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See detailMultispectral simultaneous diagnosis of Saturn's aurorae throughout a planetary rotation
Lamy, L.; Prangé, R.; Pryor, W. et al

in Journal of Geophysical Research. Space Physics (2013), 118

From 27 to 28 January 2009, the Cassini spacecraft remotely acquired combined observations of Saturn's southern aurorae at radio, ultraviolet, and infrared wavelengths, while monitoring ion injections in ... [more ▼]

From 27 to 28 January 2009, the Cassini spacecraft remotely acquired combined observations of Saturn's southern aurorae at radio, ultraviolet, and infrared wavelengths, while monitoring ion injections in the middle magnetosphere from energetic neutral atoms. Simultaneous measurements included the sampling of a full planetary rotation, a relevant timescale to investigate auroral emissions driven by processes internal to the magnetosphere. In addition, this interval coincidentally matched a powerful substorm-like event in the magnetotail, which induced an overall dawnside intensification of the magnetospheric and auroral activity. We comparatively analyze this unique set of measurements to reach a comprehensive view of kronian auroral processes over the investigated timescale. We identify three source regions for the atmospheric aurorae, including a main oval associated with the bulk of Saturn Kilometric Radiation (SKR), together with polar and equatorward emissions. These observations reveal the coexistence of corotational and subcorototational dynamics of emissions associated with the main auroral oval. Precisely, we show that the atmospheric main oval hosts short-lived subcorotating isolated features together with a bright, longitudinally extended, corotating region locked at the southern SKR phase. We assign the substorm-like event to a regular, internally driven, nightside ion injection possibly triggered by a plasmoid ejection. We also investigate the total auroral energy budget, from the power input to the atmosphere, characterized by precipitating electrons up to 20 keV, to its dissipation through the various radiating processes. Finally, through simulations, we confirm the search-light nature of the SKR rotational modulation and we show that SKR arcs relate to isolated auroral spots. We characterize which radio sources are visible from the spacecraft and we estimate the fraction of visible southern power to a few percent. The resulting findings are discussed in the frame of pending questions as the persistence of a corotating field-aligned current system within a subcorotating magnetospheric cold plasma, the occurrence of plasmoid activity, and the comparison of auroral fluxes radiated at different wavelengths. [less ▲]

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See detailA multistage field test of wheelchair users for evaluation of fitness and prediction of peak oxygen consumption
Vanderthommen, Marc ULg; Francaux, M.; Colinet, Cédrik et al

in Journal of Rehabilitation Research & Development (2002), 39(6, Nov-Dec), 685-692

An incremental multistage field test (MFT) for wheelchair users was developed to evaluate physical fitness and predict peak oxygen consumption (VO2). Using auditory feedback, the participants (n = 37 ... [more ▼]

An incremental multistage field test (MFT) for wheelchair users was developed to evaluate physical fitness and predict peak oxygen consumption (VO2). Using auditory feedback, the participants (n = 37) were directed to wheel around an octagonal course, increasing their velocity every minute until exhaustion. Wheelchair velocity and metabolic parameters were recorded with the use of a speedometer and a portable spirometer system. The average number of exercise levels performed (MFT score) was 9.17 +/- 5.81, resulting in a peak heart rate (HR) of 99.0 +/- 13.9% of the theoretical maximum. A test-retest analysis (n = 10) showed that the MFT was reliable regarding MFT score, peak VO2, and peak HR reached. Stepwise multiple regression based on individual, wheelchair, propulsion technique, and physiological parameters revealed that the MFT score was the best and only predictor of peak VO2 (mL/min/kg) (= 18.03 + 0.78 MFT score, r(2) = 0.59). The MFT assesses wheelchair mobility and estimates peak VO2 encountered during the test. [less ▲]

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See detailA multistage process to enhance cellobiose production from cellulosic materials
Vanderghem, Caroline ULg; Boquel, Pascal; Blecker, Christophe ULg et al

in Applied Biochemistry and Biotechnology (2010), 160(8), 2300-2307

Cellobiose, a disaccharide, is a valuable product that can be obtained from cellulose hydrolysis. In this study, a simple methodology is presented to enhance the production and improve the selectivity of ... [more ▼]

Cellobiose, a disaccharide, is a valuable product that can be obtained from cellulose hydrolysis. In this study, a simple methodology is presented to enhance the production and improve the selectivity of cellobiose during enzymatic hydrolysis of cellulose. The approach consisted of a multistage removal of filtrate via vacuum filtration and resuspension of the retentate. By this process, the remaining solid was further hydrolyzed without additional enzyme loading. Compared to the continuous hydrolysis process, the production of cellobiose increased by 45%. Increased selectivity of cellobiose is due to the loss of beta-glucosidases in the filtrate, while enhanced productivity is likely due to mitigated product inhibition. [less ▲]

