519 research outputs found

    Toward an automatic full-wave inversion: Synthetic study cases

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    Full-waveform inversion (FWI) in seismic scenarios continues to be a complex procedure for subsurface imaging that might require extensive human interaction in terms of model setup, constraints, and data preconditioning. The underlying reason is the strong nonlinearity of the problem that forces the addition of a priori knowledge (or bias) in order to obtain geologically sound results. In particular, when the use of a long-offset receiver is not possible or may not favor the reconstruction of the fine structure of the model, one needs to rely on reflection data. As a consequence, the inversion process is more prone to becoming stuck in local minima. Nevertheless, misfit functionals can be devised that can either cope with missing long-wavenumber features of initial models (e.g., cross-correlation-based misfit) or invert reflection-dominated data whenever the models are sufficiently good (e.g., normalized offset-limited least-squares misfit). By combining both, high-frequency data content with poor initial models can be successfully inverted. If one can figure out simple parameterizations for such functionals, the amount of uncertainty and manual work related to tuning FWI would be substantially reduced. Thus, FWI might become a semiautomatized imaging tool.We want to thank Repsol for funding this research by means of the Aurora project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 644202. Additionally, the research leading to these results has received funding from the European Union’s Horizon 2020 Programme (2014-2020) and from Brazilian Ministry of Science, Technology and Innovation through Rede Nacional de Pesquisa (RNP) under the HPC4E Project (www.hpc4e.eu), grant agreement No 689772. We acknowledge Chevron for the dataset that was used in our second example.Peer ReviewedPostprint (author's final draft

    Vigilance by Sentinels in a group of baboons (Papio hamadryas hamadryas) in a zoo setting

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    Vigilance by sentinels is an anti-predator strategy by which certain group members keep watch from strategic positions, while the group is involved in other activities. Many anti-predatory behavior patterns observed in natural habitats are also deployed similarly when provoked by human presence. This work is part of a study conducted with a group of hamadryas baboons (Papio h. hamadryas) in semi-freedom in a 15-hectare zoo complex with extensive human pressure. The animals make incursions into an adjoining high-risk area to access food resources, making use of vigilance with sentinels and other risk minimization strategies. Results reveal that human presence provokes similar reactions to natural predatory pressure, forcing them to select strategies to minimize the factors involved in risk perception, such as the degree of visibility of the surroundings, minimizing the length of the incursion and behavioral restrictions

    Proof of concept: could snake venoms be a potential source of bioactive compounds for control of mould growth and mycotoxin production

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    © 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.The objective was to screen 10 snake venoms for their efficacy to control growth and mycotoxin production by important mycotoxigenic fungi including Aspergillus flavus, Aspergillus westerdijkiae, Penicillium verrucosum, Fusarium graminearum and F. langsethiae. The Bioscreen C rapid assay system was used. The venoms from the Viperidae snake family delayed growth of some of the test fungi, especially F. graminearum and F. langsethiae and sometimes A. flavus. Some were also able to reduce mycotoxin production. The two most potent crude snake venoms (Naja nigricollis and N. siamensis; 41 and 43 fractions, respectively) were further fractionated and 83/84 of these fractions were able to reduce mycotoxin production by >90% in two of the mycotoxigenic fungi examined. This study suggests that there may be significant potential for the identification of novel fungistatic/fungicidal bioactive compounds as preservatives of raw and processed food commodities post-harvest from such snake venoms.Peer reviewedFinal Published versio

    Improvements of the particle-in-cell code EUTERPE for petascaling machines

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    In the present work we report some performance measures and computational improvements recently carried out using the gyrokinetic code EUTERPE (Jost, 2000 [1] and Jost et al., 1999 [2]), which is based on the general particle-in-cell (PIC) method. The scalability of the code has been studied for up to sixty thousand processing elements and some steps towards a complete hybridization of the code were made. As a numerical example, non-linear simulations of Ion Temperature Gradient (ITG) instabilities have been carried out in screw-pinch geometry and the results are compared with earlier works. A parametric study of the influence of variables (step size of the time integrator, number of markers, grid size) on the quality of the simulation is presented.Fil: Sáez, Xavier. Barcelona Supercomputing Center - Centro Nacional de Supercomputacion; EspañaFil: Soba, Alejandro. Barcelona Supercomputing Center - Centro Nacional de Supercomputacion; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sánchez, Edilberto. No especifíca;Fil: Kleiber, Ralf. No especifíca;Fil: Castejón, Francisco. No especifíca;Fil: Cela, José M.. Barcelona Supercomputing Center - Centro Nacional de Supercomputacion; Españ

