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See detailAccurate Non-Iterative Modelling and Inference of Longitudinal Neuroimaging Data
Guillaume, Bryan ULiege

Doctoral thesis (2015)

Despite the growing importance of longitudinal data in neuroimaging, the standard analysis methods make restrictive or unrealistic assumptions. For example, the widely used SPM software package assumes ... [more ▼]

Despite the growing importance of longitudinal data in neuroimaging, the standard analysis methods make restrictive or unrealistic assumptions. For example, the widely used SPM software package assumes spatially homogeneous longitudinal correlations while the FSL software package assumes Compound Symmetry, the state of all equal variances and equal correlations. While some new methods have been recently pro- posed to more accurately account for such data, these methods can be difficult to specify and are based on iterative algorithms that are generally slow and failure- prone. In this thesis, we propose and investigate the use of the Sandwich Estimator method which first estimates the parameters of interest with a (non-iterative) Ordinary Least Square model and, second, estimates variances/covariances with the “so-called” Sandwich Estimator (SwE) which accounts for the within-subject covariance structure existing in longitudinal data. We introduce the SwE method in its classic form, and review existing and propose new adjustments to improve its behaviour, specifically in small samples. We compare the SwE method to other popular methods, isolating the combination of SwE adjustments that provides valid and powerful inferences. While this result provides p-values at each voxel, it does not provide spatial inferences, e.g. voxel- or cluster-wise family-wise error-corrected p-values. For this, we investigate the use of the non-parametric inference approach called Wild Bootstrap. We again identify the set of procedures and adjustments that provide valid inferences. Finally, in the third and fourth projects, we investigate two ideas to improve the statistical power of the SwE method, by using a shrinkage estimator or a covariance spatial smoothing, respectively. For all the projects, in order to assess the methods, we use intensive Monte Carlo simulations in settings important for longitudinal neuroimaging studies and, for the first two projects, we also illustrate the methods by analysing a highly unbalanced longitudinal dataset obtained from the Alzheimer’s Disease Neuroimaging Initiative. [less ▲]

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See detailEtude d’un concentrateur solaire basé sur une combinaison optique diffractive/réfractive pour applications spatiales
Michel, Céline ULiege

Doctoral thesis (2015)

Continued demand for new applications from spacecrafts leads to larger power needs. For most of them, the primary energy sources are solar panels. However, these solar panels are heavy and expensive ... [more ▼]

Continued demand for new applications from spacecrafts leads to larger power needs. For most of them, the primary energy sources are solar panels. However, these solar panels are heavy and expensive, mainly due to solar cells and their coverglass. The power need increase requires thus new concepts of solar panels. Furthermore, space environment is highly constraining: the vacuum limits heat trans- fer since convection is not allowed, there is contamination modifying the light spectrum reaching cells, ultraviolet light induces a yellowing of silicone glue, radiations degrade pho- tovoltaic cells, etc. Usually, multi-junctions (MJ) cells are used, that are strongly sensitive to spectral modification in their incident spectrum due to their series connected structure (the worst cell defines the whole output performance). The power dimensioning of solar panels is then based on end of life (EOL) PV cells expected performance. Reducing the sensitivity to increase EOL output power is then another challenge for space applications. This thesis aims to answer to both problems, by the proposition and study of a new lightweight solar concentrator with spectral splitting. This conceptual concentrator is composed of a Fresnel lens for sunlight concentration, coupled to a surface relief diffraction grating to spectrally split incident light, forming a single optical element in silicone. The concentration behavior allows a reduction of solar cells area (including its coverglass), replaced by a lightweight silicone lens, reducing the global cost and mass. The lateral spectral separation will permit other types of cells than the usual MJ cells. To demonstrate the concept, two single junctions (SJ) solar cells are placed side by side, the first collecting visible light, the second collecting near IR light. Since cells are electrically independent, sensitivity is lower and EOL output power can surpass standard MJ cells systems. Moreover, cells combination is nearly free: all photovoltaic technology can be used and combined, opening the solar concentration field to other technologies than MJ. This work studies and evaluates the pros and cons of diffraction grating/Fresnel lens combinations as solar concentrator with spectral splitting. The analysis includes the choice of material, optical developments and optimizations (grating selection, freeform lenses, grating period optimization along the lens, etc.), electrical modeling and methods to find the best cells combination as well as the modeling of expected output power, a thermal simulation, weight and deployment considerations, and approaches of sensitivity with spectral modifications. Some experimental results complete the study. Two main configurations were developed: a first with a blazed grating, and a second with a symmetrical lamellar grating. Both configurations, after optimization, show similar performances: a global geometrical concentration ratio around 5-6× (ratio between lens width and the total width of the two cells), a tracking error tolerance up to 0.7◦, no drastic degradation with respect to deformations, fabrication errors, etc., an output power at begin of life (BOL) better than a classical concentrator focusing on a SJ cell or a planar solar panel composed of SJ cells. Both configurations present also a BOL specific mass [kg/W] lower than a classical planar solar panel covered by MJ cells, and a lower sensitivity to space environment, with theoretical larger EOL output power depending on chosen PV cells combinations. Existing deployment systems are proposed and discussed. Also, an experimental prototype of the optical element was realized, with optical results close to simulations. Some adaptations to terrestrial concentrators, other spectra, or using more than 2 different SJ cells are also introduced, highlighting the versatility of our concept. Results demonstrate thus the coherence of the concept, leading to experimentally feasible and quite tolerant concentrator, with interesting cost reduction thanks to concentration and specific weight reduction. However, optical losses due to the non-perfect spectral splitting of the grating is too high to be able to surpass MJ cells systems BOL up to now, and the lower sensitivity of our concentrator cannot completely compensate this lack of performance at EOL. To reach better performances than MJ systems, from cost, mass, radiation resistance, etc. point of view and to exploit the obvious gain in sensitivity, the concentrator needs thus further investigations mainly related to cells combinations. Especially as our concept opens a lot of opportunities thanks to the complete independence of cells: other technologies are allowed, specific coatings can improve performances, ... Applications for Earth or places with different/changing incident spectra is another plausible perspective. Our concentrator with spectral splitting can also be a major advantage for specific scientific space missions like deep space missions. [less ▲]

