• Journal of Information Display
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• v.6 no.2
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• pp.25-29
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• 2005

The luminescent properties of $Eu^{3+}$ and $Sm^{3+}$ doped potassium tungstate phosphor are investigated. The $K_{4-3x}(WO_4)_2:Eu^{3+}\;_x,Sm^{3+}\;_y$ phosphor is produced by firing the mixed precursors, followed by re-firing with a flux. The re-firing process results in the defect-free surface and uniform growth of the particles. The strong absorption in the region of ultra violet light is observed due to the 4f-4f electron transitions of the $Eu^{3+}$ and $Sm^{3+}$ ions. The doping concentration of europium into potassium tungstate is relatively high, compared to other host materials. It is revealed that the crystal structure is a monoclinic with space group, C2/c. This crystal structure facilitated the $Eu^{3+}$ ions to be located with the Eu-Eu distance larger than 5 ${\AA}$ so that concentration quenching does not occur even at high doping concentration. The excitation spectrum could be adjusted by the introduction of the samarium. A small amount of the $Sm^{3+}$ ions that acts as a sensitizer increases the energy absorption peak around 405 nm.

• Mass Spectrometry Letters
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• v.8 no.4
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• pp.90-97
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• 2017

Androgenic anabolic steroids (AASs) are synthetic derivatives of testosterone with a common structure containing cyclopentanoperhydrophenanthrene nucleus. Their use enhances the muscle building capacity and is beneficial during performance. The AASs are one of the most abused group of substances in horse doping. Liquid chromatography tandem mass spectrometry ($LC/MS^n$) has been successfully applied to the detection of anabolic steroids in biological samples. However, the saturated hydroxysteroids viz: nandrolone, $5{\alpha}-estrane-3{\beta}$, $17{\alpha}-diol$ exhibit lower detection responses in electrospray ionisation (ESI) because of their poor ionisation efficiency. To overcome this limitation pre-column chemical derivatization has been introduced to enhance their detection responses in $LC-ESI-MS^n$ analysis. The aim of present study was to develop a sensitive method for identification and confirmation of nandrolone and its metabolite in horse urine incorporating pre-column derivatization using picolinic acid. The method consists of extraction of targeted steroid conjugates by solid phase extraction (SPE). The eluted steroid conjugates were hydrolysed by methanolysis and free steroids were recovered with liquid-liquid extraction. The resulting steroids were derivatized to form picolinoyl esters and identification was done using LC-ESI-MS/MS in positive ionization mode. The picolinated steroid adduct enhanced the detection levels in comparison to underivatized steroids.

• Biomolecules & Therapeutics
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• v.5 no.3
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• pp.233-238
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• 1997

The distribution and excretion of radioactivity were examined after intraportal administration of sup 166/Ho-chitosan complex at a dose of 1 mcitg (10 mg chitosan/kg) to rats. Whole body macroautoluminographs showed that the radioactivity after an administration was concentrated in liver and perfused primarily to organs including kidney, spleen, and bone marrow, then to muscle and brain. Similar profiles were observed from 2 hr to 168 hr after the administration. The relative percentage of radioactivity in bone and spinal column increased with time, suggesting that free $^{166}$ Ho, released from chitosan complex deposited in the liver, selectively binds to these tissues. $^{166}$ Ho-chitosan complex administered intraportally was excreted less than 4% through urine (2.7$\pm$0.8%) and feces (0.65 $\pm$ 0.4%) up to seven days. These results demonstrate that the radio-activity of $_{166}$ Ho-chitusan complex when administered intraportally, mainly localizes in liver without affec-ting other tissues and organs. Considering the short half life of $^{166}$ Ho and the localization to the liver, $^{166}$ Ho-chitosan complex might be a useful agent in the treatment of hepatic carcinoma.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.64-67
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• 2011

The effect of Ta substitution on the crystal structure, ferroelectric, and piezoelectric properties of $Bi_{0.5}(Na_{0.82}K_{0.18})_{0.5}Ti_{1-x}Ta_xO_3$ ceramics has been investigated. The Ta doping resulted in a transition from coexistence of ferroelectric tetragonal and rhombohedral phases to an electrostrictive pseudocubic phase, leading to degradations of the remnant polarization, coercive field, and piezoelectric coefficient $d_{33}$. However, the electricfield-induced strain was significantly enhanced by the Ta substitution-induced phase transition and reached a highest value of $S_{max}/E_{max}$ = 566 pm/V under an applied electric field 6 kV/mm when 2% Ta was substituted on Ti sites. The abnormal enhancement in strain was attributed to the pseudocubic phase with high electrostrictive constants.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.972-975
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• 2001

