High-Temperature Annealing Induced He Bubble Evolution in Low Energy He Ion Implanted 6H-SiC

Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473K for 30rain. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy （XTEM） analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases. The growth of He bubbles after high temperature annealingabides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914＋0.236eV.

Influence of Temperature on Nitrogen Ion Implantation of Ti6Al4V Alloy

in order to achieve increased layer thickness, and wearing resistance, enhanced ion implantation with nitrogen has been carried out at temperatures of 100, 200, 400, and 600℃ with a dose of 4x 1018 ions' cm-2. Using the Plasma Source ion Implantation (PSII) device, specimens of Ti6Al4V alloy were implanted at elevated temperatures, using the ion flux as the heating source. Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), micro-hardness measurements and pin-on-disk wearing tester were utilized to evaluate the surface property improvements. The thickness of the implanted layer increased by about an order of magnitude when the temperature was elevated from 100 to 600℃. Higher surface hardness and wearing resistance was also obtained in implantation under higher temperature. XRD image showed the presence of titanium nitrides on the implanted surface.

Guiding of 60 keV O^(6+) ions along capillaries in an Al_2O_3 membrane

The guiding of 60 keV O6+ions along capillaries in an Al2O3 membrane is studied.The charge state distribution and the angular distribution of the ions transmitted through the capillaries are measured.The ion guiding ability of the concerned capillaries for the used projectile ions is analyzed,and is compared with other results using PC and alumina capillaries.Qualitative agreement is found.Further studies on material influence on the ion guiding power of the capillaries are needed.

Eldepryl prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced nigral neuronal apoptosis in mice

Objective To study the apoptotic effects of 1 methyl 4 phenyl 1,2,3,6 tetrahydropyridine (MPTP) on the nigral dopaminergic neurons of mice and 1 methyl 4 phenylpyridium ion (MPP +) on pheochromocytoma (PC12) cells, as well as the antagonism of Eldepryl against MPTP's apoptotic effect Methods Three groups of C 57 BL mice were treated with MPTP, Eldepryl plus MPTP and normal saline, respectively, for 7 days before performing TUNEL (terminal deoxyneucleotidyl transferase mediated dUTP x nick end labeling) and FACS (fluorescence activated cell sorting) analyses of neuronal apoptosis in the substantia nigra The same tests were employed in cell culture to examine apoptosis in PC12 cells treated with MPP +, MPTP or PBS Results Intraperitoneal administration of MPTP 30?mg/kg could induce nigral apoptosis, and oral use of Eldepryl prior to MPTP treatment could completely prevent the nigral apoptosis caused by MPTP MPP +, an intermediate metabolite of MPTP, could lead to the apoptosis of PC12 cells, whereas MPTP itself had no such effect on PC12 cells Conclusions The experiment indicated that the neurotoxin, MPTP, might cause the death of nigral neurons through a mechanism of apoptosis and this effect might be mediated by its bioactive intermediate metabolite MPP + Eldepryl could protect the neurotoxicity from MPTP

Influence of ^(12)C^(6+) ion irradiation on mutant avermitilis

The effects of 12C＋6 ion irradiation on colony morphology and mycelia morphology, as well as on mutation rate have been studied in the B1a high-product strains （ZJAV-Y1-203） mutated by heavy ion irradiation and compared with that in the original strain （ZJAV-A-1）. After irradiating the rate of a straw hat colony type having a high ability of producing B1a in ZJAV-Y1-203 strains was higher than that found in ZJAV-A-1 strains. When strains were cultured in a liquid medium for 24 hours, the mycelium becoming thinner could be observed in all of the irradiated ZJAV- Y1-203 groups, but only in the ZJAV-A-1 groups irradiated at the dose of 50 Gy or more. The early growth of mycelium was inhibited in the ZJAV- Y1-203 group irradiated with a high dose. The highest positive mutation rate （23.5%） of ZJAV - Y1 - 203 was reached at the lower dose of 30 Gy while the highest positive mutation rate of 34.2% in ZJAV-A-1 appeared at 50 Gy. These results indicate that the effects of heavy ion irradiation still exist even in the mutated Streptomyces avermitilis, and only the dose is lower and the effects not so strong compared with the one that is first irradiated with optimized heavy ion doses. This is evidence of the one directional mutation being controlled by many more factors in a organism.