[en] The CN group might have made it appearance in the early stages of chemical evolution, for this reason the radiolytic behavior of nitriles have relevance to the study of prebiotic chemistry. A systematic study of the influence of the irradiation on nitriles and dinitriles have been carried at ICN. In this paper we present the formation of polymeric material from the γ irradiation of aqueous solutions of malonitrile 0.1 M, oxygen free, at their natural ph s. The analysis of the radiolytic product was by exclusion chromatography, some characteristics of the polymer material were found by IR spectroscopy, Biuret test, etc. The results showed that in this system several polymeric materials are formed with a molecular weight about 10,000 daltons. (Author)

[en] The results of the radiolysis of aqueous solutions of thiamine (vitamin B₁) are presented. The yields for decomposition of thiamine and the production of radiolytic products were determined. The G values decrease as the dose increases. Some radiolytic products were identified. Decomposition of thiamine was slightly dependent on the presence of oxygen and on the pH of the solution. At pH 4.4, with a concentration of 2.5x10^-4 mol L^-1 of thiamine in an oxygen free aqueous solution, the G⁰ value for decomposition is 5.0

[en] This research is aimed at studying the effect of ionizing radiation in an heterogeneous system formed by a carboxylic acid adsorbed in a clay mineral. The study is focussed to discriminate if the presence of a solid surface alters the formation and distribution of radiolytic products in relation to the radiolysis of the carboxylic acid without the surface (clay). The results showed that the radiolysis of the system clay-acid goes along a defined path rather than showing various pathways of decomposition as in the case of simple aqueous solutions. The main pathway was the decarboxylation of the target compound rather than condensation/dimerization reactions

[en] Research on the radiolysis of vitamins is of considerable interest since these compounds are important nutritional constituents in foods and in dietetic supplements. In spite of these considerations there are few data and very often difficult to compare for the radiolytic behavior of vitamins. In this work we focused our attention on to the study of the radiolysis of cyanocobalamin (vitamin B₁₂) in solid state and in aqueous solutions. The procedure was followed by HPLC and UV-spectroscopy. The results obtained in aqueous solutions showed a dependence of the decomposition as a linear function of the dose. The G of decomposition for a 1x10^-5 M solution was 3.3. In the solid state the vitamin was very stable towards the irradiation in the conditions used in this study with a G=2.1x10^-3. A study made with Serratia marcescens as a microbiological contaminant showed that at the sterilization dose there is a destruction of the vitamin in aqueous solution. In the solid state the degree of decomposition was 7%. (author)

[en] Heterogeneous interstitial nucleation was observed as a result of the exposure to high dose rate and repeated irradiations of single crystals of LiF doped with Mg and Ti. A comparison under the same conditions with the irradiation of commercial LiF dosimeters was done. The temperature region for which the observations were made applies to the region where V_K centers are mobile. Therefore, the recombination of some defects produced by gamma radiation are primarily actual for the behavior around room temperature. Glow curves were obtained from irradiated LiF. The main disadvantages found are almost the same as those presented for commercial LiF. Also, in both cases we found differences in the thermoluminiscence response after storage was observed. The study was also focused to answering the question of how many times a dosimeter can be re-used after a severe irradiation

[en] In this work, the authors investigate the influence of doses and water content on the radiolysis of acetic acid adsorbed in a clay surface (Na-montmorillonite). The reaction was followed by the formation of CO₂, also for other non-volatile radiolytic products from ¹⁴C-acetic acid. The main reaction observed was a decarboxylation reaction. The mechanism of this heterogeneous catalysis is complex. This reaction can be promoted by a loss of electrons from the carbonyl group of the acid and could be accepted by acid sites on clay. Other mechanisms that are currently under study involve energy transfer process and free radical initiator by the water radiolytic products trapped in the clay lattice

[en] Homemade solid state CaSO₄:Dy detectors were tested to evaluate their response to gamma radiation at liquid nitrogen temperature (77 K). The dosemeters were irradiated with doses between 12 and 1071 Gy. For this study these dosemeters were exposed to gamma rays with a dose rate of 1.19 Gy.min^-1. The analysis for these crystals was made by thermoluminescence. The dose response at liquid nitrogen temperature was linear in the dose range studied and it is about 20% lower with respect to the response at room temperature. The response is reproducible with the same geometric set-up. (author)

[en] The aim of this work was to study the behavior of a single and poly crystalline homemade solid state dosimeters (a) LiF co-doped with Mg, Cu and P, and (b) CaSO₄ doped with Dy. We analyzed the response of these dosimeters using thermoluminescence. The dose-response at liquid nitrogen temperature was followed to observe the nature of the response. (author)

[en] The decomposition of pyruvic acid in aqueous solutions induced by gamma-irradiation has been studied with respect to the identification and estimation of degradation products. The irradiation experiments were performed under both oxygenated and oxygen-free environments. Several conditions were varied such as, radiation dose, solute concentration, and pH. The principal means of analysis was by gas chromatography. The main non-volatile radiolytic products was dimethyltartaric acid, which is a dimer of pyruvic acid. The yield in which this dimer was formed was influenced by the irradiation dose and the concentration of the target compound. In some of the experiments with 0.1M solutions the yield of this dimer was more than 70% of the non-volatile products

[en] The purpose of this work is to study the radiolytic behavior of aqueous solutions of ¹⁴C-α-ketoglutaric acid (oxygen-free). Several parameters were varied such as radiation dose, concentration and pH. Based on the identity of the major non-volatile products, the authors proposed three main pathways for the radiolysis of the α-ketoglutaric acid: (1) reduction of the keto group yielding hydroxyglutaric acid; (2) loss of the CO group yielding a saturated carboxylic acid (succinic acid); (3) addition of hydrated electron to the alpha-carbonyl group yielding a diol. The yields of these products were influenced by the irradiation dose, concentration of the target compound and pH of the solution