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See detailCoherent backscattering in the Fock space of Bose- and Fermi-Hubbard systems
Engl, Thomas; Dujardin, Julien; Tisserond, Emilie et al

Poster (2016, July)

Coherent backscattering generally refers to a significant and robust enhancement of the average backscattering probability of a wave within a disordered medium, which from a semiclassical point of view ... [more ▼]

Coherent backscattering generally refers to a significant and robust enhancement of the average backscattering probability of a wave within a disordered medium, which from a semiclassical point of view arises due to the constructive interference between backscattered trajectories and their time-reversed counterparts. We recently investigated the manifestation of this wave interference phenomenon in the Fock space of a disordered Bose-Hubbard system of finite extent [1], which can potentially be realized using ultracold bosonic atoms within optical lattices. Preparing the atoms in a well-defined Fock state of the lattice and letting the system evolve for a finite time will, for suitable parameters of the system and upon some disorder average over random on-site energies of the lattice, generally give rise to an equidistribution of the occupation probability within the energy shell of the Fock space that corresponds to the initial energy of the system, in accordance with the quantum microcanonical ensemble. We find, however, that the initial state is twice as often encountered as other Fock states with comparable total energy, which is a consequence of coherent backscattering [1]. Most recently, we showed that this phenomenon also arises in spin 1/2 Fermi-Hubbard rings that involve Rashba hopping terms (which combine inter-site hoppings with spin flips and arise from spin-orbit coupling), for which a newly developed semiclassical theory [2] correctly predicts a coherent enhancement of the occupation probabilities of the initial state and its spin-flipped counterpart. Moreover, performing a global spin flip within this Fermi-Hubbard system will give rise to significant spin echo peaks on those two Fock states, which is again a consequence of quantum many-body interference [3]. The semiclassical predictions of these enhancements and peaks are found to be in very good agreement with numerical findings obtained from the exact quantum time evolution within this Fermi-Hubbard system. [1] T. Engl, J. Dujardin, A. Argüelles, P. Schlagheck, K. Richter, and J. D. Urbina, Phys. Rev. Lett. 112, 140403 (2014). [2] T. Engl, P. Plößl, J. D. Urbina, and K. Richter, Theoretical Chemistry Accounts 133, 1563 (2014). [3] T. Engl, J. D. Urbina, and K. Richter, arXiv:1409.5684. [less ▲]

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See detailApplications of the multiple timescale spectral analysis in wind engineering
Denoël, Vincent ULg

in Zingoni, Alphose (Ed.) Proceedings of the Sixth International Conference on Structural Engineering, Mechanics and Computation (2016, July)

The random response of civil engineering structures to the buffeting action of wind loads is typically composed of several components, usually referred to as the background component, in the low fre ... [more ▼]

The random response of civil engineering structures to the buffeting action of wind loads is typically composed of several components, usually referred to as the background component, in the low fre- quency zone and the resonant component(s) in the neighborhood of modal natural frequencies. It has become customary to study separately and add the contributions of these components to the total response, at least as far as the second order response (variance of structural responses) is concerned. Such a decomposition exists but is less usual for the computation of covariances of modal coordinates or of structural displacements, which are in turn necessary for the determination of internal stresses. The question of such a decomposition also holds for nonlinear systems, or even for the higher statistical moments of a linear structural system, should the response be non Gaussian. With very wide ranges of applicability, the Multiple Timescale Spectral Analysis summarizes under a unified framework recent works aiming at the development of such decompositions. This paper briefly pictures this particular theory based on perturbation methods, and provides illustrations of its applicability to the problems cited above. [less ▲]

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See detailDistinct cerebral metabolic patterns related to high pain sensitivity in episodic or chronic migraine patients and healthy volunteers
D'Ostilio, Kevin ULg; Lisicki Martinez, Marco ULg; Schoenen, Jean ULg et al

in Frontiers in Aging Neuroscience (2016, July)

Introduction Allodynia, i.e. pain evoked by a non-painful stimulus, is prevalent in chronic pain and in migraine where it augments with disease severity and chronicity [1]. Central sensitization is ... [more ▼]

