Song Eun Lee

Hongik University, Sŏul, Seoul, South Korea

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Publications (23)58.76 Total impact

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    ABSTRACT: We have designed emitters based on Anthracene-Aryl-Anthracene moieties end-capped with 1-naphthyl groups. In particular, a device showed blue EL properties with luminous and power efficiencies of 1.95 cd/A and 0.93 lm/W at 200 cd/m2 respectively, and CIE coordinates of (0.16, 0.10) at 7.0 V.
    Journal of Nanoscience and Nanotechnology 01/2015; 15(7). · 1.15 Impact Factor
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    ABSTRACT: In this paper, we demonstrated thin film semitransparent anode electrode using Ni/Ag/Ni (3/6/3 nm) on green and red phosphorescent OLEDs, which have basically high efficiency and good optical characteristics. Moreover, we applied this semitransparent anode on flexible green and red phosphorescent OLEDs, which were then optimized for possible applications on flexible substrates. First, we studied optimization using various conditions of Ni/Ag/Ni electrodes via transmittance and sheet resistance. We then fabricated the devices on a glass substrate with ITO or Ni/Ag/Ni electrodes as well as on a flexible substrate with a Ni/Ag/Ni electrode for green and red phosphorescent OLEDs. Consequently, we could be proposed that the potential of our semitransparent anode electrode is demonstrated. Green phosphorescent OLEDs characteristics using ITO or Ni/Ag/Ni anode electrodes were coincided and those of the red phosphorescent OLEDs were improved by semitransparent electrodes at 10,000 cd/m2 criterion. Therefore, this research suggests for additional studies to be conducted on flexible and high-performance phosphorescent OLED displays and light applications for ITO-free processes.
    Journal of Nanoscience and Nanotechnology 01/2015; 15(3). · 1.15 Impact Factor
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    ABSTRACT: Green phosphorescent organic light emitting diodes (PHOLEDs) were developed using a mixed layer system. They were fabricated with 4,4′-N,N′-dicarbazolyl-biphenyl (CBP) and typical charge transporting materials, which are 4,4′-bis[N-(naphthyl)-N-phenylamino]biphenyl (NPB) as a hole transporting material and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) as an electron transporting material, mixed at each interface in a stacked organic layer to reduce the hole injection barrier and extend the recombination zone. We introduced a mixed layer for the hole transporting layer side, the electron transporting layer side, and on both sides to make a bulk heterojunction. This reduced the driving voltage, and the luminous efficiency (LE) was increased to 500 cd/m2. The optimized device showed a maximum LE of 59.87 cd/A and a maximum external quantum efficiency of 17.52%.
    Journal of Nanoscience and Nanotechnology 11/2014; 14(11). · 1.15 Impact Factor
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    ABSTRACT: We suggested that Ni/Ag/Ni semitransparent electrodes for the exchange of indium-tin-oxide (ITO) electrode, which is the most commonly used as a transparent electrode in spite of the structural defects, limited supply of indium, and toxic, could be apply on flexible Organic Light-Emitting Diodes (OLEDs). Red phosphorescent OLEDs (PHOLEDs) using different types of electrodes as ITO and various conditions of Ni/Ag/Ni electrode were fabricated and analyzed. The electrical and optical properties of device using Ni/Ag/Ni electrode were improved than that of devices on ITO glass substrate at the 10,000 cd/m2 criterion due to the micro-cavity effect even though their transmittance has lower than ITO glass. In addition, we also fabricated red PHOLEDs of same structure on Ni/Ag/Ni flexible substrate of various conditions. As a result, flexible red PHOLED showed competitive characteristics compared to the device on a glass substrate. Therefore, this study could be suggested to additional research on flexible OLEDs display and light applications for ITO-free fabrication.
    Journal of Nanoscience and Nanotechnology 11/2014; 14(11). · 1.15 Impact Factor
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    ABSTRACT: Blue phosphorescent organic light-emitting diodes with multiple quantum well (MQW) structures (from one to four quantum wells) within an emitting layer (EML) are fabricated with charge control layers (CCLs) to control carrier movement. The distributed recombination zone and balanced charge carrier injection within EML are achieved through the MQW structure with CCLs. Remarkably, the half-decay lifetime of a blue device with three quantum wells, measured at an initial luminance of 500 cd/m2, is 3.5 times longer than that using a conventional structure. Additionally, the device's efficiency improved. These results are explained with the effects of triplet exciton confinement and triplet–triplet annihilation within each EML.
