This dissertation collects five papers that discuss potential consequences of the defeasibility of knowledge. Chapters 1, 2, 3, and 5 provide arguments for a number of important epistemological consequences of the defeasibility of knowledge. Chapter 4 discusses consequences that others have claimed the defeasibility of knowledge to have. Chapter 1 argues that closure principles for knowledge are in tension with the defeasibility of knowledge. Chapter 2 argues that one of Williamson's famous arguments against the KK principle relies in a problematic way on a closure principle that is incompatible with defeat. Chapter 3 argues that a view on which knowledge just is belief safe from error is in tension the defeasibility of knowledge. Chapter 4 discusses two arguments to the effect that defeat by higher-order evidence sometimes involves the violation of rational ideals or rules of rational belief formation. As part of a response to an objection to contextualism about 'know', Chapter 5 investigates a number of social epistemological consequences of the defeasibility of knowledge.

NanopartÃculas magnÃticas de NiFe2O4 foram sintetizadas pelo mÃtodo sol-gel protÃico, a partir de uma soluÃÃo aquosa contendo gelatina comestÃvel (GelitaTM) e sais de nÃquel(II) e ferro(III), apÃs a secagem uma resina foi formada e em seguida foi analisada por Termogravimetria e OxidaÃÃo à Temperatura Programada (OTP). As amostras de NiFe2O4 foram obtidas pela calcinaÃÃo das resinas durante 4 horas em vÃrias temperaturas (250oC, 300oC, 400oC, 600oC, 800oC e 1000oC) e em 400oC com variaÃÃo de tempo (2h, 3h e 4h). O pà resultante foi caracterizado por espectroscopia de infravermelho, difraÃÃo de raios X, microscopia eletrÃnica de transmissÃo (MET), microscopia eletrÃnica de varredura (MEV) e espectroscopia de energia dispersiva (EDS). As propriedades magnÃticas das amostras foram investigadas por espectroscopia MÃssbauer e Medidas MagnÃticas, a temperatura ambiente; as medidas magnÃticas foram feitas em um magnetÃmetro de amostra vibrante (VSM). Os parÃmetros estruturais extraÃdos da difraÃÃo de raios X foram refinados pelo mÃtodo Rietveld; o tamanho mÃdio dos cristalitos foi determinado pela equaÃÃo de Scherrer e pelo mÃtodo grÃfico de Williamson-Hall, a partir dos valores da largura a meia altura dos picos de difraÃÃo (FWHM â Full Width at Half Maximum); pelo mÃtodo grÃfico de Williamson-Hall foi determinada a microdeformaÃÃo. O tamanho mÃdio de cristalito variou de 4,9nm atà 69,5nm e menores microdeformaÃÃes reduziram a diferenÃa de tamanho calculados pela equaÃÃo de Scherrer e pelo grÃfico de Williamson-Hall. A fim de indicar uma possÃvel aplicaÃÃo para as nanopartÃculas de NiFe2O4 foram realizados testes de toxicidade in vivo. / Magnetic nanoparticles of NiFe2O4 were synthesized by the proteic sol-gel method,using nickel (II) and iron (III) nitrates and aqueous solution of gelatin (GelitaTM). The dried solution in the form of resin, were characterized by thermogravimetric analysis(TGA), combined with the temperature-programmed oxidation (TPO). The sampleso o o oof NiFe2O4 were synthesized at different temperatures (250 C, 300 C, 400 C, 600 C,800o C e 1000oC), the annealing time interval was of 4 h; and 400oC for differentsintering times (2h, 3h e 4h). The obtained nanoparticles werecharacterized byinfrared spectroscopy, X-ray powder diffraction (XRD), transmission electronmicroscopy (TEM), scanning electron microscopy (SEM), energy dispersivespectrometer (EDS). Magnetic properties were investigated by spectroscopy MÃssbauer and Magnetization measurements obtained at room temperature;magnetization measurements was used a vibrating sample magnetometer (VSM).The microstructural parameters from the X-ray powder diffraction have beendetermined by means of Rietveld analysis; nanoparticle sizes calculated by theScherrer equation and size-strain by Williamson-Hall (W-H) method, using the FullWidth at Half Maximum (FWHM) of the diffraction peaks. The average particlediameter ranges from 4,9nm to 69,5nm. Toxicity tests were performed in vivo todetermine application for NiFe2O4.

