• YAKHAK HOEJI
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• v.55 no.2
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• pp.168-171
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• 2011

Chrysosplenol C [5,6-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,7-dimethoxychromen-4-one] is a flavonoid found in Miliusa balansae and Pterocaulon sphacelatum. We have recently shown that chrysosplenol C has positive inotropic effect in isolated rat ventricular myocytes. In the present study, we explored a possible mechanism for the positive inotropic effect of chrysosplenol C by examining intracellular $Ca^{2+}$ transients during action potentials. The intracellular $Ca^{2+}$ transients were measured by confocal $Ca^{2+}$ imaging in field-stimulated single rat ventricular myocytes. Chrysosplenol C (50 ${\mu}M$) significantly increased the magnitudes (${\Delta}F/F_0$) of $Ca^{2+}$ transients (control, $1.08{\pm}0.05$; chrysosplenol C, $1.25{\pm}0.03$; n=8, P<0.01). Half decay time of the action potential-induced $Ca^{2+}$ transient was not altered by chrysosplenol C (50 ${\mu}M$) (control, $154{\pm}6$ ms; chrysosplenol C, $167{\pm}11$ ms; n=21). The $Ca^{2+}$ content in the sarcoplasmic reticulum (SR), measured as caffeine (10 mM)-induced $Ca^{2+}$ transient, was significantly decreased by chrysosplenol C (50 ${\mu}M$). These results indicate that chrysosplenol C increases $Ca^{2+}$ transients without altering $Ca^{2+}$ removal kinetics in ventricular myocytes, providing a possible mechanism for its positive inotropic effect.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.4
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• pp.423-428
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• 2017

Vestibular compensation is a recovery process from vestibular symptoms over time after unilateral loss of peripheral vestibular end organs. The aim of the present study was to observe time-dependent changes in long-term potentiation (LTP) at Schaffer collateral-CA1 synapses in the CA1 area of the hippocampus during vestibular compensation. The input-output (I/O) relationships of fEPSP amplitudes and LTP induced by theta burst stimulation to Schaffer's collateral commissural fibers were evaluated from the CA1 area of hippocampal slices at 1 day, 1 week, and 1 month after unilateral labyrinthectomy (UL). The I/O relationships of fEPSPs in the CA1 area was significantly reduced within 1 week post-op and then showed a non-significant reduction at 1 month after UL. Compared with sham-operated animals, there was a significant reduction of LTP induction in the hippocampus at 1 day and 1 week after UL. However, LTP induction levels in the CA1 area of the hippocampus also returned to those of sham-operated animals 1 month following UL. These data suggest that unilateral injury of the peripheral vestibular end organs results in a transient deficit in synaptic plasticity in the CA1 hippocampal area at acute stages of vestibular compensation.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.400-405
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• 2023

Tb³⁺-doped CaNb₂O₆ (CaNb₂O₆:Tb³⁺) thin films were deposited on quartz substrates at a growth temperature of 300 ℃ using radio-frequency magnetron sputtering. The deposited thin films were annealed at several annealing temperatures for 20 min and characterized for their structural, morphological, and luminescent properties. The experimental results showed that the annealing temperature had a significant effect on the properties of the CaNb₂O₆:Tb³⁺ thin films. The crystalline structure of the as-grown CaNb₂O₆:Tb³⁺ thin films transformed from amorphous to crystalline after annealing at temperatures greater than or equal to 700 ℃. The emission spectra of the thin films under excitation at 251 nm exhibited a dominant emission band at 546 nm arising from the ⁵D₄→⁷F₅ magnetic dipole transition of Tb³⁺ and three weak emission bands at 489, 586, and 620 nm, respectively. The intensity of the ⁵D₄→⁷F₅ (546 nm) magnetic dipole transition was greater than that of the ⁵D₄→⁷F₆ (489 nm) electrical dipole transition, indicating that the Tb³⁺ ions in the host crystal were located at sites with inversion symmetry. The average transmittance at wavelengths of 370~1,100 nm decreased from 86.8 % at 700 ℃ to 80.5 % at an annealing temperature of 1,000 ℃, and a red shift was observed in the bandgap energy with increasing annealing temperature. These results suggest that the annealing temperature plays a crucial role in developing green light-emitting CaNb₂O₆:Tb³⁺ thin films for application in electroluminescent displays.