The effect of Cr$_2$O$_3$(0 to 0.5 wt%) doping on the microstructure and electrical properties of ternary Pb(Zr,Ti)O$_3$-Pb(Ni,Nb)O$_3$piezoelectric ceramic has been investigated. Abnormal grain growth (grain size 3.3 to 11.2 $\mu$m) and densification are found. Minor additives of $\leq$0.1 wt% improve the mechanical coupling factor, but with more additives of $\geq$0.2 wt% electrical properties deteriorate. Thus, these phenomna can be ascribed mainly to anomalous developed microstructure. The large grains were composed of a core region that is free of Cr and a surrounding shell region rich in Cr. The interfaces between the core and the shell were composed of misfit dislocations. The mechanical properties of the specimens were strongly influenced by this microstructural change. The microstrutural and compositonal evolution of the specimens containing different amounts of Cr$_2$O$_3$were monitored. Electrical properties were measured and related to the variations in the microstructure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.623-626
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• 2004

[ $Ba_{0.6}Sr_{0.4}TiO_3$ ] (BST) dielectric thin films doped by Cr were prepared using an alkoxide-based sol-gel method on the Pt/Ti/SiO2/Si substrate. Atomic force microscopy and x-ray diffraction analysis showed that increasing the Cr doping ratio causes increased grain size while the surface remains smooth and crack-free. It was also found that compared with undoped films the increase of Cr content in BST improves the dielectric constant and the leakage-current characteristics. The figure of merit reached the maximum value of 72.3 at the 5 mol % of Cr doping. This composition showed the dielectric constant of 426, the loss factor of 0.0065, tenability of 47.7%, and leakage-current density (at the electric field of 100 kV/cm) of $5.31{\times}10^{-8}A/cm^2$. The results show that the Cr-doped BST thin films are prospective candidates for applications in tunable devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.229-233
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• 2015

In this paper, in order to develop outstanding Pb-free piezoelectric composition ceramics, the $(Na_{0.525}K_{0.443}Li_{0.037})(Nb_{0.883}Sb_{0.08}Ta_{0.037})O_3+0.3wt%Bi_2O_3+0.4wt%Fe_2O_3+xwt%CuO$ (x= 0~0.8 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effects of CuO-doping on the structure and electrical properties of the NKL-NST ceramics were systematically studied. The results show that the ceramics exhibit a pure perovskite structure with orthorhombic phase at room temperature, and secondary phase was found in the ceramics. The 0.4 wt%CuO added ceramics sintered at $950^{\circ}C$ showed the optimum properties of piezoelectric constant($d_{33}$), planar piezoelectric coupling coefficient(kp) and mechanical quality factor(Qm) : $d_{33}=213$[pC/N], kp= 0.43, Qm= 423,respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.8
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• pp.632-635
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• 2011

Additions (ZnO, CuO) doped $0.98(Na_{0.5}K_{0.5})NbO_3-0.02Li(Sb_{0.17}Ta_{0.83})O_3$ (0.98NKN-0.02LST-x) lead free piezoelectric ceramics have been fabricated by ordinary sintering technique. The effects of additions doping on the dielectric, piezoelectric, and ferroelectric properties of the ceramics were mainly investigated. X-ray diffraction of the sample appeared orthorhombic phase. The specimen doped with additions exhibits enhanced electrical properties ($d_{33}$= 153 pC/N). These results indicate that the 0.98NKN-0.02LST-x ceramics is a promising candidate for lead-free piezoelectric ceramics for applications such as piezoelectric actuators, harmonic oscillator and so on.

• Applied Science and Convergence Technology
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• v.27 no.5
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• pp.90-94
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• 2018

The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angle-resolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene, that is observed in pristine graphene indicating intrinsic electron-doping by the substrate, completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases by the presence of manganese atoms, approaching the electron band structure calculated using the local density approximation method. The former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition. The latter suggests that its electronic correlations are efficiently screened, suggesting that the dielectric property of the substrate is modified by manganese atoms and indicating that electronic correlations in grpahene can also be tuned by foreign atoms. These results pave the way for promising device application using graphene that is semiconducting and charge neutral.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.27-33
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• 2017

The determination of disulfide bonds is important for comprehensive understanding of the chemical structure of protein. So far, many strategies for the disulfide bond analysis have been suggested in terms of speed and sensitivity. However, most of these strategies have not considered free thiol residues in the target protein in the process of determining the disulfide bond. We suggested the strategy which was composed of four steps for the identification of disulfide bonds; the first step was the prediction of possible disulfide bonds, the second step was the determination of free cysteine residues, the third step was the analysis of disulfide bond using a high-resolution mass spectrometry, and the final step was the determination of disulfide bonds based on the comprehensive verification. In this study, we performed the characterization of disulfide bonds for the recombinant protein (HRPE1), where 1 and 5 inter- and intra-chain disulfide bonds were identified, respectively.