We consider the problem of blow-up of smooth solutions for the 3-D Boussinesq equations. Owing to the viscosity, we prove that the maximum norm of the gradient of vorticity controls the breakdown of the solutions; the scalar temperature function is shown to be irrelevant to the breakdown.

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We discuss the evolution of plane curves which are described by entire graphs with prescribed opening angle. We show that a solution converges to the unique self-similar solution with the same asymptotics.

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Spiral waves are commonly observed in biological and chemical systems. Representing each wave front by a single curve, Brazhnik, Davydov, and Mikhailov introduce a kinematic model equation. The aim of this paper is to provide a detailed analysis for the steady state solutions of these equations. The existence of asymptotically Archimedean solutions is analytically shown.