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Younghwan Kwak,Heon Yoon,Seo Yeong Bae,Yong Man Yu,Young Nam Yoon 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.10
The multicolored Asian ladybeetle Harmonia axyridis is characterized by polymorphism of the elytral pattern. Melanization in Harmonia axyridis is crucial for their elytral coloration, but the molecular mechanisms are not fully understood in this species. Tyrosine hydroxylase (TH) and dopa decarboxylase (DDC), two key enzymes in the melanin pathway, convert tyrosine and dopa into dopa and dopamine, respectively. In this study, it was to determine the role of TH and DDC of Harmonia axyridis (HaTH and HaDDC) in body and wing pigmentaion produced via melanin pathway. The cDNA sequences of HaTH and HaDDC were cloned to perform RNAi-based functional analysis. Injected dsRNA to the 4th larvae caused knockdown of target genes, and it was verified by quantative realtime PCR. Both TH and DDC RNAi adult show loss of black pigmentation in their body and wing pigmentaion. These results is expected to be helpful to investigate polymorphism by melanin pigment in Harmonia axyridis.
Im, Younghwan,Lee, Jae Hyung,Kwak, Byeong Sub,Do, Jeong Yeon,Kang, Misook Elsevier Science Publishers 2018 Catalysis today Vol.303 No.-
<P><B>Abstract</B></P> <P>This study has investigated the propane steam reforming (PSR) performance of M/Ni/YSZ catalysts (M=Ru, Rh, Pd, and Ag) for effective hydrogen production. To improve the catalytic performance, particularly with respect to the duration of the catalyst, YSZ (yttria-stabilized zirconia) is used as a support and noble metals such as Ru, Rh, Pd, and Ag are introduced as promoters. YSZ is used to suppress carbon deposition as it provides lattice oxygen to carbon coke on the catalyst. Noble metals provide synergy, assisting Ni metal in improving dehydrogenation. Preferentially, the PSR performance of 1.0wt.%M/Ni/YSZ catalysts are measured to find which noble metal is suitable as a promoter. The result confirms that the Rh component is the best promoter for M/Ni/YSZ. This study also demonstrates the appropriate amount of Rh to use, based on the PSR performance over Ni/YSZ and 0.1, 0.5, and 1.0wt.% Rh/Ni/YSZ for 100h. The results confirm that Ni/YSZ becomes deactivated at 76h, but the catalysts with the Rh promoter have much higher durability. Thus, this study concludes that 0.5wt.% Rh/Ni/YSZ is the best catalyst because it does not have excessive Rh content and also does not show any discernable decrease in the PSR performance. Moreover, the Rh/Ni/YSZ catalysts had a higher resistance to carbon deposition because of the presence of the Rh promoter, which could improve lattice oxygen mobility of the Rh/Ni/YSZ catalyst.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The propane steam reforming performances of M/Ni/YSZ catalysts for effective hydrogen production. </LI> <LI> The YSZ support suppressed carbon deposition by providing lattice oxygen to carbon coke. </LI> <LI> The Rh was found out as the best promoter in M/Ni/YSZ. </LI> <LI> The 0.5wt.% Rh/Ni/YSZ was the best catalyst without notable decreased PSR performance for 100h. </LI> <LI> The Rh/Ni/YSZ catalyst had higher resistance of carbon deposition resulted from improving lattice oxygen mobility. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Misook Kang,Younghwan Im,Sora Kang,Byeong Sub Kwak,Kyoung Soo Park,Tae Woo Cho,Jin-Sik Lee 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.4
ZnO nanoparticles with three morphologies were synthesized by a hydrothermal route at 120 oC for 3 h in high alkaline aqueous solutions of LiOH, NaOH, and KOH. We analyzed them by X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), cyclic voltammetry (CV), Zeta potential measurement, and impedance. XRD and SEM showed that the obtained ZnO nanoparticles had high purity and perfect crystallinity, and the morphologies of the particles prepared in the LiOH, NaOH, and KOH solutions showed nanoplate, nanobead, and nanorod shapes, respectively. CV showed that the nanoplate ZnO-LiOH and nanorod ZnO-KOH have superior electrochemical activity to that of the other ZnO nanostructures. As electrode materials of Ni/Zn redox batteries, the nanoplate ZnO-LiOH showed a significantly improved cycle stability after the 30th cycle compared to that of ZnO-NaOH and conventional ZnO with a mean discharge capacity of 153 mA h g−1, a cell efficiency of 93%, and higher discharge voltages of 1.9. In addition, during the charging/discharging cycles, the growth of zinc dendrite clusters could be suppressed, which resulted in an improvement in the cycle stability of the Ni/nanoplate ZnO-LiOH redox cell.
