Comparison of a novel bedside portable endoscopy device with nasogastric aspiration for identifying upper gastrointestinal bleeding.

Choi, Jong Hwan,Choi, Jae Hyuk,Lee, Yoo Jin,Lee, Hyung Ki,Choi, Wang Yong,Kim, Eun Soo,Park, Kyung Sik,Cho, Kwang Bum,Jang, Byoung Kuk,Chung, Woo Jin,Hwang, Jae Seok WJG Press 2014 World journal of gastroenterology Vol.20 No.25

<P>To compare outcomes using the novel portable endoscopy with that of nasogastric (NG) aspiration in patients with gastrointestinal bleeding.</P>

Development of Detection System Using Multiplex PCR and Liquid Beadarray for Stacked Genetically Modified Rice Event (LS2S ${\times}$CrylAc)

Choi, Sun-Hee,Oh, Yong-Taek,Kwon, Ji-Yeon,Lee, Sung-Nam,Han, Byoung-Don,Ryu, Ki-Hyun The Korean Society for Applied Biological Chemisty 2010 Applied Biological Chemistry (Appl Biol Chem) Vol.53 No.5

A multiplex system was developed to assess detection of stacked genetically modified (GM) rice (LS28 ${\times}$ CrylAc) based on multiplex polymerase chain reaction (PCR) and liquid beadarray, and the accuracy of the system was analyzed. Standard and specific bulging specific (S8S) primers with standard primers were used to simultaneously detect multiple targets in stacked events of rice. Five sets of primers for the stacked events were applied to amplify their targets, and were separated distinctly in agarose gel. A liquid beadarray assay for the stacked GM rice was performed using the multiplex PCR products, followed by target biotinylation and hybridization between biotinylated-tagged target and anti-tagged bead. Fluorescent signals of the hybridized target sequences were detected by the Luminex system. The signaling patterns were analyzed by their mean fluorescent intensity (MFI) value. Results showed that liquid beadarrays with standard and SBS primers were in complete agreement with the PCR data, and detection of the different target elements was found to be very specific with no cross reaction among samples. Therefore, our detection system developed for stacked GM crop using multiplex PCR and liquid beadarray can be a useful and efficient system for screening and analyzing multiple transgenes in a single tube for qualitative analysis.

Tunable Wetting Property in Growth Mode-Controlled WS ₂ Thin Films

Choi, Byoung Ki,Lee, In Hak,Kim, Jiho,Chang, Young Jun Springer US 2017 NANOSCALE RESEARCH LETTERS Vol.12 No.1

<P>We report on a thickness-dependent wetting property of WS<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB> and WS<SUB>2</SUB>/SiO<SUB>2</SUB>/Si structures. We prepared WS<SUB>2</SUB> films with gradient thickness by annealing thickness-controlled WO<SUB>3</SUB> films at 800 °C in sulfur atmosphere. Raman spectroscopy measurements showed step-like variation in the thickness of WS<SUB>2</SUB> over substrates several centimeters in dimension. On fresh surfaces, we observed a significant change in the water contact angle depending on film thickness and substrate. Transmission electron microscopy analysis showed that differences in the surface roughness of WS<SUB>2</SUB> films can account for the contrasting wetting properties between WS<SUB>2</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB> and WS<SUB>2</SUB>/SiO<SUB>2</SUB>/Si. The thickness dependence of water contact angle persisted for longer than 2 weeks, which demonstrates the stability of these wetting properties when exposed to air contamination.</P>

Liquid crystalline and ion-conducting properties of mesogenic dendron–coil-dendron copolymers: characterization of LC phases using normalized conductivity

Choi, Sujin,Cho, Byoung-Ki The Royal Society of Chemistry 2013 Soft matter Vol.9 No.16

