published_or_final_version / Chinese / Master / Master of Philosophy

In this dissertation, guided surface acoustic wave sensors were investigated theoretically and experimentally in detail for immunosensing applications. Shear horizontal polarized guided surface acoustic wave propagation for mass loading sensing applications was modeled using analytical modeling and characterized by perturbation analysis. The model verification was performed experimentally and a surface acoustic wave immunosensor case study was presented. The results of the immunosensing were also investigated using the perturbation analysis. Guided surface acoustic wave propagation problem was investigated in detail for gravimetric (or mass loading) guided wave sensors, more specifically for immunosensors. The analytical model was developed for multilayer systems taking viscoelasticity into account. The closed form algebraic solutions were obtained by applying appropriate boundary conditions. A numerical approach was used to solve dispersion equation. Detailed parametric investigation of dispersion curves was conducted using typical substrate materials and guiding layers. Substrate types of ST-cut quartz, 41° YX lithium Niobate and 36° YX lithium tantalate with guiding layers of silicon dioxide, metals (chromium and gold), and polymers (Parylene-C and SU-8) were investigated. The effects of frequency and degree of viscoelasticity were also studied. The results showed that frequency only has effect on thickness with same shaped dispersion curves. Dispersion curves were found to be unaffected by the degree of viscoelasticity. It was also observed that when there was a large shear velocity difference between substrate and guiding layer, a transition region with a gradual decrease in phase velocity was obtained. However, when shear velocities were close, a smooth transition was observed. Furthermore, it was observed that, large density differences between substrate and guiding layer resulted in sharp and with nearly constant slope transition. Smooth transition was observed for the cases of minimal density differences. Experimental verification of the model was done using multi-layer photoresists. It was shown that with modifications, the model was able to represent the cases studied. Perturbation equations were developed with first order approximations by relating the slope of the dispersion curves with sensitivity. The equations were used to investigate the sensitivity for material selection (substrate, guiding layer, and mass perturbing layer) and degree of viscoelasticity. The investigations showed that the sensitivity was increased by using guiding layers with lower shear velocities and densities. Among the guiding layers investigated, Parylene C showed the highest sensitivity followed by gold and chrome. The perturbation investigations were also extended to viscoelasticity and to protein layers for immunosensing applications. It was observed that, viscous behavior resulted in slightly higher sensitivity; and sensitivity to protein layers was very close to sensitivity for polymers. The optimum case is found to be ST-cut quartz with Parylene-C guiding layer for protein layer sensing. Finally, an immunosensing case study was presented for selective capture of protein B-cell lymphoma 2 (Bcl-2), which is elevated in many cancer types including ovarian cancer. The immunosensor was designed, fabricated, and experimentally characterized. An application-specific surface functionalization scheme with monoclonal antibodies, ODMS, Protein A/G and Pluronic F127 was developed and applied. Characterization was done using the oscillation frequency shift of with sensor used as the feedback element of an oscillator circuit. Detection of Bcl-2 with target sensitivity of 0.5 ng/ml from buffer solutions was presented. A linear relation between frequency shift and Bcl-2 concentration was observed. The selectivity was shown with experiments by introducing another protein, in addition to Bcl-2, to the buffer. It was seen that similar detection performance of Bcl-2 was obtained even with presence of control protein in very high concentrations. The results were also analyzed with perturbation equations.

In the Groundwork for the Metaphysics of Morals, Kant gives several formulations of the categorical imperative, one being the universal law of nature formulation. One question that can be raised is why Kant formulates the categorical imperative in terms of universal laws of nature at all. In this paper, I will argue that it is necessary for Kant to formulate the categorical imperative in terms of universal laws of nature in order to demonstrate the applicability of the moral law to our maxims and hence the possibility of the moral law as a functional practical principle.

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Elsa Joubert has been a prominent author of Afrikaans novels since the 1950's and has received several important literary prizes. This dissertation is a study of issues of identity and the experience of the female characters in the following five novels by Joubert: Ons wag op die Kaptein, Die Wahlerbrug, Bonga, Die swerfiare van Poppie Nongena and Die reise van lsobelle. It is clear from the analyses of the novels that geographical. ideological and political matters greatly influence the identity of the characters. Interpersonal relations within the family and with a loved one, also play a crucial role in the development of a personal identity. Theoretical concepts from feminism and female writing, postmodernism, New Journalism and travel literature as genre are used as points of departure for the discussion of the novels. A brief overview of Joubert's oeuvre is provided. The main focus of the study is the way in which the main characters in the selected novels (Leonora, Agnes, Isobelle, Leo, Lottie, lnacia Maria, Ana-Paula and Poppie) experience a sense of identity. It becomes clear that there is a close relation between identity and space and therefore it is necessary to analyse cultural contexts, spatial relations (the country and the continent as place) and the love of travel in the novels. The lives of all these female characters are influenced deeply by experiences of love and falling in love often brings about a radical change in their sense of identity. Most of the female characters in the selected novels many men from other cultures. Often they experience an identity crisis as a consequence of being confronted with a strange culture. They might long for the comfort of what is well-known and loved, but they also want to accept and conform to the new circumstances as is expected from them by a beloved. The emotional pain resulting from being tom between their cultural inclination and love, affect their self-esteem and sense of identity. Initially the love relationship is a way to develop a new self-contained identity and is part of a personal rebellion and a quest for freedom. Often however, they have to conform to the norms of society and of the cultural context. It is remarkable that many of these characters never experience true love and they are torn between their own cultures and the 'love' for a man who expects them to conform to a new way of living and a new identity. Therefore many of these characters experience themselves as outsiders. The women in Elsa Joubert's novels do not have easy lives. They have to struggle against odds, they have to make difficult choices, they have little power and fulfillment often evades them. Joubert, however, does not present a pessimistic view of either the prospects of women in general or of life in Africa. Die reise van lsobelle ends in a positive way as the character Leo takes control of her life and makes her own decisions. She is not a victim, but a liberated woman, a victor. She is the personification of the new, emancipated woman who will survive and find a place in Africa. / Thesis (MA (Afrikaans en Nederlands))--North-West University, Potchefstroom Campus, 2004.

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The Phaedra and Hippolytus myth is a frequently dramatized narrative of uncontrollable desire. This thesis examines two versions, Euripides' Hippolytus, first presented in 428 B.C. as part of the Athenian festival of Dionysus, and Sarah Kane's 1996 play, Phaedra's Love, first presented as part of the Gate Theatre of London's "new playwrights, ancient sources" series. In each play, Phaedra's desire is constructed according to sociohistorical conditions which are temporary in their cultural significance. Once the moment of creation has passed, so have the conditions in which each version of desire is originally understood. However, these constructions of Phaedra's desire also bear a simultaneously transhistorical quality as they complicate human notions of agency. In the West, therefore, Phaedra's desire is represented as a tragically constructed emotion. This thesis posits desire as transhistorically relevant in its ability to question modes of human subjectivity.