Philip Edward Seiden, a condensed matter physicist, astronomer, immunologist, and manager, died 21 April 2001 in Briarcliff Manor, New York, of complications arising from long and largely successful battles with cancer and heart disease.
Phil was born in Troy, New York, on 25 December 1934. He received his MS in physics in 1956 from the University of Chicago and then earned his PhD in physics from Stanford University in 1960 under the direction of John Shaw. His doctoral research was on magnetic resonance of yttrium iron garnets.
Phil spent the major part of his life working at IBM Corp’s T. J. Watson Research Center in Yorktown Heights, New York. Starting in 1960 as a research staff member, he quickly rose through the management ranks and was appointed director of the physical sciences department (1972–76) and then of the general sciences department (1976–77). He worked in the areas of magnetism, superconductivity, and organic solids during the early stages of his career at IBM. As early as 1973, Phil foresaw the field of molecular electronics, and, in 1974, he and Ari Aviram received the first patent in this field. Phil championed the study of organic materials at IBM throughout his life.
Restless to do basic research, Phil left management in 1977 and spent the rest of his time at IBM working in areas that interested him. He began a second career in astronomy with his pioneering work on the spiral structure of galaxies. By introducing a stochastic model in which star formation propagates around inside a shearing galaxy disk, Phil and his colleagues Humberto Gerola and Lawrence Schulman demonstrated during the period 1978–84 that the optical appearance of spiral structure could be the result of sheared star formation. They also found that star formation in very small galaxies should vary strongly with time because of the same propagation phenomena.
In 1989, in collaboration with Bruce and Debra Elmegreen, Phil discovered symmetric interference patterns in the intensity of spiral arms. This was the first experimental evidence for the existence of spiral-wave modes in the stellar disks of galaxies, and the first confirmation of a theory proposed 10 years earlier by C. C. Lin.
In the 1990s, Phil’s astronomical work centered on solar active regions. He showed that percolation phenomena can explain the appearance, lifetime, autocorrelation, and size distribution of sunspots. These results were based on computer models that he created over time in collaboration with Donat Wentzel of the University of Maryland, College Park. From 1983 until 1997, the Smithsonian Institution’s Air and Space Museum in Washington, DC, featured a movie exhibit devoted to Phil’s spiral galaxy work.
Immunology was at the center of Phil’s attention during the last phase of his research life. He approached his work in this field in a truly multidisciplinary manner. His remarkably productive collaboration with Franco Celada, a basic immunologist from Genoa, Italy (Phil described Celada’s title as “mouse-sticking immunologist”), began in 1987, when Phil quite serendipitously met Celada, who was working at the Hospital for Joint Diseases Orthopaedic Institute (HJD) in New York City. In 1992, the collaboration resulted in a computer model called IMMSIM (for immune simulation) that was based on a modified cellular automaton. A comprehensive model was created in 1997. Both the immunologist and the physicist were fascinated by the central role of the discrete stochastic encounters among specific cells that precede and condition the clonal expansion. Phil modeled the system to reflect the fluctuations that occur because of the distinct populations that initiate the response. IMMSIM turned out to approximate the outward workings of an individual’s immune response and also to allow the performance of real immunological experiments by introducing parameter changes—each change representing a hypothesis—and observing the results on the screen. These experiments were called “in machina” in analogy to the classical in vivo and in vitro tests. The model is widely used as a research tool, for example, to predict the efficiency of a vaccine or focus experimental protocols.
When they tackled infection by model viruses, Celada and Phil, with their small team of American and Italian modelers, discovered that the relative efficiency of cell-mediated and antibody-mediated responses mounted by the immune system are dictated by the virus’s characteristics, and that the two kinds of response often collaborate but sometimes compete with the evolutionary goal of offering the most apt defense. The fluctuations captured by IMMSIM have often turned out to look like some failures of immunity, and Phil exploited these examples to try to understand autoimmunity. As a result, Phil, with Martin Weigert and collaborators at Princeton University, developed the competitive tolerance hypothesis, which proposes a novel way by which autoantibodies may be regulated.
After retiring from IBM in 1997, Phil continued his research in immunology, both as a consultant on IMMSIM grants at HJD and as an adjunct faculty member at Princeton University, where he devoted his time to research and teaching. During his years at Princeton, Phil discovered IMMSIM’s value as a teaching tool and used it for both a graduate course and a freshman seminar. His enormous talent for teaching became apparent—his students consistently rated the course as the best they had ever taken. His total commitment to the scientific process earned him the respect and awe of his students and colleagues. On the last day of his life, he modified IMMSIM to fit a particular experiment, e-mailed his students to advise and encourage them as they pursued their projects, and thanked them for discovering a bug in IMMSIM.
Phil’s zest for life was very strong. He was ebullient, energetic, interactive, and ready to debate on subjects ranging from science, through linguistics, to gastronomy. An active participant in professional committees, he also enjoyed traveling, spending sabbaticals at the University of Grenoble, France; the Technion-Israel Institute of Technology in Haifa, Israel; and Indiana University. He was a kind and generous mentor, colleague, and friend.
