Towards molecular control of elementary reactions in zeolite catalysis by advanced molecular simulations mimicking operating conditions

Zeolites are the workhorses of today's chemical industry. For decades they have been successfully applied, however many features of zeolite catalysis are only superficially understood and in particular the kinetics and mechanism of individual reaction steps at operating conditions. Herein we use state-of-the-art advanced ab initio molecular dynamics techniques to study the influence of catalyst topology and acidity, reaction temperature and the presence of additional guest molecules on elementary reactions. Such advanced modeling techniques provide complementary insight to experimental knowledge as the impact of individual factors on the reaction mechanism and kinetics of zeolite-catalyzed reactions may be unraveled. We study key reaction steps in the conversion of methanol to hydrocarbons, namely benzene and propene methylation. These reactions may occur either in a concerted or stepwise fashion, i.e. methanol directly transfers its methyl group to a hydrocarbon or the reaction goes through a framework-bound methoxide intermediate. The DFT-based dynamical approach enables mimicking reaction conditions as close as possible and studying the competition between two methylation mechanisms in an integrated fashion. The reactions are studied in the unidirectional AFI-structured H-SSZ-24, H-SAPO-5 and TON-structured H-ZSM-22 materials. We show that varying the temperature, topology, acidity and number of protic molecules surrounding the active site may tune the reaction mechanism at the molecular level. Obtaining molecular control is crucial in optimizing current zeolite processes and designing emerging new technologies bearing alternative feedstocks

Ovoids and spreads of finite classical generalized hexagons and applications

One intuitively describes a generalized hexagon as a point-line geometry full of ordinary hexagons, but containing no ordinary n-gons for n<6. A generalized hexagon has order (s,t) if every point is on t+1 lines and every line contains s+1 points. The main result of my PhD Thesis is the construction of three new examples of distance-2 ovoids (a set of non-collinear points that is uniquely intersected by any chosen line) in H(3) and H(4), where H(q) belongs to a special class of order (q,q) generalized hexagons. One of these examples has lead to the construction of a new infinite class of two-character sets. These in turn give rise to new strongly regular graphs and new two-weight codes, which is why I dedicate a whole chapter on codes arising from small generalized hexagons. By considering the (0,1)-vector space of characteristic functions within H(q), one obtains a one-to-one correspondence between such a code and some substructure of the hexagon. A regular substructure can be viewed as the eigenvector of a certain (0,1)-matrix and the fact that eigenvectors of distinct eigenvalues have to be orthogonal often yields exact values for the intersection number of the according substructures. In my thesis I reveal some unexpected results to this particular technique. Furthermore I classify all distance-2 and -3 ovoids (a maximal set of points mutually at maximal distance) within H(3). As such we obtain a geometrical interpretation of all maximal subgroups of G2(3), a geometric construction of a GAB, the first sporadic examples of ovoid-spread pairings and a transitive 1-system of Q(6,3). Research on derivations of this 1-system was followed by an investigation of common point reguli of different hexagons on the same Q(6,q), with nice applications as a result. Of these, the most important is the alternative construction of the Hölz design and a subdesign. Furthermore we theoretically prove that the Hölz design on 28 points only contains Hermitian and Ree unitals (previously shown by Tonchev by computer). As these Hölz designs are one-point extensions of generalized quadrangles, we dedicate a final chapter to the characterization of the affine extension of H(2) using a combinatorial property

A Life of One's Own: Republican Freedom and Disability

This article outlines a republican perspective on disability. We argue that a commitment to ensuring the republican freedom of disabled citizens offers a promising account of what disabled citizens are owed as a matter of justice. A republican perspective offers a particular diagnosis of the injustice of disability disadvantage, both in relation to individuals (dominium) and the state (imperium), that is congenial to prominent concerns voiced by the disability rights movement. This article also offers a brief outline of three republican remedies: the right of social participation, the right of opportunities for civic contribution, and the right of democratic contestation. These remedies constitute key guidelines for the robust institutional protection of disabled citizens' republican freedom

Effect of pH on ciprofloxacin ozonation in hospital WWTP effluent

A bubble column was used for ozonation of the quinolone antibiotic ciprofloxacin and the effect of pH was tested. Degradation at pH 7 increased the ciprofloxacin half life time to 29.1 min compared to pH 3 (26.8 min) and pH 10 (18.7 min), possibly due to increased sorption at neutral pH. Degradation product identification revealed strongest degradation at the piperazinyl substituent at pH 10 while degradation at the quinolone moiety seems promising at pH 7. For P. fluorescens and E. coli, reduction in antibacterial activity, monitored by agar diffusion tests, was in correlation with the ciprofloxacin degradation rate. For B. coagulans, however, no differences in residual antibacterial activity were found in function of pH, indicating that degradation products also affect antibacterial activity of ozonated samples

Elementos para una economía política del republicanismo: un análisis crítico de la renta básica de Alaska

En este artículo presentamos las ideas básicas que subyacen a la teoría política republicana y establecemos una línea de demarcación entre la perspectiva republicana y el libertarianismo de izquierdas, el cual tiene en la renta básica de Alaska su plasmación institucional más natural e inmediata. A partir de ahí, abordamos tres conjuntos de problemas que presenta el modelo de Alaska: la falta de una base económica sustancial, la falta de frenos a la acumulación de poder económico privado y la falta de mecanismos de control democrático sobre los procesos de extracción, imposición tributaria y distribución de los recursos naturales. Así, para que el republicanismo pueda hacerlo suyo, el modelo de Alaska debe ser sometido a importantes enmiendas y modificaciones que tienen que ver tanto con su naturaleza intrínseca como con el contexto institucional en el que opera. De este modo, concluimos sosteniendo que, aun cuando el modelo de Alaska puede ser compatible con la perspectiva republicana en un sentido débil, los republicanos deben proceder con cautela a la hora de defender el modelo en un sentido fuerte