Introduction Allodynia, i.e. pain evoked by a non-painful stimulus, is prevalent in chronic pain and in migraine where it augments with disease severity and chronicity [1]. Central sensitization is thought to be the culprit [2]. It is not known, however, which central areas are involved. The aim of the present study was to evaluate whether brain metabolism in subjects that are more sensitive to pain is different between migraine patients and healthy controls. Subjects and methods Quantitative heat sensory testing on the forehead and 18FDG-PET were performed in 55 subjects: 20 healthy volunteers (HV, 21-59 years, 5M), 21 patients with episodic migraine in the interictal phase (MO, age range: 20-63 years, 5M) and 14 patients with chronic migraine (CM, age range: 22-62 years, 1M). The 3 cohorts were subdivided according to the median heat pain threshold into subgroups with low and high pain thresholds. PET results were compared between these subgroups in each cohort. Data analyses were restricted to areas of the pain/salience matrix. Results There was no significant difference in heat pain thresholds between HV (median: 43.7 °C), MO median: 44.2°C) and CM (median: 43.3°C) (p=0.64). In an SPM-ANOVA, a contrast modelling the potential gradual effect of increased differences in pain sensitivity in relation to disease severity showed significant metabolic changes in bilateral thalamus and midbrain (p < 0.001). Additional analyses revealed that hypometabolic areas in subgroups with a low heat pain threshold differed between HV (anterior cingulate and somatosensory cortices), MO (lower pons and somatosensory cortex) and CM (midbrain and thalamus) (Figure 1). Conclusion Overall migraine patients do not have reduced heat pain thresholds. However, hypometabolic areas related to high thermal pain sensitivity are strictly cortical in HV, but comprise the pons in episodic migraine and are restricted to midbrain and thalamus in chronic migraine. The distinct central correlates of heat pain sensitivity in migraine patients might therefore represent a biomarker of migraine and its chronification. Legend to figure Figure 1. Hypometabolic areas in low pain threshold subgroups in HV (green), MO (orange) and CM (red). p < 0.01 for display purpose. Résumé en Français: Titre: Métabolisme cérébral distinct en relation avec la sensibilité à la douleur entre sujets sains, migraine épisodique et migraine chronique. Les migraineux ont une sensibilité anormale à la douleur. Les mécanismes cérébraux en sont inconnus. Nous avons comparé le métabolisme cérébral chez des sujets sains et chez des migraineux épisodiques ou chroniques et correlé les résultats avec le seuil douloureux. Les aires cérébrales hypométaboliques liées à un seuil douloureux bas diffèrent entre groupes: régions corticales chez les sujets sains, aires corticales et sous-corticales dans la migraine épisodique, régions sous-corticales dans la migraine chronique .Le contrôle central de la douleur semble modifié distinctement dans les formes de migraine, ce qui pourrait en constituer un biomarqueur et avoir des implications thérapeutiques. [less ▲]

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See detailEntretien avec Michel Dumoulin. Regards sur les mondes de la recherche et de l'histoire.
Genin, Vincent ULg

in Contemporanea (2016), XXXVIII(2),

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See detailDeuxième séminaire vélo
Frankignoulle, Pierre ULg

Diverse speeche and writing (2016)

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See detailImpact of a mountain ultra-marathon on cardiac biomarkers
Le Goff, Caroline ULg; Gergelé, Laurent; Kaux, Jean-François ULg et al

in Crossing borders through sport science (2016, July)

Objectives. While moderate exercise has beneficial effects on the cardiovascular system, consequences of a supra-physiological effort are not clear yet. In particular, the physiological consequences of ... [more ▼]

