• Progress in Superconductivity
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• v.12 no.2
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• pp.104-109
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• 2011

We have investigated the anisotropy of the superconducting properties for $CaC_6$ and $SrC_6$ using upper critical fields ($H_{c2}$) and specific heat ($C_p$). From the upper critical fields of $CaC_6$ at different magnetic field orientations, H//c and H// ab, the anisotropy is found to be ~ 5 at low temperatures, much larger than that of $SrC_6$. These results are in contrast to the stronger anisotropy in the electronic structure for $SrC_6$ than for $CaC_6$ indicating a stronger anisotropy in the superconducting gap in $CaC_6$. The findings are confirmed by the temperature dependence of the superconducting specific heat below $T_c$ for $CaC_6$ and $SrC_6$, suggesting the important role of anisotropic electron-phonon coupling in superconducting intercalated graphites.

• Journal of the Korean Chemical Society
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• v.53 no.3
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• pp.272-278
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• 2009

The optimized structures and vibrational frequencies for $Ca^+-(CO)_n$ and $Ca^+-(CO_2)_n$ (n=1,2) complexes were calculated with MP2 and B3LYP methods employing 6-311++G(2d,p) basis sets. Also the binding energies were investigated for all complexes to compare the stabilities. For $Ca^+-(CO)_n$ C-bonded complexes are more stable than O-bonded complexes. Two stable conformations, linear and $C_{2v}$ form, are possible for $Ca^+-(CO)_2$ complexes and the $C_{2v}$ form is more stable than the linear form. $Ca^+-(CO_2)_2$ also has two possible conformations and linear form has slightly lower energy than $C_{2v}$ form.

• Journal of Microbiology and Biotechnology
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• v.32 no.7
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• pp.949-954
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• 2022

The lipolytic yeast Candida aaseri SH14 contains three Acyl-CoA oxidases (ACOXs) which are encoded by the CaAOX2, CaAOX4, and CaAOX5 genes and catalyze the first reaction in the β-oxidation of fatty acids. Here, the respective functions of the three CaAOX isozymes were studied by growth analysis of mutant strains constructed by a combination of three CaAOX mutations in minimal medium containing fatty acid as the sole carbon source. Substrate specificity of the CaAOX isozymes was analyzed using recombinant C. aaseri SH14 strains overexpressing the respective genes. CaAOX2 isozyme showed substrate specificity toward short- and medium-chain fatty acids (C6-C12), while CaAOX5 isozyme preferred long-chain fatty acid longer than C12. CaAOX4 isozyme revealed a preference for a broad substrate spectrum from C6-C16. Although the substrate specificity of CaAOX2 and CaAOX5 covers medium- and long-chain fatty acids, these two isozymes were insufficient for complete β-oxidation of long-chain fatty acids, and therefore CaAOX4 was indispensable.

• Journal of the Mineralogical Society of Korea
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• v.15 no.1
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• pp.59-68
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• 2002

Chemical analyses and Rietveld structural refinement with powder X-ray diffraction data were done for Nb-rich perovskite, named latrappite ($Ca_2NbFe^{3+}O_6$)from the Oka, Quebec, Canada. Latrappite is shown to be a member of a continuous solid solution of $CaTiO_3-NaNbO_3-Ca_2NbFe^{3+}O_6$ and approximately $(Ca_{1.5}Na_{0.4})\;(Nb_{0.1}Ti_{0.6}Fe_{0.4})O_6$ in composition. The crystal structure of latrappite, determined by Rietveld refinement, is similar to that of perovskite ($CaTiO_3$). It differs in that replacement of Ti by Nb and $Fe^{3+}$ results in greater distortion and tilting of the $TiO_6$ framework octahedra relative to $CaTiO_3$. Revised unit-cell parameters of latrappite are a=5.4474(4), b=5.5264(4), c=7.7519(5) ${\AA},\;V=233.4(3){\AA}^3$ space group Pbnm.

• 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.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.618-628
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• 1998

Pure CaO, Mn-doped CaO, Mn/CaO, and K/CaO catalysts were prepared and tested as catalysts for the oxidative coupling of methane in the temperature range of 600 to 800$^{\circ}C$ to investigate the effects of Mn- and K-addition on the catalytic activity of calcium oxide. To characterize the catalysts, X-ray powder diffraction(XRD), XPS, SEM, DSC, and TG analyses were performed. The catalytic reaction was carried out in a single-pass flow reactor using on-line gas chromatography system. Normalized reaction conditions were generally $p(CH_4)/p(O_2)=250$ Torr/50 Torr, total feed flow rate=30 mL/min, and 1 atm of total pressure with He being used as diluent gas. Among the catalysts tested, 6.3 mol% Mn-doped CaO catalyst showed the best $C_2$ yield of 8.0% with a selectivity of 43.2% at 775$^{\circ}C$. The $C_2$ selectivity increased on lightly doped CaO catalysts, while decreased on heavily doped CaO([Mn] > 6.3 mol%) catalysts. 6 wt.% Mn/CaO and 6 wt.% K/CaO catalysts showed the $C_2$ selectivities of 13.2% and 30.9%, respectively, for the reaction. Electrical conductivities of CaO and Mn-doped CaO were measured in the temperature range of 500 to 1000$^{\circ}C$ at Po2's of $10^{-3}\; to\;10^{-1}\;atm.$ The electrical conductivity was decreased with Mn-doping and increased with increasing $P0_2$in the range of $10^{-3}\;to\;10^{-1}\;atm,$ indicating the specimens to be p-type semiconductors. It was suggested that the interstitial oxygen ions formed near the surface can activate methane and the formation of interstitial oxygen ions was discussed on the basis of solid-state chemistry.

