37 results on '"Ji, Un"'
Search Results
2. Effects of photobiomodulation on bone remodeling in an osteoblast–osteoclast co-culture system
- Author
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Hyung Joon Kim, Ji-Un Hong, Soon Chul Heo, Jae-Yeol Lee, Sang-Hun Shin, and Jin-Ju Kwon
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musculoskeletal diseases ,biology ,medicine.diagnostic_test ,Chemistry ,Osteoblast ,030206 dentistry ,Dermatology ,Bone healing ,Bone remodeling ,Andrology ,030207 dermatology & venereal diseases ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,Osteoprotegerin ,Western blot ,Osteoclast ,RANKL ,Bone cell ,medicine ,biology.protein ,Surgery - Abstract
The general bone anabolic effect of photobiomodulation (PBM) is largely accepted. As a result, PBM therapy is expected to be beneficial in the medical fields of dentistry and bone healing. However, most of the previous in vitro studies on PBM and bone metabolism were performed with single-cell cultures of osteoclast-lineage cells or osteoblast-lineage cells. In the present study, the bone-modulating effects of PBM were evaluated in an in vitro osteoblast/osteoclast co-culture system. Mouse bone marrow-derived macrophages (BMMs) and mouse calvarial pre-osteoblasts cells were purified and used as precursor cells for osteoclasts and osteoblasts, respectively. The PBM effects on single-cell culture of osteoclasts or osteoblasts as well as co-culture were examined by 1.2 J/cm2 low-level Ga-Al-As laser (λ = 808 ± 3 nm, 80 mW, and 80 mA; spot size, 1cm2; NDLux, Seoul, Korea) irradiation for 30 s at daily intervals throughout culture period. At the end of culture, the osteoclast differentiation and osteoblast differentiation were assessed by TRAP staining and ALP staining, respectively. The expressions of osteoclastogenic cytokines were evaluated by RT-PCR and Western blot analyses. Under the single-cell culture condition, PBM enhanced osteoblast differentiation but had minor effects on osteoclast differentiation. However, in the co-culture condition, its osteoblastogenic effect was maintained, and osteoclast differentiation was substantially reduced. Subsequent RT-PCR analyses and western blot results revealed marked reduction in receptor activator of NF-κB ligand (RANKL) expression and elevation in osteoprotegerin (OPG) expression by PBM in co-cultured cells. More importantly, these alterations in RANKL/OPG levels were not observed under the single-cell culture conditions. Our results highlight the different effects of PBM on bone cells based on culture conditions. Further, our findings suggest the indirect anti-osteoclastogenic effect of PBM, which is accompanied by a decrease in RANKL expression and an increase in OPG expression.
- Published
- 2021
3. Medical Implementation of Microarray Technology
- Author
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Ji Un Kang
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0301 basic medicine ,cytogenetic analysis ,lcsh:R5-920 ,03 medical and health sciences ,030219 obstetrics & reproductive medicine ,030104 developmental biology ,0302 clinical medicine ,Chemistry ,comparative genomic hybridization ,microarray analysis ,lcsh:Medicine (General) ,fluorescence in situ hybridization ,Molecular biology - Abstract
Microarray technology represents a critical new advance in molecular cytogenetics. The de-velopment of this approach has provided fundamental insights into the molecular pathogenesis in clinical cytogenetics and has provided a clue to many unidentified or unexplained diseases. The approach allows a comprehensive investigation of thousands and millions of genomic loci simultaneously and enables the efficient detection of copy number alterations. The application of this technology has shown tremendous fluidity and complexity of the human genome, and has provided accurate diagnosis and appropriate clinical management in a timely and efficient manner for identifying genomic alterations. The clinical impact of the genomic alterations identified by microarrays is evolving into a diagnostic tool to identify high-risk patients better and predict patient outcomes from their genomic profiles. The transformation of conventional cytogenetics into an automated discipline will improve diagnostic yield significantly, leading to accurate diagnosis and genetic counseling. This article reviews cytogenetic technologies used to identify human chromosome alterations and highlights the potential utility of present and future genome microarray technology in the diagnosis.
- Published
- 2020
4. Self-assembled cell sheets composed of mesenchymal stem cells and gelatin nanofibers for the treatment of full-thickness wounds
- Author
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Hye Sung Kim, Oanh-Vu Pham-Nguyen, Ji Un Shin, and Hyuk Sang Yoo
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0303 health sciences ,food.ingredient ,Epidermis (botany) ,Chemistry ,Mesenchymal stem cell ,Nanofibers ,Biomedical Engineering ,Cell Differentiation ,Mesenchymal Stem Cells ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Bandages ,Gelatin ,Cell biology ,03 medical and health sciences ,Cytokeratin ,food ,Nanofiber ,General Materials Science ,Full thickness ,Stem cell ,0210 nano-technology ,Cell sheet ,030304 developmental biology - Abstract
Cell sheet engineering has attracted great attention because thin layers of tissue can be easily transplanted to defect sites. Wound-dressing materials are required to support fast re-epithelization, both with keratinocytes and fibroblasts, to enhance the prognosis and therapeutic outcomes. We prepared self-assembled cell sheets composed of adipocyte-derived stem cells (ADSCs) and surface-engineered nanofibrils (NFs). NFs were surface-engineered with multilayers of gelatin so that the cell sheets could spontaneously assemble within 3 days in cell culture plates. Dorsal wounds transplanted with the cell sheets exhibited higher wound-healing rates when a high concentration of gelatin was immobilized on the surfaces of the NFs. Histochemical staining revealed that those with gelatin-immobilized NFs showed a higher expression of cytokeratin and collagen in the re-epithelized epidermis. Keratinocytic differentiation of the epidermis was molecularly evidenced by the higher expression of keratinocyte-specific genes.
- Published
- 2020
5. Facile and cost-effective strategy for fabrication of polyamide 6 wrapped multi-walled carbon nanotube via anionic melt polymerization of ε-caprolactam
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Ji-un Jang, Jaewoo Kim, Myung Koo Kang, Byung Joo Kang, Hun Su Lee, Seong Hun Kim, Inwoog Hwang, and Seong Yun Kim
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chemistry.chemical_classification ,Nanocomposite ,Materials science ,General Chemical Engineering ,Composite number ,02 engineering and technology ,General Chemistry ,Polymer ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,law.invention ,Anionic addition polymerization ,chemistry ,Chemical engineering ,Polymerization ,law ,Polyamide ,Environmental Chemistry ,0210 nano-technology ,Dispersion (chemistry) - Abstract
There is a growing demand for the development of a melt process-based nanocomposite manufacturing process capable of minimizing the incorporation of expensive carbon nanotubes (CNTs) by inducing a uniform dispersion of multi-walled CNTs (MWNTs). In this study, we proposed a nanocomposite manufacturing process that includes both physical particle mixing using high-speed rotation and anionic polymerization of e-caprolactam (CL) to induce a uniform dispersion of MWNTs. MWNTs were uniformly dispersed by powder mixing and then wrapped with polyamide 6 polymers by in-situ polymerization of CL. The synergistic effect of the two sub-processes resulted in an enhanced dispersion of MWNTs and prevented aggregation of the MWNTs. The composites fabricated by the proposed process exhibited electrical conductivities of 4.49 × 10−5 S/m and 1.45 × 10 S/m at 1 wt% and 3 wt% MWNTs, respectively, indicating that by applying the proposed process it is possible to incorporate a smaller amount of MWNT to achieve electrical conductivities applicable for electrostatic discharge (ESD) (>1 X 10−5 S/m) and electromagnetic interference shielding effectiveness (EMI SE) (>10 S/m) applications. An ESD chip tray and EMI SE mobile phone case were fabricated using the prepared composite, and it was verified that the ESD and EMI SE performances can be realized.
