Image 2 (IMAGE) Nanyang Technological University Caption Asst Prof Stephen Chua examining the sediment core using an x-ray fluorescence spectroscopy machine. Credit NTU Singapore Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.