• 접착 및 계면
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• 제9권2호
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• pp.24-31
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• 2008

본 연구에서는 EVA 에멀젼에 내수성 및 기계적 특성을 향상시키기 위하여 금속 이온 가교제인 calcium hydroxide 및 magnesium carbonate를 사용하여 이온성 가교결합을 도입하였다. EVA 에멀젼 필름의 가교밀도, 열적특성, 표면자유에너지 그리고 인장강도, 파단신율 및 인열강도 특성을 고찰하였다. 금속 이온 가교제 양이 증가함에 따라 EVA 에멀젼의 가교밀도는 증가하였고, 이에 내수성과 $T_g$ 값도 증가하였다. 그러나 EVA 에멀젼 필름의 표면에너지 및 기계적 특성들은 다소 다른 거동을 보였다. Calcium hydroxide 0.4% 그리고 magnesium carbonate 0.5%를 첨가한 경우가 EVA 에멀젼에 강한 이온성 가교결합이 형성되어 가장 높은 표면 자유에너지 값과 인장강도 및 인열강도를 보였다. 그러므로 본 연구에서 calcium hydroxide 및 magnesium carbonate와 같은 금속 이온 가교제가 EVA 에멀젼의 내수성과 기계적 물성을 향상시킴을 확인하였다.

• 대한약리학회지
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• 제31권3호
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• pp.355-363
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• 1995

Calcium수송에 대한 기전을 추구하기위하여, carbachol을 사용하여 ml muscarinic receptor-transfected RBL-2H3 cell-line에서 다음과 같은 실험결과를 얻었기에 이에 보고한다. 1) Carbachol의 투여로 이들 cell-line에서 $Ca^{2+}$ influx가 농도에 따라 증가하였고, hexosaminidase 분비양도 의의있게 증가하였다. 2) Atropine 투여로 Carbachol의 상승작용이 의의있게 억제되었다. 3) 수종의 금속양이온을 투여하여 carbachol의 $Ca^{2+}$수송에 대한 영향을 관찰한 바, 이들 금속이온들은 $Ca^{2+}$의 influx를 의의있게 억제하였다. 4) PMA(20 nM) 투여로 carbachol의 hexosaminidase의 분비는 억제되지 못했지만 $Ca^{2+}$ influx는 억제되었다. 5) PTx $(0.2\;{\mu}g/ml)$ 투여로 carbachol의 hexosaminidase 분비가 의의있게 억제되었다. 위의 결과로 미루어 보아, 이 세포의 muscarinic receptor가 calcium channel을 통한 calcium수송에 매우 중요한 영향을 나타내는데, 이들 calcium ion channel은 적어도 두 종류가 존재하며, 하나는G-protein-dependent calcium channel에 의하며, 다른 하나는 G-protein-independent calcium channel에 대한 작용에 의한 것으로 생각된다. 또한 이 calcium channel들은 2가 또는 3가의 다른 금속 ion들에 의하여 calcium수송이 억제된다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 INTERNATIONAL SYMPOSIUM ON SOIL & GROUNDWATER ENVIRONMENT
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• pp.105-106
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• 2005

• 한국재료학회지
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• 제27권5호
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• pp.237-241
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• 2017

As a basic study for the removal of oxygen in solid Nd metal by metal Ca vapour, by using the thermodynamic data such as ${\Delta}G-T$ diagrams and Nd-O and Nd-Ca equilibrium diagrams, the amount of residual oxygen in solid Nd metal formed based on deoxidation reaction by Ca vapour, instead of by direct contact of solid Nd metal and Ca solution, was determined. Deoxidation experiments were carried out for solid Nd metal in a temperature range of $890{\sim}970^{\circ}C$ for 1h to 4h and content of addition Ca of 0.6~1.8 g (5~15 wt% of solid Nd metal). As a result, it was found that as deoxidation temperature increased, dissolved oxygen decreased. Especially, it was observed that a small amount of Nd-Ca alloy liquid was formed on the surface of the solid Nd metal sample deoxidized at $970^{\circ}C$ for approximately 1 hour. Also, it was found that if the content of addition Ca was 1.8 g (15 wt% of solid Nd metal) the amount of produced Nd-Ca alloy increased slightly. However, for the Nd sample with which the deoxidation reaction was performed at $930^{\circ}C$ for 4h with content of addition of Ca of 1.5 g (13 wt% of Nd metal), the residual oxygen was found to decreased to 12.00 ppm.

