• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1163-1167
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• 1995

The structures of dehydrated Ca4Na4-A (a=12.243(1) Å) and of its bromine sorption complex (a=12.214(1) Å) have been determined by single crystal x-ray diffraction techniques in the cubic space groupPm&bar{3}m at 21(1) ℃. Both crystals were dehydrated at 360 ℃ and 2 X 10-3 Torr for 2 days and one crystal was treated with 180 Torr of bromine vapor at 24 ℃ for 1 h. The structures were refined to final error indices, R1=0.066 and R2=0.078 with 192 reflections and R1=0.109 and R2=0.093 with 100 reflections, respectively, for which I>3σ(I). In these structures, four Ca2+ and four Na+ ions are located on two different threefold axes associated with 6-ring oxygens, respectively. In Ca4Na4-A·6Br2, four Ca2+ ions are recessed 0.28(1) Å into the large cavity and four Na+ ions extend 0.63(1) Å into the sodalite unit. A total of six dibromine molecules are sorbed per unit cell. Each Br2 molecule approaches a framework oxide ion axially with O(1)-Br(1)=3.27(2) Å Br(1)-Br(2)=2.66(6) Å and O(1)-Br(1)-Br(2)=172(1)°, indicating a charge-transfer interaction.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.31-31
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• 2008

복합 싸이클 시험 모니터링을 통해 NaCl, $CaCl_2$ 제설염 환경에서 11 % Cr, 17 % Cr 페라이트 스테인리스강의 외면부식특성을 조사하고자 하였다. 용액 내 NaCl 및 $CaCl_2$의 농도가 증가함에 따라 용액의 pH가 떨어졌으며, $CaCl_2$의 농도증가에 따른 산성화도가 NaCl에 비해 크게 나타났다. 염수분무-건조-습윤 과정의 반복으로 구성되어 있는 복합싸이클 시험 중 소재의 표면상태 변화를 모니터링 한 결과, 건조 과정 중에 공식이 시작되며, NaCl 환경의 경우엔 습윤과정 중에 $CaCl_2$ 환경의 경우엔 건조 중에 공식성장이 주로 이루어지는 것으로 확인되었다.

• The Korean Journal of Physiology
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• v.24 no.2
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• pp.377-388
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• 1990

Ca movements during the late plateau phase in rabbit atrium implicate Na-Ca exchange. In single atrial cells isolated from the rabbit the properties of the inward current of Na-Ca exchange were investigated using the whole cell voltage clamp technique. The inward currents were recorded during repolarization following brief 2 ms depolarizing pulse to +40 mV from a holding potential of -70 mV. Followings are the results obtained: 1) When stimulated every 30 sec, the inward currents were activated and reached peak values $6{\sim}12\;ms$ after the beginning of depolarizing pulse. The mean current amplitude was 342 pA/cell. 2) The current decayed spontaneously from the peak activation and the timecourse of the relaxation showed two different phases: fast and slow phase. 3) The recovery of the inward current was tested by paired pulse of various interval. The peak current recovered exponentialy with a time course similar to that of Ca current recovery. 4) Relaxation timecourse was also affected by pulse interval and time constant was reduced almost linearly according to the decrease of pulse interval between 30 sec and 1 sec. 5) The peak inward current was increased by long prepulse stimulation, Bay K, isoprenaline or c-AMP. 6) The relaxation time constant of the inward current was prolonged by Bay K or c-AMP, and shortened by isoprenaline. From the above results, it could be concluded that increase of the calcium current potentiates and prolongs intracellular calcium transients, while shortening of the timecourse by isoprenaline or short interval stimulations might be due to the facilitation of Ca uptake by SR.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.160-165
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• 2007

