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See detailThe Vacuum UV Photoabsorption Spectroscopy of the Three membered Ring Systems C3H6, C2H4O and C2H4S and their open Chain Isomers.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

Book published by Berliner Elektronen Speicherring für Elektronen Synchrotron Strahlung m.b.H - on CD-ROM (2004)

The vacuum UV photoabsorption spectrum of C3H6, C2H4O and C2H4S have been measured using synchrotron radiation and are reported.

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See detailDevelopments in finite element simulations of continuous casting
Castagne, Sylvie; Pascon, Frédéric ULg; Blès, Guilhem et al

in Journal de Physique IV (2004), 120

Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which ... [more ▼]

Two complementary approaches of steel continuous casting modelling using the finite element code LAGAMINE have been developed in the M&S Department. We propose here a description of the context in which the study started, then a description of both macroscopic and mesoscopic approaches. The first one describes the whole continuous casting process, from the free surface in the mould and through the entire machine, including thermal and mechanical behaviour of the steel. The second approach focuses on the prediction of cracks and is developed at the grain scale. Some results are also presented for both models. [less ▲]

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See detailContributions aux algorithmes d'intégration temporelle conservant l'énergie en dynamique non-linéaire des structures
Noels, Ludovic ULg

Doctoral thesis (2004)

Les points fondamentaux de mes recherches consistent en une étude mathématique des algorithmes d'intégration temporelle d'une discrétisation de type éléments-finis. Les algorithmes traditionnels d ... [more ▼]

Les points fondamentaux de mes recherches consistent en une étude mathématique des algorithmes d'intégration temporelle d'une discrétisation de type éléments-finis. Les algorithmes traditionnels d'intégration temporelle (Newmark, famille alpha-généralisée, ...) peuvent introduire numériquement de l'énergie dans les systèmes non-linéaires. De nouveaux algorithmes sont dès lors apparus pour permettre d'éviter cette perte de stabilité. Lors de mes études, ces algorithmes ont été étendus, de manière originale, au traitement de la plasticité à l'aide d'un modèle de type hypo-élastique. Ils ont également été étendus au traitement généralisé, dans le cadre tridimensionnel, de l'interaction de contact. Ensuite la mise en oeuvre d'une méthode permettant de combiner, au cours du temps un algorithme implicite stable, avec un algorithme explicite traditionnel a été envisagée. La stabilité du passage d'une méthode explicite vers une méthode implicite a été démontrée par nos soins. Une définition originale de critères automatiques de choix de basculement entre les méthodes a été proposée. Des exemples numériques complexes ont mis en évidences les bonnes performances des algorithmes développés, tant du point de vue de la précision des résultats - confrontés aux résultats expérimentaux si ces derniers existent -, que du point de vue de la réduction des coûts de calcul lorsque la méthode combinée est utilisée. [less ▲]

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See detailAnisotropic elasto-plastic finite element analysis using a stress-strain interpolation method based on a polycrystalline model
Habraken, Anne ULg; Duchene, Laurent ULg

in International Journal of Plasticity (2004), 20(Issue 8-9), 1525-1560

This paper describes a stress–strain interpolation method to model the macroscopic anisotropic elasto-plastic behavior of polycrystalline materials. Accurate analytical descriptions of yield loci derived ... [more ▼]

This paper describes a stress–strain interpolation method to model the macroscopic anisotropic elasto-plastic behavior of polycrystalline materials. Accurate analytical descriptions of yield loci derived from crystallographic texture [Int. J. Plasticity 19 (2003) 647; J. Phys. IV France 105 (2003) 39] are an interesting alternative to finite element models, where the macroscopic stress is provided by an averaging of microscopic stresses computed on a set of representative crystallites [Acta Metal 22 (1985) 923; Int. J. Plasticity 5 (1989) 67]. The parameters of the analytical functions modeling the yield locus are identified by comparison with a high number of stress tensors computed, for instance, by the well-known Taylor model [J. Inst. Metal 62 (1938) 307]. This identification method depends on the crystallographic texture and should be applied each time that the plastic strain has induced a significant texture evolution. The stress–strain interpolation method accurately describes the anisotropic material behavior in a narrow stress direction defined by only five stress points. The cost of texture updating is then greatly reduced compared to a full analytical function of the yield locus. After the mathematical description of the stress–strain interpolation method, its validity is demonstrated on two non-radial strain paths. The simulations of a deep drawing experiment allow comparing model predictions and measurements. Accuracy and CPU time of the interpolation stress–strain method are judged against two other models, respectively based on a complete analytical yield locus and on the averaging of crystallite stresses. [less ▲]

