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See detailCarbon and nitrogen stable isotope ratios of subtidal benthic invertebrates in an estuarine mangrove ecosystem (Andhra Pradesh, India)
Bouillon, Steven; Raman, A. V.; Dauby, Patrick ULg et al

in Estuarine Coastal and Shelf Science (2002), 54(5), 901-913

In order to assess the relative trophic importance of mangrove litterfall and aquatic primary production in the mangrove creeks of the Coringa Wildlife Sanctuary (Andhra Pradesh, India) and the adjacent ... [more ▼]

In order to assess the relative trophic importance of mangrove litterfall and aquatic primary production in the mangrove creeks of the Coringa Wildlife Sanctuary (Andhra Pradesh, India) and the adjacent semi-enclosed Kakinada Bay, carbon and nitrogen stable isotope ratios were determined in a variety of benthic invertebrate species collected at 22 sites during the pre-monsoon period (May-June) of 1997 and 1999. delta(13)C values showed little interspecific variation at any given location, but there was a distinct spatial gradient in consumer delta(13)C values of about 7parts per thousand, with more depleted values in the mangrove creeks ( - 23.6 +/- 0.6parts per thousand), and gradually increasing in the mangrove outlets ( - 21.5 +/- 0.9parts per thousand), a relatively restricted zone in the south-eastern part of Kakinada Bay adjacent to the mangroves ( - 18.8 +/- 0.8parts per thousand), and the central and northern part of the Bay ( - 16.7 +/- 1.4parts per thousand) which opens into the Bay of Bengal. This gradient is much larger than that observed during a previous study in suspended organic matter (maximum about 2.7parts per thousand) and during this study in sediment organic matter (about 1.5-2.5parts per thousand). The observed carbon stable isotope ratios thus suggest a marked selectivity of the benthic invertebrate community for pelagic and benthic microalgal food sources and indicate that mangrove-derived and other terrestrial carbon is not a significant food source for benthic invertebrate communities in this ecosystem during the pre-monsoon period. Furthermore, delta(13)C values of sediment organic matter (SOM) suggest that terrestrial carbon is not a major contributor to the SOM-pool in this ecosystem. Evidence for seaward migration of Penaeid prawns was provided by some individuals caught in the North Bay which displayed low delta(13)C values of characteristic of fauna found in the mangrove creeks or outlets. Nitrogen stable isotope ratios were found to be a useful indicator of trophic level, even though there remained some overlap between delta(15)N values of presumed low and higher trophic levels. Benthic invertebrates showed a delta(15)N gradient of about 3.2parts per thousand between the mangrove creeks and the Central and North Bay whereas sediment delta(15)N values showed a smaller spatial gradient of about 1.6parts per thousand. This gradient which is hypothesized to reflect differences in inorganic nitrogen sources and availability. (C) 2001 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailBreathing retraining in mild asthma: What are the advantages?
DELVAUX, Muriel ULg; Etienne, Anne-Marie ULg; Bartsch, Pierre ULg et al

in Biological Psychology (2002, May), 59(3), 241-241

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See detailLa dissection aigue de l'aorte: la grande simulatrice
Limet, Raymond ULg

in Revue Médicale de Liège (2002), 57(5), 258-62

Dissecting aneurysm is capable to induce death by cardiac complications, internal haemorrhage or acute ischemia of any organ supplied by an aortic branch. Only early and precise diagnosis can oppose the ... [more ▼]

Dissecting aneurysm is capable to induce death by cardiac complications, internal haemorrhage or acute ischemia of any organ supplied by an aortic branch. Only early and precise diagnosis can oppose the fatal evolution. [less ▲]

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See detailOptimal extraction of multiple overlapping spectra using a maximum entropy algorithm
Khmil, S. V.; Surdej, Jean ULg

in Astronomy and Astrophysics (2002), 387(1), 347-355

A general algorithm of slit spectra extraction for a system of point-like sources (e.g. multiple lensed images of a quasar) has been developed, assuming that the point-spread function (PSF) induced by the ... [more ▼]

A general algorithm of slit spectra extraction for a system of point-like sources (e.g. multiple lensed images of a quasar) has been developed, assuming that the point-spread function (PSF) induced by the measuring instrument and/or atmosphere and the positions of the spectra relative to the CCD frame are unknown. The main idea of the algorithm is to successively apply the maximum entropy method to each set of parameters, such as the spectra, the PSF, and the spectra positions, in order to iteratively improve their values. The algorithm uses all the a priori knowledge about the spectra (e.g. flux positivity, flux ratios between the components, astrometry, etc.) to compute the initial parameter sets. The main features of the algorithm, its implementation, as well as some important aspects of its practical use, are discussed in detail. Two sets of simulated spectroscopic data have been built in order to show the most characteristic properties of the algorithm and to justify its aplication to the spectra extraction of the gravitational lens system Q1009-0252 A [less ▲]