- Published
- 2019
6. Overview of Cytogenetic Technologies
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Ji-Un Kang
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0301 basic medicine ,03 medical and health sciences ,030104 developmental biology ,Conventional cytogenetics ,Chemistry ,Molecular biology - Abstract
세포 유전학적 분석은 인간에서의 다양한 종류의 질환을 연구하고 진단하는데 매우 유용하게 사용되고 있다. 지난 수년 동안 세포 유전학적 분석을 통해 매우 의미 있는 결과를 얻을 수 있었으며, 현재 임상검사실에서 일반적인 검사로 확대되어 질병을 진단하고 결과를 평가하는데 매우 유용하게 사용 되고 있다. Microarray는 분자 세포 유전학적인 방법과 기존의 세포유전학적 방법이 융합된 검사방법으로 기존 검사 방법의 단점을 보완하여 유전 관련 질환을 진단하는데 매우 유용하게 사용되고 있다. 따라서 본 논문은 유전질환 진단에 있어 기존의 일반적인 세포유전학적 방법에서 마이크로어레이를 통한 분자세포유전학적 방법으로 어떻게 전환되어 왔는지, 유전 진단을 하는데 앞으로 이 검사방법들이 얼마나 의미 있게 사용될 것인지에 관하여 고찰하였다.
- Published
- 2018
7. Coaxial Hydro-Nanofibrils for Self-Assembly of Cell Sheets Producing Skin Bilayers
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Hye Sung Kim, Wei Mao, Hyuk Sang Yoo, Young Ju Son, Myun Koo Kang, and Ji Un Shin
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Thermogravimetric analysis ,Materials science ,food.ingredient ,Nanofibers ,02 engineering and technology ,010402 general chemistry ,Fibril ,01 natural sciences ,Gelatin ,Mice ,chemistry.chemical_compound ,food ,medicine ,Animals ,Humans ,General Materials Science ,Fibroblast ,Cell Proliferation ,Tissue Engineering ,Tissue Scaffolds ,Dermis ,Fibroblasts ,021001 nanoscience & nanotechnology ,Electrospinning ,0104 chemical sciences ,HaCaT ,medicine.anatomical_structure ,chemistry ,Chemical engineering ,Polycaprolactone ,NIH 3T3 Cells ,Self-assembly ,0210 nano-technology - Abstract
Bilayered cell sheets were fabricated with coaxial hydro-nanofibrils for three-dimensional (3D) cultivation in a biomimetic environment. Polycaprolactone (PCL) was electrospun and hydrolyzed to release fragmented nanofibrils (NF) in an alkaline condition. Methacrylated gelatin (GelMA) was adsorbed and phototethered on the surface of the fibrils to prepare coaxial NF composed of hydrophilic shells and hydrophobic cores. GelMA layers on the NF were characterized by X-ray photoemission spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The GelMA showed higher decoration level on NF compared to that on native gelatin. GelMA-decorated NF significantly enhanced cell proliferation rate and phenotypic expression of human dermal fibroblasts when spontaneous formation of cell sheets was observed for 7 days. HaCaT cells were layered on top of the fibroblast sheets and further cultivated in air-water interfaces to prepare bilayered skin sheets. After 21 days of incubation, the top layers of the bilayered sheets showed higher expression of pan-keratin, and the dermal cells showed higher proliferation in the GelMA-decorated NF.
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- 2018
8. Silver-Incorporated Nanocellulose Fibers for Antibacterial Hydrogels
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Hyuk Sang Yoo, Ji Un Shin, Sun-Young Lee, and Jaegyoung Gwon
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General Chemical Engineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Silver nanoparticle ,Article ,0104 chemical sciences ,Nanocellulose ,lcsh:Chemistry ,chemistry.chemical_compound ,Silver nitrate ,Adsorption ,lcsh:QD1-999 ,chemistry ,Chemical engineering ,Nanofiber ,Self-healing hydrogels ,Cellulose ,0210 nano-technology ,Antibacterial activity - Abstract
A free-standing, antibacterial hydrogel was fabricated using silver-nanoparticle-immobilized cellulose nanofibers (CNFs) and alginate. Surface hydroxyl groups of CNFs were oxidized to carboxylate groups using (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TCNF), followed by the treatment with silver nitrate solution for surface adsorption of silver ions. In situ reduction of silver ions to produce silver nanoparticles was performed for the silver-adsorbed CNFs. Electron microscopy, X-ray diffraction, and spectroscopic analysis revealed that higher amounts of silver nanoparticles were immobilized on the surface of TCNF than on the surface of native CNF. Silver-nanoparticle-immobilized TCNF was embedded in alginate gels and silver ions from the matrix were slowly released for 7 days. Silver-nanoparticle-loaded alginate gels showed comparable antibacterial activity to silver-ions-loaded alginate gels, although the former showed a significantly lower cytotoxicity against animal cells. Thus, the antibacterial gels can potentially be applied to various skin surfaces to prevent bacterial infection while minimizing skin damage.
- Published
- 2018
9. Preparation of highly conductive metal doped/substituted Li7P2S8Br(1-x)Ix type lithium superionic conductor for all-solid-state lithium battery applications
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Yuvaraj Subramanian, Sung Kang, Yoon-Cheol Ha, Rajesh Rajagopal, Yu Jin Jung, Ji-Un Cho, and Kwang Sun Ryu
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Materials science ,Ionic radius ,General Chemical Engineering ,Ionic bonding ,chemistry.chemical_element ,General Chemistry ,Electrolyte ,Electrochemistry ,Industrial and Manufacturing Engineering ,Lithium battery ,chemistry ,Chemical engineering ,Fast ion conductor ,Environmental Chemistry ,Ionic conductivity ,Lithium - Abstract
Sulfide-based lithium superionic conducting solid electrolytes for all-solid-state lithium batteries have received much attention due to their high safety, ionic conductivity, and compatibility. However, high-temperature treatment over a long time is needed to achieve high ionic conductivity. In this work, we have prepared the dual-halide-based Li7P2S8X type lithium superionic conductors by dry ball mill process and the high ionic conducting phase was achieved by low temperature (200℃) heat-treatment process. High ionic conducting halogen-halogen composition was arrived at through a series of optimization processes. Among the compositions tested, the Li7P2S8Br0.25I0.75 solid electrolyte exhibited a high ionic conductivity value of 6.16 mS cm−1, at room temperature. The ionic radius of the halogen element played an important role in the formation of the high ionic conducting phase. Further, the ionic conductivity of Li7P2S8I0.75Br0.25 solid electrolyte was improved by metal doping at P-site. The Sn-doped Li7P2S8I0.75Br0.25 solid electrolyte exhibited a high ionic conductivity value of 7.78 mS cm−1, at room temperature. The addition of large-sized Sn atoms extended the crystal lattice parameters and increased the Li-ions transport path. The partial substitution of Sn atoms at P-site was confirmed by NMR and Laser Raman analysis. The electrochemical stability of the prepared solid electrolyte was studied by cyclic voltammetry and DC charge-discharge analysis. The addition of a metal atom to the Li7P2S8Br0.25I0.75 solid electrolyte decreased the side reaction with the Li metals. Thus, low-temperature treated metal-doped Li7P2S8Br0.25I0.75 solid electrolytes are highly favourable for the fabrication of high-performance all-solid-state batteries. The fabricated all-solid-state battery using Sn doped Li7P2S8Br0.25I0.75 solid electrolyte exhibited the high specific capacity value of 170 mAh g−1 (0.1C), at room temperature.
