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Energetics of the Heart Model with the Ventricu1ar Assist Device
Chung, Chanil-Chung,Lee, Sang-Woo,Han, Dong-Chul,Min, Byoung-Goo The Korean Society of Medical and Biological Engin 1996 의공학회지 Vol.17 No.1
We investigated the energistics of the physiological heart model by comparing predictive indexes of the myocardial oxygen consumption (MOC), such as tension-time index (R), tension-time or force-time inteual (FTI), rate-pressure product (RPP), pressure-work index, and systolic pressure-volume area (PVA) when using the electro-hydraulic left ventricular device (LVAD). We developed the model of LVAD incorporated the closed-loop cardiovascular system with a baroreceptor which can control heart rate and time-varying elastance of left and right ventricles. On considering the benefit of the LVAD, the effects of various operation modes, especially timing of assistance, were evaluated using this coupled computer model. Overall results of the computer simulation shows that our LVAD can unload the ischemic (less contractile) heart by decreasing the MU and increasing coronary flow. Because the pump ejection at the end diastolic phase of the natural heart may increase the afterload of the left ventricle, the control scheme of our LVAD must prohibit ejecting at this time. Since the increment of coronary flow is proportional to the peak aortic pressure after ventricle contraction, the LVAD must eject immediately following the closure of the aortic valve to increase oxygen availability.
Combined Microchannel-Type Erythrocyte Deformability Test with Optical Tweezers: I. Basic Principles
이원구,한동철,Chanil Chung,윤호영,Hwa Joon Park,방현우,Joonmo Lee,Jun Keun Chang,Junha Park,Keunchang Cho 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.4
In this article, we report a novel combined microchannel-type erythrocyte deformability test with optical tweezers which can enhance the level of sensitivity with respect to the detection of cancerous diseases. To demonstrate the feasibility of the combined method, we introduce three major parameters, the transit velocity, a modified elongation index, and the shape recovery time of a single erythrocyte in a specifically confined region under different powers of an infrared laser. These parameters are geometrically determined and experimentally evaluated for a special blood-related disease, leukemia. The results support this method has a good detection sensitivity enough to pinpoint a minor difference in the deformability between individual erythrocytes. Furthermore, such a complementary combination of optical tweezers with microfluidic structures will be helpful for comprehensively understanding what significant effect the mechanical properties of erythrocytes have on the multiple chemical reactions inside a living erythrocyte.d
Asymmetric nozzle structure for particles converging into a highly confined region
Park, Junha,Chung, Seok,Yun, Hoyoung,Cho, Keunchang,Chung, Chanil,Han, Dong-Chul,Chang, Jun Keun Elsevier 2006 CURRENT APPLIED PHYSICS Vol.6 No.6
<P><B>Abstract</B></P><P>Asymmetric nozzle inlet was suggested for particles to converge into a highly confined region. The physical properties from the nano-scaled volumetric difference at nozzle inlet were investigated using computational fluid dynamics and particle motion measurement with fluorescence beads and erythrocytes. The asymmetric nozzle structure made particles converge efficiently without clogging at nozzle inlet. It could be used as a micro/nanofluidic unit for cell based assay in a microchip such as chip-based flow cytometer.</P>
이원구,Jun Keun Chang,Chanil Chung,한동철,윤호영,Hwa Joon Park,방현우,이준모,Junha Park,Keunchang Cho 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.4
Today’s optical trapping techniques have been frequently used in severe blood-disease-related studies using plastic microfluidic devices. Most fabrication methods provide several types of rectangular microchannels for these devices. However, most existing optical trapping models tend to reflect only a few geometric properties of these microchannels and only some morphological shapes of the targets effectively. In this article, a new model for the optical trapping efficiency of a biconcave red blood cell (RBC) flowing in a rectangular microchannel is presented. The hydrodynamic drag force is theoretically corrected using the concept of the sphericity index of the RBC. The effect of the channel geometry on the optical trapping efficiency is numerically simulated and compared with that of the existing model. Furthermore, an implication of this correction for clinical applications in a disposable plastic microfluidic device is discussed.cro
Surface tension-enhanced optical trapping for lateral close-packing
이원구,방현우,Hwa Joon Park,Keunchang Cho,Chanil Chung,한동철,Jun Keun Chang 한국물리학회 2006 Current Applied Physics Vol.6 No.1l
Here we present our initial study of a surface tension-enhanced optical trapping for lateral close-packing of dielectric objects. This is anovel approach to optically trap multiple micro-scale objects even with a lower intensity of the beam. Such lateral close-packing by indi-would be contributed to study cell-to-cell interactions and cell fusion dynamics of living cells in nano- and micro-uidic environments.
Yun, Hoyoung,Bang, Hyunwoo,Min, Junggi,Chung, Chanil,Chang, Jun Keun,Han, Dong-Chul Royal Society of Chemistry 2010 Lab on a chip Vol.10 No.23
<P>A portable flow cytometer has been recognized as an important tool for many clinical applications such as HIV/AIDS screening in developing countries and regions with limited medical facilities and resources. Conventional flow cytometers typically require multiple detectors for simultaneous identification of multiple subsets of immune cell. To minimize the number of detectors toward portable flow cytometry or to analyze multi-parametric cellular information with minimum number of detectors in conventional flow cytometers, we propose a versatile multiplexed cell-counting method using functional silica nanoparticles (SiNPs). FITC-doped SiNPs, which are 100 times brighter than the FITC molecules itself, were used as new intensity-based fluorescent dye complexes to simultaneously measure two subsets of leukocytes using a single detector. CD45<SUP>+</SUP>CD4<SUP>+</SUP> cells tagged with these FITC-doped SiNPs were 50 times brighter than CD45<SUP>+</SUP>CD4<SUP>−</SUP> cells tagged only with FITC. To make the overall system compact, a disposable microchip flow cytometer that does not require sheath flow was developed. Combining these dye-doped SiNPs based detection schemes and the sheathless microchip flow cytometer scheme, we successfully identified and counted two subsets of leukocytes simultaneously (R<SUP>2</SUP> = 0.876). These approaches can be the building blocks for a truly portable and disposable flow cytometer for various clinical cytometry applications.</P> <P>Graphic Abstract</P><P>A new labeling method using functional silica nanoparticles enables enumeration of multiple cell types with only one detector in a disposable sheathless microchip flow cytometer. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0lc00041h'> </P>