D.E. Di Gregorio

Fusion of 16O + 144Sm at sub-barrier energies

Abstract Fusion cross sections have been measured for the system 16 O+ 144 Sm at bombarding energies in the range 63 MeV ⩽E lab ( 16 O )⩽72 MeV by observation of delayed X-rays emitted by the evaporation residues. Comparison of the present results for the magic nucleus 144 Sm with those already existing for the fusion of 16 O with other samarium isotopes shows that the enhancement of the cross sections at sub-barrier energies can be explained in terms of a one-dimensional barrier-penetration model that incorporates the quadrupole deformation parameter, s 2 . There is no need to invoke the neck degree of freedom.

CHARACTERISATION OF URANIUM(VI) SORPTION BY TWO ENVIRONMENTAL FUNGAL SPECIES USING GAMMA SPECTROMETRY

Abstract Uranium(VI) sorption by two highly uranium‐resistant air‐borne fungi in a low‐pH medium was measured by means of gamma spectrometry. Growth kinetics and stoichiometry of the two fungal species were also studied. Results show acceptable growth rates in synthetic medium with glucose and ammonia as carbon and nitrogen sources, respectively. Typical oxidative metabolism of carbohydrates was found. In vivo uptake of the radionuclide was negligible, but biosorption dry biomass presented a remarkable performance. The fungal strains showed potential for use in bioremediation.

Simulations of electron trajectories under the influence of an array of permanent magnets in a compact ion source

Trajectories of electrons emitted from a filament in a discharge ion source are computer simulated in order to investigate their behavior under the influence of different magnetic fields. These calculations allowed a better understanding of the high efficiency obtained in a recently developed compact ion source.

Fusion cross sections from measurements of delayed X-rays

The program XRAY is a FORTRAN 77 computer code for the extraction of fusion cross sections from delayed X-ray measurements. This is accomplished by calculating the theoretical expressions of the time dependence of the evaporation-residue cross sections and taking them as adjustable parameters in a χ2 minimization procedure.

Aerobic Reduction of Uranium(VI) by Acidithiobacillus Thiooxidans Cultures

Acidithiobacillus thiooxidans was grown in the presence of uranium and its redox processes were studied in aerobic conditions for the first time. Results so far obtained may suggest an indirect uranium reduction, mediated by metabolically produced reducing compounds.

SEARCH FOR EXPERIMENTAL EVIDENCE OF CHAOTIC BEHAVIOR IN NUCLEAR SCATTERING

Abstract Angular distributions for the elastic and inelastic scattering in the 16 O + 28 Si system have been measured in two energy regions, one close to the Coulomb barrier and the other well above. Fine steps in both bombarding energy and scattering angle make it possible to compare the data with the theoretical calculations that predict, for each of these regions, distinctive cross-section patterns in correspondence with the classical occurrence of either regular or chaotic regimes. The experimental results show specific differences between the two explored energy ranges in qualitative agreement with the theoretical predictions.

Cold dark matter identification: Diurnal modulation reexamined

Abstract We report on new estimates of the modulation expected in semiconductor detectors due to eclipsing of dark matter particles in the Earth. We reevaluate the theoretical modulation significances and discuss the differences found with previous calculations. We find that a significantly larger statistics than previously estimated is needed to achieve the same level of sensitivity in the modulated signal.

Scattering, fusion and transfer reactions in 16O + ASm at energies close to the Coulomb barrier

Abstract Recently measured scattering cross sections for the 16 O + 144 Sm system allow to extract a bare potential which is used in a global analysis of scattering, fusion and transfer experimental data for 16 O on different samarium isotopes at energies close to the Coulomb barrier. The analysis is done within the framework of an extension of a method based on the intrinsic-coordinate-dependent phase shifts and the equivalent-spheres formalisms which has been previously reported. Consistent fits are obtained for an important amount of data covering a wide range of target deformations, bombarding energies and scattering angles for different reaction channels. As a significant exception, the fusion excitation function for 144 Sm is overestimated.