First-principles studies of K₁ ₋ _xM_xMgH₃ (M = Li, Na, Rb, or Cs) perovskite hydrides for hydrogen storage

Li, Yuanyuan,Mi, Yiming,Chung, Jin Suk,Kang, Sung Gu Elsevier 2018 International journal of hydrogen energy Vol.43 No.4

<P><B>Abstract</B></P> <P>The structural stability and hydrogen release properties of M-doped KMgH<SUB>3</SUB> (M = Li, Na, Rb, or Cs) were examined using density functional theory (DFT) calculations. The reaction enthalpies (ΔH) of the four possible dehydrogenation reaction pathways were calculated using the doped structures with different phases ( P m 3 ¯ m , P<I>nma</I>, and R3<I>c</I>). The most favorable reaction pathway among these four pathways was found. Among the dopants investigated, the most promising dopant for this reaction was Li. In addition, the application of pressure was found to be useful for tuning the reaction enthalpies of the dehydrogenation reactions. Overall, the results present an efficient means of designing new promising perovskite-type hydrides for hydrogen storage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Perovskite-type KMgH<SUB>3</SUB> is a promising candidate for hydrogen storage. </LI> <LI> The most favorable reaction pathway of dehydrogenation reactions was examined. </LI> <LI> Li was the most useful and effective dopant to release hydrogen. </LI> <LI> Pressure can be usefully employed for tuning the reaction enthalpies of dehydrogenation reactions. </LI> </UL> </P>

Robust Parameter Set Selection for a Hydrodynamic Model Based on Multi-Site Calibration Using Multi-Objective Optimization and Minimax Regret Approach

Li,Chung, Eun-Sung,Jun, Kyung Soo Springer-Verlag 2018 Water resources management Vol.32 No.12

이명박 정부의 대북정책 : 평가와 전망

문정인,이춘복 연세대학교 통일연구원 2009 통일연구 Vol.13 No.2

이명박 정부 들어 지난 1년간 남북관계는 경색, 악화 국면을 넘어 거의 단절 수준까지 이르렀다. 특히 서해안에서의 해상 충돌과 그에 따른 군사적 긴장의 고조는 역대 최악의 남북관계를 예고해 주고 있다. 이러한 상황전개는 북측의 일방적 태도와 이명박 정부의 경직된 대북정책이 빚어낸 결과라 할 수 있다. 특히 비핵·개방·3000』과 ABR(Anything But Roh Moo-hyun)이라는 이명박 정부의 대북정책 기조는 남북관계 개선에 커다란 걸림돌이 되고 있다. 대북관계에서 지나치게 지난 정권과의 차별화를 강조함으로 남북관계는 위기로 치닫고 있으며 과거 화해협력정책이 애써 이룩해 놓은 성과마저 점차 무력화되고 있다. 현재의 고착 상태를 극복하기 위해서는 남북간 신뢰 회복이 선행되어야 하며 이를 위해 역지사지의 대북정책이 모색되어야 할 것이다. 중도실용주의 원칙에 기초하여 이명박 대통령이 직접 「6.15선언」과 「10.4선언」의 존중의사를 밝히는 동시에 제 3차 남북정상회담의 개최를 통해 새로운 돌파구를 마련해야 할 것이다. Since the inauguration of the Lee Myung-bak (MB) government, inter-Korean relations have remained stalled. The Mt. Keumgang tourist project was shut down since July 2008, the Kaesung Industrial Complex is being jeopardized. And official contacts between two Koreas are virtually frozen. New hope formed through the resumption of reunion of separated families in October was again derailed by naval clash in West Sea in November. The stalemate can be attributed partly to North Korea's inertia-driven behavior and partly to the MB government's rigid stance on North Korea. The latter's blind obsession with the "De-nuke, Open 3,000" policy and the attitude of 'Anything But Roh Moo-hyun (ABR)' is likely to further strain inter-Korean relations, while heightening military tension. The most viable way to overcome the current dilemma is to engage with North Korea, to honor policy legacies of past governments such as the June 15 Joint Declaration and the October 4 North-South Summit Declaration, and to expedite the 3rd inter-Korean summit. In so doing, the MB government needs to adopt an inter-subjective approach to the understanding of North Korea because it can enhance inter-Korean trust-building, exchanges and cooperation, and eventually peaceful co-existence.

