• 열처리공학회지
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• 제17권3호
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• pp.173-179
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• 2004

In this study, the influence of heat treatment and Ca contents on the electrochemical behavior was investigated. Mg-Ca alloys, i.e., Mg-0.22wt%Ca, Mg-0.56wt%Ca, Mg-1.31wt%Ca are prepared by ingot metallurgy. As-cast Mg-Ca alloys exhibited better electrochemical properties than pure Mg. Especially, Mg-0.22wt%Ca alloy improves its anode efficiency up to 62% and lowers the OCP up to -1.72VSCE. Microstructure and XRD patterns of Mg-Ca alloys show that additive Ca element is mainly solid-solutioned. While, the others show the microstructure and XRD pattern with large $Mg_2Ca$ at grain boundary. To assess the effect of heat treatment on the as-cast Mg-alloy, the specimens were heat treated at $200^{\circ}C$ for 2 hours under $CO_2$ gas atmosphere. Although corrosion properties of Mg-Ca alloys are somewhat deteriorated by heat treatment at $200^{\circ}C$ Mg-0.22wt%Ca alloy with uniformly distributed nano-sized $Mg_2Ca$ phase in ${\alpha}$-Mg matrix show still better corrosion properties than pure Mg specimen.

• 마이크로전자및패키징학회지
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• 제11권3호
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• pp.17-22
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• 2004

[ $CaZrO_3$ ]세라믹스에 대하여 $CaTiO_3$세라믹스의 첨가량 변동에 따른 마이크로파 유전특성을 조사하였다. 또한 중유전율 LTCC 기능성 기판으로 활용하기 위하여 저융점의 유리 프리트를 첨가하여 $CaZrO_3-CaTiO_3$ 세라믹스의 저온 소결 거동과 마이크로파 유전특성을 평가하였다. 저온 소결 조제로 사용된 저응점의 유리 프리트를 $10-20 wt\%$ 범위로 첨가함으로서 $CaZrO_3-CaTiO_3$ 세라믹스의 소결온도를 $1450^{\circ}C$에서 $900^{\circ}C$이하로 낮출 수 있었다. 음의 온도계수를 갖는 $CaZrO_3$ 및 유리프리트에 대하여 양의 온도계수를 갖는 $CaTiO_3$ 세라믹스의 분율을 적정히 제어함으로서 제로의 온도계수를 구현할 수 있었다. $CaZrO_3-CaTiO_3$ 세라믹스에 저온 소결용 유리 프리트를 $15 wt\%$ 첨가하여 $875^{\circ}C$에서 소결한 경우. 유전율(k) 23, 품질계수(Q${\times}$f) 2500, 공진 주파수 온도계수$(T_f) -3 ppm/^{\circ}C$의 매우 양호한 마이크로파 유전특성을 나타내었다.

• Journal of Ginseng Research
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• 제33권1호
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• pp.59-64
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• 2009

$Ca^{2+}$ and calmodulin (CaM), a key $Ca^{2+}$ sensor in all eukaryotes, have been implicated for defense responses of plants. Eukaryotic CaM contains four structurally and functionally similar $Ca^{2+}$ domains named I, II, III and IV. Each $Ca^{2+}$ binding loop consists of 12 amino acid residues with ligands arranged spatially to satisfy the octahedral symmetry of $Ca^{2+}$ binding. To investigate the altered gene expression and the role of CaM in ginseng plant defense system, cDNA clone containing a CaM gene, designated PgCaM was isolated and sequenced from Panax ginseng. PgCaM, which has open reading frame of 450 nucleotides predicted to encode a precursor protein of 150 amino acid residues. Its sequence shows high homologies with a number of other CaMs, with more similarity to CaM of Daucus carota (AAQ63461). The expression of PgCaM in different P. ginseng organs was analyzed using real time PCR. The results showed that PgCaM expressed at different levels in young leaves, shoots, and roots of 3-week-old P. ginseng. In addition, the expressions of PgCaM under different abiotic stresses were analyzed at different time intervals.

