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( Hee Yeon Kim ),( Jong Young Choi ),( Dong Goo Kim ),( Myoung Soo Kim ),( Soon Il Kim ),( Shin Hwang ),( Sung Gyu Lee ),( Kwang Woong Lee ),( Kyung Suk Suh ),( Young Seok Han ),( Dong Lak Choi ),( Se 대한간학회 2012 춘·추계 학술대회 (KASL) Vol.2012 No.-
Background: The outcome of hepatitis B virus (HBV) infection after liver transplantation (LT) was improved by hepatitis B immunoglobulin (HBIG) and nucles(t)ide analogue (NUA). However, HBV recurrence after LT is critical because the recurrence is occasionally accompanied by a progressive destruction of graft and poor survival. The aims of this study were to investigate the significance HBV recurrence and identity factors associated with HBV recurrence. Methods: From October 1999 to February 2011, a total of 2684 consecutive LT recipients who underwent HBV-associated LT were retrospectively enrolled from 7 transplantation centers in Korea. Results: Prophylaxis regimens were HBIG monotherapy (67.7%) or a combination of HBIG with NUA (22.3%). The recurrence rate of HBV was 6.1% (164 recipients) during mean follow-up duration of 10.9 years. The median time from transplantation to recurrence was 2.1 years (0.1-7.9 years). Of the 1,071 patients with hepatocellular carcinoma (HCC) prior to LT, 155 patients (14.5%) had HCC recurrence after transplantation, and 48 patients (31.0%) had HBV recurrence. Of the 48 patients with recurrence of both HBV and HCC, 25 patients (52.1%) experienced HBV recurrence after HCC recurrence. In the multivariate analysis, pretransplant HCC, pretransplant HBV DNA above 5.5 log copies/mL was independent clinical factors influencing HBV recurrence after LT. The mortality rate among the recipients with HBV recurrence was 34.1% (56 recipients). Mean overall survival was 6.4 years in the HBV-recurrence group and 9.9 years in the HBV-nonrecurrence group (p<0.001). HBV recurrence was not an independent prognostic factor for overall survival. HCC recurrence was the most important factor for overall survival. Conclusions: The overall outcome of LT in HBV-related liver disease was excellent with the current prophylaxis regimen Choon Hyuck David Kwon,8 Suk-Koo Lee8 Pretransplant HBV DNA and HCC were important factors for HBV recurrence. HBV recurrence after LT did not significantly influence on the overall survival without combining of HCC recurrence.
Fabrication and Test of a Cryocooler Directly Cooled NbTi Superconducting Magnet
Yeon Suk Choi,Dong Lak Kim,Hyung Suk Yang,Jae Hwi Kim IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>The cryocooler directly cooled low temperature superconducting magnet is designed, fabricated and tested at the Korea Basic Science Institute (KBSI) for the crystal growth application. The magnet has one solenoidal configuration with a copper former which has a 52 mm room temperature bore. A two-stage 4 K GM cryocooler with 1.5 W refrigeration power is employed to cool the magnet from room temperature to liquid helium temperature. A pair of the binary current lead, a series combination of a normal conductor in the high temperature section and an HTS conductor in the low temperature section, is used for this application. The paper presents the process of design, fabrication and charging test. Also, the performance of the conduction cooled superconducting magnet system is discussed with respect to the supplied current and contact resistance.</P>
Progress on the Development of Superconducting Magnet System for Cyclotron K120
Yeon Suk Choi,Dong Lak Kim,Hongming Tang,Hyung Suk Yang,Joon Sun Kang,Yu Seok Kim IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>The Korea Basic Science Institute (KBSI) has targeted a 3.1 T superconducting magnet system to be used in a K120 superconducting cyclotron as one of the next cyclotron for medical application in the Korea Institute of Radiological and Medical Sciences (KIRAMS). The main superconducting magnet should be designed to accelerate various ions for the magnetic bending limit up to 120 MeV. Several ancillary requirements such as background field, space restriction due to ion beam line, and cryostat structure need technical attention. The conceptual design activities of main superconducting magnet system are completed. A quarter-scaled prototype is designed and fabricated in order to confirm the feasibility of our design. The design and fabrication of prototype superconducting magnet system is described in this paper. Also, the detail cryogenic cooling and cryostat structure are presented.</P>
Conduction-Cooled Superconducting Magnet for Material Control Application
