138 research outputs found

    La organización de la información, los lenguajes documentales y la normalización

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    La calidad de la información que se maneja actualmente ha aumentado debido a las nuevas tecnologías. Esta comunicación se plantea la calidad de la información que los bibliotecarios ofrecen a sus usuarios a través de diversas herramientas : control de autoridades, normalización, normas bibliográficas, lenguajes documentales y encabezamientos de materia

    Organic room-temperature polariton condensate in a higher-order topological lattice

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    Organic molecule exciton-polaritons in photonic lattices are a versatile platform to emulate unconventional phases of matter at ambient conditions, including protected interface modes in topological insulators. Here, we investigate bosonic condensation in the most prototypical higher-order topological lattice: a 2D-version of the Su-Schrieffer-Heeger (SSH) model, supporting both 0D and 1D topological modes. We study fluorescent protein-filled, structured microcavities defining a staggered photonic trapping potential and observe the resulting first- and higher-order topologically protected modes via spatially resolved photoluminescence spectroscopy. We account for the spatial mode patterns by tight-binding calculations and theoretically characterize the topological invariants of the lattice. Under strong optical pumping, we observe bosonic condensation into the topological modes. Via interferometric measurements, we map the spatial first-order coherence in the protected 1D modes extending over 10 microns. Our findings pave the way towards organic on-chip polaritonics using higher-order topology as a tool for the generation of robustly confined polaritonic lasing states.Comment: 23 pages, 7 figure

    Cacao flower visitation: Low pollen deposition, low fruit set and dominance of herbivores

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    Pollination services of cacao are crucial for global chocolate production, yet remain critically understudied, particularly in regions of origin of the species. Notably, uncertainties remain concerning the identity of cacao pollinators, the influence of landscape (forest distance) and management (shade cover) on flower visitation and the role of pollen deposition in limiting fruit set. Here, we aimed to improve understanding of cacao pollination by studying limiting factors of fruit set in Peru, part of the centre of origin of cacao. Flower visitors were sampled with sticky insect glue in 20 cacao agroforests in two biogeographically distinct regions of Peru, across gradients of shade cover and forest distance. Further, we assessed pollen quantities and compared fruit set between naturally and manually pollinated flowers. The most abundant flower visitors were aphids, ants and thrips in the north and thrips, midges and parasitoid wasps in the south of Peru. We present some evidence of increasing visitation rates from medium to high shade (40%–95% canopy closure) in the dry north, and opposite patterns in the semi-humid south, during the wet season. Natural pollination resulted in remarkably low fruit set rates (2%), and very low pollen deposition. After hand pollination, fruit set more than tripled (7%), but was still low. The diversity and high relative abundances of herbivore flower visitors limit our ability to draw conclusions on the functional role of different flower visitors. The remarkably low fruit set of naturally and even hand pollinated flowers indicates that other unaddressed factors limit cacao fruit production. Such factors could be, amongst others, a lack of effective pollinators, genetic incompatibility or resource limitation. Revealing efficient pollinator species and other causes of low fruit set rates is therefore key to establish location-specific management strategies and develop high yielding native cacao agroforestry systems in regions of origin of cacao. © 2022 The Authors. Ecological Solutions and Evidence published by John Wiley & Sons Ltd on behalf of British Ecological Society

    Birds and bats enhance cacao yield despite suppressing arthropod mesopredation

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    Bird- and bat-mediated biocontrol benefits the productivity of tropicalcommodity crops such as cacao, but the ecological interactions drivingthese ecosystem services remain poorly understood. Whereas birds and batsprey on herbivorous arthropods, they may also prey on arthropodmesopredators such as ants, with poorly understood consequences for pestbiocontrol. We used a full-factorial experiment excluding birds, bats, andants to assess their effects on (a) the abundanceof multiple arthropodgroups; (b) predation pressure on arthropods evaluated through artificialsentinel caterpillars; and (c) cacao yield over 1 year in shaded agroforestrysystems of native cacao varieties in Peru. Birds and bats increasedcacao yield by 118%, which translates in smallholder benefits of ca.US $959 ha−1year−1. Birds and bats decreased predation by ants and otherarthropods, but contributed to thecontrol of phytophagous taxa such asaphids and mealybugs. By contrast, ant presence increased the abundanceof these sap-sucking insects, with negative impacts for cacao yield.Notably, high abundances of the dominant antNylanderiasp., known toattend sap-sucking insects, were associated with lower cacao yield along adistance gradient from the closest forest edge. According to these results,arthropod predation by birds and bats, rather than mesopredation byarthropods, was most responsible forincreases in cacao yield. Moving for-ward, detailed research about their trophic interactions will be necessary toidentify the cause of such benefits. Retaining and restoring the large bene-fits of birds and bats as well as minimizing disservices by other taxa incacao agroforests can benefit from management schemes that prioritizepreservation of shade trees and adjacent forests within agroforestrylandscapes

    Quantifying services and disservices provided by insects and vertebrates in cacao agroforestry landscapes

