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See detailA differential Lyapunov framework for contraction analysis
Forni, Fulvio ULg; Sepulchre, Rodolphe ULg

in IEEE Transactions on Automatic Control (2014), 59(3), 614-628

Lyapunov's second theorem is an essential tool for stability analysis of differential equations. The paper provides an analog theorem for incremental stability analysis by lifting the Lyapunov function to ... [more ▼]

Lyapunov's second theorem is an essential tool for stability analysis of differential equations. The paper provides an analog theorem for incremental stability analysis by lifting the Lyapunov function to the tangent bundle. The Lyapunov function endows the state-space with a Finsler structure. Incremental stability is inferred from infinitesimal contraction of the Finsler metrics through integration along solutions curves. [less ▲]

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See detailThe feedback of massive stars on interstellar astrochemical processes
De Becker, Michaël ULg

in Astrophysics & Space Science (2014), 350(1), 237-243

Astrochemistry is a discipline that studies physico-chemical processes in astrophysical environments. Such environments are characterized by conditions that are substantially different from those existing ... [more ▼]

Astrochemistry is a discipline that studies physico-chemical processes in astrophysical environments. Such environments are characterized by conditions that are substantially different from those existing in usual chemical laboratories. Models which aim to explain the formation of molecular species in interstellar environments must take into account various factors, including many that are directly, or indirectly related to the populations of massive stars in galaxies. The aim of this paper is to review the influence of massive stars, whatever their evolution stage, on the physico-chemical processes at work in interstellar environments. These influences include the ultraviolet radiation field, the production of high energy particles, the synthesis of radionuclides and the formation of shocks that permeate the interstellar medium. [less ▲]

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See detailVieillissement: mieux comprendre pour mieux (inter)agir dans nos actes de soins
Schroyen, Sarah ULg; Marquet, Manon ULg

Conference given outside the academic context (2014)

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See detailPrognostic value of FDG PET/CT in liver transplantation for hepatocarcinoma
DETRY, Olivier ULg; Govaerts, L; BLETARD, Noëlla ULg et al

in Acta Gastro-Enterologica Belgica (2014, March), 77(1), 08

AIM : FDG uptake has been shown to predict the outcome in large series of patients with hepatocarcinoma (HCC) in Asia, but few data are available regarding European populations. Our aim was to evaluate ... [more ▼]

AIM : FDG uptake has been shown to predict the outcome in large series of patients with hepatocarcinoma (HCC) in Asia, but few data are available regarding European populations. Our aim was to evaluate the prognostic value of pretreatment FDG PET-CT in patients treated by liver transplantation. Methods: We retrospectively analyzed the data of 27 patients (24 M and 3 W, mean age 58 ± 9 years). The mean follow-up was 26 ± 18 months (min 1 month, max 66 months). All patients had an FDG PET-CT before the transplantation. The FDG PET/CT was performed according to a standard clinical protocol: 4 MBqFDG/kg body weight, uptake 60 min., low-dose non-enhanced CT. We measured the SUVmax and SUVmean of the tumor and the normal liver. The tumor/liver activity ratios (RSUVmax and RSUVmean) were tested as prognostic factors and compared to the following conventional prognostic factors: MILAN, CLIP, OKUDA, TNM stage, alphafoetoprotein level, portal thrombosis, size of the largest nodule, tumor differentiation, microvascular invasion, underlying cirrhosis and liver function. Results : The DFS was 87.2% at 1y and 72.1% at 3y. The OS was 85.2% at 1y and 80.7% at 3y. According to an univariate Cox model, RSUVmax, RSUVmean and healthy liver were predictors of DFS and RSUVmax, RSUVmean, size of the largest nodule, CLIP, liver involvement>50%, and healthy liver predicted the OS. According to a multivariate Cox model, only RSUVmax predicted DFS and RSUVmax and liver involvement>50% predicted OS. An ROC analysis of the ratios showed that the 1.15 cut-off for RSUVmax was best for predicting both the DFS (Cox regression:HR 14.4, p=0.02) and OS (HR 5.6, p=0.049). The Kaplan-Meier curves and Logrank tests confirmed those results. Even though the MILAN criteria alone were not predictive, it is worth noting that none of the patients outside the MILAN criteria and with RSUVmax<1.15 relapsed. Conclusions: The RSUVmax is a strong prognostic factor for recurrence and death in patients with HCC treated by liver transplantation with a cut-off value of 1,15. further prospective studies should test whether the metabolic index should be systematically included in the preoperative assessment. [less ▲]

