Structure of 13^{13}Be probed via secondary beam reactions

The low-lying level structure of the unbound neutron-rich nucleus $^{13}$Be has been investigated via breakup on a carbon target of secondary beams of $^{14,15}$B at 35 MeV/nucleon. The coincident detection of the beam velocity $^{12}$Be fragments and neutrons permitted the invariant mass of the $^{12}$Be+$n$ and $^{12}$Be+$n$+$n$ systems to be reconstructed. In the case of the breakup of $^{15}$B, a very narrow structure at threshold was observed in the $^{12}$Be+$n$ channel. Contrary to earlier stable beam fragmentation studies which identified this as a strongly interacting $s$-wave virtual state in $^{13}$Be, analysis here of the $^{12}$Be+$n$+$n$ events demonstrated that this was an artifact resulting from the sequential-decay of the $^{14}$Be(2$^+$) state. Single-proton removal from $^{14}$B was found to populate a broad low-lying structure some 0.70 MeV above the neutron-decay threshold in addition to a less prominent feature at around 2.4 MeV. Based on the selectivity of the reaction and a comparison with (0-3)$\hbar\omega$ shell-model calculations, the low-lying structure is concluded to most probably arise from closely spaced J$^\pi$=1/2$^+$ and 5/2$^+$ resonances (E$_r$=0.40$\pm$0.03 and 0.85$^{+0.15}_{-0.11}$ MeV), whilst the broad higher-lying feature is a second 5/2$^+$ level (E$_r$=2.35$\pm$0.14 MeV). Taken in conjunction with earlier studies, it would appear that the lowest 1/2$^+$ and 1/2$^-$ levels lie relatively close together below 1 MeV.Comment: 14 pages, 13 figures, 2 tables. Accepted for publication in Physical Review

Avaliação da transferência passiva de anticorpos em cabritos alimentados com três diferentes tipos de colostro.

Resumo: O processo de imunização passiva de caprinos se dá através do colostro. Por outro lado, o mesmo pode ser uma fonte importante de contaminação, forçando a separação da cria logo ao nascer. Faz-se necessário provê-lo de imunização passiva artificial. Dentre as alternativas sugeridas, duas têm sido bastante utilizadas na região nordeste do Brasil: colostro caprino natural termizado a 56ºC por 60 min e o formulado pela EMBRAPA/Caprinos. A finalidade deste trabalho foi observar o processo de transferência passiva de imunidade de cabritos alimentados com três tipos de colostros, através da identificação qualitativa de gamaglobulinas séricas. Para isso utilizaram-se animais machos provenientes de cabras mestiças que ao nascimento foram separados imediatamente da mãe, identificados divididos em 3 grupos. As colheitas de sangue foram realizadas através de punção jugular. Após a primeira colheita foram administrados os três tipos de colostro:termizado (A), EMBRAPA (B) e colostro natural (C). As colheitas subsequentes foram realizadas às 48 h e aos 14 dias de vida. As amostras foram processadas em centrífuga para a obtenção de soro que foi aliquotado e armazenado a -20ºC. As amostras foram submetidas à eletroforese e a leitura em densitômetro a 520nm para melhor visualização das frações separadas. No soro de cabritos (n=8) com zero hora de vida, foram detectadas três frações correspondendo a albumina, alfa e betaglobulinas. Nos cabritos (n=8) com 48 h de vida, dos grupos A e C, foi observado uma quarta fração referen te a gamaglobulina. Entretanto no grupo B (n=8) tanto com 48 h como aos 14 dias de vida a fração gamaglobulina só foi evidenciada com o auxílio do densitômetro. Dentre os tratamentos utilizados o colostro caprino termizado apresentou-se, como a melhor alternativa para transferências de imunidade passiva. [Evaluation of antibodies passive transference in kids fed with three different colostrum types]. Abstract: The passive transfer process on goats occurs by the colostrum feeding. This can confer protection against infectious diseases, but can also be a contamination source, necessitating the separation of kids from their mothers immediately after birth. Thus an artificial passive immunization is required. Among the approaches available, two are strongly used in northweastern Brazil:heat-treating goat colustrum to 56ºC for 1 h and EMBRAPA colostrum. The purpose of this study was to observe the process of passive transfer of immunity in kids fed with three kinds of colostrum. 24 male kids were immediately separated from their mothers at birth, identified, distributed into three groups A, B and C. After birth, a prefeeding blood sample was collected from the jugular vein, following which the kids with the 3 types of colostrum (heat-treating, EMBRAPA and raw colostrum). Blood samples collected at 48 h after birth and 14 days. These samples were then centrifuged and the serum was frozen adn stored at -20ºC. Serum eletrophoresis was carried out and the strips were read by a densitometer set at 520 nm of absorbance to verify the number of bands present. The 24 prefeeding samples displayed three bands, comprising the albumin, alpha and beta globulins. The 24 samples corresponding to 48 hh and day 14 showed a 4th band relative to the gammaglobulin fraction in A, B and C groups, but the strips corresponding to group B only presented a fragile band. The study indicates for the passive transference of immunity was heat-treating goat colustrum at 56ºC for 1 h

Three-body correlations in Borromean halo nuclei

Three-body correlations in the dissociation of two-neutron halo nuclei are explored using a technique based on intensity interferometry and Dalitz plots. This provides for the combined treatment of both the n-n and core-n interactions in the exit channel. As an example, the breakup of 14Be into 12Be+n+n by Pb and C targets has been analysed and the halo n-n separation extracted. A finite delay between the emission of the neutrons in the reaction on the C target was observed and is attributed to 13Be resonances populated in sequential breakup.Comment: 5 pages, 4 figures, submitted to PR

Modelo digital para a Restinga e Paleoilha da Marambaia, Rio de Janeiro.

Foi criado para a Marambaia um modelo digital de seu ambiente, com a finalidade de avaliar as diversas situações ambientais presentes na região. Acha-se representado por um conjunto de sete mapas digitais temáticos constituintes da Base de Dados Georreferenciadas, e por dois mapas digitais classificatórios, correspondentes às avaliações das áreas com potencial para testes militares e para investigação científica. Estes produtos foram desenvolvidos pelo Laboratório de Geoprocessamento Aplicado da UFRRJ, através do uso da técnica de geoprocessamento e métodos associados do programa SAGA/UFRJ - Sistema de Análise Geo Ambiental

The detection of neutron clusters

A new approach to the production and detection of bound neutron clusters is presented. The technique is based on the breakup of beams of very neutron-rich nuclei and the subsequent detection of the recoiling proton in a liquid scintillator. The method has been tested in the breakup of 11Li, 14Be and 15B beams by a C target. Some 6 events were observed that exhibit the characteristics of a multineutron cluster liberated in the breakup of 14Be, most probably in the channel 10Be+4n. The various backgrounds that may mimic such a signal are discussed in detail.Comment: 11 pages, 12 figures, LPCC 01-1