Convection in a Binary Mixture Heated from Below

Heat-transport measurements in a bulk normal-fluid ³He-⁴He mixture heated from below and over the range -0.02ψ0.02 of the separation ratio ψ reveal a forward bifurcation with an initial slope S0 of the Nusselt number for large ψ, and a backward bifurcation for ψ<ψb0.006. At ψb, S1. The critical line ΔTc(ψ) has two branches which meet at ψ-0.003, and which we attribute to the expected stationary and Hopf bifurcation lines. However, stable oscillations bifurcating from the conduction state exist only for ψ-0.015.