• Biotechnology and Bioprocess Engineering:BBE
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• 제11권5호
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• pp.396-401
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• 2006

The objective of this study was to investigate the antitumor activity of suspension cultures of tea callus cells grown in the presence of different concentrations of the growth regulator 2,4-dichlorophenoxy acetic acid (2,4-D) with or without light irradiation. The methanol and ethanol extracts of precipitated cells (MEP, EEP) exhibited stronger inhibitory effects on the growth of tumor cell lines than the water extract of precipitated cells (WEP) or the supernatant Compared to culture under dark conditions, exposure to light irradiation led to significantly higher antitumor activity. The MEP from light irradiated cells at $250{\mu}g/mL$ with 2.0mg/L 2,4-D displayed more than 64% growth inhibition of HEP-2 cells, whereas normal cells showed less than 25% growth inhibition. The some fractions of MEP obtained from Diaion HP-20 column chromatography displayed the majority of inhibitory activity against the HEP-2 cell line. These results show that 2,4-D, and light stimulated the synthesis of antitumor compounds.

• 한국세라믹학회지
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• 제55권1호
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• pp.55-60
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• 2018

In this study, quantum dots composed of $Mn^{2+}$ doped ZnS core and ZnS shell were synthesized using MPA precursor at room temperature. The ZnS: Mn/ZnS quantum dots were prepared by varying the content of MPA in the synthesis of ZnS shells. XRD, Photo-Luminescence (PL), XPS and TEM were used to characterize the properties of the ZnS: Mn/ZnS quantum dots. As a result of PL measurement using UV excitation light at 365 nm, the PL intensity was found to greatly increase when MPA was added at 15 ml, compared to the case with no MPA; the PL peaks shifted from 603 nm to 598 nm. A UV sensor was fabricated by using a sputtering process to form a Pt pattern and placing a QD on the Pt pattern. To verify the characteristics of the sensor, we measured the electrical properties via irradiation with UV, Red, Green, and Blue light. As a result, there were no reactions for the R, G, and B light, but an energy of 3.39 eV was produced with UV light irradiation. For the sensor using ZnS: Mn/ZnS quantum dots, the maximum current (A) value decreased from $4.00{\times}10^{-11}$ A to $2.62{\times}10^{-12}$ A with increasing of the MPA content. As the MPA content increases, the PL intensity improves but the electrical current value dropped because of the electron confinement effect of the core-shell.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2849-2853
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• 2010

A method to improve the photocatalytic activity of titanium dioxide by modification with a sensitizer and a metal oxide is proposed. To achieve this goal, we used metal oxides as dopants. In particular, $CaWO_4$ and $Gd_2O_2S$:Tb were used because their 2.6 eV and 2.2 eV band gap energy and optical properties have a large positive effect on photocatalysis. The improvement in the photocatalytic activity of $TiO_2$ modified with $Gd_2O_2S$:Tb under ultraviolet light irradiation is described in a previous study. The present work focuses on the sensitization of metal oxide-modified $TiO_2$. Having observed the ultraviolet-visible absorption spectra of 3,4,9,10-Perylenetetracarboxylic diimide in the wide visible-light region from 400 nm to 650 nm and the broad peaks in its photoluminescence spectra at 695 nm and 717 nm, we decided to use this perylene dye to sensitize modified $TiO_2$ to enhance its activity as a visible-light harvesting photocatalyst. We also explored the positive effects thin-film surface changes stemming from ultraviolet pre-treatment have on photocatalytic activity. Finally, we subjected several metal oxide-modified $TiO_2$ products sensitized by the perylene dye to ultraviolet pre-treatment, obtaining the most active photocatalysts.

• 한국인쇄학회지
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• 제18권2호
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• pp.41-54
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• 2000

가시광을 선택적으로 반사하는 광 응답성 코레스테릭 액정을 조제하고, 그 선택적 반사파장의 광화학적 변조를 시도함으로서 포토닉스(Photonices) 재료로서의 가능성을 검토했다. 고유의 선택 반사파장의 변조는 아조벤젠 유도체의 트란스(trans)·시스(cis)간의 광이성화에 의해 상전이 온도와 칼라의 변화와 함께 가역적으로 제어되어질 수 있었다. 또한 선택 반사파장의 변화에 수반되는 반사율의 변화는 코레스테릭 액정과 검출광의 광학적 성질에 의해 크게 좌우되어 지고, 반사율의 가역적인 스위칭에 있어서는 검출광에 대한 코레스테릭 액정의 초기 반사파장의 위치는 상반된 스위칭 모드(normal and reverse modes)를 산출하기에 매우 중요한 역할을 담당했다.

