337 research outputs found

    Antennal transcriptome profiles of anopheline mosquitoes reveal human host olfactory specialization in Anopheles gambiae

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    BACKGROUND: Two sibling members of the Anopheles gambiae species complex display notable differences in female blood meal preferences. An. gambiae s.s. has a well-documented preference for feeding upon human hosts, whereas An. quadriannulatus feeds on vertebrate/mammalian hosts, with only opportunistic feeding upon humans. Because mosquito host-seeking behaviors are largely driven by the sensory modality of olfaction, we hypothesized that hallmarks of these divergent host seeking phenotypes will be in evidence within the transcriptome profiles of the antennae, the mosquito's principal chemosensory appendage. RESULTS: To test this hypothesis, we have sequenced antennal mRNA of non-bloodfed females from each species and observed a number of distinct quantitative and qualitative differences in their chemosensory gene repertoires. In both species, these gene families show higher rates of sequence polymorphisms than the overall rates in their respective transcriptomes, with potentially important divergences between the two species. Moreover, quantitative differences in odorant receptor transcript abundances have been used to model potential distinctions in volatile odor receptivity between the two sibling species of anophelines. CONCLUSION: This analysis suggests that the anthropophagic behavior of An. gambiae s.s. reflects the differential distribution of olfactory receptors in the antenna, likely resulting from a co-option and refinement of molecular components common to both species. This study improves our understanding of the molecular evolution of chemoreceptors in closely related anophelines and suggests possible mechanisms that underlie the behavioral distinctions in host seeking that, in part, account for the differential vectorial capacity of these mosquitoes

    Lineage-specific co-evolution of the Egf receptor/ligand signaling system

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    <p>Abstract</p> <p>Background</p> <p>The epidermal growth factor receptor (Egfr) with its numerous ligands has fundamental roles in development, cell differentiation and physiology. Dysfunction of the receptor-ligand system contributes to many human malignancies. Consistent with such various tasks, the Egfr gene family has expanded during vertebrate evolution as a consequence of several rounds of whole genome duplication. Of particular interest is the effect of the fish-specific whole genome duplication (FSGD) on the ligand-receptor system, as it has supplied this largest group of vertebrates with additional opportunities for sub- and/or neofunctionalization in this signaling system.</p> <p>Results</p> <p>We identified the predicted components of the Egf receptor-ligand signaling system in teleost fishes (medaka, platyfish, stickleback, pufferfishes and zebrafish). We found two duplicated <it>egfr </it>genes, <it>egfra </it>and <it>egfrb</it>, in all available teleost genomes. Surprisingly only one copy for each of the seven Egfr ligands could be identified in most fishes, with zebrafish <it>hbegf </it>being the only exception. Special focus was put on medaka, for which we more closely investigated all Egf receptors and Egfr ligands. The different expression patterns of <it>egfra</it>, <it>egfrb </it>and their ligands in medaka tissues and embryo stages suggest differences in role and function. Preferential co-expression of different subsets of Egfr ligands corroborates the possible subfunctionalization and specialization of the two receptors in adult tissues. Bioinformatic analyses of the ligand-receptor interface between Egfr and its ligands show a very weak evolutionary conservation within this region. Using <it>in vitro </it>analyses of medaka Egfra, we could show that this receptor is only activated by medaka ligands, but not by human EGF. Altogether, our data suggest a lineage-specific Egfr/Egfr ligand co-evolution.</p> <p>Conclusions</p> <p>Our data indicate that medaka Egfr signaling occurs via its two copies, Egfra and Egfrb, each of them being preferentially coexpressed with different subsets of Egfr ligands. This fish-specific occurrence of Egf receptor specialization offers unique opportunities to study the functions of different Egf receptor-ligand combinations and their biological outputs in vertebrates. Furthermore, our results strongly support the use of homologous ligands in future studies, as sufficient cross-specificity is very unlikely for this ligand/receptor system.</p

    Measuring attitude towards Buddhism and Sikhism : internal consistency reliability for two new instruments

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    This paper describes and discusses the development and empirical properties of two new 24-item scales – one measuring attitude toward Buddhism and the other measuring attitude toward Sikhism. The scale is designed to facilitate inter-faith comparisons within the psychology of religion alongside the well-established Francis Scale of Attitude toward Christianity. Data were obtained from a multi-religious sample of 369 school pupils aged between 13 and 15 in London. Application of the two scales demonstrated that adolescents had a more positive attitude to Buddhism than Sikhism. The findings confirm the reliability of the scales and commend them for further use

    How dynamic are ice-stream beds?

