• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1993-1998
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• 2016

The effects of carbon-ion irradiation on cancer cell telomere function have not been comprehensively studied. In our previous report cancer cells with telomere dysfunction were more sensitive to carbon-ion irradiation, but the underlying mechanisms remained unclear. Here we found that telomerase activity was suppressed by carbon-ion irradiation via hTERT down-regulation. Inhibition of telomere activity by MST-312 further increased cancer cell radiosensitivity to carbon-ion radiation. hTERT suppression caused by either carbon-ion irradiation or MST-312 impaired mitochondrial function, as indicated by decreased membrane potential, mtDNA copy number, mitochondrial mass, total ATP levels and elevated reactive oxygen species (ROS). PGC-$1{\alpha}$ expression was repressed after carbion-ion irradiation, and hTERT inhibition by MST-312 could further exacerbate this effect. Lowering the mitochondrial ROS level by MitoTEMPO could partially counteract the induction of cellular senescence induced by carbon-ion radiation and MST-312 incubation. Taken together, the current data suggest that telomere-mitochondrion links play a role in the induction of senescence in MCF-7 cells after carbon-ion irradiation.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.367-372
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• 2006

Polytetrafluoroethylene (PTFE) surface was modified for improving hydrophilicity by ion irradiation in environmental gas of $N_2$ and $NH_3$, respectively. The water contact angle onto the PTFE surface increased from $104{\circ}$ to over $140{\circ}$ by Ar ion irradiation in $N_2$ gas. In the case of $NH_3$ as environmental gas, there were a slight increase of contact angle from ion dose of $1{\times}10^{15}\;to\;5{\times}10^{15}\;ions/cm^2$, and its dramatic decrease to the value of 35o at the conditions of ion dose higher than $1{\times}10^{16}\;ions/cm^2$. It was found from SEM results that the surface morphology of PTFE was changed into one with filament structure after Ar ion irradiation in $N_2$ gas environments. On the contrary, Ar ion irradiation in $NH_3$ gas condition induced the PTFE surface with network structure. Hydrogen ion irradiation resulted in a little change of PTFE surface morphology, comparing with the case of Ar ion irradiation. The water contact angle of hydrogen ion irradiated PTFE surface in reactive gas decreased with increment of ion dose. Hydrogen ion irradiation could improve hydrophilicity with little change of surface morphology. It might be considered from FT-IR results that the improvement in wettability of PTFE surface by ion irradiation in $N_2$ and $NH_3$ gases could be due to the hydrophilic groups of NHx bonds.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.63-68
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• 2017

Background: The combined effect of the low energy electron (LEE) irradiation and $Cu^{2+}$ ion on DNA damage was investigated. Materials and Methods: Lyophilized pBR322 plasmid DNA films with various concentrations (1-15 mM) of $Cu^{2+}$ ion were independently irradiated by monochromatic LEEs with 5 eV. The types of DNA damage, single strand break (SSB) and double strand break (DSB), were separated and quantified by gel electrophoresis. Results and Discussion: Without electron irradiation, DNA damage was slightly increased with increasing Cu ion concentration via Fenton reaction. LEE-induced DNA damage, with no Cu ion, was only 6.6% via dissociative electron attachment (DEA) process. However, DNA damage was significantly increased through the combined effect of LEE-irradiation and Cu ion, except around 9 mM Cu ion. The possible pathways of DNA damage for each of these different cases were suggested. Conclusion: The combined effect of LEE-irradiation and Cu ion is likely to cause increasing dissociation after elevated transient negative ion state, resulting in the enhanced DNA damage. For the decrease of DNA damage at around 9-mM Cu ion, it is assumed to be related to the structural stabilization due to DNA inter- and intra-crosslinks via Cu ion.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.18-21
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• 2019

We studied the effect of Fe ion irradiation on the upper critical field ($H_{c2}$) of 410 nm single-crystalline $MgB_2$ thin films. The irradiation energy was fixed at 140 keV when we increased the irradiation doses from $1{\times}10^{14}ion/cm^2$ to $4{\times}10^{14}ion/cm^2$. We found that $H_{c2}$ significantly increase with increasing irradiation dose, despite the low irradiation energy. The enhancement of $H_{c2}$ could be explained by the reduction of electron mean free path caused by defects induced from irradiation, leading to a decrease of coherence length (${\xi}$). We also discussed the effect of irradiation on temperature-dependent resistivity in details.

