Single-walled carbon nanotube-mediated physical gelation of binary polymer blends: An efficient route to versatile porous carbon electrode materials

Kim, Yukyung,Kim, Saerona,Noh, Seonmyeong,Kim, Semin,Park, Geunsu,Le, Thanh-Hai,Han, Hyunwoo,Kim, Yoong Ahm,Yoon, Hyeonseok Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.353 No.-

<P><B>Abstract</B></P> <P>A non-covalent approach to prepare nanotube-containing gels was developed based on the physical gelation of two polymers, polyvinyl alcohol (PVA) and polyacrylonitrile (PAN), with different microphase behaviors in water/dimethyl sulfoxide (DMSO) mixture. Single-walled carbon nanotubes (SWNTs) were incorporated into the binary-polymer/binary-solvent system to alter the physical gelation behavior and, in turn, to achieve unique physicochemical characteristics of the resulting gels. SWNTs were wrapped with PVA, which extended the binary polymer system to a ternary polymer system consisting of PVA bound to SWNTs, free PVA, and PAN. It was observed that the SWNT/PVA/PAN ensembles gelled with appropriate amounts of water in DMSO and the gelation behavior was reversible. The amounts of water and SWNT were determined to be key parameters affecting the formation of the gels. The SWNT/PVA/PAN gels were successfully converted to carbonaceous gels via heat treatment in an inert atmosphere, which can be extended to several applications such as electrode materials. The macroporous carbonaceous gels were further functionalized via manganese deposition followed by potassium hydroxide activation, which yielded excellent cell performance in a neutral electrolyte with the energy density of 9.6–24.8 Wh kg<SUP>−1</SUP> and power density of 8.0–0.1 kW kg<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of co-nonsolvents on the microstructure of the gel was demonstrated. </LI> <LI> The SWNT-mediated physical gelation of binary polymer blends were reported. </LI> <LI> Physically cross-linked gels were converted to versatile electrode materials. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Covariance-based band selection and its application to near-real-time hyperspectral target detection

Kim, Jun-Hyung,Kim, Jieun,Yang, Yukyung,Kim, Sohyun,Kim, Hyun Sook SPIE - International Society for Optical Engineeri 2017 Optical engineering Vol.56 No.5

Characterization of TNNC1 as a Novel Tumor Suppressor of Lung Adenocarcinoma

Kim, Suyeon,Kim, Jaewon,Jung, Yeonjoo,Jun, Yukyung,Jung, Yeonhwa,Lee, Hee-Young,Keum, Juhee,Park, Byung Jo,Lee, Jinseon,Kim, Jhingook,Lee, Sanghyuk,Kim, Jaesang Korean Society for Molecular and Cellular Biology 2020 Molecules and cells Vol.43 No.7

In this study, we describe a novel function of TNNC1 (Troponin C1, Slow Skeletal and Cardiac Type), a component of actin-bound troponin, as a tumor suppressor of lung adenocarcinoma (LUAD). First, the expression of TNNC1 was strongly down-regulated in cancer tissues compared to matched normal lung tissues, and down-regulation of TNNC1 was shown to be strongly correlated with increased mortality among LUAD patients. Interestingly, TNNC1 expression was enhanced by suppression of KRAS, and ectopic expression of TNNC1 in turn inhibited KRAS<SUP>G12D</SUP>-mediated anchorage independent growth of NIH3T3 cells. Consistently, activation of KRAS pathway in LUAD patients was shown to be strongly correlated with down-regulation of TNNC1. In addition, ectopic expression of TNNC1 inhibited colony formation of multiple LUAD cell lines and induced DNA damage, cell cycle arrest and ultimately apoptosis. We further examined potential correlations between expression levels of TNNC1 and various clinical parameters and found that low-level expression is significantly associated with invasiveness of the tumor. Indeed, RNA interference-mediated down-regulation of TNNC1 led to significant enhancement of invasiveness in vitro. Collectively, our data indicate that TNNC1 has a novel function as a tumor suppressor and is targeted for down-regulation by KRAS pathway during the carcinogenesis of LUAD.

지역 의료불평등 해소를 위한 미충족 의료지표 활용의 비판적 분석

박유경 ( Yukyung Park ),김진환 ( Jin-hwan Kim ),김선 ( Sun Kim ),김창엽 ( Chang-yup Kim ),한주성 ( Joo-sung Han ),김새롬 ( Saerom Kim ) 한국보건행정학회 2020 보건행정학회지 Vol.30 No.1

Background: Unmet healthcare needs have many advantages for measuring inequalities in healthcare use. However, the existing indicator is difficult to capture the reality of unmet healthcare needs sufficiently and is not quite appropriate in comparing regional inequality. The purpose of this study is to critically analyze the utilization of the unmet healthcare need indicator for regional healthcare inequalities research. Methods: We used the level of healthcare accessibility and healthcare need to categorize the regions that are known to cause differences in healthcare utilization between regions and verified how existing unmet healthcare need indicator is distributed at the regional level. Results: Four types of regions were classified according to the high and low levels of healthcare needs and accessibility. The hypothesis about the regional type expected to have the highest unmet healthcare need was not proved. The hypothesis about the lowest expected regional type was proved, but the difference in the average rate of unmet healthcare needs among regional types was not significant. The standard deviation of the rate of unmet healthcare needs among regions within the same type was also higher than the overall regional variation, which also disproved the whole frame of hypothesis. Conclusion: Failure to prove the hypothesis means the gap between the supposed meaning of the indicator and the reality. In order to understand the current state of healthcare utilization of people in various regions of Korea and to resolve inequality, fundamental research on the in-depth structure and mechanisms of healthcare utilization is needed.

