161 research outputs found

    Bartlett and Bartlett-type corrections for censored data from a Weibull distribution

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    In this paper, we obtain the Bartlett factor for the likelihood ratio statistic and the Bartlett-type correction factor for the score and gradient test in censored data from a Weibull distribution. The expressions derived are simple, we only have to define a few matrices. We conduct an extensive Monte Carlo study to evaluate the performance of the corrected tests in small sample sizes and we show how they improve the original versions. Finally, we apply the results to a real data set with a small sample size illustrating that conclusions about the regressors could be different if corrections were not applied to the three mentioned classical statistics for the hypothesis test

    Variabilidade espacial de atributos do solo e produtividade da cultura de cana-de-açúcar em relação a localização topográfica

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    Soils submitted to the same management system in places with little variation of landscape, manifest differentiated spatial variability of their attributes and crop yield. The aim of this work was to investigate the correlation between spatial variability of the soil attributes and sugarcane yield as a result of soil topography. To achieve this objective, a test area of 42 ha located at the São João Sugar Mill, in Araras, in the State of São Paulo, Brazil, was selected. Sugarcane yield was measured with a yield monitor fitted in a sugarcane harvester and GPS signal. A total of 170 soil samples were taken at regular 50 m grid, at a depth of 0 - 0.2 m. The area under study was divided into two sites based on topography. The following soil attributes were analysed: organic matter (OM) content, exchangeable potassium (K), calcium (Ca) and magnesium (Mg), their base saturation percentage (%BS), cation exchange capacity (CEC), pH, clay, silt, total sand and density. The use of landscape and geostatistics enable defining areas with different spatial variability in soil attributes and crop yield, providing the visualization and definition of homogeneous management zones. The largest spatial variability of soil attributes and sugarcane yield was in the lowest part of the field.Solos submetidos ao mesmo sistema de manejo em locais com pequena variação de relevo manifestam variabilidade espacial diferenciada de atributos do solo e das plantas. Objetivou-se com este trabalho estudar a correlação entre a variabilidade espacial de atributos físicos e químicos do solo com a produtividade da cana-de-açúcar em duas posições do relevo, de acordo com a topografia da área. O estudo foi realizado no município de Araras, SP, em uma área de 42 ha, pertencente à Usina São João. Para o mapeamento da produtividade da cultura da cana-de-açúcar utilizou-se um monitor de produtividade acoplado à colhedora e ao sinal de GPS. Coletaram-se 170 amostras do solo, em uma malha regular de 50 m entre pontos, na profundidade de 0,0 - 0,2 m. O talhão de estudo foi dividido em duas áreas menores, segundo a topografia. Os atributos do solo avaliados foram: teor de matéria orgânica (MO), potássio (K), cálcio (Ca), magnésio (Mg), saturação por bases (V%), capacidade de troca catiônica (CTC), pH, argila, silte, areia total e densidade. O uso do relevo e da geoestatística possibilitou definir áreas com diferentes variabilidades espaciais para atributos do solo e produtividade da cultura de cana-de-açúcar, proporcionando a visualização e definição de zonas homogêneas de manejo de acordo com o relevo. A maior variabilidade espacial de atributos do solo e a produtividade da cultura de cana-de-açúcar ocorreram na parte mais baixa do talhão.1250125

    Taxonomic Review of South American Butter Frogs: Phylogeny, Geographic Patterns, and Species Delimitation in the Leptodactylus latrans Species Group (Anura: Leptodactylidae)

