Young-Ok Kim's research while affiliated with Korea Institute of Energy Research and other places

Fully equipped with superconducting magnets, KSTAR has successfully conducted experimental campaigns for 15 years since 2008. The operating environment of KSTAR has become challenging due to long pulse durations, high temperatures, and large plasma currents. The 16 TF coils and 7 pairs of PF coils experience substantial electromagnetic forces during plasma discharge, given the high current and magnetic field, and the TF coil structure bears these loads. Strain gauges were installed to monitor the stresses in TF structures during cool-down and operation. This study involves electromagnetic and structural analyses. The finite element analysis model was developed, considering the strain gauge mounting positions and orientations, modified materials, and the as-built design. The structural behaviors observed during campaigns are compared with the analytical results.

High-performance long-pulse plasma operation is essential for producing economically viable fusion energy in tokamak devices. To achieve such discharges in KSTAR, firstly, the rapid increase in the temperature of plasma facing components (PFCs) was mitigated. The temperature increase of the poloidal limiter, especially, was associated with beam-driven fast ion orbit loss and the discrepancy of the equilibrium reconstructed with heated magnetic probes of signal drift. The fast ions lost to the poloidal limiter were reduced by optimizing the plasma shape and the composition of neutral beam injection (NBI). This nonlinear signal drift was successfully reduced by a new thermal shielding protector on the magnetic probes. Secondly, a lower loop voltage approach was implemented to reduce a poloidal flux consumption rate. A plasma current of 400 kA and a line-averaged electron density of ~2.0×10 ¹⁹ m ⁻³ were chosen by considering the L-H power threshold, fast ion orbit loss, and beam shine-through power loss for low loop voltage in KSTAR. In addition, the application of electron cyclotron heating (ECH) also helped maintain the plasma with low loop voltage (~25 mV) by enhancing the NBI-driven current and achieving a high poloidal beta (β P ) state. KSTAR has achieved a long pulse (~90 s) operation with the high performance of β P ≤2.7, thermal energy confinement enhancement factor (H 98y2 )~1.1, and fraction of non-inductive current ( f NI )≤0.96. Still, gradual degradation of the plasma performance has been observed over time in the discharges. In one of the long-pulse discharges, β P reduced by ~18% over the time of ~8τ R (current relaxation time, τ R ~5 s) and ~1067τ E,th (thermal energy confinement time, τ E,th ~45 ms). The degradation may be closely associated with weak, yet growing, and persistent toroidal Alfvén eigenmodes and their effect on fast ion confinement.

Cardiopulmonary resuscitation (CPR) successfully restores systemic circulation approximately 50% of the time; however, many successfully restored patients have severe neurologic damage. In adults, the gray matter to white matter attenuation ratio (GWR) in brain computed tomography (CT) correlates with the neurologic outcome. However, in children, the clinical significance of GWR still remains unclear. The aim of this study was to evaluate the clinical characteristics of children who underwent CPR for cardiac arrest according to the survival and to demonstrate the differentiation of grey/white matter by Hounsfield units of brain CT and to characterize the attenuations of grey and white matters. Methods: This is a retrospective single-center study. We enrolled those who underwent brain CT within 24 h after return of spontaneous circulation (ROSC) from January 2005 to June 2018. Brain CTs were taken within 24 h of ROSC. We measured the attenuation of grey and white matter in Hounsfield units and calculated GWR. They were compared with healthy controls. Patients were analyzed as follows: survivors vs. non-survivors and better neurologic outcome vs. worse neurologic outcome. Results: Among 100 pediatric patients who had CPR, 56 met inclusion criteria. There were 24 patients who survived and 32 non-survivors. Our study revealed that the incidence of seizure, duration of CPR, and instances of hypothermia were significantly different between survivors and non-survivors. In both survivors and non-survivors, the attenuation of the caudate nucleus, putamen, GWR-basal ganglia, and average GWR were significantly different from controls. In regression analyses, the medial cortex and average GWR were the significant variables to predict survival, and the receiver operating curves revealed areas under curve of 0.733 and 0.666, respectively. Also, the medial cortex 1 was the only variable that predicted the neurologic outcome. Conclusions: There was some predictive survival value of GWR and medial cortex at the centrum semiovale level in early brain CT within 24 h after cardiac arrest. Although we could not find the predictive value of GWR in the neurologic outcome of pediatric patients, we found that the absolute attenuation of the medial cortex was low in patients with worse neurologic outcomes. Further prospective, multicenter studies are needed to determine the predictive value of GWR and the medial cortex.

A Gram-stain-negative, aerobic, non-spore-forming, non-motile and ovoid or rod-shaped bacterial strain, MYP5 T , was isolated from seawater in Jeju island of South Korea. MYP5 T grew optimally at 30–35 °C and in the presence of 2.0 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences revealed that MYP5 T fell within the clade enclosed by the type strains of species of the genus Alteromonas , clustering with the type strains of Alteromonas confluentis and Alteromonas halophila . MYP5 T exhibited the highest 16S rRNA gene sequence similarity value (98.0 %) to the type strain of A. confluentis and similarities of 95.1–97.9 % to the type strains of the other species of the genus Alteromonas . ANI and dDDH values of genomic sequences between MYP5 T and the type strains of 22 species of the genus Alteromonas were 66.8–70.5 % and 18.6–27.5 %, respectively. The DNA G+C content of MYP5 T , determined from the genome sequence, was 46.1 %. MYP5 T contained Q-8 as the predominant ubiquinone and C 18 : 1 ω7 c , summed feature 3 (C 16 : 1 ω7 c and/or C 16 : 1 ω6 c ), C 16 : 0 and 10-methyl C 17 : 0 as the major fatty acids. The major polar lipids of MYP5 T were phosphatidylethanolamine and phosphatidylglycerol. Distinguishing phenotypic properties, along with the phylogenetic and genetic distinctiveness, revealed that MYP5 T is separated from species of the genus Alteromonas . On the basis of the data presented, MYP5 T is considered to represent a novel species of the genus Alteromonas , for which the name Alteromonas ponticola sp. nov. is proposed. The type strain is MYP5 T (=KCTC 82144 T =NBRC 114354 T ).