The synthesis and the characterization of Low Silica X (LSX) zeolite for nitrogen adsorption have been studied. The performance of LSX zeolite for nitrogen adsorption was compared to that of the commercial zeolite. The $Na_2O/(Na_2O+K_2O)$ ratio in the gel and the crystallization time were fixed as the synthetic factor. The LSX zeolite was formed at the $Na_2O/(Na_2O+K_2O)$ ratio of 0.75. The formation of LSX zeolite was confirmed by XRD and SEM. The Si/Al ratio was investigated by using XRF and FT-IR. The synthesized LSX zeolite showed a lower Si/Al ratio than the NaY and NaX zeolites although they have a same faujasite structure. The Si/Al ratio of the LSX zeolite converged close to 1. 1A (Li, Na, K) and 2A (Mg, Ca, Ba) group elements were ion-exchanged to the LSX zeolite. As the charge density of cation rises, the amount of nitrogen adsorbed increased. $Li^+$ ion-exchanged LSX zeolite showed the highest nitrogen adsorption weight. When the Li/Al ratio was over 0.65, nitrogen adsorption increased remarkably. $Li^+$ ions located on the supercage (site III, III') in the LSX zeolite played a role as nitrogen adsorption sites. When the $Ca^{2+}$ ions were added to the LiLSX zeolite by ion-exchange method, the performance for nitrogen adsorption increased more. The performance for the nitrogen adsorption was the highest at the Ca/Al ratio of 0.26. Nitrogen adsorption capacity of LiCaLSX (Ca/Al=0.26) zeolite was superior to the commercial NaX zeolite.

• Journal of Photoscience
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• v.3 no.3
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• pp.133-136
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• 1996

Calcium modulates the activity of guanylate cyclase and plays a key role in dark and light adaptation in the visual system. We have measured the Ca$^{2+}$, K$^+$ and Na$^+$ concentration in dark and light adapted bullfrog's (Rana catesbeiana) vitreous humor by using the atomic absorption spectrophotometer. The calcium concentration of the light adapted bullfrog's vitreous humor was higher than that of the dark adapted bullfrog's vitreous humor. This means that ion activity between the photoreceptor and vitreous humor side is light dependent and we have found that a Ca$^{2+}$ channel and Na$^+$ - Ca$^{2+}$ exchanger exist in the vitreous humor.

• Korean Journal of Materials Research
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• v.17 no.8
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• pp.414-419
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• 2007

We report the electrical conductivity of the mixed alkali silicate glasses in the system (60-x)$SiO_2-40Na_2O-xCaO(x=0\sim15wt%)$ in the temperature range from $150^{\circ}C$ to $620^{\circ}C$. In the range from $150^{\circ}C$ to glass transition temperature$(T_g)$, the electrical conductivities of glass samples had a tendency to be proportion with temperature. The glasses of containing over 7.5wt% CaO showed lower conductivities than the glasses of containing 0 and 5wt% CaO because two kinds of alkali ions$(Na^+,\;Ca^{2+})$ were obstructed each other. On the other hand, in the range from $T_g$ to $620^{\circ}C$, the electrical conductivity of glasses($7.5{\leq}x{\leq}12.5$) was unstable and decreased in some region. From XRD results, the $Na_4Ca(SiO_3)_3$ phase were observed in these glasses. This means the alkali ions didn't behave as carrier, it seems that this caused the conductivities decrease. In case of glass of containing 15wt% CaO, any crystal phase were not observed. This means the alkali ions behaved as carrier, it consequently seems the conductivity increased.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.151-156
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• 2013

Crystallization of $CaCO_3$ is practiced on a polymethylsiloxane (PDMS) - based microfluidic system. Liquid- liquid reaction was investigated by mixing calcium chloride ($CaCl_2$) and sodium carbonate ($Na_2CO_3$) solution to crystallize $CaCO_3$. Aspartic acid (Asp) was added to investigate the morphology change such as vaterite and calcite. Suitable ratio of $Na_2CO_3$ and $CaCl_2$ was searched for initial seed formation. Christmas tree model was used as microfluidic device to form concentration gradient of $Na_2CO_3$ and $CaCl_2$. After observing microfluidic channel by using optical microscope, we found that seeds of $CaCO_3$ were formed under the condition that the ratio of $Na_2CO_3$ and $CaCl_2$ was 2:1. Morphology of crystals were also observed as $CaCO_3$ crystals grow. When Asp was added, vaterite crystal was more frequently found in two morphologies (vaterite and calcite) and seed formation and crystal growth were inhibited.

