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A remembrance of Virgil Marple, whose critical contributions included development of the NGI and other impactors, and training entire technical populations. Back Page We count ourselves unbelievably fortunate to have worked with, been mentored by, traveled with and laughed with Virgil Alan Marple over a significant portion of his professional career. He once said "the only thing I can't do is design an impactor incor- rectly," an observation made in passing to the executive commit- tee of the Next Generation Im- pactor (NGI) Consortium. is remark did have, and does have, full credibility. It was not a boast but just his true understanding of impactors combined with his commitment to achieve the high- est technical quality. In his PhD thesis, Virgil was the first to capture the fundamentals of the multi-stage cascade impac- tor in a quantitative manner. He subsequently trained numerous graduate students as well as entire technical populations, such as the inhaler testing community, in proper impactor design. Daryl L. Roberts, PhD, Applied Particle Principles, LLC Jolyon P. Mitchell, PhD, FRSC(UK), CCHEm, CSci, Jolyon Mitchell Inhaler Consulting Services, Inc. Humble giant of cascade impactors, Virgil A. Marple August 16, 1939 to December 24, 2017 His creations for the inhalation community include the adult and pediatric Marple-Miller impactors and most recently the NGI. e quality and performance of the NGI has won over the inhaler test- ing community, well past the origi- nal dreams of the NGI consortium, to the benefit of thousands of users and ultimately to the benefit of the populations worldwide needing inhalers to manage respiratory dis- eases. In addition, his impactor de- sign expertise has had a major im- pact in the field of environmental assessments associated with nano- meter-sized airborne pollutant particles. He created the series of Micro-Orifice Uniform Deposit Impactors (MOUDIs), and even his wood-chip sampler—the Mar- ple 290 personal impactor—was adopted later for nebulizer testing. We believe that Virgil's intuitive feel for practical designs stemmed from his youth on the family farm in western Minnesota, where one quickly learns to fix mechanical "things" and keep them running. His love of learning was evident as he attacked problems in a system- atic and knowledge-centered way. We recall his ever-present napkin sketches of new ideas. ese rapid- ly produced, informal yet informa- tive, outlines stand in stark contrast to the way many of us tackle prob- lems these days, often finding it dif- ficult to function without a laptop. His collection of more than 100 cars, kept on his farming and resi- dential property in Independence, Minnesota, and never-ending fasci- nation with cars were additional outlets for a brilliant mechanical mind. To him, driving 25 miles one-way to the University of Min- nesota each day for more than 30 years was fun, not a commute. Virgil leaves a love of life that we wish upon all. May we read, and heed, his gifts to us inside these seminal publications: • Marple VA, A Fundamental Study of Inertial Impactors, PhD esis, University of Minnesota, September 1970. • Rubow KL, Marple VA, Olin J, McCawley MA, A Personal Cascade Impactor: Design, Evaluation, and Calibration, Am Ind Hyg Assoc J, 48, 532- 538 (1987). • Marple VA, Rubow KL, Behm SM, A Microorifice Uniform Deposit Impactor (MOUDI): Description, Calibration, and Use, Aerosol Sci Technol, 14, 434-446 (1991). • Marple VA, Olson, BA, Miller NC, A Low-Loss Cascade Impactor with Stage Collec- tion Cups: Calibration and Pharmaceutical Inhaler Appli- cations, Aerosol Sci Technol, 22, 124-134 (1995). continued on page 31 32 April 2018 Inhalation