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See detailEtude des mécanismes responsables du comportement agrégatif d’Harmonia axyridis (Pallas) (Coleoptera : Coccinellidae)
Durieux, Delphine ULg

Doctoral thesis (2012)

The negative impacts linked to the introductions of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), progressively increasing in Europe and in North America, it is urgent to find a way to ... [more ▼]

The negative impacts linked to the introductions of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), progressively increasing in Europe and in North America, it is urgent to find a way to manage its populations. The social interactions involved in its aggregative behavior remain misunderstood although a better understanding of the semiochemicals the ladybeetles use during this phenomenon could lead to the development of new control methods. Therefore, the main objective of this thesis was to improve the understanding of the mechanisms set up by H. axyridis during its aggregative stage. Firstly, we have demonstrated the use of two different area markings by this species during its overwintering. The first one, laid by the ladybeetles while walking, lead conspecifics towards aggregation sites whereas the second one, deposited inside these sites, ensures the cohesion of the cluster. These markings are made up of saturated, mono- and diunsaturated hydrocarbons. Among these chemicals, it seems that the unsaturated hydrocarbons, and in particular the ones containing two double bonds, present a greater biological activity. However, the response of H. axyridis towards these chemicals depends on the insect physiological state. In the second instance, we have showed for the first time that H. axyridis presents a permanent aggregative behavior. The hydrocarbons laid by the ladybeetles during their displacements do not play any role in this behavior during summer conditions. On the other hand, conspecific elytral compounds and, in a lesser extent, physical contact, are well involved. Moreover, all our experiments have pointed out that visual elements play a major role in this social behavior and so, have also to be taken into account in the design of traps to control the populations of this invasive species. [less ▲]

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See detailÉtude des médiations sur le marché du travail : l'apport de la nouvelle sociologie économique à l'économie des conventions.
Beuker, Laura ULg; Orianne, Jean-François ULg

Conference (2012, July 03)

Cette communication s’inscrit dans le cadre d’une recherche traitant des médiations sur le marché du travail, et plus précisément du rôle des intermédiaires dans la fluidification des appariements et la ... [more ▼]

Cette communication s’inscrit dans le cadre d’une recherche traitant des médiations sur le marché du travail, et plus précisément du rôle des intermédiaires dans la fluidification des appariements et la sécurisation des parcours professionnels. La nouvelle sociologie économique (NSE) et l’économie des conventions (EC) offrent des pistes intéressantes pour comprendre le fonctionnement de marchés concrets, comme celui du travail. Néanmoins, ces courants présentent tous deux des limites qu’une articulation théorique permettrait, selon nous, de dépasser. A la conception néoclassique d’un « marché autorégulateur », la NSE substitue une analyse des facteurs économiques, culturels et politiques qui contribuent à l’émergence d’une configuration particulière d’échange de biens et de services. Les théoriciens de l’EC quant à eux, portent un intérêt tout particulier pour l’analyse de l’activité de médiation sur le marché du travail et de la pluralité des modes d’évaluation des compétences. Cependant, l’EC ne cherche pas à expliquer l’émergence des conventions constitutives, considérées dans l’analyse comme variables indépendantes. En outre, l’EC présente une conception « sous-socialisée » des intermédiaires du marché du travail. Il nous semble que la NSE pourrait considérablement enrichir l’analyse des méditations à l’aide de notions clés telles que l’encastrement ou encore la construction sociale des activités économiques, restituant de la sorte au monde social toute son épaisseur. [less ▲]

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See detailEtude des modifications de l'EEG quantifié et de la VCN au cours de l'inhalation de protoxyde d'azote
Timsit-Berthier, M.; Mantanus, H.; Dethier, D. et al

in Rev EEG neurophysiol (1982), 12

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See detailEtude des modifications environnementales à partir des données pluviométriques et NDVI de NOAA-AVHRR en Afrique de l’Ouest
Hountondji, Yvon ULg; Ozer, Pierre ULg; Tychon, Bernard ULg

in Schmitz, Serge; Meert, Henk (Eds.) Les Journées des Géographes Belges: Evaluer la capacité du milieu (2003)

Since the late 1960s, The Sahel of West Africa is affected by a long-term drought and increasing human pressure on the environment leading to desertification processes. The Normalised Difference ... [more ▼]

Since the late 1960s, The Sahel of West Africa is affected by a long-term drought and increasing human pressure on the environment leading to desertification processes. The Normalised Difference Vegetation Index (NDVI), calculated from satellite imagery, is a reliable index of the vegetation status as the vegetation response to rainfall is very strong in semiarid environments. This article presents the NDVI and rainfall evolution from 1981 to 1999 in nine locations along a north-south transect from north-western Niger to north-eastern Benin. These two parameters are then statistically analysed to identify breaks in the trends within the datasets. Over the 19 years analysed, it appears that five out of the nine locations have recorded a significant increase of rainfall, while only two presented a significant increase in NDVI. This dichotomy in observed trends may highlight the on-going slow processes of environmental degradation. [less ▲]

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See detailL'étude des nouvelles localisations industrielles. Problèmes de méthodes et de sources
Merenne-Schoumaker, Bernadette ULg

in Bulletin de la Société Géographique de Liège (1975), (11), 97-128

Analysis of methodological problems and sources of information encountered in studies of industrial location

