Comment on "Electromagnetic dissociation of ^8B and the astrophysical S-factor for ^7Be(p,gamma)^8B"

Recently, Davids and Typel recommended a "low" value of S_{17}(0) based on fits to published direct and Coulomb dissociation data, in which they excluded the precise result of Junghans et al. We show that their statistical analysis is incorrect, due to a substantial underestimate of the experimental uncertainties, and leads to conclusions that are not supported by a proper analysis.Comment: submitted to Phys. Rev.

Caracterização agronômica de acessos de germoplasma, cultivares e híbridos de abacaxizeiro.

O Brasil é um dos maiores produtores mundiais de abacaxi, mas a produção brasileira é destinada basicamente ao mercado interno e nos plantios comerciais há predomínio de poucas cultivares. O melhoramento genético do abacaxizeiro no Brasil visa obter variedades produtivas, com qualidade de fruto e resistência à fusariose.PDF. 101_11

Germinação in vitro de sementes de Passiflora edulis visando a conservação de germoplasma.

gênero Passiflora possui mais de 500 espécies descritas e, dentre elas, encontra-se o maracujá-amarelo (Passiflora edulis Sims), variedade de maior importância econômica para o Brasil. Este gênero apresenta uma enorme variabilidade genética, sendo o Brasil um dos principais centros de dispersão dessa variabilidade (Ferreira, 2005). As passifloráceas apresentam potencial para utilização direta ou indireta para atender o mercado de fruta fresca, suco concentrado; apresentando também, valor ornamental e medicinal, algumas com finalidade múltipla (Vanderplank, 2000). A perda de material genético pelo desmatamento, fruto do avanço imobiliário, expansão agropecuária, construção de hidrelétricas e de rodovias, constitui parte dos problemas da cultura. Desta forma, a conservação de germoplasma é imperativa, visto ser a base para obtenção do progresso genético em programas de melhoramento (Cunha, 2004). Em bancos de germoplasma mantidos em nível de campo é fundamental a germinação de sementes para a substituição das plantas de cada acesso que forem perdidas, seja por causas naturais ou por pragas e doenças. As técnicas de cultivo in vitro são ferramentas valiosas de auxílio à conservação de bancos de germoplasma, pois podem viabilizar a germinação de sementes que não germinariam da maneira convencional. O presente trabalho objetivou testar meios de cultura na germinação in vitro de sementes de P. edulis para futuramente viabilizar a obtenção de plantas de acessos do banco de germoplasma que tenham poucas sementes e/ou que tenham dificuldades para germinar em condições de casa de vegetação.pdf 160

Experimental study of fragmentation products in the reactions 112Sn + 112Sn and 124Sn + 124Sn at 1 AGeV

Production cross-sections and longitudinal velocity distributions of the projectile-like residues produced in the reactions 112Sn + 112Sn and 124Sn + 124Sn both at an incident beam energy of 1 AGeV were measured with the high-resolution magnetic spectrometer, the Fragment Separator (FRS) of GSI. For both reactions the characteristics of the velocity distributions and nuclide production cross sections were determined for residues with atomic number Z $\geq$ 10. A comparison of the results of the two reactions is presented.Comment: 14 pages, 12 figure

First Measurement of the 64Ni(gamma,n)63Ni Cross Section

Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-ShareAlike LicenceIn the past 10 years new and more accurate stellar neutron capture cross section measurements have changed and improved the abundance predictions of the weak s process. Among other elements in the region between iron and strontium, most of the copper abundance observed today in the solar system distribution was produced by the s process in massive stars. However, experimental data for the stellar 63Ni(n,gamma)64Ni cross section are still missing, but is strongly required for a reliable prediction of the copper abundances. 63Ni (t1/2 =101.2 a) is a branching point and also bottleneck in the weak s process flow, and abehaves differently during core He and shell C burning. During core He burning the reaction flow proceeds via beta-decay to 63Cu, and a change of the 63Ni(n,gamma)64Ni cross section would have no influence. However, this behavior changes at higher temperatures and neutron densities during the shell C burning phase. Under these conditions, a significant amount of the s process nucleosynthesis flow is passing through the channel 62Ni(n,gamma)63Ni(n,gamma)64Ni. At present only theoretical estimates are available for the 63Ni(n,gamma)64Ni cross section. The corresponding uncertainty affects the production of 63Cu in present s process nucleosynthesis calculations and propagates to the abundances of the heavier species up to A=70. So far, experimental information is also missing for the inverse 64Ni(gamma,n) channel. We have measured for the first time the 64Ni(gamma,n)63Ni cross section and also combined for the first time successfully the photoactivation technique with subsequent Accelerator Mass Spectrometry (AMS). The activations at the ELBE facility in Dresden-Rossendorf were followed by the 63Ni/64Ni determination with AMS at the MLL accelerator laboratory in Garching. First results indicate that theoretical predictions have overestimated this cross section up to now. If this also holds for the inverse channel 63Ni(n,gamma)64Ni, more 63Ni is accumulated during the high neutron density regime of the C shell that will contribute to the final abundance of 63Cu by radiogenic decay. In this case, also a lower s process efficiency is expected for the heavier species along the neutron capture path up to the Ga-Ge regio

Desenvolvimento da folha D do Abacaxizeiro Imperial em função da adubação com Nitrogênio e Potássio.

A variedade de abacaxizeiro Imperial tem grande potencial de se estabelecer comercialmente, não só pela sua resistência à fusariose e folhas sem espinhos, mas também pela excelente aceitação de seus frutos devido às suas características organolépticas e boa aparência. Porém, é necessário o estabelecimento de bases tecnológicas para a viabilização dos sistemas de produção para essa nova variedade

Photoactivation experiment on 197Au and its implications for the dipole strength in heavy nuclei

The 197Au(gamma,n) reaction is used as an activation standard for photodisintegration studies on astrophysically relevant nuclei. At the bremsstrahlung facility of the superconducting electron accelerator ELBE (Electron Linear accelerator of high Brilliance and low Emittance) of Forschungszentrum Dresden-Rossendorf, photoactivation measurements on 197Au have been performed with bremsstrahlung endpoint energies from 8.0 to 15.5 MeV. The measured activation yield is compared with previous experiments as well as with calculations using Hauser-Feshbach statistical models. It is shown that the experimental data are best described by a two-Lorentzian parametrization with taking the axial deformation of 197Au into account. The experimental 197Au(gamma,n) reaction yield measured at ELBE via the photoactivation method is found to be consistent with previous experimental data using photon scattering or neutron detection methods.Comment: 9 page