5,134 research outputs found

    Water pricing: are 'polluters' paying the environmental costs of flow regulation?

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    River ecosystems are severely affected by dams and reservoirs. The Water Framework Directive states that polluters should be financially responsible for the caused environmental damage. Nevertheless, the environmental costs associated to flow regulation often are not fully paid by water users. This study presents an approach to value the environmental costs of flow regulation based on the "polluter pays" principle, i.e., the amount to be paid should be proportional to the caused environmental impact. The procedure includes three major steps: (i) assessing the admissible range of regulated flow variability based on flow data during the pre-dam period, (ii) estimating the daily environmental impact of regulated flows according to the resulting hydrological change in terms of the intensity, duration and frequency of the impact, and (iii) calculating the environmental costs of flow regulation subject to spatiotemporal characteristics. This paper applies the proposed methodology in the Luna River, Spain. The advantages over other water cost valuation methodologies are discussed. The approach enlarges the current recognition of water environmental costs and represents a simple and practical management tool for achieving the objectives of the Water Framework Directive

    On neutrino-mediated potentials in a neutrino background

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    The exchange of a pair of neutrinos with Standard Model weak interactions generates a long-range force between fermions. The associated potential is extremely feeble, GF2/r5\propto G_F^2/r^5 for massless neutrinos, which renders it far from observable even in the most sensitive experiments testing fifth forces. The presence of a neutrino background has been argued to induce a correction to the neutrino propagator that enhances the potential by orders of magnitude. In this brief note, we point out that such modified propagators are invalid if the background neutrino wavepackets have a finite width. By reevaluating the 2--ν\nu exchange potential in the presence of a neutrino background including finite width effects, we find that the background-induced enhancement is reduced by several orders of magnitude. This confirms the intuitive result that coherent enhancements to the potential can only be large for distances of the order of the background wavepacket width. Unfortunately, this pushes the resulting 2--ν\nu exchange potential away from present and near-future sensitivity of tests of new long-range forces.Comment: 11 pages, 3 figures. Results unchanged. Added Not

    Unveiling the Dynamics of the Universe

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    We explore the dynamics and evolution of the Universe at early and late times, focusing on both dark energy and extended gravity models and their astrophysical and cosmological consequences. Modified theories of gravity not only provide an alternative explanation for the recent expansion history of the universe, but they also offer a paradigm fundamentally distinct from the simplest dark energy models of cosmic acceleration. In this review, we perform a detailed theoretical and phenomenological analysis of different modified gravity models and investigate their consistency. We also consider the cosmological implications of well motivated physical models of the early universe with a particular emphasis on inflation and topological defects. Astrophysical and cosmological tests over a wide range of scales, from the solar system to the observable horizon, severely restrict the allowed models of the Universe. Here, we review several observational probes -- including gravitational lensing, galaxy clusters, cosmic microwave background temperature and polarization, supernova and baryon acoustic oscillations measurements -- and their relevance in constraining our cosmological description of the Universe.Comment: 94 pages, 14 figures. Review paper accepted for publication in a Special Issue of Symmetry. "Symmetry: Feature Papers 2016". V2: Matches published version, now 79 pages (new format

    Observations of the first electromagnetic counterpart to a gravitational wave source by the TOROS collaboration

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    We present the results of prompt optical follow-up of the electromagnetic counterpart of GW170817 by the Transient Optical Robotic Observatory of the South Collaboration (TOROS). We detected highly significant dimming in the light curves of the counterpart over the course of only 80 minutes of observations obtained ∼35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ∼59 hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a blue kilonova relatively free of lanthanides

    Transcriptome analysis of the venom gland of the Mexican scorpion Hadrurus gertschi (Arachnida: Scorpiones)

