Control of Natural Microbial Flora and Listeria monocytogenes in Vacuum-Packaged Trout at 4 and 10° C Using Irradiation

The effect of gamma irradiation on the natural microflora of whole salted vacuum-packaged trout at 4 and 10°C was studied. In addition, the effectiveness of gamma irradiation in controlling Listeria monocytogenes inoculated into trout was investigated. Irradiation at doses of 0.5 and 2 kGy affected populations of bacteria, namely, Pseudomonas spp., Brochothrix thermosfacta, lactic acid bacteria, H2S-producing bacteria typical of Shewanella putrefaciens, and Enterobacteriaceae, at both 4 and 10°C. This effect was more pronounced at the higher dose (2 kGy) and the lower temperature (4°C). Pseudomonads, H2S-producing bacteria typical of S. putrefaciens, and Enterobacteriaceae showed higher sensitivity to gamma irradiation than did the rest of the microbial species. Sensory evaluation did not show a good correlation with bacterial populations. On the basis of sensory odor scores, a shelf life of 28 days (2 kGy, 4°C) was obtained for salted vacuum-packaged freshwater trout, compared with a shelf life of 7 days for the unirradiated sample. Under the same conditions, the growth of L. monocytogenes inoculated into the samples was suppressed by 2 log cycles after irradiation (2 kGy) and storage for up to 18 days at 4°C.

Neutron irradiation and annealing of 10B doped chemical vapor deposited diamond films

10B doped diamond films grown by hot filament chemical vapor deposition were neutron irradiated at moderately high fluence levels. The as-irradiated and annealed samples, along with an unirradiated sample, were analyzed using Raman spectroscopy and x-ray diffraction. It was found that a non-diamond amorphous phase was formed on irradiation. This phase transformed back to diamond on annealing. No graphite formation was observed. A comparison with nanodiamond powder was made. A similarity between irradiated diamond films and nanocrystalline diamond powder is discussed.

THE EFFECT OF THE NEUTRON IRRADIATION ON THE CRITICAL CURRENT AND THE MICROSTRUCTURE OF THE MELT–TEXTURED GROWTH YBa2Cu3Oy

We have studied the effect of the fast neutron irradiation on the critical current properties and the microstructure of Melt-Textured Growth (MTG) YBa 2 Cu 3 O 7−δ with fluences of 2.3 × 1016 n/cm 2, 1.16 × 1017 n/cm 2, and 5.8 × 1017 n/cm 2 respectively. The hysteresis loops have been measured at 77 K and 1.5 K in the applied magnetic fields between −6 T and 6 T. The irreversibility lines H(T*) were also demonstrated. The critical magnetization current density J c is up to 4.7 × 105 A/cm 2 at 77 K in the field of 0.1 T for the irradiated sample with the fluence of 1.16 × 1017 n/cm 2. It is tenfold higher than that of the unirradiated sample. This increase of J c is due to the pinning at irradiation–induced pinning centers. Much higher neutron irradiation with fluence of 5.8 × 1017 n/cm 2 is harmful to the increase of J c value because the orthorhombic structure has been transformed into the tetragonal one. The amorphous state and the cellular structures are also observed in the irradiated MTG sample.

Large Enhancement of JC in YBacuo Single Crystals Induced by Proton Irradiation

We have used magnetization measurements to study the effect of proton irradiation on the critical current density of a YBaCuO single crystal. We have obtained a maximum value of 1.5x105 A/cm2 at 77 K and 1 T at a fluence of 2 x 1016 cm-2, representing a 50-fold increase with respect to the unirradiated sample.

Oxygen-Related Defects in Silicon

ABSTRACTIn this review we focus on oxygen-related defects created by electron irradiation (vacancy-oxygen defects) and subsequent thermal treatments. The annealing of the vacancy-oxygen pair (VO-center) at 300–350 °C is discussed as well as results from the formation and annealing of the successors to VO, the VO2 and VO3-centers. It -s found that VO2 is formed by diffusion of a vacancy-oxygen pair to an interstitial oxygen atom. It is suggested that VO3 is formed by the diffusion of interstitial oxygen to a VO2-center (in the temperature range 450–485 °C). At continued annealing at these temperatures VO3 is transferred to a new defect VO4 by attaching one more oxygen. Simultaneously thermal donors are developing in a normal way i.e. as in an unirradiated sample. It is therefore concluded that VO2 is not an important core for thermal donors but a possible nucleus for oxygen precipitation.