    Japanese Journal of Applied Physics 09/2014; 53(10):101601. · 1.07 Impact Factor
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    ABSTRACT: We demonstrate blue organic light-emitting diodes (OLEDs) based on a host-dopant system with a dual emitting layer (EML) configuration consisting of variable concentration of fluorescent doped and fixed concentration of phosphorescent doped emitting materials. We also introduce two different device designs by switching the position of the fluorescent and phosphorescent EMLs. Because 4,4'-Bis(2,2-diphenylvinyl)-1,1'-biphenyl (BCzVBi), which is the blue fluorescent dopant, exhibits the highest occupied molecular orbital (HOMO) energy level compared to the neighboring layers, the fluorescent dopant is shown to strongly correlate with hole transport in the fabricated blue OLEDs. In this study, we show how the electrical and optical properties of devices are affected by different doping concentrations due to the hole-transport-related properties of dopant molecules.
    Journal of Luminescence 04/2014; 148:72–78. · 2.14 Impact Factor
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    ABSTRACT: We investigated green phosphorescent organic light-emitting diodes (PHOLEDs) with charge control layer (CCL) to produce high efficiency and improve operational lifetime. Three types of devices were fabricated following the number of CCL within emitting layer (EML), maintaining the thickness of whole EML. The CCL and host material, which was 4,4′-bis (carbazol-9-yl)biphenyl (CBP) with bipolar property, can control carrier movement in EML. Therefore, the electroluminescent (EL) performance improvement as efficiency and lifetime was realized with a good charge balance, an effective triplet exciton confinement, and the reduced triplet exciton quenching effect in EML. Device 2 with a CCL as exciton distribution structure exhibits the remarkable EL performances for the maximum luminous and external quantum efficiency of 65.34 cd/A and 20.42%, respectively. Moreover, operational lifetime is nearly improved 2.5 times than the conventional device.
    Displays 04/2014; · 1.10 Impact Factor
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    ABSTRACT: A main requirement for achieving high efficiency in organic light-emitting diodes (OLEDs) is that all charges and electrically generated excitons should be employed for emission. We fabricated blue phosphorescent OLEDs with four types electron transporting layers, which were doped with lithium quinolate (Liq) from 0% to 10%. A series of blue devices consisted of indium tin oxide (ITO, 180 nm)/4,4-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (NPB, 50 nm)/N,N′-dicarbazolyl-3,5-benzene (mCP, 10 nm)/iridium(III)bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate (FIrpic) doped in mCP (8%, 30 nm)/1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi, 20 nm)/TPBi mixed with Liq (20 nm)/Liq (2 nm)/aluminum (Al, 100 nm). The blue OLED doped with 5% Liq, which demonstrated a maximum luminous efficiency and external quantum efficiency of 17.64 cd/A and 8.78%, respectively, were found to be superior to the other blue devices.
    Displays 12/2013; 34(5):396–398. · 1.10 Impact Factor
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    ABSTRACT: Systematic studies on carrier injection and transport are very important for achieving high efficiency in OLEDs. We demonstrate excellent green phosphorescent organic light-emitting diodes (OLED) with lithium quinolate (Liq) doped in 1,3,5-tris(N-phenylbenzimidazole-2-yl) benzene (TPBi) as the electron transport layer (ETL). The doping concentration of Liq was varied from 0% to 10%. The optimized green phosphorescent OLED with 5% Liq in the ETL showed the best efficiencies, which were maximum luminous efficiency, power efficiency, and quantum efficiency of 65.76 cd/A, 57.39 Im/W, and 20.03%, respectively. Moreover, high triplet energy states of TCTA and TPBi as a triplet exciton-blocking layer (TEBL) played a role in efficient exciton confinement.
    Journal of Nanoscience and Nanotechnology 12/2013; 13(12):7998-8001. · 1.15 Impact Factor
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    ABSTRACT: High-performance blue organic light-emitting diodes (OLEDs) are developed. A concept of using multiple-emissive layer (EML) configuration is adopted. In this letter, bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)Al (BAlq) and 9,10-di(naphtha-2-yl)anthracene (ADN), which serve n- and p-type EMLs, respectively, are used to evaluate and demonstrate the multi-EML concept for blue OLEDs. The thickness effect of individual EMLs and the number of EMLs, e.g., triple and quadruple EML components, on the power efficiency of blue OLEDs are systematically investigated. To illustrate the point, the total thickness of the emissive region in different blue OLEDs are kept contact at 30 nm for comparison. The power efficiency of blue OLEDs with a quadruple EML structure of BAlq/ADN/BAlq/ADN is about 40% higher than that of blue OLEDs having a single EML unit. The Commission Internationale deL'eclairage color coordinates of multi-EML OLEDs have values that represent the average of blue emissions from individual EMLs of BAlq and ADN.
