상아질 접착제의 중합 시간 조절에 따른 복합레진의 중합 수축 방향의 변화

배지현,오명환,김창근,손호현,엄정문,조병훈,권혁춘 대한치과보존학회 2001 Restorative Dentistry & Endodontics Vol.26 No.4

The purpose of this study was to evaluate the effect of adhesive curing timing on the direction of polymerization shrinkage of light-curing composite resin. In this study, the curing times of adhesive and composite resin were measured by differential scanning calorimeter(DSC). 28 extracted human molars were embedded in clear resin and box-type cavities were prepared. Based on DSC data. the experimental teeth were divided into 4 groups. Group 1: no bond: Group 2: late curing: Group 3: Intermediate curing: Group 4: Early curing. After treating with adhesive, the buccal cavities were filled with Z-100 hybrid composite resin and the lingual ones were filled with AEliteflo flowable composite resin. The depressions at the surface were measured by surface profilometer, then the specimens were embedded in clear resin and sectioned. Impressions were obtained and used to get epoxy resin replicas. The epoxy replicas were gold-coated and observed under SEM. Average Maximum Gap(AMG), Gap Proportion(GP), Average Marginal Index(AMI) were used to compare the shrinkage gap of each group. The results were statistically analyzed using the Kruskal-Wallis One Way ANOVA, Student-Newman-Keuls method. The results of this study were as follows. 1. Average Maximum Gap. Gap Proportion, Average Marginal Index and depression at the surface of Z-100 hybride composite resin were smailer than those of AEliteflo flowable composite resin(P(0.05) 2. When the bonding between composite resin and tooth structure was strong, the shrinkage gap was small, and depression at the surface was deep(P<0.05). 3. In the well-bonded group. light-curing composite resin shrank toward bonded cavity wall. not toward light source. The result suggested that the direction of polumerization shrinkage was affected by the quality of bonding in the dentin-resin interface. The strong was the bonding between composite resin and tooth structure, the smaller was the gap and the deeper was the depression at the surface. Then the flow to compensate the polymerization shrinkage proceeded from surface to bonded cavity wall.

SnO₂ nanotube arrays embedded in a carbon layer for high-performance lithium-ion battery applications

Um, Ji Hyun,Yu, Seung-Ho,Cho, Yong-Hun,Sung, Yung-Eun The Royal Society of Chemistry 2015 NEW JOURNAL OF CHEMISTRY Vol.39 No.4

<P>A facile strategy for preparing one-dimensional (1D) SnO<SUB>2</SUB> nanotube arrays embedded in a carbon layer (C–SnO<SUB>2</SUB> NTs) has been developed <I>via</I> a sol–gel method using polycarbonate (PC) as a template. The introduction of a carbon layer (carbonized from a PC membrane) at the top of SnO<SUB>2</SUB> nanotube arrays results in the SnO<SUB>2</SUB> nanotubes standing on the current collector and preserving their 1D structure without aggregation between each other, which enables their direct application to the anode of lithium-ion batteries. The binder- and carbon-free C–SnO<SUB>2</SUB> NTs as a self-supporting anode exhibits a stable and high reversible capacity of 500 mA h g<SUP>−1</SUP> at 0.1 A g<SUP>−1</SUP> after 40 cycles. The improved Li ion storage and stable capability are attributed to the 1D hollow structure, alleviating the large volume changes of SnO<SUB>2</SUB> and enhancing electron and Li ion diffusion transport in the nanotubes.</P> <P>Graphic Abstract</P><P>SnO<SUB>2</SUB> nanotube arrays embedded in a carbon layer were fabricated via a simple sol–gel method, which has shown good battery performance. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj01958j'> </P>

Biomass Waste, Coffee Grounds-derived Carbon for Lithium Storage

Um, Ji Hyun,Kim, Yunok,Ahn, Chi-Yeong,Kim, Jinsoo,Sung, Yung-Eun,Cho, Yong-Hun,Kim, Seung-Soo,Yoon, Won-Sub The Korean Electrochemical Society 2018 Journal of electrochemical science and technology Vol.9 No.3

Biomass waste-derived carbon is an attractive alternative with environmental benignity to obtain carbon material. In this study, we prepare carbon from coffee grounds as a biomass precursor using a simple, inexpensive, and environmentally friendly method through physical activation using only steam. The coffee-derived carbon, having a micropore-rich structure and a low extent of graphitization of disordered carbon, is developed and directly applied to lithium-ion battery anode material. Compared with the introduction of the Ketjenblack (KB) conducting agent (i.e., coffee-derived carbon with KB), the coffee-derived carbon itself achieves a reversible capacity of ~200 mAh/g (0.54 lithium per 6 carbons) at a current density of 100 mA/g after 100 cycles, along with excellent cycle stability. The origin of highly reversible lithium storage is attributed to the consistent diffusion-controlled intercalation/de-intercalation reaction in cycle life, which suggests that the bulk diffusion of lithium is favorable in the coffee-derived carbon itself, in the absence of a conducting agent. This study presents the preparation of carbon material through physical activation without the use of chemical activation agents and demonstrates an application of coffee-derived carbon in energy storage devices.

