• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.136-149
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• 1996

The effects of various All-Etching Agents (10% phosphoric acid, 10% maleic acid and 10 % citric acid) and 32 % phosphoric acid and varied etching time were evaluated by observing the morphology of the etched enamel surfaces using Scanning electron microscopy and by measuring the shear bond strength of a composite resin to human enamel. A total of 156 extracted premolar and molar teeth free of irregularities were employed in this study. Specimens for the observation of enamel morphology were divided into 12 groups of 3 teeth each, based on the type of etchant used and application time. After exposure to the etching agent specimens were washed air-dried and then glued to aluminum stubs and coated with a layer of gold for examination in the scanning electron microscope. Specimens for the evaluation of bond strength were divided into 12 groups of 10 teeth each also based on the type of etchant used and application time. After exposure to the etching agent the specimens were washed, air-dried and a thin layer of bonding agent was applied using a brush. Z 100 composite resin was light cured to the surface and stored at $37^{\circ}C$, 100% humidity for 7 days. An Instron Universal Testing Machine was used to apply a shearing force at $90^{\circ}$ angle from the enamel surface. It is concluded from this study that commercial All-etching agents can be used with a 15-second etching without adversely affecting retention of dental resin materials. At the same time, the acid concentration is probably a suitable compromise regarding the acid's function as a dentin demineralizing all-etch conditioning agent. The following results were obtained. 1. Specimens etched with 10 % citric acid showed a random superficial etching pattern which could not be related to prism morphology. 2. Specimens etched with 10 % and 32 % phosphoric acid and 10 % maleic acid showed a type I pattern in which core material was preferentially removed leaving the prism peripheries relatively intact or a type II pattern in which prism peripheries were preferentially removed. This delineation became more distinguished as etching time was increased. 3. All-Etching Agents and 32 % phosphoric acid showed a statistically significant higher shear bond strength at 15 seconds etching time.(p<0.05) 4. 10 % maleic acid and 32 % phosphoric acid exhibited a statistically significant higher shear bond strength than 10 % phosphoric and citric acid at 15 seconds etching time.(p<0.05).

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.340.1-340.1
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• 2002

Centella asiatica is an herbal plant used on different continents by diverse ancient cultures and tribal groups. Historically. the extract has been used as a wound healing agent, The extract has three different triterpenoid ingredients: asiaticoside. asiatic acid, and madecassic acid. It has been reported that its wound healing activity is associated with the modulation of collagen synthesis in the skin dermis. The wound healing property of the extract has led to its commercial introduction under the trade name, Madecrlssol. As part of our program toward the development of new wound healing agents. structere activity relationship (SAR) studies have been performed by modifying asiatic acid. In this communication. the SAR study of esiatic acid for the development of an efficient woind healing agent is reported.

• Applied Biological Chemistry
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• 제32권1호
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• pp.30-36
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• 1989

식용대두유의 산화방지를 위하여 항산화제로서 Chelating agents의 항산화효과를 mild한 조건(67ml $O_{2}/min$, $50^{\circ}C$)하에서 A.O.M.법으로 측정하였으며 기기분석법 (UV,IR,MMR)에 의한 측정의 가능여부를 시험한 결과 다음과 같다. 1. Chelating agents의 항산화 효과는 diphenic acid(109.3%), naphthoquinone(111.2%), pyremellitic acid(168.6%), Quinolinic acid(183.6%), naphthalic acid(921.2%) 순으로 증가하였으며, Control에 비하여 각각 9.3, 11.2, 68.6, 83.6, 821.2% 증가하였다. 2. Chelating agents는 항산화 효과를 나타냈으며, 철과 등을 첨가했을 경우에 현저하였다. 또 이들의 항산화 효과는 화합물의 관능기와 분자구조에 따라 다르며 diphenic acid, naphthoquinone 등에서 낮았다. 3. 본 실험과 같이 mild한 조건하에서 NMR 분석법을 이용하여 항산화 효과를 측정할 수 있었으나 UV와 IR은 적당치 않았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.158-161
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• 2003

The primary aim of this study is to investigate new semi-abrasive free slurry including acid colloidal silica and hydrogen peroxide for copper chemical-mechanical planarization (CMP). In general, slurry for copper CMP consists of colloidal silica as an abrasive, organic acid as a complex-forming agent, hydrogen peroxide as an oxidizing agent, a film forming agent, a pH control agent and several additives. We developed new semi-abrasive free slurry (SAFS) including below 0.5% acid colloidal silica. We evaluated additives as stabilizers for hydrogen peroxide as well as accelerators in tantalum nitride CMP process. We also estimated dispersion stability and Zeta potential of the acid colloidal silica with additives. The extent of enhancement in tantalum nitride CMP was verified through anelectrochemical test. This approach may be useful for the application of single and first step copper CMP slurry with one package system.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
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• pp.294.2-295
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• 2003

Gentisic acid, a skin-whitening agent, is known to possess tyrosinase inhibition activity. In order to develop an effective skin-whitening agent, hydroquinone derivatives in which the carboxylic acid moiety of gentisic acid was replaced with various functional groups, were selected and evaluated for their ability to inhibit tyrosinase activity as well as to inhibit melanin release. (omitted)