- Published
- 2022
10. Surface-Initiated Atom Transfer Polymerized Anionic Corona on Gold Nanoparticles for Anti-Cancer Therapy
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Sol Lee, Ji Un Shin, Wei Mao, and Hyuk Sang Yoo
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Pharmaceutical Science ,lcsh:RS1-441 ,02 engineering and technology ,010402 general chemistry ,Methacrylate ,01 natural sciences ,Article ,Metal ,lcsh:Pharmacy and materia medica ,In vivo ,c-myc sirna ,chemistry.chemical_classification ,Chemistry ,Atom-transfer radical-polymerization ,surface-initiated atom transfer radical polymerization ,Transfection ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Polymerization ,Colloidal gold ,visual_art ,visual_art.visual_art_medium ,Biophysics ,0210 nano-technology ,gold nanoparticle ,anti-cancer therapy - Abstract
Surface initiated atom transfer radical polymerization (SI-ATRP) documented a simple but efficient technique to grow a dense polymer layer on any surface. Gold nanoparticles (AuNPs) give a broad surface to immobilize sulfhyryl group-containing initiators for SI-ATRP, in addition, AuNPs are the major nanoparticulate carriers for delivery of anti-cancer therapeutics, since they are biocompatible and bioinert. In this work, AuNPs with a disulfide initiator were polymerized with sulfoethyl methacrylate by SI-ATRP to decorate the particles with anionic corona, and branched polyethyeleneimine (PEI) and siRNA were sequentially layered onto the anionic corona of AuNP by electrostatic interaction. The in vitro anti-cancer effect confirmed that AuNP with anionic corona showed higher degrees of apoptosis as well as suppression of the oncogene expression in a siRNA dose-dependent manner. The in vivo study of tumor-bearing nude mice revealed that mice treated with c-Myc siRNA-incorporated AuNPs showed dramatically decreased tumor size in comparison to those with free siRNA for 4 weeks. Furthermore, histological examination and gene expression study revealed that the decorated AuNP significantly suppressed c-Myc expression. Thus, we envision that the layer-by-layer assembly on the anionic brushes can be potentially used to incorporate nucleic acids onto metallic particles with high transfection efficiency.
- Published
- 2020
11. Enhanced healing of rat calvarial defects with 3D printed calcium-deficient hydroxyapatite/collagen/bone morphogenetic protein 2 scaffolds
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Yuan Zhe Jin, Shi Huan Han, GeunHyung Kim, Jae Hyup Lee, Kyung Mee Lee, Hui suk Yun, and Ji Un Lee
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Scaffold ,3d printed ,Bone Regeneration ,Biomedical Engineering ,chemistry.chemical_element ,Bone Morphogenetic Protein 2 ,02 engineering and technology ,Calcium ,Bone morphogenetic protein 2 ,Biomaterials ,03 medical and health sciences ,0302 clinical medicine ,Gene expression ,Animals ,Bone formation ,Bone regeneration ,Pcr analysis ,Chemistry ,Skull ,030206 dentistry ,021001 nanoscience & nanotechnology ,Cell biology ,Rats ,Mechanics of Materials ,Printing, Three-Dimensional ,Collagen ,0210 nano-technology - Abstract
In this paper, we mainly to evaluate the newly formed bone using the Calcium deficient hydroxyapatite (CDHA)/collagen-based bio-ceramic scaffold as Bone Morphogenetic Protein-2 (BMP-2) carrier in rat calvarial critical-sized bone defect. In the real-time PCR analysis, the CDHA/collagen scaffold loaded rhBMP-2 group showed significantly enhanced results of bone-related gene expression (p 0.05). In the in vivo study, the micro-CT showed that the main bone formation parameters of percent bone volume and trabecular number of the two experiment groups (CDHA/Collagen (CDHA) group, BV/TV: 14.21 ± 3.20, Tb.N: 2.37 ± 0.50; CDHA/Collagen/rhBMP-2(BMP) group, BV/TV: 14.51 ± 3.12, Tb.N: 2.75 ± 0.65) were significantly higher than those of the control (Blank, BV/TV: 3.25 ± 1.25, Tb.N: 0.57 ± 0.20) group (p 0.05). Although there was no significant difference between the two experimental groups, the BMP group results were slightly higher than those of the CDHA group (p 0.05). Moreover, the histological results also supported the micro-CT results. The scaffold of CDHA/collagen seems to be a suitable bio-ceramic carrier loaded rhBMP-2, and appears to enhance new bone formation and bone regeneration in bone defect after implantation.
- Published
- 2019
12. Effect of polypropylene-grafted-maleic anhydride content on physical properties of carbon fiber reinforced polypropylene composites
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Seong Yun Kim, Ji-un Jang, Min Park, and Sang Jun Youn
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Polypropylene ,chemistry.chemical_compound ,Mechanical property ,Materials science ,chemistry ,Mechanics of Materials ,Materials Science (miscellaneous) ,Polypropylene composites ,Ceramics and Composites ,Maleic anhydride ,Composite material ,Electronic, Optical and Magnetic Materials - Abstract
Polypropylene-grafted-maleic anhydride (PP-g-MAH) is known as an excellent interface modifier that can improve the interface between carbon fiber (CF) and PP. In this study, the effect of PP-g-MAH content on the physical properties of PP composites containing long-fiber CFs was investigated. It was confirmed that PP-g-MAH acted as an interface modifier between the interface between CF and PP, and when an appropriate amount of 10 wt% was incorporated, the tensile strength, tensile modulus, Izod impact strength, and heat deflection temperature were improved by 110%, 50%, 86.7% and 12.7%, respectively. On the other hand, the blending effect of PP-g-MAH, which is a low molecular weight, was greater than the compatibilizing effect when the PP-g-MAH content was mixed above the appropriate content, thereby reducing the physical properties. Therefore, the content of PP-g-MAH as the interface modifier must be designed to be the optimum content considering the CF content to be mixed in order to optimize the physical properties of the composite material.
- Published
- 2020
13. Swarm intelligence integrated micromechanical model to investigate thermal conductivity of multi-walled carbon nanotube-embedded cyclic butylene terephthalate thermoplastic nanocomposites
- Author
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Min Wook Lee, Beomjoo Yang, Seong Yun Kim, Ji-un Jang, and Bezawit F. Haile
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chemistry.chemical_classification ,Nanocomposite ,Materials science ,Thermoplastic ,Waviness ,Particle swarm optimization ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Swarm intelligence ,0104 chemical sciences ,law.invention ,Thermal conductivity ,chemistry ,Mechanics of Materials ,law ,Ceramics and Composites ,Miniaturization ,Composite material ,0210 nano-technology - Abstract
With the recent demand for miniaturization and integration of electronic devices, there has been a growing interest in device malfunction due to high temperature. In this study, a experimental and theoretical study on the composites with improved thermal conductivity by dispersing multi-walled carbon nanotubes (MWCNTs) in the thermoplastic resin was carried out. A micromechanical model was derived based on the ensemble volume-averaging method and the modified Eshelby’s tensor reflecting the interface properties. The effects of the waviness, interface, and orientation of fillers on the thermal conductivity of composites were numerically analyzed. A computational intelligence-based particle swarm optimization (PSO) algorithm was adopted to the proposed model for optimizing the model constants. The thermal conductivity of the polymerized cyclic butylene terephthalate (pCBT)/MWCNT composites was experimentally measured according to the content of MWCNT. Finally, the experimentally measured data were utilized in the PSO to improve the predictive capability of the proposed model.
