• Korean Journal of Clinical Laboratory Science
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• v.47 no.4
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• pp.273-278
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• 2015

The purpose of this study was to evaluate the in-vitro efficacy of PDT using red light emitting diode (LED) with Radachlorin for biofilm inhibition of clinical Candida albicans isolates. The suspensions containing C. albicans at $9{\times}10^8CFU/mL$ were prepared on yeast nitrogen base containing 5% glucose. The biofilm formation was grown for 3 h after seeding suspensions each 100 ul on a 96-well plate and then supernatant was discarded. Each well was treated with $0.39{\mu}g/mL$ from $50{\mu}g/mL$ concentrations of Radachlorin on adherent biofilm. After a 30-minute incubation, light was irradiated for 30, 60, or 90 minutes using the following light source of wavelength 630 nm LED, at energy densities of 14, 29, and $43J/cm^2$. Afterwards, all supernatant was removed and dried. Adherent cells were stained with safranin O and dried. The cell viability was measured using a microplate reader at 490 nm. Also, a fluorescent signal on C. albicans was observed by saturation of a photosensitizer. In conclusion, a significant inhibition of 72.5% was observed to C. albicans on biofilm at the Radachlorin dose of $50{\mu}g/mL$ with 630 nm LED. The Photosensitizer (Radachlorin) was adequate at 30 minuttes for C. albicans. Overall, the results showed that inhibition of biofilm formation was Radachlorine dose-dependent. The results suggest that PDT, using Radachlorin with 630 nm LED, is able to decrease biofilm formation of C. albicans.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.163-171
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• 2021

Conventional white light-emitting diodes (LEDs) for lighting applications consist of blue LEDs and yellow phosphors, the spectrum of which lacks deep red. To improve the color-rendering characteristics of white LEDs, a red quantum-dot film was applied to the diffuser plate of LED lighting. The mean free paths of the quantum dots and the concentration of the TiO₂ particles in the diffuser plate were adjusted to optimize the optical structure of the lighting. The color-rendering index (CRI) was greater than 90 for most conditions, which demonstrates that adoption of the red quantum-dot film is an effective way for improving the color-rendering properties of conventional white LEDs. The angular dispersion of color coordinates could be removed by utilizing the optical cavity formed between the diffuser plate and the reflector on the bottom of the lighting, where multiple passages of the light through the quantum-dot film reduced the differences in optical path length depending on the viewing angle.

• Journal of the Korea Society of Computer and Information
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• v.19 no.2
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• pp.101-107
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• 2014

This study is proposed the novel PPG sensor device and the signal processing method to replace the acceleration sensor that is used to reject motion artifacts contained in photoplethysmography(PPG). The proposed method is to reject motion artifacts by an adaptive filter based on the estimated motion artifact by using a blue LED light. To evaluate the performance of the proposed method experimentally, We did design a novel sensor consisted of blue/red LEDs and photo-sensor and implemented, and then rejected the motion artifacts by using an adaptive filter and the implemented sensor. In the results of the experiments, it is shown that the proposed sensor device and signal processing can reconstruct the PPG signal despite the occurrence of motion artifacts, and also that the SNR was 4.5 times of moving average filter. According to the experimental results, the proposed method can be applied to design a low-cost device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.194-200
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• 2020

Perylene bisimide derivatives are developed for red organic phosphor because of their advantages, such as excellent luminous efficiency and high thermal stability. Despite these advantages, they have poor solubility characteristics in organic solvents and short emission wavelength as red organic phosphor for hybrid light-emitting diodes (LEDs). In this study, we prepared terrylene bisimide using a coupling reaction and swallow-tail imide group, which has excellent solubility. The structures and properties of swallow-tail terrylene bisimide (9C) were analyzed using ¹H-nuclear magnetic resonance (¹H-NMR), Fourier-transform infrared (FT-IR), UV/Vis spectroscopy, and thermal gravimetric analysis (TGA). The maximum absorption wavelength of (9C) in the UV/Vis spectrum was 647 nm, and the maximum emission wavelength was 676 nm. In the TGA, (9C) demonstrated good thermal stability with less than 5 wt% weight loss up to 415℃. In the solubility test, (9C) has a good solubility of more than 5 wt% in chloroform and dichloromethane. When the compounds (9C) were mixed with PMMA (polymethly methacrylate), the films showed peaks at 680 nm in the PL spectra. The results verify the suitability of (9C) as a red organic phosphor for hybrid LEDs.

• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.45-52
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• 2023

In this study, we have investigated the effect of photobiomodulation (PBM) on corneal wound healing, using a low-power light-emitting diode (LED) at different wavelengths. We found that LEDs with wavelengths ranging from 623 to 940 nm had no significant cytotoxic effects on corneal epithelial cells. The effect of PBM on promoting cell migration was analyzed by scratch assay, and it was found that PBM at 623 nm significantly increased cell migration and promoted wound healing. Furthermore, the expression of genes related to cell migration and wound healing was analyzed, and it was found that PBM at 623 nm upregulated the expression of the genes FGF-1 and MMP2, which are known to promote cell proliferation and extracellular matrix degradation. These findings suggest that PBM with low-powered light at specific wavelengths, particularly 623 nm, could be utilized to treat corneal injury.

