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See detailLeaf carbohydrate status in Lolium temulentum during the induction of flowering
Périlleux, Claire ULg; Bernier, Georges ULg

in New Phytologist (1997), 135(1), 59-66

Unifoliated plants of Lolium temulentum L. ev. Ceres, a qualitative long-day grass, were induced to flower by one 24-h long day (LD) or by one 8-h short day (SD) advanced by 1 2 h in the normal regime, so ... [more ▼]

Unifoliated plants of Lolium temulentum L. ev. Ceres, a qualitative long-day grass, were induced to flower by one 24-h long day (LD) or by one 8-h short day (SD) advanced by 1 2 h in the normal regime, so-called 'displaced short day' (DSD). Standard light for SD and DSD was a mixture of fluorescence and incandescence at 400 µmol m2 s-1 whereas the extension period of the 24-h LD was solely incandescence at 10-15 µmol m2 s-1. The DSD system was first characterized by the timings of floral induction, stimulus translocation and apical development. Carbohydrates in the blade tissues and in leaf exudate were analysed comparatively in vegetative and induced plants. Fructans were not detected in the leaf tissues whereas sucrose and starch were found to be present in similar amounts. In SD, their contents exhibited a diurnal fluctuation and were not in large excess. The common change observed during the two inductive treatments was that starch remained at a high level during the LD extension, even though the lighting was unsuitable for photosynthesis, and increased transiently in DSD. Sucrose was the major sugar contained in the leaf exudate. Its content increased when flowering was induced, but not at the same time in the two systems. In LD, sucrose exudation rose when plants were returned to standard light after the inductive cycle, i.e. after the LD stimulus had left the leaf blade. By contrast, during the DSD, sucrose was transported at the same time as the floral stimulus. Results are discussed together with the methods used to time stimulus translocation and their implications. [less ▲]

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See detailThe leaf extract of Ribes nigrum L. is a potent stimulator of the endothelial formation of NO in cultured endothelial cells and porcine coronary artery rings
Tabart, Jessica; Schini-Kerth, Valérie; PINCEMAIL, Joël ULg et al

in Journal of Berry Research (2016), 6

BACKGROUND: Endothelial dysfunction is a major hallmark of most types of cardiovascular diseases. Numerous plant extracts have been shown to cause endothelium-dependent relaxations by increasing the ... [more ▼]

BACKGROUND: Endothelial dysfunction is a major hallmark of most types of cardiovascular diseases. Numerous plant extracts have been shown to cause endothelium-dependent relaxations by increasing the endothelial formation of the potent vasoprotective factor, nitric oxide (NO). OBJECTIVE: The ability of different Ribes nigrum L. extracts (Grossulariaceae) to induce endothelium-dependent relaxation by stimulating the endothelial formation of NO was assesssed. METHODS: Ribes nigrum extracts were prepared from buds, berries and leaves by extraction (Acetone:H2O:Acetic Acid; 70/28/2 (v/v/v)) and lyophilized after acetone evaporation. The ability of the extracts to stimulate the endothelial formation of NO was assessed using cultured endothelial cells and isolated porcine coronary artery rings. RESULTS: The Ribes nigrum leaf extract increased to a greater extent than the bud and the berry extracts the formation of NO, and up-regulated eNOS mRNA expression in cultured endothelial cells (the stimulatory effects amounted to 197 ± 9 %, 134 ± 6 % and 118 ± 5 %, respectively). The leaf extract induced greater relaxations of isolated coronary arteries with endothelium than the bud and the berry extracts whereas no such effects were observed in rings without endothelium. Relaxations to the leaf extract were minimally affected by indomethacin and by inhibitors of endothelium-dependent hyperpolarization response, and markedly reduced by NG-nitro-L-arginine. CONCLUSIONS: The present findings indicate that the Ribes nigrum leaf extract is a more potent inducer of the endothelial formation of NO than the bud and the berry extracts. [less ▲]

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See detailLeaf fall impact on diversity and trophic ecology of vagile macrofauna associated with exported P.oceanica litter
Remy, François ULg; Mascart, Thibaud ULg; Dauby, Patrick ULg et al

