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See detailPhylogeography of a nematode (Heligmosomoides polygyrus) in the western Palearctic region: persistence of northern cryptic populations during ice ages?
Nieberding, Caroline M. ULg; Libois, Roland ULg; Douady, C. J. et al

in Molecular Ecology (2005), 14(3), 765-79

This study establishes the continental phylogeographical pattern of a European nematode, Heligmosomoides polygyrus (Dujardin, 1845; Heligmosomoidea). We sequenced 687 base pairs of the mitochondrial DNA ... [more ▼]

This study establishes the continental phylogeographical pattern of a European nematode, Heligmosomoides polygyrus (Dujardin, 1845; Heligmosomoidea). We sequenced 687 base pairs of the mitochondrial DNA (mtDNA) cyt b gene for 136 individuals collected in 22 localities. The results revealed that H. polygyrus populations are separated into five major units corresponding to the Italian, northern European (Denmark and Ireland), Iberian, western European, and Balkan populations. Different subclades were also observed within the first two groups. Based on the rate of molecular evolution of H. polygyrus cyt b gene-estimated to 3.5%-3.7% divergence per million years (Myr) in a previous study--the isolation time of the five clades was estimated between 2.5 +/- 0.24 and 1.5 +/- 0.23 million years ago. Moreover, H. polygyrus presents a higher genetic variability in the Mediterranean peninsulas as compared to northwestern Europe, highlighting the role of these regions as refuge areas. Like its specific host, the wood mouse Apodemus sylvaticus, H. polygyrus' pattern of postglacial recolonization of northwestern Europe was initiated from Iberian populations, while Italian and Balkan populations did not expand to the north. The results also suggest the existence of forested and temperate refuges in the southern British Isles during the Quaternary. Finally, the genetic diversity as well as the level of genetic divergence between the lineages of H. polygyrus are compared to those observed in other vertebrate and invertebrate phylogeographical studies: the existence of highly differentiated lineages in H. polygyrus (5%-10% of genetic divergence) highlights that the effects of Pleistocene climate changes on free-living organisms are also reflected in their obligate parasites. [less ▲]

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See detailPhylogeography of african timber trees
Hardy, Olivier; Daïnou, Kasso ULg; Debout, Gabriel et al

Conference given outside the academic context (2012)

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See detailPhylogeography of Harbour Porpoise (Phocoena phocoena) in the Eastern North Atlantic and in the Black Sea Explored by the Analyses of Nuclear and Mitochondrial DNA
Fontaine, Michaël; Baird, C.; Stuart, J. E. et al

Poster (2005)

Study of the genetic population structure and the demographic history of the harbour porpoise (Phocoena phocoena) has been nearly comprehensive throughout its distribution in North Atlantic, most studies ... [more ▼]

Study of the genetic population structure and the demographic history of the harbour porpoise (Phocoena phocoena) has been nearly comprehensive throughout its distribution in North Atlantic, most studies using the mitochondrial control region as a genetic marker. Although these studies have shown population structure in some parts of the North Atlantic, mitochondrial DNA is a single, maternally inherited locus and therefore insufficient to fully characterize population structure and history. Polymorphism at 11 microsatellite loci was analyzed in harbour porpoises collected throughout the range of the species in the Central and Eastern North Atlantic from the Iberian peninsula northward to Arctic waters (Portugal, Spain, bay of Biscay, Irish waters, English Channel, the southern bay of the North Sea, Norway, Faroe Islands, and Iceland) and also along the coasts of the Black Sea (Turkey, Ukraine, Bulgaria and Georgia). Multilocus tests for allele frequency differences and population structure estimates indicate complete genetic isolation between Atlantic and Black Sea porpoises. No fine population structure was observed within the Black Sea, and this population displayed a low genetic diversity compared to those of Atlantic. These results can be interpreted in the light of the demographic history of this relict population and the strong founder effect and bottleneck it may have undergone in its past evolution. In Eastern North Atlantic waters, microsatellite data revealed fine scale partitioning of the genetic variation. These results will be compared to the pattern previously reported based on the analysis of the mtDNA control region, and seem to correlate with variation in oceanographic features. [less ▲]