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See detailPrésentation de "Germania anno zero" de Roberto Rossellini
Tomasovic, Dick ULiege

Conference given outside the academic context (2015)

Présentation de l'oeuvre de Rossellini et analyse de la place qu'occupe le film dans l'histoire du cinéma.

Detailed reference viewed: 8 (2 ULiège)
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See detailWhy Facebook is flying up high and Twitter can't fly away
Artige, Lionel ULiege

Article for general public (2015)

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See detailLe projet expérimental multidisciplinaire (PEMD) en 3ème Bachelier à Gembloux
Colaux, Catherine ULiege; Pochet, Bernard ULiege

in Former aux compétences informationnelles à l'heure du web 2.0 et des discovery tools (2015, September 28)

Cette courte présentation, dans l'atelier 3 du colloque ILIB15, décrit l'intégration d'un cours (« littérature scientifique et méthodologie documentaire »), dont le titulaire est un bibliothécaire, dans ... [more ▼]

Cette courte présentation, dans l'atelier 3 du colloque ILIB15, décrit l'intégration d'un cours (« littérature scientifique et méthodologie documentaire »), dont le titulaire est un bibliothécaire, dans une unité d’apprentissage intégrée basée sur la résolution d'un problème concret de recherche dans un contexte scientifique non familier. Ce cours a été proposé pour la première fois durant l'année académique 2014-2015 à une partie des étudiants du bloc trois du Master Bioingénieur, orientation Sciences et technologies de l’environnement de l'Université de Liège. Cette activité se déroule en plusieurs phases sur les deux quadrimestres. [less ▲]

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See detailPsychological benefits of a multidisciplinary rehabilitation program after breast cancer
Leclerc, Anne-France ULiege; FOIDART-DESSALLE, Marguerite ULiege; Bury, Thierry ULiege et al

in European Cancer Congress : Abstract book (2015, September 27)

Background : Breast cancer is the most frequent cancer in women, affecting 8 women out of 100. With early detection and improved treatments, the number of deaths linked to this disease has declined ... [more ▼]

Background : Breast cancer is the most frequent cancer in women, affecting 8 women out of 100. With early detection and improved treatments, the number of deaths linked to this disease has declined. However, the disease and its treatments are at the origin of many undesirable side effects such as fatigue, anxiety, weight gain and sleep disorders. The objective of this study is to determine the psychological benefits of a multidisciplinary rehabilitation program among women treated for breast cancer (on average six months after the end of the adjuvant radiotherapy or chimiotherapy). Material and methods : 122 patients were included into a control group (n = 61) and a treated group (n = 61). All participants were submitted to evaluations before the beginning of the trial and after three months. These evaluations included different questionnaires exploring the quality of life, anxiety, depression and various functions and other symptoms related to cancer (EORTC QLQ-C30, EQ-5D, STAI, HADS) and functional assessments. The control group has received no intervention unlike the treated group that received a three-month rehabilitation including supervised physical training (90 min) with three times a week and various psycho-educational sessions (120 min) once a week. Results : After three months, the health status (quality of life) (p < 0,0001), the functional role (p = 0,031), emotional state (p < 0,0001) and physical (p = 0,0045), cognitive (p = 0,0027) and social functions (p = 0,0018) improve significantly in the treated group. This observation also applies to symptoms of fatigue (p < 0,0001), insomnia (p < 0,0001), pain (p = 0,002), dyspnea (p = 0,009), loss of appetite (p = 0,04), anxiety (p < 0,0001) and depression (p < 0,0001) as well as physical parameters obtained through functional assessments. In the control group, these improvements do not appear. Conclusions : This study shows the feasibility and psychological benefits of such a multidisciplinary oncological rehabilitation program in women after their treatments for breast cancer. Additional studies are needed to know the optimal time of beginning (during treatments or after them) and the optimal management time for this support. [less ▲]