Poster (2012, August 20)

In the Mediterranean Sea, Posidonia oceanica meadows produce a huge amount of detritus, evaluated up to 300 to 2000 g dry wt m-2 yr-1. This litter is mainly composed of dead leaves but also of uprooted P ... [more ▼]

In the Mediterranean Sea, Posidonia oceanica meadows produce a huge amount of detritus, evaluated up to 300 to 2000 g dry wt m-2 yr-1. This litter is mainly composed of dead leaves but also of uprooted P.oceanica shoots and drift macro-algae from adjacent rocky bottoms. Although rich in refractory materials (lignin) and poor in P and N, these underwater accumulations of leaves are colonised by fungi, micro-algae (like diatoms), bacteria, but also by micro and macrofauna assemblages. These organisms could play an important role in leaf litter degradation and enrichment, but also in energy and carbon transfer from P.oceanica to higher trophic levels in adjacent coastal ecosystems. In this study we focus on the vagile macro-fauna (invertebrates with a size > 500µm) inhabiting the exported litter accumulations of the Calvi Bay (France). We took standardised samples at two different sites (a sheltered one and an exposed one) before and after leaf fall. We emphasised that crustaceans represent 65 – 85% of the biodiversity, followed by annelids and molluscs, representing respectively 10-20% and 10-15% of the diversity. That general pattern differs between sampling sites and we highlighted changes after leaf fall at both sites. In order to assess the impact of the autumn period litter input on the trophic structure of these invertebrates, we conducted gut contents observations and “bulk” stable isotope analysis. The isotopic compositions of C and N stable isotopes of the potential detritic food sources and of the most abundant invertebrate’s species were measured using EA-IRMS. We finally focused on the two most abundant Gammaridean Amphipoda species representing up to about 60% of the vagile macrofauna found in litter accumulations: Gammarella fucicola and Gammarus aequicauda. The results of their isotopic measurements were used in the “SIAR” Bayesian mixing model to calculate the potential contribution of their potential food sources. [less ▲]

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See detailLeaf morphology evolution in euphyllophytes of South China through the Late Palaeozoic inferred from numerical analyses
Huang, P.; Xue, J.; Benton, M. J. et al

in Cascales - Miñana, Borja; Villanueva-Amadoz, Uxue; Diez, José B. (Eds.) Proceedings of the II Agora Paleobotanica Meeting (Abstract book) (2013, July)

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See detailLEAFY expression and temporal sequence of floral transition in Sinapis alba L.
Bonhomme, Delphine ULg; Périlleux, Claire ULg

Poster (2005)

The shoot apical meristem (SAM) of Sinapis alba can be switched from vegetative to reproductive fate by exposure of 2-month old plants to a single long day (LD). Floral transition then occurs in good ... [more ▼]

The shoot apical meristem (SAM) of Sinapis alba can be switched from vegetative to reproductive fate by exposure of 2-month old plants to a single long day (LD). Floral transition then occurs in good synchrony within a population, and a number of biochemical, cellular, and morphological changes have been described. Our aim is to integrate gene expression patterns into this timing. We report here the analysis of SaLFY, orthologous to the floral meristem identity gene LEAFY of Arabidopsis. Materials and Methods: Plants of Sinapis were grown in 8-h shorts days for two months before being induced to flower by one 22-h LD. Shoot apices were harvested 24, 32, 40, 48, 56 and 80h after start of the LD, and prepared for in situ hybridization (Melzer et al., 1999). Results and Conclusions: As expected, the expression of SaLFY was very strong in flower primordia. More surprisingly, SaLFY was expressed well before the initiation of flowers. First, a strong signal was detected in the tip of young leaf primordia of vegetative plants. Secondly, SaLFY was transiently expressed in the SAM of induced plants, from 32h after the start of the LD, when cell proliferation increased. The signal formed, in transverse sections, a discontinuous ring with activation where last leaves were to be initiated. Interestingly, this activation in the SAM matched in time and space early growth changes previously described during the transition to flowering, namely an increase of leaf primordia growth and an acceleration of last leaf initiation (Bernier, 1997), suggesting that SaLFY may have dual functions in fate specification during the floral transition of the SAM. References: Bernier G 1997. J Exp Bot 48; 1071-1077. Melzer S, Kampmann G, Chandler J, Apel K 1999. Plant J 18; 395-405. [less ▲]

