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Peer Reviewed
See detailHarmonia axyridis (Pallas) secondary metabolites quantification in relation with aposematism : Part I : Harmonine quantification
Fischer, Christophe ULg; Heuskin, Stéphanie ULg; Laurent, Pascal ULg et al

Poster (2010, January)

These last few years, the multicoloured Asian ladybird, Harmonia axyridis Pallas (Insects: Coleoptera: Coccinellidae), an invasive species, has swiftly spread out in Europe. This aposematic and highly ... [more ▼]

These last few years, the multicoloured Asian ladybird, Harmonia axyridis Pallas (Insects: Coleoptera: Coccinellidae), an invasive species, has swiftly spread out in Europe. This aposematic and highly polymorphic insect is problematic in several ways. It seems to outcompete native coccinellid species; they can group on fruits in vineyards and spoil wine when crushed with grapes; they can aggregate by hundreds in houses to winter. This study aims to investigate the relations between the chemical defences of H. axyridis and warning signals expressed by this bug. To achieve this goal, two original quantification methods of H. axyridis secondary metabolites have been undertaken. The first one allows Fast-GC quantifying harmonine, its main defence alkaloid. The other one permits to determine its emission rate of 2-isopropyl-3-methoxypyrazine, a highly odorous compound probably involved in the communication between individuals and in the aposematism of this insect. This last point will be detailed in another poster. Firstly, a method of extraction, acetylation and purification of harmonine from H. axyridis has been devised to obtain a calibration standard because this molecule is not commercially available. The identity of the extracted compound has been confirmed by mass spectrometry and multidimensional NMR. The GC purity of this N,N-diacetylharmonine is of 100%. During the experiments, its stability in acetone solution at 4°C has been verified. Using this purified molecule, an original method of harmonine quantification has been developed by fast gas chromatography and validated using accuracy profile. The method has been validated for concentrations ranging from 28µg/ml to more than 264µg/ml, with a maximal error risk of 20%. From about 100µg/ml, peaks symmetry decreased, but did not influence the quantification. That accuracy profile validation has been compared with a more classical validation using AOAC (2006) norm, which confirmed the first validation. This method allows quantifying harmonine in one single insect. Harmonine has been quantified in 80 H. axyridis divided into four groups of at least 15 individuals on basis of the morph type and the elytra hue. Males and females harmonine contents did not significantly differ. The mean harmonine content was of 106.6µg/individual with a standard deviation of 80.2µg/individual. The results distribution obtained was not normal and a strong variability between individuals was observed, which explains the high standard deviation. These results and those of the pyrazine and colour analysis have been statistically analyzed in order to show potential correlations between these factors. It would appear that elytra colour is linked with the insect harmonine content. Individuals with a non-melanic orange colour presented harmonine content significantly higher than other studied colours. The harmonine content does not seem linked to the pyrazine emission rate. [less ▲]

Detailed reference viewed: 217 (24 ULg)
Peer Reviewed
See detailHarmonia axyridis (Pallas) secondary metabolites quantification in relation with aposematism : Part II : Pyrazine quantification
Fischer, Christophe ULg; Heuskin, Stéphanie ULg; Marlet, Christelle ULg et al

Poster (2010, January)

The main objective of this study is to investigate the presence of links between chemical defences and warning signals presented by Harmonia axyridis (Pallas), the multicoloured Asian ladybird (Insects ... [more ▼]