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See detailZum Verhältnis zwischen Geschichtswissenschaft und "Amateurhistorikern"
Brüll, Christoph ULiege

Speech/Talk (2015)

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See detailPhysicochimie de la pollution atmosphérique
Mahieu, Emmanuel ULiege

Conference (2015, September 25)

Detailed reference viewed: 27 (6 ULiège)
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See detailLa terminologie de la traduction en latin
Rochette, Bruno ULiege

Scientific conference (2015, September 25)

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Peer Reviewed
See detailAcetylene (C2H2) and hydrogen cyanide (HCN) from IASI satellite observations: global distributions, validation, and comparison with model
Duflot, V.; Wespes, C.; Clarisse, L. et al

in Atmospheric Chemistry and Physics (2015), 15

We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008–2010. These distributions are ... [more ▼]

We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008–2010. These distributions are obtained with a fast method allowing to retrieve C2H2 abundance globally with a 5% precision and HCN abundance in the tropical (subtropical) belt with a 10% (25 %) precision. IASI data are compared for validation purposes with ground-based Fourier transform infrared (FTIR) spectrometer measurements at four selected stations. We show that there is an overall agreement between the ground-based and space measurements with correlation coefficients for daily mean measurements ranging from 0.28 to 0.81, depending on the site. Global C2H2 and subtropical HCN abundances retrieved from IASI spectra show the expected seasonality linked to variations in the anthropogenic emissions and seasonal biomass burning activity, as well as exceptional events, and are in good agreement with previous spaceborne studies. Total columns simulated by the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) are compared to the ground-based FTIR measurements at the four selected stations. The model is able to capture the seasonality in the two species in most of the cases, with correlation coefficients for daily mean measurements ranging from 0.50 to 0.86, depending on the site. IASI measurements are also compared to the distributions from MOZART-4. Seasonal cycles observed from satellite data are reasonably well reproduced by the model with correlation coefficients ranging from -0.31 to 0.93 for C2H2 daily means, and from 0.09 to 0.86 for HCN daily means, depending on the considered region. However, the anthropogenic (biomass burning) emissions used in the model seem to be overestimated (underestimated), and a negative global mean bias of 1% (16 %) of the model relative to the satellite observations was found for C2H2 (HCN). [less ▲]

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See detailAir-sea ice gases exchange: update of recent findings, outcomes from sea ice models, caveats and open questions
Delille, Bruno ULiege; Zhou, Jiayun; Kotovitch, Marie ULiege et al

Conference (2015, September 21)

There are growing evidences that sea ice exchanges climate gases with the atmosphere. We will rapidly present a state of the art of current large scale assessment of spring and summer uptake of ... [more ▼]

There are growing evidences that sea ice exchanges climate gases with the atmosphere. We will rapidly present a state of the art of current large scale assessment of spring and summer uptake of atmospheric CO2. We will challenge these assessments with 1) new evidence of significant winter CO2 release for winter experiments 2) new finding of the role of bubbles formation and transport within sea ice and 3) impurities expulsion derived from combined artificial ice experiment and modelling. Finally, comparison of air-ice fluxes derived from automated chamber and micrometeorological method and, mechanistic and box models show significant discrepancies that suggest that the contribution of sea ice to the air-ocean fluxes of CO2 remain an open question. We will also highlight that sea ice contribute to the fluxes of other gases as CH4 ,N2O and DMS [less ▲]

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See detailEFFECT OF TRUNK MOTOR CONTROL TRAINING IN ELITE SOCCER PLAYERS WITH LOW BACK PAIN
GROSDENT, Stéphanie ULiege; Demoulin, Christophe ULiege; Rodriguez de la Cruz, Carlos ULiege et al

Poster (2015, September 18)

Background and aims: The purpose of this study was to examine the effect of a motor control training program on the lumbopelvic motor control (LMC) in elite soccer players with a history of low back pain ... [more ▼]

