Study on the improved J_c(B) performance of polyacrylic acid-doped MgB₂ bulks

Hwang, S.M.,Lee, C.M.,Lee, S.M.,Sung, K.,Joo, J.,Lim, J.H.,Kang, W.N.,Kim, C.J. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.suppl1

We fabricated polyacrylic acid (PAA)-doped MgB<SUB>2</SUB> bulks by wet mixing and in situ reaction process and studied the relationships between the phase formation, lattice change, microstructure, and critical properties according to the PAA doping level. The PAA doping increased the MgO amount and grain boundary area but decreased the a-axis lattice constant and critical temperature (T<SUB>c</SUB>), which is indicative of the substitution of B sites by C in MgB<SUB>2</SUB>. Furthermore, the critical current density (J<SUB>c</SUB>) at high magnetic fields improved with the increasing PAA content to 5.99kA/cm<SUP>2</SUP> for the 7wt% PAA-doped sample, which was about 6-fold higher than that of the pure sample at 5K and 6.6T. This improvement was mainly attributed to the C substitution and the fine grain size due to PAA doping, suggesting that PAA is an effective dopant in improving J<SUB>c</SUB>(B) performance of MgB<SUB>2</SUB>.

O-free polyacrylonitrile doping to improve the J_c(B) and H_c2 of MgB₂ wires

Hwang, S.M.,Sung, K.,Choi, J.H.,Kim, W.,Joo, J.,Lim, J.H.,Kim, C.J.,Park, Y.S.,Kim, D.H. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

We selected polyacrylonitrile (PAN, -[C<SUB>3</SUB>H<SUB>3</SUB>N]-) as an O-free organic dopant and fabricated C-doped MgB<SUB>2</SUB> wires by in situ and powder-in-tube techniques. 0-5 wt.% PAN powders were uniformly mixed with B powder using a liquid mixing method. The precursor powders were mixed with Mg powder, filled into Fe tubes, and then drawn into wires. Sintering was performed at 900<SUP>o</SUP>C for 1h in a flowing Ar gas. The PAN doping decreased the critical temperature (T<SUB>c</SUB>) and a-axis lattice parameter, but significantly improved the critical current density (J<SUB>c</SUB>) in high fields, upper critical field (H<SUB>c2</SUB>), and irreversibility field (H<SUB>irr</SUB>) performances. These results are attributed to the replacement of B sites with C by the PAN doping. Furthermore, as expected, the MgO amount did not increase as the doping content increased. The J<SUB>c</SUB> of the PAN-doped MgB<SUB>2</SUB> wires was more than one order of magnitude higher than that of the undoped MgB<SUB>2</SUB> wire at 5K and 6.6T (1.46-3.82kA/cm<SUP>2</SUP> vs. 0.11kA/cm<SUP>2</SUP>).

Nm23-M5 mediates round and elongated spermatid survival by regulating GPX-5 levels

Choi, Y.J.,Cho, S.K.,Hwang, K.C.,Park, C.,kim, J.H.,Park, S.B.,Hwang, S.,Kim, J.H. North-Holland Pub ; Elsevier Science Ltd 2009 FEBS letters Vol.583 No.8

Nucleoside diphosphate (NDP) kinases are involved in numerous regulatory processes associated with proliferation, development, and differentiation. Previously, we cloned a new member of the NDPK family from mouse, Nm23-M5, which encodes a 211-amino acid protein and has 86% identity to the human Nm23-H5 [Hwang, K.C., Ok, D.W., Hong, J.C., Kim, M.O. and Kim, J.H. (2003) Cloning, sequencing, and characterization of the murine Nm23-M5 gene during mouse spermatogenesis and spermiogenesis. Biochem. Biophys. Res. Commun. 306, 198-207]. To better understand Nm23-M5 function, we generated transgenic mice with reduced Nm23-M5 levels in vivo using a short hairpin RNA (shRNA) knock-down system. Nm23-M5 expression was markedly reduced, as indicated by Northern and Western blot analysis. Nm23-M5 shRNA transgenic mice exhibited reduced numbers of haploid cells. Furthermore, the antioxidant enzyme glutathione peroxidase 5 (GPX-5) is regulated by Nm23-M5 at the level of both expression and activity. These results reveal that expression of Nm23-M5 plays a critical role in spermiogenesis by increasing the cellular levels of GPX-5 to eliminate reactive oxygen species.

