• Bulletin of the Korean Chemical Society
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• 제22권1호
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• pp.63-67
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• 2001

The photophysical properties and the singlet oxygen generation efficiency of tetrathiarubyrin have been investigated to elucidate the possibility of its use as a photodynamic therapy (PDT) photosensitizer by steady-state and time-resolved spectroscopic methods. The observed photophysical properties were affected by various molecular aspects, such as extended ${\pi}conjugation$, structural distortion, and internal heavy atom. The steady-state electronic absorption spectrum was red-shifted due to the extended $\pi-conjugation$, and the spin orbital coupling was enhanced by the structural distortion and the internal heavy atom effect. As a result of the enhanced spin orbital coupling, the triplet quantum yield increased to 0.90 $\pm$ 0.10 and the triplet state lifetime was shortened to 7.0 $\pm$ 1.2 ${\mu}s$. Since the triplet state decays at a relatively faster rate, the efficiency of the oxygen quenching of the triplet state decreases. The singlet oxygen quantum yield was estimated to be 0.52 $\pm$ 0.02, which is somewhat lower than expected. On the other hand, the efficiency of singlet oxygen generation during the oxygen quenching of triplet state, $f{\Delta}^T$, is near unity. Such high efficiency of singlet oxygen generation can be explained by the following two possible factors: The hydrogen bonding of ethanol which impedes the deactivation pathway of the charge transfer complex with oxygen to the ground state, the less probability of the aggregation formation.

• Bulletin of the Korean Chemical Society
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• 제7권3호
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• pp.196-200
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• 1986

The solvent change and salt do not affect the fluorescence quantum yield of 1,3-dimethylnaphtho[1,2-e]uracil indicating the considerable energy gap between the lowest singlet $({\pi},\;{\pi}^{\ast})\;and\;(n,\;{\pi}^{\ast})$ states in the compound. The results are consistent with the strong quenching of fluorescence by ethyl iodide. Fluorescence quantum yield is nearly independent of temperature, probably due to the relatively inefficient internal conversion. Unusual spectral difference is observed in isopentane and ethanol at 77K. The temperature dependence of emission in isopentane and in ethanol suggests that the increase of charge transfer character by the conformational change in isopentane leads to the structureless and red-shifted fluorescence, while in ethanol the decrease of the charge transfer character by the hydrogen bonding interaction results in the structured and blue-shifted fluorescence along with phosphorescence at the low temperature. Temperature dependence of emission in poly(methylmethacrylate) matrix indicates that $T_1{\to}S_0$ radiationless decay is an important process responsible for the strong temperature dependence of phosphorescence.

• 한국초지조사료학회지
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• 제42권3호
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• pp.208-214
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• 2022

Drought stress is a condition that occurs frequently in the field, it reduces of the agricultural yield of field crops. The aim of the study was to screen drought-adapted genotype of Italian rye grass. The experiments were conducted between the two Italian ryegrass (Lolium multiflorum L.) cultivars viz. Hwasan (H) and Kowinearly (KE). The plants were exposed to drought for 14 days. The results suggest that the morphological traits and biomass yield of KE significantly affected by drought stress-induced oxidative stress as the hydrogen peroxide (H₂O₂) level was induced, while these parameters were unchanged or less affected in H. Furthermore, the cultivar H showed better adaptation by maintaining several physiological parameter including photosystem-II (Fv/Fm), water use efficiency (WUE) and relative water content (RWC%) level in response to drought stress. These results indicate that the cultivar H shows improved drought tolerance by generic variation, improving photosynthetic efficiency and reducing oxidative stress damages under drought stress. These findings can be useful to the breeder and farmer for improving drought tolerance in Italian rye grass through breeding programs.

• 한국환경농학회지
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• 제1권1호
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• pp.53-58
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• 1982

