• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.1-6
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• 1999

A piezoelectric (PZ) biosensor system detecting Salmonella spp. was developed. The system consisted of an oscillator, a frequency counter and an antibody-immobilized quartz crystal. An anti-Salmonella antibody was immobilized on one gold. surface of the quartz crystal with protein A. Salmonella detection was made by measuring resonant frequency shift owing to a mass change by specific binding of microbial cells to the gold surface of the PZ crystal. The PZ antibody sensor was operated optimally at 0.1M phosphate buffer, pH 7.2 and $35^{\circ}C$. The sensor was quite specific to Salmonella spp. The obtained frequency shift was correlated with the Salmonella concentration in the range of $10^5{\sim}10^6\;CFU/mL$. The frequency shift increased further by addition of polystyrene beads. The Salmonella detection which is indicated by a steady-state microbial adsorption to the quartz crystal was accomplished within 50min.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.355-355
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• 2012

Si (111) 기판 위에 polystyrene (PS) bead를 사용하여 만들어진 약 100 nm 나노 구멍에 GaN나노선을 molecular beam epitaxy 법으로 성장하였다. 성장 온도와 III/V 비율 변화에 대하여 성장된 GaN 나노선의 모양과 광학적 특성은 scanning electron microscopy (SEM)와 photoluminescence (PL) 등으로 조사하였으며, InN/GaN 이종접합 및 InGaN p-n 다이오드구조를 성장하여 atomic force microscopy의 tip 접촉방법으로 전기적 특성을 조사하였다. PL 측정 결과 성장온도가 높아지면 Ga 빈자리와 관계된 3.28 eV의 donor acceptor pair (DAP) 신호와 3.42 eV의 stacking faults (SF) 결함에 기인된 발광 신호세기가 감소하는 결과를 SEM으로부터 나노선 폭 및 길이는 좁아지면서 짧아지는 것을 관측하였다. 또한 nitrogen 원자양이 증가하면서 Ga 빈자리와 관련된 3.28 eV DAP 신호가 증가하는 것을 관측하였다. 이들 결과로부터 GaN 나노선의 SF 발광 신호관련 원인에 대하여 논의 하였다. AFM을 이용한 I-V 측정으로부터 성장조건 변화에 따른 GaN 나노선 및 p-n 접합 나노선의 전도 특성을 조사하여 나노선의 소자 응용에 대한 기본적인 물리특성을 규명하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.3
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• pp.261-264
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• 2009

We present a three-dimensional (3D) particle focusing channel using the positive dielectrophoresis (pDEP) guided by a dielectric structure between two planar electrodes. The dielectric structure between two planar electrodes induces the maximum electric field at the center of the microchannel, and particles are focused to the center of the microchannel by pDEP as they flow from the single sample injection port. Compared to the previous 3D particle focusing methods, the present device achieves the simple and effective particle focusing function without any additional fluidic ports and top electrodes. In the experimental study, approximately 90 % focusing efficiency were achieved within the focusing length of 2mm, on both x-z plane (top-view) and y-z plane (side-view) for $2{\mu}m$-diameter polystyrene (PS) bead at the applied voltage over 15 Vp-p (square wave) and at the flow rate below 0.01 ${\mu}l$/min. The present 3D particle focusing channel results in a simple particle focusing method suitable for use in integrated microbiochemical analysis system.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.363-369
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• 2011

Total ammonia nitrogen (TAN) removal efficiencies of a sand filter (SF), polystyrene microbead filter (PF), and Kaldnes bead filter (KF) media were evaluated under ammonia loading rates of 5, 25, and 50 g $m^{-3}day^{-1}$. The volume of each filter media tested was 7 L, and the water flow rate for all filter media was 24 L/min. The specific surface areas of the SF, PF, and KF were 7,836, 3,287, and 500 $m^2/m^3$, respectively. Sand was fluidized and the other two media were trickle filtered. The volumetric TAN removal rate increased with increasing ammonia loading rate for all filter media. Mean volumetric TAN removal rates under the ammonia loading rates of 5, 25, and 50 g $m^{-3}day^{-1}$ in SF (39.3, 168.6, and 322.7 g $m^{-3}day^{-1}$, respectively) were higher than those in PF (35.0, 157.4, and 310.5 g $m^{-3}day^{-1}$, respectively) and KF (32.1, 142.5, and 288.1 g $m^{-3}day^{-1}$, respectively). These results were related to differences in the specific surface areas of the filter media. PF was the most economic media for efficiently removing TAN.

• Journal of the Semiconductor & Display Technology
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• v.11 no.1
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• pp.21-27
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• 2012

The optical diffuser for direct-lit LED backlight unit was prepared by using extrusion compounding followed by thermoforming process. Poly(methyl methacrylate) (PMMA) with superior optical characteristics and polycarbonate (PC) with good thermal property were used as base resins, and crosslinked polystyrene (PS) and PMMA beads as diffusing agents were incorporated into resin matrix to derive light scattering and diffusing action. In the compounded plate, the diffusing beads were observed to be dispersed uniformly and distinctly in the continuous phase. The inclusion of polymeric beads up to 3 wt% substantially enhanced the optical characteristics such as luminance, luminance uniformity, haze for the diffuser. Two different diffusers of PC and PMMA-based compound with various compositions were compared in terms of measured optical, thermal, and mechanical properties, which would be expected to be utilized for the industrial application of LED backlight unit.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.905-909
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• 2010

