Gene expression in mouse liver cells. Expression levels of genes in mouse liver cells . (Top): gene Nr1d2 (probeset 1416958-at). (Bottom): gene Pde12 (probeset 1454963-at). (Left column): raw data points (circles) and a smoothing curve (line) computed using a three-hour simple moving average. (Right column): spectra for the unsmoothed (circles) and smoothed (squares) data. The spectrum component at H(p = 1) corresponds to ω = 2π/48 hours-1.