• YAKHAK HOEJI
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• v.33 no.6
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• pp.372-376
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• 1989

Equilibrium swelling and pH-sensitivity of a polyelectrolyte copolymer hydrogel were controlled by employing copolymers with different hydrophilic-hydrophobic balances. Model pH-sensitive hydrogels, e.g., poly(methacrylic acid), poly(methacrylic acid-co-acrylamide), poly(methacrylic acid-co-2-hydroxyethylmethacrylate), poly(methacrylic acid-co-styrene) were synthesized at various monomer compositions. As hydrophobicity of the copolymer hydrogels increased, the equilibrium swelling decreased while the pH-sensitivity increased. In the case of poly(methacrylic acid-co-acrylamide), polymer-polymer interaction significantly affected the equilibrium swelling and provided a wide range control of pH-sensitivity.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.213.1-213.1
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• 2015

Field effect transistors (FETs)를 기반으로 한 바이오센서는 빠른 응답속도, 저비용, label-free 등을 이유로 각광받고 있다. 그러나 3D 구조를 기반으로 한 FETs 바이오센서의 낮은 sensitivity의 한계점을 지니며, 이를 극복하기 위해 1D 구조의 나노튜브 등을 활용하였으나 여전히 높은 sensitivity의 확보는 힘들다. 최근에는 이러한 문제점을 극복하기 위해 이차원 반도체 물질 중 하나인 Transition metal dichalcogenide (TMD)를 이용하여, 700 이상의 sensitivity를 지니는 pH센서 및 100 이상의 sensitivity를 지니는 바이오센서가 보고되었다. 하지만 이보다 더 높은 정확성 및 반응성을 높이기 위한 연구는 부족한 실정이다. 우리는 DNA 템플릿을 이용하여, TMD FET 기반 pH 및 바이오센서의 반응성을 극대화시키는 연구를 선보인다. DNA는 7~8정도의 유전상수 (K)를 가지는 물질로 기존 $SiO_2$(K=3.9)보다 높은 유전상수를 가지며 두께를 0.7 nm로 매우 얇게 형성할 수 있는 장점이 있다. 이는 FET 기반 바이오센서의 표면 캐패시턴스를 높여 sensitivity를 극대화할 수 있으며, 기존에 사용된 high-k 기반 바이오센서와 비교하여도 약 10배 이상의 sensitivity 향상을 노릴 수 있다. 또한, TMD 물질로 우리는 $WSe_2$를 선택하였으며, pH 용액의 receptor로써 우리는 3-Aminopropyltriethoxysilane (APTES)를 활용하였고, 템플릿으로 사용된 DNA는 DX tile 및 Ring type의 두 가지를 사용하였다. 추가로, DNA의 phosphate backbone을 중성화시키고 DNA의 base pairing의 charge 안정화를 위해 구리 이온($Cu^{2+}$) 및 란타넘족($Tb^{3+}$)을 추가하였다. 완성된 바이오센서의 pH 센싱을 위해 우리는 pH 6,7,8의 표준 용액을 사용하였으며, 재현성 및 반복성의 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.455-460
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• 1994

This paper presents a simple methodology for reducing the order of H$_{\infty}$ controllers in the mixed sensitivity control problems. The key point of this methodology is to transform the generalized plant expression to new one, where the control object and the weighting functions for the sensitivity function may have some poles on the imaginary axis. So that, this methodology makes it possible to use the standard method to solve the general H$_{\infty}$ design problems about the mixed sensitivity problems, even for a servo system or a oscillatory system. We derive that the order of H$_{\infty}$ controllers designed by this methodology may be reduced to n$_{p}$ where n$_{p}$ is the order of the denominator of the control object. It is clear that n$_{p}$ is lower than n$_{p}$ + n$_{s}$, which is the order of H$_{\infty}$ controllers obtained by the ordinary H$_{\infty}$ design method up to now, where n$_{s}$ is the order of the denominator of the weighting function for sensitivity. Finally, a numerical example is given to illustrate the results..lts.ts..lts.lts.

• Polymer(Korea)
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• v.39 no.3
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• pp.359-364
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• 2015

A self-oscillating interpenetrating polymer network (IPN) poly(acrylic acid)/poly(ethylene glycol) (PAA/PEG) hydrogel was prepared by using radical polymerization with a two-step method. The IPN hydrogel was characterized by FTIR spectroscopy and morphological analysis. The results indicated that the chains of PEG and PAA twined to form porous structure which is beneficial to water molecules entering inside of the hydrogel. In addition, the pH-responsive behavior, salt sensitivity, swelling/de-swelling oscillatory behaviors and self-oscillation in a closed pH oscillator were also studied. The results showed that the prepared hydrogel exhibited pH-sensitivity, good swelling/de-swelling reversibility and excellent salt sensitivity. The self-oscillating behavior of swelling/de-swelling for the prepared hydrogel was caused by pH alteration coupled with the external media. This study may create a new possibility as biomaterial including new self-walking actuators and other related devices.

• Journal of Biomedical Engineering Research
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• v.18 no.2
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• pp.173-178
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• 1997

pH sensitive polymers have long been utilized as one important type among many interesting drug delivery systems. This is due to the reason of different pH environments in human organs, which requires different pH control mechanism depending upon the organs. In the present study the pH sensitivity was investigated for both pH sensitive and pH insensitive biopolymers using the diffusion effect along with the swelling effect. NMR microscopy was performed along with optical microscopy. For the analysis of diffusion effect, UMR Microscopy was perFormed to measure diffusion coefficients for various liquids such as distilled water, acetone and DMSO(dimethyl sulfoxide). Also, this technique is expected to contribute to the studies for many pH drug delivery systems.

