Photoacoustic monitoring of thermal wave interference effects during the formation of polymeric thin films from solutions

In this work, the potential of photoacoustic (PA) technique in the analysis of the formation of polymer films by evaporation from aqueous solutions is explored. Experiments are performed using different aqueous volume fractions of two different polymers, PEDT:PSS and a white liquid glue. The liquid sample is deposited on a metallic substrate attached to a modified PA cell that allows the monitoring of the evaporation process and development of the polymeric film. It is shown that when the thickness of the sample is of the order of the thermal diffusion length, maxima and minima of the PA signal, due to thermal wave interference effects, are observed. In the last stage of the process, the PA signal reaches a stable value which depends on the thickness of the formed film. The kinetics of the polymeric film formation, the dependence of the evaporation rate of the solvent as well as the final thickness of the polymeric film is discussed. These results can be useful in establishing a methodology for the photothermal monitoring and thermal characterization of the development of polymeric films from solutions.     

Formulation of the vibrational theory in terms of redundant internal coordinates

Using the generalized inverse of matrices and the method of canonical matrices, this paper develops an unambiguous formulation of the theory of small vibrations of molecules which is valid when redundant internal coordinates are used. Such treatment includes the attainment of unambiguous relationships relating the compliance matrix (the generalized inverse of the canonical force constants matrix) with experimental data (vibrational frequencies, Coriolis coupling constants, centrifugal distortion constants and mean-square amplitudes). Moreover, expressions for the elements of the Jacobian matrices of the above magnitudes with respect to the compliance constants have been also obtained as well as some sum rule relationships.     

Zeroth Poisson Homology,Foliated Cohomology and Perfect Poisson Manifolds

We prove that, for compact regular Poisson manifolds, the zeroth homology group is isomorphic to the top foliated cohomology group, and we give some applications. In particular, we show that, for regular unimodular Poisson manifolds, top Poisson and foliated cohomology groups are isomorphic. Inspired by the symplectic setting, we define what a perfect Poisson manifold is. We use these Poisson homology computations to provide families of perfect Poisson manifolds.