A B S T R A C TThis paper presents the results of experimental study with a new coconut fiber-cement composite (CFC). To obtain a material with improved performance in order to decrease the amount of calcium hydroxide present on the fiber surface, four forms of coconut fiber treatment were tested. Some combinations of natural latex, water and pozzolanic materials (silica fume or metakaolin) were evaluated by degradation test and accelerated aging through cycles of wetting and drying CFC samples. To determine the mechanical properties obtained from each treatment, flexural tests on CFC composites were performed. After the flexural tests, the fibers were removed from the specimens and analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The results indicate that the treatment carried out with the natural latex polymer film combined with a pozzolan layer improved the performance and durability of the CFC.
ABSTRACT:The interaction of two flavonoid species (resorcinolic and fluoroglucinolic) with the 20 essential amino acids was studied by the multiple minima hypersurface (MMH) procedures, through the AM1 and PM3 semiempirical methods. Remarkable thermodynamic data related to the properties of the molecular association of these compounds were obtained, which will be of great utility for future investigations concerning the interaction of flavonoids with proteins. These results are compared with experimental and classical force field results reported in the available literature, and new evidences and criteria are shown. The hydrophilic amino acids demonstrated high affinity in the interaction with flavonoid molecules; the complexes with lysine are especially extremely stable. An affinity order for the interaction of both flavonoid species with the essential amino acids is suggested. Our theoretical results are compared with experimental evidence on flavonoid interactions with proteins of biomedical interest.
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