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    <p>Abstract</p> <p>Background</p> <p>Scorpions like other venomous animals posses a highly specialized organ that produces, secretes and disposes the venom components. In these animals, the last postabdominal segment, named telson, contains a pair of venomous glands connected to the stinger. The isolation of numerous scorpion toxins, along with cDNA-based gene cloning and, more recently, proteomic analyses have provided us with a large collection of venom components sequences. However, all of them are secreted, or at least are predicted to be secretable gene products. Therefore very little is known about the cellular processes that normally take place inside the glands for production of the venom mixture. To gain insights into the scorpion venom gland biology, we have decided to perform a transcriptomic analysis by constructing a cDNA library and conducting a random sequencing screening of the transcripts.</p> <p>Results</p> <p>From the cDNA library prepared from a single venom gland of the scorpion <it>Hadrurus gertschi</it>, 160 expressed sequence tags (ESTs) were analyzed. These transcripts were further clustered into 68 unique sequences (20 contigs and 48 singlets), with an average length of 919 bp. Half of the ESTs can be confidentially assigned as homologues of annotated gene products. Annotation of these ESTs, with the aid of Gene Ontology terms and homology to eukaryotic orthologous groups, reveals some cellular processes important for venom gland function; including high protein synthesis, tuned posttranslational processing and trafficking. Nonetheless, the main group of the identified gene products includes ESTs similar to known scorpion toxins or other previously characterized scorpion venom components, which account for nearly 60% of the identified proteins.</p> <p>Conclusion</p> <p>To the best of our knowledge this report contains the first transcriptome analysis of genes transcribed by the venomous gland of a scorpion. The data were obtained for the species <it>Hadrurus gertschi</it>, belonging to the family Caraboctonidae. One hundred and sixty ESTs were analyzed, showing enrichment in genes that encode for products similar to known venom components, but also provides the first sketch of cellular components, molecular functions, biological processes and some unique sequences of the scorpion venom gland.</p

    Primeiro registro de um raro peixe parasita Pseudostegophilus paulensis no rio Paranapanema e sua distribuição atual no Brasil

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    Pseudostegophilus paulensis Miranda Ribeiro 1918 is an endemic parasitic species from the state of São Paulo, southeastern Brazil, with few registered occurrences in databases (15 records). Here, we present the first record of P. paulensis in the middle portion of the Anhumas River, a tributary of the Paranapanema River right bank. Specimens were collected in two environments with different ecological characteristics (lotic water running over gravel sediment and semi-lotic water with silty sediment on the bottom). We also present an updated occurrence map of the species in Brazil. This new record of P. paulensis in the upper Paraná River basin extends the geographic distribution of the species to the South of the state of São Paulo.&nbsp; Furthermore, important ecological information remains unknown due to the lack of data about this group, such as habitat niches, vertical migration, growth patterns, reproduction, and feeding behavior.Pseudostegophilus paulensis Miranda Ribeiro 1918 é uma espécie de peixe parasita endêmica do estado de São Paulo, sudeste do Brasil, com poucas ocorrências registradas em bancos de dados (15 registros). Aqui, apresentamos o primeiro registro de P. paulensis na porção média do rio Anhumas, afluente da margem direita do rio Paranapanema. Os espécimes foram coletados em dois ambientes com características ecológicas distintas (água lótica correndo sobre sedimento pedregulho e água semilótica com sedimento arenoso no fundo). Apresentamos também um mapa de ocorrência atualizado da espécie no Brasil. Este novo registro de P. paulensis na bacia do alto rio Paraná estende a distribuição geográfica da espécie para o sul do estado de São Paulo. Além disso, informações ecológicas importantes permanecem desconhecidas devido à falta de dados sobre esse grupo, como nichos de habitat, migração vertical, padrões de crescimento, reprodução e comportamento alimentar

    Age Appropriate Wisdom? Ethnobiological Knowledge Ontogeny in Pastoralist Mexican Choyeros

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    We investigate whether age profiles of ethnobiological knowledge development are consistent with predictions derived from life history theory about the timing of productivity and reproduction. Life history models predict complementary knowledge profiles developing across the lifespan for women and men as they experience changes in embodied capital and the needs of dependent offspring. We evaluate these predictions using an ethnobiological knowledge assessment tool developed for an off-grid pastoralist population, known as Choyeros, from Baja California Sur, Mexico. Our results indicate that while individuals acquire knowledge of most dangerous items and edible resources by early adulthood, knowledge of plants and animals relevant to the age and sex divided labor domains and ecologies (e.g., women’s house gardens, men’s herding activities in the wilderness) continues to develop into middle adulthood but to different degrees and at different rates for men and women. As the demands of offspring accumulate for parents with age, reproductive aged adults continue to develop their knowledge to meet their children’s needs. After controlling for vision, post-reproductive adults’ show the greatest ethnobiological knowledge. These findings extend our understanding of the evolved human life history by illustrating how changes in embodied capital and the needs of dependent offspring predict the development of men’s and women’s ethnobiological knowledge across the lifespan

