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Sang Jin Park,Joo Hyun Sung,Chang Sun Sim,Seok Hyeon Yun,Jeong Han Yeom,Joong-Keun Kwon,Jiho Lee 대한직업환경의학회 2016 대한직업환경의학회지 Vol.28 No.-
Background: The purpose of this study was to investigate hearing threshold changes of workers with unilateral conductive hearing loss who were exposed to workplace noise for 8-years. Methods: Among 1819 workers at a shipyard in Ulsan, 78 subjects with an air-bone gap ≥10 ㏈HL in unilateral ears were selected. Factors that could affect hearing were acquired from questionnaires, physical examinations, and biochemistry examinations. Paired t-test was conducted to compare the hearing threshold changes over time between conductive hearing loss (CHL) ear and sensorineural hearing loss (SNHL) ear. Results: The study included male subjects aged 48.7 ± 2.9, having worked for 29.8 ± 2.7 years. Hearing thresholds increased significantly in CHL ears and SNHL ears at all frequencies (0.5–6 ㎑) during follow-up period (p < 0.05). The threshold change at 4 ㎑ was 3.2 ㏈HL higher in SNHL ears which was statistically significant (p < 0.05). When workers were exposed to noise levels of 85 ㏈A and above, threshold change at 4 ㎑ was 5.6 ㏈HL higher in SNHL ears which was statistically significant (p < 0.05). Among workers aged below 50, the threshold change values were lower in low-frequency (0.5–2 ㎑) in SNHL ears, with a small range of changes, whereas in high-frequency (3–6 ㎑), the range of changes was greater SNHL ears (p < 0.05). Among workers aged 50 and above, SNHL ears showed a wider range of changes in both high- and low-frequency areas (p < 0.05). Conclusions: At high-frequencies, particularly at 4 ㎑, the range of hearing threshold changes was lower in ears with conductive hearing loss than in contralateral ears. This is suggested as a protective effect against noise exposure.
Han, Dong-Wook,Ryu, Won-Hee,Kim, Won-Keun,Lim, Sung-Jin,Kim, Yong-Il,Eom, Ji-Yong,Kwon, Hyuk-Sang American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.4
<P>Porous and coarse (5–10 μm) LiFePO<SUB>4</SUB>/C composites with excellent electrochemical performance were synthesized by a growth technology using nanostructured (100–200 nm) LiFePO<SUB>4</SUB> as seed crystals for the 2nd crystallization process. The porous and coarse LiFePO<SUB>4</SUB>/C presented a high initial discharge capacity (∼155 mA h g<SUP>–1</SUP> at 0.1 C), superior rate-capability (∼100 mA h g<SUP>–1</SUP> at 5 C, ∼65 % of the discharge capacity at 0.1 C), and excellent cycling performance (∼131 mA h g<SUP>–1</SUP>, ∼98 % of its initial discharge capacity after 100 cycles at 1 C). The improvement in the rate-capability of the LiFePO<SUB>4</SUB>/C was attributed to the high reaction area resulted from the pore tunnels formed inside LiFePO<SUB>4</SUB> particles and short Li-ion diffusion length. The improved cycling performance of the LiFePO<SUB>4</SUB>/C resulted from the enhanced structural stability against Li-deficient LiFePO<SUB>4</SUB> phase formation after cycling by the expansion of the 1D Li-ion diffusion channel in the LiFePO<SUB>4</SUB> crystal structure.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-4/am302560m/production/images/medium/am-2012-02560m_0008.gif'></P>
Han, Sang Keun,Kim, Yun Gi,Kang, Hee Cheol,Huh, Jeong Ran,Kim, Ji Yeoung,Baek, Nam-In,Lee, Dong-Kyu,Lee, Dong-Geol The Korean Society for Applied Biological Chemistr 2014 Applied Biological Chemistry (Appl Biol Chem) Vol.57 No.6
Natural products with non-toxic and environmentally friendly properties are good sources for skin-whitening and brightening cosmetic agents. Strawberries (Fragaria ananassa), and their parts are used as cosmetic agents, because they contain high levels of bioactive substances. We isolated and identified compounds from F. ananassa calyx. Oleanolic acid has multiple biological activities, including anti-tumor, anti-angiogenic, anti-inflammatory, anti-oxidant, and pro-apoptotic effects. However, no study has investigated the influence of oleanolic acid on melanin synthesis in B16-F10 melanoma cells. In the present study, we investigated the effect of oleanolic acid on melanin biosynthesis in B16-F10 melanoma cells stimulated with ${\alpha}$-melanocyte stimulating hormone (${\alpha}$-MSH). Oleanolic acid-mediated melanogenesis inhibition was studied by measuring intracellular and secreted melanin levels and by using Western blot and semi-quantitative reverse transcriptase-polymerase chain reaction analyses. Oleanolic acid suppressed melanin release and expression, resulting in a significant dose-dependent decrease in secreted and intracellular melanin levels and cellular tyrosinase activity. Furthermore, it inhibited the expression of melanogenesis-associated factors, including tyrosinase, tyrosinase-related proteins-1 and -2, and microphthalmia-associated transcription factor, in ${\alpha}$-MSH-stimulated B16-F10 melanoma cells. The results of the present study can contribute to the development of cosmetic agents utilizing the skin whitening and brightening effect of oleanolic acid, which will likely have a wide range of applications in the cosmetic industry and/or clinical practice in the future.
Han, Sang Won,Kim, Dong Keun,Hwang, In Gook,Bae, Jae Heum 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.2
Pellet-type adsorbents were made from red mud, generated as a by-product during the production of aluminum hydroxide from bauxite ore. Adsorption experiments of heavy metal ions (Pb^2+, Cu^2+, Cd^2+) in aqueous solutions by the pellet-type red mud adsorbents were studied under various experimental conditions. It was found that pellet-type red mud adsorbents made from a mixture of 58.7 wt% red mud, 25.2 wt% kaolin, 11.7 wt% sodium silicate solution, 2.9 wt% fly ash, and 1.5 wt% magnesium chloride at 600℃ exhibited the highest removal efficiency of the heavy metal ions. The removal efficiency of Pb^2+, Cu^2+, and Cd^2+ after 24 h of operation was more than 95%. The pellet-type red mud adsorbents in the present study were found to follow a Langmuir equilibrium isotherm. A continuous adsorption experiment showed that the pellet-type red mud adsorbents were effective in removing Pb^2+.
Han, In-Soo,Oh, Keun-Yeob,Lee, Sang Bin The Korea Contents Association 2013 International Journal of Contents Vol.9 No.3
This paper aims at investigating what Regional University E-Learning Centers (RUECs) has done in promoting e-learning in university education in Korea. First, the e-learning situation in university education in Korea is introduced. Secondly, the background of establishment of RUECs and its functions are explained in detail. Thirdly, a case of RUECs is suggested by using the CNU-University E-Learning Center. In particular, the performance of e-learning is evaluated based on the student satisfaction data, and a paired-t test is implemented to see if there was any difference between 'before' and 'after' e-learning. Lastly, some suggestions are made to promote the e-learning in university education.