The main objective of this study is to investigate the presence of links between chemical defences and warning signals presented by Harmonia axyridis (Pallas), the multicoloured Asian ladybird (Insects: Coleoptera: Coccinellidae). This second part describes an original quantification method for 2-isopropyl-3-methoxypyrazine (IPMP) by active sampling on thermally desorbed adsorbent (TD) coupled with GC-MS analysis. This highly odorous compound is supposed to be implicated in intra- and interspecific communication. In order to allow harmonine quantification (a defence alkaloid, see Part 1), this method avoid any hemolymph loses by the ladybird (Coccinellids can emit hemolymph when stressed). This method is non-lethal and applicable on one single insect. The quantification method has been validated from 37,5pg to 10 000 pg per adsorbent cartridge. On this range, there is no breakthrough and desorption is complete (>99.4%). At the LOQ (37.5pg/cartridge), the bias is of 20%, but rapidly decreased to less than 5% on the rest of the validated range (100 to 10 000 pg/cartridge). According to AOAC (2006) norm, this method is repeatable but not reproducible. The IPMP emission rate following a stress has been quantified on 80 H. axyridis grouped in four classes on basis of the morph type and the elytra hue. Males and females emission rates did not significantly differ. The mean emission rate is of 707 pg/4h with an extremely high standard deviation of 1766pg/4h due to a great individual variability and a strongly asymmetric distribution of the results. These results and those of the harmonine and colour analysis have been statistically analyzed in order to show potential correlations between these factors. It seems that elytra colour is linked with the insect IPMP emission rate. Individuals with a melanic red colour presented IPMP emission rate significantly lower than other studied colours. The harmonine content does not seem linked to the pyrazine emission rate. [less ▲]

Detailed reference viewed: 132 (7 ULg)
Peer Reviewed
See detailHarmonia axyridis population study in agroecosystems
Vandereycken, Axel ULg; Fassotte, Bérénice ULg; Durieux, Delphine ULg et al

Poster (2014, October)

The Multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is one of these species which was intentionally introduced for biological control and has spread from its native ... [more ▼]

The Multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is one of these species which was intentionally introduced for biological control and has spread from its native range in Central and Eastern Asia to large parts of North and South America, Europe, and Africa. The decline of native species is linked to the spread and the aggressive behaviour of H. axyridis. From 2009, we evaluated the population densities of aphids predator and predator diversities, with a special focus on H. axyridis in agroecosystems of Wallonia (South of Belgium). First, field crops preferences of H. axyridis were determined. Later, changes linked to aphid’s predator populations over time were evaluated. Finally, H. axyridis population changes between two crop farming methods were also evaluated. Samplings performed in agroecosystems highlighted that the community of aphid's predator is composed of few dominant species: three coccinellids (Coccinella septempunctata L., P. quatuordecimpunctata L., and H. axyridis), one syrphid (Episyrphus balteatus De Geer), and one chrysopid (Chrysoperla carnea Stephens). We demonstrated that H. axyridis do not invade all crops at the same rate, maize and broad bean being more infested than wheat and potato at both larval and adult stages. Moreover, H. axyridis populations in maize have strongly increased from 2009 to 2011. Finally, we showed that organic farming do not contribute to increase the abundance of H. axyridis but leads to increase the total abundance of aphid’s natural enemies. [less ▲]

Detailed reference viewed: 27 (8 ULg)
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See detailThe harmonic balance method for advanced analysis and design of nonlinear mechanical systems
Detroux, Thibaut ULg; Renson, Ludovic ULg; Kerschen, Gaëtan ULg

in Proceedings of the SEM IMAC XXXII (2014)

As a tool for analyzing nonlinear large-scale structures, the harmonic balance (HB) method has recently received increasing attention in the structural dynamics community. However, its use was so far ... [more ▼]

As a tool for analyzing nonlinear large-scale structures, the harmonic balance (HB) method has recently received increasing attention in the structural dynamics community. However, its use was so far limited to the approximation and study of periodic solutions, and other methods as the shooting and orthogonal collocation techniques were usually preferred to further analyze these solutions and to study their bifurcations. This is why the present paper intends to demonstrate how one can take advantage of the HB method as an efficient alternative to the cited techniques. Two different applications are studied, namely the normal modes of a spacecraft and the optimization of the design of a vibration absorber. The interesting filtering feature of the HB method and the implementation of an efficient bifurcation tracking extension are illustrated. [less ▲]

Detailed reference viewed: 184 (39 ULg)
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See detailThe Harmonic Balance Method for Bifurcation Analysis of Nonlinear Mechanical Systems
Detroux, Thibaut ULg; Renson, Ludovic ULg; Masset, Luc ULg et al

in Proceedings of the SEM IMAC XXXIII (2015)

Because nowadays structural engineers are willing to use or at least understand nonlinearities instead of simply avoiding them, there is a need for numerical tools performing analysis of nonlinear large ... [more ▼]