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See detailMultistage stochastic programming: A scenario tree based approach to planning under uncertainty
Defourny, Boris ULg; Ernst, Damien ULg; Wehenkel, Louis ULg

in Sucar, L. Enrique; Morales, Eduardo F.; Hoey, Jesse (Eds.) Decision Theory Models for Applications in Artificial Intelligence: Concepts and Solutions (2011)

In this chapter, we present the multistage stochastic programming framework for sequential decision making under uncertainty. We discuss its differences with Markov Decision Processes, from the point of ... [more ▼]

In this chapter, we present the multistage stochastic programming framework for sequential decision making under uncertainty. We discuss its differences with Markov Decision Processes, from the point of view of decision models and solution algorithms. We describe the standard technique for solving approximately multistage stochastic problems, which is based on a discretization of the disturbance space called scenario tree. We insist on a critical issue of the approach: the decisions can be very sensitive to the parameters of the scenario tree, whereas no efficient tool for checking the quality of approximate solutions exists. In this chapter, we show how supervised learning techniques can be used to evaluate reliably the quality of an approximation, and thus facilitate the selection of a good scenario tree. The framework and solution techniques presented in the chapter are explained and detailed on several examples. Along the way, we define notions from decision theory that can be used to quantify, for a particular problem, the advantage of switching to a more sophisticated decision model. [less ▲]

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See detailMultitasking capacities in persons diagnosed with schizophrenia: A preliminary examination of their neurocognitive underpinnings and ability to predict real world functioning
Laloyaux, Julien ULg; Van der Linden, Martial ULg; Levaux, Marie-Noëlle ULg et al

in Psychiatry Research (2014), 217

Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia and in particular during multitasking activities. However, at present, patients' multitasking capacities ... [more ▼]

Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia and in particular during multitasking activities. However, at present, patients' multitasking capacities have not been adequately examined in the literature due to an absence of suitable assessment strategies. We thus recently developed a computerized real-life activity task designed to take into account the complex and multitasking nature of certain everyday life activities where participants are required to prepare a room for a meeting. Twenty-one individuals diagnosed with schizophrenia and 20 matched healthy controls completed the computerized task. Patients were also evaluated with a cognitive battery, measures of symptomatology and real world functioning. To examine the ecological validity, 14 other patients were recruited and were given the computerized version and a real version of the meeting preparation task. Results showed that performance on the computerized task was significantly correlated with executive functioning, pointing to the major implication of these cognitive processes in multitasking situations. Performance on the computerized task also significantly predicted up to 50% of real world functioning. Moreover, the computerized task demonstrated good ecological validity. These findings suggest the importance of evaluating multitasking capacities in patients diagnosed with schizophrenia in order to predict real world functioning. [less ▲]

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See detailMultitasking capacities in persons diagnosed with schizophrenia: A preliminary examination of their neurocognitive underpinnings and ability to predict real world functioning
Laloyaux, Julien ULg; Van der Linden, Martial ULg; Levaux, Marie-Noëlle ULg et al

in Psychiatry Research (2014), 217

Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia and in particular during multitasking activities. However, at present, patients' multitasking capacities ... [more ▼]

Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia and in particular during multitasking activities. However, at present, patients' multitasking capacities have not been adequately examined in the literature due to an absence of suitable assessment strategies. We thus recently developed a computerized real-life activity task designed to take into account the complex and multitasking nature of certain everyday life activities where participants are required to prepare a room for a meeting. Twenty-one individuals diagnosed with schizophrenia and 20 matched healthy controls completed the computerized task. Patients were also evaluated with a cognitive battery, measures of symptomatology and real world functioning. To examine the ecological validity, 14 other patients were recruited and were given the computerized version and a real version of the meeting preparation task. Results showed that performance on the computerized task was significantly correlated with executive functioning, pointing to the major implication of these cognitive processes in multitasking situations. Performance on the computerized task also significantly predicted up to 50% of real world functioning. Moreover, the computerized task demonstrated good ecological validity. These findings suggest the importance of evaluating multitasking capacities in patients diagnosed with schizophrenia in order to predict real world functioning. [less ▲]

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See detailMultitasking capacities in persons diagnosed with schizophrenia: A preliminary examination of their neurocognitive underpinnings and ability to predict real world functioning
Laloyaux, Julien ULg; Van der Linden, Martial ULg; Levaux, Marie-Noëlle ULg et al

in Schizophrenia Research (2014, April), 153(Supl. 1), 344

Background: Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia. Moreover, patients seem to demonstrate particular difficulties during complex and ... [more ▼]

