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RISS 인기검색어
- 검색키워드
- 저자 : Jeonghun Nam (검색결과 65 건)
- 무료
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김남욱,구정훈,이은,최유경,정영철 大韓神經精神醫學會 2007 신경정신의학 Vol.46 No.5
Objectives : The relationship between substance dependence and poor decision making has received much attention inrecent years. This study aimed to test the hypothesis that alcohol dependent subjects would demonstrate a more perseverative decision-making pattem, during ambiguous situations. Methods : 15 alcohol dependent patients and 15 healthy normal controls performed a novel computerized decision-making task, which presented figures of coins. The subjects were instructed to guess whether the total number of coins was 'odd' or' even'. Besides these two response, one could select a third altemative - 'pass' - in case the chances were assumed to be low. Results : There was significant difference in performance between the two groups (F=4.339, P=0.008). The control groupgained 15.4±14.4 points, whereas the alcohol dependent group lost 0.6±5.3 points. The normal control group demonstrated a tendency to make more pass responses as the trials were repeated. In contrast, the alcohol dependent group didn't make use of the altemative, but kept challenging between 'odd' and 'even', although they sensed that the chances were low. Conclusion : The alcohol dependent patients demonstrated a more rigid and perseverative response pattem and showed deficits in making use of compromise altematives.
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Separation of platelets from whole blood using standing surface acoustic waves in a microchannel
Nam, Jeonghun,Lim, Hyunjung,Kim, Dookon,Shin, Sehyun Royal Society of Chemistry 2011 Lab on a chip Vol.11 No.19
<P>Platelet separation from blood is essential for biochemical analyses and clinical diagnosis. In this article, we propose a method to separate platelets from undiluted whole blood using standing surface acoustic waves (SSAWs) in a microfluidic device. A polydimethylsiloxane (PDMS) microfluidic channel was fabricated and integrated with interdigitated transducer (IDT) electrodes patterned on a piezoelectric substrate. To avoid shear-induced activation of platelets, the blood sample flow was hydrodynamically focused by introducing sheath flow from two side-inlets and pressure nodes were designed to locate at side walls. By means of flow cytometric analysis, the RBC clearance ratio from whole blood was found to be over 99% and the purity of platelets was close to 98%. Conclusively, the present technique using SSAWs can directly separate platelets from undiluted whole blood with higher purity than other methods.</P> <P>Graphic Abstract</P><P>We propose a method to separate platelets from undiluted whole blood using standing surface acoustic waves (SSAWs) in a microfluidic device. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1lc20346k'> </P>
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Nam, Jeonghun,Yoon, Jung,Kim, Jeeyong,Jang, Woong Sik,Lim, Chae Seung Elsevier 2019 Journal of chromatography A Vol.1595 No.-
<P><B>Abstract</B></P> <P>The removal of erythrocytes from whole blood is an essential step during sample preparations intended for biomedical analyses and clinical diagnoses. To address the limitations of present methods, such as centrifugation and chemical lysis, we propose a novel microfluidic device for erythrocyte removal with high-efficiency and leukocyte separation from bulk flows of highly concentrated erythrocytes using a viscoelastic non-Newtonian fluid. The proposed device is designed based on the principle of viscoelasticity-induced particle migration toward the center of the microchannel. In addition, we based the functionality of our device on a bio-inspired phenomenon known as margination according to which erythrocytes migrate to the axial center of blood vessels. Fluorescent particles (10 μm) were added to blood suspensions of various concentrations (hematocrit) of erythrocytes in viscoelastic polymer solutions. Optimal hematocrit and flow rate conditions were determined for erythrocyte removal and for the separation of 10 μm particles. We also demonstrated the capability of our device to separate leukocytes with high efficiency (˜94%) and with a high-enrichment factor (10-fold).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Continuous leukocyte separation from high-hematocrit blood sample is proposed. </LI> <LI> Effect of in vivo-margination and viscoelastic lateral migration is used. </LI> <LI> From the blood sample with 25% hematocrit, leukocytes were successfully separated. </LI> <LI> Our device could achieve 94% of separation efficiency and 10-fold enrichment. </LI> </UL> </P>
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Nam, Jeonghun,Lim, Hyunjung,Kim, Dookon,Jung, Hyunwook,Shin, Sehyun Royal Society of Chemistry 2012 Lab on a chip Vol.12 No.7
