The distal end part of an arm 5 is turnably and removably connected to the distal end part of a base part 5 through a connection mechanism 7. An auxiliary oxide is used that is made by adding the oxide of at least one of tungsten and molybdenum to lead oxide in the following proportions:PbOx+ where x+y+z=1, 0. Also disclosed are methods of treating cognitive or neurodegenerative diseases using the compounds of formula I in combination with a cholinesterase inhibitor or a muscarinic m1 agonist or m2 antagonist.