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Please read the abstract in the section 00front of this document / Thesis (DPhil)--University of Pretoria, 2005. / Microbiology and Plant Pathology / Unrestricted

Please read the abstract on page 4 of this document / Dissertation (MSc (Chemistry))--University of Pretoria, 2007. / Chemistry / MSc / unrestricted

Radio Frequency IDentification (RFID) is a wireless communications technology which allows companies to secure their assets and increase the portability of information. This research was motivated by the increased commercial use of RFID technology. Existing security protocols with high levels of security have high computation requirements, and less intensive protocols can allow a tag to be tracked. The techniques proposed in this thesis result in the increase of ciphertexts available without a significant increase in processing power or storage requirements. The addition of random inputs to the generation of ciphertexts will increase the number of possible results without requiring a more advanced encryption algorithm or an increased number of stored encryption keys. Four methods of altering the plaintext/ciphertext pair (random block, set pattern, random pattern, and indexed placement) are analyzed to determine the effectiveness of each method. The number of ciphertexts generated, generation time, and generation errors were recorded to determine which of the four proposed methods would be the most beneficial in a RFID system. The comparison of these method characteristics determined that the set pattern placement method provided the best solution. The thesis also discusses how RFID transmissions appear to attackers and explains how the random inputs reduce effectiveness of current system attacks. In addition to improving the anonymity of RFID tag transmissions, the concept of authenticating random inputs is also introduced in this thesis. These methods help prevent an adversary from easily associating a tag with its transmissions, thus increasing the security of the RFID system.

A new method is presented for rapid differentiation between coniferous woods commonly found in mixtures in major lumber producing regions of British Columbia. The species mixtures differentiated are the group known as "spruce/ pine/ fir" (SPF) containing white spruce (Picea glauca Voss), lodgepole pine (Pinus contorta Dougl.) and subalpine fir (Abies lasiocarpa Nutt.); the pair western larch (Larix occidentalis Nutt.) and Douglas-fir (Pseudotsuga menziesii Franco.); and the group of western hemlock (Tsuga heterophylla Sarg.), Sitka spruce (Picea sitchensis Carr.) and amabilis fir (Abies amabilis Dougl.). The method entailed measuring the reflectance infrared spectrum of a sample set of small wood pieces at a resolution of two wave numbers, determining which wavelengths were useful for differentiating species through a combination of correlation analyses and principal component analyses and using measurements at these wavelengths to develop species models using discriminant analysis. These models were then used to classify a larger set of samples measured under the same conditions. This approach was used to classify both green wood samples and the same samples after freeze-drying. For the SPF group the most effective overall classification model for the dry samples used 30 wavelengths and correctly classified 76% of samples, including 74% of heartwood samples and 89% of sapwood samples. For the green samples, the most effective sort used 10 wavelengths and correctly assigned species to 83% of green samples representing 84% of heartwood samples and 76% of sapwood samples. Classification was unsuccessful when the same classification parameters were applied to a matched set of extractive-free SPF samples, indicating that the sorting criteria are dependant upon the presence of extractive chemicals, both in heartwood and sapwood. The same classification parameters applied to a SPF mixture from eastern Canada (black spruce (Picea mariana B.S.P.), white spruce (Picea qlauca Voss.), jack pine (Pinus banksiana Lamb.), red pine (Pinus resinosa Ait.), white pine (Pinus strobus L.) and balsam fir (Abies balsamea Hill) were less successful than for the western SPF mixture. This suggests that each species may have unique sorting criteria based upon the somewhat different extractive chemical complex present in its wood. For the western larch/ Douglas-fir, the most effective overall classification model used 18 wavelengths and classified 98% of dry samples correctly for both heartwood and sapwood. For green samples, the best sort used 12 wavelengths and correctly assigned species to 91% of green samples, representing 90% of heartwood samples and 91% of sapwood samples. For the western hemlock/ Sitka spruce/ amabilis fir mixture, the most effective sort for the dry samples correctly classified 83% of the samples, 85% of heartwood samples and 56% of sapwood samples. Classification of the green samples proved difficult, with the best sort only 67% correct and using 15 wavelengths. However, if only western hemlock and Sitka spruce were sorted, the effectiveness rose to 82%. / Forestry, Faculty of / Graduate

