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Temperature dependence of the critical points of monolayer MoS2 by ellipsometry
Park, Han Gyeol,Kim, Tae Jung,Kim, Hwa Seob,Yoo, Chang Hyun,Barange, Nilesh S.,Le, Van Long,Kim, Hyoung Uk,Senthilkumar, Velusamy,Le, Chinh Tam,Kim, Yong Soo,Seong, Maeng-Je,Kim, Young Dong Taylor Francis 2016 Applied spectroscopy reviews Vol.51 No.7
Surface-modified polymer nanofiber membrane for high-efficiency microdust capturing
Kim, Han-Jung,Park, Seon Joo,Park, Chul Soon,Le, Thanh-Hai,Hun Lee, Sang,Ha, Tai Hwan,Kim, Hyoung-il,Kim, Jinyeong,Lee, Chang-Soo,Yoon, Hyeonseok,Kwon, Oh Seok Elsevier 2018 Chemical Engineering Journal Vol.339 No.-
<P><B>Abstract</B></P> <P>Particulate matter (PM) pollution is serious human health issue. Various filter technologies have been developed to improve the air filtration efficiency. Recently, nanofibrous membrane filters have received much attention due to its outstanding transparency and high efficiency for PM ≤ 2.5 μm (PM<SUB>2.5</SUB>) capture/removal compared to conventional micro-structured filters. Although these filters provide high-efficiency PM<SUB>2.5</SUB> capture, obtaining strong PM adhesion via surface engineering remains a challenge. In this study, we demonstrate a high efficiency PM<SUB>2.5</SUB> capture air-filter by electrospun polyacrylonitrile nanofibers (EPNFs). The surface of the EPNFs was modified by oxygen plasma treatment for generating functional groups such as CONH<SUB>2</SUB>, COOH and COOR. The EPNFs were utilized as air filter in hand-made PM removal system which is consisted of DC power supply, PM source, PM sensor and PM removal test chamber. The test result showed high air flow and effective air filtration (PM<SUB>2.5</SUB> removal efficiency: 94.02%, pressure drop: 18 Pa, Time to reach the PM level recommended by the World Health Organization (T<SUB>WHO PM2.5</SUB>): 15 min, quality factor: 0.1564 Pa<SUP>−1</SUP>) compared to commercial filters. The intermolecular interaction between the plasma-treated EPNFs (PEPNFs) and PMs was investigated by density functional theory (DFT) calculations. The PEPNF filter showed high long-term reproducibility in a cycle test with a high PM concentration (over 2,000 μg m<SUP>−3</SUP>). The filter was applied as a car interior air purifier using a cigar jack as a power supply, <I>ca.</I> 16 min was required to reach the PM level recommended by the World Health Organization (<25 μg m<SUP>−3</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Surface-modified nanofibers were effective for particulate matter (PM) filtration. </LI> <LI> Intermolecular interaction was studied using density functional theory calculation. </LI> <LI> A car interior air purifier was demonstrated using the nanofiber membrane. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Han Daewon,Kim Haeil,Kim Soojin,Le Qui Anh,Han Seung Yun,Bae Jeongyun,Shin Hye Won,Kang Hyun-Goo,한경호,Shin Jongdae,Park Hwan-Woo 생화학분자생물학회 2022 Experimental and molecular medicine Vol.54 No.-
Chronic exposure to bile acid in the liver due to impaired bile flow induces cholestatic liver disease, resulting in hepatotoxicity and liver fibrosis. Sestrin2, a highly conserved, stress-inducible protein, has been implicated in cellular responses to multiple stress conditions and the maintenance of cellular homeostasis. However, its role in cholestatic liver injury is not fully understood. In this study, we investigated the role of hepatic Sestrin2 in cholestatic liver injury and its underlying mechanisms using in vivo and in vitro approaches. Hepatic Sestrin2 expression was upregulated by activating transcription factor 4 (ATF4) and CCAAT/enhancer-binding protein-β (C/EBP-β) after treatment with bile acids and correlated with endoplasmic reticulum (ER) stress responses. Bile-duct ligation (BDL)-induced hepatocellular apoptosis and liver fibrosis were exacerbated in Sestrin2-knockout (Sesn2−/−) mice. Moreover, Sestrin2 deficiency enhanced cholestasis-induced hepatic ER stress, whereas Sestrin2 overexpression ameliorated bile acid-induced ER stress. Notably, the mammalian target of rapamycin (mTOR) inhibitor rapamycin and the AMP-activated protein kinase (AMPK) activator AICAR reversed bile acid-induced ER stress in Sestrin2-deficient cells. Furthermore, Sestrin2 deficiency promoted cholestasis-induced hepatic pyroptosis by activating NLRP3 inflammasomes. Thus, our study provides evidence for the biological significance of Sestrin2 and its relationship with cholestatic liver injury, suggesting the potential role of Sestrin2 in regulating ER stress and inflammasome activation during cholestatic liver injury.
