• 접착 및 계면
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• 제6권4호
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• pp.1-6
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• 2005

본 실험에서는 화학적 표면처리된 탄화규소의 첨가가 탄화규소(SiC)/에폭시 복합재료의 critical strain energy release rate mode II ($G_{IIC}$) 특성에 미치는 영향에 대하여 알아보았으며, 표면처리된 SiC의 표면특성은 산 염기도와 FT-IR을 사용하여 알아보았다. 또한 복합재료의 기계적 계면물성은 $G_{IIC}$를 통하여 알아보았다. 실험결과, 산성 용액으로 표면처리한 SiC (A-SiC)의 표면 산도가 염기성(B-SiC) 또는 표면처리 하지 않은 SiC (V-SiC)보다 높으며, $G_{IIC}$의 크랙저항 특성은 A-SiC가 향상되었는데, 이러한 결과는 SiC 충전재와 에폭시 수지간의 분자간 계면결합력의 향상 때문으로 판단된다.

• 한국가금학회지
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• 제20권3호
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• pp.151-159
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• 1993

본 연구는 항콕시듐 제제로 광범위하게 쓰이고 있는 nicarbazin이 닭의 고온 스트레스에 미치는 영향을 조사하고자 16수의 SCWL 수탉 성계를 사용하여 실시하였다. 옥수수-대두박 위주의 사료에 두 수준(0 및 125ppm)의 rucarbazin을 첨가하여, 두 처리의 환경온도(21 와 35~$36^{\circ}C$)하에서 4일간의 예비실험 기간을 거친 후, 2일 동안의 시료 및 자료 수집기간을 가졌다. 건물 섭취량과 건물 배설량은 고온 스트레스에 의하여 유의한 영향을 받지 않았으나, ricarbazin 첨가에 의하여 증가하였다. 그러나 건물 대사율은 nicarbazin첨가에 의하여 유의하게 감소하였다. 고온 스트레스는 또한 음수량과 증발에 의한 수분 손실을 증가시켰고, nicarbazin은 이러한 효과를 더욱 심화시켰다. 혈액 pH는 고온하에서 nicarbazin 첨가에 의해 증가되었으며, p$CO_2$는 고온하에서 nicarbazin에 의해 감소되었다. 고온 스트레스는 또한 체온을 상승시켰으며 nicarbazin 첨가는 이러한 효과를 심화시켰다. 이상의 결과를 종합하면, 닭이 고온 스트레스를 받으면 체온이 상승하게 된다. 따라서 닭은 체온 상승을 억제하기 위하여 호흡수를 증가시켜(panting) 수분 증발을 통한 체열 방출을 많게 한다. 그러나 nicarbazin 첨가는 고온하의 수탉 체온 상승 폭을 워낙 크게 하므로, panting에 의한 체열 방출량 증가만으로는 정상 체온을 유지하기가 어렵게 되는 것으로 풀이된다

• 대한치과보철학회지
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• 제45권2호
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• pp.159-168
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• 2007

Statement of problem: Literature showed different results on the durability of bonded ceramic restoration. Purpose: The purpose of this article is to review the effect of surface treatment of ceramics in resin-ceramic bond to get predictable results. Material and method: PubMed data base was utilized to search the articles which were written in English and published in 1986 and 2006. Some electronic published articles which are forthcoming to publish in paper were also included for this review. This review article focused on the effect of acid etching and silane application on the silica based ceramics. The durability of resin-ceramic bonding, the methodology for bond strength test and resin bonding to alumina or zirconia based ceramics were compared in brief at the end of the review. Results and Conclusion: the effect of silane application can be influenced by the contaminations of saliva or solutions. Micromechanical retention by acid etching as well as silane application plays an important role in initial and durable bond strength between resin and ceramic. The use of phosphate modified resin cement following tribochemical silica coating and silane application produced best bond strength for alumina or zirconia based ceramics.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1660-1669
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• 2015

