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See detailHow to Statistically Show the Absence of an Effect
Quertemont, Etienne ULg

in Psychologica Belgica (2011), 51(2), 109-127

In experimental studies, the lack of statistical significance is often interpreted as the absence of an effect. Unfortunately, such a conclusion is often a serious misinterpretation. Indeed, non ... [more ▼]

In experimental studies, the lack of statistical significance is often interpreted as the absence of an effect. Unfortunately, such a conclusion is often a serious misinterpretation. Indeed, non-significant results are just as often the consequence of an insufficient statistical power. In order to conclude beyond reasonable doubt that there is no meaningful effect at the population level, it is necessary to use proper statistical techniques. The present article reviews three different approaches that can be used to show the absence of a meaningful effect, namely the statistical power test, the equivalence test, and the confidence interval approach. These three techniques are presented with easy to understand examples and equations are given for the case of the two-sample t-test, the paired-sample t-test, the linear regression coefficient and the correlation coefficient. Despite the popularity of the power test, we recommend using preferably the equivalence test or the confidence interval. [less ▲]

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See detailA test-length correction to the estimation of extreme proficiency levels
Magis, David ULg; Béland, Sébastien; Raîche, Gilles

in Applied Psychological Measurement (2011), 35

In this paper, the estimation of extremely large or extremely small proficiency levels, given the item parameters of a logistic item response model, is investigated. On the one hand, the estimation of ... [more ▼]

In this paper, the estimation of extremely large or extremely small proficiency levels, given the item parameters of a logistic item response model, is investigated. On the one hand, the estimation of proficiency levels by maximum likelihood (ML), despite being asymptotically unbiased, may yield infinite estimates. On the other hand, with an appropriate prior distribution, the Bayesian approach of maximum a posteriori (MAP) yields finite estimates, but it suffers from severe estimation bias at the extremes of the proficiency scale. In a first step, we propose a simple correction to the MAP estimator in order to reduce this estimation bias. The correction factor is determined through a simulation study and depends only on the length of the test. In a second step, some additional simulations highlight that the corrected estimator behaves like the ML estimator and outperforms the standard MAP method for extremely small or extremely large abilities. Although based on the Rasch model, the method could be adapted to other logistic item response models. [less ▲]

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See detailFinal results of a phase IIa, randomised, open-label trial to evaluate the percutaneous intramyocardial transplantation of autologous skeletal myoblasts in congestive heart failure patients: the SEISMIC trial.
Duckers, Henricus J.; Houtgraaf, Jaco; Hehrlein, Christoph et al

in EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology (2011), 6(7), 805-12

AIMS: The SEISMIC study was an open-label, prospective, randomised study to assess the safety and feasibility of percutaneous myoblast implantation in heart failure patients with implanted cardioverter ... [more ▼]

AIMS: The SEISMIC study was an open-label, prospective, randomised study to assess the safety and feasibility of percutaneous myoblast implantation in heart failure patients with implanted cardioverter-defibrillators (ICD). METHODS AND RESULTS: Patients were randomised 2:1 to autologous skeletal myoblast therapy vs. optimal medical treatment. The primary safety end-point was defined as the incidence of procedural and device related serious adverse events, whereas the efficacy endpoints were defined as the change in global LVEF by MUGA scan, change in NYHA classification of heart failure and in the distance achieved during a six-minute walk test (6MW) at 6-month follow-up. Forty subjects were randomised to the treatment arm (n=26), or to the control arm (n=14). There were 12 sustained arrhythmic events and one death after episodes of ventricular tachycardia (VT) in the treatment group and 14 events in the control group (P=ns). At 6-month follow-up, 6MW distance improved by 60.3+/-54.1?meters in the treated group as compared to no improvement in the control group (0.4+/-185.7?meters; P=ns). In the control group, 28.6% experienced worsening of heart failure status (4/14), while 14.3% experienced an improvement in NYHA classification (2/14). In the myoblast-treatment arm, one patient experienced a deterioration in NYHA classification (8.0%), whereas five patients improved one or two classes (20.0%; P=0.06). However, therapy did not improve global LVEF measured by MUGA at 6-month follow-up. CONCLUSIONS: These data indicate that implantation of myoblasts in patients with HF is feasible, appears to be safe and may provide symptomatic relief, though no significant effect was detected on global LVEF. [less ▲]

