Disclosed are novel compounds of formula wherein A1, A2, Ar, R5, R6, R8, M, Q, Y, Z, k, m and n are as defined in the specification. Each of the word line drivers includes a pull-up device that is coupled to a node via a shared line. The impeller is radially centered via the magnetic coupling. Additionally, any fix installed on a target machine running a particular version may be migrated when updating the target machine to a new version without losing the fix and regressing the change. In addition, the desktop management software provides an administrative console, which allows an administrator to set various parameters, including QoS parameters, and parameters specifying the resources allocated to each user.