PubMed · 5146821
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G W Crockford, K P Foster, J Haspineall. 1971. Factors determining the sweating threshold.. https://doi.org/10.1007/bf01803913
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We report the results of an investigation on stratum corneum lipids, which present the main barrier of the skin. Molecular dynamics simulations, thermal analysis and FTIR measurements were applied. The primary objective of this work was to study the effect of cholesterol on skin structure and dynamics. Two molecular models were constructed, a free fatty acid bilayer (stearic acid, palmitic acid) and a fatty acid/cholesterol mixture at a 1:1 molar ratio. Our simulations were performed at constant pressure and temperature on a nanosecond time scale. The resulting model structures were characterized by calculating surface areas per headgroup, conformational properties, atom densities and order parameters of the fatty acids. Analysis of the simulations indicates that the free fatty acid fraction of stratum corneum lipids stays in a highly ordered crystalline state at skin temperatures. The phase behavior is strongly influenced when cholesterol is added. Cholesterol smoothes the rigid phases of the fatty acids: the order of the hydrocarbon tails (mainly of the last eight bonds) is reduced, the area per molecule becomes larger, the fraction of trans dihedrals is lower and the hydrophobic thickness is reduced. The simulation results are in good agreement with our experimental data from FTIR analysis and NIR-FT Raman spectroscopy.
OBJECTIVES: To assess the accuracy of a new noninvasive temporal artery (TA) thermometer in infants; to compare the accuracy of the TA thermometer with that of a tympanic thermometer, using rectal thermometry as the criterion standard; and to compare the tolerability of the TA thermometer with that of the tympanic and rectal thermometers. DESIGN: Prospective evaluation of the accuracy of TA and tympanic thermometry, using rectal thermometry as the criterion standard. SETTING: Emergency department of an urban pediatric hospital. SUBJECTS: Convenience sample of 304 infants younger than 1 year presenting for care. MAIN OUTCOME MEASURES: Temperatures were measured using TA, tympanic, and rectal thermometers for all infants. Agreement between TA or tympanic and rectal temperatures was assessed. The sensitivity and specificity of TA or tympanic thermometers for detecting rectal fever were determined. Discomfort scores, using a standardized scale, were assessed by trained observers after each temperature measurement was made. RESULTS: Linear regression analysis of the relation between TA and rectal temperatures yielded a model with a slope of 0.79 (vs a slope of 0.68 for tympanic vs rectal temperature; P =.02) and an r of 0.83 (vs r = 0.75 for tympanic vs rectal temperature; P<.001). Among 109 patients with a rectal temperature of 38 degrees C or higher, the TA thermometer had a sensitivity of 0.66 compared with the tympanic thermometer's sensitivity of 0.49 (P<.001). Discomfort scores with TA thermometry were significantly lower than with rectal thermometry (P =.007). CONCLUSIONS: The TA thermometer has limited sensitivity for detecting cases of rectal fever in infants. However, the TA thermometer is more accurate than the tympanic thermometer in infants, and it is better tolerated by infants than rectal thermometry.
An implementation is reported of an imaging method to obtain MUltiple Resolutions along Phase-encode and Slice-select dimensions (MURPS), which enables dynamic imaging of focal changes using a graded, multiresolution approach. MURPS allows one to trade spatial resolution in part of the volume for improved temporal resolution in dynamic imaging applications. A unique method of Hadamard slice encoding is used, enabling the varying of the phase encode and slice resolution while maintaining a constant effective TR throughout the entire 3-D volume. MURPS was implemented using a gradient-recalled echo sequence, and its utility was demonstrated for MR temperature monitoring. In this preliminary work, it has been shown that changes throughout a large volume can be effectively monitored in times that would normally only permit dynamic imaging in one or a very few slices.