Reconstruction of three-dimensional porous media using generative adversarial neural networks

To evaluate the variability of multi-phase flow properties of porous media at the pore scale, it is necessary to acquire a number of representative samples of the void-solid structure. While modern x-ray computer tomography has made it possible to extract three-dimensional images of the pore space, assessment of the variability in the inherent material properties is often experimentally not feasible. We present a novel method to reconstruct the solid-void structure of porous media by applying a generative neural network that allows an implicit description of the probability distribution represented by three-dimensional image datasets. We show, by using an adversarial learning approach for neural networks, that this method of unsupervised learning is able to generate representative samples of porous media that honor their statistics. We successfully compare measures of pore morphology, such as the Euler characteristic, two-point statistics and directional single-phase permeability of synthetic realizations with the calculated properties of a bead pack, Berea sandstone, and Ketton limestone. Results show that GANs can be used to reconstruct high-resolution three-dimensional images of porous media at different scales that are representative of the morphology of the images used to train the neural network. The fully convolutional nature of the trained neural network allows the generation of large samples while maintaining computational efficiency. Compared to classical stochastic methods of image reconstruction, the implicit representation of the learned data distribution can be stored and reused to generate multiple realizations of the pore structure very rapidly.Comment: 21 pages, 20 figure

Uncovered diversity of a predominantly andean butterfly clade in the brazilian atlantic forest : a revision of the genus praepedaliodes forster (Lepidoptera: Nymphalidae, Satyrinae, Satyrini)

The genus Praepedaliodes Forster, 1964, the only representative of the mega-diverse mostly Andean Pedaliodes complex lineage in the Brazilian Atlantic Forest, is revised. Prior to this study, four species were known, P. phanias (Hewitson, 1862), P. granulata (Butler, 1868), P. amussis (Thieme, 1905) and P. exul (Thieme, 1905). Here, a further six are described, all from SE Brazil, expanding to 10 the number of species in this genus. Lectotypes are designated for P. phanias, P. granulata and P. amussis. The genus is most diverse in the Serra da Mantiqueira (São Paulo, Rio de Janeiro, Minas Gerais) and in the Serra Geral (Paraná, Santa Catarina) with seven species occurring in both ranges. Praepedaliodes phanias is the most widespread species and the only one found in the western part of the Atlantic Forest; only this species and P. duartei Dias, Dolibaina & Pyrcz n. sp. occurring to near sea level. Other species, P. zaccae Dolibaina, Dias & Pyrcz n. sp., P. francinii Freitas & Pyrcz n. sp., P. sequeirae Pyrcz, Dias & Dolbaina n. sp., P. landryi Pyrcz & Freitas n. sp. and P. pawlaki Pyrcz & Boyer n. sp. are strictly montane and the highest species richness is reached at 1400–1800 m. One species, P. sequeirae n. sp., is a narrow endemic found only at timberline in the Agulhas Negras massif above 2300 m. Immature stages are described for two species, P. phanias and P. landryi n. sp. Molecular data (barcode region of cytochrome oxidase, subunit I) and adult morphology, including male and female genitalia, support the genus as monophyletic, belonging to a predominantly Andean clade of the Pedaliodes Butler, 1867 complex. Morphological evidences, in particular female genitalia comparative analysis, indicate the genera Physcopedaliodes Forster, 1964 and Panyapedaliodes Forster, 1964 as possibly the closest relatives to Praepedaliodes. Molecular data are inconclusive in this respect472211255CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP302585/2011-7, 303834/2015-3; 563332/2010-7; 41143/2009-6; 150542/2013-5; 308247/2013-2; 304639/2014-1Não tem2016/15873-8; 2011/50225-3; 2013/50297-0We would like to express our gratitude the following persons who contributed at different stages in the elaboration of this paper: Alfred Moser (Porto Alegre), Ronaldo Francini (UNISANTOS) and André Tacioli, Junia Y. O. Carreira, Jessie P. Santos and Ana K. Silva (Unicamp) for logistical help in the field, comparison material and hosting Tamara M. C. Aguiar spread most of the adult DNA vouchers and the old material collected by K. S. Brown Jr. The following people helped by sending material and information: Roberto R. Greve (Foz do Iguaçu), Richard Raby (Serra da Bocaina), Augusto H. B. Rosa (Mantiqueira region), Geanne C. N. Pereira (Serra do Cipó) and Keith S. Brown Jr. (several places in SE Brazil). The authors also thank the ICMBio for the permits (#10438-1, #26712-4 and #10802-9), the CNPq by aproving our Scientific Expedition (portaria N° 240, de 11 de março de 2014) and all managers of the Conservation Unities visited during the development of the present study, in special Waldomiro P. Lopes (Parque Nacional do Caparaó), Léo Nascimento (Parque Nacional do Itatiaia), Mara P. Pais (Parque Nacional da Serra da Bocaina), Ingo Grantsau (Paranapiacaba) and Cecilia Cronemberger (Parque Nacional da Serra dos Órgãos). EPB thanks Fundação de Amparo à Pesquisa no Estado de São Paulo (FAPESP) for a Post-doc fellowship (2016/15873-8). AVLF thanks the CNPq (fellowships 302585/2011-7, 303834/2015-3 and SISBIOTABrasil/CNPq - 563332/2010-7), the National Science Foundation (DEB-1256742), the “Rede Nacional de Identificação Molecular da Biodiversidade - BR-BoL” (MCT/CNPq/FNDCT 50/2010) and the BIOTA-FAPESP Program (2011/50225-3 and 2013/50297-0). Kim Garwood kindly provided the photographs of two species of Praepedaliodes in their natural habitat. Keith Willmott read the manuscript and added several valuable suggestions. Carlos Prieto provided the photograph of the syntype of Praepedaliodes amussis. TWP field work in SE Brazil was supported by MZ/IZ/UJ internal grants. FMSD, DRD, OHHM and MMC thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Edital 15/2014 CAPES/EMBRAPA) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, 141143/2009-6, 150542/2013-5, 308247/2013-2, 304639/2014-1), for the fellowships granted to the author