AUTHOR=Popov Valentin L. TITLE=Contacts With Negative Work of “Adhesion” and Superlubricity JOURNAL=Frontiers in Mechanical Engineering VOLUME=5 YEAR=2020 URL=https://www.frontiersin.org/journals/mechanical-engineering/articles/10.3389/fmech.2019.00073 DOI=10.3389/fmech.2019.00073 ISSN=2297-3079