The present study describes the gene cloning, overexpression and characterization of a novel nitrilase from hyperthermophilic bacterium Thermotoga maritima MSB8. The nitrilase gene consisted of 804 base pairs, encoding a protein of 268 amino acid residues with a molecular mass of 30.07 kDa after SDS-PAGE analysis. The optimal temperature and pH of the purified enzyme were 45℃ and 7.5, respectively. The enzyme demonstrated good temperature tolerance, with 40% residual activity after 60 min of heat treatment at 75℃. The kinetic constants V_max and K_m of this nitrilase toward 3-cyanopyridine were 3.12 μmol/min/mg and 7.63 mM, respectively. Furthermore, this novel nitrilase exhibited a broad spectrum toward the hydrolysis of the aliphatic nitriles among the tested substrates, and particularly was specific to aliphatic dinitriles like succinonitrile, which was distinguished from most nitrilases ever reported. The catalytic efficiency k_cat/K_m was 0.44 /mM/s toward succinonitrile. This distinct characteristic might enable this nitrilase to be a potential candidate for industrial applications for biosynthesis of carboxylic acid.

• BMB Reports
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• 제29권4호
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• pp.321-326
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• 1996

Spinach glycolate oxidase was subjected to a series of chemical modifications aimed at identifying amino acid residues essential for catalytic activity. The oxidase was reversibly inactivated by treatment with pyridoxal 5'-phosphate (PLP). The inactivation by PLP was accompanied by the appearance of an absorption peak of around 430 nm, which was shifted to 325 nm upon reduction with $NaBH_4$. After reduction, the PLP-treated oxidase showed a fluorescence spectrum with a maximum of around 395 nm by exciting at 325 nm. The substrate-competitive inhibitors oxalate and oxaloacetate provided protection against inactivation of the oxidase by PLP. These results suggest that PLP inactivates the enzyme by fonning a Schiff base with lysyl residue(s) at an active site of the oxidase. The enzyme was also inactivated by tryptophan-specific reagent N-bromosuccinimide (NBS). However, competitive inhibitors oxalate and oxaloacetate could not protect the oxidase significantly against inactivation of the enzyme by NBS. The results implicate that the inactivation of the oxidase by NBS is not directly related to modification of the tryptophanyl residue at an active site of the enzyme. Treatments of the oxidase with cysteine-specific reagents iodoacetate, silver nitrate, and 5,5'-dithiobis-2-nitrobenzoic acid did not affect significantly the activity of the enzyme.

• 한국연초학회지
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• 제6권2호
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• pp.117-129
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• 1984

In this study, clinoptilolites were subjected to an array of experimental conditions, such as variations in heating temperature, reaction time, and molarity of acid and bass, and their responses measured. The activation levels were measured by adsorption indexes of toluene and ethyl alcohol and the X-ray spectra of clinoptilolites treated with acid and base. The effect of clinoptilolites on the menthol fuation was estimated by the amount of menthol produced after a given time of storage. The results were as follows: The optimum conditions for the clinoptilolites treatment were found to be IM HCI, IM NaOH, IMHCl-lM NaOH, and IM NaOH-lM HCl at $100^{\circ}C$ for 2 hours. 2. It was noted that clinoptilolites, untreated or treated with HCl, could not be used for the menthol fixation since the catalytic crating of menthol occurred with them. 3. The results from the residual menthol measurement in clinoptilolites after a specific period of storage showed that the best menthol fixation occurred in those treated with IM NaOH. 4. The menthol fuation by cigarettes with mentholated clinoptilolites was far better than that obtained by the use of mentholated tobacco column. 5. Most components in cigrettes smoke were generally reduced by the adsorption to clinoptilolites treated with IM NaOH.

• Journal of Periodontal and Implant Science
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• 제31권4호
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• pp.749-763
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• 2001

