Plasmonic bipyramids for fluorescence enhancement and protection against photobleaching.

A great number of studies focus their interest on the photophysical properties of fluorescent hybrid gold nanoparticles for potential applications in biotechnologies such as imaging and/or treatment. Spherical gold nanoparticles are known to quench a chromophore fluorescent signal, when moieties are located in their close vicinity. The use of a polymer spacer on such a system allowed only partial recovery of the dye emission by controlling the surface to dye distance. Gold-based anisotropic sharp nanostructures appear to exhibit more interesting features due to the strong electric field generated at their edges and tips. In this paper, a complete study of hybrid fluorescent bipyramidal-like gold nanostructures is presented. We describe the chemical synthesis of gold bipyramids functionalized with fluorescent water-soluble polymers and their photophysics both in solution and on a single object. We show that the use of a bipyramidal shape instead of a spherical one leads to total recovery of the fluorescence and even to an enhancement of the emission of the dyes by a factor of 1.4.

[Unstable or hyperkinetic children. A comparative study of the concepts]. / L'enfant instable ou hyperkinétique. Une étude comparée des concepts.

In this literature, the authors analyze and compare the concepts of instability and hyperkinesia. One historic chapter shows that we are dealing with two parallel bibliographies that don't cross-check. It's a question of two different ways of naming and describing the same children. A differential semiological analysis in relation to three conceptual pairs, chosen because of their key positions (agitation-excitation, motor weakness-dyspraxia, personality problems-psychopathy) shows that it's sometimes impossible to clearly separate instability-hyperkinesia from these other concepts, insofar as they have been blown out of proportion and deformed. Nosographic categories overlap and cross-penetrate each other, which greatly limits their interest. Finally, it seems as if instability, a vast idea originally, had been progressively dismembered to the advantage of other categories, then disappeared from french literature entirely only to be replaced by hyperkinesia. This hyperkinesia can be taken literally as a personality disorder like any other, and also covers whatever is left of "instability". But the very concept of hyperkinesia, as was the case with instability, is blurred. The idea of MBD, and currently TDA, has historically been placed as a return to a huge category encompassing disorders that instability had progressively been differentiated from, and might be an attempt to anchor this nosology more firmly in medical speech. But the amalgam of social, physiological and psychological data resolves nothing and the problem remains intact.