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See detailcompte rendu de : Philip Hardie, Lucretian Receptions. History, The Sublime, Knowledge
Rochette, Bruno ULg

in Phoenix (2011), 65(1-2), 176-179

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See detailAntibiotic resistance: lessons from the soil
Rigali, Sébastien ULg

Scientific conference (2011)

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See detailAcetylation-dependent regulation of endothelial Notch signalling by the SIRT1 deacetylase.
Guarani, Virginia; Deflorian, Gianluca; Franco, Claudio A et al

in Nature (2011), 473(7346), 234-8

Notch signalling is a key intercellular communication mechanism that is essential for cell specification and tissue patterning, and which coordinates critical steps of blood vessel growth. Although subtle ... [more ▼]

Notch signalling is a key intercellular communication mechanism that is essential for cell specification and tissue patterning, and which coordinates critical steps of blood vessel growth. Although subtle alterations in Notch activity suffice to elicit profound differences in endothelial behaviour and blood vessel formation, little is known about the regulation and adaptation of endothelial Notch responses. Here we report that the NAD(+)-dependent deacetylase SIRT1 acts as an intrinsic negative modulator of Notch signalling in endothelial cells. We show that acetylation of the Notch1 intracellular domain (NICD) on conserved lysines controls the amplitude and duration of Notch responses by altering NICD protein turnover. SIRT1 associates with NICD and functions as a NICD deacetylase, which opposes the acetylation-induced NICD stabilization. Consequently, endothelial cells lacking SIRT1 activity are sensitized to Notch signalling, resulting in impaired growth, sprout elongation and enhanced Notch target gene expression in response to DLL4 stimulation, thereby promoting a non-sprouting, stalk-cell-like phenotype. In vivo, inactivation of Sirt1 in zebrafish and mice causes reduced vascular branching and density as a consequence of enhanced Notch signalling. Our findings identify reversible acetylation of the NICD as a molecular mechanism to adapt the dynamics of Notch signalling, and indicate that SIRT1 acts as rheostat to fine-tune endothelial Notch responses. [less ▲]

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See detailSpatial aggregation of tropical trees at multiple spatial scales
Réjou-Méchain, Maxime; Flores, Olivier; Bourland, Nils ULg et al

in Journal of Ecology (2011), 99

1. In tropical forests, species distribution patterns may be strongly context-dependent owing to local stochasticity of recruitment and⁄ or to the specific history and environment of each site. Recent ... [more ▼]

1. In tropical forests, species distribution patterns may be strongly context-dependent owing to local stochasticity of recruitment and⁄ or to the specific history and environment of each site. Recent studies have reported, however, that the degree of spatial aggregation of tropical tree species is partly determined by some species traits irrespectively of site conditions, at least at a very local scale (<200 m). 2. Here, we used standardized large-scale forest inventories of five Central African tropical forests (9670 0.5-ha plots spread over 5550 km2) to quantify the spatial aggregation of 106 tropical tree species at larger spatial scales. For this purpose, we developed a new statistic to quantify the respective contributions of different spatial scales to the aggregation patterns, and we tested whether patterns were consistent across sites. We finally asked whether species characteristics related to dispersal ability, to response to disturbances and to biogeographical range could significantly explain aggregation patterns. 3. Although aggregation patterns varied substantially among sites within each species, they displayed inter-site consistencies (21–24%of the total variance explained by species identity) at the local scale (0.2–1 km) and at the mesoscale (1–10 km) but not at the landscape scale (>10 km). At the two former scales, upper taxonomical levels (family and⁄or order) significantly explained variation in the degree of species aggregation, while at the landscape scale, aggregation was entirely contingent on the site considered. Few species characteristics, except dispersal syndromes and wood density, were able to significantly explain aggregation patterns. 4. Synthesis. One of our most striking results is the high context dependence of species aggregation patterns, whatever the spatial scale considered. However, we showed that species distribution patterns can be predicted, to an extent, at spatial scales much larger than previously investigated in this context. Such patterns may be explained by traits displaying phylogenetic conservatism [less ▲]