• Environmental Engineering Research
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• 제17권4호
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• pp.179-184
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• 2012

The light absorbance of photocatalysts and reaction kinetics of environmental pollutants at the liquid-solid and gas-solid interfaces differ from each other. Nevertheless, many previous photocatalytic studies have applied the science to aqueopus applications without due consideration of the environment. As such, this work reports the surface and morphological characteristics and photocatalytic activities of carbon-embedded (C-$TiO_2$) photocatalysts for control of gas-phase methyl tertiary-butyl ether (MTBE) under a range of different operational conditions. The C-$TiO_2$ photocatalysts were prepared by oxidizing titanium carbide powders at $350^{\circ}C$. The characteristics of the C-$TiO_2$ photocatalysts, along with pure TiC and the reference pure $TiO_2$, were then determined by X-ray diffraction, scanning emission microscope, diffuse reflectance ultraviolet-visible-near infrared (UV-VIS-NIR), and Fourier transform infrared spectroscopy. The C-$TiO_2$ powders showed a clear shift in the absorbance spectrum towards the visible region, which indicated that the C-$TiO_2$ photocatalyst could be activated effectively by visible-light irradiation. The MTBE decomposition efficiency depended on operational parameters, including the air flow rate (AFR), input concentration (IC), and relative humidity (RH). As the AFRs decreased from 1.5 to 0.1 L/min, the average efficiencies for MTBE increased from 11% to 77%. The average decomposition efficiencies for the ICs of 0.1, 0.5, 1.0, and 2.0 ppm were 77%, 77%, 54%, and 38%, respectively. In addition, the decomposition efficiencies for RHs of 20%, 45%, 70%, and 95% were 92%, 76%, 50%, and 32%, respectively. These findings indicate that the prepared photocatalysts could be effectively applied to control airborne MTBE if their operational conditions were optimized.

• 한국환경과학회지
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• 제28권11호
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• pp.971-981
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• 2019

This study evaluated the photocatalytic oxidation efficiency of volatile organic compounds by $Cu_2O-TiO_2$ under visible-light irradiation. $Cu_2O-TiO_2$ was synthesized by an ultrasonic-assisted method. The XRD result indicated successful p-n type photocatalysts. However, no diffraction peaks belonging to $TiO_2$ were observed for the $Cu_2O-TiO_2$. The Uv-vis spectra result revealed that the synthesized $Cu_2O-TiO_2$ can be activated under visible-light irradiation. The FE-TEM/EDS result showed the formation of synthesized nanocomposites in the commercial P25 $TiO_2$, the undoped $TiO_2$, and $Cu_2O-TiO_2$ and componential analysis in the undoped $TiO_2$ and $Cu_2O-TiO_2$. The photocatalytic oxidation efficiencies of benzene, toluene, ethylbenzene, and o-xylene with $Cu_2O-TiO_2$ were higher than those of P25 $TiO_2$ and undoped $TiO_2$. These results indicate that the prepared $Cu_2O-TiO_2$ photocatalyst can be applied effectively to control gaseous BTEX.

• 치과방사선
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• 제16권1호
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• pp.49-58
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• 1986

This study was designed to investigate the irradiation effects on the rat parotid gland, applied to the head and neck region. For this experiment, twenty-four rats, feeded under the even condition, were used as experimental animals. Twenty rats were used for experimental group and the rest were assigned to the control group. The experimental group was singly irradiated with 10Gray through Cobalt-60 radiotherapy device, Picker model 4M 60 (Field size; l2×5㎝, SSD; 50㎝, Depth; 1㎝). The experimental animals of both group were sacrificed each four animals in 2 days, 1week, 2weeks, 3weeks and 4weeks after irradiation. The specimens were examined through the light microscope using the H-E stain and H stain by routin procedure. The other specimens were observed under the fluorescence microscope using the B-O dichroic mirror and Y455 barrier filter after PA-ACH stain. 1. The results of this study were obtained as follows, The parotid acini were severely degenerated and the intraacinar spaces were widened. Within the acini, retained secretory granules and increased fibrosis were observed. Also the shape and the size of the acini showed very irregular atrophic degenerations. 2. The nuclei showed severe pyknosis, displacement and irregular aggregated appearance. 3. The tissue changes of the parotid acini were initiated after 2 days of irradiation and most severely appeared at the second week of irradiation, but almost returned to normal. 4. The salivary ducts of the parotid gland were severely atrophied, discontinued but initiated to regenerated after 3 weeks of irradiation.

