Resumo em Inglês:

The accumulation and distribution of 40K and 137Cs in tropical plant species were studied through measurements of gamma-ray spectra from mango, avocado, guava, pomegranate, chili pepper, papaya and manioc trees. Our goal was to infer their differences in the uptake and translocation of ions to the aboveground plant parts and to establish the suitability of using radiocaesium as a tracer for the plant uptake of nutrients such as K+.

Resumo em Inglês:

In this work we perform quasiparticle-rotor coupling model calculations within the usual BCS and the projected BCS for the carbon isotopes 15C, 17C and 19C using 13C as the building block. Owing to the pairing correlation, we find that 13C as well as the cores of the other isotopes, namely 14C, 16C and 18C acquire strong and varied deformations. The deformation parameter is large and negative for 12C, very small (or zero) for 14C and large and positive for 16C and 18C. This finding casts a doubt about the purity of the supposed simple one-neutron halo nature of 19C.

Resumo em Inglês:

In this work, a model based on single particle plus pairing residual interaction was used to study the low-lying excited states of the 193Ir nucleus. In this model, the deformation parameters in equilibrium were obtained by minimizing the total energy calculated by the Strutinsky prescription; the macroscopic contribution to the potential was taken from the Liquid Droplet Model, with the shell and paring corrections used as as microscopic contributions. The nuclear shape was described using the Cassinian ovoids as base figures; the single particle energy spectra and wave functions for protons and neutrons were calculated in a deformed Woods-Saxon potential, where the parameters for neutrons were obtained from the literature and the parameters for protons were adjusted in order to describe the main sequence of angular momentum and parity of the bandheads, as well as the proton binding energy of 193Ir. The residual pairing interaction was calculated using the BCS prescription with Lipkin-Nogami approximation. The results obtained for the first three bandheads (the 3/2+ ground state, the 1/2+ excited state at E ~ 73keV and the the 11/2- isomeric state at E ~ 80keV) showed a very good agreement, but the model so far greatly overestimated the energy of the next bandhead, a 7/2- at E ~ 299keV.

Resumo em Inglês:

We present general explicit expressions for a shell-model calculationof the vector hypernuclear parameter in nonmesonic weak decay. We use a widely accepted effective coupling Hamiltonian involving theexchange of the complete pseudoscalar and vector meson octets(<FONT FACE=Symbol>p, h</FONT>, K, <FONT FACE=Symbol>r, w</FONT>, K*). In contrast to the approximated formula widely used in the literature,we correctly treat the contribution of transitions originated fromsingle-proton states beyond the s-shell. Exact and simple analytical expressions are obtained for the particularcases of $^5_Lambda$He and $^{12}_\Lambda$C, within theone-pion-exchange model. Numerical computations of the asymmetry parameter, $a_\Lambda$, are presented. Our results show a qualitative agreementwith other theoretical estimates but also acontradiction with recent experimental determinations. Our simple analytical formulas provide a guide in searchingthe origin of such discrepancies, andthey will be useful for helping to solve the hypernuclearweak decay puzzle.

Resumo em Inglês:

Low-lying levels of 103Pd have been investigated through the (d,t) reaction on 104Pd, at an incident deuteron energy of 15.0 MeV. Outgoing particles were momentum analyzed by an Enge magnetic spectrograph and detected in nuclear emulsion plates, with an energy resolution of 8 keV. Previous (d,t) work suffered from a much worse resolution than that here achieved. A partial analysis of the data obtained is reported, referring to six out of the fourteen scattering angles for which data were obtained. Angular distributions associated with eight of the thirteen levels seen up to 1.1 MeV of excitation have been compared to DWBA one-neutron pick-up predictions. Both, the attributed excitation energy values and the transferred angular momenta are in excellent agreement with the results of other kind of experiments, as tabulated by the Nuclear Data Sheets. Some peculiar structure characteristics, associated with the yrast 5/2+, 3/2+ and 7/2+ states found in the Ru chain could be recognized also in 103Pd, pointing to the possibility of a more global understanding of this transitional mass region.

Resumo em Inglês:

The in-medium influence on pi0 photoproduction from spin zero nuclei is carefully studied in the GeV range using a straightforward Monte Carlo analysis. The calculation takes into account the relativistic nuclear recoil for coherent mechanisms (electromagnetic and nuclear amplitudes) plus a time dependent multi-collisional intranuclear cascade approach (MCMC) to describe the transport properties of mesons produced in the surroundings of the nucleon. A detailed analysis of the meson energy spectra for the photoproduction on 12C at 5.5 GeV indicates that both the Coulomb and nuclear coherent events are associated with a small energy transfer to the nucleus ($\lesssim$ 5 MeV), while the contribution of the nuclear incoherent mechanism is vanishing small within this kinematical range. The angular distributions are dominated by the Primakoff peak at extreme forward angles, with the nuclear incoherent process being the most important contribution above $\theta_{\pi^{0}}\gtrsim2^{0}$. Such consistent Monte Carlo approach provides a suitable method to clean up nuclear backgrounds in some recent high precision experiments, such as the PrimEx experiment at the Jefferson Laboratory Facility.

