Publications ORBi OA
Bookmark and Share    
Full Text
See detailInfluence of environmental conditions on trophic niche partitioning among sea stars assemblages
Le Bourg, Baptiste ULg; Blanchard, Alice; Danis, Bruno et al

Conference (2017, July 10)

The Southern Ocean undergoes intense and contrasted impacts linked to climate change. The Western Antarctic Peninsula is one of the most rapidly warming regions of the world (Meredith and King, 2005 ... [more ▼]

The Southern Ocean undergoes intense and contrasted impacts linked to climate change. The Western Antarctic Peninsula is one of the most rapidly warming regions of the world (Meredith and King, 2005), resulting in sharp sea ice cover decrease (Parkinson and Cavalieri, 2012). In contrast, surface temperature and sea ice cover remain stable in other regions such as the Weddell Sea. Sea stars (Echinodermata: Asteroidea) are a key group of the Southern Ocean benthos, thought to be quite resistant to seawater temperature changes (Peck et al., 2008). Other, more indirect environmental changes, might induce important shifts in food web structure and fluxes, that may affect sea stars trophic ecology. In this context, the aim of this study was to use stable isotopes ratios of C, N and S to study sea stars trophic ecology to characterise their trophic diversity and plasticity regarding food web changes. Sea stars were sampled during the austral summer in the South Georgia (sub-Antarctic) in 2011 and in the South Shetland (2006) and South Orkney Islands (2016), as well as in the Weddell Sea (2015-2016). Trophic diversity, i.e. differences of trophic ecology between sea star species, and variability, i.e. differences of trophic ecology between individuals of the same species, were investigated in each region by investigating isotopic dispersion and isotopic niche (proxy of the trophic niche) areas and overlap. Difference in niche width and overlap between the regions may be the result of different environmental conditions, including sea ice coverage and dynamics. For example, in the South Shetland, sea stars had small and poorly differentiated isotopic niches. This result indicate that they may exploit the same benthic communities relying on few common food sources such as organic matter released during sea ice melting (Isla et al., 2006) or sinking phytoplankton (Mincks et al., 2008). Whether this situation leads to competition or not depends on the resources availability. In contrast, isotopic niches were larger and better separated for sea stars from South Georgia. South Georgia is an oligotrophic environment with no sea ice (Korb et al., 2008). As available food items are more limited but, perhaps, more diversified, a higher trophic segregation may appear between species. Ultimately, this project will help delineating processes determining trophic ecology of Southern Ocean sea stars. This research was funded by the Belgian Federal Science Policy Office (BELSPO) in the framework of the vERSO and RECTO project (rectoversoprojects.be). [less ▲]

Detailed reference viewed: 19 (0 ULg)
Full Text
Peer Reviewed
See detailEffects of a giant exercising board game intervention on ambulatory physical activity among nursing home residents: a preliminary study
Mouton, Alexandre ULg; Gillet, Nicolas; Mouton, Flore et al

Conference (2017, July 08)

Purpose: This study examined the effects of a giant (4 meters by 3 meters) exercising board game intervention on ambulatory physical activity (PA) and on a broader array of physical and psychological ... [more ▼]

Purpose: This study examined the effects of a giant (4 meters by 3 meters) exercising board game intervention on ambulatory physical activity (PA) and on a broader array of physical and psychological outcomes among nursing home residents. Materials and methods: A quasi-experimental longitudinal study was carried out in two comparable nursing homes. Ten participants (aged 82.5 ± 6.3 and comprising 6 women) meeting the inclusion criteria took part to the one-month intervention in one nursing home, whereas eleven participants (aged 89.9 ± 3.1 with 8 women) were assigned to the control group in the other nursing home. The giant exercising board game required participants to perform strength, flexibility, balance and endurance activities. The assistance provided by an exercising specialist decreased gradually during the intervention in an autonomy-oriented approach, based on the self-determination theory (SDT). The following were assessed at baseline, after the intervention and after a follow-up period of three months: PA (steps/day and energy expenditure/day with ActiGraph, GT3X+), cognitive status (MMSE), quality of life (EQ-5D), motivation for PA (BREQ-2), gait and balance (Tinetti and SPPB), functional mobility (Timed Up and Go) and the muscular isometric strength of the lower limb muscles. Results and conclusions: In the intervention group, PA increased from 2921 steps/day at baseline to 3358 steps/day after the intervention (+14.9%, p = 0.04) and 4083 steps/day (+39.8%, p = 0.03) after three months. Energy expenditure/day also increased after the intervention (+110 kcal/day, +6.3%, p = 0.01) and after three months (+219 kcal/day, +12.3%, p = 0.02). Quality of life (p < 0.05), balance and gait (p < 0.05), and strength of the ankle (p < 0.05) were also improved after three months. Such improvements were not observed in the control group. The preliminary results are promising but further investigation is required to confirm and evaluate the longterm effectiveness of PA interventions in nursing homes [less ▲]