Near-field focusing and magnification through self-assembled nanoscale spherical lenses

Lee, Ju Young,Hong, Byung Hee,Kim, Woo Youn,Min, Seung Kyu,Kim, Yukyung,Jouravlev, Mikhail V.,Bose, Ranojoy,Kim, Keun Soo,Hwang, In-Chul,Kaufman, Laura J.,Wong, Chee Wei,Kim, Philip,Kim, Kwang S. Macmillan Publishers Limited. All rights reserved 2009 Nature Vol.460 No.7254

It is well known that a lens-based far-field optical microscope cannot resolve two objects beyond Abbe’s diffraction limit. Recently, it has been demonstrated that this limit can be overcome by lensing effects driven by surface-plasmon excitation, and by fluorescence microscopy driven by molecular excitation. However, the resolution obtained using geometrical lens-based optics without such excitation schemes remains limited by Abbe’s law even when using the immersion technique, which enhances the resolution by increasing the refractive indices of immersion liquids. As for submicrometre-scale or nanoscale objects, standard geometrical optics fails for visible light because the interactions of such objects with light waves are described inevitably by near-field optics. Here we report near-field high resolution by nanoscale spherical lenses that are self-assembled by bottom-up integration of organic molecules. These nanolenses, in contrast to geometrical optics lenses, exhibit curvilinear trajectories of light, resulting in remarkably short near-field focal lengths. This in turn results in near-field magnification that is able to resolve features beyond the diffraction limit. Such spherical nanolenses provide new pathways for lens-based near-field focusing and high-resolution optical imaging at very low intensities, which are useful for bio-imaging, near-field lithography, optical memory storage, light harvesting, spectral signal enhancing, and optical nano-sensing.

Antimicrobial activity of fermented Maillard reaction products, novel milk-derived material, made by whey protein and Lactobacillus rhamnosus and Lactobacillus gasseri on Clostridium perfringens

Kim, Yujin,Kim, Sejeong,Lee, Soomin,Ha, Jimyeong,Lee, Jeeyeon,Choi, Yukyung,Oh, Hyemin,Lee, Yewon,Oh, Nam-su,Yoon, Yohan,Lee, Heeyoung Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.9

Objective: The objective of this study was to evaluate the antimicrobial effects of fermented Maillard reaction products made by milk proteins (FMRPs) on Clostridium perfringens (C. perfringens), and to elucidate antimicrobial modes of FMRPs on the bacteria, using physiological and morphological analyses. Methods: Antimicrobial effects of FMRPs (whey protein plus galactose fermented by Lactobacillus rhamnosus [L. rhamnosus] 4B15 [Gal-4B15] or Lactobacillus gasseri 4M13 [Gal-4M13], and whey protein plus glucose fermented by L. rhamnosus 4B15 [Glc-4B15] or L. gasseri 4M13 [Glc-4M13]) on C. perfringens were tested by examining growth responses of the pathogen. Iron chelation activity analysis, propidium iodide uptake assay, and morphological analysis with field emission scanning electron microscope (FE-SEM) were conducted to elucidate the modes of antimicrobial activities of FMRPs. Results: When C. perfringens were exposed to the FMRPs, C. perfringens cell counts were decreased (p<0.05) by the all tested FMRPs; iron chelation activities by FMRPs, except for Glc-4M13. Propidium iodide uptake assay indicate that bacterial cellular damage increased in all FMRPs-treated C. perfringens, and it was observed by FE-SEM. Conclusion: These results indicate that the FMRPs can destroy C. perfringens by iron chelation and cell membrane damage. Thus, it could be used in dairy products, and controlling intestinal C. perfringens.

