Fig. 4. Impact of exposure on ciliary beating functionality. Ciliary beating functionality in the small airway cultures was assessed longitudinally before, immediately after (0 h), and 24 h, 48 h, and 72 h after exposure. (A) Weighted frequency (Hz) is the mean frequency over the pixel, weighted by the fast Fourier transformation (FFT) power at the pixel-dominant frequency. (B) Frequency uniformity (arbitrary unit, AU) is an index expressing the distribution of the detected frequency over the FFT spectrum (0 = blank noise; 1 = unique frequency). (C) The active area (%) is the percentage of detected pixel that differs from the blank noise. (D) The log₁₀(FFT power) is an estimate of the detected power based on the beating signal of the ciliary movement. Nicotine concentrations (mg L^–1) in 3R4F smoke or THS2.2 aerosol are indicated for each group.