Dong Wook Kwak

Catholic Kwandong University, Gangneung, Gangwon-do, South Korea

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Publications (38)72.4 Total impact

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    ABSTRACT: This study aimed to examine clinical practice patterns in the management of pregnant women admitted with threatened preterm labor (TPL) in Korea. Data from women admitted with a diagnosis of TPL were collected from 22 hospitals. TPL was defined as regular uterine contractions with or without other symptoms such as pelvic pressure, backache, increased vaginal discharge, menstrual-like cramps, bleeding/show and cervical changes. Data on general patient information, clinical characteristics at admission, use of tocolytics, antibiotics, and corticosteroids, and pregnancy outcomes were collected using an online data collections system. A total of 947 women with TPL were enrolled. First-line tocolysis was administered to 822 (86.8%) patients. As a first-line tocolysis, beta-agonists were used most frequently (510/822, 62.0%), followed by magnesium sulfate (183/822, 22.3%), calcium channel blockers (91/822, 11.1%), and atosiban (38/822, 4.6%). Of the 822 women with first-line tocolysis, second-line tocolysis were required in 364 (44.3%). Of 364 with second-line, 199 had third-line tocolysis (37.4%). Antibiotics were administered to 29.9% of patients (284/947) with single (215, 22.7%), dual (26, 2.7%), and triple combinations (43, 4.5%). Corticosteroids were administered to 420 (44.4%) patients. Betamethasone was administered to 298 patients (71.0%), and dexamethasone was administered to 122 patients (29.0%). Practice patterns in the management of TPL in Korea were quite various. It is needed to develop standardized practice guidelines for TPL management.
    05/2015; 58(3):203-9. DOI:10.5468/ogs.2015.58.3.203
  • Hoon Young Cho · Dong Wha Lee · Dong Wook Kwak
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    ABSTRACT: The size evolution of gold (Au) nanoparticles (NPs) on the sidewall surface of silicon (Si) nanowires (NWs) has been investigated by thermal treatments, using high-angle annular dark field scanning transmission electron microscopy. The Si NWs grown at 550°C by rapid thermal chemical vapour deposition have been observed to be surrounded by Au NPs with less than 5 nm diameter and ∼1012 cm-2 density on the whole Si NW surface. To explore the size change of Au NPs, the Au NPs on the Si NW were annealed ex situ at the temperature range of 700-900°C for 20 min. The sizes of NPs for samples annealed at 700, 800 and 900°C represent Gaussian distribution with the average size of 4, 6 and 7 nm, respectively, while at high temperatures above 900°C, they change to a bimodal distribution. It is suggested that the surface diffusion rate of Au NPs on Si NW is much lower than that on the Si substrate because of the substitutional diffusion mechanism.
    Micro & Nano Letters 03/2015; 10(3):161-166. DOI:10.1049/mnl.2014.0389 · 0.85 Impact Factor
  • S.Y. Kim · H J Kim · S.Y. Park · D E Lee · K S Kim · M H Kim · D W Kwak · H M Ryu
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    ABSTRACT: To investigate the association between pregnancies with small for gestational age (SGA) neonates and the concentration of cell-free fetal DNA or cell-free total DNA in maternal plasma during the first and second trimesters using tissue-specific epigenetic characteristics of the SERPINB5 gene. A nested case-control study was conducted with maternal plasma collected at 11 to 26 gestational weeks from 51 women with SGA neonates and 102 controls. We performed a real-time quantitative methylation-specific PCR to quantify concentrations of unmethylated-SERPINB5 (U-SERPINB5) as a cell-free fetal DNA marker and methylated-SERPINB5 (M-SERPINB5) as a cell-free total DNA marker. A positive correlation was observed between U-SERPINB5 and M-SERPINB5 concentrations in both control (r = 0.363, p < 0.001) and SGA groups (r = 0.548, p < 0.001). Moreover, the concentration of U-SERPINB5 or M-SERPINB5 was significantly positive correlated with gestational age at sampling in both controls (U-SERPINB5: r = 0.397, p < 0.001; M-SERPINB5: r = 0.275, p = 0.005) and SGA (U-SERPINB5: r = 0.274, p = 0.052; M-SERPINB5: r = 0.439, p = 0.001). However, the concentration of U-SERPINB5 or M-SERPINB5 was not correlated with birthweight. At 11-14 weeks, U-SERPINB5 and M-SERPINB5 concentrations in SGA did not differ significantly from those of controls. There were also no statistically significant differences in the concentrations of U-SERPINB5 and M-SERPINB5 between SGA and controls at 15-26 weeks of gestation. Our findings suggest that U-SERPINB5 and M-SERPINB5 concentrations in maternal plasma during early pregnancy are not associated with pregnancies who delivered SGA neonates. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Placenta 02/2015; 36(2). DOI:10.1016/j.placenta.2014.09.020 · 2.71 Impact Factor
