• Bulletin of the Korean Chemical Society
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• v.8 no.6
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• pp.471-475
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• 1987

Benzotriazol-1-yl Diethyl phosphate and benzotriazol-1-yl diphenyl phosphate were conveniently prepared in essentially quantitative yields by the reaction of diethyl chlorophosphate and diphenyl chlorophosphate with equal amounts of 1-hydroxybenzotriazole and triethylamine in tetrahydrofuran at room temperature, respectively. Benzotriazol-1-yl diethylphosphate was effective for the preparation of amides from carboxylic acids amines. Young test and Anderson test for racemization studies using benzotriazol-1-yl diethyl phosphate were investigated and practically no racemization occurred. However, racemization occurred to some extent during coupling of Z-Phe-Val-OH with Pro-OBu. Several dipeptides and tripeptides were prepared without little racemization using benzotriazol-1-yl diethyl phosphate. Benzotriazol-1-yl diphenyl phosphate was less effective than benzotriazol-1-yl diethyl phosphate in terms of the degree of racemization.

• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1329-1334
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• 1999

The curing characteristics of diglycidyl ether of bisphenol A (DGEBA) with diaminodiphenylmethane (DDM) as a curing agent were studied using differential scanning calorimetry (DSC), rheometrics mechanical spectrometry (RMS), and dielectric analysis (DEA). The isothermal curing kinetics measured by DSC were well represented with the generalized auto-catalytic reaction model. With the temperature sweep, the inverse relationship between complex viscosity measured by RMS and ionic conductivity obtained from DEA was established indicating that the mobility of free ions represented by the ionic conductivity in DEA measurement and the chain segment motion as revealed by the complex viscosity measured from RMS are equivalent. From isothermal curing measurements at several different temperatures, the ionic conductivity contribution was shown to be dominant in the dielectric loss factor at the early stage of cure. The contribution of the dipole relaxation in dielectric loss factor became larger as the curing further proceeded. The critical degrees of cure, at which the dipolar contribution in the dielectric loss factor starts to appear, increases as isothermal curing temperature is increased. The dielectric relaxation time at the same degree of cure was shorter for a sample cured at higher curing temperature.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.28 no.1
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• pp.150-165
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• 2002

The purpose of this study was to evaluate bacteriocin activity against human flora. Lactobiocin, a bacteriocin produced by Lactococcus sp. HY 449, inhibited the growth of Starphylococcus epidermidis, Starphylococcus aureus, Streptoccoccus pyogenes and Propionibacterium acnes. When crude bacteriocin was added to indicator cells during logarithmic growth, the optical density(O.D 650nm) of cells without bacteriocin increase after 5h of incubation. Whereas in the presence of bacteriocin, the O.D of cell suspensions decreased. The similar patterns were observed for absorbance readings at 280 nm and 260 nm. The release of cellular components when cell were treated with Lactobiocin suggests some degree of membrane damage or cell lysis. Scanning electron microscopy of cells following treatments with Lactobiocin in PBS buffer revealed disruptures of cell morphology. These results indicate that bacteriocin appears to cause cell lysis of tested strains. In cytotoxicity on human fibroblast, LD$\_$50/ of Lactobiocin was ca. 50 mg/ml and no change was observed cell proliferation at the same concentration. Any irritation and allergic reaction did not observed when evaluated by human patch test for Lactobiocin.

• Clinical and Experimental Pediatrics
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• v.63 no.12
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• pp.463-468
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• 2020

Pollen-food allergy syndrome (PFAS) is an immunoglobulin E-mediated immediate allergic reaction caused by cross-reactivity between pollen and the antigens of foods-such as fruits, vegetables, or nuts-in patients with pollen allergy. A 42.7% prevalence of PFAS in Korean pediatric patients with pollinosis was recently reported. PFAS is often called oral allergy syndrome because of mild symptoms such as itching, urticaria, and edema mainly in the lips, mouth, and pharynx that appear after food ingestion. However, reports of systemic reactions such as anaphylaxis have been increasing recently. This diversity in the degree of symptoms is related to the types of trigger foods and the characteristics of allergens, such as heat stability. When pediatric patients with pollen allergy are treated, attention should be paid to PFAS and an active effort should be made to diagnose it.

• Elastomers and Composites
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• v.25 no.4
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• pp.273-279
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• 1990

The graft polymerization of 2-hydroxyethylmethacrylate(HEMA) and vinyltriethoxysilane(VTES) onto styrene-butadiene-styrene block copolymer(SBS) was carried out in toluene, with radical initiator such as benzoyl peroxide(BPO) and 2, 2'-azo-bis-isobutyronitrile(AIBIN) under nitrogen atmosphere. The degree of grafting was increased with the increases of the reaction temperature and time. And the effeciency of BPO was superior to that of AIBN. The mechanical properties and molecular weight of graft products were measured and the applicability as adhesive of plasticized PVC leather was examined.