수도(水稻) 및 대두(大豆)를 pot재배(栽培)하여 가스접촉실내(接觸室內)에서 $Cl_2$가스 및 HCl가스를 0.1, 0.25, 0.50, $1.0g/m^3$의 농도(濃度)로 1시간(時間)씩 접촉(接觸)시켜 가스접촉후(接觸後)에 나타나는 피해증상(被害症狀), 피해엽률(被害葉率), 수풍(收豊) 및 chlorophyll함양등(含量等)을 조사(調査)한 결과(結果)는 다음과 같다. 1) 염소(鹽素)가스는 수도(水稻), 대두(大豆) 모두 엽전면(葉全面)에 회백색(灰白色)의 미세(微細)한 반점(斑點)이 나타나며 심(甚)할 경우(境遇)는 백색(白色)으로 고사(枯死)하나, 염화수소(鹽化水素)가스는 엽(葉)의 가장자리에서부터 회백색(灰白色)으로 고사(枯死)한다. 2) 가스농도(濃度) 증가(增加)에 따라서 감수(減收)가 컸으며 수도(水稻)는 염화수소(鹽化水素)가스에서 대두(大豆)는 염소(鹽素)가스에서 피해(被害)가 컸다. 3) 동일농도(同一濃度)에서의 피해엽률(被害葉率)은 염소(鹽素)가스에서는 대두(大豆)가, 염화수소(鹽化水素)가스에서는 수도(水稻)가 크게 나타났다. 4) 수도엽(水稻葉)의 chlorophyll함량(含量)은염소(鹽素)가스접촉(接觸)이 염화수소(鹽化水素)가스 접촉(接觸)보다 피해(被害)가 적었다. 5) 수도엽(水稻葉)의 chlorophyll함양(含量)과 피해엽률(被害葉率)과는 고도(高度)의 유의성(有意性)있는 부(否)의 상관(相關)을 나타내었다.

• 한국작물학회지
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• 제63권2호
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• pp.140-148
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• 2018

본 논문은 수수에 엽면처리된 과산화수소의 한발 스트레스 완화 효과가 있는지 알아보기 생리적 연구를 실시하였다. 수분 스트레스가 가장 심한 -0.15 MPa와 -0.20 MPa에서 과산화수소 처리에 의한 발아율 증가가 20%로 발아율의 차이가 가장 크게 조사되었다. 이는 과산화수소가 발아 과정에서 자극을 주어 대사 활성을 유도하여 수분스트레스가 심한 조건에서 일어나는 대사 저하가 완화되었기 때문으로 보인다. 1. 수분 스트레스 하에서 10 mM 과산화수소 처리는 무처리 보다 20% 높은 발아율을 보였고, 유아 유근의 신장을 촉진하였다. 2. 온실 pot 실험 결과 한발 하에서 과산화수소 처리는 형태적 형질(초장, 줄기 직경, 엽장, 엽수)과 생리적 형질(SPAD, 엽록소형광, 기공전도도) 모두 증가시켰다. 토양수분 구배장치를 이용한 실험 결과 역시 과산화수소 엽면처리가 광합성 능력(SPAD, 기공전도도)과 뿌리 발근(지하부 건물중, 뿌리길이)이 우수하여 생육, 건물 생산량이 무처리 보다 높았다. 결과적으로 과산화수소의 처리는 수수의 발아율 향상과 기공 폐쇄를 억제하여 광합성능력을 향상시켰다. 이를 통해 한발 스트레스 대한 내성을 높여 수수의 생육을 유지 및 회복시켜 주었다.

• 에너지공학
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• 제5권2호
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• pp.176-182
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• 1996

소형의 고온 고압 반응장치에서의 석탄액화시 흑액, 리그닌, NaOH, 물, 나무 등을 첨가제로 사용하여 375$^{\circ}C$ 근처에서의 액체생성물의 수율과 비점분포를 분석하였다. 흑액을 석탄액화 과정 중에 첨가하게 되면 석탄액화율이 38.6% 정도 증가하나, 액화율 상승효과의 대부분은 NaOH 때문인 것으로 판단되며, 흑액 중에 포함된 황화합물은 액화과정에서 수소와 결합함으로서 휘발성의 자극성 악취를 발생시키기 때문에 불리한 요인이 될 수 있다. 액화공정에 물이 존재하면 액화 수율에는 변화가 없었으나 액화생성물 중에는 저비점 성분이 증가되며, 가스 중에는 CO가 줄고, $CO_2$성분이 증가되었다. 나무를 석탄액화시 첨가하면 생성물 중 가스의 비율이 증가하고 액체생성물도 다소 증가하게 되는데, 석탄전환율로 보면 나무의 첨가효과는 거의 무시할 수 있는 값이며, 액체 생성물 수율만으로 보면 375$^{\circ}C$에서는 3%, 40$0^{\circ}C$에서는 약 8%정토의 액체생성물의 수율 증가를 보여주었으며, 4$25^{\circ}C$에서는 가스생성물의 증가로 액체생성물의 오히려 감소하였다.

