Comparing non-perturbative models of the breakup of neutron-halo nuclei

Breakup reactions of loosely-bound nuclei are often used to extract structure and/or astrophysical information. Here we compare three non-perturbative reaction theories often used when analyzing breakup experiments, namely the continuum discretized coupled channel model, the time-dependent approach relying on a semiclassical approximation, and the dynamical eikonal approximation. Our test case consists of the breakup of 15C on Pb at 68 MeV/nucleon and 20 MeV/nucleon.Comment: 8 pages, 6 figures, accepted for publication in Phys. Rev.

Mechanisms of direct reactions with halo nuclei

Halo nuclei are exotic nuclei which exhibit a strongly clusterised structure: they can be seen as one or two valence nucleons loosely bound to a core. Being observed at the ridge of the valley of stability, halo nuclei are studied mostly through reactions. In this contribution the reaction models most commonly used to analyse experimental data are reviewed and compared to one another. A reaction observable built on the ratio of two angular distributions is then presented. This ratio enables removing most of the sensitivity to the reaction mechanism, which emphasises the effects of nuclear structure on the reaction.Comment: Invited talk given by Pierre Capel at the "10th International Conference on Clustering Aspects of Nuclear Structure and Dynamics" (Cluster12), Debrecen, Hungary, 24-28 September 2012. To appear in the Cluster12 Proceedings in the Open Access Journal of Physics: Conference Series (JPCS). (5 pages, 3 figures

Mecanizacao agricola a tracao animal experiencias com chassi porta-implementos e algumas experiencias no CPATSA.

O trabalho faz um breve historico de varios tipos de chassi porta-implementos disponiveis no mundo, seguindo-se uma completa abordagem sobre a construcao dos dois modelos denominados Multicultor CPATSA e Multicultur CPATSA II. A fabricacao desses dois prototipos foi iniciada em novembro de 1979 e novembro de 1980, respectivamente, como atividade do Programa de Mecanizacao Agricola do Centro de Pesquisa do Tropico Semi-Arido (CPATSA) da EMBRAPA, Petrolina. O primeiro esta sendo fabricado em escala pre-comercial para ser testado em varios locais, enquanto que o prototipo inicial do Multicultor CPATSA II, vem sendo testado para se comparar o seu desempenho com o de outros equipamentos semelhantes. Ha possibilidade de que cada um desses chassi porta-implementos tenha tres modelos: a) com o eixo das rodas completo com o das carrocas tradicionais da regiao; b) com o eixo das rodas cortado abaixo do chassi para facilitar a capina, quando as culturas estiverem mais altas; c) com a bitola ajustavel, para facilitar a aracao

Recent developments in the eikonal description of the breakup of exotic nuclei

The study of exotic nuclear structures, such as halo nuclei, is usually performed through nuclear reactions. An accurate reaction model coupled to a realistic description of the projectile is needed to correctly interpret experimental data. In this contribution, we briefly summarise the assumptions made within the modelling of reactions involving halo nuclei. We describe briefly the Continuum-Discretised Coupled Channel method (CDCC) and the Dynamical Eikonal Approximation (DEA) in particular and present a comparison between them for the breakup of 15C on Pb at 68AMeV. We show the problem faced by the models based on the eikonal approximation at low energy and detail a correction that enables their extension down to lower beam energies. A new reaction observable is also presented. It consists of the ratio between angular distributions for two different processes, such as elastic scattering and breakup. This ratio is completely independent of the reaction mechanism and hence is more sensitive to the projectile structure than usual reaction observables, which makes it a very powerful tool to study exotic structures far from stability.Comment: Contribution to the proceedings of the XXI International School on Nuclear Physics and Applications & the International Symposium on Exotic Nuclei, dedicated to the 60th Anniversary of the JINR (Dubna) (Varna, Bulgaria, 6-12 September 2015), 7 pages, 4 figure

Structure Effects on Coulomb Dissociation of 8^8B

Coulomb Dissociation provides an alternative method for determining the radiative capture cross sections at astrophysically relevant low relative energies. For the breakup of $^8$B on $^{58}$Ni, we calculate the total Coulomb Dissociation cross section and the angular distribution for E1, E2 and M1. Our calculations are performed first within the standard first order semiclassical theory of Coulomb Excitation, including the correct three body kinematics, and later including the projectile-target nuclear interactions.Comment: 6 pages, proceedings from International Workshop on RNB, Puri, India, January 1998 - to be published in J. Phys.

Scaling Behavior of Driven Interfaces Above the Depinning Transition

We study the depinning transition for models representative of each of the two universality classes of interface roughening with quenched disorder. For one of the universality classes, the roughness exponent changes value at the transition, while the dynamical exponent remains unchanged. We also find that the prefactor of the width scales with the driving force. We propose several scaling relations connecting the values of the exponents on both sides of the transition, and discuss some experimental results in light of these findings.Comment: Revtex 3.0, 4 pages in PRL format + 5 figures (available at ftp://jhilad.bu.edu/pub/abbhhss/ma-figures.tar.Z ) submitted to Phys Rev Let

Transfer reactions and the dispersive optical-model

The dispersive optical-model is applied to transfer reactions. A systematic study of $(d,p)$ reactions on closed-shell nuclei using the finite-range adiabatic reaction model is performed at several beam energies and results are compared to data as well as to predictions using a standard global optical-potential. Overall, we find that the dispersive optical-model is able to describe the angular distributions as well as or better than the global parameterization. In addition, it also constrains the overlap function. Spectroscopic factors extracted using the dispersive optical-model are generally lower than those using standard parameters, exhibit a reduced dependence on beam energy, and are more in line with results obtained from $(e,e'p)$ measurements.Comment: Phys. Rev. C 84, 044611 (2011

The relationships between portuguese banks and their customers in a recessionary context

Financial institutions were in the genesis of the crisis that led to the current recession. This study aims to understand better the relationship Portuguese people have with their banks in a recessionary context, as well as to provide knowledge that may contribute to the consumer behavior field of research linking to the Banking industry. Having that purpose in mind, a quantitative study was conducted using data gathered by questionnaire using a sample of 488 respondents, which was further complemented by the information collected applying Netnography. The overall analysis suggests that the impact of the crisis on the household financial situation throughout the last couple of years influences attitudes towards money and expenses. The way customers’ purchase and consumption behaviors were affected by crisis are, to some extent, positively related to their satisfaction with the main bank.info:eu-repo/semantics/publishedVersio

Comparing different machine learning approaches for disfluency structure detection in a corpus of university lectures

This paper presents a number of experiments focusing on assessing the performance of different machine learning methods on the identification of disfluencies and their distinct structural regions over speech data. Several machine learning methods have been applied, namely Naive Bayes, Logistic Regression, Classification and Regression Trees (CARTs), J48 and Multilayer Perceptron. Our experiments show that CARTs outperform the other methods on the identification of the distinct structural disfluent regions. Reported experiments are based on audio segmentation and prosodic features, calculated from a corpus of university lectures in European Portuguese, containing about 32h of speech and about 7.7% of disfluencies. The set of features automatically extracted from the forced alignment corpus proved to be discriminant of the regions contained in the production of a disfluency. This work shows that using fully automatic prosodic features, disfluency structural regions can be reliably identified using CARTs, where the best results achieved correspond to 81.5% precision, 27.6% recall, and 41.2% F-measure. The best results concern the detection of the interregnum, followed by the detection of the interruption point.info:eu-repo/semantics/publishedVersio