Improvement of high-field J_c of MgB₂ wires by polymethyl-methacrylate doping

Park, G.C.,Hwang, S.M.,Lee, C.M.,Choi, J.H.,Joo, J.,Lim, J.H.,Kang, W.N.,Kim, C.J. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.suppl1

We applied polymethyl-methacrylate (PMMA) as a new doping material for MgB<SUB>2</SUB> and fabricated C-doped MgB<SUB>2</SUB> wires by in situ powder-in-tube (PIT) process. With increasing PMMA doping level, the transition temperature (T<SUB>c</SUB>) decreased and the MgO content increased, whereas the magnetic field dependence of the critical current density (J<SUB>c</SUB>) weakened. The MgB<SUB>2</SUB> wires doped with 3-10wt.% PMMA showed significantly higher J<SUB>c</SUB> by more than one order of magnitude than that of the undoped wire at 5K and 6.6T. These results confirmed the potential of PMMA as a promising material for the effective substitution of B by C in MgB<SUB>2</SUB>.

Fabrication of ex situ processed MgB₂ wires using nano carbon doped powder

Lee, C.M.,Park, J.H.,Hwang, S.M.,Lim, J.H.,Joo, J.,Kang, W.N.,Kim, C.J. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

We fabricated ex situ MgB<SUB>2</SUB> wires using C-doped MgB<SUB>2</SUB> powder as a precursor in order to improve the core density of the wires and their C doping content. The C-doped powder was prepared with Mg, B, and nano carbon (NC) powders by the in situ technique and then MgB<SUB>2-x</SUB>C<SUB>x</SUB> (x=0, 0.01, and 0.03) wires were fabricated by the ex situ technique using the powder-in-tube method. The phase formation, lattice change, and microstructure were characterized and correlated with the T<SUB>c</SUB> and J<SUB>c</SUB> variations. We observed that the ex situ wire had a higher core density than the in situ wire, however its morphology consisted of agglomerated particles, indicating that sintering and grain growth did not occur completely, even though the sintering was conducted at high temperature (1000<SUP>o</SUP>C). As the C content increased, T<SUB>c</SUB> decreased, while the decrease of J<SUB>c</SUB> with increasing magnetic field became smaller. The J<SUB>c</SUB> of MgB<SUB>1.97</SUB>C<SUB>0.03</SUB> wire made by the ex situ technique was 3.34kA/cm<SUP>2</SUP> at 6.6T and 5K which is comparable to that of the in situ wire (4.81kA/cm<SUP>2</SUP> at 6.6T and 5K).

Novel dentin phosphoprotein frameshift mutations in dentinogenesis imperfecta type II

Lee, K‐,E,Kang, H‐,Y,Lee, S‐,K,Yoo, S‐,H,Lee, J‐,C,Hwang, Y‐,H,Nam, KH,Kim, J‐,S,Park, J‐,C,Kim, J‐,W Blackwell Publishing Ltd 2011 Clinical genetics Vol.79 No.4

<P>Lee K‐E, Kang H‐Y, Lee S‐K, Yoo S‐H, Lee J‐C, Hwang Y‐H, Nam KH, Kim J‐S, Park J‐C, Kim J‐W. Novel dentin phosphoprotein frameshift mutations in dentinogenesis imperfecta type II.</P><P>The dentin sialophosphoprotein (<I>DSPP</I>) gene encodes the most abundant non‐collagenous protein in tooth dentin and DSPP protein is cleaved into several segments including the highly phosphorylated dentin phosphoprotein (DPP). Mutations in the <I>DSPP</I> gene have been solely related to non‐syndromic form of hereditary dentin defects. We recruited three Korean families with dentinogenesis imperfecta (DGI) type II and sequenced the exons and exon–intron boundaries of the <I>DSPP</I> gene based on the candidate gene approach. Direct sequencing of PCR products and allele‐specific cloning of the highly repetitive exon 5 revealed novel single base pair (bp) deletional mutations (c.2688delT and c.3560delG) introducing hydrophobic amino acids in the hydrophilic repeat domain of the DPP coding region. All affected members of the three families showed exceptionally rapid pulp chambers obliteration, even before tooth eruption. Individuals with the c.3560delG mutation showed only mild, yellowish tooth discoloration, in contrast to the affected individuals from two families with c.2688delT mutation. We believe that these results will help us to understand the molecular pathogenesis of DGI type II as well as the normal process of dentin biomineralization.</P>

Construction of a pilot-scale continuous-flow intense pulsed light system and its efficacy in sterilizing sesame seeds

Hwang, H.J.,Cheigh, C.I.,Chung, M.S. ELSEVIER 2017 INNOVATIVE FOOD SCIENCE AND EMERGING TECHNOLOGIES Vol. No.