- Published
- 2020
14. Electrically and Thermally Conductive Carbon Fibre Fabric Reinforced Polymer Composites Based on Nanocarbons and an In-situ Polymerizable Cyclic Oligoester
- Author
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Seong Yun Kim, Myung-Seob Khil, Ji-un Jang, Hyeong Cheol Park, and Hun Su Lee
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Thermoplastic ,Materials science ,lcsh:Medicine ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,01 natural sciences ,Article ,law.invention ,Thermal conductivity ,Electrical resistivity and conductivity ,law ,Oligoester ,Composite material ,lcsh:Science ,Electrical conductor ,chemistry.chemical_classification ,Multidisciplinary ,lcsh:R ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,lcsh:Q ,0210 nano-technology ,Dispersion (chemistry) - Abstract
There is growing interest in carbon fibre fabric reinforced polymer (CFRP) composites based on a thermoplastic matrix, which is easy to rapidly produce, repair or recycle. To expand the applications of thermoplastic CFRP composites, we propose a process for fabricating conductive CFRP composites with improved electrical and thermal conductivities using an in-situ polymerizable and thermoplastic cyclic butylene terephthalate oligomer matrix, which can induce good impregnation of carbon fibres and a high dispersion of nanocarbon fillers. Under optimal processing conditions, the surface resistivity below the order of 10+10 Ω/sq, which can enable electrostatic powder painting application for automotive outer panels, can be induced with a low nanofiller content of 1 wt%. Furthermore, CFRP composites containing 20 wt% graphene nanoplatelets (GNPs) were found to exhibit an excellent thermal conductivity of 13.7 W/m·K. Incorporating multi-walled carbon nanotubes into CFRP composites is more advantageous for improving electrical conductivity, whereas incorporating GNPs is more beneficial for enhancing thermal conductivity. It is possible to fabricate the developed thermoplastic CFRP composites within 2 min. The proposed composites have sufficient potential for use in automotive outer panels, engine blocks and other mechanical components that require conductive characteristics.
- Published
- 2018
15. Thermal conductivity of polymer composites based on the length of multi-walled carbon nanotubes
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Ji-un Jang, Seong Yun Kim, Jaesang Yu, and Hyun Su Kim
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chemistry.chemical_classification ,Materials science ,Mechanical Engineering ,Isotropy ,Contact resistance ,Carbon nanotube ,Polymer ,Industrial and Manufacturing Engineering ,law.invention ,Thermal conductivity ,chemistry ,Mechanics of Materials ,law ,Thermal ,Ceramics and Composites ,Polymer composites ,Composite material ,Anisotropy - Abstract
The anisotropic development of thermal conductivity in polymer composites was evaluated by measuring the isotropic, in-plane and through-plane thermal conductivities of composites containing length-adjusted short and long multi-walled CNTs (MWCNTs). The thermal conductivities of the composites were relatively low irrespective of the MWCNT length due to their high contact resistance and high interfacial resistance to polymer resins, considering the high thermal conductivity of MWCNTs. The isotropic and in-plane thermal conductivities of long-MWCNT-based composites were higher than those of short-MWCNT-based ones and the trend can accurately be calculated using the modified Mori-Tanaka theory. The in-plane thermal conductivity of composites with 2 wt% long MWCNTs was increased to 1.27 W/m·K. The length of MWCNTs in polymer composites is an important physical factor in determining the anisotropic thermal conductivity and must be considered for theoretical simulations. The thermal conductivity of MWCNT polymer composites can be effectively controlled in the processing direction by adjusting the length of the MWCNT filler.
- Published
- 2015
16. Effects of long-chain fatty acids on in vitro rumen microbial population, dry matter degradability and methane production
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Shin Ja Lee, Da Som Oh, Ji Un Ok, Jung Hwa Lim, Sung Sill Lee, Su Kyoung Lee, and Do-Hyung Kim
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Rumen ,education.field_of_study ,Chemistry ,Population ,Ruminal fermentation ,Dry matter ,Food science ,Methane production ,Long chain fatty acid ,education ,Long chain ,In vitro - Published
- 2015
17. Effects of Mustard Seeds and Powder on In vitro Ruminal Fermentation Characteristics and Methane Production
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Sang-Suk Lee, Kang Yeon Lee, Keun Kyu Park, Che Ok Jeon, Ki Jun Han, Ji Un Ok, Ho Tae Ryu, Kyoung Hoon Kim, Young Kyoon Oh, Yong Joo Seol, and Youl Chang Baek
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chemistry.chemical_classification ,food.ingredient ,Ecology ,Veterinary (miscellaneous) ,Mustard seed ,Allyl isothiocyanate ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,In vitro ,Methane ,chemistry.chemical_compound ,Ammonia ,food ,Animal science ,Agronomy ,chemistry ,Ruminal fermentation ,Propionate ,Animal Science and Zoology ,Methane production ,Food Science - Abstract
Dept. of Life Science, Chung-Ang University, KoreaABSTRACTThe purpose of this study was to investigate the effects of mustard, which contains allyl isothiocyanate, on ruminal fermentation and methane emission in vitro. To this end, diluted ruminal fluid(30ml) was incubated anaerobically at 39for 6, 12, and 24h with or without seeds or powdered mustard. Either mustard seed or powdered mustard was weighed and serially(0, 3.33, 5.00, 6.67, and 8.33g/L) mixed with ruminal fluid. Ammonia-N was increased(P
- Published
- 2013
18. Effects of Organic Acids on In Vitro Ruminal Fermentation Characteristics and Methane Emission
- Author
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Sung Sill Lee, Kyoung Hoon Kim, Shin Ja Lee, Eun Tae Kim, Ji Un Ok, Young Kyun Oh, Dong Uk Ha, and Sang-Suk Lee
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chemistry.chemical_classification ,Fumaric acid ,education.field_of_study ,animal structures ,Population ,food and beverages ,Biology ,Lactic acid ,chemistry.chemical_compound ,Rumen ,chemistry ,Biochemistry ,Succinic acid ,Propionate ,Fermentation ,Food science ,Malic acid ,education - Abstract
The objective of this study was to evaluate the in vitro effects of organic acids on methane emission and ruminal fermentation characteristics. We expected our methodology to result in a decrease of methanogens attached to the surface of rumen ciliate protozoa by addition of organic acids and in particular a decrease in methane emission. A fistulated Holstein cow of 650 kg body weight was used as a donor of rumen fluid. Organic acids (aspartic acid, fumaric acid, lactic acid, malic acid, and succinic acid) known to be propionate enhancers were added to an in vitro fermentation system and incubated with rumen fluid. The microbial population, including bacteria, protozoa, and fungi, were enumerated, and gas production, including methane and fermentation characteristics, were observed in vitro. Organic acids appeared to affect the rumen protozoan community. The rumen protozoal popuation decreased with the addition of aspartic acid, fumaric acid, lactic acid, and malic acid. In particular, the methane emission was reduced by addition of lactic acid. The concentration of propionate with all organic acids that were added appeared to be higher than that of the control at 12 h incubation. Addition of organic acids significantly affected rumen bacteria and microbial growth. The bacteria in added fumaric acid and malic acid was significantly higher (p
- Published
- 2012
19. Effects of Halogenated Compounds on in vitro Fermentation Characteristics in the Rumen and Methane Emissions
- Author
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Young Kyoon Oh, Gyo Moon Chu, Ji Un Ok, Sung Sill Lee, Hee Soon Hwang, Kyoung Hoon Kim, Sang-Suk Lee, and Shin Ja Lee
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chemistry.chemical_classification ,education.field_of_study ,animal structures ,Chloroform ,biology ,Population ,food and beverages ,Sulfonic acid ,biology.organism_classification ,Methane ,chemistry.chemical_compound ,Rumen ,Bromochloromethane ,chemistry ,Organic chemistry ,Fermentation ,Food science ,education ,Bacteria - Abstract
This study was conducted to evaluate effects of halogenated compounds on in vitro rumen fermentation characteristics and methane emissions. A fistulated Holstein cow of 650 kg body weight was used as a donor of rumen fluid. Five kinds of halogenated compounds (bromochloromethane (BCM), 2-bromoethane sulfonic acid (BES), 3-bromopropanesulfonic acid (BPS), chloroform (CLF), and pyromellitic diimide (PMDI) known to inhibit methyl-coenzyme M reductase activity were added to an in vitro fermentation incubated with rumen fluid. The microbial population including bacteria, protozoa, and fungi were enumerated, and gas production including methane and fermentation characteristics were observed in vitro. The pH values ranged from 6.25 to 6.72 in all the treatments, and these showed a similar level at 48 hr. The total gas production in the treatments showed a similar pattern with C at 48 hr, whereas methane production in the treatments was lower (p methane emissions by inhibiting methanogens in the rumen. Further studies on safety are needed.
