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See detailMultisite photometric and spectroscopic campaign of the magnetic β Cep star V2052 Ophiuchi
Briquet, Maryline ULg

Diverse speeche and writing (2012)

We present an asteroseismic study of the magnetic β Cep star V2052 Ophiuchi. Based on extensive ground-based multisite photometry and spectroscopy, the pulsational, rotational and chemical properties of ... [more ▼]

We present an asteroseismic study of the magnetic β Cep star V2052 Ophiuchi. Based on extensive ground-based multisite photometry and spectroscopy, the pulsational, rotational and chemical properties of the star were derived and stellar models accounting for the observed characteristics were computed. We discuss our results showing that the combination of asteroseismology and spectropolarimetry can allow us to probe the impact of a magnetic field on the physics of mixing inside stellar interiors. [less ▲]

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See detailA multisite photometric study of two unusual β Cep stars: the magnetic V2052 Oph and the massive rapid rotator V986 Oph
Handler, G.; Shobbrook, R. R.; Uytterhoeven, K. et al

in Monthly Notices of the Royal Astronomical Society (2012), 424

We report a multisite photometric campaign for the β Cep stars V2052 Oph and V986 Oph. 670 h of high-quality differential photoelectric Strömgren, Johnson and Geneva time-series photometry was obtained ... [more ▼]

We report a multisite photometric campaign for the β Cep stars V2052 Oph and V986 Oph. 670 h of high-quality differential photoelectric Strömgren, Johnson and Geneva time-series photometry was obtained with eight telescopes on five continents during 182 nights. Frequency analyses of the V2052 Oph data enabled the detection of three pulsation frequencies, the first harmonic of the strongest signal, and the rotation frequency with its first harmonic. Pulsational mode identification from analysing the colour amplitude ratios confirms the dominant mode as being radial, whereas the other two oscillations are most likely l = 4. Combining seismic constraints on the inclination of the rotation axis with published magnetic field analyses we conclude that the radial mode must be the fundamental mode. The rotational light modulation is in phase with published spectroscopic variability, and consistent with an oblique rotator for which both magnetic poles pass through the line of sight. The inclination of the rotation axis is 54° < i < 58° and the magnetic obliquity 58° < β < 66°. The possibility that V2052 Oph has a magnetically confined wind is discussed. The photometric amplitudes of the single oscillation of V986 Oph are most consistent with an l = 3 mode, but this identification is uncertain. Additional intrinsic, apparently temporally incoherent light variations of V986 Oph are reported. Different interpretations thereof cannot be distinguished at this point, but this kind of variability appears to be present in many OB stars. The prospects of obtaining asteroseismic information for more rapidly rotating β Cep stars, which appear to prefer modes of higher l, are briefly discussed. [less ▲]

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See detailMultisite spectroscopic seismic study of the β Cep star V2052 Ophiuchi: inhibition of mixing by its magnetic field
Briquet, Maryline ULg; Neiner, C.; Aerts, C. et al

in Monthly Notices of the Royal Astronomical Society (2012), 427

We used extensive ground-based multisite and archival spectroscopy to derive observational constraints for a seismic modelling of the magnetic β Cep star V2052 Ophiuchi. The line-profile variability is ... [more ▼]

We used extensive ground-based multisite and archival spectroscopy to derive observational constraints for a seismic modelling of the magnetic β Cep star V2052 Ophiuchi. The line-profile variability is dominated by a radial mode (f1 = 7.148 46 d-1) and by rotational modulation (P_rot = 3.638 833 d). Two non-radial low-amplitude modes (f2 = 7.756 03 d-1 and f3 = 6.823 08 d-1) are also detected. The four periodicities that we found are the same as the ones discovered from a companion multisite photometric campaign and known in the literature. Using the photometric constraints on the degrees ℓ of the pulsation modes, we show that both f_2 and f_3 are prograde modes with (ℓ, m) = (4, 2) or (4, 3). These results allowed us to deduce ranges for the mass (M ∈ [8.2, 9.6] M_sun) and central hydrogen abundance (X_c ∈ [0.25, 0.32]) of V2052 Oph, to identify the radial orders n1 = 1, n2 = -3 and n3 = -2, and to derive an equatorial rotation velocity v_eq ∈ [71, 75] km s-1. The model parameters are in full agreement with the effective temperature and surface gravity deduced from spectroscopy. Only models with no or mild core overshooting (α_ov ∈ [0, 0.15] local pressure scale heights) can account for the observed properties. Such a low overshooting is opposite to our previous modelling results for the non-magnetic β Cep star θ Oph having very similar parameters, except for a slower surface rotation rate. We discuss whether this result can be explained by the presence of a magnetic field in V2052 Oph that inhibits mixing in its interior. [less ▲]

