Mesoscopic deals with submicron materials, generally between the size of a molecule and the largest bacterium. The lower limit can be atoms; so it is more of a superset of "nano" than an adjoining range on the high side; but it can be that as well. Mesoscopic usually implies at least a few dozen atoms, as with an 'exciton', up to many thousands, as in single biological cells.
A macroscopic object obeys classical mechanics but when scaled down to a nano-size, it starts having overwhelming quantum mechanical properties. Why do we need a competing term with nano? Because the mesoscopic object has BOTH classical and quantum features as well as a mix of both, all at the same time in the same particle. It is simply a wider range, and implies a composite. It also implies complexity. The paper by Takahashi and Kitamura "Mesoscopic Catalyst and D-Cluster Fusion" http://rxiv.org/pdf/1012.0041v1.pdf supplies a number of interesting factoids and implications about Mesoscopic particles in LENR. The paper does not seem to be on the LENR/CANR site yet, but it could become a classic, so it should be. Under the auspices of "Technova Inc" (as in Toyota) these guys may have answers to the technical questions that the Rossi demo raises, but which Rossi is apparently ill-equipped to understand, or at least does not want to share. BTW - Technova is probably as close to solving the Rossi riddle as anyone, and with Toyota's money, they may try to upstage the MW demo with one of their own. Wouldn't it be a hoot if an alternative to E-Cat it turned up as a prototype in a Prius ??? One senses, in watching these developments as they emerge, that beating Rossi may become almost an issue of national pride for the Japanese in some ways, due to the pioneering work of Arata and Mizuno. Sadly, there is no deep pocket funder in the USA with the kind of longer range foresight as Toyota. On page 8 of the paper, there is an crude image worth only 999 words, showing why "mesoscopic" describes the active powder for this kind of LENR (which was discovered by Arata) better than "nano". The nano-constituent of the particle requires a "support" which can be micron sized, and is usually a ceramic within which are imbedded the nano particles, and with subnano structural features, like pits and cavities. The 'support' at the meso level is needed to avoid "stiction" . which as we all remember from not-too-long ago was the bugaboo of hard-drives, in their swift evolution to terabyte, back when they started to go over 100 megs. The drive would fail due to the close tolerances and stiction. Any non-dielectric in the meso-size range, and some dielectrics will experience stiction, becoming less active. This is related to van der Waals forces. Jones
