(1) A soldier high on the roof behind his machine gun watched vigilantly over the far horizon - a silent sentinel .

(2) The sentinel still stood at attention directly under the lantern, not moving but to breathe.

(3) By the third week the men practiced guard duty, receiving instructions on walking their posts and performing interior and exterior guard duty, and learning the general and specific orders of a sentinel posted for guard duty.

(4) The beetles' affinity for certain trees, like maples, poplars, willows, and elms, is significant because such attractive species may be used as sentinel trees.

(5) We here present a model of field study, based on the use of sentinel species, that we are currently applying to risk assessment in the area around a focus of pollution.

(6) The first national HIV sentinel surveillance programme in the developing world

(7) A sentinel stood on top of the wall, an easy target.

(8) Amphibians are regarded as sentinel vertebrates in the current drama of global extinctions.

(9) Performing sentinel lymph node biopsy requires coordinated expertise between nuclear medicine physicians, pathologists, and surgeons.

(10) Surveillance for West Nile is also conducted by testing pools of mosquitoes and flocks of sentinel chickens.

(11) After walking down a short hall another door came into view; this one had only one sentinel .

(12) Immediately, a sentinel standing guard near the jail confronted him.

(13) She knew not whether to fear it or love it; at this moment she only wished to find someplace where she could sit, unnoticed by the sentinel who stood near the fire at the east end of the encampment.

(14) A lone sentinel stood in the middle of the roadway to the castle standing on the hill.

(15) Soldiers stood sentinel with their muskets

(16) The first national HIV sentinel surveillance program in the developing world

(17) The sentinel stood lounging by the shaft that led down into the underground labor system.

(18) There has been some speculation that Charles was assassinated, but from forensic examination of his skull it is fairly certain that an enemy sentinel caught sight of his head peering over the parapet and managed a lucky hit.

(19) Flanking the elevator on both sides stood the Shadow Lord's black-garbed sentinels , his sinister Warrior disciples.

(20) So say the sentinels guarding the long coastline of the country this weekend.