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The amount of smoke that may be produced by wildland or rural fires as a consequence of a large-scale nuclear exchange is estimated. The calculation is based on a compilation of rural military facilities, identified from a wide variety of unclassified sources, together with data on their geographic positions, surrounding vegetation (fuel), and weather conditions. The ignition area (corrected for fuel moisture) and the amount of fire spread are used to calculate the smoke production. The results show a substantially lower estimated smoke production (from wildland fires) than in earlier "nuclear winter" studies. The amount varies seasonally and at its peak is less by an order of magnitude than the estimated threshold level necessary for a major attenuation of solar radiation.

A method for including three-dimensional boundary corrections in the analysis of interferograms of two-dimensional flows is described. An effective optical pathlength is calculated using a displacement thickness concept. Expressions and methods for determining the correction to the optical pathlength are given for laminar and turbulent boundary layers in isoenergetic or diabatic flow. An exact expression is derived for the turbulent case and results given showing the correction to be of the order of 10%.

Regression models of the type proposed by McCullagh (1980, Journal of the Royal Statistical Society, Series B 42, 109-142) are a general and powerful method of analyzing ordered categorical responses, assuming categorization of an (unknown) continuous response of a specified distribution type. Tests of significance with these models are generally based on likelihood-ratio statistics that have asymptotic chi 2 distributions; therefore, investigators with small data sets may be concerned with the small-sample behavior of these tests. In a Monte Carlo sampling study, significance tests based on the ordinal model are found to be powerful, but a modified test procedure (using an F distribution with a finite number of degrees of freedom for the denominator) is suggested such that the empirical significance level agrees more closely with the nominal significance level in small-sample situations. We also discuss the parallels between an ordinal regression model assuming underlying normality and conventional multiple regression. We illustrate the model with two data sets: one from a study investigating the relationship between phosphorus in soil and plant-available phosphorus in corn grown in that soil, and the other from a clinical trial comparing analgesic drugs.

A standard single pass schlieren system was converted into a single beam schlieren interferometer by replacing the knife edge with a polarizer-Wollaston prism-analyzer combination. The system is described and an analysis given that relates the fringe shifts on the interferogram to density changes in the test section. The proper location of the density difference is discussed.A complex gas dynamic flow field was investigated with this interferometer, and the results were shown to compare well with theoretical predictions.