Polymorphisms of the MDR1 and MIF genes in children with nephrotic syndrome.

Choi, Hyun Jin,Cho, Hee Yeon,Ro, Han,Lee, So Hee,Han, Kyung Hee,Lee, Hyunkyung,Kang, Hee Gyung,Ha, Il Soo,Choi, Yong,Cheong, Hae Il Springer International 2011 Pediatric nephrology Vol.26 No.11

<P>Oral steroid treatment is the first line of therapy for childhood nephrotic syndrome (NS). Nonetheless, some patients are resistant to this treatment. Many efforts have been made to explain the differences in the response to steroid treatment in patients with NS based on the genetic background. We have investigated single nucleotide polymorphisms of the MDR1 [C1236T (rs1128503), G2677T/A (rs2032582), and C3435T (rs1045642)] and MIF (G-173C, rs755622) genes in 170 children with NS. Of these children, 69 (40.6%) were initial steroid non-responders, and 23 (13.5% of total) developed chronic kidney disease. Renal biopsy findings, which were available for 101 patients, showed that 35 patients had minimal change lesion and 66 had focal segmental glomerulosclerosis. The frequencies of the MDR1 1236 CC (18.8 vs 7.2%) or TC (53.5 vs 43.5%) genotype and C allele (45.5 vs 29.0%) were significantly higher in the initial steroid responders than in the non-responders. Analysis of MDR1 three-marker haplotypes revealed that the frequency of the TGC haplotype was significantly lower in the initial steroid responders than in the non-responders (15.8 vs 29.0%). There was no association between the MIF G-173C polymorphism and clinical parameters, renal histological findings, and steroid responsiveness. These data suggest that the initial steroid response in children with NS may be influenced by genetic variations in the MDR1 gene.</P>

Mössbauer studies of inter/deintercalation process features in cathode

Hyunkyung Choi,Chul Sung Kim 한국자기학회 2022 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2

Study on cathode materials using Mössbauer spectroscopy

Hyunkyung Choi,Chul Sung Kim 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1

Various energy storage technologies have been commercialized and used domestically, and technology development is actively underway. The fastest-growing lithium-ion battery in the Energy Storage System is lightweight, has no memory effect, and easily maintains it charge capacity. It is widely used in portable electronic devices and electric vehicles because it can save energy without loss for a long time because of a low natural discharge. A lithium-ion battery is composed of a cathode material, an anode material, an electrolyte, and a separator. Lithium ions, which exist in an ionic state, generate electricity by moving from the cathode to the anode during charging and from the anode to the cathode during discharging. These cathode materials are a reactant participating in an actual electrochemical reaction, and they are required to have an energy density, an output characteristic, increased lifetime characteristics, and improved stability. Therefore, the lithium-on activation capability of the cathode material determines the performance of the battery. In this presentation, the magnetic properties of iron-based cathode materials were analyzed X-ray diffraction and Mössbauer spectroscopy. The Mössbauer spectroscopy allowed us to determine the valence states of iron in the crystal structures of cathode and also to unveil the presence of different iron-containing phases. In addition, we present the changes in the structure and iron oxidation state accompanied with lithium extraction and insertion in cathode materials, and study magnetic hyperfine interaction with temperature.

Structural and magnetic properties of lithium cathode materials Li_xFe_1/3Co_1/3Ni_1/3PO₄ (x=0, 1)

Choi, Hyunkyung,Kim, Hyung Joon,Shim, In-Bo,Lee, In Kyu,Kim, Chul Sung Elsevier 2017 Materials research bulletin Vol.93 No.-

<P><B>Abstract</B></P> <P>LiFe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> and its fully deintercalated Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> compounds were prepared by the vacuum-sealed solid state reaction method, and chemical-oxidation process with reaction of LiFe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> and No<SUB>2</SUB>BF<SUB>4</SUB> in acetonitrile. The crystal structure of LiFe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> is orthorhombic with the space group of <I>P</I>nma, which is same as Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> during deintercalation. Temperature-dependent magnetization curves of Li<SUB>x</SUB>Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> exhibit the enhancement of antiferromagnetic ordering due to the valence transition of transition metal ions with the increase in the Néel temperature from 35K for x=0 to 51K for x=1. The room-temperature Mössbauer spectra shows the valence transition with the LiFe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> exhibiting Fe<SUP>2+</SUP> doublet whereas fully deintercalated Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> showing one Fe<SUP>3+</SUP> doublet induced by the lithium ion diffusion. Experimental determined effective moment of Li<SUB>x</SUB>Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> was found to be 5.63 <I>μ</I> <SUB>B</SUB> for x=0 and 6.95 <I>μ</I> <SUB>B</SUB> for x=1, which can be interpreted as incomplete absence of orbital contribution by crystal field around distorted MO<SUB>6</SUB> octahedron.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Li<SUB>x</SUB>Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> (x=0, 1) material were synthesized via a solid state reaction method. </LI> <LI> Chemical delithiaition was performed by using NO<SUB>2</SUB>BF<SUB>4</SUB> oxidizing agent. </LI> <LI> The magnetic Néel temperatures of Li<SUB>x</SUB>Fe<SUB>1/3</SUB>Co<SUB>1/3</SUB>Ni<SUB>1/3</SUB>PO<SUB>4</SUB> were determined to be 51 for x=0 and 35K for x=1. </LI> <LI> The valence state of Fe ion can be provided the understanding of the charge/discharge mechanism for lithium-ion battery. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Study on the hyperthermia and magnetic properties of MNPs using Mössbauer spectroscopy

