• E2M - 전기 전자와 첨단 소재
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• 제9권7호
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• pp.719-726
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• 1996

DLTS measurements were performed to study the annealing induced changes of the trap centers in MOV and to shed more light on the stability mechanism of the MOV. Two electron traps, Ec-0.26[eV] and Ec-(O.2-0.3)[eV], were observed in the unannealed samples in large quantities(7-9 X 1014[CM 3]), whereas the three electron traps Ec-0.17 [eV], Ec-0.26[eV] and Ec-(O.2-0.3)[eV] were observed far less in the annealed samples. The minima in the Ec-0.26[eV] trap density, coupled with the presented results that unannealed devices are unstable whereas 600.deg. C annealed devices are most stable, suggests that the instability of the MOV under long term electrical stressing is related to the Ec-0.26[eV] trap. This results support that the ion migration model for the device instability where the Ec-0.26[eV] defects may be the interstitial zinc or the migrating ions. The interstitial zinc originated as a result of the nonstoichiometric nature of ZnO might cause the degradation of the I-V characteristics of the MOV with long term electrical stressing.

• 한국식품과학회지
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• 제43권6호
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• pp.754-759
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• 2011

본 연구는 세포의 사멸 및 성장변화 등의 평가에 널리 이용되는 MTT assay에서 생성된 formazan dye에 미치는 ZnPP의 영향을 조사하였다. ZnPP는 생체 내에 자연적으로 생성되거나 다양한 관련 실험에 인위적으로 첨가해주는 물질로서, MTT formazan dye의 빛에 의한 탈색을 가속화시키는 것으로 밝혀졌다. Formazan dye의 분해는 5와 $10{\mu}M$ ZnPP 존재 시 반감기를 기준하여 각각 10 및 20배 가량 가속화되었으며, 빛이 차단된 조건에서는 영향을 미치지 않았다. ZnPP 구조 중 Zn는 formazan dye의 탈색에 영향을 미치지 않았으나, porphyrin 구조와 공통적인 감광체 성질을 나타내는 MB에 의해서 ZnPP 존재 시와 유사하게 dye의 탈색을 가속화 시켰다. 이러한 ZnPP와 MB에 의한 formazan dye의 탈색반응은 NAC와 ${\beta}$-carotene에 의해 지연되었으나, BHT에 의한 저해효과는 나타나지 않았다. 본 결과는 세포 중에 존재하는 ZnPP 등의 감광체류가 MTT tetrazolium으로부터 환원된 formazan dye의 빛에 의한 신속한 분해를 유도하며, 관련 실험에서 빛의 차단 등의 조치와 함께 각별히 유의해야함을 시사한다.

• 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.

• 한국재료학회지
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• 제32권1호
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• pp.14-22
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• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• Current Photovoltaic Research
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• 제2권3호
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• pp.95-102
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• 2014

Light trapping techniques can change the propagation direction of incident light and keep the light longer in the absorption layers of solar cells to enhance the power conversion efficiency. In thin film silicon (Si) solar cells, the thickness of absorption layer is generally not enough to absorb entire available photons because of short carrier life time, and light induced degradation effect, which can be compensated by the light trapping techniques. These techniques have been adopted as textured transparent conduction oxide (TCO) layers randomly or periodically textured, intermediate reflection layers of tandem and triple junction, and glass substrates etched by various patterning methods. We reviewed the light trapping techniques for thin film Si solar cells and mainly focused on the commercially available techniques applicable to textured TCO on patterned glass substrates. We described the characterization methods representing the light trapping effects, texturing of TCO and showed the results of multi-scale textured TCO on etched glass substrates. These methods can be used tandem and triple thin film Si solar cells to enhance photo-current and power conversion efficiency of long term stability.

• 마이크로전자및패키징학회지
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• 제17권4호
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• pp.19-26
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• 2010

포화 수증기압이 고출력 형광체 변환 백색 LED 패키지의 열화현상에 미치는 주요 스트레스 인자임을 확인하였다. 또한 LED 패키지의 가속 수명시험을 통하여 포화 수증기압이 효과적인 가속 스트레스 인자임을 확인하였다. 실험조건은 350 mA 전류를 인가한 것과 인가하지 않은 2가지 조건에 대해 $121^{\circ}C$, 100% R.H. 환경에서 최대 168 시간동안 진행하였다. 실험결과 두 실험 모두 광 출력 감소, 스펙트럼 세기의 감소, 누설전류 및 열 저항이 증가하였다. 고장분석 결과 광 특성의 열화는 봉지재의 변색과 기포에 의해 발생한 것으로 나타났다. LED 패키지의 변색과 흡습에 의해 유발되는 기계적 (hygro-mechanical) 스트레스에 의한 기포 발생은 패키지 열화의 중요한 인자로써, 포화 수증기압이 고출력 LED의 수명시험 시간을 단축하기 위한 스트레스 인자로 적합함을 알 수 있었다.

