Foam-like evolution in polycrystalline systems following successive 'melt and growth' cycles

in Philosophical Magazine B-Physics of condensed matter statistical mechanics electronic optical and magnetic properties (1998), 78(4), 397-408

A stochastic model of multigrain growth which allows for successive melting-growth cycles is investigated on a square lattice. Two fundamental constraints are introduced: (i) the melted mass amplitude and ... [more ▼]

A stochastic model of multigrain growth which allows for successive melting-growth cycles is investigated on a square lattice. Two fundamental constraints are introduced: (i) the melted mass amplitude and (ii) the number of cycles guide the process. The evolution of the microstructure is found to be quite similar to foam systems, i.e. topological rearrangements are observed together with the increase of the-mean grain area. A drastic crossover between two types of growth regimes is found as a function of the amplitude of the melting-growth cycles. This allows one to envisage the existence of optimal conditions for polycrystal processing. [less ▲]

Participation et intérêt politiques de lycéens français, belges et québécois au début des années quatre-vingt-dix : Une analyse plurielle fondée sur la dynamique de construction des univers de référence

Doctoral thesis (1998)

Although certain recent theoretical developments insist more on the plurality of social and individual realities, the answers to empirical questions such as Are the young involved? or Are they interested ... [more ▼]

Although certain recent theoretical developments insist more on the plurality of social and individual realities, the answers to empirical questions such as Are the young involved? or Are they interested in politics? still too often fit in a univocal logic of comprehension where concepts used are thought to be homogeneous, as if they were “subsumptions”. This is why it is coherent to explain phenomena from a linear point of view which supposes a precise vision of the processes of construction of individual worlds of reference. Jean Piaget’s perspective of socialization reminds us that the individual is not a passive being in the dynamics of appropriation of the world, but that he assimilates the social context, accommodates it to what he already understands and, thus, transforms it. Consequently, this opens the way to a form of conceptual relativism, with a plural logic of comprehension where each reality, each concept cannot be defined without being replaced in the context of the singular worlds of reference. Thus, the theoretical consideration of the plural possibilities must also emerge from our interpretations. This research challenge is raised in this thesis by studying a series of profiles of dimensions, where each dimension can be replaced in a context which materializes a certain organization of realities. The complexity thus introduced into the analysis is synthesized by multivariate statistical methods (analysis of multiple correspondences and hierarchical ascending classification) which respect the initial organization of profiles. On the basis of data from an original inquiry among French, Belgian and Québécois high-school students, series of “clusters” of similar individuals are presented to describe, in a plural way, their participation and their political interests at the beginning of the nineties. [less ▲]

Procédures particulières de droit judiciaire privé : scellés - inventaire - divorce par consentement mutuel

in chronique du 10 octobre 1998 (1998)

Reproducibility and Diagnostic Sensitivity of Ultrasonometry of the Phalanges to Assess Osteoporosis

in International Journal of Gynecology & Obstetrics (1998), 63(1), 21-8

OBJECTIVE: The present study was designed to assess the reproducibility and the diagnostic sensitivity of the amplitude-dependent speed of sound (SoS) at the distal metaphysis of the proximal phalanges ... [more ▼]

OBJECTIVE: The present study was designed to assess the reproducibility and the diagnostic sensitivity of the amplitude-dependent speed of sound (SoS) at the distal metaphysis of the proximal phalanges. METHOD: Fourteen presumably healthy volunteers were repeatedly measured every 6 weeks for approximately 6 months in order to assess the reproducibility of the SoS of the phalanges. We recruited 91 post-menopausal women, aged 55-75 years, who were divided in three groups according to their lumbar bone mineral density (BMD) and the existence of prevalent vertebral fractures. The objective was to evaluate the diagnostic sensitivity of SoS measurements. We used DBM Sonic 1200 equipment, and assessed the velocity at which US cross the phalanx in a lateral-medial direction. In post-menopausal women, BMD was measured by dual energy X-ray absorptiometry (DXA) at the level of the lumbar spine, the total zone of the non-dominant hip and the femoral neck zone of the non-dominant hip. RESULTS: The precision of the SoS measurements was 0.71+/-0.05% (mean+/-S.E.M) whereas the reproducibility was 0.95+/-0.06%. Subjects with low BMD or prevalent fractures had significantly lower values of SoS (P < 0.001) than the controls. ROC curve analysis applied to the study population confirmed that SoS was able to discriminate between the controls and osteoporotic subjects (area under the ROC curves were 0.82 (low bone mineral density) and 0.85 (prevalent fractures), respectively). Hip BMD was found to be the most significant variable when comparing the controls and the low density patients by stepwise discrimination and SoS significantly improved the discrimination between the groups when added to the hip BMD. The hip BMD was again the most discriminant variable when applying the same techniques to controls and patients with prevalent fractures, followed by SoS and lumbar BMD. A cut-off value of 1881 m/s is defined for SoS by logistic discrimination and likelihood ratio function. With this value, the sensitivity and the specificity for SoS used in the diagnosis of established osteoporosis were, 81.5% and 79.3%, respectively. Sensitivity and specificity were significantly improved when combining ultrasonometry and densitometry. CONCLUSION: Measurement of ultrasound velocity at the phalanges appears to be a precise and reproducible technique. SoS discriminates between normal post-menopausal women and patients with either low lumbar BMD or prevalent fractures to the same extent as BMD measurements. [less ▲]