Phase Dynamics on Conversion-Reaction-Based Tin-Doped Ferrite Anode for Next-Generation Lithium Batteries

Um, Ji Hyun,Palanisamy, Kowsalya,Jeong, Mihee,Kim, Hyunchul,Yoon, Won-Sub American Chemical Society 2019 ACS NANO Vol.13 No.5

<P>The conventional view of conversion reaction is based on the reversibility, returning to an initial material structure through reverse reaction at each cycle in cycle life, which impedes the complete understanding on a working mechanism upon a progression of cycles in conversion-reaction-based battery electrodes. Herein, a series of tin-doped ferrites (Fe<SUB>3-<I>x</I></SUB>Sn<SUB><I>x</I></SUB>O<SUB>4</SUB>, <I>x</I> = 0-0.36) are prepared and applied to a lithium-ion battery anode. By achieving the ideal reoxidation into SnO<SUB>2</SUB>, the Fe<SUB>2.76</SUB>Sn<SUB>0.24</SUB>O<SUB>4</SUB> composite anchored on reduced graphene oxide shows a high reversible capacity of 1428 mAh g<SUP>-1</SUP> at 200 mA g<SUP>-1</SUP> after 100 cycles, which is the best performance of Sn-based anode materials so far. Significantly, a newly formed γ-FeOOH phase after 100 cycles is identified from topological features through synchrotron X-ray absorption spectroscopy with electronic and atomic structural information, suggesting the phase transformation from magnetite to lepidocrocite upon cycling. Contrary to the conventional view, our work suggests a variable working mechanism in an iron-based composite with the dynamic phases from iron oxide to iron oxyhydroxide in the battery cycle life, based on the reactivity of metal nanoparticles formed during reaction toward the solid electrolyte interface layer.</P> [FIG OMISSION]</BR>

Nocturia and Sleep: Focus on Common Comorbidities and Their Association with Obstructive Sleep Apnea

Um Yoo Hyun,Oh Ji-Hye,Kim Tae Won,서호준,Kim Sung-Min,Chung Jun-Soo,Jeong Jong-Hyun,Hong Seung-Chul 대한수면학회 2020 sleep medicine research Vol.11 No.2

Nocturia is a frequently encountered complaint in patients visiting sleep clinics. Nocturia and its detrimental effect on sleep continuity and quality have been frequently discussed in previous studies. Moreover, abundant research has been conducted to delineate the close relationship between nocturia and the pathophysiology of obstructive sleep apnea (OSA). In this review, we discuss the common comorbidities that can provoke nocturia and their relationship with OSA and sleep.

Parkin Directly Modulates 26S Proteasome Activity.

Um, Ji Won,Im, Eunju,Lee, Hyun Jung,Min, Boram,Yoo, Lang,Yoo, Jiho,Lü,bbert, Hermann,Stichel-Gunkel, Christine,Cho, Hyun-Soo,Yoon, Jong Bok,Chung, Kwang Chul The Society 2010 The Journal of neuroscience Vol.30 No.35

<P>Parkinson's disease (PD) is a common neurodegenerative disease that involves the deterioration of dopaminergic neurons in the substantia nigra pars compacta. Although the etiology of PD remains poorly understood, recent genetic, postmortem, and experimental evidence shows that abnormal protein accumulation and subsequent aggregate formation are prominent features of both sporadic and familial PD. While proteasome dysfunction is observed in PD, diverse mutations in the parkin gene are linked to early-onset autosomal-recessive forms of familial PD. We demonstrate that parkin, an E3 ubiquitin ligase, activates the 26S proteasome in an E3 ligase activity-independent manner. Furthermore, an N-terminal ubiquitin-like domain within parkin is critical for the activation of the 26S proteasome through enhancing the interaction between 19S proteasomal subunits, whereas the PD-linked R42P mutant abolishes this action. The current findings point to a novel role for parkin for 26S proteasome assembly and suggest that parkin mutations contribute to the proteasomal dysfunction in PD.</P>

SnO₂-Coated 3D Etched Cu Foam for Lithium-ion Battery Anode

Um, Ji Hyun,Kim, Hyunwoo,Cho, Yong-Hun,Yoon, Won-Sub The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.1

SnO₂-based high-capacity anode materials are attractive candidate for the next-generation high-performance lithium-ion batteries since the theoretical capacity of SnO₂ can be ideally extended from 781 to 1494 mAh g^-1. Here 3D etched Cu foam is applied as a current collector for electron path and simultaneously a substrate for the SnO₂ coating, for developing an integrated electrode structure. We fabricate the 3D etched Cu foam through an auto-catalytic electroless plating method, and then coat the SnO₂ onto the self-supporting substrate through a simple sol-gel method. The catalytic dissolution of Cu metal makes secondary pores of both several micrometers and several tens of micrometers at the surface of Cu foam strut, besides main channel-like interconnected pores. Especially, the additional surface pores on etched Cu foam are intended for penetrating the individual strut of Cu foam, and thereby increasing the surface area for SnO₂ coating by using even the internal of Cu foam. The increased areal capacity with high structural integrity upon cycling is demonstrated in the SnO₂-coated 3D etched Cu foam. This study not only prepares the etched Cu foam using the spontaneous chemical reactions but also demonstrates the potential for electroless plating method about surface modification on various metal substrates.