Anion-controlled sulfidation for decoration of graphene oxide with iron cobalt sulfide for rapid sonochemical dyes removal in the absence of light

Molla, Aniruddha,Li, Yuanyuan,Khandelwal, Mahima,Hur, Seung Hyun,Chung, Jin Suk Elsevier 2018 Applied Catalysis A Vol.561 No.-

<P><B>Abstract</B></P> <P>Anion-controlled sulfidation was used to decorate graphene oxide with iron cobalt sulfide via a simple hydrothermal reaction. Anion exchange was carried out using sodium sulfide as an exchanger without any templates or backbone architecture, and in an easy and economical way. Interchange of oxalate, chloride, and hydroxide anions with sulfide anions was performed to tune the morphology of the materials, which subsequently affected their surface area (48.64–83.52 m<SUP>2</SUP>/g) and band gap (2.45–2.91 eV). Ultrasonically-cavity-induced degradation activity without light was rapid (1–3 min) for both positive dyes (rhodamine B and methylene blue), a negative dye (methyl orange), and their mixture. Degradation of the dyes and their mixture in the presence of the prepared samples was a pseudo first-order reaction with rate constant value from 0.780 to 1.702 min<SUP>−1</SUP> that followed the sequence <B>FCS@GO-2 </B>> <B>FCS@GO-1</B> ∼ <B>FCS@GO-3</B> and MB > RhB > MO for catalyst and dyes, respectively. By using terephthalic acid, it was found that the sono-Fenton process quickly generated reactive oxygen species (ROS) even in absence of light. The ROS production was greater for <B>FCS@GO-2</B> than <B>FCS@GO-1</B> or <B>FCS@GO-3</B>, consistent with the catalytic activities of the different catalysts. The prompt production of ROS resulted in a very active process, and the presence of mixed valance states of iron and cobalt resulted in an effective and stable process. It is the synergistic effect of the catalyst that allowed effective breakdown of dyes even in absence of light. The auto-cleaning effect of sonication allowed reuse of the decorated graphene oxide for at least five cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Iron cobalt sulfide@GO was obtained via anion-controlled hydrothermal reaction. </LI> <LI> The band gap, morphology and surface area were tuned via anion exchange. </LI> <LI> The cavity induced sonochemical dyes degradation without light was rapid (1–3 min). </LI> <LI> Generation of ROS by sono-Fenton process was identified using terephthalic acid. </LI> <LI> Dyes degradation was quantitative and repetitive even after five cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Using anion-controlled sulfidation, the morphology, surface area, and band gap (2.45–2.91 eV) of iron cobalt sulfide-decorated graphene oxide was tuned via a simple hydrothermal reaction and allowed for ultrasonic cavity-induced catalytic removal of organic dyes via a sono-Fenton process in the absence of light.</P> <P>[DISPLAY OMISSION]</P>

Single precursor mediated one-step synthesis of ternary-doped and functionalized reduced graphene oxide by pH tuning for energy storage applications

Khandelwal, Mahima,Li, Yuanyuan,Molla, Aniruddha,Hyun Hur, Seung,Suk Chung, Jin Elsevier 2017 Chemical engineering journal Vol.330 No.-

<P><B>Abstract</B></P> <P>The present work reports for the first time a one-step hydrothermal synthesis of ternary-doped (N, S, and P) reduced graphene oxide (rGO) under acidic pH conditions (NSPrGO2-12) using thiamine pyrophosphate (TPP) as both a reducing agent and a single source N, S, and P doping agent under mild experimental conditions. The change in pH of the reaction mixture from acidic (∼2.2) to basic (∼8.5) creates a change in the surface chemistry of rGO, resulting in TPP-functionalized rGO with modified morphology, structure, surface area and electrochemical performance. This change has been analyzed in terms of the different interactions between the graphene oxide functional groups and various functionalities of TPP at different pH conditions. Under acidic pH conditions, the sample had a crumpled sheet morphology with wrinkles on its surface having interconnected network and possessing a relatively large surface area. Meanwhile, under basic pH conditions, the sample exhibited stacked layer-by-layer sheets that formed an aggregated network-like structure with a smaller surface area. NSPrGO2-12 delivers a high specific capacitance (C<SUB>s</SUB>) value of 269F/g at 20A/g with long cyclic stability (93% retention after 5000 cycles at 20A/g), high coulombic efficiency (100%) and high energy/power density (23.55Wh/kg/7923.4W/kg) in an aqueous electrolyte. Moreover, the C<SUB>s</SUB> value of the ternary-doped rGO is significantly higher than its mono- and co-doped counterparts under similar experimental conditions. These features clearly demonstrate the tremendous potential of NSPrGO2-12 as an electrode material for energy storage applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A one-step synthesis of ternary (N, S and P) – doped rGO is demonstrated. </LI> <LI> Thiamine pyrophosphate act as single source precursor for N, S and P dopants. </LI> <LI> Change in pH from acidic (∼2.2) to basic (∼8.5) results in functionalized rGO. </LI> <LI> The resulted tri-doped rGO showed high capacitance of 269F/g at 20A/g. </LI> <LI> Tri-doped rGO shows excellent cycling stability and high energy/power density. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microfluidic platform for single cell analysis under dynamic spatial and temporal stimulation

