• Corrosion Science and Technology
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• 제4권4호
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• pp.121-129
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• 2005

Basic design concept of the future steel structure requires environmental compatibility and maintenance free capability to minimize economic burdens. Recent trends in alloy design for advanced weathering steel include addition of various alloying elements which can enhance formation of stable and protective rust layer even in polluted urban and/or high $Cl^{-}$ environment. The effects of Ca, Ni, W, and Mo addition on the corrosion property of Ca-modified weathering steel were evaluated through a series of electrochemical tests (pH measurement and electrochemical impedance spectroscopy: EIS) and structural analysis on rust layer formed on the steel surface. Ca-containing inclusions of Ca-Al-Mn-O-S compound are formed if the amount of Ca addition is over 25 ppm. Steels with higher Ca content results in higher pH value for condensed water film formed on the steel surface, however, addition of Ni, W, and Mo does not affect pH value of the thin water film. The steels containing a high amount of Ca, Ni, W and Mo showed a dense and compact rust layer with enhanced amount of ${\alpha}-FeOOH$. Addition of Ni, W and Mo in Ca-modified weathering steel shows anion-selectivity and contributes to lower the permeability of $Cl^{-}$ ions. Effect of each alloying element on the formation of protective rust layer will be discussed in detail with respect to corrosion resistance.

• 한국재료학회지
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• 제30권4호
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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.

• The Korean Journal of Physiology
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• 제21권1호
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• pp.47-58
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• 1987

It has been reported that the luteal function may be regulated by the intracellular $Ca^{++}$ level which may be adjusted partially by the high affinity $Ca^{++}-ATPase$ in luteal cell membranes. Then, one may expect that luteotropic and/or luteolytic agents, such as gonadotropins, prostaglandin $F_{2{\alpha}}\;(PGF_{2{\alpha}})$ and ouabain, affect the intracellular $Ca^{++}$ level. In this present study, therefore, we examined the effects of luteinizing hormone (LH, or human chorionic gonadotropin, hCG), $PGF_{2{\alpha}}$ and ouabain on the kinetic properties of the high affinity $Ca^{++}-ATPase$ in light membrane, heavy membrane, and microsomal fractions from the highly luteinized ovary. LH (or hCG) increased the affinity and the Vmax for $Ca^{++}$ both in light membrane and heavy membrane. $PGF_{2{\alpha}}$ increased the Vmax in light membrane and decreased the Km in heavy membrane for $Ca^{++}$ at low concentration $(5\;{\mu}g/ml)$. At higher concentration, however, $PGF_{2{\alpha}}$ oppositly affected on kinetic properties, that shown at low concentration. Ouabain, a potent inhibitor of $Na^+-K^+-ATPase$, increased the Km at high concentration $(10^{-4}\;M)$, however, decreased the Vmax for $Ca^{++}$ in light membrane at low concentration $(10^{-6}\;M)$. Also, ouabain increased the Km for $Ca^{++}$ in heavy membrane without changes in the Vmax at both concentrations. It seems that LH and low dose of $PGF_{2{\alpha}}$ increase the intracellular $Ca^{++}$ level and cause in activation of $Ca^{++}-ATPase$, however, higher dose of $PGF_{2{\alpha}}$ and ouabain inhibit directly $Ca^{++}-ATPase$ activity and result in increase in intracellular $Ca^{++}$ level. According to the above results, we suggest that luteotropic and/or luteolytic agents regulate the luteal progesterone $(P_4)$ production through two different pathways; one is cyclic adenosine monophosphate (cAMP)-dependent and another is $Ca^{++}-dependent$. Intracellula. $Ca^{++}$ level regulated by the high affinity $Ca^{++}-ATPase$ may affect both pathways in a time-dependent fashion. LH (or hCG) acts on the luteal $P_4$ production via both pathways. The initial step is $Ca^{++}$ dependent, and the late step is cAMP dependent. $PGF_{2{\alpha}}$ and ouabain increase the intracellular $Ca^{++}$ concentration so that basal luteal $P_4$ production is increased and LH-stimulated $P_4$ production is inhibited by the inhibiting LH-dependent adenylate cyclase activity.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.95-99
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• 2011

$CaTi_{1-x}Fe_xO_3(0{\leq}x{\leq}0.4)$ solid solution photocatalysts were synthesized by iron doping during the conventional solid state reaction at $1100^{\circ}C$ for 5 h and characterized by ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction, morphological analysis. We found that $CaTi_{1-x}Fe_xO_3$ samples not only absorb UV but also the visible light photons. This is because the Fe substitution at Ti-site in $CaTi_{1-x}Fe_xO_3$ lattice induces the band transition from Fe3d to the Fe3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $CaTiO_3$ samples for hydrogen production under UV light irradiation decreased with the increase in the Fe concentration. There exists an optimized concentration of iron in $CaTiO_3$, which yields a maximum photocatalytic activity under visible light ($\lambda\geq420nm$) photons.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.177-180
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• 2009