Objectives. While moderate exercise has beneficial effects on the cardiovascular system, consequences of a supra-physiological effort are not clear yet. In particular, the physiological consequences of ultramarathons need to be further documented. The aim of the study was to assess the changes of various cardiac biomarkers after a mountain ultra-marathon. Material and methods. Blood and urine samples were collected on 28 runners (17 men) participating to the Ultra-Trail du Mont Blanc (105km, total positive elevation: 5600 m) at 3 different times: before the race (Pre), within 1 h after the finish (Post) and 7 days after the finish (D+7). Several biomarkers involved in heart disease (coronary syndrome, heart failure and fibrosis) and in inflammation were assayed on different analyzers such a COBAS® (for CKMB,TnThs, NT-proBNP, H-FABP and CRPs) and KRYPTOR® (for Copeptin). ST2 was measured manually with the Presage kit from CRITICAL DIAGNOSTIC®. Results. Plasma levels of cardiac markers (CKMB, TnThs, NT-proBNP, copeptin, H FABP, ST2) and inflammation (CRPs) increased significantly at Post. Means values increased from Pre to Post as follows: 2.3 to 91.9 UI/L for CKMB (p<0.0001); 7.6 to 31.7 ng/L for TnThs (p<0.0001); 41.7 to 1190.5 ng/L for NT-proBNP, 4.2 to 22.9 pmol/L for copeptin (p=0.001); 3.6 to 107.8 ng/mL for H-FABP (p<0.0001), 29.7 to 126.2 ng/mL for ST2 (p<0.0001); 0.5 to 29.1 mg/L for CRPs (p<0.0001). With the exception of a few (H-FABP, ST2, CRPs) biomarkers in some subjects, all values were back to Pre values at D+7. Discussion-conclusion. Prolonged strenuous running exercise caused an elevation in cardiac biomarkers. Elevation in CK-MB levels lacks specificity for cardiac damage as runners have increased CKMB from skeletal muscles as well. Previous studies suggested that exercise induced TnThs elevation is a benign reversible physiologic phenomenon but this parameter, as well as H-FABP, could be a sign of ischemia. Different phenomena occurred such as stretch of myocytes causing an increase in pressure or volume and neurohormonal activation which can explain the Copeptine and NT-proBNP increase, while ST2 is a biomarker of cardiac remodeling and fibrosis. CRP is an acute phase compound that tends to increase following a strenuous and prolonged bout of exercise and/or muscular injury. As the values tended to return within the normal reference range values within 7 days after the race, our study suggests that there is no permanent structural damage at the myocardium level. [less ▲]

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See detailValidity and reliability of the French translation of the Patient-Related Tennis Elbow Evaluation Questionnaire
Kaux, Jean-François ULg; DELVAUX, François ULg; SCHAUS, Jean ULg et al

in Crossing borders through sport science (2016, July)

Background: The lateral elbow tendinopathy is a common injury in tennis players and physical workers. The Patient-Rated Tennis Elbow Evaluation (PRTEE) questionnaire was created to measure pain and ... [more ▼]

Background: The lateral elbow tendinopathy is a common injury in tennis players and physical workers. The Patient-Rated Tennis Elbow Evaluation (PRTEE) questionnaire was created to measure pain and functional disabilities specifically reported in patient with lateral epicondylitis (tennis elbow). Developed in English, this questionnaire has since then been translated into several languages but not in French. Objectives: The aims of the study were to translate and cross-culturally adapt the PRTEE questionnaire into French and to evaluate the reliability and validity of this new version of the questionnaire (PRTEE-F). Methods: The PRTEE was cross-culturally adapted into French according to the international guidelines. To assess the reliability and validity of the PRTEE-F, 115 participants filled in the PRTEE-F twice, and the Disabilities of Arm, Shoulder and Hand questionnaire (DASH) and the Short Form Health Survey (SF-36) once. Internal consistency (with Cronbach’s alpha), test-retest reliability (with intra-class correlation (ICC)), convergent and divergent validity (by calculating the Spearman’s correlation coefficients with the DASH and some sub scales of the SF-36, respectively) were assessed. Results: The PRTEE was translated in French without problem. PRTEE-F showed a good test-retest reliability for the overall score (ICC 0.83) and for each items (ICC 0.71-0.9) and a high internal consistency (Cronbach’s alpha = 0.98). The correlation analyses revealed high correlation coefficients between PRTEE-F and DASH (good convergent validity) and, as expected, a low or moderate correlations with the divergent subscales of the SF-36 (discriminant validity). There was no floor or ceiling effect. Conclusions: The PRTEE questionnaire was successfully cross-culturally adapted into French the PRTEE-F is reliable and valid for evaluating the French-speaking patient with lateral elbow tendinopathy. [less ▲]

