• Analytical Science and Technology
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• v.31 no.6
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• pp.225-231
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• 2018

Benzoic acid, methyl paraben, and butyl paraben are preservatives that have been used in pharmaceutical, cosmetic, and food products. However, as their toxicities for human have been reported, many nations and organizations including Korea have established a regulation limit for thier usage of these preservatives in food products. The present study developed the isotope dilution liquid chromatography mass spectrometry method for accurate determination of three target preseratives in soysauce. In this study, the isotope dilution liquid chromatography mass spectrometry method was developed for accurate determination of three target preservatives in soy sauce. LC separation was optimized considering the pKa of benzoic acid which is lower than those of methyl and butyl parabens. A C18 column was used with 5 mM ammonium acetate and methanol as mobile phases. Mass spectrometry was operated in negative mode and selected reaction monitoring mode (SRM). Soy sauce sample was cleaned-up with C18 SPE cartridge for removing matrix inferences and color material. Optimized conditions and the method were validated with soy sauce reference materials for the analysis of food preservatives from Health Science Authority in Singapore. The measured values of benzoic acid, methyl and butyl paraben agreed well with reference values within their uncertainties.

• Journal of the Korean Magnetic Resonance Society
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• v.16 no.1
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• pp.34-45
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• 2012

Melanocortin-4 receptor (MC4R) subtype is associated with obese humans. Especially, in a patient with severe early-onset obesity, novel heterozygous mutation in the MC4R gene was detected, resulting in an exchange of aspartic acid to asparagine in $90^{th}$ amino acid residue located in the predicted second trans-membrane domain (TM2). Mutations in the melanocortin-4 receptor (MC4R) gene are the most frequent monogenic causes of severe obesity which have been described as heterozygous with loss of function. In order to compare structure difference between MC4R wild type (MC4R-TM2-wt) and mutant (MC4R-TM2-D90N), we designed both MC4R-TM2-wt and MC4R-TM2-D90N construct in pET 21b vector. In this study, we optimized high-yield purification procedure for recombinant TM2-D90N. Eluted recombinant protein was resolubilized under urea condition for thrombin cleavage reaction and we conducted the high-performance liquid chromatography (HPLC) with reverse phase column under 1% acetonitrile, 0.01% TFA buffer solution. The molecular size of purified target peptide was confirmed by Tricine-SDS page analysis. To characterize MC4R-TM2-D90N, we have performed $^{15}N$-isotope labeling of peptide using M9 media and purified labeled target peptide for hetero-nuclear NMR spectroscopy.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.105-113
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• 2015

In order to accelerate hydrogen society in current big renewable energy trend, it is very important that hydrogen can be transported and stored as a fuel in efficient and economical fashion. In this perspective, liquid hydrogen can be considered as one of the most prospective storage methods that can bring early arrival of the hydrogen society by its high gravimetric energy density. In this study, a small-scale hydrogen liquefier has been designed and developed to demonstrate direct hydrogen liquefaction technology. Gifford-McMahon (GM) cryocooler was employed to cool warm hydrogen gas to normal boiling point of hydrogen at 20K. Various cryogenic insulation technologies such as double walled vacuum vessels and multi-layer insulation were used to minimize heat leak from ambient. A liquid nitrogen assisted precooler, two ortho-para hydrogen catalytic converters, and highly efficient heat pipe were adapted to achieve the target liquefaction rate of 1L/hr. The liquefier has successfully demonstrated more than 1L/hr of hydrogen liquefaction. The system also has demonstrated its versatile usage as a very efficient 150L liquid hydrogen storage tank.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.328-330
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• 2002

