• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.799-801
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• 1988

This paper was studied on the effects of Ca-La-Nb substitution and Zr/Ti ratio variation to Pb(Zr, Ti)$O_3$ system on structural, electrical, optical and sound level characteristics in order to develope the piezoelectric and electrooptic ceramic devices. Also the specimens were prepared by the two stage sintering technique. The molecular formular was X($CaO{\cdot}1/4La_{2}O_{3}{\cdot}1/4Nb_{2}O_{5}){\cdot}(1-X)Pb(Zr_{Y}Ti_{1-Y})O_{3}$(x=100X, y=100Y), and the variation of x was $6{\sim}12$, y was 60${\sim}$49 and second stage sintering time was 20${\sim}$40 hours. The experimental results obtained from this study are as follows : 1. The density was decreased, the grain size was increased according to increase of Ca-La-Nb substitution. 2. The crystal structure was rhombohedral in composition 6/60/40, and the crystal structure was tetragonal and cubic according to increase of Ca-La-Nb substitution. 3. The Ca substitution of PZT system enhanced the sintering property. The Pb site vacancy resulting from the substitution of La-Nb increased the dielectrical constant, the piezoelectric charge constant, the dielectric loss and decreased the coercive field. 4. The resistivity of PZT system which has the P type conduction mechanism increased according to substitution of La-Nb because of the substituent acting as donor. 5. The PZT ceramics varied from ferroelectric substance according to increase of Ca-La-Nb substituent. The coercive field and saturation remanent polarization decreased, and at last straight line according to increase of La-Nb substitution. 6. The amount of Ca-La-Nb substitution to improve the light transmittance of speciment was 10 mol%, the Zr/Ti ratio was 49/51, and the second stage sintering time was 40 hours. 7. According to Ca-La-Nb substitution, the specimens was to be transparent. The 7.5/51/49 specimen was suitable for transparent sound vibrator because it had 58% light transmittance (thick 0.2[mm], wave length 700[mm]) and 48% electromechanical coupling factor.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.647-659
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• 2008

Colloids are a heterogeneous system in which particles of a few nanometers to hundreds micrometers in size are finely dispersed in liquid medium, but show homogeneous properties in macroscopic scale. They have attracted much attention not only as model systems of natural atomic and molecular self-assembled structures but also as novel structural materials of practical applications in a wide range of areas. In particular, recent advances in colloidal science have focused on nano-bio materials and devices which are essential for drug discovery and delivery, diagnostics and biomedical applications. In this review, first we introduce nano-bio colloidal systems and surface modification of colloidal particles which creates various functional groups. Then, various methods of fabrication of colloidal particles using holographic lithography, microfluidics and virus templates are discussed in detail. Finally, various applications of colloids in metal inks, three-dimensional photonic crystals and two-dimensional nanopatterns are also reviewed as representative potential applications.

• Journal of Life Science
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• v.19 no.9
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• pp.1218-1225
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• 2009

Difractose anhydrides (DFAs) is studied as a sweetener for diabetics because of its structural property. DFAs have four types: DFA I, III, IV (degradation of levan) and V (degradation of inulin). Especially, DFA IV has been shown to enhance the absorption of calcium in experiments using rats. Levan fructotransferase is an enzyme for producing di-d-fructose-2,6':6,2-dianhydride (DFA IV). To identify structural characterization, we purified wild-type and mutants (D63A, D195N and N85S) of levan fructotransferase (LFTase) from Microbacterium sp. AL-210. These proteins were purified to apparent homogeneity by Ni-NTA affinity column, Q-sepharose ion exchange and gel filtration chromatography and detected by SDS-PAGE. They were also analyzed by circular dichroism (CD) measurements, JNET secondary structure prediction, activity measurements at various temperatures, and pH analysis. The optimum pH for the enzyme-catalyzed reaction was pH 7.5 and optimum temperature was observed at $55^{\circ}C$. Along with wild-type LFTase, mutants were analyzed by CD measurement, fluorescence analysis and differential scanning calorimetry (DSC). N85S showed less $\alpha$-helix and more $\beta$ strand than others. Also, N85S showed almost the same curve as wild-type in their steady-state fluorescence spectra, whereas mutant D63A and D195N showed higher intensity than wild-type. The amino acid sequence of wild-type LFTase was compared to the sequences of exo-inulinase from Aspergillus awamori, a plant fructan 1-exohydrolase from Cichorium intybus, and Thermotogo maritime (Tm) invertase and showed a high identity with Exo-inulinase from Aspergillus awamori.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.81-85
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• 2007

