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Scanning electron micrograph of multiwalled carbon nanotubes on the graphite cathode of an arc-discharge apparatus. The diameter of the large central region is about 3 mm. [E. Cazzanelli, M. Castriota, L. S. Caputi, A. Cupolillo, C. Giallombardo, and L. Papagno, Phys. Rev. B 75, 121405 (2007)] |


