• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.172.1-172
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• 2002

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.97-102
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• 2003

Synthetic ferrimagnetic layer (SyFL) with structure NiFe/Ru/NiFe which can be applied high density TMR device in free layer were prepared by an inductively coupled plasma (ICP) helicon-sputter. We proposed a model of predicting coercivity (H$\_$c/), spin-flopping field (H$\_$sf/), and saturation field (H$\_$s/) as a function of Ru thicknesses, from the equilibrium state of energies of Zeeman, exchange, and uniaxial anisotropy. We fabricated the samples of Ta(50 ${\AA}$)/NiFe(50${\AA}$)nu(4∼20${\AA}$)NiFe(30 ${\AA}$)/Ta(50${\AA}$), and measured the M-H loops with a superconduction quantum interference device (SQUID) applying the external field up to ${\pm}$ 15 kOe. The result was well agreed with the proposed model, and reveal K$\_$u = 1000 erg/㎤, J$\_$ex/ =0.7 erg/$\textrm{cm}^2$. We report that H$\_$c/ below 10 Oe is available, and R$\_$u/ thickness range should be in 4-10 ${\AA}$ for MRAM application. Our result implies that permalloy layers may lead to considerable magnetostriction effect in SyFL and intermixing in NiFe/Ru interfaces.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.51.4-52
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• 2017

We present the derived kinematic characteristics of low-${\alpha}$ thin-disk and high-${\alpha}$ thick-disk stars in the Milky Way, investigated with a sample of about 33,900 G- and K-type dwarfs from the Sloan Extension for Galactic Understanding and Exploration (SEGUE). Based on the level of ${\alpha}$-element enhancement as a function of [Fe/H], we separate our sample into thin- and thick-disk stars and then derive mean velocity, velocity dispersion, and velocity gradients for the U, V and W velocity components, respectively, as well as the orbital eccentricity distribution. There are notable gradients in the V velocity over [Fe/H] in both populations: -23 km s-1 dex-1 for the thin disk and +44 km s-1 dex-1 for the thick disk. The velocity dispersion of the thick disk decrease with increasing [Fe/H], while the velocity.

• Journal of The Korean Astronomical Society
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• v.28 no.2
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• pp.139-146
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• 1995

The bright part of the halo luminosity function is derived from a sample of the 233 NLTT propermotion stars, which are selected by the 220 km/ see of cutoff velocity in transverse to rid the contamination by the disk stars and corrected for the stars omitted in the sample by the selection criterion. It is limited to the absolute magnitude range of $M_v=4-8$, but is based on the largest sample of halo stars up to now. This luminosity function provides a number density of $2.3{\cdot}10^{-5}pc^{-3}$ and a mass density of $2.3{\cdot}10^{-5}M_{o}pc^{-3}$ for 4 < $M_v$ < 8 in the solar neighborhood. These are not sufficient for disk stability. The kinematics of the sample stars are < U > = - 7 km/sec, < V > = - 228 km/sec, and < W > = -8 km/sec with (${\sigma_u},{\sigma_v},{\sigma_w}$) = (192, 84, 94) km/sec. The average metallicity of them is [Fe/H] = $- 1.7{\pm}0.8$. These are typical values for halo stars which are selected by the high cutoff velocity. We reanalyze the luminosity function for a sample of 57 LHS proper-motion stars. The newly derived luminosity function is consistent with the one derived from the NLTT halo stars, but gives a somewhat smaller number density for the absolute magnitude range covered by the LF from NLTT stars. The luminosity function based on the LHS stars seems to have a dip in the magnitude range corresponding to the Wielen Dip, but it also seems to have some fluctuations due to a small number of sample stars.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.479-483
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• 2005

Antioxidative and protective effects of Ulmus davidiana var. japonica against oxidative damages induced by glutamate in PC 12 cells were investigated. Inhibitory activity against $FeSO_{4}-H_{2}O_{2}$-induced oxidative stress and DPPH radical-scavenging activity were detected in ethyl acetate and butanol fractions of ethanol extracts from stems and roots. Ethyl acetate and butanol fractions of ethanol extracts from roots significantly inhibited glutamate-induced cytotoxicity and reactive oxygen species in PC 12 cells. These results demonstrate ethyl acetate and butanol fractions of ethanol extracts of U. davidiana var. japonica have potent protective effect against glutamate-induced oxidative stress.

