Physicist and mathematical chemist Dan Gillespie will give a STEM Lecture at Bethel College at 11 a.m. Thursday in the Administration Building chapel.

Physicist and mathematical chemist Dan Gillespie will give a STEM Lecture at Bethel College at 11 a.m. Thursday in the Administration Building chapel.

STEM stands for Science, Technology, Engineering and Mathematics, a grouping used by the U.S. National Science Foundation to describe key fields of study and research in an advanced technological society. At Bethel, STEM covers biology, chemistry, computer science, mathematics, pre-engineering, physics and psychology.

Gillespie said that in the last 10 years, he has gone from “undeserved obscurity to undeserved fame.” The latter refers to his work, originally done in 1977, on stochastic chemical kinetics. In recent years, biologists and chemists have developed the tools to observe chemical reactions in a cell in detail and find exactly the fluctuations Gillespie predicted.

The algorithm he proposed, the “Gillespie Algorithm,” generates a statistically correct trajectory (possible solution) of a stochastic equation. It was developed to simulate chemical or biochemical systems of reactions efficiently and accurately, using limited computational power. As computers have become faster, the algorithm has been used to simulate increasingly complex systems.

The Gillespie Algorithm is particularly useful for simulating reactions within cells where the number of reagents typically number in the tens of molecules or fewer. Mathematically, it is a variety of a dynamic Monte Carlo method and similar to the kinetic Monte Carlo methods. It is used heavily in computational systems biology.

Gillespie’s title for his Bethel lecture is “Making Differential Equations Non-Deterministic.”

According to Gillespie’s abstract of the lecture: “Ordinary differential equations are used to describe the time-evolution of a great many physical systems. Any physical process that evolves according to an ordinary differential equation is necessarily continuous and deterministic. It is also memoryless or ‘Markovian,’ in that its future depends on its past only through its present.

“Suppose we wish to describe a process that is continuous, memoryless and non-deterministic or ‘stochastic.’ What changes to the theory of ordinary differential equations would we have to make? In this elementary tutorial, we will peek into the world of ‘continuous Markov processes,’ where the governing equations bear names like Langevin and Fokker-Planck. We will try to understand what some of those equations say, why they have the forms they do and what some of their applications are.”

Gillespie has a bachelor of arts from Rice University and a doctorate from Johns Hopkins University. For three decades, he worked for the Navy as a civilian research scientist at China Lake, Calif. Since his retirement in 2001, he has been a private consultant in computational biochemistry under contract with the California Institute of Technology and the University of California at Santa Barbara. This work has been aimed at developing improved methods for numerically simulating biochemical systems, extending procedures he devised earlier while at China Lake.

Gillespie has authored approximately 80 research journal articles in such diverse areas as high energy physics, classical transport theory, raindrop formation in clouds, Monte Carlo methodology, random variable theory, stochastic chemical kinetics, light scattering in aerosols, Brownian motion, thermal electrical noise, stochastic process theory and quantum mechanics. He is the author of two highly regarded books in his professional field: “A Quantum Mechanics Primer” (International Textbook Co., 1973) and “Markov Processes: An Introduction for Physical Sciences” (Academic Press, 1992). His most recent book is “Bob and Ray and Tom” (BearManor Media, 2004), a biography of Tom Koch, a MAD Magazine writer and one of the primary writers for radio performers Bob and Ray.

Gillespie’s lecture at Bethel is free and open to the public. He also will speak at 3 p.m. Wednesday at Wichita State University, in Room 128 of Jabara Hall (the physics department) on “Stochastic Chemical Kinetics.” For more information, call 284-5210 or e-mail