Orthogonal parallel MCMC methods for sampling and optimization

Monte Carlo (MC) methods are widely used for Bayesian inference and optimization in statistics, signal processing and machine learning. A well-known class of MC methods are Markov Chain Monte Carlo (MCMC) algorithms. In order to foster better exploration of the state space, specially in high-dimensional applications, several schemes employing multiple parallel MCMC chains have been recently introduced. In this work, we describe a novel parallel interacting MCMC scheme, called {\it orthogonal MCMC} (O-MCMC), where a set of "vertical" parallel MCMC chains share information using some "horizontal" MCMC techniques working on the entire population of current states. More specifically, the vertical chains are led by random-walk proposals, whereas the horizontal MCMC techniques employ independent proposals, thus allowing an efficient combination of global exploration and local approximation. The interaction is contained in these horizontal iterations. Within the analysis of different implementations of O-MCMC, novel schemes in order to reduce the overall computational cost of parallel multiple try Metropolis (MTM) chains are also presented. Furthermore, a modified version of O-MCMC for optimization is provided by considering parallel simulated annealing (SA) algorithms. Numerical results show the advantages of the proposed sampling scheme in terms of efficiency in the estimation, as well as robustness in terms of independence with respect to initial values and the choice of the parameters

Breathing synchronization in interconnected networks

Global synchronization in a complex network of oscillators emerges from the interplay between its topology and the dynamics of the pairwise interactions among its numerous components. When oscillators are spatially separated, however, a time delay appears in the interaction which might obstruct synchronization. Here we study the synchronization properties of interconnected networks of oscillators with a time delay between networks and analyze the dynamics as a function of the couplings and communication lag. We discover a new breathing synchronization regime, where two groups appear in each network synchronized at different frequencies. Each group has a counterpart in the opposite network, one group is in phase and the other in anti-phase with their counterpart. For strong couplings, instead, networks are internally synchronized but a phase shift between them might occur. The implications of our findings on several socio-technical and biological systems are discussed.Comment: 7 pages, 3 figures + 3 pages of Supplemental Materia

Critical Cooperation Range to Improve Spatial Network Robustness

A robust worldwide air-transportation network (WAN) is one that minimizes the number of stranded passengers under a sequence of airport closures. Building on top of this realistic example, here we address how spatial network robustness can profit from cooperation between local actors. We swap a series of links within a certain distance, a cooperation range, while following typical constraints of spatially embedded networks. We find that the network robustness is only improved above a critical cooperation range. Such improvement can be described in the framework of a continuum transition, where the critical exponents depend on the spatial correlation of connected nodes. For the WAN we show that, except for Australia, all continental networks fall into the same universality class. Practical implications of this result are also discussed

Dung beetle diversity and functions suggest no major impacts of cattle grazing in the Brazilian Pantanal wetlands

1. Dung beetles perform relevant ecological functions in pastures, such as dung removal and parasite control. Livestock farming is the main economic activity in the Brazilian Pantanal. However, the impact of cattle grazing on the Pantanal's native dung beetle community, and functions performed by them, is still unknown. 2. This study evaluated the effects of cattle activity on dung beetle community attributes (richness, abundance, biomass, composition, and functional group) as well as their ecological functions (dung removal and soil bioturbation) in the Pantanal. In January/February 2016, dung beetles were sampled and their ecological functions measured in 16 sites of native grasslands in Aquidauana, Mato Grosso do Sul, Brazil, 10 areas regularly grazed by cattle and six control ungrazed areas (> 20 years of abandonment). 3. In all, 1169 individuals from 30 species of dung beetles were collected. Although abundance, species richness, and biomass did not differ between grasslands with and without cattle activity, species composition and functional groups differed among systems. Large roller beetles were absent from non-cattle grasslands, and the abundance, richness, and biomass of medium roller beetles was higher in those systems. 4. Despite causing changes in species/functional group composition, the results of this study show that a density compensation of functional groups in cattle-grazed natural grasslands seems to have conserved the ecological functions (dung removal and soil bioturbation), with no significant differences between systems. 5. Therefore, these results provide evidence that cattle breeding in natural grasslands of the Brazilian Pantanal can integrate livestock production with the conservation of the dung beetle community and its ecological functions. © 2019 The Royal Entomological Societ

Within-tree and between-tree variation of wood density components in cork oak trees in two sites in Portugal

The axial and radial variation of wood density was studied using microdensitometry in cork oaks ( Quercus suber ) in two sites in Portugal. The observations were made in mature trees under cork production and in juvenile trees before the fi rst cork extraction, at three height levels (stem base, 1.3 m and before stem bifurcation). The cork oak wood revealed a very high mean density (0.884 – 1.068 g cm 3 ). Differences between earlywood and latewood were small (0.866 and 1.061 g cm 3 , respectively). Latewood corresponded on average to 61 per cent of the total. The variation of density between trees was statistically highly signifi cant, but no differences were found between the two sites. The within-tree axial variation was negligible but the radial direction within a cross-section was one of the main origins of variation of the density components (18 per cent of the total variation). The density decreased from pith to cambium and this radial variation corresponded to 19 – 24 per cent of the total variation of wood density. Overall, the magnitude of density variations between and within cork oaks was small and an advantageous factor for their use for quality wood productsinfo:eu-repo/semantics/publishedVersio

Biodiversity in tropical plantations is influenced by surrounding native vegetation but not yield:A case study with dung beetles in Amazonia