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    ABSTRACT: To estimate the odds ratio of prepregnant body mass index (BMI), gestational weight gain (GWG), and gestational diabetes mellitus (GDM) for excessive fetal growth, which we define as large for gestational age (LGA). We included 16,297 women who delivered a live-born singleton baby at term. We fit logistic regressions to estimate the odds ratios of variables, including maternal age, parity, prepregnant BMI ≥23, GWG ≥15 kg, and GDM, for LGA. We classified GWG into four categories (<10, 10-14.9, 15-19.9, and ≥20 kg) and BMI into four categories (underweight, normal, overweight, and obese). After adjusting for age and parity, we analyzed the odds ratios of prepregnant BMI according to GWG between non-GDM and GDM women for LGA. The odds ratios of GWG ≥15 kg and prepregnancy BMI ≥23 for LGA were 2.40 (95% confidence interval [CI], 2.16-2.67) and 2.24 (95% CI, 1.99-2.51), respectively. The odd ratio of GDM was 1.37 (95% CI, 1.09-1.71). The risk of GDM women with normal/-overweight BMI and GWG <15 kg for LGA was not significantly greater than those of the reference group. The odd ratios of GDM women with overweight/obese BMI and GWG 15 to 19.9 kg were 3.95 (95% CI, 1.26-12.38) and 9.70 (95% CI, 3.79-24.87), respectively. GWG ≥15 kg might be a more important risk factor for LGA than either prepregnancy BMI ≥23 or GDM. Risk for LGA was highest in obese GDM women with GWG ≥15 kg.
    11/2014; 57(6):442-447. DOI:10.5468/ogs.2014.57.6.442
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    ABSTRACT: This study aimed to survey the current clinical practice of first-trimester ultrasonography among members of the Korean Society of Ultrasound in Obstetrics and Gynecology (KSUOG) and to provide basic data for making practical recommendations about first-trimester ultrasonography scan in Korea. This survey was conducted using a self-administered anonymous questionnaire. The first-trimester in this survey was divided into two parts: early and late first-trimester. The survey was focused on safety issue, nuchal translucency (NT) cutoff, the anatomic structures they check, and the need for practical recommendations or educational courses during the first-trimester. During the study period, 194 KSUOG members participated into this survey. The survey on early first-trimester scan reveal that 173 (89.2%) of respondents had used pulsed-wave Doppler or color Doppler imaging to monitor fetal heart beat. For the late first-trimester scan, 145 (74.7%) of respondents was found to check for fetal anatomical assessments during their NT screening performance; however, the clinical practice patterns were considerably varied among participants. More than half of the respondents used the criterion of NT ≥3.0 mm to define increased NT. Approximately 80% of respondents stated that the screening ultrasonography of fetal structures in the first-trimester was necessary. Furthermore, 187 (96.4%) of respondents were in favor of a recommendation for first-trimester ultrasonography in Korea. This is the first survey of the current clinical practice of first-trimester ultrasonography in Korea. Our survey findings highlight the need for the practical recommendation or educational course for first-trimester ultrasonography.
    11/2014; 57(6):448-456. DOI:10.5468/ogs.2014.57.6.448
  • Dong Wook Kwak · Yong Won Park · Young Han Kim
    Placenta 09/2013; 34(9):A68. DOI:10.1016/j.placenta.2013.06.205 · 2.71 Impact Factor
  • 223th ECS Meeting; 05/2013
  • Dong Wook Kwak · Dong Wha Lee · Dong Hyuk Suh · Hoon Young Cho
    223th ECS Meeting; 05/2013
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    ABSTRACT: This study was designed to determine the frequency and echocardiographic findings of 22q11.2 deletions in fetuses with cardiac defects on fetal ultrasound or familial backgrounds of 22q11.2 deletions.
