• 한국응용과학기술학회지
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• 제20권2호
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• pp.141-147
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• 2003

Oxidized polyethylene wax is obtained by oxidation of polyethylene wax and it is composed of various chemicals, e.g., fatty acid, alcohol, ketone and ester. The application of oxidized polyethylene wax is determined by the composition of these chemical substances. In this basic study we observed the basic reaction parameters of time, temperature, oxygen concentration and catalysts on the oxidation reaction of low molecular weight polyethylene(PE wax) by analyzing the acid value, physical and chemical properties of oxidized PE wax to develop a new oxidation process. Acid values are increased with temperature increase in the rage of $150^{\circ}C^{\sim}180^{\circ}C$ but decreased beyond 190$^{\circ}C$. Acid values are also increased with oxygen concentration. As the oxidation reaction proceeds the molecular weight and softening points of oxidation products are decreased by cracking reaction, but the viscosities are increased. To observe the crystallinity of oxidation products SEM experiment was performed. To obtain a high acid-value product in a mild condition, we adopted free radical catalysts and the acid value of the product using catalyst was higher than the product obtained without catalyst in the same reaction condition. The effective initiators were dicumyl peroxide(DCPO), t-butylperoxy-2-ethyl hexanoate(HOPO) and benzoyl peroxide(BPO) having long half-life.

• 산업식품공학
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• 제15권4호
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• pp.289-296
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• 2011

Twenty four fractions by solvent extraction and/or acid precipitation from fruit body and culture broth of Inonotus obliquus were prepared, and their inhibitory effect against acetylcholinesterase (AChE) was investigated. Among these fractions, acid (1 M HCl) precipitates from cell-free culture broth and fruit body exhibited the highest inhibitory effect on AChE in vitro. Acid precipitates inhibited AChE activity in a concentration-dependant manner and $IC_{50}$ values of both acid precipitates were 0.53 mg/mL. The inhibition pattern was general non-competitive inhibition. The energetic parameters were also determined by dual substrate/temperature design. Both acid precipitates increased the values of Ea, ${\Delta}H,/;{\Delta}G$ and ${\Delta}H^{\ast}$ decreasing the value of ${\Delta}S$ for AChE. The results implied that the acid precipitates from I. obliquus increased the thermodynamic barrier, leading to the breakdown of ES complex and the formation of products as inhibitory mechanism.

• 한국축산식품학회지
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• 제30권5호
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• pp.717-721
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• 2010

The objective of this study was to evaluate the inhibition of Listeria monocytogenes growth by oleanolic acid under sublethal stresses of NaCl and pH. L. monocytogenes ATCC15313 (6 log CFU/mL) was inoculated in microplate wells containing brain heart infusion (BHI) broth supplemented with oleanolic acid in various amounts (0, 0.25, 0.5, 1.0, 1.5, 2.0, and $4.0\;{\mu}g/mL$), and different pHs (5 and 7) and NaCl concentrations (0, 3, and 6%), followed by incubation under accelerated storage condition ($37^{\circ}C$, 48 h). The optical density (OD) of the samples was measured at 0, 6, 12, 24, and 48 h at 600 nm. After the lag phase duration was observed at the early stage of incubation, the OD values of L. monocytogenes significantly increased (p<0.05) in BHI broth formulated with 0 and 3% of NaCl during accelerated storage at pH 5 and 7. However, the growth of L. monocytogenes in 6% NaCl and at less than $0.5\;{\mu}g/mL$ of oleanolic acid had no growth at pH 5 and only gradual growth at pH 7. Moreover, L. monocytogenes generally had lower OD values as the concentrations of oleanolic acid increased. As expected, the OD values of L. monocytogenes were generally higher (p<0.05) at pH 7 than at pH 5. These results indicate that oleanolic acid should be useful in inhibiting the growth of L. monocytogenes.

