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This thesis reports a new method for stability analysis and maximum time delay estimation in networked control systems with applications to distributed energy systems. The proposed new method is based on using finite difference approximation for the delay term and then the Lyapunov system stability theorem is applied to derive the time delay boundary allowed to the system. The proposed method has been applied to networked control systems with state feedback controllers, with dynamic controllers, and to multi-units interconnected networked control systems. The proposed method is then extended to a class of networked control system with bounded nonlinearity and uncertainties. It is found that increasing the nonlinearity in the system will result in decreasing the maximum allowable time delay. Compared with most of the methods reported in the published literature, the new method is simple to use while the results are comparable. When the time delay is modelled using Markov Chain the stability of the networked control system is formulated as finding the solutions for Bilinear Matrix Inequalities. An improved V-K iteration algorithm is used to solve the Bilinear Matrix Inequalities in order to derive a controller to stabilize the systems.

The objective of this study was to measure the immune response of female possums to ovalbumin coadministered either with cholera toxin orally and intraileally or with Incomplete Freund's Adjuvant into the Peyer's patches. This study was also carried out to determine whether the reproductive tract of the female possum is a part of the common mucosal immune system; an important factor if an oral contraceptive vaccine was to be developed. Inducing specific antibodies in the mucosa and secretions of the reproductive tract could interfere with the process of fertilization or implantation according to the type of the protein antigen inserted in the vaccine. Cholera toxin is an effective mucosal antigen and acts as an adjuvant when given orally with various antigens. However, no previous studies have determined its efficacy as an oral adjuvant when given with ovalbumin in possums. In the first experiment fifteen mature female possums were immunised orally with 3mg ovalbumin plus either 0 µg (n=5), 250 µg (n=3), 500µg (n=3), 750µg (n=2) or 1000µg (n=2) of CT adjuvant. Animals were boostered with a second dose two weeks later. In a second experiment 4 possums received 3 mg ovalbumin injected with 250µg cholera toxin directly into the lumen of the small intestine (intra-ileum), followed by a second dose given orally two weeks later. In a third experiment 4 possums were immunised with ovalbumin and IFA injected into Peyer's patches, followed by a second dose injected intra-peritoneally two weeks later. The levels of cholera toxin and ovalbumin IgG antibodies secreted in serum and ileal and reproductive tract secretions were determined by ELISA. Nine of ten possums that received different doses of oral cholera toxin produced antibodies to cholera toxin in serum. However, only one animal produced ovalbumin antibodies in serum. Mean cholera toxin antibody titre was significantly affected by CT dose and time (p0.05). Cholera toxin and ovalbumin antibodies were significantly increased in vaginal secretions at week 7 as compared to pre-immunisation levels. Also, cholera toxin and ovalbumin antibody levels in vaginal secretions were significantly higher than ileal and other reproductive tract secretions. The direct immunisation of cholera toxin and ovalbumin into ileal lumen, significantly increased cholera toxin antibody levels in serum and reproductive tract secretions but it did not reliably increase ovalbumin antibodies in serum or mucosal secretions which suggests that cholera toxin was not an effective adjuvant to potentiate the serum immune response to ovalbumin in this experiment. Ovalbumin binding in serum, 6 weeks after immunisation via Peyer's patches was higher than binding detected following oral or intra-ileal immunisation. In addition, ovalbumin binding of oviduct and ileal secretions in animals immunised via Peyer's patches was higher than the binding in animals immunised directly into the ileum. The relative importance of IgG and IgA in the possum reproductive tract is yet to be established. In general, production of specific antibodies to ovalbumin and cholera toxin in the reproductive tract secretion and serum following immunisation into the gut indicates that the possum possesses a common mucosal immune system.

The aim of this study was to compare the in vitro lymphocyte proliferation and antibody responses to ovalbumin (OVA) and keyhole limpet haemocyanin (KLH) after being given intragastrically or subcutaneously to female possums. Fifty four mature female possums were assigned to nine treatment groups (6 possums /group). For intragastric treatments (6 groups), possums received either 2 mg KLH, 2 mg KLH + 100 µg cholera toxin (CT), 2 mg OVA, 2 mg OVA + 100 µg CT, 100 µg CT or phosphate buffer saline (PBS). For subcutaneous administration (3 groups), possums received either 2 mg KLH incorporated in Freund's adjuvant (FA), 2 mg OVA with FA or FA alone, where complete Freund's adjuvant (CFA) was used at week 0, and incomplete Freund's adjuvant (IFA) was used at weeks 2 and 4. Treatments were administered and blood samples collected at 2 weekly intervals and all animals were euthanised at week 6 of the trial to allow for collection of samples for the lymphocyte blastogenic test (LBT) and ELISA. Intragastric administration of KLH or OVA did not enhance antigen-specific lymphocyte blastogenic activity from blood, mesenteric or axillary lymph nodes. The addition of CT as a mucosal adjuvant enhanced lymphocyte proliferative responses to KLH (and to a lesser extent OVA) from mesenteric and axillary lymph nodes (p