408 research outputs found

    Testing for distributional features in varying coefficient panel data models

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    This article provides several tests for skewness and kurtosis for the error terms in a one-way fixed-effects varying coefficient panel data model. To obtain these tests, estimators of higher-order moments of both error components are obtained as solutions of estimating equations. Additionally, to obtain the nonparametric residuals, a local constant estimator based on a pairwise differencing transformation is proposed. The asymptotic properties of these estimators and tests are established. The proposed estimators and test statistics are augmented by simulation studies, and they are also illustrated in an empirical analysis regarding the technical efficiency of European Union companies.The authors would like to thank two anonymous referees for their very helpful comments and suggestions. Furthermore, the authors gratefully acknowledge financial support from the Programa Estatal de Fomento de la Investigaci´on Cient´ıfica y T´ecnica de Excelencia/Spanish Ministry of Economy and Competitiveness. Ref. ECO2016-76203-C2-1-P. In addition, this work is part of the Research Project APIE 1/2015-17: “New methods for the empirical analysis of financial markets” of the Santander Financial Institute (SANFI) of UCEIF Foundation resolved by the University of Cantabria and funded with sponsorship from Banco Santander. Stute’s work was partly done while he was on leave at BCAM, the Basque Center of Applied Mathematics in Bilba

    Larvicidal activity of Piper tuberculatum on Spodoptera frugiperda (Lepidoptera: Noctuidae) under laboratory conditions

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    The larvicidal activity of the neotropical "matico" Piper tuberculatum was evaluated. The secondary compounds were extracted of leaves, stems and mature spikes with fruits and seeds from wild plants and in vitro plants of Piper tuberculatum. The acute toxicities to the fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), of extracts of spikes with fruits and seeds and in vitro plants of P tuberculatum were evaluated by means of contact bioassays. Only CH2Cl2:MeOH (2:1) and EtOH extracts of mature spikes and CH2C12:MeOH (2:1) extract from in vitro plants showed significant levels of larval mortality. The CH2Cl2:MeOH (2:1) and EtOH extracts of mature spikes caused 90% mortality when doses of 0.1850 mg/mu L were applied to the S. frugiperda in 24 and 48 h of exposure, respectively. The CH2Cl2:MeOH (2:1) extract from in vitro plants caused 95% mortality when doses of 0.1850 mg/mu L were too applied in 48 h of exposure. The mature spikes test best results were: LD50 0.001 mg/mu L with EtOH and 0.007 mg/mu L with CH2Cl2:MeOH (2:1) and LD90 0.027 mg/mu L with EtOH and 0.103 mg/mu L with CH2Cl2:MeOH (2:1); and, in the case of in vitro plants, only CH2Cl2:MeOH (2:1) extract was: LD50 0.003 mg/mu L and LD90 0.060 mg/mu L. The potential value of extracts derived from P. tuberculatum as efficient insecticides against S.frugiperda is discussed

    Identification of a Novel Aminopeptidase P-Like Gene (OnAPP) Possibly Involved in Bt Toxicity and Resistance in a Major Corn Pest (Ostrinia nubilalis)

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    Studies to understand the Bacillus thuringiensis (Bt) resistance mechanism in European corn borer (ECB, Ostrinia nubilalis) suggest that resistance may be due to changes in the midgut-specific Bt toxin receptor. In this study, we identified 10 aminopeptidase-like genes, which have previously been identified as putative Bt toxin receptors in other insects and examined their expression in relation to Cry1Ab toxicity and resistance. Expression analysis for the 10 aminopeptidase-like genes revealed that most of these genes were expressed predominantly in the larval midgut, but there was no difference in the expression of these genes in Cry1Ab resistant and susceptible strains. This suggested that altered expression of these genes was unlikely to be responsible for resistance in these ECB strains. However, we found that there were changes in two amino acid residues of the aminopeptidase-P like gene (OnAPP) involving Glu305 to Lys305 and Arg307 to Leu307 in the two Cry1Ab-resistant strains as compared with three Cry1Ab-susceptible strains. The mature OnAPP contains 682 amino acid residues and has a putative signal peptide at the N-terminus, a predicted glycosylphosphatidyl-inositol (GPI)-anchor signal at the C-terminal, three predicted N-glycosylation sites at residues N178, N278 and N417, and an O-glycosylation site at residue T653. We used a feeding based-RNA interference assay to examine the role of the OnAPP gene in Cry1Ab toxicity and resistance. Bioassays of Cry1Ab in larvae fed diet containing OnAPP dsRNA resulted in a 38% reduction in the transcript level of OnAPP and a 25% reduction in the susceptibility to Cry1Ab as compared with larvae fed GFP dsRNA or water. These results strongly suggest that the OnAPP gene could be involved in binding the Cry1Ab toxin in the ECB larval midgut and that mutations in this gene may be associated with Bt resistance in these two ECB strains

    Ecological Niche and Geographic Distribution of Human Monkeypox in Africa

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    Monkeypox virus, a zoonotic member of the genus Orthopoxviridae, can cause a severe, smallpox-like illness in humans. Monkeypox virus is thought to be endemic to forested areas of western and Central Africa. Considerably more is known about human monkeypox disease occurrence than about natural sylvatic cycles of this virus in non-human animal hosts. We use human monkeypox case data from Africa for 1970–2003 in an ecological niche modeling framework to construct predictive models of the ecological requirements and geographic distribution of monkeypox virus across West and Central Africa. Tests of internal predictive ability using different subsets of input data show the model to be highly robust and suggest that the distinct phylogenetic lineages of monkeypox in West Africa and Central Africa occupy similar ecological niches. High mean annual precipitation and low elevations were shown to be highly correlated with human monkeypox disease occurrence. The synthetic picture of the potential geographic distribution of human monkeypox in Africa resulting from this study should support ongoing epidemiologic and ecological studies, as well as help to guide public health intervention strategies to areas at highest risk for human monkeypox

    Incorporating uncertainty associated with habitat data in marine reserve design

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    One of the most pervasive forms of uncertainty in data used to make conservation decisions is error associated with mapping of conservation features. Whilst conservation planners should consider uncertainty associated with ecological data to make informed decisions, mapping error is rarely, if ever, accommodated in the planning process. Here, we develop a spatial conservation prioritization approach that accounts for the uncertainty inherent in coral reef habitat maps and apply it in the Kubulau District fisheries management area, Fiji. We use accuracy information describing the probability of occurrence of each habitat type, derived from remote sensing data validated by field surveys, to design a marine reserve network that has a high probability of protecting a fixed percentage (10-90%) of every habitat type. We compare the outcomes of our approach to those of standard reserve design approaches, where habitat-mapping errors are not known or ignored. We show that the locations of priority areas change between the standard and probabilistic approaches, with errors of omission and commission likely to occur if reserve design does not accommodate mapping accuracy. Although consideration of habitat mapping accuracy leads to bigger reserve networks, they are unlikely to miss habitat conservation targets. We explore the trade-off between conservation feature representation and reserve network area, with smaller reserve networks possible if we give up on trying to meet targets for habitats mapped with a low accuracy. The approach can be used with any habitat type at any scale to inform more robust and defensible conservation decisions in marine or terrestrial environments. (C) 2013 Elsevier Ltd. All rights reserved
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