Suicide cancer gene therapy using pore-forming toxin, streptolysin O.

Yang, Wan Seok,Park, Sue-O,Yoon, A-Rum,Yoo, Ji Young,Kim, Min Kyung,Yun, Chae-Ok,Kim, Chul-Woo American Association for Cancer Research, Inc 2006 Molecular Cancer Therapeutics Vol.5 No.6

<P>We cloned the streptolysin O gene from the Streptococcus pyogenes genome and tested the possibility of using it as an anticancer reagent. Transient transfection of the streptolysin O gene efficiently killed 293T cells after 12 hours of transfection as determined by lactate dehydrogenase release and propidium iodide uptake. No caspase activity was observed and necrosis was prominent during streptolysin O-induced cell death. Biochemical analysis of streptolysin O protein revealed that the deletion of only 5 amino acids from the COOH-terminal region of streptolysin O, which is essential for cholesterol binding activity, abolished its cell-killing activity, whereas the NH2-terminal region was more resilient, i.e., up to 115 amino acids could be deleted without changing its cell-killing activity. We generated a streptolysin O-expressing adenovirus and injected it into human cervical cancer cell-derived tumors grown in a nude mouse model. Twenty-one days postinjection, the average size of tumors in the streptolysin O adenovirus-injected group was 29.3% of that of the control PBS-treated group. Our results show that the genes of pore-forming toxins, like streptolysin O protein, have the potential to establish a novel class of suicide gene therapeutic reagents.</P>

Graphene paper with controlled pore structure for high-performance cathodes in Li–O₂ batteries

Kim, Do Youb,Kim, Mokwon,Kim, Dong Wook,Suk, Jungdon,Park, Jung Jin,Park, O Ok,Kang, Yongku Elsevier 2016 Carbon Vol.100 No.-

<P>In non-aqueous Li-O-2 batteries, relatively large amounts of discharge products are formed on air cathodes. As such, the expansion of air cathodes is a critical issue that remains to be solved. Here, we report the fabrication of highly porous free-standing graphene paper by introducing macropores within the paper using polystyrene colloidal particles as a sacrificial template. The as-prepared macroporous graphene paper (mp-GP) have a large BrunauereEmmetteTeller (BET) surface area (ca. 373 m(2) g(-1)), a large pore volume (ca. 10.9 cm(3) g(-1)), and a high porosity (91.6%). Owing to the high surface area and large pore volume, the mp-GPs exhibit a high specific capacity of ca. 12,200 mAh g(-1) at a current density of 200 mA g(-1), as well as good rate capability, when used as an air cathode in a non-aqueous Li-O-2 battery. Moreover, the mp-GP shows good stability up to 100 and 78 cycles at a current density of 500 mA g(-1) and 2000 mA g(-1) respectively, with a limiting capacity of 1000 mAh g(-1). It is found that formation and decomposition of the discharge product, Li2O2, occur within the macropores, and thus, the mp-GP maintains its original structure without considerable expansion during cycling. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Flexible binder-free graphene paper cathodes for high-performance Li-O₂ batteries

Kim, Do Youb,Kim, Mokwon,Kim, Dong Wook,Suk, Jungdon,Park, O Ok,Kang, Yongku Elsevier 2015 Carbon Vol.93 No.-

<P><B>Abstract</B></P> <P>In this study, free-standing porous graphene papers for high-capacity and reversible Li-O<SUB>2</SUB> battery cathodes are investigated. The graphene paper-like films were fabricated by the assembling of graphene nanoplatelets (GNPs) with the aid of graphene oxides (GOs) as a stabilizer, using a vacuum-assisted filtration method. By using GOs as a stabilizer, the GNP/GO films were fabricated with a paper-like form and they exhibited a highly wrinkled and disordered morphology. Moreover, the use of GNPs as a basic material eliminated the need for a post-annealing to recover the intrinsic electrical conductivity of graphene sheets. Subsequently, the GNP/GO paper could be directly used as a Li-O<SUB>2</SUB> battery cathode without any conducting additives and binders. The GNP/GO paper electrode showed a much higher discharge capacity in comparison to the reduced-GO paper and commercially available carbon papers. We also found that toroidal Li<SUB>2</SUB>O<SUB>2</SUB> mainly nucleated and grew on discharge, and decomposed on charge with a relatively high O<SUB>2</SUB> evolution/consumption efficiency of 87%. However, a large number of Li<SUB>2</SUB>O<SUB>2</SUB> particles grew inside the GNP/GO paper electrode, resulting in severe volume expansion of the electrode. This volume expansion could be the primary reason for the capacity fading on cycling.</P>

