th  - 1988 - 51st ENC Conference

-- 50 I PIQABLE: AUTOMATIC AND RELIABLE QUANTIFICATION OF LOW SIGNAL TO
NOISE SPECTRA. Sarah J. Nelson and Truman R. Brown, Fox Chase Cancer Center,
Philadelphia, PA
Interpretation of the results of in vivo spectroscopy requires a rapid, unbiased and
reproducible method for quantifying low signal to noise spectra. Typically, these
spectra have variable baseline, a variety of peak shapes and some partially overlapping
peaks. We have recently developed a technique which performs peak identification,
quantification and automatic baseline estimation (hence PIQABLE) for such spectra. The
original version of PIQABLE was calibrated on simulated spectra (Nelson and Brown,
1987). We have now refined the algorithms to include the options of automatically
estimating phase correction parameters and of detecting and estimating areas of
partially overlapping peaks. The accuracy of these refinements has been examined on
simulated data which have peak signal to noise ratios in the range I00:I to 3:1. The
parameter values and error estimates which PIQABLE provides are accurate to within the
limitations imposed by the random noise. The new version of PIQABLE has been applied
to a wide range of experimental data, including human calf, liver, heart and brain.
Because the analysis is automated, it has proved particularly useful for application to
situations where multiple spectra are collected such as kinetic data or chemical shift
imaging data.
-- 51 I SOLID STATE NMR INVESTIGATIONS OF CERAMICS AND GLASSES
WITH EXTREMELY LONG SP•IN-LATTICE RELAY~TION TIMES: T. E. Hammond*,
R. D. Boyer, J. R. Mooney, BP America Research & Development, Cleveland,
Ohio 44128.
Several inorganic ceramics and glasses have been studied by solid state
N~[R which have been found to have extremely long spim-lattice relaxation
times. These materials are typically void of hydrogens. Therefore,
single pulse, Bloch decay-experiments are usually the only method which
can be used to acquire an NMR spectrum. Included in these studie~ have
been the C-13 and Si-29 spectra of alpha silicon carbide, Si-29 spectrum
of silicon sulfide glasses, and the Y-89 spectrum of yttrium oxides.
The worst case appears to be for certain compositions of the silicon
sulfide glass, where the Si-29 T I can be on the order of 15-25 hours.
The silicon carbide appears to have a di,tribution of T.'s, ranging from
several seconds to over a thouoand seconds. In the SiC case, it is beiieved
that metal impurities provide paramagnetic sites that induce relaxation
of neighboring silicon atoms. Since there are no abundant spin active
nuclei present, spin diffusion is not a possible mechanism to induce
relaxation of those silicon atoms removed from the paramagnetic centers.
Yttrium Tl'S appear to be on the order of 200-1500 seconds for several
yttrium compounds studied.
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