9 research outputs found
A fast Metropolis-Hastings method for generating random correlation matrices
We propose a novel Metropolis-Hastings algorithm to sample uniformly from the
space of correlation matrices. Existing methods in the literature are based on
elaborated representations of a correlation matrix, or on complex
parametrizations of it. By contrast, our method is intuitive and simple, based
the classical Cholesky factorization of a positive definite matrix and Markov
chain Monte Carlo theory. We perform a detailed convergence analysis of the
resulting Markov chain, and show how it benefits from fast convergence, both
theoretically and empirically. Furthermore, in numerical experiments our
algorithm is shown to be significantly faster than the current alternative
approaches, thanks to its simple yet principled approach.Comment: 8 pages, 3 figures, 2018 conferenc
Efflux in Fungi: La Pièce de Résistance
Pathogens must be able to overcome both host defenses and antimicrobial treatment in order to successfully infect and maintain colonization of the host. One way fungi accomplish this feat and overcome intercellular toxin accumulation is efflux pumps, in particular ATP-binding cassette transporters and transporters of the major facilitator superfamily. Members of these two superfamilies remove many toxic compounds by coupling transport with ATP hydrolysis or a proton gradient, respectively. Fungal genomes encode a plethora of members of these families of transporters compared to other organisms. In this review we discuss the role these two fungal superfamilies of transporters play in virulence and resistance to antifungal agents. These efflux transporters are responsible not only for export of compounds involved in pathogenesis such as secondary metabolites, but also export of host-derived antimicrobial compounds. In addition, we examine the current knowledge of these transporters in resistance of pathogens to clinically relevant antifungal agents