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Reversible self-bending soft hydrogel microstructures with mechanically optimized designs
Kim, Jongmin,Kim, Cheolgyu,Song, YoungShin,Jeong, Seong-Geun,Kim, Taek-Soo,Lee, Chang-Soo Elsevier 2017 Chemical Engineering Journal Vol.321 No.-
<P><B>Abstract</B></P> <P>A rational design methodology for materials with optimal mechanical properties is a prerequisite for developing programmable soft matter that undergoes structural changes in response to external stimuli. The goals of this study are to experimentally characterize the capabilities of a self-bending reconfigurable microstructure, provide fundamental information in engineering design, and validate simulations of physics-based models. In this study, the self-bending behavior of hydrogel bilayers, composed of an active layer and a passive layer, is investigated experimentally and theoretically. This self-bending is completely reversible and allows the structure to fold and unfold without permanent deformation. Experimentally, the effects of design parameters on the self-bending behavior of the microstructures of hydrogel bilayers are explored by varying the extrinsic geometric variables. The study of finite element method (FEM) simulations shows that the final shape of the bilayer sheet is governed by intrinsic properties, including the elastic modulus and the swelling ratio, and extrinsic geometrical factors, such as the thickness ratio of the bilayer and the aspect ratio of the structure. Therefore, the self-bending behavior of the planar hydrogel bilayer was confirmed by experiments and simulations in which multiple values were assigned for each of the primary design parameters in origami-based engineering.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The capabilities of self-folding reconfigurable microstructure are characterized. </LI> <LI> The finite element method (FEM) provides information in engineering design. </LI> <LI> A rational design methodology for programmable soft materials is provided. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Pitna,Park, Jin Hee,Choi, Chang Soon,Choi, Inah,Joo, So Hyun,Kim, Min Kyoung,Kim, Soo Young,Kim, Ki Chan,Park, Seung Hwa,Kwon, Kyoung Ja,Lee, Jongmin,Han, Seol-Heui,Ryu, Jong Hoon,Cheong, Jae Hoo Kluwer Academic/Plenum Publishers 2013 Neurochem Res Vol.38 No.3
<P>Prenatal exposure to alcohol has consistently been associated with adverse effects on neurodevelopment, which is collectively called fetal alcohol spectrum disorder (FASD). Increasing evidence suggest that prenatal exposure to alcohol increases the risk of developing attention deficit/hyperactivity disorder-like behavior in human. In this study, we investigated the behavioral effects of prenatal exposure to EtOH in offspring mice and rats focusing on hyperactivity and impulsivity. We also examined changes in dopamine transporter and MeCP2 expression, which may underlie as a key neurobiological and epigenetic determinant in FASD and hyperactive, inattentive and impulsive behaviors. Mouse or rat offspring born from dam exposed to alcohol during pregnancy (EtOH group) showed hyper locomotive activity, attention deficit and impulsivity. EtOH group also showed increased dopamine transporter and norepinephrine transporter level compared to control group in the prefrontal cortex and striatum. Prenatal exposure to EtOH also significantly decreased the expression of MeCP2 in both prefrontal cortex and striatum. These results suggest that prenatal exposure to EtOH induces hyperactive, inattentive and impulsive behaviors in rodent offspring that might be related to global epigenetic changes as well as aberration in catecholamine neurotransmitter transporter system.</P>
Kim, Jigeon,Koo, Bonkee,Kim, Wook Hyun,Choi, Jongmin,Choi, Changsoon,Lim, Sung Jun,Lee, Jong-Soo,Kim, Dae-Hwan,Ko, Min Jae,Kim, Younghoon Elsevier 2019 Nano energy Vol.66 No.-
<P><B>Abstract</B></P> <P>Fully inorganic CsPbI<SUB>3</SUB> perovskite quantum dots (CsPbI<SUB>3</SUB>-PQDs) are known as the best-performing photovoltaic absorber in colloidal quantum dot solar cells. This is achieved by improving the cubic-phase-stabilization and electronic-coupling in CsPbI<SUB>3</SUB>-PQD solids. In conventional approaches, the hydrolysis of methyl acetate (MeOAc) resulting in acetic acid and methanol as intermediate substances plays a key role in replacing long-chain hydrocarbons with short-chain ligands, which improves charge transport in the CsPbI<SUB>3</SUB>-PQD solids. However, CsPbI<SUB>3</SUB>-PQDs suffer from lattice distortion and instability under acidic conditions including protons and polar media, leading to CsPbI<SUB>3</SUB>-PQD fusion and poor photovoltaic performance. Herein, we report that electronic coupling and photovoltaic performance of CsPbI<SUB>3</SUB>-PQD solids are improved by efficient removal of long-chain oleate ligands using a solution of sodium acetate (NaOAc) in MeOAc, which results in the direct generation of