• 폴리머
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• 제26권2호
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• pp.209-217
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• 2002

편광 푸리에 변환 적외선 분광법과 자외선 분광법을 이용하여 액정 display (LCD)의 배향막으로 널리 사용되는 폴리이미드 (PI) 필름의 편광 자외선 (PUV) 조사에 따른 액정의 배향 메카니즘을 연구하였다. UV 측정 결과, PI 필름은 360 nm 이하 파장의 자외선을 주로 흡수하여 광화학 반응이 유도됨을 알 수 있었다. 또한, PUV가 조사된 PI의 경우, PI 분자들의 분해로 인해 FT-IR 흡수 피크들의 강도가 조사시간에 따라 감소하였고, $3244 cm^{-1}$ 부근에서 완만한 곡선 형태의 새로운 피크가 형성되었다. 또한 조사된 PUV의 극성 방향에 평행한 PI 분자들의 우선적인 광분해 반응으로 인하여 PUV 조사 후 남아 있는 PI 분자들은 조사된 PUV 극성 방향과 수직 배향을 나타내었다. 하지만 러빙 처리된 PI 필름은 러빙 방향과 평행하게 PI 분자들의 재배향이 유도됨을 확인하였다. 또한 러빙 처리 및 PUV가 조사된 PI 배향막을 차용하여 제조된 액정 셀에서는 액정이 러빙 방향에 대해서는 평행하게, 조사된 PUV의 극성방향과는 수직으로 배향함을 확인하였다.

• Journal of Korean Society for Atmospheric Environment
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• 제22권E1호
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• pp.19-26
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• 2006

The decomposition of gaseous $CH_3CHO$ was investigated by metal loaded $TiO_2$ (pure $TiO_2,\;Pt/TiO_2,\;Pd/TiO_2,\;Mn/TiO_2\;and\;Ag/TiO_2$) with $UV/TiO_2$ process and $UV/TiO_2/O_3$ process at room temperature and atmospheric pressure. Metal loaded $TiO_2$ was prepared by photodeposition. Decomposition of $CH_3CHO$ was carried out in a flow-type photochemical reaction system using three 10W black light lamps ($300{\sim}400nm$) as a light source. The experimental results showed that the degradation rate of $CH_3CHO$ was increased with Pt and Ag on $TiO_2$ compared to pure $TiO_2$, but decreased with depositing Pd and Mn on pure $TiO_2$. The considerable increase in the degradation efficiency of the $CH_3CHO$ was found by a combination of photocatalysis and ozonation as compared to only by ozonation or photocatalysis. Loading of Pt on $TiO_2$ promoted conversion of gaseous ozone. The degradation rate of gaseous $CH_3CHO$ decreased with an increase of water vapor in the feed stream for the both $UV/TiO_2\;and\;UV/TiO_2/O_3$ processes. The pure $TiO_2$ was more affected by the water vapor than Pt loaded $TiO_2$.

• 생물환경조절학회지
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• 제20권4호
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• pp.311-319
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• 2011

본 연구는 칼륨의 독성에 따른 배추의 생육과 생리적 특성 그리고 형태적 변화를 관찰하기 위하여 수행하였다. 100mM의 칼륨 농도 처리구까지 전체적인 생육이 증가한 반면, 600mM 처리구에서 생육이 가장 저조하였다. 칼륨 처리 농도가 높을수록 N, P, K, 함량은 증가하였지만 Ca, Mg, Na 함량은 감소하는 경향을 보였으며 미량원소, Fe, Mn, Zn의 경우 100mM의 처리구에서 가장 높은 함량을 나타내었다. 생체중당 Chl a, b와 carotenoid 함량은 600mM에서 가장 많이 증가하였으나 증가한 엽록소 함량에 비해 광합성효율($F_v/F_m$)은 처리구간에 차이가 없었고 $CO_2$ 동화율은 오히려 감소하였다. 이는 칼륨 과다에 의한 삼투스트레스의 결과로 기공의 퇴화와 $CO_2$ 동화능력과 밀접한 관계가 있는 것을 형태학적 관찰로 확인되었다. Total free amino acid의 경우 100mM 처리구까지 칼륨 처리 농도가 증가함에 따라 증가한 반면 600mM에서 급격히 감소하였다. 따라서 본 실험에서의 배추는100mM의 칼륨 농도까지는 긍정적인 효과가 있는 것으로 판단되었다.

