• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2877-2883
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• 2010

The folding kinetics of $WT^*$ ubiquitin variant with valine to alanine mutation at sequence position 26 (HubWA) was studied by stopped-flow fluorescence spectroscopy. While unfolding kinetics showed a single exponential phase, refolding reaction showed three exponential phases. The semi-logarithmic plot of urea concentration vs. rate constant for the first phase showed v-shape pattern while the second phase showed v-shape with roll-over effect at low urea concentration. The rate constant and the amplitude of the third phase were constant throughout the urea concentrations, suggesting that this phase represents parallel process due to the configurational isomerization. Interestingly, the first and second phases appeared to be coupled since the amplitude of the second phase increased at the expense of the amplitude of the first phase in increasing urea concentrations. This observation together with the roll-over effect in the second folding phase indicates the presence of intermediate state during the folding reaction of HubWA. Quantitative analysis of Hub-WA folding kinetics indicated that this intermediate state is on the folding pathway. Folding kinetics measurement of a mutant HubWA with hydrophobic core residue mutation, Val to Ala at residue position 17, suggested that the intermediate state has significant amount of native interactions, supporting the interpretation that the intermediate is on the folding pathway. It is considered that HubWA is a useful model protein to study the contribution of residues to protein folding process using folding kinetics measurements in conjunction with protein engineering.

• Bulletin of the Korean Chemical Society
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• 제22권5호
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• pp.467-475
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• 2001

A triblock copolymer based on $poly(\varepsilon-caprolactone)$ (PCL) as the hydrophobic part and poly(ethylene glycol) (PEG) as the hydrophilic portion was synthesized by a ring-opening mechanism of ${\varepsilon}-caprolactone$ with PEG containing a hydroxyl group at bot h ends as an initiator. The synthesized block copolymers of PCL/PEG/PCL (CEC) were confirmed and characterized using various analysis equipment such as 1H NMR, DSC, FT-IR, and WAXD. Core-shell type nanoparticles of CEC triblock copolymers were prepared using a dialysis technique to estimate their potential as a colloidal drug carrier using a hydrophobic drug. From the results of particle size analysis and transmission electron microscopy, the particle size of CEC core-shell type nanoparticles was determined to be about 20-60 nm with a spherical shape. Since CEC block copolymer nanoparticles have a core-shell type micellar structure and small particle size similar to polymeric micelles, CEC block copolymer can self-associate at certain concentrations and the critical association concentration (CAC) was able to be determined by fluorescence probe techniques. The CAC values of the CEC block copolymers were dependent on the PCL block length. In addition, drug loading contents were dependent on the PCL block length: the larger the PCL block length, the higher the drug loading content. Drug release from CEC core-shell type nanoparticles showed an initial burst release for the first 12 hrs followed by pseudo-zero order release kinetics for 2 or 3 days. CEC-2 block copolymer core-shell type nanoparticles were degraded very slowly, suggesting that the drug release kinetics were governed by a diffusion mechanism rather than a degradation mechanism irrelevant to the CEC block copolymer composition.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 1998년도 봄 학술발표회 프로그램
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• pp.144-153
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• 1998

Sorbents of calcined limestone and oyster particles having a diameter of about 0.63mm were exposed to simulate fuel gases containing 5000ppmv H2S for temperatures ranging from 600 to 800C in a TGA. The reaction between CaO and H2S proceds via an unreacted shrinking core mechanism. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. The kinetics of the sorption of H2S by CaO is sensitive to the reaction temperature and particle size, and the reaction rate of oyster was faster than the calcined limestone.

