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Investor Relations



Sotirios J. Vahaviolos
Founder and Executive Chairman

Sotirios J. Vahaviolos is the company’s Founder and Executive Chairman. After founding MISTRAS in 1978 under the name Physical Acoustics Corp., Dr. Vahaviolos served as Chairman, President, and Chief Executive Officer until 2017. Prior to joining Mistras, Dr. Vahaviolos worked at AT&T Bell Laboratories. Dr. Vahaviolos received a BS in Electrical Engineering and graduated first in his class from Fairleigh Dickinson University and received a Master of Science (EE), Masters in Philosophy and a Ph.D.(EE) from the Columbia University School of Engineering. During Dr. Vahaviolos' career in NDT, he has been elected Fellow of The Institute of Electrical and Electronics Engineers, a member of The American Society for Nondestructive Testing (ASNT) where he served as its President from 1992-1993 and its Chairman from 1993-1994, a member of Acoustic Emission Working Group (AEWG) and an honorary life member of the International Committee for Nondestructive Testing. Additionally, he was the recipient of ASNT's Gold Medal in 2001 and AEWG's Gold Medal in 2005. He was also one of the six founders of NDT Academia International in 2008.

Dennis M. Bertolotti
President and Chief Executive Officer (CEO)

Dennis M. Bertolotti is the President and Chief Executive Officer of MISTRAS Group, having previously served as Group Executive Vice President, Chief Operating Officer, and President of Services of the Americas. Mr. Bertolotti has been with MISTRAS since MISTRAS acquired Conam Inspection Services in 2003, where Mr. Bertolotti was a Vice President at the time of the acquisition. Mr. Bertolotti has been in the NDT business for over 25 years, and previously held ASNT Level III certifications and various American Petroleum Institute certifications, and received his Associate of Science degree in NDT from Moraine Valley Community College in 1983. Mr. Bertolotti received a Bachelor of Science and MBA from Otterbein College.

Jonathan H. Wolk
Senior Executive Vice President and Chief Operating Officer

Jonathan H. Wolk is Senior Executive Vice President & Chief Operating Officer. He joined MISTRAS as Chief Financial Officer (CFO) in November 2013 with 30 years of experience providing financial leadership and driving strong results. Before joining MISTRAS, Mr. Wolk was most recently the Senior Vice President and Chief Financial Officer of American Woodmark Corporation, a publicly-traded manufacturer of kitchen and bath cabinets. He began his career at KPMG and also held senior financial positions at Pitney Bowes and GE Capital. Mr. Wolk earned a Bachelor of Science degree in Accounting from the State University of New York at Albany, where he graduated Summa Cum Laude, and is a Certified Public Accountant.

Michael J. Lange
Senior Group Executive VP Business Development & Strategic Planning; Vice Chairman

Michael J. Lange is Senior Group Executive VP Business Development & Strategic Planning; Vice Chairman. He joined MISTRAS when it acquired Quality Services Laboratories in November 2000. He was elected a Director in 2003. Mr. Lange is a well recognized authority in Radiography and has held an ASNT Level III Certificate for almost 20 years. Mr. Lange received an Associate of Science degree in NDT from the Spartan School of Aeronautics in 1979.

Michael C. Keefe
Executive Vice President, General Counsel and Secretary
Michael C. Keefe is Executive Vice President, General Counsel. He joined Mistras in late 2009. Michael served in various legal roles with Lucent Technologies and AT&T as well as with a private practice at New Jersey's largest law firm, McCarter & English, LLP. In 1996, he began working for Lucent Technologies, where he served as Law Vice President and Corporate Counsel for ten years. Most recently, Michael joined International Fight League, a sports promotion company, as Executive Vice President, General Counsel and Corporate Secretary, and eventually its President, General Counsel and Chief Financial Officer and led the sale of the company's assets and the Chapter 11 liquidation of its operating subsidiary. Michael graduated with a Bachelors of Science in Accounting from Seton Hall University and continued his education at Seton Hall University School of Law, where he graduated first in his class with a Juris Doctorate degree. Before starting his legal career, Michael served as a Certified Public Accountant for Coopers & Lybrand, a predecessor firm to PricewaterhouseCoopers, LLP. He worked in accounting for seven years before making the switch into the legal profession.
Edward J. Prajzner
Senior Vice President, Chief Financial Officer and Treasurer

Edward J. Prajzner is Senior Vice President, Chief Financial Officer and Treasurer.  He joined MISTRAS in January 2018.  Before joining MISTRAS Group, Mr. Prajzner was Chief Financial Officer and Secretary of CECO Environmental Corp, a publicly-traded global diversified and energy technology company. He began his career with Ernst & Young and also held senior financial positions with CDI Corporation and American Infrastructure.  Mr. Prajzner earned a Bachelor of Science degree in Accountancy from Villanova University, an M.B.A. (Finance) from Temple University and is a Certified Public Accountant.