Magnetic beads (Dynabeads$^{(R)}$) embedded in ~1 micron size polystyrene beads bearing surface carboxylic acid groups were modified with aminobenzyl ethylenediaminetetraacetic acid (ABEDTA) to concentrate or separate metal ions using pH gradients on micro and nano scales. The immobilization of ABEDTA was achieved by amide formation. The presence of the metal chelating functional group in the fully deprotonated form was confirmed by FT-IR. The chelation efficiency of beads was tested by determining metal ions in supernatant using GFAAS when pH gradients from 3 to 7. Mixtures of Cu and Mg and of Cd and Mn (at 10 ng/mL of metal) were separated as the difference in formation constant with the functional group of ABEDTA. The separation was repeated twice with relative standard deviation of <18%. A polydimethylsiloxane (PDMS) microchip column packed with EDTA-coated magnetic beads was optimized to concentrate metal ion for practical applications by eluting a Cu solution of micro scale at pH 3.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.1
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• pp.41-48
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• 2009

The present study has been performed to investigate the thermal characteristics of under-ventilated compartment fire which is a typical fire condition in structures. A series of fire experiments was conducted to characterize the thermally driven flow in a 2/5 scale ISO 9705 fire compartment. Three different fuels were used in this test series, methane gas, heptane pool, and polystyrene pellets fire. In order to measure accurate temperature, double shield aspirated thermocouples reducing the effect of radiative energy exchange on temperature measurement were used in addition to bare bead thermocouples. The upper layer temperature for well ventilated fire was increased with increasing heat release rate, but it was slightly decreased for under-ventilated fire. The measured temperatures in the upper layer at the front sampling location were higher than at the rear. Thermal characteristics through the doorway were also analysed for a wide range of heat release rates. This study provides a comprehensive and quantitative assessment of fire behavior for under-ventilation condition of fire.

• Journal of Marine Life Science
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• v.8 no.2
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• pp.104-114
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• 2023

As plastic usage increases globally, the amount of plastic waste entering the marine environment is steadily rising. Microplastics, in particular, can be ingested by marine organisms and accumulated in their digestive tracts, causing harmful effects on their growth and reproduction. Cytochrome P450 (CYP) enzymes are known to metabolize various environmental pollutants as detoxification enzymes, but their role in crustaceans is not well understood. In this study, sequences of nine CYP genes (CYP370A4, CYP370C5 from clan 2; CYP350A1, CYP350C5, CYP361A1 from clan 3; CYP4AN-like, CYP4AP2, CYP4AP3, CYP4C33-like1 from clan 4) were analyzed using conserved domains in the brackish water flea Diaphanosoma celebensis. Additionally, after exposure to three different sizes of polystyrene beads (0.05-, 0.5-, 6-㎛ PS beads; 0.1, 1, and 10 mg/L) for 48 hours, the expression of these nine CYP genes were investigated using real-time reverse transcription polymerase chain reaction (RT-PCR). The results showed that all CYP genes possessed conserved motifs, indicating that D. celebensis CYP has evolutionarily conserved functions. Among these CYP genes, the expression of CYP370C5, CYP360A1, and CYP4C122 showed a significant increase after exposure to 0.05-㎛ PS beads, suggesting their involvement in PS metabolism. This research will contribute to understanding the molecular mode of actions of microplastics on marine invertebrates.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.274-280
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• 2014

Polysulfone (PSf) hollow fiber membranes were prepared via the nonsolvent induced phase separation technique. The cosolvent of ${\gamma}$-butyrolactone (GBL) was added to the polymer solution containing a mixture of PSf and N,N-dimethylacetamide (DMAc). Water was utilized as a precipitation nonsolvent. The morphology of prepared membranes was investigated using a field emission scanning electron microscopy. The fabricated membrane showed a typical asymmetric structure such as the dense layer on the porous support layer by the addition of GBL to the polymer solution. As the concentration of GBL increased, the asymmetric porous structure was shown to be more intensified. It was thought that the added GBL played a role of enhancing the liquid-liquid phase separation of the polymer solution, since the cosolvent of GBL might change the thermodynamic solubility parameter of the doping solution. Permeation properties through the prepared hollow fiber membranes were characterized by measuring the pure water flux and the solute rejection using $0.05{\mu}m$ polystyrene latex (PSL) beads. Experimental results revealed that the use of PEG as the internal coagulant enhanced the pure water flux up to 130 times compared to the use of EG while the rejection of the PSL beads decreased only 5%.

• Journal of fish pathology
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• v.12 no.1
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• pp.24-31
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• 1999

Optimization and standardization of solid phase enzyme immunoassay were done for the diagnosis of edwardsiellosis in fish. The analyzed degree of immobilized antibody on surface of solid phase with peroxidase saturation method showed the optimized result by using partially purified $50{\mu}g/ml$ of rabbit anti-E. tarda Edk-2 antibody in sodium bicarbonate buffer for overnight incubation to cover the surface of polystyrene beads. Optimized immunoreaction was observed in the treatment of $50{\mu}g/ml$ of biotin conjugated antibody followed extravidin-peroxidase diluted 1 : 2,000 in PBS. The detectable concentrations of the this method were $1{\times}10^5$ cells/ml and $1{\times}10^5$ cells/ml expressed as the source of antigen amount for EDTA extraction and heat extraction, respectively. High cross-reaction of solid phase ELISA with the prepared rabbit and-E. tarda Edk-2 was observed against E. tarda strains isolated from flounder suffering from edwardsiellosis in aquatic farms of Korea. It suggested that the potential of this solid phase of ELISA technique is very powerful for the application to different strains of E. tarda isolated in farms of many different areas.