• 한국환경보건학회지
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• 제40권2호
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• pp.147-156
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• 2014

Objectives: This study was carried out to examine whether the apparent photolysis with or without sensitizers [NaOH and humic acid (HA)] was prompted photodegradation of polychlorinated biphenyl (PCB) in aqueous solution. Methods: PCBs photodegradation occurred using fluorescence black lamps at ${\lambda}_{max}=300nm$. PCB congeners were exposed in 10 ppm HA or 0.05N NaOH solutions, to investigate the decreasing profile of PCB concentration with time. The PCBs were then analyzed by gas chromatography/mass spectrometry (GC-MS). Reductive degradation profile of PCB congeners in the presence of both sensitizers under oxygen-saturated protic conditions was described using the wind-rose diagrams. Results: Use of HA or NaOH decreased PCB concentration with time in the dark and on irradiation, indicating that photolysis underwent through reductive dechlorination through energy transfer and possibly with reactive oxygens. The dechlorination was marked by a chromatographic shift, observed in the GC-MS plots. Therefore it is logical to assume that increasing the dose of sensitizers would increase the photodegradation rates of PCBs. The half-lives of pentachloro-PCB (penta-3) in 0.05N NaOH and 10 ppm HA were estimated at about 47 hours and 39 hours, respectively, under the same experimental conditions of photolysis. It was found that the rate of photolysis of pentachloro-PCB in aqueous solution followed apparent first-order kinetics compared to other congeners. Conclusion: Photochemical degradation (using 328 nm UV light) of penta- and hexa-PCBs in HA or alkaline solution is a viable method for pretreatment method. The results are helpful for the further comprehension of the reaction mechanism for photolytic dechlorination of PCBs in aquatic system.

• BMB Reports
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• 제33권3호
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• pp.256-262
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• 2000

In this study the disassembly process of chlorophyII (ChI)protein complexes of a stay-green mutant (ore10 of Arabidopsis thaliana) was investigated during the dark incubation of detached leaves. During this dark-induced senescence (DIS), the Chi loss was delayed in the mutant, while the photochemical efficiency of photosystem II (PSII) or Fv/Fm was accelerated when compared with the wild type (WT) leaves. This indicates that the decrease in Fv/Fm is a separate process and not causally-linked to the degradation of Chi during DIS of Arabidopsis leaves. In the native green gel electrophoresis of the Chi-protein complexes, which was combined with an additional twodimensional SDS-PAGE analysis, the delayed senescence of this mutant was characterized by the appearance of an aggregate at 1 d or 2 d, as well as very stable light harvesting complex II (LHCII) trimers until 5 d after the start of DIS. The polypeptide composition of the aggregates varied during the whole DIS at 5 d. Dl protein appeared to be missing in the aggregates. This result supports the idea of a faster depletion of functional PSH in the mutants compared with WT, as suggested by the earlier reduction of Fv/Fm and the stable Chl a/b ratio in the mutants. At 5 d, the WT leaves also often showed aggregates, but the polypeptide composition was different from those of ore10. The results presented suggest that the formation of aggregates, or stable LHCII trimers in the stay-green mutants, is a way to structurally protect Chi-protein complexes from serious proteolytic degradation. Detailed disassembly processes of Chi-protein complexes in WT and ore10 mutants are discussed.

• 청정기술
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• 제12권4호
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• pp.244-249
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• 2006

지하수 오염의 주요원인 중 하나인 TCE를 태양광과 $TiO_2$ 광촉매를 사용하여 광분해할 때 주요변수인 오염물의 초기농도, $TiO_2$ 주입량, pH, 산화제로서 persulphate($S_2O{_8}^-$) 및 $H_2O_2$가 광촉매 반응에 미치는 영향을 파악코자 하였다. 분석 결과 $TiO_2$ 주입량, pH 및 산화제를 증가시킬수록 TCE의 분해효율이 향상되었으나, TCE의 초기주입농도를 증가시킨 경우에는 분해효율이 감소되었다. 첨가제의 종류에 따른 영향을 살펴본 결과 $H_2O_2$를 사용한 경우가 persulphate를 사용한 경우보다 더욱 효과적인 것으로 나타났다. 또한 상대독성에 대한 분석결과 $solar/TiO_2/H_2O_2$ 공정이 가장 효과적인 것으로 나타났으며 반응시간 150분에서 $solar/TiO_2/persulphate$ 공정보다 약 15%, $solar/TiO_2$ 공정보다 약 35% 낮게 나타났다.

