• 대한치과교정학회지
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• 제18권1호
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• pp.55-63
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• 1988

It has been suggested that the frictional force between bracket and arch wire may impede the tooth movement. The present study was aimed to compare and analyze the effect of wire size, type of ligation, and duration of ligation on the magnitude of frictional force between cobalt chromium wire and stainless steel bracket under the artificial saliva. The results were as follows: 1. Type of ligation and size of wire were the main influencing factor on the level of friction. 2. Stainless steel ligature generated higher frictional forces than elastomeric module. 3. The rectangular wire consistently exhibited more frictional force values than round wires, while there was no significant difference between frictional forces of round wires. 4. In elastic ligature, frictional force decreased with time. 5. Artificial saliva had no significant influence on the frictional force between cobalt chromium wire and bracket.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.33-33
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• 2003

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2004년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.10-10
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• 2004

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.939-940
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• 2011

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.285.2-285.2
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• 2008

• BMB Reports
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• 제41권4호
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• pp.305-309
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• 2008

Cobalt is an essential microelements in many biological processes involving enzymatic activity. We found that $Zn^{2+}$ and $Mg^{2+}$, which are in the active site of native calf intestine alkaline phosphatase (CIP), can be replaced by $Co^{2+}$ directly in solution. The effect of $Co^{2+}$ concentration on the substitution reaction was examined at ratios of [$Co^{2+}$]/[CIP] from 0:1 to 8:1. The quantity of $Zn^{2+}$ in CIP decreased progressively as the ratio was increased, but the amount of $Mg^{2+}$ changed in irrregular fashion. A series of active site models of the reaction mechanism of CIP are proposed. Low pH was found to promote the replacement of $Mg^{2+}$ by $Co^{2+}$. To understand how the substitution affects the enzyme, we also solved the secondary structure of CIP after reaction with $Co^{2+}$ in different conditions.

• 대한한의학회지
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• 제18권2호
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• pp.15-32
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• 1997

This study was undertaken to define the mechanism of Siegesbeckiae Herba-induced relaxation in rabbit common carotid artery contracted by agonists. In order to investigate the effect of Siegesbeckiae Herba on contracted rabbit carotid arterial strips, transverse strips with intact or damaged endothelium were used for the experiment using organ bath. To analyze the mechanism of Siegesbeckiae Herba-induced relaxation, Siegesbeckiae Herba extract infused into contracted arterial strips induced by agonists after treatment of lanthanum chloride, indomethacin, atropine, $N\omega-nitro-{_L}-arginine$, cobalt chloride or methylene blue. The relaxation effect of Siegesbeckiae Herba was dependent on the presence of endothelium, showing that Siegesbeckiae Herba-induced relaxation was not observed in the strips without endothelium. The endothelium-dependent relaxation induced by Siegesbeckiae Herba was suppressed by the pretreatment of lanthanum chloride, $N\omega-nitro-{_L}-arginine$, cobalt chloride or methylene blue, but it was not observed in the strips pretreated with indomethacin or atropine. These results demonstrated that Siegesbeckiae Herba may inhibit agonist-induced contraction through an increase in the cyclic GMP by the production of nitric oxide in the vascular endothelial cells.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.3005-3012
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• 2013

The effect of Mn-promotion on high surface area Al-pillared montmorillonite (AlMMT) supported Co nanoparticles prepared by hydrothermal method have been investigated. A series of different weight% Mn-promoted Co nanoparticles were prepared and characterized by XRD, TPR, TGA, BET and SEM techniques. An increase in the surface area of MMT is observed with Al-pillaring. Fischer-Tropsch catalytic activity of the as prepared catalysts was studied in a fixed bed micro reactor at $225^{\circ}C$, $H_2/CO$ = 2 and at 1 atm pressure. The data showed that by the addition of Mn the selectivity of $C_1$ dropped drastically while that of $C_2-C_{12}$ hydrocarbons increased significantly over all the Mn-promoted Co/AlMMT catalysts. The $C_{13}-C_{20}$ hydrocarbons remained almost same for all the catalysts while the selectivity of $C_{21+}$ long chain hydrocarbons decreased considerably with the addition of Mn. The catalyst with 3.5%Mn showed lowest $C_{21+}$ and highest $C_2-C_{12}$ hydrocarbons selectivity due to cracking of long chain hydrocarbons over acidic sites of MMT.