    01/2013; 10(2):99. DOI:10.5734/JGM.2013.10.2.99
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    Dong Wook Kwak · In Suk Yoo · June-Seek Choi
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    ABSTRACT: Various fetal and maternal conditions are known to be associated with oligohydramnios. In general, oligohydramnios developed early in pregnancy is less common but frequently has a poor prognosis. The use of angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists during pregnancy has been associated with oligohydramnios as well as growth restriction, pulmonary hypoplasia with respiratory distress, acute renal failure, cranial malformation and fetal death. Although many researchers report a use of oral hypoglycemic agents such as glyburide or metformin in gestational diabetes mellitus, but potential adverse effects of glimepiride, which is relatively recently developed, is not well known owing to the lack of clinical data, especially early in pregnancy. A 41-year-old woman with chronic hypertension and type 2 diabetes mellitus was treated with drugs including metformin, glimepiride and angiotensin receptor antagonist until approximately 20 weeks' gestations, when severe oligohydramnios was noted. After the hospitalization for bed rest, fetal surveillance, and discontinuation of the agents, amniotic fluid reaccumulated, and the infant was delivered at term. We report this case with a brief review of literatures.
    01/2013; 24(2):95. DOI:10.14734/kjp.2013.24.2.95
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    ABSTRACT: The purpose of this study was to assess the characteristics of achondroplasia (ACH) diagnosed in fetuses or neonates and to evaluate the usefulness of a molecular genetic testing to confirm ACH.
    01/2013; 10(1):38. DOI:10.5734/JGM.2013.10.1.38
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    D. W. Lee · M. S. Seol · D. W. Kwak · J. S. Oh · J. H. Jeong · H.Y. Cho
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    ABSTRACT: Hydrogen effects on deep level defects and a defect generation in proton implanted Cu(In,Ga)Se2 (CIGS) based thin films for solar cell were investigated. CIGS films with a thickness of 3 μm were grown on a soda-lime glass substrate by a co-evaporation method, and then were implanted with protons. To study deep level defects in the proton implanted CIGS films, deep level transient spectroscopy measurements on the CIGS-based solar cells were carried out, these measurements found 6 traps (including 3 hole traps and 3 electron traps). In the proton implanted CIGS films, the deep level defects, which are attributed to the recombination centers of the CIGS solar cell, were significantly reduced in intensity, while a deep level defect was generated around 0.28 eV above the valence band maximum. Therefore, we suggest that most deep level defects in CIGS films can be controlled by hydrogen effects.
    Thin Solid Films 08/2012; 520(20):6382–6385. DOI:10.1016/j.tsf.2012.06.046 · 1.76 Impact Factor
  • D. W. Kwak · D. W. Lee · J. S. Oh · Y.H. Lee · H.Y. Cho
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    ABSTRACT: SiGe-on-Insulator (SGOI) structures were created using the Ge condensation method, where an oxidation process is performed on the SiGe/Si structure. This method involves rapid thermal chemical vapor deposition and H+/He+ ion-implantations. Deep level defects in these structures were investigated using deep level transient spectroscopy (DLTS) by varying the pulse injection time. According to the DLTS measurements, a deep level defect induced during the Ge condensation process was found at 0.28 eV above the valence band with a capture cross section of 2.67 × 10− 17 cm2, two extended deep levels were also found at 0.54 eV and 0.42 eV above the valence band with capture cross sections of 3.17 × 10− 14 cm2 and 0.96 × 10− 15 cm2, respectively. In the SGOI samples with ion-implantation, the densities of the newly generated defects as well as the existing defects were decreased effectively. Furthermore, the Coulomb barrier heights of the extended deep level defects were drastically reduced. Thus, we suggest that the Ge condensation method with H+ ion implantation could reduce deep level defects generated from the condensation and control the electrical properties of the condensed SiGe layers.
    Thin Solid Films 06/2012; 520(17):5593–5596. DOI:10.1016/j.tsf.2012.04.035 · 1.76 Impact Factor
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    Nano Letters 03/2012; 12(4). DOI:10.1021/nl301031u · 13.59 Impact Factor
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    ABSTRACT: We report on rapid thermal chemical vapor deposition growth of silicon nanowires (Si NWs) that contain a high density of gold nanoclusters (Au NCs) with a uniform coverage over the entire length of the nanowire sidewalls. The Au NC-coated Si NWs with an antibody-coated surface obtain the unique capability to capture breast cancer cells at twice the highest efficiency currently achievable (~88% at 40 min cell incubation time) from a nanostructured substrate. We also found that irradiation of breast cancer cells captured on Au NC-coated Si NWs with a near-infrared light resulted in a high mortality rate of these cancer cells, raising a fine prospect for simultaneous capture and plasmonic photothermal therapy for circulating tumor cells.
    Nano Letters 02/2012; 12(3):1638-42. DOI:10.1021/nl2045759 · 13.59 Impact Factor
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    ABSTRACT: The aim of this nested case-control study was to investigate the association between hepatocyte growth factor (HGF) concentrations in maternal plasma and the risk of developing preeclampsia.