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    The Leptodactylus latrans species group currently comprises eight medium- to large-sized frog species with a convoluted taxonomic history, particularly related to the specific limits of the L. latrans complex, and the species pair Leptodactylus chaquensis–Leptodactylus macrosternum. Their homogeneous external morphology and continental geographic distribution in South America have posed severe limitations to a comprehensive review, such that taxonomic consensus and species limits remain uncertain. This is further worsened by the presence of chromatic polymorphism among coexisting species that can hardly be distinguished by external morphology. Based on a large-scale geographic sampling including multilocus DNA analyses, and acoustic and morphological data, we provide a comprehensive evaluation of the taxonomic status and species limits of the L. latrans group, focusing on the resolution of the L. latranscomplex and the species pair L. chaquensis–L. macrosternum. We gathered 728 mitochondrial sequences from 429 localities, encompassing the entire geographic distribution of the group. Both generalized mixed Yule coalescent and automatic barcode gap discovery species delimitation methods recovered four major mitochondrial evolutionary lineages within the L. latrans complex, also supported by distribution patterns, multilocus molecular, morphological and/or bioacoustic data. One lineage is linked to nominal L. latrans,one revalidated as Leptodactylus luctator, and the other two are formally named and described. Another lineage encompasses all specimens previously assigned to the species pair L. chaquensis–L. macrosternum, clustered as a single evolutionary entity and is now regarded as L. macrosternum. We provide a revised diagnosis for these species based on acoustic data, morphological/chromatic variation, and phylogenetic relationships of all species currently included in the L. latrans group. Our findings reinforce the view that Neotropical diversity is highly underestimated and stress that appropriate geographic sampling in an integrative framework is crucial for the establishment of specific limits among broadly distributed and morphologically cryptic Neotropical frogs

    Hippocampal Astrocytes in Migrating and Wintering Semipalmated Sandpiper

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    Seasonal migratory birds return to the same breeding and wintering grounds year after year, and migratory long-distance shorebirds are good examples of this. These tasks require learning and long-term spatial memory abilities that are integrated into a navigational system for repeatedly locating breeding, wintering, and stopover sites. Previous investigations focused on the neurobiological basis of hippocampal plasticity and numerical estimates of hippocampal neurogenesis in birds but only a few studies investigated potential contributions of glial cells to hippocampal-dependent tasks related to migration. Here we hypothesized that the astrocytes of migrating and wintering birds may exhibit significant morphological and numerical differences connected to the long-distance flight. We used as a model the semipalmated sandpipe

    DarkCideS 1.0, a global database for bats in karsts and caves

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    Tanalgo, Krizler C., Tabora, John Aries G., de Oliveira, Hernani Fernandes Magalhães, Haelewaters, Danny, Beranek, Chad T., Otálora-Ardila, Aída, Bernard, Enrico, Gonçalves, Fernando, Eriksson, Alan, Donnelly, Melissa, González, Joel Monzón, Ramos, Humberto Fernández, Rivas, Alberto Clark, Webala, Paul W., Deleva, Stanimira, Dalhoumi, Ridha, Maula, Jaycelle, Lizarro, Dennis, Aguirre, Luis F., Bouillard, Nils, Quibod, Ma. Niña Regina M., Barros, Jennifer, Turcios-Casco, Manfredo Alejandro, Martínez, Marcio, Ordoñez-Mazier, Diego Iván, Orellana, José Alejandro Soler, Ordoñez-Trejo, Eduardo J., Ordoñez, Danny, Chornelia, Ada, Lu, Jian Mei, Xing, Chen, Baniya, Sanjeev, Muylaert, Renata L., Dias-Silva, Leonardo Henrique, Ruadreo, Nittaya, Hughes, Alice Catherine (2022): DarkCideS 1.0, a global database for bats in karsts and caves. Scientific Data 9 (1): 155, DOI: 10.1038/s41597-022-01234-4, URL: http://dx.doi.org/10.1038/s41597-022-01234-

    Variability in herbivore-induced defence signalling across different maize genotypes impacts significantly on natural enemy foraging behaviour

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    ‘Smart’ plants that release volatile defence compounds in response to pest damage, and which recruit beneficial natural enemies, offer an opportunity for exploiting biological control in future crop protection strategies. Using six maize genotypes, Zapalote Chico (‘landrace’), Mirt2A, Sintético Spodoptera (SS), L3, and two commercial hybrids BRS 4103 and BRS 1040, the aim of this work was to evaluate maize responses to larval damage from the fall armyworm Spodoptera frugiperda, a major maize pest in Brazil, and the ability of the egg parasitoid Telenomus remus to respond to HIPVs induced by S. frugiperda damage. Y-tube olfactometer bioassays with T. remus showed preferential responses to the S. frugiperda-induced volatiles of SS and BRS 4103 compared to constitutive volatiles of the same genotypes, but to none of the other genotypes tested. Chemical analysis of maize volatile extracts showed that SS produced more volatile compounds in response to S. frugiperda damage, followed by BRS 4103. In addition, higher levels of mono, homo-, or sesquiterpenes, together with green leaf volatiles (GLVs) were the most attractive blend for T. remus; however, there was no attraction when only GLVs were produced in higher levels. In summary, these results show that volatile defence signalling produced by maize plants due to S. frugiperda damage varies significantly depending on maize genotype and this variability influences T. remus foraging behaviour

