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Human blood was irradiated with accelerated ions: 20 MeV 4He, 425 MeV 12C and 1480 MeV and 996 MeV 16O. For each ion, the blood was exposed to a range of doses as thin specimens in the track segment mode, so that irradiations took place at nearly constant LETs of 31.4, 61, 52 and 69 keV microm(-1), respectively. Lymphocytes were cultured to the first in vitro metaphase, analysed for chromosomal damage and the dicentric aberration frequencies fitted to the linear quadratic model of dose-response. For these high LET radiations, the linear (alpha) yield coefficient predominated and increased with LET, at least up to 60 keV microm(-1). Apart from the 996 MeV oxygen ions, the data indicated the presence of a quadratic (beta) coefficient, statistically consistent with values obtained with low LET radiations. However, the associated uncertainties on the measured beta values were large, illustrating the general problem that beta is more difficult to measure against a dominating and ever-increasing alpha term. The existence or otherwise of a beta component of the dose-response at these radiation qualities has important consequences for modelling mechanisms of aberration induction by radiation.

We describe a new method for in situ study of solar cell degradation that accumulates the damage produced by several subsequent fluences of radiation on the same cell. We have used this method to obtain a full characterization of silicon cells after inducing radiation damage with 8-MeV and 10-MeV protons and with 2.65-MeV electrons. A flexible portable setup was developed with this purpose. We have used this setup to compare the equivalent proton fluences between the JPL method and a new method, proposed by Alurralde, for estimation of the damage produced in solar cells by the protons present in low-altitude orbits.Index Terms-Electron radiation effects, photovoltaic cells, photovoltaic space power systems, proton radiation effects, test equipment.

Long-term exposure of aquatic organisms to metals, even those considered micronutrients, may affect their metabolism and produce sublethal effects. We evaluated the effects of long-term exposure of adult amphibian (Bufo arenarum) females to 4 microg/L of Zn(2+) (ZnSO(4) x H(2)O) in Ringer solution on the concentration of Zn and Fe, the activity of the key enzyme of the pentose phosphate pathway glucose 6-phosphate dehydrogenase, and glutathione content, both in the liver and ovary of these animals. We also performed early embryonic development studies by in vitro insemination from control and treated females. Zn exposure rendered lower Zn concentrations in the ovaries than did exposure of animals to Ringer solution without metal addition (97 +/- 50 versus 149 +/- 46 Zn microg/wet tissue g). Zn and Fe concentration correlation was positive and linear in the ovary, but was negative and nonlinear in the liver of the studied females. The activity of the enzyme glucose 6-phosphate dehydrogenase decreased (0.0599 +/- 0.0109 versus 0.0776 +/- 0.0263 micromol of NADPH/min x mg of proteins) and the endogenous glutathione content increased (0.027 +/- 0.005 versus 0.018 +/- 0.007 mg/10 mg of proteins) in the ovary but remained unaltered in the liver as a consequence of Zn treatment. Our results suggest the existence of different mechanisms of regulation of Zn and Fe concentrations in the ovary and in the liver of adult B. arenarum females. Binding of Zn to low-molecular-weight proteins, as metallothioneins, may occur in the liver, thus protecting this organ from toxic effects. In the ovary high-molecular-weight proteins, like glucose-6-phosphate dehydrogenase, should be able to bind Zn, leading to oxidative stress responsible for the observed increase in endogenous glutathione content. Inhibition of the pentose phosphate pathway in the ovary by Zn can be responsible for the reproductive failure that we detected through embryos survival studies during early life stages: 81.3 +/- 6.3% of embryos from control females survived versus 63.1 +/- 13.8% of embryos from Zn-treated females at the branchial circulation stage of development.