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Kwak, Da-Hee,Han, Sang-Beom,Lee, Young-Woo,Park, Hyun-Suk,Choi, In-Ae,Ma, Kyeng-Bae,Kim, Min-Cheol,Kim, Si-Jin,Kim, Do-Hyoung,Sohn, Jung-Inn,Park, Kyung-Won Elsevier 2017 Applied Catalysis B Vol.203 No.-
<P><B>Abstract</B></P> <P>Many alternatives to typical Pt-based catalysts have been developed to enhance oxygen reduction reaction (ORR) performance in acid medium due to their scarcity and high activation loss during the ORR. We synthesized mesoporous carbon nanostructures with multi-dopants such as iron, nitrogen, and sulfur as a cathode catalyst using the ordered silica templates and porphyrinic iron. The co-doped mesoporous carbon cathode catalysts exhibited a high ORR performance in an acid medium, <I>i.e.</I> complete ORR process and improved durability. The enhanced ORR properties of the catalysts might be ascribed to iron-containing catalytic active sites surrounded by nitrogen/sulfur species and a well-defined mesoporous carbon nanostructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Doped mesoporous carbon nanostructures were synthesized using a template method. </LI> <LI> The as-prepared samples exhibited a well-ordered mesoporous structure. </LI> <LI> The mesoporous carbon nanostructures contained multi-dopants such as Fe, N, and S. </LI> <LI> The doped carbon nanostructures showed highly improved ORR activity and stability. </LI> <LI> The improved properties were due to a well-doped mesoporous carbon nanostructure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Leydig Cell Tumors of Canine Testis
Da-Hee Jeong,Sun-Hee Do,Hai-Jie Yang,Dong-Wei Yuan,Il-Hwa Hong,Jin-Kyu Park,Moon-Jung Ku,Tae-Hwan Kim,Dong-Mi Kwak,Kyu-Shik Jeong 한국실험동물학회 2006 Laboratory Animal Research Vol.22 No.2
The testicular tumor is one of the most common tumors in dogs of advanced age, less common in older bulls and stallions, and rare in other species. In general, there are some marked differences in the gross appearance of the three most common canine testicular tumors. In our report, however, the canine Leydig cell tumor, occupying the major part of the testicle, diagnosed rarely. Microscopically, the neoplasm was composed of polyhedral cells arranged in nests, supported by a fine fibrovascular stroma. The neoplastic cells had abundant eosinophilic cytoplasm and round nuclei with prominent nucleoli. These cells were featured intermediate between the Leydig-like cells and the poorly differentiated cells. Histopathological findings of this report might be very useful for comparative diagnosis of testicular tumor.
Kwak, Da-Hee,Han, Sang-Beom,Kim, Do-Hyoung,Won, Ji-Eun,Park, Kyung-Won Elsevier 2018 Applied Catalysis B Vol.238 No.-
<P><B>Abstract</B></P> <P>In polymer electrolyte membrane fuel cells (PEMFCs), slow kinetics and high over-potential of oxygen reduction reaction (ORR) can result in a significantly large amount of Pt usage. Thus, non-precious metal (NPM) catalysts, especially, for ORR, that can be utilized instead of Pt-based catalysts, have been intensively studied. Herein, doped carbon nanostructures as NPM catalysts for ORR in an acid medium were synthesized using a template method with nontoxic, eco-friendly cysteine and iron (III) tetramethoxyphenylporphyrin (Fe-TMPP, 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin iron(III) chloride) used as carbon and doping sources, respectively. To obtain the doped mesoporous carbon nanostructure, mixtures of cysteine and Fe-TMPP with intended ratios (Cys<SUB>X</SUB>/Fe<SUB>Z</SUB>) were heated under an N<SUB>2</SUB> atmosphere at 900 °C for 3 h. In particular, Cys2/Fe0.3/C synthesized with an appropriate ratio of cysteine and Fe-TMPP showed a relatively high specific surface area and fairly high portion of doped species such as pyridinic and pyrrolic N, thiophenic S, and Fe-N<SUB>x</SUB>. Moreover, Cys2/Fe0.3/C exhibited significantly enhanced ORR activity and stability in 0.5 M H<SUB>2</SUB>SO<SUB>4</SUB> and superior tolerance of methanol in 0.5 M H<SUB>2</SUB>SO<SUB>4</SUB> in the presence of CH<SUB>3</SUB>OH.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Doped mesoporous carbon nanostructures were synthesized using template method. </LI> <LI> Doped porous carbon nanostructures were synthesized using amino acid cysteine. </LI> <LI> The mesoporous carbon nanostructures contained multi-dopants such as Fe, N, and S. </LI> <LI> The doped carbon nanostructures showed highly improved ORR activity and stability. </LI> <LI> The doped carbon nanostructures showed an superior tolerance of methanol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kwak, Da-Hee,Han, Sang-Beom,Kim, Do-Hyoung,Park, Jin-Young,Ma, Kyeng-Bae,Won, Ji-Eun,Kim, Min-Cheol,Moon, Sang-Hyun,Park, Kyung-Won Elsevier 2018 Carbon Vol.140 No.-
