• Molecules and Cells
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• v.20 no.3
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• pp.452-452
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• 2005

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.54-59
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• 2006

Biophotonic sensors based on polymer waveguide with Bragg reflection grating are demonstrated in this work. Waveguide Bragg reflectors were designed by using the effective index method and the transmission matrix method. The grating pattern was formed by exposing the laser interference pattern on a photoresist. On top of the inverted rib waveguide, the Bragg reflection grating was inscribed by the O2 plasma etching. In order to perform the bio-molecule detection experiment, a calixarene molecule was self-assembled on top of thin Au film deposited on the waveguide Bragg reflector. To measure the response of the sensor, several PBS solutions with different concentrations of potassium ion from 1 pM to $100\;{\mu}M$ were dropped on the sensor surface. The shift of Bragg reflection wavelength was observed from the fabricated sensor device, which was proportional to the concentration of potassium ion ranging from 1 pM to 108 pM.

• The Korean Journal of Physiology and Pharmacology
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• v.17 no.2
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• pp.175-180
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• 2013

Resveratrol is a phytoalexin found in grapes, red wine, and berries. Resveratrol has been known to have many beneficial health effects, such as anti-cancer, neuroprotective, anti-inflammatory, and life-prolonging effects. However, relatively little is known about the effects of resveratrol on the regulation of ligand-gated ion channels. We have previously reported that resveratrol regulates subsets of homomeric ligand-gated ion channels such as those of 5-$HT_{3A}$ receptors. The ${\gamma}$-aminobutyric $acid_C$($GABA_C$) receptor is mainly expressed in retinal bipolar cells and plays an important role in visual processing. In the present study, we examined the effects of resveratrol on the channel activity of homomeric $GABA_C$ receptor expressed in Xenopus oocytes injected with cRNA encoding human $GABA_C$ ${\rho}$ subunits. Our data show that the application of GABA elicits an inward peak current ($I_{GABA}$) in oocytes that express the $GABA_C$ receptor. Resveratrol treatment had no effect on oocytes injected with $H_2O$ or with $GABA_C$ receptor cRNA. Co-treatment with resveratrol and GABA inhibited $I_{GABA}$ in oocytes with $GABA_C$ receptors. The inhibition of $I_{GABA}$ by resveratrol was in a reversible and concentration-dependent manner. The $IC_{50}$ of resveratrol was $28.9{\pm}2.8{\mu}M$ in oocytes expressing $GABA_C$ receptor. The inhibition of $I_{GABA}$ by resveratrol was in voltage-independent and non-competitive manner. These results indicate that resveratrol might regulate $GABA_C$ receptor expression and that this regulation might be one of the pharmacological actions of resveratrol on the nervous system.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.438-444
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• 2011

Magnesium is one of the abundant natural resources in the earth crust and seawater, which is directly related to various organisms activities interconnecting with water-rock system. In aqueous system, magnesium is known to predominantly exist in the form of $Mg^{2+}$ ion which is verified in its $E_h-pH$ diagram. When it is at equilibrium in aqueous system, temperature takes an essential role to complete equilibrium states. This study represents the change of the stable region of magnesium ion according to temperature, and how the consequences would affect aquatic organisms. It was revealed that there is a noticeable tendency shrinking the stable region of magnesium ion in a diagram as temperature increases, and as a result, aquatic bio-species presumably have difficulties to absorb the nutrient. Also, it was considered that the water system would be acidified by decreasing alkalinity.

• Safety and Health at Work
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• v.15 no.1
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• pp.114-117
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• 2024

A lithium-ion battery is a rechargeable battery that uses the reversible reduction of lithium ions to store energy and is the predominant battery type in many industrial and consumer electronics. The lithium-ion batteries are essential to ensure they operate safely. We conducted an exposure assessment five days after a fire in a battery-testing facility. We assessed some of the potentially hazardous materials after a lithium-ion battery fire.We sampled total suspended particles, hydrogen fluoride, and lithium with real-time monitoring of particulate matter (PM) 1, 2.5, and 10 micrometers (㎛). The area sampling results indicated that primary potential hazardous materials such as dust, hydrogen fluoride, and lithium were below the recommended limits suggested by the Korean Ministry of Labor and the American Conference of Governmental Industrial Hygienists Threshold Limit Values. Based on our assessment, workers were allowed to return to work.