Detailed reference viewed: 21 (3 ULg)
Full Text
See detailPratiques d'évaluation en enseignement supérieur
Detroz, Pascal ULg

Scientific conference (2017, July 07)

Detailed reference viewed: 26 (0 ULg)
Full Text
Peer Reviewed
See detailImplicit Belittlements Call for Implicit Measures: Emotional Reactions to Youth Paternalistic Stereotypes
Silvestre, Aude ULg; Huart, Johanne ULg; Dardenne, Benoît ULg

in Psychologica Belgica (2017), 57(2), 133-153

Age discrimination at work can potentially affect every worker. Indeed, like ‘old’ workers, young ones hired in their first job elicit the idea that they have quite interesting social abilities but lack ... [more ▼]

Age discrimination at work can potentially affect every worker. Indeed, like ‘old’ workers, young ones hired in their first job elicit the idea that they have quite interesting social abilities but lack of competence, which constitutes a case of paternalistic stereotypes (Fiske, Cuddy, Glick, & Xu, 2002). Generally, the negative (incompetence) facet of such stereotypes is not blatantly expressed, but is subtly conveyed behind an apparently positive discourse. Consequently, it is considered as being generally under-detected, while harmful. In this paper, we examine whether paternalistic stereotyping’s under-detection is real or if it is due to the use of inadequate measures. Based on a study showing that targets feel that something is wrong (Dardenne, Dumont, & Bollier 2007), we rely on affective measures to investigate whether the detection of the subtly conveyed negative facet of paternalistic stereotypes calls for subtle, implicit measures. In Study 1, explicit self-reports of targets’ affective states after a meeting with a paternalistic boss revealed mainly positive affect. In Study 2, an implicit emotional measure however revealed the presence of a negative affective state. The last Study, using a more ecological affective measure, demonstrates that paternalistic stereotypes trigger an ambivalent affective reaction. Altogether, the three studies suggest that the negative facet of paternalistic stereotypes is not as under-detected as we thought. [less ▲]

Detailed reference viewed: 18 (1 ULg)
Full Text
Peer Reviewed
See detailHealth and physical education from a European perspective
Cloes, Marc ULg

Conference (2017, July 07)

At the end of the 20th century, several authors pointed out that physical education (PE) was crossing a crisis. The emphasis on the fight against a growing sedentariness of the society became ... [more ▼]

