References of "Brostaux, Yves"
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See detailFactors involved in the aggregation of Harmonia axyridis Pallas
Durieux, Delphine ULg; Fischer, Christophe ULg; Deneubourg, Jean-Louis et al

Conference (2012, May 22)

In order to survive cold winters, the invasive multicoloured Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) forms large aggregations in dwellings to overwinter. The factors ... [more ▼]

In order to survive cold winters, the invasive multicoloured Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) forms large aggregations in dwellings to overwinter. The factors involved in the selection of aggregation sites remain misunderstood. The work presented herein focussed on the study of the chemical compounds involved in this phenomenon. Chemical and behavioural analyses highlighted that long-chain hydrocarbons lead congeners towards aggregation sites and ensure the cohesion of the cluster. Subsequently, physical factors were investigated. We studied the influence of (1) the density of individuals and (2) the quality of available shelters on H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in laboratory showed that the multicoloured Asian ladybeetles present a permanent aggregative behaviour, even during non-wintering conditions. These experiments also highlighted the existence of social interactions between individuals. All these results contribute to improve knowledge of this behaviour in H. axyridis and could be used in the design of species-specific traps in order to control infestations in dwellings. [less ▲]

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See detailA Semiochemical Slow-release Formulation in a Biological Control Approach to Attract Hoverflies
Heuskin, Stéphanie ULg; Lorge, Stéphanie ULg; Leroy, Pascal ULg et al

in Journal of Environment and Ecology (2012), 3(1), 72-85

E-β-Farnesene, the alarm pheromone of many aphid species, and E-β-caryophyllene are considered as two sesquiterpenes attractive for aphid predators, among which Syrphidae species. Both compounds were ... [more ▼]

E-β-Farnesene, the alarm pheromone of many aphid species, and E-β-caryophyllene are considered as two sesquiterpenes attractive for aphid predators, among which Syrphidae species. Both compounds were formulated in alginate gel beads as slow-release devices in a biological control approach against aphids. Semiochemical diffusion from beads was studied in the laboratory according to abiotic parameters. Efficiency of formulations as hoverfly attractant was demonstrated in field experiments from June to August 2009. The diffusion of semiochemicals from alginate bead formulations was principally limited by high values (>85%) of relative humidity in the air. Temperature also impacts the release of volatile compounds. In field experiments, these two abiotic factors were supposed to highly condition the trapping of hoverflies. These field trappings demonstrated the efficiency of both semiochemical formulations compared to control (formulation without semiochemical) to catch females of Syrphidae during three months. [less ▲]

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See detailCould current Pericopsis elata (Fabaceae) patches in southeastern Cameroon be reasonably linked to past anthropogenic activities ?
Bourland, Nils ULg; Cerisier, François ULg; Livingstone Smith, Alexandre et al

Poster (2012, March 01)

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at ... [more ▼]

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at understanding its origins so as to help securing its future. This study, lead away from engineering works, was conducted in four different sites located within the natural distribution area of the species and took into account the different growing conditions were the species occurs. Our observations were based on an analysis of charcoal elements and pottery fragments discovered in subsurface layers of soils as well as on current botanical and pedological surveys. Discovered evidence of past human activities led to the assumption that this part of the Congo Basin was much more inhabited than previously thought. Some of the results obtained for P. elata could apply for other long lived light demanding species growing in the same environment. [less ▲]

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See detailSelf-assemblage and quorum in the earthworm Eisenia fetida (Oligochaete, Lumbricidae)
Zirbes, Lara ULg; Brostaux, Yves ULg; Mescher, Mark et al

in PLoS ONE (2012), 7(3), 32564

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See detailModelling realized niche of metallophyte species along copper and cobalt gradients on Katanga copper hills
Boisson, Sylvain ULg; Seleck, Maxime ULg; Guillaume, Arielle et al

Poster (2012, February 10)

In South Central Africa were identified more than 650 plant species tolerant to heavy metals, several of which endemic to Katanga and critically endangered by mining activities. These metallophyte are ... [more ▼]

In South Central Africa were identified more than 650 plant species tolerant to heavy metals, several of which endemic to Katanga and critically endangered by mining activities. These metallophyte are distributed over a hundred hills containing high copper and cobalt concentrations (20 to 10000 mg/kg for copper and 2 to 1000 mg/kg for cobalt). To understand the response of metallophyte to heavy metals, the ecological niches of 80 cupro-cobaltophytes were modeled with general additive models (GAM). Results show that (1) three groups of species were identified according to their optimum along a metal concentrations gradient and (2) a positive relationship exists between niche amplitude and optimum copper concentration. [less ▲]

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See detailDépenses en viande par les ménages belges en 2008
Ferrandis Vallterra, Salvador ULg; Brostaux, Yves ULg; Claustriaux, Jean-Jacques ULg et al

