199 research outputs found
EARLY AND DELAYED REPRODUCTIVE DEATH IN HUMAN CELLS EXPOSED TO HIGH ENERGY IRON ION BEAMS
No full textThe aim of this research was to determine the biological effectiveness for early and delayed effects of high energy, high linear energy transfer (LET) charged particles. Survival and delayed reproductive death were measured in AG1522 human fibroblast cells exposed to Fe-ion beams of energies between 0.2 and 1 GeV/n, 0.97 GeV/n Ti-ion and 0.49 GcV/n Si-ion beams. The cells were irradiated at the HIMAC accelerator in Chiba, Japan (0.2 and 0.5 GeV/n Fe and 0.49 GeV/n Si) and at the NASA Space Radiation Laboratory in Brookhaven, USA (1 GeV/n Fe and 0.97 GeV/n Ti ions). The dose-effect curves were measured in the dose range between 0.25 and 2 Gy. For comparison cells were exposed to Co-60 gamma rays. Analysis of the dose-effect curves show that all the heavy ion beams induce inactivation and delayed reproductive death more effectively than 60 Co rays. The only exception is the 0.2 GeV/n Fe-ion beam at low doses. The progeny of the irradiated cells show delayed damage in the form of reproductive death with all the heavy ion beams with the 1 GeV/n Fe-ion beam being the most effective. The relative biological effectiveness at low doses of the iron beams is highest for LET values between 140 and 200 keV/mu m with values of 1.6 and 3 for early and delayed reproductive death, respectively. Analysis of the fluence-effect curves shows that the cross-sections for early and delayed inactivation increase with increasing LET up to 442 keV/mu m. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved
Ambiente e territorio: L'esperienza bresciana
No full textCollana del Dipartimento di Scienze Giuridiche dell'Università di Bresci
Full Temperature Dependence Compensation and Low Polarisation Dependent Loss in Long Period Gratings
No full textDirect writing of waveguides on tellurite glasses
No full textWe report the application of the direct writing technique to tellurite glasses of three different compositions and the achievement of the first examples, to our knowledge, of directly written channel waveguides in tellurite glasses
GROWTH-KINETICS OF C3H10T1/2 CELLS EXPOSED TO LOW-LET RADIATION
No full textGrowth curves and size of the colonies of C3H10T1/2 cells exposed to low-LET radiation (31 MeV protons) were determined after 0, 1, 3, 5, and 7 Gy. The data show that: cell density at confluence was 3.3 x 10(4) cells/cm2; the initial division delay was very small; in the first 15 h the increase in the cell number was essentially the same at all doses; at 100 h the colony size distribution was very large, ranging from 0 to 7 generations, even within the control population. The temporal dependence of the growth properties of surviving and non-surviving cells was represented by the equation N = N0(Fe(a(t - dD] + (1 - F)ea/bD(1 - e - bD(1 - e - bD(t - dD]) where F is the surviving fraction, t the time of sampling, a the growth rate, d the division delay per unit dose, b the rate per unit of dose at which the non-surviving cells lose their ability to divide. The resulting values were: a = 0.029 +/- 0.002 h-1; b = 0.0041 +/- 0.0009 h-1 Gy-1 and d = 1 +/- 0.8 h Gy-1. It was found that growth curves are affected by non-surviving progeny up to 150, 200 and 250 h after irradiation at 3, 5 and 7 Gy, whereas at longer times the population consists essentially of progeny of surviving cells
Criteria and techniques for analysing cell survival data
No full textCell survival was studied by analyzing the inactivation probability density function and its fundamental parameters. Mean , varianceσ2 and modeDmode were evaluated and a set of equations relating these parameters to the usual parameters of the multitarget, multihit and linear-quadratic modelsDo andn, α andβ, k andλ are reported. The multihit equation used was an extension of the usual equation, to allow parameterk to assume values that are not necessarily integers. In the multitarget curve, the mode of inactivation probability density function, proved to be the quasi-threshold doseDq =Do ln(n). Relative variance, degree of asymmetry and degree of peakedness can be calculated from the shape parametersn in the multitarget model,k in the multihit model, and in the linear-quadratic model. From an analysis of eight published cell survival sets of data, on C3H10T1/2 cells exposed to low LET radiations, it was found that ,σ, andSF2 are the parameters which exhibit the least variation from experiment to experiment and the least variation in selecting the range of data available for estimation
Studio del danno al DNA indotto da radiazioni ionizzanti mediante simulazioni Montecarlo
No full textModelli interpretativi dell'inattivazione e della trasformazione di cellule irraggiate con radiazioni a basso ed alto LET
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