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See detailPhylogeography of the garden dormouse Eliomys quercinus in the western Palearctic region
Perez, Grégoire; Libois, Roland ULg; Nieberding, Caroline

in Journal of Mammalogy (2013), 94(1),

The garden dormouse, Eliomys quercinus (Rodentia, Gliridae), displays a surprisingly high karyotypic diversity, with the number of chromosomes varying between 2N ¼ 48 and 2N ¼ 54. We aimed to assess ... [more ▼]

The garden dormouse, Eliomys quercinus (Rodentia, Gliridae), displays a surprisingly high karyotypic diversity, with the number of chromosomes varying between 2N ¼ 48 and 2N ¼ 54. We aimed to assess whether the karyotypic diversity is congruent with the mitochondrial differentiation of the populations; improve our understanding of the taxonomic relationships between garden dormouse populations based on both chromosomal and mitochondrial information; and establish the phylogeographic history of the species and the time of differentiation of mitochondrial lineages of E. quercinus and E. melanurus. For this purpose we sequenced the mitochondrial cytochrome-b (Cytb) gene for 62 E. quercinus and 4 E. melanurus from 27 localities representing all the known chromosomal races of the genus Eliomys in the western Palearctic region. Our results 1st showed that populations of E. quercinus are separated into 4 evolutionarily significant units partially congruent with the chromosomal races and corresponding to Iberian (2N¼48), Italian (2N¼48 or 50), western European (2N¼48, 49, or 50), and Alpine (2N ¼ 52 or 54) mitochondrial lineages or clades. The existence of hybrid individuals between chromosomal races and the presence of several chromosomal races within each mitochondrial lineage both indicate that gene flow persists between chromosomal races. Second, we estimated that the major mitochondrial lineages differentiated from each other around 4.2 6 SD 1 million years ago, thus predating the Quaternary glaciations. Third, E. quercinus displayed a higher haplotypic variability in the Mediterranean peninsula than in the northwestern European populations. However, E. quercinus did not show a pattern of ostglacial recolonization of northwestern Europe from Iberian or Italian populations. Our results also suggest that additional, unexpected refuge regions around the Alps exist for the species. Such information will be useful for deciphering the priorities for the protection of E. quercinus, which is listed as ‘‘Near Threatened’’ on the International Union for the Conservation of Nature Red List of Threatened Species and is protected by Appendix III of the Bern Convention. [less ▲]

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See detailPhylogeography, risk factors and genetic history of hepatitis C virus in Gabon, central Africa.
Njouom, Richard; Caron, Melanie; Besson, Guillaume et al

in PLoS ONE (2012), 7(8), 42002

BACKGROUND: The epidemiological and molecular characteristics of hepatitis C virus (HCV) infection in the general population have been poorly investigated in Africa. The aim of this study was to determine ... [more ▼]

BACKGROUND: The epidemiological and molecular characteristics of hepatitis C virus (HCV) infection in the general population have been poorly investigated in Africa. The aim of this study was to determine the prevalence, genotype distribution and epidemic history of HCV in the Gabonese general population. METHODS/PRINCIPAL FINDINGS: A total of 4042 sera collected from adults in 220 villages in all nine administrative areas of the country were screened for antibodies to HCV. HCV NS5B region sequencing was performed for molecular characterization and population genetic analyses. Of 4042 tested sera, 455 (11.2%) were positive. The seroprevalence of HCV varied significantly by administrative area, with the highest rate in Ogooue-Lolo province (20.4%) and the lowest in Ogooue-Maritine province (3.7%). History of parenteral injections, past hospital admission and age over 55 years were independent risk factors for HCV infection (p<0.0001). Phylogenetic analyses showed that 91.9% of the strains were genotype 4 (HCV-4), 5.7% genotype 1 and 2.2% genotype 2. HCV-4 strains were highly heterogeneous, with more than eight subtypes; subtype 4e predominated (57.3%). Coalescence analyses indicated that subtype 4e was the oldest, with an estimated most recent common ancestor of 1702 [95% CI, 1418-1884]. The epidemic profile indicated that it spread exponentially during the first part of the 20th century, probably by iatrogenic transmission. CONCLUSIONS/SIGNIFICANCE: These results confirm the endemicity of HCV subtype 4e in Gabon and show that its spread is due to a cohort effect, with previous, possibly iatrogenic events. More extensive epidemiological studies are needed to better characterize the route of transmission and the dissemination of HCV in Gabon. [less ▲]

