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See detailAn asymptotic expansion-based method for a spectral approach in equivalent statistical linearization
Canor, Thomas ULg; Blaise, Nicolas ULg; Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2014), 38

Equivalent linearization consists in replacing a nonlinear system with an equivalent linear one whose parameters are tuned with regard to the minimization of a suitable function. In particular, the ... [more ▼]

Equivalent linearization consists in replacing a nonlinear system with an equivalent linear one whose parameters are tuned with regard to the minimization of a suitable function. In particular, the Gaussian equivalent linearization expresses the properties of an equivalent linear system in terms of the mean vector and the covariance matrix of the responses, which are the unknowns of the optimization problem in a spectral approach. Even though the system has been linearized, the resulting set of equations is nonlinear. The computational effort in this method pertains to the solution of a possibly large set of nonlinear algebraic equations involving integrals and inversions of full matrices. This work proposes to develop and apply an asymptotic expansion-based method to facilitate and to improve the statistical linearization for large nonlinear structures. The proposed developments demonstrate that for slightly to moderately coupled nonlinear systems, the equivalent linearization can be applied with an appropriate modal approach and eventually seen as a convergent series initiated with the stochastic response of a main decoupled linear system. With this method, the computational effort is attractively reduced, the conditioning of the set of nonlinear algebraic equations is improved and inversion of full transfer matrices and repeated integrations are avoided. The paper gives a formal description of the method and illustrates its implementation and performances with the computation of stationary responses of nonlinear structures subject to coherent random excitation fields. [less ▲]

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See detailRetrospective analysis of a suburban out-ofhours clinic in Belgium
Belche, Jean-Luc ULg; Berrewaerts, Marie-Astrid ULg; Burette, Philippe ULg et al

in Acta Clinica Belgica (2014), 69(5), 341-347

Introduction: In many countries, out-of-hours medical care is under scrutiny. The aim of this article is to study the activities recorded by the first out-of-hours clinic that has been opened, as a pilot ... [more ▼]

Introduction: In many countries, out-of-hours medical care is under scrutiny. The aim of this article is to study the activities recorded by the first out-of-hours clinic that has been opened, as a pilot study, in two Walloon communes. Material and method: A retrospective analysis of anonymized data was conducted for 2009. Coding of diagnoses was conducted using the International Classification of Primary Care (ICPC-2). Results: A total of 3949 contacts were recorded in 2009 with the out-of-hours clinic, 3294 related to inhabitants of the two communes covered, which was equivalent to 13% of the total population in question. Compared to 7.2% of contacts between midnight and 8 a.m., 82.9% of contacts took place between 8 a.m. and 9 p.m., and 91.6% of contacts were handled locally, with only 8.4% resulting in hospitalization. In addition, 52% of contacts were with patients aged between 25 and 65; 29.9% of contacts were with paediatric patients (,15 years). Patients over the age of 65 made up 18% of contacts. The most common pathologies were respiratory (R). Analysis of flu diagnoses identified two epidemic peaks. Discussion: The suburban out-of-hours clinic studied fulfilled an important role in managing the demand for health care. The large majority of health problems were resolved locally, and the inhabitants did not need to go to hospital. Appointments between midnight and 8 a.m. were in the minority, which points towards adjusting the organization of the out-of-hours service during the night. The geriatric population is not highly over-represented contrary to what might be expected considering its largest number of pathologies. The on-call doctor’s skills profile should take account of the populations and morbidities encountered. Out-ofhours clinics could possibly play a sentinel role in terms of flu epidemics. Conclusion: This study describes a pilot suburban out-of-hours clinic which met three of recommendations set by the KCE in its report on out-of-hours care in general medicine: the organization of an out-of-hours clinic with logistical support, the use of a single telephone number and merging out-of-hours areas. While debate exists on the management of out-of-hours care, this study provides evidence on the role of the physician during these hours. [less ▲]

