存在期间 meaning in Chinese

duration of existence

During its brief existence, the pion carries momentum from one nucleon to the other .
在它短暂的存在期间内，它将动量从一个核子带到另一个核子。
It is hereby further declared that the trustee shall ， during the subsistence of this deed ， have power of appointing new or additional trustees
并在此声明，在本文据存在期间，一受托人有权指定新的或额外的受托人。
Nutrients are with the lowest content in the upper layer and the highest content in the lower layer during the stratified period in the yscmw
总无机氮和无机磷的浓度除冬季上、下层水体间比较均匀外，在黄海冷水团存在期间，表层浓度最低，底层最高。