Song, Jiyoung,Ryu, Hyunryul,Chung, Minhwan,Kim, Youngtaek,Blum, Yannick,Lee, Sung Sik,Pertz, Olivier,Jeon, Noo Li Elsevier 2018 Biosensors & bioelectronics Vol.104 No.-

<P><B>Abstract</B></P> <P>Recent research on cellular responses is shifting from static observations recorded under static stimuli to real-time monitoring in a dynamic environment. Since cells sense and interact with their surrounding microenvironment, an experimental platform where dynamically changing cellular microenvironments should be recreated <I>in vitro</I>. There has been a lack of microfluidic devices to support spatial and temporal stimulations in a simple and robust manner. Here, we describe a microfluidic device that generates dynamic chemical gradients and pulses in both space and time using a single device. This microfluidic device provides at least 12h of continuous stimulations that can be used to observe responses from mammalian cells. Combination of the microfluidic de­vice with live-cell imaging facilitates real-time observation of dynamic cellular response at single cell level. Using stable HEK cells with biosensors, ERK (Extracellular signal-Regulated Kinase) activities were observed un­der the pulsatile and ramping stimulations of EGF (Epidermal Growth Factor). We quantified ERK activation even at extremely low EGF concentration (0.0625µg/ml), which can not be observed using conventional techniques such as western blot. Cytoskeleton re­arrangement of the 3T3 fibroblast (stable transfection with Lifeact-GFP) was compared under abrupt and gradually changing gradient of PDGF.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A long-term live cell monitoring was performed under the spatial and temporal dynamic stimulations. </LI> <LI> Versatile stimulation profiles were generated in a single device without further modification. </LI> <LI> Quantitative observation of the persistent ERK activation with the increasing concentrations of EGF was made initially. </LI> <LI> Prior to the development of our device, ramping down stimulation of certain matters was unable to be achieved. </LI> <LI> Dynamically changing gradients were proposed and can be applied in directed cell migration. </LI> </UL> </P>

Phase transformation processes in karst-type bauxite deposit from Yunnan area, China

Zhang, Li,Park, Changyun,Wang, Genhou,Wu, Chunjiao,Santosh, M.,Chung, Donghoon,Song, Yungoo Elsevier 2017 Ore geology reviews Vol.89 No.-

<P><B>Abstract</B></P> <P>Bauxite is the only resource of aluminum metal and forms through weathering, leaching, and deposition (i.e., bauxitization processes). Here we characterize the bauxite deposit in Yunnan area, China, through mineralogical and textural characteristics using XRD, SEM-EDX, and micro-Raman analyses. The Al-oxyhydroxide polymorphs (AlO(OH)) such as diaspore and boehmite are the dominant phases in most of the samples. Gibbsite (Al(OH)<SUB>3</SUB>) is the main mineral in two samples from Quaternary bauxite, and these three Al-rich minerals mixed with goethite, hematite, kaolinite, and small amounts of TiO<SUB>2</SUB> polymorphs (anatase and rutile). Considering the textural characteristics and the stratigraphy of the bauxite deposit, some of the Al-oxyhydroxides and Ti-oxides are inferred to be products of the bauxitization in the lateritic soil during late Permian weathering. In the subsequent transgression stage, the earlier formed (Al-rich minerals and anatase) phases were transformed to diaspore or boehmite as spherulitic form and to rutile, respectively, with the processes of diagenesis, burial metamorphism, tectonic movements and magmatic activity. Following crustal uplift in the Yunnan Province after the late Triassic, diaspore was transformed into boehmite and the bauxite deposit formed earlier was exposed again to weathering resulting in the formation of gibbsite, hematite, goethite, kaolinite, and anatase, with diaspore, boehmite, and rutile remaining as relics. Our study provides insights into phase transformation during bauxitization and subsequent processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al-, Fe-, and Ti-minerals were identified mineralogically and texturally in a karst-type bauxite deposit. </LI> <LI> Phase transformation of Al-, Fe-, and Ti-minerals were defined by textural characteristics. </LI> <LI> The phase transformation processes were caused by Dongwu movement and Indosinian movement since Permian after bauxitization. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ash formation characteristics of two Indonesian coals and the change of ash properties with particle size

