Identification of irradiated foods by monitoring radiolytically produced hydrocarbons

Many countries allow the treatment of foods with low doses of ionizing radiation to reduce microbial and insect infestations, inhibit maturation, and extend shelf life. Therefore, a reliable method is needed to identify irradiated foods and to determine their compliance with respect to allowable absorbed radiation dose. Several approaches for the identification of irradiated foods have been developed such as measurement of radiolytic products, chemiluminescence, and thermoluminescence, and the use of electron spin resonance spectroscopy to measure free radicals trapped in bone. A method for the determination of radiolytically produced hydrocarbons was developed in our laboratory to evaluate the utility of monitoring these compounds as indicators of food irradiation. The method involves the extraction of the radiolytic hydrocarbons from foods and their quantitation by gas chromatography. Concentrations of the radiolytically produced hydrocarbons increased linearly with radiation doses ranging from 0 to 6 kGy. The limit of detection appears to be approximately 1 kGy. The method was found to be useful for the identification of gamma-irradiated foods such as shrimp, frog legs, pork, beef, and poultry. Results of the method evaluation studies of these food matrices as well as factors affecting hydrocarbon production and determination will be presented.     

Thermal decomposition of basic cobalt and copper carbonates

Basic cobalt and copper carbonates were prepared by precipitation from solutions of their nitrates using KHCO₃ at room temperature in CO₂ atmosphere. The thermal decomposition of the prepared basic carbonates was studied by means of TG and DTA techniques and the phases produced were identified by XRD measurements. The products obtained at 400C were subjected to different doses of gamma-rays (40–160 M rad) and the thermal stabilities of these solids were investigated.The results obtained revealed that basic cobalt carbonate decomposed at 335C to produce Co₃O₄ which remained stable up to 850 and then decomposed above this temperature giving CoO which transformed into Co₃O₄ on cooling to room temperature. Basic copper carbonate dissociated at 290C yielding CuO which yielded Cu₂O and metallic copper at 1060 and 1150C, respectively. However, the produced cuprous oxide and metallic copper solids were converted into CuO and CU₂O, respectively by cooling in air to room temperature.Gamma-irradiation decreased the thermal stability of Co₃O₄ to an extent proportional to the dose employed. On the other hand, this treatment increased the thermal stability of both CuO and Cu₂O.     

Low dose 60Co gamma-irradiation effects on electronic carrier transport and DC characteristics of AlGaN/GaN high-electron-mobility transistors

The impact of internal irradiation with secondary Compton electrons, generated by gamma-photons, on the characteristics of III-N/GaN-based devices was explored. N-channel AlGaN/GaN high-electron-mobility transistors (HEMTs) were exposed to gamma-radiation from a ⁶⁰Co source for doses up to 600?Gy. Temperature-dependent electron beam-induced current (EBIC) was employed to measure minority carrier transport properties. For low doses below ～250?Gy, the minority carrier diffusion length in AlGaN/GaN HEMTs is shown to increase by about 40%. This increase is likely due to longer minority carrier lifetime induced by internal Compton electron irradiation. An associated decrease in activation energy, extracted from temperature-dependent EBIC, was also found. The obtained increase in transconductance and decrease in gate leakage current indicate an improvement in performance of the devices after low doses of irradiation. For high doses of gamma-irradiation, above ～300?Gy, the performance of HEMTs showed a deterioration. The deterioration results from the onset of increased carrier scattering due to additional radiation-induced defects, as is translated in a decrease of minority carrier diffusion length.     

Influence of Fluorine Impurity on the Spectroscopic Characteristics of Quartz Glasses under Gamma Irradiation

We consider the absorption, luminescence, and Raman spectra upon gamma-quanta irradiation of quartz glasses manufactured by a sol-gel technology. The influence of the change in a regime of synthesis of the glass on its radiation stability is considered.     