Human-modified forests, including plantations and managed forest, will be a major component of tropical landscapes in the near future. To conserve biodiversity across modified tropical landscapes we must first understand what influences diversity in planted areas. We studied dung beetle communities in Eucalyptus plantations to assess the influence of local (canopy openness and soil texture)and landscape factors (surrounding native forest cover)on taxonomic and functional diversity, and to determine whether biodiversity in plantations is affected by timber production. Dung beetle community composition in Eucalyptus plantations was largely explained by the surrounding native forest cover, as Simpson's diversity and functional diversity (Rao's quadratic entropy)increased with the extent of native forest in buffer areas. However, the abundance of dung beetle species associated with native forest was not explained by any of the explanatory variables. The coarse sand content of the soil explained much of the functional similarity between plantations and native forests, as well as variation in dung beetle community structure. The total abundance of dung beetles in plantations increased with coarse sand content, whereas body mass declined, and dung beetle abundance and functional originality decreased with canopy openness. Timber production intensity did not explain the variation in any of the measured diversity parameters. If enhancing biodiversity in plantations is a management goal, then these results highlight the importance of restoring or retaining native forest areas in modified landscapes. They also suggest that integrated management could improve biodiversity in Eucalyptus plantations without reducing timber production. © 2019 Elsevier B.V

First Report On Dung Beetles In Intra-amazonian Savannahs In Roraima, Brazil

This is the first study to address the dung beetle (Coleoptera: Scarabaeidae: Scarabaeinae) diversity in intra-Amazonian savannahs in the state of Roraima, Brazil. Our aim was to survey the dung beetle fauna associated with these savannahs (regionally called ‘lavrado’), since little is known about the dung beetles from this environment. We conducted three field samples using pitfall traps baited with human dung in savannah areas near the city of Boa Vista during the rainy seasons of 1996, 1997, and 2008. We collected 383 individuals from ten species, wherein six have no previous record in intra-Amazonian savannahs. The most abundant species were Ontherus appendiculatus (Mannerheim, 1829), Canthidium aff. humerale (Germar, 1813), Dichotomius nisus (Olivier, 1789), and Pseudocanthon aff. xanthurus (Blanchard, 1846). We believe that knowing the dung beetles diversity associated with the intra-Amazonian savannahs is ideal for understanding the occurrence and distribution of these organisms in a highly threatened environment, it thus being the first step towards conservation strategy development. © 2016, Universidade Estadual de Campinas UNICAMP. All rights reserved.16

Caracterização de paredes tradicionais de tabique

Neste artigo discutem-se aspectos construtivos relacionados com as paredes divisórias tradicionais de tabique, de forma a contribuir para um conhecimento mais aprofundado sobre este tipo de elementos, que são parte integrante de um estilo de construção marcante no panorama do património construído português que imperou até inícios do século XX. Informação relativa aos materiais utilizados e às soluções construtivas adoptadas é fornecida e descrita. Simultaneamente, algumas propriedades físicas avaliadas também são apresentadas com a intenção de auxiliar processos de reabilitação e outros trabalhos de investigação que visem o estudo de soluções construtivas alternativas de paredes divisórias, tendo em conta que o tabique pode ser uma técnica construtiva sustentável, económica e versátil

Efeito da umidade do solo na biologia de Rhopalosiphum maidis (FITCH, 1856) (Hemiptera: aphididae) em milho.

O efeito da umidade do solo na biologia de Rhopalosiphum maidis (Fitch) em plantas de milho (Zea mays) foi avaliado em casa de vegetação. Foi utilizado o delineamento experimental inteiramente casualizado, com três tratamentos (20%, 40% e 100% de rotação hídrica) e quatro repetições, sendo cada parcela experimental constituída por um vaso de polietileno de cinco litros contendo duas plantas de milho no estádio fenológico três e com dez pulgões adultos confinados em microgaiolas de 10 mm de altura por 10 mm de diâmetro (cinco pulgões/microgaiola/planta), perfazendo um total de 40 pulgões/tratamento. As variáveis biológicas do pulgão estudadas foram: a duração de cada instar, dos períodos pré-reprodutivo, pós-reprodutivo e reprodutivo, a produção diária, total de ninfas e de alados e o ciclo de vida de R. maidis. Houve efeito da umidade do solo onde estavam as plantas de milho, tanto na duração do desenvolvimento dos pulgões, em cada um dos quatro ínstares, quanto na duração da fase ninfal, sendo que os pulgões que se desenvolveram em plantas de milho com défice de água de 80% completaram os estádios ninfais num menor período. De igual forma, o período reprodutivo e a longevidade dos adultos foram mais curtos nos pulgões que se desenvolveram em plantas de milho em solo com 20% da capacidade de campo. Porém, não houve efeito dos tratamentos na duração do período pós-reprodutivo. Por outro lado, adultos de pulgões que se desenvolveram nas plantas em solo com 20% da água necessária produziram a primeira ninfa num menor período do que os desenvolvidos nas plantas que receberam 40% de água na capacidade de campo. Pulgões cuja fase jovem ocorreu em plantas de milho sob estresse hídrico de 80% desapareceram mais rapidamente do que aqueles desenvolvidos em plantas sob regime de estresse hídrico de 60%. Esses resultados indicam que o manejo da água no milho pode ser uma estratégia no controle de fatores naturais que afetam tanto a população como o número de gerações do pulgão no ambiente, podendo reduzir a necessidade do controle químico