Fig. 1. (A) Pulse sequence used to measure D_|| and D in lobster abdominal muscle fibers. The solid bars represent excitatory radiofrequency pulses, with the magnetization tip angle (degrees) indicated over each pulse. The stippled bars represent magnetic field gradient pulses. TM is the mixing time, T_e, echo time, is the duration of the spatial-encoding gradients, is a short delay, is the approximate diffusion time (corrected as described in text), AQ is the signal acquisition period, and WS1 and WS2 are water suppression sequences that were used in the ¹H spectra only. (B) The water suppression sequences are shown diagrammatically (for details, see Kinsey and Ellington, 1996). Diffusion coefficients at a given diffusion time were determined by collecting a series of spectra at different amplitudes of the spatial-encoding gradients. The diffusion time was adjusted by changing the value of . Additional details are given in the text.