Limitation of double folding potentials to simulate the polarization in reactions involving halo nuclei

In this work, we investigate the limitation of the use of strength coefficients on double folding potentials to study the presence of the threshold anomaly in the elastic scattering of halo nuclei at near barrier energies. For this purpose, elastic angular distributions and reaction cross sections for the He-6 on Bi-209 are studied. (c) 2008 Elsevier B.V. All rights reserved.

Transfer reactions in the investigation of light-nuclei nucleosynthesis

Cross sections for the (6)Li(p,gamma)(7)Be, (7)Li(n,gamma)(8)Li (8)Li(n,gamma)(9)Li and (8)Li(p,gamma)(9)Be capture reactions have been investigated in the framework of the potential model. The main ingredients of the potential model are the potentials used to generate the continuum and bound-state wave functions and spectroscopic factors of the corresponding bound systems. The spectroscopic factors for the (7)Li circle times n=(8)Li(gs), (8)Li circle times n=(9)Li(gs) bound systems were obtained from a FR-DWBA analysis of neutron transfer reactions induced by (8)Li radioactive beam on a (9)Be target, while spetroscopic factor for the (8)Li circle times n=(9)Be(gs) bound system were obained from a proton transfer reaction. From the obtained capture reaction cross section, reaction rate for the (8)Li(n,gamma)(9)Li and (8)Li(p,gamma)(9)Be direct neutron and proton capture were determined and compared with other experimental and calculated values.

Investigation of the properties of galactic cosmic rays with the KASCADE-Grande experiment

The properties of galactic cosmic rays are investigated with the KASCADE-Grande experiment in the energy range between 10(14) and 10(18) eV. Recent results are discussed. They concern mainly the all-particle energy spectrum and the elemental composition of cosmic rays. (C) 2010 Elsevier B.V. All rights reserved.

The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays

Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found.

A doorway to Borromean halo nuclei: the Samba configuration

We exploit the possibility of new configurations in three-body halo nuclei, Samba type (the neutron-core form a bound system) as a doorway to Borromean systems. The nuclei Be-12, B-15, N-23 and F-27 are of such nature, in particular N-23 with a half-life of 37.7 s and a halo radius of 6.07 fm is an excellent example of Samba-halo configuration. The fusion below the barrier of the Samba halo nuclei with heavy targets could reveal the so far elusive enhancement and a dominance of one-neutron over two-neutron transfers, in contrast to what was found recently for the Borromean halo nucleus He-6 + U-238.

Tensor coupling and pseudospin symmetry in nuclei

In this work we study the contribution of the isoscalar tensor coupling to the realization of pseudospin symmetry in nuclei. Using realistic values for the tensor coupling strength, we show that this coupling reduces noticeably the pseudospin splittings, especially for single-particle levels near the Fermi surface. By using an energy. decomposition of the pseudospin energy splittings, we show that the changes in these splittings come mainly through the changes induced in the lower radial wave function for the low-lying pseudospin partners and through changes in the expectation value of the pseudospin-orbit coupling term for surface partners. This allows us to confirm the conclusion already reached in previous studies, namely that the pseudospin symmetry in nuclei is of a dynamical nature.

Spin and pseudospin symmetries in the antinucleon spectrum of nuclei

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Accessory Nuclei in the Oocytes of Pachycondyla (Neoponera) villosa (Hymenoptera: Ponerinae) as a Source of Annulate Lamellae

In insects' oocytes, structures called accessory nuclei can be observed. They are similar to the nucleus of the oocyte and have been detected in Hymenoptera as well as in other groups, with their source and functions still under discussion (Cassidy & King 1972). Through the use of histochemical techniques as well as ultrastructural ones, it was possible to observe several accessory nuclei surrounding the oocyte nucleus in the immature oocytes of Pachycondyla (Neoponera) villosa ants. Morphologically they were seen to be round and smaller than the germinal vesicle. When using these histochemical techniques, the only positive reaction was for proteins. Ultrastructurally they have the same morphology as the oocyte nucleus and a fine and electrondense granulation was observed inside them. The function of accessory nuclei in P (Neoponera) villosa is probably as a source of anullate lamellae and as an RNA reservoir in the oocytes. In mature oocytes (stage III), these structures are not observed, suggesting that they disappeared before this stage by releasing their contents into the oocytes' cytoplasm, according to Camargo-Mathias and Caetano (1993).

