Summary
Lesion area measurement of enamel caries using polarized light microscopy (PLM) is currently performed in a large number of studies, but measurements are based mainly on a mislead qualitative interpretation of enamel birefringence in a single immersion medium. Here, five natural enamel caries lesions are analysed by microradiography and in PLM, and the differences in their histopathological features derived from a qualitative versus a quantitative interpretation of enamel birefringence are described. Enamel birefringence in different immersion media (air, water and quinoline) is interpreted by both qualitative and quantitative approaches, the former leading to an underestimation of the depth of enamel caries mainly when the criterion of validating sound enamel as a negatively birefringent area in immersion in water is used (a current common practice in dental research). Procedures to avoid the shortcomings of a qualitative interpretation of enamel birefringence are presented and discussed.
SummaryThis in vitro study aimed to quantify water loss at histological points in ground sections of normal enamel during air drying at room temperature (25• C) and relative humidity of 50%. From each of 10 ground sections of erupted permanent human normal enamel, three histological points (n = 30) located at 100, 300 and 500 μm from enamel surface and along a transversal following prisms paths were characterized regarding the mineral, organic and water volumes. Water loss during air drying was from 0 to 48 h. Drying occurred with both falling and constant-drying rates, and drying stabilization times (T eq ) ranged from 0.5 to 11 h with a mean 0.26 (±0.12)% weight loss. In some samples (n = 5; 15 points), T eq increased as a function of the distance from the enamel surface, and drying occurred at an apparent diffusion rate of 3.47 × 10 −8 cm 2 s −1 . Our data provide evidence of air drying resulting in air replacing enamel's loosely bound water in prisms sheaths following a unidirectional water diffusion rate of 3.47 × 10 −8 cm 2 s −1 (from the original enamel surface inward), not necessarily resulting in water evaporating directly into air, with important implications for transport processes and optical and mechanical properties.
A radiodifusão brasileira tem suas raízes em uma programação educativa e as rádios universitárias, enquanto inseridas no campo educativo da radiodifusão, abarcam alguns elementos das matrizes de programação pioneiras que foram se transformando e incorporam também aspectos que são próprios do espaço universitário. O trabalho buscou nos modelos de programação das rádios universitárias federais os aspectos característicos dessas emissoras relacionando ao caráter público da comunicação. A partir desse movimento, os aspectos referentes à pluralidade do espaço universitário, à divulgação científica e à função laboratorial dessas emissoras foram observados através da análise descritiva da programação da Rádio UFMG Educativa.Palavras-chave: Rádios Universitárias Públicas. Programação de rádio. Rádio UFMG Educativa.
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