30 research outputs found

    Remote Sensing Applications for Abating Aircraft–Bird Strike Risks in Southeast Brazil

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    The rising number of aircraft collisions with birds requires the development of appropriate mitigation measures to control their populations in the vicinity of airports. The black vulture (Coragyps atratus; vultures) is considered one of the most dangerous species for aviation in Brazil. To better understand the spatial distribution patterns of flying vultures and the risks they may pose to aviation, we studied natural and anthropogenic superficial factors and then numerically estimated and mapped the risk of collision with birds over the Airport Safety Area (ASA) for the Amarais Airport and Presidente Prudente Airport in the southeast part of Brazil. To conduct our research, we surveyed soaring black vultures monthly between September 2012 and August 2013 from 26 points within 20-km ASA zones. We obtained the environmental parameters (i.e., relief, surface temperature, surface covering type, and anthropogenic pressure) from satellite imagery and georeferenced them with our vulture survey. The tabulated data were examined using Spearman’s rank correlation and principal component analysis to determine if any the relationships existed between vulture flight patterns and ASA environmental characteristics. We found that the contrast in surface temperatures correlated well with the intensity of vulture soaring flights. Vultures tend to soar using the strongest thermals in their surroundings. Relief parameters, including altitude above sea level, slope exposure, and inclination, were not related with the vulture soaring activity. Water bodies and roadways were the most attractive landscapes for soaring vultures. We recorded the least number of soaring vultures over the uninterrupted urbanized lands. However, the scattered enclaves of urban settlement surrounded by natural and rural landscapes were selected by soaring birds. To mitigate the bird strike risk in ASA zones, we propose that managers should plot the objects generating thermals that attract vultures on risk assessment maps and reroute aviation to avoid them

    Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes

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    The environmental conditions on the Earth before 4 billion years ago are highly uncertain, largely because of the lack of a substantial rock record from this period. During this time interval, known as the Hadean, the young planet transformed from an uninhabited world to the one capable of supporting, and inhabited by the first living cells. These cells formed in a fluid environment they could not at first control, with homeostatic mechanisms developing only later. It is therefore possible that present-day organisms retain some record of the primordial fluid in which the first cells formed. Here we present new data on the elemental compositions and mineral fingerprints of both Bacteria and Archaea, using these data to constrain the environment in which life formed. The cradle solution that produced this elemental signature was saturated in barite, sphene, chalcedony, apatite, and clay minerals. The presence of these minerals, as well as other chemical features, suggests that the cradle environment of life may have been a weathering fluid interacting with dry-land silicate rocks. The specific mineral assemblage provides evidence for a moderate Hadean climate with dry and wet seasons and a lower atmospheric abundance of CO2 than is present today.Fil: Novoselov, Alexey A.. Universidad de Concepción; ChileFil: Silva, Dailto. Universidade Estadual de Campinas; BrasilFil: Schneider, Jerusa. Universidade Estadual de Campinas; BrasilFil: Abrevaya, Ximena Celeste. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Chaffin, Michael S.. State University Of Colorado Boulder; Estados UnidosFil: Serrano, Paloma. Alfred Wegener Institute Helmholtz Centre For Polar And Marine Research,; AlemaniaFil: Navarro, Margareth Sugano. Universidade Estadual de Campinas; BrasilFil: Conti, Maria Josiane. André Tosello Institute; BrasilFil: Souza Filho, Carlos Roberto de. Universidade Estadual de Campinas; Brasi

    Transition metal dichalcogenide nanospheres for high-refractive-index nanophotonics and biomedical theranostics

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    Recent developments in the area of resonant dielectric nanostructures have created attractive opportunities for concentrating and manipulating light at the nanoscale and the establishment of the new exciting field of all-dielectric nanophotonics. Transition metal dichalcogenides (TMDCs) with nanopatterned surfaces are especially promising for these tasks. Still, the fabrication of these structures requires sophisticated lithographic processes, drastically complicating application prospects. To bridge this gap and broaden the application scope of TMDC nanomaterials, we report here femtosecond laser-ablative fabrication of water-dispersed spherical TMDC (MoS2 and WS2) nanoparticles (NPs) of variable size (5 to 250 nm). Such NPs demonstrate exciting optical and electronic properties inherited from TMDC crystals, due to preserved crystalline structure, which offers a unique combination of pronounced excitonic response and high refractive index value, making possible a strong concentration of electromagnetic field in the NPs. Furthermore, such NPs offer additional tunability due to hybridization between the Mie and excitonic resonances. Such properties bring to life a number of nontrivial effects, including enhanced photoabsorption and photothermal conversion. As an illustration, we demonstrate that the NPs exhibit a very strong photothermal response, much exceeding that of conventional dielectric nanoresonators based on Si. Being in a mobile colloidal state and exhibiting superior optical properties compared to other dielectric resonant structures, the synthesized TMDC NPs offer opportunities for the development of next-generation nanophotonic and nanotheranostic platforms, including photothermal therapy and multimodal bioimaging

