Accelerated Nitrogen Ions Research Articles

Chemical Activity and Morphology of Nanostructured Plasma-Sprayed Titanium Induced by Nitrogen and Argon Ions

The paper focuses on the chemical characteristics of ion-beam passivation effects (of the first-third order) of titanium depending on the dose of implanted ions. The key objective is electron microscopy and SPM-based analysis of nanostructured VT1-00 titanium surfaces produced by entering nitrogen and argon ions of high energy. This type of surfaces can find application in fabrication of devices for the power engineering industry. The obtained experimental data provide evidence of a carbon nanocoating over the surface of titanium implanted with accelerated nitrogen ions, which is similar to that acquired upon titanium implantation with argon ions. A hypothesis is formulated about the existence of a mechanism for changing the chemical activity of titanium as a result of ion-beam nanostructuring – ion-stimulated synthesis of.

Different G2/M accumulation in M059J and M059K cells after exposure to DNA double-strand break–inducing agents

To investigate and compare the cell cycle progression in relation to cell death in the human glioma cell lines, M059J and M059K, after exposure to DNA double-strand break-inducing agents. The M059J and M059K cells, deficient and proficient in the catalytic subunit of the DNA-dependent protein kinase, respectively, were exposed to 1 and 4 Gy of photons or accelerated nitrogen ions. In addition, M059J and M059K cells were treated with 10 and 40 mug/mL of bleomycin for 30 min, respectively. Cell cycle progression, monitored by DNA flow cytometry, was measured up to 72 h after treatment. M059J, but not M059K, cells displayed G(2)/M accumulation after low linear energy transfer irradiation. High linear energy transfer radiation exposure however, resulted in a substantial increase of M059K cells in the G(2)/M phase detected at 48 h. At 72 h, the number of cells in the G(2)/M phase was equivalent to its control. M059J cells accumulated mainly in S phase after high linear energy transfer irradiation. In contrast to M059K, M059J cells were still blocked at 72 h. Bleomycin induced G(2)/M accumulation for both M059J and M059K cells detected 24 h after treatment. At 48 h, the percentage of bleomycin-treated M059J cells in G(2)/M phase remained high, and the number of M059K cells had decreased to control levels. Neither cell line showed cell cycle arrest (< or =10 h) after exposure to these agents. Distinct cell cycle block and release is dependent on the complexity of the induced DNA damage and the presence of the DNA-dependent protein kinase catalytic subunit.

Rejoining of double-stranded DNA-fragments studied in different size-intervals

Purpose : To measure rejoining of radiation-induced doublestranded DNA-fragments of different sizes and to evaluate the effects of size-resolution in the analysis of rejoining. Material and methods : Normal human fibroblasts (GM5758) were irradiated with photons or accelerated nitrogen ions (linear energy transfer, LET = 125keV μ m -1) and incubated for repair for 0-22h. Double-stranded DNA-fragments from the irradiated cells were separated by pulsed-field gel electrophoresis in the range ~ 5kbp to 5.7 Mbp. Results : For cells irradiated with high LET nitrogen ions, there was an increase in the fast half-time from ~ 5min for fragments < 400kbp to 10 min when all fragments < 5.7 Mbp were measured. Further, the fraction of fragments rejoined by the slowrejoining phase increased significantly for increased threshold sizes. The fraction of unrejoined fragments after 22h and the half-time for the slow-rejoining phase remained constant for all threshold sizes. For cells irradiated with lower doses of low LET radiation the rejoining was shifted towards a slower kinetics when fragments up to 10 Mbp were excluded in the analysis. Conclusion : DNA exclusion-size and resolution may affect the estimates of DNA double-strand break rejoining. Using a lowresolution technique that does not detect small fragments will result in an underestimation, or even disappearance of the fast-rejoining phase. This is due to substantial rejoining of fragments taking place before the fragments are of sufficient size to be monitored.

High-LET radiation induces apoptosis in lymphoblastoid cell lines derived from ataxia-telangiectasia patients

Purpose : To investigate and compare the propensity of Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCL), derived from ataxia-telangiectasia (A-T) patients and from unaffected healthy individuals (controls), to undergo apoptosis after exposure to high-linear energy transfer (LET) radiation. Materials and methods : Four A-T (ARO, BMA, CSA and RJO) and two control (JAC and KKB3) LCL were exposed to doses of up to 4 Gy of accelerated nitrogen ions (32-45 MeV/u, 8-12 Gy/min). For comparative purposes X-ray irradiation (1.36 Gy/min) was also performed. The induction of apoptosis was studied 0-48h after irradiation with the use of two methods: (1) monitoring of high molecular weight (HMW) DNA fragments by field inversion pulse gel electrophoresis (FIGE); and (2) morphological characterization of apoptotic cells after fluorescent staining. In parallel, cell-cycle distribution, monitored by DNA flow cytometry, as well as measurements of p53/p21(WAF1) protein levels by Western blots, were investigated in these cells. Results : High-LET radiation-induced apoptosis and G2/M-arrest in both A-T and control LCL. No significant increase in the amount of p53/p21(WAF1) proteins preceded apoptosis in control or in A-T LCL after high-LET irradiation. However, low-LET radiation did induce significant enhanced levels of p53 proteins in control but not in A-T LCL. Conclusions : LCL from both A-T homozygous and unaffected healthy individuals undergo apoptosis without accumulation of p53/p21(WAF1) proteins after exposure to high-LET radiation. In contrast, low-LET radiation induces apoptosis and significantly increases levels of p53 protein in control but not in A-T LCL.