Pulse YAG Laser 제어 시스템에 의한 공구강의 조직 특성에 관한 연구

옥철호,서영백,배춘익,박흥식,전태옥 동아대학교 생산기술연구소 1999 生産技術硏究所硏究論文集 Vol.4 No.2

Case Organization Characteristics of tool steel (SK5) was investigated after Pulse YAG laser control system irradiation. In the case of beam passes, martensite formed in the melt zone and in former pearlite regions of the austenization zone exhibited very high vickers hardness values. Molten depth and width depend on defocusing distance and radius, micro structure, hardness were investigated as a function of defocusing distance, pulse width, power density and black color painting have a energy absorption more than other any color painting.

Electrocatalytic effect of NiO nanoparticles evenly distributed on a graphite felt electrode for vanadium redox flow batteries

Yun, Nari,Park, Jung Jin,Park, O.Ok,Lee, Ki Bong,Yang, Jung Hoon Elsevier 2018 ELECTROCHIMICA ACTA Vol.278 No.-

<P><B>Abstract</B></P> <P>Vanadium redox flow batteries (VRFBs) have attracted considerable attention for potential use in the development of large-scale energy storage systems. However, the commercialization of VRFBs is still challenging because of their various overpotentials, which are due to the poor reversibility and electrochemical activity of graphite felt (GF) electrodes. In this study, we fabricated a NiO-decorated GF electrode that exhibited a clear electrocatalytic effect on the V<SUP>2+</SUP>/V<SUP>3+</SUP> and VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox reactions. Vanadium ions preferentially attached to each NiO site because of strong electrostatic affinity to the local negatively charged O<SUP>2−</SUP> species. In particular, a significant amount of NiO bound to graphite by replacement of hydrogen from the hydroxyl groups with nickel ion, leading to an increase in the ratio of carboxyl groups to hydroxyl groups. The increase in the number of carboxyl groups also improved the VRFB performance, since the carboxyl functional group on GF surface acts as effective catalyst for the vanadium redox reactions. Furthermore, NiO nanoparticles enhanced the mass-transfer property of vanadium ions by the increased area and hydrophilicity of the electrode surface. To optimize the electrode structure for high electrochemical performance, the crystallinity and morphology of the NiO catalyst on GF were controlled via the operating temperature and precursor concentration. When optimized NiO/GF<SUB>300</SUB> was applied to VRFBs, it exhibited high energy efficiency (74.5%) at a high current rate (125 mA cm<SUP>−2</SUP>), compared with GF without the catalyst (55.4%). Moreover, NiO-decorated GF exhibited durability and stability in acidic electrolyte during long-term operation for 300 cycles.</P>

Fabrication of Silver Nano-Hole Pattern with Different Hole Sizes by Thermal Transfer Printing

Yang, Young Jo,Choi, Hong Kyoon,Park, O. Ok American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.8

<P>The surface plasmon effect occurs in the silver nano-hole films; however, it is hard to make large-area patterns for use in optoelectronic devices. The aim of our research was to fabricate Ag nanohole patterns in a relatively large area with a cost effective method, called thermal transfer printing. Thermal transfer printing is combined with colloidal lithography and soft lithography to fabricate two-dimensional hexagonal arrays of colloidal particles without an interlayer between polymeric colloidal particles and the target substrate. First, three-dimensional colloidal crystals consisting of polystyrene colloidal particles with diameters of 270 nm, 370 nm, and 480 nm were prepared. Next, a top layer of colloidal crystals, which had been pre-etched by oxygen plasma treatments, was transferred to a properly heated glass substrate using a polydimethylsiloxane stamp. Thus, Ag nanohole patterns could be obtained after the metal layer was deposited and the colloidal particles were removed from the film. The hole diameter was easily controlled by O-2 plasma etching. The Ag nano-hole patterns absorb half of the visible light in the region between 541 nm and 725 nm. It can be immediately applied in optoelectronic devices.</P>

