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See detailDecoding Directed Brain Activity in fMRI using Support Vector Machines and Gaussian Processes
Schrouff, Jessica ULg; Kussé, Caroline ULg; Wehenkel, Louis ULg et al

Poster (2011, June 26)

Predicting a particular cognitive state from a specific pattern of fMRI voxel values is still a methodological challenge. Decoding brain activity is usually performed in highly controlled experimental ... [more ▼]

Predicting a particular cognitive state from a specific pattern of fMRI voxel values is still a methodological challenge. Decoding brain activity is usually performed in highly controlled experimental paradigms characterized by a series of distinct states induced by a temporally constrained experimental design. In more realistic conditions, the number, sequence and duration of mental states are unpredictably generated by the individual, resulting in complex and imbalanced fMRI data sets. This study tests the classification of brain activity, acquired on 16 volunteers using fMRI, during mental imagery, a condition in which the number and duration of mental events were not externally imposed but self-generated. To deal with these issues, two classification techniques were considered (Support Vector Machines, SVM, and Gaussian Processes, GP), as well as different feature extraction methods (General Linear Model, GLM and SVM). These techniques were combined in order to identify the procedures leading to the highest accuracy measures. Our results showed that 12 data sets out of 16 could be significantly modeled by either SVM or GP. Model accuracies tended to be related to the degree of imbalance between classes and to task performance of the volunteers. We also conclude that the GP technique tends to be more robust than SVM to model unbalanced data sets. [less ▲]

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See detailDecoding of the light changes in eclipsing Wolf-Rayet binaries. I. A non-classical approach to the solution of light curves
Perrier, C.; Breysacher, J.; Rauw, Grégor ULg

in Astronomy and Astrophysics (2009), 503

Aims. We present a technique to determine the orbital and physical parameters of eclipsing eccentric Wolf-Rayet + O-star binaries, where one eclipse is produced by the absorption of the O-star light by ... [more ▼]

Aims. We present a technique to determine the orbital and physical parameters of eclipsing eccentric Wolf-Rayet + O-star binaries, where one eclipse is produced by the absorption of the O-star light by the stellar wind of the W-R star. Methods: Our method is based on the use of the empirical moments of the light curve that are integral transforms evaluated from the observed light curves. The optical depth along the line of sight and the limb darkening of the W-R star are modelled by simple mathematical functions, and we derive analytical expressions for the moments of the light curve as a function of the orbital parameters and the key parameters of the transparency and limb-darkening functions. These analytical expressions are then inverted in order to derive the values of the orbital inclination, the stellar radii, the fractional luminosities, and the parameters of the wind transparency and limb-darkening laws. Results: The method is applied to the SMC W-R eclipsing binary HD 5980, a remarkable object that underwent an LBV-like event in August 1994. The analysis refers to the pre-outburst observational data. A synthetic light curve based on the elements derived for the system allows a quality assessment of the results obtained. [less ▲]

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See detailDecoding Semi-Constrained Brain Activity from fMRI Using Support Vector Machines and Gaussian Processes
Schrouff, Jessica ULg; Kussé, Caroline ULg; Wehenkel, Louis ULg et al

in PLoS ONE (2012), 7(4),

Predicting a particular cognitive state from a specific pattern of fMRI voxel values is still a methodological challenge. Decoding brain activity is usually performed in highly controlled experimental ... [more ▼]

Predicting a particular cognitive state from a specific pattern of fMRI voxel values is still a methodological challenge. Decoding brain activity is usually performed in highly controlled experimental paradigms characterized by a series of distinct states induced by a temporally constrained experimental design. In more realistic conditions, the number, sequence and duration of mental states are unpredictably generated by the individual, resulting in complex and imbalanced fMRI data sets. This study tests the classification of brain activity, acquired on 16 volunteers using fMRI, during mental imagery, a condition in which the number and duration of mental events were not externally imposed but self-generated. To deal with these issues, two classification techniques were considered (Support Vector Machines, SVM, and Gaussian Processes, GP), as well as different feature extraction methods (General Linear Model, GLM and SVM). These techniques were combined in order to identify the procedures leading to the highest accuracy measures. Our results showed that 12 data sets out of 16 could be significantly modeled by either SVM or GP. Model accuracies tended to be related to the degree of imbalance between classes and to task performance of the volunteers. We also conclude that the GP technique tends to be more robust than SVM to model unbalanced data sets. [less ▲]

Detailed reference viewed: 43 (16 ULg)
See detailDecoding semi-constrained brain activity from fMRI using SVM and GP
Schrouff, Jessica ULg; Kussé, Caroline ULg; Wehenkel, Louis ULg et al

