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      • Effects of nano-carbon doping and sintering temperature on microstructure and properties of MgB<sub>2</sub>

        Lim,,J.H.,Shim,,J.H.,Choi,,J.H.,Park,,J.H.,Kim,,W.,Joo,,J.,Kim,,C.J. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

        We fabricated nano-carbon (NC) doped MgB<SUB>2</SUB> bulks using an in situ process in order to improve the critical current density (J<SUB>c</SUB>) under a high magnetic field and evaluated the correlated effects of the doped carbon content and sintering temperature on the phase formation, microstructure and critical properties. MgB<SUB>2-x</SUB>C<SUB>x</SUB> bulks with x=0 and 0.05 were fabricated by pressing the powder into pellets and sintering at 800<SUP>o</SUP>C, 900<SUP>o</SUP>C, or 1000<SUP>o</SUP>C for 30min. We observed that NC was an effective dopant for MgB<SUB>2</SUB> and that part of it was incorporated into the MgB<SUB>2</SUB> while the other part remained (undoped), which reduced the grain size. The actual C content was estimated to be 68-90% of the nominal content. The NC doped samples exhibited lower T<SUB>c</SUB> values and better J<SUB>c</SUB>(B) behavior than the undoped samples. The doped sample sintered at 900<SUP>o</SUP>C showed the highest J<SUB>c</SUB> value due to its high doping level, small amount of second phase, and fine grains. On the other hand, the J<SUB>c</SUB> was decreased at a sintering temperature of 1000<SUP>o</SUP>C as a result of the formation of MgB<SUB>4</SUB> phase.

      • Regulation of cancer cell death by a novel compound, C604, in a c-Myc-overexpressing cellular environment

        Jo,,M.J.,Paek,,A.R.,Choi,,J.S.,Ok,,C.Y.,Jeong,,K.C.,Lim,,J.H.,Kim,,S.H.,You,,H.J. North-Holland ; Elsevier Science Ltd 2015 european journal of pharmacology Vol.769 No.-

        <P>The proto-oncogene c-Myc has been implicated in a variety of cellular processes, such as proliferation, differentiation and apoptosis. Several c-Myc targets have been studied; however, selective regulation of c-Myc is not easy in cancer cells. Herein, we attempt to identify chemical compounds that induce cell death in c-Myc-overexpressing cells (STF-cMyc and STF-Control) by conducting MTS assays on approximately 4000 chemical compounds. One compound, C604, induced cell death in STF-cMyc cells but not STF-Control cells. Apoptotic proteins, including caspase-3 and poly(ADP-ribose) polymerase (PAPP), were cleaved in C604-treated STF-cMyc cells. In addition, 5W620, HCT116 and NCI-H23 cells, which exhibit higher basal levels of c-Myc, underwent apoptotic cell death in response to C604, suggesting a role for C604 as an inducer of apoptosis in cancer cells with c-Myc amplification. C604 induced cell cycle arrest at the G2/M phase in cells, which was not affected by apoptotic inhibitors. Interestingly, C604 induced accumulation of c-Myc and Cdc25A proteins. In summary, a chemical compound was identified that may induce cell death in cancer cells with c-Myc amplification specifically through an apoptotic pathway. (C) 2015 Elsevier B.V. All rights reserved.</P>

      • Investigation of lauric acid dopant as a novel carbon source in MgB<sub>2</sub> wire

        Lee,,C.M.,Lee,,S.M.,Park,,G.C.,Joo,,J.,Lim,,J.H.,Kang,,W.N.,Yi,,J.H.,Jun,,B.H.,Kim,,C.J. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

        We fabricated lauric acid (LA) doped MgB<SUB>2</SUB> wires and investigated the effects of the LA doping. For the fabrication of the LA-doped MgB<SUB>2</SUB> wires, B powder was mixed with LA at 0-5wt.% of the total amount of MgB<SUB>2</SUB> using an organic solvent, dried, and then the LA-treated B and Mg powders were mixed stoichiometrically. The powder mixture was loaded into an Fe tube and the assemblage was drawn and sintered at 900<SUP>o</SUP>C for 3h under an argon atmosphere. We observed that the LA doping induced the substitution of C for the B sites in MgB<SUB>2</SUB> and that the actual content of C increased monotonically with increasing LA doping level. The LA-doped MgB<SUB>2</SUB> wires exhibited a lower critical temperature (T<SUB>c</SUB>), but better critical current density (J<SUB>c</SUB>) behavior in a high magnetic field: the 5wt.% LA-doped sample had a J<SUB>c</SUB> value of 5.32x10<SUP>3</SUP>A/cm<SUP>2</SUP>, which was 2.17 times higher than that of the pristine sample (2.45x10<SUP>3</SUP>A/cm<SUP>2</SUP>) at 5K and 6T, suggesting that LA is an effective C dopant in MgB<SUB>2</SUB> for enhancing the high-field J<SUB>c</SUB> performance.