Ke, Xiwei,Li, Dongfang,Zhang, Man,Jeon, Chung-hwan,Cai, Runxia,Cai, Jin,Lyu, Junfu,Yang, Hairui Elsevier Scientific Pub. Co. 2019 Fuel processing technology Vol.186 No.-

<P><B>Abstract</B></P> <P>It is difficult to maintain enough high circulating ash rate in circulating fluidized bed (CFB) boilers if they burn the Indonesian coals due to their low ash content. Hence, the ash formation data for these coals is of significance to assessing mass balance in CFB boilers. Two kinds of Indonesian coal that were burned in the 550 MW supercritical CFB boilers in Korea, Kideco and KCH, were tested with static combustion and cold sieving method to study their ash formation characteristics. Results showed that the average primary ash particle size of these two coals is quite fine overall and nearly no gangue exists. Besides, their attrition rate constant <I>K</I> <SUB>af</SUB> is much higher than that of some other bituminous or lean coals, and with the increase of particle size, the <I>K</I> <SUB>af</SUB> decays exponentially for Kideco, while it initially increases and then decreases for KCH. In addition, the physical and chemical properties of these two Indonesian coals' ash obviously change in particle size, including density, pore structure, chemical composition, etc. The larger ash particles are composed of some hard materials, such as quartz (SiO<SUB>2</SUB>) and mullite (Al<SUB>6</SUB>Si<SUB>2</SUB>O<SUB>13</SUB>). While some other materials with lower hardness value, like hematite (Fe<SUB>2</SUB>O<SUB>3</SUB>) and gehlenite (Ca<SUB>2</SUB>Al<SUB>2</SUB>SiO<SUB>7</SUB>), become major mineral components of smaller and softer ash particles. These results indicate that the difference of chemical compositions results in the discrepancy of attrition capability for different size ash particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two kinds of Indonesian coal were tested to obtain their ash formation data. </LI> <LI> The ash properties obviously change in particle size. </LI> <LI> The difference of chemical compositions may result in the discrepancy of attrition rate for different size ash particles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The ash attrition rate of low-rank coals including these two Indonesian coals is much higher than that of some other bituminous or lean coals, and larger ash particles are more difficult to be worn.</P> <P>[DISPLAY OMISSION]</P>

Evidence for the presence of cell-surface-bound and intracellular bactericidal toxins in the dinoflagellate <i>Heterocapsa circularisquama</i>

Cho, Kichul,Wencheng, Li,Takeshita, Satoshi,Seo, Jung-Kil,Chung, Young-Ho,Kim, Daekyung,Oda, Tatsuya Elsevier 2017 Aquatic toxicology Vol.189 No.-

