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This paper aims to develop an approach for performance calculation of an SR motor, which is suitable for use within mathematical design optimization. For this reason the requirement is to develop procedures, which are both accurate and fast. The procedures adopted here rely on flux-linkage-current-position curves of the motor. A series of tests are carried out on a test motor. The results are compared with estimations from the developed algorithms. It is shown that the current waveform, torque-speed curve, total loss and efficiency can be accurately calculated using the proposed algorithms, provided that the motor data is accurate. The computation time required is about 0.7s and in this respect much depends on the procedures used for accessing and processing the motor data.

The accuracy of flux linkage-current-position curves has vital importance for designing SR motors. Analytical prediction of these curves is very difficult and as shown in this paper 2D approach leads to erroneous prediction of the flux linkage curves and hence significant errors in performance prediction of SR motors. This paper makes an important contribution to the design process by developing an approach for the analytical calculation of flux linkage-current-position curves including the end effect. As shown here, using flux-linkage curves predicted with this method leads to accurate prediction of motor performance

The inactivation kinetics of Escherichia coli penicillin G acylase (PGA), and cross-linked stabilization of the enzyme by dextran-dialdehyde derivatives of molecular weights of 11500, 37000 and 71000, were similar from pH 2 to pH 10. Inactivation of the native and modified PGA obeyed first order kinetics. The lowest inactivation rate constants for native and dextran-11500-dialdehyde modified PGA were 9.0 x 10(-4) and 1.5 x 10(-4) min(-1) respectively at pH 7.0. The highest pH stabilization (nearly ten-fold) was obtained at pH 7.0.

In order to establish a simple and economic purification scheme for penicillin G acylase (PGA) (EC 3.5.1.11) from a mutant strain of Escherichia coli 11105 with high yield, various protein extraction methods were employed including osmotic and chloroform shocks, and osmotic shock after lysozyme and cetyltrimethylammonium bromide (CTAB) pretreatments of E. coli cells. A purification factor of 7.82 and recovery of 53 % were obtained with osmotic shock when sucrose and EDTA were used at 20 % and 1.22 % concentrations, respectively. Various treatment times of osmotic shock and lysozyme and CTAB pretreatments did not affect the yield of released PGA. The yield of released PGA was found to be lower using chloroform shock than when osmotic shock was employed. Two steps purification procedure developed in this research was satisfactory to obtain the high specific activity required for the production of immobilized PGA.

We investigated the effects of three different bisimidoesters as homobifunctional cross-linking agents on the thermostabilization of penicillin G acylase (PGA) obtained from a mutant of Escherichia coli ATCC 11105. Cross-linkers were dimethyladipimidate (DMA), dimethylsuberimidate (DMS), and dimethyl-3,3'-dithiobispropionimidate (DTBP). The thermal inactivation mechanisms of the native and cross-linked PGA were both considered to obey first-order inactivation kinetics during prolonged heat treatment, forming fully active, susceptible transient stares. The efficacy of the cross-linkers on the thermostabilization of PGA was estimated to be DMA > DMS > DTBP. Optimal concentrations of DMA, DMS, and DTBP for cross-linking of PGA were found to be 0.5, 0.4, and 0.3% (w/v), respectively. The greatest enhancement of the thermostabilities was observed during DMA cross-linking, as a nearly 15-fold increase at temperatures above 50 degrees C. Cross-linking by DMA did not cause much change in the parameters V-m, K-m, and the optimal temperature values of PGA, but the activation energy of the enzyme was slightly decreased and k(cat) value slightly increased after cross-linking.