<P>We synthesized three dendron–coil-dendron block copolymers consisting of ionophilic poly(ethylene oxide) (PEO) coils and mesogenic dendrons with four octadecyl peripheries <I>via</I> stepwise click reactions. The obtained polymers were doped with lithium triflate, whose concentration per ethylene oxide unit was 0.05. As characterized by optical polarized microscopy (POM) and X-ray scattering techniques, polymer <B>1</B> with the shortest PEO coil (<I>M</I><SUB>n</SUB> = 2000 g mol<SUP>−1</SUP>) did not show the liquid crystalline (LC) phase, while its ionic sample (<B>1-Li<SUP>+</SUP></B>) exhibited a hexagonal columnar LC phase. On the other hand, <B>2</B> and <B>3</B> (with PEOs of <I>M</I><SUB>n</SUB> = 4000 and 8000 g mol<SUP>−1</SUP>, respectively) displayed identical LC morphologies to <B>2-Li<SUP>+</SUP></B> and <B>3-Li<SUP>+</SUP></B>, respectively, although the phase transition temperatures increased upon salt doping. For <B>2</B> and <B>2-Li<SUP>+</SUP></B>, gyroid and lamellar LC phases were observed with increasing temperature, while <B>3</B> and <B>3-Li<SUP>+</SUP></B> showed only a lamellar LC phase. The observed ion-transporting behavior was strongly dependent upon the connectivity of ion-conducting domain structures. The investigation of the morphology–conductivity correlation using a normalized conductivity (<I>σ</I>* = <I>σ</I>/<I>f</I>, where <I>σ</I> and <I>f</I> are the original conductivity and the PEO volume fraction) indicated that the 3-D gyroid LC phase showed the highest value, while the lowest conductivity was found in the 1-D columnar structure at identical temperatures. Additionally, the gyroid to lamellar phase transition temperature of <B>2-Li<SUP>+</SUP></B> could be determined by the <I>σ</I>*, which was consistent with the X-ray data. Consequently, the results can be explained by the fact that the ionic pathway becomes complicated when going from higher to lower dimensional structures in polygrain samples.</P> <P>Graphic Abstract</P><P>Ion-conducting properties of dendron–coil-dendron block copolymers are dependent upon the domain dimensionality of the liquid crystalline morphologies, which can be properly analyzed using a normalized conductivity (<I>σ</I>*) instead of original conductivity (<I>σ</I>). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3sm27959f'> </P>

Synthesis and Characterization of Triblock Copolymers Containing Amphiphilic Dendron

Cho, Byoung-Ki,Chung, Yeon-Wook Korean Chemical Society 2006 Bulletin of the Korean Chemical Society Vol.27 No.1

Degree of chain branching-dependent assemblies and conducting behavior in ionic liquid crystalline Janus dendrimers

Choi, Jin-Woo,Cho, Byoung-Ki Royal Society of Chemistry 2011 SOFT MATTER Vol.7 No.8

<P>We prepared two Janus dendrimers 1 and 2 bearing a hydrophobic Percec-type minidendron (<I>i.e.</I>, 3,4,5-tridodecyloxybenzyl group) and hydrophilic aliphatic ether dendrons with different degrees of branching <I>via</I> stepwise click reactions. The obtained Janus dendrimers have the same hydrophilic volume fraction (<I>f</I> = 0.34), but a different number of hydrophilic chains, <I>i.e.</I>, tetrabranched and dibranched oligo(ethylene oxide) coils for 1 and 2, respectively. Upon doping with lithium salt, liquid crystalline (LC) ionic samples 1-Li<SUP>+</SUP> and 2-Li<SUP>+</SUP> were obtained. As characterized by polarized optical microscopy (POM) and X-ray scattering techniques, 1-Li<SUP>+</SUP> showed an optically isotropic cubic LC phase, while 2-Li<SUP>+</SUP> displayed a birefringent hexagonal columnar LC structure with a bilayered cross-section. Interestingly, the conductivity values of the cubic phase were considerably higher than those of the columnar phase, with which the cubic phase could be assigned as a bicontinuous cubic structure rather than a micellar one. On the basis of the experimental observations, the morphological contrast between two ionic Janus dendrimers is strongly attributed to the degree of chain branching, which is one of the major parameters governing the morphological features in the Janus dendrimer assemblies.</P> <P>Graphic Abstract</P><P>Two ionic Janus dendrimers 1-Li<SUP>+</SUP> and 2-Li<SUP>+</SUP> with an identical volume fraction but tetra-and dibranched hydrophilic blocks form liquid crystalline bicontinuous cubic and hexagonal columnar phases, respectively, which can be confirmed by their ionic conducting behavior. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm01435d'> </P>

Supramolecular transformation from ordered columnar to disordered columnar to tetragonal micellar structures in clicked dodeca-alkylated discotic triphenylene liquid crystals

Cho, Byoung-Ki,Kim, Seung-Hyun The Royal Society of Chemistry 2014 SOFT MATTER Vol.10 No.4