    Catálogo de la familia Orchidaceae en Guinea Ecuatorial

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    The current state of knowledge on Orchidaceae in Equatorial Guinea is provided, based on herbarium collections and bibliographic revision. Orchidaceae are represented in Equatorial Guinea (Annobon, Bioko and Rio Muni) by 225 taxa, and 12 more requiring confirmation, belonging to 43 genera and 10 tribes of the subfamilies Vanilloideae, Orchidoideae and Epidendroideae. Eighty eight taxa have been added for Rio Muni to the previous checklists. The tribe Vandeae is the best represented with 118 taxa. Analysing the habit, 53 taxa are terrestrial, 6 scandent and 166 are epiphytes. The island of Bioko and the western provinces of Rio Muni show the major diversity in orchids. Thirty one species have been described from materials collected in Equatorial Guinea, six of which are considered endemics.Se presenta un catálogo actualizado de las especies y táxones infraespecíficos de la familia Orchidaceae en Guinea Ecuatorial, obtenido a partir de testimonios de herbario y revisión bibliográfica. Nuestros resultados indican la presencia de 225 táxones más 12 que requieren confirmación en el conjunto del territorio (Annobón, Bioko y Río Muni), incluidos en 43 géneros y 10 tribus pertenecientes a las subfamilias Vanilloideae, Orchidoideae y Epidendroideae. Se aportan 88 táxones más en el catálogo de Río Muni respecto a publicaciones precedentes. La tribu Vandeae es la más representada, con 118 táxones. Atendiendo al hábito, 53 táxones son terrestres, seis son trepadores y 166 son epífitos. La mayor riqueza de orquídeas se manifiesta en la isla de Bioko y en las provincias occidentales de Río Muni. De las 31 especies descritas sobre materiales ecuatoguineanos, seis son consideradas endemismos de Guinea Ecuatorial

    Assessing Overall Diet Quality: Development and Evaluation of the Performance of a Short Self-Administrated Questionnaire SCASA.

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    Several tools assessing diet quality have been developed over the last decades, but their use in public health and clinical practice is limited because they necessitate detailed quantitative assessment of food intake. Our goal was to develop and validate a score (Score d'Alimentation Saine, SCASA) based on a short self-administrated online questionnaire to assess overall diet quality. SCASA targets the adult population in French-speaking Switzerland, but it was designed in a way enabling its adaptation for other regions. The choice of the items involved experts and lay volunteers. Construct validation and inter-method reliability were assessed by screening meal plans and by comparing the self-rated scores with food-record derived scores (kappa and Bland-Altman). SCASA (17 components) discriminated adequately balanced from imbalanced meal plans (93-95% and 44-46% of maximal score). Agreement between self-assessed and food record-based scores ranged between >90% (3 items), 80-89% (3 items), 70-79% (4 items), and <70% (5 items). The Bland-Altman plot showed a mean difference of -1.60 (95% CI -2.36 to -0.84), indicating a slight overestimation of the self-assessed diet quality compared to the food record. SCASA offers a reliable way to assess overall diet quality without requiring burdensome data collection or nutrient calculations

    Gene Expression in Trypanosomatid Parasites

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    The parasites Leishmania spp., Trypanosoma brucei, and Trypanosoma cruzi are the trypanosomatid protozoa that cause the deadly human diseases leishmaniasis, African sleeping sickness, and Chagas disease, respectively. These organisms possess unique mechanisms for gene expression such as constitutive polycistronic transcription of protein-coding genes and trans-splicing. Little is known about either the DNA sequences or the proteins that are involved in the initiation and termination of transcription in trypanosomatids. In silico analyses of the genome databases of these parasites led to the identification of a small number of proteins involved in gene expression. However, functional studies have revealed that trypanosomatids have more general transcription factors than originally estimated. Many posttranslational histone modifications, histone variants, and chromatin modifying enzymes have been identified in trypanosomatids, and recent genome-wide studies showed that epigenetic regulation might play a very important role in gene expression in this group of parasites. Here, we review and comment on the most recent findings related to transcription initiation and termination in trypanosomatid protozoa

    Influence of storage environment on maize grain: CO2 production, dry matter losses and aflatoxins contamination

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    Poor storage of cereals, such as maize can lead to both nutritional losses and mycotoxin contamination. The aim of this study was to examine the respiration of maize either naturally contaminated or inoculated with Aspergillus flavus to examine whether this might be an early and sensitive indicator of aflatoxin (AF) contamination and relative storability risk. We thus examined the relationship between different interacting storage environmental conditions (0.80–0.99 water activity (aw) and 15–35°C) in naturally contaminated and irradiated maize grain + A. flavus on relative respiration rates (R), dry matter losses (DMLs) and aflatoxin B1 and B2 (AFB1-B2) contamination. Temporal respiration and total CO2 production were analysed by GC-TCD, and results used to calculate the DMLs due to colonisation. AFs contamination was quantified at the end of the storage period by HPLC MS/MS. The highest respiration rates occurred at 0.95 aw and 30–35°C representing between 0.5% and 18% DMLs. Optimum AFs contamination was at the same aw at 30°C. Highest AFs contamination occurred in maize colonised only by A. flavus. A significant positive correlation between % DMLs and AFB1 contamination was obtained (r = 0.866, p < 0.001) in the irradiated maize treatments inoculated with A. flavus. In naturally contaminated maize + A. flavus inoculum loss of only 0.56% DML resulted in AFB1 contamination levels exceeding the EU legislative limits for food. This suggests that there is a very low threshold tolerance during storage of maize to minimise AFB1 contamination. This data can be used to develop models that can be effectively used in enhancing management for storage of maize to minimise risks of mycotoxin contamination
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