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See detailLeakage tests applied to the breadboards
Dardenne, Laurent; Ngendakumana, Philippe ULg

Report (2007)

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See detailThe leaky funnel model revisited
Mouchet, Anne ULg; Deleersnijder, Eric; Primeau, François

in Tellus : Series A (2012), 64

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See detailThe leaky funnel model, a metaphor of the ventilation of the World Ocean as simulated in an OGCM
Mouchet, Anne ULg; Deleersnijder, Eric

in Tellus : Series A (2008), 60(4), 761-774

It is seen that an idealized model may suggest an appropriate scaling of the water age in the World Ocean, which is a measure of the ventilation rate. We use a 1-D advection-diffusion model in which the ... [more ▼]

It is seen that an idealized model may suggest an appropriate scaling of the water age in the World Ocean, which is a measure of the ventilation rate. We use a 1-D advection-diffusion model in which the deep ocean is represented as a leaky funnel, allowing recirculation towards the surface. The analytical solutions to the steady-state problem are readily obtained. The three parameters of the leaky funnel model are estimated in such a way that the behaviour of the domain-averaged water age be as similar as possible to that derived from a 3-D model in a series of sensitivity runs. The agreement between both sets of mean ages is excellent, with a linear correlation coefficient very close to unity. A good agreement is also found for the age of radioactive tracers and the associated radioages. The parameters of the leaky funnel model have a clear physical meaning, that is, the order of magnitude of the horizontal velocity, the mean length of water parcel trajectories in the deep ocean, and a horizontal diffusivity scale. The values of all of them turn out to be consistent with our current knowledge of the World Ocean circulation. [less ▲]

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See detailLeaky-wave-induced disks around Be stars: a pulsational analysis on their formation
Godart, Mélanie ULg; Shibahashi, Hiromoto; Dupret, Marc-Antoine ULg et al

in New windows on massive stars: asteroseismology, interferometry, and spectropolarimetry, Proceedings of the International Astronomical Union, IAU Symposium, Volume 307 (2015, January 01)

Be stars are B-type stars near the main sequence which undergo episodic mass loss events detected by emission lines, whose line shape and intensity vary with a timescale of the order of decades ... [more ▼]

Be stars are B-type stars near the main sequence which undergo episodic mass loss events detected by emission lines, whose line shape and intensity vary with a timescale of the order of decades. Spectroscopic observations show a large rotation velocity such that one of the prevailing scenarios for the formation of the equatorial disk consists in an increasing equatorial rotation velocity to the break-up limit where gravity is challenged by the centrifugal force. We investigate here a new scenario recently suggested by Ishimatsu & Shibahashi (2013), in which the transport of angular momentum through the photosphere would be achieved by leaky waves, keeping the rotation velocity still below the break-up limit. [less ▲]

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See detailLearn-Nett : un dispositif d'apprentissage collaboratif à distance au service de la formation des enseignants. Communication présentée au séminaire de recherche 'Technologies de l'Information et de la Communication pour l'Education : instruments, dispositifs et usages, Paris, INRP
Denis, Brigitte ULg; Peeters, Robert ULg

Scientific conference (2002, March)

Présentation du dispositif d'apprentissage collaboratif Learn-Nett. Options épistémologiques, organisation, compétences visées chez les apprenants, méthodologie, tutorat.

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See detailLearn-Nett : une expérience d'apprentissage collaboratif à distance
Denis, Brigitte ULg; Peeters, Robert

in Actes du 1er congrès des chercheurs francophones en éducation (2000, May)

Présentation du dispositif d'apprentissage collaboratif (Learn-Nett).

