• Journal of Hydrogen and New Energy
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• v.26 no.1
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• pp.15-20
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• 2015

During the liquefaction of hydrogen, the ortho hydrogen is converted into the para form with heat release that evaporates the liquefied hydrogen into the gaseous one backwards. The ortho-para conversion catalysts are usually used during liquefaction to avoid such boil-off. In order to compare and analyze the performance of the ortho-para hydrogen conversion catalysts, in-situ FT-IR device was designed and manufactured to measure the para hydrogen conversion rate in real-time. $LaFeO_3$ and $La_{0.7}Sr_{0.3}Cu_{0.3}Fe_{0.7}O_3$ perovskite catalysts were prepared by the citrate sol-gel method and their spin conversion characteristics from ortho to para hydrogen were investigated by in-situ FTIR spectroscopy at 17K. It was found that the spin conversion was affected by surface area, particle size, and crystallite size of the catalysts. Thus, the $La_{0.7}Sr_{0.3}Cu_{0.3}Fe_{0.7}O_3$ perovskite catalyst that had higher surface area, higher crystallite size, and smaller particle size than $LaFeO_3$ showed the better spin conversion property of 32.3% at 17K in 120min interaction with the perovskite catalysts.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.240-244
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• 2001

Recycling process involving mechanical, thermal, hydrometallurgical, and sol-gel step has been applied to recover cobalt and lithium from spent lithium ion batteries and to synthesize LiCoO$_2$from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt could be concentrated with 2-step thermal and mechanical treatment. Leaching behaviors of the lithium and cobalt in nitric acid media was investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO$_3$solution turned out to be an effective reducing agent by enhancing the leaching efficiency. O f many possible processes to produce LiCoO$_2$, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO$_2$with nitric acid, the molar ratio of Li/Co in the leach liquor was adjusted at 1.1 by adding a fresh LiNO$_3$solution. Then, 1 M citric acid solution at a 100% stoichiometry was also added to prepare a gelatinous precursor. When the precursor was calcined at 95$0^{\circ}C$ for 24 hr, purely crystalline LiCoO$_2$was successfully obtained. The particle size and specific surface area of the resulting crystalline powders were 20 пm and 30 $\textrm{cm}^2$/g, respectively The LiCoO$_2$powder was proved to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance.

• Journal of Magnetics
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• v.20 no.3
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• pp.229-240
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• 2015

In this study, nanocrystalline ferrite powders with the composition $Ni_{0.5}Zn_{0.5}Fe_2O_4$ were prepared by the autocombustion method. The obtained powders were sintered at $800^{\circ}C$, $900^{\circ}C$ and $1,000^{\circ}C$ for 4 h in air atmosphere. The as-prepared and the sintered powders were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and magnetization studies. An increase in the crystallite size and a slight decrease in the lattice constant with sintering temperature were observed, whereas microstrain was observed to be negative for all the samples. Two significant absorption bands in the wave number range of the $400cm^{-1}$ to $600cm^{-1}$ have been observed in the FT-IR spectra for all samples which is the distinctive feature of the spinel ferrites. The force constants were found to vary with sintering temperature, suggesting a cation redistribution and modification in the unit cell of the spinel. The M-H loops indicate smaller coercivity, which is the typical nature of the soft ferrites. The observed variation in the saturation magnetization and coercivity with sintering temperature has been attributed to the role of surface, inhomogeneous cation distribution, and increase in the crystallite size.

• Molecules and Cells
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• v.19 no.3
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• pp.328-333
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• 2005

Small heat shock proteins (sHSPs) are widely distributed, and their function and diversity of structure have been much studied in the field of molecular chaperones. In plants, which frequently have to cope with hostile environments, sHSPs are much more abundant and diverse than in other forms of life. In response to high temperature stress, sHSPs of more than twenty kinds can make up more than 1% of soluble plant proteins. We isolated a genomic clone, NtHSP18.3, from Nicotiana tabacum that encodes the complete open reading frame of a cytosolic class I small heat shock protein. To investigate the function of NtHSP18.3 in vitro, it was overproduced in Escherichia coli and purified. The purified NtHSP18.3 had typical molecular chaperone activity as it protected citrate synthase and luciferase from high temperature-induced aggregation. When E. coli celluar proteins were incubated with NtHSP18.3, a large proportion of the proteins remained soluble at temperatures as high as $70^{\circ}C$. Native gel analysis suggested that NtHSP18.3 is a dodecameric oligomer as the form present and showing molecular chaperone activity at the condition tested. Binding of bis-ANS to the oligomers of NtHSP18.3 indicated that exposure of their hydrophobic surfaces increased as the temperature was raised. Taken together, our data suggested that NtHSP18.3 is a molecular chaperone that functions as a dodecameric complex and possibly in a temperature-induced manner.