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See detailTroubles anxieux et pathologies organiques: un diagnostic differentiel difficile
Scantamburlo, Gabrielle ULg; Fuchs, Sonia; Lancellotti, Patrizio ULg et al

in Revue Médicale de Liège (2002), 57(5), 303-306

The diagnostic criteria for panic disorder include symptoms commonly experienced by patients with organic diseases. We report a case of coronary artery spasm in a patient with chest pain, exhibiting ... [more ▼]

The diagnostic criteria for panic disorder include symptoms commonly experienced by patients with organic diseases. We report a case of coronary artery spasm in a patient with chest pain, exhibiting atypical characteristics, and accompanied by symptoms of nervousness. The approach and the management of anxiety disorders are discussed. [less ▲]

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See detailUtilisation de la méthode LQRT (Lecture / Questions - Réponses / Test) -- SAFE (Système Adulte de Formation et d'Évaluation) en médecine vétérinaire.
Castaigne, Jean-Loup ULg

in Actes du 19ème Colloque de l'AIPU : Les méthodes actives dans l'enseignement supérieur : Regards pluriels et critiques sur les pratiques. (2002, May)

Suite aux résultats d’une évaluation des enseignements par les étudiants, nous avons décidé de mettre en place une nouvelle stratégie de formation centrée sur l’étudiant. La méthode des LQRT (Lecture ... [more ▼]

Suite aux résultats d’une évaluation des enseignements par les étudiants, nous avons décidé de mettre en place une nouvelle stratégie de formation centrée sur l’étudiant. La méthode des LQRT (Lecture, Questions-Réponses, Test) - SAFE (Système Adulte de Formation et d’Évaluation) a été choisie pour dispenser 5 cours portant sur des matières dont la compréhension est importante pour la réussite de l’examen oral de fin d’année. La conclusion directe de l’utilisation de ce système d’enseignement a été une participation plus active des étudiants au cours mais également une responsabilisation de l’apprenant dans le processus de formation par la définition des performances cognitives. Les tests pratiqués durant l’année constituent une évaluation diagnostic pour l’enseignant qui a pu remédier dès le cours suivant aux problèmes de compréhension mis en évidence par le test. Les retombées indirectes comme les gains métacognitifs et l’acquisition d’autres compétences ne sont pas mesurables. Une nouvelle évaluation de l’enseignement a montré que les étudiants ont apprécié l’instauration des LQRT-SAFE en médecine vétérinaire. [less ▲]

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See detailClosure of "a unified approach to transient stability contingency filtering, ranking, and assessment"
Ernst, Damien ULg; Ruiz-Vega, Daniel; Pavella, Mania ULg et al

in IEEE Transactions on Power Systems (2002), 17(2), 528-529

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See detailLa sténose d'artère rénale: cause possible de décompensation cardiaque aiguë
Krzesinski, Jean-Marie ULg

in Revue Médicale de Liège (2002), 57(5), 253-257

Among the different causes of pulmonary edema, there are all the clinical situations with hydrosaline overload. A significant (> 70%) bilateral renal artery stenosis or a unilateral stenosis in the ... [more ▼]

Among the different causes of pulmonary edema, there are all the clinical situations with hydrosaline overload. A significant (> 70%) bilateral renal artery stenosis or a unilateral stenosis in the presence of a solitary kidney is one possibility. Recurrent acute pulmonary edema not fully explained on a cardiac basis is rather typical for such a disease in a cardiac patient with moderate renal failure aggravated when angiotensin converting enzyme inhibitors are used. [less ▲]

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See detailPreventive control of voltage security margins: A multicontingency sensitivity-based approach
Capitanescu, Florin ULg; Van Cutsem, Thierry ULg

in IEEE Transactions on Power Systems (2002), 17(2), 358-364

This paper addresses the problem of changing the operating point of a power system in order to keep voltage security margins with respect to contingencies above some minimal value. Margins take on the ... [more ▼]

This paper addresses the problem of changing the operating point of a power system in order to keep voltage security margins with respect to contingencies above some minimal value. Margins take on the form of maximum pre-contingency power transfers either between a generation and a load area or between two generation areas. They are determined by means of a fast time-domain method. We will first discuss the use of a general optimal power flow, in which linear voltage security constraints are added. The simultaneous control of several (possibly conflicting) contingencies is considered. Then, we will focus on the minimal control change objective. Among the possible controls, emphasis is put on generation rescheduling and load curtailment. Examples are presented on an 80-bus test system as well as on a real system. [less ▲]

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See detailL'allocation pour l'aide d'une tierce personne et son indexation
Michiels, Olivier ULg

in Lexius Actua (2002), 5

L'article fait le point sur l'aide d'une tierce personne en accident du travail et sur l'indexation de cette allocation.