<P><B>Abstract</B></P> <P>The relatively sluggish oxygen reduction reaction (ORR) and high overpotential at the cathode, compared to anode, increases the loading amount of Pt cathode catalysts. Thus, non-precious metal (NPM) catalysts such as nitrogen-doped carbon nanostructures and macrocyclic structure of transition metal and nitrogen have been studied as an alternative to conventional Pt catalyst. Previously, we reported the synthesis of a Fe/N-doped mesoporous carbon nanostructure (denoted as Fe/NC) by a template method with 5,10,15,20-tetrakis(4-methoxyphenyl)-21H, 23H-porphyrin iron(III) chloride (Fe-TMPP) as a doping and carbon source. The Fe/N-doped carbon nanostructure as a NPM cathode catalyst showed the improved ORR activity owing to electrocatalytic active sites such as pyridinic and pyrrolic N states, and FeN<SUB>4</SUB> macrocycles. In this study, the degradation mechanism of Fe/NC during the ORR in an acidic medium was intensively investigated by chemical acid treatment and electrochemical cycling tests in the half and unit cells in different potential ranges. The crystal and pore structures of the sample before and after the durability test were measured and compared using X-ray diffraction method and N<SUB>2</SUB> adsorption/desorption analyzer. Furthermore, followed by the durability test, the surface chemical composition and state of the samples were characterized by X-ray photoelectron spectroscopy.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ultrasmall PtSn alloy catalyst for ethanol electro-oxidation reaction
Kwak, Da-Hee,Lee, Young-Woo,Han, Sang-Beom,Hwang, Eui-Tak,Park, Han-Chul,Kim, Min-Cheol,Park, Kyung-Won Elsevier 2015 Journal of Power Sources Vol.275 No.-
<P><B>Abstract</B></P> <P>To improve the electrocatalytic properties for an ethanol electro-oxidation reaction, modifications of Pt nanocrystallites have been used by alloying with other elements such as Ru, Sn, and Au. Here we demonstrate carbon supported Pt<SUB>3</SUB>Sn alloy electrocatalyst (Pt<SUB>3</SUB>Sn/C) synthesized using a thermal-decomposition method. The PtSn/C prepared by the present synthetic process shows a homogeneous distribution of ultrasmall alloy nanoparticles (∼2.5 nm) in the presence of Pt and Sn metallic states. At 0.45 V, the Pt<SUB>3</SUB>Sn/C (0.35 mA cm<SUP>−2</SUP>) exhibits much higher current density as compared with Pt/C (0.13 mA cm<SUP>−2</SUP>). In an electrochemical stability test, the Pt<SUB>3</SUB>Sn/C supported quite high current density and thus showed 3% current reduction after the stability test.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt<SUB>3</SUB>Sn nanoparticles with an ultrasmall size of 2.5 nm were synthesized. </LI> <LI> Pt<SUB>3</SUB>Sn nanoparticles showed improved electrocatalytic activity and stability. </LI> <LI> The improved activity may be attributed to a well-defined alloy formation. </LI> </UL> </P>
Changes of Lipid Peroxide and Antioxidant Enzymes by UVB-Induced Oxidative Stress
Wook-Hee Choi,Ryoung-Me Ahn,Sun Hee Do,Da-Hee Jeong,Si-Yun Ryu,Dong-Mi Kwak,Oh-Deog Kwon,Kyu-Shik Jeong,Tae-Hwan Kim 한국실험동물학회 2006 Laboratory Animal Research Vol.22 No.3
Ultraviolet B (UVB) exposure is known to cause oxidative damage in the skin. In this study, we investigated the acute effects of UVB exposure on the skin and liver. Lipid peroxide levels, the mRNA level and activities of superoxide dismutase (SOD) and catalase (CAT) were examined in ICR mice which were exposed to a single dose of UVB (3 KJ/㎡). In the exposed skin, lipid peroxides increased at 3 h after the UVB exposure (p<.001) and then the amount gradually decreased in a time dependent manner. In the liver, lipid peroxides peaked at 24 h after the exposure and maintained at that level for up to 3 days (p<.001). The mRNA level and activity of SOD and CAT increased in the exposed skin, but there was no significant change reported in the liver. Our results exhibited that oxidative damage by the exposure of UVB has an effects not only on the exposed skin, but also on liver. The increase of the antioxidant enzymes in response to UVB, might induce the recovery of damaged lesions.