• Archives of Pharmacal Research
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• 제8권1호
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• pp.7-14
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• 1985

Membrane-coated tablet of isonicotinic acid hydrazide (INAH) which releases INAH at the zero-order kinetics was deveoped. It consisted of a soluble tablet core surrounded by a porous membrane which controls the diffusion rate. Tablet cores were prepared by compressing granules of INAH and polyvinyl chloride (PVC) dissolved in methyl ethyl ketone in which micronized sucrose were suspended. Diffusion rate of INAH from the tablet through the membrane was constant until the loaded INAH in the core was almost released. The rate was independent of pH of the dissolution medium. Water-soluble sucrose particles behaved as a poreproducing material in the water-insoluble PVC film coat. The pH independency of the rate was probably due to the high solubility of INAH in the water of wide pH range. The diffusion rate of INAH could be controlled by chnaging the composition of the membrane or the coat weight. This membrane-coated INAH tablet seemed to be a powerful candidate for the controlled release drug delivery system (DDS) of INAH or other highly watersoluble drugs.

• 한국환경과학회지
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• 제8권1호
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• pp.125-133
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• 1999

Sorbents of calcined limestone and oyster particles having a diameter of about 0.63mm were exposed to simulated fuel gases containing 5000ppm $H_2S$ for temperatures ranging from 600 to 80$0^{\circ}C$ in a TGA (Thermalgravimetric analyzer). The reaction between CaO and $H_2S$ proceeds via an unreacted shrinking core mechanism. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. The kinetics of the sorption of $H_2S$ by CaO is sensitive to the reaction temperature and particle size, and the reaction rate of oyster was faster than the calcined limestone.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2725-2732
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• 2020

This paper presents the neutronics benchmark analysis of the first core of the Indonesian multipurpose research reactor RSG-GAS (Reaktor Serba Guna G.A. Siwabessy) calculated by the Serpent Monte Carlo code and the newly released ENDF/B-VIII.0 nuclear data library. RSG-GAS is a 30 MWth pool-type material testing research reactor loaded with plate-type low-enriched uranium fuel using light water as a coolant and moderator and beryllium as a reflector. Two groups of critical benchmark problems are derived on the basis of the criticality and control rod calibration experiments of the first core of RSG-GAS. The calculated results, such as the neutron effective multiplication factor (k) value and the control rod worth are compared with the experimental data. Moreover, additional calculated results, including the neutron spectra in the core, fission rate distribution, burnup calculation, sensitivity coefficients, and kinetics parameters of the first core will be compared with the previous nuclear data libraries (interlibrary comparison) such as ENDF/B-VII.1 and JENDL-4.0. The C/E values of ENDF/B-VIII.0 tend to be slightly higher compared with other nuclear data libraries. Furthermore, the neutron reaction cross-sections of ¹⁶O, ⁹Be, ²³⁵U, ²³⁸U, and S(𝛼,𝛽) of ¹H in H₂O from ENDF/B-VIII.0 have substantial updates; hence, the k sensitivities against these cross-section changes are relatively higher than other isotopes in RSG-GAS. Other important neutronics parameters such as kinetics parameters, control rod worth, and fission rate distribution are similar and consistent among the nuclear data libraries.

• Macromolecular Research
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• 제16권4호
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• pp.329-336
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• 2008

Core/shell ($\pm$)PS/(-)silica nanocomposite particles were synthesized by dispersion polymerization using an amphoteric initiator, 2,2'-azobis [N-(2-carboxyethyl)-2,2-methylpropionamidine] ($HOOC(CH_2)_2HN$(HN=) $C(CH_3)_2CN$=NC $(CH_3)_2C$(=NH)NH $(CH_2)_2COOH$), VA-057. Negatively charged (-6.9 mV) silica was used as the stabilizer. The effects of silica addition time and silica and initiator concentrations were investigated in terms of polymerization kinetics, ultimate particle morphology, and size/size distribution. Uniform hybrid microspheres with a well-defined, core-shell structure were obtained at the following conditions: silica content = 10-15 wt% to styrene, VA-057 content=above 2 wt% to styrene and silica addition time=0 min after initiation. The delay in silica addition time retarded the polymerization kinetics and broadened the particle size distribution. The rate of polymerization was strongly affected by the silica content: it increased up to 15 wt% silica but then decreased with further increase in silica content. However, the particle size was only marginally influenced by the silica content. The zeta potential of the composite particles slightly decreased with increasing silica content. With increasing VA-057 concentration, the PS microspheres were entirely coated with silica sol above 1.0 wt% initiator.