- Published
- 2012
20. Effects of Synchronization of Energy and Nitrogen Release in the Rumen on the Starch Disappearance in the Gastrointestinal Tract and Growth Performance of Hanwoo Steers
- Author
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Kyoung Hoon Kim, Dong-Hua Li, Young-Kyoon Oh, Ok-Ji Un, Sang-Rak Lee, Seong Ho Choi, Yong-Joo Seol, Sang-Ho Moon, and Whan-Gook Nho
- Subjects
Ecology ,Starch ,Veterinary (miscellaneous) ,Soybean meal ,food and beverages ,Biology ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,Feed conversion ratio ,Rumen ,chemistry.chemical_compound ,chemistry ,Latin square ,Hanwoo ,Feedlot ,Animal Science and Zoology ,Food science ,Corn gluten meal ,Food Science - Abstract
The objectives of experiments were to compare directly the effects of synchrony of slowly fermented (corn and corn gluten meal; C-CGM) and of rapidly fermented ingredients (barley and soybean meal; B-SBM) in the rumen on starch disappearances in gastrointestinal tracts (Experiment 1) and growth performance (Experiment 2) of Hanwoo steers in the feedlot barn. In experiment 1, four Hanwoo steers (288 ± 21 kg) fitted with ruminal and "T" shaped duodenal cannula were placed in one pen with Calan gate and assigned randomly to a duplicate 2 × 2 Latin square design. In experiment 2, eight intact Hanwoo steers (311 ± 8 kg) were assigned randomly to one of two pens with Calan gate to evaluate the effect of the same diets as like in experiment 1 on growth performance. There were no differences in ruminal pH, ammonia and total VFA concentrations between treatments. Percentage of apparent ruminal starch disappearance was 33.3% unit lower (p
- Published
- 2011
21. Production and Determination of the Magnetic Properties of the Fe-36Ni Nanopowder via Electrical Explosion of Wire in Water and Compacted Alloy
- Author
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Kim Bk, Luong Huu Bac, Ji-Un Kim, Ho Jin Ryu, and Jung Sub Kim
- Subjects
Materials science ,Hydrogen ,Alloy ,Metallurgy ,Biomedical Engineering ,Spark plasma sintering ,chemistry.chemical_element ,Nanoparticle ,Bioengineering ,General Chemistry ,engineering.material ,Condensed Matter Physics ,Hysteresis ,Chemical engineering ,Ferromagnetism ,chemistry ,Transmission electron microscopy ,engineering ,General Materials Science ,Solid solution - Abstract
Fe-36Ni alloy nanopowder was prepared via electrical explosion of wire in DI water. The nanopowder was reduced in hydrogen at 500 degrees C for 30 min. Spark plasma sintering at 800 and 1000 degrees C for 10 min was used to obtain bulk samples from the hydrogen-reduced nanopowder. The sintered samples were annealed at 500 degrees C for 2 h. X-ray diffraction was used to analyze the phases of the nanopowder and sintered samples. The results showed that the sintered samples were formed in gamma-(Fe-Ni) solid solution. The particles sizes and morphologies of the as-synthesized and hydrogen-reduced nanoparticles were observed via transmission electron microscopy. The morphologies of the as-synthesized nanoparticles had spherical core-shell structures. Core was gamma-(Fe-Ni) and the shell was FeO. The nanoparticles of the as-synthesized and hydrogen reduced samples were found to be nearly spherical in shape, with average diameters of 32 and 70 nm, respectively. The hysteresis loops of the as-synthesized nanopowder, hydrogen reduced nanopowder, and sintered samples revealed ferromagnetic characteristics.
- Published
- 2011
22. Effects of Saponin Contained Plant Extracts on Ruminal Fermentation Characteristics and Methane Production
- Author
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Che Ok Jeon, Yong Joo Seol, Youl Chang Baek, Kyoung Hoon Kim, Young Kyoon Oh, Kang Yeon Lee, Ji Un Ok, Sang Cheol Lee, Sung Sil Lee, Chang Weon Choi, and Sang-Suk Lee
- Subjects
chemistry.chemical_classification ,education.field_of_study ,Ecology ,Veterinary (miscellaneous) ,Microorganism ,Population ,Saponin ,food and beverages ,Biology ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,Incubation period ,Rumen ,Animal science ,Agronomy ,chemistry ,Propionate ,Animal Science and Zoology ,Fermentation ,education ,Incubation ,Food Science - Abstract
This study was conducted to evaluate the effects of saponin contained plant extracts on in vitro rumen fermentation characteristics and methane production. Ruminal fluid was collected from rumen cannulated Hanwoo steers fed rice straw and concentrate (5:5). Collected rumen fluids, corn starch and buffer including saponin contained plant extracts (ginseng, Ogapi, soapwort, tea plant and yucca; 0.5%/15 ml) were incubated at 39 for 24 h. All incubations were repeated five times. Rumen pH in all treatments was lower (p
- Published
- 2011
23. Determination of Maintenance Energy Requirements for Growing Hanwoo Steers
- Author
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Youl-Chang Baek, Sun-Sik Jang, Chang-Weon Choi, Sang-Cheol Lee, Ji-Un Ok, Yong-Joo Seol, Man-Kang Song, Kang-Yeon Lee, Sung-Sil Lee, Kyoung Hoon Kim, Young-Kyoon Oh, and Seong-Koo Hong
- Subjects
Energy loss ,Ecology ,Chemistry ,Veterinary (miscellaneous) ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,Energy requirement ,Rumen ,Animal science ,Latin square ,Hanwoo ,Animal Science and Zoology ,Dry matter ,Methane production ,Feces ,Food Science - Abstract
Present experiment was carried out to determine maintenance energy requirements for growing Hanwoo steers. Six Hanwoo steers (BW = kg) were used in two 3 3 latin square design with three different energy intake levels; TDN 1.70 kg (Low), 2.05 kg (Medium), 2.80 kg (High), respectively, based on the Korean Feeding Standards. Each period lasted 18 days including a 14-day adaptation and a 4-day measuring period. The steers were in the head hood chamber system (one cattle per chamber) during each measuring time to measure heat and methane production for 1 day. Dry matter intake was 2,058, 3,256 and 3,881 g/day for Low, Medium and High TDN, respectively. Increase in energy intake did not affect digestibilities of dry matter, crude protein, crude fiber, crude fat, NDF, ADF and nitrogen-free extract. Gross energy intake averaged 180.21, 292.74 and 337.15 kcal/ for Low, Medium and High TDN, respectively. Energy loss was 28.7% in feces and 2.1% in urine of gross energy intake. Further, energy loss from methane produced during rumen fermentation was 6~8.3%, while body heat loss averaged 34~60%. Intercept of regression equation between ME intake and retained energy indicated that the energy requirement was 109.84 kcal ME/.
