A Journey Through Nonlinear Dynamics: The Case of Temperature Gradients

Abstract

The overall effect of temperature gradients is stressed for the Earth's core and surface, but also for the Sun's surface. Using Rayleigh–Bénard convection in helium and mercury, we measured all of the scaling properties of the period-doubling cascade and quasiperiodicity. Hard turbulence scaling properties are presented in an experiment using helium gas at low temperature. A [Formula: see text] scaling law is measured and also an exponential distribution for temperature fluctuations is observed. We present a study of a Rayleigh–Bénard convection cell with an open top and a floater. One of the simplest limit cycles is observed for the floater position. It follows a model proposed by Wilson for continent motion. Using the Soret effect, we study how temperature differences lead to strong accumulation of DNA suspensions. Also using polyethylene glycol concentration gradients, we measured local DNA and RNA accumulation. Finally, using thermal convection, we build one of the smallest PCR machines.