• Molecules and Cells
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• v.20 no.1
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• pp.69-73
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• 2005

The flavonoid, quercetin, is a low molecular weight substance found in apple, tomato and other fruit. Besides its antioxidative effect, quercetin, like other flavonoids, has a wide range of neuropharmacological actions including analgesia, and motility, sleep, anticonvulsant, sedative and anxiolytic effects. In the present study, we investigated its effect on mouse 5-hydroxytryptamine type 3 ($5-HT_{3A}$) receptor channel activity, which is involved in pain transmission, analgesia, vomiting, and mood disorders. The $5-HT_{3A}$ receptor was expressed in Xenopus oocytes, and the current was measured with the two-electrode voltage clamp technique. In oocytes injected with $5-HT_{3A}$ receptor cRNA, quercetin inhibited the 5-HT-induced inward peak current ($I_{5-HT}$) with an $IC_{50}$ of $64.7{\pm}2.2{\mu}M$. Inhibition was competitive and voltage-independent. Point mutations of pre-transmembrane domain 1 (pre-TM1) such as R222T and R222A, but not R222D, R222E and R222K, abolished inhibition, indicating that quercetin interacts with the pre-TM1 of the $5-HT_{3A}$ receptor.

• Korean Journal of Microbiology
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• v.38 no.4
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• pp.254-259
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• 2002

A psychrotrophic bacterium was isolated from Antarctic marine sediment and identified as Shewanella sp. species based on the biochemical properties and 16S rRNA sequence, and designated as Shewanella sp. L93. Extracellular protease produced by this strain was purified through ammonium sulfate precipitation, High-Q column chromatography, first gel permeation chromatography, BioScale Q2 ion exchange chromatography and second gel permeation chromatography, and basic properties of this enzyme were investigated.

• Journal of Bio-Environment Control
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• v.1 no.2
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• pp.162-168
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• 1992

As the automation of nutrient solution management proceeds in the field of hydroponics, effective supporting systems to manage the nutrient solution by computer become needed. This study was attempt to predict the EC of nutrient solution using the neural networks. The multilayer perceptron consisting of 3 layers with the back propagation learning algorithm was selected for EC prediction, of which nine variables in the input layer were the concentrations of each ion and one variable in the output layer the EC of nutrient solution. The meq unit in ion concentration was selected fir input variable in the input layer. After the 10,000 learning sweeps with 108 sample data, the comparison of predicted and measured ECs for 72 test data showed good agreements with the correlation coefficient of 0.998. In addition, the predicted ECs by neural network showed relatively equal or closer to the measured ones than those by current complicated models.

• Transactions of Materials Processing
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• v.14 no.5 s.77
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• pp.473-476
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• 2005

The demand of on-chip total analyzing system with MEMS (micro electro mechanical system) bio/chemical sensor is rapidly increasing. In on-chip total analyzing system, to detect the bio/chemical products with submicron feature size, a filtration system with nano-filter is required. One of the conventional methods to fabricate nano-filter is to use direct patterning or RIE (reactive ion etching). However, those procedures are very costly and are not suitable fur mass production. In this study, we suggested new fabrication method for a nano-filter based on replication process, which is simple and low cost process. After the Si master was fabricated by laser interference lithography and reactive ion etching process, the polymeric mold was replicated by UV-imprint process. Metallic nano-filter was fabricated after removing the polymeric part of metal deposited polymeric mold. Finally, our fabrication method was applied to metallic nano-filter with $1{\mu}m$ pitch size and $0.4{\mu}m$ hole size for bacteria sensor application.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1219-1220
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• 2015

마이크로, 나노유체 (micro-, nanofluidics)을 이용한 종이 기반 분석 소자 (paper-based analytical devices, micro-PADs)에 대한 관심이 증가하고 있다. 종이 기반의 분석 소자는 초저가의 비용과 간단한 공정 방법으로 인하여 상용화 컨셉의 바이오센서로 각광받고 있다. 하지만, 종이 기반의 분석 소자는 낮은 검출 한계 (limit of detection, LOD)와 민감도 (sensitivity)의 제한이 있다. 그로 인해 우리는 이온 선택적 투과층 (ion permselective membrane, i.e. Nafion)을 종이 기반의 분석 소자와 결합하여 이온 농도 분극 (ion concentration polarization, ICP) 현상을 구현하여 낮은 검출한계와 민감도를 개선할 수 있었다. 접착력이 있는 테이프 표면에 이온 선택적 투과층을 패터닝 (patterning)하여 종이 기반 분석 소자와 결합하여 매우 간단하게 소자를 제작할 수 있었다. 따라서 종이 기반의 채널 양단에 직류 전압을 인가했을 때 발생하는 ICP 현상으로 인하여 형광 물질 (fluorescence dye)이 농축(preconcentration)되는 것을 확인할 수 있었다. 구체적으로, 초기 농도가 1.55 nM인 형광 물질을 이용하여 200 V의 외부전압을 인가했을 때, 500 초 이내에 1000 배 이상의 농축비를 얻을 수 있었다. 따라서, 외부 전압을 상용화된 건전지 출력값으로 낮출 수 있다면 다양한 종이 기반 분석 소자와 간단한 결합 방법을 통해 상용화 컨셉의 바이오센서로도 구현이 가능할 것이다.