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See detailEGFR activation and signaling in cancer cells are enhanced by the membrane-bound metalloprotease MT4-MMP.
Paye, Alexandra ULg; Truong, Alice ULg; Yip, Cassandre ULg et al

in Cancer research (2014)

MT4-MMP (MMP-17) is a GPI-anchored matrix metalloprotease expressed on the surface of cancer cells which promotes tumor growth and metastasis. In this report, we identify MT4-MMP as an important driver of ... [more ▼]

MT4-MMP (MMP-17) is a GPI-anchored matrix metalloprotease expressed on the surface of cancer cells which promotes tumor growth and metastasis. In this report, we identify MT4-MMP as an important driver of cancer cell proliferation through CDK4 activation and retinoblastoma protein (Rb) inactivation. We also determine a functional link between MT4-MMP and the growth factor receptor EGFR. Mechanistic experiments revealed direct association of MT4-MMP and its positive effects on EGFR phosphorylation in response to TGF- and EGF in cancer cells. Notably, the effects of MT4-MMP on proliferation and EGFR activation did not rely on metalloprotease activity. Clinically, MT4-MMP and EGFR expression were correlated in human triple negative breast cancer specimens. Altogether our results identify MT4-MMP as a positive modifier of EGFR outside-in signaling that acts to cooperatively drive cancer cell proliferation. [less ▲]

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See detail6-Years Experience of NBS for Hemoglobin Disorders using TMS
BOEMER, François ULg

Conference (2014, October)

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See detailNumerical investigation of cut-edge effect using the Gurson-Tvergaard-Needleman model
Lemoine, Xavier; Tudor, Balan; Habraken, Anne ULg

in Procedia Engineering (2014, October)

In this contribution, the formability of sheet metal cut edges is investigated using damage model.Classical forming limit diagrams are known not to apply properly to the cut edges. However, with mild ... [more ▼]

In this contribution, the formability of sheet metal cut edges is investigated using damage model.Classical forming limit diagrams are known not to apply properly to the cut edges. However, with mild steels the sheet edges usually behave better than the Forming Limit Diagram prédictions, so this phenomenon has not been given sufficient attention. In contrast, for Advanced High Strengh Steels the cut edges exhibit reduced formability as compared to the plain sheet;this effect is very sensitive to the quality of the cutting process. The current investigation is aimed to evaluate the ability of available damage models to predict this effect on sample applications. The Gurson-Tvergaard-Needleman model is used and the material parameters for a Dual Phase are considered [1]. The effect of the cutting process is described by means of initial fields of equivalent plastic strain and porosity. The geometrical distribution and typical values for these two initial fields are devised based on literature . Numerical simulations of flat notched tensile tests are used within the FE code Abaqus/Explicit to illustrate the impact of the initial fields on the moment and the location of the failure initiation. The influence of the mesh size in the cutting-affected area is also investigated. The hole expansion test and a flat bending test are further simulated to investigate the influence of the cut edge. [less ▲]

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See detailLes valeurs et les valorisations des images
Dondero, Maria Giulia ULg

in Biglari, Amir (Ed.) Les valeurs. Aux fondements de la sémiotique (2014)

Cet article vise à explorer la manière dont la sémiotique greimassienne a traité la question des valeurs dans le cadre de l’image, notamment photographique et artistique. Après une relecture critique de ... [more ▼]

Cet article vise à explorer la manière dont la sémiotique greimassienne a traité la question des valeurs dans le cadre de l’image, notamment photographique et artistique. Après une relecture critique de l’ouvrage de Jean-Marie Floch, Les formes de l’empreinte, et de la distinction entre valeurs dans l’image et valorisations des images, ce travail se consacre à l’exposition de nouvelles propositions de la sémiotique des pratiques de Jacques Fontanille en essayant de les lier à des réflexions sur les objets et les pratiques de la photographie artistique (l’utilisation des séries, de l’original, des différents tirages, etc.). Si l’attention est portée surtout sur la photo artistique, ce texte envisage également une comparaison avec les pratiques de l’original et de l’authenticité dans la photo de guerre, la photo de famille et la photo-image pieuse. L’objectif majeur de ce travail est d’étudier les diverses pratiques de valorisation des images photographiques afin de faire éclater la notion ontologique de trace photographique. [less ▲]