Kwak, Sang Hyun,Kim, Ji Hoon,Kim, Da Hee,Kim, Jung Min,Byeon, Hyung Kwon,Kim, Won Shik,Koh, Yoon Woo,Kim, Se-Heon,Choi, Eun Chang Elsevier 2018 Auris, nasus, larynx Vol.45 No.3
<P><B>Abstract</B></P> <P><B>Objectives</B></P> <P>To report outcomes with regard to clinical aspects and medical costs of adenotonsillectomy and tonsillectomy at a single institution before and after implementation of the Diagnosis-Related Groups (DRG) payment system in Korea.</P> <P><B>Methods</B></P> <P>We retrospectively reviewed the records of patients treated with adenotonsillectomy or tonsillectomy between July 2012 and June 2014. The Korean DRG payment system was applied to seven groups of specific diseases and surgeries including adenotonsillectomy and tonsillectomy from July 2013 at all hospitals in Korea. We divided patients into four groups according whether the fee-for-service (FFS) or DRG payment system was implemented and operation type (FFS-adenotonsillectomy (AT), DRG-AT, FFS-tonsillectomy (T), and DRG-T).</P> <P><B>Results</B></P> <P>A total of 1402 patients were included (485 FFS-AT, 490 DRG-AT, 203 FFS-T, and 223 DRG-T). The total medical cost of the DRG-AT group was significantly lower than that of the FFS-AT group (1191±404 vs. 1110±279 USD, <I>P </I><0.05). There were no significant differences in length of hospital stay or postoperative complications among groups.</P> <P><B>Conclusion</B></P> <P>The Korean DRG system for adenotonsillectomy and tonsillectomy reduced medical costs and clinical outcomes were not significantly altered by the adoption of the DRG system.</P> <P><B>Level of evidence</B></P> <P>4.</P>
Impact of Sufficient Sleep and Its Change During Pregnancy on Reducing Postpartum Depression
( Da Kyung Hong ),( Bo Seong Yun ),( So Hyun Shim ),( Hee Young Cho ),( You Jung Han ),( Dong Wook Kwak ),( Min Hyoung Kim ),( Hee Jin Park ),( Jin Hoon Jung ),( Dong Hyun Cha ),( Moon Young Kim ),( S 대한산부인과학회 2019 대한산부인과학회 학술대회 Vol.105 No.-
Objective: This study aimed to elucidate whether sufficient sleep in each stage of pregnancy impacted on reducing PPD, and whether changes in sleep pattern during the prenatal period was associated with PPD, using a longitudinal and large cohort. Methods: The study participants were recruited at two special hospitals from Mar 2013 to Nov 2017, and included Korean pregnant women around 12 gestational weeks (GW); women with pregnancy of triplets or quadruplets were excluded. They completed a sleep questionnaire regarding whether or not they had sufficient sleep at 12 GW, 24 GW, and 36 GW. Participants were divided into Group0 (sustained sufficient sleep), Group1 (change from sufficient to insufficient sleep), Group2 (change from insufficient to sufficient sleep), and Group3 (sustained insufficient sleep). Depressive symptoms were assessed by the Edinburgh Postnatal Depression Scale (EPDS) at postpartum 4 weeks and cutoff score for PPD was ≥10. Results: Out of 2512 participants, 410 (16.3%) women were diagnosed with PPD. Only sufficient sleep at 36 GW was significantly associated with lowering PPD, after adjusting for confounding factors in multivariate regression analysis (odds ratio, 0.560; 95% confidence interval, 0.440-0.714; P < .001). When the sleep change between three time points (pre-pregnancy, 12 GW, or 24 GW) and 36 GW was assessed, both Group1 (worsening sleep) and Group3 (sustained insufficient sleep) were significantly associated with developing PPD at all starting time points in the multivariate analysis, while there was no significant association between Group2 (improving sleep) and PPD. Conclusion: Sufficient sleep in late pregnancy (at 36 GW) had the impact of lowering PPD. Whether or not participants had sufficient sleep at the pre-pregnancy or prenatal periods until 36 GW, having insufficient sleep at 36 GW was highly associated with developing PPD.