• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.4
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• pp.641-645
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• 2004

Crude chondroitin sulfates extracted from midduck tunics (Styela clava) and munggae tunics (Halocynthia roretzi) were examined in vivo in order to be utilized as a cosmetic material which was followed by an in vitro assay. Examinations, such as acute oral toxicity, skin sensitization, acute eye irritation, and primary skin irritation, were peformed with a variety of laboratory animals. Phototoxic and photosensitization tests were not conducted since all chondroitin sulfates failed to absorb U.V. light at the range of 280 to 420 nm. In acute dermal and eye irritation, both specific clinical signs and dead cases were not demonstrated during the test period, but crude chondroitin sulfates from midduck and munggae tunics, and standard chondroitin sulfate from bovine trachea were showed 2.5, 1 and 1.25 of acute ocular irritation index (A.O.I.), respectively. In the case of skin sensitization, crude chondroitin sulfate from midduck tunics exhibited neither specific clinical signs nor dead cases in the entire course of the examination. While in acute oral toxicity, crude chondroitin sulfates from both midduck and munggae tunics found neither specific clinical signs nor dead cases during the test, and LD50 was suspected to be over 2 g/kg. Based on this study, it was proven that crude chondroitin sulfates from either midduck or munggae tunics can be used safely as a cosmetic material.

• Journal of Aquaculture
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• v.17 no.2
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• pp.97-102
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• 2004

We examined the effects of stimulants including sunlight and UV-irradiation on the spawning induction and early development of the noble scallop, Chlamys nobilis. The sunlight stimulation resulted in nuch faster spawning induction (100% success within 40 minutes) compared to UV-irradiation (100% success within 70 minutes). Early development of the scallop larva took place between 15$^{\circ}C$ to 3$0^{\circ}C$. The time to reach the early D-shaped stage was 63.5, 31.5, 18.5 and 17.0 hours at 15, 20, 25 and 3$0^{\circ}C$, respectively. The correlations between the water temperature-(WT) regimes and the time (t) required for each developmental stage are as follows. 2 cell stage: 1/t=0.0606WT-0.6194 ($r^2$=0.9791) 8 cell stage: 1/t=0.0304WT-0.3453 ($r^2$=0.9941) Morula: 1/t=0.0100WT-0.1049 ($r^2$=0.9663) Trochophore: 1/t=0.0058WT-0.0618 ($r^2$=0.9848) D-shaped larva: 1/t=0.0030WT-0.0282 ($r^2$=0.9731) These correlations indicated that the biological minimum temperature of the species is around 10.44$^{\circ}C$. The highest survival rate up to D-shaped larva at different water temperature was observed at $25^{\circ}C$.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.1
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• pp.75-81
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• 2015

Purpose: The present study was conducted to investigate whether the changes in structure and activity of antioxidative enzymes, superoxide dismutase(SOD) and catalase(CAT) present in the eyes appeared when they were repeatedly exposed to UV-A, and reveal the correlation of these changes. Methods: Each enzyme solution was prepared from the standardized SOD and CAT, and repeatedly exposed to UV-A of 365 min under the condition of 30 minutes, 1 hour and 2 hours a day over 1, 2, 3, 4 and 5 days. Structural denaturation of SOD and CAT induced by repeat UV-A irradiation was confirmed by the electrophoretic analysis, and their enzyme activity was determined by the colorimetric assay using the proper assay kit. Results: SOD exposed repeatedly to UV-A showed the polymerization pattern through the electrophoretic analysis when it was repeatedly exposed under the condition of at least 1 hour a day however, the change of its activity was found to be less than 12%. On the other hand, CAT repeatedly exposed to UV-A showed reduced size of the electrophoretic band which indicated a structure denaturation and its activity was significantly decreased. In the case of that the repeat exposure time was longer, CAT activity was completely lost even though some enzyme band was shown in the electrphoretic analysis. Conclusions: From these results, it was revealed that the degree and pattern in structural denaturation of antioxidative enzymes differently appeared according to the type of enzyme, and the degree of structural denaturation was not always consistent with the reduction in enzyme activity.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.471-475
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• 2013

