Diameter and rigidity of multiwalled carbon nanotubes are critical factors in mesothelial injury and carcinogenesis Hirotaka Nagai, Yasumasa Okazaki, Shan Hwu Chew, Nobuaki Misawa, Yoriko Yamashita, Shinya Akatsuka, Toshikazu Ishihara, Kyoko Yamashita, Yutaka Yoshikawa, Hiroyuki Yasui, Li Jiang, Hiroki Ohara, Takashi Takahashi, Gaku Ichihara, Kostas Kostarelos, Yasumitsu Miyata, Hisanori Shinohara