<P>We prepared three discotic liquid crystals (DLCs) based on a triphenylene (TP) disc functionalized with twelve alkyl peripheries. The synthesis of the discogens was performed by a click reaction using Cu(OAc)<SUB>2</SUB> as the catalyst, with six triazolyl groups connecting the TP core with twelve alkyl chains. According to thermal data from differential scanning calorimetry (DSC), discogen <B>1</B>, which has the shortest hexyl peripheries, exhibited two LC phases, and <B>2</B> and <B>3</B>, with decyl and tetradecyl peripheries, respectively, displayed three LC phases as a function of the temperature. Structural analyses using small- and wide-angle X-ray scattering (SAXS and WAXS) techniques revealed ordered and disordered hexagonal columnar LC phases in all the discogens. On the other hand, an unconventional micellar phase with <I>P</I>4<SUB>2</SUB>/<I>mnm</I> symmetry consisting of thirty micelles was found only in <B>2</B> and <B>3</B>, when the temperature increased. The thermally induced transformation from the columnar to the micellar phase can be explained by increased chain entropy at higher temperatures. The complex micellar packing in the noncubic phase is attributed to the softness of the DLC micelles because the micellar corona consists of flexible alkyl chains. The discogen design concept in this study (<I>i.e.</I>, the introduction of multibranched alkyl peripheries to the discotic mesogens <I>via</I> click chemistry) resulted in unconventional columnar-to-micellar transformation in conventional TP DLCs.</P> <P>Graphic Abstract</P><P>The dodeca-alkylated discotic triphenylenes prepared simply by click chemistry exhibit an unusual morphological transformation from an ordered columnar to a disordered columnar to a tetragonal micellar liquid crystalline phase as the temperature increases. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3sm52669k'> </P>

Cucumber mosaic virus 2a polymerase and 3a movement proteins independently affect both virus movement and the timing of symptom development in zucchini squash

Choi, Seung Kook,Palukaitis, Peter,Min, Byoung Eun,Lee, Mi Yeon,Choi, Jang Kyung,Ryu, Ki Hyun Microbiology Society 2005 The Journal of general virology Vol.86 No.4

<P>The basis for differences in the timing of systemic symptom elicitation in zucchini squash between a pepper strain of Cucumber mosaic virus (Pf-CMV) and a cucurbit strain (Fny-CMV) was analysed. The difference in timing of appearance of systemic symptoms was shown to map to both RNA 2 and RNA 3 of Pf-CMV, with pseudorecombinant viruses containing either RNA 2 or RNA 3 from Pf-CMV showing an intermediate rate of systemic symptom development compared with those containing both or neither Pf-CMV RNAs. Symptom phenotype was shown to map to two single-nucleotide changes, both in codons for Ile at aa 267 and 168 (in Fny-CMV RNAs 2 and 3, respectively) to Thr (in Pf-CMV RNAs 2 and 3). The differential rate of symptom development was shown to be due to differences in the rates of cell-to-cell movement in the inoculated cotyledons, as well as differences in the rate of egress of the virus from the inoculated leaves. These data indicate that both the CMV 3a movement protein and the CMV 2a polymerase protein affect the rate of movement of CMV in zucchini squash and that these two proteins function independently of each other in their interactions with the host, facilitating virus movement.</P>

Ion-Induced Bicontinuous Cubic and Columnar Liquid-Crystalline Assemblies of Discotic Block Codendrimers

Choi, Jin-Woo,Ryu, Mi-Hee,Lee, Eunji,Cho, Byoung-Ki WILEY-VCH Verlag 2010 Chemistry Vol.16 No.30

<B>Graphic Abstract</B> <P>Discotic block codendrimers, consisting of two different nonmesogenic aliphatic polyether dendrons and a discotic linker, exhibited induced hexagonal columnar and bicontinuous cubic (unprecedented in dendrimers) liquid-crystalline (LC) phases by the addition of lithium salt (see figure). The interior and exterior of these morphologies can be altered by changing the majority dendritic block. <img src='wiley_img_2010/09476539-2010-16-30-CHEM201001337-content.gif' alt='wiley_img_2010/09476539-2010-16-30-CHEM201001337-content'> </P>

Electrical properties of ZnO nanowire field effect transistors with varying high-k Al2O3 dielectric thickness

Choe, Minhyeok,Jo, Gunho,Maeng, Jongsun,Hong, Woong-Ki,Jo, Minseok,Wang, Gunuk,Park, Woojin,Lee, Byoung Hun,Hwang, Hyunsang,Lee, Takhee American Institute of Physics 2010 JOURNAL OF APPLIED PHYSICS - Vol.107 No.3