This study is about photosensitive microspheres prepared by coating alginate microspheres with gelatin-cinnamic acid conjugate. Firstly, alginate microspheres was prepared in water-in-oil (W/O) emulsion and then they were coated with gelatin- cinnamic acid conjugate. Herein, gelatin-cinnamic acid conjugate is obtained by the amidation between an amine group of gelatin and a carboxy group of cinnamic acid. Cinnamic acid is widely used as a photo-responsive material easy to dimerize and dedimeriz under UV irradiation at ${\lambda}$ = 254 nm and ${\lambda}$ = 365 nm, respectively. As shown in SEM-EDS, alginate was successfully coated with gelatin-ciannmic acid. By determining the absorbance of coated microspheres at 270nm, the amount of cinnamic acid per microspheres was 0.13/1. The SEM photos showed the size of coated microspheres is around $10{\mu}m$. And the degrees of dimerization and dedimerization were calculated to be 49% and 23% respectively. Then the release of FITC-dextran from the coated micrspheres was studied and release the degree was 42%. As a result, the coated microspheres have potential to be used as a photo-responsive drug carrier to delivery drugs.

• Journal of the Korean Chemical Society
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• v.15 no.6
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• pp.312-317
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• 1971

The interactions of aniline, o-toluidine, o-ethylaniline and o-chloroaniline with iodine in carbon tetrachloride solution have been examined through spectrophotometric measurements. The results indicate that both aniline and the o-substituted anilines examined form one-to-one complexes with I2in solution. The formation constants of the complexes measured at room temperature are 12.8, 9.31, 3.15 and 0.576 l $mole^{-1}$, respectively. Comparison of these results with previous experimental results indicates that the relative stabilities of the $I_2$-amine complexes decrease in the following order: $C_6H_5N(C_2H_5)_2 >C_6H_5N(CH_3)_2 >C_6H_5NH_2 >o-CH_3C_6H_4NH_2 >o-C_2H_5C_6H_4NH_2 >o-ClC_6H_4NH_2$. This may support the conclusion that the relative stabilities of these complexes are explained by the inductive effect and steric hindrance of the substituents.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.291-298
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• 2020

ZITO/Ag/ZITO multilayer transparent electrodes at room temperature on glass substrates were prepared using RF/DC magnetron sputtering. Transparent conductive films with a sheet resistance of 9.4 Ω/㎡ and a transmittance of 83.2% at 550 nm were obtained for the multilayer structure comprising ZITO/Ag/ZITO (100/8/42 nm). The sheet resistance and transmittance of ZITO/Ag/ZITO multilayer films meant that they would be highly applicable for use in polymer-dispersed liquid crystal (PDLC)-based smart windows due to the ability to effectively block infrared rays (heat rays) and thereby act as an energy-saving smart glass. Effects of the thickness of the PDLC layer and the intensity of ultraviolet light (UV) on electro-optical properties, photopolymerization kinetics, and morphologies of difunctional urethane acrylate-based PDLC systems were investigated using new transparent conducting electrodes. A PDLC cell photo-cured using UV at an intensity of 2.0 mW/c㎡ with a 15 ㎛-thick PDLC layer showed outstanding off-state opacity, good on-state transmittance, and favorable driving voltage. Also, the PDLC-based smart window optimized in this study formed liquid crystal droplets with a favorable microstructure, having an average size range of 2~5 ㎛ for scattering light efficiently, which could contribute to its superior final performance.

• Journal of Korean Society on Water Environment
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• v.32 no.4
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• pp.357-366
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• 2016

N-nitrosamines are a class of carcinogenic chemicals that can pose significant hazards to the human life. Ultraviolet (UV) light irradiation is considered as one of the effective methods to reduce N-nitrosamines in the aqueous phase. This study aimed to investigate the pH influence on UV photodegradation of N-nitrosamines (i.e., N-nitrosodibutylamine (NDBA) and N-nitrosopyrrolidine (NPYR)) closely related to water treatment. Photodegradation rate constants of NDBA and NPYR remained between 3.26×10^-2 L/W-min to 5.08×10^-3 L/W-min and 1.14×10^-2 L/W-min to 2.80×10^-3 L/W-min at pH2-10, respectively. This study also focused on the formation of oxidized products (i.e., primarily NO^2- and NO^3-). Under slightly acidic and neutral conditions, NO^2- formation was more prevalent than NO^3- formation, while under strong acidic conditions, NO^3- was more prevalent. There was no significant change in total organic carbon (TOC) and total nitrogen (TN), suggesting negligible loss of N-nitrosamines and degradation products from the system. NDBA was easily photodegraded than NPYR. This study also demonstrated that a lower pH is a favorable condition for photolytic degradation of N-nitrosamines in water.

