Location of the shear-NO eigenvalues in the complex plane as the baseline radius R₁ increases parametrically.

The arrows indicate the direction of increasing R₁. The eigenvalues during contraction always have a negative real part indicating stability. When the baseline radius is large enough to move the eigenvalues beyond point B the system is inherently stable during dilation. At point B the system is marginally stable and will oscillate at frequency f = (E₁K_NO/D)^1/2/2π. For smaller baseline radius, between points A and B, the response is unstable, but oscillatory. And when the baseline radius is smaller at point A, the dynamic component of the radius increases exponentially without oscillation until the radius is large enough to reach the range between A and B where oscillations can occur.