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Nonextensive statistical mechanics as in Tsallis formalism was used in this study, along with the dynamical Hamiltonian rod-like DNA model and the maximum entropy criteria for Tsallis’ entropy, so as to obtain length distribution of plasmid fragments, after irradiation with very high doses, assuming that the system reaches metaequilibrium. By intensively working out the Grand Canonical Ensemble (used to take into account the variation of the number of base pairs) a simplified expression for Fragment Size Distribution Function (FSDF) was obtained. This expression is dependent on two parameters only, the Tsallis q value and the minimal length of the fragments. Results obtained from fittings to available experimental data were adequate and the characteristic behavior of the shortest fragments was clearly documented and reproduced by the model, a circumstance never verified from theoretical distributions. The results point to the existence of an entropy which characterizes fragmentation processes and depending only on the q entropic index

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Cobb broilers and domestic ducks, both one-day-old, were treated using ration doped with 20 ppm of uranyl nitrate. Uranium concentrations in the tibia (μg-U/g-bone) were measured by neutron activation analysis as function of the animals' age, from the neonatal period to maturity. Results show that Uranium and Calcium qualitatively follow the same metabolic pathway, and that adult ducks incorporate on average ten times more Uranium than broilers. Data interpretation shows that the Uranium clearance rate in broilers is substantially higher than that in ducks, suggesting that metabolic characteristics favoring Calcium retention in bone may hinder the elimination of Uranium in ducks. The need for further comparative biochemistry studies between Galliformes and Anseriformes is addressed.