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Although additional experiments are required for the medium- and low-visibility search objects and in the dry-domain ecoregion, we suggest search planners use the following correction factors to convert field-measured Rd to an estimate of the effective sweep width (W): high-visibility W = 1.8 × Rd; medium-visibility W = 1.6 × Rd; and low-visibility W = 1.1 × Rd.

Background Although lost-person search managers try to direct search efforts quantitatively, it has historically been difficult to quantify the efficacy of search efforts accurately. The effective-sweep-width (ESW) methodology represents an avenue for accomplishing this goal but has not yet been widely disseminated among practitioners. Methods We obtained ESW values in the summer and winter in a typical disturbed-forest environment in southwest Pennsylvania. We used nonparametric statistics to compare individual ESW values for two types of search objects detected by 18 summer and 20 winter searchers, cumulating the P values for similar comparisons and correcting for false discovery via a stepped method. Results We detected robust differences (all at P <.001) associated with search object color, season, and vegetation thickness. In contrast with earlier studies, we found a significant correlation between individual searchers' ESWs for different search objects and different types of vegetation ( P <.001). We also found that adolescent searchers had significantly lower ESW values than adults ( P = .002). Apparently significant positive correlations between time spent on the course or field search experience and ESW disappeared when teens were excluded from the comparisons. Conclusions These results (the first comparison of seasonal ESW effects in identical terrain) represent the first statistical demonstration that the ESW methodology provides more than enough resolution to answer fundamental questions about the efficacy of visual search for lost persons by human searchers. They also add support to the imperative of operationally disseminating these methods among search-and-rescue practitioners, and offer some initial operational lessons for search managers.

Elements of the quaternary structure of the native and dithiothreitol- (DTT) reduced rat adipocyte insulin receptor have been elucidated by vectorial probing and subunit cross-linking. The charged reducing agents glutathione and beta-mercaptoethylamine were used to reduce the class I disulfides of the receptor in intact adipocytes, demonstrating the extracellular location of the disulfide directly. This interpretation was confirmed by use of DTT as a reducing agent and the nonpermeant sulfhydryl blocking reagent Thiolyte MQ to prevent the reoxidation of the class I sulfhydryl groups which occurred when they were not blocked. It was found that the above reoxidation of the receptor is dependent on the concentration of insulin in the nanomolar range, not occurring measurably at 4 degrees C in its absence. Cross-linking studies with ethylene glycol bis(succinimidyl succinate) demonstrated that the alpha subunits could not be cross-linked to each other after reduction of the class I disulfides, suggesting that the interaction between the receptor heterodimers may be due primarily to the disulfide bonds.

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