Phenyl siloxane hybrid xerogels: structure and porous texture

The aim of this research is to investigate the effect of phenyltriethoxysilane (PhTEOS) and tetraethoxysilane (TEOS) molar ratios as silicon precursors on the structure and porous texture of xerogels. We have prepared phenyl-silane hybrid xerogels from mixtures of PhTEOS and TEOS at pH 10 and 333 K, using ethanol as a solvent. Characterization techniques include 29Si NMR, FTIR, XRD, FE-SEM, HRTEM, TGA-DSC, helium density, and gas adsorption (N2 at 77 K and CO2 at 273 K). In order to assess the contribution of the quadrupolar moment of N2 and CO2 in the adsorption we obtained the adsorption–desorption isotherm of Ar at 87.3 K for the xerogel synthesized from 50% PhTEOS. The morphology of xerogels changed from aggregates of spherical particles for 20% PhTEOS to lamellae for samples obtained with PhTEOS percentages equal or larger that 60%. The incorporation of phenyl groups into the xerogel matrix caused an increase in the spacing bond between silicon atoms and led to an intramolecular reaction and the formation of lamellar domains. Increasing the PhTEOS molar ratio in the mixture of silicon precursors produced hybrid xerogels with lower specific surface area, pore volume and characteristic energy. The similarity between the isotherms of N2 at 77 K and Ar at 87.3 K indicates that the main retention mechanism is physisorption and that the variation in the surface chemistry with the incorporation of phenyl groups doesn’t inhibit the retention of N2.This work was backed by the “Ministerio de Ciencia y Tecnología” (Grant No. CTQ2009-07993) and by the “Ministerio de Economía, Industria y Competitividad” (Grant No. MAT2016-78155-C2-2-R). Paula Moriones is grateful to the “Departamento de Industria y Tecnología, Comercio y Trabajo” of the Navarre Government for the fellowships granted (Ref. Number 175/01/08 and 269/01/08, respectively)

A comparison of heart rate variability in women at the third trimester of pregnancy and during low-risk labour

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Temperatura e umidade relativa na qualidade da tangerina "Montenegrina" armazenada Temperature and relative humidity during cold storage of 'Montenegrina' tangerine

O presente trabalho foi conduzido com o objetivo de avaliar o efeito da temperatura e da umidade relativa do ar (UR) sobre a manutenção da qualidade de tangerinas durante o período de armazenamento refrigerado (AR). O delineamento experimental utilizado foi inteiramente casualizado, em esquema bifatorial, com oito repetições, contendo 15 frutos cada. Os tratamentos avaliados constituíram-se da combinação das temperaturas 2, 3 e 4&deg;C, com UR do ar de 90 e 96%. Após oito e 12 semanas de armazenamento, mais três dias de exposição a 20&deg;C, foram realizadas as seguintes análises: acidez total titulável (ATT), sólidos solúveis totais (SST), consistência dos frutos, incidência de podridões e suculência. De acordo com os resultados obtidos, os frutos armazenados a 3&deg;C + UR do ar de 90% apresentaram ATT, SST e consistência mais elevada, após oito e 12 semanas de AR. A incidência de podridão foi significativamente superior nos tratamentos com alta UR do ar (96%). Injúrias provocadas pela baixa temperatura ocorreram em alguns frutos no tratamento a 2&deg;C. Não se constatou diferença significativa na suculência entre os tratamentos em ambas as datas de avaliação. A temperatura de 3&deg;C combinada com UR de 90% apresentou os melhores resultados na conservação de tangerinas "Montenegrina", que podem ser armazenadas por um período de até oito semanas.<br>This research was conducted in order to evaluate the effect of temperature and relative humidity (RH) on the quality of tangerines during cold storage. The experimental design was entirely randomized, in a bifatorial design with eight replications of 15 fruits. The treatments were the combination of three temperatures (2, 3 and 4oC) and two RH levels (90 and 96%). Evaluations of quality were performed after 8 and 12 weeks of cold storage plus 3 days of shelf life at 20&deg;C. The analyzed parameters were: total titratable acidity (TTA), total soluble solids (TSS), fruits consistency, rot incidence and juiciness. According to the results, fruits stored at 3oC + 90% of RH presented higher TTA, TSS, fruits consistency and lower rot incidence after 8 and 12 weeks of cold storage. The rot incidence increased with high RH (96%). Some pitting caused by low temperature was found at 2oC. There was no difference between treatments for juiciness in both evaluations. The temperature of 3&deg;C with 90% of RH showed the best results on quality maintenance of 'Montenegrina' tangerines, which can be stored during 8 weeks