ABSTRACT
Mean-field models have the ability to predict the evolution of grain size distribution that occurs through thermomechanical solicitations. This article focuses on a comparison of mean-field models under grain-growth conditions. Different microstructure representations are considered and discussed, especially regarding the consideration of topology in the neighborhood construction. Experimental data obtained with a heat treatment campaign on 316L austenitic stainless steel are used for the identification of material parameters and as a reference for model comparisons. Mean-field models are also applied to both mono- and bimodal initial grain size distributions to investigate the potential benefits of introducing neighborhood topology in microstructure prediction models. This article demonstrates that improvements in the predictions can be obtained in monomodal cases for topological models. In the bimodal test, no comparison with experimental data was performed as no data were available. But relative comparisons between models indicated few differences in the predictions. Although of interest, the consideration of neighborhood topology in grain-growth mean-field models generally results in only small improvements compared to classical mean-field models, especially in terms of implementation complexity.
ABSTRACT
BACKGROUND: The in vitro experiments described in this study were aimed at exploring a synergistic effect between 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) and hypericin. In a previous study, enhanced phototoxicity was observed in a patient during a clinical study on 5-ALA-based photodynamic tumor localization of breast cancer. This patient ingested a hypericin containing plant extract in parallel to orally applied 5-ALA. METHODS: Human endometrial cancer cells (HEC-1A) were treated with 0.5mM of 5-ALA and 60 nM of hypericin, either separately or combined. Colony formation was assessed after illumination of the cells with both red (635 nm) and white light (400-800 nm) at a dose of 2.5 J/cm(2). Porphyrin metabolites were quantified by HPLC in cells treated with photosensitizers without subsequent illumination. RESULTS: After white light illumination, cells treated with a combination of 5-ALA and hypericin had a significant reduction in colony formation compared with cells treated with 5-ALA only. No significantly enhanced toxicity was found with red light and the 5-ALA plus hypericin combination. In addition, cells treated with both 5-ALA and hypericin tended to produce more PpIX than cells treated with 5-ALA only. CONCLUSIONS: This study demonstrated that treatment of endometrial cancer cells with both 5-ALA and hypericin followed by illumination with white light induced a significantly higher phototoxicity as revealed by colony formation. This setting which generated an in vitro effect similar to the patient's situation, might be applied in the future as an affordable and effective photodynamic therapy (PDT) modality.
