Abstract: [Problem] To provide a system for inference of a measurement target dynamic state, the system being capable of providing not only information as to whether a culture solution is aerobic or anaerobic, but also data for determining a culture operation and for optimizing various conditions of the culture solution.

Abstract: An electronic tuning circuit for an AM radio receiver in which a signal of a specific frequency is selected from the input signal from an antenna is provided, this tuning circuit having a tuning transformer with a first winding and a second winding, the number of turns on the first winding being greater than the number of turns on said second winding, the input from the antenna being applied to the second winding of the tuning transformer, and further having two varactor diodes, each of which is connected in series with a DC-blocking capacitor, these series-connected varactor-capacitor combinations being connected in parallel with the first winding of the tuning transformer such that the polarities of the varactor diodes are mutually opposing.