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Measurement of oxygen concentration in wells that were first sealed under ambient oxygen conditions and then subjected to a low (0%)-oxygen environment, demonstrating sealing. Circle, well 1; plus, well 2; six-tailed star, well 3; cross, well 4; square, well 5; diamond, well 6; up triangle, well 7; down triangle, well 8; five-tailed star, well 9.
