Sample materials (IMAGE) Optica Caption The researchers tested the new technique with 19 threat materials and 56 non-threat materials, some of which are pictured. Credit Thomas Partridge, University College London Usage Restrictions None License Original content 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.