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See detailPhysical activity and cardiovascular risk factors in children. The Belgian Luxembourg Child Study.
Guillaume, Michèle ULg; Lapidus, L.; Bjorntorp, P.

in Obesity Research (1997)

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See detailPhysical activity patterns of children after neonatal arterial switch operation.
Massin, Martial M; Hovels-Gurich, Hedwig H; Gérard, Paul ULg et al

in Annals of Thoracic Surgery (2006), 81(2), 665-70

BACKGROUND: Physical inactivity is a major atherosclerosis risk factor. The exercise tolerance is usually excellent after neonatal arterial switch operation, but those patients in whom coronary anomalies ... [more ▼]

BACKGROUND: Physical inactivity is a major atherosclerosis risk factor. The exercise tolerance is usually excellent after neonatal arterial switch operation, but those patients in whom coronary anomalies remain the main late complication, risk developing atherosclerotic coronary disease owing to perceived physical activity restrictions. METHODS: We investigated physical activity patterns of 52 unselected children 7 to 14 years after neonatal arterial switch operation for transposition of the great arteries by 24-hour continuous heart rate monitoring. The percentage of heart rate reserve was used to measure the amounts of activities. Comparisons were made with 35 children with repaired atrial or ventricular septal defect and with 127 age-matched healthy children. RESULTS: Children after arterial switch operation accumulated 167.3 +/- 70.6, 25.3 +/- 12.9, and 15.7 +/- 11.3 minutes a day (mean +/- SD) of light, moderate, and vigorous physical activities, respectively. At the same activity levels, children with repaired septal defect accumulated 165.2 +/- 82.2, 26.2 +/- 11.7, and 16.2 +/- 9.1 minutes a day, and their healthy peers 164.8 +/- 74.5, 31.8 +/- 13.9, and 21.9 +/- 11.3 minutes a day. Both cardiac groups were significantly less active than the control group when considering moderate (p = 0.026) and vigorous activities (p = 0.006). Only 19% and 27% of the children after arterial switch operation engaged, respectively, in more than 30 minutes a day of moderate activity and 20 minutes a day of vigorous activity. CONCLUSIONS: Children after arterial switch operation, just like other cardiac children, do not meet the guidelines for physical activity. We should encourage regular physical activity to offset adult sedentary behavior and to prevent atherosclerotic cardiovascular disease in those patients whose long-term function of the coronary arteries remains a matter of concern. [less ▲]

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See detailPhysical activity promotion among older adults: Short term effects of a neighbourhood environment internet-based intervention
Mouton, Alexandre ULg; Rompen, Jérôme ULg; Cloes, Marc ULg

Poster (2013, May)

Purpose. Recent research suggests that internet-based physical activity interventions can be suitable and effective, even for older adults. Besides, neighbourhood environment internet-based interventions ... [more ▼]