• Tribology and Lubricants
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• 제34권6호
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• pp.226-234
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• 2018

Copper chemical mechanical planarization (CMP) has become a key process in integrated circuit (IC) technology. The results of copper CMP depend not only on the mechanical abrasion, but also on the slurry chemistry. The slurry used for Cu CMP is known to have greater chemical reactivity than mechanical material removal. The Cu CMP slurry is composed of abrasive particles, an oxidizing agent, a complexing agent, and a corrosion inhibitor. Citric acid can be used as the complexing agent in Cu CMP slurries, and is widely used for post-CMP cleaning. Although many studies have investigated the effect of citric acid on Cu CMP, no studies have yet been conducted on the interfacial friction characteristics and step height reduction in CMP patterns. In this study, the effect of citric acid on the friction characteristics and step height reduction in a copper wafer with varying pattern densities during CMP are investigated. The prepared slurry consists of citric acid ($C_6H_8O_7$), hydrogen peroxide ($H_2O_2$), and colloidal silica. The friction force is found to depend on the concentration of citric acid in the copper CMP slurry. The step heights of the patterns decrease rapidly with decreasing citric acid concentration in the copper CMP slurry. The step height of the copper pattern decreases more slowly in high-density regions than in low-density regions.

• 펄프종이기술
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• 제33권4호
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• pp.42-48
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• 2001

The spent liquor (BSL) obtained from alkaline sulfite-anthraquinone (AS-AQ) cooking of pine bark was applied as a deinking agent. In the ONP deinking system, although BSL removed the small size of ink particles (${\geq}$$12.5{\mu}m$), it did not improve the brightness of pulp. The brightness of pulp slightly improved when treated with BSL at 150~$180^{\circ}C$. However, the brightness of the pulp was lower than that of a commercial deinking agent (oleic acid). It seems that BSL treated with a high temperature still had a high dispersing ability on the ink particles. Intensive oxidations were introduced, and remarkable deinking effects were observed at 13kgf/$cm^2$ oxygen pressure, $160^{\circ}C$ and 2h. When BSL treated at 13kgf/$cm^2$ oxygen pressure, $170^{\circ}C$ and a time period of 30~90 min is added to the pulp, at 0.1% or lower, the deinking effect became higher than that of oleic acid. On the other hand, additional alkali treatments during the oxidation possibility as a deinking agent when oxidized. However, since the oxidized BSL still has a high dispersing ability and lower molecular weight, several modifications need to be done in the near future in order to be applied as a high quality deinking agent.

• Corrosion Science and Technology
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• 제21권2호
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• pp.89-99
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• 2022

A versatile method for performing non-cyanide electroless gold plating using thiomalic acid (TMA) as a complexing agent and 2-aminoethanethiol (AET) as a reducing agent was investigated. It was found that TMA was an excellent complexing agent for gold. It can be used in electroless gold plating baths at a neutral pH with a high solution stability, makes it a potential candidate to replace conventional toxic cyanide complex. It was found that one gold atomic ion could bind to two TMA molecules to form the [2TMA-Au⁺] complex in a solution. AET can be used as a reducing agent in electroless gold plating solutions. The highest current density was obtained at electrode rotation rate of 250 to 500 rpm based on anodic and cathodic polarization curves with the mixed potential theory. Increasing AET concentration, pH, and temperature significantly increased the anodic polarization current density and shifted the plating potential toward a more negative value. The optimal gold ion concentration to obtain the highest current density was 0.01 M. The cathodic current was higher at a lower pH and a higher temperature. The current density was inversely proportional to TMA concentration.

• 한국재료학회지
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• 제34권2호
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• pp.95-104
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• 2024

Nanoparticles are commonly used to avoid the opaque white color of TiO₂ based sunscreen. However, a dispersing agent is typically required because of the tendency of the nanoparticles (NPs) to agglomerate. Stearic acid is one kind of dispersing agent often used for sunscreen products. However, according to the MSDS data sheet on stearic acid, stearic acid is highly hazardous to aquatic life and causes irritation on human skin. To avoid this problem, in this study a safer organic dispersing agent extracted from Korean seaweed has been studied to disperse TiO₂ nanoparticles, and further use as an active agent in sunscreen products. The presence of phytochemicals in seaweed extract, especially alginate, can disperse TiO₂ nanoparticles and improve TiO₂ dispersion properties. Results show that seaweed extract can improve the dispersion properties of TiO₂ nanoparticles and sunscreen products. Reducing the agglomeration of TiO₂ nanoparticles improves sunscreen properties, by making it less opaque white in color, and increasing UV protection value. It was also confirmed that adding seaweed extract into sunscreen products had no irritating effects on the human skin, making it more desirable for cosmetics application.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.77-80
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• 2009

Because buildings which apply color that is various to concrete recently are introduced, value as design element of building is rising gradually in townscape. Even if expense is increased according as importance of concrete that have variety of design because do such social background and connection is emphasized, development of color concrete is pressing. Therefore, in this research, examined concrete physical & chemical characteristics by use of acid agent as part of research to embody diverse surface color of cement material. Here, embodiment of various color by unique color that stained hydrate has as that Color Concrete forms stained oxide that react with hydrate within concrete spreading stained agent that contain acid and metallic-ion in matrix that have cement ingredient on the surface is available.