Prediction of efficient energy transfer in emissive polymer blends based on Förster radius and the excited state lifetime of acceptors

Yu, Jae-Woong,Kim, Jai Kyeong,Kim, Dong Young,Kim, Chulhee,Song, Nam Woong,Kim, Dongho Elsevier 2006 Current Applied Physics Vol.6 No.1

<P><B>Abstract</B></P><P>The energy transfer process upon photoexcitation in binary polymer blends with different donor/acceptor pairs were investigated with the aid of the steady-state and time-resolved photoluminescence methods. The observed differences in the energy transfer efficiency are not fully explained by the Förster radius, deduced from the spectral overlap calculation. The order of energy transfer efficiencies for different donor/acceptor pairs does not follow the sequence of Förster radius, particularly for the acceptors having relatively long PL lifetimes. Hence, an alternative simple model is proposed to account for the order of energy transfer efficiency, which is to include the effect of the acceptor PL lifetime, specifically in the presence of excess donor. Such is the case with usual polymer LED devices.</P>

The Cloning of putative B function MADS gene from pepper (Capsicum annum)

Yu Jae Woong,Kim Byung-Dong 한국원예학회 1998 원예과학기술지 Vol.16 No.1

Prediction of efficient energy transfer in emissive polymer blends based on F?rster radius and the excited state lifetime of acceptors

Jae-Woong Yu,Jai Kyeong Kim,Dong Young Kim,Chulhee Kim,Nam Woong Song,Dongho Kim 한국물리학회 2006 Current Applied Physics Vol.6 No.1

The energy transfer process upon photoexcitation in binary polymer blends with dierent donor/acceptor pairs were investigatedwith the aid of the steady-state and time-resolved photoluminescence methods. The observed dierences in the energy transfer e-ciency are not fully explained by the Fo¨rster radius, deduced from the spectral overlap calculation. The order of energy transfer¨rster radius, particularly for the acceptors havingrelatively long PL lifetimes. Hence, an alternative simple model is proposed to account for the order of energy transfer eciency,which is to include the eect of the acceptor PL lifetime, specically in the presence of excess donor. Such is the case with usualpolymer LED devices.

Enhanced Secondary Electron Emission in Nanoscale Thin Metal Containing MgO Film: Laser Irradiation on Creation of F Centers

Yu, Hak Ki,Kim, Woong-Kwon,Park, Eung Chul,Kim, Jae Sung,Koo, Bon-Woong,Kim, Young-Woon,Ryu, Jae Hwa,Lee, Jong-Lam American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.36

<P>A number of oxygen vacancies were found in the MgO film when a nanoscale-metal embedded MgO film (MgO/nanoscale metal film/MgO) was exposed to a pulsed KrF excimer laser. This was due to the interfacial reaction between embedding nanoscale metal and MgO film. In a case of Nb embedding metal, the Nb<SUB>2</SUB>O<SUB>5</SUB> crystallites were evidenced to proceed the reaction at the MgO/Nb interface; 5MgO + 2Nb → Nb<SUB>2</SUB>O<SUB>5</SUB> + 5Mg + 5V<SUB>O</SUB><SUP>··</SUP>. The oxygen vacancies formed the F centers in the MgO bandgap, resulting in high cathodoluminescence intensity at the 431 and 526 nm region, corresponding to F<SUP>+</SUP> and F centers. The F centers in MgO played a role in increasing secondary electron emission coefficient (γ). As several kinds of nanoscale metals for creating F centers (Cr, Ti, V, In, Ta, and Nb) were embedded into MgO film, the γ values were found to be inversely linear with the Δ<I>G</I><SUB>f</SUB> for the formation of metal oxides. The Nb embedded MgO film showed the highest γ value of ∼0.232 compared with normal MgO film (0.034).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-36/jp205759s/production/images/medium/jp-2011-05759s_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp205759s'>ACS Electronic Supporting Info</A></P>

SEASONAL VARIABILITY OF WATER BALANCE IN THE YELLOW SEA

Jae Hak Lee,이흥재,Byoung Woong An,Yu Xiang Tang 한국해안해양공학회 1999 학술강연회 발표논문초록집 Vol.1 No.1

We analyze the CTD data obtained in the Yellow Sea through a Korea-China joint project during 1996-1998. Most of water masses analyzed here show that the seasonal variation is dominant. It is found that the low salinity core waters are formed in the southern surface layer in mid summer and their seasonal distribution exhibit a well posed annual cycle. Overall distribution patterns indicate that the low salinity core waters drift like a single body to adjust the seasonal basin-scale pressure fields, implying an eddy-like system. Another founding is that the temporal intermediate water characterized by its temperature minimum appears in the region of 50 m depth in the western Yellow Sea in spring. This water might be the remnants of cold waters formed during the winter season and the temperature minimum core appears as a result of different tidal mixing. Summertime data indicate that warm and saline waters provided from the southeast into the southern Yellow Sea in winter are isolated in the bottom layer of the region in summer, which modify continuously. In the future it is very necessary to study water masses in the bottom layer in summer to clarify the variation of the Yellow Sea Warm Current.

