To roughly mimic this and to construct Figure , 500 relaxation rate distributions consisting of three components each were randomly synthesized to create a test data set. To generate each distribution, intensities of three components were randomly chosen and scaled to a total intensity of 1. To each of the three intensities, a relaxation rate was assigned. These relaxation rates were chosen randomly from within three pre-specified ranges (1.0-2.65, 7.0-18.5, 49.0-129.6) with components in each range having pre-specified widths (log widths = 0.15, 0.4, 0.4). Gaussian (on the log axis) distributions for each component centered on the randomly chosen relaxation rate, with the specified widths and intensities, were summed to create an underlying distribution for each simulated sample. These distributions of relaxation rates were used to generate a decay curve for each simulated sample. The decay curves had 2001 points evenly spaced over 5 seconds, with the slowest and fastest relaxation rates residing in the range 0.5 and 700 per second. Random Gaussian noise with a standard deviation of 0.003 was added to each curve.