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See detailCarbonate system in the water masses of the Southeast Atlantic sector of the Southern Ocean during February and March 2008
Gonzalez-Davila, M.; Santana-Casiano, J. M.; Fine, R. A. et al

in Biogeosciences (2011), 8

Carbonate system variables were measured in the South Atlantic sector of the Southern Ocean along a transect from South Africa to the southern limit of the Antarctic Circumpolar Current (ACC) from ... [more ▼]

Carbonate system variables were measured in the South Atlantic sector of the Southern Ocean along a transect from South Africa to the southern limit of the Antarctic Circumpolar Current (ACC) from February to March 2008. Eddies detached from the retroflection of the Agulhas Current increased the gradients observed along the fronts. Minima in the fugacity of CO2, fCO2, and maxima in pH on either side of the frontal zone were observed, noting that within the frontal zone fCO2 reached maximum values and pH was at a minimum. Vertical distributions of water masses were described by their carbonate system properties and their relationship to CFC concentrations. Upper Circumpolar Deep Water (UCDW) and Lower Circumpolar Deep Water (LCDW) offered pHT,25 values of 7.56 and 7.61, respectively. The UCDW also had higher concentrations of CFC-12 (>0.2 pmol kg−1) as compared to deeper waters, revealing that UCDW was mixed with recently ventilated waters. Calcite and aragonite saturation states (Ω) were also affected by the presence of these two water masses with high carbonate concentrations. The aragonite saturation horizon was observed at 1000 m in the subtropical area and north of the Subantarctic Front. At the position of the Polar Front, and under the influence of UCDW and LCDW, the aragonite saturation horizon deepened from 800 m to 1500 m at 50.37° S, and reached 700 m south of 57.5° S. High latitudes proved to be the most sensitive areas to predicted anthropogenic carbon increase. Buffer coefficients related to changes in [CO2], [H+] and Ω with changes in dissolved inorganic carbon (CT) and total alkalinity (AT) offered minima values in the Antarctic Intermediate Water and UCDW layers. These coefficients suggest that a small increase in CT will sharply decrease the status of pH and carbonate saturation. Here we present data that suggest that south of 55° S, surface water will be under-saturated with respect to aragonite within the next few decades. [less ▲]

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See detailNucleolar structure across evolution: the transition between bi- and tri-compartmentalized nucleoli lies within the class Reptilia.
Lamaye, Francoise; Galliot, Sonia; Alibardi, Lorenzo et al

in Journal of Structural Biology (2011), 174(2), 352-9

Two types of nucleolus can be distinguished among eukaryotic cells: a tri-compartmentalized nucleolus in amniotes and a bi-compartmentalized nucleolus in all the others. However, though the nucleolus ... [more ▼]

Two types of nucleolus can be distinguished among eukaryotic cells: a tri-compartmentalized nucleolus in amniotes and a bi-compartmentalized nucleolus in all the others. However, though the nucleolus' ultrastructure is well characterized in mammals and birds, it has been so far much less studied in reptiles. In this work, we examined the ultrastructural organization of the nucleolus in various tissues from different reptilian species (three turtles, three lizards, two crocodiles, and three snakes). Using cytochemical and immunocytological methods, we showed that in reptiles both types of nucleolus are present: a bi-compartmentalized nucleolus in turtles and a tri-compartmentalized nucleolus in the other species examined in this study. Furthermore, in a given species, the same type of nucleolus is present in all the tissues, however, the importance and the repartition of those nucleolar components could vary from one tissue to another. We also reveal that, contrary to the mammalian nucleolus, the reptilian fibrillar centers contain small clumps of condensed chromatin and that their surrounding dense fibrillar component is thicker. Finally, we also report that Cajal bodies are detected in reptiles. Altogether, we believe that these results have profound evolutionarily implications since they indicate that the point of transition between bipartite and tripartite nucleoli lies at the emergence of the amniotes within the class Reptilia. [less ▲]

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See detailHourglass chondrules
Warin, Roger; Hatert, Frédéric ULg; Kashuba, John

in Meteorite (2011), November 2010

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See detailAction des cultures protectrices : cas des germes lactiques sur la flore alimentaire indésirable.
Privat, Kouakou; Thonart, Philippe ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(2), 339-348

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See detailBelgian Report
Kohl, Benoît ULg; Imbrechts, L.; Mattei, P. et al

in Dutch Construction contracts: views from abroad (2011)