Here is presented the measurement on SrO- and SrCaO-PDP operated at lower voltage. SrO- and SrCaO-PDP attain high luminous efficacy at low voltage, where the breakdown voltage is 30 % lower than that of the ordinary MgO-PDP. A one-dimensional fluid model is applied for the simulation of PDP discharge. High VUV radiation efficiency is confirmed at high ${\gamma}_i$ and both low and high $V_s$ as in the experiment. Discharge analysis in simulation also shows that the high ${\gamma}_i$ protective layer leads to high plasma density especially near the cathode electrode, being responsible for high efficiency.

• 약학회지
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• 제28권3호
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• pp.129-138
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• 1984

Specific [$^{3}H$] ouabain binding and $Ca^{2+}$ -uptake were measured to elucidate the role of high affinity [$^{3}H$] ouabain binding site in rat cardiac myocytes which contain 65% of rod cells. High affinity [$^{3}$H] ouabain binding site, which is about 3% of total pump sites, with apparent dissociation constant ($K_{D}$) of $1.1{\times}10^{-7}M$ and maximum binding site concentration (Bmax) of 1.2 pmol/mg protein ($1.754{\times}10^{5}cells$) were identified. At the concentration of $10^{-7}M$ to $10^{-4}M$, ouabain produced concentration dependent increase in $Ca^{2+}$-uptake of myocytes. The effect of ouabain on $Ca^{2+}$-uptake was not effected by membrane depolarization (elevated K+ in incubation medium) or verapamil. These results suggest that in rat ventricular myocytes the ouabain receptor complex to high affinity site may increase Na+ - $Ca^{2+}$ exchange across the sarcolemmal membrane by inhibition of Na+, K+ - ATPase.

• Journal of Nutrition and Health
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• 제28권4호
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• pp.298-308
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• 1995

To investigate the effect of estrogen and dietary protein level on Ca metabolism, female rats were undergone ovariectomy or sham-operation. Ovariectomized rate were divided into either estrogen-or vehicle-treated groups. Each treatment group was again divided into 40%-casein(H) or 10%-casein(L) diet groups. All experimental diets contained 0.2% Ca, 0.4% P and fed to rats for 8 weeks. Apparant Ca absorption and Ca balance were not affected by dietary protein level and ovariectomy, however they were increased by estrogen injection and this effect was even higher in low protein groups. Urinary Ca excretion were higher in high protein groups. GFR was not affected by dietary protein level, ovariectomy, or by estrogen injection. Urinary protein excretion was higher in high protein groups, which implies that the kidney funtion was deteriorated by high protein diet, and this may account partly for the higher urinary Ca in high protein groups. Ovariectomy or estrogen treatment had no effect on urinary protein excretion. Urinary hydroxyproline was higher in ovariectomized rats and increased in high protein grous. Elevated value of ovarictomized rats was lowered by estrogen injection, especially in low protein group. Alkaline phosphatase tended to increase in ovariectomized groups and lowered with estrogen treatment, but this difference was not statistically significant. Serum PTH was not affected by ovariectomy and dietary protein level. Therefore the increased hydroxproline excretion does not seem to be attributed to PTH. Dietary protein level, ovariectomy and estrogen treatment did not affect the weights and components of femur, scapular, and 4th vertebra. Ash/wt ratio of femur was, however, lower in ovariectomized rats and increased with estrogen treatment. Therefore, among the bones studied, femur seemed to be the most vulnerable. The results of this study shows that estrogen treatment may alleviate or reduce bone loss in postmenopausal women somewhat, especially for those people with low protein diet.

• The Korean Journal of Physiology and Pharmacology
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• 제5권6호
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• pp.511-519
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• 2001

Nimopidine, one of dihydropyridine derivatives, has been widely used to pharmacologically identify L-type Ca currents. In this study, it was tested if nimodipine is a selective blocker for L-type Ca currents in sensory neurons and heterologous system. In mouse dorsal root ganglion neurons (DRG), low concentrations of nimodipine $(<10\;{\mu}M),$ mainly targeting L-type Ca currents, blocked high-voltage-activated calcium channel currents by ${\sim}38%.$ Interestingly, high concentrations of nimodipine $(>10\;{\mu}M)$ further reduced the 'residual' currents in DRG neurons from ${\alpha}_{1E}$ knock-out mice, after blocking L-, N- and P/Q-type Ca currents with $10\;{\mu}M$ nimodipine, $1\;{\mu}M\;{\omega}-conotoxin$ GVIA and 200 nM ${\omega-agatoxin$ IVA, indicating inhibitory effects of nimodipine on R-type Ca currents. Nimodipine $(>10\;{\mu}M)$ also produced the inhibition of both low-voltage-activated calcium channel currents in DRG neurons and ${\alpha}_{1B}\;and\;{\alpha}_{1E}$ subunit based Ca channel currents in heterologous system. These results suggest that higher nimodipine $(>10\;{\mu}M)$ is not necessarily selective for L-type Ca currents. While care should be taken in using nimodipine for pharmacologically defining L-type Ca currents from native macroscopic Ca currents, nimodipine $(>10\;{\mu}M)$ could be a useful pharmacological tool for characterizing R-type Ca currents when combined with toxins blocking other types of Ca channels.

