acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

Electrostatic interactions and electrokinetic transport in ion-exchange membranes have been investigated using analytical and computational methods. First, electrostatic interactions of electric double layers bounded by curved concave surfaces were studied using the Poisson-Boltzmann equation. Unlike the case of two charged parallel plates, the electric double layer force inside spherical cavities or cylindrical pores was predicted to diverge as surface potential goes to infinity. For typical values of surface potential, the double layer forces for curved surfaces were found to be significantly larger than the corresponding force between two parallel plates for most values of salt concentration and separation distance. It was found that at constant surface charge density, the double layer forces for curved surfaces decrease with increasing dielectric constant, opposite to the trend between two parallel plates. The dielectric constant also plays a special role in a force decomposition which led to a reformulation of the double-layer force for different geometries, as weighted averages of the hydrostatic pressures The electrokinetic transport of ions and water in ion-exchange membranes has been investigated using a new mathematical model. The model takes into account ion/fixed-charge site electrostatic interactions, water dipole orientation, ion hydration forces, and concentration dependent transport properties inside a membrane pore. Electric potential, solvent dielectric constant variations, water velocity, and cation and anion concentration profiles in the radial and axial pore directions were computed by solving Poisson's Equation, Booth's Equation, the Navier-Stokes Equations, and the Nernst-Planck Equations, respectively. A numerical technique, which can be applied to general cases of variable pore radius and wall charge density, has been devised by approximating the pore with small segments of straight cylinders that are then coupled through the Donnan relation and mass conservation equation. The computer model was tested by comparison with experimental data for Donnan dialysis separations with DuPont Nafion 117 cation-exchange membrane, where the membrane separates an aqueous acid solution from a mixture of monovalent/divalent cation salts. Both computer predictions and experimental measurements showed that monovalent ions with a larger hard sphere radius was selectively absorbed in and transported across the membrane in a multicomponent separation system. In addition to predicting ion transport for monovalent/monovalent and monovalent/divalent salt mixtures, the transport model also predicted accurately water transport through membranes for multicomponent component as well as for single salt systems. The multicomponent transport model was also applied to ion and water transport in ion-exchange membranes with non-uniform pore properties, where it was found theoretically that a variation in membrane pore radius changed significantly the water flux across the membrane, while the ion fluxes were relatively independent of pore size variation. Interesting ion transport, osmosis and electroosmosis behaviors in a multicomponent system have been observed and interpreted based on the transport model / acase@tulane.edu

A specific therapy for visceral larva migrans is not yet available. Although thiabendazole is being used in the treatment of human and animal infections with Toxocara canis, there is no evidence that it has a specific anthelmintic action against the larvae. Treatment of human toxocariasis with thiabendazole is reported to produce clinical improvement, however, this is apparently due to a non-specific effect of the drug and this action is not fully understood. Structural modifications of the thiabendazole molecule have produced a new class of anthelmintics: the benzimidazoles. These compounds have not yet been evaluated under standard conditions for their effects on toxocariasis. The aim of the present study was to assess the specific and non-specific effects of the benzimidazole anthelmintics on toxocariasis, taking murine toxocariasis as a model. Using thiabendazole as a prototype for the newer benzimidazole anthelmintics, its effects on murine toxocariasis were studied in more detail. Screening of the newer benzimidazoles was then done on the basis of the findings with thiabendazole. The effects of thiabendazole on the survival and the migratory behavior of T. canis larvae in mice were studied. Larval migration was assessed in relation to the dose level of thiabendazole, the method of administration of the drug, the duration of treatment and the route of inoculation of the infective eggs. The effect of thiabendazole on the histopathology of toxocariasis was studied in mice treated with thiabendazole during the migratory phase of infection. Peripheral blood eosinophilia was followed in treated and untreated mice that were infected with T. canis eggs by oral inoculation and mice that were injected intravenously with killed eggs. In vitro tests were done to study the effect of thiabendazole on production of antigenic metabolites by T. canis larvae as measured by amounts of precipitates formed around larvae in immune serum. The newer benzimidazole anthelmintics: fenbendazole, flubendazole, cambendazole, mebendazole, oxfendazole, oxibendazole, parbendazole and albendazole, were compared with thiabendazole for their larvicidal actions and their effects on larval migration. Thiabendazole was found to have a weak larvicidal effect but produced a reversible inhibition of larval migration. Inhibition of larval migration required administration of the drug in medicated diet, and was correlated with the concentration of thiabendazole in the diet. T. canis larvae were arrested in the liver after oral inoculation and in the lungs after intravenous inoculation of the infective eggs. As treatment with thiabendazole was prolonged, the effect of thiabendazole on larval migration became less reversible after treatment was terminated. Thiabendazole treatment had a suppressive effect on the pathology induced by the larvae during the migratory phase of infection. The in vitro production of precipitates by T. canis larvae in immune serum was inhibited by the presence of 100 mcg/ml of thiabendazole, which indicates that the drug may inhibit production of antigenic metabolites by the larvae. The course of peripheral blood eosinophilia was not affected by thiabendazole treatment in infected mice but was slightly inhibited in mice injected with killed eggs. All of the newer benzimidazoles tested had significant effects on larval migration but significant larvicidal effects were observed only in mice treated with albendazole, oxfendazole and cambendazole. It was concluded that the non-specific effect of thiabendazole in toxocariasis is mainly due to the inhibition of larval migration. The newer benzimidazole anthelmintics have high efficacy in causing temporary arrest of larval migration but they varied in the permanent damage they inflict on the larvae / acase@tulane.edu

