Fig. 4From: Theory of synergistic effects: Hill-type response surfaces as ‘null-interaction’ models for mixturesIso-surfaces for ternary mixtures at 10, 25, 50, 75 and 90% effect levels. Shown on logarithmic (a–c) and linear (d–f) dose scales. a, d sham combination, α=1,u max =1; b, e Mixture with variable slopes, α=0.5,β=5,γ=1 and u max =1; c, f Mixture with variable maximum effects, a max =0.8, b max =0.4, c max =1 and slope λ=1Back to article page