SVM-based recursive feature elimination (SVM-rfe) select physiologically meaningful features. As they are slow (computation times on the order of days and hours respectively) and thus cannot practically be used for BCIs, a modified version of the Fast Correlation-Based Filter (FCBF) is proposed. In this study, FCBF generalizes well and achieves good classification accuracies with very few features. The correspondence of the selected EEG signals with neurophysiological evidence is even stronger than for GAs and SVM-rfe. In addition, this algorithm is fast (computation time on the order of minutes) and so it can be applied between two recording sessions. Comparing the classification results obtained with broadband and narrowband power and PLV features selected by FCBF learns that power features are preferably computed in the narrower 8–12Hz frequency band and that for PLV features, the 8–30Hz frequency band is the better one. Furthermore, FCBF is used to evaluate a set of features comprising, on the one hand, the PLV for all possible electrode pairs, PLV averages, the cluster participation index and power features (band power and statistical mean frequency (SMF)), computed from the EEG signals. On the other hand, power (total power and SMF) and synchronization features derived from the empirical mode decomposition of these signals were included. They all proved useful. It is recommended to initially consider power features and only the PLV averages, because the resulting set of features is substantially smaller than when using PLV for all possible electrode pairs. Automatic detection of artifacts and rejection of the corresponding data window for selecting the features and training the classifier, results in, if any, an increase of classification accuracy that is generally not greater than 1%, for our data. Application of global and local PCA-based denoising techniques never yielded improved results for two of the five subjects we analyzed. If it yields better results for the other 3 subjects, the increase never exceeds 1.84%. Application of the proposed methods to blind data of the third international BCI competition held in 2005 gave significant classification accuracies. This further illustrates the relevance and the potential of the investigated techniques. We conclude that PLV may complement currently used features and improve future BCI systems. PLV is well suited for BCI applications, because of its fast computation, needed for online feedback systems. The Fast Correlation-Based Filter is a valuable tool for evaluating features and selecting a subset of relevant features

Genetische structuur en evolutieve patronen van <i>Pomatoschistus</i> grondels op het Europees Continentaal Plat en in de Middellandse Zee = Genetic structure and evolutionary patterns in <i>Pomatoschistus</i> gobies on the European Continental Shelf and in the Mediterranean Sea

Large-scale and small-scale genetic patterns in three species of marine gobies, Pomatoschistus minutus (Pallas, 1770), P. lozanoi (de Buen, 1923) and P. microps (Kroyer, 1838) were studied. We used the available knowledge of the biology of the species and past and present-day oceanographic features throughout their distributional range for inferring population genetic structure and phylogeographical history of small demersal fish species along the European coasts. These three species occur sympatrically throughout a large part of their distributional range, which comprises the European Atlantic coasts and the Mediterranean Sea. They have a similar potential for dispersal with an extended pelagic larval stage, but differ ecologically. Small-scale patterns along the Belgian coast were studied with allozyme electrophoresis at fourteen putative loci. No evidence for population differentiation was found, except for a clinal change in allele frequencies at one locus in P. lozanoi. We suggest that this is due to differential selective pressure in distinct habitats (resp. estuarine, coastal and marine), rather than reproductive isolation. Contrary to other studies, we did not find any correlation between environmental heterogeneity and levels of genetic diversity. For studying large-scale genetic structure we employed a combination of allozyme electrophoresis, SSCP- and sequence analysis of fragment of the cytochrome b locus on the mtDNA. Overall patterns of P. minutus and P. microps revealed (1) the highest amount of divergence between Atlantic and Mediterranean species, (2) a pattern of isolation-by-distance, consistent with a larval dispersal via oceanic currents and (3) a shallow phylogeographical structure with a few common (ancestral) haplotypes and a large number of rare variants radiating. In the Atlantic basin, phylogeographical analysis of both species points to a range expansion into northern areas with a loss of variation at higher latitudes and a possible glacial refugium in the English Channel or the Southem Bight. However, despite similar overall patterns, striking interspecific differences were recorded. P. microps is much more differentiated than P. minutus on the same scale, and has a different phylogeographical history in the Mediterranean Sea. We suggest that this is due to ecological constraints on dispersal in the estuarine-marine P. microps. We postulate that species-specific behavioural patterns play a more important role in shaping population structure than usually accounted for

Distribution of antiretroviral treatment through self-forming groups of patients in Tete province, Mozambique

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