Protocol of each cooling procedure.

*1/4 ml sample straw was covered with a 1/2 ml straw, a 7 mm OD ×90 mm glass tube, and a 10 mm OD ×90 mm glass tube.†The Cryotop was covered with the Cryotop-cap-straw and a 7 mm OD ×90 mm glass tube.‡The straw or Cryotop were placed horizontally on a Styrofoam disk (14 cm diameter, 1.5 cm thick) floated on the surface of LN2 in a 41 Dewar flask for >5 min before being immersed in LN2.§The cooling rates were determined from 20 to −120°C. N = 5.¶The cooling rates were determined in [14].