• The Korean Journal of Physiology and Pharmacology
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• 제2권5호
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• pp.611-616
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• 1998

Although the $Ca^{2+}-activated\;K^+\;(I_{K,Ca})$ channel is known to play an important role in the maintenance of resting membrane potential, the regulation of the channel in physiological condition is not completely understood in vascular myocytes. In this study, we investigated the role of cytoplasmic $Mg^{2+}$ on the regulation of $I_{K,Ca}$ channel in pulmonary arterial myocytes of the rabbit using the inside-out patch clamp technique. $Mg^{2+}$ increased open probability (Po), but decreased the magnitude of single channel current. $Mg^{2+}-induced$ block of unitary current showed strong voltage dependence but increase of Po by $Mg^{2+}$ was not dependent on the membrane potential. The apparent effect of $Mg^{2+}$ might, thus, depend on the proportion between opposite effects on the Po and on the conductance of $I_{K,Ca}$ channel. In low concentration of cytoplasmic $Ca^{2+},\;Mg^{2+}$ increased $I_{K,Ca}$ by mainly enhancement of Po. However, at very high concentration of cytoplasmic $Ca^{2+},$ such as pCa 5.5, $Mg^{2+}$ decreased $I_{K,Ca}$ through the inhibition of unitary current. Moreover, $Mg^{2+}$ could activate the channel even in the absence of $Ca^{2+}.\;Mg^{2+}$ might, therefore, partly contribute to the opening of $I_{K,Ca}$ channel in resting membrane potential. This phenomenon might explain why $I_{K,Ca}$ contributes to the resting membrane potential where membrane potential and concentration of free $Ca^{2+}$ are very low.

• 한국환경농학회지
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• 제30권3호
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• pp.229-233
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• 2011

BACKGROUND: Soil acidification, which is known to be one of the reasons of forest decline, is associated with decreases in exchangeable Ca and increases in Al concentration, leading to low Ca/Al ratio in soil solution. As tree rings are datable archives of environmental changes, Ca/Al ratios of annual growth ring may show decreasing pattern in accordance with the progress of soil acidification. This study was conducted to investigate Ca/Al pattern of Pinus densiflora tree ring in an attempt to test its usefulness as an indicator of historical soil acidification. METHODS AND RESULTS: Three P. densiflora tree disks were collected from P. densiflora forests in Jeonnam province, and soil samples (0-10, 10-20, and 20-30 cm in depth) were also collected from the tree locations. Soils were analyzed for pH and exchangeable Ca and Al concentrations, and Ca/Al was calculated. Annual growth rings formed between 1969 and 2007 were separated and analyzed for Ca/Al. Soil Ca/Al was positively (P<0.01) correlated with soil pH, suggesting that soil acidification decreased Ca while increasing Al availability, lowering Ca/Al in soil solution. The Ca/Al of tree rings also showed a decreasing pattern from 18.2 to 5.5 during the period, and this seemed to reflect historical acidification of the soils. CONCLUSION(s): The relationship between soil pH and Ca/Al and the decreasing pattern of Ca/Al of tree ring suggest that Ca/Al of tree ring needs to be considered as a proxy of the progress of soil acidification in P. densiflora forest in southern Korea.

• 생물환경조절학회지
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• 제22권3호
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• pp.202-208
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• 2013

본 연구애서는 '후지' 사과의 CA 저장을 실용화하기 위하여 수확시기와 일정기간 저온저장한 후 CA 환경을 설정하는 지연 CA 처리가 저장 중 내부갈변장해와 과실품질에 미치는 영향을 조사하였다. 1차 년도에 '후지' 사과를 10월 22일에 수확하였을 때 밀병 발생율이 40%였고, CA 환경 조성($O_2\;2.5{\pm}0.5%+CO_2\;2.5{\pm}0.5%$)을 20일 지연 CA 저장하였을 때는 내부갈변이 발생하였으나, 30일 지연 CA 저장에서는 내부갈변이 발생하지 않았다. 2차 년도에는 수확시기가 늦어질수록 밀병 발생율이 높았고, 이러한 과실은 10~30일 지연 CA 처리구에서 내부갈변장해가 발생하였으나, 40일 지연 CA 처리구에서는 내부갈변장해가 발생하지 않았다. 호흡량은 저온저장 과실에서는 저장기간이 길어질수록 급격히 증가하였으나 지연 CA 저장에서는 호흡량이 낮게 유지되었고, 급속 CA 저장에 비해서 차이를 보이지 않았다. 에틸렌 발생량은 지연 CA 저장한 과실들이 저온저장에 비해서 낮았으나, 급속 CA 저장에 비해서는 다소 높은 발생량을 보였다. 산 함량은 지연 CA 저장이 급속 CA 저장에 비해 저장기간이 길어질수록 감소하는 경향이었고, 경도는 저장 8개월 후에도 급속 CA 처리구와 지연 CA 처리구간에는 차이를 보이지 않았다.