• 생명과학회지
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• 제19권8호
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• pp.1139-1144
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• 2009

옥수수 뿌리에 BL을 처리하면 양성굴중성 반응이 촉진되고, ethylene 생성도 증가한다는 것이 알려져 있다. BL에 의해 유도된 굴중성 반응과 ethylene 생성과의 관계를 조사하였다. ethylene 생성 억제제인 $10^{-4}$ M AVG를 처리하면 ethylene 생성은 90% 이상 억제되었으나, 굴중성 반응은 13% 정도 억제되었다. AVG를 BL과 함께 처리한 뿌리는 ethylene 생성은 약 60% 억제되었으나 굴중성 반응은 대조구 보다 증가하였다. 다른 ethylene 생성 억제제인 cobalt ion을 처리하면 ethylene 생성은 약 10% 정도 억제되었으나 굴중성 반응은 억제되지 않았다. BL과 cobalt ion을 함께 처리한 뿌리는 ethylene 생성이 억제되었으나 굴중성 반응은 증가되었다. 이러한 BL의 효과가 auxin transport와 관계가 있는지 알아보기 위하여 auxin transport inhibitor인 TIBA를 처리하였다. $10^{-5}$ M TIBA와 BL과 TIBA를 함께 처리한 경우(BL+TIBA), ethylene 생성은 각각 96%, 132% 증가하였으나 굴중성 반응은 모두 일어나지 않았다. 또한, BL, TIBA 그리고 IAA를 함께 처리한 뿌리 (BL+TIBA+IAA)는 음성굴중성 반응을 나타냈으나 뿌리 생장은 오히려 증가시켰으며, 이는 수평으로 있는 뿌리에서 IAA가 아랫면으로 transport 되지 못하고 윗면에 축적된 것을 의미한다. 이러한 결과는 BL이 뿌리 내에 존재하는 IAA의 차등분포에 영향을 주어 양성굴중성 반응을 촉진할 가능성을 제시한다.

• 자원리싸이클링
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• 제19권4호
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• pp.41-50
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• 2010

초경공구의 제조공정에서 발생하는 WC-Co 초경합금 슬러지로부터 텅스텐의 순환활용을 위한 기초연구가 수행되었다. 왕수를 사용하여 슬러지로부터 코발트를 침출함과 동시에 탄화텅스텐을 텅스텐산으로 변환시켜 회수하였다. 왕수농도, 반응온도와 시간, 광액농도 등이 코발트의 침출과 텅스텐산의 생성에 미치는 영향을 조사하였으며 최적조건을 도출하였다. 왕수농도 100 vol.%, 반응온도 $100^{\circ}C$, 반응시간 60분에서슬러지의 광액농도가 400 g/L에 도달할 때 까지 슬러지로부터 코발트의 완전한 추출이 이루어졌으나, 슬러지에 존재하는 모든 탄화텅스텐이 텅스텐산으로 완전히 전환되는 것은 광액농도가 150 g/L 이하일 때 이었다. 생성된 텅스텐산을 암모니아 용액에 용해함으로서 금속 불순물들을 불용성 잔사로 제거하는 것이 가능하였다. 증발결정 공정을 통하여 정제된 암모늄 텅스테이트 용액으로부터 99.85%의 순도를 가지는 암모늄 파라텅스테이트($(NH_4)_{10}{\cdot}H_2W_{12}O_{42}{\cdot}4H_2O$)를 얻을 수 있었다.