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See detailPrediction of distortion during cooling of steel rolled rings using thermal-mechanical-metallurgical finite element model
Pascon, Frédéric ULg; Blès, Guilhem; Bouffioux, Chantal ULg et al

in Steel Grips 2 (2004), Supplement Metal Forming 1-3

This work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and ... [more ▼]

This work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and dimension measurement devices. The final goal of the project is to develop and set up a system, integrated in the industrial process, capable of predicting the geometrical characteristics of final pieces just after the ring rolling stage and to allow the rolling process to avoid dimensional defects through online adaption. In fact, ring rolling production does not imply only the rolling process, but also the cooling and quench stages of steel rings. During all these phases, the dimensions of the pieces change dramatically. In particular, due to the lack of symmetry in the cooling conditions, ring distortions include contraction and rotation of the ring section. The modeling of the cooling phase requires taking into account a large number of phenomena resulting from the coupling of thermal, mechanical and metallurgical effects. A numerical model has been implemented in the non-linear finite element code LAGAMINE, developed by the University of Liège. Such a model can help to better understand the evolution of the geometry during the cooling phase and also the effects of each physical and microstructural parameter implemented in the model on the ring final shape. Effectively, several parameters can affect the ring distortions and the model should take them into account; in particular, the mechanical and thermal behavior of each phase present in the material (metastable austenite, ferrite, pearlite, bainite and martensite). Phase transformation modeling implies the integration of a wide data base of material properties (thermo-physical and mechanical properties of the phases, TTT and CCT diagrams, enthalpy and strain of phase transformation, strain of transformation plasticity…) but only a few of these data are available in literature. Some of them have been found for the reference material (42CrMo4 steel), but additional laboratory experiments have been performed at the Universities of Padua and Liège in order to characterize thermal, mechanical and plastic behaviour of phases. Finally, this paper presents the model validation on an industrial case (measurements of temperature and dimensions of rings have been provided by the manufacturer). Then, some applications are presented, demonstrating the importance of some factors such as some material properties, the shape of the rings, the type of cooling (and the cooling rate) or the symmetry of the cooling scheme on final ring distortion. [less ▲]

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See detailSuspension de l’exigibilité de créances de l’Etat : l’incidence d’un fédéralisme centrifuge sur le principe d’égalité
Rosoux, Géraldine ULg

in Revue de Jurisprudence de Liège, Mons et Bruxelles (2004)

The article analyzes a mechanism of compensation of State debts, and examines the question of the protection of fundamental rights such as equality in the Belgian federal State.

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See detailDeux chansons wallonnes sur la translation des reliques de sainte Alénie à Liège en 1843
Droixhe, Daniel ULg

in Bulletin de la Société Royale Le Vieux-Liège (2004), XIV(304), 502-508

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See detailBeaux vieux mots de Braine-le-Comte (Belgique)
Droixhe, Daniel ULg

in Linguistique picarde (2004), 44(170), 1-13

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See detailDesign of a versatile device for measuring whole plant gas exchanges in Arabidopsis thaliana
Tocquin, Pierre ULg; Périlleux, Claire ULg

in New Phytologist (2004), 162(1), 223-229

Because of its small size and rosette growth habit, measuring gas exchanges in Arabidopsis thaliana is difficult with standard leaf cuvettes. Here, we designed a versatile system that is usable at the ... [more ▼]

Because of its small size and rosette growth habit, measuring gas exchanges in Arabidopsis thaliana is difficult with standard leaf cuvettes. Here, we designed a versatile system that is usable at the whole rosette level, as small as possible for fast and accurate measurements, but adaptable to plant size, and suitable for in situ measurements whatever the growing substrate of the plant. This cuvette is in two parts: the basic unit, which contains the sensors and is connected to the infra-red gas analyzer, and the clear chamber, where the rosette is enclosed. We made a set of three interchangeable chambers of different sizes to measure the rate of CO2 assimilation [A] of 26-, 33- and 40-d-old plants. The dependence of A to light irradiance and to intercellular CO2 concentration was recorded as typical response curves, which validate our device. Measurements were not only consistent in saturating conditions, but accurate CO2 exchange measurements in limiting conditions also reflected important physiological features related to plant ageing. [less ▲]