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See detailControlled DCD donation is part of the solution to liver graft shortage, regardless of donor age
DETRY, Olivier ULg; MEURISSE, Nicolas ULg; DELWAIDE, Jean ULg et al

in Acta Gastro-Enterologica Belgica (2014, March), 77(1), 16

Aim: Results of donation after circulatory death (DCD) liver transplantation (LT) are impaired by ischemic bile duct lesions caused by procurement warm ischemia. Donor age is a risk factor in deceased ... [more ▼]

Aim: Results of donation after circulatory death (DCD) liver transplantation (LT) are impaired by ischemic bile duct lesions caused by procurement warm ischemia. Donor age is a risk factor in deceased donor LT, and particularly in DCD-LT. At the authors institute, age is not an absolute exclusion criterion to discard DCD liver grafts, controlled DCD donors receive comfort therapy before withdrawal, and cold ischemia is minimized. The aim of the present study was to report on the results of the first 10 years of this experience, and particularly on graft survival and the rate of post-transplant biliary complications, according to DCD donor age. 
 Methods: The authors retrospectively studied a consecutive series of 70 DCD-LT performed from 2003 to 2012, with at least one year of follow-up. This series was divided according to donor’s age, including 32 liver grafts from donors <55years, 20 between 56 and 69 years, and 18 from older donors >69 years. The three groups were compared in terms of donor and recipient demographics, procurement and transplantation conditions, peak laboratory values during the first post-transplant 72 hours, and results at one and four years. Median follow-up was 43 months. 
 Results: Overall graft survival was 98.5%, 91.4% and 69.5% at 1 month, 1 year and 4 years, respectively, without graft loss secondary to ischemic bile duct lesions. Cancer was the primary cause of graft loss and patient death. No difference other than age was noted between the three groups in donor and recipient characteristics, and in procurement conditions. There was no primary non-function but one patient needed re-transplantation for artery thrombosis. Biliary complications occurred similarly in the three groups. Graft and patient survival rates were not different at one and four years between the three groups. During the study period, there was an increasing liver procurement and transplantation activity, and in 2012, 30% of performed LT were DCD-LT, allowing a mean LT waiting time of 66 days. 
 Conclusions: This study shows comparable results between controlled DCD-LT from younger and older donors. Donor age >50 years should not be a contraindication to DCD-LT if other donor risk factors (such as warm and cold ischemia time) are minimized. DCD-LT with short cold ischemia may provide a significant source of liver grafts, decreasing waiting time. [less ▲]

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See detailShergottites: Partial Melts of a Depleted Martian Mantle
Médard, Etienne; Collinet, Max ULg

Poster (2014, March)

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See detailPourquoi tant de richesse? Dossier Reliques & reliquaires
George, Philippe ULg

in Arts Sacrés (2014), 28

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See detailReliability and validity of the Quality of Life Systemic Inventory for Children (QLSI-C): Preliminary result of a modular assessment tool of quality of life using e-Health technologies
Toucheque, Malorie ULg; Etienne, Anne-Marie ULg

Poster (2014, March)

Objective: Use of generic versus specific tools in psychological assessment is a controversial issue. Generic instruments can be used to measure QOL for numerous chronic illnesses; however, they may not ... [more ▼]

