ultralow temperature meaning in English

超低温

Primary research on preservation under ultralow temperature and plant regeneration of papaya
番木瓜种质的超低温保存与植株再生初探
Some interest has been generated in studying the rationale for assisted hatching . some reports suggest that embryos with lower zona pellucida thickness ( zpt ) and higher zona pellucida thickness variation ( zptv ) had a better chance of successful hatching and so the patient become pregnant ; another reports suggest that in vivo aging ; in vitro culture and exposure to ultralow temperature may induce zona hardening and then impair the embryo ability of hatching
有作者提出胚胎透明带厚度( zonapellucidathickness ， zpt )小的胚胎孵出时阻力减小，而透明带厚度变化率( zonapellucidathicknessvariation ， zptv )高的胚胎由于透明带上有一个明显薄的区域而使胚胎易于孵出；还有作者推测病人年龄、体外培养天数的增加及冷冻处理会增加透明带的硬度，使胚胎孵出困难。