• SUVANNABHUMI
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• v.8 no.1
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• pp.77-94
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• 2016

The paper examined Southeast Asia as a whole and focused on similarities among countries composing what is now known as the Association of Southeast Asian Nations (ASEAN). In order to determine these similarities, the analysis focused on the fact that during World War II the whole of Southeast Asia was occupied by one political power: Japan. The policies the Japanese implemented in the region were to a degree very similar in terms of pressures and tensions that occurred in the different countries. The paper argues that these pressures and the responses of the various peoples of Southeast Asia instilled a nucleus of common identity in Southeast Asia as a whole. Basically, the policies that the Japanese implemented all over Southeast Asia were the following: the setting up regional administrations; the extraction of resources and emphasis on local self-sufficiency; the implementation of cultural Japanization; and local indigenization policies. The Southeast Asian responses that crystalized this joint Southeast Asian identity may be described as: accommodating and resisting the Japanese; commemorating portraying; and collectively remembering the era. The process of action and reaction between Japan and Southeast Asia was formative of this joint Southeast Asian identity.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.756-765
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• 2004

We present extraction process and reaction mechanism of boric acid from one of calcium borate ores, colemanite by reaction with sulfuric acid. Colemanite has been fully decomposed under pH 5 with sufficiency amount of sulfuric acid, more than the amount stoichiometrically required. Calcium sulfate was separated out, leaving boron in the liquid phase after sulfuric acid addition. The extraction process of boric acid was affected by dissolution temperature and time, amount of sulfuric acid and ammonium sulfate, pH and a degree of concentration before recrystallization. The $SiO_2$ of the impurities which colemanite contains was insoluble so that it was separated out with calcium sulfate from liquid phase. The species of $CaO,\;Al_2O_3,\;Fe_2O_3,\;MgO$ were remained in a liquid phase after reaction with sulfuric acid. These impurities were separated out by addition of ammonia to the liquid phase, funhermore, boric acid was produced by process of pH adjustments and acidification, concentration, and recrystallization.

• Journal of Adhesion and Interface
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• v.3 no.2
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• pp.9-16
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• 2002

In the synthesis of water-based polyurethane using self-emulsification process, after being neutralized, polyurethane pre-polymers containing ionic pendant groups are dispersed by simple convective mixing. Preparation of dispersion is followed by chain extension reaction, which is considered as important step for growth of the molecular weight of polyurethane. In this work, pH variations in the aqueous phase were monitored during the chain extension process in the presence of water-soluble diamines. The optimum degree of chain extension and the average particle size in the polyurethane dispersions were examined with varying ionic pendent group contents, type of chain extenders, and feed rate of chain extenders, The initial pH value in the aqueous phase linearly increased and the optimum chain extension point could be obtained from the intersection of two linear lines having different slopes, All average particle sizes before chain extension reaction were almost same, however, the final average particle size increased as feed rates of chain extenders increased, In addition, as the ionic pendant group contents increased, the particle size decreased since the hydrophilicity and hydrodynamic volume increased. As carbon numbers of the chain extenders increased, the final particle size increased significantly. From the results, it was concluded that the chain extension reaction took place among the particles not only in a particle.

• Journal of Radiation Protection and Research
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• v.20 no.3
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• pp.181-186
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• 1995

UV irradiation causes a variety of biologic effects on the skin. These effects can be devided to acute reactuons and chronic reacxtions by duration of UV irradiation. Acute reactions are erythema reaction, pigment reactions and changes in epidermal thickness. Among them erythema reaction is most common and conspicuous acute effects of the skin. Upon exposure to sun or artificial UV soures, a faint redness response of skin may begin. Larger exposure causes sunburn reaction which is exaggerated erythema reactionassociated with pain, swelling, vesicle and dulla. Extent and time course of erythema reaction depend upon several factors including wavelength and dose of UVR, skin conditions likeas skin type, site, color, temperature, humidity and environmental factors. Evaluation of erythema erythema induced by UV irradiation is difficult to quantify. Degree of redness of skin are usually estimated by subjective visual evaluation. The lowest exposure dose required to protuce erythema is called minimal erythema dose (mod). Repeated exposures of UVR result in photaging skin. In this condition we can see wrinkling, skin atrophy, dilated blood vessels and keratoses. In sensitive persons photocarcinogenesis is can Be developed on exposed area of skin. Recently skin canser is increasing now in our country. An effective public education and photopreventive method must be developed.

• Journal of the Korean Chemical Society
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• v.24 no.4
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• pp.329-336
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• 1980

A domestic phosphogypsum was calcined in a batch type fluidized bed reactor at various reaction temperatures ranging 90∼180$^{\circ}$ without and with an alkaline additive amounting up to 5% of gypsum, and physical properties of the resultant products were compared following their characterization by X-ray diffraction pattern and DTA. It has been found that dehydration reactions were uniformly carried out in the fluidized bed reactor and only hemihydrate was obtained at 90$^{\circ}$ whereas at higher temperatures dehydration reaction progressed further. When gypsum was charged to the reactor preheated at over 140$^{\circ}$, a considerable degree of dehydration occurred before the reactant reached the initially set reactor temperature and in particular, at over 160$^{\circ}$ most of dehydration reaction was performed prior to the present reactor temperature. However, it has been found that gypsum mostly transforms into hemihydrate around the reactant temperature of 140$^{\circ}$ while transformation into anhydrite mostly occurs around $160^{\circ}C.$ When calcium hydroxide was added to gypsum in the reactor, the optimum physical properties of the calcined product were obtained at the weight ratio of $Ca(OH_2)/P_2O_5$ = 3.2.