• Journal of Nutrition and Health
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• 제29권9호
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• pp.958-970
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• 1996

This study was performed to investigate the effect of dietary calcium level on cadmium and lead toxicity in rats. Fifty-four male rats of Sprague-Dawely strain weighing 152$\pm$12g were blocked into 9 groups according to body weight, and were raised for 30 days. Nine experimental diets different with cadmium(0%, 0.04%), lead (0%, 0.071%) and calcijm(0.5%, 1.0%, 1.5%) levels were prepared. The results are summarized as follow. Weight gain, F.E.R.(food efficiency ratio), and weights of liver, kidney and femur were lower in cadmium exposed groups than those of heavy metal free groups. Weight gain F.E.R. and ash weight of lead groups were lower than those of heavy metal free groups. But, these were increased with increasing dietary calcium level. Cadmium and lead concentrations in blood, liver, kidney and femur were lower in rats fed 1.5% calcium than 0.5% calcium diet. Fecal cadmium and lead excretions were remarkably increased in 1.5% calcium groups, and cadmium and lead retention rates were decreased in 1.5% calcium groups. Metallothionein concentrations in liver, kidney and small intestine were higher in rats exposed to cadmium and lead. Calcium content in blood, femur and daily urinary and fecal calcium excretion were decreased by cadmium and lead additions, and increased in 1.5% calcium groups. Creatinine clearance were decreased with cadmium administratino and calcium addition. In conclusion, weight gain and organ weights were decreased with cadmium or lead administration. But, cadmium administration was more toxic than lead adminstration. Cadmium or lead toxicity was alleviated by increasing dietary calcium level. Especially, lead toxicity was alleviated in proportion to dietary calcium level.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권1호
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• pp.56-64
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• 2015

Acid mine drainage occurrence is a serious environmental problem by mining industry, it usually contains high levels of metal ions, such as iron, copper, zinc, aluminum, and manganese, as well as metalloids of which arsenic is generally of the greatest concern. An indigenous plant extract was used to produce calcium carbonate from Canavalia ensiformis as effective biomaterial, and its ability to form the calcium carbonate under stable conditions was compared to that of purified urease. X-ray diffraction and scanning electron microscopy were employed to elucidate the mechanism of calcium carbonate formation from the crude plant extracts. The results revealed that urease in the plant extracts catalyzed the hydrolysis of urea in liquid state cultures and decreased heavy metal amounts in the contaminated soil. The heavy metal amounts were decreased in the leachate from the treated mine soil; 31.7% of As, 65.8% of Mn, 50.6% of Zn, 51.6% of Pb, 45.1% of Cr, and 49.7% of Cu, respectively. The procedure described herein is a simple and beneficial method of calcium carbonate biomineralization without cultivation of microorganisms or further purification of crude extracts. This study suggests that crude plant extracts of Canavalia ensiformis have the potential to be used in place of purified forms of the enzyme during remediation of heavy metal contaminated soil.

