sentinels

n.

岗哨，哨兵( sentinel的名词复数 )；

stand sentinel站岗，放哨，守卫

1. The sentinel was stationed on a hill.
   哨兵被派在山上站岗。
2. The press is a sentinel of our liberty.
   新闻界是捍卫我们自由的卫兵。
3. At either end of the bridge a sentinel stood with rifle at ready.
   桥的两头各有一名哨兵，荷枪实弹守卫着。

Lakes and streams as sentinels of environmental change in terrestrial atmospheric processes
Skin immune sentinels in health and disease
HMGB proteins function as universal sentinels for nucleic-acid-mediated innate immune responses.
Lakes as sentinels of climate change
Mast cells as sentinels of innate immunity.
Selfish sentinels in cooperative mammals.
Epithelial Cells in the Female Reproductive Tract: a Central Role as Sentinels of Immune Protection
Transmission of Toxoplasma: clues from the study of sea otters as sentinels of Toxoplasma gondii flow into the marine environment
Bcl-2 family proteins: The sentinels of the mitochondrial apoptosis pathway
Lakes and reservoirs as sentinels, integrators, ...