• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.929-932
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• 2004

It is known that small amount of MgO in excess is often added to develop pure perovskite single phase of PMN-based composite, however, extra MgO precipitates in grains and inhibits densification of PMN. In this study PMN-PT-BT (PBT) powder was prepared by a conventional mixed oxide method using $(MgCO_3)_4{\cdot}Mg(OH)_2{\cdot}5H_{2}O$ instead of MgO. The precursor was heated at $500^{\circ}C/1h$ and its surface was modified with MgO sol. This effect was investigated in the aspects of sintering and dielectric properties. Small amount of added MgO sol ($0.5{\sim}1.0wt\%$) enhanced sintering substantially below $1000^{\circ}C$. The PBT with $0.5wt\%$ MgO sol sintered at $900^{\circ}C/2h$ had density of $7.62\;g/cm^3$, room temperature dielectric constant of 14800, loss of dielectric constant of $1.1\%$, which were comparable to those of the PBT sintered at $1000^{\circ}C/2h$. It was noticeable that the extra MgO precipitated mostly on triple points and grain boundaries and resulted in inhibition of grain growth.

• Mass Spectrometry Letters
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• v.5 no.2
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• pp.42-48
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• 2014

A specific and sensitive liquid chromatography-electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed and validated for the simultaneous quantification of porphyrins (coproporphyrin, pentacarboxylporphyrin, hexacarboxylporphyrin, heptacarboxylporphyrin, and uroporphyrin) in human plasma and urine. Acidified plasma samples and urine samples were prepared by using liquid-liquid extraction using ethyl acetate and protein precipitation with acetonitrile, respectively. The separation was achieved onto a Synergi Fusion RP column ($150mm{\times}2.0mm$, $4{\mu}m$) with a gradient elution of mobile phase A (0.1% formic acid in 2 mmol/L ammonium acetate, v/v) and mobile phase B (20% methanol in acetonitrile, v/v) at a flow rate of $450{\mu}L$/min. Porphyrins and the internal standard (IS), coproporphyrin I-$^{15}N_4$, were detected by a tandem mass spectrometer equipped with an electrospray ion source operating in positive ion mode. Multiple reaction monitoring (MRM) transitions of the protonated precursor ions and the related product ions were optimized to increase selectivity and sensitivity. The proposed method was validated by assessing selectivity, linearity, limit of quantification (LOQ), precision, accuracy, recovery, and stability. The calibration curves were obtained in the range of 0.1-100 nmol/L and the LOQs were estimated as 0.1 nmol/L for all porphyrins. Results obtained from the validation study of porphyrins showed good accuracy, precision, recovery, and stability. Finally, the proposed method was successfully applied to clinical studies on the autism spectrum disorder (ASD) diagnosis of 203 Korean children.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.174-181
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• 2007

In this study, $SiO_2/poly(ethylene-co-vinyl$ alcohol)(EVOH) hybrid coating materials with gas barrier property could be produced using sol-gel method. The biaxially oriented polypropylene (BOPP) substrate with surface pretreatment was coated with the prepared hybrid sols containing various inorganic silicate component by a spin coating method. Crystallization behavior of the hybrids was investigated in terms of analysis of X-ray diffraction and cooling thermogram from DSC experiment. From the morphological observation of the $SiO_2/EVOH$ hybrid gel, it was confirmed that there existed an optimum content of inorganic silicate precursor, Tetraethylorthosilicate (TEOS), to produce hybrid materials with dense microstructure, exhibiting uniformly dispersed silica particles with average size below 100 nm. When TEOS was added at below or above the optimum content, particle clusters with large domain were observed, resulting in phase separation. This morphological result was found to be in good agreement with that of oxygen permeability of the hybrid coated films. In the case of film coated with hybrid prepared from addition of 0.01 - 0.02mol of TEOS, a remarkable improvement in barrier property could be obtained, however, with the addition of TEOS more than 0.04 mol, the barrier property was dramatically reduced because of phase separation and micro-crack formation on the film surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.146-147
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• 2011