At the end of the 20th century, several authors pointed out that physical education (PE) was crossing a crisis. The emphasis on the fight against a growing sedentariness of the society became progressively one of the priorities of the national education leaders all around the world. In many countries, PE teachers had to implement new approaches in order to teach to the youth how to adopt a healthy lifestyle. Pre- and in-service PE teachers’ training started to propose programmes integrating health education in PE lessons while the reputation of the physical literacy concept spread quickly. Recently, Chin and Edginton (2014) invited scholars from 40 nationalities to describe the contemporary policies and practices of health and PE applied in their countries. Among those contributions, 23 concerned European countries. In this presentation, we will propose an overview of the trends that can be identified in this sample of European nations. Preliminary analysis underlines that combination of PE and health education is distributed along a continuum. At one extremity, PE’s input on health is not clearly expressed even if PE is expected to improve pupils and students’ health through selected activities like endurance training. At the opposite extremity, countries emphasize the role of the PE teacher as a health educator and not only through a limited focus on PA promotion and on the preparation of physically educated citizens. The second part of the paper will illustrate some actions that are undertaken in order to motivate the PE teachers to implement 'health enhanced physical activity' projects in their lessons. Such approaches respect principles associated with the concept of quality physical education (QPE). These PE classes should allow students to have positive individual and collective learning experiences where they develop knowledge, skills and dispositions that allow them to be autonomous and responsible decision makers relative to engagement in PA and sport in their lives (AIESEP, 2014). PE teachers need a new framework (Haerens et al., 2011) in order to leave their ingrained professional practices.. That starts by changing their representations on physical activity. Action-research, development of communities of practice, pedagogical cases and demonstration of the students’ interest for teaching approaches focusing on lifestyle aspects represent promising strategies to succeed in the process of changing the priorities. AIESEP (2014). 2014 AIESEP Position Statement on Physical Education Teacher Education. Available on Internet: http://aiesep.org/wp-content/uploads/2014/11/2014-AIESEP-Position-Statement-on-Physical-Education-Teacher-Education.pdf Chin, M.-K. & Edginton, C.R. (2014). Physical Education and Health Global Perspectives and Best Practice. Urbana, IL: Sagamore. Haerens, L., Kirk, D., Cardon, G., & De Bourdeaudhuij, I. (2011). Toward the Development of a Pedagogical Model for Health-Based Physical Education, Quest, 63:3, 321-338. [less ▲]

Detailed reference viewed: 31 (0 ULg)
Full Text
Peer Reviewed
See detailDéveloppement régional au départ des pôles extérieurs : typologie, enjeux et ressources territoriales en Wallonie
Wilmotte, Pierre-François ULg; Bianchet, Bruno ULg

Conference (2017, July 06)

The aim of our paper is to present how an European region can insert its region in some cross-border (potential) metropolitan and polycentric areas. Wallonia is interesting to understand a case where no ... [more ▼]

The aim of our paper is to present how an European region can insert its region in some cross-border (potential) metropolitan and polycentric areas. Wallonia is interesting to understand a case where no metropolitan centres are located in the region. The objective is to indicate how territorial resources are influenced by these foreign cities and the original combination of territorial resources in order to emerge a typology for the European regions. [less ▲]

Detailed reference viewed: 27 (5 ULg)
Full Text
See detailUtilisation du béton recyclé dans la formulation des bétons auto-compactants
Bouarroudj, Mohamed Elkarim ULg; Colman, Charlotte ULg; Robinet, Eva ULg et al

Scientific conference (2017, July 06)

Notre travail porte sur l'étude du comportement des bétons auto-compactants ou auto-plaçants réalisés à base de sable recyclé et de sable recyclé broyé. La première étape consiste en une caractérisation ... [more ▼]

Notre travail porte sur l'étude du comportement des bétons auto-compactants ou auto-plaçants réalisés à base de sable recyclé et de sable recyclé broyé. La première étape consiste en une caractérisation physico-chimique et minéralogique (masse volumique, absorption d’eau, teneur en sulfates, composition chimique...) d’un sable de béton recyclé. Dans un deuxième temps, une étude des propriétés rhéologiques et mécaniques est réalisée sur des mortiers afin de réduire la quantité de matériaux naturels utilisés. La composition du mortier de base est dérivée d’une formulation type de béton auto-compactant préalablement vérifié sur la base de différents critères classiques (étalement au cône, t500, teneur en air,…). Notre étude s’intéresse d’une part aux impacts de la substitution du filler calcaire par du sable recyclé broyé (série 1) et d’autre part aux impacts de la substitution du sable naturel par du sable recyclé (série 2). [less ▲]

Detailed reference viewed: 28 (4 ULg)
Full Text
Peer Reviewed
See detailVers une politique de la ville en Wallonie (Belgique) : évolution socio-économique des villes wallonnes et recommandations
Claeys, Dorian ULg; Descamps, Julien; Wilmotte, Pierre-François ULg et al

Conference (2017, July 06)

The aim of the presentation is to present the recent trajectories of the urban neighbourhoods of 12 Walloon cities. The objective is to connect these evolutions with the urban development and policies of ... [more ▼]