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See detailLifetime stability study of a NIR hyperspectral imaging system
Eylenbosch, Damien ULg; Bodson, Bernard ULg; Baeten, Vincent et al

Conference (2016, July)

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See detailApplication of NIR hyperspectral imaging combined to chemometrics to assess the impact of tillage on the root system development of a winter wheat crop
Fraipont, Guillaume ULg; Eylenbosch, Damien ULg; Baeten, Vincent et al

Poster (2016, July)

This poster presents de results of a study of the influence of tillage on the root development of a winter wheat crop. The originality of this research lies in the application of an innovative root ... [more ▼]

This poster presents de results of a study of the influence of tillage on the root development of a winter wheat crop. The originality of this research lies in the application of an innovative root quantification method based on the near infrared hyperspectral imaging. [less ▲]

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See detailInterspecific variation of warning calls in piranhas: comparative analysis
Mélotte, Geoffrey ULg; Michel, Christian ULg; Vigouroux, Régis et al

Poster (2016, July)

Fish sounds are often considered as species-specific with unique temporal and spectral features. Differences between acoustic signals of closely related species could be considered as pre-zygotic barrier ... [more ▼]

Fish sounds are often considered as species-specific with unique temporal and spectral features. Differences between acoustic signals of closely related species could be considered as pre-zygotic barrier and could be related to the evolutionary history of the species. In the present study, sounds were recorded and compared in eight piranha species (Serrasalmus elongatus, Serrasalmus marginatus, Serrasalmus compressus, Serrasalmus manueli, Serrasalmus spilopleura, Serrasalmus rhombeus, Serrasalmus eigenmanni and Pygocentrus nattereri) in order to evaluate the potential role of acoustic communication as a driving force in the clade diversification. The same kind of sound-producing mechanism was found in all the species: sonic muscles originate on vertebrae and attach to a tendon surrounding ventrally the bladder. Contractions of the sound-producing muscles force swimbladder vibration. Having the same kind of sound-producing mechanism, the calling features of the eight piranha species show logically many common characteristics. In all the species, the calls are harmonic sounds composed of several pulses without inter-pulse interval. It was possible to discern species-specific sounds, but the differences among species could be, in part, explained by the size. Only the sounds of S. elongatus and S. manueli are really distinguishable from the other species. Serrasalmus elongatus differed by having a higher number of pulses and high-pitched fundamental frequency, whereas S. manueli differed by having long pulse periods and a low fundamental frequency. In the framework of this study, acoustic communication cannot be considered as the main driving force in the diversification process of piranhas. Behavioral studies are however needed to clearly understand the eventual role of the calls during the spawning events. [less ▲]

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See detailLeibniz et J.S. Bach
Dony, Arthur ULg

in Li, Wenchao (Ed.) "Für unser Glück oder das Glück anderer" : Vorträge des X. Internationalen Leibniz-Kongresses (2016, July)

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See detailTemporal habitat shift of a polymorphic newt species under predation risk
Winandy, Laurane ULg; Colin, Mélanie; Denoël, Mathieu ULg

in Behavioral Ecology (2016), 27(4), 1025-1032

The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of ... [more ▼]

The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of habitat use induced by predation has rarely been observed. The study of such a mechanism is particularly relevant for introduced species because it might explain how native species can persist or decline in response to the presence of alien species. The introduction of fish into ponds inhabited by amphibians has severe consequences for their occurrence and abundance. Fish particularly affect an alternative newt phenotype, the paedomorph, which does not undergo metamorphosis and maintains larval traits such as gills at the adult stage. In a laboratory design, we assessed the diel patterns of habitat use in the 2 distinct morphological phenotypes of palmate newt (Lissotriton helveticus) in the presence or absence of goldfish (Carassius auratus). Both newt phenotypes avoided a risky habitat more in the presence than in the absence of fish. This habitat shift was more pronounced during the daytime (i.e., when the risk could be considered higher for the newts) than during nighttime. However, in contrast to metamorphs, paedomorphs showed less adaptive changes according to temporal risk and remained in their shelter for most of the time. Temporal and habitat partitioning at the diel scale between native and alien species might promote their coexistence, but diel change can also imply a cost in the overall reduction of the time allocated to essential activities, showing that species interactions remain complex. [less ▲]