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>
Le, Vu Ngoc Han,Zhao, Yan,Cho, Chong Woon,Na, MinKyun,Quan, Khong Trong,Kim, Jang Hoon,Hwang, Sung Yeoun,Kim, Sang Wook,Kim, Kyung Tae,Kang, Jong Seong Elsevier 2018 Journal of chromatography. B, Analytical technolog Vol.1102 No.-
<P><B>Abstract</B></P> <P>Nardostachyos Radix et Rhizoma (NR) is a valuable medicinal herb widely used in Korea, India, and China for the treatment of many diseases. Desoxo-narchinol A (DA) and nardosinonediol (ND) are the two main bioactive compounds belonging to the sesquiterpene group. Desoxo-narchinol A possesses anti-inflammatory activity while ND exhibits anti-depressant and cardioprotective activities. A pharmacokinetic study is important to decide whether the isolated compounds or the NR extract have better pharmacological activity. Hence, we developed an analytical method for studying the pharmacokinetics of DA and ND after oral administration of the pure compounds and herbal extract. An optimized liquid chromatography-mass spectrometry method (LC-MS/MS) with solid-phase extraction (SPE) for sample preparation was developed. A ZORBAX Extend C18 column (2.1 × 50 mm, 3.5 μm) was used under gradient elution with acetonitrile and 0.1% formic acid in water as the mobile phase. Validation experiments assessing accuracy, precision, and stability were satisfactory; the lower limit of quantification was 5 ng/mL. For the pharmacokinetic study, three groups of rats were administrated pure DA, pure ND, or NR extract orally. Concentrations of DA and ND in their plasma were determined by the developed method. Pharmacokinetic parameters, including the time to achieve maximum plasma concentration (<I>T</I> <SUB> <I>max</I> </SUB>) and the area under the plasma concentration curve from time zero to infinity (<I>AUC</I> <SUB>0–∞</SUB>), were compared for the herbal extract and pure compounds. The <I>T</I> <SUB> <I>max</I> </SUB> of the pure compound and the NR extract for DA was 7.50 and 8.33 min, respectively, compared to 5.00 and 5.83 min for the pure compound and the NR extract for ND, respectively. The <I>AUC</I> <SUB>0–∞</SUB> of the pure compound and the NR extract for DA was 156.34 and 133.90 μg min/mL, respectively, and that for the NR extract for ND was 6.42 and 4.15 μg min/mL, respectively. LC-MS/MS was used to determine DA and ND in rat plasma. The pharmacokinetic profile of each pure compound and those in the extract were characterized and compared.</P>
Optical Properties of GaFeO<sub>3</sub>
Kim, Tae Jung,Park, Han Gyeol,Long Le, Van,Kim, Hwa Seob,Yoo, Chang Hyun,Uk Kim, Hyoung,Kim, Young Dong,Park, Chang Bae,Shin, Kwangwoo,Kim, Kee Hoon American Scientific Publishers 2018 Science of advanced materials Vol.10 No.2
<P>The complex dielectric function epsilon and critical-point (CP) structures of orthorhombic GaFeO3 are reported at temperatures from 39 to 350 K and photon energies from 0.74 to 6.42 eV. Data were obtained by rotating-compensator spectroscopic ellipsometry on the (010) direction of single-crystalline GaFeO3. A multilayer version of the B-splines method was used to extract the optical properties of GaFeO3, and CP energies were accurately determined by analyzing numerically calculated second-energy-derivatives of the data. At low temperature the CP structures are clearly enhanced and their energies are blue-shifted. Temperature dependencies were obtained by fitting the data to a phenomenological expression that contains a Bose-Einstein statistical factor and a temperature coefficient.</P>
Han, Ji Su,Le, Quyet Van,Choi, Jaeho,Kim, Hyojung,Kim, Sun Gil,Hong, Kootak,Moon, Cheon Woo,Kim, Taemin Ludvic,Kim, Soo Young,Jang, Ho Won American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.8
<P>Recently, organometallic and all-inorganic halide perovskites (HPs) have become promising materials for resistive switching (RS) nonvolatile memory devices with low power consumption because they show current-voltage hysteresis caused by fast ion migration. However, the toxicity and environmental pollution potential of lead, a common constituent of HPs, has limited the commercial applications of HP-based devices. Here, RS memory devices based on lead-free all-inorganic cesium tin iodide (CsSnI<SUB>3</SUB>) perovskites with temperature tolerance are successfully fabricated. The devices exhibit reproducible and reliable bipolar RS characteristics in both Ag and Au top electrodes (TEs) with different switching mechanisms. The Ag TE devices show filamentary RS behavior with ultralow operating voltages (<0.15 V). In contrast, the Au TE devices have interface-type RS behavior with gradual resistance changes. This suggests that the RS characteristics are attributed to either the formation of metal filaments or the ion migration of defects in HPs under applied electric fields. These distinct mechanisms may permit the opportunity to design devices for specific purposes. This work will pave the way for lead-free all-inorganic HP-based nonvolatile memory for commercial application in HP-based devices.</P> [FIG OMISSION]</BR>
Kim, Han-Jong,Kim, Joon-Young,Lee, Sun Joo,Kim, Hye-Jin,Oh, Chang Joo,Choi, Young-Keun,Lee, Hyo-Jeong,Do, Ji-Yeon,Kim, Sun-Yee,Kwon, Taeg-Kyu,Choi, Hueng-Sik,Lee, Mi-Ock,Park, In-Sun,Park, Keun-Gyu,Le Ovid Technologies Wolters Kluwer -American Heart A 2010 Arteriosclerosis, thrombosis, and vascular biology Vol.30 No.11