Nonlinear spectral calculus and super-expanders

Nonlinear spectral gaps with respect to uniformly convex normed spaces are shown to satisfy a spectral calculus inequality that establishes their decay along Cesaro averages. Nonlinear spectral gaps of graphs are also shown to behave sub-multiplicatively under zigzag products. These results yield a combinatorial construction of super-expanders, i.e., a sequence of 3-regular graphs that does not admit a coarse embedding into any uniformly convex normed space.Comment: Typos fixed based on referee comments. Some of the results of this paper were announced in arXiv:0910.2041. The corresponding parts of arXiv:0910.2041 are subsumed by the current pape

Differences in Accumulation and Virulence Determine the Outcome of Competition during Tobacco etch virus Coinfection

Understanding the evolution of virulence for RNA viruses is essential for developing appropriate control strategies. Although it has been usually assumed that virulence is a consequence of within-host replication of the parasite, viral strains may be highly virulent without experiencing large accumulation as a consequence of immunopathological host responses. Using two strains of Tobacco etch potyvirus (TEV) that show a negative relationship between virulence and accumulation rate, we first explored the evolution of virulence and fitness traits during simple and mixed infections. Short-term evolution experiments initiated with each strain independently confirmed the genetic and evolutionary stability of virulence and viral load, although infectivity significantly increased for both strains. Second, competition experiments between hypo- and hypervirulent TEV strains have shown that the outcome of competition is driven by differences in replication rate. A simple mathematical model has been developed to analyze the dynamics of these two strains during coinfection. The model qualitatively reproduced the experimental results using biologically meaningful parameters. Further analyses of the model also revealed a wide parametric region in which a low-fitness but hypovirulent virus can still outcompete a high-fitness but hypervirulent one. These results provide additional support to the observation that virulence and within-host replication may not necessarily be strongly tied in plant RNA viruses

Some aspects of topological Galois theory

We establish a number of results on the subject of the first author's topos-theoretic generalization of Grothendieck's Galois formalism. In particular, we generalize in this context the existence theorem of algebraic closures, we give a concrete description of the atomic completion of a small category whose opposite satisfies the amalgamation property, and we explore to which extent a model of a Galois-type theory is determined by its symmetries. (C) 2019 Published by Elsevier B.V

Teatro rioplatense (1886-1930)

El presente volumen reúne las obras más representativas del teatro rioplatense y ofrece un panorama general de un ciclo dramático coherente y original dentro del teatro de América Latina que se extendió por más de medio siglo. Esta edición incluye las siguientes piezas: Juan Moreira, de Eduardo Gutiérrez y José Podestá; Calandria, de Martiniano Leguizamón; Los políticos, de Nemesio Trejo; Canillita y Barranca abajo, de Florencio Sánchez; Las de Barranco, de Gregorio de Laferrere; El león ciego, de Ernesto Herrera; Los escrushantes, de Alberto Vacarezza; La montaña de las brujas, de Julio Sánchez Gardel; Babilonia, de Armando Discépolo; y He visto a Dios, de Francisco Defilippis Novoa