• Journal of Photoscience
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• 제3권2호
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• pp.91-93
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• 1996

In connection with our interest on the photochemical properties of heteroaryl halides, which are currently the subject of heterocyclic ring formation and haloarene degradation, we have studied the photochemistry of the haloarene linked to N-heteroarene compounds. Imidazo[5,1-a]isoindole was synthesized from N-(ochlorobenzyl)imidazole or N-(o-bromobenzyl) imidazole in acidic aqueous solution or acetonitrile via the intramolgcular photocyclization (Table 1). This type of reaction provides the synthetic methods for 5- and 6-membered polyheteroatomic heterocyclic ring compounds. However, the reaction mechanism for the intramolecular photocyclization of haloarene tethered heteroarenes has not yet been established. Grimshaw et al. suggested a mechanism for homolyric carbonhalogen bond fission assisted by radical complexation to explain their results in the photocyclization of 5-(2-chlorophenyl)-1,3-diphenylpyrazole. They also reported the detection of acyclohexadienyl intermediate involved in the above reaction. Park et al. reported several transient 'intermediates involved in the laser flash photolysis of N-(o-halobenzyl) pyridinium and N-benzyl-2-halopyridinium salts. Thus we performed the laser flash photolysis study on the photocyclization reaction of N-(o-chlorobenzyl) imidazole to identify the intermediate species involved in the reaction. Here, we report on the preliminary results in the photocyclization reaction of N-(o-halobenzyl)imidazole through the detection of reaction intermediates.

• 폴리머
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• 제28권6호
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• pp.545-550
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• 2004

광조사에 의하여 발색단 분해를 유도함으로써 고분자의 굴절률을 변화시켜 공중합체 박막의 굴절률을 조절하고, FTIR과 UV/Vis 분광 실험으로 굴절률에 영향을 미치는 구조의 변화를 조사하였다. 광표백에 따라 공중합체 박막의 굴절률이 작아지는 것은 광반응에 의하여 발색단 내 C=C 이중결합이 끊어져 고분자의 편극률이 작아지기 때문이다. 입사되는 빛의 전기장 방향에 의존하는 선택적인 광반응에 의하여 필름 면에 평행한 방향으로 존재하는 발색단이 먼저 분해가 되면서 고분자 필름 면에 평행한 방향의 굴절률이 수직한 방향에서 보다 더 급격하게 감소하였다. 이와 같은 고분자 박막 내의 굴절률 차이를 편광 ATR-FTIR 실험에서 얻어지는 고분자 특성 피크의 변화를 조사하여 증명하였다.

• 한국지역사회생활과학회지
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• 제23권2호
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• pp.129-136
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• 2012

Dioxins are chemical substances that are not properly decomposed degradation under natural photochemical, biological and chemical conditions in the environment, and bio-accumulate through the food chain, so pose a risk of causing adverse effects to human health and the environment. Ninety seven percent of human exposure to dioxins comes through meat, fish, dairy consumption and so on. Pork is the largest proportion meat aspect of daily intake in the Korean food. Pigs are three times more than Cattle in terms of breeding population and production amount in the world, and the amount is increasing every year. Therefore, it is necessary to monitor the exposure level of dioxins in pig's body. Also, it is required to evaluate the presence of these chemical substances in the pig's feed grain such as corn, soybeans, and tallow. The purpose of this study was to evaluate PCDD/Fs in pig's feed to search the origin of PCDD/Fs. Feed samples obtained were wheat from East Europe, corn from South America and America, soybean meal from Korea, America, South America and India and tallow from Korea. The preparation of samples was based on the EPA method 1613. Instrumental analysis was based on the use of high resolution gas chromatography coupled to high resolution mass spectrometry (HRGC/HRMS). The concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD), which are the most toxic potent dioxins, were not observed in any of the samples. However OCDD was detected in most of the samples. The TEQs in the feed samples were ranged from 0 pg TEQ/g to 0.09841 pg TEQ/g. Especially, the high level of TEQs was observed in the samples of wheat from East Europe and soybean meal from Korea.

• 대한환경공학회지
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• 제28권4호
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• pp.429-437
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• 2006

화학세정폐수에 함유되어 있는 citric acid의 효율적인 처리방안을 수립하기 위해 $UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton 산화방법을 이용하여 각각 citric acid의 제거효율 및 그에 따른 전력소비량을 평가하였다. 그 결과 조사된 최적 처리조건에서 $UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton 산화방법을 이용한 citric acid 농도에 근거한 TOC 제거효율은 각각 95.5%, 92.3%, 91.5%로 조사되었으며, 그에 따른 전력소비량은 $11.26kWh/m^3,\;3.85kWh/m^3,\;0.799kWh/m^3$으로 조사되었다. 이 결과에 의하면 세가지 광화학적 산화방법 모두 유기물질이 90% 이상 제거되어 citric acid의 분해에 효과적인 것으로 판단되었다. 그러나 Photo-Fenton 산화방법이 다른 방법에 비해 처리에 소요되는 반응시간이 짧은 것으로 나타났다. 또한 광화학적 산화방법의 운영비를 결정짓는데 중요한 요소인 전력소모량 측면에서도 Photo-Fenton 산화방법이 다른 방법에 비해 우수한 것으로 조사되어 본 연구에서 비교하는 세가지 방법 중 citric acid 처리에는 Photo-Fenton 방법이 효율적인면과 경제성면에서 가장 적합한 처리기술로 결론지을 수 있었다.