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    Animals provide services such as pollination and pest control in cacao agro- forestry systems, but also disservices. Yet, their combined contributions to crop yield and fruit loss are mostly unclear. In a full-factorial field exper- iment in northwestern Peru, we excluded flying insects, ants, birds and bats from cacao trees and assessed several productivity indicators. We quan- tified the contribution of each group to fruit set, fruit loss and marketable yield and evaluated how forest distance and canopy closure affected pro- ductivity. Fruit set dropped (from 1.7% to 0.3%) when flying insects were excluded and tripled at intermediate (40%) compared to high (greater than 80%) canopy cover in the non-exclusion treatment. Fruit set also dropped with bird and bat exclusion, potentially due to increased abundances of arthropods preying on pollinators or flower herbivores. Overall, cacao yields more than doubled when birds and bats had access to trees. Ants were generally associated with fruit loss, but also with yield increases in agroforests close to forest. We also evidenced disservices generated by squir- rels, leading to significant fruit losses. Our findings show that several functional groups contribute to high cacao yield, while trade-offs between services and disservices need to be integrated in local and landscape-scale sustainable cacao agroforestry managemen

    Conditional normalizing flows for IceCube event reconstruction

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    Galactic Core-Collapse Supernovae at IceCube: “Fire Drill” Data Challenges and follow-up

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    The next Galactic core-collapse supernova (CCSN) presents a once-in-a-lifetime opportunity to make astrophysical measurements using neutrinos, gravitational waves, and electromagnetic radiation. CCSNe local to the Milky Way are extremely rare, so it is paramount that detectors are prepared to observe the signal when it arrives. The IceCube Neutrino Observatory, a gigaton water Cherenkov detector below the South Pole, is sensitive to the burst of neutrinos released by a Galactic CCSN at a level >10σ. This burst of neutrinos precedes optical emission by hours to days, enabling neutrinos to serve as an early warning for follow-up observation. IceCube\u27s detection capabilities make it a cornerstone of the global network of neutrino detectors monitoring for Galactic CCSNe, the SuperNova Early Warning System (SNEWS 2.0). In this contribution, we describe IceCube\u27s sensitivity to Galactic CCSNe and strategies for operational readiness, including "fire drill" data challenges. We also discuss coordination with SNEWS 2.0

    All-Energy Search for Solar Atmospheric Neutrinos with IceCube

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    The interaction of cosmic rays with the solar atmosphere generates a secondary flux of mesons that decay into photons and neutrinos – the so-called solar atmospheric flux. Although the gamma-ray component of this flux has been observed in Fermi-LAT and HAWC Observatory data, the neutrino component remains undetected. The energy distribution of those neutrinos follows a soft spectrum that extends from the GeV to the multi-TeV range, making large Cherenkov neutrino telescopes a suitable for probing this flux. In this contribution, we will discuss current progress of a search for the solar neutrino flux by the IceCube Neutrino Observatory using all available data since 2011. Compared to the previous analysis which considered only high-energy muon neutrino tracks, we will additionally consider events produced by all flavors of neutrinos down to GeV-scale energies. These new events should improve our analysis sensitivity since the flux falls quickly with energy. Determining the magnitude of the neutrino flux is essential, since it is an irreducible background to indirect solar dark matter searches

    Recent neutrino oscillation results with the IceCube experiment

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    The IceCube South Pole Neutrino Observatory is a Cherenkov detector instrumented in a cubic kilometer of ice at the South Pole. IceCube’s primary scientific goal is the detection of TeV neutrino emissions from astrophysical sources. At the lower center of the IceCube array, there is a subdetector called DeepCore, which has a denser configuration that makes it possible to lower the energy threshold of IceCube and observe GeV-scale neutrinos, opening the window to atmospheric neutrino oscillations studies. Advances in physics sensitivity have recently been achieved by employing Convolutional Neural Networks to reconstruct neutrino interactions in the DeepCore detector. In this contribution, the recent IceCube result from the atmospheric muon neutrino disappearance analysis using the CNN-reconstructed neutrino sample are presented and compared to the existing worldwide measurements

    Angular dependence of the atmospheric neutrino flux with IceCube data

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    IceCube Neutrino Observatory, the cubic kilometer detector embedded in ice of the geographic South Pole, is capable of detecting particles from several GeV up to PeV energies enabling precise neutrino spectrum measurement. The diffuse neutrino flux can be subdivided into three components: astrophysical, from extraterrestrial sources; conventional, from pion and kaon decays in atmospheric Cosmic Ray cascades; and the yet undetected prompt component from the decay of charmed hadrons. A particular focus of this work is to test the predicted angular dependence of the atmospheric neutrino flux using an unfolding method. Unfolding is a set of methods aimed at determining a value from related quantities in a model-independent way, eliminating the influence of several assumptions made in the process. In this work, we unfold the muon neutrino energy spectrum and employ a novel technique for rebinning the observable space to ensure sufficient event numbers within the low statistic region at the highest energies. We present the unfolded energy and zenith angle spectrum reconstructed from IceCube data and compare the result with model expectations and previous measurements
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