Senior Dynamicist, ins Research and Development, y/ je Reynolds number dependence of Cf, Uo, H and other bulk flow parameters in "two dimensional" (high aspect ratio) rectangular duct flow is explored and the empirical relations C, = 0.013 fie-" 4 and U 0 /U = 1.28 i2e-»-wl « are presented.The values A = 2.12 and K = 0.41 for the log-law constants and II = 0.14 for Coles' wake parameter are derived and are shoiun to be independent of Re. The integration of Dean's formula for the complete velocity profile provides close agreement with all parameters when these values of A, K and H are used and is shown to coincide with the "optimum log-law" for skin friction (which contains II),

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Extreme values for the negative pressures and the degrees of superheat which water will withstand without forming bubbles are contrasted with the ease of forming bubbles by vibration or by the turbulent flow of liquids. The subject of bubble nuclei is briefly reviewed, and it is pointed out that such nuclei usually function by virtue of sorbed or trapped air which can be removed, rendering the nuclei ineffective. Technique for avoiding extraneous bubble nuclei is presented with some experiments on the formation of bubbles by mechanical action. It is pointed out that free vortices in liquids produce sufficient tension to rupture the liquid, and it is suggested that mechanical disturbance produces bubbles only in such vortices and not by general pressure lowering in sound waves.

Two experiments were conducted to examine the effects of forewarning of persuasive intent upon opinion change. Experiment I, a field study, used forewarning versus no forewarning, high-versus low-involvement issues, and high-versus low-status message sources in an attempt to further test Apsler and Sears's hypothesis that forewarning serves to magnify the response that subjects would have made in its absence. The high-involvement message produced a boomerang effect, while the low-involvement message changed opinion substantially in the advocated direction. Both the main effect of issue and the main effect of forewarning were significant, with the forewarned conditions producing less opinion change, regardless of issue involvement or source status. Experiment II, conducted in the classroom, again examined the effects of forewarning with involving and uninvolving issues, in addition to testing the effect of sex of subjects and an item-ordering effect, where subjects either first answered opinion items for the issue read and then for the other issue (normal order), or else the reverse of this. The high-involvement issue resulted in little opinion change in any condition. For the low-involvement issue, a significant three-way interaction was obtained, such that in the normal item-ordering condition, forewarning inhibited opinion change for males but facilitated change for females, while in the reverse ordering condition, neither variable made any difference. These results are discussed in terms of their degree of support for the hypotheses advanced by both Apsler and Sears and Papageorgis.