<P>Pure separation and sorting of microparticles from complex fluids are essential for biochemical analyses and clinical diagnostics. However, conventional techniques require highly complex and expensive labeling processes for high purity separation. In this study, we present a simple and label-free method for separating microparticles with high purity using the elasto-inertial characteristic of a non-Newtonian fluid in microchannel flow. At the inlet, particle-containing sample flow was pushed toward the side walls by introducing sheath fluid from the center inlet. Particles of 1 관m and 5 관m in diameter, which were suspended in viscoelastic fluid, were successfully separated in the outlet channels: larger particles were notably focused on the centerline of the channel at the outlet, while smaller particles continued flowing along the side walls with minimal lateral migration towards the centerline. The same technique was further applied to separate platelets from diluted whole blood. Through cytometric analysis, we obtained a purity of collected platelets of close to 99.9%. Conclusively, our microparticle separation technique using elasto-inertial forces in non-Newtonian fluid is an effective method for separating and collecting microparticles on the basis of size differences with high purity.</P>
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Lamb wave-based blood coagulation test
Nam, Jeonghun,Choi, Hyunjoo,Kim, Jae Young,Jang, Woongsik,Lim, Chae Seung Elsevier 2018 Sensors and actuators. B Chemical Vol.263 No.-
<P><B>Abstract</B></P> <P>Blood coagulation tests are a critical part in diagnosis of patients with bleeding disorders and cardiovascular diseases. However, most conventional blood coagulation tests require large and expensive instruments and skilled personnel. Here, we present a simple and low-cost approach to evaluate blood coagulation using Lamb wave-based device. To assess coagulation, we monitored the acoustic streaming of 5 μm fluorescent particles suspended in citrated plasma. Using a Lamb wave, citrated blood plasma and coagulation reagents can be mixed in a few seconds and the viscosity of the droplet increases due to blood coagulation. Then, the acoustic streaming of particles eventually stops, at which the “coagulation time” is defined. As a preliminary test, coagulation time was reduced with increasing calcium concentration from 0 to 25 mM. Prothrombin time results from the Lamb wave-based device were validated by comparing with those of commercial instruments with the correlation coefficient (R<SUP>2</SUP>) as 0.9432. Using the Lamb wave for blood coagulation test, the temperature can be controlled as 37 °C simultaneously by modulating experimental conditions. Our device enables lithography-free, simple and low-cost measurement of blood coagulation, which can be applied to clinical settings and developing countries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Using a Lamb wave device, acoustic streaming of fluorescent particles suspended in citrated plasma is induced in a droplet. </LI> <LI> The viscosity of the sample droplet increases due to blood coagulation, so that the acoustic streaming velocity decreases. </LI> <LI> The acoustic streaming of particles finally stops at the “coagulation time (CT)”. </LI> <LI> With increasing calcium concentration, CT decreases drastically due to improved blood coagulation. </LI> <LI> Prothrombin time measured by the Lamb wave device was highly correlated with that of commercial instrument. </LI> </UL> </P>
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Micromixing using a conductive liquid-based focused surface acoustic wave (CL-FSAW)
Nam, Jeonghun,Jang, Woong Sik,Lim, Chae Seung Elsevier 2018 Sensors and actuators. B, Chemical Vol.258 No.-
<P><B>Abstract</B></P> <P>Acoustic manipulation of fluids and particles has gained much attention in microfluidics, owing to its advantages of non-invasive manipulation and low power consumption. Microchannel mixing has been limited to diffusion-based mixing, because of low Reynolds number that has a low mixing efficiency. In this study, we firstly introduce a conductive liquid-based focused surface acoustic wave (CL-FSAW) device for mixing. Using the concentrated acoustic force of CL-FSAW, rapid and efficient mixing of deionized water and fluorescent particle suspension was demonstrated in a microfluidic channel. Effects of the applied voltage and the flow rate on the mixing efficiencies were investigated. As the flow rate decreased or the applied voltage increased, the mixing efficiency increased. At 21V, mixing efficiencies were higher than 90% at a flow rate lower than 120μLmin<SUP>−1</SUP>. In addition, our device was applied to silver nanoparticle synthesis at the optimal mixing condition (100μLmin<SUP>−1</SUP> and 21V).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Using the concentrated acoustic force of a conductive liquid-based focused surface acoustic wave (CL-FSAW) device, rapid and efficient mixing can be achieved. </LI> <LI> In the CL-FSAW mixer, high efficiency mixing performance can be achieved (efficiency ∼97%) at a flow rate of <I>Q</I> ≤80μLmin<SUP>−1</SUP> with an applied voltage of 21V. </LI> <LI> For further application, CL-FSAW mixer device was applied to continuous synthesis of monodispersed silver nanoparticles at <I>Q</I> =100μLmin<SUP>−1</SUP> and <I>V</I> =21V. </LI> </UL> </P>
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