Towards the end of the nineteenth century, a philosophical movement of German origin, called krausismo, was introduced in Spain by a University professor, Julian Sanz de R(')io. As a philosophy krausismo was short-lived, but it evolved to become a powerful cultural and educational movement destined to transform many facets of Spanish society. One of the principal concerns of the followers of Krausism was the reform of the country's educational system. They believed that many of the Spain's problems stemmed from the dogmatic, partisan education which isolated it from the rest of Europe. Krausismo became the burning issue of the day, and the liberal krausistas found irreconcilable enemies in the neo-Catholics. In 1876, when a group of the Krausist professors was expelled from their chairs, they found the Institucion Libre de Ensenanza, the first independent educational institution in Spain. This act was to become Krausism's most valuable contribution to the country. A large number of intellectuals were attracted by the institucionistas, among them such writers as Leopold Alas, Emilia Pardo Bazan, and Benito Perez Galdos, as well as members of the Generation of 1898 The cultural climate created by the krausistas led to a change of attitude towards literature in general and the novel in particular. This genre was considered the best medium by which to carry a message to the people. In our opinion, it is not mere coincidence that the years of greatest Krausist activity were also those of the rebirth of the modern Spanish novel. This dissertation explores the relationship between Krausism and the novel of the turn of the century, in order to establish this movement's link with the Generation of 1898 The study is divided into an introduction, five chapters, a conclusion, and two appendixes. In Chapter I, we define krausismo and summarize its origin and evolution. Chapter II, analyzes its influence on the novelists Alas, Pardo Bazan, and Galdos. It is our conclusion that their novels reflect the krausist concept regarding this genre. A third chapter systematically explores the contact between nineteenth century writers and intellectuals associated with Krausism and the Institucion Libre, and the Generation of 1898 in the years 1898-1905. For this purpose we have examined their correspondence as well as newspaper and magazines of that period In Chapter IV, we study the content of those periodicals and letters, in order to point out krausist ideas echoed or shared by Unamuno, Azor(')in, and Baroja in their formative years. Principal among them are their ideas about pedagogy, antidogmatism, and the 'Europeanization' of Spain. Chapter V, analyzes krausist themes in such works as En torno al casticismo, El alma castellana, La voluntad, El arbol de la ciencia and Camino de perfeccion, thus establishing the strong link between krausismo and the early works of Unamuno, Baroja, and Azor(')in. The appendixes reproduce two documents which are difficult to obtain. One is Krause's 'Mandamientos de la Humanidad al Individuo', and the other is an article on Francisco Giner de los Rios by Azor(')in, in which he evaluates this educator's influence on 98 / acase@tulane.edu

acase@tulane.edu

acase@tulane.edu