Development of Hepatocellular Carcinoma in Patients with Chronic Hepatitis B under Oral Antiviral Therapy

( Jae-jun Shim ),( Tae-woong Choi ),( Chi Hyuck Oh ),( Soyung Park ),( Yu Jin Um ),( Byung-ho Kim ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: Risk for hepatocellular carcinoma (HCC) development decreases but not completely disappears by long-term use of nucleos(t)ide analogues in patients with chronic hepatitis B (CHB). The aim of this study was to investigate incidence of HCC in CHB patients under antiviral therapy and to reveal clinical parameters related with HCC development. Methods: We collected clinical data retrospectively from 364 consecutive naive patients with CHB (40 to 70 years of age), who received entecavir for more than 6 months from January 1, 2007 to December 31, 2013. Incidence of HCC according to various clinical parameters including presence of liver cirrhosis was estimated. Kaplan-Meyer analysis and a multivariable Cox proportional hazards model were used for analysis. Results: Median age of patients was 51 years. Among the patients, 228 (62.6%) had liver cirrhosis, and 338 (92.9%) achieved complete virological response. Median ALT was 74 U/L and serum HBV DNA level was 6.79 log10 copies/mL. Total observation time of all patients was 1,293 years (mean 3.6 years per patient). During the period, 46 patients (12.6%) developed HCC. In univariate analysis, presence of liver cirrhosis, old age more than 50 years, low albumin (< 3.8 g/dL), and low platelet counts (< 120,000/mm3) were associated with higher risk of HCC development. In multivariate analysis, only presence of liver cirrhosis at the starting time of antiviral therapy was significantly associated with higher risk of HCC development (hazard ratio 6.9; 95% confidence interval [CI], 1.6-30.8) Annual incidence of HCC between cirrhotic and non-cirrhotic patients was 5.6% and 0.4% per year, respectively (P<0.001 by Log Rank test). Conclusions: Once CHB progressed to liver cirrhosis, risk for HCC development is unacceptably high despite of long-term antiviral therapy. We should consider earlier initiation of antiviral therapy before too late.

Application of REACH-B Model to Predict Hepatocellular Carcinoma Risk in Patients with Chronic Hepatitis B under Oral Antiviral Therapy

( Jae-jun Shim ),( Tae-woong Choi ),( Chi Hyuck Oh ),( Soyung Park ),( Yu Jin Um ),( Byung-ho Kim ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: REACH-B is a simple scoring system to predict HCC risk in non-cirrhotic patients with chronic hepatitis B (CHB). However, it is not known whether the model can accurately predict HCC risk in patients under long-term antiviral therapy. This study aimed to validate modified REACH-B model to predict HCC risk in patients receiving entecavir. Methods: From 2007 to 2013, total 136 naive patients (40 to 70 years of age) with CHB who had been treated for more than 6 months were retrospectively collected. None of them had liver cirrhosis. We hypothesized that HCC risk remains unchanged during the first two year and decrease thereafter. Two-year HCC risk was calculated from baseline data before antiviral therapy and the remaining 3-year risk was calculated from improved parameters following 2-year antiviral therapy. Results: Median age of patients was 49 years. HBeAg positive CHB were 77 (56.6%). Median ALT was 102 U/L. Baseline serum HBV DNA level was 7.51 log10 copies/mL. The patients were observed for total 507.5 years. The 5-year HCC risk of non-treated patients was predicted as 7.36%. It was equivalent to annual incidence of 1,472 per 100,000 persons with CHB. If they were treated, the 5-year HCC risk was dramatically decreased to 2.48%. Annual incidence was 496 per 100,000 persons with CHB. During actual follow-up period, two patients developed HCC. The incidence was 394 per 100,000 person year and 5-year cumulative incidence was estimated to 1.97%. There was no difference between predicted and actual incidence of HCC (P = 0.907 by Log Rank test). Actual and predicted incidence following antiviral therapy decreased as compared with that of non-treatment, however, the difference did not meet statistically significance (P = 0.176 by Log Rank test). Conclusions: Modified REACH-B model can predict 5-year risk of HCC in patients with CHB under long-term antiviral therapy.

Characterization of Cholangiocarcinoma-like Hepatocellular Carcinoma Using Gene Expression Pattern Analysis

( Jae-jun Shim ),( Tae-woong Choi ),( Chi Hyuck Oh ),( Soyung Park ),( Yu Jin Um ),( Byung-ho Kim ),( Ju-seog Lee ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: Hepatocelluar carcinoma (HCC), the most common primary liver cancer, shows very heterogeneous gene expression patterns compared with intrahepatic cholangiocarcinoma (CC). Recent studies revealed a subset of HCCs showing CC - like features in histopathologic and genomic levels. We tried to identify these overlapping tumors and to characterize this unique phenotype of HCC in clinical perspective. Methods: Genomic data were downloaded from The Cancer Genome Atlas (TCGA) on human HCC (n=374) and intrahepatic CC (n=30). Using uniquely expressed genes between HCC and intrahepatic CC, total 52 tumors (13.9%) were predicted as “CC-like” phenotype among HCCs (BRB array tool, BCCP model, P<0.001, cut off probability = 0.1). We found uniquely expressed 1,122 genes (CC signature set) between CC-like HCCs and the other HCCs ((P<0.0001, four fold changes). Using the CC signature set, we identified CC-like subgroup in other independent HCC cohorts. Results: Gene expression patterns of CC-like HCCs were significantly correlated with poor prognosis. They shared gene expressions with hepatic progenitor-origin tumors suggesting their origin might be shared with intrahepatic CC. The CC-like HCC also showed more aggressive gene expression patterns. Finally, CC-like HCCs showed significantly shorter overall survival than non-CC type in validation cohorts. Conclusions: Unique phenotype of HCC exists sharing similar gene expressions with CC and its genetic features are correlated with aggressive tumor biology.