Due to the importance of carbohydrates in biological systems, many efforts have been made to develop a quantitative method for analysis of carbohydrates in natural waters. The low concentrations of dissolved sugars in natural waters require a sensitive analytical method. In this study, gas chromatography of alditol acetate derivatives of sugars was investigated for quantitative and qualitative analysis of individual dissolved sugars in natural waters. The alditol acetate derivatives of sugars give only one derivative for each sugar, yielding qualitative and quantitative results. The detection limit was 25 nM for each sugar. Because of this very low detection limit, only 100 ml of sample was required for analysis. From measurements of the alditol acetate derivatives, qualitative and quantitative analysis of pentoses (arabinose and xylose) and hexoses (mannose, galactose, and glucose) were obtained from The Williamson River and its tributaries, which are located near Klamath Falls, Oregon. Total organic carbon concentrations vary greatly in this river system as a result of the river passing through Klamath Marsh, which introduces very high amounts of humic substances into the river system. The range of total concentrations of dissolved sugars is 0.07 to 7.3 μM; the lowest occurring in the spring waters, and the highest in humic-rich waters. Monosaccharide, polysaccharide, and humic-bonded saccharide concentrations, which were obtained from three sample sites, showed very low concentrations of monosaccharides, moderate concentrations of polysaccharides, and moderately high concentrations of humic-bonded saccharides.

Thesis (MA (Hons)) -- University of Western Sydney, Nepean, 1997. / Bibliography : leaves 73-75.

Neste trabalho foi desenvolvido um conjunto de ferramentas computacionais, em linguagem de programação Python, para a análise de perfis de difração de raios X, tanto para o estudo quanto para obtenção dos valores microestruturais como tamanhos médios de cristalitos e microdeformações, através de dos métodos de: Scherrer, Single-Line, Williamson-Hall e Warren-Averbach. Para aplicar os métodos de análise de perfis, foram também implementados métodos de remoção da contribuição instrumental pelo método de Stokes e ajuste de funções, remoção de ruídos pelo método de Savitzky-Golay, correção da radiação de fundo pelo método de ajuste linear, correção do fator de Lorentz-Polarização e correção do dubleto Kalfa2 . / In this work, a set of computational tools was developed, in the Python programming language, for the analysis of X-ray diffraction profiles, both for the study and for obtaining the microstructural values, as well as the mean values of crystallites and microdeformations, using Scherrer, Single-Line, Williamson-Hall and Warren-Averbach. To apply the methods of profile analysis, methods were also implemented for the removal of instrumental contributions by the Stokes method and adjustment of functions, removal by the Savitzky-Golay method, correction of the background radiation by the linear adjustment method, correction of the factor of Lorentz-Polarization and correction of dubleto Kalfa2 .

Neste trabalho foi desenvolvido um conjunto de ferramentas computacionais, em linguagem de programação Python, para a análise de perfis de difração de raios X, tanto para o estudo quanto para obtenção dos valores microestruturais como tamanhos médios de cristalitos e microdeformações, através de dos métodos de: Scherrer, Single-Line, Williamson-Hall e Warren-Averbach. Para aplicar os métodos de análise de perfis, foram também implementados métodos de remoção da contribuição instrumental pelo método de Stokes e ajuste de funções, remoção de ruídos pelo método de Savitzky-Golay, correção da radiação de fundo pelo método de ajuste linear, correção do fator de Lorentz-Polarização e correção do dubleto Kalfa2 . / In this work, a set of computational tools was developed, in the Python programming language, for the analysis of X-ray diffraction profiles, both for the study and for obtaining the microstructural values, as well as the mean values of crystallites and microdeformations, using Scherrer, Single-Line, Williamson-Hall and Warren-Averbach. To apply the methods of profile analysis, methods were also implemented for the removal of instrumental contributions by the Stokes method and adjustment of functions, removal by the Savitzky-Golay method, correction of the background radiation by the linear adjustment method, correction of the factor of Lorentz-Polarization and correction of dubleto Kalfa2 .

