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June 1, 1999


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The Scientist Who Loves To Push Most Advanced Computers To Their Limit

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Sonia Chopra

When the National Aeronautics and Space Administration purchased a massive parallel computer some years ago, they looked for scientists who could advise them on its use for basic research.

Tara Prasad Das One of the few experts that NASA called upon nationwide was Tara Prasad Das, professor of physics at the State University of Albany. Although, Das was not a computer scientist, he was ideal for NASA's task because he, along with his research group, has extensive experience performing calculations that can challenge the most advanced computers.

By performing their vast computations on both traditional computers and NASA's new machine, Das and his assistants have been able to provide an important basis for comparison between the two computing systems.

"It is important to know how something works, but it is more important to know why. Finding out the 'why' is basic research; the 'how' is technology. If you know more 'whys,' you will produce a lot more 'hows,' said 66-year-old Das, in an interview last week.

Das is a computational theoretical physicist who routinely drives the most powerful computers to their limits. Why? Because he uses these computers as a tool in solving complex mathematical equations that describe the inner workings of atoms and molecules.

Most of us have learned an elementary approximation of what occurs in atoms of high school physics. We were taught to think of the atom as a tiny solar system with the nucleus, containing protons and neurons, as the sun and the electrons, like planets, orbiting the nucleus.

This planetary model may be a neat and structured way for ordinary mortals to conceive of atoms but it's highly misleading. In fact, in an atom, the forces between the electrons make a shambles of neat and orderly orbits. Unlike planets in the solar system, which orbit in the same planes, electrons in the atom orbit in countless planes. As atoms bind together from molecules, they share electrons.

This actually gets a bit complicated for a few minutes more -- electrons have a tendency to act like waves. These wavelike characteristics require quantum mechanics for their description -- and the nucleus also acts like a magnet -- the magnetism or so-called magnetic moment, of the nucleus is caused by the spinning of protons and neutrons insides the nucleus.

The magnetic field caused by the orbiting electrons interacts with the magnetism of the nucleus of the atoms. This interaction, known as hyperfine interaction is what Das has spent his career studying.

"You can figure what precisely what electrons are doing in atoms by studying these hyperfine fields," said Das, adding that by using complex mathematical equations to represent the motions of electrons in atoms and other systems, he calculates electron distribution and then tests his solutions against the data obtained by the experimental physicists.

One of the projects that Das and other physicists have improved the scientists' knowledge of the electronic structure of hemoglobin since 1967. Their study deals with cooperativity in hemoglobin, which refers to the fact that as soon as one of the hemoglobin's protein chains attaches to oxygen, it prompts the second protein to get hungry for oxygen and so on and so forth.

It would be natural to expect a man who spends his time wrapped up in mathematical theory and computer calculations to be eccentric, distant, distracted and very difficult to comprehend or communicate with but that's not the case with Das.

Charming, gracious, almost apologetic, Das sometimes broke into his native Bengali with this reporter knowing that she has been born and brought up in Calcutta, where the I-don't-care-what-the-official-language-is-we speak-Bengali attitude rules.

He was excited and animated in his discussions of physics, which he liberally sprinkles with his observations on philosophy and religion, which are drawn largely from his upbringing in India.

On his curiosity with electrons, structures and other scientific stuff, Das said, "God sends us into the world. We can just live and not ask questions. But if we can follow up our observations and find out a little bit more about how something works, then we can get a better understanding about the relationship between ourselves and the divine."

Das earned his PhD in 1955 from Calcutta University's Saha Institute of Nuclear Physics. He joined the Chemistry Department at Cornell University for a year, where his immediate interest as a post-doctoral scientist was the newly discovered field of nuclear magnetic resonance, which today is a vital part of medical scanning technology used in hospitals to provide noninvasive pictures of the interior of the body.

For him, though, the interest was purely in understanding the theory of nuclear magnetic resonance better. "What fascinated me at that time was, what can you learn from this new toy," he said.

This led him to co-author the book Nuclear Induction, published by the Saha Institute -- this book is still used today. His interest in hyperfine interactions have continued since then.

Das then joined the Physics Department at the University of California, Berkeley, where he collaborated on a second book on a technique closely related to NMR. The book Nuclear Quadruple Resonance Spectroscopy published by Academic Press is also still in use, 30 years later.

Then he came to SUNY Albany.

In 1973, Das also wrote a textbook, Relativistic Quantum Mechanics of Electrons, published by Harper & Row. Das has published 251 papers and nine review articles. He attributes his extraordinary productivity to his "excellent graduate students, post-doctoral associates and experimental colleagues."

Das has guided 50 graduate students through their PhDs and he is supervising the research of seven doctoral candidates. He working on papers with scientists in West Germany, Sweden, The Netherlands, Belgium, Japan and India and has been invited to international conferences to present papers almost every few months.

Examples of these are the International Conference on Hyperfine Interactions held last August in Dublin.

Then in October, Das was invited at the Institute of Physical and Chemical Research in Wako-Shi, Japan to lecture on fusion techniques for energy production. From there, he went to Bangalore for the meeting of the International Union of Materials Research Societies, where he presented a review of the current understanding of ferromagnetism in solid state systems. In January, he traveled to the University of Zurich in Switzerland to discuss the understanding of magnetic and hyperfine products.

His wife, Basanta Manjori Das, sometimes accompanies Das; they live in Guilderland, a few miles north of Albany.

Industry has also drawn on Das's talents. He has had numerous associations, either as a visiting scientist or consultant at the industrial research laboratories of GTE, IBM, RCA, Gulf General Dynamics and the Xerox Corporation.

Das collaborates with numerous other experimenters, as well. Worldwide, the physicist provides theoretical support for the work of several atomic and molecular and solid state physicists. There is only a handful of physicists worldwide who do the work Das does.

Das offers a favorite anecdote, one he often uses in the classroom, to explain why it is so important for experimental and theoretical physicists to interact closely.

"There were once three blind men who met an elephant. They weren't sure what it was they had encountered," he said. "One of them touched the elephant's tusk and said, `it is something hard.' Another touched the leg and said, `It is like a pillar.' The third touched the elephant's ears and thought he was touching a fan. But it was only when the three of them put their observations together that they came up with a total picture."

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