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See detailContributions to decision tree induction: bias/variance tradeoff and time series classification
Geurts, Pierre ULg

Doctoral thesis (2002)

Because of the rapid progress of computer and information technology, large amounts of data are nowadays available in a lot of domains. Automatic learning aims at developing algorithms able to produce ... [more ▼]

Because of the rapid progress of computer and information technology, large amounts of data are nowadays available in a lot of domains. Automatic learning aims at developing algorithms able to produce synthetic high-level information, or models, from this data. Learning algorithms are generally evaluated according to three different criteria: interpretability (how well the model helps to understand the data), predictive accuracy (how well the model can predict unseen situations), and computational efficiency (how fast is the algorithm and how it scales to large databases). This thesis explores two issues in automatic learning: the improvement of the well-known decision tree induction method and the problem of learning classification models for time series data. Decision tree induction method is an automatic learning algorithm which focuses on the modeling of input/output relationships. While this algorithm is among the fastest and most interpretable methods, its accuracy is not always competitive with respect to other algorithms. It is commonly admitted that this suboptimality is due to the excessive variance of this method. We first carry out an empirical study which shows quantitatively how important this variance is, i.e. how strongly decision trees depend on the random nature of the database used to infer them. These experiments confirm that this variance is detrimental not only from the point of view of accuracy but also from the point of view of interpretability. With the goal of improving both interpretability and accuracy, we consider three variance reduction techniques for decision trees. First, in the goal of improving mainly interpretability, we propose several methods which try to stabilize the parameters chosen during tree induction. While these methods succeed in reducing the variability of the parameters, they produce only a slight improvement of the accuracy. Then, we consider perturb and combine algorithms (e.g. bagging, boosting) which consist in combining the predictions of several models obtained by randomizing in some way the learning process. Inspired by the high variance of the parameters defining a decision tree, we propose an extremely randomized decision tree induction algorithm, called extra-tree, which chooses all parameters at random during induction. The aggregation of several of these extra-trees gives an important reduction of variance and this algorithm compares favorably in terms of accuracy and computational efficiency with both bagging and boosting. Because of the randomization of the parameters, the resulting method is also competitive with classical decision tree induction in terms of computational efficiency. In addition to these two approaches, we propose a ``dual'' perturb and combine algorithm which delays the perturbation at the prediction stage and hence requires only one model. In combination with decision tree, this method actually bridges the gap between single decision trees and perturb and combine algorithms. Of the first, it saves the interpretability (by using only one model), and with perturb and combine algorithm, it shares some of the accuracy (by reducing the variance). The second topic of the thesis is the problem of time series classification. The most direct way to solve this problem is to apply existing learning algorithms on low-level variables which correspond to the values of a time series at several time points. Experiments with the tree-based algorithms studied in the first part of the thesis shows that this approach is limited. A variance reduction techniques is then proposed specifically for this kind of data which consists in aggregating the prediction given by a classification model for subsequences of time series. Since this method does not provide interpretable models, we propose a second method which extends decision tree tests by allowing them to detect local shift invariant properties, or patterns, in time series. The study proposed in this part of the thesis is only a first step in the domain but our conclusions give some future work directions for handling complex type of data with automatic learning methods. [less ▲]

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See detailFinite Element Analysis of the Electro-Mechanical Coupling in MEMS
Rochus, Véronique ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

Conference given outside the academic context (2002)

This paper concerns the modelling of the strong electro-mechanical coupling appearing in micro-electro-mechanical systems (MEMS). These systems are very small devices (typical size of a few microns), in ... [more ▼]

This paper concerns the modelling of the strong electro-mechanical coupling appearing in micro-electro-mechanical systems (MEMS). These systems are very small devices (typical size of a few microns), in which electric phenomena as well as mechanical and dynamical phenomena exist. The coupling between the electric and mechanical fields induce non-linear terms in the dynamic equilibrium equations of these microscopic structures so that instability may occur. In this paper, the finite element method (FEM) is used to perform modal analysis around non-linear equilibrium positions, taking into account large displacements. [less ▲]