The Quench Detection System (QDS) of the Korea Superconducting Tokamak Advanced Research (KSTAR) has been operated to prevent from overheating the superconducting coil system for 11 years. The QDS discriminates a normal voltage of ∼100 mV on NbTi or Nb3Sn cable-in-conduit conductors in the event of quench, while the Poloidal Field coils are applied with voltages of up to some kV by pulsed operation of the magnet power supply system. Three VME systems (VMEs) are used to compensate remaining induced voltage in the quench detection signals; however, products of the VMEs are probably discontinued on the global markets before the end of the KSTAR project. Accordingly a Backup Signal-processing System (BSS) is being developed and tested by mostly using generic and reliable commercial-off-the-shelf devices. The BSS is designed to replicate all the logical functions of the VMEs, and conducts quench detection by using FPGAs; whereas, the VMEs are using CPUs. Both the VMEs and the BSS simultaneously operate to detect quench, and quench alarms are voted by 1-out-of-2 logic to generate interlock signals in normal operation. A subset of the BSS integrated with the QDS has demonstrated expected performances in the KSTAR campaign 2018.

Primary cell culture is a sufficient method frequently used to study the cellular properties and mechanisms of isolated cells in a controlled environment. In this study, an embryonic cell line (FGBC8) derived from the blastula stages of embryos of olive flounder Paralichthys olivaceus was developed. Furthermore, conditions for optimal long-term maintenance of this primary embryonic cell culture were investigated. Morphologically, FGBC8 cells were composed primarily of epithelial-like cells. FGBC8 cells were subcultured for >160 passages over ~830 days. The doubling time of FGBC8 cells was 73.8 h, and the modal diploid chromosome number was 48. FGBC8 cells transfected with green fluorescence protein (GFP)-expression plasmid exhibited a strong signal 48 h after transfection. Consequently, we demonstrated that fish serum is a crucial supplement for the long-term survival and maintenance of comparable morphology in these primary embryonic cells. Our results can be used as a guide for primary embryonic cell cultures for other fish species and may be useful for cell biotechnological applications.

Hepcidin, an antimicrobial peptide produced by the liver, also controls the iron balance and regeneration in vertebrates. Two types of hepcidin (Hamp1 and Hamp2) have been found in the bodies of black rockfish (Sebastes schlegelii). The full-length cDNA of hepcidin was cloned to enable a study of the antibacterial roles of these two hepcidins (Hamp) in black rockfish. The antimicrobial function of recombinant hepcidins was tested both in vitro and in vivo by the synthesis in Escherichia coli of recombinant hepcidin (approximately 11 kDa) from black rockfish. The recombinant hepcidins inhibited the growth of two bacterial species, Streptococcus iniae FP5228 and Pseudomonas aeruginosa, at various concentrations, in vitro after 6 h post-incubation, respectively. During infection, the production of ferroportin was reduced, suggesting the preservation of iron to prevent microbial proliferation. In vivo administration of Hamp1, but not Hamp2, synthetic peptides induced a substantial reduction in the expression of ferroportin, suggesting that in black rockfish with two forms of hepcidin, ferroportin production is regulated by the iron-regulator Hamp1, and not by the dedicated antimicrobial Hamp2. The findings of this study suggest the various antimicrobial roles of these two types of hepcidin.

We isolated and purified an antimicrobial peptide (AMP) from the mantle of the hard-shelled mussel, Mytilus coruscus. The peptide was purified through C18 reversed-phase high-performance liquid chromatography, and displayed antibacterial activity. Total molecular mass of 11,182 Da was determined using matrix-assisted laser desorption ionization time-of-flight mass spectrophotometry. The N-terminal 23-amino acid sequence of its purified peak was obtained through Edman degradation, revealing 82% identity with myticusin-1 of M. coruscus. Complete sequence of the target peptide was determined through cDNA cloning and rapid amplification of cDNA ends. The complete sequence comprised 574 bp with a 387-bp open reading frame (ORF) encoding 24 amino acids of a signal peptide and 104 amino acids of a mature peptide, which was named myticusin-beta. Furthermore, we discovered two novel isoforms of myticusin-beta. We constructed and expressed recombinant myticusin-beta, which displayed antimicrobial activity against gram-positive (Bacillus cereus, Bacillus subtilis, Clostridium perfringens, Staphylococcus aureus, Streptococcus iniae, Streptococcus mutans) and gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Vibrio alginolyticus, Klebsiella pneumoniae). Purified recombinant myticusin-beta also showed anti-parasitic activity at various concentrations. A short AMP analog was designed and synthesized based on the sequence of myticusin-beta, with markedly improved antimicrobial activity. Expression of myticusin-beta was detected in the mantle at the highest level, followed by hemocytes. The results obtained in this work suggest that myticusin-beta is an immune-related AMP of M. coruscus and an effective alternative to antibiotics.