Methods of controlling rheological properties of polymer compositions comprising at least one high molecular weight polymer and one low molecular weight polymer are disclosed. The retaining element is adapted to retrieve nuts from the ground and includes a plurality of resilient pieces arranged in rows on a sleeve. After being transferred, the testing data may be analyzed at the central location, and a sensory training plan may be developed for the individual. The substrate potential fixed cells and the substrate potential variable cells are mixed together on a semiconductor chip so as to be properly used according to the functions or the like of circuit portions in which the cells are used.