A new carrier-free cross-linked aggregates of cellulase (CLEAs-C) via precipitation with ammonia sulfate and cross-linking with glutaraldehyde was prepared. Efficient enzyme activity was obtained when cellulase and glutaraldehyde concentration was 50mg/mL and 3% (v/v) respectively. The cross-linking time and temperature were also important parameters for immobilization. Optimal temperature and pH of the CLEA–C were evaluated. The CLEAs-C displayed good stabilities, after stored at 4○C for 28 days storage, the CLEAs retained more than 80% initial activities.

The cellulase was immobilized onto magnetic chitosan microspheres carrier as cross-linked enzymes aggregates (CLEAs). It was precipitated with 95% saturation ammonia sulfate and cross-linked with 3% (v/v) glutaraldehyde. Efficient enzyme activity about 50.6% was obtained when cellulase concentration was 1.0mg/mL after cross-linking for 7 h at 30○C. The CLEAs was advantageous on stabilities and magnetic responsiveness for separation.

Cluster has become a new generation of distributed system. Among the server cluster technologies, request distribution technology is used to distribute requests among server nodes, providing support to large-scale concurrent access to server cluster. In order to overcome the weakness of existing request distribution strategies for server cluster in average response time and computation cost, this paper proposes a request distribution strategy based on static time interval. Its basic idea is that it divides the update interval into several subintervals and introduces randomness into the selection of server node for the requests arrived in a subinterval. We give an implementation of the strategy and use MATLAB as the simulation platform to carry out simulation experiments in testing the performance of the strategy. Our theoretical analysis and experimental results show that, the strategy we propose achieves shorter average waiting time, more convenient implementation and lower computation cost than other several existing request distribution strategies.

It is much easier to store data with cloud storage. However, the development of cloud storage was restricted to many security factors. This paper introduces the basic concept of cloud storage, proposes a security framework in architecture of cloud storage, analyzes existing security problems in architecture of cloud storage, and reviews the current research progress. Cloud storage will be inestimable if we resolve security problems of cloud storage.