Morphogenesis mechanisms in the solvothermal synthesis of BaTiO3 from titanate nanorods and nanotubes.

A rich variety of single crystalline BaTiO3 (BT) nanostructures have been synthesized by two different routes using titanate nanorods and nanotubes as precursors. Free standing, mixed or agglomerated nanotori, solid or hollow nanospheres and nanocubes were obtained. A careful analysis of the shape evolution of the resulting BT nano-objects obtained with both types of precursors and different parameters (precursor composition and shape, temperature, Ba/Ti molar ratio) allowed an improved understanding of the nanostructure formation.

Axial dipolar dynamo action in the Taylor-Green vortex.

We present a numerical study of the magnetic field generated by the Taylor-Green vortex. We show that periodic boundary conditions can be used to mimic realistic boundary conditions by prescribing the symmetries of the velocity and magnetic fields. This gives insight into some problems of central interest for dynamos: the possible effect of velocity fluctuations on the dynamo threshold, and the role of boundary conditions on the threshold and on the geometry of the magnetic field generated by dynamo action.