• Fibers and Polymers
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• 제7권2호
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• pp.129-138
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• 2006

Using a strain-controlled rheometer, the steady shear flow properties of aqueous xanthan gum solutions of different concentrations were measured over a wide range of shear rates. In this article, both the shear rate and concentration dependencies of steady shear flow behavior are reported from the experimentally obtained data. The viscous behavior is quantitatively discussed using a well-known power law type flow equation with a special emphasis on its importance in industrial processing and actual usage. In addition, several inelastic-viscoplastic flow models including a yield stress parameter are employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models is also examined in detail. Finally, the elastic nature is explained with a brief comment on its practical significance. Main results obtained from this study can be summarized as follows: (1) Concentrated xanthan gum solutions exhibit a finite magnitude of yield stress. This may come from the fact that a large number of hydrogen bonds in the helix structure result in a stable configuration that can show a resistance to flow. (2) Concentrated xanthan gum solutions show a marked non-Newtonian shear-thinning behavior which is well described by a power law flow equation and may be interpreted in terms of the conformational status of the polymer molecules under the influence of shear flow. This rheological feature enhances sensory qualities in food, pharmaceutical, and cosmetic products and guarantees a high degree of mix ability, pumpability, and pourability during their processing and/or actual use. (3) The Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have equivalent ability to describe the steady shear flow behavior of concentrated xanthan gum solutions, whereas both the Bingham and Casson models do not give a good applicability. (4) Concentrated xanthan gum solutions exhibit a quite important elastic flow behavior which acts as a significant factor for many industrial applications such as food, pharmaceutical, and cosmetic manufacturing processes.

• 대한한의학방제학회지
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• 제22권2호
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• pp.15-24
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• 2014

Objectives : Gwakhyangjeonggi-san (GJS) which consists of 13 herbal medicines has been used to treat gastrointestinal disorders caused by common cold. This study was performed to compare GJS decoctions produced using different pressure levels for various extraction times. Methods : Decoctions were prepared by the pressure levels of $0kgf/cm^2$ (non-pressurized) or $1kgf/cm^2$ (pressurized) for 30-180 min. The extraction yield, total soluble solid content (TSSC), and hydrogen ion concentration (pH) were measured, and the contents of the nine marker compounds were determined using high performance liquid chromatography. Results : The higher pressure and longer extraction time significantly increased TSSC value, while decreased the pH value. However, only extraction time affected the extraction yield of pressurized decoction. Variation of the amounts of chemical compounds was shown in pressurized and non-pressurized decoctions during extraction time. The result of regression analysis showed that pressure and extraction time can influence to extraction yield, TSSC, pH, and the content of chemical compounds. Conclusions : This study suggests that the pressure and extraction time can significantly affect the extraction efficiency of components from GJS decoctions.

• 한국응용과학기술학회지
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• 제21권4호
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• pp.289-299
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• 2004

Multi-walled carbon nanotubes (CNTs) were prepared by microwave plasma chemical vapor deposition (MPCVD) using various combination of binary catalysts and methane precursor. The maximum yield (10.3 %) of CNTs was obtained using a methane-hydrogen-nitrogen mixture with volume ratio of 1:1:2 at 1000 W of microwave power. As the microwave power increased up to 1000 W, the deposition yield of CNTs raised from 4.1 % to 10. 3 %. However, the prepared CNTs at 800 W showed the more crystalline structure than those prepared at 1000 W. The prepared CNTs over different binary catalysts had various structural conformations such as aligned cylinder, bamboo, and nanofibers. The Id/Ig value of CNTs over$Fe-Fe/Al_2O_3, $Co-Co/Al_2O_3, and $Co-Cu/Al_2O_3 were in the range of 0.89${\sim}$0.93. Among the various binary catalysts used, $Fe-Co./Al_2O_3 showed the highest yield.

• Journal of the Korean Wood Science and Technology
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• 제41권6호
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• pp.497-506
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• 2013

유칼립투스(Eucalyptus globulus)의 반탄화 최적조건을 탐색하기 위하여 반응표면분석법을 이용하였다. 반탄화 바이오매스의 탄소함량은 반탄화 정도를 나타내는 severity factor (SF)에 따라 증가하였으며 바이오매스에 포함된 수소와 산소의 함량은 감소하였다. 반탄화 바이오매스의 발열량은 조건에 따라 20.23~21.29 MJ/kg을 나타냈으며 처리 전 바이오매스와 비교하여 1.6~6.9% 에너지함량이 증가한 것으로 나타났다. 바이오매스의 중량감소율은 SF 증가에 따라 증가하였다. 에너지수율에서 반탄화 온도는 중요한 인자로 작용하였으며 상대적으로 반응시간에 대한 영향은 낮았다. 최대 에너지수율은 낮은 SF에서 반탄화를 수행하였을 때 얻을 수 있었다.