Purpose. Recent research suggests that internet-based physical activity interventions can be suitable and effective, even for older adults. Besides, neighbourhood environment internet-based interventions are currently considered as more effective than traditional motivational interventions. Therefore, the main purpose of this study was to explore the effects of a neighbourhood environment internet-based intervention on physical activity behaviours of older adults. Methods. At baseline, 87 older adults (60.69 ± 7.85 years) from the same district were assigned to an intervention (n = 41) or a control (n = 46) group. The two months intervention was composed of a comprehensive physical activity promotion website, with an emphasis on neighbourhood environment contents, and a monthly personalized email based on the stage of change theory. Physical activity behaviours were assessed by the IPAQ short-form and the stage of change questionnaire at baseline, after one and two month of the intervention, and after one month follow-up. Results. Significant improvements were observed for the stage of change questionnaire in the intervention group from baseline to the end of the intervention (p = 0.003), they remained at follow-up (p = 0.012) while the control group remained unchanged. Physical activity level declined progressively in the control group as it remained constant in the intervention group, with as significant difference between groups after two months intervention (p = 0.027). Conclusions. These findings suggest that a neighbourhood environment internet-based intervention can improve physical activity behaviours in older adults. Further research on this topic is needed to examine longer term effects with larger sample. [less ▲]

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See detailPhysical Activity Promotion In Overweight/Obese Children. A Project Implemented In A Hospital Context
Cloes, Marc ULg; Dewandre, Anne-Cécile; LEBRETHON, Marie-Christine ULg

Conference (2012)

BACKGROUND. Overweight and obesity in youth must be combated through a multiple approach combining management principles in nutrition and physical activity (PA). In the hospital context, medical staff ... [more ▼]

BACKGROUND. Overweight and obesity in youth must be combated through a multiple approach combining management principles in nutrition and physical activity (PA). In the hospital context, medical staff seems to be more focused on nutrition. AIM. In this study, we proposed to implement a specific intervention focusing on PA in parallel with traditional paediatric and dietetic visits designed to 6-12 year-old children. METHODS. Data were collected in three steps: (1) after a visit at the hospital, subjects and their parents answered to a questionnaire (lifestyle, representation about PA) and attended to a meeting during which they received written (illustrated booklet) and oral cues about PA as well as an invitation to use a PA diary and a pedometer; (2) before the next visit (almost 8 weeks interval), they were free to apply the recommendations; (3) after the next visit to the hospital, subjects analyzed the diary with one of the researchers and answered to questions about their current lifestyle and representations about PA. 34 children respected the whole protocol. FINDINGS. Among the children and their parents, representations of PA changed between the visits (PA was no longer regarded merely as sport). Major changes were also identified in children’s lifestyle (increase of number of weekly PA, family PA, weekly PA time; decrease of inactivity time like TV or video games). Only 27 children out of 34 used the PA diary at least once (information were recorded for a mean of 18 days/child between the 2 visits – a third of the duration of the interval). The pedometer has been used by 15 children and was considered as a motivating tool. 58.5% of comments collected at the end of the second meeting were positive and emphasized the interest of the intervention; 24.6% were negative and mainly focused the PA diary). DISCUSSION. This study underlines the need to improve the family's representations about PA in paediatric and dietetic visits. It supports PA experts' integration in the staff. [less ▲]

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See detailPhysical activity, obesity, and cardiovascular risk factors in children. The Belgian Luxembourg Child Study II.
Guillaume, Michèle ULg; Lapidus, L.; Bjondorp, P. et al

in Obesity Research (1997), 5(6), 549-56

Physical activity was measured in relation to cardiovascular (CV) risk factors in a randomly selected population of 1028 children from Province de Luxembourg in Belgium, a mainly rural area with a high ... [more ▼]

