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Search Results: 1 - 10 of 25017 matches for " Chang Hwan Choi "
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Do we have enough evidence for expanding the indications of ESD for EGC?
Hang Lak Lee,Chang Hwan Choi,Dae Young Cheung
World Journal of Gastroenterology , 2011, DOI: 10.3748/wjg.v17.i21.2597
Abstract: Endoscopic submucosal dissection (ESD) is the most advanced and representative technique in the field of therapeutic endoscopy and has been used for the treatment of gastrointestinal neoplasms, including early gastric cancer. The major difference and advantage of ESD compared to existing endoscopic resection techniques, such as endoscopic mucosal resection (EMR) and polypectomy, are the width and depth of the resection. Newly developed cutting devices, distal attachable endoscopic accessories, and an advanced electrosurgical unit have helped to overcome the limitations of therapeutic endoscopy in terms of lesion size, location, presence of fibrotic scarring, and accompanying ulcers. As a result, the indications for ESD have been expanded from the classical indication for EMR and polypectomy, and there is now support for a further expansion of ESD indications. At present, the most critical factor to consider in the decision of whether to perform ESD is the probability of unexpected lymph node metastasis. The guidelines for ESD are continually being updated and debated. In this review, we discuss the strengths and weaknesses of the expanded guidelines, based on evidence found in the literature.
Enhancement of Tumor Regression by Coulomb Nanoradiator Effect in Proton Treatment of Iron-Oxide Nanoparticle-Loaded Orthotopic Rat Glioma Model: Implication of Novel Particle Induced Radiation Therapy  [PDF]
Seung-Jun Seo, Jae-Kun Jeon, Eun-Ju Jeong, Won-Seok Chang, Gi-Hwan Choi, Jong-Ki Kim
Journal of Cancer Therapy (JCT) , 2013, DOI: 10.4236/jct.2013.411A004
Abstract:

Background: Proton-impact metallic nanoparticles, inducing low-energy electrons emission and characteristic X-rays termed as Coulomb nanoradiator effect (CNR), are known to produce therapeutic enhancement in proton treatment on experimental tumors. The purpose of this pilot study was to investigate the effect of CNR-based dose enhancement on tumor growth inhibition in an iron-oxide nanoparticle (FeONP)-loaded orthotopic rat glioma model. Methods: Proton-induced CNR was exploited to treat glioma-bearing SD rat loaded with FeONP by either fully-absorbed single pristine Bragg peak (APBP) or spread-out Bragg peak (SOBP) 45-MeV proton beam. A selected number of rats were examined by MRI before and after treatment to obtain the size and position information for adjusting irradiation field. Tumor regression assay was performed by histological analysis of residual tumor in the sacrificed rats 7 days after treatment. The results of CNR-treated groups were compared with the proton alone control. Results: Intravenous injection of FeONP (300 mg/kg) elevated the tumor concentration of iron up to 37 μg of Fe/g tissue, with a tumor-to-normal ratio of 5, 24 hours after injection. The group receiving FeONP and proton beam showed 65% - 79% smaller tumor volume dose-dependently compared with the proton alone group. The rats receiving FeONP and controlled irradiation field by MR imaging demonstrated more than 95% -

Transanal excision of a malignant fibrous histiocytoma of anal canal: A case report and literature review
Beom Gyu Kim, In Taik Chang, Jun Seok Park, Yoo Shin Choi, Gi Hyeon Kim, Eon Sub Park, Chang Hwan Choi
World Journal of Gastroenterology , 2008,
Abstract: Malignant fibrous histiocytoma, which is composed of spindle-shaped cells arranged in a pleomorphic and storiform pattern, is rarely found in the colorectum. Although complete surgical excision remains the main stem of therapy, an optimal treatment strategy according to the stage has not been elucidated. We report a case of a 63-year-old woman with an ulcerative lesion in the anorectal junction and a final diagnosis of malignant fibrous histiocytoma. We introduced an access for transanal local excision and adjuvant radiotherapy because the patient refused abdominoperineal resection. No local recurrences or distant metastases were observed 15 mo after the operation. To our knowledge, this is the first case reported in the English literature of a malignant fibrous histiocytoma treated with the transanal local excision and adjuvant radiotherapy. This report showed that this approach is selectively reserved for early-stage malignant fibrous histiocytoma and for those patients who refuse radical surgery because of the risk in a permanent colostomy.
Synthesis of Hollow Conductive Polypyrrole Balls by the Functionalized Polystyrene as Template
Choo Hwan Chang,Pyung Soo Son,Jeong-Ah Yoon,Seong-Ho Choi
Journal of Nanomaterials , 2010, DOI: 10.1155/2010/168025
Abstract: We report the preparation of hollow spherical polypyrrole balls (HSPBs) by two different approaches. In the first approach, core-shell conductive balls, CSCBs, were prepared with poly(styrene) as core and polypyrrole (PPy) as shell by in situ polymerization of pyrrole in the presence of polystyrene (PS) latex particles. In the other approach, CSCBs were obtained by in situ copolymerization of pyrrole in the presence of PS(F) with hydrophilic groups like anhydride, boronic acid, carboxylic acid, or sulfonic acid, and then HSPBs were obtained by the removal of PS or PS(F) core from CSCBs. TEM images reveal the spherical morphology for HSPBs prepared from PS(F). The conductivity of CSCBs and HSPBs was in the range of 0.20–0.90 S/cm2.