The aim of the presentation is to present the recent trajectories of the urban neighbourhoods of 12 Walloon cities. The objective is to connect these evolutions with the urban development and policies of Walloon cities. [less ▲]

Detailed reference viewed: 31 (2 ULg)
Full Text
Peer Reviewed
See detailEmergence d’une Politique de la Ville en Wallonie en regard de la vision européenne
Mercenier, Chloé ULg; Bianchet, Bruno ULg; Ruelle, Christine ULg et al

Conference (2017, July 06)

The aim of our presentation is to present some issues for Wallonia regarding to the urban strategy of European Union (European Council of Ministers and European Commission). We present these two ... [more ▼]

The aim of our presentation is to present some issues for Wallonia regarding to the urban strategy of European Union (European Council of Ministers and European Commission). We present these two strategies: the European (Urban Agenda/Pact of Amsterdam) and the Walloon strategies. We focus our communication on two regional specific issues: cooperation between municipalities ("supracommunalité") and the rehabilitation of residential and economic functions of urban neighbourhoods. [less ▲]

Detailed reference viewed: 28 (3 ULg)
Full Text
See detailLANDSLIDE SUSCEPTIBILITY PREDICTION IN A MOUNTAINOUS CATCHMENT: THE NARANJO BASIN, WESTERN GUATEMALA
Estrada Orozco, Nick Kenner ULg

Doctoral thesis (2017)

In tropical mountain areas, landslides triggered by heavy rainfall represent a natural hazard, especially where meteorological events such as tropical cyclones are recurrent. Rainfall-triggered landslides ... [more ▼]

In tropical mountain areas, landslides triggered by heavy rainfall represent a natural hazard, especially where meteorological events such as tropical cyclones are recurrent. Rainfall-triggered landslides may also increase in highly seismic active areas. This is the case of Guatemala, located in the Circum-Pacific Belt and between Pacific and Atlantic Oceans, sources of cyclonic events. Although Guatemala is a region where landslides are a widespread phenomenon, landslide inventories, maps and quantitative susceptibility assessments that are useful for land use planners and decision makers are hitherto non-existent. The aim of this research is to produce quantitative landslide susceptibility assessments, using logistic regression multivariate statistical method. The study area is a watershed located in the department of San Marcos (western Guatemala), impacted by a tropical storm event in October 2005. A total of 766 landslides were identified and mapped using orthoimages from 2005. Then, 99 landslides were mapped in 2011 based on field data. The main landslide type is shallow landslide (61 % in 2005), while 39 % of those landslides from 2005 evolved into debris flows. In total, susceptibility models using multivariate probabilistic approach were developed for shallow landslides, evaluating two different strategies for the sample size of non-landslides events and three different numbers of input variable in the models. Susceptibility models were developed for debris flows dataset and the union of both dataset (shallow and debris flows). The comparison of the models and the associated susceptibility maps highlighted 6 significant input variables that are associated with landslide occurences - elevation, slope, aspect, profile curvature, planform curvature and distance to roads. Performance comparisons of models were also carried out. To validate the performance of the model results, the ROC curve was used, as well as the four-fold and confusion matrix plots. A susceptibility map was generated to display the results of the models in terms of probability values. A proposal and discussion on the operational use of susceptibility maps where cutoff values can be chosen to define the lowest and highest landslide susceptibility were also made. These will help land use planners in decision-making and in implementing protective measures. [less ▲]

Detailed reference viewed: 72 (9 ULg)
Full Text
See detailVers une Politique de la Ville en Wallonie : recommandation pour la mise en oeuvre d'une politique transversale et intégrée de dynamisation des quartiers urbains
Ruelle, Christine ULg; Mercenier, Chloé ULg; Bastin, Florine et al

E-print/Working paper (2017)

La note de recherche propose les principaux résultats de la recherche CPDT 2015-2016 sur la Politique de la Ville en Wallonie. Elle concerne, plus précisément, les constats et recommandations pour le ... [more ▼]

La note de recherche propose les principaux résultats de la recherche CPDT 2015-2016 sur la Politique de la Ville en Wallonie. Elle concerne, plus précisément, les constats et recommandations pour le développement des quartiers urbains selon trois grandes catégories de difficultés : le cadre de vie dégradé, le contexte social défavorable et le contexte économique défavorable. [less ▲]