Physical activity was measured in relation to cardiovascular (CV) risk factors in a randomly selected population of 1028 children from Province de Luxembourg in Belgium, a mainly rural area with a high prevalence of such risk factors among adults and children. Physical activity was estimated as participation in sport activities, a major indicator of leisure-time physical activity in schoolchildren, and physical inactivity was estimated as frequency and duration of television (TV) watching. Boys participated more frequently in sport activities than girls did (p = 0.001). A majority of the children watched TV daily. After age adjustment, bodyweight (girls, p < 0.012; boys, p < 0.027) and, in boys, body mass index (BMI) (p < 0.039) were related to days per week of TV watching. No significant relationships with other CV risk factors remained after adjustments for BMI. In analyses of independent contributions of age, TV watching, and sports activity on CV risk factors, age showed highly significant relationships. In boys, TV showed relationships with BMI (p < 0.04) and (borderline) with systolic blood pressure, independent of age and sports activity, whereas the latter was significantly related to subscapular skinfold (p < 0.04) and (borderline) with triceps skinfold and cholesterol. In girls, no significant independent contributions to risk factor associations were found. The father's education was directly associated with sports activities, whereas the mother being a housewife showed negative relationships to physical activity and positive to TV watching in their children, suggesting socioeconomic influence on the activity patterns of children. Furthermore, registrations suggested less physical activity in the most rural part of the area. It is concluded that children in this mainly rural area watch TV frequently. In boys, physical inactivity, measured both as TV watching and as registrations of sports activities, contributes independently to body fat mass. In girls, no contribution or weaker contributions of physical inactivity were found. This suggests that contributory factors leading to obesity might be different in girls and boys. [less ▲]

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See detailPhysical and bacterial controls on inorganic nutrients and dissolved organic carbon during a sea ice growth and decay experiment
Zhou, Jiayun ULg; Delille, Bruno ULg; Kaartokallio, Hermanni et al

in Marine Chemistry (2014), 166

We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day ... [more ▼]

We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day experiment that included periods of both ice growth and decay. The experiment was performed using two series of mesocosms: the first consisted of seawater and the second consisted of seawater enriched with humic-rich river water. We grew ice by freezing the water at an air temperature of -14 °C for 14 days after which ice decay was induced by increasing the air temperature to -1 °C. Using the ice temperatures and bulk ice salinities, we derived the brine volume fractions, brine salinities and Rayleigh numbers. The temporal evolution of these physical parameters indicate that there was a succession of 3 stages in the brine dynamics: forced-convection, followed by bottom convection during ice growth, and then brine stratification during ice decay. The major findings are: (1) the incorporation of dissolved compounds (nitrate, nitrite, ammonium, phosphate, silicate, and DOC) into the sea ice was not conservative (relative to salinity) during ice growth. Brine convection clearly influenced the incorporation of the dissolved compounds, since the non-conservative behavior of the dissolved compounds was particularly pronounced in the absence of brine convection. (2) Bacterial activity further regulated nutrient availability in the ice: ammonium and nitrite accumulated as a result of remineralization processes, although bacterial production was too low to induce major changes in DOC concentrations. (3) Different forms of DOC have different properties and hence incorporation efficiencies. In particular, the terrestrially-derived DOC from the river water was less efficiently incorporated into sea ice than the DOC in the seawater. Therefore the main factors regulating the distribution of the dissolved compounds within sea ice are clearly a complex interaction of brine dynamics, biological activity and in the case of dissolved organic matter, the physico-chemical properties of the dissolved constituents themselves. [less ▲]

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See detailPhysical and biogeochemical properties in landfast sea ice (Barrow, Alaska): insights on brine and gas dynamics across seasons
Zhou, Jiayun ULg; Delille, Bruno ULg; Eicken, H. et al

in Journal of Geophysical Research (2013), 118(6), 3172-3189

The impacts of the seasonal evolution of sea-ice physical properties on ice-ocean biogeochemical exchanges were investigated in landfast ice at Barrow (Alaska) from January through June 2009. Three stages ... [more ▼]

The impacts of the seasonal evolution of sea-ice physical properties on ice-ocean biogeochemical exchanges were investigated in landfast ice at Barrow (Alaska) from January through June 2009. Three stages of brine dynamics across the annual cycle have been identified based on brine salinity, brine volume fraction and porous medium Rayleigh number [less ▲]

