Comparison of azimuthal variations in abundance gradients for oxygen, europium, iron, and barium predicted by Model A (first row) with models where the condition of transient spiral have been considered. Model A+C1 is reported in the second row, where the condition Ω_s, j(R) = Ω_d(R) is valid for all Galactic radii (co-rotation extended at all distances) during the last 100 Myr of Galactic evolution; Model A+C2 is shown in the third row, where the above-mentioned condition is only met for the last 300 Myr; and Model A+C3 is shown in the last row, where this condition is met for 1 Gyr. The colour convention of the lines is the same as in Fig. 6. The vertical lines indicate the corotations of Model A.