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See detailL’aide juridique de S. Boonen
Berthe, Aude ULg

in Revue de Jurisprudence de Liège, Mons et Bruxelles (2011)

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See detailRhoGDI alpha-dependent balance between RhoA and RhoC is a key regulator of cancer cell tumorigenesis
Ho, Thi Thanh Giang ULg; Stultiens, Audrey; Dubail, Johanne ULg et al

in Molecular Biology of the Cell (2011), 22(17), 3263-75

RhoGTPases are key signaling molecules regulating main cellular functions such as migration, proliferation, survival, and gene expression through interactions with various effectors. Within the RhoA ... [more ▼]

RhoGTPases are key signaling molecules regulating main cellular functions such as migration, proliferation, survival, and gene expression through interactions with various effectors. Within the RhoA-related subclass, RhoA and RhoC contribute to several steps of tumor growth, and the regulation of their expression affects cancer progression. Our aim is to investigate their respective contributions to the acquisition of an invasive phenotype by using models of reduced or forced expression. The silencing of RhoC, but not of RhoA, increased the expression of genes encoding tumor suppressors, such as nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1), and decreased migration and the anchorage-independent growth in vitro. In vivo, RhoC small interfering RNA (siRhoC) impaired tumor growth. Of interest, the simultaneous knockdown of RhoC and NAG-1 repressed most of the siRhoC-related effects, demonstrating the central role of NAG-1. In addition of being induced by RhoC silencing, NAG-1 was also largely up-regulated in cells overexpressing RhoA. The silencing of RhoGDP dissociation inhibitor alpha (RhoGDIalpha) and the overexpression of a RhoA mutant unable to bind RhoGDIalpha suggested that the effect of RhoC silencing is indirect and results from the up-regulation of the RhoA level through competition for RhoGDIalpha. This study demonstrates the dynamic balance inside the RhoGTPase network and illustrates its biological relevance in cancer progression. [less ▲]

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See detailCompétenes et transférabilité au sein d'une famille de situations
Chenu, Florent ULg

Scientific conference (2011)

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See detailNZEB Definitions: current market status and certification in Belgium
Mlecnik; Attia, Shady ULg

Report (2011)

The recast of the European Performance of Buildings Directive (EPBD) requires the uptake of a definition of so called ‘nearly zero energy’ buildings (nZEB). Belgium was first to set a definition for a ... [more ▼]

The recast of the European Performance of Buildings Directive (EPBD) requires the uptake of a definition of so called ‘nearly zero energy’ buildings (nZEB). Belgium was first to set a definition for a ‘net zero energy house’ (NZEB) in 2009. Every year the definition is revised for consistency with shortcomings and emerging issues. The Belgian definition raised many questions regarding (1) the net balance, (2) the application and calculation method (3) the indoor air quality and comfort, (4) energy use included in the balance, (5) the type of buildings, (6) the accepted renewable energy supply options, (7) the quality assurance and monitoring and (8) energy storage and the connection to the energy infrastructure. Therefore, the paper presents a review on the current Belgian definition and its market status in comparison with the international context. The aim of the paper is to review current definition discussions and pave the way to a more consistent definition. [less ▲]

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See detailMéthodologie des essais cliniques et Notion d'Evidence Based Medicine
Bruyère, Olivier ULg

Learning material (2011)

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See detailModélisation par changement d’échelle de l’endommagement et des évolutions de perméabilité dans l’argilite
Levasseur, Séverine ULg; Collin, Frédéric ULg; Charlier, Robert ULg et al

in 20ème Congrès Français de Mécanique (2011)

Le creusement d’excavations souterraines dans une roche est à l’origine de la formation d’une zone endommagée, où des microfissures se développent et perturbent fortement les propriétés de transport du ... [more ▼]

Le creusement d’excavations souterraines dans une roche est à l’origine de la formation d’une zone endommagée, où des microfissures se développent et perturbent fortement les propriétés de transport du matériau. L’objectif de cette étude est de représenter ces phénomènes hydromécaniques par une approche micromécanique d’endommagement, couplée aux évolutions de perméabilité, en présence de contraintes initiales, puis d’en discuter les avantages et les inconvénients sur la base d’une simulation du creusement d’un tunnel dans l’argile à Opalinus relatif à l’expérience SELFRAC. [less ▲]

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