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Correlation between Yellow Emission and Misoriented Structure in GaN Epilayers
Ok Hwan Cha,Mun Seok Jeong,고도경,Eun-Kyung Suh,Jongmin Lee,Kee Suk Nahm 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.3
A strong relationship between misoriented structure and yellow luminescence (YL) was found from the X-ray diffraction (XRD) and the photoluminescence measurements of GaN films grown by using radio-frequency induction-heated chemical vapor deposition and metal-organic chemical vapor deposition. YL was observed to be emitted from GaN films which contained peaks associated with the (10.10) and the (10.11) planes in their XRD spectra, and intensity variation of YL with some parameters, such as the growth temperature and the film thickness, had quite similar trends to that of the misoriented peak in XRD. We suggest that this tendency is due to point defects acting as YL centers trapped at the interface between the (0001) oriented structure and an unintentional structure oriented in the [10.10] and the [10.11] directions.0
Jeong-Eun Park,Ju-Ryoun Soh,Jeong-Ok Rho,Youn-Soo Cha 한국식품과학회 2007 Food Science and Biotechnology Vol.16 No.6
This study investigated the effects of cell cultured Acanthopanax senticosus extract (ASE) supplementation and swimming exercise on lipid profiles and carnitine concentrations in C57BL/6J mice fed high fat diets. Male C57BL/6J mice (n=50), aged 4 weeks, were divided into 5 groups based on exercise and/or ASE supplementation (0.5 g/kg of body weight): normal diet (N-C), high fat diet (H-C), high fat diet non-supplement & exercise (H-NSE), high fat diet supplement & no exercise (H-SNE), high fat diet supplement & exercis (H-SE). Liver nonesterified carnitine (NEC) was significantly higher in the H-SNE group than in the H-C group, and liver total carnitine (TCNE) levels were significantly higher in the H-SNE group than in the H-NSE and H-SE groups. Liver and muscle carnitine palmitoyltransferase-I (CPT-I) mRNA levels tended to be higher with ASE supplementation and/or exercise. These results suggest that supplementation with ASE and/or exercise might have a role in improving lipid oxidation.
Ok-Hwan Cha,Mun-Seok Jeong,Clare C. Byeon,Hyun Jeong,Jong-Hun Han,Young-Chul Choi,Kay-Hyeok An,Kyung-Hui Oh,Ki-Kang Kim,Young-Hee Lee 한국탄소학회 2009 Carbon Letters Vol.10 No.1
We propose an evaluation method of the relative content of single-walled carbon nanotubes (SWCNT) in SWCNT soot synthesized by arc discharge using UV-VIS-NIR absorption spectroscopy. In this method, we consider the absorbance of semiconducting and metallic SWCNTs together to calculate the relative content of SWCNTs with respect to a highly purified reference. Our method provides the more reliable and realistic evaluation of SWCNT content with respect to the whole carbonaceous content than the previously reported method.
Jeong, Jin-Woo,Lee, Hye Hyeon,Kim, Jongsik,Choi, Eun-Ok,Hwang-Bo, Hyun,Kim, Hong Jae,Kim, Min Young,Ahn, Kyu Im,Kim, Gi-Young,Lee, Ki Won,Kim, Ki Young,Kim, Sung Goo,Hong, Su Hyun,Park, Cheol,Cha, Hee D.A. Spandidos 2017 MOLECULAR MEDICINE REPORTS Vol.16 No.4
<P>Mori folium, the leaf of <I>Morus alba</I> L. (Moraceae), has been widely used in traditional medicine for the treatment of various diseases. It has been recently reported that Mori folium possesses potential chondroprotective effects in interleukin (IL)-1β-stimulated human chondrocytes; however, its protective and therapeutic potential against osteoarthritis (OA) in an animal model remains unclear. In this study, as part of an ongoing screening program to evaluate the anti-osteoarthritic potential of Mori folium, the protective effects of a water extract of Mori folium (MF) on cartilage degradation and inflammatory responses in a monosodium iodoacetate (MIA)-induced OA rat model were evaluated. The results demonstrated that administration of MF had a tendency to attenuate the damage to articular cartilage induced by MIA, as determined by knee joint swelling and the histological grade of OA. The elevated levels of matrix metalloproteinases-13 and two bio-markers for the diagnosis and progression of OA, such as the cartilage oligomeric matrix protein and C-telopeptide of type II collagen, were markedly ameliorated by MF administration in MIA-induced OA rats. In addition, MF significantly suppressed the production of pro-inflammatory cytokines, including IL-1β, IL-6 and tumor necrosis factor-α. MF also effectively inhibited the expression of inducible nitric oxide (NO) synthase and cyclooxygenase-2, thus inhibiting the release of NO and prostaglandin E<SUB>2</SUB>. Although further work is required to fully understand the critical role and clinical usefulness, these findings indicate that MF may be a potential therapeutic option for the treatment of OA.</P>
Ok Hwan Cha,Cheol-Hoi Kim,Jun Seok Lee,Jong Pil Jeong,Joong Seo Park,Jandi Kim,정현,Eun-Kyung Suh 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
The temperature dependence of the electroluminescence spectra of InGaN/GaN multi-quantumwell light-emitting diodes (LEDs) has been investigated over a range of temperatures and currents. The presence of localization effects in the active InGaN layers can be deduced from the observed considerable blue shifts of the electroluminescence emission peak with increasing temperature in the low-temperature region. Exciton-phonon couplings in the active layer are also observed at low temperatures. The electroluminescence intensity was measured to determine the internal quantum efficiency of the LEDs as a function of temperature. When the temperature decreases from room temperature to 170~200 K, the electroluminescence intensity increases due to a reduction in the nonradiative recombination, and the internal quantum efficiency is improved. At T < 170 K, the electroluminescence intensity is reduced significantly. This reduction of the electroluminescence intensity mainly results from the low carrier capture efficiency in the active layer due to the high Mg activation energy, the electron-hole separation in multi quantum wells, and the high internal piezoelectric field. However, in the case of LEDs using a narrow barrier, the electroluminescence intensity is reduced slightly at low temperatures. Therefore, in order to measure the internal quantum efficiency by using the temperature dependence of the electroluminescence spectra in LEDs, one must carefully consider the effects of carrier injection at low temperature.