• The Korean Journal of Physiology and Pharmacology
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• 제10권1호
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• pp.25-30
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• 2006

Lysophosphatidylcholine (LPC), which accumulates in atherosclerotic arteries, has been reported to inhibit endothelium-dependent relaxation (EDR) in many different species. However, the underlying mechanism of LPC-induced inhibition of EDR is still uncertain. In the present study, we measured simultaneously both isometric tension and cytosolic free $Ca^{2+}$ ($[Ca^{2+}]_i$) in rabbit carotid strips, and examined the effect of LPC on tension and $[Ca^{2+}]_i$. In carotid strips with intact-endothelium, high $K^+$ (70 mM) increased both tension and $[Ca^{2+}]_i$, and cumulative addition of acetylcholine (ACh) from 0.1 to $10{\mu}M$ induced dose dependent increase of $[Ca^{2+}]_i$ with concomitant relaxation. In the presence of L-NAME (0.1 mM), ACh increased $[Ca^{2+}]_i$ without affecting the amplitude of high $K^+-induced$ tension. These ACh-induced change of $[Ca^{2+}]_i$ and tension was abolished by removal of endothelium or 10 nM 4-DAMP (muscarinic receptor antagonist) pretreatment. Pretreatment of LPC ($10{\mu}M$) inhibited ACh ($10{\mu}M$)-induced change of tension and $[Ca^{2+}]_i$ in endothelium-intact carotid artery. On the other hand, LPC had no effect on ACh-induced change of tension and $[Ca^{2+}]_i$ in endothelium denuded artery. In $Ca^{2+}$-free external solution, ACh transiently increased $[Ca^{2+}]_i$, and pretreatment of LPC significantly inhibited ACh-induced transient $[Ca^{2+}]_i$ change. Based on the above results, it may be concluded that LPC inhibits the ACh-induced $[Ca^{2+}]_i$ change through inhibition of $Ca^{2+}$ mobilization in vascular endothelial cells, resulting in decreased production of NO and concomitant inhibition of endotheliumdependent vascular relaxation.

• 대한한의학회지
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• 제18권1호
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• pp.198-207
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• 1997

To explore the action mechanism of Ijintang in the brain, the authors investigated the effects of Ijintang fractions on MgNaK ATPase and MgCa ATPase in rat brain synaptosomes prepared from cerebral cortex. The activities of MgNaK ATPase and MgCa ATPase were assayed by the level of inorganic phosphate liberated from the hydrolysis of ATP. Fraction WH-95-7 at the concentration of $10^{-2}%$ decreased the activity of MgNaK ATPase about 34.1% and also reduced the activity of MgCa ATPase about 49.3% But, other fractions (WB-95-7, WC-95-7, MB-95-7, MC-95-7, MH-95-7) did not significantly changed the activities of the MgNaK ATPase and MgCa ATPase The decreased activity of MgNaK ATPase by WH-95-7 will decrease the rate of $Ca^{2+}$ efflux, probably via an Na-Ca exchange mechanism and will increase the rate of $Ca^{2+}$ entry by the depolarization of nerve terminals. The reduced activity of MgCa ATPase by WH-95-7 will result in the decreased efflux of $Ca^{2+}$. As a conclusion, it can be speculated that lithium elevates the intrasynaptosomal $Ca^{2+}$ concentration via inhibition of the activities of MgNaK ATPase and MgCa ATPase. and this increased $[Ca^{2+}]i$ will cause the release of neurotransmitters.

