Sunmog Yeo and Yong-Gi Kim (KAERI, KOMAC), Journal of the Korean Physical Society, 66, 474 (2015)
The enhancement of the wear resistance for tungsten carbide (WC-Co) is investigated by using an ion implantation technique. A ball-on-disc-type tribometer confirmed that the wear resistance was systematically increased with increasing dose and implantation energy of the nitrogen ions. In accordance with the increase in the wear resistance, the nano-indentation measurements showed that the hardness for the nitrogen-implanted WC-Co with an energy of 120 keV (dose: 1 × 1018 ions/cm2) was increased by about 2.8 times compared to that for as-received WC-Co.
Figure1. Mass loss data as a function of wear distance for the (a) 70 keV and (b) 90 keV nitrogen implanted WC-Co with different doses.
Journal of the Korean Physical Society, 66, 474 (2015)
Byungtak Kim(Dongguk Univ.) et al, Journal of Cancer 7, 344 (2016)
The effects of proton beams on DNA methylation were evaluated in the breast cell lines MCF-10A and MCF-7. Pyrosequencing analysis of the long interspersed element 1 (LINE1) gene indicated that a few specific CpG sites were induced to be hypermethylated by proton beam treatment from 64.5 to 76.5% and from 57.7 to 60.0% (p < 0.05) in MCF-10A and MCF-7, respectively. Genome-wide methylation analysis identified “Developmental Disorder, Hereditary Disorder, Metabolic Disease” as the top network in the MCF-7 cell line. The proliferation rate significantly decreased in proton beam-treated cells, as judged by colony formation and cell proliferation assay. Upon treatment with the proton beam, expression of selected genes (MDH2, STYXL1, CPE, FAM91A1, and GPR37) was significantly changed in accordance with the changes of methylation level. Taken together, the findings demonstrate that proton beam-induced physiological changes of cancer cells via methylation modification assists in establishing the epigenetic basis of proton beam therapy for cancer.
Figure1. Anti-proliferation effect of proton beam treatment on mammary gland cells. The indicated cells were treated with a proton beam at a strength of 8 Gy, and their proliferation was monitored alongside the non-treated cells. (A) Cell proliferation assay using cell counting kit-8 was carried out for a normal cell line, MCF-10A, and cancerous cell lines MCF-7 and MDA-MB-231. (B) Colony formation assay was carried out for the MCF-7 cell. The bar graph denotes the ratio of colonies shown by the colony formation assay.
Journal of Cancer 7, 344 (2016)
Jun Kue Park(KAERI, KOMAC), Hyeok-Jung Kwon(KAERI, KOMAC) & Cheol Eui Lee (KOREA Univ.), Scientific Reports 6, 23378 (2016)
The diffusion properties of H+ in ZnO nanorods are investigated before and after 20 MeV proton beam irradiation by using 1H nuclear magnetic resonance (NMR) spectroscopy. Herein, we unambiguously observe that the implanted protons occupy thermally unstable site of ZnO, giving rise to a narrow NMR line at 4.1 ppm. The activation barrier of the implanted protons was found to be 0.46 eV by means of the rotating-frame spin-lattice relaxation measurements, apparently being interstitial hydrogens. High energy beam irradiation also leads to correlated jump diffusion of the surface hydroxyl group of multiple lines at ~1 ppm, implying the presence of structural disorder at the ZnO surface.
Figure1. 1H MAS NMR spectra for the samples (a) before and (b) after irradiation at 430 K following various spin-locking pulse lengths. Vertical arrows denote the peaks at 1.0 (H1) and 1.4 ppm (H2) before irradiation, as well as those and 4.1 ppm (H3) after irradiation. Inset shows the spectra before and after irradiation following a spin-locking pulse of 0.1 ms for comparison.
Scientific Reports 6, 23378 (2016)