Large balloon angio catheter is used for Percutaneous Transluminal Angioplsty(TPA) of the iliac, femoral and renal arteries as well as after Transjugular Intrahepatic portosystemic shunt(TIPS). The use of angioplasty balloon filled with liquid form of radioisotope reduces the rate of restenosis after PTA. The purpose of this study was to evaluate the absorbed dose to the target vessels from various sized large balloon filled with liquid form of Ho-166-DTPA. Four balloons of balloon dilatation catheters evaluated were 5, 6, 8 and 10 mm in diameter. GafChromic film was used for the estimation of the absorbed dose near the surface of the balloon catheters. Absorbed dose rates are plotted in units of Gy/min/GBq/ml as a function of radial distance in mm from the surface of balloon. The absorbed dose rate was 1.1, 1.6, 2.2 and 2.3 Gy/min/GBq/ml at a balloon surface, 0.3, 0.4, 0.5 and 0.6 Gy/min/GBq/ml at 1 mm depth for various balloon diameter 5, 6, 8 and 10 mm in diameter respectively. The study was conducted to estimate the absorbed doses to the vessels from various sized large balloons filled with liquid form of Ho-166-DTPA for clinical trial of radiation therapy after the PTA. The absorbed dose distribution of Ho-166 appeared to be nearly ideal for vascular irradiation since beta range is very short avoiding unnecessary radiation to surrounding normal tissues.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.57-60
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• 2007

This study is to discuss the effect of the liquid type high early strength agent considering early strength, developing strength, and economics of the concrete using admixtures. The powder type high early strength agent does not helpful because the field application is not available such as the problem of mixing process and rack of economics. To make up these subjects, the plain mixture contains the standard type AE water reducing agent, and the types of the agents are the standard type AE water reducing agent(P),liquid type high early strength agent(AD),poly carboxylate high early strength type AE water reducing agent(E1), and naphthalene + melamine high early strength type AE water reducing agent(E2). As the Contents of the agents, E1 and E2 is two types each cases, and P is one type to satisfy the target fluidity and air content, AD is three types as 0.5, 1.0,and 1.5%. In the case that AD is mixed, the fluidity is decreased, but air content is increased. For increasing strength of the early age, using OPC is more effective than FA and BS for increasing the early strength of the concrete, and if the air content is secure as plain, the effect of the developing strength can be increased because the air content is increased about 2% in the case that AD is used.

• Analytical Science and Technology
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• v.37 no.4
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• pp.211-219
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• 2024

This study presents a sensitive and reliable method for determining tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC) residues in shrimp samples. A two-step process involving liquid-liquid extraction (LLE) followed by solid-phase extraction (SPE) was developed prior to HPLC analysis. The target analytes were effectively extracted using EDTA/McIlvaine buffer (pH 4.0): methanol (80:20, %v/v), with subsequent clean-up using a C18 SPE cartridge. HPLC separation was conducted on a C18 column (250 mm × 4.6 mm i.d., 5 ㎛) at 30 ℃, using 0.01 % trifluoroacetic acid (A) and acetonitrile (B) as the mobile phase. A gradient elution protocol was applied, transitioning from 85(A):15(B) %v/v to 70(A):30(B) %v/v at 7 min, with a 5 min hold, followed by adjustment to 85(A):15(B) %v/v for 13-14 min. The detection was performed using photodiode array (PDA) at 365 nm with a flow rate of 1.0 mL/min. The calibration curves exhibited good linearity within a concentration range of 0.4-6.0 ㎍/mL (R² > 0.995). The limits of detection (LOD) for TC, OTC, and CTC in shrimp were 0.034, 0.029, and 0.021 ㎍/mL, respectively. The limits of quantitation (LOQ) for TC, OTC, and CTC were found to be 0.114, 0.097, and 0.071 ㎍/mL, respectively. Recoveries of TC, OTC, and CTC from spiked shrimp samples ranged from 91.0 % to 95.5 %, 92.4 % to 97.2 %, and 93.3 % to 96.6 %, respectively. This method was successfully applied to the determination of TC, OTC, and CTC residues in shrimp samples sourced from various local markets.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.16-20
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• 2017

