A rotary damper 1 includes a synthetic resin-made accommodating case 4 for accommodating in its interior 2 a viscous fluid 3 which is constituted by silicone oil or the like and whose viscosity declines with a temperature rise, and a synthetic resin-made rotor 9 which is disposed in the interior 2 of the accommodating case 4 rotatably, i. The screen of the display includes pixels arranged in a grid pattern, each pixel having at least three colored mirrors, arranged next to one another or behind one another for the colors red, green and blue or cyan, magenta and yellow. A word line control circuit applies a plural-bit data read voltage as a word line voltage to the word line. The velocity information acquisition section acquires at least one of a velocity fluctuation component of individual photosensitive drums and a velocity fluctuation component of the transfer belt in accordance with the result of sensing by a mark sensor for two registered marks formed by the pattern generation section. The compositions of the present invention are useful clinically, per se or as cell-bearing implants.