• 대한치과보철학회지
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• 제41권3호
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• pp.379-386
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• 2003

Statement of problem. Resin cements are widely used in adhesive dentistry specially on all ceramic restorations. It is needed to find out adequate bonding strength between different porcelain surface treatments, commercially available porcelains, and different resin cement systems. Purpose. The purpose of this study was to evaluate shear bond strength of resin cements bonded to porcelains in three different modalities; 5 different porcelain surface treatments, 3 different resin cement systems and 3 different commercially available pressable porcelains. Material and Method. This study consisted of 3 parts. Part I examined the effect of five different surface treatments on the pressable porcelain. Fifty discs (5 mm in diameter and 3 mm in height) of Authentic porcelain were randomly divided into 5 groups (n = 10). The specimens were sanded with 320 grit SiC paper followed by 600 grit SiC paper. The specimens were treated as follow: Group 1-Sandblasting (aluminum oxide) only, Group 2 - sandblasting/ silane, Group 3 - sandblasting/ acid etching/ silane, Group 4 - acid etching only, Group 5 - acid etching/ silane. Part II examined the shear bond strength of 3 different resin cement systems (Duolink, Variolink II, Rely X ARC) on acid etching/ silane treated Authentic pressable porcelain. Part 3 examined the shear bond strength of Duolink resin cement on 3 different pressable porcelains (Authentic, Empress I, Finesse). All cemented specimens were stored in distilled water for 2 hours and tested with Ultradent shear bond strength test jig under Universal Instron machine until fracture. An analysis of variance(ANOVA) test was used to evaluate differences in shear bond strength. Result. The shear bond strength test resulted in the following: (1) Acid etched porcelains recorded greater shear bond strength values to the sandblasted porcelains. (2) Silane treated porcelains recorded greater shear bond strength values to non-silane treated porcelains. (3) There was no significant difference between sandblasting/ acid etching/ silane treated and acid etching/ silane treated porcelains. However those values were much higher than other three groups. (4) The shear bond strength with Variolink II was lower than the value of Duolink or Rely X ARC. (5) The shear bond strength of Finesse was lower than the value of Authentic or Empress I.

• 동아시아식생활학회지
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• 제3권2호
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• pp.147-153
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• 1993

Phenolics as antioxidant were added to linoleic acid to prevent lipid oxidation. Antioxidative effectiveness of them was measured by peroxie value at each 24hour interval in order to compare with 0.02% protocatechuic acid(PRL) and phloroglucinol(PHL) in linloleic acid, contrast tube at 37$^{\circ}C$for 96 hours blowing oxygen into specimen. Perocide values of oxidized linoleic acid, PRL, PHL for 96 hours were 78, 42, 30, From that the effect is more clearly demonstrated by NMR rather than UV and that the effect was dependent on the functional group and geometric molecular structure of phenolics.

• 한국안전학회지
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• 제22권2호
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• pp.47-52
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• 2007

The flash points and the fire points for the m-xylene+n-propionic acid and n-butanol+n-pentanol systems were measured by using Tag open-cup apparatus(AS1M D 1310-86). The experimental flash points of two binary systems were compared with the values calculated by the Raoult's law, Van Laar equation and Wilson equation. The calculated values based on the Raoult's law on m-xylene+n-propionic acid system were found to be better than those based on Van Laar and Wilson equations. The calculated values based on Van Laar equation on n-butanol+n-pentanol system were found to be better than those based on the Raoult's law and Wilson equation. The the fire points for the m-xylene+n-propionic acid system were about $7{\sim}8^{\circ}C$ above the flash points. In the case of n-butanol+n-pentanol system, the flash points and the fire points had been found to be identical.

• 환경위생공학
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• 제4권1호
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• pp.29-36
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• 1989

The purpose of this investigation was performed for chemical values related to rancidity of fat and oils extracted from deep-frying food in Seoul. The samples were collected according to kinds of fat and oils, sampling sites and food stuffs for frying. The results were as follows 1. The most used frying oils were rice bran oil $(37.0\%)$ and shortening $(29.6\%)$, followed by rapeseed oil $(14.8\%)$. 2. The chemical values related to rancidity of fat and oils extracted from deep-frying foods were the next on average. Acid value-1.42, peoxide value-39.82, dinitrophenyl hydrazine value-16.73 thiobarbituric acid value-0.263. However the highest value among oils was showed in rice bran oil and the lowest value was shortening. 3. For the classification of sampling sites, acid value and peroxide value of samples of the markets were found higher than them of environs of school and roadside, and the differences between them were significant (P> 0.01), while dinitrophenyl hydrazine value and thiobar bituric acid value were not showed the significant differences. 4. For the classification of foodstuffs for frying, there were not recognized significant differences among all kinds of them.