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See detailImpact of low frequency transcranial magnetic stimulation on event-related brain potentials.
Hansenne, Michel ULg; Laloyaux, Olivier ULg; Mardaga, Solange et al

in Biological Psychology (2004), 67(3), 331-41

Contradictory findings exist concerning the inhibitory function of low frequency repetitive transcranial magnetic stimulation (rTMS). Therefore, the study examines the impact of different duration of low ... [more ▼]

Contradictory findings exist concerning the inhibitory function of low frequency repetitive transcranial magnetic stimulation (rTMS). Therefore, the study examines the impact of different duration of low frequency rTMS on ERPs. In 17 subjects, auditory ERPs were measured before and after 1 Hz rTMS delivered over the left prefrontal cortex during 10 min (600 pulses) and 15 min (900 pulses). Results showed that 15 min of 1 Hz rTMS induced a significant increase of P300 latency. There was no effect for early ERP components (N100, P200 and N200). This study confirms and extends that 1 Hz rTMS produces a real inhibitory effect only when the duration of the stimulation is about 15 min. The data suggest that rTMS modifies the speed of cognitive processing rather than the energetical aspect of information processing, and that cortical inhibition induced by the magnetic stimulation affects principally the controlled cognitive processes and not the automatic ones. [less ▲]

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See detailPersonality profile and drug of choice; a multivariate analysis using Cloninger's TCI on heroin addicts, alcoholics, and a random population group.
Le Bon, O.; Basiaux, P.; Streel, E. et al

in Drug and Alcohol Dependence (2004), 73(2), 175-82

As personality may predispose, precipitate or perpetuate substance abuse and/or dependence, and as it is considered to remain stable across the years in a given subject, potential links with the drug of ... [more ▼]

As personality may predispose, precipitate or perpetuate substance abuse and/or dependence, and as it is considered to remain stable across the years in a given subject, potential links with the drug of choice may help screen future patients before drug consumption. The present study compared three groups: 42 patients with heroin dependence (mean age: 31.2; standard deviation (SD): 5.5; 10 females), 37 patients with alcohol dependence (mean age 44.2; SD: 9.1; 9 females) and 83 subjects from a random population sample (mean age: 38.8; SD: 6.9; 20 females). Personality was measured by Cloninger's Temperament and Character Inventory (TCI). Pillai's MANCOVA with age as a covariate and gender as a cofactor was highly significant. Univariate ANOVA analyses using TCI dimensions as dependent variable showed most variables to vary in parallel for the two patient groups in comparison with controls. Post-hoc tests showed heroin patients to score higher in Novelty-Seeking and Self-Directedness than alcohol patients. Sub-dimensions Exploratory Excitability, Fear of the Uncertain, Responsibility, Congruent Second Nature and Transpersonal Identification were also significantly different in the two patient samples. Logistic regression showed Exploratory Excitability to segregate up to 76% of heroin patients from alcohol patients. In conclusion, personality profiles were linked to some preferential choice of drug and personality screening might be tested in preventive strategies. [less ▲]

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See detailGas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt and Thames)
Borges, Alberto ULg; Delille, Bruno ULg; Schiettecatte, Laure-Sophie et al

in Limnology & Oceanography (2004), 49(5), 1630-1641

We measured the flux of CO2 across the air–water interface using the floating chamber method in three European estuaries with contrasting physical characteristics (Randers Fjord, Scheldt, and Thames). We ... [more ▼]

We measured the flux of CO2 across the air–water interface using the floating chamber method in three European estuaries with contrasting physical characteristics (Randers Fjord, Scheldt, and Thames). We computed the gas transfer velocity of CO2 (k) from the CO2 flux and concomitant measurements of the air–water gradient of the partial pressure of CO2 (pCO2). There was a significant linear relationship between k and wind speed for each of the three estuaries. The differences of the y-intercept and the slope between the three sites are related to differences in the contribution of tidal currents to water turbulence at the interface and fetch limitation. The contribution to k from turbulence generated by tidal currents is negligible in microtidal estuaries such as Randers Fjord but is substantial, at low to moderate wind speeds, in macrotidal estuaries such as the Scheldt and the Thames. Our results clearly show that in estuaries a simple parameterization of k as a function of wind speed is site specific and strongly suggest that the y-intercept of the linear relationship is mostly influenced by the contribution of tidal currents, whereas the slope is influenced by fetch limitation. This implies that substantial errors in flux computations are incurred if generic relationships of the gas transfer velocity as a function of wind speed are employed in estuarine environments for the purpose of biogas air–water flux budgets and ecosystem metabolic studies. [less ▲]

