Approximate Bayesian Computation by Modelling Summary Statistics in a Quasi-likelihood Framework

Approximate Bayesian Computation (ABC) is a useful class of methods for Bayesian inference when the likelihood function is computationally intractable. In practice, the basic ABC algorithm may be inefficient in the presence of discrepancy between prior and posterior. Therefore, more elaborate methods, such as ABC with the Markov chain Monte Carlo algorithm (ABC-MCMC), should be used. However, the elaboration of a proposal density for MCMC is a sensitive issue and very difficult in the ABC setting, where the likelihood is intractable. We discuss an automatic proposal distribution useful for ABC-MCMC algorithms. This proposal is inspired by the theory of quasi-likelihood (QL) functions and is obtained by modelling the distribution of the summary statistics as a function of the parameters. Essentially, given a real-valued vector of summary statistics, we reparametrize the model by means of a regression function of the statistics on parameters, obtained by sampling from the original model in a pilot-run simulation study. The QL theory is well established for a scalar parameter, and it is shown that when the conditional variance of the summary statistic is assumed constant, the QL has a closed-form normal density. This idea of constructing proposal distributions is extended to non constant variance and to real-valued parameter vectors. The method is illustrated by several examples and by an application to a real problem in population genetics.Comment: Published at http://dx.doi.org/10.1214/14-BA921 in the Bayesian Analysis (http://projecteuclid.org/euclid.ba) by the International Society of Bayesian Analysis (http://bayesian.org/

Optimization and mechanisms for biodecoloration of a mixture of dyes by Trichosporon akiyoshidainum HP 2023

Trichosporon akiyoshidainum HP2023 is a basidiomycetous yeast isolated from Las Yungas rainforest (Tucumán, Argentina) and selected based on its outstanding textile-dye-decolorizing ability. In this work, the decolorization process was optimized using Reactive Black 5 as dye model. Lactose and urea were chosen as carbon and nitrogen sources through a one-at-time approach. Afterwards, factorial designs were employed for medium optimization, leading to the formulation of a simpler optimized medium which contains in g L−1: lactose 10, yeast extract 1, urea 0.5, KH2PO4 1 and MgSO4 1. Temperature and agitation conditions were also optimized. The optimized medium and incubation conditions for dye removal were extrapolated to other dyes individually and a mixture of them. Dye removal process happened through both biosorption and biodegradation mechanisms, depending primarily on the dye structure. A positive relation between initial inoculum and dye removal rate and a negative relation between initial dye concentration and final dye removal percentages were found. Under optimized conditions, T. akiyoshidainum HP2023 was able to completely remove a mixture of dyes up to a concentration of 300 mg L−1, a concentration much higher than those expected in real effluents.Fil: Martorell, María Martha. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Direccion Nacional del Antártico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rosales Soro, Maria del Milagro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Planta Piloto de Procesos Industriales Microbiologicos; ArgentinaFil: Pajot, Hipolito Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Planta Piloto de Procesos Industriales Microbiologicos; ArgentinaFil: Castellanos, Lucia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Planta Piloto de Procesos Industriales Microbiologicos; Argentin

Opinion formation by belief propagation: A heuristic to identify low-credible sources of information

With social media, the flow of uncertified information is constantly increasing, with the risk that more people will trust low-credible information sources. To design effective strategies against this phenomenon, it is of paramount importance to understand how people end up believing one source rather than another. To this end, we propose a realistic and cognitively affordable heuristic mechanism for opinion formation inspired by the well-known belief propagation algorithm. In our model, an individual observing a network of information sources must infer which of them are reliable and which are not. We study how the individual's ability to identify credible sources, and hence to form correct opinions, is affected by the noise in the system, intended as the amount of disorder in the relationships between the information sources in the network. We find numerically and analytically that there is a critical noise level above which it is impossible for the individual to detect the nature of the sources. Moreover, by comparing our opinion formation model with existing ones in the literature, we show under what conditions people's opinions can be reliable. Overall, our findings imply that the increasing complexity of the information environment is a catalyst for misinformation channels

Les importacions etrusques del segle V a.C. al nord-est peninsular i el comerç mediterrani