      • Fabrication of ex situ processed MgB<sub>2</sub> 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).

      • SCOPUSKCI등재

        Effects of electron beam irradiation on the superconducting properties of YBCO thin films

        Lee,,Y.J.,Choi,,J.H.,Jun,,B.H.,Joo,,J.,Kim,,C.S.,Kim,,C.J. The Korea Institute of Applied Superconductivity a 2016 한국초전도저온공학회논문지 Vol.18 No.4

        The effects of electron beam (EB) irradiation on the superconducting critical temperature ($T_c$) and critical current density ($J_c$) of YBCO films were studied. The YBCO thin films were irradiated using a KAERI EB accelerator with an energy of 0.2 MeV and a dose of $10^{15}-10^{16}e/cm^2$. A small $T_c$ decrease and a broad superconducting transition were observed as the EB dose increased. The value of $J_cs$ (at 20 K, 50 K and 70 K) increased at doses of $7.5{\times}10^{15}$ and $2.2{\times}10^{16}e/cm^2$. However, $J_cs$ decreased as the dose increased further. The X-ray diffraction (XRD) analysis showed that the c axis of YBCO was elongated and the full width at half maximum (FWHM) increased as the dose increased, which is strong evidence of the atomic displacement by EB irradiation. The transmission electron microscopy (TEM) showed that the amorphous layer formed in the vicinity of the surfaces of the irradiated films. The amorphous phase was often present as an isolated form in the interior of the films. In addition to the formation of the amorphous phase, many striations running along the a-b direction of YBCO were observed. The high magnification lattice image showed that the striations were stacking faults. The enhancement of $J_c$ by EB irradiation is likely to be due to the lattice distortion and the formation of defects such as vacancies and stacking faults. The decrease in $J_c$ at a high EB dose is attributed to the extension of the amorphous region of a non-superconducting phase.

      • Hepatoprotective effect of vitamin C on lithocholic acid-induced cholestatic liver injury in Gulo(-/-) mice

        Yu,,S.J.,Bae,,S.,Kang,,J.S.,Yoon,,J.H.,Cho,,E.J.,Lee,,J.H.,Kim,,Y.J.,Lee,,W.J.,Kim,,C.Y.,Lee,,H.S. North-Holland ; Elsevier Science Ltd 2015 european journal of pharmacology Vol.762 No.-

        <P>Prevention and restoration of hepatic fibrosis from chronic liver injury is essential for the treatment of patients with chronic liver diseases. Vitamin C is known to have hepatoprotective effects, but their underlying mechanisms are unclear, especially those associated with hepatic fibrosis. Here, we analyzed the impact of vitamin Con bile acid induced hepatocyte apoptosis in vitro and lithocholic acid (LCA) induced liver injury in vitamin C-insufficient Gulo(-/-) mice, which cannot synthesize vitamin C similarly to humans. When Huh BAT cells were treated with bile acid, apoptosis was induced by endoplasmic retiiculum stress related JNK activation but vitamin C attenuated bile acid induced hepatocyte apoprosis in vitro. In our in vivo experiments. LCA feeding increased plasma marker of cholestasis and resulted in more extensive liver damage and hepatic fibrosis by more prominent apoptotic cell death and recruiting more intrahepatic inflammatory CD11b(+) cells in the liver of vitamin C-insufficient Gulo(-/-) mice compared to wild type mice which have minimal hepatic fibrosis. However, when vitamin C was supplemented to vitamin C-insufficient Gulo(-/-) mice, hepatic fibrosis was significantly attenuated in the liver of vitamin C-sufficient Gulo(-/-) mice like in wild type mice and this hepatoprotective effect of vitamin C was thought to be associated with both decreased hepatic apoptosis and necrosis. These results suggested that vitamin C had hepatoprotective effect against cholestatic liver injury. (C) 2015 Elsevier B.V. All rights reserved.</P>

