RESUMO
We report the first experimental demonstration of a humidity insensitive polymer optical fiber Bragg grating (FBG), as well as the first FBG recorded in a TOPAS polymer optical fiber in the important low loss 850 nm spectral region. For the demonstration we have fabricated FBGs with resonance wavelength around 850 nm and 1550 nm in single-mode microstructured polymer optical fibers made of TOPAS and the conventional poly (methyl methacrylate) (PMMA). Characterization of the FBGs shows that the TOPAS FBG is more than 50 times less sensitive to humidity than the conventional PMMA FBG in both wavelength regimes. This makes the TOPAS FBG very appealing for sensing applications as it appears to solve the humidity sensitivity problem suffered by the PMMA FBG.
Assuntos
Tecnologia de Fibra Óptica/instrumentação , Umidade , Fibras Ópticas , Polímeros/química , Refratometria/instrumentação , Transdutores , Desenho de EquipamentoRESUMO
We have systematically measured the differential stress-optic coefficient, DeltaC, in a number of poly(methyl methacrylate) (PMMA) fibers drawn with different stress, ranging from 2 up to 27 MPa. DeltaC was determined in transverse illumination by measuring the dependence of birefringence on additional axial stress applied to the fiber. Our results show that DeltaC in PMMA fibers has a negative sign and ranges from -4.5 to -4.5x10(-12) Pa(-1), depending on the drawing stress. Increase of the drawing stress results in greater initial fiber birefringence and lower DeltaC.
RESUMO
In search of nonconventional sources of protein to combat widespread malnutrition, the possibility of developing a protein concentrate as an alternative dietary supplement from abundantly available yet poorly valorized leaves of Albizia lebbeck (siris) was examined. A process for recovery of leaf protein concentrate (LPC) from these leaves was optimized and applied for isolation of LPCs from lower, middle, and upper canopies of the tree. The optimized conditions (leaves to water 1:9, coagulation at pH 4.0 using 1 N citric acid at 90°C for 11 minutes) afforded LPCs containing protein 37.15%, 37.57%, and 37.76% in 5.99%, 5.97%, and 6.07% yield, respectively. The proximate nutritional composition, pigments, minerals, in vitro digestibility, and antinutritional factors of these LPCs were determined. Analysis of variance of these data revealed no significant difference with respect to canopy. Use of Albizia lebbeck leaves for development of LPC as a food/feed supplement was revealed.
Assuntos
Albizzia , Proteínas Alimentares/administração & dosagem , Folhas de Planta/química , Proteínas de Plantas/administração & dosagem , Carboidratos da Dieta/análise , Gorduras na Dieta/análise , Suplementos Nutricionais , Digestão , Manipulação de Alimentos/métodos , Humanos , Concentração de Íons de Hidrogênio , Minerais/análise , Valor Nutritivo , Pigmentos Biológicos/análise , Proteínas de Plantas/isolamento & purificação , Recomendações Nutricionais , TemperaturaRESUMO
The purpose of this study was to explore the influence of organic matter in soils while removing heavy metals by sodium metabisulfite and EDTA solutions. The results obtained show that both sodium metabisulfite and sodium EDTA solutions have good removal efficiencies of zinc and lead. However, sodium metabisulfite was effective in extracting lead from a low organic content silty clay soil, and 0.05 M EDTA solution was a better extraction agent for soils with high organic matter content. These preliminary experimental results indicate that it might be worthwhile to consider the use of a chelating agent like sodium EDTA in the treatment of heavy-metal contaminated soils.