Speech (2012)

Analysis of meat expenditure by Belgian households in 2008. Meat expenditure by Belgian households during 2008 is analyzed. Expenditure is extracted from the Belgian Household Budget Survey at the FPS ... [more ▼]

Analysis of meat expenditure by Belgian households in 2008. Meat expenditure by Belgian households during 2008 is analyzed. Expenditure is extracted from the Belgian Household Budget Survey at the FPS Economy, S.M.E.s, Self-employed and Energy. The database also provides sociodemographic information about the households participating in the survey. To explain the observed variability of the meat expenditure based on the explanatory factors available, an analysis of the covariance is performed. The three quantitative factors have a bigger effect on the meat expenditure than the three other qualitative factors. The proportion of meat expenditure variability explained by the explanatory factors of the selected model is 31,41%. [less ▲]

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See detailTables de contingence à trois dimensions : aspects théoriques, applications et analogie avec l'analyse de la variance à trois critères de classification
Claustriaux, Jean-Jacques ULg; Palm, Rodolphe ULg; Ferrandis Vallterra, Salvador ULg et al

in Notes de Statistique et d'Informatique (2012), (1), 19

For contingency table, concepts of independence are not so easy to understand in statistical practice. So, theoretical aspects of the log-linear model are described and applied to a three levels example ... [more ▼]

For contingency table, concepts of independence are not so easy to understand in statistical practice. So, theoretical aspects of the log-linear model are described and applied to a three levels example; an analogy with analysis of variance is also established. [less ▲]

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See detailTesting semiochemicals from aphid, plant and conspecific: attraction of Harmonia axyridis
Leroy, Pascal ULg; Schillings, Thomas ULg; Farmakidis, Julien ULg et al

in Insect Science (2012), 19

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an invasive specie affecting the dynamics and composition of several guilds. Nowadays, no biological control method is available to reduce the ... [more ▼]

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an invasive specie affecting the dynamics and composition of several guilds. Nowadays, no biological control method is available to reduce the populations of this harmful coccinellid. Attractants and semiochemicals seem to be the best alternative but only few studies have tested the impact of semiochemicals on this Asian lady beetle. In this work, through wind-tunnel experiments, semiochemicals from aphids [Z,E-nepetalactone, (E)-β-farnesene, α-pinene and β-pinene], from coccinellids [(-)-β-caryophyllene] and from the nettle Urtica dioica L. were envisaged as potential attractants. The nettle volatile compounds [(Z)-3-hexenol and (E)-2-hexenal] were extracted using a Clevenger Apparatus® and identified by headspace-GC-MS. The main components of the aphid alarm pheromone as well as a component of the aphid sexual pheromone strongly attracted both sexes of the Asian lady beetle while (-)-β-caryophyllene only attracted few individuals and had no impact on the males. The nettle extract as well as the (Z)-3-hexenol oriented both males and females to the odour source. The (E)-2-hexenal was showed to have no effect on females even if this green leaf volatile attracted males. This study highlighted that some semiochemicals from aphids and from nettle extracts orientated the harlequin ladybird H. axyridis. These volatile compounds could certainly help for an efficient biological control approach against this invasive specie. [less ▲]

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See detailDevelopment and application of a microplate method to evaluate the efficacy of essential oils against Penicillium italicum Wehmer, Penicillium digitatum Sacc. and Colletotrichum musea (Berk. M.A. Curtis) Arx, three postharvest fungal pathogens of fruits
Kouassi, Kouadio Hugues Sosthène ULg; Bajji, M.; Brostaux, Yves ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(3), 325-336

A microbioassay was developed for evaluating the in vitro antifungal activity of 30 preselected essential oils. A template based on 10 serial dilutions with eight replicates per dilution arranged on two ... [more ▼]

A microbioassay was developed for evaluating the in vitro antifungal activity of 30 preselected essential oils. A template based on 10 serial dilutions with eight replicates per dilution arranged on two 96-well ELISA plates was used as a reproducible and standardized design to identify the in vitro effectiveness of these essential oils against Penicillium italicum Wehmer, Penicillium digitatum Sacc. and Colletotrichum musea (Berk. M.A. Curtis) Arx, three postharvest fungal pathogens, on fruits. Growth of mycelium was monitored by measuring optical density (492 nm). Cinnamomum zeylanicum, Cinnamomum verum and Eugenia caryophyllus were found to be still active against all the three pathogens even at 100 ppm. Compared to other methods, this microbioassay proved to be a rapid, reproducible, and efficient method for testing the efficacy of essential oils that inhibit spore germination in P. italicum, P. digitatum and C. musea. The assay requires relatively small amounts of essential oils. [less ▲]