    Comparisons between Cambrian Lagerstätten assemblages using multivariate, parsimony and Bayesian methods

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    © 2017 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (Dec 2017) in accordance with the publisher’s archiving policyExceptional fossil deposits exhibiting soft-part preservation, or Konservat-Lagerstätten, are prevalent in Cambrian rocks and provide detailed information on fossil assemblages not available from conventional deposits. It has long been recognised that many of these assemblages exhibit certain taxonomic similarities, with many elements seemingly having cosmopolitan distributions. These types of assemblages, particularly those of Cambrian age, have become known as Burgess Shale-type (BST) biotas, named for the famous deposit in the Canadian Rocky Mountains where fossils preserved in this way were first discovered. This study provides the first broad-scale analysis of the assemblage relationships between all major BST biotas. We compiled a database of the presences and absences of over 600 genera within 12 Lagerstätten from Laurentia, Siberia, South China and East Gondwana, ranging in age from Cambrian Series 2 through Series 3 (late-early to middle Cambrian; c. 518–502 Ma), and analysed this using a variety of quantitative methods in order to investigate the relationships between these sites. Non-metric multidimensional scaling (NMDS) ordination, cluster analysis and Parsimony Analysis of Endemicity (PAE) were used to group localities and examine relationships. We also used Bayesian inference and illustrate the benefits of this approach to biogeographic studies. Results suggest that both space and time have important effects on the taxonomic constitution of BST biotas, and that the similarity of these assemblages appears to increase from Series 2 through Series 3, largely driven by increases in cosmopolitanism of biomineralised taxa such as trilobites and brachiopods. There is also evidence of higher-level taxonomic turnover across this period. Endemic taxa help amplify these patterns, despite their frequent exclusion from biogeographic analyses

    Elucidating how the saprophytic fungus Aspergillus nidulans uses the plant polyester suberin as carbon source

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    Lipid polymers in plant cell walls, such as cutin and suberin, build recalcitrant hydrophobic protective barriers. Their degradation is of foremost importance for both plant pathogenic and saprophytic fungi. Regardless of numerous reports on fungal degradation of emulsified fatty acids or cutin, and on fungi-plant interactions, the pathways involved in the degradation and utilisation of suberin remain largely overlooked. As a structural component of the plant cell wall, suberin isolation, in general, uses harsh depolymerisation methods that destroy its macromolecular structure. We recently overcame this limitation isolating suberin macromolecules in a near-native state.work partially supported by a grant from Iceland, Liechtenstein and Norway through the EEA financial mechanism (Project PT015), FCT: grant (PEst-OE/EQB/LA0004/2013) and fellowships (SFRH/BD/38378/2007, SFRH/BD/66396/2009, SFRH/BD/66030/2009, SFRH/BD/48286/2008), Fundação Calouste Gulbenkian fellowship (21-95587-B)

    Spin diffusion versus proximity effect at ferromagnet/superconductor La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7-δ) interfaces

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    We report on the interplay between magnetism and superconductivity in La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7) structures. We have grown heterostructures (bilayers and trilayers) with a constant thickness of the ferromagnetic layer of 40 unit cells (15 nm) and changing the thickness of the superconductor between 1 (1.2 nm) and 40 unit cells (48 nm). The critical temperature of the bilayers decreases when the thickness of the superconductor is reduced below 10 unit cells, thus providing an estimate of the length scale of superconductivity suppression by spin-polarized quasiparticles in YBa_(2)Cu_(3)O_(7-δ) (YBCO) of 10 nm, much larger than the coherence length. For thickness of the YBCO layer smaller than 4 unit cells; a second mechanism of superconductivity depression comes into play, probably related to the ferromagnetic/superconducting proximity effect. The relative importance in depressing the critical temperature of intrinsic mechanisms (quasiparticle diffusion and proximity effect) and extrinsic ones (intralayer disorder, interface roughness, or reduced dimensionality of ultrathin layers) is discussed
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