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See detailVariability of the gas transfer velocity of CO2 in a macrotidal estuary (The Scheldt)
Borges, Alberto ULg; Vandenborght, Jean-Pierre; Schiettecatte, Laure-Sophie et al

in Estuaries (2004), 27(4), 593-603

We report a large set of 295 interfacial carbon dioxide (CO2) flux measurements obtained in the Scheldt estuary in November 2002 and April 2003, using the floating chamber method. From concomitant ... [more ▼]

We report a large set of 295 interfacial carbon dioxide (CO2) flux measurements obtained in the Scheldt estuary in November 2002 and April 2003, using the floating chamber method. From concomitant measurements of the air-water CO2 gradient, we computed the gas transfer velocity of CO2. The gas transfer velocity is well correlated to wind speed and a simple linear regression function gives the most consistent fit to the data. Based on water current measurements, we estimated the contribution of water current induced turbulence to the gas transfer velocity, using the conceptual relationship of O’Connor and Dobbins (1958). This allowed us to construct an empirical relationship to compute the gas transfer velocity of CO2 that accounts for the contribution of wind and water current. Based on this relationship, the spatial and temporal variability of the gas transfer velocity in the Scheldt estuary was investigated.Water currents contribute significantly to the gas transfer velocity, but the spatial and temporal variability (from daily to seasonal scales) is mainly related to wind speed variability. [less ▲]

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See detailCarbon dynamics and CO2 air-sea exchanges in the eutrophicated coastal waters of the Southern Bight of the North Sea: a modelling study
Gypens, N.; Lancelot, Christiane; Borges, Alberto ULg

in Biogeosciences (2004), 1(2), 147-157

A description of the carbonate system has been incorporated in the MIRO biogeochemical model to investigate the contribution of diatom and Phaeocystis blooms to the seasonal dynamics of air-sea CO2 ... [more ▼]

A description of the carbonate system has been incorporated in the MIRO biogeochemical model to investigate the contribution of diatom and Phaeocystis blooms to the seasonal dynamics of air-sea CO2 exchanges in the Eastern Channel and Southern Bight of the North Sea, with focus on the eutrophied Belgian coastal waters. For this application, the model was implemented in a simplified three-box representation of the hydrodynamics with the open ocean boundary box ‘Western English Channel’ (WCH) and the ‘French Coastal Zone’ (FCZ) and ‘Belgian Coastal Zone’ (BCZ) boxes receiving carbon and nutrients from the rivers Seine and Scheldt, respectively. Results were obtained by running the model for the 1996–1999 period. The simulated partial pressures of CO2 (pCO2) were successfully compared with data recorded over the same period in the central BCZ at station 330 (51 26.050 N; 002 48.500 E). Budget calculations based on model simulations of carbon flow rates indicated for BCZ a low annual sink of atmospheric CO2 (−0.17 mol C m−2 y−1). On the opposite, surface water pCO2 in WCH was estimated to be at annual equilibrium with respect to atmospheric CO2. The relative contribution of biological, chemical and physical processes to the modelled seasonal variability of pCO2 in BCZ was further explored by running model scenarios with separate closures of biological activities and/or river inputs of carbon. The suppression of biological processes reversed direction of the CO2 flux in BCZ that became, on an annual scale, a significant source for atmospheric CO2 (+0.53mol C m−2 y−1). Overall biological activity had a stronger influence on the modelled seasonal cycle of pCO2 than temperature. Especially Phaeocystis colonies which growth in spring were associated with an important sink of atmospheric CO2 that counteracted the temperature-driven increase of pCO2 at this period of the year. However, river inputs of organic and inorganic carbon were shown to increase the surface water pCO2 and hence the emission of CO2 to the atmosphere. Same calculations conducted in WCH, showed that temperature was the main factor controlling the seasonal pCO2 cycle in these open ocean waters. The effect of interannual variations of fresh water discharge (and related nutrient and carbon inputs), temperature and wind speed was further explored by running scenarios with forcing typical of two contrasted years (1996 and 1999). Based on these simulations, the model predicts significant variations in the intensity and direction of the annual air-sea CO2 flux. [less ▲]

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See detailLes "bêtes à Bon-Dieu", un bestiaire au croisement des imaginaires hagiographique et carnavalesque
Donneau, Olivier ULg

in Révelard, Michel; Grimaldi, Piercarlo; Kostadinova, Guergana (Eds.) Bêtes, saints, divinités, Masques et animaux dans la tradition européenne (2004)

