PT Journal AU Floet, DW Baselmans, JJA Klapwijk, TM Gao, JR TI Resistive transition of niobium superconducting hot-electron bolometer mixers SO Applied Physics Letters JI Appl. Phys. Lett. PY 1998 BP 2826 VL 73 IS 19 DI 10.1063/1.122603 DE HEB ER