Introduction Immobilisation of biomaterials has been widely used in many fields, such as industry, biochemistry and immunology (Cheetham, 1985; Hermanson et al., 1992). This technology employs a large number of natural and artificial materials as matrices (Kennedy and Cabral, 1987). In our laboratory, we have proposed immobilisation procedures using dacron (Carneiro Leão et al., 1994), polyaniline (Nadruz et al., 1996) and glyptal (Jordão et al., 1996). Here, polyvinyl alcoholglutaraldehyde (PVA-glutaraldehyde) network is described for antigen and enzyme immobilisation. Previously, this material was used for the diagnosis of plague as a solid-phase in ELISA (Araujo et al., 1996) and also in laser induced fluorescence (Carvalho et al., 1996). Materials and methods Synthesis of PVA-glutaraldehyde beads Polyvinyl alcohol (2.0 g; Reagen ®) was dissolved in deionised water (20 mL) containing sodium dodecylsulfate (10 mg; Sigma) under heating and stirring. Glutaraldehyde (25%, w/v; 4.12 mL; Sigma) and H 2 SO 4 (0.3 M; 1 mL) were successively added to the dissolved PVA and then the solution was slowly poured into a beaker containing mineral oil/water mixture (45:45; v/v) with stirring. After about 15 min, PVA-glutaraldehyde beads were synthesised. In order to remove oil and sodium dodecylsulfate the beads were exhaustively washed with ethanol 95% v/v (500 mL) and deionised water (1 L). Synthesis of PVA-glutaraldehyde discs According to Araujo et al. (1996). Enzyme immobilisation ␣-Amylase (20 mL of 65 U/mg protein; Termamyl, Novo Nordisk, Paraná, Brazil) prepared in 50 mM citrate-phosphate buffer, pH 4.5, was incubated with PVA-glutaraldehyde beads (1 g) under stirring overnight at 4°C. After immobilisation, the water insoluble enzymatic derivative was washed with 1 M NaCl (100 mL) in buffer. Amyloglucosidase (20 mL of 6.5 U/mg protein; AMG, Novo Nordisk, Paraná, Brazil), prepared in 50 mM citrate-phosphate buffer, pH 6.5, was incubated with PVA-glutaraldehyde as described above. Xanthine oxidase (10 mL; Nutritional Biochemichals Corporation) prepared in 0.1 M phosphate buffer, pH 8.0, was incubated with PVAglutaraldehyde beads (0.6 g) under mild stirring overnight at 4°C. Then, the immobilised enzymatic derivative was exhaustively washed with deionised water and 1 M NaCl, successively. Afterwards, overnight incubation with 1 M glycine was carried out to inactivate free carbonyl groups and washings were carried out again.

Abstract:There are two general approaches for scheduling tasks in real-time systems: runtime and pre-runtime scheduling. However, there are several situations where the runtime approach does not find a feasible schedule even if such a schedule exists. The proposed approach uses state space exploration for finding a preruntime scheduling. The main problem with such methods is the space size, which can grow exponentially. This paper shows how to minimize this problem, and presents a depth-first search method on a timed labeled transition system derived from the time Petri net model.

Software synthesis is defined as the task of translating a specification into a software program, in a general purpose language, in such a way that this software can be compiled by conventional compilers. In general, complex real-time systems rely on specialized operating system kernels. However, the operating system usage may introduce significant overheads as in execution time as in memory requirement. In order to eliminate such overheads, automatic software synthesis methods should be implemented. Such methods comprise real-time operating system services (scheduling, resource management,communication, synchronization), and code generation. Formal methods are a very promising alternative to deal with the complexity of embedded systems, and for improving the degree of confidence in critical systems. We present a formal approach for automatic embedded hard real-time software synthesis based on time Petri nets. In order to illustrate the practical usability of the proposed method, it is shown how to synthesize a C code implementation using a heated-humidifier case study.

Embedded hard real-time systems have stringent timing constraints that must be satisfied for the correct functioning of the system. Hence all tasks must be finished before their deadlines. In addition, there are systems where energy is another constraint that must also be satisfied. In this paper, a pre-runtime scheduling algorithm is presented in order to find schedules satisfying both timing and energy constraints. The proposed approach uses state space exploration for finding pre-runtime schedules. However, the main problem with such methods is the space size, which can exponentially grow. This paper tackles this problem through a depth-first search method for generating a partial timed labeled transition system derived from the time Petri net model.

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