[en] A phenomenological two-step reaction model is proposed, in which a direct projectile fragmentation in the initial stage is succeeded by a binary dissipative interaction between the heavy projectile fragment and the target in the final state. Multi-different cross sections are estimated by folding the fragmentation cross section given in the local plane-wave Born approximation with the cross section for deep-inelastic collisions calculated within the classical friction model, including statistical fluctuations and mass transfer. For forward angles satisfactory results are obtained in comparison with the experimental data on inclusive spectra, angular distributions, angular correlations, γ-multiplicities, and element distributions in ²⁰Ne-induced reactions for bombarding energies of 10-20 MeV/nucleon. (orig.)

[en] The level density parameter is a very important ingredient in statistic study of nuclear reaction, it has been studied to low energies excitation E < 2MeV where it values is approximately constant, experimental results to energies of excitation more than 2 MeV has been obtained of evaporation spectrum, to nuclei with A=160. In this work we present a calculation of densities level parameter, for a wide range of mass and temperature, taking in accounts the shell effects and the mass effective interaction. The result has been carried out within the semi classical approximation, for the single particle level densities. We results have a reasonable agreement with the experimental data available. (Author)

[en] One of the problems in the changing world is the preservation of knowledge for the next human generation, and nuclear knowledge is not an exception. Cuba has worked for reproducing, preserving, developing and capturing nuclear knowledge, mainly through a higher education centre, the Higher Institute of Nuclear Sciences and Technologies. This institute is a component of a national network in the preparation of manpower not only for nuclear activities but also for environmental and managerial activities too. (author)

[en] In this paper a simple statistical formalism that takes into account the diabatic motion of a compound system to calculate total level density is given. The diabatic motion is introduced by coupling the adiabatic collective motion to an environment consisting of intrinsic degrees of freedom. The collective enhancement of level density is studied. It has an adiabatical coefficient that depends only on the excitation energy and a dynamical one that depends on the excitation energy and the coupling between intrinsic and collective modes. Qualitatively, the coefficients of the vibrational enhancement factor for A=240 have been studied. The coupling is understood as the initial effect of the oscillatory motion of the mass asymmetry of fragments on the nucleonic motion. The damping effect of the vibrational motion is taken into account considering the collective motion of the fragments as a zero-sound wave propagating in the Fermi-liquid. The intrinsic state in the framework of the Fermi Gas Model (FGM) is described. The Pashkevich's pa- rametrization is used to describe the binary decay of the compound nucleus. (orig.). With 3 figs

[en] Cluster emission at pre-equilibrium stage, in heavy ion fusion reactions of ₁₂C and ₁₆O nuclei with ₁₁₆Sn, ₂₀₈Pb, ₂₃₈U are studied. the energy of the projectile nuclei was chosen at 0.25GeV, 0.5GeV and 1GeV. A cluster formation model is developed in order to calculate the cluster size. Thermodynamics of small systems was used in order to examine the cluster behavior inside the nuclear media. This model is based on considering two phases inside the compound nucleus, on one hand the nuclear media phase, and on the other hand the cluster itself. The cluster acts like an instability inside the compound nucleus, provoking an exchange of nucleons with the nuclear media through its surface. The processes were simulated using Monte Carlo methods. We obtained that the cluster emission probability shows great dependence on the cluster size. This project is aimed to implement cluster emission processes, during the pre-equilibrium stage, in the frame of CRISP code (Collaboration Rio-Sao Paulo). (Author)

[en] Exotic decays of super-heavy elements with atomic number ζ (114,118,120) are studied taking Coulomb and proximity potential as interacting barrier. We computed, in fission model, the formation probability for different clusters, taking a law of powers potential. we also calculated the half-life times for the cluster radioactivity more probable of being preformed in the WKB approach. We obtained that some of these clusters, are in the actual limit of measure 10³0s and show also a strong dependence of the formation probability. (Author)

[en] Within the new concept of cluster radioactivity (CR) to allow emitted particles with ζ ≥28 we systematically investigate the CR and spontaneous fission for super-heavy elements whit atomic number ζ ≥118. The CR hal-lives are obtained taking Coulomb and proximity potential to the overlap zone and exponential law for the effective inertia. The spontaneous fission half-lives are calculated with a phenomenological formula. The competition between CR and spontaneous fission is analyzed in detail and the branching ratios of these two decays modes are predicted. (Author)

[en] An interpretation of the cold fission events in thermal-neutron-induced fission of heavy nuclei is given. The descent from the saddle point is considered as a dynamical process with reversible coupling between collective and intrinsic degrees of freedom. The distribution function for the collective variables is expressed as a product of two terms: the adiabatical and the dynamical factors. A simple model for symmetric fission to study the mass distribution is presented. As example, the calculations are performed for the nucleus ²⁶⁴Fm. Gross features of the cold fission are discussed as well as the dependence of the theoretical mass distribution on the parameters of the model. (orig.)

[en] Vegetable tannins are polyphenolic substances of different chemical mixtures, in correspondence with the characteristics of groups of polyphenols. Taking into consideration its composition, we can find different types of flavonoids, mainly in the so-called condensed tannins. In general, many applications have been explored, including the medical ones, due to their proven biological activity as antiviral, antibacterial and others characteristics derived from their reactions with metal ions and amino acids of the protein components. Therefore it is promising to examine the effects of gamma radiation on the structure of tannin, looking for the possible modification of its biological activity. To this end, samples of tannins are irradiated at different doses (maximum dose 35 kGy) with the use of a Cobalt-60 irradiator. Scanning Electron Microscopy (SEM) permitted to characterize the samples in morphology and composition. The changes were analyzed by using infrared spectroscopy Fourier transform (FT-IR) and High Resolution Liquid Chromatography (HPLC). At the end we discuss the implication of the results for a dosage range above 5 kGy. (Author)