OBJECTIVES To evaluate whether a water-fat magnetic resonance imaging (MRI) cooling-reheating protocol could be used to detect changes in lipid content and perfusion in the main human brown adipose tissue (BAT) depot after a three-hour long mild cold exposure. MATERIALS AND METHODS Nine volunteers were investigated with chemical-shift-encoded water-fat MRI at baseline, after a three-hour long...

We present a gauge-invariant formalism to study the evolution of the curvature and entropy perturbations in the case in which spatial and time variations of the inflaton decay rate into ordinary matter are present. During the reheating stage after inflation curvature perturbations can vary with time on super-horizon scales sourced by a a gauge-invariant inflaton decay rate perturbation. We show...

The reheating process in in ationary universe models is considered as an out-of-equilibrium mixture of two interacting and reacting uids, and studied within the framework of causal, irreversible thermodynamics. The evolution of the temperature and the decay rate as determined by causal thermodynamics are estimated at di erent stages of the process. A simple model is also used to nd the perturba...