PubMed · 15435517
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K MIESCHER, R ROMETSCH. 1950-08-15. [Standard white].. https://doi.org/10.1007/bf02170907
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OBJECTIVES: The objectives were to measure the color change of varied shades of dental resin composites after polymerization, and to determine the correlation among the polymerization color change and the changes in color parameters after polymerization. METHODS: Eight light-curing resin composites, a total of 41 shades, were studied. Color of specimens (1 mm in thickness) was measured on a reflection spectrophotometer before and after polymerization over a white background. Changes in color (Delta E*(ab)), and color parameters (Delta L*, Delta C*(ab), Delta a*, and Delta b*: value after polymerization - value before polymerization) were calculated. RESULTS: The range of changes in each shade of resin composites was 1.1-7.9 for color (Delta E*(ab)), -7.5 to 2.3 for Delta L*, -6.8 to 3.1 for Delta C*(ab), -0.9 to 1.2 for Delta a*, and -6.8 to 3.1 for Delta b*. Delta E*(ab), Delta L*, Delta C*(ab), Delta a*, and Delta b* were influenced by the brand and shade of resin composites, and there was a significant interaction between two independent variables (p < 0.05). On the basis of the multiple regression analysis, in which Delta E*(ab) after polymerization was set as a dependent variable and Delta L*, Delta C*(ab), Delta a* and Delta b* as independent variables, multiple correlation coefficient (r) was 0.842 and the included predictors were Delta L* [standardized partial correlation coefficient (beta) = -0.760] and Delta C*(ab) (beta = -0.715). This result indicated that the polymerization changes in color and color parameters were varied by the brand and shade of resin composites, and the polymerization color change was caused by the changes in lightness and chroma with the similar power of influence.
A semianalytical approach to the problem of determining inherent optical properties from satellite and in situ ocean color data is presented. The model uses empirically derived spectral slopes between neighboring wavebands in combination with radiative transfer modeling to determine the spectral absorption (alpha) and backscatter (b(b)); these values are then further decomposed into absorption due to phytoplankton, detrital, and colored dissolved organic matter components. When compared with over 400 in situ data points the model makes good retrievals of the total absorption and backscatter across the entire spectrum, with regression slopes close to unity, little or no bias, high percentage of variance explained, and low rms errors.
BACKGROUND: Lack of a second sample often precludes the ability to perform repeat lead measurements on filter paper bloodspot samples. We investigated whether annular specimens remaining from once-punched filter paper bloodspot specimens could provide accurate Pb measurements when measurements were scaled for the remainder area relative to the original punch area. METHODS: 50 microl bloodspot specimens were prepared using Pb-spiked EDTA whole blood. After removal of 6 mm punches, bitmap images of the remainder specimens were obtained using a scanner. Image analysis was used to determine the bloodspot area of the remainder sample relative to the area of the original punch. Measurement of Pb for punches and for remainder specimens was performed by ICP-MS. RESULTS: Area-corrected Pb measurements for remainder samples were significantly higher than for the punches, by an average factor of 1.52+/-0.12 (p<0.05, n=28). The difference was due to a discontinuity (an increase) in the per-area Pb at the bloodspot perimeter. Area-corrected results for annular specimens that excluded the perimeter were identical to those of the punch. CONCLUSION: Area-corrected Pb measurement using annular once-punched bloodspot remainder specimens can accurately reproduce lead measurements obtained from the original punch when the bloodspot perimeter area is excluded.