Processing a large area substrate for liquid crystal display (LCD) or solar panel applications in a capacitively coupled plasma (CCP) reactor is becoming increasingly challenging because of the size of the substrate size is no longer negligible compared to the wavelength of the applied radio frequency (RF) power. The situation is even worse when the driving frequency is increased to the Very High Frequency (VHF) range. When the substrate size is still smaller than 1/8 of the wavelength, one can obtain reasonably uniform process results by utilizing with methods such as tailoring the precursor gas distribution by adjustingthrough shower head hole distribution or hole size modification, locally adjusting the distance between the substrate and the electrode, and shaping shower head holes to modulate the hollow cathode effect modifying theand plasma density distribution by shaping shower head holes to adjust the follow cathode effect. At higher frequencies, such as 40 MHz for Gen 8.5 (2.2 m${\times}$2.6 m substrate), these methods are not effective, because the substrate is large enough that first node of the standing wave appears within the substrate. In such a case, the plasma discharge cannot be sustained at the node and results in an extremely non-uniform process. At Applied Materials, we have studied several methods of modifying the standing wave pattern to adjusting improve process non-uniformity for a Gen 8.5 size CCP reactor operating in the VHF range. First, we used magnetic materials (ferrite) to modify wave propagation. We placed ferrite blocks along two opposing edges of the powered electrode. This changes the boundary condition for electro-magnetic waves, and as a result, the standing wave pattern is significantly stretched towards the ferrite lined edges. In conjunction with a phase modulation technique, we have seen improvement in process uniformity. Another method involves feeding 40 MHz from four feed points near the four corners of the electrode. The phase between each feed points are dynamically adjusted to modify the resulting interference pattern, which in turn modulate the plasma distribution in time and affect the process uniformity. We achieved process uniformity of <20% with this method. A third method involves using two frequencies. In this case 40 MHz is used in a supplementary manner to improve the performance of 13 MHz process. Even at 13 MHz, the RF electric field falls off around the corners and edges on a Gen 8.5 substrate. Although, the conventional methods mentioned above improve the uniformity, they have limitations, and they cannot compensate especially as the applied power is increased, which causes the wavelength becomes shorter. 40 MHz is used to overcome such limitations. 13 MHz is applied at the center, and 40 MHz at the four corners. By modulating the interference between the signals from the four feed points, we found that 40 MHz power is preferentially channeled towards the edges and corners. We will discuss an innovative method of controlling 40 MHz to achieve this effect.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.543-553
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• 1996

Oxygen reduction in an alkaline fuel cell was studied by using perovskite type oxides as an oxygen electrode catalyst. The high surface area catalysts were prepared by malic acid method and had a formula of $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$(x=0.00, 0.01, 0.10, 0.20, 0.35 and 0.50). From the result of XRD pattern and specific surface area due to the amount of Fe substitution and the consumption of ammonia-water, the complex formation of Fe ion with $NH_3$ was the main factor for both the phase stability of perovskite and the increase of specific surface area. Multi-step calcination was necessary to give a single phase of perovskite in catalyst precursor. The crystal structure of the catalysts was simple cubic perovskite, which was verified from the XRD patterns of the catalysts. The activity of oxygen reduction was monitored by the techniques of cyclic voltammetry, static voltage-current method, and current interruption method. The activity(current density) of oxygen reduction showed its minimum at x=0.01 and its maximum between 0.20 and 0.35 of x-value in $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$. This tendency was independent of the change of surface area.

• Microbiology and Biotechnology Letters
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• v.26 no.3
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• pp.195-199
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• 1998

AH alkalophilic Bacillus SP. AIk-7, isolated from soil, produced ethylene. The characteristics of this microorganism is the ability to grow well under the alkaline condition, at pH 10.3. This strain is similar to Bacillus alkalophilus in terms of morphological, physiological and biological characteristics. In observation of relationship of cell growth and ethylene production according to incubation times, the ethylene synthesis mostly occur from the late exponential phase to the death phase of growth. The purpose of this paper is to study the effects of various substrates on the biosynthesis of ethylene in the intact cell and the cell-free system by the Bacillus sp. AIk-7. In both intact cell and cell-free extract, optimum conditions for ethylene production was achieved at pH 10.3 and 3$0^{\circ}C$. Ethylene was effectively produced from L-Met and 1-aminocyclopropane-1-carboxylic acid (ACC). In this case, ACC as the substrate on ethylene production were two fold higher than L-met at each concentration of substrates. On the other hand, the cell-free ethylene-forming system was used as a tool for the elucidation of the biochemical reaction involved in the formation of ethylene by Bacillus sp. AIk-7. Ethylene production in the cell-free system required the presence of manganese and cobalt ion to be stimulated a little. The result obtained in this work suggests that L-met and ACC may be a precursor more directly related to bacterial ethylene production than any other substrates tested.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.1023-1029
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• 2001

