Friday, September 28, 2012

Benedek and Villars, Volume 3

This is the third and final entry in a series of blog entries about Benedek and Villars’ textbook Physics With Illustrative Examples From Medicine and Biology. Today I discuss Volume 3, about electricity and magnetism. In the preface to the first edition of Volume 3, Benedek and Villars write
“With this volume on Electricity and Magnetism, we complete the third and final volume of our textbooks on Physics, with Illustrative Examples from Medicine and Biology. We believe that this volume is as unique as our previous books on Classical Mechanics (Vol. 1) and Statistical Physics (Vol. 2). Here, we continue our program of interweaving into the rigorous development of classical physics, an analysis and clarification of a wide variety of important phenomena in physical chemistry, biology, physiology, and medicine.”
The topics covered in Volume 3 are similar to those Russ Hobbie and I discuss in Chapters 6-9 in the 4th edition of Intermediate Physics for Medicine and Biology. Because I do research in the fields of bioelectricity and biomagnetism, you might expect that this would be my favorite volume of the three, but it is not. I don’t find that it contains as many rich and interesting biological examples. Yet it is a solid book, and contains much useful electricity and magnetism.

Before leaving this topic, I should say a few words about George Benedek and Felix Villars. Benedek is currently the Alfred H. Caspary Professor of Physics and Biological Physics in the Department of Physics in the Harvard-MIT Division of Health Sciences and Technology. His group' research program “centers on phase transitions, self-assembly and aggregation of biological molecules. These phenomena are of biological and medical interest because phase separation, self-assembly and aggregation of biological molecules are known to play a central role in several human diseases such as cataract, Alzheimer's disease, and cholesterol gallstone formation.” Villars was born in Switzerland. In the late 1940s, he collaborated with Wolfgang Pauli, and developed Pauli-Villars regularization. He began work at the MIT in 1950, where he collaborated with Herman Feshbach and Victor Weisskopf. He became interested in the applications of physics to biology and medicine, and helped establish the Harvard-MIT Division of Health Sciences and Technology. He died in 2002 at the age of 81.

4 comments:

  1. On the subject of biomagnetism--though I've not checked the primary source, Wikswo and Barach, 1980--I read an interesting claim in Essential Neuromodulation by Jeffrey Arle:

    "an estimate of magnetic field strength required to produce potentially a 10% reduction in neural activity itself was calculated to be 24 Tesla"

    As a kid, my reading of Roth and Wikswo's, "Magnetic Field of a Single Axon", began for me a dream to one day halt conduction with an applied E&M field.

    Certainly the Arle claim must refer to a time-independent field. Conventional TMS would be a counterexample to the general claim IMHO

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  2. Yes, Wikswo and Barach 1980 is for a static magnetic field. It is interesting you say "halt" conduction. Conventional TMS is a good counterexample of exciting conduction. I designed a 4-leaf clover coil that had some promise of halting conduction, but we could not get it to work, probably because the threshold for block was too high. See: Roth, B. J., P. J. Maccabee, L. Eberle, V. E. Amassian, M. Hallett, J. Cadwell, G. D. Anselmi and G. T. Tatarian, 1994, In-vitro evaluation of a four-leaf coil design for magnetic stimulation of peripheral nerve. Electroenceph. clin. Neurophysiol., 93:68-74.

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  3. People currently halt conduction with 10kHz current--I wonder if you could pulse a TMS coil that fast?

    Have read, and enjoyed the four leaf clover, btw. What was your original goal for the 4 leaf device? Was it with the aim of achieving conduction block?

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  4. The original goal was that with a figure-8 coil, it is a bit unclear where excitation of a peripheral nerve occurs. It is off to one side. The 4-leaf coil is like a cross-hairs. Excitation occurs under the "+". The conduction block idea was secondary.

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