PubMed · 8827329
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C Stewart. 1996. Color-coding tapes.. https://doi.org/10.1016/s0001-2092(06)63365-6
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Calculations of radiofrequency magnetic (B1) field and specific energy absorption rate (SAR) distributions in a sphere of tissue and a multi-tissue human head model in a 12-element birdcage coil are presented. The coil model is driven in linear and quadrature modes at 63, 175, 200, and 300 MHz. Plots of B1 field magnitude and SAR distributions, average SAR, maximum local SAR, and measures of B1 field homogeneity and signal-to-noise ratio are given. SAR levels for arbitrary pulse sequences can be estimated from the calculated data. Maximum local SAR levels are lower at lower frequencies, in quadrature rather than in linear coils, and in linear fields oriented posterior-to-anterior rather than left-to-right in the head. It should be possible to perform many experiments in the head at frequencies up to 300 MHz without exceeding standard limits for local or average SAR levels.
The chemical reactions contributing to sucrose loss and color formation in evaporators in sugar manufacture (i.e., hydrolysis of sucrose and degradation of monosaccharides at acid pH) are reviewed. A case study of a sugar factory's evaporator system demonstrates that the measurement of small but real losses of sucrose across the process is not possible by conventional sugar factory analyses. Alternative, more accurate techniques (e.g., capillary gas chromatography or high performance ion chromatography [HPIC] with pulsed amperometric detection [PAD]) are considered. In the case study, glucose:sucrose ratios are determined by HPIC, and sucrose loss across the evaporator is estimated to be 1.39% of total sucrose. Loss measurements are thought to be underestimates; reasons for underestimation and the sources of errors are discussed. An approach to a more definitive loss measurement is proposed.