Nickel clusters embedded in carbon nanotubes as high performance magnets

Ensembles of fcc nickel nanowires have been synthesized with defined mean sizes in the interior of single wall carbon nanotubes. The method allows the intrinsic nature of single domain magnets to emerge with large coercivity as their size becomes as small as the exchange length of nickel. By means of X ray magnetic circular dichroism we probe electronic interactions at nickel carbon interfaces where nickel exhibit no hysteresis and size dependent spin magnetic moment. A manifestation of the interacting two subsystems on a bulk scale is traced in the nanotube s magnetoresistance as explained within the framework of weak localizatio

Mobility in geometrically confined membranes

Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbruck, who predicted a logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the "membrane size" for membranes of finite size [Saffman P, Delbruck M (1975) Proc Natl Acad Sci USA 72:3111-3113]. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10 nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbruck to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous Saffman-Delbruck theory and elucidates the role of membrane geometry and size in regulating lateral diffusion