<P><B>Abstract</B></P> <P> <I>Heterocapsa circularisquama</I>, a harmful dinoflagellate, has multiple haemolytic toxins that are considered to be involved in the toxic mechanism against shellfish and certain species of zooplankton. To evaluate the further nature of the toxins of <I>H. circularisquama</I>, we investigated its effects on several species of bacteria. By colony formation assay, we found that <I>H. circularisquama</I> had antibacterial activity toward the marine bacterium <I>Vibrio alginolyticus</I> in a cell density-dependent manner. When the inoculated bacterial cells were co-cultured with <I>H. circularisquama</I> under dinoflagellate cell culture conditions, the bacterial growth was significantly suppressed, whereas the number of live bacterial cells increased when cultured in the medium alone. Since the cell-free culture supernatant and the ruptured dinoflagellate cell suspension showed no toxic effects on <I>V. alginolyticus</I>, it is speculated that direct cell-to-cell contact mediated by the live dinoflagellate cells may be the major toxic mechanism. The decrease in bactericidal activity of theca-removed dinoflagellate cells may further support this speculation. <I>H. circularisquama</I> also showed bactericidal activities towards <I>Escherichia coli</I> and <I>Staphylococcus aureus</I>. In the dinoflagellate/bacteria co-culture system, the number of live bacterial cells declined with increasing incubation time. Light-dependent antibacterial activity of the ruptured dinoflagellate cells against <I>S. aureus</I> was observed, whereas no such activity was detected against <I>E. coli</I>. These results suggest that intracellular photosensitising bactericidal toxins, which were previously found to be porphyrin derivatives, may have specificity towards gram-positive bacteria. Based on these results together with previous studies, it is obvious that <I>H. circularisquama</I> possesses antibacterial activity, which may be mediated through toxins located on its cell surface. It is likely that such toxins play a role in the defence mechanism against predators and infectious bacteria. Although the exact biological significance of intracellular photosensitising toxins is still unclear, such toxins may have potential to be developed as novel photo-controllable antibiotics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>H. circularisquama</I> (HC) exhibits anti-bacterial activity toward <I>V. alginolyticus</I>. </LI> <LI> Direct cell contact mediated by the live HC cells may be the major toxic mechanism. </LI> <LI> HC also shows bactericidal activities towards <I>E. coli</I> and <I>S. aureus</I>. </LI> <LI> HC has intracellular photosensitizing agents toxic to <I>S. aureus</I>. </LI> </UL> </P>

Urban particulate matter in air pollution penetrates into the barrier-disrupted skin and produces ROS-dependent cutaneous inflammatory response <i>in vivo</i>

Jin, Seon-Pil,Li, Zhenyu,Choi, Eun Kyung,Lee, Serah,Kim, Yoen Kyung,Seo, Eun Young,Chung, Jin Ho,Cho, Soyun Elsevier 2018 Journal of dermatological science Vol.91 No.2

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>Particulate matter (PM) is an integral part of air pollution, which is a mixture of particles suspended in the air. Recently, it has been reported that PM is associated with increased risks of skin diseases, especially atopic dermatitis in children. However, it is unclear if PM directly goes into the skin and what mechanisms are involved in response to PM.</P> <P><B>Objective</B></P> <P>To see whether PM could penetrate into the barrier-disrupted skin, produce reactive oxygen species (ROS), and elicit an inflammatory response.</P> <P><B>Methods</B></P> <P>We collected PMs during a winter in Seoul and used cultured keratinocytes for <I>in vitro</I> study and tape-stripped BALB/c mice for <I>in vivo</I> study.</P> <P><B>Results</B></P> <P>Keratinocyte cytotoxicity increased in a dose-dependent manner by PM treatment. IL-8 and MMP-1 mRNA expression and protein levels were significantly increased compared to control by qPCR and ELISA, respectively. Cellular ROS production was increased by PM treatment, and antioxidant N-acetyl cysteine pretreatment prevented induction of inflammatory cytokines IL-8 and MMP-1. In PM-treated keratinocytes, electron-dense subcellular particles were observed by transmission electron microscopy. PM was observed inside hair follicles in both intact and barrier-disrupted skin <I>in vivo</I>. Additionally, intercellular penetration of PM was seen in the barrier-disrupted skin. Repeated PM application induced epidermal thickening and dermal inflammation with neutrophil infiltration. Finally, N-acetyl cysteine could ameliorate skin inflammation induced by PM application.</P> <P><B>Conclusion</B></P> <P>PM penetrates into the barrier-disrupted skin, causing inflammation, demonstrating detrimental effects in the skin.</P> <P><B>Highlights</B></P> <P> <UL> <LI> It is unclear if particulate matter (PM) directly goes into the skin. </LI> <LI> We provide visual images of PM penetrating into epidermis in the barrier-disrupted skin. </LI> <LI> Repeated PM application leads to cutaneous inflammation via ROS-dependent manner. </LI> <LI> It may have clinical implications especially for patients with deficient skin barrier including atopic dermatitis, diabetics. </LI> </UL> </P>