    11/2013; 12(1).
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    ABSTRACT: Anatomical variations of the biceps brachii have been described by various authors, but the occurrence of bilateral asymmetric supernumerary heads is rare and has not been reported. We found three accessory heads of the biceps brachii muscle on right arm and an anomalous third head of biceps brachii on left arm. The third, fourth, and fifth heads of right arm originated from the body of humerus at the insertion site of coracobrachialis and inserted into the distal part of biceps brachii short head in order. The third head of left arm originated from humerus at the insertion site of coracobrachialis and combined with the distal part of biceps brachii and continued to the proximal part of common biceps tendon. Understanding the existence of bilateral asymmetric supernumerary heads of biceps brachii may influence preoperative diagnosis and surgery on the upper limbs.
    Anatomy & cell biology 09/2011; 44(3):238-40.
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    ABSTRACT: During potassium (K) depletion, many adaptive responses are likely mediated through a complex network that involves expression of a variety of genes. We identified that the Nrf2 gene was differentially expressed between normal and K-depleted rat kidney. To investigate the effect of Nrf2 on colonic H/K-ATPase and kNBC1, overexpression of Nrf2 was carried out in 293T and CV1 cell lines, and experiments were conducted in low-K media. Sp family was cotransfected with Nrf2 to examine the relationship between the 2 molecules and their effect on ion transporters. Ion transporters were activated by overexpression of Nrf2 and cotransfection of Nrf2 with Sp family genes showed additional enhancement of colonic H/K-ATPase and kNBC1 expression and their promoter activities. Pretreatment with low-K media increased the transcriptional activity of Nrf2, colonic H/K-ATPase and kNBC1. Furthermore, transfection of dominant-negative Nrf2 completely abolished low-K-mediated expression of the ion transporters. These results suggest that Nrf2 mediates transcriptional activation of colonic H/K-ATPase and kNBC1 in response to K-depleted stress and augments Sp family-mediated expression of these ion transporters.
    Journal of nephrology 06/2011; 25(2):225-32. · 2.02 Impact Factor
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    ABSTRACT: To identify genes that participate in the abortion process, normal pregnant uteri were compared to lipopolysaccharide (LPS)-induced abortion uteri. At day 6 of pregnancy, mice were treated with LPS at various time points to induce an abortion. Total RNAs were applied to a cDNA microarray to analyze genes with altered expression. At the early stage (2 hours) of LPS-induced abortion, upregulated genes were mainly composed of immune responsive genes, including Ccl4, Ccl2, Cxcl13, Gbp3, Gbp2, Mx2, H2-Eb1, Irf1 and Ifi203. Genes related to toll-like receptor signaling were also overexpressed. At late stages of abortion (12-24 hours), many genes were suppressed rather than activated, and these were mainly related to the extracellular matrix, cytoskeleton, and anti-apoptosis. Altered expression of several selected genes was confirmed by real time reverse transcription-polymerase chain reaction. The results demonstrated that many known genes were altered in the LPS-treated pregnant uterus, implying that the molecular mechanisms of the genes involved in LPS-induced abortion are complicated. Further analysis of this expression profile will help our understanding of the pathophysiological basis for abortion.
    Anatomy & cell biology 06/2011; 44(2):98-105.
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    ABSTRACT: The dynamic exchange of histone lysine methylation status by histone methyltransferases and demethylases has been previously implicated as an important factor in chromatin structure and transcriptional regulation. Using immunoaffinity TAP analysis, we purified the WHISTLE-interacting protein complexes, which include the heat shock protein HSP90α and the jumonji C-domain harboring the histone demethylase JMJD1C. In this study, we demonstrate that JMJD1C specifically demethylates histone H3K9 mono- and di-methylation, and mediates transcriptional activation. We also provide evidence suggesting that both WHISTLE and JMJD1C performs functions in the development of mouse testes by regulating the expression of the steroidogenesis marker, p450c17, via SF-1-mediated transcription. Furthermore, we demonstrate that WHISTLE is recruited to the p450c17 promoter via SF-1 and represses the transcription of prepubertal stages of steroidogenesis, after which JMJD1C replaces WHISTLE and activates the expression of target genes via SF-1-mediated interactions. Our results demonstrate that the histone methylation balance mediated by HMTase WHISTLE and demethylase JMJD1C perform a transcriptional regulatory function in mouse testis development.
