선택적 촉매 산화 반응에 의한 황화 수소의 제거 Ⅱ . TiO2 / SiO2 촉매 상에서 황화 수소의 선택적 산화 반응

천승우,박대원,우희철,홍성수,정종식 ( S . W . Chun,D . W . Park,H . C . Woo,S . S . Hong,J . S . Chung ) 한국공업화학회 1996 공업화학 Vol.7 No.4

본 연구는 H₂S를 TiO₂/SiO₂촉매상에서 산소와의 직접 산화 반응을 통해 원소 황의 형태로 제거하는 반응에 관한 것이다. 순수한 TiS₂Ti(SO₄)_2를 사용한 반응 실험과 순수한 TiO₂에 대한 주기적 온도 조작 실험 결과로부터 TiO₂는 황 회수 공정에서 사용되는 촉매의 비활성화의 주원인으로 알려진 sulfation이나 salfidation에 대해 매우 안정한 것으로 나타났다. TiO₂/SiO₂촉매에서 TiO₂의 담지량이 증가함에 따라 H₂S 전화율이 증가하였고, 원소 황의 선택도는 아주 소폭으로 감소하였다. 반응 실험결과 O₂/H₂S의 비가 증가할수록 원소 황의 선택도는 크게 감소하였다. 10 wt.% TiO₂/SiO₂ 촉매는 화학 양론비의 조성(H₂S=5 vol.% O₂=2.5 vol.%)의 반응물에 10 vol.%의 수증기를 첨가한 경우 활성과 선택도가 감소하였으나 여전히 80% 이상의 원소 황 수율을 유지하고 있었다. Selective catalytic oxidation of H₂S to elemental sulfur using TiO₂/SiO₂ catalysts was investigated in this study. The reaction test with pure TiS₂and Ti(SO₄)₂and cyclic temperature operation revealed that TiO₂had a good resistance to sulfation and sulfidation, which are known as the main cause of catalytic deactivation in sulfur recovery process. With the increase of TiO₂loading amount in Tio₂/SiO₂catalysts, the conversion of H₂S increased and the selectivity of elemental sulfur was very slightly decreased. As the ratio of O₂/H₂S increased, the selectivity to elemental sulfur was drastically decreased. In the presence of 10 vol.% water vapor to a stoichiometric mixture of H₂S and O₂(H₂S =5 vol.% O=2.5 vol.%), both activity and selectivity of 10 wt.% TiO₂/SiO₂catalyst are decreased, but it still showed more than 80% of sulfur yield.

Reoxygenation following hypoxia activates DNA-damage checkpoint signaling pathways that suppress cell-cycle progression in cultured human lymphocytes

Kim, B.M.,Choi, J.Y.,Kim, Y.J.,Woo, H.D.,Chung, H.W. North-Holland Pub ; Elsevier Science Ltd 2007 FEBS letters Vol.581 No.16

Cellular responses to DNA damage after hypoxia and reoxygenation (H/R) were examined in human lymphocytes. Cultured lymphocytes exposed to H/R showed a lower cytokinesis block proliferation index and a higher frequency of micronuclei in comparison to control cells. Western blots showed that H/R exposure induced p53 expression; however, p21 and Bax expression did not increase, indicating that H/R did not affect p53 transactivational activity. Phosphorylation of p53 (Ser15), Chk1 (Ser345), and Chk2 (Thr68) was also observed, suggesting that H/R activates p53 through checkpoint signals. In addition, H/R exposure caused the phosphorylation and negative regulation of Cdc2 and Cdc25C, proteins that are involved in cell-cycle arrest at the G2/M checkpoint. The S-phase checkpoint, regulated by the ATM-p95/NBS1-SMC1 pathway, was also triggered in H/R-exposed lymphocytes. These results demonstrate that H/R exposure triggers checkpoint signaling and induces cell-cycle arrest in cultured human lymphocytes.

