The role of DNA cluster damage and chromosome aberrations in radiation-induced cell killing: a theoretical approach.

The role played by DNA cluster damage and chromosome aberrations in radiation-induced cell killing was investigated, assuming that certain chromosome aberrations (dicentrics, rings and large deletions, or 'lethal aberrations') lead to clonogenic inactivation and that chromosome aberrations are due to micrometre-scale rejoining of chromosome fragments derived from DNA cluster lesions (CLs). The CL yield and the threshold distance governing fragment rejoining were left as model parameters. The model, implemented as a Monte Carlo code called BIANCA (BIophysical ANalysis of Cell death and chromosome Aberrations), provided simulated survival curves that were compared with survival data on AG1522 and V79 cells exposed to different radiation types, including heavy ions. The agreement between simulation outcomes and experimental data suggests that lethal aberrations are likely to play an important role in cell killing not only for AG1522 cells exposed to X rays, as already reported by others, but also for other radiation types and other cells. Furthermore, the results are consistent with the hypothesis that the critical DNA lesions leading to cell death and chromosome aberrations are double-strand break clusters (possibly involving the ∼1000-10 000 bp scale) and that the effects of such clusters are modulated by micrometre-scale proximity effects during DNA damage processing.

Risk assessment for chemical pickling of metals contaminated by radioactive materials.

In recent years, many cases of contamination of metal scraps by unwanted radioactive materials have occurred. Moreover, international organisations are evaluating the possibility to re-use or to recycle metals coming from nuclear power plants. The metal recycling industry has started to worry about radiation exposure of workers that could be in contact with contaminated metals during each manufacturing phase. Risks are strongly dependent on the radiation source features. The aim of this study is to perform risk assessment for workers involved in chemical pickling of steel coils. Monte Carlo simulations have been performed, using the MCNP package and considering coils contaminated with (60)Co, (137)Cs, (241)Am and (226)Ra. Under the most conservative conditions (coil contaminated with 1.0 kBq g(-1) of (60)Co), the dose assessment results lower than the European dose limit for the population (1 mSv y(-1)), considering a maximum number of 10 contaminated coils handled per year. The only exception concerns the case of (241)Am, for which internal contamination could be non- negligible and should be verified in the specific cases. In every case, radiation exposure risk for people standing at 50 m from the coil is widely <1 mSv y(-1).

[Risk of exposure to UV radiation at biochemical laboratories]. / Rischio da esposizione a radiazione UV nei laboratori biochimici.

In biological and chemical laboratories UV radiation is largely used, particularly in photo biological and photochemical studies, with the objective to sterilize or to visualize the samples in different technical analysis. In this work we present the results of the evaluation of UV exposition levels and the hazards for researchers and students, that the results shows elevated if they don't use correct laboratory procedures and protective wear.

[Fractal behavior of indoor radon variations]. / Comportamento frattale delle variazioni di radon negli interni.

Recently, a new mathematical theory has been developed which describes the non-linear dynamic and complex systems which are widely diffused in nature. In spite of great variability in the phenomenon appearances, so great as to seem chaotic, the phenomena are described by algorithms which are, at times, very simple; they are characterized by a parameter, the so-called fractal dimension, which is a fractional number. We employed this new theory to verify the fractal behavior of temporal variations of radon 222 concentration, as measured in a house at Angera (Italy), 1986-1987. With significant correlation, the experimental data show the statistics of the system not to be casual and Gaussian, but chaotic and persistent, with Hurst exponent approximately 0.77 and fractal dimension 1.23. If the fractality of radon phenomena is verified also in other systems, the implications will be consistent. Particularly, punctual time predictability of radon concentration would no longer be possible, but a new prevision strategy would be necessary, considering the chaotic behavior of the phenomenon. This would imply, e.g., a new scientific approach both in planning surveys on the doses absorbed by people exposed to radon and in predicting seismic and volcanic phenomena, where radon is known to be a primary precursors of these catastrophic events.

[EPR and TL measurements of BeO "Termalox 995" irradiated with photons]. / Misure EPR e TL di BeO "Termalox 995" irraggiato con fotoni.

Beryllium oxide dosimeters (Termalox 995) have been irradiated (at 60-Co facility) with graduated doses from 3 X 10(-1) to 1 X 10(2) Gy (30 to 10.000 rad). EPR measurements show a very good linear correlation between the amplitude of signal and the absorbed dose. This method has the advantage that the stored information into dosimeter doesn't regress "after reading procedure".