23,975 research outputs found

    Acceptance of fluorescence detectors and its implication in energy spectrum inference at the highest energies

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    Along the years HiRes and AGASA experiments have explored the fluorescence and the ground array experimental techniques to measure extensive air showers, being both essential to investigate the ultra-high energy cosmic rays. However, such Collaborations have published contradictory energy spectra for energies above the GZK cut-off. In this article, we investigate the acceptance of fluorescence telescopes to different primary particles at the highest energies. Using CORSIKA and CONEX shower simulations without and with the new pre-showering scheme, which allows photons to interact in the Earth magnetic field, we estimate the aperture of the HiRes-I telescope for gammas, iron nuclei and protons primaries as a function of the number of simulated events and primary energy. We also investigate the possibility that systematic differences in shower development for hadrons and gammas could mask or distort vital features of the cosmic ray energy spectrum at energies above the photo-pion production threshold. The impact of these effects on the true acceptance of a fluorescence detector is analyzed in the context of top-down production models

    VLTI/PIONIER images the Achernar disk swell

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    Context. The mechanism of disk formation around fast-rotating Be stars is not well understood. In particular, it is not clear which mechanisms operate, in addition to fast rotation, to produce the observed variable ejection of matter. The star Achernar is a privileged laboratory to probe these additional mechanisms because it is close, presents B-Be phase variations on timescales ranging from 6 yr to 15 yr, a companion star was discovered around it, and probably presents a polar wind or jet. Aims. Despite all these previous studies, the disk around Achernar was never directly imaged. Therefore we seek to produce an image of the photosphere and close environment of the star. Methods. We used infrared long-baseline interferometry with the PIONIER/VLTI instrument to produce reconstructed images of the photosphere and close environment of the star over four years of observations. To study the disk formation, we compared the observations and reconstructed images to previously computed models of both the stellar photosphere alone (normal B phase) and the star presenting a circumstellar disk (Be phase). Results. The observations taken in 2011 and 2012, during the quiescent phase of Achernar, do not exhibit a disk at the detection limit of the instrument. In 2014, on the other hand, a disk was already formed and our reconstructed image reveals an extended H-band continuum excess flux. Our results from interferometric imaging are also supported by several H-alpha line profiles showing that Achernar started an emission-line phase sometime in the beginning of 2013. The analysis of our reconstructed images shows that the 2014 near-IR flux extends to 1.7 - 2.3 equatorial radii. Our model-independent size estimation of the H-band continuum contribution is compatible with the presence of a circumstellar disk, which is in good agreement with predictions from Be-disk models

    The Adaptation and Feasibility of Narrative Enhancement and Cognitive Therapy (NECT) for Late-Onset Psychosis

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    The aim of this study is to adapt and feasibility test the narrative component of Narrative Enhancement and Cognitive Therapy (NECT) for late-onset psychosis. This study followed the development and feasibility phases of the Medical Research Council framework. The original NECT intervention was adapted based on consultations with service users, experts, and clinicians. The evaluation of the feasibility test of the adapted intervention was guided by Orsmond and Cohn (Occup Particip Health 35(3):169-177, 2015)'s model for feasibility studies. The final adaptations consist of language, readability, and delivery. The adapted intervention was tested for feasibility and acceptability with one group of five patients recruited from a National Health Service (NHS) Trust in UK Results were mixed in participant outcomes and a likelihood of acceptability of the intervention. This indicates the need for a larger scale feasibility test to explore the identified benefits and challenges of implementing NECT in NHS or community settings for late-onset psychosis

    Phantoms for diffusion-weighted imaging and diffusion tensor imaging quality control: a review and new perspectives

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    FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQIntroduction: Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) combine magnetic resonance imaging (MRI) techniques and diffusion measures. In DWI, the contrast is defined by microscopic motion of water protons. Nowadays, DWI has become important for early diagnostic of acute stroke. DTI images are calculated from DWI images acquired in at least six directions, which give information of diffusion directionality, making it possible to reconstruct axonal or muscle fiber images. Both techniques have been applied to study body structures in healthy and pathological conditions. Currently, it is known that these images and derived parameters are quite sensitive to factors related to acquisition and processing. Magnetic field inhomogeneity, susceptibility, chemical shift, radiofrequency (RF) interference, eddy currents and low signal-to-noise ratio (SNR) can have a more harmful effect in diffusion data than in T1- or T2-weighted image data. However, even today there are not reference phantoms and guidelines for DWI or DTI quality control (QC). Review: Proposals for construction and use of DWI and DTI QC phantoms can be found in literature. DWI have been evaluated using containers filled by gel or liquid with tissue-like MRI properties, as well as using microfabricated devices. DTI acquisitions also have been checked with these devices or using natural or artificial fiber structures. The head phantom from American College of Radiology (ACR) is also pointed out as an alternative for DTI QC. This article brings a discussion about proposed DWI and DTI phantoms, challenges involved and future perspectives for standardization of DWI and DTI QC.332156165FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2013/07559-3310860/2014-

    Tidal effects and the Proximity decay of nuclei

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    We examine the decay of the 3.03 MeV state of 8^8Be evaporated from an excited projectile-like fragment following a peripheral heavy-ion collision. The relative energy of the daughter α\alpha particles exhibits a dependence on the decay angle of the 8^8Be^*, indicative of a tidal effect. Comparison of the measured tidal effect with a purely Coulomb model suggests the influence of a measurable nuclear proximity interaction.Comment: 5 pages, 4 figure

    Sugarcane: the evolution of technological thinking in agriculture.

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    The purpose of this study is to show the importance of technological progress in sugarcane production and its impact on the Brazilian economy. The evolution is shown using the time line concept to separate the most important cycles of the sugar-alcohol sector, while economic, social and environmental indicators are used to measure the results. The indicators clearly point out the sector?s progress and modernization. The study focuses on the advances achieved through the generation of new crop varieties with specific characteristics and the development of new products and byproducts of the sugarcane industrialization process. Special attention is accorded to the growth and increasing importance of the crop in the local and national economies, shown on the basis of the harvest values for the last ten years and production forecasts until 2020. The study concludes that the evolution of the agricultural and industrial technology in the recent past has enabled the sugarcane sector to become the most important and competitive in the world

    Timescale for equilibration of N/Z gradients in dinuclear systems

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    Equilibration of N/Z in binary breakup of an excited and transiently deformed projectile-like fragment (PLF*), produced in peripheral collisions of 64Zn + 27Al, 64Zn, 209Bi at E/A = 45 MeV, is examined. The composition of emitted light fragments (3<=Z<=6) changes with the decay angle of the PLF*. The most neutron-rich fragments observed are associated with a small rotation angle. A clear target dependence is observed with the largest initial N/Z correlated with the heavy, neutron-rich target. Using the rotation angle as a clock, we deduce that N/Z equilibration persists for times as long as 3-4 zs (1zs = 1 x 10^-21 s = 300 fm/c). The rate of N/Z equilibration is found to depend on the initial neutron gradient within the PLF*.Comment: 6 pages, 4 figure
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