58 research outputs found

    Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV

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    The three-body photodisintegration of 3He has been measured with the CLAS detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first time to cover a wide momentum and angular range for the two outgoing protons. Three kinematic regions dominated by either two- or three-body contributions have been distinguished and analyzed. The measured cross sections have been compared with results of a theoretical model, which, in certain kinematic ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications: removed 2 figures, improvements on others, a few minor modifications to the tex

    A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments

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    We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.Comment: revtex4 18 pp., 12 figure

    Study of polarized-e polarized-p --> e-prime p pi0 in the Delta(1232) mass region using polarization asymmetries

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    Measurements of the angular distributions of target and double spin asymmetries for the Delta(1232) in the exclusive channel (polarized-p polarized-e,e-prime p)pi0 obtained at Jefferson Lab in the Q2 range from 0.5 to 1.5 gev2 are presented. Results of the asymmetries are compared with the unitary isobar model, dynamical models, and the effective Lagrangian theory. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly.Comment: 14 pages, 13 figure

    Estudo comparativo dos efeitos do extrato de Ginkgo biloba L. e Panax ginseng C.A. Meyer na reprodução de ratos machos e fêmeas Wistar

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    Ginkgo biloba e Panax ginseng são plantas utilizadas na medicina tradicional. O objetivo do estudo foi avaliar a histologia gonadal de ratos machos e fêmeas Wistar submetidos aos tratamentos com o extrato de G. biloba (120 mg kg-1) ou P. ginseng (200 mg kg-1), e avaliar os parâmetros reprodutivos e fetais das ratas tratadas com as plantas. O grupo controle recebeu solução fisiológica 0,9%. Os tratamentos foram efetuados por via oral através de gavage, duas vezes ao dia, durante quinze dias consecutivos. Após este período, machos (n=18) e fêmeas (n=18) foram sacrificados e as gônadas coletadas, pesadas e processadas para avaliação microscópica. Outras fêmeas (n=18) foram acasaladas com machos não tratados para avaliação da fertilidade e produtos da gestação. Os resultados indicaram que o peso dos órgãos reprodutivos masculino e feminino não foi afetado pelos tratamentos. A estrutura gonadal dos machos e fêmeas mostrou o mesmo padrão histológico nos três grupos experimentais. O tratamento materno pré-gestacional com os extratos não promoveu alterações no desempenho reprodutivo das matrizes e nos parâmetros fetais. Concluiu-se que o extrato de P. ginseng ou G. biloba não causou toxicidade reprodutiva em ratos machos e fêmeas.Ginkgo biloba and Panax ginseng are plants used in the traditional medicine. The aim of study was to analyse the gonadal histology of the Wistar male and female rats submitted to the treatments with extract of G. biloba (120 mg kg-1) or P. ginseng (200 mg kg-1), and to evaluate the reproductive and fetal parameters of female rats treated with the plants. The control group received physiological solution 0.9%. The treatments were administered by oral gavage, twice/day, during fifteen consecutive days. After this period, male (n=18) and female rats (n=18) were sacrificed and the gonads collected, weighed and processed for microscopic evaluation. Another females (n=18) were matted with not treated males for evaluation of fertility and pregnancy outcome. The results indicated that the male and feminine reproductive organs weight was not affected by treatments. The gonadal structure of male and female rats showed same histologic pattern in the three experimental groups. The pre-gestational treatment with the extracts not promoted alterations in the reproductive performance of dams and in the fetal parameters. It was concluded that the extract of P. ginseng or G. biloba not presented reproductive toxicity in the male and female rats

    Basic Formal Education Quality, Information Technology and Inclusive Human Development in Sub-Saharan Africa

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    This study assesses the relevance of basic formal education in information technology for inclusive human development in 49 countries in sub-Saharan Africa for the period 2000-2012. The question it aims to answer is the following: what is the relevance of basic formal education in the effect of mobile phone penetration on inclusive human development in sub-Saharan Africa when initial levels of inclusive human development are taken into account? The empirical evidence is based on instrumental quantile regressions. Poor primary education dampens the positive effect of mobile phone penetration on inclusive human development. This main finding should be understood in the perspective that, the education quality indicator represents a policy syndrome because of the way it is computed, notably: the ratio of pupils to teachers. Hence, an increasing ratio indicates decreasing quality of education. It follows that decreasing quality of education dampens the positive effect of mobile phone on inclusive development. This tendency is consistent throughout the conditional distribution of inclusive human development. Policy implications for sustainable development are discussed

    Influenza vaccine effectiveness against hospitalizations associated with influenza a in Hong Kong children aged 9 months to 17 years, 2024/25

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    Influenza began circulating in Hong Kong in mid-December 2024. As of 12 March 2025, 1279 children were enrolled in a prospective test negative study for influenza vaccine effectiveness (VE). Among 209 influenza-positive cases, 71 % had influenza A(H1N1), 11 % had influenza A(H3N2), 3 % had influenza A with unknown subtype, and 15 % had influenza B. Among the test-negative controls, 53 % had received influenza vaccination since August 2024. End of the winter season VE estimates against hospitalization associated with influenza A(H1N1) was 64.8 % (95 % CI: 38.1 % to 80.3 %) and for influenza A(H3N2) was 59.9 % (95 % CI: −42.0 % to 89.6 %). These findings indicate that influenza vaccination provided protection against hospitalization for influenza A(H1N1) and A(H3N2) in children, highlighting the importance of continued vaccination efforts in Hong Kong

    Spin-isospin excitation in 12C(γ, π+)12B∗ using tagged photons

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    The energy spectra of positive pions from the reaction 12C(γ, π+)12B∗ were measured at five angles, using quasi-monochromatic, tagged photons in the energy range from 176 to 182 MeV. Strong transitions to the isovector nuclear states in 12B at 0–1, 4.5, and 7.5 MeV were observed. The differential cross sections to these states have been obtained for the momentum transfers 0.5 &#60; q &#60; 1.2 fm−1. DWIA calculations have been carried out in momentum space for each observed state or group of states. Comparisons are made between the present data, previous data from bremsstrahlung experiments, and various DWIA calculations
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