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Since the beginning of microgravity materials research, studies of diffusion in liquids have been performed as the typical research that efficiently uses the microgravity environment. Successful experiments in microgravity have demonstrated the ability of the Canadian Microgravity Program (QUEST I, QUELDs I and II) to make significant contributions to this field of international microgravity research. Recently, Millenium Biologix was selected to develop and build the advanced thermal environment facility (ATEN) for the International Space Station. The design of this new processing facility builds on the considerable experience gained in designing and building the QUELD II furnace and developing sealed samples for use on board a manned space platform. The system requirements for ATEN are presented, along with preliminary test data from a prototype furnace.

This paper reports on a technique for providing a frequency-stabilized helium - neon gas laser by using inherently stable ultralow thermal expansion optical cavities. Four longitudinal monoblock cavity lasers were constructed and tested. These had their laser mirrors optically contacted to the bulk material. A 1 mm diameter hole along the axis of the block served as the discharge channel with electrodes optically contacted to the sides of the block. One of these lasers had a glass capilliary for the discharge channel. A fifth laser had a gain tube with Brewster angle windows fixed in a Zerodur box with the mirrors contacted to the ends. The warm-up characteristics of the five different lasers have been obtained and a theoretical model using finite element analysis was developed to determine the thermal expansion during warm-up. Using this computer model the thermal expansion coefficient of the material Zerodur was obtained. The results suggest that monoblock lasers can produce a free-running laser frequency stability of better than 10 MHz and show a repeatable warm-up characteristic of 100 MHz frequency drift.

The theory of laser cavity birefringence induced by insertion of two quarter-wave plates into the cavity is developed to show how the intermode frequency of a two-mode laser can be tuned through a free spectral range by relative rotation of the plates. Birefringence is demonstrated in a helium-neon laser at 633 nm using an open cavity having a tube with anti-reflection coated windows. The lock-in between modes when the intermodal frequency approaches zero was investigated and found to be smallest when the tube was placed between the plates which were aligned with axes parallel. Active frequency stabilization at a frequency separation of 50 MHz was demonstrated using the mode-balancing technique.

Knowledge of Vancomycin Use Guidelines among Residents, Fellows, and Attending Physicians in a Pediatric Tertiary Care Center