Effects of Nematic Liquid Crystal Additives on the Performance of Polymer Solar Cells
Jeong, Seonju,Kwon, Younghwan,Choi, Byeong‐,Dae,Kwak, Giseop,Han, Yoon Soo WILEY‐VCH Verlag 2010 Macromolecular Chemistry and Physics Vol.211 No.23
<P><B>Abstract</B></P><P>Nematic liquid crystals (NLCs), 4‐cyano‐4′‐pentylbiphenyl and 4‐cyano‐4′‐octylbiphenyl, were applied as additives to polymer solar cells with P3HT:PC<SUB>61</SUB>BM blend films. The incorporation of NLC additives led to a higher absorbance of the blend film, a higher crystallinity of P3HT, closer P3HT chains, larger PC<SUB>61</SUB>BM domains and enhanced hole/electron mobilities even without post‐thermal annealing. The non‐annealed PSC with 4 wt.‐% 8CB additives showed an increase in all parameters, resulting in a power conversion efficiency of 3.72% compared to 2.14% of the reference device without NLC additives. </P>
Kim, Soon Hak,Kwon, Younghwan,Han, Yoon Soo,Hur, Youngjune,Kwak, Giseop,Woo, Chang Min,Hur, Byung Ki,Park, Lee Soon Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of applied polymer science Vol.107 No.1
<P>Ag electrodes with line width uniformity for large-sized plasma display panels were successfully fabricated through a photolithographic process using photosensitive Ag pastes with optimized photosensitive properties. The photosensitivity of the Ag electrode pastes in the photolithographic process was investigated as a function of the types and contents of photoinitiators, the molecular weights and acid values of acrylic binders with carboxylic acid groups, and the process variables, such as the UV-light intensity and dose, with a step tablet. This study revealed that the photoinitiator was a major parameter for the photosensitivity of the Ag electrode pastes. With the photosensitivity of the photosensitive Ag electrode pastes optimized by the study of the photoinitiator contents, Ag electrodes with line width uniformity were achieved with an HSP-188 photoinitiator content of 15 wt % on the basis of the reactive monomers, regardless of the variation of the light dose from 250 to 350 mJ/cm<SUP>2</SUP> and intensity from 15 to 25 mW/cm<SUP>2</SUP>. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008</P>
Kim, Kang Min,Kwak, Byeong Sub,Im, Younghwan,Park, No-Kuk,Lee, Tae Jin,Lee, Sang Tae,Kang, Misook Elsevier 2017 Journal of industrial and engineering chemistry Vol.51 No.-
<P><B>Abstract</B></P> <P>In this study, the activities of core@shell-structured SiO<SUB>2</SUB>@Co<SUB>1−x</SUB>Mg<SUB>x</SUB>O catalysts in ethanol steam reforming (ESR) were investigated, and the promotion effect of Mg upon H<SUB>2</SUB> production was assessed. The loading of SiO<SUB>2</SUB>@CoO with Mg resulted in an increase in ethanol conversion and H<SUB>2</SUB> yield with the concomitant suppression of carbon coke deposition and CO emission. Oxygen transfer from the MgO supporter (or improver) to the main cobalt catalytic species during ESR might play a role in maintaining the partially oxidized Co state. In longevity tests, the SiO<SUB>2</SUB>@Co<SUB>1−x</SUB>Mg<SUB>x</SUB>O core@shell material, despite being reused three times, exhibited superior H<SUB>2</SUB> production for 100h without structural collapse or coke formation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The core@shell structured SiO<SUB>2</SUB>@Co<SUB>1−x</SUB>Mg<SUB>x</SUB>O was prepared. </LI> <LI> CO-WGS on the core@shell structured SiO<SUB>2</SUB>@Co<SUB>1−x</SUB>Mg<SUB>x</SUB>O was promoted. </LI> <LI> Carbon coke deposition was suppressed by Mg loading. </LI> <LI> Both Co<SUP>0</SUP> and Co<SUP>2+</SUP> played the active sites on SiO<SUB>2</SUB>@Co<SUB>1−x</SUB>Mg<SUB>x</SUB>O. </LI> <LI> SiO<SUB>2</SUB>@Co<SUB>1−x</SUB>Mg<SUB>x</SUB>O exhibited high hydrogen production. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>