      • SCOPUSKCI등재

        Effect of boron milling on phase formation and critical current density of MgB<sub>2</sub> bulk superconductors

        Kang,,M.O.,Joo,,J.,Jun,,B.H.,Park,,S.D.,Kim,,C.S.,Kim,,C.J. The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.1

        This study was carried out to investigate the effect of milling of boron (B), which is one of raw materials of $MgB_2$, on the critical current density ($J_c$) of $MgB_2$. B powder used in this study is semi-amorphous B (Pavezyum, Turkey, 97% purity, 1 micron). The size of B powder was reduced by planetary milling using $ZrO_2$ balls (a diameter of 2 mm). The B powder and balls with a ratio of 1:20 were charged in a ceramic jar and then the jar was filled with toluene. The milling time was varied from 0 to 8 h. The milled B powders were mixed with Mg powder in the composition of (Mg+2B), and the powder mixtures were uniaxially pressed at 3 tons. The powder compacts were heat-treated at $700^{\circ}C$ for 1 h in flowing argon gas. Powder X-ray diffraction and FWHM (Full width at half maximum) were used to analyze the phase formation and crystallinity of $MgB_2$. The superconducting transition temperature ($T_c$) and $J_c$ of $MgB_2$ were measured using a magnetic property measurement system (MPMS). It was found that $B_2O_3$ was formed by B milling and the subsequent drying process, and the volume fraction of $B_2O_3$ increased as milling time increased. The $T_c$ of $MgB_2$ decreased with increasing milling time, which was explained in terms of the decreased volume fraction of $MgB_2$, the line broadening of $MgB_2$ peaks and the formation of $B_2O_3$. The $J_c$ at 5 K increased with increasing milling time. The $J_c$ increase is more remarkable at the magnetic field higher than 3 T. The $J_c$ at 5 K and 4 T was the highest as $4.37{\times}10^4A/cm^2$ when milling time was 2 h. The $J_c$ at 20 K also increased with increasing milling time. However, The $J_c$ of the samples with the prolonged milling for 6 and 8 h were lower than that of the non-milled sample.

      • KCI등재후보

        가온온도 및 진탕시간이 전란, 난황 및 난백의 점도 변화에 미치는 효과

        하정기,나재천,강보석,이진건,이상진,김지혁,Ha,J.,K.,Na,J.,C.,Kang,B.,S.,Lee,J.,G.,Lee,S.,J.,Kim,J.,H 한국가금학회 2004 韓國家禽學會誌 Vol.31 No.3

        전란(whole egg), 난황 및 난백이 가온 온도와 진탕 시간에 따라 점도가 어떻게 변화하는가를 구명하기 위하여 본 실험을 실시하였다. 가열처리는 진탕 수조를 사용하여 35$^{\circ}C$, 45$^{\circ}C$, 및 5$0^{\circ}C$에서 점도는 진탕후 0, 3, 6, 9, 12시간에 측정하였다. 전란은 처리온도(over-all mean)간에 있어서 35$^{\circ}C$와 45$^{\circ}C$구간에서는 유의차가 없었으나, 5$0^{\circ}C$구는 35$^{\circ}C$와 45$^{\circ}C$구 에 비하여 유의하게 점도가 낮았으며(P < 0.05), 난황의 경우처리 온도간에서 유의성이 없었으나, 진탕 시간간에서는 유의성이 인정되었다(P < 0.05). 그리고 난백은 처리 온도와 진탕 시간간에서는 유의성(P < 0.05)이 없었다. 위의 실험결과 계란을 가공 이용코자 할 경우 전란은 5$0^{\circ}C$에서는 3시간 이상, 난황은 35$^{\circ}C$와 45$^{\circ}C$에서는 3시간 이상, 그리고 5$0^{\circ}C$에서는 3~9시간, 난백의 경우는 5$0^{\circ}C$에서 0, 9 및 12시간 각각 진탕 처리한 후 사용할 수 있으리라 판단된다. The experiment was performed to investigate the effect of heating temperature and shaking time on viscosity change of whole egg, yolk, and albumen. Shaking water bath was used at 35, 45, and 50$^{\circ}C$ and the viscosity was measured at 0, 3, 6, 9, and 12 hours. There were no significant differences in viscosity of whole egg between 35$^{\circ}C$ and 45$^{\circ}C$( over-all mean). However, the 50$^{\circ}C$ group showed significantly lower viscosity compared to 35 or 45$^{\circ}C$ groups(P < 0.05). Non-significant differences were noticed in yolk viscosity among temperature treatments, but there were significant differences among shaking times(P < 0.05). Heating temperature and shaking time did not show significant effect on the viscosity of albumen, but the lowest viscosity was shown at 0, 9, and 12 hours at 50$^{\circ}C$. The results suggest that whole egg, yolk, and albumen should be treated for more than 3 hours at 50$^{\circ}C$, more than 3 hours at 35$^{\circ}C$ and 45$^{\circ}C$ and 3~9 hours at 50$^{\circ}C$, and 0, 9, 12 hours at 50$^{\circ}C$, respectively and then can be used in the processing.

