Figure 2.

Analysis of the relative net force. (A) Plot of the area a_i(t) for a single amnioserosa cell (blue trace is data, black trace is low-pass, filtered data). (B) Calculated time dependence of f(t)/f₀ (negative indicates contraction). (C) The function $\overline{f}\left(t\right)/f_0$, where the overline indicates the data from panel B has been filtered to remove the high-frequency oscillations. (D) The function |f(ω)|/f₀, where the Fourier transform of the data in panel B was taken for the entire time series. (E) The average of Fourier transforms for all the segmented amnioserosa cells (embryo #2). (F) Spectrogram of the data from panel B. For this panel, the x axis reports time, the y axis reports frequency, and the normalized amplitude is reported in the false color-scale. (G) The analogous sum of the spectrograms for all the segmented cells. The two pairs of vertical dashed lines indicate when zipping commences (black indicates posterior, red indicates anterior); the ranges track the onset and full engagement of the zipping processes.