The main objective of the present study is to identify the impacts of bed mobility on the vertical profile of the mean longitudinal velocity and on resistance in flows over water‐worked beds of poorly sorted mixtures of sand and gravel. Water‐worked beds with sediment transport are explicitly distinguished from immobile beds with imposed sediment feed. Flows with different equilibrium sediment transport rates are generated in a laboratory flume. The initial bed mixtures featured combinations of sand and gravel modes. Data collection included instantaneous velocities measured with Laser Doppler Annemometry. Wall similarity, in the sense of Townsend (1976), is assumed. The parameters of the formulae are discussed within three scenarios comprising different definitions ofu* and ks combined with different conceptions of the Von Kármán constant (κ flow independent or flow dependent). It is shown that the parameters of the formulae that express the velocity profile vary with the Shields number and with the initial bed composition. The variation is independent of the adopted scenario, except in what concerns the formulation of hydraulic smoothening in the presence of sand sizes, which depends on the definition of ks.
The erosion caused in vitro by cola-type and guaraná-type beverages (the latter is a soft drink sold in Brazil), and a canned lemon juice on the enamel of human deciduous teeth was analyzed. Morphological analysis of affected enamel was done using stereomicroscopy and scanning electron microscopy (SEM). The harmful effect of all test products on deciduous enamel was clearly demonstrated. Stereomicroscopy showed loss of gloss and an alteration in normal color of enamel, with irregular loss of dental tissue in variable degrees. Such a loss became more serious as the time of incubation increased. Different degrees of solubilization of enamel prisms were demonstrated by SEM, affecting initially the sheaths and the heads of prisms and later their tails. Areas of erosion increased in proportion to the time of incubation. All the products showed a great erosive potential on human deciduous dental enamel.
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