Hyunkyung Choi,Chul Sung Kim 한국자기학회 2020 한국자기학회 학술연구발표회 논문개요집 Vol.30 No.1

Ficus deltoidea Extract Inhibits Enhancement of Inflammatory CytokinesInduced by UVB Irradiation in a Cultured Keratinocytes

Hyunkyung CHOI 한국생물공학회 2009 한국생물공학회 학술대회 Vol.2009 No.10

Magnetic property-based provenance investigation of Hokkaido (Japan) archaeological obsidian tools

Choi Hyunkyung,Uhm Young Rang,Lee Jaegi,Sun Gwang-Min 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.12

The obsidian obtained from Shirataki, Japan, was analyzed with a Mössbauer spectrometer. The Mössbauer spectra at 295 K were characterized by two sextets (magnetite-tet/oct sites), two ferrous iron doublets (olivine and pyroxene), and a ferric iron doublet (tentatively associated to the nano-oxide phase). The main phases of the Hokkaido obsidians are olivine, pyroxene, magnetite, and nano-oxide. The biotite found in Kyushu obsidian was absent in the Hokkaido obsidian. Instead, the Hokkaido obsidian consisted of nano-iron oxide. In obsidians, iron species are mostly hosted by divalent ions of olivine and pyroxene. Some Hokkaido obsidian showed the presence of hematite. The distribution and presence of these iron species indicates that they were formed diferently from the environments of Kyushu, Japan. This study further entailed a comparison of the magnetic behavior of the archaeological and geological obsidian by examining the magnetic parameters based on the Mössbauer spectroscopy, thus demonstrating its applicability in obsidian sourcing research.

Spectroscopic analysis study of excavated iron artifacts

Hyunkyung Choi,Jaegi Lee,Young Rang Uhm 한국자기학회 2023 한국자기학회 학술연구발표회 논문개요집 Vol.33 No.2

Mössbauer studies and inductive thermal properties of Mgx-doped maghemite nanoparticles

Choi Hyunkyung,김철성,Lee Young Bae 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.12

The Mgx-doped maghemite γ-Fe2O3 (x=0.05, 0.10, 0.15, and 0.20) were investigated, with the aim of enhancing the magnetic hyperthermia properties. We precisely tuned the magnetic and thermal properties of Mgx-doped γ-Fe2O3 prepared using a slightly modifed high-temperature thermal decomposition method. The analysis of X-ray difraction patterns confrmed the spinel phase, crystallite size, and lattice constant. Magnetization measurements performed on Mgx-doped γ-Fe2O3 revealed that the magnetization was maximum for the x=0.15 sample. Accordingly, this sample was exposed to plasma for 30 min. The thermal properties of Mgx-doped γ-Fe2O3 were studied with temperature rise dependent on magnetic hyperthermia measurements under an externally applied magnetic feld of 25 mT at 112 kHz. The change in magnetic properties before and after plasma treatment was investigated with Mössbauer spectroscopy and further analyzed with one sextet each for the tetrahedral A-site and octahedral B-site. The Fe ion state for each site was determined to be Fe3+ at all temperatures. It was confrmed that the hyperfne magnetic feld of the sample increased after plasma treatment.

Superparamagnetic Hyperfine Relaxation in Zn0.75Ni0.25Fe2O4

Choi Hyunkyung,Kim Hyung Joon 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.11

We studied Zn0.75Ni0.25Fe2O4 magnetic nanoparticles before and after plasma treatment by employing X-ray diffraction, magnetic measurements, hyperthermia measurements using the magneTherm device, and Mössbauer spectroscopy. The Mössbauer spectra of Zn0.75Ni0.25Fe2O4 were recorded at various temperatures from 4.2 to 295 K. The Mössbauer spectra for temperatures below the superparamagnetic transition temperature exhibited two sextets ascribed to tetrahedral and octahedral sites. Furthermore, the spectra demonstrated superparamagnetic behavior, as indicated by the doublet with zero hyperfine field at 295 K. The Mössbauer spectra exhibited line broadening with increasing temperature, indicating superparamagnetic relaxation. The temperature dependence of the anisotropy energy was calculated based on the relaxation frequency.