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SYNOPSISThe cure kinetics of neat and carbon fiber-reinforced commercial epoxy systems, based on Tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) and 4,4'-diaminodiphenylsulfone (DDS) were studied by means of differential scanning calorimetry (DSC). Analysis of DSC data indicated that the presence of the carbon fibers has a very small effect on the kinetics of cure. A kinetic model, arising from an autocatalyzed reaction mechanism, was applied to isothermal DSC data. The effect of diffusion control was incorporated into the reaction kinetics by modifying the overall rate constant, which is assumed to be a combination of the chemical rate constant and the diffusion rate constant. The chemical rate constant has the usual Arrhenius form, while the diffusion rate constant is described by a type of the Williams-Landel-Ferry (WLF) equation. The kinetic model, with parameters determined from isothermal DSC data, was successfully applied to dynamic DSC data over a broad temperature range that covers usual processing conditions.

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This study investigated how the design of surface topography may stimulate stem cell differentiation towards a neural lineage. To this end, hydrogenated amorphous carbon (a-C:H) groove topographies with width/spacing ridges ranging from 80/40μm, 40/30μm and 30/20μm and depth of 24 nm were used as a single mechanotransducer stimulus to generate neural cells from human bone marrow mesenchymal stem cells (hBM-MSCs) in vitro. As comparative experiments, soluble brain-derived neurotrophic factor (BDNF) was used as additional biochemical inducer agent. Despite simultaneous presence of a-C:H micropatterned nanoridges and soluble BDNF resulted in the highest percentage of neuronal-like differentiated cells our findings demonstrate that the surface topography with micropatterned nanoridge width/spacing of 40/30μm (single stimulus) induced hBM-MSCs to acquire neuronal characteristics in the absence of differentiating agents. On the other hand, the alternative a-C:H ridge dimensions tested failed to induce stem cell differentiation towards neuronal properties, thereby suggesting the occurrence of a mechanotransducer effect exerted by optimal nano/microstructure dimensions on the hBM-MSCs responses.