• 한국토양비료학회지
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• 제47권6호
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• pp.391-397
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• 2014

Acid mine drainage occurrence is a serious environmental problem by mining industry; it usually contain high levels of metal ions, such as iron, copper, zinc, aluminum, and manganese, as well as metalloids of which arsenic is generally of greatest concern. It causes mine impacted soil pollution with mining and smelting activities, fossil fuel combustion, and waste disposal. In the present study, three bacterial strains capable of producing urease were isolated by selective enrichment of heavy metal contaminated soils from a minei-mpacted area. All isolated bacterial strains were identified Sporosarcina pasteurii with more than 98% of similarity, therefore they were named Sporosarcina sp. KM-01, KM-07, and KM-12. The heavy metals detected from the collected mine soils containing bacterial isolates as Mn ($170.50mg\;kg^{-1}$), As ($114.05mg\;kg^{-1}$), Zn ($92.07mg\;kg^{-1}$), Cu ($62.44mg\;kg^{-1}$), and Pb ($40.29mg\;kg^{-1}$). The KM-01, KM-07, and KM-12 strains were shown to be able to precipitate calcium carbonate using urea as a energy source that was amended with calcium chloride. SEM-EDS analyses showed that calcium carbonate was successfully produced and increased with time. To confirm the calcium carbonate precipitation ability, urease activity and precipitate weight were also measured and compared. These results demonstrate that all isolated bacterial strains could potentially be used in the bioremediation of acidic soil contaminated by heavy metals by mining activity.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제10권S_2호
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• pp.89-95
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• 2001

The solidification and leaching characteristics of cyclone ash collected from an industrial incineration plant were investigated. Cement and calcium hydroxide were used as the solidifying materials. The leaching characteristics of the solidified cyclone ash were found to vary depending on both the quantitative and the qualitative aspects of the solidifying materials. Except for copper and lead, all the heavy metal ions in the leachate of the solidified material composed of 10~20 % cement or 10~20 % calcium hydroxide were found to be within their standard limit. Moreover, all the heavy metal ions were also observed to be within satisfactory limits in the leachate obtained from the solidified material composed of 30 % cement or 30 % calcium hydroxide. Therefore, to satisfy the standard compressive intensity and permissible limits of heavy metal ions leached from solidified material, it would appear that a 30 % proportion of either additive in the solidification product can meet the required standard for the leachate. The cost of solidifying cyclone ash per ton for ash-30 % cement and ash-30 % lime was calculated as 26,750 and 26,070 won, respectively. Accordingly, significant reduction in the waste toxicity and mobility as well as an improvement in the engineering properties of the solidified products were successfully achieved.

• 한국환경과학회지
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• 제9권6호
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• pp.505-509
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• 2000

The purpose of this study was to evaluate the effects of $Ca(OH)_2$ and $CO_2$ additions on the corrosion of metal coupons(ductile iron, galvanized steel, copper and stainless steel). Corrosion rate and released metal ion concentration of ductile iron and galvanized steel decreased by adjusting alkalinity, calcium hardness and pH with $Ca(OH)_2$ & $CO_2$ additions on copper and stainless steel were less than those on ductile iron and galvanized steel. When ductile iron coupon was exposed to water treated with Ca(OH)$_2$&$CO_2$, additions, the main components of corrosion product formed on its surface were $CaCO_3$ and $Fe_2 O_3 or Fe_2 O_4$ which often reduce the corrosion rate by prohibiting oxygen transport to the metal surface.

• 천문학회보
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• 제39권2호
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• pp.47.1-47.1
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• 2014

The calcium infrared triplet (CaT) is one of the prominent absorption features in the infrared wavelength regime. Recently, this absorption feature has been getting attention in the prediction of metallicity of stellar populations because of its strong sensitivity to the calcium abundance and metallicity of a star. However, we find that measuring metallicity directly from CaT is very dangerous because the formation mechanism of CaT is very inefficient in the cool stars which are abundant in metal-rich populations. This characteristics of CaT make the CaT-metallicity relation to converge around ~ $8{\AA}$ in the metal-rich regime. Our results suggest that, because of the converging CaT-metallicity relation in the metal-rich regime, the metallicity of simple stellar populations greater than [Fe/H]~-0.5 is unreliable when the linear conversion between CaT and metallicity is applied to derive metallicity. Based on these results, we suggest that CaT is not a good metallicity indicator for the metal-rich stellar populations.