A dispensing mechanism for a liquid container includes a hollow flexible dispensing portion and a dispenser. The invention addresses specifically to current challenges with adaptive control in these areas: 1) persistent excitation, 2) complex nonlinear input-output mapping, 3) large inputs and persistent learning, and 4) the lack of stability analysis tools for certification. The items may be products such as online media downloads, games, merchandise, etc. Filtering section calculates estimated value S\u20322 of second spectrum S2 based on pitch coefficient T. The agents can be used to image angiogenesis, inflammation or other physiological processes in a subject.