    Nucleic Acids Research 10/2010; 38(19):6389-403. · 8.81 Impact Factor
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    ABSTRACT: 90K, a tumour-associated glycoprotein, interacts with galectins and has roles in host defence by augmenting the immune response, but the serum 90K level was suggested to indicate poor prognosis in several cancers. The cellular mechanisms of 90K action on colorectal cancer (CRC) cell motility and its effect on CRC progression were investigated. The impact of 90K was analysed by combining cell cultures, in vitro assays, and immunohistochemistry. Secreted 90K suppresses CRC cell invasion, but this action of 90K is masked through binding with extracellular galectins. A novel pathway is identified comprising a secretory 90K and a CD9/CD82 tetraspanin web; in this pathway, 90K interacts with CD9/CD82, suppresses the Wnt/beta-catenin signal via a novel proteasomal-ubiquitination mechanism of beta-catenin that is dependent on ISG15 (interferon-stimulated gene-15) modification (ISGylation) but not on glycogen synthase kinase 3beta (GSK-3beta) and Siah/Adenomatous polyposis coli (APC). In a syngeneic mouse colon tumour model, tumour growth and lung metastasis were increased with 90K knockdown. In colon tissues from stage IV human CRC and invading cancer cells of corresponding metastatic liver tissues, in which beta-catenin and galectin expression was higher, immunostained 90K and CD9/CD82 were lower than in adjacent hepatic tissues or colon tissues from stage I. 90K itself has antitumour activity in CRC cells via suppression of Wnt signalling with a novel mechanism of ISGylation-dependent ubiquitination of beta-catenin when it interacts with CD9/CD82, but is downregulated in advanced CRC tissues. The data suggest a strategy of strengthening this novel pathway with concomitant knockdown of galectins as a potential therapeutic approach to CRC progression.
    Gut 07/2010; 59(7):907-17. · 10.73 Impact Factor
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    ABSTRACT: The relationship between the interstitial cells of Cajal (ICC) and enteric nerves or smooth muscles cells is not fully defined. Presently, distribution and appearance of ICC in the rat stomach and duodenum was studied by immunohistochemistry, electron microscopy, and three-dimensional reconstruction. c-kit expressing ICC were regularly observed in the Auerbach's myenteric plexus (AP) of the stomach and duodenum. ICC in stomach and duodenum muscle layers was dissimilarly distributed. c-kit immunoreactive cells were sparsely distributed in the stomach circular muscle layer but were abundant in the duodenum deep muscular plexus (DMP). Electron microscopy revealed that stomach ICC-AP were irregular ovals with few cytoplasmic processes, and possessed an electron-dense cytoplasm, numerous mitochondria, intermediate filaments, and caveolae. Duodenum and stomach ICC-AP were similar in appearance. Ultrastructure observations and three-dimensional reconstructions revealed ICC-AP processes wrapping the nerve fibers and projecting into the space between smooth muscle cells. While ICC-AP was occasionally close to enteric nerves or smooth muscle cells, no connections were observed. ICC-DMP in duodenum was elongated and adopted the same cell axis orientation as the circular muscle cells. Unlike ICC-AP, ICC-DMP formed gap junctions with smooth muscle cells and had close contact with nerves. These results indicate that ICC-AP is regularly distributed in stomach and duodenum, while ICC-DMP is exclusively located in the duodenum. ICC-DMP, which possess gap junctions and closely contacts nerves, may participate in neuromuscular transmission. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc.
    Microscopy Research and Technique 05/2009; 72(12):951 - 956. · 1.59 Impact Factor
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    ABSTRACT: To investigate the anti-angiogenic effects of photodynamic therapy with verteporfin in a rabbit model of corneal neovascularization. One week after suturing, the localization of verteporfin in the neovascularized cornea was examined through fluorescent microscopy 1 hr after administration. Rabbits were treated with one or two times of photodynamic therapy with verteporfin at 1-week intervals. Analysis of corneal neovascularization was performed by biomicroscopic and histological examinations. Fluorescent microscopy showed green fluorescence in the vascular walls and interstitial tissue of the corneal stroma. The mean percentages of neovascularized corneal area at 3 days, 1 week, and 2 weeks after one time of photodynamic therapy were 90.3% +/- 3.5%, 71.6% +/- 6.2%, and 43.6% +/- 15.1% in treated eyes and 96.4% +/- 1.9% (p = 0.10), 88.6% +/- 4.6% (p = 0.01), and 76.8% +/- 4.4% (p < 0.01) in control eyes, respectively. The mean percentages 3 days, 1 week, and 2 weeks after two times of photodynamic therapy were also significantly lower in treated eyes compared with control eyes. In quantitative histological examination at 1 and 2 weeks after therapy, treated eyes showed significantly less neovascular area and number of vessels than control eyes. Photodynamic therapy with verteporfin is a safe and useful procedure to reduce experimental corneal neovascularization and can be used to inhibit angiogenesis in the cornea.
