• Title, Summary, Keyword: ca15-3

Search Result 1,915, Processing Time 0.066 seconds

Affecting factors on low-temperature sintering of 0.85CaWO4-0.15SmNbO4 ceramics

  • Kim, Su-Jung;Kim, Eung-Soo
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.17 no.6
    • /
    • pp.245-250
    • /
    • 2007
  • This study was focused on the effect of sintering additive and particle size on the low temperature sintering of $0.85CaWO_4-0.15SmNbO_4$ ceramics. With an increase of $CaV_2O_6$ content, the sintering temperature of the specimens was reduced from $1150^{\circ}C\;to\;800^{\circ}C$. The dielectric constant (K) and Qf value were increased with $CaV_2O_6$ content. These results are due to the enhancement of the density by the liquid phase sintering. Temperature coefficient of resonant frequency (TCF) was slightly shifted to the positive value with $CaV_2O_6$ content. Typically, K of 12.64, Qf of 23,106 GHz, TCF of $-34ppm/^{\circ}C$ were obtained for the specimens with 7 wt.% $CaV_2O_6$ sintered at $900^{\circ}C$ for 3 h.

Lovastatin Induces Apoptotic Cell Death by Activation of Intracellular Ca2+ Signal in HepG2 Human Hepatoma Cells

  • Lee, Yong-Soo
    • Biomolecules & Therapeutics
    • /
    • v.15 no.3
    • /
    • pp.137-144
    • /
    • 2007
  • Although lovastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase, has been shown to have anti-cancer actions, the effect on human hepatoma cells was not investigated. Moreover, the exact mechanism of this action is not fully understood. In this study we investigated the mechanism by which lovastatin induces apoptosis using HepG2 human hepatoblastoma cells. Lovastatin induced apoptotic cell death in a dose-dependent manner in the cells, assessed by the flow cytometric analysis. Treatment with mevalonic acid, a precursor of cholesterol, did not significantly suppress the lovastatin-induced apoptosis. Lovastatin induced a rapid and sustained increase in intracellular $Ca^{2+}$ concentration. Treatment with EGTA, an extracellular $Ca^{2+}$ chelator did not significantly alter the lovastatin-induced intracellular $Ca^{2+}$ increase and apoptosis, whereas intracellular $Ca^{2+}$ reduction with BAPTA/AM and intracellular $Ca^{2+}$ release blockers (dantrolene and TMB-8) completely blocked these actions of lovastatin. In addition, the lovastatin-induced apoptosis was significantly reduced by a calpain inhibitor, a broad spectrum caspase inhibitor z-VAD-fmk and inhibitors specific for caspase-9 and caspase-3 (z-LEHD-fmk and z-DEVD-fmk, respectively), but not by an inhibitor specific for caspase-8 (z-IETD-fmk). Collectively, these results suggest that lovastatin induced apoptosis of HepG2 hepatoma cells through intracellular $Ca^{2+}$ release and calpain activation, leading to triggering mitochondrial apoptotic pathway. These results further suggest that lovastatin may be valuable for the therapeutic management of human hepatoma.

Dielectric properties and microstructures of (CaxSr1-x)ZrO3 ceramics

  • Li, Yu-De;Chen, Jian-Ming;Lee, Ying-Chieh
    • Journal of Ceramic Processing Research
    • /
    • v.19 no.6
    • /
    • pp.461-466
    • /
    • 2018
  • The effects of Ca/Sr ratio and the sintering temperature on the properties of $(Ca_xSr_{(1-x)})ZrO_3$ (CSZ) ceramics were investigated in this study. CSZ ceramics were prepared using solid-state reaction process, which were sintered in air at temperatures ranging from $1350^{\circ}C$ to $1450^{\circ}C$. Their structures were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The change in Ca/Sr ratio significantly affected the crystalline phase and the dielectric properties of the $(Ca_xSr_{(1-x)})ZrO_3$ ceramics. The secondary phase, $Ca_{0.15}Zr_{0.85}O_{1.85}$, was observed and increased correspondingly with the rising of sintering temperatures. In order to understand the effects of secondary phase on the dielectric properties of CSZ ceramics, the $Ca_{0.15}Zr_{0.85}O_{1.85}$ phase was prepared individually using solidstate method. The $Ca_{0.15}Zr_{0.85}O_{1.85}$ ceramics sintered at $1500^{\circ}C$ for 2 hours possessed a dielectric constant (${\varepsilon}_r$) of 21.7, a dielectric loss ($tan{\delta}$) of $49.510^{-4}$ and an Insulation Resistance (IR) of $2.1{\times}10^{10}{\Omega}$. The ($Ca_{0.7}Sr_{0.3})ZrO_3$ ceramics exhibited the best dielectric properties, with a permittivity of 29, a dielectric loss ($tan{\delta}$) of $2.7{\times}10^{-4}$, and an Insulation Resistance (IR) of $2.6{\times}10^{12}{\Omega}$.

