Methods for delivering first and second fluid compositions to a target location of a subject include delivering the first composition from reservoir of an implantable infusion pump and delivering the second composition through a catheter access port of the implantable infusion device. For many types of functions, an optimum output value is possible, corresponding to a predetermined optimum input value or, where there is more than one input, to a set of such input values, which may be considered to define an input vector. Typically, TDD systems have significant latency due to the time to change from transmission to reception and the propagation delay time. Profile information associated with the determined third-party service providers is retrieved by the computing device. A Fourier transform of the interferogram may also be performed, in accordance with an FTIR technique.