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    Projections of sea-level rise contributions from West Antarctica's dynamically thinning ice streams contain high uncertainty because some of the key processes involved are extremely challenging to observe. An especially poorly observed parameter is sub-decadal stability of ice-stream beds, which may be important for subglacial traction, till continuity and landform development. Only two previous studies have made repeated geophysical measurements of ice-stream beds at the same locations in different years, but both studies were limited in spatial extent. Here, we present the results from repeat radar measurements of the bed of Pine Island Glacier, West Antarctica, conducted 3–6 years apart, along a cumulative ∼ 60 km of profiles. Analysis of the correlation of bed picks between repeat surveys shows that 90 % of the bed displays no significant change despite the glacier increasing in speed by up to 40 % over the last decade. We attribute the negligible detection of morphological change at the bed of Pine Island Glacier to the ubiquitous presence of a deforming till layer, wherein sediment transport is in steady state, such that sediment is transported along the basal interface without inducing morphological change to the radar-sounded basal interface. Given the precision of our measurements, the upper limit of subglacial erosion observed here is 500 mm a‾¹, far exceeding erosion rates reported for glacial settings from proglacial sediment yields, but substantially below subglacial erosion rates of 1.0 m a‾¹ previously reported from repeat geophysical surveys in West Antarctica

    Changing control and accounting regimes in an african gold mine: emergence of new despotic control

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    Purpose – To examine whether the framework of management accounting transformations in Hopper et al. (2009) applies to accounting changes in the Ashanti Gold Corporation (AGC) in Ghana over 120 years from pre-colonialism to recent times. Design/methodology/approach – Mixed data sources are used, namely interviews, observations of practices, historical documentation, company reports, and research papers and theses. The results are categorized within the periods and contextual factors in the Hopper et al. framework. Findings –The Hopper et al. model was robust. Despotic controls with minimal management accounting but stewardship accounting to the head office in London prevailed under colonialism. Upon independence state capitalist policies descended into politicized state capitalism. Under nationalization the performance of mines deteriorated and accounting became decoupled from operations. However, AGC remained privately owned, it embraced profit centres and budgeting, and was relatively successful commercially. In the early 1980s fiscal crises forced Ghana’s government to turn to the World Bank and IMF for loans. Their conditions precipitated market capitalism embracing widespread privatisations. This marked a gradual transformation of AGC into a foreign multinational, organized along divisional lines that today exercises despotic control through supply chain management that renders labour precarious, and neglects corporate social accounting. Practical implications – The work challenges neo-classical economic prescriptions and analyses of accounting in developing countries by indicating its neglect of the interests of other stakeholders, especially labour and civil society. Originality/value – The paper tests and extends the Hopper et al. framework with respect to a large private multinational in the commodity sector over an extended period

    The Al-Rich Part of the Fe-Al Phase Diagram

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    The Al-rich part of the Fe-Al phase diagram between 50 and 80 at.% Al including the complex intermetallic phases Fe5_{5}Al8_{8} (ε), FeAl2_{2}, Fe2_{2}Al5_{5}, and Fe4Al13_{13} was re-investigated in detail. A series of 19 alloys was produced and heat-treated at temperatures in the range from 600 to 1100 °C for up to 5000 h. The obtained data were further complemented by results from a number of diffusion couples, which helped to determine the homogeneity ranges of the phases FeAl2_{2}, Fe2_{2}Al5_{5}, and Fe4_{4}Al13_{13}. All microstructures were inspected by scanning electron microscopy (SEM), and chemical compositions of the equilibrium phases as well as of the alloys were obtained by electron probe microanalysis (EPMA). Crystal structures and the variation of the lattice parameters were studied by x-ray diffraction (XRD) and differential thermal analysis (DTA) was applied to measure all types of transition temperatures. From these results, a revised version of the Al-rich part of the phase diagram was constructed

    AVATAR - Machine Learning Pipeline Evaluation Using Surrogate Model

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    © 2020, The Author(s). The evaluation of machine learning (ML) pipelines is essential during automatic ML pipeline composition and optimisation. The previous methods such as Bayesian-based and genetic-based optimisation, which are implemented in Auto-Weka, Auto-sklearn and TPOT, evaluate pipelines by executing them. Therefore, the pipeline composition and optimisation of these methods requires a tremendous amount of time that prevents them from exploring complex pipelines to find better predictive models. To further explore this research challenge, we have conducted experiments showing that many of the generated pipelines are invalid, and it is unnecessary to execute them to find out whether they are good pipelines. To address this issue, we propose a novel method to evaluate the validity of ML pipelines using a surrogate model (AVATAR). The AVATAR enables to accelerate automatic ML pipeline composition and optimisation by quickly ignoring invalid pipelines. Our experiments show that the AVATAR is more efficient in evaluating complex pipelines in comparison with the traditional evaluation approaches requiring their execution

    Evolution of Scikit-Learn Pipelines with Dynamic Structured Grammatical Evolution

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    The deployment of Machine Learning (ML) models is a difficult and time-consuming job that comprises a series of sequential and correlated tasks that go from the data pre-processing, and the design and extraction of features, to the choice of the ML algorithm and its parameterisation. The task is even more challenging considering that the design of features is in many cases problem specific, and thus requires domain-expertise. To overcome these limitations Automated Machine Learning (AutoML) methods seek to automate, with few or no human-intervention, the design of pipelines, i.e., automate the selection of the sequence of methods that have to be applied to the raw data. These methods have the potential to enable non-expert users to use ML, and provide expert users with solutions that they would unlikely consider. In particular, this paper describes AutoML-DSGE - a novel grammar-based framework that adapts Dynamic Structured Grammatical Evolution (DSGE) to the evolution of Scikit-Learn classification pipelines. The experimental results include comparing AutoML-DSGE to another grammar-based AutoML framework, Resilient ClassificationPipeline Evolution (RECIPE), and show that the average performance of the classification pipelines generated by AutoML-DSGE is always superior to the average performance of RECIPE; the differences are statistically significant in 3 out of the 10 used datasets.Comment: EvoApps 202
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