    Hidden among bromeliads in the Brazilian semiarid: first records of Phyllopezus lutzae for the Caatinga domain and its predation by Tropidurus hispidus

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    During wildlife rescue and monitoring activities, we recorded 142 individuals of Phyllopezus lutzae in the municipalities of Tucano and Nova Soure, state of Bahia, Northeastern Brazil. These records are the first of this species in the Caatinga domain. Moreover, an adult individual of Tropidurus hispidus was recorded attempting to subdue an adult P. lutzae. Beyond to expand the known distribution range of the species, our records show that P. lutzae inhabits an ecological and climate domain different from Atlantic Forest where it was previously known, and that it is a potential prey of T. hispidus.Asociación Herpetológica Argentin

    Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization

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    Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprecedented sensitivity. We use these data to characterize the frequency dependence of dust emission. We make use of the Planck 353 GHz I, Q, and U Stokes maps as dust templates, and cross-correlate them with the Planck and WMAP data at 12 frequencies from 23 to 353 GHz, over circular patches with 10 degrees radius. The cross-correlation analysis is performed for both intensity and polarization data in a consistent manner. The results are corrected for the chance correlation between the templates and the anisotropies of the cosmic microwave background. We use a mask that focuses our analysis on the diffuse interstellar medium at intermediate Galactic latitudes. We determine the spectral indices of dust emission in intensity and polarization between 100 and 353 GHz, for each sky patch. Both indices are found to be remarkably constant over the sky. The mean values, 1.59 +/- 0.02 for polarization and 1.51 +/- 0.01 for intensity, for a mean dust temperature of 19.6 K, are close, but significantly different (3.6 sigma). We determine the mean spectral energy distribution (SED) of the microwave emission, correlated with the 353 GHz dust templates, by averaging the results of the correlation over all sky patches. We find that the mean SED increases for decreasing frequencies at v <60 GHz for both intensity and polarization. The rise of the polarization SED towards low frequencies may be accounted for by a synchrotron component correlated with dust, with no need for any polarization of the anomalous microwave emission. We use a spectral model to separate the synchrotron and dust polarization and to characterize the spectral dependence of the dust polarization fraction. The polarization fraction (p) of the dust emission decreases by (21 +/- 6)% from 353 to 70 GHz. We discuss this result within the context of existing dust models. The decrease in p could indicate differences in polarization efficiency among components of interstellar dust (e.g., carbon versus silicate grains). Our observational results provide inputs to quantify and optimize the separation between Galactic and cosmological polarization.Peer reviewe

    Whole-genome sequencing of 1,171 elderly admixed individuals from Brazil

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    As whole-genome sequencing (WGS) becomes the gold standard tool for studying population genomics and medical applications, data on diverse non-European and admixed individuals are still scarce. Here, we present a high-coverage WGS dataset of 1,171 highly admixed elderly Brazilians from a census-based cohort, providing over 76 million variants, of which ~2 million are absent from large public databases. WGS enables identification of ~2,000 previously undescribed mobile element insertions without previous description, nearly 5 Mb of genomic segments absent from the human genome reference, and over 140 alleles from HLA genes absent from public resources. We reclassify and curate pathogenicity assertions for nearly four hundred variants in genes associated with dominantly-inherited Mendelian disorders and calculate the incidence for selected recessive disorders, demonstrating the clinical usefulness of the present study. Finally, we observe that whole-genome and HLA imputation could be significantly improved compared to available datasets since rare variation represents the largest proportion of input from WGS. These results demonstrate that even smaller sample sizes of underrepresented populations bring relevant data for genomic studies, especially when exploring analyses allowed only by WGS
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