Study on bisbenzocyclobutene bonding for the development of a Si-based miniaturized reformer of fuel cell systems

Choi, Dae-Hyun,Yeo, Chan-Hyeok,Kim, Jean-Tae,Ok, Chi-Won,Kim, Jong-Seok,Kwon, Yongchai,Im, Yeon-Ho IOP 2009 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.19 No.7

<P>This paper reports the results of a systematic study of bisbenzocyclobutene (BCB) bonding for a Si-based miniaturized reformer system. The micro reformer system, which included microchannels with a depth and a width of 250 µm and 600 µm, respectively, was fabricated using conventional semiconductor processing and BCB bonding. The structural, thermo-mechanical and chemical stability of Pyrex to Si wafer bonding using BCB as an adhesive was examined at temperatures up to 350 °C. The BCB interfaces at the Pyrex to Si wafer bonding pairs were mechanically stable to withstand the typical pressure and temperature conditions of the reforming process (1 atm and 300 °C) with little outgassing during reforming at 1 atm and 300 °C. The thermo-mechanical and chemical stability during wafer bonding and during reforming was examined using an optical inspection, and pressure pop-up test, FTIR test and gas chromatograph (GC) test were performed. The results showed that Pyrex to Si wafer bonding using BCB is suitable for a miniaturized reformer in fuel systems.</P>

The Effect of Cucumber mosaic virus 2b Protein to Transient Expression and Transgene Silencing Mediated by Agro-infiltration

Choi, Min-Sue,Yoon, In-Sun,Rhee, Yong,Choi, Seung-Kook,Lim, Sun-Hyung,Won, So-Youn,Lee, Yeon-Hee,Choi, Hong-Soo,Lee, Suk-Chan,Kim, Kook-Hyung,Lomonossoff, George,Sohn, Seong-Han The Korean Society of Plant Pathology 2008 Plant Pathology Journal Vol.24 No.3

The transient and rapid expression system of a foreign protein in planta is a very useful technique in biotechnology application. We have investigated optimum condition of Agrobacterium-infiltration technique in which expression level of foreign proteins were maximized without detrimental effects on plants using GFP and Cucumber mosaic virus 2b protein, which is known as an enhancer of gene expression and a suppressor of post-transcriptional gene silencing(PTGS). The optimum expression level of both RNA and protein of GFP with minimum leaf impairment was obtained at $OD_{600}$=0.2 of Agrobactrium inocula. The steady-state levels of GFP RNA and protein generally peaked at 3 and 7 days post-infiltration(dpi), respectively. In the presence of 2b, both the magnitude and duration of GFP expression was highly increased and we could detect GFP level until 17 dpi. On the other hands, the 2b-mediated higher accumulation of foreign proteins resulted in the repression of normal leaf growth, possibly due to the limitation of supply of energy or materials required for growth maintenance. Using this Agrobacterium-infiltration system with 2b and GFP, we tested a hypothesis for the threshold model of PTGS initiation. Four GFP transgenic lines of N. benthamiana, which shows different expression level of GFP were tested to determine the threshold level for PTGS initiation. Agrobacterium-infiltration of GFP into those GFP-transgenic plants resulted in the co-silencing of the transgenic GFP. It was found that very low concentration of Agrobacterium with GFP and GFP+2b($OD_{600}$=0.002-0.02) which could not phenotypically induce an additive GFP expression, was enough to trigger PTGS pathway in all GFP transgenic plants. This strongly indicates that each GFP-transgenic plant should be expressing the transgenic GFP at its own pre-determined level and there was no buffer zone of additive GFP-expression to the threshold. In other words, the PTGS seems to be immediately activated as a self-defensive mechanism if an internal balance of gene expression is broken.

Long-term management impact on SOC pool in paddy and upland soils

Chan-Yong Kim(김찬용),Young-Jin Seo(서영진),Tae-Young Kwon(권태영),Chung-Don Choi(최충돈),Won-Kyo Jung(정원교) 한국토양비료학회 2009 한국토양비료학회 학술발표회 초록집 Vol.2009 No.5

UV-curable organic-inorganic hybrid hard coatings for metal sheets

Choi, Woo-Chan,Kim, Seong-Hyeop,Lee, Won-Ki,Nagappan, Saravanan,Ha, Chang-Sik Springer-Verlag 2019 Journal of coatings technology and research Vol.16 No.3

Effects of anesthetics on resistive index of the medial long posterior ciliary artery and ophthalmic artery using color doppler imaging

Choi, Ho-jung,Lee, Young-won,Yoon, Jung-hee,Yeon, Seong-chan,Lee, Hyo-jong,Lee, Hee-chun The Korean Society of Veterinary Science 2005 大韓獸醫學會誌 Vol.45 No.3

Color Doppler imaging (CDI) was carried out to evaluate the anesthetics effect on ophthalmic circulation using CDI-derived resistive index (RI) values. CDI was preformed on 24 dogs, and RI values were calculated for the medial long posterior ciliary artery (mLPCA) and ophthalmic artery (OA) before and after administration of anesthetics. After administration of benoxinate or acepromazine, a significant change of the mLPCA RI was not found. But, a significant decrease of the RI following ketamine (p < 0.001) or xylazine (p < 0.01) administration could be observed as compared with the self-control. Mean RI value of OA also showed this same trend. Intraocular pressure was significantly decrease following benoxinate (p < 0.01), acepromazine (p < 0.01), and xylazine (p < 0.001) administration within normal range. The results suggest that some anesthetics influence on ophthalmic vascular resistance. Therefore, chemical restraint was carefully used in clinical application of CDI-derived RI measurement. Particularly, benoxinate and acepromazine is useful chemical restraint without a change of the ophthalmic vascular resistance.