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See detailMultispectral Imaging in Cathodoluminescence Microscopy
Charlier, Bernard ULg; De Colnet, Laurence; Pirard, Eric ULg

in Proceedings - Annual Meeting - Belgian Soc. Microscopy (2001)

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See detailMultispectral imaging of ore minerals in optical microscopy
Pirard, Eric ULg

in Mineralogical Magazine (2004), 68(2), 323-333

Multispectral imaging of ore minerals under the microscope is a logical extension of quantitative colour analysis and microspectrophotometric analysis of minerals. This paper describes, step by step, how ... [more ▼]

Multispectral imaging of ore minerals under the microscope is a logical extension of quantitative colour analysis and microspectrophotometric analysis of minerals. This paper describes, step by step, how the proper calibration of a scientific video camera can be performed in order to obtain precise reflectance measurements at each pixel within the field of view. After having reviewed the different sources of noise and aberration, practical formulae are presented that allow for the acquisition of a set of images at different wavelengths in the visible spectrum. The advantage of using a multispectral image acquisition system based on narrow bandwidth (10 nm) interference filters is discussed and quantitatively compared to colour imaging using tri-stimulus (red, green, blue) filters. Images taken from major sulphide parageneses are shown as examples of well contrasted multispectral images. Finally, the potential for automatic identification of ore minerals is discussed with reference to supervised multivariate image classification algorithms similar to those used in remote sensing. Additional comments on extending the principles for handling optical anisotropy and developing a multiradial imaging system are made. [less ▲]

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See detailMultispectral observations of Jupiter's Aurora
Waite, J. H.; Grodent, Denis ULg; Mauk, B. M. et al

in Advances in Space Research (2000), 26(10), 1453-1475

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on the upper atmosphere ... [more ▼]

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on the upper atmosphere of Jupiter, As indicated by the combination of x-ray and ultraviolet observations, both energetic heavy ions and electrons energized in the outer magnetosphere contribute to auroral excitation. Imaging with the Hubble Space Telescope in the ultraviolet and with the InfraRed Telescope Facility at infrared wavelengths shows several distinct regions of interaction: 1) a dusk sector where turbulent auroral patterns extend well into the polar cap; 2) a morning sector generally characterized by a single spatially confined auroral are originating in the outer or middle magnetosphere of Jupiter; 3) diffuse emissions associated with the Io plasma - spectroscopy has provided important information about the thermal structure of Jupiter's auroral atmosphere and the altitude distribution of auroral particle energy deposition, while Lyman alpha line profiles yield clues to the nature of thermospheric dynamical effects. Galileo observations at visible wavelengths on the nightside offer a new view of the jovian aurora with unprecedented spatial information. Infrared observations have added much to the understanding of thermal structure at all latitudes, the dynamics of the thermospheric wind system, and auroral morphology, and may hold the key to understanding the role of Joule heating in Jupiter's thermosphere. ROSAT observations have revealed soft x-ray emissions from Jupiter's lower latitudes as well as from the auroral zones, implying that energetic particle precipitation also occurs at low latitudes in regions magnetically linked to the inner radiation belts. In this review, multispectral observations of jovian auroral emissions are presented within a theoretical/modeling framework that is intended to provide some insight into magnetosphere-ionosphere coupling and its effects on the upper atmosphere. (C) 2000 COSPAR. Published by Elsevier Science Ltd. All rights reserved. [less ▲]

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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 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

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

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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