M J Mallett | PubMed Health

PubMed2001

NMR stray-field analysis of oil drop size distribtuion in peanut cotyledons.

The technique of stray-field NMR has been applied to the study of an oil-bearing seed. It is found to provide additional information about the smallest size of oil drops within the cotyledon not easily measurable by other methods. A peanut was chosen as a convenient seed to investigate so as to allow comparison with previously published NMR pulsed field gradient data. We find a broad distribution of oil drop sizes ranging from a lower limit of order 0.26 microm up to a maximum of approximately 1.3 microm.

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PubMed1996

A three-dimensional NMR imaging scheme utilizing doubly resonant gradient coils.

A 3DFT gradient-echo technique has been developed which, in conjunction with series-resonant gradient-coil circuits, can produce three-dimensional NMR images with an echo time of less than 100 microseconds. The method involves a read-gradient waveform composed of two sinusoids of different frequencies. This is an improvement on previous imaging sequences using a single sinusoid where only half of k space was sampled and where the second half was calculated using conjugate symmetry. The inaccuracies involved in the necessary "cut and paste" of k space inevitably lead to artifacts in the final image. The important features of the new method are that with suitable phase encoding all octants of k space are sampled, the RF pulse is applied when the gradients are all zero, and the echo forms when the gradient is essentially constant. This method will allow more extensive application of solid imaging techniques to biological samples in vivo.

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