SEARCH Articles Figures Tables It was also revealed that both the NDR and current oscillation appeared only in the presence of cationic surfactant and not in the presence of anionic surfactant. [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint] [Publishers Imprint]