(LORL) 수중운동체 에너지 효율 증대를 위한 다기능성 샌드위치 구조에 관한 연구

노현지(Hyun-Ji Rho),엄희진(Hui-Jin Um),전나현(Na-Hyun Jeon),신지환(Ji-Hwan Shin),김민재(Min-Jae Kim),김학성(Hak-Sung Kim) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11

동축전기방사에 의해 제조된 Poly(vinyl alcohol)/Poly(ethylene terephthalate) 복합 나노섬유

김지윤(Ji Yoon Kim),김우진(Woo Jin Kim),이승빈(Seung Bin Lee),이현영(Hyun Young Lee),박가영(Ga Young Park),엄인철(In Chul Um),염정현(Jeong Hyun Yeum),최진현(Jin Hyun Choi) 한국고분자학회 2018 폴리머 Vol.42 No.5

동축전기방사에 의해 poly(vinyl alcohol)(PVA)(core)/poly(ethylene terephthalate)(PET)(shell) 복합 나노섬유를 제조하고 이의 특성을 고찰하였다. 성공적인 동축전기방사를 위해서 두 고분자 용액의 공급속도와 전압의 설정이 중요하였으며, 이를 상호 조절하여 선형성과 규칙성이 양호한 복합 나노섬유를 제조하였다. 전자현미경을 통하여 나노크기의 섬유 및 core-shell 구조가 관찰되었으며, 분광분석으로부터 동축전기방사된 나노섬유 내에 존재하는 각각의 고분자의 존재를 확인하였다. 또한 PVA의 존재에 기인하여 복합 나노섬유 웹의 접촉각이 PET 나노섬유 웹 대비 감소하였다. 따라서 동축전기방사는 나노구조를 유지하면서 수용성 고분자를 블렌드함으로써 소수성 나노섬유의 친수성을 개선할 수 있을 뿐만 아니라, 수분산성 나노입자나 단백질을 포함한 수용성 생리활성 물질을 도입할 수 있는 효과적인 방법이라고 생각된다. Poly(vinyl alcohol) (PVA) (core)/poly(ethylene terephthalate) (PET) (shell) composite nanofibers were produced by coexial electrospinning and their characteristics were investigated. It was important to establish feed rate of each polymer solution and voltage for a successful coaxial electrospinning, and the composite nanofibers with good linearity and regularity were produced by an interactive control of these factors. The nano-sized fibers and core-shell structures were observed through electron microscopes and the presence of each polymer in the coaxially electrospun nanofibers was confirmed by spectroscopic analyses. Also, the contact angle between water and composite nanofiber web decreased compared with that of PET nanoweb due to the presence of PVA. It is suggested that coaxial electrospinning is an effective technique to improve hydrophilicity of hydrophobic nanofibers by blending a water-soluble polymer with maintaining nanostructures, and to incorporate water-dispersable nanoparticles and water-soluble bioactive components including proteins in the nanofibers.

Adhesive layer properties as a determinant of dentin bond strength

Bae, Ji-Hyun,Cho, Byeong-Hoon,Kim, Jong-Soon,Kim, Min-Soo,Lee, In-Bog,Son, Ho-Hyun,Um, Chung-Moon,Kim, Chang-Keun,Kim, Oh-Young Wiley Subscription Services, Inc., A Wiley Company 2005 Journal of Biomedical Materials Research Part B Vol. No.

<P>The goal of this study is to evaluate the hypothesis that the properties of the resin adhesive might affect the microtensile bond strength (MTBS) of multibottle dental adhesive system. In order to alter the properties, the experimental resin adhesives containing 2,2-bis (4-2-hydroxy-3-methacryloyloxypropoxyphenyl)propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) at various ratios were prepared. Degree of conversion immediately after curing (DC-immed), degree of conversion at 48 h after curing (DC-48h) of a thin coat of the experimental adhesives, the flexural strength (FS) of the bulk specimens made of the experimental adhesives, pH, viscosity at shear rate of 1 S<SUP>−1</SUP>, and the microtensile bond strength (MTBS) values of the adhesives to dentin were investigated. The maximum MTBS and FS values of the resin adhesives were observed when the ratio of Bis-GMA/TEGDMA was 60/40. However, pH and viscosity values increased with increasing Bis-GMA content in the adhesives. When Bis-GMA content was more than 60 wt %, the viscosity increased exponentially and restricted the DC and FS, and accordingly decreased the bond strength. The stronger the resin adhesives were, the higher the bond strength to dentin could be obtained. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005</P>