Administration of clavulanic acid and related compounds at low dosages provides significant neurotropic effects in warm-blooded vertebrates evidenced inter alia by anxiolytic and anti-aggressive behavior and enhanced cognition believed to be mediated by inhibition of neurogenic enzyme activity. The active ingredient is selected from a class of N-hydrocarboyl phosphoroamidothioate and phosphoroamidodithioate compounds as described in the specification. Flotation devices are affixed to rotational devices and submerged into a heavy fluid encased within a chamber that does not interfere with the normal operation of the said rotational device. In an image fetching part, the image data of the photographed character image is fetched.