Antineutrophil Cytoplasmic Antibody-Associated Vasculitis in Korea: A Narrative Review

Choi, Chan-Bum,Park, Yong-Beom,Lee, Sang-Won Yonsei University College of Medicine 2019 Yonsei medical journal Vol.60 No.1

<P>Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is a group of systemic necrotising vasculitides, which often involve small vessels, and which lead to few or no immune deposits in affected organs. According to clinical manifestations and pathological features, AAV is classified into three variants: microscopic polyangiitis, granulomatosis with polyangiitis (GPA), and eosinophilic GPA. The American College of Rheumatology 1990 criteria contributed to the classification of AAV, although currently the algorithm suggested by the European Medicines Agency in 2007 and the Chapel Hill Consensus Conference Nomenclature of Vasculitides proposed in 2012 have encouraged physicians to classify AAV patients properly. So far, there have been noticeable advancements in studies on the pathophysiology of AAV and the classification criteria for AAV in Western countries. However, studies analysing clinical features of Korean patients with AAV have only been conducted and reported since 2000. One year-, 5 year-, and 10 year-cumulative patient survival rates are reported as 96.1, 94.8, and 92.8%. Furthermore, initial vasculitis activity, prognostic factor score, age and specific organ-involvement have been found to be associated with either all-cause mortality or poor disease course. The rate of serious infection is 28.6%, and 1 year-, 5 year- and 10 year-cumulative hospitalised infection free survival rates range from 85.1% to 72.7%. The overall standardised incidence ratio of cancer in AAV patients was deemed 1.43 compared to the general Korean population.</P>

Improvement of Field-Emission Characteristics of Carbon Nanotubes by Post Electrical Treatment

Chan-Wook Baik,Jeonghee Lee,Deuk Seok Chung,Seong Chan Jun,Jun Hee Choi,Byung Kwon Song,Min Jong Bae,Tae Won Jeong,Jung Na Heo,Yong Wan Jin,Jong-Min Kim,SeGi Yu,Kyu-Ha Jang,Gun-Sik Park Institute of Electrical and Electronics Engineers 2007 IEEE transactions on electron devices Vol.54 No.9

<P>The field-emission characteristics of carbon nanotubes (CNTs), such as uniformity and brightness, were improved by electrical treatment using nonstationary electric fields between the cathode of screen-printed CNT emitters and the anode of a phosphor-coated indium-tin-oxide glass substrate in diode configuration. Dead or weak emission spots, where almost no emission of electrons was observed, started to emit electrons by applying an alternating-current voltage to the cathode electrode and a constant voltage to the anode electrode. The nonstationary electrical treatment was more effective than the direct-current (dc) and the square-pulsed electrical treatments for the emission uniformity and brightness. It was found that the nonstationary electrical treatment not only activated CNT emitters but also suppressed abnormally high emission spots without the drawbacks of electrical breakdown. Consequently, more than 1.8 and 1.3 times improvements of emission uniformity and brightness, respectively, were obtained after the treatment, when compared with the dc electrical treatment for the same amount of emission currents and the same duration of the treatments. Therefore, the method can be effectively applied to field-emission devices based on CNTs for the enhancement of emission properties.</P>

Effect of Leptin on Odontoblastic Differentiation and Angiogenesis: An <i>In Vivo</i> Study

Choi, Sung-Hyeon,Jang, Ji-Hyun,Koh, Jeong-Tae,Chang, Hoon-Sang,Hwang, Yun-Chan,Hwang, In-Nam,Lee, Bin-Na,Oh, Won-Mann Elsevier 2019 JOURNAL OF ENDODONTICS - Vol.45 No.11