• Korean Journal of Microbiology
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• v.41 no.2
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• pp.112-116
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• 2005

Moderately halophilic bacterium, Kordia algicida gen. nov., sp. novo was isolated from seawater of Masan Bay, Korea, during algal blooming caused by Skeletonema costatum. This bacterium was grown on the ZoBell 2216e medium supplied aged seawater, but not grown the medium supplied $3\%$ NaCl. This bacterium showed absolute requirements for mono and divalent cations such as $Na^+,\;Mg^{2+}\;and\;Ca^{2+}$, since no growth was observed in the medium, which is not supplemented with one of $Na^+,\;Mg^{2+}\;and\;Ca^{2+}$ ions. In kinetic studies for three kinds of cation, Km values of $Na^+,\;Ca^{2+}\;and\;Mg^{2+}$ were determined to 0.202 M, 0.089 mM, and 0.189 mM, respectively. Also, $V_{max}({\mu}max)$ was 0.442 h, 0.411 hand 0.316 h. The bacterial cells were quickly lysed in the condition limited by the cations. This result should be suggested that Kordia algicida originated from marine.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.329-334
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• 2002

The $CaTio_3$powder with perovskite structure was synthesized by mixing anatase $TiO_2$and $Ca(OH)_2$powders as starting materials, and KOH or NaOH as mineralizer, followed by hydrothermal method. The change of crystal structure, particle shape and size of the synthesized $CaTiO_3$powder was investigated with kind and concentration of mineralizer. It was found that the spherical particles of 0.7 $\mu$m were obtained when using 1N KOH and the hexahedrons particles of 3$\mu$m were obtained for the case of using 10 N KOH. With increasing KOH concentration, the particle shape was changed from sphere to hexahedrons and its size also increased. When using 1 N NaOH, the powder was consisted of 0.5~1 $\mu$m particle in size, whereas hexahedrons of 1~4 $\mu$m and whiskers more than 10$\mu$m in size was obtained for the 10 N NaOH solution. With increasing NaOH concentration, the particle shape was varied from hexahedrons to whiskers, showing the similar result with the KOH case. It was confirmed from EDS analysis that Na element, which was detected in hexahedrones was not contained in the whiskers.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.203-209
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• 1998

The quality of groundwater used for natural mineral water should be strictly regulated on international level by hydrogeology experts and officials because groundwater is greatly subjected to contaminations and its aquifer system may be easily destroyed by external reasons. A total of 18 natural mineral water plants exist in Precambrian metamorphic terrains of the Gyunggi massif and Yeungam massif. The g개undwater quality for the natural mineral water investigated in hydrochemical aspects shows that pH ranges from 6.85 to 8.02 with an average of 7.52. The electric conductivity (EC) and hardness average 134.1 $\mu$S/cm and 43.5, respectively, which are relatively low to the total average (151.4 $\mu$S/cm and 57.9). The contents of major cations and anions are in the order of $Ca^{2＋}$＞$Na^{＋}$＞Mg$^{2＋}$＞K$^{＋}$ and HCO$_3$$^{-}$ ＞SO$_4$$^{2－}$ ＞Cl$^{-}$ ＞F$^{-}$ , respectively. The dominant water types determined by Piper diagram are $Ca^{2＋}$－$Na^{＋}$－HCO$^{-}$ $_3$and $Ca^{2＋}$-HCO$^{-}$ $_3$, mainly due to the dissolution of plagioclase in the host rocks. Representative correlation coefficients between chemical species are $Ca^{2＋}$－HCO$^{-}$ $_3$(0.92), $Ca^{2＋}$－Cl$^{-}$ (0.63), $Na^{＋}$－F$^{-}$ (0.67), HCO$^{-}$ $_3$－Cl$^{-}$ (0.66), and $Na^{＋}$－HCO$^{-}$ $_3$(0.63). The determinative. coefficients between $Ca^{2＋}$ and HCO$^{-}$ $_3$, and (Ca$^{2＋}$＋$Na^{＋}$＋K$^{＋}$ and EC art highest among the elements. According to the saturation index, most chemical species are undersaturated with respect to major minerals, except for some silica phases. In viewpoint of phase equilibrium, the chemical evolution of the groundwater may continue to proceed with increasing pH because the groundwater is undersaturated with respect to feldspars.