Proton Implantation Mechanism in GaN Layer Transfer by Using the Ion-Cut Process

H. J Woo,C. H Eum,G. D Kim,H. W Choi,J. K Kim,W. Hong,Y. H Bae 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I

The proton implantation condition for the ion-cut process in wurtzite-phase GaN and the associated mechanisms of surface blistering of GaN films were investigated. Etch-pit density (EPD) measurements, photoluminescence (PL) spectroscopy, and high resolution X-ray diffraction (HRXRD) were used to investigate the crystalline quality of the as-grown GaN epi-wafers. The proton beam was implanted at 60 keV with fluences in the range of 3 $\sim$ 5 $\times$ 10$^{17}$ H$^+$/cm$^2$ at room temperature. The influences of the crystallinity of the GaN wafers, the ion fluence and the post-implantation annealing conditions (200 $\sim$ 450 $^\circ$C) on the blistering process were studied. Optical microscopy, field emission scanning electron microscopy (FE-SEM), HRXRD, Rutherford backscattering Spectrometry (RBS)/channeling (RBS/C), and cross-sectional transmission electron microscopy (XTEM) were used to investigate splitting kinetics, and the optimum conditions for achieving exfoliation only after post-implantation annealing were determined for the GaN ion-cut process. Our results suggest that the ion-cut process is sensitive to both the implant fluence and the annealing conditions, however, so far as the measured crystal quality is concerned, against our expectations, there was no notable influence on the blistering property. The optimum post-implantation annealing temperature was less than 350 $^\circ$C, and low temperature splitting is of importance for layer transfer between dissimilar materials with very different thermal expansion coefficients.

Overestimation of on-road air quality surveying data measured with a mobile laboratory caused by exhaust plumes of a vehicle ahead in dense traffic areas

Woo, S.H.,Kwak, K.H.,Bae, G.N.,Kim, K.H.,Kim, C.H.,Yook, S.J.,Jeon, S.,Kwon, S.,Kim, J.,Lee, S.B. Elsevier Applied Science Publishers 2016 Environmental pollution Vol.218 No.-

The unintended influence of exhaust plumes emitted from a vehicle ahead to on-road air quality surveying data measured with a mobile laboratory (ML) at 20-40 km h<SUP>-1</SUP> in dense traffic areas was investigated by experiment and life-sized computational fluidic dynamics (CFD) simulation. The ML equipped with variable sampling inlets of five columns by four rows was used to measure the spatial distribution of CO<SUB>2</SUB> and NO<SUB>x</SUB> concentrations when following 5-20 m behind a sport utility vehicle (SUV) as an emitter vehicle equipped with a portable emission monitoring system (PEMS). The PEMS measured exhaust gases at the tailpipe for input data of the CFD simulations. After the CFD method was verified with experimental results of the SUV, dispersion of exhaust plumes emitted from a bus and a sedan was numerically analyzed. More dilution of the exhaust plume was observed at higher vehicle speeds, probably because of eddy diffusion that was proportional to turbulent kinetic energy and vehicle speed. The CO<SUB>2</SUB> and NO<SUB>x</SUB> concentrations behind the emitter vehicle showed less overestimation as both the distance between the two vehicles and their background concentrations increased. If the height of the ML inlet is lower than 2 m and the ML travels within 20 m behind a SUV and a sedan ahead at 20 km h<SUP>-1</SUP>, the overestimation should be considered by as much as 200 ppb in NO<SUB>x</SUB> and 80 ppm in CO<SUB>2</SUB>. Following a bus should be avoided if possible, because effect of exhaust plumes from a bus ahead could not be negligible even when the distance between the bus and the ML with the inlet height of 2 m, was more than 40 m. Recommendations are provided to avoid the unintended influence of exhaust plumes from vehicles ahead of the ML during on-road measurement in urban dense traffic conditions.

Hospital-based Influenza Morbidity and Mortality (HIMM) Surveillance for A/H7N9 Influenza Virus Infection in Returning Travelers

Song, Joon Young,Noh, Ji Yun,Lee, Jacob,Woo, Heung Jeong,Lee, Jin Soo,Wie, Seong-Heon,Kim, Young Keun,Jeong, Hye Won,Kim, Shin Woo,Lee, Sun Hee,Park, Kyung-Hwa,Kang, Seong Hui,Kee, Sae Yoon,Kim, Tae H KOREAN ACADEMY OF MEDICAL SCIENCE 2018 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.33 No.7