Effects of $B_2O_3$ Addition on the Sintering Behavior and the Microwave Dielectric Properties of $(Mg_{0.93}Ca_{0.07})TiO_3$ Ceramics ($(Mg_{0.93}Ca_{0.07})TiO_3$ 세라믹스의 소결 및 마이크로파 유전특성에 미치는 $B_2O_3$의 영향)

  • 이득우;박재환;김인태;박재관;김윤호;최덕균
    • Journal of the Korean Ceramic Society
    • /
    • v.35 no.3
    • /
    • pp.287-293
    • /
    • 1998
  • The effects of B2O3 addition on the sintering behavior and th microwave dielectric properties of $(Mg_{0.93}Ca_{0.07})TiO_3$ ceramics were investigated. By addition of $B_2O_3$, increases the density of the ceramics increases and grain growth enhances, It was densified to over 94% of $(Mg_{0.93}Ca_{0.07})TiO_3$ theoretical density by the addition of 0.15-1.0wt% B2O3 and stable microwave dielectric properties observed by the addition of 0.2-0.4wt% $B_2O_3.\;(Mg_{0.93}Ca_{0.07})TiO_3$ ceramics sintered at $1200^{\circ}C$ exhibits maximum dielectric constants of 24-25 quality factor($Q{\times}f$) of more than 70000 and temperature coefficient of resonant frequency of $0\;ppm/^{\circ}C$ by adding of 0.15-0.4wt% $B_2O_3$.

  • PDF

Assessment of Applicability of a Calcium Carbonate-Alginate Beads as Neutralizer for the High Cell Density Cultivation of Isolated Sourdough Lactic Acid Bacteria (Sourdough에서 분리된 유산균의 고농도 배양을 위한 중화제로서 Calcium Carbonate-Alginate Bead의 이용가능성 평가)

  • Jung, Seung-Won;Lee, Kwang-Geun;Kim, Cheol Woo;Lee, Su Han
    • Food Engineering Progress
    • /
    • v.14 no.3
    • /
    • pp.208-216
    • /
    • 2010
  • Lab scale experiments were conducted in order to assess the applicability of $CaCO_{3}$-alginate beads as neutralizer for the high cell density cultivation and prepare the direct vat inoculation cultures of isolated sourdough lactic acid bacteria. With increasing the amount of bead and decreasing the diameter of bead in acidic solution, the neutralizing effect of $CaCO_{3}$-alginate bead became higher. In batch process with $CaCO_{3}$-alginate beads, Lactobacillus amylovorus DU-21 isolated from sourdough showed the highest viable cell counts and optical density in MRS broth. The values of viable cell counts and optical density were 9.996 log CFU/mL and 3.97, respectively. Experiments on the conditions which increase viability during lyophilization were carried out and the following results were obtained; 15% glycerol revealed the high cryoprotective effect on the concentrated cultures during lyophilization among the two cryoprotective agents. Consequently, $CaCO_{3}$-alginate beads and 15% glycerol were found to be useful not only to cultivate Lactobacillus amylovorus DU-21 but also to preserve strain.

An Effect of $Al_{2}O_{3}$ on the Reaction between Molten Converter Slag and CaO pellet (용융전로(熔融轉爐)슬래그와 CaO펠렛의 상호반응(相互反應)에 미치는 $Al_{2}O_{3}$의 영향(影響))

  • Kim, Young-Hwan;Ko, In-Yong
    • Journal of the Korean Institute of Resources Recycling
    • /
    • v.15 no.2
    • /
    • pp.3-9
    • /
    • 2006
  • As a basic study on the conversion of molten converter slag to the ordinary portland cement, the effects of $Al_{2}O_{3}$ addition on the interface reaction between solid CaO and molten converter slag has been studied. Alumina added converter slag whose basicity was controlled to 1 and 2 was melted and hold for 30 minutes in MgO crucible at $1500^{\circ}C$. Then sintered CaO pellet heated at the same temperature was dipped into the molten slag and held for 30minutes. After the reaction, the crucible was cooled in air and the specimen was cut off to the horizontal direction of the crucible. The dissolution rate of CaO pellet with the addition of $Al_{2}O_{3}$ was measured by the change of the radius or sintered CaO pellet and the interface layer was observed by SEM/EDX. As a result. At the basicity 2 slag, thickness of created $C_{3}S$ layer increased 3.5 times and quantity of $C_{6}AF_{2}\;or\;C_{4}AF$ phase increase 2 times than baisicy 1 slag.