• Journal of Sericultural and Entomological Science
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• v.30 no.1
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• pp.33-39
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• 1988

In the case of white cocoon, the fluorescence colors are classified as a yellowish fluorescence cocoon(Y.F.C.) and a violet fluorescence cocoon(V.F.C.) by exposing to ultra-violet ray. Accordingly, experiments were carried out to investigate the difference of sericin behaviors between Y.F.C. and V.F.C. by measuring the sericin solubility, surface tension and viscosity of the sericin solution. Also, the reelability of two different type of cocoons was investigated in the silk reeling process. The results were summarized as follows; 1. The sericin solubility of Y.F.C. shell is higher than that of V.F.C. shell with the dissolution temperature and time. It is shown that the sericin solubility curves of Y.F.c. and V.F.C. are similar in shape, but the difference of sericin solubility between Y.F.C. and V.F.C. is more significant at higher bath temperature. 2. The initial sericin dissolution curves of Y.F.C. and V.F.C. cocoon shell can be divided by four parts within the range of dissolving time from 5 minutes to 60 minutes. The initial dissolution velocity of Y.F.C. shell is faster than that of V.F.C. but the velocity difference is negligible after 30 minutes of dissolving time. 3. The gelation of V.F.C. sericin solution is faster than that of Y.F.C. at early stage(in the range of 15 minutes to 60 minutes). 4. In the silk reeling process, the reelability of Y.F.C. is better than that of V.F.C. with about 11%. This is mainly due to the higher sericin solubility in Y.F.C. followed by the fast dissolution velocity.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.91-91
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• 2010

본 논문은 펄스 직류전원 (Pulse DC) 플라즈마 소스와 반응성 가스인 $CF_4$와 불활성 가스인 Ar를 혼합하여 산업에서 널리 사용되는 유기고분자인 Polymethylmethacrylate (PMMA), Polyethylene terephthalate (PET), 그리고 Polycarbonate (PC) 샘플을 건식 식각한 결과에 대한 것이다. 각각의 샘플은 감광제 도포 후에 자외선을 조사하는 포토레지스트 방법으로 마스크를 만들었다. 펄스 직류전원 플라즈마 시스템을 사용하면 다양한 변수를 줄 수 있다는 장점이 있다. 공정 변수는 Pulse DC Voltage는 300 - 500 V, Pulse DC reverse time $0.5{\sim}2.0\;{\mu}s$, Pulse DC Frequency 100~250 kHz 이었다. 변수 각각의 값이 높아질수록 고분자의 식각률이 높아졌다. 특히, PMMA의 식각률이 가장 높았으며 PET, PC 순이었다. 샘플 중 PC의 식각률이 가장 낮은 이유는 고분자 결합 중에 이중결합의 벤젠 고리 모양을 포함하고 있어 분자 결합력이 비교적 높기 때문으로 사료된다. 기계적 펌프만을 사용한 공정 전 압력은 30 mTorr이었다. 쓰로틀 밸브를 완전 개방한 상태에서 식각 공정 중 진공 압력은 $CF_4$ 가스유량이 늘어날수록 증가하였다. 식각률 역시 $CF_4$ 가스유량(총 가스 유량은 10 sccm)이 많을수록 증가함을 보여주었다 (PMMA: 10 sccm $CF_4$에서 330 nm/min, 3.5 sccm $CF_4$/6.5 sccm Ar에서 260 nm/min., PET: 10 sccm $CF_4$에서 260 nm/min, 3.5 sccm $CF_4$/6.5 sccm Ar에서 210 nm., PC: 10 sccm $CF_4$에서 230 nm, 3.5 sccm $CF_4c$/6.5 sccm Ar에서 160 nm). 이는 펄스 직류전원 플라즈마 식각에서 $CF_4$와 Ar의 가스 혼합비를 조절함으로서 고분자 소재의 식각률을 적절히 변화시킬 수 있다는 것을 의미한다. 표면 거칠기는 실험 후 표면단차 측정기와 전자 현미경 등을 이용하여 식각한 샘플의 표면을 측정하여 알 수 있었다. 실험전 기준 샘플 표면 거칠기는 PMMA는 1.53nm, PET는 3.1nm, PC는 1.54nm 이었다. 식각된 샘플들의 표면 거칠기는 PMMA는 3.59~10.59 nm, PET은 5.13~11.32 nm, PC는 1.52~3.14 nm 범위였다. 광학 발광 분석기 (Optical emission spectroscopy)를 이용하여 식각 공정 중 플라즈마 발광특성을 분석한 결과, 탄소 원자 픽 (424.662 nm)과 아르곤 원자 픽 (751.465 nm, 763.510 nm)의 픽의 존재를 확인하였다. 이 때 탄소 픽은 $CF_4$ 가스에서 발생하였을 것으로 추측한다. 본 발표를 통해 펄스 직류전원 $CF_4$/Ar의 고분자 식각 결과에 대해 보고할 것이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.309.1-309.1
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• 2014