Osseointegrated titanium implants have become an integral therapy for the replacement of teeth lost. For dental implant materials, titanium, hydroxyapatite and alumina oxide have been used, which of them, titanium implants are in wide use today. Titanium is known for its high corrosion resistance and biocompatability, because of the high stability of oxide layer mainly consists of $TiO_2$. With the development of peri-implantitis, the implant surface is changed in surface topography and element composition. None of the treatments for cleaning and detoxification of implant surface is efficient to remove surface contamination from contaminated titanium implants to such extent that the original surface elemental composition. In this sights, the purpose of this study was to evaluate rough surface titanium implants by means of scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS) with respect to surface appearance and surface elemental composition. Moreover, it was also the aim to get the base for treatments of peri-implantitis. For the SEM and XPS study, rough surface titanium models were fabricated for control group. Six experimental groups were evaluated: 1) long-time room exposure, 2 ) air-powder abrasive cleaning for 1min, 3) burnishing in citric acid(pH1) for 1min, 4) burnishing in citric acid for 3min, 5) burnishing in tetracycline for 1min, 6) burnishing in tetracycline for 3min. All experimental treatments were followed by 1min of rinsing with distilled water. The results were as follows: 1. SEM observations of all experimental groups showed that any changes in surface topography were not detected when compared with control group. (750 X magnification) 2. XPS analysis showed that in all experimental groups, titanium and oxygen were increased and carbon was decreased, when compared with control group. 3. XPS analysis showed that the level of titanium, oxygen and carbon in the experimental group 3(citric acid treatment for 1min, followed by 1min of distilled water irrigation) reached to the level of control group. 4. XPS analysis showed that significant differences were not detected between the experimental group 1 and the other experimental groups except of experimental group 3. The Ti. level of experimental group 2, airpowder abrasive treatment for lmin followed by 1min of saline irrigation, was lower than the Ti. level of tetracycline treated groups, experimental group 5 and 6. From the result of this study, it may be concluded that the 1min of citric acid treatment followed by same time of rinsing with distilled water gave the best results from elemental points of view, and can be used safely to treat peri-implantitis.

• 한국의류학회지
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• 제34권11호
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• pp.1880-1888
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• 2010

This study was a preliminary investigation of the influence of surface characteristics of substrates on the detergency of particulate soil. A PET film was surface modified with NaOH and DMF for different times. The surface morphology of the film was scanned by AFM and the surface energies were calculated from the measured contact angles between several solutions and film based on a geometric mean and the Lewis acid base method. The surface morphology of the PET film treated with NaOH and DMF became more etched and swelled with an increased treatment time, respectively. The surface roughness and surface area of film treated with NaOH enlarged with increased treatment time. However, the coefficient of friction of film treated with NaOH and coefficient of friction, surface roughness, and surface area of film treated with DMF increased and then decreased with increased treatment time. The contact angle of film treated with DMF decreased with increased treatment time in water and surfactant solution; however, the effect of treatment time on the contact angle was different in both solutions for film treated with NaOH. By the treatment of PET film with NaOH and DMF, the polar group of the surface energy increased and the nonpolar group decreased; however, the change of total surface energy was not significant.

• Korean Chemical Engineering Research
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• 제44권6호
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• pp.644-649
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• 2006

본 연구에서는 다양한 조건에서 기체상태의 오존처리된 활성탄소를 이용하여 수용액 상태에서의 Cr(VI)의 흡착특성에 대하여 고찰하였다. 오존처리된 활성탄소의 표면특성의 변화는 pH, 산도-염기도, FT-IR을 이용하였으며, $N_2$/77K 등온 흡착특성은 BET식, Boer의 t-plot, 그리고 Horvath-Kawazoe의 slit pore model을 이용하여 확인하였다. 또한, 총 Cr의 흡착량은 ICP-AES를 이용하여 확인하였다. 실험 결과, 오존처리는 활성탄소의 표면에 산소를 함유한 극성 관능기를 증가시켰으며, 이로 표면산도 또한 증가되었다. 한편, 오존처리의 영향으로 보이는 활성탄소의 비표면적과 미세기공 부피의 감소가 관찰되었지만, 활성탄소의 총 Cr 흡착량은 오존처리 시간이 증가할수록 비례적으로 증가하였다. 이는 활성탄소의 Cr 흡착특성이 비표면적보다 상대적으로 표면에 형성된 극성 관능기의 영향을 크게 받는 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.473-478
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• 2003

3-Amino-2-hydroxy-4(3H)-quinazolinone (3) was prepared via condensation of 1 with hydrazine hydrate. Treatment of 3 with appropriate acid in $POCl_3$, ethyl chloroacetate and activated olefinic compounds in DMF yielded the corresponding 3-(substituted)amino-2-hydroxy-4(3H)-quinazolinones 4, 5 and 6. The electron impact ionization mass spectra of compounds 3 and 4 show a weak molecular ion peak and a base peak of m/z 146 resulting from a cleavage fragmentation. The compounds 5 and 6 give a characteristic fragmentation pattern with a very stable fragment of benzopyrazolone (m/z 132).