Cytochemical studies of the nuclei of the venom glands' cells of Apis mellifera (Hymenoptera, Apidae)

Cytochemistry studies of the nuclei of the venom glands' cells of worker bees of Apis mellifera indicated that there is a higher activity in the young workers while there is a predominance of degenerative characteristics in the older workers. In addition, we demonstrated that there is an occurrence of differential nuclear synthetic activities between the cells of the distal and the proximal regions of the secretory filament and of the venom reservoir. Signs of a higher nuclear activity were evidenced at the distal regions of this gland in 14-day old workers, while at the more proximal regions of the venom gland of 40-day old workers we identified the most obvious signs of degeneration. Therefore, it was evident that the process of glandular degeneration begins at the distal region of the venom gland instead of beginning at the proximal region as had been established previously. In addition, characteristics of nuclear synthetic activities were noted in the cells of the proximal region of the reservoir; these cells were thought to be non-secretory.

A simple procedure for rehybridization of nuclei analyzed previously by fish

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Radii in weakly-bound light halo nuclei

A systematic study of the root-mean-square distance between the constituents of weakly-bound nuclei consisting of two halo neutrons and a core is performed using a renormalized zero-range model. The radii are obtained from a universal scaling function that depends on the mass ratio of the neutron and the core, as well as on the nature of the subsystems, bound or virtual. Our calculations are qualitatively consistent with recent data for the neutron-neutron root-mean-square distance in the halo of Li-11 and Be-14 nuclei. (C) 2004 Published by Elsevier B.V.

The few scales of nuclei and nuclear matter

The well-known correlations of low-energy three and four-nucleon observables with a typical three-nucleon scale (e.g., the Tjon line) is extended to light nuclei and nuclear matter. Evidence for the scaling between light nuclei binding energies and the triton one are pointed out. We argue that the saturation energy and density of nuclear matter are correlated to the triton binding energy. The available systematic nuclear matter calculations indicate a possible band structure representing these correlations. (c) 2006 Elsevier B.V. All rights reserved.

Structure of large two-neutron halos in light exotic nuclei

The structure of three-body halo nuclei formed by two neutrons and a core (nnc) is studied using zero-range interactions. The halo wave function can be completely parameterized only by the s-wave scattering lengths and two-neutron separation energy. The sizes and the neutron-neutron correlation function of Li-11 and Be-14 are calculated and compared to experimental data. A general classification scheme for three-body halos with two identical particles is discussed as well as the critical conditions to allow excited Efimov states.

Neutron-neutron correlation in the halo dissociation of light exotic nuclei

We present model results for the two-halo-neutron correlation functions, C-nn, for the dissociation process of light exotic nuclei modelled as two neutrons and a core. A minimum is predicted for C-nn as a function of the relative momentum of the two neutrons, p(nn), due to the coherence of the neutrons in the halo and final state interaction. Studying the systems Be-14, Li-11, and He-6 within this model, we show that the numerical asymptotic limit, C-nn-> 1, occurs only for p(nn)greater than or similar to 400 MeV/c, while such limit is reached for much lower values of p(nn) in an independent particle model as the one used in the analysis of recent experimental data. Our model is consistent with data once the experimental correlation function is appropriately normalized.

GALACTIC NONLINEAR DYNAMIC MODEL

We develop a model for spiral galaxies based on a nonlinear realization of the Newtonian dynamics starting from the momentum and mass conservations in the phase space. The radial solution exhibits a rotation curve in qualitative accordance with the observational data.