• Title/Summary/Keyword: Functional group modification

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Hydrophilic surface formation of polumer treated by ion assisted reaction and its applications (이온빔보조 반응법을 이용한 고분자 표면의 친수성처리와 그 응용)

  • Cho, J.;Choi, S. C.;Yun, K.H.;Koh, S. K.
    • Journal of the Korean Vacuum Society
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    • v.8 no.3B
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    • pp.262-268
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    • 1999
  • Polycarbonate (PC) and Polymethylmethacrylate (PMMA) surface was modified by ion assisted reaction (IAR) technique to obtain the hydrophilic functional groups and improve the wettability. In conditions of ion assisted reaction, ion beam energy was changed from 500 to 1500eV, and ion dose and oxygen gas blown rate were fixed $1\times10^{16}$ ions/$\textrm{cm}^2$ and 4ml/min, respectively. Wetting angle of water on PC and PMMA surface modified by $Ar^+$ ion without blowing oxygen at 4ml/mon showed $5^{\circ}$ and $10^{\circ}$. Changes of wetting angle with oxygen gas and $Ar^+$ ion irradiation were explained by considering formation of hydrophilic group due to a reaction between irradiated polymer chain by energetic ion irradiation and blown oxygen gas. X-ray photoelectron spectroscopy analysis shows that hydrophilic groups such as -C-O, -(C=O)- and -(C=O)-O- are formed on the surface of polymer by chemical interaction. The polymer surface modification using ion assisted reaction only changed the surface physical properties and sept the bulk properties. In comparison with other modification methods, the surface modification by IAR treatment was chemically stable and enhanced the adhesion between metal and polymer surface. The applications of various kinds of polymer surface modification methods, metal and polymer surface. The applications of various kinds of polymer surface modification could be appled to the new materials about hydrophilic surface properties by IAR treatment. The adhesion between metal film and polymer measured by Scotch tape test whether the hydrophilic surfaces could improve the adhesion strength or not.

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Groupware: Current Status Analysis II (그룹웨어의 현황 분석 II)

  • Kim, Sun-Uk;Gim, Bong-Jin
    • IE interfaces
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    • v.11 no.2
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    • pp.211-225
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    • 1998
  • As mentioned in Part I all groupware products have been categorized into three areas which include cooperation/document management systems(CMS), collaborative writing systems(CWS), and decision-making/meeting system(DMS). This study deals with a comparative analysis of the last two areas, which is added to the first. It turns out that DMS has a higher market share than CWS. However. since effective collaboration requires the functions inherent to these two systems. they should be integrated somehow. The systems' functions that have been implemented in response to design issues have been described. Each group of the functions has been divided into three parts which consist of basic function, quasi-basic function. and others. Such a decision has been made according to the frequency rate of the functions provided in the products. While the basic functions in CWS include collaboraive writing beyond restriction of time and place, group awareness. version control. and others, in DMS realtime collaboration. brainstorming. presentation. various task support. policy formation. document management, multimedia, subgroup communication. topic commenter, categorizer, screen capture and various rile transfer. The basic functions are merged into the integrated functional model which was proposed in Part I. Since the model is so flexible that it can partially include the quasi-functions in addition to the hasic functions. a large number of products may stem from the modification of the functional model.

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Effects of NaOH Treatment on the Adsorption Ability of Surface Oxidized Activated Carbon for Heavy Metals

  • Min-Ho Park;So-Jeong Kim;Jung Hwan Kim;Jae-Woo Park
    • Journal of Soil and Groundwater Environment
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    • v.28 no.6
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    • pp.16-23
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    • 2023
  • Heavy metal (Zinc, Cadmium, Lead) adsorption onto surface modified activated carbon was performed in order to better understand the effect of sodium ion addition to activated carbon. Surface modification methods in this research included water washing, nitric acid washing, and sodium addition after nitric acid washing. These surface modifications generated oxygen functional groups with sodium ions on the surface of the activated carbon.. This caused the change of the specific surface area as well as in the ratio of the carboxyl groups. Heavy metal adsorption onto sodium-containing activated carbon was the most among the three modifications. After the adsorption of heavy metals, the carboxyl group ratio decreased and sodium ions on the surface of the activated carbon were almost non-existent after the adsorption of heavy metals onto sodium-containing activated carbon. The results from this research indicated that ion exchange with sodium ions in carboxyl groups effectively improved heavy metal adsorption rather than electrostatic adsorption and hydrogen ion exchange.