Objective: Use of generic versus specific tools in psychological assessment is a controversial issue. Generic instruments can be used to measure QOL for numerous chronic illnesses; however, they may not be sensitive to particular aspects of the disease. Unfortunately, disease-specific measures cannot be used to compare results across diseases or conditions. The QLSI-C is an assessment tool that uses a modular approach developed to overcome these shortcomings. QLSI-C was devised as a generic scale to be integrated with disease specific modules. The purpose of this study is to report on reliability and validity of the QLSI-C generic scale and the cystic fibrosis (CF)-specific module. Methods: QLSI-C was administered to 20 children with CF and 20 healthy children (ages 8-12 years) in Belgium. Internal consistency was assessed using Cronbach’s coefficient. Validity of the QLSI-C was measured using the known-groups method, i.e., analysis of variance (ANOVA) to distinguish between healthy children and children with CF. To examine the validity of the QLSI-C, correlations were calculated between the generic scale and CF-specific module. Results: Internal consistency for the QLSI-C generic scale with the CF-specific module was good ( =.82). ANOVA results revealed a significant difference between CF and healthy children for the QOL score (p=.005), with higher average scores (i.e., lower QoL) for CF children (M=4.35) than healthy children (M=1.25). Correlations between QoL scores on the generic scale and CF-specific module demonstrated medium effect size (r=0.47; p=.04). Conclusions: To date, three specific modules are available for the QLSI-C: (1) cancer; (2) asthma; (3) cystic fibrosis. Originality of this tool is strengthened by use of e-Health technologies (i.e., iPad app for administering the QLSI-C). Satisfactory psychometric properties and state-of-the-art use of technology suggests that the QLSI-C has potential utility for use in clinical trials, research, and clinical practice. [less ▲]

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See detailAssessment using e-Health technologies in pediatric psychology: Developing an App on iPad for the Quality of Life Systemic Inventory for Children (QLSI-C)
Toucheque, Malorie ULg; Tilkin, Caroline; Dupuis, Gilles et al

Poster (2014, March)

Objective:Integration of e-Health technologies for purposes of both assessment and intervention has recently become an interest area in pediatric psychology. The purpose of this study is to present ... [more ▼]

Objective:Integration of e-Health technologies for purposes of both assessment and intervention has recently become an interest area in pediatric psychology. The purpose of this study is to present psychometric characteristics of a technology-based (i.e., iPad administration) approach for measuring quality of life (QoL) in children. Methods: Sample consisted of 80 children (8-12 years) recruited from elementary schools in Belgium. They completed the Quality of Life Systemic Inventory for Children (QLSI-C) twice over a two-week delay, in a crossover design that used paper and iPad-based modes of administration. QLSI-C takes a unique approach to assessing QoL relative to existing measures. Specifically, it considers QoL to be the difference (gap score) between the present situation (state score) and the child’s expectations (goal), weighted by the importance (rank) assigned for each life domain. Cronbach’s coefficient was computed to assess internal consistency for each of the four global scores (State, Goal, Gap, Rank). ANOVA was used to assess the equivalence of the new iPad and paper formats. Test-retest reliability was assessed using correlational analysis. Results: Alpha coefficients for the global scores were as follows: State (.87), Goal (.94), Gap (.72), and Rank (.79). ANOVA results indicate that main effects for group (p = 0.75) and time (p= 0.31) were not statistically significant, nor was the interaction effect (p = 0.86) for the QoL score (Gap). Correlations for the test-retest reliability of the 4 global scores ranged from .66 to .90. Conclusions: The iPad format of QLSI-C appears valid in comparison to the original paper format and test-retest stability for the iPad format is good. This technology approach to assessment is more attractive for children, decreases time for administration, and enhances the ease of scoring. Thus, these advantages might encourage both clinicians and researchers to consider using e-Health developments in assessment in pediatric psychology. [less ▲]

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See detailQui est Georges Simenon?
Demoulin, Laurent ULg

in Baradel, Anne (Ed.) Simenon. Reporter-photographe. 1931-1935. De la Belgique à la Turquie (2014)

Présentation générale de la vie et de la carrière littéraire de Georges Simenon.