Incidence of Hepatocellular Carcinoma in Subjects with Hepatitis B Virus Positive in Korean National Liver Cancer Screening Program

( Jae-jun Shim ),( Tae-woong Choi ),( Chi Hyuck Oh ),( Soyung Park ),( Yu Jin Um ),( Byung-ho Kim ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: To optimize efficacy of National Liver Cancer Screening Program (NLCSP) for subjects with hepatitis B surface antigen (HBsAg) positive, it is crucial to know the incidence of hepatocellular carcinoma (HCC) development and its predisposing factors in the program. Methods: From January 2010 to December 2014, all the HBsAg positive participants who received at least two or more abdominal ultrasonography under NLCSP were retrospectively enrolled in a single tertiary hospital. Annual incidence of HBV-related HCC was calculated and related clinical factors were investigated. Results: During 5 years, 541 subjects were enrolled. Mean age was 53 years old and 310 (57.3%) were male. Most subjects (86.5%) were patients of current hospital. Two hundred ninety two subjects (54%) were receiving antiviral agents at the moment. Liver cirrhosis (LC) was diagnosed in 212 (39.2%) by ultrasonography or upper endoscopy. Esophageal varices were found in 63 (14.8%). Total bilirubin, albumin, platelets, and aminotransferases were normal in most subjects. HBV DNA were less than 2,000 IU/mL in 356 subjects (79.6%). Mean follow-up time was 2.4 years and 16 new HCCs were diagnosed. Annual incidence of HBV-related HCCs were 980 per 100,000 patient year (1% per year). Subjects more than 60 years old (2.2% per year) had higher risk of HCC development than those under 60 years (0.6% per year, P<0.005 by Log Rank test). Presence of LC (2.2% per year) also showed higher risk of HCC than LC-free state (0.2% per year, P<0.0001 by Log Rank test). In cirrhotic patients older than 60 years old, the incidence increased up to 3.8% per year. Conclusions: Despite of high rate of antiviral therapy, incidence of HBV-related HCC is not low in participant of NLCSP in Korea. Old age and presence of liver cirrhosis are associated with higher risk of HCC development.

Purification and Characterization of β-N-Acetylhexosaminidase from Rice Seeds

(Yu Lan Jin),(Yu Young Jo),(Kil Yong Kim),(Jae Han Shim),(Yong Woong Kim),(Ro Dong Park) 생화학분자생물학회 2002 BMB Reports Vol.35 No.3

N-Acetyl-β-D-hexosaminidase (β-HexNAc’ase) (EC 3.2.1.52)was purified from rice seeds (Oryza sativa L. var. Dongjin)using ammonium sulfate (80%) precipitation, Sephadex G-150, CM-Sephadex, and DEAE-Sephadex chromatography, sequentially. The activities were separated into 7 fractions(F1-F7) by CM-Sephadex chromatography. Among them, F6 was further purified to homogeneity with a 13.0% yield and 123.3 purification-fold. The molecular mass was estimated to be about 52 kDa on SDS-PAGE and 37.4 kDa on Sephacryl S-300 gel filtration. The enzyme catalyzed the hydrolysis of both p-nitrophenyl-N-acetyl-β-D-glucosaminide (pNP-GlcNAc) and p-nitrophenyl-N-acetyl-β-D-galactosaminide (pNPGalNAc) as substrates, which are typical properties of β-HexNAc’ase. The ratio of the pNP-GlcNAc’ase activity to the pNP-GalNAc’ase activity was 4.0. However, it could not hydrolyze chitin, chitosan, pNP-β-glucopyranoside, or pNP-β-galactopyranoside. The enzyme showed Km, Vmax and Kcat for pNP-GlcNAc of 1.65mM, 79.49mM min?1, and 4.79 × 10^6 min^-1, respectively. The comparison of kinetic values for pNPGlcNAc and pNP-GalNAc revealed that the two enzyme activities are associated with a single binding site. The purified enzyme exhibited optimum pH and temperature for pNPGlcNAc of 5.0 and 50oC, respectively. The enzyme activity for pNP-GlcNAc was stable at pH 5.0-5.5 and 20-40oC. The enzyme activity was completely inhibited at a concentration of 0.1 mM HgCl2 and AgNO_3, suggesting that the intact thiol group is essential for activity. Chloramine T completely inhibited the activity, indicating the possible involvement of methionines in the mechanism of the enzyme.