Characteristics and antifungal activity of chitinases in Semillon grapes were investigated. Chitinases were isolated from the juice of Semillon grapes by chitin affinity chromatography. Native and SDS-PAGE analyses of the fraction showing chitin affinity (active fraction) demonstrated only the presence of protein bands of chitinases. Three types of class IV chitinases (chi-1a, chi-1b and chi-2) were purified from the active fraction. These chitinases actively hydrolyzed chitin under acidic conditions (pH 4.0-4.5). The isoelectric points and the molecular weights of chi-1a, chi-1b and chi-2 were 4.73, 4.60, and 7.87, and 32.1 kDa, 31.6 kDa, and 29.0 kDa, respectively. The active fraction was found to inhibit Botrytis cinerea mycelial growth and the inhibitory effect was due to the activity of chitinases. The active fraction inhibited twenty strains of B. cinerea collected from the experimental vineyard. The effect of chitinases was enhanced in media containing more than 20% sugar. When the active fraction was tested on Glomerella cingulata, the growth inhibitory effect observed was markedly less than that seen on B. cinerea.
In the past studies of checkpointing for the computer system, the event that a system failure may be generated due to the checkpointing has not been considered. In practice, it is highly probable that this kind of failure arises in the checkpointing.
From such a viewpoint, this paper considers the event where a failure due to the checkpointing is produced at the time of checkpointing and proposes a procedure to derive the optimal checkpointing sequence as the optimal checkpointing strategy. As the evaluation function, the expected cost per cycle and the expected cost per unit time in the steady state are used. the optimal checkpointing strategy is considered to minimize the expected cost.
Finally, numerical investigation is made assuming the exponential and the Weibull distributions as the failure time distribution.
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