<P><B>Abstract</B></P> <P><B>Introduction</B></P> <P>Leptin is secreted as a peptide hormone from adipose tissues. The aim of this study was to evaluate the effects of leptin on reparative dentin formation and angiogenesis in the pulp tissue of teeth <I>in vivo</I>.</P> <P><B>Methods</B></P> <P>Twenty-four 7-week-old male rats were anesthetized. Cavities were prepared in maxillary first molars. Pulp cappings were performed with collagen scaffold (Col) with a phosphate-buffered saline (PBS) vehicle (Col + PBS), leptin 1 μmol/L with Col (L1 + Col), or leptin 10 μmol/L with Col (L10 + Col). For the negative control group (no pulp capping), pulp capping was not performed. All cavities were sealed with resin-modified glass ionomer followed by a micro–computed tomographic scan, histologic examination, and immunohistochemical analysis.</P> <P><B>Results</B></P> <P>The volume of newly formed mineralized tissue in the leptin group was significantly (<I>P</I> < .01) higher than that in the control group based on micro–computed tomographic analysis. In histologic examination, hard tissue formation was rarely shown in the no pulp capping and Col + PBS groups. However, significantly (<I>P</I> < .01) larger amounts of newly mineralized tissue deposition were observed in the leptin groups. In immunohistochemical analysis, reparative dentin and new vessels formed in the pulp cavity of the leptin groups. Vascular endothelial growth factor, dentin sialoprotein, and dentin sialophosphoprotein were expressed around the newly formed mineralized tissue area.</P> <P><B>Conclusions</B></P> <P>Leptin showed the ability to induce angiogenesis, odontogenic differentiation, and mineralization in exposed rat pulps. Leptin also exhibited favorable inflammatory responses in the pulp tissue. Not only osteodentin but also tubular dentin and new vessels were observed in the pulp cavity.</P>

Sequentially Vapor-Grown Hybrid Perovskite for Planar Heterojunction Solar Cells

Choi, Won-Gyu,Kang, Dong-Won,Na, Sungjae,Park, Chan-Gyu,Gokdemir, Fatma Pinar,Moon, Taeho SPRINGER SCIENCE + BUSINESS MEDIA 2018 NANOSCALE RESEARCH LETTERS Vol.13 No.1

<P>High-quality and reproducible perovskite layer fabrication routes are essential for the implementation of efficient planar solar cells. Here, we introduce a sequential vapor-processing route based on physical vacuum evaporation of a PbCl<SUB>2</SUB> layer followed by chemical reaction with methyl-ammonium iodide vapor. The demonstrated vapor-grown perovskite layers show compact, pinhole-free, and uniform microstructure with the average grain size of ~ 320 nm. Planar heterojunction perovskite solar cells are fabricated using TiO<SUB>2</SUB> and spiro-OMeTAD charge transporting layers in regular <I>n</I>-<I>i</I>-<I>p</I> form. The devices exhibit the best efficiency of 11.5% with small deviation indicating the high uniformity and reproducibility of the perovskite layers formed by this route.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (10.1186/s11671-017-2401-5) contains supplementary material, which is available to authorized users.</P>

Supplementation with extract of <i>Gynostemma pentaphyllum</i> leaves reduces anxiety in healthy subjects with chronic psychological stress: A randomized, double-blind, placebo-controlled clinical trial

Choi, Eun-Kyung,Won, Yu Hui,Kim, Soon-Young,Noh, Soon-Ok,Park, Soo-Hyun,Jung, Su-Jin,Lee, Chong Kil,Hwang, Bang Yeon,Lee, Myung Koo,Ha, Ki-Chan,Baek, Hyang-Im,Kim, Hye-Mi,Ko, Myoung-Hwan,Chae, Soo-Wan Urban und Fischer Verlag 2019 Phytomedicine Vol.52 No.-

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>The ethanol extract of <I>Gynostemma pentaphyllum</I> Makino leaves (EGP) has been reported recently to have anxiolytic effects on chronically stressed mice models.</P> <P><B>Purpose</B></P> <P>We aimed to investigate the efficacy and safety of EGP on anxiety level in healthy Korean subjects under chronic stressful conditions.</P> <P><B>Study design</B></P> <P>Double-blind, placebo-controlled trial.</P> <P><B>Methods</B></P> <P>This study was conducted with 72 healthy adults who had perceived chronic stress and anxiety with a score on the State-Trait Anxiety Inventory (STAI) from 40 to 60. Participants were randomly assigned to receive either EGP (200 mg, twice a day, <I>N</I> = 36) or placebo (<I>N</I> = 36). All participants were exposed to repetitive loads of stress by performing the serial subtraction task for 5 min every second day during the 8-week intervention. Primary outcome of Trait-STAI and secondary outcomes of State-STAI, total score of STAI, Hamilton Anxiety Inventory (HAM-A), Beck Anxiety Inventory (BAI), blood norepinephrine and adrenocorticotropic hormone (ACTH), salivary cortisol and alpha-amylase, cardiovascular autonomic nervous system (ANS) functional test, and heart rate variability (HRV) test were measured before and after intervention.</P> <P><B>Results</B></P> <P>After the 8-week intervention, the EGP significantly lowered the score of the Trait Anxiety Scale of the STAI (T-STAI) by 16.8% compared to the placebo (<I>p</I> = 0.041). The total score on the STAI decreased by 17.8% in the EGP group and tended to improve compared with that of the placebo group (<I>p</I> = 0.067). There were no significant differences in the changes in score of S-STAI, HAM-A, BAI, and other parameters from baseline between the two groups. There was no causal relationship between the ingestion of EGP and adverse drug reactions.</P> <P><B>Conclusion</B></P> <P>We found that supplementation with EGP reduced “anxiety proneness” in subjects under chronic psychological stress, as shown by a decrease in the score of T-STAI and the tendency for decrease in the total score of STAI. This result suggests that EGP supplementation can be used as a regimen to safely reduce stress and anxiety; however, more studies are needed to establish the long-term safety and effectiveness.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>