Journal of Research of the
National Institute of
Standards and Technology

Cover Explanation:

The cover illustration shows the major sources and sinks of gas in a vacuum chamber; arrows represent the flow of gas molecules (1) desorption and outgassing from surfaces; (2) permeation from the atmosphere through seals; (3) “virtual leaks” of trapped gas; (4) evacuation through chamber pump(s).  See the paper, “Vacuum Technology Considerations For Mass Metrology” by Patrick J. Abbott and Zeina J. Jabour in this issue for more detail on this topic.  Cover arranged by C. Carey.