• Journal of Preventive Medicine and Public Health
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• v.18 no.1
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• pp.51-57
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• 1985

To attempt to measure the effect of domestic product P.H.A. kit 'Hepa-S' after completion of 'Hepa-Vax' vaccination schedule, P.H.A. test and R.I.A. test on the 330 healthy adults were carried out. The results obtained were as follow ; 1. The positive anti HBs rate after completion of 'Hepa-Vax' vaccination were; in P.H.A. test with domestic product P.H.A. kit 81.2%, in P.H.A. test with foreign product P.H.A. kit 82.7%, and in R.I.A. test 95.8% 2. Using the result of R.I.A. test as the standard, sensitivity of P.H.A. test with domestic product P.H.A. kit was 84.8% and specificity was 100.0% 3. Using the result of R.I.A. test as standard, sensitivity of P.H.A. test with foreign P.H.A. kit was 86.4% and specificity was 100.0%. 4. The concordance rate of P.H.A. test with domestic product and foreign product kit was 98.5%. On the result of this study, there was no significant difference in the validity between the domestic product P.H.A. kit 'Hepa-S' and the foreign P.H.A. kit $'Hebsgencell^{TM}'$. So that it is recommendable to use domestic product P.H.A. kit instead of foreign product P.H.A. kit.

• Journal of Sensor Science and Technology
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• v.10 no.2
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• pp.118-124
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• 2001

When particles are dissolved in solution, they have different zeta-potentials depending on pH. Zeta-potential has an influence on particle separation, which can control particle size. And the size of $WO_3$ particle affects the sensitivity of $WO_3$ sensor for detecting NO gas. Therefore we study influence of pH on NO-sensing $WO_3$ gas sensor fabricated by Sol-Coprecipitation method. As pH increases from 2 to 7, dynamic mobility of $WO_3$ precursor was increased. When pH was 7, it showed the largest distribution separation. It means when pH is 7, we can make $WO_3$ powder which has smaller particle size. And it is confirmed by particle size analysis of $WO_3$ powder, X-ray diffration result of $WO_3$ sensing layer and surface morphology. It also affect NO sensing characteristics of $WO_3$ gas sensor. The sensing film synthesized at pH 7 showed the largest sensitivity.

• Macromolecular Research
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• v.16 no.8
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• pp.670-675
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• 2008

A series of pH and temperature-responsive (N,N-diethylacrylamide-co-methylacrylic acid) copolymers were synthesized by radical copolymerization and characterized by elemental analysis, Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR) $^1H$, $^{13}C$ and LLS. The effects of salt and pH on the phase transition behaviors of the copolymers were investigated by uv. With increasing NaCl concentration, significant salt effects on their phase transition behaviors were observed. UV spectroscopic studies showed that the phase transition became faster with increasing NaCl concentration. In addition, the phase transition behaviors of copolymers were sensitive to pH. The pH and temperature sensitivity of these copolymers would make an interesting drug delivery system.

• Korean Journal of Poultry Science
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• v.15 no.1
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• pp.39-44
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• 1988

This study was undertaken to find out the effect of heating time and temperature, pH and NaCl concentration on heat sensitivity of egg albumen during heat treatment. Sharp increase of the turbidity and rapid decrease of the foaming power were observed when egg albumen was heated at above $60^{\circ}C$. Egg albumen became opaque when it was heated at $60^{\circ}C$ for above 13 minutes or at $65^{\circ}C$ for above 5 minutes. The turbidity was markedly increased at below pH 7 and the foaming power was largely decreased at around pH 4.0 by the heat treatment ($60^{\circ}C$, 5 min). The foam stability was slightly decreased at alkaline pH range by the heat treatment (60t, 5 min). The addition of NaCl up to 0.3M decreased the turbidity. There was no effect of NaCl addition on the foaming power, but the foam stability was decreased by the addition of NaCl at above 0.2M before and after the heat treatment ($60^{\circ}C$, 5 min).

• Macromolecular Research
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• v.13 no.6
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• pp.467-476
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• 2005

The main objective of this study was to develop and characterize pH-sensitive biodegradable polymeric materials. For pH-sensitivity, we employed three kinds of moieties: 2-amino-3-(lH-imidazol-4-yl)-propionic acid (H), N-[4-( 4,6-dimethyl-pyrimidin-2ylsulfamoyl)-phenyl]succinamic acid (SM), and 2- {3-[ 4-( 4,6-dimethyl-pyrim­idin- 2-ylsulfamoyl)-phenylcarbamoyl]-propionylamino} -3-(3 H - imidazol-4-yl)-propionic acid (SH). The pH -sensitive diblock copolymers were synthesized by ring opening polymerization and coupling reaction from poly(ethylene glycol) (MPEG), $\varepsilon$-caprolactone (CL), D,L-lactide (LA) and pH-sensitive moieties. The pH-sensitive SH molecule was synthesized in a two-step reaction. The first step involved the synthesis of SHM, a methyl ester derivative of SH, by coupling reaction of SM and L-histidine methyl ester dihydrochloride, whereas the second step involved the hydrolysis of the same. The synthesized SM, SHM and SH molecules were characterized by FTIR, $^{1}H$-NMR and $^{13}C$-NMR spectroscopy, whereas diblock copolymers and pH-sensitive diblock copolymer were characterized by $^{1}H$-NMR and GPC analysis. The critical micelle concentrations were determined at various pH conditions by fluorescence technique using pyrene as a probe. The micellization and demicellization studies of pH-sensitive diblock copolymers were also done at different pH conditions. The pH-sensitivity was further established by acid-based titration and DLS analysis.