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See detailCulture astro : vous avez une bonne note
Nazé, Yaël ULg

Article for general public (2014)

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See detailA learning procedure for sampling semantically different valid expressions
St-Pierre, David Lupien; Maes, Francis; Ernst, Damien ULg et al

in International Journal of Artificial Intelligence (2014), 12(1), 18-35

A large number of problems can be formalized as finding the best symbolic expression to maximize a given numerical objective. Most approaches to approximately solve such problems rely on random ... [more ▼]

A large number of problems can be formalized as finding the best symbolic expression to maximize a given numerical objective. Most approaches to approximately solve such problems rely on random exploration of the search space. This paper focuses on how this random exploration should be performed to take into account expressions redundancy and invalid expressions. We propose a learning algorithm that, given the set of available constants, variables and operators and given the target finite number of trials, computes a probability distribution to maximize the expected number of semantically different, valid, generated expressions. We illustrate the use of our approach on both medium-scale and large-scale expression spaces, and empirically show that such optimized distributions significantly outperform the uniform distribution in terms of the diversity of generated expressions. We further test the method in combination with the recently proposed nested Monte-Carlo algorithm on a set of benchmark symbolic regression problems and demonstrate its interest in terms of reduction of the number of required calls to the objective function. [less ▲]

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See detailSubspace and maximum likelihood identification of nonlinear mechanical systems
Noël, Jean-Philippe ULg; Schoukens, Johan; Kerschen, Gaëtan ULg

Conference (2014, March)

The present work focuses on a recent nonlinear generalisation of the existing (linear) frequency-domain, discrete-time subspace methods applicable to mechanical systems. The proposed estimator, termed ... [more ▼]

The present work focuses on a recent nonlinear generalisation of the existing (linear) frequency-domain, discrete-time subspace methods applicable to mechanical systems. The proposed estimator, termed FNSI method, is interesting because it benefits from the numerical robustness and efficacy of subspace algorithms, while maintaining an acceptable computational burden. However, it derives estimates of the model parameters, namely the modal properties of the underlying linear system and the coefficients of the nonlinearities, based on deterministic arguments and one has thus no guarantee that the estimates still behave well in the presence of disturbing noise. A possible alternative is to embed the identification problem in a stochastic framework through the minimisation of a well-chosen cost function incorporating noise information. In particular, the maximum likelihood cost function is attractive because it yields estimates of the model parameters with optimal stochastic properties, and simplifies to a weighted least-squares expression in the frequency domain. However, the maximum likelihood suffers from issues typically encountered in optimisation problems, especially related to initialisation. The contribution of this work lies in the utilisation of the model parameter estimates provided by the FNSI method to serve as starting values for the minimisation of the maximum likelihood cost function. This initialisation strategy possesses the important advantage that the FNSI method generates a fully nonlinear model of the system under test, while classical approaches commonly use a linear model of the nonlinear system as starting point. This ensures that the resulting maximum likelihood model performs at least as good as the nonlinear subspace model. The complete methodology is demonstrated using experimental data measured on the Silverbox benchmark, an electronic circuit emulating the behaviour of a mechanical system with cubic nonlinearity. [less ▲]

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See detailEpidemiological tools for effective surveillance of porcine cysticercosis in Africa
Goussanou, J.S.E; Kpodekon, M.T.; Youssao, A.K.I. et al

in Veterinary World (2014), 7(3), 125-134

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See detailTGF-B induced protein IG-H3 is essential for the growth of human liver metastases
Castronovo, Vincenzo ULg; Blomme, Arnaud; Delvenne, Philippe ULg et al

in Acta Gastro-Enterologica Belgica (2014, March), 77(1), 05

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