220 research outputs found

    The DEAR experiment on DAΦNE

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    DEAR is one of the first experiments at the new DAΦNE Ø-factory at the Laboratori Nazionali di Frascati dell'INFN. The objective of the DEAR experiment is to perform a precision measurement of the strong interaction shifts and widths of the K-series lines in kaonic hydrogen and the first observation of the same quantities in kaonic deuterium. The aim is to obtain a precise determination of the isospin-dependent kaon-nucleon scattering lengths which will represent a breakthrough in KN low-energy phenomenology and will allow us to determine the kaon-nucleon sigma terms. The sigma terms give a direct measurement of chiral symmetry breaking and are connected to the strangeness content of the proton. First results on background measurements with the DEAR NTP setup installed on DAΦNE are reported

    Muon capture by 3He nuclei followed by proton and deuteron production

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    The paper describes an experiment aimed at studying muon capture by 3He{}^{3}\mathrm{He} nuclei in pure 3He{}^{3}\mathrm{He} and D2+3He\mathrm{D}_2 + {}^{3}\mathrm{He} mixtures at various densities. Energy distributions of protons and deuterons produced via μ+3Hep+n+n+νμ\mu^-+{}^{3}\mathrm{He}\to p+n+n + \nu_{\mu } and μ+3Hed+n+νμ\mu^-+{}^{3} \mathrm{He} \to d+n + \nu_{\mu} are measured for the energy intervals 104910 - 49 MeV and 133113 - 31 MeV, respectively. Muon capture rates, λcapp(ΔEp)\lambda_\mathrm{cap}^p (\Delta E_p) and λcapd(ΔEd)\lambda_\mathrm{cap}^d (\Delta E_d) are obtained using two different analysis methods. The least--squares methods gives λcapp=(36.7±1.2)s1\lambda_\mathrm{cap}^p = (36.7\pm 1.2) {s}^{- 1}, λcapd=(21.3±1.6)s1\lambda_\mathrm{cap}^d = (21.3 \pm 1.6) {s}^{- 1}. The Bayes theorem gives λcapp=(36.8±0.8)s1\lambda_\mathrm{cap}^p = (36.8 \pm 0.8) {s}^{- 1}, λcapd=(21.9±0.6)s1\lambda_\mathrm{cap}^d = (21.9 \pm 0.6) {s}^{- 1}. The experimental differential capture rates, dλcapp(Ep)/dEpd\lambda_\mathrm{cap}^p (E_p) / dE_p and dλcapd(Ed)/dEd d\lambda_\mathrm{cap}^d (E_d) / dE_d, are compared with theoretical calculations performed using the plane--wave impulse approximation (PWIA) with the realistic NN interaction Bonn B potential. Extrapolation to the full energy range yields total proton and deuteron capture rates in good agreement with former results.Comment: 17 pages, 13 figures, accepted for publication in PR

    Escrevendo em aulas de Ciências

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    Neste artigo, apresentamos uma análise dos registros escritos dos alunos do 3° ano do Ensino Fundamental nas aulas de Ciências, em que a professora utilizou as atividades de conhecimento físico, criadas pelo Laboratório de Pesquisa e Ensino de Física da Faculdade de Educação da Universidade de São Paulo. Os registros analisados foram coletados na Escola de Aplicação da Feusp, no ano de 2001, durante o acompanhamento de três aulas de Ciências: o problema do submarino, o problema do barquinho e o problema da pressão. O artigo procura mostrar um panorama de como aparecem os registros realizados pelos alunos, após uma aula de Ciências em que eles são levados a resolver situações problemáticas por meio da experimentação, argumentar e escrever sobre os fenômenos físicos. Durante a análise, levou-se em consideração os tipos de textos que os alunos escrevem, o uso da primeira pessoa, o uso de verbos de ação, o respeito à ordem cronológica dos eventos e quais os tipos de explicações os alunos atribuem aos fenômenos trabalhados

    Overexpression of Human and Fly Frataxins in Drosophila Provokes Deleterious Effects at Biochemical, Physiological and Developmental Levels

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    10 pages, 5 figures. 21779322[PubMed] PMCID: PMC3136927BACKGROUND: Friedreich's ataxia (FA), the most frequent form of inherited ataxias in the Caucasian population, is caused by a reduced expression of frataxin, a highly conserved protein. Model organisms have contributed greatly in the efforts to decipher the function of frataxin; however, the precise function of this protein remains elusive. Overexpression studies are a useful approach to investigate the mechanistic actions of frataxin; however, the existing literature reports contradictory results. To further investigate the effect of frataxin overexpression, we analyzed the consequences of overexpressing human (FXN) and fly (FH) frataxins in Drosophila. METHODOLOGY/PRINCIPAL FINDINGS: We obtained transgenic flies that overexpressed human or fly frataxins in a general pattern and in different tissues using the UAS-GAL4 system. For both frataxins, we observed deleterious effects at the biochemical, histological and behavioral levels. Oxidative stress is a relevant factor in the frataxin overexpression phenotypes. Systemic frataxin overexpression reduces Drosophila viability and impairs the normal embryonic development of muscle and the peripheral nervous system. A reduction in the level of aconitase activity and a decrease in the level of NDUF3 were also observed in the transgenic flies that overexpressed frataxin. Frataxin overexpression in the nervous system reduces life span, impairs locomotor ability and causes brain degeneration. Frataxin aggregation and a misfolding of this protein have been shown not to be the mechanism that is responsible for the phenotypes that have been observed. Nevertheless, the expression of human frataxin rescues the aconitase activity in the fh knockdown mutant. CONCLUSION/SIGNIFICANCE: Our results provide in vivo evidence of a functional equivalence for human and fly frataxins and indicate that the control of frataxin expression is important for treatments that aim to increase frataxin levels.This work was supported by grants from Fondo Investigaciones Sanitarias (ISCIII06- PI0677) and La Fundació la Marató TV3 (exp 101932) of Spain. JVL is supported by the European Friedreich's Ataxia Consortium for Translational Studies. SS is a recipient of a fellowship from Ministerio de Ciencia e Innovación of Spain.Peer reviewe
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