Highly Productive Process Technologies of Cantilever type Microprobe Arrays for Wafer Level Chip Testing
Woo-Chang Choi,Jae-Hwan Lim,Jee-Youl Ryu
Transactions on Electrical and Electronic Materials , 2013, DOI: http://dx.doi.org/10.4313/teem.2013.14.2.63
Abstract: This paper describes the highly productive process technologies of microprobe arrays, which were used for a probecard to test a Dynamic Random Access Memory (DRAM) chip with fine pitch pads. Cantilever-type microprobearrays were fabricated using conventional micro-electro-mechanical system (MEMS) process technologies. Bondingmaterial, gold-tin (Au-Sn) paste, was used to bond the Ni-Co alloy microprobes to the ceramic space transformer.The electrical and mechanical characteristics of a probe card with fabricated microprobes were measured by aconventional probe card tester. A probe card assembled with the fabricated microprobes showed good x-y alignmentand planarity errors within ±5 μm and ±10 μm, respectively. In addition, the average leakage current and contactresistance were approximately 1.04 nA and 0.054 ohm, respectively. The proposed highly productive microprobes canbe applied to a MEMS probe card, to test a DRAM chip with fine pitch pads.
Characterization of ZnO Nanorods and SnO2-CuO Thin Film for CO Gas Sensing
Woo-Chang Choi,Sung-Eun Kim,Jae-Hwan Lim,Jee-Youl Ryu
Transactions on Electrical and Electronic Materials , 2012,
Abstract: In this study, ZnO nanorods and SnO2-CuO heterogeneous oxide were grown on membrane-type gas sensor platformsand the sensing characteristics for carbon monoxide (CO) were studied. Diaphragm-type gas sensor platforms withbuilt-in Pt micro-heaters were made using a conventional bulk micromachining method. ZnO nanorods were grownfrom ZnO seed layers using the hydrothermal method, and the average diameter and length of the nanorods wereadjusted by changing the concentration of the precursor. Thereafter, SnO2-CuO heterogeneous oxide thin films weregrown from evaporated Sn and Cu thin films. The average diameters of the ZnO nanorods obtained by changing theconcentration of the precursor were between 30 and 200 nm and the ZnO nanorods showed a sensitivity value of 21%at a working temperature of 350℃ and a carbon monoxide concentration of 100 ppm. The SnO2-CuO heterogeneousoxide thin films showed a sensitivity value of 18% at a working temperature of 200℃ and a carbon monoxideconcentration of 100 ppm.
Design and Synthesis of Cross-Linked Copolymer Membranes Based on Poly(benzoxazine) and Polybenzimidazole and Their Application to an Electrolyte Membrane for a High-Temperature PEM Fuel Cell
Seong-Woo Choi,Jung Ock Park,Chanho Pak,Kyoung Hwan Choi,Jong-Chan Lee,Hyuk Chang
Polymers , 2013, DOI: 10.3390/polym5010077
Abstract: Elevated-temperature (100~200 °C) polymer electrolyte membrane (PEM) fuel cells have many features, such as their high efficiency and simple system design, that make them ideal for residential micro-combined heat and power systems and as a power source for fuel cell electric vehicles. A proton-conducting solid-electrolyte membrane having high conductivity and durability at elevated temperatures is essential, and phosphoric-acid-containing polymeric material synthesized from cross-linked polybenzoxazine has demonstrated feasible characteristics. This paper reviews the design rules, synthesis schemes, and characteristics of this unique polymeric material. Additionally, a membrane electrode assembly (MEA) utilizing this polymer membrane is evaluated in terms of its power density and lifecycle by an in situ accelerated lifetime test. This paper also covers an in-depth discussion ranging from the polymer material design to the cell performance in consideration of commercialization requirements.
Stable Isolation of Phycocyanin from Spirulina platensis Associated with High-Pressure Extraction Process
Yong Chang Seo,Woo Seok Choi,Jong Ho Park,Jin Oh Park,Kyung-Hwan Jung,Hyeon Yong Lee
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms14011778
Abstract: A method for stably purifying a functional dye, phycocyanin from Spirulina platensis was developed by a hexane extraction process combined with high pressure. This was necessary because this dye is known to be very unstable during normal extraction processes. The purification yield of this method was estimated as 10.2%, whose value is 3%–5% higher than is the case from another conventional separation method using phosphate buffer. The isolated phycocyanin from this process also showed the highest purity of 0.909 based on absorbance of 2.104 at 280 nm and 1.912 at 620 nm. Two subunits of phycocyanin namely α-phycocyanin (18.4 kDa) and β-phycocyanin (21.3 kDa) were found to remain from the original mixtures after being extracted, based on SDS-PAGE analysis, clearly demonstrating that this process can stably extract phycocyanin and is not affected by extraction solvent, temperature, etc. The stability of the extracted phycocyanin was also confirmed by comparing its DPPH (α,α-diphenyl-β-picrylhydrazyl) scavenging activity, showing 83% removal of oxygen free radicals. This activity was about 15% higher than that of commercially available standard phycocyanin, which implies that the combined extraction method can yield relatively intact chromoprotein through absence of degradation. The results were achieved because the low temperature and high pressure extraction effectively disrupted the cell membrane of Spirulina platensis and degraded less the polypeptide subunits of phycocyanin (which is a temperature/pH-sensitive chromoprotein) as well as increasing the extraction yield.