    01/2012; 9(2):78. DOI:10.5734/JGM.2012.9.2.78
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    ABSTRACT: Paracentric inversion of chromosome 18 is a rare cytogenetic abnormality. The vast majority of paracentric inversions are harmless and the offspring of paracentric inversion carriers have only slightly elevated risks for unbalanced karyotypes. However, various clinical phenotypes are seen due to breakpoint variation or recombination. We report a prenatally detected case of familial paracentric inversion of chromosome 18, inv(18)(q21.1q22), with normal clinical features.
    01/2012; 9(2):101. DOI:10.5734/JGM.2012.9.2.101
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    ABSTRACT: Photoinduced current transient spectroscopy was used to investigate the defect states and capture kinetics of charge carriers for traps in low temperature polycrystalline silicon (poly-Si) films. A broad deep trap was found to be located 0.30 eV from the conduction band edge of poly-Si with capture cross section of 1.51× 10-15 cm2. The variation of the trap capture kinetics with filling pulse time showed extended traps and linear arrays of traps, which might be grain boundary defects. Proton implantation and H-plasma treatment were used to improve poly-Si device characteristics, with traps more effectively suppressed by the former treatment. The ionized hydrogen atoms implanted into the poly-Si films are imputed to amorphize the defective poly-Si film with post-annealing enhancing re-crystallization, resulting films with fewer defects.
    Japanese Journal of Applied Physics 12/2010; 49(12). DOI:10.1143/JJAP.49.125802 · 1.13 Impact Factor
  • Hoon-Young Cho · Won-Sik Kim · J. S. Oh · D. H. Kim · D. W. Kwak
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    ABSTRACT: Ultrathin oxide-nitride-oxide (ONO) dielectric stacked layers are fundamental structures of silicon-oxide-nitride-oxide-silicon (SONOS) non-volatile memory devices in which information is known to be stored as charges trapped in silicon nitride. Deep-level transient spectroscopy (DLTS) and a capacitance-voltage (CV) analysis were introduced to observe the trap behavior related to the memory effect in memory devices. The DLTS results verified that the nitride-related traps were a dominant factor in the memory effect. The energy of hole traps was 0.307 eV above the balance band. To improve the memory effects of the non-volatile memory devices with ONO structures, we introduced a nitrogen plasma treatment. After the N-plasma treatment, the flat-band voltage shift (Delta V(FB)) was increased by about 1.5 times. The program and the erase (P-E) characteristics were also shown to be better than those for the as-ONO structure. in addition, the retention characteristics were improved by over 2.4 times.
    Journal- Korean Physical Society 08/2010; 57(2). DOI:10.3938/jkps.57.255 · 0.42 Impact Factor
  • M.S. Seol · D.H. Kim · D.W. Kwak · D.W. Lee · J.H. Jeong · W.S. Kim · H.Y. Cho
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    ABSTRACT: The suppression effect on deep level defects and the defect generation in Cu(InGa)Se<sub>2</sub> solar cells by a proton implantation have been investigated using deep level transient spectroscopy (DLTS) and optical DLTS measurements. CIGS films with the thickness of ~3μm were grown on a soda-lime glass as substrate by co-sputtering method and implanted by proton with 2× 10<sup>16</sup> cm<sup>-3</sup> dose and in 50 keV energy, and post-annealed under various conditions. To study the proton effect on deep level defects in CIGS films, DLTS and ODLTS were carried out and 5 hole traps and 3 electron traps were found. The calculated trap energies and densities for observed traps were summarized. After proton implantation and post annealing at 200°C for 5 min in N<sub>2</sub> ambient, the deep defects which is known to attribute to loss of the CIGS solar cell efficiency were remarkably reduced in intensity. Therefore, we report that electrical deep level defects in CIGS films can be passivated by proton implantation and post annealing and that a deep level defect with the activation energy of E<sub>v</sub>+0.28 eV generates newly.
    Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE; 07/2010

Publication Stats

208 Citations
72.40 Total Impact Points


  • 2013–2015
    • Catholic Kwandong University
      • College of Medicine
      Gangneung, Gangwon-do, South Korea
  • 2012–2013
    • Cheil General Hospital
      Sŏul, Seoul, South Korea
  • 2007–2013
    • Dongguk University
      • Quantum-functional Semiconductor Research Center
      Sŏul, Seoul, South Korea
    • Hannam University
      Daiden, Daejeon, South Korea
  • 2008
    • Yonsei University
      Sŏul, Seoul, South Korea
  • 2006
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea