Structure and process for compensating threshold voltage variation due to process variation. The cells are configured to have artificial magnetic conductor effects corresponding to different frequency bands in a first direction and a second direction, and the first antenna element and the second antenna element are arranged parallel to the surface of the cell structure, respectively along the first direction and the second direction. The image-taking apparatus has a vibration detecting section which obtains vibration information about vibrations. The transmitter may send synchronization packets to the receiver. Upon determining the identity of an individual using, for instance, a software recognition program, various protocols may be used to implement the formation of the ad hoc network. Some methods and systems employ portable monitors carried by participants of the studies along with publications fitted with various devices, such as piezoelectric transducers, RFID tags and others devices and circuits.