In Memorium: Stefan Machlup

Stefan Machlup
July 1, 1927 - August 16, 2008

“He was just so generous with ideas. His conversation was always full of original thoughts, and ‘ownership’ never came up. Of course, many of those thoughts I was not ready to absorb, to understand. I think he liked it that I didn’t pretend to.”1

These words, written about Lars Onsager, by his former student, Stefan Machlup, could just as well describe Machlup himself. A friend and colleague to many BEMS members, Machlup passed away on August 16, 2008 at the age of 81. Machlup is especially well-known as co-author of a pair of the most influential papers in the thermodynamics of dissipative non-equilibium systems.

Machlup was born in Vienna, Austria in 1927. He immigrated with his parents to the United States in the 1930s. He earned his BS at Swarthmore, PhD at Yale, and enjoyed a string of post-doctoral appointments, including positions at Cambridge, Bell Labs, the University of Illinois, Urbana, and the University of Amsterdam. For most of his career, he taught physics at what is now Case Western Reserve University from 1956 until retiring in 2000.

His dissertation, “Fluctuations and Irreversible Behavior in Thermodynamic Systems,” led to two publications with his research director, Lars Onsager, the physical chemist who would subsequently win the 1968 Nobel Prize in chemistry. This work developed the Onsager-Machlup-Laplace approximation2 that was an elaboration of a theory of irreversible processes developed two decades earlier by Onsager.

Their theory applies to a very wide variety of systems: nuclei with spins aligned by magnetic fields, excited atoms in a laser, molecules undergoing chemical reactions, vortices in a liquid, and ions transported through biological membranes. Machlup explored the applicability of some of these ideas to biology3: “Biological clocks share with excitable membrane (nerve, muscle) the requirement that the chemical systems that underlie them have unstable steady states and hence are capable of limit-cycle oscillations…. The oscillators responsible for biological clocks are surely not mechanical mass-and-spring systems, nor are they electrical inductance-capacitance combinations. They are chemical oscillators.”

In a 1975 paper4, Machlup described the common features of systems characterized by negative temperatures and negative dissipation: “If we think of absolute temperature as a measure of kinetic energy per (classical) degree of freedom, then a negative absolute temperature seems absurd. If, however, we use the (quantum-mechanical) idea of the population of energy levels and measure this population with a Boltzmann factor, then a negative T makes sense: It means higher energy levels are more populated than lower ones.” The paper concludes: “This article has attempted to make more intuitive the connection between negative temperature and negative resistance, and to suggest that a large class of nonlinear systems involves negative-temperature subsystems.” One such system, he suggests, might be current vortices in type II superconductors.

Making physics more intuitive was a lifelong passion for Machlup. Based on many years of class-room experience, he published an introductory text for pre-med physics students, “Physics” (Wiley, 1988), that emphasized biological examples of special interest to health science students. He enjoyed working with high school physics teachers and helped to develop new teaching materials.

Dr. B.S. Chandrasekhar, professor of physics at Case Western Reserve University and a colleague of Stefan Machlup, commented, “Stefan was a good and close friend since we first knew each other as post-docs at the University of Illinois in Urbana in the early fifties. A friendship of more than half a century is at an end. He was a source of good humor and cheerfulness who enlivened with his comments and contributions the often dull aftermath of a colloquim or seminar. He never walked from here to there on campus, but covered the distance with a hop, step, and jump. To some physicists physics is a job; to Stefan it was a joy. He worked hard to convey this feeling to students and colleagues. He would preform a Bach cello sonata with the same profound understanding and wonder that he would explain a concept in statistical mechanics.”

1S. Machlup, “Lars Onsager was my Thesis Director,” Journal of Statistial Physics, 78, 1&2, 589, 1995.
2Phys. Rev. 91, 1505 and 1515, 1952.
3Oscillatory Chemical Reactions: the Tomita-Kitahara Model” BioSystems 8, 241, 1977.
4Amer. J. Phys. 43, 991, 1975.

BEMS board member and former student of Machlup, Indira Chatterjee, noted that “Stefan Machlup was a passionate teacher inspiring many graduate students who helped him teach laboratory classes to non-physics majors to aspire to be great teachers like him. He thoroughly enjoyed working in the laboratory teaching his graduate assistants how to perform the experiments in the right manner before they went out in front of their class. His constant exuberance and cheerful enthusiasm never ceased to amaze me. He was a mentor and a friend and I will never forget him as one of the great teachers that inspired me to go into academics.”

In the 1980s, Machlup joined colleague T. Hoshiko of the CWRU School of Medicine’s Department of Physiology and Biophysics in a research collaboration that applied statistical mechanics to the analysis of biological phenomena such as ionic transport in frog skin cells5.

Later in life, Machlup developed an interest in the biological effects of magnetic fields. He published his most recent paper on this topic in 2007, noting that the “impossible” effects observed in cell cultures as a result of exposure to magnetic fields tuned for ion parametric resonances (IPR) could be “resolved by taking account of the coherent absorption of the ELF energy and showing how the energy of several trillion ELF photons can free a single ion from its trap on the surface of a cell of the culture.”6

Remembering his interactions with Dr. Machlup, BEMS board member Carl Blackman noted, “Stefan started with his own premises regarding the mechanisms behind our experimental results and participated in many poster sessions, at the Biophysics Society, Bologna BEMS/EBEA meeting, several DOE Contractor Reviews, and the BEMS Hawaii meeting. He greatly enjoyed interacting with scientists, sharing concepts and sharpening his thoughts. He always enjoyed seeing and talking with Charles Polk when they met because of their early acquaintance in Vienna. Stefan and I would steal away to someplace where we could be alone to talk about his latest concepts and our latest data. I remember the most recent time was at the 2004 BEMS meeting in Washington, DC. We spent a grand time talking science for most of an afternoon. Stefan was always upbeat, curious and energized about his interests in EMF biological effects. Certainly, he is a role model for many scientists.”

Colleague Asher Sheppard added: “Stefan Machlup was a bundle of enthusiasm and joy, whether beaming his engaging broad smile to lure me to a poster which he saw raised an exciting or problematic idea, or to engage in conversation on one of the topics of interest to his encyclopedic mind. Although I never saw him in a classroom, it was instantly recognizable at our first meeting that this was a man who loved ideas and loved to teach. While his scientific accomplishments in thermodynamics and biophysics are the stuff of more formal remembrances, I, and no doubt others in The Bioelectromagnetics Society know our good fortune to have shared the wonder and happiness that he radiated. I fondly recall the times when his first class mind held an intellectual specimen in the beam at just the right angle so that his excitement for ideas completely overtook the moment. A moment later, with twinkling eyes he would ask a question to turn the conversation back to me. It was as if Socrates stood there.”

Stefan Machlup was also fluent in five modern languages and an accomplished cellist, participating in Cleveland-area string quartets for five decades. He is survived by his wife, Marilyn, and sons Peter and Eric, as well as the greater Bioelectromagnetics community. He was a full member of BEMS from 1997 through his retirement to an Emeritus member in 2001.

5Biochimica et Biophysica Acta 942, 186, 1988.
6Electromagnetic Biology and Medicine, 26, 3, 251, 2007.