Scientific conference (2011, November 22)

Predicting a particular cognitive state from a specific pattern of fMRI voxel values is still a methodological challenge. Decoding brain activity is usually performed in highly controlled experimental ... [more ▼]

Predicting a particular cognitive state from a specific pattern of fMRI voxel values is still a methodological challenge. Decoding brain activity is usually performed in highly controlled experimental paradigms characterized by a series of distinct states induced by a temporally constrained experimental design. In more realistic conditions, the number, sequence and duration of mental states are unpredictably generated by the individual, resulting in complex and imbalanced fMRI data sets. This study tests the classification of brain activity, acquired on 16 volunteers using fMRI, during mental imagery, a condition in which the number and duration of mental events were not externally imposed but self-generated. To deal with these issues, two classification techniques were considered (Support Vector Machines, SVM, and Gaussian Processes, GP), as well as different feature extraction methods (General Linear Model, GLM and SVM). These techniques were combined in order to identify the procedures leading to the highest accuracy measures. Our results showed that 12 data sets out of 16 could be significantly modeled by either SVM or GP. Model accuracies tended to be related to the degree of imbalance between classes and to task performance of the volunteers. We also conclude that the GP technique tends to be more robust than SVM to model unbalanced data sets. [less ▲]

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See detailDecoding spontaneous brain activity from fMRI using Gaussian Processes: tracking brain reactivation
Schrouff, Jessica ULg; Kussé, Caroline ULg; Wehenkel, Louis ULg et al

in 2012 Second International Workshop on Pattern Recognition in NeuroImaging (PRNI 2012): proceedings (2012, July 03)

While Multi-Variate Pattern Analysis techniques based on machine learning have now been regularly applied to neuroimaging data, decoding brain activity is usually performed in highly controlled ... [more ▼]

While Multi-Variate Pattern Analysis techniques based on machine learning have now been regularly applied to neuroimaging data, decoding brain activity is usually performed in highly controlled experimental paradigms. In more realistic conditions, the number, sequence and duration of mental states are unpredictably generated by the individual, resulting in complex and imbalanced fMRI data sets. Moreover, in the case of spontaneous brain activity, the mental states can not be linked to any external or internal stimulation, which makes it a highly difficult condition to decode. This study tests the classification of brain activity, acquired on 14 volunteers using fMRI, during mental imagery, a condition in which the number and duration of mental events were not externally imposed but self-generated. Application of the obtained model on rest sessions allowed classifying spontaneous brain activity linked to the task which, overall, correlated with their behavioural performance to the task. [less ▲]

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See detailDecoding the folding of Burkholderia glumae lipase: folding intermediates en route to kinetic stability
Pauwels, Kris; Sanchez del Pino, Manuel M.; Feller, Georges ULg et al

in PLoS ONE (2012), 7(5), 36999

Detailed reference viewed: 18 (4 ULg)
See detailDecoherence of an Entangled Atomic Pair
Agarwal, G. S.; Bastin, Thierry ULg; von Zanthier, J.

Conference (2006)

Detailed reference viewed: 6 (1 ULg)
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See detailDecoherence, entanglement and irreversibility in quantum dynamical systems with few degrees of freedom
Jacquod, Ph; Petitjean, Cyril ULg

in ADVANCES IN PHYSICS (2009), 58(2), 67-196

In this review we summarize and amplify recent investigations of coupled quantum dynamical systems with few degrees of freedom in the short-wavelength, semiclassical limit. Focusing on the correspondence ... [more ▼]

In this review we summarize and amplify recent investigations of coupled quantum dynamical systems with few degrees of freedom in the short-wavelength, semiclassical limit. Focusing on the correspondence between quantum and classical physics, we mathematically formulate and attempt to answer three fundamental questions. (i) How can one drive a small dynamical quantum system to behave classically? (ii) What determines the rate at which two single-particle quantum-mechanical subsystems become entangled when they interact? (iii) How does irreversibility occur in quantum systems with few degrees of freedom? These three questions are posed in the context of the quantum-classical correspondence for dynamical systems with few degrees of freedom, and we accordingly rely on two short-wavelength approximations to quantum mechanics to answer them: the trajectory-based semiclassical approach on the one hand, and random matrix theory on the other hand. We construct novel investigative procedures towards decoherence and the emergence of classicality out of quantumness in dynamical systems coupled to external degrees of freedom. In particular, we show how dynamical properties of chaotic classical systems, such as local exponential instability in phase space, also affects their quantum counterparts. For instance, it is often the case that the fidelity with which a quantum state is reconstructed after an imperfect time-reversal operation decays with the Lyapunov exponent of the corresponding classical dynamics. For related reasons, but perhaps more surprisingly, the rate at which two interacting quantum subsystems become entangled can also be governed by the subsystem's Lyapunov exponents. Our method allows us to differentiate quantum coherent effects (those related to phase interferences) from classical ones (those related to the necessarily extended envelope of quantal wavefunctions) at each stage in our investigations. This makes it clear that all occurrences of Lyapunov exponents we witness have a classical origin, although they require rather strong decoherence effects to be observed. We extensively rely on numerical experiments to illustrate our findings and briefly comment on possible extensions to more complex problems involving environments with many interacting dynamical systems, going beyond the uncoupled harmonic oscillators model of Caldeira and Leggett. [less ▲]