High Frequency Dielectric Properties of $CaF_2$ filled Glass-Composites ($CaF_2$가 Filler로 첨가된 유리복합체의 고주파 유전특성)

  • Kim, Sun-Young;Lee, Kyoung-Ho;Kim, Sung-Won
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.277-281
    • /
    • 2003
  • Effects of $CaF_2$ addition as a filler on the high frequency dielectric properties and sintering of CaO-$Al_2O_3-SiO_2-B_2O_3$(CASB) and ZnO-MgO-$B_2O_3-SiO_2$(ZMBS) glass composites were investigated. The optimal glass composition in the CASB system was 33.0CaO-$17.0Al_2O_3-35.0SiO_2-15.0B_O_3$(in wt%). The corresponding dielectric properties were k=8.1 and $Q{\times}fo$=1,200GHz. The sintering temperature was $800{\mu}m$. In case of 2MBS system, 25.0ZnO-25.0MgO-20.0$B_2O_3-30.0SiO_2$(in wt%) glass showed k=6.8 and $Q{\times}fo$=5,200GHz when it was sintered at $750^{\circ}C$. The maximum amount of $CaF_2$ in the CASB and 2MBS glass system without any detrimental effect on the sintering was 25.0 v/o and 15.0 v/o, respectively. The addition of $CaF_2$ in the glass systems improved the high frequency dielectric properties. In case of CASB+$CaF_2$ composite, k was 7.1 and $Q{\times}fo$ was 2,300GHz. And in case of 2MBS+$CaF_2$ composite, k was 5.9 and $Q{\times}fo$ was 8,100GHz. $CaF_2$ addition also reduced sintering temperature. Effects of $CaF_2$ on the dielectric and sintering properties was analyzed in terms of viscosity and crystallization behavior changes due to the interaction between $CaF_2$ and the glass systems.

  • PDF

Isolation and Characterization of Insoluble Phosphate-Solubilizing Bacteria with Antifungal Activity (항진균능을 가진 불용성 인산 가용화 세균의 분리 및 특성)

  • Park, Ki-Hyun;Son, Hong-Joo
    • Korean Journal of Microbiology
    • /
    • v.42 no.3
    • /
    • pp.223-229
    • /
    • 2006
  • To develop multifunctional microbial inoculant, an insluble phosphate-solubilizing bacterium with antifungal activity was isolated from plant rhizospheric soil. On the basis of its morphological, cultural and physiological characteristics and Biolog analysis, this bacterium was identified as Pseudomonas fluorescens RAF15. P. fluorescens RAF15 showed antifungal activities against phytopathogenic fungi Botrytis cinerea and Rhizoctonia solani. The optimal medium composition and cultural conditions for the solubilization of insoluble phosphate by P. fluorescens RAF15 were 1.5% of glucose, 0.005% of urea, 0.3% $MgCl_2{\cdot}6H_2\;0.01%\;of\;MgSO_4{\cdot}7H_2O\;0.01%,\;of\;CaCl_2{\cdot}2H_2O$, and 0.05% of NaCl along with initial pH 7.0 at $30^{\circ}C$. The soluble phosphate production under optimum condition was 863 mg/L after 5 days of cultivation. The solubilization of insoluble phosphates was associated with a drop in the pH of the culture medium. P. fluorescens RAF15 showed resistance against different environmental stresses like $10-35^{\circ}C$ temperature, 1-4% salt concentration and pH 2-11 range. The strain produced soluble phosphate to the culture broth with the concentrations of 971-1121 mg/L against $CaHPO_4$, 791-908 mg/L against $Ca_3(PO_4){_2}$, and 844 mg/L against hydroxyapatite, respectively. However, the strain produced soluble phosphate to the culture broth with the concentrations of 15 mg/L against $FePO_4$, and 5 mg/L against $AlPO_4$, respectively.

Grain boundary structure and electrical characteristics of alkaline metallic cation-diffused $(SrCa)TiO_3$ ceramics (알칼리 금속 이온의 입계확산에 따른 $(SrCa)TiO_3$ 소결체의 입계구조 및 전기적 특성)

  • Heo, Hyeon;Cho, Nam-Hui
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.2 no.1
    • /
    • pp.183-193
    • /
    • 1999
  • Semiconducting (Sr0.85Ca0.15)TiO3 ceramics were prepared by conventional powder synthesis techniques, and then alkaline metallic cations were diffused into the ceramic bodies. The threshold voltage of the ceramics increases with increasing diffusion time and the amount of diffused materials. The ceramics had boundary potential heights of 0.01 ~ 2.89 eV, while their boundary resistance ranged from 2.2 $M{\Omega}$ to 120.4 $M{\Omega}$. Such electrical characteristics of the boundaries were correlated with the boundary structure of the ceramics obtained by transmission electron microscopy.

  • PDF

Microstructure and Dielectric Properties of ($Sr_{1-x}Ca_x)TiO_3$ Ceramic Thin Film by RF Sputtering Method (RF 스퍼터링법에 의한 ($Sr_{1-x}Ca_x)TiO_3$ 세라믹 박막의 미세구조 및 유전특성)

  • 김진사;오재한;이준웅
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.11 no.11
    • /
    • pp.984-989
    • /
    • 1998
  • The ($Sr_{1-x}Ca_x)TiO_3$(SCT) thin films are deposited on Pt-coated electrode($Pt/TiN/SiO_2/Si$) using RF sputtering method with substitutional contents of Ca. The maximum grain of thin films is obtained by substitution of Ca at 15[mol%]. All SCT thin films had (111) preferred orientation. The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over 15[mol%]. The dielectric constant changes almost linearly in temperature ranges of -80~+90[$^{\circ}C$]. The temperature properties of the dielectric loss have a stable value within 0.02 independent of the substitutional contents of Ca. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

  • PDF