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See detailEtude des odeurs émises par des carcasses de porc (Sus domesticus L.) en décomposition et suivi de la colonisation postmortem par les insectes nécrophages
Dekeirsschieter, Jessica ULg

Master's dissertation (2007)

La présente étude s’articule autour de deux axes ; la caractérisation des odeurs émises par des carcasses de porc (Sus domesticus L.) en décomposition en plein air et leur colonisation postmortem par les ... [more ▼]

La présente étude s’articule autour de deux axes ; la caractérisation des odeurs émises par des carcasses de porc (Sus domesticus L.) en décomposition en plein air et leur colonisation postmortem par les insectes nécrophages. Six carcasses ont été disposées dans trois biotopes distincts : un milieu forestier, une zone agricole et un garage désaffecté. Deux techniques de prélèvements des composés organiques volatils (COVs) présents dans l’espace de tête des carcasses ont été utilisées : une technique passive et une technique dynamique. La technique passive utilise le système Radiello® muni de cartouches adsorbantes de Carbograph 4 analysées par TDS-GCMS tandis que la méthode dynamique piège les molécules volatiles sur une phase adsorbante de SuperQ. Les composés volatils piégés dynamiquement sont désorbés par solvant et analysés par GC-MS. Les principaux COVs identifiés sont le 1-butanol, l’indole, le phénol, le p-crésol, l’acide butanoique ainsi que le 2-et 3-méthylbutanoïque, le diméthyldisulfure, le diméthyltrisulfure ainsi que plusieurs aldéhydes. Les insectes nécrophages ont été piégés à l’aide de bacs jaunes et de « pitfall trap », des prélèvements manuels ont également été effectués. Deux ordres sont nettement prépondérants : les Diptères, essentiellement des Calliphoridae, et les Coléoptères avec les familles des Silphidae et des Staphylinidae. [less ▲]

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See detailÉtude des paramètres opératoires de pressage mécanique des amandes de Vitellaria paradoxa Gaertn C.F. (karité)
Yé, S.; Lebeau, Frédéric ULg; Wathelet, Jean-Paul ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2007), 11(4), 267-273

Study of the operational parameters of mechanical pressing of almonds of Vitellaria paradoxa Gaertn C.F. (shea tree). Sheabutter is one of the most diffi cult oleaginous resources to extract by ... [more ▼]

Study of the operational parameters of mechanical pressing of almonds of Vitellaria paradoxa Gaertn C.F. (shea tree). Sheabutter is one of the most diffi cult oleaginous resources to extract by traditional way. In Burkina Faso, where production of sheanuts is estimated at 70 000 tons per year, presses manufactured locally are used to improve the production. In order to optimize the handcraft process of sheabutter production, extraction parameters of Vitellaria paradoxa Gaertn C.F. were studied under laboratory controlled conditions on 3 g samples of ground almonds using a uni-axial compression test machine specifi cally instrumented for this purpose. The studied operational parameters were the grinding (unsieved sample 0.5 mm<Ø<5 mm ; sieved samples 0.5 mm<Ø<1 mm ; 1 mm<Ø<2 mm ; 2 mm<Ø<4 mm ; 4 mm<Ø<5 mm), the heating temperature (30; 50; 70; 90; 110; 130; 150°C) and the extraction pressure (7; 10; 13.4; 15; 16.17; 17.44; 20; 22.43 and 25 MPa). The grinding has favourably infl uenced the extraction rate. The fi nest sieved fraction (0.5 mm<Ø<1 mm) presented the highest extraction rate, 84%. When using unsieved samples, the best results were obtained with a heating temperature of 90°C and an extraction pressure of 20 MPa. In these conditions, the extraction rate reached 78% and the chemical characteristics of the sheabutter were not altered. As a result, a signifi cant increase of the handcrafted presses effi ciency could be reached by simple and inexpensive modifi cations as an increase of the pressure applied to the product, by a decrease of the pressing chamber diameter. [less ▲]

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See detailEtude des perceptions d’équité des candidats dans une situation de sélection: influence de la justice procédurale et distributive.
Marzucco, Laurence ULg; Hansez, Isabelle ULg

in Psychologie du Travail et des Organisations (2013), 19(1), 45-70

Which are the applicants fairness perceptions with regard to a situation of selection in which they are involved? The study has been carried out with 97 applicants through promotion and selection ... [more ▼]

Which are the applicants fairness perceptions with regard to a situation of selection in which they are involved? The study has been carried out with 97 applicants through promotion and selection examinations set up by the Walloon Public Service (Belgium). Based on the model of reactions of the applicants (Gilliland, 1993), their perceptions of equity have been assessed. To this end, a questionnaire has been set up based on the SPJS scale (Bauer & al., 2001). The results indicate that applicants in a promotional process (based on a situational interview) perceive higher equity than applicants in a selection process (based on a classical structured interview). Recruited applicants also perceive higher equity than the other applicants. Equity perceptions are more favourable after publication of the results than at the end of the examination. [less ▲]

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See detailEtude des performances d'appareils de melange Unguator pour la preparation magistrale a usage dermatologique
Stassen, T.; Piette, Marie ULg; Kinget, R. et al

in Journal de Pharmacie de Belgique (2006), 61(1), 1-10

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See detailEtude des phénotypes et des facteurs de virulence des Escherichia coli Att25
Pohl, P.; Lintermans, P.; Mainil, Jacques ULg et al

in Annales de Médecine Vétérinaire (1987), 131

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