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RISS 인기검색어
- 검색키워드
- 저자 : Hwang Youngsoo (검색결과 58 건)
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Self-powered deep brain stimulation via a flexible PIMNT energy harvester
Hwang, Geon-Tae,Kim, Youngsoo,Lee, Jeong-Ho,Oh, SeKwon,Jeong, Chang Kyu,Park, Dae Yong,Ryu, Jungho,Kwon, HyukSang,Lee, Sang-Goo,Joung, Boyoung,Kim, Daesoo,Lee, Keon Jae The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.9
<P>Deep brain stimulation (DBS) is widely used for neural prosthetics and brain-computer interfacing. Thus far <I>in vivo</I> implantation of a battery has been a prerequisite to supply the necessary power. Although flexible energy harvesters have recently emerged as alternatives to batteries, they generate insufficient energy for operating brain stimulation. Herein, we report a high performance flexible piezoelectric energy harvester by enabling self-powered DBS in mice. This device adopts an indium modified crystalline Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIMNT) thin film on a plastic substrate to transform tiny mechanical motions to electricity. With slight bending, it generates an extremely high current reaching 0.57 mA, which satisfies the high threshold current for real-time DBS of the motor cortex and thereby could efficiently induce forearm movements in mice. The PIMNT based flexible energy harvester could open a new avenue for future <I>in vivo</I> healthcare technology using self-powered biomedical devices.</P>
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Recombinant mussel adhesive protein Mgfp-5 as cell adhesion biomaterial
Hwang, Dong Soo,Gim, Youngsoo,Kang, Dong Gyun,Kim, Yeon Kyu,Cha, Hyung Joon Elsevier 2007 Journal of biotechnology Vol.127 No.4
<P><B>Abstract</B></P><P><I>Mytilus galloprovincialis</I> foot protein type-5 (Mgfp-5) is one of the mussel adhesive proteins that participate in adhesion with the substratum. We previously reported the production of recombinant Mgfp-5 in <I>Escherichia coli</I> and showed that the recombinant protein had superior adhesion abilities versus those of Cell-Tak, a commercially available mussel adhesive protein mixture. In the present work, we investigated the feasibility of using recombinant Mgfp-5 as a cell adhesion agent. Purified and tyrosinase-modified recombinant Mgfp-5 was used to adhere living anchorage-independent cells such as insect <I>Drosophila</I> S2 cells and human MOLT-4 cells onto glass slides. Our results revealed that these cell lines efficiently attached to recombinant Mgfp-5-coated glass surfaces, and that surface-immobilized S2 cells were viable and able to undergo cell division for up to 1 week. Cytochemical studies with 4′,6-diamidino-2-phenylindole (DAPI) staining of nuclei and immunofluorescence for secreted foreign human erythropoietin (hEPO) from recombinant S2 cells and quantitative comparative analyses of S2 cell binding ability with Cell-Tak and poly-<SMALL>L</SMALL>-lysine, the main cell adhesion agent, were performed to demonstrate successful usage of recombinant Mgfp-5 for cell biological applications. Collectively, these results indicate that recombinant Mgfp-5 may be a useful new cell adhesion biomaterial for anchorage-independent cells.</P>
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Hwang, Yu Jin,Han, Dohyun,Kim, Ki Yoon,Min, Sun-Joon,Kowall, Neil W.,Yang, Liu,Lee, Junghee,Kim, Youngsoo,Ryu, Hoon Oxford University Press 2014 Nucleic acids research Vol.42 No.3
<P>The remodeling of chromatin in the nucleolus is important for the control of ribosomal DNA (rDNA) transcription and ribosome biogenesis. Herein, we found that upstream binding factor (UBF) interacts with ESET, a histone H3K9 methyltransferase and is trimethylated at Lys (K) 232/254 by ESET. UBF trimethylation leads to nucleolar chromatin condensation and decreased rDNA transcriptional activity. UBF mutations at K232/254A and K232/254R restored rDNA transcriptional activity in response to ESET. Both ESET-ΔSET mutant and knockdown of ESET by short hairpin RNA reduced trimethylation of UBF and resulted in the restoration of rDNA transcription. Atomic force microscopy confirmed that UBF trimethylated by ESET modulates the plasticity of nucleolar chromatin. We further demonstrated that UBF trimethylation at K232/254 by ESET deregulates rDNA transcription in a cell model of Huntington’s disease. Together, our findings show that a novel epigenetic modification of UBF is linked to impaired rDNA transcription and nucleolar chromatin remodeling, which may play key roles in the pathogenesis of neurodegeneration.</P>
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Hwang, Joonsik,Park, Youngsoo,Kim, Kihyun,Lee, Jinwoo,Bae, Choongsik Elsevier 2017 Fuel Vol.197 No.-
<P><B>Abstract</B></P> <P>A series of diesel spray combustion tests was carried out in a constant volume combustion chamber (CVCC) to investigate the effect of multiple injection strategies on cold startability. The experiments were performed under a simulated low temperature cold start condition. In-chamber pressure analysis and high speed flame imaging were conducted to compare the effectiveness of each injection strategy on cold startability. Spray targeting visualization was also performed to examine the wall impingement of injected fuel. The diesel fuel was injected into the CVCC with an injection pressure of 35MPa. Multiple injection strategies with different amounts of pilot injection quantities were applied to improve the diesel combustion under simulated cold start ambient condition. The flame imaging and in-chamber pressure results showed that the multiple injection strategy provided better cold startability than the single injection condition. According to the pilot injection quantity, the peak of the flame luminosity and in-chamber pressure were gradually increased with larger pilot injection quantity cases. The peak of the variation rate of the in-chamber pressure with a multiple injection strategy was approximately 2 times higher than that of the single injection case. In terms of spray targeting imaging, the results indicated that the fuel impingement and flow to the piston crevice volume were increased with a larger amount of pilot2 injection. Therefore, the increment of the pilot1 injection quantity rather than the pilot2 injection quantity was suggested not only to improve cold startability, but also to reduce unburned hydrocarbon emissions under a cold start condition in a real engine.