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See detailThe impact and retention of spray droplets on a horizontal hydrophobic surface
Zwertvaegher, Ingrid; Verhaeghe, Micheline; Brusselman, Eva et al

in Biosystems Engineering (2014), 126

Spray retention, i.e. the overall capture of spray droplets by plants on initial or subsequent impact, and after loss due to run-off, is an important stage in the spray application process as droplet ... [more ▼]

Spray retention, i.e. the overall capture of spray droplets by plants on initial or subsequent impact, and after loss due to run-off, is an important stage in the spray application process as droplet losses may result in reduced efficacy, economic loss, and environmental contamination. The aim of this exploratory study is to determine whether a new method based on calculating the volumetric proportions per impact type, i.e. adhesion, rebound and shatter, can be used to predict spray retention. These volumetric proportions are calculated based on logistic regression models, derived from vision-based droplet characteristics and impact assessments, and laser-based spray characteristics. The advantages and limitations of such a method are explored. The volumetric proportions per impact type on a horizontal, synthetic hydrophobic surface were determined for four different nozzles (XR 110 01 VS flat-fan nozzle, XR 110 04 VS flat-fan nozzle, XR 110 08 VS flat-fan nozzle and AI 110 08 VS air-induction nozzle) under controlled realistic conditions, and compared to the results of a retention test. The volumetric proportions of adhesion were much lower than the relative retentions, indicating that a considerable amount of rebound and shatter also contributed to final retention. The method should thus be improved by including the droplets retained after first impact and the retained proportions of partial droplet fragmentation but it is nevertheless considered a promising technique. [less ▲]

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See detailAzione, testualizzazione, notazione
Dondero, Maria Giulia ULg

in Espressione e contenuto. Rivista on-line dell'AISS Associazione Italiana di Studi Semiotici (2014, October)

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See detailEccentric muscle contractions: risks and benefits
Hody, Stéphanie ULg; Croisier, Jean-Louis ULg; Lacrosse, Zoé ULg et al

in Proceedings of the Belgian Royal Academies of Medicine (2014)

La contraction musculaire excentrique se caractérise par le développement d'une tension musculaire associée à l'étirement concomitant du complexe musculo-tendineux. Ce mode de contraction présente un ... [more ▼]

La contraction musculaire excentrique se caractérise par le développement d'une tension musculaire associée à l'étirement concomitant du complexe musculo-tendineux. Ce mode de contraction présente un intérêt croissant dans de nombreux domaines tels que l’entraînement sportif, la médecine physique et la rééducation. De plus, certaines indications de l’entraînement en mode excentrique ont été posées chez des patients porteurs de maladies chroniques. Cependant, lorsqu’il est réalisé de manière intense et inhabituelle, l’exercice excentrique peut entraîner diverses altérations de l’ultrastructure musculaire qui se manifestent par une série de symptômes cliniques comme des douleurs musculaires d’apparition retardées (Delayed-Onset Muscle Soreness, DOMS) et une altération de la fonction musculaire. Malgré la littérature abondante consacrée à la description du phénomène des DOMS, aucune théorie cohérente n’est actuellement disponible pour expliquer la survenue différée des sensations douloureuses et des signes associés. De même, toujours à l’analyse de la littérature, on ne peut que constater l’absence de solution thérapeutique susceptible d’atténuer significativement l’intensité des DOMS et de leurs conséquences fonctionnelles associées à l’exception, paradoxalement, de l’exercice excentrique lui-même qui, lorsqu’il est proposé en conditions sous-maximales d’intensité progressivement croissante, semble constituer la seule prévention réellement efficace de l’apparition des DOMS. De même, si l’efficacité d’un entraînement spécifique dans la prévention des DOMS a été confirmée par de nombreux travaux, la nature de cet effet protecteur reste sujette à conjectures. Nous sommes néanmoins convaincus qu’une meilleure compréhension des réponses aiguës et/ou adaptatives à l’exercice excentrique contribuerait d’une part, à la mise au point d’interventions thérapeutiques efficaces et d’autre part, à élucider les évènements moléculaires impliqués dans des conditions pathologiques telles que les myalgies et certaines maladies neuromusculaires. [less ▲]