• Journal of the Mineralogical Society of Korea
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• v.13 no.4
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• pp.221-230
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• 2000

이성분 희토류 원소로 치환된 4종류의 합성불화인회석(synthetic fluorapatite) (Ap49: La+Gd, Ap50:Ce+Dy, Ap51: Pr+Er, Ap54: Eu+Lu; $Ca{10-x-2y}$ $Na_{y}$ $REE_{x+y}$($P_{1-x}$ //$Si_{x}$ $_{4}$)$_{6}$ $F_{2}$, x=0.13~0.12, y=0.26~0.42)을 대상으로 X-선 회절분석을 통해 얻어진 자료를 이용하여 리트벨트 구조분석을 실시하고 치환된 희토류원소의 거동을 단결정법으로 구해진 결과와 비교.분석하였다. 리트벨트 구조분석결과 합성불화인회석은 공간군 $P6_3$/m, 단위포는 평균하여 a=9.3906(1) $\AA$, c=6.8924(1) $\AA$, V=527.36 $\AA^3$의 값을 갖는다. 구조의 정밀도를 나타내는 R 지수를 보면 $R_{B}$ / 값은 17.29~18.80이고 S(GofF)값은 1.44~1.68로 계산되었다. 불화인회석은 9개의 산소를 배위하는 Ca1자리와 6개의 산소와 하나의 불소가 배위하는 Ca2자리가 있으며 Ca1-O의 평균거리는 2.563 $\AA$이고 Ca2-O의 평균거리는 $2.460 \AA$으로 Ca1자리가 Ca2자리보다 다소 크다. 구조자리 치환식에서는 $Ca^{2+}$ / 자리를 치환하는 $REE^{3+ }$ 로 인하여 전하균형을 맞춰주기 위해서 인과규소가 함께 참여하였다. ($REE^{3}$+Si$^{ 4+}$ $2Ca^{2+}$ : Ca1) 계산된 희토류원소의 자리점유율(REE-Ca2/REE-Cal)은 원자번호가 증가함에 따라 일정하게 감소하는 경향을 보여주며 이는 희토류원소의 거동이 LREE는 크기가 상대적으로 작은 Ca2 자리에 우선 치환되고 HREE는 크기가 큰 Ca1자리에 우선 치환되는 경향을 지시한다.

• The Korean Journal of Pharmacology
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• v.32 no.1
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• pp.39-49
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• 1996

In the present study, we observed change in intracellular $Ca^{2+}$$([Ca^{2+}]_i)$ as measured with the fluorescent $Ca^{2+}-indicator$ fura-2 in association with force development of the rat basilar arteries during activation by$K^+$ depolarizing solution and U46619, a thromboxane analogue, in the absence and the presence of calcitonin-gent related peptide (CGRP). CGRP (30 and 100 nM) caused a concentration-dependent inhibition of U46619-induced contraction with decrease in $[Ca^{2+}]_i$, whereas it did not exert any effect on the $K^+$ (90 mM)-induced contraction and increase in $[Ca^{2+}]_i$, Further, $[Ca^{2+}]_i-force$ relationships were determined by plotting the ratio of $F_{340}/F_{380}$ $([Ca^{2+}]_i)$ as a function of the force induced by U46619, and the results were compared with those obtained in the presence of CGRP. The curves obtained in the presence of CGRP (30 and 100 nM) were significantly moved to downward without right shift of the curves suggesting that CGRP inhibited the U46619-induced contraction only by mediation of reduction in $[Ca^{2+}]_i$ with out any change in the sensitivity of contractile apparatus to $Ca^{2+}$. The CGRP-induced attenuation of $[Ca^{2+}]_i$ and force development was significantly inhibited under pretreatment with CGRP $(8{\sim}37)$ fragment (100 nM), a CGRP1 receptor antagonist. Both the reduced contraction and reduction in $[Ca^{2+}]_i$ caused by CGRP were fully reversed by pretreatment with charybdotoxin (100 nM) and iberiotoxin (100 nM), large conductance $Ca^{2+}-activated$ $K^+$ channel blockers, but not by apamin (300 nM), a small conductance $Ca^{2+}-activated$ $K^+$ channel blocker, and glibenclamide ( 1 ${\mu}M$), an ATP-sensitive $K^+$ channel blocker. In conclusion, it is suggested that the CGRP1 receptor, upon activation by CGRP, are coupled to opening of $Ca^{2+}-activated$ $K^+$ channel and cause to decrease in $[Ca^{2+}]_i$, thereby leading to vasodilation of the rat basilar artery. However, it is not defined that the mechanism underlying vasodilation whether the $K^+$ channel blockers, charybdotoxin and iberiotoxin directly block the CGRP receptors and that CGRP-evoked relaxation is dependent on the cyclic AMP or $K^+$ channel opening or both actions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.312-312
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• 2009

본 연구에서는 Thermal evaporator(저항 가열 식 진공 증착법) 장비를 활용하여 ZnS/$Na_3AlF_6$/ZnS/Cu-$0.25\lambda$, ZnS/$CaF_2$/ZnS/Cu-$0.25\lambda$의 다층 박막을 glass 기판위에 증착하였다. 증착 전에 EMP(Essential Macleod Program)을 활용하여 광학적 특성을 simulation하였으며 다층 박막 제작 후 Spectrophotometer를 사용하여 반사율 및 색상을 CIE $L^*a^*b^*$ 좌표에 표시하여 고 굴절 물질에 따른 광학적 특성을 EMP simulation과 비교하였다. AES depth profile을 분석하여 막의 두께 및 층간 확산여부에 관하여 관측 하였다. 저굴절 물질을 Na3AlF6로 사용하였을 경우 simulation과 결과 값 모en purple 계통의 색상을 나타냈으며 CaF2를 사용하였을 경우 simulation은 purple 계통의 색상, 결과값은 red-yellow 계통의 색상으로 나타났다.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.55-61
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• 2006