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See detailNestin-positive mesenchymal stem cells favour the astroglial lineage in neural progenitors and stem cells by releasing active BMP4.
Wislet-Gendebien, Sabine ULg; Bruyere, Françoise ULg; Hans, Grégory ULg et al

in BMC Neuroscience (2004), 5

BACKGROUND: Spontaneous repair is limited after CNS injury or degeneration because neurogenesis and axonal regrowth rarely occur in the adult brain. As a result, cell transplantation has raised much ... [more ▼]

BACKGROUND: Spontaneous repair is limited after CNS injury or degeneration because neurogenesis and axonal regrowth rarely occur in the adult brain. As a result, cell transplantation has raised much interest as potential treatment for patients with CNS lesions. Several types of cells have been considered as candidates for such cell transplantation and replacement therapies. Foetal brain tissue has already been shown to have significant effects in patients with Parkinson's disease. Clinical use of the foetal brain tissue is, however, limited by ethical and technical problems as it requires high numbers of grafted foetal cells and immunosuppression. Alternatively, several reports suggested that mesenchymal stem cells, isolated from adult bone marrow, are multipotent cells and could be used in autograft approach for replacement therapies. RESULTS: In this study, we addressed the question of the possible influence of mesenchymal stem cells on neural stem cell fate. We have previously reported that adult rat mesenchymal stem cells are able to express nestin in defined culture conditions (in the absence of serum and after 25 cell population doublings) and we report here that nestin-positive (but not nestin-negative) mesenchymal stem cells are able to favour the astroglial lineage in neural progenitors and stem cells cultivated from embryonic striatum. The increase of the number of GFAP-positive cells is associated with a significant decrease of the number of Tuj1- and O4-positive cells. Using quantitative RT-PCR, we demonstrate that mesenchymal stem cells express LIF, CNTF, BMP2 and BMP4 mRNAs, four cytokines known to play a role in astroglial fate decision. In this model, BMP4 is responsible for the astroglial stimulation and oligodendroglial inhibition, as 1) this cytokine is present in a biologically-active form only in nestin-positive mesenchymal stem cells conditioned medium and 2) anti-BMP4 antibodies inhibit the nestin-positive mesenchymal stem cells conditioned medium inducing effect on astrogliogenesis. CONCLUSIONS: When thinking carefully about mesenchymal stem cells as candidates for cellular therapy in neurological diseases, their effects on resident neural cell fate have to be considered. [less ▲]

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See detailHadron spin-flip amplitude: an analysis of the new A(N) data from RHIC
Cudell, Jean-René ULg; Selyugin, Oleg Viktorovich

in Czechoslovak Journal of Physics (2004), 54(Suppl. B), 161-166

Through a direct analysis of the scattering amplitude, we show that the preliminary measurement of AN obtained by the E950 Collaboration at different energies leads to the large slope of the scattering ... [more ▼]

Through a direct analysis of the scattering amplitude, we show that the preliminary measurement of AN obtained by the E950 Collaboration at different energies leads to the large slope of the scattering amplitude and are mainly sensitive to the chosen of the energy behavior of the p(s,t). [less ▲]

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See detailAnalyse d'un dispositif innovant d'ingénierie docimologique permettant aux étudiants d'obtenir des feedbacks individualisés et diagnostiques via le web après une épreuve standardisée en amphithéâtre
Gilles, Jean-Luc ULg

in Arzola Medina, Sergio (Ed.) XIV congreso mundial de ciencias de la educacion : educatores para una nueva cultura (2004)

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See detailUtilisation du cycle SMART de gestion qualité des évaluations standardisées dans le contexte d'une Haute Ecole: regard critique en termes de validité, fidélité, sensibilité des mesures, diagnosticité, praticabilité, équité et communicabilité
Gilles, Jean-Luc ULg; Lovinfosse, Vinciane

in Arzola Medina, Sergio (Ed.) XIV congreso mundial de ciencias de la educacion : educatores para una nueva cultura (2004)

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See detailGérer la qualité des évaluations des acquis des grands groupes d'étudiants à l'aide d'un Système Méthodologique d'Aide à la Réalisation de Tests (SMART)
Gilles, Jean-Luc ULg

in Arzola Medina, Sergio (Ed.) XIV congreso mundial de ciencias de la educacion : educatores para una nueva cultura (2004)

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