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EPR Simulation Programs

James Boswell (18th Century Biographer)

I've developed an XOP (external operation) that adds powder and isotropic EPR simulation capabilities to the Macintosh graphing and numerical analysis program, Igor Pro.

Note: You need Igor Pro v2 or v3 to use this XOP!

Specifically, the XOP adds:
  • Simulate(). This function uses the QPOW powder simulation engine of Nilges (for S=1/2 spectra)
  • SimulateIso(). This function simulates isotropic spectra

I've also put together a Demo Experiment (included with the XOP) that shows how the functions work, and also contains some macros to allow for easy editing of parameters.

Grab the files from our ftp server (see links at end of this page). These files are binhexed self-extracting archives.


Bug Fix Alert
April 11, 1996: Fixed a bug in the XOP that caused crashes in version 3 of Igor Pro. MANY thanks to Howard Rodstein of Wavemetrics who was kind enough to look at my code and find the bug for me.

For those of you who are interested, my problem was writing one value too far to the simulation wave (i.e. trying to write 501 values to a wave with 500 points). I never noticed this problem with v2 of Igor Pro, since there were extra bits at the end of the wave structure that were not being used. However, those extra bits were removed from the wave structure in version 3 of Igor Pro, so that 501st point was being written to a random place in memory. This is a Bad Thing To Do.

Interface NOTE: In the PPC version of the XOP, the cursor does NOT spin during a simulation. When running on a PPC this is typically not a problem, as the simulations are very fast. Just keep in mind that during a simulation the mac is completely tied up doing numbercrunching; no backgrounding is possible.

The XOP is email-ware. Please send me a note if you download this XOP and let me know how you like it, how I can improve it, or if you discover a bug.

One plan for the future is to allow Igor Pro to use the XOP in its curve-fitting routines so you will be able to iteratively fit the simulation to an experimental spectrum. I can't say right now when this will be...

(For Powermacs ONLY)

(For 68K Machines ONLY; REQUIRES a math coprocessor)

John Boswell
Currently at:
Active Digital Library, Eskind Biomedical Library
Vanderbilt University Medical Center
Nashville, TN 37232
Last Updated: 8-Feb-99
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