Astrobiology is a multidisciplinary topic that addresses the origin, distribution and evolution of life in the universe. One of the key questions relates to whether life could have evolved on other planetary bodies, and Mars has been the major focus. Biologists contribute to this question by studying the ecology of extreme environments on Earth that share closest analogy to Mars’ past or present environment. In this thesis, molecular-level interrogations were used to address some aspects of microbial biodiversity, ecology and stress tolerance in two such extreme environments. The high-altitude cold and intense UV irradiance of central Tibet was selected as an analogue for Mars surface today, whilst cold alkaline high-carbonate freshwater lakes were chosen as an analogue for Mars’ previous late wet phase. Biological soil crusts from central Tibet supported a diverse microflora and these were variously bacteria or eukarya dominated. The relatively well-developed eukarya-dominated crusts were characterized and showed they comprised of Stichococcus bacillaris, plus alphaproteobacteria, betaproteobacteria, bacteroidetes and gemmatimonadetes. In order to evaluate the diversity of radiation-tolerant taxa in these soils, samples were exposed to ionizing radiation and viability, physiology and phylogenetic identity determined. The most radio-tolerant taxa isolated and characterized were from the radiation tolerant phylum Deinococci (15kGy), whilst a relatively diverse range of Actinobacteria, Bacilli, Cyanobacteria and Proteobacteria were also recovered after exposure to doses up to 10kGy. This implies the high-radiation environment has selected for tolerance among diverse phyla, with tolerances that far exceed environmental exposure. It is not known at this stage if they all employ similar protective strategies. Microbial reefs that have developed in cold alkaline lakes in British Columbia were studied as analogues for a late-wet Mars environment. Molecular ecological analysis revealed that communities consisted largely of of Proteobacteria (alpha), Cyanobacteria (Leptolyngbya) and Acidobacteria, with similarities in community assembly to marine stromatolites. Microbial diversity varied spatially and temporally within microbialites, and indicated that geographically proximal structures can develop with different communities. Significant changes also occur between summer and winter when the lake surface is frozen. Investigation of other nearby lakes with similar geochemistry but not supporting microbialites revealed extensive microbial mats. These developed in the presence of relatively high concentrations of methane or sulfate, and their biodiversity reflected this with several putative methanotrophic and sulphate utilizing taxa identified. No obvious cues that inhibit or promote microbialite formation were observed in this study. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

The main part of the introduction illustrates the health care provision made in the past for workforces of the oil and gas industries functioning in remote places usually associated with an environmental hazard. Much of the past work has been carried out in the North Sea and the provision made there has been reviewed in some detail together with the gradual development of health care in the United Arab Emirates for both the offshore and the onshore oil-related workforces. There follows a short review of the provision made for two analogous situations - Newfoundland and Labrador and the British Antarctic Territories - since the developments there are of direct relevance to the Middle East situation. The main environmental hazard in the Middle East is heat and so the physiology and pathology of thermal balance in man are addressed in some detail. The first study is on the identification of the particular thermal problem which occurs in the offshore workings on the Abu Dhabi oil and gas companies, namely heat cramps. This problems had not been previously identified and the work done in determining its presence and its management is duly reported, indicating the problems of accepting health education material designed for one environment by another. In the development of systems of health care for both oil and non-oil related remote populations, the importance of training of the population at risk has been repeatedly emphasised. The perceived problems in that area are skill retention by laymen and the acceptance of the guidelines of the European and US Resuscitation Councils. A second study was therefore carried out to examine skill retention in laymen together with the feasibility of carrying out resuscitation manoeuvres in high temperatures.

The impacts of extreme temperatures on human health and morbidity have been well documented in many studies. In literature, changes in the trends of extreme temperatures have been studied using percentiles, indicators and climate modeling. The aim of this study is to determine if the trend exhibited in the literature of statistically significant increases in extreme minimum temperatures, is also exhibited in the Greater Toronto Area during the 1971 to 2000 timeframe. A methodological approach using counts is the basis for the analysis. Statistical significance is determined through the use of Spearman’s Rank, Kendal-Tau and T-tests. A total of five stations are analysed, three being urban and two representing the surrounding suburban areas. The results indicate that statistically significant decline in extreme minimum temperature counts have occurred. In agreement with the literature, statistically significant increases in extreme maximum temperature counts can not be determined.

The impacts of extreme temperatures on human health and morbidity have been well documented in many studies. In literature, changes in the trends of extreme temperatures have been studied using percentiles, indicators and climate modeling. The aim of this study is to determine if the trend exhibited in the literature of statistically significant increases in extreme minimum temperatures, is also exhibited in the Greater Toronto Area during the 1971 to 2000 timeframe. A methodological approach using counts is the basis for the analysis. Statistical significance is determined through the use of Spearman’s Rank, Kendal-Tau and T-tests. A total of five stations are analysed, three being urban and two representing the surrounding suburban areas. The results indicate that statistically significant decline in extreme minimum temperature counts have occurred. In agreement with the literature, statistically significant increases in extreme maximum temperature counts can not be determined.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 80-84). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 60-169) Also available in print.

Thesis (M.A. in education)--Washington State University. / Includes bibliographical references.

Thesis (J.C.L.)--Catholic University of America, 1985. / Typescript. Includes vita. Includes bibliographical references (leaves 123-126).

Proefschrift Erasmus Universiteit Rotterdam. / Met lit. opg. - Met samenvatting in het Nederlands.

Probabilistic and statistical aspects of extremes of univariate processes have been extensively studied, and recent developments in extremes have focused on multivariate theory and its application. Multivariate extreme value theory encompasses two separate aspects: marginal features, which may be handled by standard univariate methods, and dependence features. Both will be examined in this study. First we focus on testing independence in multivariate extremes. All existing score tests of independence in multivariate extreme values have non-regular properties that arise due to violations of the usual regularity conditions of maximum likelihood. Some of these violations may be dealt with using standard techniques, for example when independence corresponds to a boundary point of the parameter space of the underlying model. However, another type of regularity violation, the infinite second moment of the score function, is more difficult to deal with and has important consequences for applications, resulting in score statistics with non-standard normalisation and poor rates of convergence. We propose a likelihood based approach that provides asymptotically normal score tests of independence with regular normalisation and rapid convergence. The resulting tests are straightforward to implement and are beneficial in practical situations with realistic amounts of data. A fundamental issue in applied multivariate extreme value (MEV) analysis is modelling dependence within joint tail regions. The primary aim of the remainder of this thesis is to develop a pseudo-polar framework for modelling extremal dependence that extends the existing classical results for multivariate extremes to encompass asymptotically independent tails. Accordingly, a constructional procedure for obtaining parametric asymptotically independent joint tail models is developed. The practical application of this framework is analysed through applications to bivariate simulated and environmental data, and joint estimation of dependence and marginal parameters via likelihood methodology is detailed. Inference under our models is examined and tests of extremal asymptotic independence and asymmetry are derived which are useful for model selection. In contrast to the classical MEV approach, which concentrates on the distribution of the normalised componentwise maxima, our framework is based on modelling joint tails and focuses directly on the tail structure of the joint survivor function. Consequently, this framework provides significant extensions of both the theoretical and applicable tools of joint tail modelling. Analogous point process theory is developed and the classical componentwise maxima result for multivariate extremes is extended to the asymptotically independent case. Finally, methods for simulating from two of our bivariate parametric models are provided.