<P>Since 2013, the Hospital-based Influenza Morbidity and Mortality (HIMM) surveillance system began a H7N9 influenza surveillance scheme for returning travelers in addition to pre-existing emergency room (ER)-based influenza-like illness (ILI) surveillance and severe acute respiratory infection (SARI) surveillance. Although limited to eastern China, avian A/H7N9 influenza virus is considered to have the highest pandemic potential among currently circulating influenza viruses. During the study period between October 1st, 2013 and April 30th, 2016, 11 cases presented with ILI within seven days of travel return. These patients visited China, Hong Kong, or neighboring Southeast Asian countries, but none of them visited a livestock market. Seasonal influenza virus (54.5%, 6 among 11) was the most common cause of ILI among returning travelers, and avian A/H7N9 influenza virus was not detected during the study period.</P>

An outbreak of highly pathogenic H5N1 avian influenza in Korea, 2008

Kim, H.R.,Park, C.K.,Lee, Y.J.,Woo, G.H.,Lee, K.K.,Oem, J.K.,Kim, S.H.,Jean, Y.H.,Bae, Y.C.,Yoon, S.S.,Roh, I.S.,Jeong, O.M.,Kim, H.Y.,Choi, J.S.,Byun, J.W.,Song, Y.K.,Kwon, J.H.,Joo, Y.S. Elsevier Scientific Pub. Co 2010 Veterinary microbiology Vol.141 No.3

In spite of intensive surveillance programs for the control of HPAI, an outbreak of highly pathogenic avian influenza (HPAI) H5N1 in Korea in April 2008 caused serious damage to poultry farms, as did previous outbreaks in 2003/2004 and 2006/2007. Six viruses were selected from the Korean 2008 isolates for genetic analysis, and all eight gene segments from each of the influenza viruses were sequenced. A phylogenetic analysis showed that all of the viruses were of the same virus type and that the hemagglutinin (HA) gene was clustered with that of clade 2.3.2 viruses. However, the internal and neuraminidase (NA) genes were closely related to those of the clade 2.3.4 viruses (recent human and bird isolates from Southeast Asia).

선택적 촉매 산화 반응에 의한 황화수소의 제거 1 . 촉매의 개발

천승우,박대원,우희철,홍성수,정종식 ( S . W . Chun,D . W . Park,H . C . Woo,S . S . Hong,J . S . Chung ) 한국공업화학회 1995 공업화학 Vol.6 No.5

본 연구는 H₂S를 산소와의 직접 산화 반응을 통해 원소 황의 형태로 제거하는 반응에서 고농도의 H₂S를 처리할 수 있는 촉매의 개발에 관한 것이다. 최적의 촉매를 개발하기 위해 각 담체와 금속 산화물에 대한 반응성 실험을 실시하였다. 실험 결과 담체로는 Al₂O₃, TiO₂, ZrO₂ 등이 금속 산화물로서는 Fe₂O₃, V₂O_5, SnO₂, Cr₂O₃ 등이 좋은 활성을 보였다. 반응물 중의 산소의 분압 영향과 반응물에 포함되어질 수 있는 물의 영향에 대해서 관찰한 결과 산소의 분압이 높을수록 전화율은 증가하나 황 선택도는 급격히 감소하는 경향을 보였고, 10vol.%의 물을 반응물에 첨가한 경우 전화율과 황 선택도가 동시에 감소하는 경향을 보였다. In this study, development of catalysts far the direct oxidation of hydrogen sulfide to elemental sulfur, specially for the treatment of high concentrantion of H₂S, was investigated. To find out optimum catalysts, a screenig test for various supports and metal oxides was carried out. Among the supports tested, Al₂O₃, TiO₂ and ZrO₂ showed good catalytic activity. Fe₂O₃, V₂O_5, SnO₂ and Cr₂O₃ have been considered to be active metal oxides. The study on the effects of oxygen partial pressure revealed that the conversion of H₂S increased with increasing the ratio of O₂/H₂S, but the selectivity to sulfur was drasctically decreased. Bath of the conversion of H₂S and the selectivity to sulfur were decreased when 10 vol.% of water was added to the mixture of H₂S and oxygen.

