Sukjin Choi

Osteopontin might be involved in bone remodelling rather than in inflammation in ankylosing spondylitis

OBJECTIVES To determine whether osteopontin (OPN) is increased in patients with AS and to investigate its relationship to inflammatory disease activity and bone remodelling process. METHODS This cross-sectional study included 30 patients with AS and 23 age- and sex-matched healthy controls. We assessed clinical characteristics and laboratory parameters including the ESR, CRP, lipid profiles, the Bath AS disease activity index (BASDAI) and the Bath AS radiographic index (BASRI). To evaluate bone metabolism, we tested ALP, OCN and C-telopeptide of type I collagen (CTX-I). Plasma levels of OPN, TNF-alpha and IL-6 were measured by ELISA, and mRNA expression in peripheral blood mononuclear cells (PBMCs) was performed by RT-PCR. Changes in OPN level were also evaluated in eight patients after the treatment with a TNF-alpha blocker. RESULTS Patients with AS had significantly higher plasma OPN, TNF-alpha and IL-6 levels and more mRNA expression than healthy controls. Plasma OPN levels were correlated with serum ALP, OCN and CTX-I levels, but not with ESR, CRP, lipid profiles, BASDAI or BASRI. Treatment with a TNF-alpha blocker did not alter OPN levels, although it reduced the disease activity. CONCLUSIONS Patients with AS had higher levels of OPN compared with controls. The plasma OPN level was correlated with serum ALP, OCN and CTX-I levels, but not with disease activity in AS. OPN might be involved in bone remodelling rather than in inflammation in AS.

A Study on the No Insulation Winding Method of the HTS Coil

This paper reports a study on BSCCO and ReBCO HTS (high temperature superconducting) test coils, layer-wound and double-pancake, with and without turn-to-turn insulation. Over current tests were performed in a bath of liquid nitrogen to compare stabilities of the test coils at 77 K. Saturation of magnetic fields from the NI (no insulation) coils, both BSCCO and ReBCO, was observed owing to current bypassing through turn-to-turn contacts in local quenches at operating currents higher than their critical currents. In the NI ReBCO coils, global quenches occurred at operating currents higher than the coil critical currents and quench recoveries were observed during discharge of the coils. The experimental results, obtained to date, demonstrate that the NI winding method enables remarkable improvement of thermal stability of the HTS coils.

Serum leptin levels correlate with interleukin‐6 levels and disease activity in patients with ankylosing spondylitis

Objective: To determine whether serum leptin levels are elevated in men with ankylosing spondylitis (AS) and whether the levels correlate with serum cytokine profiles and disease activity of AS. Methods: Forty‐two male patients with newly diagnosed AS were enrolled. Their Bath AS Disease Activity Index (BASDAI), body mass index (BMI), and acute phase reactants, such as erythrocyte sedimentation rate (ESR) and C‐reactive protein (CRP) levels, were assessed. Serum leptin levels were determined using radioimmunoassay (RIA) and serum cytokine profiles, including tumour necrosis factor (TNF)‐α, interleukin (IL)‐6, and interferon (IFN)‐γ, were determined using enzyme‐linked immunosorbent assay (ELISA). These results were compared with those from 42 age‐matched healthy men. After a follow‐up period of 31.0±20.1 months, clinical and biochemical variables were reassessed in the men with AS. Results: At baseline, patients with AS had significantly elevated serum levels of leptin, leptin adjusted for BMI (leptin/BMI), TNFα, and IL‐6, but not IFN‐γ, as compared to the controls. Serum leptin/BMI levels correlated well with IL‐6 levels, and both leptin/BMI and IL‐6 levels correlated well with BASDAI and CRP levels in patients with AS. The changes in leptin/BMI and IL‐6 levels between the baseline and follow‐up measurements correlated well with one another (p<0.05) and both correlated well with the changes in BASDAI (p<0.05). Conclusion: Serum leptin/BMI levels were increased and significantly associated with IL‐6 levels and disease activity in men with AS, suggesting a possible role for leptin in the inflammatory reactions of AS.

Superconducting magnets for the RAON electron cyclotron resonance ion sourcea)

The RAON linear accelerator of Rare Isotope Science Project has been developed since 2011, and the superconducting magnet for ECRIS was designed. The RAON ECR ion source was considered as a 3rd generation source. The fully superconducting magnet has been designed for operating using 28 GHz radio frequency. The RAON ECRIS operates in a minimum B field configuration which means that a magnetic sextupole field for radial confinement is superimposed with a magnetic mirror field for axial confinement. The highest field strength reaches 3.5 T on axis and 2 T at the plasma chamber wall for operating frequency up to 28 GHz. In this paper, the design results are presented of optimized superconducting magnet consisting of four solenoids and sextupole. The prototype magnet for ECRIS was fabricated and tested to verify the feasibility of the design. On the basis of test results, a fully superconducting magnet will be fabricated and tested.