Because nowadays structural engineers are willing to use or at least understand nonlinearities instead of simply avoiding them, there is a need for numerical tools performing analysis of nonlinear large-scale structures. Among these techniques, the harmonic balance (HB) method is certainly one of the most commonly used to study finite element models with reasonably complex nonlinearities. However, in its classical formulation the HB method is limited to the approximation of periodic solutions. For this reason, the present paper proposes to extend the method to the detection and tracking of codimension-1 bifurcations in the system parameters space. As an application, the frequency response of a spacecraft is studied, together with two nonlinear phenomena, namely quasiperiodic oscillations and detached resonance curves. This example illustrates how bifurcation tracking using the HB method can be employed as a promising design tool for detecting and eliminating such undesired behaviors. [less ▲]

Detailed reference viewed: 124 (29 ULg)
Peer Reviewed
See detailHarmonic Trusses : the Search for Minimum Weight
Samyn, Philippe; Latteur, Pierre ULg

(1998, February)

Detailed reference viewed: 19 (0 ULg)
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Peer Reviewed
See detailHarmonic-Balance Finite-Element Modelling of Electromagnetic Devices: A Novel Approach
Gyselinck, J.; Dular, Patrick ULg; Geuzaine, Christophe ULg et al

in IEEE Transactions on Magnetics (2002), 38(2), 521--524

Detailed reference viewed: 20 (2 ULg)
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Peer Reviewed
See detailL’Harmonie des doctrines dans le néoplatonisme tardif. Platon et Aristote chez Simplicius
Gavray, Marc-Antoine ULg

in Annuaire de l'École Pratique des Hautes Etudes. Section des Sciences Religieuses (2013), 120(2011-2012), 83-39

Detailed reference viewed: 18 (4 ULg)
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See detailL'harmonie et le chaos. Le rationalisme leibnizien et la "nouvelle science"
Bouquiaux, Laurence ULg

Book published by Peeters (1994)

Detailed reference viewed: 6 (0 ULg)
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See detailL’harmonisation des conditions individuelles de travail en cas de transfert conventionnel d’entreprise
Kefer, Fabienne ULg

in La cession d’entreprise : les aspects sociaux (2011, April 07)

Detailed reference viewed: 64 (11 ULg)
Peer Reviewed
See detailHarmonisation des démarches de validation, est-elle possible ?
Hubert, Philippe ULg; Chiap, Patrice ULg; Laurentie, M. et al

Conference (2003)

Detailed reference viewed: 27 (1 ULg)
See detailL'harmonisation des législations des Etats membres de la C.E.E. en matière d'impôts directs
Thilmany, Jean ULg

in Revue pratique des sociétés (1981)

Detailed reference viewed: 13 (0 ULg)
See detailL'harmonisation des statuts entre ouvriers et employés
Baukens, Michèle; Rozenberg, Fanny ULg; Kéfer, Fabienne ULg

Book published by Anthemis (2014)

Detailed reference viewed: 60 (22 ULg)
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See detailHarmonisation des strategies de validation et estimation de l'incertitude associee dans le cadre de l'accreditation des laboratoires d'essais
Hubert, Philippe ULg; Rozet, Eric ULg; Boulanger, Bruno ULg et al

in Acta Clinica Belgica. Supplementum (2006), S1(1), 53-55

In order to achieve the harmonization of validation strategies, the interpretation of several validation criteria is proposed. Furthermore, a simple and visual decision tool to assess the validity of an ... [more ▼]

In order to achieve the harmonization of validation strategies, the interpretation of several validation criteria is proposed. Furthermore, a simple and visual decision tool to assess the validity of an analytical procedure is described: the accuracy profile based on the estimation of the total error of the measurements. This profile build with beta-expectation tolerance intervals can also compute with efficiency the uncertainty related to the results of a laboratory, which is an essential parameter for the accreditation of laboratories under ISO 17025. [less ▲]

Detailed reference viewed: 86 (18 ULg)
See detailHarmonisation du droit de la construction et protection du consommateur
Kohl, Benoît ULg

Scientific conference (2008, May 08)

Detailed reference viewed: 12 (0 ULg)
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Peer Reviewed
See detailHarmonisation et construction
Kohl, Benoît ULg

Article for general public (2009)

Detailed reference viewed: 35 (14 ULg)