Detailed reference viewed: 74 (3 ULg)
Full Text
See detailUnsteady pressure distributions on a 4:1 rectangular cylinder: comparison of numerical and experimental results using decomposition methods.
Guissart, Amandine ULg; Andrianne, Thomas ULg; Dimitriadis, Grigorios ULg et al

Conference (2017, July 04)

Detached flows around bluff bodies are ubiquitous in civil engineering applications. In this work, the flow around a static 4:1 rectangular cylinder at moderate Reynolds number and at different angles of ... [more ▼]

Detached flows around bluff bodies are ubiquitous in civil engineering applications. In this work, the flow around a static 4:1 rectangular cylinder at moderate Reynolds number and at different angles of incidence is studied using both Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD). Typically, the integration of EFD and CFD allows a better understanding of the flow of interest by leveraging the complementary of their respective outputs. However, the comparison of computational and experimental results is an important but difficult step of this integration, particularly in the case of local quantities related to unsteady flows. In this work, decomposition methods are used to compare unsteady loads and pressure distributions coming from EFD and CFD. In particular, Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) are used to extract the dominant structures of the aerodynamic coefficients. The experimental data are obtained from dynamic pressure measurements in wind tunnel while numerical data come from two-dimensional unsteady Reynolds-Averaged Navier-Stokes (uRANS) simulations and tri-dimensional Delayed-Detached Eddy Simulations (DDES). This work shows that the decomposition methods represent a powerful tool enabling the analysis and the quantitative comparison of the main spatial and temporal characteristics of unsteady flows. Moreover, the accuracy of uRANS and DDES results is analyzed in light of the capacity of both CFD techniques to capture the reattachment occurring on the upper part of the rectangular cylinder. [less ▲]

Detailed reference viewed: 25 (3 ULg)
Full Text
Peer Reviewed
See detailInfluence of environmental factors on food intake among nursing home residents: a survey combined with a video approach
Buckinx, Fanny ULg; Reginster, Jean-Yves ULg; Morelle, Alison et al

in Clinical Interventions in Aging (2017), 12

Background: In addition to the well-known physiological factors, dietary behavior that affects health seems to be influenced by a wide variety of environmental factors. The aim of this study was to assess ... [more ▼]

Background: In addition to the well-known physiological factors, dietary behavior that affects health seems to be influenced by a wide variety of environmental factors. The aim of this study was to assess, by means of an original video approach, the influence of the environment on food intake in nursing homes. Methods: The perception of the environment during meals in nursing homes was evaluated by residents and by two groups of volunteers who either work in the field of geriatrics, or who do not work in the field of geriatrics. First, a random sample of residents answered a self-administered questionnaire related to different indicators (ie, noise, space, comfort, light, odors, perceived satisfaction of meals, taste of meals, presentation of meals, service and setting). Second, two separate panels, one including the people who work in the field of geriatrics (ie, experts) and one including the people who have no particular interest in geriatrics (ie, nonexperts), were asked to answer a questionnaire on their perception of the environment after having watched a video of the lunch in each nursing home. Then, the food intake of the residents was measured by a precise food-weighing method. Results: A total of 88 residents from nine different nursing homes, 18 experts and 45 nonexperts answered the questionnaires. This study highlighted that, on the one hand, after adjustment on confounding variables, the perception of the quantity of food served by the residents is the only single factor associated with food consumption (P=0.003). On the other hand, experts and nonexperts did not perceive any environmental factor that seems to be significantly associated with residents’ food intake. Conclusion: Our results highlighted that, in a nursing home setting, environmental factors have limited influence on the food intake of the residents, with the exception of their own perception of the quantity served. The relevance of this factor deserves further investigation. [less ▲]

Detailed reference viewed: 48 (2 ULg)
Full Text
Peer Reviewed
See detailFor your ka! How to give something as a present to the tomb owner?
Motte, Aurore ULg

Conference (2017, July 04)