• The Korean Journal of Physiology and Pharmacology
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• 제2권3호
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• pp.313-322
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• 1998

In a myocyte freshly isolated from rabbit cerebral artery, the characteristics of $Ca^{2+}$ release by histamine or caffeine were studied by microspectrofluorimetry using a $Ca^{2+}-binding$ fluorescent dye, fura-2. Histamine (5 ${\mu}M$) or caffeine (10 mM) induced a phasic rise of cytoplasmic free $Ca^{2+}$ concentration $([Ca^{2+}]_C)$ which could occur repetitively with extracellular $Ca^{2+}$ but only once or twice in $Ca^{2+}-free$ bathing solution. Also, the treatment with inhibitor of sarcoplasmic reticulum $Ca^{2+}-ATPase$ suppressed the rise of $[Ca^{2+}]_C$ by histamine or caffeine. In $Ca^{2+}-free$ bathing solution, short application of caffeine in advance markedly attenuated the effect of histamine, and vice versa. In normal $Ca^{2+}-containing$ solution with ryanodine (2 ${\mu}M$), the caffeine-induced rise of $[Ca^{2+}]_C$ occurred only once and in this condition, the response to histamine was also suppressed. On the other hand, in the presence of ryanodine, histamine could induce repetitive rise of $[Ca^{2+}]_C$ while the amplitude of peak rise became stepwisely decreased and eventually disappeared. These results suggest that two different $Ca^{2+}-release$ mechanisms (caffeine-sensitive and histamine-sensitive) are present in rabbit cerebral artery myocyte and the corresponding pools overlap each other functionally. Increase of $[Ca^{2+}]_C$ by histamine seems to partially activate ryanodine receptors present in caffeine-sensitive pool.

• 대한약리학회지
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• 제27권2호
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• pp.167-181
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• 1991

Adenylate cyclase 효소를 활성화시키는 약물인 Forskolin의 흰쥐 적출관류 부신으로부터 Ach, excess $K^+$, McN-A-343 및 caffein에 의한 catecholamines (CA) 분비작용에 대한 영향을 검색하고, 그 기전을 규명코자 연구를 시행하여 다음과 같은 연구결과를 얻었다. Forskolin (1.0 uM)은 흰쥐 부신적출정맥내로 1분동안 관류시킨 후 Ach(50 ug), excess $K^+$(56 mM), DMPP (100 uM) 및 caffeine (0.3 mM)에 의한 CA 분비작용을 현저히 증강시켰으나 McN-A-343에 의한 CA분비작용에는 영향을 미치지 않았다. Forskolin 자체는 CA분비작용을 일으키지 못하였다. 또한 세포의 calcium을 제거한 상태에서도 위 약물에 의한 CA분비작용에 대하여 유의한 증강작용을 나타내었다. 그러나 McN-A-343의 CA작용에는 영향이 없었으나 위의 약물의 CA분비작용을 유의하게 강화시켰다. Cyclic AMP를 증가시키는 약물로 알려져 있는 dibutyryl cyclic AMP (DBcAMP)는 300 uM농도를 1분간 관류시 Ach, excess $K^+$ 및 DMPP의 CA 분비작용을 뚜렷하게 증강시켰으나 McN-A-343 및 caffeine의 CA분비에는 별다른 영향이 없었다. DBcAMP 자체도 CA분비작용에는 영향을 미치지 못하였으나 또한 DBcAMP는 세포의 칼슘제거시에도 위의 약물에 의한 CA분비작용을 의의있게 증강시켰다. 그렇지만, McN-A-343의 CA분비작용은 증강시키지 못하였다. 이상의 연구결과로 보아 Forskolin는 adenylate cyclase를 활성화 시킴으로써 cyclic AMP 농도를 증가시켜 세포내로 칼슘유입을 증강시키며, 또한 세포내의 칼슘이동에도 관여함으로써 cholinergic nicotinic stimulation 및 depolarization에 의한 CA분비작용을 상승시키는 것으로 사료되어진다.