• Korean Journal of Materials Research
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• v.25 no.6
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• pp.269-273
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• 2015

The effect of adding Ca on the microstructural and mechanical properties of as-cast Mg-11Li-3Zn-1Sn(wt%) alloys were investigated. Mg-11Li-3Zn-1Sn-0.4Mn with different Ca additions (0.4, 0.8, 1.2 wt%) were cast under an $SF_6$ and $Co_2$ atmosphere at $720^{\circ}C$. The cast billets were homogenized at $400^{\circ}C$ for 12h and extruded at $200^{\circ}C$. The microstructural and mechanical properties were analyzed by OM, XRD, SEM, and tensile tests. The addition of Ca to the Mg-11Li-3Zn-1Sn-0.4Mn alloy resulted in the formation of $Ca_2Mg_6Zn_3$, MgSnCa intermetallic compound. By increasing Ca addition, the volume fraction and size of $Ca_2Mg_6Zn_3$ with needle shape were increased. This $Ca_2Mg_6Zn_3$ intermetallic compound was elongated to the extrusion direction and refined to fine particles due to severe deformation during hot extrusion. The elongation of the 0.8 wt% Ca containing alloy improved remarkably without reduction strength due to the formation of fine grain and $Ca_2Mg_6Zn_3$ intermetallic compounds by Ca addition. It is probable that fine and homogeneous $Ca_2Mg_6Zn_3$ intermetallic compounds played a significant role in the increase of mechanical properties.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.76-82
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• 1993

Two crystal structures of fully dehydrated Ca(II) and Tl(I) exchanged zeolite A, $Ca_{5.6}Tl_{0.8}-A (a = 12.242(2){\AA})\;and\;Ca_{1.4}Tl_{9.2}-A (a = 12.191(1){\AA})$, have been determined by single-crystal X-ray diffraction methods in the cubic space group Pm3m at 21(1)$^{\circ}C$. All crystals were ion exchanged in flowing streams of mixed $Ca(NO_3)_2\;and\;TINO_3$ aqueous solution with total concentration of 0.05M. All crystals were dehydrated at 360$^{\circ}C$ under $2{\times}10^{-6}\;torr$ for two days. The structures of the dehydrated $Ca_{5.6}Tl_{0.8}-A$ and $Ca_{1.4}Tl_{9.2}-A$ were refined to the final error indicies, $R_1$ = 0.072 and $R_2$ = 0.076 with 179 reflections for I > 3$\sigma$(I), and $R_1$ = 0.048 and $R_2$ = 0.043 with 226 reflections for I > 3$\sigma$(I), respectively. In each structure, Ca(II) ions are located on threefold axes associated with three 6-ring oxygens. $Ca^{2+}$ ions prefer to 6-ring sites and $Tl^+$ ions prefer to 8-ring sites when total number of exchanged cations per unit cell is more than 8.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.121-126
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• 2003

The electromagnetic properties and microstructures of the basic composition of (N $i_{0.2}$C $u_{0.2}$Z $n_{0.6}$)$_{1.085}$(F $e_2$ $O_3$)$_{0.915}$ were invested by changing of the additive Sn $O_2$, CaO amounts and ferrite processes. There is no variation of grain size by changing additive amount. It can reduce the total loss when (N $i_{0.2}$C $u_{0.2}$Z $n_{0.6}$)$_{1.085}$(F $e_2$ $O_3$)$_{0.915}$ composition sintered at 1150 $^{\circ}C$ better than 130$0^{\circ}C$. Additive CaO confirmed of useful addition for the reduce total loss, because it increasing sintering density. Decreasing total loss were observed by adding both Sn $O_2$ 0.06 wt％ and CaO 0.4 wt％.

• KSBB Journal
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• v.30 no.2
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• pp.58-62
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• 2015

A 3-weeks feeding trial with 288 laying hens were conducted to determine the efficacy of lecithin-free egg yolk at different levels of dietary Ca on performance and Ca absorption. Laying hens were divided into 6 groups according to calcium level and testing agent; 0% calcium feed (A), 0.2% calcium feed (B), 0.4% calcium feed (C, normal feed), 0.6% calcium feed (D), 0.4% calcium feed + 0.2% egg byproduct (C+0.2), 0.4% calcium feed + 0.4% egg byproduct (C+0.4). The final body weight gain of C+0.2 and C+0.4 groups were higher by 1.5% and 7.4% respectively than group C. Tibia ash contents did not show significantly difference, but calcium contents increase (p<0.05) in C+0.2 and C+0.4 groups. Parallel undecalcified tibia joint sections were stained for calcium absorption by the von Kossa's stain. This result show that lecithin free egg byproduct supplementation to normal calcium feed improved growth performance and calcium utilization in laying hens.