    Giant Faraday rotation in single- and multilayer graphene

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    Optical Faraday rotation is one of the most direct and practically important manifestations of magnetically broken time-reversal symmetry. The rotation angle is proportional to the distance traveled by the light, and up to now sizeable effects were observed only in macroscopically thick samples and in two-dimensional electron gases with effective thicknesses of several nanometers. Here we demonstrate that a single atomic layer of carbon - graphene - turns the polarization by several degrees in modest magnetic fields. The rotation is found to be strongly enhanced by resonances originating from the cyclotron effect in the classical regime and the inter-Landau-level transitions in the quantum regime. Combined with the possibility of ambipolar doping, this opens pathways to use graphene in fast tunable ultrathin infrared magneto-optical devices

    Graphene transistors are insensitive to pH changes in solution

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    We observe very small gate-voltage shifts in the transfer characteristic of as-prepared graphene field-effect transistors (GFETs) when the pH of the buffer is changed. This observation is in strong contrast to Si-based ion-sensitive FETs. The low gate-shift of a GFET can be further reduced if the graphene surface is covered with a hydrophobic fluorobenzene layer. If a thin Al-oxide layer is applied instead, the opposite happens. This suggests that clean graphene does not sense the chemical potential of protons. A GFET can therefore be used as a reference electrode in an aqueous electrolyte. Our finding sheds light on the large variety of pH-induced gate shifts that have been published for GFETs in the recent literature

    The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

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    Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

    Potassium metasomatism of Precambrian paleosols

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    FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOIndependent of substratum composition, ancient regoliths formed by subaerial weathering are characterized by accumulation of K and other alkaline elements. Potassium enrichment due to the formation of clay-minerals is a trend typically observed in regoliths developed by modern hypergene processes. However, the K content in Precambrian paleosols is much higher than in modern weathering profiles. K-metasomatism affecting buried hypergen targets is a possible mechanism for K accumulation. A novel reaction-transport dissolution-precipitation model designed as part of this work proved able to reproduce many essential features of post-burial alterations of a subaerial weathering profile formed on basaltic rocks, including potassium enrichment, dehydration, compaction and pore filling that impacted the buried regolith. The phenomena of preservation of the primary basaltic structure, the apparent selective alteration of soil levels and immobility of Al, Ti and P could be explained by the model.Independent of substratum composition, ancient regoliths formed by subaerial weathering are characterized by accumulation of K and other alkaline elements. Potassium enrichment due to the formation of clay-minerals is a trend typically observed in regoliths developed by modern hypergene processes. However, the K content in Precambrian paleosols is much higher than in modern weathering profiles. K-metasomatism affecting buried hypergen targets is a possible mechanism for K accumulation. 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    Evaluation of uncertainties in solid–aqueous–gas chemical equilibrium calculations

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    FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOThermodynamic calculations are traditionally carried out under the assumption of specified input parameters. Errors associated to the results are not often estimated. Here, we propose a novel algorithm that propagates the uncertainty intervals on thermodynamic constants to the uncertainty in chemical equilibrium compositions. The computing uses a dataset of uncertainties on thermodynamic parameters for minerals, solution species and gases consistent with the SUPCRT92 database. Also the algorithm of nonlinear optimization is thoroughly described and realized on a base of the CRONO software. This code can be incorporated into reactive mass transport models as a core for calculating equilibrium compositions. The performance of the algorithm is tested in an experimental system involving Mont Tern's Opalinus Clay interacting with pore water. Its effectiveness is also evaluated against Monte Carlo simulations and Latin Hypercube sampling. (C) 2015 Elsevier Ltd. All rights reserved.Thermodynamic calculations are traditionally carried out under the assumption of specified input parameters. Errors associated to the results are not often estimated. Here, we propose a novel algorithm that propagates the uncertainty intervals on thermodynamic constants to the uncertainty in chemical equilibrium compositions. The computing uses a dataset of uncertainties on thermodynamic parameters for minerals, solution species and gases consistent with the SUPCRT92 database. Also the algorithm of nonlinear optimization is thoroughly described and realized on a base of the CRONO software. This code can be incorporated into reactive mass transport models as a core for calculating equilibrium compositions. The performance of the algorithm is tested in an experimental system involving Mont Tern's Opalinus Clay interacting with pore water. Its effectiveness is also evaluated against Monte Carlo simulations and Latin Hypercube sampling79118128FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP [2011/12682-3]CNPq [164939/2014-8]2011/12682-3164939/2014-
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