Single-Walled Carbon Nanotube-in-Binary-Polymer Nanofiber Structures and Their Use as Carbon Precursors for Electrochemical Applications

Kim, Yukyung,Le, Thanh-Hai,Kim, Saerona,Park, Geunsu,Yang, Kap Seung,Yoon, Hyeonseok American Chemical Society 2018 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.122 No.8

<P>Hierarchical structuring of materials in the nanometer regime provides opportunities to achieve extraordinary characteristics of the resulting products. Here, we report unique one-dimensional hierarchical nanostructures consisting of single-walled carbon nanotubes (SWNTs), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN). First, SWNT-in-binary-polymer nanofiber (SbPNF) structures were obtained through the incorporation of PVA-wrapped SWNTs into PAN, followed by the electrospinning of the SWNT/PVA/PAN solution. Importantly, the SbPNFs exhibited an aligned SWNT-in-nanofiber structure and enhanced ordering of the polymer chains. The SbPNFs were successfully converted to carbonized products [SWNT-in-carbon nanofibers (SbCNFs)] with enhanced crystallinity and tunable electrochemical properties. Compared to those of the control samples (no SWNT), the charge-transfer resistance and the surface area of the SbCNFs were two orders of magnitude lower and 11–20% higher, respectively, which resulted in better electrochemical properties. The major factors determining the properties of the SbCNFs included the SWNT content and PVA/PAN microphase behavior. Furthermore, the removal of the PVA phase from the SbPNFs provided another opportunity to control the textural properties of the carbonized products. It was found that meso- and macropores were more developed in the carbonized products (SCNFs). The specific capacitance of the SCNFs increased to a maximum of 577 F g<SUP>–1</SUP>, which was 3.7 times higher than that of the SbCNFs. The SCNF with the best properties was successfully applied to electrochemical capacitors as the electrode material. It is believed that further optimization of the hierarchical nanostructures will impart attractive properties for various applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2018/jpccck.2018.122.issue-8/acs.jpcc.7b12145/production/images/medium/jp-2017-12145m_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp7b12145'>ACS Electronic Supporting Info</A></P>

Flexible Electrochemical Capacitors Based on Graphene/Polyaniline Nanohybrids

Yukyung Kim,Hyeonseok Yoon 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Antimicrobial Effect of Phytochemicals to Listeria monocytogenes Isolated from Slaughterhouses

Kim, Hyeji,Oh, Hyemin,Lee, Heeyoung,Kim, Sejeong,Ha, Jimyeong,Lee, Jeeyeon,Choi, Yukyung,Lee, Yewon,Kim, Yujin,Yoon, Yohan,Lee, Soomin The Korean Society of Food Hygiene and Safety 2018 한국식품위생안전성학회지 Vol.33 No.4

본 연구에서는 도축장에서 분리된 Listeria monocytogenes를 저해할 수 있는 식물성 항균 물질을 탐색하고, 각 항균 물질의 최소살균농도(MBC)를 확인하였다. 잠재적인 항균 물질로 자몽종자 추출물, 감귤류 추출물, 생강 추출물, 배 추출물, 매실 농축액, 도라지 추출물, 대추 추출물, 오미자 추출물을 선정하였고, 대상 균주로는 국내 도축장에서 분리한 15 개의 L. monocytogenes 균주를 혼합하여 사용하였다. MBC 확인 결과, 최대 $4.0{\mu}g/mL$ 농도의 생강 추출물, 배 추출물, 매실 농축액, 도라지 추출물, 대추 추출물, 오미자 추출물은 고농도의 L. monocytogenes (7 Log CFU/mL)에 대해 균 저해 효과가 전혀 나타나지 않았다. 반면, 7 Log CFU/mL의 L. monocytogenes에 대한 자몽종자 추출물과 감귤류 추출물의 MBC는 $0.002{\mu}g/mL$인 것으로 확인되었다. 3 Log CFU/mL의 L. monocytogenes에 대한 MBC를 시험해 본 결과, 자몽종자 추출물과 감귤류 추출물의 MBC는 $0.001{\mu}g/mL$로 나타났다. 이상의 결과로 볼 때 자몽종자 추출물과 감귤류 추출물은 L. monocytogenes를 제어하기 위해 적용될 수 있을 것으로 판단된다. The objective of this study was to investigate the inhibitory effect of natural antimicrobials on Listeria monocytogenes isolated from Korean slaughterhouses. A mixture of 15 strains of L. monocytogenes at low (3 Log CFU/mL) or high (7 Log CFU/mL) concentration was exposed to various extracts (grapefruit seed extract, citrus fruit extract, ginger extract, pear extract, Japanese apricot concentrate, balloon flower extract, jujube extract, and omija extract) at $0.001-4.0{\mu}g/mL$. Ginger extract, pear extract, Japanese apricot concentrate, balloon flower extract, jujube extract, or omija extract showed no antimicrobial effects on high-concentration of L. monocytogenes (7 Log CFU/mL). However, grapefruit seed extract and citrus fruit extract showed antibacterial effects against L. monocytogenes at 3 and 7 Log CFU/mL with MBCs of 0.001 and $0.002{\mu}g/mL$, respectively. These results indicate that grapefruit seed extract and citrus fruits extract can be used to control L. monocytogenes as natural antimicrobials.

Growth of Salmonella in napa cabbage kimchi during fermentation

Yukyung Choi,Soomin Lee,Heeyoung Lee,Hyun Jung Kim,Sejeong Kim,Jimyeong Ha,Jeeyeon Lee,Hyemin Oh,Yohan Yoon 한국식품저장유통학회 2021 한국식품저장유통학회지 Vol.28 No.4