Restriction of mobility in model liquid crystalline ionomers

in Macromolecular Chemistry and Physics (1998), 199(10), 2205-2210

Model liquid crystalline ionomers have been analyzed by SAXS both in bulk and in toluene solution. These compounds are referred to as liquid crystalline halatosemitelechelic polystyrenes (LC HSTP's) and ... [more ▼]

Model liquid crystalline ionomers have been analyzed by SAXS both in bulk and in toluene solution. These compounds are referred to as liquid crystalline halatosemitelechelic polystyrenes (LC HSTP's) and consist of low molecular weight polystyrene chains end-capped at one end by a sulfonate group associated to a mesogenic counterion. The results are in agreement with a microphase separation between the polymer chain and the mesogenic counterion. The main characteristic feature of the SAXS profile for the bulk material is the so-called ionic peak, whose position obeys a general law which is in favor of a rod-like organization of the multiplets and which shows that the polymer chains are stretched in the very close vicinity of the mesogenic core, in agreement with the Eisenberg, Hird and Moore model for ionomers. The thickness of this region of restricted mobility has been estimated to 1 nm, which is the order of magnitude of the persistence length of polystyrene. This very local restriction in mobility persists in toluene solution, in contrast to what is observed for the ω-Li-sulfonato-polystyrene precursors. The results also agree with an isotropic distribution of the multiplets in toluene. [less ▲]

The use of thermal regulations to classify architectural projects from their energy performance

Report (1998)

The choice to himself interest with lawful methods results from the will to widen the evaluation of the project performances with a set of criteria (sound insulation, fire resistance, illumination, etc ... [more ▼]

The choice to himself interest with lawful methods results from the will to widen the evaluation of the project performances with a set of criteria (sound insulation, fire resistance, illumination, etc.), all criteria which are not necessarily objects of a collection of evaluation tools, like in energy matters. Such an approach justifies of hold with some simplified methods for the evaluation of the performance energy and, when they exist, for the evaluation of the other qualities. [less ▲]

Conception des ouvrages hydrauliques

in Ingénieur et Industrie, APPS éditions, n°5 (1998)

Prevalence and Molecular Typing of Attaching and Effacing Escherichia Coli among Calf Populations in Belgium

in Veterinary Microbiology (1998), 63(2-4), 249-259

Attaching and effacing Escherichia coli are involved in diarrhea in 2 to 8-week old calves. The virulence factors of these bacteria include: (i) the secretion of proteins (i.e. EspB) involved in ... [more ▼]

Attaching and effacing Escherichia coli are involved in diarrhea in 2 to 8-week old calves. The virulence factors of these bacteria include: (i) the secretion of proteins (i.e. EspB) involved in microvilli effacement, (ii) the production of the intimin, a 94 kDa outer membrane protein encoded by the eaeA gene and involved in the intimate attachment of bacteria to epithelial cell and (iii) the production of verotoxins: VT1 and/or VT2. We investigated the presence and the pathotype of these strains in several calf populations by colony hybridization or by genetic amplification. Using the colony hybridization method we showed first that only 5% of calves who died from diarrhea presented EaeA+ E. coli strains and secondly that 19% of healthy calves showed an asymptomatic carriage. However, using colony hybridization and genetic amplification, we identified EaeA+ strains in 91% of calves living in farms with recurrent diarrhea problems. In 66% of the calves, there was a correlation between the presence of AEEC and diarrhea. At the pathotype level, most of the EaeA+ isolates were negative for VT probes. In VT+ bacteria, the majority were VT1+. The number of VT positive bacteria was significantly higher in calves who died from diarrhea than in healthy or sick calves. This underlined the aggravating role of verotoxins in the disease. Moreover, only 25% of the bovine AEEC were positive with the EaeB probe. Surprisingly, the proportion of EaeB+ strains was significantly higher in healthy calves than in other populations. [less ▲]

Les productions animales à l'aube du troisième millénaire: enjeux et défis.

Learning material (1998)

Expression and Modulation of Homeobox Genes from Cluster B in Endothelial Cells

in Laboratory Investigation : Journal of Technical Methods & Pathology (1998), 78(10), 1291-9

Angiogenesis is a complex phenomenon likely to be under the strict control of a group of transcription factor(s). Homeobox (HOX)-containing proteins have been identified as regulators controlling the ... [more ▼]

Angiogenesis is a complex phenomenon likely to be under the strict control of a group of transcription factor(s). Homeobox (HOX)-containing proteins have been identified as regulators controlling the coordinated expression of genes involved in organ development and tissue differentiation. In this study, we have demonstrated that human umbilical vein endothelial cells (HUVEC) express 8 of the 10 HOX genes contained in cluster B. Treatment of HUVEC with tissue plasminogen activator (TPA), an agent known to induce morphologic changes in endothelial cells, or vascular endothelium growth factor (VEGF), a proliferative and angiogenesis inducer, results in a specific time-dependent modulation of the eight HOX genes identified. Interestingly, neither basic fibroblast growth factor, an endothelial proliferative agent, nor TNP-470, a fumagillin derivative with potent antiendothelial cell proliferation properties, affected expression of these HOX genes. Specific modulation of HOX genes by differentiating agents but not by proliferative or antiproliferative molecules suggests that they could be involved in the control of the genetic program that coordinates the construction of new blood vessels. [less ▲]