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See detailPhysical and biological controls on DMS,P dynamics in ice-shelf influenced fast ice during a winter-spring and a spring-summer transitions
Carnat, G.; Zhou, Jiayun ULg; Papakyriakou, T. et al

in Journal of Geophysical Research. Oceans (2014), 119

We report the seasonal and vertical variations of dimethylsulphide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer ... [more ▼]

We report the seasonal and vertical variations of dimethylsulphide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer transition in 2011 and winter-spring transition in 2012. We compare the variations of DMS,P observed to the seasonal evolution of the ice algal biomass and of the physical properties of the ice cover, with emphasis on the ice texture and brine dynamics. Isolated DMS and DMSP maxima were found during both seasonal episodes in interior ice and corresponded to the occurrence of platelet crystals in the ice texture. We show that platelet crystals formation corresponded in time and depth to the incorporation of dinoflagellates (strong DMSP producers) in the ice cover. We also show that platelet crystals could modify the environmental stresses on algal cells and perturb the vertical redistribution of DMS,P concentrations. We show that during the winter-spring transition in 2012, the DMS,P profiles were strongly influenced by the development and decline of a diatom dominated bloom in the bottom ice, with DMSP variations remarkably following chl a variations. During the spring-summer transition in 2011, the increase in brine volume fraction (influencing ice permeability) on warming was shown to trigger (1) an important release of DMS to the under-ice water through brine convection (2) a vertical redistribution of DMSP across the ice [less ▲]

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See detailPhysical and chemical properties of pyropheophorbide)a-methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-a-phosphatidylcholine vesicles
Delanaye, Lisiane; Bahri, Mohamed Ali ULg; Tfibel, Francis et al

in Photochemical & Photobiological Sciences (2006), 5

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second generation hotosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the ... [more ▼]

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second generation hotosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-α-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS). [less ▲]

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See detailPhysical and mechanical properties of black locust (Robinia pseudoacacia) wood grown in Belgium
Pollet, Caroline; Verheyen, Cécile; Hebert, Jacques ULg et al

in Revue canadienne de recherche forestière (2012), 42(5), 831-840

The objective of this study was to characterize black locust (Robinia pseudoacacia L.) wood on the basis of its physical and mechanical properties. The results are compared with those reported in the ... [more ▼]

The objective of this study was to characterize black locust (Robinia pseudoacacia L.) wood on the basis of its physical and mechanical properties. The results are compared with those reported in the literature for English oak (Quercus robur L.), teak (Tectona grandis L. f.), and afzelia (Afzelia sp.), since black locust is likely to be used for the same purposes as the former species. The variations between sites, trees, and radial positions in the trunk were also studied. The physical and mechanical properties of black locust wood were evaluated on clear wood specimens taken from 27 trees distributed over five sites in Wallonia (Belgium) according to Belgian and French standards. Most of the black locust’s mechanical properties are higher than those of oak and teak. The black locust is classified as a “mid-heavy” (734 kg·m–3) and “half-hard” (5.22) wood type with very high resilience (17.2 J·cm–2), modulus of elasticity (15 700 MPa), and tensile strength in static bending (138 MPa). Its resilience is exceptional, higher than that of teak and afzelia, while its modulus of elasticity and bending strength, which surpass those of teak, are comparable with those of afzelia. Black locust shows high total volumetric shrinkage (16%), placing it in the “nervous” class, average tangential (8.8%) and radial shrinkage (5.5%) as well as average axial compressive (63 MPa) and splitting strength (17.8 N·mm–1). No technological incompatibilities would prevent the use of this wood for many value-added purposes (floor, deck, exterior woodwork, and furniture); however, significant shrinkage makes it necessary to condition the wood to its service moisture. [less ▲]

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See detailPhysical and numerical modeling of overbank flow with a groyne on the floodplain
Peltier, Yann ULg; Proust, S.; Bourdat, A. et al

in River Flow 2008: 4th Int. Conf. on Fluvial Hydraulics (2008)