The microwave dielectric properties and low temperature sintering of $Ca[Ti_{1-x}(Ni_{1/3}Nb_{2/3})_x]O_3$ system were investigated at the sintering temperature $1,200\~1,350^{\circ}C$. The density and quality factors $(Q{\times}f)$ increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency $(\tau_f)$ were 64, 17,000 GHz, and $-9.1\;ppm/^{\circ}C$ respectively, when $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ ceramics were sintered at $1,300^{\circ}C$ for 4 h. $2Li_2O-B_2O_3$ was added to $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at $925^{\circ}C$ for 2 h with the addition of $6\;wt\%\;2Li_2O-B_2O_3$ were $\varepsilon_r=48.7,\;Q{\times}f=8,460\;GHz$, and $\tau_f=+5.6ppm/^{\circ}C$. Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.215-219
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• 2012

Red phosphors $Ca_{1-1.5x}WO_4:{Eu_x}^{3+}$ were synthesized with different concentrations of $Eu^{3+}$ ions by using a solid-state reaction method. The crystal structure of the red phosphors was found to be a tetragonal system. X-ray diffraction (XRD) results showed the (112) main diffraction peak centered at $2{\theta}=28.71^{\circ}$, and the size of crystalline particles exhibited an overall decreasing tendency according to the concentration of $Eu^{3+}$ ions. The excitation spectra of all the phosphors were composed of a broad band centered at 275 nm in the range of 230-310 nm due to $O^{2-}{\rightarrow}W^{6+}$ and a narrow band having a peak at 307 nm caused by $O^{2-}{\rightarrow}Eu^{3+}$. Also, the excitation spectrum presents several strong lines in the range of 305-420 nm, which are assigned to the 4f-4f transitions of the $Eu^{3+}$ ion. In the case of the emission spectrum, all the phosphor powders, irrespective of $Eu^{3+}$ ion concentration, indicated an orange emission peak at 594 nm and a strong red emission spectrum centered at 615 nm, with two weak lines at 648 and 700 nm. The highest red emission intensity occurred at x = 0.10 mol of Eu3+ ion concentration with an asymmetry ratio of 12.5. Especially, the presence of $Eu^{3+}$ in the $Ca_{1-1.5x}WO_4:{Eu_x}^{3+}$ shows very effective use of excitation energy in the range of 305-420 nm, and finally yields a strong emission of red light.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.14-21
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• 1997

This study was conducte dto fabricate 2GHz circulator using Ca,Sn substituted UIG(yttrium iron garnet)ceramics. When the electric, magnetic and microwave properties were measured in Ca, Sn substituted YIG, the measured perimittivity and perfmeability in microwave frequencies were 16.25, 0.8964. For $Y_{2.4}$C $a_{0.3}$A $n_{0.3}$F $e_{3.5}$A $l_{1.5}$ $O_{12}$ garnet ceramics sintered at 1400.deg. C, the ferrimagnetic resonance line width (.DELTA.H) at 10GHz was 53 Oe and saturation magnetization was 375G. The strip-line circulator was simulated with 3-D FEM (finite element method) software and designed at the center frequency of 2GHz. The fabricated strip-line junction circulator using above YIG ceramics had insertion loss of 1.271dB, return loss of 23.843dB, isolation of 21.751dB at the center frequency 1.855GHz.z.z.z.z.z.z.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.176-183
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• 2020

The high-temperature stability of YSZ specimens fabricated by die pressure and cold isostatic press (CIP) is investigated in CaCl₂-CaF₂-CaO molten salt at 1,150 ℃. The experimental results are as follows: green density 46.7 % and 50.9 %; sintering density 93.3 % and 99.3 % for die press and CIP, respectively. YSZ foremd by CIP exhibits higher stability than YSZ formed by die press due to denseness dependency after high-temperature stability test. YSZ shows peaks mainly attributed to CaZrO₃, with a small t-ZrO₂ peak, unlike the high-intensity tetragonal-ZrO₂ (t-ZrO₂) peak observed for the asreceived specimen. The t-ZrO₂ phase of YSZ is likely stabilized by Y₂O₃, and the leaching of Y₂O₃ results in phase transformation from t-ZrO₂ to m-ZrO₂. CaZrO₃ likely forms from the reaction between CaO and m-ZrO₂. As the exposure time increases, more CaZrO₃ is observed in the internal region of YSZ, which could be attributed to the inward diffusion of molten salt and outward diffusion of the stabilizer (Y₂O₃) through the pores. This results in greater susceptibility to phase transformation and CaZrO₃ formation. To use SOM anodes for the electroreduction of various metals, YSZ stability must be improved by adjusting the high-density in the forming process.