OAc ions without forming protons and methanol. NaOAc-based ligand exchange of CsPbI<SUB>3</SUB>-PQDs enables preservation of their nanocrystal size without fusion and minimization of surface trap states originating from metal hydroxide formation on their surfaces. Consequently, the best solar cell comprising NaOAc-treated CsPbI<SUB>3</SUB>-PQDs shows an improved device performance with a power conversion efficiency (<I>PCE</I>) of 13.3%, as compared with a lead nitrate-treated control device (12.4% <I>PCE</I>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> NaOAc directly generates short-chain OAc ions to exchange the oleate ligands of CsPbI<SUB>3</SUB>-PQDs. </LI> <LI> Our strategy enables minimizing the formation of protons and methanol during the ligand exchange. </LI> <LI> NaOAc-based ligand exchange enables preserving nanocrystal size and minimizing surface traps. </LI> <LI> Resultant CsPbI<SUB>3</SUB>-PQD solids show enhanced electronic coupling with improved charge transport. </LI> <LI> NaOAc-treated CsPbI<SUB>3</SUB>-PQD solar cells show improved photovoltaic performance up to 13.33% PCE. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>We demonstrate that sodium acetate (NaOAc) directly generates short-chain OAc ions to exchange the long-chain oleate ligands of CsPbI<SUB>3</SUB> perovskite quantum dots (CsPbI<SUB>3</SUB>-PQDs). NaOAc-based ligand exchange enables preservation of CsPbI<SUB>3</SUB>-PQD size, minimization of surface trap states, and enhancement of electronic coupling in the resultant CsPbI<SUB>3</SUB>-PQD solids. Consequently, NaOAc-treated CsPbI<SUB>3</SUB>-PQD solar cells show improved device performance with 12.4% power conversion efficiency.</P> <P>[DISPLAY OMISSION]</P>
Synthesis of Vinyl Sulfone-tethered Proline Derivatives as Highly Selective Cathepsin S Inhibitors
Kim, Mira,Jeon, Jiyoung,Baek, Jongouk,Choi, Jaeyul,Park, Eun Ju,Song, Jiyeon,Bang, Hyojeong,Suh, Kwee Hyun,Kim, Young Hoon,Kim, Jongmin,Kim, Doran,Min, Kyung Hoon,Lee, Kwang-Ok Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.2
( Ran Kim ),( Seokyeon Lee ),( Jihyun Lee ),( Minji Kim ),( Won Jung Kim ),( Hee Won Lee ),( Min Young Lee ),( Jongmin Kim ),( Woochul Chang ) 생화학분자생물학회 2018 BMB Reports Vol.51 No.8
Exosomes are small membranous vesicles which contain abundant RNA molecules, and are transferred from releasing cells to uptaking cells. MicroRNA (miRNA) is one of the transferred molecules affecting the adopted cells, including glioma cells. We hypothesized that mesenchymal stem cells (MSCs) can secrete exosomes loading miRNA and have important effects on the progress of gliomas. To determine these effects by treating exosomal miRNA in culture media of miRNA mimic transfected MSCs, we assessed the in vitro cell proliferation and invasion capabilities, and the expression level of relative proteins associated with cell apoptosis, growth and migration. For animal studies, the mice injected with U87 cells were exposed to exosomes derived from miRNA-584-5p transfected MSCs, to confirm the influence of exosomal miRNA on the progress of glioma. Based on our results, we propose a new targeted cancer therapy wherein exosomes derived from miRNA transfected MSCs could be used to modulate tumor progress as the anticancer vehicles. [BMB Reports 2018; 51(8): 406-411]
De-Embedding 기술을 이용한 IC 내부의 전원분배망 추출에 관한 연구
김종민(Jongmin Kim),이인우(In-Woo Lee),김성준(Sungjun Kim),김소영(So-Young Kim),나완수(Wansoo Nah) 한국전자파학회 2013 한국전자파학회논문지 Vol.24 No.6
IC 내부의 전원분배망(PDN: Power Delivery Network) 회로를 분석하기 위해서는 IC의 디자인 정보가 담긴 파일이 필요하지만, 상용 IC(Commercial IC)의 경우 보안상의 이유로 디자인 정보를 제공하지 않고 있다. 하지만 온-칩 전원분배망(On-chip PDN) 특성이 포함된 경우에는 PCB와 패키지의 특성만으로는 정확한 해석이 어려우므로 본 연구에서는 IC 내부의 정보가 제공하지 않는 전원분배망(PDN) 회로의 추출에 관하여 연구를 하였다. IC 내부의 전원분배망(PDN)의 주파수에 대한 특성을 추출하기 위하여, IEC62014-3에서 제안하고 있는 추출용보드를 제작하였고, 추출용 보드를 구성하고 있는 SMA 커넥터, 패드, 전송 선로, 그리고 QFN 패키지의 주파수에 대한 특성들을 분석하였다. 추출된 결과들은 디임베딩(de-embedding) 기술에 적용하여 IC 내부의 전원분배망 (PDN) 회로를 S-parameter 기반으로 모델을 추출하였고, 평가용 보드의 전원분배망 결합회로(PDN Co-simulation) 모델에 적용하여 측정과 비교한 결과, ~4 ㎓까지 잘 일치하였다. GDS format files, as well as layout of the chip are noticeably needed so as to analyze the PDN (Power Delivery Network) inside of IC; however, commercial IC in the market has not supported design information which is layout of IC. Within this, in terms of IC having on-chip PDN, characteristic of inside PDN of the chip is a core parameter to predict generated noise from power/ground planes. Consequently, there is a need to scrutinize extraction method for unknown PDN of the chip in this paper. To extract PDN of the chip without IC circuit information, the de-embedding test vehicle is fabricated based on IEC62014-3. Further more, the extracted inside PDN of chip from de-embedding technique adopts the Co-simulation model which composes PCB, QFN (Quad-FlatNo-leads) Package, and Chip for the PDN, applied Co-simulation model well corresponds with impedance from measured S-parameters up to 4 ㎓ at common measured and simulated points.