Background: Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia. Moreover, patients seem to demonstrate particular difficulties during complex and multitasking activities, such as cooking a meal (Semkovska et al., 2004). Multitasking refers to activities where the person has to: carry out and alternate between different tasks that vary in terms of priority, difficulty and duration; define the tasks’ targets; and where the person is faced with unexpected problems during the realization of these tasks (Burgess, 2000). However, at present, patients’ multitasking capacities have not been adequately examined in the literature due to an absence of suitable assessment strategies. We thus recently developed a computerized real-life activity task designed to take into account the complex and multitasking nature of certain everyday life activities where participants are required to prepare a room for a meeting – the Computerized Meeting Preparation Task (CMPT) Methods: Twenty-one individuals diagnosed with schizophrenia and 20 matched healthy controls completed the CMPT. During the CMPT, participants found themselves in a virtual room that they had to prepare for a meeting while respecting a list of instructions (the placement of the guests, the needed objects, the desired drinks, etc.). Patients were also evaluated with an extensive cognitive battery (assessing executive functions, attention, processing speed and memory), measures of symptomatology and real world functioning. To examine the ecological validity of the CMPT, 14 others patients were recruited and were given the computerized version and a real version of the meeting preparation task. Results: Results demonstrated that performance on the CMPT significantly differentiated patients and healthy controls for the total time to complete task, planning efficiency, and the respect of the instructions. Moreover, these variables were significantly correlated with executive functioning (i.e. cognitive flexibility and planning), suggesting the major implication of these cognitive processes in multitasking activities. Performance on the CMPT also significantly predicted up to 50% of real world functioning. Finally, performances on the computerized version and the real version of the meeting preparation task were highly correlated, suggesting good ecological validity. Discussion: In this study, we created a novel task involving the multitasking nature of real world activities. The results demonstrated that this approach provides a good indication of the real world functioning in patients diagnosed with schizophrenia. Moreover, results suggest a particular implication of executive functioning in multitasking activities. These findings suggest the importance of evaluating multitasking capacities in patients diagnosed with schizophrenia in order to predict real world functioning. [less ▲]

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See detailMultitasking capacities in persons diagnosed with schizophrenia: A preliminary examination of their neurocognitive underpinnings and ability to predict real world functioning
Laloyaux, Julien ULg; Van der Linden, Martial ULg; Levaux, Marie-Noëlle ULg et al

Poster (2014, April 08)

Background: Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia. Moreover, patients seem to demonstrate particular difficulties during complex and ... [more ▼]

Background: Difficulties in everyday life activities are core features of persons diagnosed with schizophrenia. Moreover, patients seem to demonstrate particular difficulties during complex and multitasking activities, such as cooking a meal (Semkovska et al., 2004). Multitasking refers to activities where the person has to: carry out and alternate between different tasks that vary in terms of priority, difficulty and duration; define the tasks’ targets; and where the person is faced with unexpected problems during the realization of these tasks (Burgess, 2000). However, at present, patients’ multitasking capacities have not been adequately examined in the literature due to an absence of suitable assessment strategies. We thus recently developed a computerized real-life activity task designed to take into account the complex and multitasking nature of certain everyday life activities where participants are required to prepare a room for a meeting – the Computerized Meeting Preparation Task (CMPT) Methods: Twenty-one individuals diagnosed with schizophrenia and 20 matched healthy controls completed the CMPT. During the CMPT, participants found themselves in a virtual room that they had to prepare for a meeting while respecting a list of instructions (the placement of the guests, the needed objects, the desired drinks, etc.). Patients were also evaluated with an extensive cognitive battery (assessing executive functions, attention, processing speed and memory), measures of symptomatology and real world functioning. To examine the ecological validity of the CMPT, 14 others patients were recruited and were given the computerized version and a real version of the meeting preparation task. Results: Results demonstrated that performance on the CMPT significantly differentiated patients and healthy controls for the total time to complete task, planning efficiency, and the respect of the instructions. Moreover, these variables were significantly correlated with executive functioning (i.e. cognitive flexibility and planning), suggesting the major implication of these cognitive processes in multitasking activities. Performance on the CMPT also significantly predicted up to 50% of real world functioning. Finally, performances on the computerized version and the real version of the meeting preparation task were highly correlated, suggesting good ecological validity. Discussion: In this study, we created a novel task involving the multitasking nature of real world activities. The results demonstrated that this approach provides a good indication of the real world functioning in patients diagnosed with schizophrenia. Moreover, results suggest a particular implication of executive functioning in multitasking activities. These findings suggest the importance of evaluating multitasking capacities in patients diagnosed with schizophrenia in order to predict real world functioning. [less ▲]

