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The increasing use of ambient cured resin systems for the fabrication of composites used in structural components such as in civil infrastructure creates a need for monitoring cure progression over time as well as for tracking changes due to environmental exposure during the extended period of time needed to attain full cure. Further, there is a need for the development of methods to monitor the health of structures in the field for applications such as column retrofit, external strengthening of girders and slabs, and even bridge decks. This paper investigates the application of dielectrometry to the characterization of E-glass epoxy composites exposed to deionized water. Results are correlated with DSC and moisture absorption. It is shown that a direct correlation between moisture absorption and permittivity can be obtained.

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SummaryThe conserved MAP3K Dual leucine zipper kinases can activate JNK via MKK4 or MKK7. Vertebrate DLK and LZK share similar biochemical activities and undergo auto-activation upon increased expression. Depending on cell-type and nature of insults DLK and LZK can induce pro-regenerative, pro-apoptotic or pro-degenerative responses, although the mechanistic basis of their action is not well understood. Here, we investigated these two MAP3Ks in cerebellar Purkinje cells using loss- and gain-of function mouse models. While loss of each or both kinases does not cause discernible defects in Purkinje cells, activating DLK causes rapid death and activating LZK leads to slow degeneration. Each kinase induces JNK activation and caspase-mediated apoptosis independent of each other. Significantly, deleting CELF2, which regulates alternative splicing of Mkk7, strongly attenuates Purkinje cell degeneration induced by activation of LZK, but not DLK. Thus, controlling the activity levels of DLK and LZK is critical for neuronal survival and health.