• Journal of Bio-Environment Control
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• v.25 no.1
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• pp.42-48
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• 2016

Angelica gigas, belonging family Apiaceae, is a perennial and famous medical plant growing in Korea, Japan, and China. The aims of this study was to analyze the growth and accumulated Decursin and its precursor Decursinol angelate of A.gigas grown under fluorescent lamp and LED. A. gigas 'Manchu' were sowed and managed for seedlings stage in a glass house for 4 weeks. One hundred twenty seedlings with 3 true leafs were transplanted at an ebb & flow system with fluorescent lamp and LED [red: peak wavelength 660nm, blue: peak wavelength 455 nm, white = 3:2:4 ratio] irradiated at $180{\pm}7{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at the top of plant canopy for 5 weeks. The number of leaves increased by 13.5% in the LED treatment, though it is not statistically significant. Leaf length/width ratio of A. gigas grown under the fluorescent lamps was 24% bigger than the LED treatment and also the stem was 13% larger. Maximum root length was similar to both groups. Fresh weight and dry weight of shoots grown under the LED increased by 50% and 42% and the both weights of roots increased by 125% and 45%, respectively. The contents of Decursin and Decursinol angelate grown under the florescent lamps were larger than LED by 188% and 27% in shoot and 78% and 8% in root. The contents of Decursin and Decursinol angelate per plant grown under LED and florescent lamps were 132mg and 122mg. In conclusion, functional materials in A. gigas were increased by florescent light and its growth was promoted by LEDs light.

• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.294-301
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• 2016

This study was conducted to analyze the seedling quality of korean melon and the growth after transplanting of korean melon nursed under the LED sources. LED sources were RB7 (Red:Blue=14:2), RB3 (Red:Blue=12:4) and Blue(B=16). Photosynthetic photon flux density(PPFD) was 50, 100 and $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The lighting treatment was started after graft-taken and was applied for 20 days at 4 hours(05:30 and 07:30, 17:30 and 19:30) per day. Plant height and stem diameter of scion were longer and thicker under a high ratio of blue light condition. Dry matter ratio and compactness were highest in RB3 compared to the other LED sources treatments. $CO_2$ exchange rate increased $5.44{\mu}molCO_2{\cdot}m^{-2}{\cdot}s^{-1}$ under RB7 $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ and dropped to negative values under control. PPFD $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ of RB3 resulted in the longest plant height by 132.3cm and flowering ratio also was the highest by 75%.

• Journal of Plant Biotechnology
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• v.49 no.4
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• pp.307-315
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• 2022

Artemisinin is a secondary metabolite of Artemisia annua that shows potent anti-malarial, anti-bacterial, antiviral, and anti-tumor effects. The supply of artemisinin depends on its content in Artemisia annua, in which various environmental factors can affect the plant's biosynthetic yield. In this study, the effects of different light-emitting diode (LED)-irradiation conditions were tested to optimize the germination and growth of Artemisia annua for the enhanced production of artemisinin. Specifically, the ratio between the red and blue lights in the irradiating LED was varied for investigation as follows: [Red : Blue] = [6 : 4], [7 : 3], and [8 : 2]. Furthermore, additional stress factors like UV-B-irradiation (1,395 ㎼/cm²), low temperature (4℃), and dehydration were also explored to induce hormetic expressions of ADS, CYP, and ALDH1, which are essential genes for the biosynthesis of artemisinin. Quantitative polymerase chain reaction (qPCR) was used to analyze the expression levels of the respective genes and their correlation with the specified conditions. [8 : 2] LED-irradiation was the most optimal among the tested conditions for the cultivation of Artemisia annua in terms of both fresh and dry weights post-harvest. For the production of artemisinin, however, [7 : 3] LED-irradiation with dehydration for six hours pre-harvest was the most optimal condition by inducing around twofold enhancement in the biosynthetic yield of artemisinin. As expected, a correlation was observed between the expression levels of the genes and the contents of artemisinin accumulated.

• Journal of the Korean Chemical Society
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• v.49 no.2
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• pp.138-144
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• 2005

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.783-785
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• 1998

In this study the emission characteristics of Sq dye undoped and doped specimen investigated. In Sq 14mol% doped specimen, OXD7 and Alq3 layer interpolated. This effect has been observed and mechanism characteristics have been examined. For OXD7 insert, hole flow the cathode intercept, and then hole accumulated. Because of increasing recombination probability of electron and hole highly pure color maintained. Simultaneously brightness characteristics and emission efficiency could improve.