• Journal of the Korean Wood Science and Technology
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• 제25권3호
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• pp.83-95
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• 1997

The degradation mode of lignocellulose by anaerobic ruminal cellulolytic bacterium Ruminococcus albus F-40 was investigated. Birchwood holocellulose and filter paper were incubated as the sole carbohydrate sources with using the Hungate techniques. After 2 or 4 days of incubation, samples were employed for chemical and electron microscopic evaluations. The degradation rate of cellulosic substrates and the adhesion rate of bacteria to the substrates increased proportionally with the decrease of relative crystallinity of cellulose, indicating the preferential breakdown of amorphous cellulose, by this bacterium. X-ray diffraction analyses and polarized light microscopy showed, however, that crystalline cellulose was also degraded by R. albus. FT-IR spectra indicated that not only cellulose but hemicellulose was also degraded by this bacterium. Electron microscopic investigations showed the protuberant structures on the surface of R. albus. These structures were much more significant when bacterial cells were grown in the media containing insoluble substrates, such as cellulose, indicating clearly that bacterial protuberant structures were induced by the substrates. Protuberant structures extended from the bacterial cells adhered tightly to the substrates and numerous vesicles covered the surface of cellulosic substrates affected. Cellulosome-like structures were distributed on the cellulose matrix. Electron microscopic works showed that diverse surface organells of R. albus were involved in the degradation of cellulosic materials. SEM examinations showed the breakdown of cellulose by R. albus was proceeded by severeal routes : short fiber formation, defibrillation and destrafication of cellulose microfibril.

• 한국미생물·생명공학회지
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• 제36권3호
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• pp.209-214
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• 2008

VBNC(Viable but nonculturable)란 생존에 불리한 환경하에서 살아 있으나 일반 영양배지에서 자라지 못하는 미생물의 상태를 나타낸다. 본 연구는 구리를 이용해 Escherichia coli에서 VBNC를 유도하고 이의 특성을 살펴보았다. 구리를 처리한 후 전통적인 평판 배양법에 의한 집락 형성계수(colony forming unit, CFU)를 측정한 결과 배양되지는 않으나, Live/Dead BacLight bacterial viability kit 염색 후 유세포계수기로 측정한 결과 살아있는 미생물로 계수되어 VBNC 상태가 확인하였다. VBNC 유도된 미생물로부터 genomic DNA와 RNA를 분리하고 이들의 안정성을 관찰하였는데 DNA에 비해 RNA의 붕괴가 많이 진행되었음을 확인할 수 있었고 RNA의 붕괴는 특정크기로 붕괴되는 것으로 관찰되었다. 또한 생물전용 투과전자현미경(Bio-Transmission Electron Microscope, Bio-TEM)을 통해 VBNC 세포의 형태를 관찰하였는데 VBNC 상태에서는 정상상태에 비해 periplasmic space가 온전하지 못하고 세포내막과 세포 외막이 분리되었으며 세포질의 양이 현저히 감소됨이 관찰되었다.

• 한국자원식물학회지
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• 제28권6호
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• pp.727-733
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• 2015

Although Sophorae Flos (SF) has been reported to exert an anti-cancer activity, molecular targets and mechanisms associated with anti-cancer activity of SF have been unclear. Because cyclin D1 has been regarded as an important regulator in the cell proliferation, we focused cyclin D1 and investigated the effect of SF on the cyclin D1 regulation in light of elucidating the molecular mechanism for SF’s anti-cancer activity. The treatment of SF decreased cellular accumulation of cyclin D1 protein. However, SF did not change the level of cyclin D1 mRNA. Inhibition of proteasomal degradation by MG132 attenuated SF-mediated cyclin D1 downregulation and the half-life of cyclin D1 was decreased in the cells treated with SF. In addition, a point mutation of threonine-286 to alanine attenuated SF-mediated cyclin D1 downregulation. Inhibition of ERK1/2 by a selective inhibitor, PD98059 suppressed cyclin D1 downregulation by SF. From these results, we suggest that SF-mediated cyclin D1 downregulation may result from proteasomal degradation through its threonine-286 phosphorylation via ERK1/2. SF-induced proteasomal degradation of cyclin D1 might inhibit proliferation in human colorectal cancer cells. The current study provides information on molecular events for an anti-cancer activity of SF

• 한국결정성장학회지
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• 제33권4호
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• pp.132-138
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• 2023

Doped and undoped-BiVO₄ samples with different elements (Li, Mg) and amounts were synthesized with a hydrothermal method. The synthesized samples were characterized using various techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffusion reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity of the samples was evaluated by measuring the degradation of methyl blue (MB) under visible light irradiation. The results indicated that the incorporation of Mg and Li into BiVO₄ caused lattice distortion, the presence of surface hydroxyl groups, a narrower band gap, and a reduced recombination ratio of photo-induced electron-hole pairs. Notably, the photocatalytic activity of Mg5%-Li5% co-doped BiVO₄ sample exhibited a significant improvement compared to that of undoped BiVO₄ sample.