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See detailContribution to the study of semiochemical slow-release formulations as biological control devices
Heuskin, Stéphanie ULg

Doctoral thesis (2011)

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis ... [more ▼]

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis, two sesquiterpenoids, E-β-farnesene and E-β-caryophyllene, were formulated for their related properties as aphid enemy attractants. E-β-farnesene, the alarm pheromone of many aphid species, was also identified as a kairomone by attracting and inducing oviposition of aphid predators (Episyrphus balteatus De Geer (Diptera: Syrphidae)) and by attracting aphid parasitoids (Aphidius ervi Haliday (Hymenoptera: Braconidae)). E-β-caryophyllene was identified as a potential component of the aggregation pheromone of the Asian ladybird, Harmonia axyridis Pallas, another aphid predator. The two products were purified from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) for E-β-farnesene and E-β-caryophyllene, respectively. Natural and biodegradable slow-release formulations were then investigated in order to deliver these molecules on crop fields for a long period of time as biological control devices. Due to their sensitivity to oxidation, both sesquiterpenes needed to be protected from oxygen degradation. For this purpose, alginate – hydrophilic matrix with low oxygen permeability – was used as polymer for the formulations: the main objective was to deliver semiochemical substances in the air in a controlled way. Consequently, a careful selection of alginates was realised. Formulated beads showed different structural and encapsulation properties depending on various formulation factors. Alginate formulations were characterized by texturometry and by confocal microscopy in order to observe the distribution of semiochemicals in alginate network. The last step of alginate bead characterisation consisted in studying release rate of semiochemicals in laboratory-controlled conditions by optimised trapping and validated Fast-GC procedures. Finally, the efficiency of formulations as aphid predator (Syrphidae) and parasitoids (A. ervi) attractants was demonstrated by field trapping and olfactometry experiments. [less ▲]

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See detailContribution to the study of stress cracking phenomenon by oxidative induction time measurements
Rigo, Jean-Marie ULg; Courard, Luc ULg; Detaille, Laurence et al

in Delmas, Philippe; Gourc, Jean-Pierre (Eds.) Proceedings of the Rencontres 95 (1995)

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See detailContribution to the study of Strychnos usambarensis GILG, main ingredient of an African curarizing arrow poison
Angenot, Luc ULg

in Dissertation Abstracts (1974), 34(11), 338

The thesis is subdivided in four parts and two annexes . the first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of ... [more ▼]

The thesis is subdivided in four parts and two annexes . the first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of arrow poisons in the World and particularly in Africa; the third part describes the isolation of eight indole alkaoids ( 5 new and 3 known ones) and their structure determination thanks to modern spectroscopic methods.The fourth part is applied to the biosynthesis of these alkaloids and to the identification of loganic acid.The first appendix describes the phytochemical screening of 33 Rwandan plants mainly collected in the National Park of Akagera. The second appendix relates pharmacological experiments on crude fractions and some isolated alkaloids. [less ▲]

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See detailContribution to the study of the allosteric properties of acetylcholinesterase
Gridelet, J.; Foidart, Jean-Michel ULg; Wins, P.

in Archives Internationales de Physiologie et de Biochimie (1970), 78

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See detailContribution to the study of the flora and the ecology of cave blue-green algae.
Garbacki, Nancy ULg; Hoffmann, Lucien

Conference (1995)

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See detailContribution to the study of the relations between fish of the family of Carapidae and their holothurian hosts
Parmentier, Eric ULg

in SPC Bêche de mer, Information Bulletin (2004), 19

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See detailContribution to the study of the resistance to drying of Pseudomonas fluorescens
Mputu Kanyinda, Jean-Noël ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013)

The objective of this thesis is to study the resistance to drying of Pseudomonas fluorescens. Freeze-drying is the most suitable method for drying P. fluorescens. However, freeze-drying induced loss of ... [more ▼]

The objective of this thesis is to study the resistance to drying of Pseudomonas fluorescens. Freeze-drying is the most suitable method for drying P. fluorescens. However, freeze-drying induced loss of cell viability. This loss of viability is mainly due to membrane rupture, temperature and oxidation of fatty acids, membrane proteins and glutathione. For this purpose, the use of protective compounds during freeze-drying has allowed us to obtain a powder having a high viability. We then studied the impact of these protective compounds, oxygen and storage temperature on the viability of P. fluorescens during storage. Analyses of fatty acids, proteins, glutathione and the study of membrane integrity during the various manufacturing processes and storage have established a link between the degree of oxidation and cell death. The results of flow cytometry showed that the freeze-drying longer affects the viability of P. fluorescens rather than storage. We have increased the yield of the production in bioreactor of P. fluorescens and time of culture was halved. [less ▲]

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See detailA contribution to the study of β Canis Majoris.
Struve, Otto; Swings, Polydore ULg

in Astrophysical Journal (1941), 94

Coudé spectrograms obtained at the McDonald Observatory on January 22 and 24, 1941, show a velocity range of about 9 km/sec, in a period of 6 hours. The lines are diffuse and shallow near minimum velocity ... [more ▼]

Coudé spectrograms obtained at the McDonald Observatory on January 22 and 24, 1941, show a velocity range of about 9 km/sec, in a period of 6 hours. The lines are diffuse and shallow near minimum velocity and sharper and deeper near maximum velocity. The Ca II line K shares in the oscillations. It is probably a blend of a stellar and an interstellar line. The lines suggest turbulence of an appreciable amount. A line at λ 4469.71 is probably a blend of O II and forbidden He I. A comparison with β Cephei shows that β Canis Majoris is more luminous. It is, however, not a supergiant. The similarity in the periods suggests similarity of internal structure. [less ▲]

