Understanding the Dynamics of Dosage Response: A Nonlinear Meta-Analysis of Recent Reading Interventions

Researchers have noted a nonlinear association between reading instruction dosage (i.e., hours of instruction) and reading outcomes for Grade K–3 students with reading difficulties (K–3 SWRD). In this article, we propose a nonlinear meta-analysis as a method to identify both the maximum effect size and optimal dosage of reading interventions for K–3 SWRD using 26 peer-reviewed studies including 186 effect sizes. Results suggested the effect sizes followed a concave parabolic shape, such that increasing dosage improved intervention effects until 39.92 hours of instruction (dmax = 0.77), after which the intervention effects declined. Moderator analyses found that maximum intervention effects on fluency outcomes were significantly larger (dmax = 1.34) than the overall maximum effect size. Also, when students received 1:1 instruction, the dosage response curve displayed a different functional form than the concave parabolic shape, showing the effect increased indefinitely after approximately 16.8 hours of instruction. Implications for research and practice are discussed.

Adaptive tolerance of Fusarium solani to benzimidazole derivatives in vitro

The growth response of Fusarium solani to benomyl or thiabendazole in the medium was found to differ from that of many other Fusarium species tested. In contrast to the steep, linear dosage–response curve typical for this genus, the curve for F. solani invariably reaches a maximum at about 1.0 μg/ml and is horizontal from there on. During a single exposure to either benomyl or thiabendazole, F. solani develops tolerance to both toxicants, but its subsequent growth on untreated medium is retarded. Cross-tolerance to other benzimidazoles is also induced. Such adapted strains generally maintain their slow growth habit and tolerance indefinitely through successive transfers to either untreated or treated medium. Occasionally a colony growing slowly on untreated medium will produce a sector which grows normally but proves to be sensitive when transferred to treated medium. Conversely, colonies of this sensitive strain, while growing extremely slowly on treated medium, more frequently produce a sector like the resistant strain. From observation of the response of a large number of single-spore isolates it is concluded that in the presence of a benzimidazole a high proportion of the wild population can mutate to the slow-growing, resistant type. Such mutants occasionally revert to the wild type.

AN EVALUATION OF CAPTAN SMOKE GENERATORS FOR CONTROLLING ROTS IN STORED TOMATOES

Fungitoxic residues of captan were deposited on the surfaces of stored produce using an electrically operated smoke generator. Deposits were heavier on upper surfaces than on side or undersurfaces.The slope of the captan smoke deposit dosage-response curve was similar to that of captan, which indicated that the active ingredient was not destroyed during the smoking process.Deposits from captan smoke showed some promise for the control of tomato storage rots.