III-N계 기반의 광 반도체는 직접 천이형 넓은 밴드갭 구조를 갖고 있기 때문에 자외선에서 가시광을 포함한 적외선까지 포함한 폭 넓은 발광이 가능하여 조명 및 디스플레이 관련 차세대 광원으로 많은 관심을 받고 있다. 하지만 p형 GaN의 경우, 상온에서 도펀트로 사용되는 마그네슘(Mg)이 수소(H)와 결합하여 보상 효과를 나타내기 때문에 높은 정공농도를 갖기에 어려움이 있다고 알려져 있다. 따라서, 대부분의 연구 그룹에서는 GaN계 LED 소자를 성장 후 rapid thermal annealing 공정이 요구되고 있고, 최근에는 박막 성장 후 반응로 내에서 자체적으로 열처리를 진행하고 있는 실정이다. 하지만, 열처리 조건은 LED 소자의 발광특성에 큰 영향을 주기 때문에 본 연구에서는 반응로에서 열처리가 된 LED 샘플에 대해 추가적인 열처리 공정의 유무에 따른 GaN계 LED소자의 광학적 및 전기적 특성에 대해 알아보고자 하였다. 금속유기화학증착법을 이용하여 c-면 사파이어 기판에 저온 GaN 완충층 및 $2.0{\mu}m$두께의 GaN 박막을 성장한 후, $3.0{\mu}m$두께의 n-형 GaN에피층과 InGaN/GaN 5주기의 양자우물구조를 형성하고 $0.1{\mu}m$두께의 p형 GaN층을 성장하였다. P-형 GaN층 성장 후 온도를 내리면서 $750^{\circ}C$, N2 분위기에서 5분간 Mg 활성화를 위한 열처리를 반응로에서 in-situ로 진행하였다. 그 후 급속열처리 장비에 장입하여 $650^{\circ}C$, N2 분위기에서 5분간 추가적인 열처리를 진행하여 추가 열처리 유무에 따른 LED소자의 특성을 분석하였다. 추가적인 열처리 유무에 따른 LED소자의 레이저 여기에 의한 포토루미네선스 스펙트럼과 전계발광 스펙트럼을 조사한 바, 포토루미네선스 스펙트럼의 경우 추가적인 열처리를 진행하였을 경우, 이전보다 발광 세기가 감소함을 나타내었다. 이는 추가적인 열처리에 의해 InGaN/GaN 활성층이 손상되었기 때문이라고 추측된다. 그러나 전계발광 스펙트럼에서는 활성층이 손상되었음에도 불구하고 전계 발광세기가 3배 가량 증가한 것을 확인할 수 있었다. 또한, 20 mA 인가 시 4.2 V 에서 3.7 V로 전압이 감소하였다. 상기 결과로 미루어 볼 때 열처리에 의한 InGaN/GaN 활성층 손상에도 불구하고 광 세기가 크게 증가한 것은 금속유기화학증착장치의 in-situ 열처리에 의한 Mg가 충분히 활성화되지 못하였고, 추가적인 열처리에 의하여 p형 GaN에서 Mg-H 복합체의 분리로 인한 Mg 활성화가 더욱더 효과적으로 이루어졌기 때문이라고 추측된다.