Note on the Demkov-Ostrovsky nodeless sector
  We briefly tackle the following concepts in the Demkov-Ostrovsky (DO) nodeless sector: (i) orbital impedance, (ii) orbital capacity, (iii) closeness to reflectionlessness. Moreover, using previous supersymmetric results for the DO problem, a strictly isospectral effect in the DO orbital impedances is discussed and explicit plots are displayed for the Maxwell fisheye lens. This effect, though rather small, is general, that is, it may apply to any focusing structure. 
H.C. Rosu, J. Socorro