• Animal cells and systems
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• v.9 no.2
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• pp.57-64
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• 2005

Cortical reaction and polyspermy block are well defined in most marine invertebrates. In Urechis species, the function of cortical granules (CGs) is not yet known, and there is controversy on whether the cortical reaction occurs, or the fertilization envelope (FE) is attributed to CG releases or functions to prevent polyspermy. This study was carried out to determine the cortical reactions and functions of the FE in Urechis unicinctus. Artificial insemination of the eggs revealed that CG release occurred to give rise to perivitelline space (PS) into the final FE. Both PS and final FE effectively blocked polyspermy. The final FE was accomplished within 10 min after sperm-egg initial binding. No massive release of CGs occurred within the early phase of 5 min after the initial binding, initially and the PS seemed to playa role to prevent polyspermy. The CG massively released its content into the PS in late phase of FE formation, and differentiated PS into five intermediate layers. The layers opened into each other by anastomosis, so that the final FE consisted of two layers, the inner layer ($15{\mu}m$ in thickness) and the outer layer ($1{\mu}m$ in thickness). The outer layer derived from vitelline layer and the inner layer consisted of PS and CG secretions. Immunofluorescence and confocal laser microscopy revealed that the spermatozoon took up residence in the egg cortex during FE formation and successive meioses of the fertilized egg. These results suggest that both PS and final FE of U. unicinctus were equivalent to the early and late block, respectively, of other marine animals.

• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.233-238
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• 1992

Melt-spun $Nd_{14}Fe_{76}Co_4B_6$ and $Nd_{10.5}Fe_{79}Co_2Zr_{1.5}B_7$ ribbons were prepared under an externally applied magnetic field. Magnetic properties in terms of anisotropy were evaluated by discussing the effect of textured structure of the ribbon samples as well as its powders. About 32 % increase in $(B{\cdot}H)_{max}$ and 18.8 % increase in $B_r$ were observed along the perpendicular direction of the ribbon plane which is more prominent for the Nd-Fe-Co-Zr-B than for the Nd-Fe-Co-B alloy. The enhancement of magnetic anisotropy was monitored by measuring the anisotropy constant of each alloy as a function of quenching rate of the ribbon. It was found that for the melt-spun ribbon quenched at slow rate(less than 7 m/s) the magnetic field effect was overwhelmed by the heat gradient effect through the ribbon thickness while the field effect was prominent at intermediate quenching rate (more than 7~11 m/s). The reproducible maximum energy product, $(B{\cdot}H)_{max}$=16.4 MGOe can be obtained from the Nd-Fe-Co-Zr-B alloy.

• Journal of Microbiology and Biotechnology
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• v.24 no.12
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• pp.1699-1706
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• 2014

A lichenase gene (mt-lic) was identified for the first time through function-based screening of a soil metagenomic library. Its deduced amino acid sequence exhibited a high degree of homology with endo-${\beta}$-1,3-1,4-glucanase (having both lichenase and chitosanase activities), encoded by the bgc gene of Bacillus circulans WL-12. The recombinant lichenase overexpressed and purified from Escherichia coli was able to efficiently hydrolyze both barley ${\beta}$-glucan and lichenan. The enzyme showed maximal activity at a pH of 6.0 at $50^{\circ}C$, with Azo-barley-glucan as the substrate. The metal ions $Mn^{2+}$, $Mg^{2+}$, $Ca^{2+}$, and $Fe^{2+}$ enhanced the enzymatic activity, whereas the $Cu^{2+}$ and $Zn^{2+}$ ions inhibited the enzymatic activity. The $K_m$ and $V_{max}$ values of the purified lichenase were determined to be 0.45 mg/ml and 24.83 U/min/mg of protein, respectively.

• Journal of the Korean earth science society
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• v.27 no.5
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• pp.557-568
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• 2006

We present CCD UBVI photometry for more than 10,000 stars in $20'.5{\times}20'.5$ field of the halo globular cluster M30. From a color-magnitude diagram, main sequence turnoff was obtained when $V_{TO},\;(B-V)_{TO},\;and\;(V-I)_{TO}\;are\;8.63{\pm}0.05,\;0.44{\pm}0.05\;and\;0.63{\pm}0.05$, respectively. From a (U-B)-(B-V) diagram, reddening parameter, E(B-V) equals $0.05{\pm}0.01$ and a UV color excess ${\delta}(U-B)\;is\;0.27{\pm}0.01$. The abundance is derived, where [Fe/H] equals $-2.05{\pm}0.09$ according to the photometric method and spectroscopic data. The observed luminosity function of M30 shows an excess in the number of red giants relative to the number of turnoff stars, when comparing with the predictions of canonical models. Using the Hipparcos parallaxes for subdwarfs, we estimate distance modulus, $(m-M)_o\;as\;14.75{\pm}0.12$. Using the R and R' method, we find helium abundances, Y(R) as $0.23{\pm}0.02$, Y(R') as $0.29{\pm}0.02$, respectively. Finally, the cluster' sage dispersion was deduced from 10.71 Gyr to 17 Gyr.