96 resultados para electrostatic surface potential
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The aim of this study was to analyze the anticaries potential of pit and fissure sealants containing amorphous calcium phosphate (ACP) by synchrotron microtomography. Bovine enamel blocks (4x4 mm; n=50) were selected through surface hardness (Knoop) analysis. Slabs were obtained through cross-sections taken 1 mm from the border of the enamel. Five indentations, spaced 100 mu m apart, were made 300 mu m from the border. Ten specimens were prepared for each tested material (Ultraseal XT plus TM, Aegis, Embrace, Vitremer and Experimental Sealant). The materials were randomly attached to the sectioned surfaces of the enamel blocks and fixed with sticky wax. The specimens were submitted to pH cycling. After that, the surface hardness (SH1) was determined, and the blocks were submitted to synchrotron microcomputed tomography analysis to calculate the mineral concentration (Delta g(HAp) cm(-3)) at different areas of the enamel. The comparison between the SH1 and DgHAp cm(-3) showed a correlation for all groups (r=0.840; p<0.001). The fluoride groups presented positive values of DgHAp cm(-3), indicating a mineral gain that was observed mainly in the outer part of the enamel. The ACP showed mineral loss in the outer enamel compared with fluoride groups, although it inhibited the demineralization in the deeper areas of enamel. The combination of two remineralizing agents (fluoride and ACP) was highly effective in preventing demineralization.
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Rot caused by Fusarium pallidoroseum has had a severely negative impact on the export of melons from Brazil. Uncertainty regarding the health of the fruit due to the quiescent infection of the pathogen has led producers to use fungicides in the postharvest treatment of the fruit, thereby causing contamination and risking the health of consumers. Consequently, there is a demand for clean and safe natural technologies for the postharvest treatment of melons, including biological control. The present study aimed at evaluating bioagents for use in controlling Fusarium rot in 'Galia'melon. The following bioagents were evaluated: two isolates of Bacillus subtilis, B. licheniformis and a mixture of B. subtilis and B. licheniformis, as well as the yeasts Sporidiobolus pararoseus, Pichia spp., Pichia membranifaciens, P. guilliermondii, Sporobolomyces roseus, Debaryomyces hansenii and Rhodotorula mucilagenosa. Treatment with imazalil and water were used as controls. Two experiments were conducted in a completely randomised design with 10 replicates per treatment with four fruit per replicate; the disease incidence was evaluated in the first experiment, and the disease severity was evaluated in the second. Similarity analysis of the temporal evolution profiles of rot incidence caused by F. pallidoroseum allowed the evaluated treatments to be clustered into four groups. In the first experiment, the yeasts P. membranifaciens and D. hansenii produced results similar to that of the fungicide imazalil. The second experiment highlighted the yeasts P. guilliermondii and R. mucilaginosa. Electron microscopy studies confirmed that once applied to the fruit, the yeasts colonised the skin and damaged the pathogen mycelium; the action of the yeasts affected the mycelium of F. pallidoroseum, which had infected wounds on the fruit's surface. Bacillus spp. did not provide good disease control. These results demonstrated that yeasts have the potential to control postharvest rot caused by F. pallidoroseum in 'Galia'melon.
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Conselho Nacional de Desenvolvimento Científico e Tecnologico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação Amparo à Pesquisa Estado de São Paulo (FAPESP)
