Aqueous solutions of poly(ethylene oxide) were investigated using the ultrasonic technique, photon correlation spectroscopy (PCS) and nuclear magnetic resonance (NMR), in a wide range of molecular weight (from ethylene glycol to poly(ethylene oxide) 4 000 000 Da). Ultrasonic data reveal that the mixing process is not ideal and show that the polymer–water interaction strength increases with the polymerization degree. PCS and NMR, on the other hand, furnish a free particle diffusion coefficient which satisfies a unique scaling law from 8000 to 4 000 000 Da and demonstrates the good solvent nature of water. These experimental findings indicate that polymer–polymer aggregation processes are not an inherent property of these systems.
Aqueous micellar solutions of sodium taurocholate (NaTC) have been studied by using quasi-elastic lightscattering (QELS) and 1 H pulse-gradient-stimulated-echo NMR (PGSTE-NMR). The collective and selfdiffusion coefficients have been obtained as a function of NaTC concentration (0.05-0.20 M) and the ionic strength of the solution (0-0.8 M NaCl added). The comparison of the two techniques' data in each solution has been performed in the context of micellar growth and intermicellar interactions. The model of monodisperse Brownian particles with hydrodynamic interaction and hard core repulsion gives rise to a satisfactory agreement with the experimental data. The translational diffusion coefficient of the single micellar aggregate has been calculated for each solution. The size of the micellar aggregates depends on the ionic strength and bile salt concentration.
Some effects of extremely low frequency electromagnetic fields (ELF-EMFs) on human spermatozoa are reported. Significant increases in the values of the motility and of the other kinematic parameters have been observed when spermatozoa were exposed to an ELF-EMF with a square waveform of 5 mT amplitude and frequency of 50 Hz. By contrast, a 5 mT sine wave (50 Hz) and a 2.5 mT square wave (50 Hz) exposure did not produce any significant effect on sperm motility. The effects induced by ELF-EMF (50 Hz; 5 mT) during the first 3 h of exposure persisted for 21 h after the end of the treatment. These results indicate that ELF-EMF exposure can improve spermatozoa motility and that this effect depends on the field characteristics.
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