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Mubwindi Swamp in the Rukiga Highlands of south west Uganda is today surrounded by dense stands of moist lower montane forest. A survey of the present-day vegetation combined with an investigation of the surface pollen spectra indicate pollen accumulating on the swamp surface mainly result from taxa within the catchment. This survey also highlights that a combination of climatic, edaphic, demographic and human factors control the present-day composition and distribution of montane forest. Mubwindi Swamp comprises deep accumulations of peat-rich deposits. Pollen data from three cores of sediment provide a partial record of montane vegetation history since at least 43,000 yr B.P. This record is broken by at leat two, and possibly three, sedimentary hiati. Twelve radiocarbon ages, charcoal data from two cores using combination of three methods, and investigations into particle size characteristics place this record of montane vegetation dynamics within a wider palaeoenvironmental debate concerning Pleistocene climates, forest refugia, and human induced impacts on montane forests. Pollen deposited before and soon after the last glacial maximum represents a vegetation composition very different to that of the modern vegetation within the Mubwindi Swamp catchment. Specifically there were increased amounts of Artemisia, Ericaceae, Faurea and Stoebe. However, some elements found within the modern vegetation persisted during these periods, these include Ilex, Olea, Podocarpus and Zanthoxylum. These taxa may have persisted possibly because of favourable topography or soils. The uppermost 5m of deposits in core MB6 from the site are dated to the last 2100 years, and thus provide an opportunity, so far unique for Uganda, and much of central Africa, to record variations in the composition of montane vegetation during the late Holocene. Results of analyses of pollen indicate that lower montane forest has been present in the catchment for Mubwindi Swamp throughout the last 2100 years, despite extensive clearance in other parts of the region over the same period. A transition to a more open - and possibly drier - form of forest is apparent from around 680 yr B.P. This montane forest composition is thought to stem from a recent period of climatic change to less humid conditions. This change is followed by an increased occurrence of pollen from plants presently associated with areas of degraded forest from around 200 yr B.P. and a decrease in pollen from important sources of timber. Some recovery of timber trees is apparent from around 50 yr B.P. Changes in forest composition around 200 years ago could be interpreted as representing slightly increased humidity. However, in view of the nature of these changes, a low level of human impact was probably the most important causal factor. The gazetting of Bwindi-Impenetrable Forest as a Forest Reserve in the early 1930s may have facilitated a recovery of timber trees during the present century.

The production of new rose cultivars by sexual crossing is problematic and time consuming due to sexual incompatibility. the failure of seeds to genninate. and to a limited gene pool. Biotechnology provides an obvious alternative for the creation of genetic novelty in rose. This thesis focuses on the development of novel approaches, based on embryo rescue, pollen cryopreservation, protoplast and transformation technologies. A reproducible embryo rescue technique was developed in which embryos were excised and genninated on agar solidified medium containing a basic salt mixture and carbohydrate. The choice of carbohydrate and the growth conditions employed were demonstrated to markedly affect the percentage germination and subsequent plantlet development. This technique was used to greatly increase the production of F, hybrid progeny when compared to conventional germination methods. The failure of sexual crosses between several English rose cultivars was shown to be due to a combination of low pollen viability and to the operation of a pollen-style incompatibility mechanism (probably of the gametophytic self-incompatibility type). Degree of flower opening and method of pollen dehiscence were shown to significantly affect pollen viability. A technique was developed for the effective cryopreservation of English rose pollen. Using this technique it was possible to store pollen at ultra-low temperatures without any significant loss in viability. Such a technique compared favourably with conventional techniques (refrigeration and freezing) in which a loss in viability over time was demonstrated to occur. In vitro shoot cultures of English rose were established on MS-based media containing BAP. GA3 and NAA following the treatment of explants with an antioxidant solution to negate the effects of phenolic oxidation. The production of callus was shown to be genotype dependant and lacked regeneration potential. Rhizogenic responses were observed in leaf discs of two cultivars however shoot regeneration was not observed. Using a variety of enzyme mixtures it was possible to isolate protoplasts from both In vitro leaf material and from cell suspensions. Both mesophyll and cell suspension derived protoplasts were cultured to a microcallus stage. Plating density, growth regulator concentration and the use of antioxidants were all demonstrated to have a significant effect on the protoplast plating efficiency. Rhizogenesis was achieved from mesophyll protoplast-derived calli. Protoplasts, sometimes labelled with a fluorescent marker, were subjected to both chemical and electrofusion. Using micromanipulation, heterokaryons, formed during electrofusion, were recovered. Such heterokaryons, when cultured. underwent division and formed microcalli which subsequently developed into calli. The hybrid nature of such calli were conftrmed by isozyme analysis, determination of ploidy level and RAPD analysis. The introduction of a plasmid containing a gus marker gene into zygotic embryos of English rose was shown to be possible. This was achieved by microprojectile-mediated DNA delivery using a laboratory built electrical discharge device. The efficiency of this technique was influenced by the concentration of microprojectiles and DNA used. And by firing distance and choice of DNA construct. The relevance of this study and its applications, in the context of rose breeding are discussed.

Vulnerabilities of Information Technology (IT) Infrastructure have grown at the similar pace (at least) as the sophistication and complexity of the technology that is the cornerstone of our IT enterprises. Despite massive increased funding for research, for development, and to support deployment of Information Assurance (IA) defenses, the damages caused by malicious attackers to the IT infrastructure are growing at an accelerated rate. An entire industry, the Information Assurance (IA) industry, has grown up and currently exists only to provide methods and products for protecting IT assets and the data and services provided and maintained by these IT enterprise assets. For the manager, attempting to evaluate the security of products and services of the IA industry is exacerbated by the almost complete lack of universally recognized, reliable, and scalable methods to measure the "security" of those assets at the "enterprise" level and to determine the cost of protecting those assets. What Information Technology Enterprise Leadership needs is a quantitative security risk management methodology that is as affective to the enterprise manager as the traditional, non-IT risk, program management quantitative risk management methodologies. The topic of this dissertation is to describe from the perspective of IA professionals how probably it is that the issue stated above is perceived as real and what (if any) are the obstacles for achieving this goal. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]