Cha, Jeong-Ok,Jung, Young-Hee,Lee, Ha Rim,Yoo, Jae Il,Lee, Yeong Seon Churchill Livingstone [etc.] 2012 Journal of medical microbiology Vol.61 No.8
<P>This study was conducted to investigate the molecular characteristics and genetic relatedness of vancomycin-resistant Enterococcus faecium (VREF) isolates obtained from humans and poultry in Korea. A total of 147 VREF isolates from humans (71 clinical isolates) and poultry (76 isolates) in Korea were compared with respect to their antibiotic susceptibilities, organization of the Tn1546 transposon element, detection of virulence genes (esp and hyl), pulsed-field gel electrophoresis (PFGE) typing and multilocus sequence typing (MLST). All of the human and poultry isolates had the vanA gene and 11.3% (8/71) of the clinical isolates showed the VanB phenotype/vanA genotype. PCR mapping of the Tn1546 elements was different for isolates of the two groups: human isolates were classified into five transposon types, whereas all poultry isolates were identical to Tn1546 of E. faecium strain BM4147. The esp gene was detected in both human (93.0%, 66/71) and poultry (26.3%, 20/76) isolates, as was the hyl gene (human isolates: 80.3%, 57/71; poultry isolates: 26.3%, 20/76). Using MLST, the 71 human isolates could be divided into ten sequence types (STs) belonging to clonal complex (CC) 17 (except for one singleton). The 76 poultry isolates were categorized into 14 STs and 88.2% (67/76) of the poultry isolates belonged to CC26. PFGE typing of the human isolates demonstrated diverse PFGE profiles among the strains. However, the PFGE patterns of the poultry isolates were possibly related to the strains collected from individual farms. These data suggest that epidemic clonal groups of human and poultry VREFs in Korea have evolved through different evolutionary processes.</P>
Jeong, Jin-Woo,Park, Sejin,Park, Cheol,Chang, Young-Chae,Moon, Dong-Oh,Kim, Sung Ok,Kim, Gi-Young,Cha, Hee-Jae,Kim, Heui-Soo,Choi, Young-Whan,Kim, Wun-Jae,Yoo, Young Hyun,Choi, Yung Hyun National Hellenic Research Foundation 2014 ONCOLOGY REPORTS Vol.32 No.1
<P>Epidemiological studies indicate that components of garlic (Allium sativum) have anti-proliferative effects against various types of cancer. In the present study, we investigated the effect of newly isolated phenylamine derivative N-benzyl-N-methyldecan-1-amine (NBNMA) from garlic cloves on the inhibition of the growth and apoptosis of human leukemia U937 cells and its potential anticancer mechanism. NBNMA exhibited an antiproliferative effect in U937 cells by inducing cell cycle arrest at the G2/M phase and apoptotic cell death. Western blot analyses revealed that NBNMA decreased the expression of the regulator genes of G2/M phase progression, cyclin dependent kinase (Cdk) 2 and Cdc2 and elevated the expression of the Cdk inhibitor p21WAF1/CIP1 in a p53-independent manner. In addition, NBNMA activated caspase-8 and caspase-9, initiator caspases of the extrinsic and intrinsic pathways of apoptosis, respectively, which led to activation of executioner caspase-3 along with degradation of poly(ADP-ribose) polymerase. NBNMA-induced apoptosis was observed in parallel with an increased ratio of pro-apoptotic Bax and Bad/anti-apoptotic Bcl-2 and Bcl-xL, and inhibition of inhibitor of apoptosis protein (IAP) family members XIAP and cIAP-1. Furthermore, NBNMA-treated cells displayed enhanced release of cytochrome c from the mitochondria into the cytosol concomitant with a loss of mitochondrial membrane potential and downregulation of Bid, suggesting that NBNMA-induced apoptosis occurred via the extrinsic and intrinsic apoptotic pathways with a possible link to Bid protein activity between the two pathways. These results indicate that NBNMA has promising potential to become a novel anticancer agent for the treatment of leukemia. We provide new insight into the mechanisms underlying the anticancer effect of NBNMA.</P>