The treated scarred vocal folds showed persistent MSC. Injection of scarred rabbit vocal folds with MSC rendered improved viscoelastic parameters and less signs of scarring expressed as collagen content in comparison to the untreated scarred vocal folds.

Effect of free volume and temperature on the structural relaxation in polymethylphenylsiloxane: A positron lifetime and pressure-volume-temperature study Positron annihilation lifetime spectroscopy was used to study the free-volume size distribution and the o-Ps ͑ortho-positronium͒ formation in two amorphous polymers. We performed positron lifetime measurements on poly͑vinyl acetate͒ ͑PVAc͒ in the temperature range of 84-414 K and on poly͑methyl methacrylate͒ ͑PMMA͒ in the temperature range of 84-454 K and as a function of time (Ͻ200 h) at four temperatures ͑Tϭ84, 149, 224, and 249 K͒. The glass transition temperature T g and secondary transition temperature were determined from the average o-Ps lifetime 3 versus temperature. The width of the o-Ps lifetime distribution was evaluated using the maximum entropy method ͑MELT͒. Analysis by the MELT program on the spectra shows that ͑i͒ the standard deviation ( 3 ) of the o-Ps lifetime distribution in PVAc and PMMA increases slightly with temperature in the glassy state, and then increases significantly with temperature above the glass transition temperature T g ; ͑ii͒ the ( 3 ) in PMMA has no observable variation as a function of positron irradiation time, which suggests that the measured free-volume distribution is not influenced by the positron irradiation. The o-Ps formation probability shows large variations with temperature, thermal history, and measuring time. These effects are discussed in the framework of the spur model.

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Amino-functional benzoxazine monomers have been successfully prepared. Several routes have been applied to incorporate amino group into benzoxazine structure. These approaches include reduction of the corresponding nitro-functional benzoxazines and deprotection of protected aminofunctional benzoxazine monomers. Various approaches that allow primary amine groups to be prepared without damaging the existing benzoxazine groups have been evaluated. Tetrachlorophthalimide and trifluoroacetyl are found to be suitable protecting groups. In addition, a model compound of amidefunctional benzoxazines is prepared from primary amine-functional benzoxazine. Fourier transform infrared spectroscopy (FTIR) and 1 H and 13 C nuclear magnetic resonance spectroscopy (NMR) are used to characterize the structure of the monomers. The polymerization behavior of amino-functional monomers and model compound are studied by differential scanning calorimetry (DSC).