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See detailContribution to the study on sound production in clownfishes (Perciformes, Pomacentridae): a multidisciplinary approach
Colleye, Orphal ULg

Doctoral thesis (2011)

Clownfishes (Amphiprion spp.) are brightly colored fishes that are members of the Pomacentridae family. They are well known for their mutualistic relationship with tropical sea anemones. These fishes live ... [more ▼]

Clownfishes (Amphiprion spp.) are brightly colored fishes that are members of the Pomacentridae family. They are well known for their mutualistic relationship with tropical sea anemones. These fishes live in social groups in which there is a size-based dominance hierarchy. In this structure where sex is socially controlled, agonistic interactions are numerous and serve to maintain size differences between individuals adjacent in rank. Several studies have reported that vocalizations are associated with agonistic interactions but precise data are lacking and further investigations are needed. The nature of the sound-producing mechanisms also remained unresolved, only resting on few assumptions. Thereby, the main aim of the present thesis is (1) to determine the fundamental components of the acoustic communication in clownfishes, and (2) to explain the mechanisms of sound production. In order to achieve these objectives, the research has been divided into three different axes. Firstly, the study of the acoustic behaviors shows that no acoustic signal is associated with reproductive activities in clownfishes. Sound recordings during agonistic interactions indicate that these fishes produce two types of sounds. Aggressive sounds are produced during chases and threat displays while submissive (or head shaking) sounds are emitted in reaction to aggressive acts by dominant. Both types of sounds show size-related intraspecific differences in dominant frequency and pulse duration: smaller individuals produce higher frequency and shorter duration pulses than larger individuals, and inversely. Consequently, these sonic features might be useful cues for individual recognition and maintenance of cohesion within the group. Secondly, the study of the sound-producing mechanism highlights that aggressive sounds are initiated by buccal jaw teeth snapping caused by rapid mouth closure attributed to a sonic ligament. It appears that the swimbladder does not function as a resonator that amplifies and changes the quality of sounds. This structure is a highly damped sound source prevented from prolonged resonant vibrations. On the other hand, the rib cage might be the major acoustic radiator and its resonant properties might explain the size-related variations observed in pulse duration and dominant frequency. Thirdly, the comparison of aggressive sounds among fourteen clownfish species indicates that the same relationship between fish size and both dominant frequency and pulse duration is spread over the entire group (i.e. tribe Amphiprionini). These results highlight all species use a highly conservative mechanism of vocalization. Pulse period appears to be the most variable acoustic feature and could be involved in species-specific recognition, as well as pulse duration and dominant frequency in a lesser extent through their relationship with body size. Although sound production appears to be restricted to some agonistic behaviors, these sounds seem to constitute an integral part of the peculiar way of life of clownfishes. The aggressive and submissive sounds would also result from two different mechanisms.   [less ▲]

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See detailContribution to the valorisation of pomegranate (Punica granatum L.)
Bchir, Brahim ULg; Roiseux, Olivier; Attia, Hamadi et al

Poster (2007, October 11)

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See detailContribution to the valorization of^pomegranate (Punica granatum L.)
Bchir, Brahim; Roiseux, Olivier; Attia, Hamadi et al

Poster (2007, October 11)

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See detailContribution to the water disinfection study by photosensitization with plants extracts.
Sunda, M.; Rosillon, Françis ULg; Taba, K. M.

in European Journal of Water Quality = Journal Européen d’Hydrologie (2008), 39(2), 199-209

Solar water disinfection study using plants extracts, in tryptophan media (1%), has revealed a photodynamic activity of Cassia alata, Cassia occidentalis, Carica papaya, Phyllantus niruri and Coleus ... [more ▼]

Solar water disinfection study using plants extracts, in tryptophan media (1%), has revealed a photodynamic activity of Cassia alata, Cassia occidentalis, Carica papaya, Phyllantus niruri and Coleus kilimandschari aqueous extracts. Aqueous extracts of Lantana camara, Cymbopogon citratus and Hibiscus rosa-sinensis produce a bactericidal effect. Water disinfection by alkaloid extracts of Cassia alata, Cassia occidentalis, Carica papaya, Phyllantus niruri and Coleus kilimandschari shows a bactericidal effect. On the other hand, unalkaloid extracts of the same compounds especially present a photodynamic activity. The photodynamic activity of unalkaloid extract is due to the presence of quinones and anthraquinones which generate singlet oxygen.The singlet oxygen generated attacks and damages the microorganisms contained in polluted water. The necessary sunlight time for coliform inactivation and other germs is one hour for 2 ml of extracts/liter of polluted water. [less ▲]

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See detailcontribution to understanding of sedimentological and diagenetic processus related to a major emersive surface : example of the middle paleocene unconformity (MPU).
Loisy, Corinne; Kiefer-Ollier, Eloise; Cerepi, Adrian et al

in Book of Abstracts - 26th IAS meeting, Alghero, Sardenia (2009)

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See detailContribution to understanding of sedimentological and diagenetic processus related to major emersive surfaces and their spatial variation
Loisy, Corinne; Da Silva, Anne-Christine ULg; Kieffer, Eloise et al

in Book of Abstracts - 25th meeting of the IAS, Patras, Greece (2007)

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