Background and aims: The purpose of this study was to examine the effect of a motor control training program on the lumbopelvic motor control (LMC) in elite soccer players with a history of low back pain (LBP). Methods: Twenty-four male elite soccer players (mean age of 18.3 years) filled in questionnaires related to LBP and were divided into two groups: 12 players with a history of LBP (LBP group) and 12 players without a history of LBP (no LBP group). Then, they performed five LMC tests [the Bent Knee Fall Out test (BKFO), the Knee Lift Abdominal Test (KLAT), the Sitting Knee Extension Test (SKET), the Waiter’s Bow (WB) and the test of the transversus abdominis (TrA)] which were conducted and scored (0=failed, 1=correct) by a physiotherapist, blinded to the medical history of the participants. The total LMC score (ranging from 0 to 5) was calculated by adding the score at each test. During the following 10 weeks, the no LBP group conducted a soccer training as usual while LBP group performed an additional specific core stability program (1h/week). Results: At baseline, the participants of the LBP group had a worse LMC than the no LBP group (mean LMC score of 1.1 vs 3.1, p<0.01). The between-groups difference was particularly marked for the BKFO (p<0.01), KLAT (p<0.01) and SKET (p<0.05) tests. At the end of the intervention program, the LMC score of the players with a history of LBP increased significantly (p<0.0001) and was similar to the score of the players without a history of LBP (mean LMC score of 3.2 vs 3.3, p=1.00). Conclusions: LMC can be decreased in elite active soccer players with a history of LBP. Specific core stability program is effective to improve LMC in these players. [less ▲]

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See detailLa protection de la vie privée et familiale et le service public
Bouhon, Frédéric ULiege

Conference given outside the academic context (2015)

L'exposé fait le point sur la jurisprudence de la Cour européenne des droits de l'homme en ce qui concerne la protection de la vie privée et familiale des fonctionnaires.

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See detailLes libertés de réunion et d’association dans le service public
Bouhon, Frédéric ULiege

Conference given outside the academic context (2015)

L'exposé fait le point sur la jurisprudence de la Cour européenne des droits de l'homme en ce qui concerne la liberté de réunion et la liberté d'association des fonctionnaires.

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Peer Reviewed
See detailTree-level metastability bounds for the most general two Higgs doublet model
Ivanov, Igor ULiege; Silva, João

in Physical Review. D : Particles and Fields (2015), 92

Within two Higgs doublet models, it is possible that the current vacuum is not the global minimum, in which case it could possibly decay at a later stage. We discuss the tree-level conditions which must ... [more ▼]

Within two Higgs doublet models, it is possible that the current vacuum is not the global minimum, in which case it could possibly decay at a later stage. We discuss the tree-level conditions which must be obeyed by the most general scalar potential in order to preclude that possibility. We propose a new procedure which is not only more general but also easier to implement than the previously published one, including CP conserving as well as CP violating scalar sectors. We illustrate these conditions within the context of the Z2 model, softly broken by a complex, CP violating parameter. [less ▲]

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See detailEfficient and Precise Trajectory Planning for Nonholonomic Mobile Robots
Lens, Stéphane ULiege

Doctoral thesis (2015)

Trajectory planning is one of the fundamental problems in mobile robotics. A wide variety of approaches have been proposed over the years to deal with the various issues of this problem. This thesis ... [more ▼]

Trajectory planning is one of the fundamental problems in mobile robotics. A wide variety of approaches have been proposed over the years to deal with the various issues of this problem. This thesis presents an original and complete solution to tackle the motion planning problem for nonholonomic mobile robots in two-dimensional space. Given a set of obstacles, an initial and a goal configuration, the problem consists in computing efficiently a physically feasible trajectory that reaches the specified target as fast as possible. One of the original aspects of this work lies in the decomposition of the general problem into several simpler subproblems, for which very efficient solutions are developed. Their combination provides a complete trajectory planning approach that is one of the most computationally effective method suited for the motion of cylindrically shaped wheeled mobile robots in the presence of polygonal obstacles. This complete solution consists of three main steps. The first one is aimed at finding a short path that avoids obstacles and manages to reach the destination, without taking into account nonholonomic constraints of the robot. Our path planning method relies on an original refinement procedure of a constrained Delaunay triangulation of the obstacles, that outperforms other existing planning techniques. The second step consists in interpolating paths into smooth curves that can be followed by a real robot without slowing down excessively. By joining only two arcs of clothoids for moving from one curvature to another, our approach is simpler and also computationally cheaper than other interpolation methods. Finally, thanks to the introduction of an original discretization scheme, an efficient algorithm for computing a time-optimal speed profile for arbitrary paths is presented. The speed profile that results from this procedure not only allows the robot to follow the synthesized path as fast as possible while taking into account a broad class of velocity and accelerations constraints, but also provides the accurate advance information necessary to implementing coordinated actions during the displacement of the robot (e.g., between the locomotion system and other actuators). [less ▲]

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See detailPt-Ni Hollow Nanoparticles for Oxygen Reduction Reaction : Controlling the Nanoparticle Morphology
Asset, Tristan ULiege; Zubiaur, Anthony ULiege; Chattot, Raphael et al

Poster (2015, September 13)

Detailed reference viewed: 56 (4 ULiège)