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See detailSelection of approximation schemes in topology optimization
Bruyneel, Michaël ULg; Duysinx, Pierre ULg

in Hogge, Michel (Ed.) Proceedinsg of the ACOMEN 2002, 2nd International Conference on Advanced Computational Methods in Engineering (2002, May)

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See detailNestin expression in cultivated mesenchymal stem cells: Regulation and potential role in their neural differentiation
Wislet-Gendebien, Sabine ULg; Leprince, Pierre ULg; Moonen, Gustave ULg et al

in Glia (2002, May), (Suppl. 1), 87

Bone marrow stromal cells can differentiate into many types of mesenchymal cells, i.e. osteocyte, chondrocyte, fibroblast and adipocyte, but can also differentiate into non-mesenchymal cell, i.e. neural ... [more ▼]

Bone marrow stromal cells can differentiate into many types of mesenchymal cells, i.e. osteocyte, chondrocyte, fibroblast and adipocyte, but can also differentiate into non-mesenchymal cell, i.e. neural cells in appropriate in vivo experimental conditions (Kopen and al.,PNAS,96, 10711,1999, Brazelton and al, Science, 290,1175, 2000, Mezey and al, Science, 290,1179, 2000). In neurological disorders, such as Alzheimer's and Parkinson's diseases, auto-transplantation of neural cell types derived from mesenchymal stem cells offers the potential of replacing lost cells and recovering lost functions. Nestin is an intermediate filament protein predominantly expressed by neural stem cells and is used to identify neural progenitor. In this study, we demonstrate that cultured rat mesenchymal stem cells (rMSC) can express nestin in appropriate conditions. Two factors contribute to the regulation of nestin expression by rMSC : 1) the presence of serum-derived components in the culture medium which repress nestin expression and 2) the cell’s number of passages. LPA and thrombin mimic this serum effect. Furthermore, when nestin- positive cells are trypsinized and resuspended into culture conditions used for neural stem cells (NSC), sphere formation is observed. Likewise, by co-cultivating nestin-positive rMSC with NSC derived from green mouse, heterogenous spheres were obtained. When those heterogenous spheres are placed on polyornithine-coated surfaces, a differentiation of some rMSC into GFAP-positive cells occurs. These results indicate that nestin expression might be a pre-requisite for the acquisition by rMSC of the capacity to differentiate into some neural cell types. [less ▲]

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See detailThe application of EIA/SEA procedures to the urban cultural heritage active conservation
Teller, Jacques ULg; Dupagne, Albert ULg

in Proc. of 5th European Commission Conference on Research for Protection, Conservation and Enhancement of Cultural Heritage (2002)

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See detailEvaluation de l'huile de chaîne à base végétale
Debouche, Charles ULg; Novak, Marie Hélène; Sonneville, G.

in Forêt Wallonne (2002), 58

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See detailComputer-Aided Design of Redundant Sensor Networks
Heyen, Georges ULg; Dumont, Marie-Noëlle ULg; Kalitventzeff, Boris ULg

Poster (2002, May)

A systematic method to design sensor networks able to identify key process parameters with a required precision at a minimal cost is presented. The procedure is based on a linearised model, derived ... [more ▼]

A systematic method to design sensor networks able to identify key process parameters with a required precision at a minimal cost is presented. The procedure is based on a linearised model, derived automatically from a rigorous non-linear data reconciliation model. A genetic algorithm is used to select the sensor types and locations. [less ▲]

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See detailpH-Dependence of the morphology of micelles formed by poly(2-vinylpyridine)-block-poly(ethylene oxide) copolymers in water
Gohy, Jean-François; Mores, Sandrine; Varshney, Sunil K et al

in e-Polymers (2002), (21), 1-8

The morphology of micelles formed by two poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-b-PEO) copolymers has been studied in phosphate-buffered water by dynamic light scattering and transmission ... [more ▼]

The morphology of micelles formed by two poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-b-PEO) copolymers has been studied in phosphate-buffered water by dynamic light scattering and transmission electron microscopy. Spherical micelles are observed when the P2VP block is the minor component of the diblock copolymer. When P2VP dominates the composition, transition from spheres-to-rods-to-vesicles takes place in a narrow pH range that straddles the pKa of P2VP. This transition is controlled by the degree of protonation of the P2VP blocks. At high pH, the copolymer precipitates from the solution. [less ▲]

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