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See detailDecoherence-enhanced measurements
Braun, Daniel; Martin, John ULg

Conference (2009, May)

Detailed reference viewed: 13 (0 ULg)
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See detailDecommissioned dates: chemical composition and fermentation substrate for the production of extracellular catalase by an Aspergillus phoenicis mutant
Kacem-Chaouche, N.; Dehimat, L.; Meraihi, Z. et al

in Agriculture and Biology Journal of North America (2013)

The recovery of dates downgraded as a fermentation medium for the production of extracellular catalase by Aspergillus phoenicis K30 was studied. Analysis of the chemical composition of pulp and kernel ... [more ▼]

The recovery of dates downgraded as a fermentation medium for the production of extracellular catalase by Aspergillus phoenicis K30 was studied. Analysis of the chemical composition of pulp and kernel flour of dates showed that the pulp had a considerably greater carbohydrate content compared to the kernel (84 vs 2.93% respectively). However, the kernel flour was richer in nitrogen (0.68% vs 0.34), mineral elements (3.63 vs 1.28%) and in essential fatty acids C18: 2 vs C18: 3 than the pulp flour. The soluble extract of the date flour showed that sugars solubilised at 90% consisted of sucrose, fructose and glucose. Therefore, this extract, being an important source of carbon and energy, was used in the current study as a fermentation medium (after supplementation with 20% of corn steep) for the production of extracellular catalase by A. Phoenicis K30. During the course of this fermentation, the biomass was estimated at 18.6 g / L after 72 h of culture, while the maximum concentration of extracellular catalase (47.5 U / ml) was reached at 96 h of fermentation. The mycelium obtained in pellet form is suitable for industrial exploitation of this process. [less ▲]

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See detailDécompensation cardiaque, fonction rénale et anti-inflammatoires non stéroïdiens
Krzesinski, Jean-Marie ULg; Piront, Patricia ULg

in Revue Médicale de Liège (2002), 57(9), 582-586

Thanks to a case report of heart failure in an old people with a cardiovascular history treated by the new coxib-inhibitors, we would like to remember and insist to the risk of renal and cardiac ... [more ▼]

Thanks to a case report of heart failure in an old people with a cardiovascular history treated by the new coxib-inhibitors, we would like to remember and insist to the risk of renal and cardiac complications which appear to be the same as those with the non specific antiinflammatory drugs. Old age, diuretic or converting enzyme inhibitor treatment, heart failure, liver insufficiency, nephrotic syndrome are risk factors for acute renal failure and cardiac failure during such treatment. [less ▲]

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See detailDecomposing efficiency into its managerial and its regulatory components: The case of European railways
Gathon, Henry-Jean ULg; Pestieau, Pierre ULg

in European Journal of Operational Research (1995), 80

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See detailDecomposition of metabolic brain clusters in the frontal variant of frontotemporal dementia
Salmon, Eric ULg; Kerrouche, Nacer; Herholz, Karl et al

in NeuroImage (2006), 30(3), 871-878

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research ... [more ▼]

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research program the principal brain clusters characterized by a common variability in cerebral metabolism in FTD. Seventy patients with frontal variant (fv) FTD were selected according to international clinical recommendations; principal component analysis (PCA) was performed on FDG-PET metabolic images, looking for covariance clusters in this large population. A first metabolic cluster included most of the lateral and medial prefrontal cortex, bilaterally; PC1 scores correlated with performances on memory and executive neuropsychological tasks. Moreover, FDG-PET images in fv-FTD were further characterized by a metabolic covariance in two clusters comprising the subcallosal medial frontal region, the temporal pole, medial temporal structures and the striatum, separately in the left and in the right hemisphere. The study provides original data-driven arguments for metabolic involvement of separate brain clusters in the rostral limbic system, corresponding to pathological poles differentially affected in each FTD patient. [less ▲]