• 한국식품저장유통학회지
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• 제17권3호
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• pp.425-429
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• 2010

햄버거 패티에 L. monocytogenes cocktail을 인위적으로 접종한 후 UV-C 조사 처리에 따른 저장 중 미생물 수 변화를 조사하였다. 햄버거 패티에 접종된 L. monocytogenes의 초기 균수가 6-7 log CFU/mL가 되게 하였고, 사용된 UV-C 조사선량은 1, 5, 10 kJ/$m^2$이었으며 조사된 시료는 $4{\pm}1^{\circ}C$에서 7일 동안 저장하였다. UV-C 조사는 L. monocytogenes 수에 있어서 조사선량이 증가할수록 유의적으로(p<0.05) 감소하는 것을 나타냈다. 특히, 10 kJ/$m^2$ 처리구는 대조구와 비교하여 L. monocytogenes 수를 2.03 log CFU/g까지 감소시켰다. 햄버거 패티의 UV-C 처리에 의한 품질 변화 척도로써 측정한 TBARS 값은 저장 중 UV-C 처리 여부와 관계없이 증가하였다. 따라서 본 연구결과, UV-C 조사 처리는 햄버거 패티의 저장 중 품질 변화에 큰 영향을 주지 않으면서 미생물학적 안전성 확보에 효과적인 것으로 판단된다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제33권1호
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• pp.1-10
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• 2007

To verify the inhibitory or protective effects of light-emitting diode(LED) irradiation on apoptotic cell death induced by $CoCl_2$, human SH-SY5Y cells were treated with $CoCl_2$ and LED were used to irradiate the cells. In the cell viability assay, cells were died slowly from $50{\mu}M$ to $250{\mu}M$ and about 50% of cells died after 12 hours at $400{\mu}M$ of $CoCl_2$. The Diff-Quik staining revealed that cells showed condensation of DNA and blebbing of the cell membrane. The DNA fragmentation assay revealed the DNA fragmentation, which is another apoptosis marker, occurred in cells treated with $400{\mu}M$ $CoCl_2$ for 16 hours. In the western blot for HIF-$1{\alpha}$, HIF-$1{\alpha}$ was expressed after 3 hours from induction and peaked maximally at 16 hours. In the cell viability assay of the effects of LED irradiation (at 590 nm for 1 hour 20 minutes), the cells showed more proliferation (about 20%) than the control group. The RPA assay of various apoptosis-related molecules showed that pro-apoptosis molecules such as Bax, Bak, and Bid were upregulated in the $CoCl_2$ treatment group. This means that the apoptotic cell population was increased. However there was some significant changes in LED irradiated cells. In the $CoCl_2$-treated LED irradiation group, those molecules were down-regulated more than in the only $CoCl_2$-treated group. These results have shown that $CoCl_2$ may induce apoptotic cell death in human SH-SY5Y neuroblastoma cells. And LED irradiation has a positive effect on apoptotic cells by down-regulation of pro-apoptotic molecules.

• Journal of Ginseng Research
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• 제30권4호
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• pp.188-193
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• 2006

We induced the activation of melanocytes in the epidermis of C57BL/6 mice by ultraviolet B (UVB) irradiation and observed the effect of red ginseng (RG) on the formation, and decrease of UVB-induced epidermal mel-anocytes. C57BL/6 mice were irradiated by UVB $80mJ/cm^2$ (0.5 mW/sec) daily for 7 days, and RG was intraperitoneally or topically applied pre- or post-irradiation. For the estimation of change of epidermal melanocytes, light microscopic observation with dihydroxyphenylalanine (DOPA) stain was performed. Split epidermal sheets prepared from the ear of untreated mice exhibited 11-16 $melanocytes/mm^2$, and one week after UV irradiation, the applied areas show an increased number of strongly DOPA-positive melanocytes with stout dendrites. But intraperitoneal or topical treatment with RG before each irradiation interrupted UVB-induced pigmentation and resulted in a marked reduction in the number of epidermal melanocytes as compared to radiation control skin. The number and size of DOPA-positive epidermal mel-anocytes were also significantly decreased in intraperitoneally injected or topically applicated group after irradiation with RG at 3rd and 6th weeks after irradiation. The present study suggests the RG as inhibitor of UVB-induced pigmentation and depigmenting agent.