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See detailQuand Caïn scrute Abel. Reflets mutuels des neutralités belge et suisse autour de la Première Guerre mondiale
Genin, Vincent ULg

in Revue Générale (2016), 2016/4(juillet-août),

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See detailPhilosophie et esthétique de la modernité: Approches phénoménologiques et sociologiques
Hagelstein, Maud ULg; Zincq, Aurélien ULg

in Bulletin d'Analyse Phénoménologique (2016), 12 (2016)(4),

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See detailCognitive processes across anxiety disorders related to intolerance of uncertainty: Clinical Review
Vander Haegen, Marie ULg; Etienne, Anne-Marie ULg

in Cogent Psychology (2016), 3

Abstract: Objective: Being a relatively recent concept, the intolerance of uncertainty (IU) suffers from inconsistent definitions and conceptual overlap. The core objective of the study is to clarify its ... [more ▼]

Abstract: Objective: Being a relatively recent concept, the intolerance of uncertainty (IU) suffers from inconsistent definitions and conceptual overlap. The core objective of the study is to clarify its clinical manifestations and its involved cognitive processes. Method: The procedure is based on algorithms (equations of keywords) encoded simultaneously in databases (Scopus, PubMed, and PsycArticles). Results are filtered by the year (range of 10 years [2005–2015] because it is a recent concept) and the relevance of abstracts. Once the studies are appraised, results are categorized in two groups: studies which examine the IU in a clinical perspective (relations with one or several anxiety disorders) (cluster A) and those which measure the IU through a cognitive perspective (cognition, metacognition) (cluster B). Results: 66 results are retrieved: 50 results concern the cluster A and 16 examine the cluster B. The state of the IU varies between studies (e.g. predictor and mediator), which make comparisons difficult. Notwithstanding, the IU construct seems to be a broad transdiagnostic maintaining risk factor involved in a range of psychological disorders. Conclusion: This clustering supported that researchers and clinicians may benefit from incorporating IU within cognitive and computational research design and as a specific treatment target. [less ▲]

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See detailBoosting shape classifiers accuracy by considering the inverse shape
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

in Journal of Pattern Recognition Research (2016), 11(1), 41-54

Many techniques exist for describing shapes. These techniques almost exclusively consider the contour or the inside of the shape; the major problem for describing the outside of a shape, or inverse shape ... [more ▼]

Many techniques exist for describing shapes. These techniques almost exclusively consider the contour or the inside of the shape; the major problem for describing the outside of a shape, or inverse shape, being that it has an infinite extension. In this paper, we show how to adapt two shape descriptors, one region based, the Cover By Rectangles, and one transform based, the Zernike moments, to be applicable to the inverse shape. We analyze their properties, and show how to deal with the infinite extension of the inverse shape. Then, we apply these descriptors to shape classification and compare representations that use the shape, its inverse, or both. Our experiments establish that, for shape classification, a representation integrating the inverse shape often outperforms a representation restricted to the shape. This opens the path for better techniques that could use, as a rule of thumb, both the representations of a shape and its inverse for the purpose of classification. [less ▲]

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See detailLeveraging orientation knowledge to enhance human pose estimation methods
Azrour, Samir ULg; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in Articulated Motion and Deformable Objects AMDO 2016 (2016, July)

Predicting accurately and in real-time 3D body joint positions from a depth image is the cornerstone for many safety, biomedical, and entertainment applications. Despite the high quality of the depth ... [more ▼]

Predicting accurately and in real-time 3D body joint positions from a depth image is the cornerstone for many safety, biomedical, and entertainment applications. Despite the high quality of the depth images, the accuracy of existing human pose estimation methods from single depth images remains insufficient for some applications. In order to enhance the accuracy, we suggest to leverage a rough orientation estimation to dynamically select a 3D joint position prediction model specialized for this orientation. This orientation estimation can be obtained in real-time either from the image itself, or from any other clue like tracking. We demonstrate the merits of this general principle on a pose estimation method similar to the one used with Kinect cameras. Our results show that the accuracy is improved by up to 45.1 %, with respect to a method using the same model for all orientations. [less ▲]

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