• Transactions on Electrical and Electronic Materials
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• v.9 no.5
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• pp.202-205
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• 2008

We have studied the liquid crystal (LC) orientation behavior on the organic hybrid overcoat layer with ion beam irradiation. Excellent LC alignments of the nematic liquid crystal (NLC) on the ion beam irradiated organic hybrid overcoat layers were observed in various intensities above 600 eV. Pretilt angles of the NLC on the organic hybrid overcoat layers for all ion beam energy intensities were observed from 0.2 to 0.5 degrees. Also, we used the atomic force microscopy (AFM) images for measuring the roughness of the organic hybrid overcoat layers with ion beam irradiation before and after. The surface of organic hybrid overcoat layers was leveled off by the ion beam irradiation. Finally, a good LC alignment thermal stability on the organic hybrid overcoat layer with ion beam irradiation can be achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.382-386
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• 2019

The alignment characteristics of liquid crystal (LC) molecules on a solution-derived lanthanum zinc oxide (LZO) film under ion-beam irradiation were demonstrated. Using the solution process, an LZO film was fabricated on the glass substrate and cured at $100^{\circ}C$. Afterwards, ion-beam irradiation was performed following the LC alignment method. Using this film, an LC cell was fabricated and the characteristics of the LC alignment were verified. Cross polarizing microscopy and the crystal rotation method were used to investigate the alignment state of the LC molecules on the LZO films. Furthermore, field emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to explore the effect of the ion-beam irradiation on the LZO film. Through these, it was confirmed that the ion-beam irradiation induced surface modification, which demonstrated anisotropic physical and chemical surface characteristics. Due to this, uniform LC alignment was achieved. Finally, the residual DC and anchoring energy of the LC cell based on the LZO films were measured using a capacitance-voltage curve.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.29-36
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• 2000

This investigation has been studied about friction and wear properties which were important problem, when carbon fiber reinforced plastic(CFRP) was used practically. Unidirection carbon fiber reinforced composites was fabricated with epoxy resin matrix and carbon fiber as a reinforced, and its surface was modified by the ion-assisted reaction. And then we tested the their friction and wear properties according to the ion-irradiation. when the amount of ion-irradiation was 1${\times}$10l6$\^$16/ ions/$\textrm{cm}^2$, the friction coefficient values were about 0.1, where as, the friction coefficient values of non-treatment composites were about 0.16. The former was the stablest in wear mode. We know that ion-irradiation was not proportioned to the friction coefficient, so we found the optimal conditions of the friction and wear according to the ion-irradiation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.2
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• pp.130-135
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• 2021

Wrinkle patterns were fabricated on styrene-butadiene-styrene (SBS) block copolymer substrates using ion-beam (IB) irradiation with various intensities. The wavelength of the wrinkle pattern increased as the IB intensity was increased from 800 to 1,600 eV. IB irradiation-induced changes in the surface properties that were confirmed via physicochemical surface analyses. X-ray photoelectron spectroscopy analysis revealed chemical surface reformation due to the IB irradiation, resulting in C-O/C=O bonds after IB irradiation that were not reported before. These results indicate that the surface chemical modification caused by IB irradiation is strongly related to the surface modulus, which is important when fabricating wrinkle patterns. Furthermore, a strong IB irradiation induced a strong compressive strain; thus the size of the wrinkle pattern was increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.330-330
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• 2008

It is widely investigated to liquid crystal (LC) alignment using non-contact alignment method such as ion-beam (IB) irradiation, UV alignment, and oblique deposition. Because conventional rubbing method has some drawbacks. These include defects from dust and electrostatic charges and rubbing scratch during rubbing process. In addition, rubbing method needs additional process to remove these defects. Therefore rubbing-free methods like ion-beam irradiation are strongly required. We studied LC alignment effect on poly imide surface by IB irradiation and electro-optical (EO) characteristics of twisted nematic liquid crystal display (TN-LCD). In this experiment, a good uniform alignment of the nematic liquid crystal (NLC) with the ion-beam exposure on the polyimide (PI) (SE-150 from Nissan Chemical) surface was observed. We also achieved low pretilt angle as a function of ion-beam irradiation intensity. In addition, it can be obtained the good EO properties of the IB-aligned TN-LCD on PI surface. Some other experiments results and discussion will be included in the poster.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.19-19
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• 2008