Surface Modification of Polypropylene Fiber by Plasma Discharge (방전처리에 의한 Polypropylene섬유의 표면개질)

  • 허만우;이창재;강인규;한명호;김삼수;임학상
    • Textile Coloration and Finishing
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    • v.11 no.2
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    • pp.27-37
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    • 1999
  • Polypropylene(PP) films were treated with plasma glow discharge to produce peroxy radicals on the surfaces. The peroxy radicals formed on the PP film surfaces were subsequently used for the graft polymerization of acrylic acid and acrylamide in an aqueous solution by heating, respectively. Introduction of acrylic acid and acrylamide on the PP film could be confirmed by the observation of carbonyl and primary amine absorptions based on carboxylic acid and amide, respectively. And introduction of functional group could be confirmed by weight analysis and ESCA. The water contact angle(90$^{\circ}$) of PP film was constant, irrespective of elapsed time, while plasma-treated and functional monomer-grafted PP films were slowly increased with elapsed time, showing the rearrangement of surface polar groups in air condition. The water contact angle$(90^\circ)$ of PP film was decreased by the plasma treatment$(56^\circ)$ and further decreased by the grafting of acrylic acid$(34^\circ)$ and acrylamide$(37^\circ)$, indicating increased hydrophilicity of the modified surfaces. The water contact angle of plasma-treated PP film increased a little as time elapsing. The half-life periods of surface voltage on acrylic acid-(31sec) and acrylamide-grafted PP(42sec) were significantly decreased when compared to those on PP(950sec) and plasma-treated PP film(241sec). In the experiments using acid, basic and disperse dyes, absorbance and $\Delta{E}$ values of functional monomer-grafted PP films were significantly increased than that of oxygen plasma-treated one.

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Isolation and Identification of an Unauthorized Sildenafil Analogue in a Commercial Functional Food (시판 기능성식품으로부터의 실데나필 유도체 부정첨가물질의 분리 및 구조규명)

  • Baek, Du-Jong
    • Journal of the Korean Chemical Society
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    • v.54 no.4
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    • pp.443-446
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    • 2010
  • HPLC analysis of a commercial herb drink marketed as a functional food revealed to contain an unauthorized substance similar to sildenafil, the active ingredient of the prescription drug Viagra$^{(R)}$ approved for the treatment of male erectile dysfunction. In order to identify the illegal additive, the herb drink was extracted with methylene chloride, and the extract was purified further using semipreparative HPLC. The chemical structure of the isolated substance was elucidated based on IR, LC/MS-ESI, and NMR spectroscopy, which showed the characteristics similar to sildenafil with minor modification. The only difference was the substitution of the methylpiperazine moiety of sildenafil to the hydroxyethylpiperazine group of the illegal additive.

Adhesion of Cu on Polycarbonate Modified by O2/ Ar Plasma Treatment (O2/ Ar 플라즈마 처리에 의해 개질된 폴리카보네이트 기판에서 Cu의 밀착성)

  • Park, Jun-Kyu;Kim, Dong-Won;Kim, Sang-Ho;Lee, Youn-Seoung
    • Korean Journal of Materials Research
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    • v.12 no.9
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    • pp.740-746
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    • 2002
  • In this study, the polycarbonate surface was treated by $O_2$/ Ar gases plasma for the enhancement of adhesion with Cu electrode. From the point of view of hydrophilicity and the functionality, the micro-roughness, new functional groups and oxygen content of the polycarbonate surface were increased by the $O_2$/ Ar gases plasma treatment. The Cu films deposited on the as-received polycarbonate were easily detached while, after the$ O_2$/ Ar gases plasma treatment the adhesive Cu films on polycarbonate could be obtained. These results can be explained that the polycarbonate had a hydrophilic surface with uniform micro-roughness and new functional groups by $O_2$/ Ar gases plasma treatment. Therefore,$O_2$/ Ar gases plasma treatment is a promising method for improvement of adhesion between polycarbonate and Cu electrode.

Mechanical Device Design for Solvent Usage Reduction for Amine Group Substitution and Production of NH2-HNT (아민기 치환 시 용매 사용량 절감을 위한 기계 장치 설계 및 NH2-HNT 제조)

  • Moon il Kim
    • Journal of Environmental Science International
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    • v.32 no.6
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    • pp.477-482
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    • 2023
  • Halloysite nanotube (HNT) has a nanotube structure with the chemical formula of Al2Si2O5(OH)4 · nH2O and is a natural sediment of aluminosilicate. A lot of research has been conducted to improve the mechanical properties of epoxy composites by generating interactions between HNTs and polymers through surface treatment of HNTs, such as exchange of amine group as a terminal functional group. However, most of the surface modification methods are performed under wet conditions, which require a relatively large amount of time, manpower and solvent. In order to save time and simplify complicated procedures, a dry coating machine was designed and used for amine group exchange. Comparing the XPS results, it was found that the results of NH2-HNT prepared using a dry coating machine and the substitution through the wet method were not significantly different, and it has been confirmed that the amount of solvent used and the time savings can be made.