Optical and electron beam studies of gamma-irradiated AlGaN/GaN high-electron-mobility transistors

The impact of ⁶⁰Co gamma-irradiation on n-channel AlGaN/GaN high-electron-mobility transistors was studied by means of temperature-dependent electron beam-induced current (EBIC) and cathodoluminescence (CL) techniques. For the doses up to ～250?Gy, an enhancement of minority carrier transport was observed as evident from the EBIC measurements. This enhancement is associated with internal electron irradiation induced by the primary gamma photons. For the doses above ～250?Gy, deterioration in minority carrier transport was explained by carrier scattering on radiation-induced defects. It is shown that calculated activation energy from the EBIC and CL measurements follows exactly the same trend, which implies that the same underlying phenomenon is responsible for observed findings.     

FTIR study of gamma-irradiated cis-1,4-polyisoprene

The effect of γ-irradiation on the structure and oxidation of cis-1,4-polyisoprene is investigated by ATR-FTIR technique. This method provides the valuable insight into the type of oxidation products produced and the extent and nature of intramolecular cyclization and chain scission reactions. The formation of ketones, alcohols and/or ethers, and hydroperoxides is apparent already at small doses of γ-radiation and it increases with the exposure time significantly. At the highest dose of 309 kGy a decrease in the intensity of C=O stretching mode of ketones (1717 cm⁻¹) was observed while the overall area of the band remained the same as in the case of 188 kGy dose. The shoulders observed at 1740 cm⁻¹ and 1772 cm⁻¹ could be assigned to C=O stretching frequency of esters and five-membered-ring lactones, respectively. Higher doses of γ-radiation also cause the formation of two relatively strong bands in the region of conjugated double bonds. These could origin from the aromatic products or cycloenes with one double bond formed by cyclization and chain scission processes.     

Low dose production studies of platinum at irradiation temperature of 140 K

An ansatz is developed to find out an analytical expression for energy levels of the anharmonic oscillators, of the typeV(X) =X²/2 + λX2m (m = 2, 3) which is valid for all values ofn and all regimes of parameter space. The procedure is extended to find out an analytical expression for the energy levels of the oscillatorV(X) =X²/2 + λ1X4 + λ₂X⁶. As a practical application, it has been applied to calculate characteristics of radiation emitted due to channeling of relativistic positrons channeled between (100) planes in silicon.     

Radiation effect studies on some glycine derivatives in solid state

Five glycyl derivatives, glycyl-L-histidine, L-alanyl-glycine, glycine hydrochloride, gly-gly hydrochloride and, gly-gly-glycine in powder form were exposed to 20?kGy doses of ⁶⁰Co gamma radiation to study the effects of ionizing radiation. In these compounds, the paramagnetic centers formed after irradiation were attributed to the R─NHCH─?O^?OH, ?H₂CHNH, H₂NCH₂?O^?OHHCl, NH₂?HCONHCH₂COOHHCl and HNCH₂?O^?OH radicals, respectively. The effect of gamma irradiation to the radical structures and time stability of the radicals were investigated by EPR spectroscopy. The spectra were computer simulated and the hyperfine coupling constants were determined.     

Optical and ESR studies in pure and Mn-doped LiF crystals

Growth of F absorption band with the time of X-irradiation at RT and the changes caused in the F absorption as a function of F light and thermal bleaching along with the simultaneous ESR studies in pure and Mn-doped LiF single crystals are reported.     

Thermomechanical and adhesive properties of radiation-modified polymer composites for thermosetting products

Gamma-irradiated blends of polyethylene (PE) with ethylene-propylene-diene copolymer (EPDM) and a thermotropic liquid-crystalline polymer (LCP) are investigated at absorbed radiation doses not exceeding 150 kGy (10 kGy=1 Mrad). The temperature dependences of elastic moduli, tension diagrams at a temperature above the melting point of the crystalline phase of PE, and long-term strain recovery curves for oriented test specimens are presented. The kinetics of thermal relaxation and shrinkage stresses in previously oriented composite specimens upon their heating and cooling is investigated. Data on the influence of LCP additions on the adhesive interaction of the compositions with steel are obtained. The peculiarities of thermomechanical and adhesion properties of these composites are discussed taking into account the morphologic and calorimetric data obtained. Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 379–394, May–June, 2000.