Low-temperature formation of alpha-alumina from various polyhydroxoaluminum-hydroxy acid composite gels

Low-temperature alpha-alumina formation was attempted using various polyhydroxoaluminum (PHA)-hydroxy acid composite gels, which were prepared from PHA solutions containing different amounts of hydroxy acids, such as lactic acid, glycolic acid, malic acid, citric acid or mandelic acid. The composite gels began to transform into alpha-alumina when heated at lower temperatures of around 500 degrees C and the alpha-alumina fraction of the heat-treated products increased with increasing temperature. The alpha-alumina fraction was also dependent on both the type and amount of hydroxy acid additive. Among the composite gels studied, significant low-temperature alpha-alumina formation was observed for the PHA-mandelic acid, PHA-citric acid and PHA-lactic acid series. Low-temperature alpha-alumina formation was further promoted by employing a two-step heat-treatment method. The interaction between the functional groups of PHA and hydroxy acid and the seeding effect appear to play important roles in the course of the gelation and calcination processes for low-temperature alpha-alumina formation.ArticleCERAMICS INTERNATIONAL. 37(1):201-206 (2011)journal articl

Low-temperature formation of α-alumina from various polyhydroxoaluminum–hydroxy acid composite gels

Low-temperature alpha-alumina formation was attempted using various polyhydroxoaluminum (PHA)-hydroxy acid composite gels, which were prepared from PHA solutions containing different amounts of hydroxy acids, such as lactic acid, glycolic acid, malic acid, citric acid or mandelic acid. The composite gels began to transform into alpha-alumina when heated at lower temperatures of around 500 degrees C and the alpha-alumina fraction of the heat-treated products increased with increasing temperature. The alpha-alumina fraction was also dependent on both the type and amount of hydroxy acid additive. Among the composite gels studied, significant low-temperature alpha-alumina formation was observed for the PHA-mandelic acid, PHA-citric acid and PHA-lactic acid series. Low-temperature alpha-alumina formation was further promoted by employing a two-step heat-treatment method. The interaction between the functional groups of PHA and hydroxy acid and the seeding effect appear to play important roles in the course of the gelation and calcination processes for low-temperature alpha-alumina formation.ArticleCERAMICS INTERNATIONAL. 37(1):201-206 (2011)journal articl

Robo4 stabilizes the vascular network by inhibiting pathologic angiogenesis and endothelial hyperpermeability

The angiogenic sprout has been compared to the growing axon, and indeed, many proteins direct pathfinding by both structures1. The Roundabout (Robo) proteins are guidance receptors with well-established functions in the nervous system2,3; however, their role in the mammalian vasculature remains ill defined4–8. Here we show that an endothelial-specific Robo, Robo4, maintains vascular integrity. Activation of Robo4 by Slit2 inhibits vascular endothelial growth factor (VEGF)-165–induced migration, tube formation and permeability in vitro and VEGF-165–stimulated vascular leak in vivo by blocking Src family kinase activation. In mouse models of retinal and choroidal vascular disease, Slit2 inhibited angiogenesis and vascular leak, whereas deletion of Robo4 enhanced these pathologic processes. Our results define a previously unknown function for Robo receptors in stabilizing the vasculature and suggest that activating Robo4 may have broad therapeutic application in diseases characterized by excessive angiogenesis and/or vascular leak