    Current Eye Research 04/2006; 31(3):215-24. · 1.71 Impact Factor
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    ABSTRACT: The tyramide signal amplification (TSA) technique has been shown to detect scarce tissue antigens in light and electron microscopy. In this study we applied the TSA technique at the electron microscopic level to pre-embedding immunocytochemistry. This protocol was compared to the non-amplified protocol. With the TSA protocol, the labeling of GM130, a cis-Golgi matrix protein, was tested in a cell line and found to be highly sensitive and more enhanced than that with the simple protocol. Moreover, the gold particles were well localized to the cis-side of the Golgi apparatus in both the TSA and the simple protocol.
    Journal of Histochemistry and Cytochemistry 03/2005; 53(2):249-52. · 2.26 Impact Factor
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    ABSTRACT: To investigate whether intracavernosal injection of vascular endothelial growth factor (VEGF) can restore erectile function in the aging rat. Ten young (4-5 months) and 30 old (24 months) Sprague-Dawley male rats were used. The old rats were divided into 3 groups: vehicle-only (phosphate buffered saline plus 0.1% bovine serum albumin; n = 10), VEGF 1 microg/kg (n = 10), and VEGF 10 microg/kg (n = 10). At 2 and 4 weeks after treatment, erectile function and histology were evaluated by hemodynamic study, histomorphometric analysis, and immunohistochemistry. After 4 weeks of treatment, the ratio of peak intracavernosal pressure to systemic arterial blood pressure in response to neurostimulation was significantly higher in both the VEGF 1 microg/kg (79.9 +/- 7.7%) and the VEGF 10 microg/kg group (76.8 +/- 5.8%) compared to the vehicle-only group (63.1 +/- 8.5%; p < 0.05). The percentage of cavernosal smooth muscle was significantly higher in the VEGF 10 microg/kg group (16.1 +/- 1.4%) compared to the vehicle-only group (12.8 +/- 2.2%; p = 0.047). VEGF treatment in old rats increased e-NOS and VEGF expression in both treatment groups. Intracavernosal injection of VEGF appears to restore smooth muscle integrity and improve erectile function in aged rats.
    European Urology 10/2004; 46(3):403-7. · 10.48 Impact Factor
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    ABSTRACT: To examine whether zinc accumulation occurs during retinal neuronal death after pressure-induced ischemia in rats and whether pyruvate protects against such death. To induce transient retinal ischemia, intraocular pressure was increased above systolic pressure for 65 minutes. Pyruvate was administered through the tail vein for 12 hours after ischemia to determine its effect on degeneration of retinal neurons. Retinas were removed and sectioned, and zinc accumulation was visualized with N-(6-methoxy-8-quinolyul)-p-carboxybenzoyl-sylphonamide (TFL-Zn) fluorescence microscopy, and neuronal death was determined with acid fuchsin staining. For in vitro studies, retinal cell cultures were prepared from newborn rat pups and used for experiments at days in vitro (DIV) 7 to 10. After retinal ischemia, staining revealed that most zinc-accumulating neurons were injured neurons, suggesting that endogenous zinc may contribute to ischemic neuronal death in the retina. In vitro studies showed that 15 minutes of exposure to 300 to 500 microM zinc resulted in the death of a substantial number of retinal cells in culture, and that this death was preceded by poly(ADP-ribose) polymerase (PARP)-mediated depletion of nicotinamide-adenine dinucleotide (NAD+) and adenosine triphosphate (ATP). Pyruvate, but not lactate, protected against this zinc-induced cell death in vitro. Consistent with this finding, in vivo studies showed that compared with control rats, pyruvate-treated rats had a substantial reduction in the number of cells showing signs of cell death. The present results suggest endogenous zinc contributes to retinal cell death after ischemia. Pyruvate potently protected against zinc toxicity in cultured rat retinal cells and reduced ischemia-induced cell death in rat retinas.
    Investigative Ophthalmology &amp Visual Science 06/2004; 45(5):1523-30. · 3.44 Impact Factor