Young-Jin Chung

Monitoring of Nitrite and N-Nitrosamine Levels in Irradiated Pork Sausage

Residual nitrite and N-nitrosamine levels were monitored on irradiated emulsion-type cooked pork sausage in aerobic or vacuum packaging states during storage. The sausage was irradiated at 0, 5, 10, and 20 kGy and stored at 4 degrees C for 4 weeks. The residual nitrite levels were significantly reduced by gamma irradiation (P < 0.05), whereas the vacuum packaging was more effective for nitrite reduction than aerobic packaging during storage. N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) levels were significantly reduced in the vacuum packaged sausage irradiated with 20 kGy after 4 weeks. Reduction of NPYR in aerobically packaged sausage was also found after 4 weeks by irradiating with a 5-kGy or higher dose. NDMA reduction was shown in vacuum packaging and irradiation at 20 kGy. Gamma irradiation was effective in reducing the residual nitrite all throughout storage and N-nitrosamines in sausage after storage.

Investigation on radiation degradation of carboxymethylcellulose by ionizing irradiation.

This study was done to compare the effects of irradiations with gamma-rays and electron beams, on the viscosity of the carboxymethylcellulose (CMC), on the functional groups of CMC, and on the production of radicals. It was observed that the relative viscosities decreased as the irradiation doses increased, but the decrease was more significant when irradiation with gamma rays. FT-IR spectra showed no significant difference between the gamma-ray and the electron beam irradiated samples. ESR spectra showed that the gamma-ray irradiation produced more radicals than electron beam irradiation in CMC.

Distribution of Microflora in Powdered Raw Grains and Vegetables and Improvement of Hygienic Quality by Gamma Irradiation

Improvement of hygienic quality of powdered raw grains and vegetables by gamma irradiation was investigated. Five products of powdered raw grains and vegetables were collected in a local market and analysed. The total viable cell counts of Bacillus were 10~10 cfu/g, filamentous fungi l0~10cfu/g, coliform 10~10cfu/g, enteric bacteria on SS agar plate 10~10cfu/g. Coliform, enteric bacteria on SS agar plate and filamentous fungi were eliminated by 3 kGy of gamma irradiation. The D values of coliform, enteric bacteria on SS agar plate, Bacillus, and filamentous fungi were 0.68~0.80 kGy, 0.59~0.74 kGy, 1.84~2.18 kGy and 0.36~0.57 kGy, respectively. It was considered that optimal irradiation dose for radappertization was about 25 kGy, while 3~5 kGy of gamma irradiation was effective for radicidation.

Recent experiments on near-threshold electron-impact excitation of multiply charged ions

Some recent measurements of excitation of multiply charged ions by electrons studied in beam-beam experiments are highlighted. The emphasis is on absolute total cross sections measured with the merged electron-ion beams energy-loss (MEIBEL) technique, although some results obtained with the crossed-beams fluorescence method are also presented. The MEIBEL technique allows the investigation of optically-allowed and forbidden transitions with sufficient energy resolution, typically about 0.2 eV, to resolve resonance structures in the cross sections. Results from the JILA/ORNL MEIBEL experiment on dipole-allowed transitions in several ions demonstrate the success of various theoretical methods in predicting cross sections in the absence of resonances. Comparisons of R-matrix calculations and measured cross sections for spin-forbidden transitions in Mg-like Si{sup 2+} and Ar{sup 6+}, however, show that further refinements to the theory are needed in order to more accurately predict cross sections involving significant contributions from dielectric resonance`s and interactions between neighboring resonances.

Electron-impact excitation of multicharged ions: Merged beams experiments

Electron-impact excitation cross sections for several multicharged ions have been measured near threshold using the merged electron-ion beams energy loss (MEIBEL) technique. This technique allows the investigation of optically-allowed and forbidden transitions with sufficient energy resolution, typically about 0.2 eV, to resolve resonance structures in the cross sections. Results from the JILA/ORNL MEIBEL experiment on allowed transitions in several multicharged ions demonstrate the ability of various theoretical methods to predict cross sections in the absence of resonances. Comparisons of R-matrix calculations and measured cross sections for transitions in Mg-like Si2+ and Ar6+, however, indicate that theory must continue to evolve in order to more accurately predict cross sections involving significant contributions from dielectronic resonances and interactions between neighboring resonances.

Absolute measurements of cross-sections for near-threshold electron-impact excitation of Na-like and Mg-like multiply-charged ions

Abstract The JILA-ORNL merged electron–ion beam energy-loss apparatus has been used to measure absolute cross-sections for excitation of multiply-charged ions over the past several years. Recent measurements for the Na-like ions Al2+ and Cl6+ and the Mg-like ion Cl5+ are presented and are compared with earlier measurements on the isoelectronic ions and with theoretical results.