      • SCOPUSKCI등재

        Effects of heat treatment temperature on the formation of MgB<sub>2</sub> bulk superconductors prepared using MgB<sub>4</sub> and Mg powder

        Kim,,S.H.,Kang,,W.N.,Lee,,Y.J.,Jun,,B.H.,Kim,,C.J. The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.1

        The effects of the heat treatment temperature ($600^{\circ}C-1050^{\circ}C$) on the formation of $MgB_2$ and the superconducting properties have been examined. The self-synthesized $MgB_4$ and commercial Mg powders were used as raw materials for the formation of $MgB_2$. The superconducting critical temperatures ($T_cs$) of $MgB_2$ bulk superconductors prepared at $600^{\circ}C-850^{\circ}C$ were as high as 37-38 K regardless of the heat treatment temperature. However, because $MgB_4$ is more stable than $MgB_2$ at above $850^{\circ}C$, no superconducting signals were detected in the susceptibility-temperature curves of the samples prepared above $850^{\circ}C$. As for the critical current density ($J_c$), the sample heat-treated at a low temperature ($600^{\circ}C$) for a prolonged period (40 h) showed a Jc higher than those prepared at $650^{\circ}C-850^{\circ}C$ for a short period (1 h). The FWHM (full width at half maximum) result showed that the grain size of $MgB_2$ of the $600^{\circ}C$ sample was smaller than that of the other samples. The high $J_c$ of the $600^{\circ}C$sample is attributed to the presence of large numbers of grain boundaries, which can act as flux pinning centers of $MgB_2$.

      • Measurement of the ratio of the production cross sections times branching fractions of B c ± → J/ψπ ± and B± → J/ψK ± and ℬ B c ± → J / ψ π ± π ± π ∓ / ℬ B c ± → J / ψ π ± $$ \mathrm{\mathcal{B}}\left({\mathrm{B

        Khachatryan,,V.,Sirunyan,,A.,M.,Tumasyan,,A.,Adam,,W.,Bergauer,,T.,Dragicevic,,M.,Erö,,,J.,Fabjan,,C.,Friedl,,M.,Frü,hwirth,,R.,Ghete,,V.,M.,Hartl,,C.,,rmann,,N.,Hrubec,,J.,Jeitler,,M.,K Institute of Physics Pub 2015 The journal of high energy physics Vol.2015 No.1

        <P>The ratio of the production cross sections times branching fractions (sigma(B-c(+/-))B(B-c(+/-) -> J/psi pi(+/-)))/(sigma(B-+/-)B(B-+/- -> J/psi K-+/-)) is studied in proton-proton collisions at a center-of-mass energy of 7TeV with the CMS detector at the LHC. The kinematic region investigated requires B-c(+/-) and B-+/- mesons with transverse momentum p(T) > 15 GeV and rapidity vertical bar y vertical bar < 1.6. The data sample corresponds to an integrated luminosity of 5.1 fb(-1). The ratio is determined to be [0.48 +/- 0.05 (stat) +/- 0.03 (syst) +/- 0.05 (tau(Bc))]%. The B-c(+/-) -> J/psi pi(+/-)pi(+/-)pi(-/+) decay is also observed in the same data sample. Using a model-independent method developed to measure the efficiency given the presence of resonant behaviour in the three-pion system, the ratio of the branching fractions B-c(+/-) -> J/psi pi(+/-)pi(+/-)pi(-/+)/B(B-c(+/-) -> J/psi pi(+/-)) is measured to be 2.55 +/- 0.80 (stat) +/- 0.33 (syst)(-0.01)(+0.04) (tau(Bc)), consistent with the previous LHCb result.</P>

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