旭硝子財団助成研究成果報告2018

66/82

80Patcha Chatraphorn81Amornchai Arpornwichanop82Kuakarun KrusongSelf-assembled Island Formation in Heteroepitaxial Thin Films on Patterned Substrates: A Fast Kinetic Monte Carlo Study(Project 2016)Design methodology and analysis of integrated fuel cell systems for clean power production(Project 2016)Insight into large-ring cyclodextrin production mechanism of amylomaltase from Corynebacterium glutamicum(Project 2016)62旭硝子財団　助成研究成果報告（2018）We study heteroepitaxial thin films grown on patterned substrates using a two-dimensional ball and spring model. Island size and its uniformity as a function of patterned substrate parameters and growth conditions are investigated in an early stage of growth using fast kinetic Monte Carlo simulations. In contrast to the flat substrate, patterned substrates provide preferred sites for island formation at the beginning of growth and promote island size uniformity. A patterned substrate parameter enables us to modify island size in a considerable range. Island size uniformity is further enhanced by stress suppression at the island edges when lattice mismatch is increased. Island size, however, decreases as the growth temperature is increased due to the constraint of periodicity of patterned substrates imposed. An upper bound of a patterned substrate parameter before island size becomes less uniform seems to closely connect to island period and island edge spacing of the flat substrate.A solid oxide fuel cell (SOFC) based power plant incorporated with an oxyfuel combustion process to reduce CO2 emissions is analyzed in this work. The effect of key parameters, such as the steam-to-carbon ratio and fuel utilization factor, on the current density, voltage, heat production and requirements of each unit is investigated. In addition, the overall performance of SOFC-oxyfuel integrated systems with anode recycling and steam recycling are studied and compared. The SOFC system with anode recycling provides better electrical efficiency than that with steam recycling due to the high utilization of fuel in the SOFC and the capability to integrate the fuel turbine. Regarding the SOFC with the steam recycling case, the fuel turbine cannot be implemented due to insufficient heat for preheating the inlet streams, which is primarily used to vaporize the recycling stream. SOFC-oxyfuel combustion with the anode and steam recycling cases at the optimal conditions providing the highest electrical efficiency is also analyzed.Amylomaltase is a well-known glucan transferase enzyme that can produce large-ring cyclodextrins (LR-CDs) via cyclization reaction. Based on crystal structure of amylomaltase from Corynebacterium glutamicum (CgAM), mutations P228Y, A413F and G417F were generated by site-directed mutagenesis. G417F exhibited similar specific activities of starch transglycosylation, starch degradation and disproportionation to WT CgAM. However, P228Y showed similar specific activities of starch transglycosylation and starch degradation but had much lower disproportionation activity than the wild-type enzyme, suggesting that P228 may play an important role in disproportionation. A413F possessed much lower specific activities of all reactions than the WT and other mutant enzymes. For LR-CD synthesis at 6 h, the principal LR-CD of P228Y, A413F and G417F were larger than that of the WT enzyme. Molecular dynamic simulation revealed interactions of CgAM and LR-CD, suggesting amino acid residues involved in LR-CDs production.