• Nuclear Engineering and Technology
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• 제34권2호
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• pp.117-131
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• 2002

Core disruptive accidents have been investigated at Korea Atomic Energy Research Institute(KAERI) as part of the work to demonstrate the inherent and ultimate safety of conceptual design of the Korea Advanced Liquid Metal Reactor(KALIMER), a 150 MWe pool- type sodium cooled prototype fast reactor that uses U-Pu-Zr metallic fuel. In this study, a simple method and associated computer program, SCHAMBETA, was developed using a modified Bethe-Tait method to simulate the kinetics and thermodynamic behavior of a homogeneous spherical core over the period of the super-prompt critical power excursion induced by the ramp reactivity insertion. Calculations of the energy release during excursions in the sodium-voided core of the KALIMER were subsequently performed using the SCHAMBETA code for various reactivity insertion rates up to 100 S/s, which has been widely considered to be the upper limit of ramp rates due to fuel compaction. Benchmark calculations were made to compare with the results of more detailed analysis for core meltdown energetics of the oxide fuelled fast reactor. A set of parametric studies were also performed to investigate the sensitivity of the results on the various thermodynamics and reactor parameters.

• 접착 및 계면
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• 제14권1호
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• pp.1-12
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• 2013

Core 입자로 methyl methacrylate (MMA), ethyl methacrylate (EMA)를 사용하고 shell 입자로 MMA, EMA, 2-hydroxyl ethyl methacrylate (2-HEMA), glycidyl methacrylate (GMA) 및 methacrylic acid (MAA)를 각각 사용하여 개시제 ammonium persulfate (APS), 유화제로 sodium dodecyl benzene sulfonate (SDBS)의 농도(0.01~0.03 wt%), 단량체의 종류와 조성을 변화시켜 수용성 유화중합으로 다중 core-shell복합입자를 제조하여 전환율, 입자경 및 입도분포, 평균분자량, 분자구조, 유리전이온도, 플라즈마 처리후의 접촉각, 등온열분해속도 및 인장강도를 각각 측정하여 다음과 같은 결론을 얻었다. SDBS 농도 0.02 wt%에서 MMA core-(EMA/GMA) shell 복합입자의 전환율이 98.5%로 우수하였고, 입자직경은 SDBS 농도 0.03 wt%에서 EMA core-(MMA/GMA) shell의 복합입자가 $0.48{\mu}m$로 높게 나왔다. 유리전이온도 측정으로부터 공중합체는 1~2개의 전이곡선 그리고 다중 core-shell 복합입자는 3개의 전이곡선을 얻었다. 전체적으로 접착박리강도의 크기는 shell 단량체가 MMA core인 경우 EMA/MAA > EMA/2-HEMA > EMA/GMA의 순으로 되었다.

• 한국환경보건학회지
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• 제30권5호
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• pp.395-401
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• 2004

In this study, lots of methods have been studing to utilize energy and decrease contaminated effluents. There has been great progress on IGCC (Integrated gasification combined cycle) to reduce thermal energy losses. The following results have been conducted from desulfurization experiments using waste shell to remove $H_{2}S$. Unreacted core model ior desulfuriration rate prediction of sorbent was indicated. These were linear relationship between time and conversion. So co-current diffusion resistance was conducted reaction rate controlling step. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. Maximum desulfurization capacity was observed at 0.631 mm for lime, oyster and hard-shelled mussel. The kinetics of the sorption of $H_{2}S$ by CaO is sensitive to the reaction temperature and particle size at $800^{\circ}C$, and the reaction rate of oyster was faster than the calcined limestone at $700^{\circ}C$.