Detailed reference viewed: 24 (2 ULg)
Full Text
See detailOmics insights into rumen ureolytic bacterial community and urea metabolism in dairy cows
Jin, Di ULg

Doctoral thesis (2017)

Urea has been used in the diets of ruminants as a non-protein nitrogen source. Ureolytic bacteria are key organisms in the rumen producing urease enzymes to catalyze the breakdown of urea to ammonia (NH3 ... [more ▼]

Urea has been used in the diets of ruminants as a non-protein nitrogen source. Ureolytic bacteria are key organisms in the rumen producing urease enzymes to catalyze the breakdown of urea to ammonia (NH3), and the NH3 is used as nitrogen for microbial protein synthesis. In the rumen, hydrolysis of urea to NH3 occurs at a greater rate than NH3 can be utilized by rumen bacteria, and excess ammonia absorbed into blood may be harmful to the animals. Nowadays, little is known about the information of ureolytic microorganisms in the rumen, and the changes that occur in the rumen microbial and host metabolites induced by urea nitrogen have not been fully characterized. ‘Omics’ approaches, such as metagenomics and metabolomics have been applied to analyzing rumen microbial community and nutrients metabolism in dairy cows. The objective of this study is to investigate the rumen predominant ureolytic bacteria community and the mechanisms of urea utilization in ruminants using sequencing and metabolomics approaches. Firstly, an in vitro experiment trying to explore the ruminal ureolytic bacterial community was performed. Urea or acetohydroxamic acid were supplemented into the rumen simulation systems as the stimulator and inhibitor for ureolytic bacteria, respectively. The bacterial 16S rRNA genes were analyzed by Miseq sequencing and used to reveal the ureolytic bacteria by comparing different treatments. We found that urea supplementation significantly increased the proportion of ureC genes. The rumen ureolytic bacteria were abundant in the genera of Pseudomonas, Haemophilus, Neisseria, Streptococcus, Actinomyces, Bacillus and unclassified Succinivibrionaceae. Secondly, an in vivo experiment was taken to investigate differences in ureolytic bacterial composition between the rumen digesta and rumen wall based on ureC gene classification. Six dairy cows with rumen fistula were assigned to a two-period cross-over trial. One group was fed a total mixed ration without urea and the treatment group was fed rations plus 180 g urea per cow per day. Rumen bacterial samples from rumen content and rumen wall fractions were collected for ureC gene amplification and sequencing using Miseq. More than 55% of the ureC sequences did not affiliate with any known taxonomically assigned urease genes. The wall-adherent bacteria had a distinct ureolytic bacterial profile compared to the bacteria in the rumen content. The most abundant ureC genes were affiliated with Methylococcaceae, Clostridiaceae, Paenibacillaceae, Helicobacteraceae and Methylophilaceae families. Relative abundance of the operational taxonomic units (OTUs) affiliated with Methylophilus and Marinobacter genera were significantly higher in the bacteria on the rumen wall than that in the rumen content. Thirdly, based on the in vivo experiment, rumen fluid and blood samples were collected and analyzed using nuclear magnetic resonance spectroscopy and multivariate analysis of variance. Concentrations of valine, aspartate, glutamate, and uracil in the rumen, and urea and pyroglutamate in the plasma were increased after urea supplementation. Metabolic pathways include pantothenate and CoA biosynthesis, beta-alanine metabolism, valine, leucine, and isoleucine metabolism in the rumen, and urea and glutathione metabolism in the plasma were significantly increased by urea nitrogen. In conclusion, this study identified significant populations of ureolytic bacterial community that have not been recognized or studied previously in the rumen and provides a basis for obtaining regulatory targets to moderate urea hydrolysis in the rumen. The findings also provided novel information to aid understanding of the metabolic pathways affected by urea nitrogen in dairy cows, and could potentially help to guide efforts directed at improving the efficiency of urea utilization in the rumen. [less ▲]

Detailed reference viewed: 46 (5 ULg)
Full Text
See detailHistoire évolutive du complexe Afzelia Smith (Leguminosae - Caesalpinioideae) dans les écosystèmes forestiers et savanicoles en Afrique tropicale
Donkpegan, Segbedji ULg

Doctoral thesis (2017)