- Published
- 2011
24. Preparation and Stability of Gold Colloid by Electrical Explosion of Wire in Various Media
- Author
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Jung Sub Kim, Ji-Un Kim, G. S. Yun, Luong Huu Bac, and Hye-Seon Choi
- Subjects
Polysorbate ,Materials science ,Biomedical Engineering ,Analytical chemistry ,Nanoparticle ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,Ascorbic acid ,Light scattering ,Gold Colloid ,chemistry.chemical_compound ,Colloid ,Pulmonary surfactant ,chemistry ,Transmission electron microscopy ,General Materials Science - Abstract
Gold colloids were prepared by electrical explosion of wire in various media: cold water (0 degrees C), room temperature water (25 degrees C), hot water (80 degrees C), 0.01 M polysorbate surfactant 20 (TW 20) solution, mixture of 0.01 M TW 20 and 0.01 M ascorbic acid. The size distribution of nanoparticles measured by transmission electron microscope was found to shift to a smaller size with a decrease of temperature and a presence of TW 20 surfactant. The multiple light scattering results showed that medium temperature and ambient medium of explosion process is much influence on the stability of colloid. The gold colloid prepared in cold water is unstable in comparison with one prepared in warm and hot water. The best stability of gold colloid obtained with explosion medium of TW 20 and ascorbic acid solution.
- Published
- 2011
25. Dye-sensitized solar cells based on electrospun polymer blends as electrolytes
- Author
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Mi-Ra Kim, Sung-Il Jang, Ji-Un Kim, Jung-Heon Kim, Sung-Hae Park, H. W. Choi, Won-Pil Hwang, Du-Hyun Won, Seong-Hoon Jeong, and Jin-Kook Lee
- Subjects
chemistry.chemical_classification ,Materials science ,Renewable Energy, Sustainability and the Environment ,Scanning electron microscope ,Polymer ,Electrospinning ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Dye-sensitized solar cell ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Nanofiber ,Polymer chemistry ,Ionic conductivity ,Polymer blend ,Polystyrene - Abstract
We prepared electrospun polymer nanofibers by the electrospinning method and investigated about their applications to dye-sensitized solar cells (DSSCs). Electrospun poly(vinylidenefluoride–co-hexafluoropropylene) (PVDF–HFP) and PVDF–HFP/polystyrene (PS) blend nanofibers were prepared and examined the uptake, the ionic conductivity, and the porosity by impedance measurement and Scanning Electron Microscope (SEM). The best results of Voc, Jsc, FF, and efficiency of the DSSC devices using the electrospun PVDF–HFP/PS(3:1) blend nanofibers were 0.76 V, 11.8 mA/cm2, 0.66, and 5.75% under AM 1.5.
- Published
- 2011
26. Thermal Management in Polymer Composites: A Review of Physical and Structural Parameters
- Author
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Jaewoo Kim, Seong Yun Kim, Ji-un Jang, Hyun Su Kim, Beomjoo Yang, Seong Hun Kim, Hyeseong Lee, and Jung Yong Chae
- Subjects
Materials science ,Composite number ,chemistry.chemical_element ,Aerogel ,02 engineering and technology ,Thermal management of electronic devices and systems ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Thermal conductivity ,chemistry ,Polymer composites ,General Materials Science ,Composite material ,0210 nano-technology ,Carbon - Published
- 2018
27. Effects of Dietary Synbiotics from Anaerobic Microflora on Growth Performance, Noxious Gas Emission and Fecal Pathogenic Bacteria Population in Weaning Pigs
- Author
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Shin Ja Lee, Ji Un Ok, Sung Sill Lee, Gyo Moon Chu, Jong Duk Kim, Ho Sik Jung, Nyeon Hak Shin, and In Ho Kim
- Subjects
education.field_of_study ,Synbiotics ,Population ,Tiamulin ,Oxytetracycline ,Biology ,Fecal coliform ,chemistry.chemical_compound ,chemistry ,medicine ,Weaning ,Animal Science and Zoology ,Dry matter ,Food science ,Lactose ,education ,Food Science ,medicine.drug - Abstract
Synbiotics is the term used for a mixture of probiotics (live microbial feed additives that beneficially affects the host animal) and prebiotics (non-digestible food ingredients that beneficially affect the organism). This study investigated the effect of probiotics from anaerobic microflora with prebiotics on growth performance, nutrient digestibility, noxious gas emission and fecal microbial population in weaning pigs. 150 pigs with an initial BW of 6.80±0.32 kg (20 d of age) were randomly assigned to 5 dietary treatments as follows: i) US, basal diet+0.15% antibiotics (0.05% oxytetracycline 200 and 0.10% tiamulin 38 g), ii) BS, basal diet+0.2% synbiotics (probiotics from bacteria), iii) YS, basal diet+0.2% synbiotics (probiotics from yeast), iv) MS, basal diet+0.2% synbiotics (probiotics from mold), v) CS, basal diet+0.2% synbiotics (from compounds of bacteria, yeast and mold). The probiotics were contained in 10 9 cfu/ml, 10 5 cfu/ml and 10 3 tfu/ml of bacteria, yeast and molds, respectively. The same prebiotics (mannan oligosaccharide, lactose, sodium acetate and ammonium citrate) was used for all the synbiotics. Pigs were housed individually for a 16-day experimental period. Growth performance showed no significant difference between antibiotic treatments and synbiotics-added treatments. The BS treatment showed higher (p
- Published
- 2009
28. Effect of electrolyte in electrospun poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers on dye-sensitized solar cells
- Author
-
Ji-Un Kim, Jin-Kook Lee, Won-Ki Lee, Hyong-Ju Choi, Sung-Hae Park, and Mi-Ra Kim
- Subjects
Photocurrent ,Materials science ,Renewable Energy, Sustainability and the Environment ,Concentration effect ,Electrolyte ,Electrospinning ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Dye-sensitized solar cell ,Chemical engineering ,chemistry ,Nanofiber ,Polymer chemistry ,Ionic conductivity ,Hexafluoropropylene - Abstract
We prepared poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers by the electrospinning method and applied to the polymer matrix in polymer electrolytes for dye-sensitized solar cells (DSSCs). The uptake, ionic conductivity, and porosity of the electrospun PVDF-HFP nanofiber films showed 653±50%, 4.53±1.3×10−3 S/cm, and 70±2.3%, respectively, regardless of the diameter and morphology of nanofibers. In addition, several DSSC devices using the electrospun PVDF-HFP nanofiber films as the polymer matrix were prepared to investigate the photovoltaic effect of iodine (I2) concentrations on DSSC devices. With an increase of I2 concentration in electrolyte solutions, the ionic conductivity increased, while the photocurrent density of DSSC devices decreased.
- Published
- 2009
29. Photovoltaic Properties of Dye-Sensitized Solar Cells using Metallophthalocyanines with Poly(ethylene glycol) Electrolytes
- Author
-
Young-Wook Jang, Ji-Un Kim, Bo-Hwa Jeong, Sung-Il Jang, Mi-Ra Kim, Kisuck Jung, Young-Geun Kim, and Jin-Kook Lee
- Subjects
Materials science ,Photovoltaic system ,Energy conversion efficiency ,General Chemistry ,Electrolyte ,Condensed Matter Physics ,Photochemistry ,Dye-sensitized solar cell ,Electron transfer ,chemistry.chemical_compound ,Adsorption ,Chemical engineering ,chemistry ,PEG ratio ,General Materials Science ,Ethylene glycol - Abstract
Dye-sensitized solar cells (DSSCs) were prepared with a poly(ethylene glycol) (PEG) electrolyte using various metallophthalocyanines (MPcs) as an additive. The DSSC device using MPcs has higher power conversion efficiency than that without MPcs, due to decrease of electron transfer distance by the interface adsorption between TiO2 film and PEG electrolyte. The best result on power conversion efficiency was 4.18% in DSSC device using InOHPc. The open-circuit voltage (Voc) was 0.70 V, the short-circuit current density (Jsc) was 10.20 mA/cm2, and the Fill Factor (FF) was 0.58. The addition of MPcs as an additive is useful to improve the performances of DSSC devices such as Voc, Jsc, and power conversion efficiency.