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See detailEvidence of oxidative stress and mitochondrial respiratory chain dysfunction in an in vitro model of sepsis-induced kidney injury
Quoilin, Caroline ULg; Mouithys-Mickalad, Ange ULg; Lécart, Sandrine et al

in Biochimica et Biophysica Acta-Bioenergetics (2014), 1837(10), 1790-1800

To investigate the role of oxidative stress and/or mitochondrial impairment in the occurrence of acute kidney injury (AKI) during sepsis, we developed a sepsis-induced in vitro model using proximal ... [more ▼]

To investigate the role of oxidative stress and/or mitochondrial impairment in the occurrence of acute kidney injury (AKI) during sepsis, we developed a sepsis-induced in vitro model using proximal tubular epithelial cells exposed to a bacterial endotoxin (lipopolysaccharide, LPS). This investigation has provided key features on the relationship between oxidative stress and mitochondrial respiratory chain activity defects. LPS treatment resulted in an increase in the expression of inducible nitric oxide synthase (iNOS) and NADPH oxidase 4 (NOX-4), suggesting the cytosolic overexpression of nitric oxide and superoxide anion, the primary reactive nitrogen species (RNS) and reactive oxygen species (ROS). This oxidant state seemed to interrupt mitochondrial oxidative phosphorylation by reducing cytochrome c oxidase activity. As a consequence, disruptions in the electron transport and the proton pumping across the mitochondrial inner membrane occurred, leading to a decrease of the mitochondrial membrane potential, a release of apoptotic-inducing factors and a depletion of adenosine triphosphate. Interestingly, after being targeted by RNS and ROS, mitochondria became in turn producer of ROS, thus contributing to increase the mitochondrial dysfunction. The role of oxidants in mitochondrial dysfunction was further confirmed by the use of iNOS inhibitors or antioxidants that preserve cytochrome c oxidase activity and prevent mitochondrial membrane potential dissipation. These results suggest that sepsis-induced AKI should not only be regarded as failure of energy status but also as an integrated response, including transcriptional events, ROS signaling, mitochondrial activity and metabolic orientation such as apoptosis. [less ▲]

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See detailUnderstanding Random Forests: From Theory to Practice
Louppe, Gilles ULg

Doctoral thesis (2014)

Data analysis and machine learning have become an integrative part of the modern scientific methodology, offering automated procedures for the prediction of a phenomenon based on past observations ... [more ▼]

Data analysis and machine learning have become an integrative part of the modern scientific methodology, offering automated procedures for the prediction of a phenomenon based on past observations, unraveling underlying patterns in data and providing insights about the problem. Yet, caution should avoid using machine learning as a black-box tool, but rather consider it as a methodology, with a rational thought process that is entirely dependent on the problem under study. In particular, the use of algorithms should ideally require a reasonable understanding of their mechanisms, properties and limitations, in order to better apprehend and interpret their results. Accordingly, the goal of this thesis is to provide an in-depth analysis of random forests, consistently calling into question each and every part of the algorithm, in order to shed new light on its learning capabilities, inner workings and interpretability. The first part of this work studies the induction of decision trees and the construction of ensembles of randomized trees, motivating their design and purpose whenever possible. Our contributions follow with an original complexity analysis of random forests, showing their good computational performance and scalability, along with an in-depth discussion of their implementation details, as contributed within Scikit-Learn. In the second part of this work, we analyze and discuss the interpretability of random forests in the eyes of variable importance measures. The core of our contributions rests in the theoretical characterization of the Mean Decrease of Impurity variable importance measure, from which we prove and derive some of its properties in the case of multiway totally randomized trees and in asymptotic conditions. In consequence of this work, our analysis demonstrates that variable importances as computed from non-totally randomized trees (e.g., standard Random Forest) suffer from a combination of defects, due to masking effects, misestimations of node impurity or due to the binary structure of decision trees. Finally, the last part of this dissertation addresses limitations of random forests in the context of large datasets. Through extensive experiments, we show that subsampling both samples and features simultaneously provides on par performance while lowering at the same time the memory requirements. Overall this paradigm highlights an intriguing practical fact: there is often no need to build single models over immensely large datasets. Good performance can often be achieved by building models on (very) small random parts of the data and then combining them all in an ensemble, thereby avoiding all practical burdens of making large data fit into memory. [less ▲]