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See detailMultithreaded ClustalW with improved optimization for intel multi-core processor
Chaichoompu, Kridsadakorn ULg; Kittitornkun, S.

in the International Symposium on Communications and Information Technologies, 2006 (ISCIT2006) (2006, October)

This paper presents the methodology that assists the compiler to optimize ClustalW; the most widely used tool for aligning multiple text-based protein or nucleotide sequences in Bioinformatics. Our goal ... [more ▼]

This paper presents the methodology that assists the compiler to optimize ClustalW; the most widely used tool for aligning multiple text-based protein or nucleotide sequences in Bioinformatics. Our goal is to minimize latency and maximize the throughput of execution on multithreading ClustalW called MT-ClustalW: our previous work. As a result, Optimized MT-ClustalW is able to fully utilize the machine resources and achieves higher throughput on multicore computers. The experiment results show that our methodology can assist the compiler to optimize the code better than only compiler-optimization and achieve over 2 times faster than the sequential Clustal W. Finally, we analyze the overall result with Amdahl's Law. © 2006 IEEE. [less ▲]

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See detailMultitude et pouvoir : approche des pensées politiques de Spinoza et Hobbes
Herla, Anne ULg

Master's dissertation (1999)

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See detailMultivariate analyses for biomarkers hunting and validation through on-tissue bottom-up or in-source decay in MALDI-MSI: application to prostate cancer.
Bonnel, David; Longuespée, Rémi ULg; Franck, Julien et al

in Analytical and Bioanalytical Chemistry (2011), 401(1), 149-65

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See detailMultivariate analysis of a fine-scale breeding bird atlas using a geographical information system and partial canonical correspondence analysis: Environmental and spatial effects
Titeux, N.; Dufrêne, Marc ULg; Jacob, J.-P. et al

in Journal of Biogeography (2004), 31(11), 1841-1856

Aim: To assess the relative roles of environment and space in driving bird species distribution and to identify relevant drivers of bird assemblage composition, in the case of a fine-scale bird atlas data ... [more ▼]

Aim: To assess the relative roles of environment and space in driving bird species distribution and to identify relevant drivers of bird assemblage composition, in the case of a fine-scale bird atlas data set. Location: The study was carried out in southern Belgium using grid cells of 1 x 1 km, based on the distribution maps of the Oiseaux nicheurs de Famenne: Atlas de Lesse et Lomme which contains abundance for 103 bird species. Methods: Species found in < 10% or > 90% of the atlas cells were omitted from the bird data set for the analysis. Each cell was characterized by 59 landscape metrics, quantifying its composition and spatial patterns, using a Geographical Information System. Partial canonical correspondence analysis was used to partition the variance of bird species matrix into independent components: (a) 'pure' environmental variation, (b) spatially-structured environmental variation, (c) 'pure' spatial variation and (d) unexplained, non-spatial variation. Results: The variance partitioning method shows that the selected landscape metrics explain 27.5% of the variation, whilst 'pure' spatial and spatially-structured environmental variables explain only a weak percentage of the variation in the bird species matrix (2.5% and 4%, respectively). Avian community composition is primarily related to the degree of urbanization and the amount and composition of forested and open areas. These variables explain more than half of the variation for three species and over one-third of the variation for 12 species. Main conclusions: The results seem to indicate that the majority of explained variation in species assemblages is attributable to local environmental factors. At such a fine spatial resolution, however, the method does not seem to be appropriated for detecting and extracting the spatial variation of assemblages. Consequently, the large amount of unexplained variation is probably because of missing spatial structures and 'noise' in species abundance data. Furthermore, it is possible that other relevant environmental factors, that were not taken into account in this study and which may operate at different spatial scales, can drive bird assemblage structure. As a large proportion of ecological variation can be shared by environment and space, the applied partitioning method was found to be useful when analysing multispecific atlas data, but it needs improvement to factor out all-scale spatial components of this variation (the source of 'false correlation') and to bring out the 'pure' environmental variation for ecological interpretation. [less ▲]

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See detailMultivariate analysis of biochemical data in acute myocardial infarction
Heusghem, C.; Chapelle, Jean-Paul ULg; Albert, Adelin ULg et al

Poster (1978)

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See detailMultivariate analysis of cognitive profiles in Alzheimer's disease
Bastin, Christine ULg; Leclercq, Yves ULg; Collette, Fabienne ULg et al

in Proceedings of the 8th bi-annual Meeting of the Belgian Society for Neuroscience (2009)