- Published
- 2008
30. Effects of Biologically Active Materials Prepared for Several Minerals and Plants on the Growth of Rumen Microbes
- Author
-
Ji-Un Ok, Sung-Whan Shin, Shin-Ja Lee, Sang Min Lee, Kyoung Hoon Kim, Sung Sill Lee, Yea-Hwang Moon, and Jung-Hwa Lim
- Subjects
education.field_of_study ,Conjugated linoleic acid ,Population ,food and beverages ,Bacterial growth ,Biology ,medicine.disease_cause ,Antimicrobial ,biology.organism_classification ,Microbiology ,chemistry.chemical_compound ,Rumen ,chemistry ,Listeria monocytogenes ,medicine ,Fermentation ,education ,Bacteria - Abstract
In order to know the effects of scoria, germanium, charcoal, ginger, stevia, and CLA(Conjugated Linoleic Acid) as biologically active materials on pathogenic microbes and rumen anaerobic microbes, the growth rate of pathogens (including Escherichia coli O157, Salmonella paratyphi, Listeria monocytogenes and Staphylococcus aureus) and in vitro lumen microbial growth, gas production, ammonia concentration, carboxymethyl-cellulase (CMCase) activity, and microbial populations were investigated. The growth of pathogenic microbes was inhibited by the supplement of 0.10% ginger. Ginger had powerful antimicrobial properties on all the pathogens used in this experiments. Additionally in the antibacterial assay by paper disc method, we could observe the clear zone of similar area with the positive control(antibiotics) for E. coli as applied with the 10% stevia or the 10% CLA only. The supplements of ginger, stevia and CLA in vitro rumen fermentation inhibited populations of rumen bacteria and protozoa. Particularly supplement of ginger resulted in remarkable reduction of the protozoa population, which means it might serve as a source inhibiting material of methane creation in the rumen.
- Published
- 2007
31. Preparation of Nanocrystalline Nickel Powders by Chemical Reduction in Nonaqueous Media
- Author
-
Seong-Soo Hong, Ji Un Im, Kwang Ho Kim, Hong Chae Park, Seong Soo Park, Gun Dae Lee, and Seong Yup Jun
- Subjects
Reduction (complexity) ,Nickel ,Materials science ,chemistry ,Mechanics of Materials ,Mechanical Engineering ,Metallurgy ,Chemical reduction ,Particle ,chemistry.chemical_element ,General Materials Science ,Nanocrystalline material - Published
- 2007
32. A Study for Microwave Enhanced Synthesis of NIR Absorbing Materials
- Author
-
Gun Dae Lee, Se Mo Son, Seong Soo Park, Chan Yong Yu, Ji Un Im, and Jeong Yi Yoo
- Subjects
Spectrum analyzer ,Materials science ,Mechanical Engineering ,Analytical chemistry ,chemistry.chemical_element ,Infrared spectroscopy ,Condensed Matter Physics ,Nickel ,chemistry ,Mechanics of Materials ,Yield (chemistry) ,Thermal ,General Materials Science ,Spectroscopy ,Microwave ,Benzoin compound ,Nuclear chemistry - Abstract
Symmetrically and unsymmerically substituted bis-dithiobenzil nickel complexes containing four substituted and unsubstituted methoxy groups were synthesized from a benzoin compound using phosphorous pentasulfide under the conventional thermal and microwave processing. The efficiency of microwave synthesis over the conventional thermal synthesis was illustrated by the yield of bisdithiobenzil nickel complex dyes. The samples were characterized by the means of elemental analyzer, 1HNMR, IR spectroscopy, Uv-vis spectroscopy and DSC.
- Published
- 2006
33. Change in Renal Function among HIV-Infected Koreans Receiving Tenofovir Disoproxil Fumarate-Backbone Antiretroviral Therapy: A 3-Year Follow-Up Study
- Author
-
Su Jin Jeong, Nam Su Ku, Kyoung Hwa Lee, June Myung Kim, Jun Yong Choi, Ji Un Lee, Sang Hoon Han, and Young Goo Song
- Subjects
Adult ,Male ,0301 basic medicine ,medicine.medical_specialty ,Tenofovir ,Anti-HIV Agents ,Urology ,Renal function ,HIV Infections ,Urine ,Kidney ,Kidney Function Tests ,urologic and male genital diseases ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Post-hoc analysis ,eGFR ,Humans ,Medicine ,030212 general & internal medicine ,renal toxicity ,cystatin-C ,Creatinine ,biology ,business.industry ,Follow up studies ,HIV ,anti-retroviral therapy ,General Medicine ,030112 virology ,Antiretroviral therapy ,Virology ,tenofovir ,Diet ,Infectious Diseases ,Kidney Tubules ,chemistry ,Cystatin C ,HIV-1 ,biology.protein ,Original Article ,Female ,business ,Follow-Up Studies ,medicine.drug - Abstract
Purpose Tenofovir disoproxil fumarate (TDF) is commonly prescribed as a fixed-dose, co-formulated antiretroviral drug for HIV-1 infection. The major concern of long-term TDF use is renal dysfunction. However, little is known about the long-term patterns of changes in renal function in HIV-infected Koreans receiving TDF. Materials and methods We prospectively followed 50 HIV-infected Koreans, performing laboratory tests every 3 months during the first year and every 6 months for the next 2 years. Urine N-acetyl-β-D-glucosaminidase (NAG) and plasma cystatin-C were measured using samples collected in the first year. Data on renal function were retrospectively collected on HIV-infected patients receiving first-line TDF (n=40) and in antiretroviral therapy (ART)-naive patients (n=24) for 3 years. Renal function was evaluated as estimated glomerular filtration rate (eGFR) from serum creatinine [Modification of Diet in Renal Disease (MDRD)] and cystatin-C. Results The eGFR (cystatin-C) showed significant changes from 0 to 48 wks (p=0.002), with the lowest levels at 24 wks (84.3±18.8 mL/min vs. 90.3±22.5 mL/min, p=0.021 by post hoc test). Urine NAG levels did not differ at 0, 12, 24, and 48 wks, although eGFR (MDRD) significantly decreased from 0 (98.7±18.9 mL/min/1.73 m²) to 144 wks (89.0±14.7 mL/min/1.73 m²) (p=0.010). The first-line TDF group had significantly lower eGFR (MDRD) than the ART-naive group at 144 wks (89.7 mL/min/1.73 m² vs. 98.4 mL/min/1.73 m², p=0.036). Thirteen (26%) participants experienced a decrease in renal impairment of 10 mL/min/1.73 m² in eGFR (MDRD) at 144 wks. Conclusion These data suggest that clinically meaningful renal injury can develop in HIV-infected Koreans receiving long-term TDF.
