We report on two mesoscopic phenomena observable in nano-porous alumina films. One is Coulomb blockade associated with weak localization in an array of single nano-tunnel junctions/multi-walled carbon nanotubes (MWNTs), and the other is an abrupt magnetoresistance (MR) jump in Ni-nanowire system. Weak localization yields CB in single tunnel junction system by acting as high impedance external electromagnetic environment, following phase correlation theory. The CB is very sensitive to phase modulation in the MWNTs. An abrupt MR jump is associated with magnetic domain walls. Its correlation with macroscopic quantum tunneling and weak localization is discussed.