Les sphères diplomatique et culturelle sont souvent créditées de liens étroits. Nombreuses sont les monographies consacrées à des figures de diplomates écrivains, artistes ou savants, en particulier pour l’Époque moderne. L’objet de cette thèse est d’interroger cette association et de la mettre en doute, comme fondée sur des approximations et un refus de considérer les milieux diplomatiques aussi bien dans leur globalité à une date donnée, que dans leurs spécificités temporelles et géographiques, pour se focaliser sur quelques éléments brillants, mais finalement peu représentatifs. Le choix a été fait de recentrer la réflexion au sein d’un cadre culturel de référence à l’Époque moderne, celui de la République des Lettres, et de se saisir de l’ensemble d’un réseau d’information diplomatique qui puisse servir de témoin, en l’espèce celui qu’organisa depuis Whitehall Sir Joseph Williamson, entre 1660 et 1680.Cet exemple de Williamson a paru particulièrement judicieux, car il incarne l’un des principaux diplomates britanniques de la fin du XVIIe siècle, mais aussi un savant à part entière. Enfin, l’historiographie l’a souvent noté comme le grand organisateur d’un système de renseignement au profit de l’Angleterre de la Restauration, et les archives découlant de ses activités ont été remarquablement bien conservées.Après avoir présenté et justifié les sources, cette étude s’attache à la reconstitution du système d’information diplomatique de Williamson. Loin de s’y presser en grand nombre, les savants s’y révèlent finalement plutôt rares. De plus, lorsqu’ils sont présents, leur participation survient à la faveur de circonstances spécifiques, que nous entreprenons d’expliciter. / Diplomatic and cultural spheres are often regarded as being very close, especially in Early Modern Europe. Many biographies are devoted to diplomats who were also authors, artists or scholars. The purpose of this PhD is to question this association, and to argue that it results from inaccurate observations, and from a refusal to consider diplomatic structures globally at a given date, so that brilliant individuals tend to attract all attention, even if they are exceptions.In order to draw a more accurate picture of the actual relations between diplomatic and cultural spheres, I decided to focus on the Republic of Letters, as the prominent cultural structure of Early Modern Europe, and on a specific diplomatic network of informants: the international network which was developed by Sir Joseph Williamson between 1660 and 1680. This case is particularly appealing, because Williamson was one of the major British diplomats of the time, and also an accomplished scholar. Finally, his extensive records have been remarkably well preserved. Thanks to these materials, it has been possible to reconstitute Williamson’s network of informants, and to establish that few of them were men of letters, most of whom only appear in specific circumstances, which are depicted and discussed in this work.

Recent research has indicated that dissolved organic matter (DOM) may plan an important role in the ability of natural waters to complex metals. This research was conducted because the quantitative nature of this role is uncertain. Gas-liquid chromatography was used to study the hydrolyzable amino acids at twelve sampling sites on the Williamson River at monthly intervals for two years. The relative abundances showed little spacial or temporal variation. The two-year averages for total amino acids ranged from about 0.5 (mu)M to about 8 (mu)M. A separation technique was used to show that (GREATERTHEQ) 96% of the dissolved amino acids were associated with aquatic humus. Since it was found that amino acids contributed less than 1% to humic carbon and since a published report found that carbohydrates contributed less than 2% to humic carbon, this research provided the necessary data to conclude that DOM in the Williamson River is essentially aquatic humus. Humus complexation capacity is often operationally defined as amount of metal bound per unit weight of humus. This research has shown that the titrimetric methods commonly used to obtain this parameter underestimate its magnitude. However, it was shown that these methods can be combined with acidic functional group analyses to determine upper and lower limit for this parameter. For Williamson River humus, the range was 7.2 - 15.4 (mu)mols copper per mg humic carbon. Titrations of humus into a copper-oxalate metal-ion buffer enabled the determination of the copper-humus binding "constant" at humas : copper ratios found in the Williamson River, (LESSTHEQ) 4300. The binding "constant" was a variable and a function of pH. At a humus: copper ratio of 4300, the values of the function at pH 5.0, 5.5, 6.0, and 6.5 were: 3.0 x 10('6), 8.9 x 10('6), 3.0 x 10('7), and 1.7 x 10('8). Current models of metal-humus complexation, were shown to be inappropriate via rigorous mathematical examination and via application to computer-simulated titrations. A model, in which it is assumed that the concentrations of binding sites in humus are normally distributed with respect to the log of the metal binding constant for each site, is proposed. Application of this model to simulated titrations and to experimental data proved it to be superior to other current models.

Doctor of Philosophy / 'Entrepreneurs, Empires and Pantomimes' examines how Williamson influenced the form and content of one theatrical genre within his theatrical empire between 1882 and 1914. As the frontispiece signals in spectacular fashion, the pantomime was a vitally popular dramatic form. I believe that my findings have serious implcations for the formation of an Australian theatre industry with regard to the 'development'of Australian drama. Ironically, as J.W. Gough points out in 'The Rise of the Entrepreneur' (1969), the word 'entrepreneur' first appeared in the 'Oxford English Dictionary' in 1897 as referring to "the director or manager of a public musical institution: one who 'gets up' entertainments, especially musical performances."

Doctor of Philosophy / 'Entrepreneurs, Empires and Pantomimes' examines how Williamson influenced the form and content of one theatrical genre within his theatrical empire between 1882 and 1914. As the frontispiece signals in spectacular fashion, the pantomime was a vitally popular dramatic form. I believe that my findings have serious implcations for the formation of an Australian theatre industry with regard to the 'development'of Australian drama. Ironically, as J.W. Gough points out in 'The Rise of the Entrepreneur' (1969), the word 'entrepreneur' first appeared in the 'Oxford English Dictionary' in 1897 as referring to "the director or manager of a public musical institution: one who 'gets up' entertainments, especially musical performances."