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See detailMesozoic marine crises and ichthyosaur history: a non-direct relationship
Fischer, Valentin ULg

Conference (2014, October)

Marine ecosystems underwent several profound crises throughout the Mesozoic; many of them are correlated with supra-regional to worldwide anoxic events. The impact of these crises is relatively well ... [more ▼]

Marine ecosystems underwent several profound crises throughout the Mesozoic; many of them are correlated with supra-regional to worldwide anoxic events. The impact of these crises is relatively well understood among animals occupying lower trophic levels but their influence on top predators of that time, fishes and marine reptiles, remains unclear. The fossil record of marine reptiles is of fluctuating quality but thoroughly revised taxonomic and phylogenetic frameworks now allow assessment of the influence of past climatic and oceanic changes on these top predators, by quantifying their cladogenesis and extinction rates across selected intervals. Here, I focus on ichthyosaurs, a successful clade of marine reptiles that colonized marine ecosystems during most of the Mesozoic. The ichthyosaur record indicates relatively few severe turnovers and a non direct relationship with environmental drivers, notably anoxic events. New fossils from France reveal the middle-late Norian extinctions did not eradicate the clade of whale-sized shastasaurid ichthyosaurs; similarly, the severe early Toarcian anoxic event, the end-Jurassic climate changes and several Cretaceous anoxic events did not impacted ichthyosaurs significantly, at least at the suprageneric level. On the other hand, severe turnovers or extinctions occurred during the latest Triassic and the Cenomanian and are coincident with a number of profound environmental and biotic changes. This indicates that unique drivers fail to explain the turnover patterns in ichthyosaur evolutionary history. Notably, oceanic anoxic events only impacted ichthyosaurs during the end-Cenomanian and did so during a period of intense climatic and biological upheavals. These major crises in ichthyosaur history are seemingly protracted over several million years and are probably best explained by a conjunction of causes. This is part of a wider project that will incorporate data from other contemporaneous groups to shed a new light on the general turnover patterns among marine top predators of the Mesozoic and the influence of ancient environmental changes in shaping their biodiversity. [less ▲]

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See detailRugose corals at the Tournaisian-Viséan transition in the Central Taurides (S Turkey) - Palaeobiogeography and Palaeoceanography of the Gondwana margin
Denayer, Julien ULg

in 4th International Palaeontological Congress, Mendoza, Abstracts volume (2014, October)

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See detailPour l'amour du grec : le voyage de Villoison en Grèce et au Levant (1784-1786)
Famerie, Etienne ULg

in Art&Fact (2014), 33

How the French scholar d'Ansse de Villoison describes, analyses and judges the state of Ottoman Greece in the end of the 18th century