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See detailPhenological patterns in a natural population of a tropical timber tree species, Milicia excelsa (Moraceae): evidence of Isolation By Time and its interaction with feeding strategies of dispersers
Daïnou, Kasso ULg; Laurenty, Eric; Mahy, Grégory ULg et al

in American Journal of Botany (2012), 99(9), 1-11

Population genetic structuring over limited timescales is commonly viewed as a consequence of spatial constraints. Indirect approaches have recently revealed existence of reproductive isolation due to ... [more ▼]

Population genetic structuring over limited timescales is commonly viewed as a consequence of spatial constraints. Indirect approaches have recently revealed existence of reproductive isolation due to flowering time (the so-called isolation by time, IBT). Since phenological processes can be subject to selection, the persistence of flowering asynchrony may be due to opposing selective pressures during mating, dispersal and regeneration phases. Our study aimed to investigate phenology, fruit-handling by animals and their interaction, in a timber tree species, Milicia excelsa. We analyzed phenological data collected over a 6-year period on 69 genotyped trees in a Cameroonian natural rainforest complemented by data from germination trials and field observations of dispersers. Initiation of flowering correlated with variation in temperature and relative humidity, but was also affected by genetic factors: pairwise differences in flowering time between nearby individuals correlated with kinship coefficient, and earliness of flowering remained stable over time. A decrease in mean seed production per fruit with increasing flowering time suggests selection against late bloomers. However, germination rate was not affected by seed collection date, and the main seed disperser, the bat Eidolon helvum, seemed to increase in abundance at the end of the reproductive season, and preferred trees in open habitats where early and late bloomers are expected. The pairwise approach performs well to detecting IBT. The persistence of different mating pools in such a case may result from a trade-off between selective forces during the mating and seed dispersal processes. [less ▲]

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See detailRole of long-chain hydrocarbons in the aggregation behaviour of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Durieux, Delphine ULg; Fischer, Christophe ULg; Brostaux, Yves ULg et al

in Journal of Insect Physiology (2012)

The multicoloured Asian ladybeetles, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyances to householders from their number and sometimes the ... [more ▼]

The multicoloured Asian ladybeetles, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyances to householders from their number and sometimes the induction of allergic reactions. Migratory flight and macrosite choice of this species is well documented. H. axyridis shows a hypsotactic behaviour and a clear preference for contrasting visual elements. However, how the microsite is selected remains undocumented, although a better understanding of the implicated factors could lead to the development of new control methods for this pest. In this work, we have hypothesized that non-volatile compounds are involved in the microsite choice and the aggregation process of this beetle. Long chain hydrocarbons were identified inside aggregation sites, comprising saturated and unsaturated homologues. An aggregation bioassay was then conducted on overwintering individuals, highlighting the retention capacity of the previously cited compounds on the tested ladybeetles. Additional investigations have shown that H. axyridis males and females, originating from overwintering sites, deposit a similar blend of molecules while walking. A Y-shaped tube assay revealed that this blend is used by male and female congeners as cue, allowing individuals to orientate towards the treated side of the olfactometer. These results suggest the use of two different blends of long chain hydrocarbons by H. axyridis during its aggregative period, the first one to lead conspecifics towards aggregation sites (microsites) and the second to ensure the cohesion of the aggregation. These findings support the potential use of these blends, in association with volatiles, in the design of traps in order to control infestations of this species in dwellings. [less ▲]

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See detailStudy of the factors involved in the aggregation of Harmonia axyridis Pallas (Coleoptera : Coccinellidae)
Durieux, Delphine ULg; Fischer, Christophe ULg; Deneubourg, Jean-Louis et al

in Communications in Agricultural and Applied Biological Sciences (2012), 77(1), 101-104

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in ... [more ▼]

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in the selection of its aggregation sites. Chemical and behavioural analyses highlighted that long-chain hydrocarbons lead congeners towards aggregations and ensure the cohesion of the cluster. On the other hand, we investigated the influence of (1) the density of individuals and (2) the quality of available shelters on H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in laboratory highlighted a permanent aggregative behaviour of H. axyridis, even during non-wintering conditions, and the existence of social interactions between individuals. [less ▲]

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See detailOptimization of formic/acetic acid delignification of Miscanthus ×giganteus for enzymatic hydrolysis using response surface methodology
Vanderghem, Caroline ULg; Brostaux, Yves ULg; Jacquet, Nicolas ULg et al

in Industrial Crops & Products (2012), 35

A Box–Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus ×giganteus for ... [more ▼]

