Abstract: A disk file management system for use in a data processing system that includes at least one disk drive. The disk space is organized on the basis of logical cylinders, with each logical cylinder including a plurality of disk pages and a cylinder control block ("CCB"). Each entry in the CCB corresponds to a page in the CCB's cylinder. Depending on whether a page is allocated to a file or not, the corresponding CCB entry is a file map entry for a file to which the page is allocated or an entry in a free space map. For a given file, each file map entry includes up to two pointers so that the totality of page map entries for the file defines an unbalanced binary tree structure that consists of a sequence of balanced binary trees of increasing size. The free space map for a given cylinder is preferably a chained free space list.

Abstract: A closed cycle, high repetition pulsed laser having a laser flow channel with an annular flow return surrounding the laser flow channel. Ultra high vacuum components and low out-gassing materials are used in the device. An externally driven axial flow fan is used for gas recirculation. A thyratron-switched low-inductance energy storage capacitor is used to provide a transverse discharge between profiled electrodes in the laser cavity.

Abstract: Method of making TiO.sub.2 --CaCO.sub.3 combinations without involving a chemical reaction, said combinations, containing up to 50% CaCO.sub.3 in the combination, having the same scattering coefficient in paper as 100% TiO.sub.2 and method of making opaque paper containing the resulting combination.

Abstract: The combination of a snowmobile and a watertight hull with propeller drive shaft wherein the snowmobile has a drive shaft which includes telescopically extensible section on both ends of which universal joints are provided so that the snowmobile drive shaft can be readily disconnected from its traction tread and connected to the propeller drive shaft of said hull.