Reduction Effect on Magnetization Loss in the Stacked Conductor With Striated and Transposed YBCC Coated Conductor

Recently, it is proposed to make striations on the YBCO coated conductor and to transpose each other as one of the solutions to decrease the perpendicular magnetization loss. For large power application using HTS, the stacked conductor packing the YBCO coated conductors should be used because the current carrying capacity of a single conductor is limited. The stacked conductor has different AC loss characteristics from single conductor because the screening currents in the adjacent conductors affect the local magnetic field at the position of each conductor in the stacked conductors. In this paper, we research the effect by the stack, striation and transposition on magnetization loss of YBCO coated conductors in perpendicular magnetic field. To estimate the reduction effects of perpendicular magnetization loss, several short samples as the stacked conductor with striation and transposition are prepared and tested. We compare the measured results of the conductors with that of the single YBCO coated conductor to estimate the reduction effects.

Design and Tests of Prototype Hybrid Superconducting Fault Current Limiter With Fast Switch

This paper deals with design and operating tests of prototype hybrid superconducting fault current limiter (SFCL) which is series connected non-inductive solenoid resistive coil and asymmetric non-inductively wound coils. The role of resistive SFCL is for reducing the fault current in the first swing. Moreover, resistive SFCL can reduce a load of dielectric strength in hybrid SFCL. Two kinds of high temperature superconductor (HTS) wires were used to fabricate asymmetric HTS coil. These HTS wires had different quench characteristics such as different critical current and n-value. Unbalanced current distribution between two HTS wires in the asymmetric HTS coil during the fault should occur. Thus, the asymmetric HTS coil generates impedance and repulsive force from magnetic flux. The finite element method was performed to calculate maximum repulsive force. From experimental tests and FEM simulation results, proper combination of HTS wires and configuration of asymmetric HTS coil with fast switch were determined to increase maximum repulsive force. Also, the prototype hybrid SFCL with fast switch was fabricated and performed.

Evaluations on AC Electrical Characteristics of No-Insulation Coil for Power Devices

This paper deals with the ac electrical characteristics of high temperature superconducting pancake coils without turn-to-turn insulation (no-insulation coils). Several research groups have done studies of the electrical characteristics of no-insulation coils. However, most of the studies have been done with respect to the dc electrical characteristics, and studies with respect to the ac electrical characteristics are rare. In this paper, we evaluated the ac electrical characteristics, such as the fault current, recovery time, and ac loss of the no-insulation coil. The results can be expected to suggest useful data for the application of no-insulation coils in the area of power devices.

Design, Fabrication, and Operating Test of the Prototype HTS Electromagnet for EMS-Based Maglev

The prototype high-Tc superconducting electromagnet (HTS-EM) for high-speed EMS Maglev was successfully demonstrated in EMS system up to the vehicle running speed of 500 km/h. The EM was designed to interface with the existing propulsion system used in the German high-speed Maglev. The rating levitation force of the EM was designed to correspond to the weight of the EM at a 20 mm levitation gap. Electromagnetic forces were simulated and compared with the test results in order to verify the design feasibility of the HTS-EM. Operating tests revealed that the HTS-EM was fully operational in zero-power control mode. However, the operating current of the HTS coil was affected by the control current when the guideway disturbance occurred. The design feasibility and operability of the HTS-EM was verified in the study.

Characteristic Comparison for the Various Winding Methods of HTS Magnets

Recently various high temperature superconducting (HTS) conductors have been commercialized in the power applications. While a BSCCO becomes tape or wire, others coated conductors (CC) are tapes. An HTS magnet utilized with these conductors can be fabricated as a form of pancake winding or layer winding. In the case of HTS magnet using a thin and rectangular tape, the pancake winding method is satisfied in the practical cases because of its suitable features. However, one of the disadvantages of this winding method is increasing brands and splices. From this point of view, we propose a layer winding method using an HTS tape and fabricated HTS layer coils. To verify the feasibility of the proposed winding method, critical current and over-current tests are investigated in liquid nitrogen and the results are compared with those of pancake coils. In addition, operating characteristics on the condition of various winding tensions are analyzed.

Design of the plasma chamber and beam extraction system for SC ECRIS of RAON acceleratora)

The RAON accelerator is the heavy ion accelerator being built in Korea. It contains a 3rd generation SC ECRIS which uses 28 GHz/18 GHz microwave power to extract 12 puA uranium ion beams. A plasma chamber for that ECRIS is made of aluminum machined from bulk Al. That chamber contains cooling channels to remove dumped power and another access port for microwave introduction and plasma diagnostics. Beam extraction electrodes were designed considering the engineering issues and preliminary beam extraction analysis was done. That plasma chamber will be assembled with a cryostat, and beam extraction experiment will be done.