Apparatus and methods are described including a location sensing system that comprises a plurality of location sensors, and which is configured to identify respective locations of a plurality of clinicians, and to generate a location-sensing-system signal in response thereto. The methods comprise modulating the concentration of amyloid-beta in the brain interstitial fluid. The controller includes a state estimator which is configured to estimate the following system states: wafer x-translation, wafer y-translation, wafer scale in x, wafer scale in y, wafer rotation, wafer non-orthogonality, reticle magnification, asymmetric magnification, reticle rotation, asymmetric reticle rotation. A clutch mechanism supported on the ring member is associated with each arm to individually selectively engage each such arm with a rotatable main gear such that upon rotation of the main gear by a single actuator any one, all or any desired combination of arms may be translated relative to the ring member to move the blades and expand the opening in one or more selected desired directions.