Evolutionary Meta Layout of Graphs

A graph drawing library is like a toolbox, allowing experts to select and configure a specialized algorithm in order to meet the requirements of their diagram visualization application. However, without expert knowledge of the algorithms the potential of such a toolbox cannot be fully exploited. This gives rise to the question whether the process of selecting and configuring layout algorithms can be automated such that good layouts are produced. In this paper we call this kind of automation "meta layout." We propose a genetic representation that can be used in meta heuristics for meta layout and contribute new metrics for the evaluation of graph drawings. Furthermore, we examine the use of an evolutionary algorithm to search for optimal solutions and evaluate this approach both with automatic experiments and a user study. The results confirm that our methods can actually help users to find good layout configurations

Multiscale characterization of an extensive stromatolites field: a new correlation horizon for the Crato Member, Araripe Basin, Brazil

There is wide recognition of lacustrine sediments as excellent archives of a basin’s depositional history due to their high sensitivity to environmental changes. Among them, microbial limestones are one of the most valuable tools for paleoenvironmental reconstruction, because the biological agents responsible for their genesis tend to respond to short-lived variations of the depositional setting creating specific precipitation patterns. We here document and investigate the sedimentary features of a specific sedimentary layer, remarkable by the extraordinary lateral continuity of its textural attributes over kilometer distances. This marker horizon occurs among the first carbonate layers of the Crato Member (Aptian, Araripe Basin, NE Brazil), commonly assigned a paleolacustrine system. We build on a multiscale comparative analysis (mesoscale, microscale, and chemical) to outline the main processes and paleoenvironmental settings that prompted this interval’s widespread and laterally nearly uniform deposition. A lamination pattern identified in different well cores was scrutinized and compared, and shows striking lateral continuity attesting to autochthonous biologically induced mineralization as the primary mechanism of the formation of the microbialites. Compositional and stable-isotope results also show similar trends throughout the well cores, where minor differences represent the influence of local processes. The studied interval encompasses the relatively swift transition of organic shales rich in ostracod valves to planar stromatolites, where both developed in the anoxic benthonic zone of a freshwater lake. The precipitation of the overlying thinly laminated limestones is related to a change in the carbonate genetic mechanism as a response to a more stable lacustrine stratification. The widespread formation of microbialites preserving an almost identical textural pattern must be related to a regional event, constituting a rare example of a preserved ancient biostrome. Moreover, the investigation of this sedimentary layer can further contribute to determining the roles of different biotic and abiotic processes in microbialite precipitation over large areas

Diet of two syntopic species of Crenuchidae (Ostariophysi: Characiformes) in an Amazonian rocky stream

Abstract This study assessed the diet of two poorly known syntopic fish species of the family Crenuchidae, Characidium aff. declivirostre and Leptocharacidium omospilus, in a Presidente Figueiredo´ rocky stream, Amazonas, Brazil. The stomach contents were analyzed and their Frequency of Occurrence (FO %) and Relative Volume (Vol %) were combined in a Feeding Index (IAi). We examined 20 individuals of C. aff. declivirostre and 23 of L. omospilus. The Morisita-Horn Index was used to estimate the overlap between the diets of these species. Immature insects were the most valuable items consumed by both fish species. The diet of C. aff. declivirostre was mainly composed of larvae and pupae of Chironomidae, while L. omospilus predominantly consumed larvae of Hydroptilidae, Hydropyschidae and Pyralidae. Thus, both species were classified as autochthonous insectivorous. Characidium aff. declivirostre was considered a more specialized species, probably reflecting lower feeding plasticity or the use of more restricted microhabitats compared to L. omospilus. When the food items were analyzed at the family taxonomic level, the diet overlap between these species was considered moderate (Morisita-Horn Index = 0.4). However, a more thorough analysis, at the genus level, indicates a very low diet overlap. Therefore, we conclude that the feeding segregation between C. aff. declivirostre and L. omospilus may favor their co-existence, despite their high phylogenetic closeness