Hidetoshi Arima

Isolation of Antimicrobial Compounds from Guava (Psidium guajava L.) and their Structural Elucidation

Four antibacterial compounds were isolated from leaves of guava (Psidium guajava L.), and the structures of these compounds were established on the basis of chemical and spectroscopic evidence. Two new flavonoid glycosides, morin-3-O-α-L-lyxopyranoside and morin-3-O-α-L-arabopyranoside, and two known flavonoids, guaijavarin and quercetin, were identified. The minimum inhibition concentration of morin-3-O-α-L-lyxopyranoside and morin-3-O-α-L-arabopyranoside was 200 μg/ml for each against Salmonella enteritidis, and 250 μg/ml and 300 μg/ml against Bacillus cereus, respectively.

Rutin-enhanced antibacterial activities of flavonoids against Bacillus cereus and Salmonella enteritidis.

The antibacterial activities of flavonoids were found by the paper disk method to be enhanced by combining or mixing them. The combinations of quercetin and quercitrin, quercetin and morin, and quercetin and rutin were much more active than either flavonoid alone. Although rutin did not show activity in itself, the antibacterial activities of quercetin and morin were enhanced in the presence of rutin. The antibacterial activities of flavonoids, in combination with morin and rutin, were evaluated, based on the minimum inhibition concentration (MIC) in a liquid culture, by using Salmonella enteritidis and Bacillus cereus as the test bacteria. The activities of galangin, kaempherol, myricetin and fisetin were each enhanced in the presence of rutin when S. enteritidis was used as the test bacterium. The MIC value for kaempherol was markedly decreased by the addition of rutin. Morin inhibited DNA synthesis, and this effect was promoted by rutin at a concentration of 25 μg/ml.

Basic Plan of LNG Carriers based on System Dynamics

The replacement of steam turbine to diesel engine after the oil crisis, has not taken place with regard to LNG carriers and still continuing using steam turbine. However, the alternative ship has appeared because of the shortage of an engineer of steam turbine, progress of technology or due to the environmental problem in recent years. So we tried to propose a decision-making system for building and operating LNG carriers by system dynamics. It turned out in a way that, compared to the Steam turbine system (S/T), Oil burning diesel engine with reliquefaction plant system (DRL) was cost advantageous assuming that the Boil-off gas price is equal to the LNG one.

Optimizing Ship Machinery Maintenance Scheduling Through Risk Analysis and Life Cycle Cost Analysis

Ship maintenance scheduling management integrated with risk evaluation and Life Cycle Cost (LCC) assessment approach is developed in this research. It improves upon existing practices in arranging an optimal maintenance schedule by modeling operational and economical risks. This paper researches maintenance scheduling algorithm with explicitly consider risks associated with some operation problems such as operating schedule, routes, ship position, resources availability, and achievement of reliability-availability-maintainability (RAM) of system. Modeling of components RAM with their failures consequences results risk evaluation. Time value of maintenance cost, replacement cost, earning rate, and penalty cost are also simulated. When the system reaches the lowest level of lower limit reliability, one or more components should be maintained or replaced. Since maintenance task may interrupt the operation, to minimize time-to-maintain all possible events of maintaining other components at the same time will be evaluated together with resources availability. By researching those possibilities, constraining the risk, and based on LCC calculation result, an optimal maintenance scheduling can be then well established.Copyright