Distributed and Parallel Big Textual Data Parsing for Social Sensor Network
Jung-Ho Um,Chang-Hoo Jeong,Sung-Pil Choi,Seungwoo Lee,Hwan-Min Kim,Hanmin Jung
International Journal of Distributed Sensor Networks , 2013, DOI: 10.1155/2013/525687
Abstract: Recently, due to the popularization of the smartphone and social network service (SNS), many SNS users write their opinions for social events. According to these social phenomena, social sensor network which analyzes social events by utilizing those users’ text data is proposed. Parsing is essential module to analyze user’s text contents because it gives the understanding of semantics by extracting the words and their classes from texts. However, parsing requires much time because it needs to analyze all context information from the users’ text. In addition, as users’ text data are generated and transferred in streaming, the required parsing time increases too. This situation occurs that it is hard to parse the text on the single machine. Therefore, to drastically enhance the parsing speed, we propose distributed and parallel parsing system on the MapReduce. It applies the legacy parser to the MapReduce through loose coupling. Also, to reduce communication overheads, the statistical model used by the parser is resided on local cache in each mapper. The experimental result shows that the speed of proposed system is 2–19 times better than that of the legacy parser. As a result, we prove that the proposed system is useful for parsing text data in social sensor network. 1. Introduction Currently, as a result of the development of smartphone device techniques and active use of the social network service (SNS), many people use SNS smartphone applications. In the United States, there are 30 million smartphone users in 2011 and had increased by million users per week in the last quarter of 2012 (http://tech.fortune.cnn.com/2012/03/07/u-s-smartphones-inching-toward-1-million-per-week/). In addition, Twitter, a representative SNS provider, has about 50 million cases of uploading per day and FaceBook, another provider, has about 60 million cases of uploading (http://allfacebook.com/twitter-facebook-status_b11613). Smartphone users post writings about their daily life or share major social events or issues using SNS such as Twitter, Facebook, U-tube, and flicker. Many studies have been made to find out social issues or to solve scientific problems through these smartphone users’ big text data [1–11]. For example, to detect radiation values generated by the japan’s Fukushima Daiichi nuclear disaster, crowd sourced real-time radiation maps are developed by providing detecting radiation information from the smart-phone users. Another example is constructing the citizen sensor network for the scientific discovery by offering volunteers’ location information with their
Characteristics of Mesenchymal Stem Cells Originating from the Bilateral Inferior Turbinate in Humans with Nasal Septal Deviation
Se Hwan Hwang, Sun Hwa Park, Jin Choi, Dong Chang Lee, Jeong Hoon Oh, Sung Won Kim, Jin Bae Kim
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100219
Abstract: Background and objectives Nasal septal deviation (NSD) is often associated with overgrowth of the unilateral inferior turbinate. In vivo and in vitro studies indicate that human mesenchymal stem cells (MSCs) are able to differentiate into multiple cell types, including osteoblasts. We tested the hypothesis that turbinate size affects human turbinate-derived MSC (hTMSCs) quantity, proliferation, and differentiation into osteogenic lineages, and that hypertrophic turbinates may predispose to NSD on the contralateral side. Subjects and Methods The hypertrophic and contralateral inferior turbinate tissues used in our study were obtained and cultured from the tissue discarded from 10 patients who underwent septoplasty and partial turbinectomy. After isolating the hTMSCs from both turbinates, the cells were enumerated using an automated cell counter. The expression of surface markers for MSCs over four passages was assessed by fluorescent-activated cell sorting analysis (FACS), and cell proliferation was assessed using a cell counting kit (CCK)-8 according to turbinate size. In addition, osteogenic differentiation of hTMSCs was identified using alkaline phosphatase (ALP) and alizarin red S staining, after which osteoblastic gene expression was evaluated. Results There was no significant difference in the number of hTMSCs. FACS analysis revealed that the hTMSCs were negative for CD14, CD19, CD34, and HLA-DR, and positive for CD29, CD73, and CD90, representing a characteristic MSC phenotype, with no significant difference between the two groups. The cellular proliferation and osteogenic differentiation potential of the hTMSCs were also not significantly different between the two groups. Conclusions We conclude that turbinate size does not affect the characterization, proliferation, and osteogenic differentiation potential of hTMSCs in vitro test, and therefore should not affect the clinical decision of whether to use autologous or allogenic hTMSCs. However, more experiments are required to definitively state the relationship of hTMSCs with turbinate size or the process NSD in humans.
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