A model for computation of the free volume fraction from the temperature dependence of positron lifetime is presented. The model is based on the idea that the total free volume of the sample is expanding in the same rate as the volume of holes seen by positrons. Then, having the values of thermal expansion coefficients of bulk and free volume, it is possible to compute the temperature dependence of fraction of free volume $f\left(T\right)\mathrm{}$ and the thermal expansion coefficient of occupied volume ${\alpha }_0.$ It is also possible to compute the Vogel temperature $T_0,$ WLF coefficient $c_{2g},$ and the ratio $c_{1g}/B,$ where $c_{1g}$ is the WLF coefficient and B is the Doolittle constant. The paper also presents computed values of abovementioned parameters for six different polymers. In the case of poly(isobutylene) and cis-trans 1,4 poly(butadiene) the results are compared with that obtained from viscosity $\eta \mathrm{}\left(T\right)\mathrm{}$ and temperature shift parameter $a_T\mathrm{}\left(T\right)\mathrm{}$ measurements.

Liver fibrosis is a major cause of morbidity and mortality worldwide due to chronic liver damage and leading to cirrhosis, liver cancer, and liver failure. To date, there is no effective and specific therapy for patients with hepatic fibrosis. As a result of their various advantages such as biocompatibility, imaging contrast ability, improved tissue penetration, and superparamagnetic properties, magnetic nanoparticles have a great potential for diagnosis and therapy in various liver diseases including fibrosis. In this review, we focus on the molecular mechanisms and important factors for hepatic fibrosis and on potential magnetic nanoparticles-based therapeutics. New strategies for the diagnosis of liver fibrosis are also discussed, with a summary of the challenges and perspectives in the translational application of magnetic nanoparticles from bench to bedside.

A free-volume theory is developed based on the defect diffusion model (DDM). In addition, positronium annihilation lifetime spectroscopy (PALS) ortho-positronium free-volume and intensity data are presented for poly(propylene glycol) with a molecular weight of 4000 (PPG 4000) in both the glassy and liquid states and dielectric relaxation and electrical conductivity data are reported for PPG 4000 in the liquid state. The DDM is used to interpret all of the data for PPG 4000 and previously reported PALS and dielectric relaxation data for glycerol. It is shown that while the PPG 4000 data exhibit a preference for the three-halves power law, the data for glycerol favor the first power (standard Vogel-Fulcher-Tammann) law. Good agreement between the DDM and the experimental results is found for all of the electrical data and the PALS free-volume data. While reasonable agreement is also found for the PALS intensity data for PPG 4000, a discrepancy exists between the experimental PALS intensity data and theory for glycerol. For the electrical conductivity for PPG 4000, a transition is observed at the same temperature (about 1.4 T(g) where T(g) is the glass transition temperature) where the PALS free volume changes from steeply rising with temperature to approximately independent of temperature. The same behavior is observed at about 1.5 T(g) for previously reported dielectric relaxation and PALS data for glycerol. Model parameters are presented that show the dominance of mobile single defects above (1.4-1.5) T(g) and the dominance of immobile clustered single defects below T(g) . Finally, a coherent picture of glasses and glass-forming liquids is presented based on the theory and results of the experiments.