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See detailPhysical and numerical modelling in low-head structures design
Dewals, Benjamin ULg; Archambeau, Pierre ULg; Rulot, François ULg et al

in Bung, Daniel; Pagliara, Stefano (Eds.) Proceedings of the International Workshop on Hydraulic Design of Low-Head Structures (2013, February)

Physical and numerical modelling may be combined within so-called composite or hybrid modelling. This enables to optimally take benefit of the respective strengths of each modelling approach, while ... [more ▼]

Physical and numerical modelling may be combined within so-called composite or hybrid modelling. This enables to optimally take benefit of the respective strengths of each modelling approach, while compensating for their specific drawbacks. Different types of composite modelling may be identified, such as embedding a detailed physical model within a broader scale numerical model, interconnecting different physical and numerical models focusing each on specific processes, or validating a numerical model from experimental data before exploiting the numerical model to generate more results than availa-ble from the experimental facility. Besides, specifically in more basic research, composite modelling may also be used to improve in-depth understanding of the relative importance of different processes which act simultaneously in the experimental test and may be artificially separated in numerical simulations. [less ▲]

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See detailPhysical and physiological impacts of different foam control strategies during a process involving hydrophobic substrate for the lipase production by Yarrowia lipolytica
Kar, Tambi ULg; Destain, Jacqueline ULg; Thonart, Philippe ULg et al

in Bioprocess and Biosystems Engineering (2012), 35(4), 483-492

The potentialities for the intensification of the process of lipase production by the yeast Yarrowia lipolytica on a renewable hydrophobic substrate (methyloleate) have been investigated. The key factor ... [more ▼]

The potentialities for the intensification of the process of lipase production by the yeast Yarrowia lipolytica on a renewable hydrophobic substrate (methyloleate) have been investigated. The key factor governing the lipase yield is the intensification of the oxygen transfer rate, considering the fact that Y. lipolytica is a strict aerobe. However, considering the nature of the substrate and the capacity for protein excretion and biosurfactant production of Y. lipolytica, intensification of oxygen transfer rate is accompanied by an excessive formation of foam. Two different foam control strategies have thus been implemented: a classical chemical foam control strategy (CFM) and a mechanical foam control (MFM) based on the Stirring As Foam Disruption (SAFD) principle. The second strategy allows foam control without any modifications of the physico-chemical properties of the broth. However, the MFM system design induced the formation of a persistent foam layer in the bioreactor. This phenomenon has led to the segregation of microbial cells between the foam phase and the liquid phase in the case of the bioreactors operated with MFM control, and induced a reduction at the level of the lipase yield. More interestingly, flow cytometry experiments have shown that residence time of microbial cells in the foam phase tends to induce a dimorphic transition which could potentially explain the reduction of lipase excretion. [less ▲]

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See detailPhysical and textural characteristics of hydrogenated low-erucic acid rapeseed oil and low-erucic acid rapeseed oil blends
Danthine, Sabine ULg; Deroanne, Claude ULg

in Journal of the American Oil Chemists' Society (2003), 80(2), 109-114

Low-erucic acid rapeseed oil (LERO) and hydrogenated low-erucic acid rapeseed oil (HLERO) were blended in binary systems. The blends were then studied for their physical properties such as solid fat ... [more ▼]

Low-erucic acid rapeseed oil (LERO) and hydrogenated low-erucic acid rapeseed oil (HLERO) were blended in binary systems. The blends were then studied for their physical properties such as solid fat content, melting curves by DSC, textural properties, and polymorphism. Phase behavior diagrams were constructed from the DSC and X-ray results, and isosolid diagrams were constructed from the NMR results. The mixture of HLERO and LERO displayed a monotectic behavior for all the storage time at 15degreesC. The aim of this work was to evaluate physical characteristics of binary blends of HLERO and nonhydrogenated LERO in order to use only LERO and hardened LERO in bakery shortenings. The mixture of 60% HLERO and 40% LERO is suitable to use as a plastic shortening, This blend is beta tending upon storage at 15degreesC. It could be used in pie crust applications. [less ▲]

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