The genus Afzelia Smith (Fabaceae, Caesalpinioideae) is known to have seven African tree species two of which are found in the Zambezian region, one is distributed in the Sudanian region and the four ... [more ▼]

The genus Afzelia Smith (Fabaceae, Caesalpinioideae) is known to have seven African tree species two of which are found in the Zambezian region, one is distributed in the Sudanian region and the four other are endemic to the Guineo-Congolian region. These taxa, of high commercial value, are difficult to identify. They are therefore marketed under the same "doussié" name. These difficulties of distinction can prove detrimental to the sustainable management of populations. The aim of this doctoral thesis is to characterize the evolutionary history of the Afzelia genus. More specifically, this study aims to: (i) evaluate the level of morphological divergences within the Afzelia genus and describe the phylogenetic relationships in order to quantify the reproductive isolation between taxa by highlighting the role of past climate change and / or ecological gradients in the speciation of the genus; (ii) proceed to an analysis of the spatial genetic diversity and structure of Afzelia spp.; (iii) identify and describe ecological, biotic and abiotic factors that may influence population-level gene flows of an Afzelia species (A. bipindensis). A morpho-genetic analysis of Afzelia species was carried out and confirmed the strong botanical resemblance between the taxa. The savannah species are diploid and have half the size of the genome of forest species that are tetraploid. The phylogenies of genes (nuclear and chloroplastic) differ from one another and do not allow the separation of tetraploid taxa from one another. Such differences can be generated as a result of episodes of ancestral hybridization between species. These hybridizations would probably be old and would have occurred between lineages of the forest species and A quanzensis (a species of the Zambezian savannahs) lineages. Polyploidy would have occurred between 7 and 9.4 million years in the evolutionary history of the genus. In addition, Bayesian assignment and reproductive isolation analyzes suggested interspecific crosses, but only in forest species distributed sympatrically. At a more limited spatial scale, we observed two well differentiated genetic groups in sympatry in A. bipindensis. These show a morphological differentiation and a phenological shift of flowering which can contribute to their reproductive isolation. This study highlighted some important points: the discovery of a polyploid complex within the Afzelia genus, the confirmation of the delimitation of the diploid savannah species and the need to revise the delimitation of forest tetraploid species. [less ▲]

Detailed reference viewed: 42 (11 ULg)
Full Text
See detailOn the Use of Principal Component Analysis for Parameter Identification and Damage Detection in Structures
Golinval, Jean-Claude ULg

Conference (2017, July 03)

In this lecture, an approach based on principal component analysis (PCA) is considered for three purposes, namely damage detection, structural health monitoring and identification of nonlinear parameters ... [more ▼]

In this lecture, an approach based on principal component analysis (PCA) is considered for three purposes, namely damage detection, structural health monitoring and identification of nonlinear parameters in structural dynamics. The key idea of PCA is to reduce a large number of measured data to a much smaller number of uncorrelated variables while retaining as much as possible of the variation in the original data. The first problem to which PCA is applied here is the damage detection problem. When applied to vibration measurements, it can be shown that the basis of eigenvectors (called the proper orthogonal modes) span the same subspace as the mode-shape vectors of the monitored structure. Thus the damage detection problem may be solved using the concept of subspace angle between a reference subspace spanned by the eigenvectors of the initial (undamaged) structure and the subspace spanned by the eigenvectors of the current (possibly damaged) structure. The second problem concerns structural health monitoring of civil engineering structures when environmental effects (e.g. the influence of the variation of the ambient temperature) have to be removed from the structural changes. In this case, PCA may be applied on identified modal features (e.g. the natural frequencies) to separate the changes due to environmental variations from the changes due to damage sources. The third problem is related to the estimation of nonlinear parameters using model updating techniques. In this case, the most interesting property of PCA is that it minimizes the average squared distance between the original signal and its reduced linear representation. When applied to nonlinear problems, PCA gives the optimal approximating linear manifold in the configuration space represented by the data. The linear nature of the method is appealing because the theory of linear operators is still available. However, it should be borne in mind that it also exhibits its major limitation when the data lie on a nonlinear manifold. [less ▲]

Detailed reference viewed: 10 (0 ULg)