Resumo em Inglês:

High-spin states in the neutron-deficient140Gd nucleus have been studied with the 92Mo(54Fe,alpha2p) reaction at a beam energy of 240 MeV. The level scheme of 140Gd was considerably extended from what was previously known. In this work we concentrate on one of the 9 bands observed, which presents relatively strong M1 transitions and negligible signature splitting, and has an isomeric band-head, indicating a strongly coupled or high-K configuration. We compare this band to the Kpi = 8- bands observed in N=74 isotones and propose a similar configuration assignment, but with a somewhat larger deformation.

Resumo em Inglês:

We use the Peierls-Yoccoz projection method to evaluate the center-of-mass correction of a relativistic system of nucleons and sigma and omega mesons, described in a mean-field Hartree approach. This correction for 4He, 16O and 40Ca is compared with the pure harmonic oscillator center-of-mass energy correction.

Resumo em Inglês:

We compare the cross sections for Coulomb excitation of multiple giant dipole resonances in 208Pb + 208Pb scattering using Coulomb trajectories and straight-line trajectories that have the same point of closest approach as the Coulomb one. We find the effects of the Coulomb deflection relative to the straight line trajectory to be small at incident energies above about 500 MeV/nucleon.

Resumo em Inglês:

Nuclear fissilities obtained from recent photofission reaction cross section measurements carried out at Saskatchewan Accelerator Laboratory (Saskatoon, Canada) in the energy range 60-130 MeV for 232Th, 233U, 235U, 238U, and 237Np nuclei have been analysed in a systematic way. To this aim, a semiempirical approach has been developed based on the quasi-deuteron nuclear photoabsorption model followed by the process of competition between neutron evaporation and fission for the excited nucleus. The study reproduces satisfactorily well the increasing trend of nuclear fissility with parameter Z²/A.

Resumo em Inglês:

The purpose of this work is to correlate Sr/Ca ratio with internal body temperature from teeth and bones. Results obtained in exploratory measurements using human, bovine and swine teeth indicated some relation between temperature and Sr/Ca ratio, but no other parameters, as feeding habits that certainly has some influence over Sr/Ca ratio, were controlled. In this work, to eliminate feeding effects, we decided to compare Sr/Ca ratio of bones from some individual. The first bones irradiated were from a crocodile (Caiman Yacare), which regulates the internal body temperature by the temperature of its surroundings. The pieces irradiated were from the crocodile's tail, vertebral column and leg. To quantify Sr and Ca a 2.4 MeV proton beam was used in PIXE beam line at LAMFI - USP. Emitted X-rays were collected using a Si(Li) detector (150eV @ 6.4 KeV). First results show that the bones closer to the heart have a lower Sr/Ca ratio.

Resumo em Inglês:

Recent results obtained in the Chromodielectric Model (CDM) have shown that strange quark matter at very high densities may appear in two phases, namely a chiral broken and a chiral symmetric phase, which may not be absolutely stable. In the chiral symmetric phase, the abundance of the quarks flavors u, d and s is the same and there are no electrons. In this paper we study an extended version of the Chromodielectric model (CDM) with a BCS quark pairing implemented, and analyze the superconducting color flavor locked phase. We show that the inclusion in the free energy density of a negative term of the diquark condensate guarantees the stability of quark matter. We also analyze the phase transition between matter described by different equations of state and only find a first order transition, at a very low pressure, from the CFL phase to the unpaired strange quark matter, which opens the possibility for a quark-hadron phase transition. Our study has implications in astrophysics, in particular regarding the formation and the structure of compact quark stars. We explicitly show that CFL stars can be absolutely stable and more compact than strange stars.

Resumo em Inglês:

We review the existing mass and decay width determinations of pentaquarks with QCD Sum Rules (QCDSR). We give special attention to the intermediate assumptions and choices which we are obliged to do in this approach. As an example, we present the full calculation of the pentaquark mass with Borel sum rules and also with Finite Energy Sum Rules (FESR). We also work out the calculation of the theta decay width. We take the opportunity to comment our publications on this subject and include new and unpublished material.