Yeon Suk Choi,Dong Lak Kim,Byoung Seob Lee,Hyung Suk Yang,Painter, T.A. IEEE 2009 IEEE transactions on applied superconductivity Vol.19 No.3
<P>The conduction-cooled superconducting magnet with operating current of 180 A is designed, fabricated, and tested for material control application. The superconducting magnet has the effective standard warm bore of 52 mm and the maximum central field of 3 Tesla. Since magnetic field gradient should be larger at the end rather than at the center of the magnet for material control, we developed design method to optimize magnet for this purpose. The safety of the superconducting magnet is evaluated, taking into account the electro-magnetic field, heat and structure, and the superconducting coil is successfully wound by the wet-winding method. The superconducting coil is installed in the cryostat maintaining high vacuum and cooled by a two-stage GM cryocooler. The performance of the conduction-cooled superconducting magnet is discussed with respect to the supplied current, Joule heating, and cooling medium.</P>
Design Considerations of Cryogenic Cooling System for High Field Magnets
Choi, Yeon-Suk,Kim, Dong-Lak,Lee, Byoung-Seob,Yang, Hyung-Suk,Yoo Jong-Shin,Painter Thomas A.,Miller John R. The Korean Society of Superconductivity and Cryoge 2006 한국초전도저온공학회논문지 Vol.8 No.4
Several crucial issues are discussed in the design of cryogenic cooling system for high field magnets. This study is mainly motivated by our ongoing program to develop a 21 T Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS). The magnets of this system will be built horizontally to accomplish the requirement of user friendliness and reliability, and the replenishment of cryogen will not be necessary by a closed-loop cooling concept. The initial cool-down and safety are basically considered in this paper. The effects of the helium II volume and the gap distance of the weight load relief valve (or safety valve) on the cool-down time and temperature rising during an off-normal state are discussed. The total amount of cryogenic cooling loads and the required helium flow rate during cool-down are also estimated by a relevant heat transfer analysis. The temperatures of cryogen-free radiation shield are finally determined from the refrigeration power of a cryocooler and the total cryogenic loads.
Progress on the Development of a 5 T HTS Insert Magnet for GHz Class NMR Applications
Yeon Suk Choi,Dong Lak Kim,Hahn, S Y IEEE 2011 IEEE transactions on applied superconductivity Vol.21 No.3
<P>The Korea Basic Science Institute (KBSI) has initiated the development of a 5 T HTS insert magnet system. The objective of this program is the design and fabrication of HTS insert magnet for GHz class LTS/HTS NMR applications. Compact and efficient HTS magnet system is designed to be inserted into 15 T conduction-cooled superconducting magnet with 100 mm room-temperature bore. In this paper, the status of the HTS insert magnet development in KBSI is presented. The design issues of the 5 T HTS insert magnet including 2G HTS conductor properties with additional reinforcement and insulation, coil configuration with supporting structures, magnetic winding and bending stress-strain, detect and activate protection, and spatial and temporal field performance are discussed. In addition, the design of cryostat for 5 T HTS insert magnet is presented.</P>
Intermediate Joint of Current Lead in Conduction-Cooled Superconducting Magnet System
Yeon Suk Choi,Myung Su Kim,Dong Lak Kim IEEE 2013 IEEE transactions on applied superconductivity Vol.23 No.3
<P>The semi-retractable current lead is composed of a normal metal element, conducting the current from room temperature to intermediate temperature, and a high-temperature superconducting element, conducting the current down to liquid helium temperature. The normal metal element is disengaged from the high-temperature superconducting element through the multicontact connector without disturbance to the insulating vacuum space and without requiring complete removal of the normal metal element. The current lead is applied into the conduction-cooled superconducting magnet system developed by ourselves. The intermediate joint with a lockable set point is thermally connected to the first-stage of a cryocooler and carries current through a strip of louvered material. The performance of current lead is investigated with respect to the electrical contact resistance during the magnet charging process. The effects of current level and operating temperature on the heat generation in the intermediate joint are also discussed.</P>