• Asian-Australasian Journal of Animal Sciences
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• 제31권2호
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• pp.245-251
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• 2018

Objective: This study was conducted to determine the effects of dietary maifanite supplementation and fecal collection method on the apparent total tract digestibility (ATTD) of calcium (Ca) and phosphorus (P) and blood parameters in growing pigs. Methods: Thirty-six growing barrows (Duroc${\times}$Landrace${\times}$Yorkshire; $27.0{\pm}2.6kg$) were allotted to six dietary treatments with 6 pigs per treatment according to body weight in a completely randomized design. The experimental treatments were: i) Low Ca+cornstarch (2.25%), ii) Low Ca+maifanite (2.25%), iii) Medium Ca+cornstarch (1.42%), iv) Medium Ca+maifanite (1.42%), v) High Ca+cornstarch (0.64%), and vi) High Ca+maifanite (0.64%). Feces were collected by the total collection (TC) and indicator method (IM). At the beginning and the end of the experiment, blood samples were collected from each pig. Results: For the TC method, there were no difference in Ca intake, fecal Ca output, Ca retention and the ATTD of Ca between cornstarch and maifanite diets at the same dietary Ca level. However, urinary Ca excretion was lower (p = 0.01) in pigs fed low Ca diets without maifanite supplementation compared with other dietary treatments. Dietary maifanite supplementation had no effect on the P metabolism in growing pigs. For the IM method, there was no difference in Ca digestibility between cornstarch and maifanite diets at the same dietary Ca level. The ATTD of P was greater (p<0.01) in pigs fed the high Ca diet with maifanite supplementation compared with the high Ca diet with cornstarch treatment. Dietary inclusion of maifanite had no effect on blood parameters in growing pigs. Conclusion: Dietary maifanite supplementation had no effect on the ATTD of Ca and P and serum parameters in growing pigs. The IM resulted in lower digestibility values than the TC method.

• The Korean Journal of Physiology and Pharmacology
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• 제6권4호
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• pp.215-223
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• 2002

The present study was undertaken to investigate the effect of doxorubicin (DX) on secretion of catecholamines (CA) evoked by ACh, high $K^+,$ DMPP and McN-A-343 from the isolated perfused rat adrenal gland and to establish the mechanism of its action. DX $(10^{-7}{\sim}10^{-6}\;M)$ perfused into an adrenal vein for 60 min produced relatively dose- and time-dependent inhibition of CA secretory responses evoked by ACh $(5.32{\times}10^{-3}\;M),$ DMPP $(10^{-4}\;M)$ and McN-A-343 $(10^{-4}\;M).$ However, lower dose of DX did not affect CA secretion by high $K^+\;(5.6{\times}10^{-2}\;M),$ but its higher doses depressed time-dependently CA secretion evoked by high $K^+.$ DX itself did also fail to affect basal CA output. In adrenal glands loaded with DX $(3{\times}10^{-7}\;M),$ CA secretory responses evoked by Bay-K-8644, an activator of L-type $Ca^{2+}$ channels and cyclopiazonic acid, an inhibitor of cytoplasmic $Ca^{2+}-ATPase$ were time-dependently inhibited. Furthermore, daunorubicin $(3{\times}10^{-7}\;M),$ given into the adrenal gland for 60 min, attenuated CA secretory responses evoked by ACh, high $K^+,$ DMPP and McN-A-343. Taken together, these results suggest that DX causes relatively dose- and time-dependent inhibition of CA secretory responses evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors from the isolated perfused rat adrenal gland. However, lower dose of DX did not affect CA secretion by high $K^+,$ and higher doses of DX reduced time-dependently CA secretion of high $K^+.$ It is thought that these effects of DX may be mediated by inhibiting both influx of extracellular calcium into the rat adrenomedullary chromaffin cells and intracelluar calcium release from the cytoplasmic store. Also, there was no difference in the mode of action between DX and daunorubicin in rat adrenomedullary CA secretion.