Influence of mineral dust mixing-state and reaction probabilities on size-resolved sulfate formation in Northeast Asia

Song, C.H.,Nam, J.E.,Han, K.M.,Lee, M.K.,Woo, J.H.,Han, J.S. Pergamon Press ; Elsevier [distribution] 2012 Atmospheric environment Vol.58 No.-

Significant differences were found between two particulate sulfate size-distributions measured using a MOUDI impactor at Gosan, Jeju Island, Korea, and simulated via the Lagrangian photochemical model under a condition of aerosol internal mixing between mineral dust and urban pollution particles. It was suspected that these differences might have resulted from: (1) the assumption of aerosol internal mixing and (2) the uses of identical reaction probabilities (γ) of the gaseous sulfate precursors (SO<SUB>2</SUB> and H<SUB>2</SUB>SO<SUB>4</SUB>) onto both urban pollution particles and mineral dust in the Lagrangian photochemical model simulations. In this study; therefore, some cases of aerosol external mixing between urban-derived pollution aerosols and mineral dust were investigated, with different magnitudes of γ for the gas-phase sulfate precursors onto the two different condensing media. The model simulations under the external mixing condition, with different magnitudes of the reaction probabilities (γ<SUB>i,urban</SUB> and γ<SUB>i,dust</SUB>) onto urban pollution particles and mineral dust, successfully reproduced the size-dependent particulate sulfate formation measured at the Gosan station. Further attempts were made to approximate the magnitudes of γ<SUB>SO'2,urban</SUB> and γ<SUB>H'2SO'4,dust</SUB> under external mixing state conditions with the fixed γ<SUB>SO'2,dust</SUB> and γ<SUB>H'2SO'2,urban</SUB> values of 10<SUP>-4</SUP> and 1.0. The best-estimates of γ<SUB>SO'2,urban</SUB> and γ<SUB>H'2SO'4,dust</SUB> found in this study were in the orders of 10<SUP>-4</SUP>-10<SUP>-5</SUP> and 10<SUP>-2</SUP>-10<SUP>-3</SUP>, respectively.

Influence of <i>CYP2D6*10</i> on the pharmacokinetics of metoprolol in healthy Korean volunteers

Jin, S. K.,Chung, H. J.,Chung, M. W.,Kim, J.-I.,Kang, J.-H.,Woo, S. W.,Bang, S.,Lee, S. H.,Lee, H. J.,Roh, J. Blackwell Publishing Ltd 2008 Journal of clinical pharmacy and therapeutics Vol.33 No.5

<P>Summary</P><P>Background and objective: </P><P>Genetic polymorphism of <I>CYP2D6</I> leads to differences in pharmacokinetics of CYP2D6 substrates. The <I>CYP2D6*10</I> allele is clinically important in Koreans because of its high frequency in Asians. We investigated whether the pharmacokinetics of metoprolol was altered by the presence of the <I>CYP2D6*10</I> allele in Korean subjects.</P><P>Methods: </P><P>One hundred and seven volunteers were recruited and grouped as <I>CYP2D6*1/*1</I>, <I>CYP2D6*1/*10</I> and <I>CYP2D6*10/*10</I> according to their genotypes. Metoprolol tartrate 100 mg (Betaloc<SUP>®</SUP>) was administered orally once to each subject in these three groups (<I>n</I> = 6, 7 and 5, respectively). The pharmacokinetic parameters of metoprolol and its metabolite, &agr;-hydroxymetoprolol, and the metabolic ratio for the three groups were estimated and compared.</P><P>Results and discussion: </P><P>The area under the plasma concentration–time curve (AUC<SUB>0→∞</SUB>), the maximum plasma concentration (<I>C</I><SUB>max</SUB>) and the elimination half-life (<I>T</I><SUB>1/2</SUB>) of metoprolol and &agr;-hydroxymetoprolol for the <I>CYP2D6*10/*10</I> group were all significantly different from those of the <I>CYP2D6*1/*1</I> group (<I>P</I> < 0·05). The AUC<SUB>0→∞</SUB>s of metoprolol were 443·7 ± 168·1, 995·6 ± 321·4 and 2545·3 ± 632·0 ng·h/mL, and the AUC<SUB>0→∞</SUB>s of &agr;-hydroxymetoprolol were 1232·0 ± 311·2, 1344·0 ± 288·1 and 877·4 ± 103·4 ng·h/mL for groups <I>CYP2D6*1/*1</I>, <I>*1/*10</I> and <I>*10/*10</I>, respectively. The corresponding <I>T</I><SUB>1/2</SUB> values of metoprolol were 2·7 ± 0·5, 3·2 ± 1·3 and 5·0 ± 1·1 h, while those of &agr;-hydroxymetoprolol were 5·4±1·5, 6·0 ± 1·4 and 10·5 ± 4·2 h, respectively. The metabolic ratios of the three groups were significantly different (<I>P</I> < 0·05).</P><P>Conclusion: </P><P>The <I>CYP2D6*10</I> allele altered the pharmacokinetics of metoprolol in Korean subjects and is likely to affect other drugs metabolized by the CYP2D6 enzyme, similarly.</P>

