Defect dynamics in clusters of self-propelled rods in circular confinement Zhengjia Wang, Tieyan Si, Junhua Hao, Yu Guan, Feng Qin, Bin Yang and Wenwu Cao Eur. Phys. J. E, 42 11 (2019) 150 Published online: 27 November 2019 DOI: 10.1140/epje/i2019-11911-y