A study of the secondary metabolism of two nudibranchs and one soft coral has led to the isolation of eighteen new and two known secondary metabolites. The structures of all compounds were determined by a combination of the interpretation of spectral data, chemical degradations and interconversions, and single crystal x-ray diffraction analysis. The British Columbian dorid nudibranch Diaulula sandiegensis yielded two new steroidal metabolites, diaulusterols A (41) and B (42). The 25-(3-hydroxybutanoate) residue of diaulusterol A (41) and the 2α,3α-diol array of both 41 and 42 are not commonly encountered in naturally occurring steroids. Both metabolites exhibited considerable antibacterial and antifungal activity. Steroid 41 exhibited fish antifeedant activity. The relative concentration of 4.1 and 42 in the skin extracts of D. sandiegensis appears to be related to the animals' seasonal abundance. Extracts of the British Columbian soft coral Gersemia rubiformis yielded a series of ten diterpenes possessing cembrane (170-175), pseudopterane (167-169) and gersolane (176) carbon skeletons. The structure of an eleventh diterpene remains unresolved. In addition, the structure of a degraded diterpene possessing a 13-membered ring (177) is tentatively proposed. G. rubiformis represents the first example of a soft coral to yield pseudopterane diterpenes. The organism is the first to contain cembrane, pseudopterane and gersolane metabolites, a fact which has biogenetic implications. Two new sesquiterpenes were also isolated. Tochuinyl acetate (165) and dihydrotochuinyl acetate (166) represent the first examples of cuparane sesquiterpenes to be isolated from a soft coral. A biogenesis is proposed. Metabolite 166 exhibited fish antifeedant activity. Investigations of Gersemia rubiformis collected in Newfoundland waters revealed that the secondary metabolism differed from west coast specimens. The isolation of the new unstable sesquiterpene (+)-β-cubebene-3-acetate (178) resulted. Skin extracts of the dendronotoid nudibranch Toquina tetraquetra were examined in an attempt to correlate its feeding dependency and lack of predation to the presence of allomones. Metabolites 165, 166, 170, 179 and the new butanoate diterpene 180 could be traced to the coelenterates which make up the animal's diet. Tochuinyl acetate (165), dihydrotochuinyl acetate (166) and rubifolide (170) were previously found in extracts of Gersemia rubiformis. Ptilosarcenone (179) has been reported as one of the major metabolites of the sea pen Ptilosarcus gurneyi²¹³. The exact origin of a sixth metabolite, pukalide (63), remains unknown. It is proposed that Tochuina tetraquetra selectively sequesters dietary metabolites for defensive purposes. / Science, Faculty of / Chemistry, Department of / Graduate

Background Bleeding can be an adverse side effect from hospital treatment. The aim was to develop an electronic identification method for patients who are bleeding within The Ottawa Hospital. Methods A retrospective exploratory cohort (N=1000) was used to identify potential candidate markers for bleeding. Electronic data were extracted to evaluate candidate identifiers. Data which were associated with bleeding events were assessed in a model derivation cohort (N=700). Multivariate analysis was used to establish the best model for identifying all bleeding events and in-hospital bleeding events. Results Overall 38% of the exploratory cohort had bleeding. In the model derivation set 29% had bleeding. The model predicting all bleeding included number of transfusions, admitting specialty, re-operation and endoscopy (C-statistic 0.82, 95%CI 0.79-0.86). The model predicting in-hospital bleeding included number of transfusions, admitting specialty and re-operation (C-statistic 0.78, 95% CI 0.73-0.84). Conclusion We have developed two models for identifying hospital bleeding events from The Ottawa Hospital electronic medical records. These should be validated prospectively on the hospital-wide population.