• Applied Biological Chemistry
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• v.39 no.6
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• pp.501-505
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• 1996

우리나라에서 오랫동안 적색 및 황색색소원으로 널리 사용하여 왔던 홍화(Carthamus tinctorius)로부터 전통적인 추출방법을 응용한 새로운 방법을 사용하여 적색소를 효과적으로 분리정제하였다. 홍화꽃잎을 물 및 메탄올로 처리하여 황색소를 제거한 다음 건조파쇄하여 0.5 M $Na_2CO_3$로 홍색소를 추출하고 0.5 M citrate 수용액으로 침전시킨 후 cellulose 흡착, Sephadex LH-20 관크로마토그라피로 분리정제하였다. 분리정제된 적색소는 $300^{\circ}C$에서 분해되었고 silica gel TLC 상에서 BAW(n-BuOH : HOAc : $H_2O$=4 : 1 : 5)로 전개하였을 때 $R_f$값이 0.56이었다. 에탄올 용액에 녹인 적색소의 UV/Vis 흡수스펙트럼은 519, 372, 311, 244 nm에서 최대 흡수피크를 나타내었고, IR 스펙트럼은 특히 $3400\;cm^1$ 넓은 영역에서 hydroxyl기에 의한 강한 흡수띠를 보여주었다. $^{1}H$ 및 $^{13}C$ NMR data로 부터 enolized ${\beta}-triketone$, p-hydroxycinnamoyl, methine 및 glucosyl moieties를 확인하였고 그 값을 제시하였다. 이상의 data를 문헌과 비교한 결과 분리한 홍화적색소의 화학구조는 $6-{\beta}-D-glucopyranosyl-2-[[3-{\beta}-D-glucopyranosyl-2,3,4-trihydroxy-5-[3#-(4@-hydroxyphenyl)-1#-oxo-2#-propenyl]-6-oxo-1,4-cyclohexadien-1-yl]methylene]-5,6-dihydroxy-4-[3#-(4@-hydroxyphenyl)-1#-oxo-2#-propenyl]-4-cyclohexene-1,3-dione$인 carthamin으로 확인하였다.

• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.50-56
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• 2010

$La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ (LSCF) powders with different particle sizes, synthesized through a citrate complexation method and a gel-casting technique, are used to fabricate porous LSCF cathodes with graded microstructures via tape casting. To create porous electrodes with desired porosity and pore structures, graphite and starch are used as pore former for different layers of the graded cathode. Examination of the microstructures of the as-prepared LSCF cathode using an SEM revealed that both grain size and porosity changed gradually from the catalytically active layer (near the electrodeelectrolyte interface) to the current collection layer (near the electrode-interconnect interface). Impedance analysis showed that a 3-layer LSCF cathode with graded microstructures exhibited much-improved performance compared to that of a single-layer LSCF cathode, corresponding to interfacial resistance of 0.053, 0.11, and 0.27 $\Omega{\cdot}cm^2$ at 800, 750, and $700^{\circ}C$ respectively.

• Bulletin of the Korean Chemical Society
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• v.25 no.1
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• pp.97-100
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• 2004

Tetragonal $K_2NiF_4$-type $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$ solid-solution have been synthesized by citrate based sol-gel method. The valence state of iron was determined by Mossbauer spectroscopy and subsequent iodometric titration clearly showed that the copper ions in this solid-solution are in the mixed valence state Cu(II/III). When x ${\geq}$ 0.3, Fe(III) is competing with the mixture of Cu(II) and Cu(III) and $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$ exhibits a metallic character. No evidence for Cu(II)-O-Fe(IV) ${\leftrightarrow}$ Cu(III)-O-Fe(III) valence degeneracy was observed. In contrast, a small amount of Fe(IV) is observed with increasing x (x = 0.4 and 0.5), revealing a semiconducting behavior. These results suggest that the electronic interaction of Cu(III)-O-Fe(III) contributes greatly to the metallic character, while the electronic interaction of Cu(II)-O-Fe(IV) deteriorates the metallic character of $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$.