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lower peak of flame luminosity was observed under cold start condition. </LI> <LI> Cold startability was improved by applying pilot injections before main injection. </LI> <LI> Increase in pilot injection quantity was advantageous for better main combustion. </LI> <LI> Fuel flow toward crevice volume was detected with first pilot injection. </LI> </UL> </P>
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Effects of diesel fuel temperature on fuel flow and spray characteristics
Park, Youngsoo,Hwang, Joonsik,Bae, Choongsik,Kim, Kihyun,Lee, Jinwoo,Pyo, Soonchan Elsevier 2015 Fuel Vol.162 No.-
<P><B>Abstract</B></P> <P>The cold start issue has been a problem in diesel engines. Thus, in the present research, the diesel fuel flow and macroscopic spray characteristics over a wide fuel temperature range were investigated to provide valuable insights for solving the cold start problem. An injection system including a common-rail and a fuel supplier was designed to control the fuel temperature from 243K to 313K. For the fuel flow characteristics, the results showed that the injection quantity decreased by 50% as the fuel temperature decreased from 313K to 243K under the same energizing time. It was also confirmed that the real start of injection timing was retarded as the fuel temperature decreased. The reason is that increased fuel viscosity disturbed the injector needle motion and fuel flow in the nozzle. The spray test was performed under the simulated cold start condition using a constant-volume combustion chamber (CVCC). For the macroscopic spray characteristics, the liquid-phase fuel penetration increased and the spray angle decreased with cold fuel due to attenuated fuel evaporation process and interaction with ambient gas. These results could cause poor air–fuel mixing process under the cold starting.</P>
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A highly conducting graphene film with dual-side molecular n-doping.
Kim, Youngsoo,Park, Jaesung,Kang, Junmo,Yoo, Je Min,Choi, Kyoungjun,Kim, Eun Sun,Choi, Jae-Boong,Hwang, Chanyong,Novoselov, K S,Hong, Byung Hee RSC Pub 2014 Nanoscale Vol.6 No.16
<P>Doping is an efficient way to engineer the conductivity and the work function of graphene, which is, however, limited to wet-chemical doping or metal deposition particularly for n-doping, Here, we report a simple method of modulating the electrical conductivity of graphene by dual-side molecular n-doping with diethylenetriamine (DETA) on the top and amine-functionalized self-assembled monolayers (SAMs) at the bottom. The resulting charge carrier density of graphene is as high as -1.7 10(13) cm(-2), and the sheet resistance is as low as 86 39 ω sq(-1), which is believed to be the lowest sheet resistance of monolayer graphene reported so far. This facile dual-side n-doping strategy would be very useful to optimize the performance of various graphene-based electronic devices.</P>
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Poor People and Poor Health: Examining the Mediating Effect of Unmet Healthcare Needs in Korea
Kim, Youngsoo,Kim, Saerom,Jeong, Seungmin,Cho, Sang Guen,Hwang, Seung-sik The Korean Society for Preventive Medicine 2019 Journal of Preventive Medicine and Public Health Vol.52 No.1
Objectives: The purpose of this study was to estimate the mediating effect of subjective unmet healthcare needs on poor health. The mediating effect of unmet needs on health outcomes was estimated. Methods: Cross-sectional research method was used to analyze Korea Health Panel data from 2011 to 2015, investigating the mediating effect for each annual dataset and lagged dependent variables. Results: The magnitude of the effect of low income on poor health and the mediating effect of unmet needs were estimated using age, sex, education level, employment status, healthcare insurance status, disability, and chronic disease as control variables and self-rated health as the dependent variable. The mediating effect of unmet needs due to financial reasons was between 14.7% to 32.9% of the total marginal effect, and 7.2% to 18.7% in lagged model. Conclusions: The fixed-effect logit model demonstrated that the existence of unmet needs raised the likelihood of poor self-rated health. However, only a small proportion of the effects of low income on health was mediated by unmet needs, and the results varied annually. Further studies are necessary to search for ways to explain the varying results in the Korea Health Panel data, as well as to consider a time series analysis of the mediating effect. The results of this study present the clear implication that even though it is crucial to address the unmet needs, but it is not enough to tackle the income related health inequalities.
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