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Seyong Choi,Wooseok Lee,Jihyun Yun,Jeongseok Seo,Inja Lim 대한생리학회-대한약리학회 2008 The Korean Journal of Physiology & Pharmacology Vol.12 No.2
Cardiac fibroblasts constitute one of the largest cell populations in the heart, and contribute to structural, biochemical, mechanical and electrical properties of the myocardium. Nonetheless, their cardiac functions, especially electrophysiological properties, have often been disregarded in studies. Ca<sup>2+</sup>-activated K<sup>+</sup> (K<sub>Ca</sub>) channels can control Ca<sup>2+</sup> influx as well as a number of Ca<sup>2+</sup>-dependent physiological processes. We, therefore, attempted to identify and characterize K<sub>Ca</sub> channels in rat Cardiac fibroblasts. First, we showed that the cells cultured from the rat ventricle were cardiac fibroblasts by immunostaining for discoidin domain receptor 2 (DDR-2), a specific fibroblast marker. Secondly, we detected the expression of various K<sub>Ca</sub> channels by reverse transcription polymerase chain reaction (RT-PCR), and found all three family members of K<sub>Ca</sub> channels, including large conductance K<sub>Ca</sub> (BK-Ձ1- and -Ղ1∼4 subunits), intermediate conductance K<sub>Ca</sub> (IK), and small conductance K<sub>Ca</sub> (SK1∼4 subunits) channels. Thirdly, we recorded BK, IK, and SK channels by whole cell mode patch clamp technique using their specific blockers. Finally, we performed cell proliferation assay to evaluate the effects of the channels on cell proliferation, and found that the inhibition of IK channel increased the cell proliferation. These results showed the existence of BK, IK, and SK channels in rat ventricular fibroblasts and involvement of IK channel in cell proliferation.
The AC Loss Estimation of Bi-2223/Ag Superconductor Tapes in Polygonal Configuration
Seyong Choi,Wansoo Nah IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>In this paper, we have studied the electromagnetic phenomenon and AC losses of assembled high-T<SUB>c</SUB> superconductor (HTS) tapes using the finite element method (FEM) approach. The model cable is composed of several Bi-2223/Ag tapes with polygonal shape on the cylindrical former that was arranged in parallel along the conductor axis. The HTS tape usually shows complex material properties, which are described by the nonlinear resistivity and the anisotropy against the external magnetic flux density as well as its angle. The numerical calculation was carried out considering the field dependence of critical current density and index value, which accounts for the anisotropy of the Bi-2223/Ag tape. The calculated AC losses were compared with the experimental results and with the theoretical values. It was observed that the analytic formulae are not proper to predict the AC loss of the multi-stranded conductor that is presented here. The adjacent tape's effect of the conductor on the AC loss was also investigated and discussed.</P>
Seyong Choi,Jang-Hee Yoon,Mi-Sook Won,Byoung-Seob Lee,Jung-Woo Ok,Byoung Chul Kim,Jin Yong Park,Jung Ho Kim,Shi Xue Dou,Se-Hee Lee,Kiyoshi, T. Institute of Electrical and Electronics Engineers 2012 IEEE transactions on applied superconductivity Vol.22 No.3
<P>We propose two methods to predict the AC transport current losses of MgB<SUB>2</SUB> superconducting wires with respect to various operating currents (I<SUB>tr</SUB>) and temperatures (T). Firstly, the transport current loss was estimated by a numerical method (finite element analysis). In order to consider the highly nonlinear behavior of the superconducting properties according to magnetic flux density (B) at each temperature, the measured J<SUB>c</SUB> - B - T characteristics were used in the calculation. The numerical results were compared with these of conventional Norris theory and showed quite good coincidence. A second method to predict the transport current loss at various temperatures, which used a loss at a specific temperature and the critical current data, is suggested. We deduce a formula for the prediction of the loss by a simple analogy through normalization, which performs excellently. The comparison of the transport current loss values calculated using the two methods is addressed.</P>