자장강화된 유도결합형 플라즈마를 이용한 산화막 식각에 대한 연구

안경준(K. J. An),김현수(H. S. Kim),우형철(R. Woo),유지범(J. B. Yoo),염근영(G. Y. Yeom) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.4

본 연구에서는 자장강화된 유도결합형 플라즈마를 사용하여 이 플라즈마의 특성을 조사하고 또한 산화막 식각에 미치는 영향에 대하여 조사하였다. 자장 강화를 위해 4쌍의 영구자석이 사용되었고, 산화막 식각을 위해 C₂F_6, CHF₃, C₄F_8 가스 및 이들 혼합가스가 사용되었으며 첨가가스로 H₂를 사용하였다. 자장강화된 유도결합형 플라즈마 특성 분석을 위해 Langmuir probe 와 optical emission spectrometer를 이용하였으며 산화막 식각 속도 및 photoresist에 대한 식각 선택비를 stylus profilometer를 이용하여 측정하였다. 이온 밀도에 있어서 자장 유무에 따른 큰 변화는 관찰되지 않았으나 이온전류밀도의 균일도는 자장을 가한 경우 웨이퍼가 놓이는 기판 부분에서 상당히 증가된 것을 알 수 있었다. 또한 자장이 가해진 경우, 자장을 가하지 않은 경우에 비해 플라즈마 전위가 감소된 반면 전자온도 및 라디칼 밀도는 크게 증가되는 것을 알 수 있었으며 산화막 식각시에도 높은 식각 속도와 식각 균일도를 보였다. 산화막 식각을 위해 수소가스를 사용한 가스조합중에서 C₄F_8/H₂가스조합이 가장 우수한 식각 속도및 photoresist에 대한 식각 선택비를 나타내었으며 공정변수를 최적화 함으로써 순수 C₄F_8에서 4이상의 선택비와 함께 8000 Å/min의 가장 높은 식각속도를 얻을 수 있었으며, 50%C₄F_8/50%H₂에서 4000 Å/min의 산화막 식각 속도와 함께 15이상의 식각 선택비를 얻을 수 있었다. In this study, the effects of multi-dipole type of magnets on the characteristics of the inductively coupled plasmas and SiO₂ etch properties were investigated. As the magnets, 4 pairs of permanent magnets were used and, to etch SiO₂, C₂F_6, CHF₃, C₄F_8, H₂, and their combinations were used. The characteristics of the magnetized inductively coupled plasmas were investigated using a Langmuir probe and an optical emission spectrometer, and SiO₂ etch rates and the etch selectivity over photoresist were measured using a stylus profilometer. The use of multi-dipole magnets increased the uniformity of the ion density over the substrate location even though no significant increase of ion density was observed with the magnets. The use of the magnets also increased the electron temperature and radical densities while reducing the plasma potential. When SiO₂ was etched using the fluorocarbon gases, the significant increase of SiO₂ etch rates and also the increase of etch uniformity over the substrate were obtained using the magnets. In case of gas combinations with hydrogen, C₄F_8/H₂showed the highest etch rates and etch selectivities over photoresist among the gas combinations with hydrogen used in the experiment. By optimizing process parameters at 1000 Watts of inductive power with the magnets, the highest SiO₂ etch rate of 8000 Å/min with the etch selectivity of 4 could be obtained for 100% C₄F_8 and the highest etch selectivity of over 15 with the SiO₂ etch rate of 4000 Å/min could be obtained for 50% C₄F_8/50% H₂.