- Published
- 2017
34. Effects of Catechins and Wheat Bran on the Beef Color in the LateFattening Period of Hanwoo Steers
- Author
-
Ji Un Ok, Eung Gi Kwon, Yong Joo Seol, Sung Sill Lee, Sun Sik Jang, Kyoung Hoon Kim, Keun Kyu Park, Do Hyung Kim, and Young Kyoon Oh
- Subjects
Meat Color ,Bran ,Chemistry ,Dietary supplement ,lcsh:Animal biochemistry ,Catechins ,Wheat Bran ,Hanwoo Steer ,food and beverages ,Article ,Blood iron ,chemistry.chemical_compound ,Metmyoglobin ,Myoglobin ,Hanwoo ,Animal Science and Zoology ,Dietary supplementation ,Food science ,Hemoglobin ,lcsh:Animal culture ,lcsh:QP501-801 ,Food Science ,lcsh:SF1-1100 - Abstract
This study was conducted to evaluate the effects of dietary supplementation of catechins and wheat bran on growth performance, carcass characteristics and meat color using forty-eight Hanwoo steers. Each steer was randomly assigned to one of four treatments. Treatments were as follows: control, catechins, wheat bran, and catechins+wheat bran (CW). At the end of the feeding trial, blood samples were collected for analysis of hemoglobin and iron concentration, and then steers were slaughtered at a commercial abattoir. Catechins, wheat bran, and CW had no effect on growth performance and carcass characteristics. Percentage of myoglobin in M. longissimus dorsi was not affected by treatments. Percentage of oxymyoglobin was increased (p
- Published
- 2012
35. Dye-Sensitized Solar Cells Based on Polymer Electrolytes
- Author
-
Sung-Hae Park, Mi-Ra Kim, Ji-Un Kim, and Jin-Kook Lee
- Subjects
chemistry.chemical_classification ,Dye-sensitized solar cell ,Auxiliary electrode ,Membrane ,Materials science ,Chemical engineering ,chemistry ,Energy conversion efficiency ,Regenerated cellulose ,Electrolyte ,Polymer ,Electrospinning - Abstract
Dye-sensitized solar cells (DSSCs) using organic liquid electrolytes have received significant attention because of their low production cost, simple structure and high power conversion efficiency [1-5]. Recently, the power conversion efficiencies of DSSCs using Ruthenium complex dyes, liquid electrolytes, and Pt counter electrode have reached 10.4 % (100 mW/cm2, AM 1.5) by Gratzel group [6]. However, the important drawback of DSSCs using liquid electrolyte is the less long-term stability due to the volatility of the electrolyte contained organic solvent. In the viewpoint for commercialize, durability is a crucial component. Then, gel electrolytes are being investigated to substitute the liquid electrolytes [7-10]. One way to make a gel electrolyte is to add organic or inorganic (or both) materials. In the past decades, many studies have been carried out on this kind of gel electrolyte, and great progress has been achieved [11-12]. The advantages of them include; limited internal shorting, leakage of electrolytes and non-combustible reaction products at the electrode surface existing in the gel polymer electrolytes [13-14]. However, because of their complicated preparing technology and poor mechanical strength, they cannot be used in commercial production [15-16]. To overcome this problem, the polymer membrane is soaked in an electrolyte solution that has been examined [17-19]. To prepare the polymer membrane for polymer electrolyte, a number of processing techniques such as drawing [20], template synthesis [21-22], phase separation [23], electrospinning [24], etc. have been used. Among of these, the electrospinning technology is a simple and low-cost method for making ultra-thin diameter fibers. This technique, invented in 1934, makes use of an electrical field that is applied across a polymer solution and a collector, to force a polymer solution jet out from a small hole [25]. When the diameters of polymer fiber materials are shrunk of micrometers to submicrons or nanometers, several amazing characteristics appear such as a very large surface area to volume ratio, flexibility in surface functionalities, and superior mechanical performance compared to any other known forms of this material [26]. In recent years, the electrospinning method has gained greater attention. A vastly greater number of synthetic and natural polymer solutions were prepared with electrospun fibers, such as poly(ethylene oxide) (PEO) in distilled water [27], polyurethane in N,N-dimethylformamide (DMF) [28], poly(e-caprolactone) (PCL) in acetone [29], PVDF in acetone/ N,N-dimethylacetamide (DMAc) (7:3 by weight) [30], and regenerated cellulose in 2:1(w/w) acetone/DMAc [31].
- Published
- 2011
36. Dye-sensitized solar cells using polymer electrolytes based on poly(vinylidene fluoride-hexafluoro propylene) nanofibers by electrospinning method
- Author
-
Sung-Hae Park, Won-Ki Lee, Ji-Un Kim, Mi-Ra Kim, Jin-Kook Lee, and Seong-Yeop Lee
- Subjects
chemistry.chemical_classification ,Materials science ,Open-circuit voltage ,Energy conversion efficiency ,Biomedical Engineering ,Bioengineering ,General Chemistry ,Polymer ,Condensed Matter Physics ,Electrospinning ,law.invention ,Dye-sensitized solar cell ,chemistry ,law ,Nanofiber ,Solar cell ,General Materials Science ,Composite material ,Short circuit - Abstract
The dye-sensitized solar cell (DSSC) devices using polymer electrolytes based on electrospun poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) nanofibers were fabricated and investigated the photovoltaic performances. The electrospun PVDF-HFP nanofibers were prepared by various parameters such as; polymer concentrations, applied voltages, and tip to collector distances (TCD) by the electrospinning method. The open circuit voltage (VOC), short circuit current (JSC), fill factor (FF), and overall power conversion efficiency (η) of DSSC devices using electrospun PVDF-HFP nanofibers were 0.7180–0.7420 V, 9.7200–10.8837 mA/cm2, 0.5610–0.6250, and 4.1700–5.0186%, respectively. When 15 wt% of polymer concentration, 14 kV of applied voltage, and 14 cm of TCD is applied to fabricate the PVDF-HFP nanofiber, the electrospun PVDF-HFP nanofiber should be the regular diameter of a nanofiber, the power conversion efficiency of the DSSC device reached 5.0186% as the best result.
- Published
- 2008
37. Dye-Senstitized Solar Cells based on poly(vinylidene fluoride-hexafluoro propylene)/LiClO4 nanofibers by electrospinning method
- Author
-
Mi-Ra Kim, Ji-Un Kim, Sung-Hae Park, H. W. Choi, and Jin-Kook Lee
- Subjects
chemistry.chemical_classification ,Photocurrent ,Dye-sensitized solar cell ,Materials science ,chemistry ,Chemical engineering ,Nanofiber ,Polymer chemistry ,Electrode ,Polymer ,Photovoltaic effect ,Electrolyte ,Electrospinning - Abstract
In this study, we fabricated the electrospun poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) /LiClO 4 nanofibers by electrospinning method and applied as polymer membrane on the Dye-Sensitized Solar Cells. We have prepared the DSSC devices, using Ruthenium dye as a photosensitizer, sandwiched with TiO 2 -deposited and Pt-coated electrode as two electrodes. To compare with the effect of LiClO 4 in PVDF-HFP nanofibers on photovoltaic performance, we prepared electrospun PVDF-HFP nanofibers without LiClO 4 . Photovoltaic characteristics were measured by using Solar Simulator with a black mask under AM 1.5. The V oc of the DSSC device was 0.773 V, the J sc was 9.77 mA/cm2, and the overall power conversion efficiency achieved up to 4.19 %. The photovoltaic performances of the DSSC device using electrospun PVDF-HFP nanofibers without LiClO 4 were lower than that of device using electrospun PVDF-HFP/LiClO 4 nanofibers. To investigate the photovoltaic effect of different LiClO 4 concentrations in electrolyte solutions, the electrospun PVDF-HFP nanofibers without LiClO 4 were soaked into the electrolyte solution with different LiClO 4 concentrations. An increase of concentration of LiClO 4 in electrolyte solution results in a decrease of photocurrent and efficiency due to the desorption of dyes by LiClO 4 .
- Published
- 2008
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