MnTe layers of high crystalline quality were successfully grown on Si(100) : B and Si(111) substrates by molecular beam epitaxy (MBE). Under tellurium-rich condition and the substrate temperature around $400^{\circ}C$, a layer thickness of $700{\AA}$ could be easily obtained with the growth rate of $1.1 {\AA}/s$. We investigated the structural, magnetic and transport properties of MnTe layers by using x-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometry, and physical properties measurement system (PPMS). Characterization of MnTe layers on Si(100) : B and Si(111) substrates by XRD revealed a hexagonal structure of polycrystals with lattice parameters, ${\alpha}=4.143{\pm}0.001{\AA}\;and\;c=6.707{\pm}0.001{\AA}$. Investigation of magnetic and transport properties of MnTe films showed anomalies unlike antiferromagnetic powder MnTe. The temperature dependence of the magnetization data taken in zero-field-tooling (ZFC) and field-cooling (FC) conditions indicates three magnetic transitions at around 21, 49, and 210 K as well as the great irreversibility between ZFC and FC magnetization in the films. These anomalies are attributable to a magnetic-elastic coupling in the films. Magnetization measurements indicate ferromagnetic behaviour with hysteresis loops at 5 and 300 K for MnTe polycrystalline film. The coercivity ($H_c$) values at 5 and 300 K are 55 and 44 Oe, respectively. In electro-transport measurements, the temperature dependence of resistivity revealed a noticeable semiconducting behaviours and showed conduction via Mott variable range hopping at low temperatures.

• Journal of Conservation Science
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• v.31 no.3
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• pp.227-241
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• 2015

Fungi were isolated from mural painting in tomb no.6 at songsan-ri, Gong-ju. Antifungal susceptibility of essential oils extracted from natural medicine was tested and it confirmed applicability for mural painting in tombs. 26 species of fungi collected from air-borne and wall surfaces were identified to 15 species of Ascomycetes, 2 species of Zygomycetes, 1 of Basidiomycetes. Wheat starch and gelatin degradability were evaluated as isolated fungi. SY-18, SY-23, SY-25 showed high degradability of wheat starch. SY-18, SY-21, SY-23 were decomposed into gelatin. Biochemical characteristics of decomposing fungi to wheat starch glue and cowhide glue were analyzed by using ${\alpha}-amylase$ and gelatinase activity. An Antifungal test was conducted in Anethole and Eugenol. Anethole and Eugenol mixture(1:2) showed high antifungal susceptibility. Natural adhesives help microbial growth and can cause structural damage in mural painting. The expectation of this study is the possibility to control microbial growth in wall painting using natural essential oils. It can be used as a data for conservation method to control microbial damages.

• The Korean Journal of Pharmacology
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• v.29 no.1
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• pp.131-137
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• 1993

Human neutrophil elastase (HNE, EC 3,4,21, 11), a mediator of tissue breakdown, was inhibited by tetracycline, oxytetracycline and demeclocycline. Among them, oxytetracycline showed the most potent inhibitory effect on the activity of HNE. IC50 of this drug at our specific condition was less than 1 mM. Tetracycline inhibited human neutrophil elastase non-competitively, and oxytetracycline inhibited competitively. Ki values of tetracycline and oxytetracycline were 4.9 mM and 0.39 mM, respectively. Structural modified tetracycline, de-dimethylaminotetracycline, which showed no antibiotic activity since the active dimethylamino radical was removed from the position #4 of the tetracycline, showed similar inhibition effect on the activity of human neutrophil elastase to that of tetracycline. Thus, we speculated that inhibition of human neutrophil elastase by tetracyclines was not depended on the dimethylamino radical which is a critical active site for antibiotic effect, rather it was depended on the hydoxyl radical of tetracyclines. Therefore, the property of inhibiting elastase may be an additional molecular biochemical mechanism of action of these drugs at the inflammatory sites.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.90-95
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• 2014

Nylon66 extrudates as a function of the extrusion number were prepared by a twin screw extruder. Chemical structures, thermal properties, melt index, crystal structures, mechanical properties such as the tensile strength, elongation at break and impact strength, and rheological property were measured by FT-IR, $^1H$-NMR, melt indexer, DSC, TGA, XRD, universal tensile tester, Izod impact tester, and rheometer. FT-IR and $^1H$-NMR characterizations indicated that the number of extrusions did not affect the chemical structure. The decrease in the molecular weight was checked by the melt index of extrudates. There were no effects of the thermal history on the melting and degradation temperature. The tensile and impact strength and modulus were found to be similar, regardless of the number of extrusions, but the elongation decreased significantly. The complex viscosity of extrudates at low frequencies decreased with the extrusion number. No structural changes after extrusion were confirmed from the fact that there was no change in the slope and shape of G'-G" plot.