L’observation de résistances chez certaines espèces de moustiques aux pesticides synthétiques les plus couramment utilisés a conduit à l’utilisation et au développement d’alternatives efficaces aux insecticides chimiques. Ainsi, l’insecticide d’origine bactérienne Bacillus thuringiensis israelensis (Bti) est devenu pratiquement la seule substance active autorisée pour le traitement des gîtes larvaires de moustiques en milieu naturel en France métropolitaine. Si le Bti est un biolarvicide intéressant, son efficacité dépend de sa présence et de sa rémanence à la surface de l’eau, c’est‐à‐dire là où les larves de moustiques se nourrissent, exclusivement pour certaines espèces anophèles. Le projet de recherche "MicroBti" consiste à étudier deux stratégies de formulation qui permettraient de prolonger la présence de Bti à la surface de l’eau au-delà de quelques jours (à l’exception des eaux usées), pour le traitement des gîtes larvaires.

When we make rapid reaching movements, we have to trade speed for accuracy. To do so, the trajectory of our hand is the result of an optimal balance between feed-forward and feed-back control in the face of signal-dependant noise in the sensorimotor system. How far do these principles of trajectory formation still apply after a stroke, for persons with mild to moderate sensorimotor deficits who recovered some reaching ability? Here, we examine the accuracy of fast hand reaching movements with a focus on the information capacity of the sensorimotor system and its relation to trajectory formation in young adults, in persons who had a stroke and in age-matched control participants. We find that persons with stroke follow the same trajectory formation principles, albeit parameterized differently in the face of higher sensorimotor uncertainty. Higher directional errors after a stroke result in less feed-forward control, hence more feed-back loops responsible for segmented movements. As a consequence, movements are globally slower to reach the imposed accuracy, and the information throughput of the sensorimotor system is lower after a stroke. The fact that the most abstract principles of motor control remain after a stroke suggests that clinicians can capitalize on existing theories of motor control and learning to derive principled rehabilitation strategies.

Gliadins are edible wheat storage proteins well known for their surface active properties1, 2. Although their foaming3 and emulsifying4 capability is useful in food industry, the physical mechanisms of their adsorption at an interface are not well understood and the resulting structure of the protein interfacial films not yet well characterized. In this talk, we will present experimental results on the interfacial properties of acidic gliadin solutions studied over 4 decades of concentrations from 0.01 up to 110 mg/ml.Dynamic pendant drop tensiometry reveals that the surface pressure of gliadin solutions builds up in a multistep process. We show that the series of curves of the time evolution of alpha.time collected at different protein concentrations can be merged onto a single master curve when surface pressure is plotted as a function of alpha.time where t is the time elapsed since the formation of the air/water interface and alpha is a shift parameter that varies with the bulk protein concentration as a power law with an exponent 1.6. The existence of a master curve indicates that the surface pressure is the relevant parameter to characterize the interfaces covered with gliadin proteins.Optical and elastic properties of the interfaces are studied by dilatational rheology and ellipsometry and provide a consistent physical picture of the adsorption processes. Correlated evolutions of ellipsometry and rheological properties show a simple and progressive coverage of the interface by individual proteins at low surface pressure. This stage is followed, at higher surface pressure, by conformational rearrangements of the protein film, which are identified by a strong increase of the dissipative viscoelastic properties of the film concomitantly with an anomalous evolution of its optical profile that we have quantitatively rationalized. In the last stage, at even higher surface pressure, the optical profile is not modified while the elasticity of the film dramatically increases resulting from the gelation of the film due to the formation of intermolecular bonds. [1] J.Ornebro, T. Nylander, A-C Eliasson (2000). Journal of Cereal Science 31, 195-221[2] R. C. A Keller, R. Orsel, R. J. Hamer (1997). Journal of Cereal Science 25, 175-183[3] Martin A. Bos, Bertus Dunnewind, Ton van Vliet (2003). Colloids and Surfaces B 31, 95-105[4] Y.Popineau, F.Pineau, P. Evon, S. Bérot (1999). Nahrung 6, S. 361-367

An organogelator based on a N,N′-substituted H-bonding perylenebisimide (PBI-C10) self-assembles to form either a green J-type (form I) or a red H-type (form II) aggregate structure. The molecular packing of both polymorphs was determined from a combination of Transmission Electron Microscopy (TEM) (low dose electron diffraction and high resolution), Grazing incidence X-ray diffraction and polarized infrared spectroscopy. To that aim, highly oriented films have been prepared by mechanical rubbing at controlled film temperature and DFT calculations were performed to identify representative vibrational IR bands and their associated polarizations. H-Bonding between amides generates either a rectangular columnar phase (form I) in the dried gel or a hexagonal packing of supramolecular 21/1 helices with a long period of 97 Å (form II) in annealed thin films. In aligned films of form I, polarized FTIR spectroscopy helps determine the orientation of both intermolecular H-bonds and the PBI core with respect to the substrate. In form II, PBI-C10 molecules assemble into pairs to form off-centered 21/1 helices whose helical axis is made of strongly H-bonded amides. TEM investigations show that three 21/1 helices are packed in a frustrated trigonal structure formed by H-bonding. The Form I → Form II transformation implies a redistribution of a single population of strong intra-columnar H-bonds between amides in form I to a mixture of strong and weak H-bonds in the supramolecular helices, the strong H-bonds forming the spine of the helices.

Suicidal behaviors result from a complex interaction between social stressors and individual vulnerability. However, little is known of the specific neural network supporting the sensitivity to social stressors in patients at risk of suicidal acts. Using functional Magnetic Resonance Imaging, we investigated brain processing of social rejection in suicide attempters. Thirty-six euthymic women with a history of depression and suicidal behavior were compared to 41 euthymic women with a history of depression but no suicidal attempt, and 28 healthy controls. The Cyberball Game was used as a validated social exclusion paradigm. Relative to healthy controls, both patient groups reported higher levels of social distress related to the task, without significant differences according to suicidal status. Compared to patients without any history of suicide attempt and healthy controls, suicide attempters showed decreased contrast in the left insula and supramarginal gyrus during the exclusion vs. inclusion condition, after controlling for number of depressive episodes, medication, mood disorder type or social phobia. Our study highlights impaired brain response to social exclusion in euthymic female suicide attempters in regions previously implicated in pain tolerance and social cognition. These findings suggest sustained brain dysfunctions related to social perception in suicide attempters.