High molecular weight bio furan-based co-polyesters for food packaging applications: synthesis, characterization and solid-state polymerization

Hong, Sungmin,Min, Kyung-Deok,Nam, Byeong-Uk,Park, O Ok The Royal Society of Chemistry 2016 Green Chemistry Vol.18 No.19

<P>The goal of this study was to develop ecofriendly bioplastics, which could be applicable in beverage packaging, by synthesizing furan-based co-polyesters and incorporating them into bottles. The furan-based co-polyesters were synthesized by a two-step melt polycondensation reaction using ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), and dimethyl furan dicarboxylate (DM-FDCA). The incorporation of CHDM into the main chain of polymers has been found to increase the chain mobility due to its ring-conformational transition, and it also affects the co-polyesters. The co-polyesters show not only high elongations at break, but also improved Izod impact strengths compared to that of pure poly(ethylene furanoate) (PEF). Despite these characteristics, however, the molecular weights of the co-polyesters were not sufficient for manufacturing purposes. Thus, some samples were further reacted in the solid state by solid state polymerization (SSP) to generate higher-molecular-weight polymers. The crystallization kinetics of the co-polyesters prepared were analyzed to determine the reaction parameters, and the sample whose intrinsic viscosity was greater than 1.0 dL g(-1) was successfully processed into bottles. The bottles prepared had higher O-2-barrier properties and lower acetaldehyde contents than those of commercially available PET bottles. The results obtained so far show that furan-based co-polyesters can be used for food-packaging applications.</P>

발사체 공력해석 프로그램 RocketAeroMaster2005 개발

김재수,김종록,우철훈,김태훈,임오택,박정주,오범석,옥호남 朝鮮大學校 機械技術硏究所 2005 機械技術硏究 Vol.8 No.1

예비설계 단계에서 외형설계, 구조설계를 위한 하중분포 계산, 발사체의 안정성 및 성능분석을 위하여 데이터베이스형 발사체 공력코드를 개발하였다. 분석방법으로는 동체, 스트랩온 부스터의 공력계수와 동체와 스트랩온 부스터의 간섭 동의 분석을 거쳐 전체 발사체에 대한 분석이 이루어졌다. 발사체 공력코드의 데이터베이스구성은 기존의 DATCOM의 데이터베이스를 기반으로 발사체 형상에 대한 실험데이터(MD)를 추가 구성함으로서 발사체 공력코드의 신뢰성을 증대시켰다. 또한, 기존의 발사체 공력설계코드와 비교 분석을 수행하여 발사체 공력코드를 검증하였다. For the development of launch vehicle, the aerodynamic characteristics have to be performed for the configuration design in the preliminary design, the load distribution in the detail design, and the performance analysis. The static and dynamic coefficients are analyzed for strap on booster, body and strap on booster-body interface characteristics. A detail analysis is required during the detail design phase, but a rapid analysis is better in the preliminary design. Therefore, the database code, based on the theory and experimental datum, is useful to analyze the variety of models during the preliminary design phase, and the computational aerodynamic code is required to calculate the detail load distribution during the detail design phase. In this computational aerodynamic code, based on the database of theoretical and experimental datum, have been developed.

EXPERIMENTAL ELECTROHYDRODYNAMICS OF POLY(γ-BENZYL-L-GLUTAMATE) IN M-CRESOL SOLUTION SUBJECTED TO SHEAR FLOW AND ELECTRIC FIELDS

Park, O Ok,Kwon, Moo Hyun,Lee, Young Sil 한국화학공학회 1999 Korean Journal of Chemical Engineering Vol.16 No.2

Enhancing Device Performance of Organic Photovoltaics with Various Approaches

O Ok Park 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2