12. What is the most common magnetic nanoparticle oxide compound family? What are the variants, and why is it used more commonly than other compounds? 13. Is diffusion of solutes in nano-channels the same as in bulk solvent? Give two mechanisms that can be expected to modify the diffusion coefficient. 14. Can the chemical properties of materials change at the nanoscale? Give an example, and a plausible cause for such a change.