Background: The design of deuteron accelerator neutron source facilities requires reliable yield estimation of gamma-rays as well as neutrons from deuteron-induced reactions. We have so foar measured systematically double-differential thick target neutron yields (DDTTNYs) for carbon, aluminum, titanium, copper, niobium, and SUS304 targets. In the neutron data analysis, the events of gamma-rays taken simultaneously were treated as backgrounds. In the present work, we have re-analyzed the experimental data for a thick carbon target with particular attention to gamma-ray events. Materials and Methods: Double-differential thick target gamma-ray yields from carbon irradiated by 5 and 9 MeV deuterons were measured using an NE213 liquid organic scintillator at the Kyushu University Tandem accelerator Laboratory. The gamma-ray energy spectra were obtained by an unfolding method using FORIST code. The response functions of the NE213 detector were calculated by EGS5 incorporated in PHITS code. Results and Discussion: The measured gamma-ray spectra show some pronounced peaks corresponding to gamma-ray transitions between discrete levels in residual nuclei, and the measured angular distributions are almost isotropic for both the incident energies. Conclusion: PHITS calculations using INCL, GEM, and EBITEM models reproduce the spectral shapes and the angular distributions generally well, although they underestimate the absolute gamma-ray yields by about 20%.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1629-1630
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• 2006

This paper describes a micro total analysis system ($\mu$ TAS) for detecting and digesting the target protein which includes a bead based temperature controllable microchip and computer based controllers for temperature and valve actuation. We firstly combined the temperature control function with a bead based microchip and realized the on-chip sequential reactions using two kinds of beads. The PEG-grafted bead, on which RNA aptamer was immobilized, was used for capturing and releasing the target protein. The target protein can be chosen by the type of RNA aptamer. In this paper, we used the RNA aptamer of HCV replicase. The trypsin coated bead was used for digesting the released protein prior to the matrix assisted laser desorption ionization time of flight mass spectrometer (MALDI TOF MS). Heat is applied for release of the captured protein binding on the bead, thermal denaturation and trypsin digestion. PDMS microchannel and PDMS micro pneumatic valves were also combined for the small volume liquid handling. The entire procedures for the detection and the digestion of the target protein were successfully carried out on a microchip without any other chemical treatment or off-chip handling using $20\;{\mu}l$ protein mixture within 20 min. We could acquire six matched peaks (7% sequence coverage) of HCV replicase.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.898-903
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• 2011

Units assembled in the liquid-propellant propulsion system of launch vehicles should guarantee their on- and off-design performances under the various environments as well as at the various operation modes for the launch preparation and flight of launch vehicles. Units of liquid-propellant propulsion system can be installed in launch vehicle to insert satellite(s) into target orbit(s) only under the condition that all units must pass a series of tests to confirm whether those units perform normally as designed under the environment, which may be occurred in such stages of all development and operations as development, qualification, acceptance, assembly, pre-launch preparation, launch, and flight, and whether those units have been developed according to design requirements. Requirements for such tests have been already prepared in the advanced countries in launch vehicle systems based on experiences for decades. In Korea, where is now pursuing the development of KSLV-II, the research and development of launch vehicles using liquid-propellant propulsion system have been undergone during over 10 years. Hence test requirements for the development of units consisting of liquid-propellant propulsion system should be defined and Koreanized according to the domestic environment and circumstances and based on the experiences accumulated. In this paper requirements for the tests of units in liquid-propellant propulsion system, which can be feasible domestically, have been reviewed and defined.

• Journal of computational fluids engineering
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• v.11 no.3 s.34
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• pp.46-51
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• 2006

This paper presents the numerical results of fluid flow and mixing in a microfluidic device for electro-osmotic flow (EOF) with an trapezoidal electrode array on the bottom wall (ETZEA). Differently from previous EOF in a channel which only transports fluid in colloidal system. ETZEA can also be utilized to mix a target liquid with a reagent. In this study we propose a method of controlling fluid flow and mixing enhancement. To obtain the flow and mixing characteristics, numerical computations are performed by using a commercial code, CFX-10, and a self-made code LBM-D. It was found that the flow near the trapezoidal electrode in the ETZEA is of 3-D complex flows due to the zeta potential difference between the trapezoidal electrode and channel walls, and as a consequence the hetrogeneous zeta potential on the electrodes plays an important role in mixing the liquid.