The Monte Carlo (MC) method has been widely implemented in studies of radiation effects on human genetic material. Most of these works have used specific-purpose MC codes to simulate radiation transport in condensed media. PENELOPE is one of the general-purpose MC codes that has been used in many applications related to radiation dosimetry. Based on the fact that PENELOPE can carry out event-by-event coupled electron-photon transport simulations following these particles down to energies of the order of few tens of eV, we have decided to investigate the capacities of this code in the field of nanodosimetry. Single and double strand break probabilities due to the direct impact of gamma rays originated from Co60 and Cs137 isotopes and characteristic x-rays, from Al and C K-shells, have been determined by use of PENELOPE. Indirect damage has not been accounted for in this study. A human genetic material geometrical model has been developed, taking into account five organizational levels. In an article by Friedland et al. [Radiat. Environ. Biophys. 38, 39-47 (1999)], a specific-purpose MC code and a very sophisticated DNA geometrical model were used. We have chosen that work as a reference to compare our results. Single and double strand-break probabilities obtained here underestimate those reported by Friedland and co-workers by 20%-76% and 50%-60%, respectively. However, we obtain RBE values for Cs137, AlK and CK radiations in agreement with those reported in previous works [Radiat. Environ. Biophys. 38, 39-47 (1999)] and [Phys. Med. Biol. 53, 233-244 (2008)]. Some enhancements can be incorporated into the PENELOPE code to improve its results in the nanodosimetry field.

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The critical behaviour of a mixed ferrimagnetic Ising system on a square lattice in which the two interpenetrating square sublattices have spins σ (± 1 2 ) and S (±2, ±1, 0) has been studied. We carried out exact ground state calculations and performed Monte Carlo simulations to obtain the finite-temperature phase diagram of the model. We found that the system that includes only a nearest-neighbour interaction and the crystal field does not have a compensation point. Also, our study seems to indicate that, contrary to effective-field predictions, there is no tricritical point at nonzero temperature for this model; however a more elaborate analysis will be needed to draw a definite conclusion on this point.

12 C( 7 Li,␣) angular distributions have been obtained for 16 states in 15 N at E( 7 Li)ϭ52.5 MeV. Also, 12 C( 6 Li ជ , 3 He) angular distributions and vector analyzing powers have been measured at E( 6 Li ជ )ϭ50 MeV. Finite-range distorted-wave Born-approximation ͑FRDWBA͒ triton cluster transfer calculations are able to describe the ( 7 Li,␣) data for transfer to states with known J values. Comparison with known levels in 19 F suggests that the 12 C( 7 Li,␣) reaction selectively populates negative parity states. FRDWBA calculations support this idea. Several previously suggested J levels are confirmed and new J values are proposed for six other levels. The previously observed ( 6 Li ជ , 3 He) J dependence has been used along with coupled-channel Born-approximation calculations to confirm the J values for states in 15 N.

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