1.   But if crust is recycled, the elements should be redistributed, leaving more complex chemical signatures in both mantle rocks and recycled crust.

2.   But investigators found no evidence that Baghdad ever obtained the Ames strain and no signs of Iraqi chemical signatures in the powdered anthrax sent to the Senate.

3.   By acting as a kind of chemical signature for human waste, caffeine may serve as a warning that sewage is nearby.

4.   He compared their chemical signatures to see if they could possibly have different sources.

5.   If the analysis also produces chemical signatures of minerals typically formed in liquid water, then scientists will gain even more evidence that Mars once was much more hospitable.

6.   It can only match one chemical signature to another.

7.   Large amounts of caffeine have been found in Boston Harbor and scientists want to use it as a kind of chemical signature for human waste.

8.   The idea is that if two bullets have the same chemical signatures, they must have been made at the same time from the same batch of smelted lead.

9.   Experts said the achievement demonstrates that it may be possible to search for the chemical signature of life on planets beyond the solar system.

10.   So shining light on a living structure, such as an artery wall, produces a specific chemical signature, depending on what it contains.