• Journal of Veterinary Clinics
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• v.6 no.2
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• pp.291-305
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• 1989

Present experiment was performed to establish the optimal reaction conditions for measurement of urinary gamma-glutamyltranspeptidase(${\gamma}$-GTP), N-acetyl-${\beta}$-D-glucosaminidase (AGS) and alanine aminopeptidase(AAP) activities in bovine and to investigate in vitro stability of the enzymes, within-run imprecision of the methods, and normal ranges. 1. The optimal wavelength for measurement of ${\gamma}$-GTP activity was 545nm. 2. The optimal pH of Tris-HCI buffer containing glycylglycine for measurement of urinary ${\gamma}$-GTP activity was 7.6～7.8(37$^{\circ}C$). 3. Coefficient of variance for within-run imprecision of urinary ${\gamma}$-GTP activity ranged from 4.8 to 7.2% and there was no significant difference among replications, 4. The optimal wavelength for measurement of urinary AGS activity was 405nm. 5. The optimal pH of citrate buffer for measurement urinary of AGS activity was 4.0(37$^{\circ}C$). 6. Coefficient of variance for within-run imprecision of urinary AGS activity ranged from 3.9 to 6.1％ and there was no significant difference among replications. 7. The optimal wavelength for measurement of urinary AAP activity was 400nm. 8. The optimal pH of phosphate buffer for measurement of urinary AAP was 7.8. 9. Coefficient of variance for within-run imprecision of urinary AAP activity ranged from 2.5 to 4.8% and there was no significant difference among replications. 10. ${\gamma}$-GTP and AGS activities were increased significantly by gel-filtration. 11. Turbidity interfered with measurement of urinary AAP activity in bovine unless the specimen was gel-filterated. 12. Preservation of the specimen at 5$^{\circ}C$ or -20$^{\circ}C$ did not affect the AGS activity at least for 7 days after collection. 13. Preservation of the specimen at 5$^{\circ}C$ or 20$^{\circ}C$ did not affect the ${\gamma}$-GTP and AAP activities statistically, but some individual specimens revealed fluctuation during preservation. 14. ${\gamma}$-GTP, AGS and AAP activities revealed fluctuation by the tine of the day when the specimen was collected. 15. The normal ranges of urinary ${\gamma}$ -GTP, AGS and AAP activities were 6.60${\pm}$3.26(2.36-14.50), 1.31 ${\pm}$ 0.81(0.33-3.78), and 1.73 ${\pm}$ 0.55(0.77-3.03)U/l. respectively.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.45-50
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• 2015

The goal of this research is the create novel magnets with no rare-earth contents, with larger energy product by comparison with currently used ferrites. For this purpose we developed nano-sized hard-type/soft-type composite ferrite in which high remanent magnetization (Mr) and high coercivity (Hc). Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ composite ferrites were prepared by sol-gel combustion method by use of glicine-nitrate and citric acid. Nanocomposite ferrites were calcined at temperature range $700-900^{\circ}C$ for 1h. According to the X-ray diffraction patterns and FT-IR spectra, single phase of NiZn-ferrite and Ba-ferrite were detected and hard/soft nanocomposite ferrite was indicated to the coexistence of the magnetoplumbite-structural $BaFe_{12}O_{19}$ and spinel-structural $Ni_{0.5}Zn_{0.5}Fe_2O_4$ that agreed with the standard JCPDS 10-0325 data. The particle size of nanocomposite turn out to be less than 120 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite ferrite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that of the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite, and $(BH)_{max}$ is increased slightly.

• Journal of Life Science
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• v.18 no.4
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• pp.482-487
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• 2008

In this study, we screened and identified the bacterial strain showing high alkaline pretense inhibitor activity from marine environment. Nine bacterial strains with alkaline pretense inhibitor activity were isolated from marine sediments. Among them, strain C12 had the highest alkaline pretense inhibitor activity and was selected for further taxonomical study. On the basis of morphological and physiological characteristics, strain C12 was identified as the genus Streptomyces. A phylogenetic analysis of the 165 rDNA showed that the isolated strain was actually a member of the genus Streptomyces, because the determined sequence exhibited a higher homology with Streptomyces thermocarboxydus. Morphological characteristics showed cylindrical spore chain and smooth spore surface by scanning electron microscope. Strain C12 was grown on all media except for ISP 9 agar. This strain could be grown in the medium containing up to 9% NaCl.