Hexagonal ferrite $Co_2$Z(B $a_3$ $Co_2$F $e_{24}$ $O_{41}$ ) was prepared by various coprecipitation-oxidation methods. The formation of $Co_2$Z was studied in order to determine the optimal method. The $Co_2$Z composition hydroxides were prepared with the different oxidation and precipitation from the aqueous solution of $Ba^{2+}$, $Co^{2+}$ and F $e^{2+}$ chloride mixture. The coprecipitates were heat-treated at various temperatures, and their formation phases and microstructures were investigated from the analyses of DTA/TGA, powder XRD and SEM. The $Co_2$Z phase was observed in the case where the precursor will have the amorphous like oxyhydoxide($\delta$-FeOOH), and formed from $Ba_3$F $e_{32}$ $O_{51}$ , BaF $e_{12}$ $O_{19}$ (M-type) and $Ba_2$ $Co_2$F $e_{12}$ $O_{22}$ (Y-type). The $Co_2$Z was synthesized by the heat-treatment of the coprecipitate, which was prepared from the precipitation after oxidizing the chloride mixed solution, above 110$0^{\circ}C$.EX>.

• The Korean Journal of Zoology
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• v.14 no.4
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• pp.199-204
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• 1971

The effect of 400 R total-body X-irradiation on the rate of deoxycytidine-2-$^14 C$(CdR-2-$^14 C$) into DNA and on the degradation of DNA has been studied in the liver, spleen and thymus of the rat. The postirradiation period can be divided into a radiation reaction period followed by a regeneration period. During the period of radiation reaction, which consists of days 1-2, markdely decreased CdR-2-$^14 C$ incorporation into DNA of each organ is observed. Rate of incorporation of labeled precursor in the thymus shows the most profound decrease, whereas those in the liver and spleen show similar decrease when expressed as percent of normal. The change in the amount of DNA as percent of normal exhibits a similar pattern in all organs, but the rate of decrease is larger in the spleen and thymus compared to that in the liver. The period of regeneration as judged by the incorporation experiment appears day 4 to 5, which consists of the second phase of the regeneration period. The second phase is highlighted by a markedly increased rate of CdR-2-$^14 C$ incorporation and by a slow and continued increase in the amount of DNA in all organs. The regeneration occurs faster in the liver and spleen than in the thymus which is the most radiosensitive of the all. The findings of the present experiments are strongly suggestive of the fact that the radiation-induced loss of spleen and thymus DNA as well as the radiation-caused inhibition in the CdR incorporation into DNA of the thymus are the important factors in the elevated levels of CdR in the urine and plasma.

• The Korean Journal of Zoology
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• v.15 no.1
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• pp.1-14
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• 1972

The effect of 400 R of whole-body X-irradiation on DNA synthesis, DNA degradation, CdR-aminohydrolase activity and oxygen uptake in the liver, spleen and thymus of the rat has been studied in connection with the radiosensitivity of these tissues. The rate of CdR-2-$^14 C$ incorporation has been followed during the postirradiation period and has been correlated with the increased levels of CdR-aminohydrolase activity druing this period. The postirradiation period comprises radiation reaction and tissue regeneration periods. During the period of radiation reaction, markedly decreased precursor incorporation, decreased tissue levels of DNA and decreased uptake of oxygen are noted as well as an increase in the CdR-aminohydrolase activity. The period of regeneration appears to consist in two discrete phases. The first phase reveals a return of CdR-aminohydrolase activity and the second phase is highlighted by a markedly increased rate of labeled CdR incorporation. Various events occurring during the radiation reaction period and the regeneration period in the three tissues studied can be considered qualitatively the same, differing only in the degree of acute cell death, in the duration of the delay of DNA synthesis in the sruviving cells, and in the rate of recovery resulting from accelerated cell replication during the period of regeneration. A possible biochemical mechanism involved in the DNA synthesis and degradation, in connection with the inreased levels of CdR-aminohydrolase after irradiation, has been briefly discussed.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.51-56
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• 2016

To fabricate a copper (Cu)-based fine conductive filler having antioxidation property, submicron silver (Ag)-coated Cu particles were fabricated and their antioxidation property was evaluated. After synthesizing the Cu particles of $0.705{\mu}m$ in average diameter by a wet-reduction process, Ag-coated Cu particles were fabricated by successive Ag plating using ethylene grycol solvent. Main process parameters in the Ag plating were the concentration of reductant (ascorbic acid), the injection rate of Ag precursor solution, and the stirring rate in mixed solution. Thus, Ag plating characteristics and the formation of separate fine pure Ag phase were observed with different combinations of process parameters. As a result, formation of the separate pure Ag phase and aggregation between Ag-coated Cu particles could be suppressed by optimization of the process parameters. The Ag-coated Cu particles which were fabricated using optimal conditions showed slight aggregation, but excellent antioxidation property. For example, the particles indicated the weight gain not exceeding 0.1% until $225^{\circ}C$ when they were heated in air at the rate of $10^{\circ}C/min$ and no weight gain until 75 min when they were heated in air at $150^{\circ}C$.