An Essential Histidine Residue in the Catalytic Mechanism of the Rat Kidney γ-Glutamyl Transpeptidase

  • Kim, Soo-Ja;Ko, Moon-Kyu;Chai, Kyu-Yun;Cho, Seong-Wan;Lee, Woo-Yiel
    • Bulletin of the Korean Chemical Society
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    • v.28 no.2
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    • pp.271-275
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    • 2007
  • γ -Glutamyl transpeptidase (EC 2.3.2.2) plays a key role in glutathione metabolism by catalyzing the transfer of the γ -glutamyl residue and hydrolysis of glutathione. The functional residues at the active site of the rat kidney γ -glutamyl transpeptidase were investigated by kinetic studies at various pH, the treatment of diethylpyrocarbonate (DEPC), and photooxidation in presence of methylene blue. An ionizable group affecting the enzymatic activity with an apparent pKa value of 7.1, which is in the range of pKa values for a histidine residue in protein, was obtained by examining the pH-dependence of kinetic parameters. The pH effect on the photoinduced inactivation rate of the enzyme corresponds to that expected for the photooxidation of the free histidine. The involvement of a histidine in the catalytic site of the enzyme was further supported by DEPC modification accompanied by an increase in absorbance at 240 nm, indicating the formation of Ncarbethoxyhistidine. The histidine located at the position of 382 in the precursor of the enzyme is primarily suspected based on the amino acid sequence alignment of the transpeptidases from various organisms.

Surface Treatment with CO2 to Improve Electrochemical Characteristics of Carbon Felt Electrode for VRFB

  • Yechan Park;Sunhoe Kim
    • Journal of Electrochemical Science and Technology
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    • v.14 no.2
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    • pp.131-138
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    • 2023
  • The carbon felt is usually hired as electrodes for vanadium redox flow battery (VRFB). In the study, surface modification of carbon felt under CO2 atmosphere with variables of operating various temperature ranges between 700℃ and 900℃. The qualitative and quantitative analysis were carried out such as scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to observe degree of surface modification. Result of XPS analysis confirmed increase of carbon and oxidation functional group on the surface with increase of temperature. SEM image was discovered similar phenomena. Electrochemical characteristics such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed the improved electrode performance with increase of temperature. However, the electrochemical performance under treatments temperature of 900℃ was less than that of under treatment temperature of 850℃ due to weight loss at the treatment temperature of 900℃. From the CV and EIS results, the best electrochemical characteristics was at the temperature of 850℃. That of at the temperature of 900℃ was decreased due to weight loss. The energy efficiencies (EE) obtained from full cell test were 69.37, 80.76, 82.45, and 75.47%, at the temperature of 700, 800, 850, and 900℃, respectively.

Binding Site of Heavy Metals in the Cell of Heavy Metal-Tolerant Microorganisms (중금속 내성균의 세포내 중금속 결합 위치)

  • Cho, Ju-Sik;Lee, Hong-Jae;Lee, Young-Han;Sohn, Bo-Kyoon;Jung, Yeun-Kyu;Heo, Jong-Soo
    • Korean Journal of Environmental Agriculture
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    • v.17 no.3
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    • pp.246-253
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    • 1998
  • Heavy metal-tolerant microorganisms, such as Pseudomonas putida, P. aeruginosa, P. chlororaphis and P. stutzeri which possessed the ability to accumulate cadmium, lead, zinc and copper, respectively, were isolated from industrial wastewaters and mine wastewaters polluted with various heavy metals. The binding sites of heavy metal in the cells were investigated by chemical modification of functional groups the cell walls. To determine the binding sites of heavy metal in the cells, electrochemical charge of amine and carboxyl groups in the cell walls of heavy metal-tolerant microorganisms were chemically modified. Chemical modifications of amine groups did not affect the heavy metal uptake as compared to native cell walls. In contrast, modifications of carboxyl groups drastically decreased heavy metal uptake as compared to native cell walls, and electron microscopy confirmed that the form and structure of the heavy metal uptake were different from those of native cell walls. The results suggested that the carboxyl groups were the major sites of heavy metal uptake in the heavy metal-tolerant microorganism cell.

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