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See detailJosé Muñoz: La poética de las manchas
Dejasse, Erwin ULg

in Entre Líneas: Revista de Estudios Sobre Historieta y Humor Gráfico (2014), 1

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See detailPSI Mehler reaction is the main alternative photosynthetic electron pathway in Symbiodinium sp., symbiotic dinoflagellates of cnidarians
Roberty, Stéphane ULg; Bailleul, Benjamin ULg; Berne, Nicolas et al

in New Phytologist (2014), 204(1), 81-91

• Photosynthetic organisms have evolved various photoprotective and regulatory mechanisms to cope with changing and high light intensities. The nature and relative amplitude of these mechanisms is matter ... [more ▼]

• Photosynthetic organisms have evolved various photoprotective and regulatory mechanisms to cope with changing and high light intensities. The nature and relative amplitude of these mechanisms is matter of debate in dinoflagellates that live in symbiosis with cnidarians. In this work, the amplitude of photosynthetic alternative electron flows to oxygen (chlororespiration, Mehler reaction, mitochondrial respiration) and PSI cyclic electron flow were investigated in Symbiodinium clades A1, B1 and F1. • Cultured Symbiodinium strains were maintained semi-continuously under identical environmental conditions. Joint measurements of oxygen evolution, fluorescence emission, and absorption changes at specific wavelengths were used to evaluate PSI and PSII electron transfer rates (ETR). • A light-dependent and O2-dependent ETR was observed in all strains. This ETR involved PSII and PSI and was insensitive to addition of mitochondrial and carbon fixation inhibitors. • These results demonstrate that photoreduction of oxygen downstream of PSI by the so-called Mehler reaction is the main alternative electron sink at the onset and steady state of photosynthesis in all strains. This mechanism in Symbiodinium sustains significant levels of photosynthetic electron flux under high light, thus acting as a photoprotective mechanism and increasing the ATP/NADPH ratio by the electron transfer chain. [less ▲]

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See detailOptimal Assignment of Off-Peak Hours to Lower Curtailments in the Distribution Network
Merciadri, Luca ULg; Mathieu, Sébastien ULg; Ernst, Damien ULg et al

in Proceedings of the 5th European Innovative Smart Grid Technologies (ISGT) (2014, October)

We consider a price signal with two settings: off-peak tariff and on-peak tariff. Some loads are connected to specific electricity meters which allow the consumption of power only in off-peak periods ... [more ▼]

We consider a price signal with two settings: off-peak tariff and on-peak tariff. Some loads are connected to specific electricity meters which allow the consumption of power only in off-peak periods. Historically, off-peak periods were located during the night and on-peak periods during the day. Changing the assignment of off-peak periods is an easy method for distribution system operators to access to the flexibility of small consumers. This solution can be implemented quickly as the infrastructure needed already exists in some countries. We propose a mixed-integer linear model to assign optimally the off-peak hours so as to minimize a societal cost. This cost gathers together the cost of electricity, the financial losses due to energy curtailments of photovoltaic installations and the loads' wellbeing. Our model considers automatic tripping of inverters and constraints of the electrical distribution networks. Simulation results show that the new disposition of off-peak hours could reduce significantly the photovoltaic energy curtailed in the summer. [less ▲]

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See detailDynamic Simulation of Large-scale Power Systems Using a Parallel Schur-complement-based Decomposition Method
Aristidou, Petros ULg; Fabozzi, Davide; Van Cutsem, Thierry ULg

in IEEE Transactions on Parallel and Distributed Systems (2014), 25(10), 2561-2570

Power system dynamic simulations are crucial for the operation of electric power systems as they provide important information on the dynamic evolution of the system after an occurring disturbance. This ... [more ▼]

Power system dynamic simulations are crucial for the operation of electric power systems as they provide important information on the dynamic evolution of the system after an occurring disturbance. This paper proposes a robust, accurate and efficient parallel algorithm based on the Schur complement domain decomposition method. The algorithm provides numerical and computational acceleration of the procedure. Based on the shared-memory parallel programming model, a parallel implementation of the proposed algorithm is presented. The implementation is general, portable and scalable on inexpensive, shared-memory, multi-core machines. Two realistic test systems, a medium-scale and a large-scale, are used for performance evaluation of the proposed method. [less ▲]

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