The invention includes auxotrophic attenuated mutants of Listeria and methods of their use as vaccines. For supplying the driving power of the actuator is arranged a drive shaft which is arranged to rotate concentrically with respect to the axis of rotation of the roll, but independently with respect to the axis of rotation, and which drive shaft is, on the other hand, arranged to be rotated by a power means. The visual element can also include an actionable value indicator to specify a value about the middle portion and the first and second extremity portions. In structures according to the present invention, a patch antenna radiates into the waveguide while the antenna’s ground plane reduces back scattering from the waveguide. The ring is biased radially outward to engage the coupling nut, thereby biasing the coupling nut in a rearward direction and, at the same time, biasing the post in a forward direction to engage a terminal.