Investigations of the superfluid (sf) transition in liquid helium 4: 1) Study helium containing aerogels as an impurity, measuring the thermal expansion and thermal conductivity. Data on the concentration and pressure dependences will illuminate the relationship between the phase transitions in the pure and impure systems. 2) Study the propagation of second sound near the sf transition in the presence of superfluid and normal-fluid velocity fields, to test the correctness of a recent theory. %%% Quantum mechanics underlies and governs the behavior of all matter. Liquid helium is almost unique in being a substance which behaves as a quantum mechanical system on a macroscopic scale. Studies such as are here proposed can be expected to advance their understanding of quantum physics, as well as phase transitions and the special properties of porous materials.
