Osvaldo A. Curzio

Model linear ethylene–butene copolymers irradiated with γ-rays

Two model linear polyethylenes of different molecular weights and very narrow molecular weight distributions were subject to γ-ray irradiation under vacuum. Irradiations were conducted at two temperatures: 25 and 135°C. Number average and weight average molecular weight of irradiated samples was measured by LALLS and membrane osmometry, and the distribution of molecular weights was studied by GPC. The presence of a low but measurable amount of scission was verified. A mathematical model of the irradiation process was developed, which gave very good predictions of the measured values.

Effect of the phenolic antioxidants on the structure of gamma-irradiated model polyethylene

Abstract High energy radiation has been successfully employed to modify the chemical structure of commercial polymers. It induces at least two types of reaction in polyethylene: crosslinking and chain scission. In addition the efficiency of the radio-induced reactions can be affected by the presence of antioxidants. The purpose of this work is to study the effect of the irradiation on a model polyethylene containing a phenolic type antioxidant. Samples containing 0.1% and 1% by weight of Irganox 1010 (Ciba-Geigy) were irradiated under vacuum at room temperature with different doses of gamma rays from a 60 Co source. Changes in structure and the average molecular weight were followed by gel permeation chromatography and low angle laser light scattering. The critical doses for gelation were determined as a function of the antioxidant concentration. Theoretical calculations to predict the evolution of molecular structure with extent of radiation were performed using a probability model. The agreement between the calculated and the measured molecular weights is very good.

γ-glutamyl transpeptidase/γ-glutamyl peptidase in sprouted Alliumsati vum

Abstract The activities of γ-glutamyl transpeptidase/γ-glutamyl peptidase enzymes have been measured in sprouted garlic bulbs ( Allium sativum cv Red). Effects of γ-glutamyl p -nitroanilide concentration, enzyme concentration, temperature and time of incubation on enzyme activity, and distribution of this activity between sprouts and storage leaves of sprouted garlic cloves were determined.

Calculated and measured dose in a 60Co irradiation unit

Abstract Dose distribution in a 60Co irradiation unit has been calculated. Some aspects of the radiation field within the irradiation chamber for which there is no information available were considered. The dose rate was measured by means of Fricke and Ferrous-Cupric dosimetry. Isodose curves distribution and results of comparison between dose measurement and calculation are presented.

Effects of γ-irradiation on the lipid composition of inner sprout of garlic

Abstract The aim of this work was to evaluate the effects of a dose of 60.0 Gy of 60Co γ-rays on the concentration and composition of lipids from the inner sprout of garlic cloves. 210 days after treatment, the levels of phospholipids, triacylglycerols and glycolipids were significantly reduced as a result of radiation. Levels of polyunsaturated fatty acids from these lipid fractions such as linoleic acids showed a similar trend of decrease. Irradiation also brought about an increase in diacylglycerols. Results are correlated with sprouting inhibition induced by γ-irradiation in garlic.

A theoretical model to improve the design of gamma irradiators

Improvement in the design of the source and the transport system in a multipurpose gamma irradiation plant is of fundamental importance. With this in mind we propose the implementation of a mathematical model permitting the improved design of gamma irradiators as a function of the efficiency of the facility and the parameters of the irradiation process. A linear relationship between the height of the container and the dose ratio can be deduced from the analysis of the results. Such relationship provides a useful and economic tool for calculating the most advantageous dimensions of the source and the volume of the material to be irradiated.

Theoretical evaluation of dose rate for a cobalt-60 source in a pool irradiator

Abstract An underwater dose rate evaluation method for 60 Co linear sources is presented. It will permit better design of pool irradiation facilities. An additional simplification for γ-irradiation in air is also presented in this paper.

Total volatile acids content as a quality index of irradiated hake (Merluccius merluccius hubbsii) fillets

Abstract Irradiation of hake (Merluccius merluccius hubbsii) fillets with 500 krad (5 k Gy) of Co60 gamma rays caused a delay in the formation of volatile acids during storage under refrigeration at 4–5°C. Loss in organoleptic acceptability could be correlated with the increase in volatile acids both in the unirradiated and irradiated fish stored at 4–5°C, suggesting that the volatile acids number (VAN) can be a useful tool for the quality evaluation of hake fillets.