Assuntos
Resinas Compostas , Restauração Dentária Permanente , Materiais Biocompatíveis/química , Cor , Resinas Compostas/química , Colagem Dentária , Polimento Dentário , Restauração Dentária Permanente/métodos , Facetas Dentárias , Estética Dentária , Feminino , Seguimentos , Humanos , Propriedades de Superfície , Fatores de TempoRESUMO
Ultraviolet (UV) sunlight actinometers were developed based on the photolysis of nitrate and nitrite. Photon exposures (i.e. time-integrated irradiances) were quantified from the photochemical production of salicylic acid (SA) or p-hydroxybenzoic acid (pHBA) formed by the reaction of the hydroxyl radical with benzoic acid. The solar response bandwidth for the nitrate actinometer in quartz tubing was 322 +/- 11 nm during the Spring of 1999, while the response bandwidth of the Mylar D-filtered nitrite actinometer was 355 +/- 25 nm. Intercomparisons of the nitrate and nitrite actinometers with a Smithsonian Environmental Research Center SR-18 scanning UV-B radiometer (SERC SR-18) and an Optronics OL-754 spectroradiometer (OL-754) were performed during the summer of 1998, and the winter and spring of 1999. Photon exposures determined by the nitrate actinometer were in excellent agreement with the SERC SR-18, with a slope (95% confidence interval [CI]) of 0.98 +/- 0.01 based on SA production and 0.94 +/- 0.02 based on pHBA production. Excellent agreement was also found between the nitrite actinometer and the OL-754, with a slope (95% CI) of 1.00 +/- 0.01 using SA production and 1.00 +/- 0.02 using pHBA production. These actinometers are well suited for use in the water column and are sufficiently sensitive to determine photon exposures below the 0.1% UV lightlevel.
Assuntos
Fenda Labial/reabilitação , Fissura Palatina/reabilitação , Estética Dentária , Qualidade de Vida , Adolescente , Atitude Frente a Saúde , Fenda Labial/psicologia , Fissura Palatina/psicologia , Resinas Compostas , Restauração Dentária Permanente , Facetas Dentárias , Feminino , Retração Gengival/terapia , Humanos , Mordida Aberta/terapia , Planejamento de Assistência ao Paciente , Ácidos Polimetacrílicos , Preparo do DenteRESUMO
Photochemical production rates and steady-state concentrations of hydroxyl radicals (.OH) were measured in sunlight-irradiated seawater. Values ranged from 110 nanomolar per hour and 12 x 10(-18) molar in coastal surface water to 10 nanomolar per hour and 1.1 x 10(-18) molar in open ocean surface water. The wavelengths responsible for this production are in the ultraviolet B region (280 to 320 nanometers) of the solar spectrum. Dissolved organic matter (DOM) appears to be the main source for .OH over most of the oceans, but in upwelling areas nitrite and nitrate photolysis may also be important. DOM in the deep sea is degraded more readily by .OH (and its daughter radicals), by a factor of 6 to 15, than is DOM in open-ocean surface water. This finding may in part bear on major discrepancies among current methods for measuring dissolved organic carbon in seawater.
