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In this work we investigate the feasibility of the project of showing that a certain kind of generalisations that philosophers call 'Epistemic Principles', which state conditions for the achievement of epistemic goods such as justifications and entitlements, fulfil general conditions for their correctness. First, we identify the veritistic commitments underlying the project it is argued that some common interpretations of such commitments are mistaken and a minimal interpretation of them is outlined. The minimal interpretation is then defended against some charges of explanatory deficits. We explicate how the project of showing that an epistemic principle is correct is motivated and constrained by the veritistic commitments expounded in the first chapter. Then we show how a form of epistemic circularity constitutes a major obstacle for that project. We discuss several forms of circularity and argue that only one of them threatens the project, we explain the exact nature of the obstacle it poses for the project. Then we examine various strategies that attempt to avert the obstacle some by freeing the project from the veritistic commitments that constrain it, others by constructing an allegedly apriori way of carrying out the project, without giving up its initial veritistic commitments, and still another by reconceptualising the very explanatory goal of the project. All of them are examined in detail and found unsatisfactory. However, it is argued that the doubt that our results cast on the feasibility of the project does not warrant a generalised pessimism about the possibility of obtaining philosophical knowledge concerning epistemic principles, for the results that sustain that doubt constitute themselves knowledge of epistemic principles.

There are very few reports of ruthenium complexes for olefin polymerization and the active species are unknown. In this dissertation we explore a series of new ruthenium II and IV complexes for olefin polymerization catalysis. We synthesized an arene-tethered ruthenium complex (eta6-C6H5(CH2)3SCH3RuCl2) capable of catalyzing ethylene polymerization using AlMe2Cl as cocatalyst. Homologous dimethylated eta6-C6H5(CH2)3SCH3Ru(CH3)2 complex in the presence of ethylene also yielded polyethylene when activated with HBArF ([H(Et2O)2]+[BAr'4]- (where Ar'=3,5-(CF3)2C6H3)). Mechanistic studies by 1H-NMR and mass spectrometry support a ruthenium cationic [eta6-C6H5(CH2)3SCH3Ru(oligomer)]+ complex as the polymerization active species. This has unambiguously demonstrated for the first time a ruthenium complex as the active species for catalyzing olefin insertion polymerization.We also studied heteroatom effect eta6-Arene tethered ruthenium (II) complexes on polymerization activity. Complexes (eta6-C6H5(CH2)3SCH3RuCl2), (eta6-C6H5(CH2)3N(CH3)2RuCl2), and [(eta6-C6H5(CH2)3OCH3RuCl2)]2 with coordinating oxygen, sulfur, and nitrogen heteroatoms in the tethered arms have been compared for olefin polymerization. Nitrogen and sulfur-containing complexes are active for olefin polymerization while oxygen-containing complex is inactive. The nitrogen-containing complex is 1.5-fold more active than the sulfur-containing complex. The polymers obtained are composed of two different fractions, a high molecular weight fraction (55-161 kg*mol-1) and a low molecular weight fraction (276-761 g*mol-1). The polydispersities of both fractions are narrow, indicating a single-site catalyst. DFT calculations were carried out on to determine the migratory insertion barriers. Nitrogen-containing complex was found to have a migratory insertion barrier of the chain propagation of 19.4 kcal*mol-1 while sulfur-containing was found to be 21.8 kcal*mol-1. Theoretical calculations are in agreement with the experimental polymerization activity results.We hypothesize that a more electron deficient ruthenium complex will be more active. We synthesized Ru(IV) dimethyl complex [Cp*(k2-S2CNMe2)RuIVMe2] that polymerizes ethylene with higher activity. The polymers obtained were linear with high molecular weights (up to 322 kg*mol-1) and narrow monomodal molecular weight distributions (Mw/Mn=1.69-2.50). Pronounced counterion effects were observed: the methylaluminoxane activator gave the highest productivities, whereas HBArF resulted in no activity. These results are further supported by DFT calculations, which indicate a low migratory insertion barrier for chain propagation (9.8 kcal*mol-1) but high ethylene uptake energies (15.6 kcal*mol-1).

Our understanding of how species will respond to global change is still limited. Species distribution models (SDMs) are used to generate hypotheses regarding the potential distributions of species under different environmental conditions. However, that species observations and climatic variables are not measured at the same spatial and temporal resolution still hinders our ability to forecast species range shifts and expansions in response to global change. One of the possible consequences of this data mismatch is the observed discrepancy between realized climate niches in species' native and invasive ranges. In the first chapter of my dissertation, I address this issue by evaluating niche similarity between native and invaded ranges for 10 species using a combination of monthly and inter-annual climatic variability data. My results suggest that some species' ranges may be constrained by one aspect of climatic variability in the native range but a different one in the invaded range. A second issue, also a consequence of the spatio-temporal mismatch, is that weather station data are often spatially interpolated to match the species observations without any uncertainty assessment. The second chapter evaluates and quantifies the effects of three complementary aspects of uncertainty present in weather station data interpolations. I examine the influence of topographic heterogeneity, interannual climatic variability, and distance to weather station on SDM performance for 20 well observed North American breeding birds, and show that topographic heterogeneity has the highest contribution to omission errors, or false absences. A third consequence of the spatio-temporal data mismatch is the inability of global simulations to capture local manifestations of climate change. This inability can limit the capacity of SDMs to produce accurate simulations for species whose distributions depend on small-scale climate phenomena. While changes in global climatic patterns are projected using global climate model (GCM) simulations, local climatic trends are not always well represented by GCMs, or by simple downscaled projections derived from GCMs. In the final chapter of my dissertation, I use interpolated, fine-scale historic climate records in a novel approach to estimate the sensitivity of SDM's to locally coherent changes in temperature and precipitation at larger scales, using coast redwood (Sequoia sempervirens) as an example. Overall, the results of this thesis confirm the importance of establishing an appropriate relational basis in time and space between species and climatic observations. Historical collection records should be thoroughly analyzed and integrated with historical climatic time series to gain a better understanding of species' response to climate variability in the past, thereby informing the selection of appropriate spatio-temporal scales of climate variability for projections under present and future conditions.