• Bulletin of the Korean Chemical Society
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• 제25권12호
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• pp.1898-1906
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• 2004

Nonclassical quinazolinone analogs I, II, and III, in which the glutamic acid moiety of the classical antifolates is substituted by phenylglycine, phenylalanine or aminobenzoic acid and their methyl esters, were synthesized and evaluated as lipophilic inhibitors of thymidylate synthase (TS). The target compounds were generally potent inhibitors of L. casei and human TS with $IC_{50}$ values within the narrow range of 0.2-10 ${\mu}$M and 0.003-0.03 ${\mu}$M, respectively. Further, most of the target compounds showed cytotoxicity against tumor cell lines of murine and human origin with $IC_{50}$ values of as low as 0.050 ${\mu}$M. Substitution of another hydroxyl or carboxylic acid/ester group at the phenyl ring further increased the potency of TS inhibition and cell growth inhibition. Most effective were compounds If and Ic in which extra carboxylic acid/ester was present at the phenyl ring with nanomolar $IC_{50}$ values of 0.0044 and 0.0093 ${\mu}$M against human TS and submicromolar cytotoxic growth inhibition against all four tumor cell lines.

• 한국식품저장유통학회지
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• 제19권5호
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• pp.639-644
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• 2012

본 실험은 형광분광법을 이용하여 분말화된 대두의 산패도를 유지의 추출과정 없이 직접 측정하는 방법을 확립하기 위해 실시하였다. FST와, TBA test, 산가 측정법을 이용하여 $25^{\circ}C$와 $90^{\circ}C$에서 20일 동안 저장하면서 산패도에 따라 값을 비교하였다. $25^{\circ}C$에서 저장 기간 중의 산패도는 변화가 없음을 알 수 있었다. 모든 측정치들은 초기값에 비해 20일 후의 값이 크게 차이 없이 일정한 것을 알 수 있었다. 반면 $90^{\circ}C$에서는 FST의 경우 8일에서 11일 사이에 FI값이 크게 증가하는 경향을 보인 후 일정하게 값이 증가하는 경향을 볼 수 있었는데 TBA test에서는 0일에서 꾸준하게 증가하던 값이 다시 감소하는 것을 보였으며 이는 oleic acid와 linoleic acid의 함량이 높은 대두의 특징이라 할 수 있다. 본 연구에서 실험한 시료의 경우 산가는 FST와 같은 경향을 보여주었다. 본 연구의 중요한 결과는 FST를 이용하여 대두의 산패를 분말상에서 직접 측정하는 법을 확립한 것이며 이는 일반적으로 사용되는 TBA test와 산가를 이용한 직접측정법에 비해 측정시간이 빠르며 추출과정에 의한 오차를 최소화 할 수 있음을 보여주었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.259-263
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• 2001

There are several steps such as slicing, lapping, chemical etching and mechanical polishing in the silicon wafer production process. The chemical etching step is necessary to remove damaged layer caused In the slicing and lapping steps. The typical etching liquor is the acid mixture comprising nitric acid, acetic acid and hydrofluoric acid. At present, the waste acid is treated by a neutralization method with a high alkali cost and balky solid residue. A solvent extraction method is applicable to separate and recover each acid. Acetic acid is first separated from the waste liquor using 2-ethlyhexyl alcohols as an extractant. Then, nitric acid is recovered using TBP(Tri-butyl phosphate) as an extractant. Finally hydrofluoric acid is separated with the TBP solvent extraction. The expected recovered acids in this process are 2㏖/l acetic acid, 6㏖/1 nitric acid and 6㏖/l hydrofluoric acid. The yields of this process are almost 100% for acetic acid and nitric acid. On the other hand, it is important to recover and reuse the metal values contained in various industrial wastes in a viewpoint of environmental preservation. Most of industrial products are made through the processes to separate impurities in raw materials, solid and liquid wastes being necessarily discharged as industrial wastes. Chemical methods such as solvent extraction, ion exchange and membrane, and physical methods such as heavy media separation, magnetic separation and electrostatic separation are considered as the methods for separation and recovery of the metal values from the wastes. Some examples of the application of solvent extraction to the treatment of wastes such as Ni-Co alloy scrap, Sm-Co alloy scrap, fly ash and flue dust, and liquid wastes such as plating solution, the rinse solution, etching solution and pickling solution are introduced.