Abstract: A picture puzzle assembling platform, that includes at least two inclined panels, symmetrically arranged around a central axis, such that a person can sit facing each panel to assemble a puzzle, from pieces placed on a table surface in front of the panel. Preferably, each person assembles a different puzzle on one of the inclined panels. The inclination of each panel, enables the person facing the panel, to have a direct view of the partially assembled picture puzzle, so that the person can move more quickly to locate the correct puzzle piece for each puzzle space. The panel inclination thus facilitates the puzzle assembling process, and adds to the person's interest in completing the assembly of the picture puzzle. Each inclined panel, forms a support surface for a different puzzle, so that persons sitting in front of the inclined panels, may engage in a contest, with each person trying to complete his/her puzzle before the other person completes theirs.

Abstract: The invention is an improved form of an ultracentrifuge used in the separation of gases, particularly those of high molecular weight. Through the introduction of an inner cylinder within the outer cylinder of a high speed centrifuge, a higher over-all flow profile efficiency is created. In addition, although a gain of lesser significance, the vacuum core present in ultra centrifuges, which does not contribute to the separative power of the centrifuge, is virtually eliminated. Moreover, for those gases in which the maximum pressure in the centrifuge is limited by a phase change, i.e. the maximum pressure in the centrifuge must be kept below the vapor pressure, the addition of the inner cylinder raises the pressure in the central core region by several orders of magnitude, which permits the subsequent reduction of pressure on the outer walls of both inner and outer cylinders without any portion of the centrifuge being in the Knudsen regime.