RBE for the induction of apoptosis in human peripheral lymphocytes exposed in vitro to high-LET radiation generated by accelerated nitrogen ions

Purpose: To investigate the relative biological effectiveness (RBE) of accelerated nitrogen ions (32-45 MeV/u) compared with 137Cs gamma -rays for the induction of apoptosis in G lymphocytes. 0 Materials and methods: Human peripheral G lymphocytes were 0 exposed in vitro to doses up to 3 Gy. RBE for the induction of apoptosis was studied at different times after irradiation (0, 24, 48 and 72 h) with the use of three different methods: (1) morphological characterization of apoptotic cells after fluorescence staining; (2) cell size distribution analysis of the cell population to detect apoptotic bodies; and (3) electrophoretic analysis of DNA to detect 'DNA-ladders'. Results: RBE values in the range of 1.3-3.0 were obtained from the linear components of the dose-response curves. The variation in RBE was primarily dependent on post-irradiation time, where the highest RBE values were obtained after 48 h. The three different techniques used for analysis of apoptosis gave similar results. The significantly increased RBE was also seen as an earlier appearance of DNA-ladders, as well as a more rapid disappearance of the total number of viable cells. Conclusions: These results show that nitrogen ions of high linear energy transfer (LET) produce RBE 1.0 and induce a faster apoptotic response as compared with gamma -photons of low-LET radiation.

Hydrogen migration in stainless steel and alloys stimulated by ionizing radiation

Hydrogen behaviour in stainless steel, titanium and vanadium alloys during ionising radiation (accelerated nitrogen ions, γ-quanta) has been studied. It was shown that ionizing radiation stimulates intensive migration of hydrogen (H-migration). The cross-section of interaction between the accelerated ions and H-atoms has been determined to be 10 −16 cm 2. A phenomenological model of ionisation-accelerated hydrogen migration in metals was suggested. Mechanisms of γ- and electron-stimulated dissociation of H-containing bonds inside a solid have been specified as Mensel—Gomer mechanisms, Auger process electron transfers from the therm of bond state to the therm of repulsion one, which subsequently will decay into fragments. The calculated probability of H-migration on the base of these mechanisms is in a good agreement with the experimental results.

Rejoining of DNA double-strand breaks induced by accelerated nitrogen ions.

Rejoining of radiation-induced DNA double-strand breaks (dsb) was measured in cultured cells with pulsed-field gel electrophoresis after radiation doses in the range of 5-30 Gy. Human glioma, U-343MG and Chinese hamster, V79, cells were irradiated with either accelerated nitrogen ions of high linear energy transfer, LET approximately 125 keV/ microns, or photons from 60Co. The induction frequencies of dsb were similar for the two radiation qualities with a relative biological effectiveness, RBE, of 0.90 and 0.89 for the human and hamster cell lines respectively. The biphasic rejoining kinetics differed significantly between the two radiation qualities when studied in the human glioma cells. The difference was seen within the first hour after irradiation and after 6 h there were considerable differences in both the total amount of unrejoined dsb and the fraction of dsb rejoined during the slow phase. When rejoining was analysed 20-22 h after irradiation, the nitrogen ions gave 2.5-2.9 times more residual dsb than the gamma photons. The results for the hamster V79 cells were, up to 2h after irradiation, similar, but the difference between the two radiation qualities was less accentuated. In summary, similar initial yields of dsb after exposure of cells to high or low LET resulted in both radiation quality and cell type-dependent differences when the rejoining of these breaks were compared.

Migration of hydrogen in steel and alloys, stimulated by ionizing radiation

A study is made of the behavior of hydrogen in stainless steel and alloys of titanium and vanadium during exposure of the metals to ionizing radiation (accelerated nitrogen ions, γ-quanta). It is shown that the radiation stimulates intensive migration of hydrogen. The cross section of the accelerated ions is 10−16 cm2. This shows that hydrogen is released from traps as a result of excitation of the electronic subsystem and vibrational degrees of freedom of the hydrogen bonds, with the excitation energy subsequently being transferred to the nuclear subsystem. A phenomenological model is proposed to describe the ionization-accelerated migration of hydrogen in metals. Gamma- and electron-stimulated dissociation of hydrogen-containing bonds inside a solid occur by the Mensell — Homer and Auger mechanisms, as well as by nonadiabatic transition and vibrational-translational exchange. The calculated probability of the migration of hydrogen by these mechanisms is found to agree well with the experimental data.

Cu3N Thin Film for a New Light Recording Media

Copper nitride thin films were prepared by using the ion-assisted deposition in which accelerated nitrogen ions were irradiated during the deposition of copper metal. The degree of nitrification of the film was controlled by changing the ion current density. The reflection coefficient of the prepared copper nitride films decreased with the increase of the ion current density. The reflection coefficient was about 30% at 780 nm wavelength, and it recovered to 70% after the film was heated at 300°C. The preliminary experiment of write-once optical recording of this film was carried out, and the viability of its practical use in new media was confirmed.

Ion etching of tobacco mosaic virus and T4 bacteriophage

A technique for the etching of biological materials by accelerated nitrogen ions is described. Upon exposure to such a beam, tobacco mosaic virus becomes thinner in diameter and the head of T4 becomes smaller. Experiments on radioactively labeled T4 suggest that the particle's protein is more susceptible to removal by the incident ions, and that the residual material is predominantly nucleic acid.

Inactivation of cultured human cells and control of C3H mouse mammary tumors with accelerated nitrogen ions.

Inactivation of cultured human cells and control of C3H mouse mammary tumors with accelerated nitrogen ions.