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See detailLEARN-NETT : une expérience d'apprentissage collaboratif à distance
Charlier, Bernadette; Daele, Amaury; Docq, Françoise et al

in Le point sur la recherche en éducation en Communauté française : actes du 1er congrès des chercheurs en éducation, Bruxelles, 24-25 mai 2000 (1998)

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See detailLearned material content and acquisition level modulate cerebral reactivation during posttraining rapid-eye-movements sleep
Peigneux, Philippe ULg; Laureys, Steven ULg; Fuchs, Sonia et al

in NeuroImage (2003), 20(1), 125-134

We have previously shown that several brain areas are activated both during sequence learning at wake and during subsequent rapid-eye-movements (REM) sleep (Nat. Neurosci. 3 (2000) 831-836), suggesting ... [more ▼]

We have previously shown that several brain areas are activated both during sequence learning at wake and during subsequent rapid-eye-movements (REM) sleep (Nat. Neurosci. 3 (2000) 831-836), suggesting that REM sleep participates in the reprocessing of recent memory traces in humans. However, the nature of the reprocessed information remains open. Here, we show that regional cerebral reactivation during posttraining REM sleep is not merely related to the acquisition of basic visuomotor skills during prior practice of the serial reaction time task, but rather to the implicit acquisition of the probabilistic rules that defined stimulus sequences. Moreover, functional connections between the reactivated cuneus and the striatum-the latter being critical for implicit sequence learning-are reinforced during REM sleep after practice on a probabilistic rather than on a random sequence of stimuli. Our results therefore support the hypothesis that REM sleep is deeply involved in the reprocessing and optimization of the high-order information contained in the material to be learned. In addition, we show that the level of acquisition of probabilistic rules attained prior to sleep is correlated to the increase in regional cerebral blood flow during subsequent REM sleep. This suggests that posttraining cerebral reactivation is modulated by the strength of the memory traces developed during the learning episode. Our data provide the first experimental evidence for a link between behavioral performance and cerebral reactivation during REM sleep. (C) 2003 Elsevier Inc. All rights reserved. [less ▲]

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See detailLearner Support in the Formasup degree: variety as a key feature and close coaching to drive innovation
Poumay, Marianne ULg

in Supporting the Learner in Distance Education and E-Learning (2004)

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See detailLearning a Dictionary of Prototypical Grasp-predicting Parts from Grasping Experience
Detry, Renaud ULg; Ek, Carl Henrik; Madry, Marianna et al

in IEEE International Conference on Robotics and Automation (2013)

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See detailLearning a motor skill: Effects of blocked versus random practice. A review
Merbah, Sarah ULg; Meulemans, Thierry ULg

in Psychologica Belgica (2011), 51

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See detailLearning a motor skill: Effects of Blocked vs. Random Practice. A review
Merbah, Sarah ULg; Meulemans, Thierry ULg

in Psychologica Belgica (2011), 51(1), 15-48

Procedural learning refers to the ability to learn new perceptual, motor or cognitive skills. While many studies have explored procedural learning abilities in patients with different types of brain ... [more ▼]

Procedural learning refers to the ability to learn new perceptual, motor or cognitive skills. While many studies have explored procedural learning abilities in patients with different types of brain damage, the cognitive mechanisms involved in the acquisition of a new skill are still not well understood. The present review focuses on the conditions that optimize skill acquisition, and more specifically on the contextual interference effect (CIE), which refers to the advantage of a ‘random’ over a ‘blocked’ practice condition in skill learning tasks. According to both the ‘elaboration’ and ‘reconstruction’ hypotheses, the CIE can be explained by the fact that the random schedule requires more cognitive activity than the blocked one. However, if the CIE has been consistently demonstrated in laboratory studies, it is not so clear in fieldbased studies. We discuss this ‘laboratory and field dilemma’, and suggest that two main factors – task complexity and individual variables – may explain the discrepancy between the two types of studies. [less ▲]

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See detailLearning about domestic violence- gender violence and women victimization
Garcet, Serge ULg

Conference given outside the academic context (2004)

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