Afí d'ubicar geogràfica i històricament les importacions etrusques del segle V a.e. al nord-est peninsular, partim d'un estudi actualitzat deis objectes en si i de llur context arqueològic. Tot seguit, observem quina és la situació històrica a Etrúria, tenint en compte els esdeveniments interns i la seva política comercial. A través de l'anillisi de les influències púniques i gregues en les nostres terres, esbossem la situació interna de la societat ibèrica, receptora d'aquestes importacions mediterranies. És així com arribem a tenir una visió força completa de tot el procés que segueixen els diversos productes etruscs i com en podem treure conclusions tant pel que fa al context de fabricació i exportació com pe! que fa al moment d'arribada a la Península Iberica. _____________________________________________ Dans le but de situer geographiquement et historiquement les importations étrusques du Veme siecle ay. Je. du nord-est de la Péninsule Ibérique, nous proposons une étude mise a jour de ces différents objets ainsi que de leur contexte archéologique. Nous examinons ensuite quelle est la situation historique en Etrurie en tenant compte des évenements internes et de sa politique commerciale. A partir de l'analyse des influences puniques et grecques dans la zone étudiée, nous observons la situation interne de la société ibérique, réceptrice de ces importations méditerranéennes. Arrivés a ce point, nous disposons d'une vision assez large de tout le chemin suivit par les produits étrusques et nous sommes, donc, capables d' en tirer des conclusions sur leur contexte de fabrication et exportation mais aussi sur leur moment d'arrivée a la Péninsule Ibérique

Inferential revision in narrative texts:an ERP study

We evaluated the process of inferential revision during text comprehension in adults. Participants with high or low working memory read short texts, in which the introduction supported two plausible concepts (e.g., ‘guitar/violin’), although one was more probable (‘guitar’). There were three possible continuations: a neutral sentence, which did not refer back to either concept; a no revise sentence, which referred to a general property consistent with either concept (e.g., ‘…beautiful curved body’); and a revise sentence, which referred to a property that was consistent with only the less likely concept (e.g., ‘…matching bow’). Readers took longer to read the sentence in the revise condition, indicating that they were able to evaluate their comprehension and detect a mismatch. In a final sentence, a target noun referred to the alternative concept supported in the revise condition (e.g., ‘violin’). ERPs indicated that both working memory groups were able to evaluate their comprehension of the text (P3a), but only high working memory readers were able to revise their initial incorrect interpretation (P3b) and integrate the new information (N400) when reading the revise sentence. Low working memory readers had difficulties inhibiting the no longer relevant interpretation and thus failed to revise their situation model, and they experienced problems integrating semantically related information into an accurate memory representation

Rediseño humedal artificial para depuración de aguas residuales y reúso: modelo didáctico laboratorio de recursos hídricos Universidad Católica de Colombia

Trabajo de investigaciónEn esta investigación son presentados los resultados del rediseño del prototipo de humedal artificial, que sirve como modelo didáctico para laboratorio. Donde se ha llevado a cabo investigaciones, para el desarrollo de sistemas de tratamiento de agua al interior del Semillero de Investigación EcoCivil. Este diseño tiene como propósito la depuración de agua residual del río Arzobispo y la reutilización de esta para riego de plantas.MARCO CONCEPTUAL RESUMEN 1. INTRODUCCIÓN 2. DIAGNÓSTICO PROCESO DE DISEÑO MODELO HUMEDAL ARTIFICIAL 2012 3. REDISEÑO PROTOTIPO HUMEDAL ARTIFICIAL. 4. EFICIENCIA DEL SISTEMA DE DEPURACIÓN DE AGUAS RESIDUALES DADO POR EL HUMEDAL ARTIFICIAL REDISEÑADO 5. CONCLUSIONES Y RECOMENDACIONES ANEXOS BIBLIOGRAFÍAPregradoIngeniero Civi

Evaluation of VirB binding site contribution to the regulation of the icsP promoter in Shigella flexneri

Shigella species are gram-negative, rod-shaped bacteria that are closely related to Escherichia coli. Virulent Shigella spp. are intracellular pathogens that invade, replicate and spread through epithelial cells of the lower intestine and cause bacillary dysentery in humans. This disease is characterized by a robust inflammatory response that results in fever, abdominal pain, and bloody diarrhea (3). According to the CDC, approximately 14,000 cases are reported each year in the United States alone. This number however, does not reflect the actual incidence of this disease as many cases go unreported. The molecular pathogenesis of these bacteria lies in the large virulence plasmid (~230-kb) that is found in all virulent Shigella spp. Two key virulence determinants include the ability to invade colonic epithelia (mediated by the ipa-mxi-spa gene locus) and the ability to spread to adjacent cells, a process known as actin-based-motility (mediated and controlled by icsA and icsP respectively). These events are largely regulated by VirB, a transcription factor (2, 3). Canonically, transcription factors are known to bind sequences proximal to the transcriptional start site (within 200-bp). Recent work has focused on the regulation of icsP (encodes a protease of the outer membrane) by VirB and has shed light on a novel regulatory strategy, whereby VirB regulates the activation of icsP from sites located more than 1-kb upstream of the transcriptional start site (1). Nine putative VirB binding sites have been found upstream of the icsP gene. This work seeks to characterize the contribution made by these putative binding sites to the VirB-dependent regulation of icsP