The neuropsychological profiles of patients with early Alzheimer’s disease (AD) appear to be heterogeneous. In this study, we examined whether this heterogeneity corresponds to the existence of ... [more ▼]

The neuropsychological profiles of patients with early Alzheimer’s disease (AD) appear to be heterogeneous. In this study, we examined whether this heterogeneity corresponds to the existence of cognitively distinct subtypes of AD or rather to impairments along a continuum of performances in different cognitive domains. A large group of 187 AD patients recruited in the European project NEST-DD performed a neuropsychological battery. A factor analysis of cognitive performance identified three factors, which respectively reflected attentional/instrumental function, declarative memory and executive function. Three clustering methods were applied on the factor scores in order to explore the existence of separate groups. The clustering methods indicated that cognitive profiles among the patients were sufficiently variable to identify clusters, but there was continuity between clusters rather than clear-cut subtypes. Moreover, clusters corresponded to various combinations of relatively impaired and preserved functions, suggesting multidimensional distribution within a large population of patients. Finally, clusters of cognitive profiles were characterized by different levels of metabolism in brain regions commonly (but variably) involved or relatively preserved in AD. [less ▲]

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See detailMultivariate and multidimensional analysis
Van Steen, Kristel ULg; Molenberghs, G.

in Wilson (Ed.) Biometrics (2003)

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See detailThe multivariate coefficient of variation for comparing serum protein electrophoresis techniques in External Quality Assessment schemes
Zhang, Lixin ULg; Albarède, Stéphanie; Dumont, Gilles et al

in Accreditation and Quality Assurance (2010)

External Quality Assessment (EQA) schemes are national or transnational programmes designed to control the analytical performance of clinical laboratories and to maintain inter-laboratory variability ... [more ▼]

External Quality Assessment (EQA) schemes are national or transnational programmes designed to control the analytical performance of clinical laboratories and to maintain inter-laboratory variability within acceptable limits. In such EQA programmes, participants are usually grouped by the type of assay technique/equipment they use. The coefficient of variation (CV) is a simple tool for comparing the inter-laboratory reproducibility of such techniques: the lower the CV, the better the analytical performance. Serum protein electrophoresis, a laboratory test profile consisting of five fractions (albumin, α1, α2, β and γ globulins) summing up to 100% of total proteins, can also be assayed in different ways depending on the media or the analytical principle. We propose a multivariate coefficient of variation for comparing the performance of electrophoretic techniques in EQA, thus extending the univariate CV concept. First, the compositional nature of electrophoretic data requires a one-to-one transformation from the 5-dimensional to the 4-dimensional space. Next, robust estimations of the mean and the covariance matrix are needed to avoid the effect of outliers. The new approach is illustrated on electrophoretic datasets from the French and Belgian national EQA programmes. [less ▲]

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See detailMultivariate coefficients of variation: comparison and influence functions
Aerts, Stéphanie ULg; Haesbroeck, Gentiane ULg; Ruwet, Christel ULg

E-print/Working paper (2014)

In the univariate setting, coefficients of variation are well known and used to compare the variability of populations characterized by variables expressed in different units or having really different ... [more ▼]

In the univariate setting, coefficients of variation are well known and used to compare the variability of populations characterized by variables expressed in different units or having really different means. When dealing with more than one variable, the use of such a relative dispersion measure is much less common even though several generalizations of the coefficient of variation to the multivariate setting have been introduced in the literature. In this paper, the lack of robustness of the sample versions of the multivariate CV's is illustrated by means of influence functions and a robust counterpart based on the Minimum Covariance Determinant (MCD) estimator is advocated. Then, focusing on two of the considered multivariate CV's, a diagnostic tool based on their influence functions is derived and its efficiency in detecting observations having an unduly large effect on variability is illustrated on a real-life data set. The influence functions are also used to compute asymptotic variances under elliptical distributions, yielding approximate confidence intervals. Finally, simulations are conducted in order to compare the performance of the classical and robust multivariate CV's in a finite sample setting. As expected, when the data are normally distributed, the classical estimator performs better than the robust counterpart based on the MCD estimator, while the reverse is true when the data are contaminated. [less ▲]

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See detailThe multivariate Dale model and genetic associations
Van Steen, Kristel ULg; Molenberghs, G.; Tahri, N.

in American Journal of Human Genetics (2002), 71

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See detailMultivariate discrimination of sands using elongation and abrasivity indices
Pirard, Eric ULg; Vergara, Nicolas

in Proceedings PARTEC (9th European Symposium on Particle Characterization) (2004)

Detailed reference viewed: 13 (1 ULg)