José Alberto Giacometti

A review on the Foucault pendulum motion is presented using Cartesian coordinates for the ideal case and for small amplitude of oscillations. The choice of referential frames, the formulation and solution of Newton’s differential equation for the non-inertial frame of the Earth and the validity of the approximations used to simplify the determination of the solution are given. Using the angular position of the trajectory cusps, a new method to determine the precession angular velocity of the Foucault pendulum is shown. The pendulum bob trajectories and velocities for the referential frame in rotation with the Earth as well as for the inertial frame are given and the Chevilliet theorem was demonstrated. In addition, the pendulum bob trajectories are shown when an initial velocity is impinged in the direction perpendicular to the pendulum oscillation plane.

This work describes the experimental apparatus based on the Mach-Zehnder interferometer for measuring the electro-optic coefficient during and after the photo-assisted poling process using a continuous light excitation. We also show that the poling can be performed at cryogenic temperatures. The setup is based on the superposition of a Mach-Zehnder AC modulation voltage on the DC bias voltage required to promote the chromophore orientation during light excitation. The effect of the reversible polarization due to the DC bias voltage applied to the polymer film is considered to calculate the electro-optic coefficient during the photo-assisted poling process. The usefulness of our setup is demonstrated with three polymer films, with different electro-optic activities: guest-host, copolymer, and homopolymer, all based on methyl methacrylate monomers and containing disperse red-1 chromophores.

This work describes a guiding method to select the best sensing units to compose the array of an electronic tongue. It is based on the principal component analysis (PCA), in which use is made of the PCA plot of the transposed matrix of experimental data, e.g., for different concentration of an analyte. When points in such a plot appear very close to each other, it means that one of the corresponding sensing unit can be removed from the array without hampering the discrimination capability of the e-tongue. The method was validated with electric capacitance data obtained with aqueous solutions made with ultrapure water and KCl or HCl or glucose at different concentrations.