II.in [美 ɪn, 英 ɪn]副in often appears as the second element of certain verb structures in English (close in, hand in, stand in, etc). For translations, see the relevant verb entry (close, hand, stand, etc).
A small drop in brake fluid level in the master cylinder reservoir can be topped up but if the level consistently drops, the cause should be investigated and repaired.
As the pressurized molten protein mixture exits the extruder, the sudden drop in pressure causes rapid expansion into a puffy solid that is then dried.