<P>The purpose of this study was to identify the decontamination level of a laboratory-scale intense pulsed light (IPL) system and compared with that of newly constructed pilot-scale system in our laboratory. Sesame seeds, in which the initial microbial load was 10(4)-10(5) CFU/g, were treated by laboratory-scale IPL treatment at a total fluence of 39.85 J/cm(2). 0.86 log microbial reduction was achieved and adding a mixing step increased this to a 1.02 log reduction. We concluded that combining a mixing process and powerful IPL is essential to decontaminate sesame seeds satisfactorily, and so a pilot-scale IPL device in which the sample is placed in a cyclonic flow was designed and constructed in our laboratory. The xenon lamp and power supply were also upgraded. This modified device achieved a 1.46 log reduction at a total fluence of 44.46 J/cm(2). Changing the material of the treatment chamber from acrylic to stainless steel induced light reflections that resulted in improvement of the decontamination efficiency. Although this study showed a potential of a pilot-scale IPL device for treating larger amount of sample at once, further studies of technical improvement are essential to achieve higher decontamination level. (C) 2016 Elsevier Ltd. All rights reserved.</P>

The Magnetic Entropy Change on La<SUB>0.7</SUB>Ba<SUB>0.3</SUB>Mn<SUB>1-x</SUB>Fe<SUB>x</SUB>O₃ Compound

J. S. Hwang,D. M. Jang,K. S. Kim,J. S. Lee,S. C. Yu 한국자기학회 2013 Journal of Magnetics Vol.18 No.1

The magnetocaloric effect and magnetization behavior have been analyzed in the double-perovskite La0.7Ba0.3Mn1-XFeXO₃ compound with the sintering temperature at 1273 K. Samples were fabricated by the conventional solid-state reaction method. X-ray diffraction measurement revealed that all the samples had a single phase in orthorhombic. Detailed investigations of the magnetic entropy behavior of the samples were discussed with the variation of TC. The magnetic entropy changes, ΔSM of approximately 0.36-1.14 J/㎏ K were obtained in the temperature range of 145-350 K for the La0.7Ba0.3Mn1-XFeXO₃ compound. The enhancement of the magnetic entropy change is believed to be due to changes in the microstructure, which changes the magnetic part of the entropy of a solid around the magnetic ordering temperature.

Ultraviolet B-Induced Apoptosis of Normal Human Melanocytes and G361 Cells

Kim, Y. G Korean Dermatological Association 1998 Annals of Dermatology Vol.10 No.3

간호 전공과 비 간호 전공 여대생의 여성 갱년기에 관한 지식, 태도 및 어머니와 친밀감에 대한 연구

이다영,이다은,이정원,김봄경,황은주,류정미,김하연,신은지,박혜미,임은지 이화여자대학교 간호과학대학 2015 이화간호학회지 Vol.- No.49

Purpose: This study investigated the difference of menopausal knowledge, attitude between nursing students and non-nursing students. The relationships of the level of menopausal knowledge and attitude and the level of closeness to mother were investigated. Methods: A correlational descriptive design was used with a convenience sample. The survey was conducted with 206 female college students, 106 nursing and 100 non-nursing students, between September 1 and September 14, 2014. The instruments were the Knowledge of Menopause scale, the Menopausal Attitude Measurement scale, and the Level of Closeness to Mother scale. SPSS v22.0 is used to statistical analysis of descriptive statistics, independent t-tests, correlation and χ2-tests. Results: The difference in menopause knowledge between nursing students and non-nursing students is statistically significant (t=6.085, p<001). Nursing and non-nursing college students’ menopause knowledge had a positive relationship with attitude (r = 0.241, p<001). In closeness to mother, there is no significant difference was shown between nursing and non-nursing college students, even though the levels of menopause knowledge are different (t=1.336, p=.183). Conclusion: Results showed having menopausal knowledge positively influences students’ attitudes about menopause. Educators should develop programs imparting menopausal knowledge for non-nursing college students to increase positive menopausal attitude.