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See detailDecomposition of symmetric tensor fields in the presence of a flat contact projective structure
Frégier, Yaël; Mathonet, Pierre ULg; Poncin, Norbert

in Journal of Nonlinear Mathematical Physics (2008), 15(2), 252-269

Let M be an odd-dimensional Euclidean space endowed with a contact 1-form \alpha. We investigate the space of symmetric contravariant tensor fields over M as a module over the Lie algebra of contact ... [more ▼]

Let M be an odd-dimensional Euclidean space endowed with a contact 1-form \alpha. We investigate the space of symmetric contravariant tensor fields over M as a module over the Lie algebra of contact vector fields, i.e. over the Lie subalgebra made up of those vector fields that preserve the contact structure defined by \alpha. If we consider symmetric tensor fields with coefficients in tensor densities (also called symbols), the vertical cotangent lift of the contact form \alpha defines a contact invariant operator. We also extend the classical contact Hamiltonian to the space of symbols. This generalized Hamiltonian operator on the space of symbols is invariant with respect to the action of the projective contact algebra sp(2n+2) the algebra of vector fields which preserve both the contact structure and the projective structure of the Euclidean space. These two operators lead to a decomposition of the space of symbols, except for some critical density weights, which generalizes a splitting proposed by V. Ovsienko. [less ▲]

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See detailDécomposition spectrale stochastique pour une formulation intégrale du problème de diffraction d'onde
Gaignaire, R.; Geuzaine, Christophe ULg

in Proceedings of 6ème Conférence Européenne sur les Méthodes Numériques en Electromagnétisme (NUMELEC2008) (2008)

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See detailDecomposition, Localization and Time-Averaging Approaches in Large-Scale Power System Dynamic Simulation
Fabozzi, Davide ULg

Doctoral thesis (2012)

Present-day interconnected electric power systems are the largest machines in the world. Guaranteeing a stable supply of electric power is vital for modern societies: power systems must be able to ... [more ▼]

Present-day interconnected electric power systems are the largest machines in the world. Guaranteeing a stable supply of electric power is vital for modern societies: power systems must be able to withstand plausible disturbances. A certain number of simulations of the post-disturbance behavior are routinely executed by some transmission system operators to assess that the system is operated in a secure way. Usually this assessment has to be performed within a predefined time frame, using the available computing resources. Improving the simulation speed allows the operators to perform a wider assessment, thus making better use of the available computational power. A large part of this research took place in the context of the PEGASE project, supported by European Commission (Seventh Framework Programme) and has resulted in some novel algorithms for faster dynamic simulations, one of the PEGASE project main goals. First, this thesis revisits the Newton method used to solve the differential-algebraic model. Then, three original algorithmic improvements are presented, namely (i) decomposition, (ii) localization and (iii) time-averaging of the system response. Finally, the combination of these approaches is shown to provide a fast and reliable tool for dynamic security assessment. All the presented techniques have been thoroughly tested on an academic system, a large real-life system and a realistic system of unprecedented size, representative of the whole continental European synchronous grid. [less ▲]

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See detailDeconsecrating a doctrinal monument: Raymond M. Lemaire and the revisions of the Venice Charter
Houbart, Claudine ULg

Conference (2014, April 04)

Considering himself as the “main author” of the charter, Raymond M. Lemaire has been one of the first, together with Piero Gazzola, to plead for a revision of the document. As early as 1971, the two men ... [more ▼]

Considering himself as the “main author” of the charter, Raymond M. Lemaire has been one of the first, together with Piero Gazzola, to plead for a revision of the document. As early as 1971, the two men, respectively first Secretary General and President of ICOMOS, tended to launch a debate in favour of a better consideration of the social value of heritage, and the development of specific principles for historical cities conservation, to be included in the Venice charter. Lemaire’s recent experience in that field had indeed convinced him that, contrary to the assertion of article 14, “a literal application of principles valid for monuments, considered as such, is not always possible, nor desirable, for the ensembles”. The adoption of the Amsterdam declaration didn’t put an end to his efforts. Despite his unsuccessful attempt to get a revised version approved by the ICOMOS General assembly in Moscow (1978), R.M.Lemaire always remained critical towards the charter and the application of its principles in the field, underlining, in the eighties, its shortcomings in terms of cultural diversity and, in one of his last texts, in 1996, the negative effect of article 9, leading to the idea that “the mere essence of a conservation operation is a modernist intervention on the edifice or neighbourhood”. Beyond its interest for conservation history, the awareness of Lemaire’s early critical position towards the Venice Charter should inspire the current debates and help us overcome our reluctance to challenge the sacred principles of what we consider a doctrinal monument. [less ▲]

Detailed reference viewed: 22 (6 ULg)