A Box–Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus ×giganteus for enzymatic hydrolysis. The effects of three independent variables, namely cooking time (1, 2 and 3 h), formic acid/acetic acid/water ratio (20/60/20, 30/50/20 and 40/40/20) and temperature (80, 90 and 107 ◦C) on pulp yield, residual Klason lignin content, concentration of degradation products (furfural and hydroxymethylfurfural) in the black liquor, and enzymatic digestibility of the pulps were investigated. The major parameter influencing was the temperature for pulp yield, delignification degree, furfural production and enzymatic digestibility. According to the response surface analysis the optimum conditions predicted for a maximum enzymatic digestibility of the glucan (75.3%) would be obtained using a cooking time of 3 h, at 107 ◦C and with a formic acid/acetic acid/water ratio of 40/40/20%. Glucan digestibility was highly dependent on the delignification degree. [less ▲]

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See detailThe ecological study of an unknown non-timber forest product (NTFP): the African walnut (Coula edulis Baill.)
Moupela, Christian ULg; Vermeulen, Cédric ULg; Lebailly, Philippe ULg et al

Conference (2011, November 15)

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux ... [more ▼]

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux de son écologie, dont le potentiel de production, la dispersion et la prédation des fruits, demeurent inconnus, ce qui pourrait constituer un frein à sa valorisation. L’étude s’est déroulée au Gabon et s’est attachée à quantifier la production fruitière de l’espèce et à identifier les prédateurs et disperseurs des fruits. Trente-neuf collecteurs circulaires ont été installés sous les houppiers, les données récoltées (nombre et masse des fruits) étant ensuite mises en relation avec le diamètre. Par ailleurs, sept semenciers ont fait l’objet d’observations indirectes grâce à un dispositif de caméras-pièges. Les premières fructifications apparaissent sur les semenciers à partir de 12,3 cm de diamètre. Elle se produit de janvier à avril. Les quantités de fruits sont corrélées positivement au diamètre (r² = 0,493 ; p = 0,001). Dix espèces animales ont été observées aux pieds des arbres en fruits, leur rôle dans la dynamique de population de l’espèce est potentiellement important. [less ▲]

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See detailThe ecological study of an unknown non-timber forest product (NTFP) : The African walnut (Coula edulis Baill.)
Moupela, Christian; Vermeulen, Cédric ULg; Brostaux, Yves ULg et al

Conference (2011, November)

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux ... [more ▼]

Le noisetier d’Afrique, Coula edulis Bail., produit des graines de grande valeur nutritive régulièrement collectées et commercialisées par les populations locales. Toutefois, certains aspects fondamentaux de son écologie, dont le potentiel de production et la prédation des fruits, demeurent inconnus, ce qui peut constituer un frein à sa valorisation. L’étude s’est déroulée au Gabon et s’est attachée à quantifier la production fruitière de l’espèce et à identifier les prédateurs potentiels des fruits. Trente-neuf collecteurs circulaires ont été installés sous les houppiers, les données récoltées (nombre et masse des fruits) étant ensuite mises en relation avec le diamètre. Par ailleurs, sept semenciers ont fait l’objet d’observations indirectes grâce à un dispositif de caméras-pièges. Le diamètre minimum de fertilité est de 12,3 cm, tandis que 23 cm dhp constitue pour l’espèce le diamètre effectif de fructification. Celle-ci se produit de décembre à avril. Les quantités de fruits sont corrélées positivement au diamètre. Dix espèces animales ont été observées aux pieds des arbres en fruits, leur rôle dans la dynamique de l’espèce est potentiellement important. [less ▲]

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See detailInférence statistique et critères de qualité de l'ajustement en régression logistique binaire
Palm, Rodolphe ULg; Brostaux, Yves ULg; Claustriaux, Jean-Jacques ULg

in Notes de Statistique et d'Informatique (2011), (5), 32

The principles of statistical inference based on the maximum likelihood function are described and applied to binary logistic regression. Several goodness of fit statistics are also given. These topics ... [more ▼]

The principles of statistical inference based on the maximum likelihood function are described and applied to binary logistic regression. Several goodness of fit statistics are also given. These topics are illustrated by an example processed by Minitab and SAS softwares. [less ▲]

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See detailLa régression logistique avec Minitab
Palm, Rodolphe ULg; Brostaux, Yves ULg

in Notes de Statistique et d'Informatique (2011), (4), 15

This note describes the Minitab commands BLOGISTIC, NLOGISTIC and OLOGISTIC and proposes a macro, which can be downloaded, for coding the data in order to fit the continuation-ratio logits model. The ... [more ▼]

This note describes the Minitab commands BLOGISTIC, NLOGISTIC and OLOGISTIC and proposes a macro, which can be downloaded, for coding the data in order to fit the continuation-ratio logits model. The commands are illustrated by an example. [less ▲]

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See detailInfluence of the processing parameters on the physicochemical properties of puff pastry margarines
Lefebure, Emilie ULg; Ronkart, Sébastien; Brostaux, Yves ULg et al

Poster (2011, September 18)

Detailed reference viewed: 37 (13 ULg)