Stable non-BPS D-branes of type I

We review the boundary state description of the non-BPS D-branes in the type I string theory and show that the only stable configurations are the D-particle and the D-instanton. We also compute the gauge and gravitational interactions of the non-BPS D-particles and compare them with the interactions of the dual non-BPS particles of the heterotic string finding complete agreement. In this way we provide further dynamical evidence of the heterotic/type I duality.Comment: 8 pages, 1 figure.eps, JHEP.cls, talk given by A. Lerda at the TMR Conference "Quantum aspects of gauge theories, supersymmetry and unification", Paris, September 199

Hybrid aligned nematics and second order elasticity

The effect of the second order elasticity on the critical thickness of Hybrid Aligned Nematic cells possessing either weak planar or weak homeotropic anchoring has been analysed. It is found that the critical thickness of such cells is strictly dependent on the surface elastic constant K13 and on the second order bulk elastic constant K*. Moreover, an experimental method for an indirect measurement of K13 and K* is proposed

Thermal diffusivity of amorphous plastic materials

The paper presents thermal diffusivity data on amorphous plastic materials, obtained by means of a method previously developed by the authors. This methods ensures high sensitivity (<1%) and good reproducibility (<3%