• Nuclear Engineering and Technology
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• 제25권2호
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• pp.265-275
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• 1993

증기폭발이 발생하면 파괴적인 동력에너지가 방출될 가능성이 있으므로. 이 현상은 원자력 발전소 안전성 연구 분야에서 중요한 현상으로 지목되어 왔다. 따라서 증기폭발이 미치는 영향을 분석하기 위해서는 폭발시 수반되는 열에너지가 동력에너지로 전환되는 비율을 정확히 해석할 수 있어야 한다. 그러나, 정확한 해석 방법의 개발이 이루어지지 않은 현 상황에서는 순수히 이론에 근거한 열역학적 해석 방법 등을 이용할 수 있으며 이러만 접근 방식은 그 결과가 보수적이라는데 그 의미가 있다. 본 논문에서는 현재까지 알려진 열역학적 해석 방법들을 정리하였고. 이론적으로 모순된 부분을 수정하여 비교하였다. 지금까지 알려진 바와는 달리. Hicks-Menzies 모델과 Board-Hall 모델은 에너지 전환율에서 동일한 결과를 나타냄을 보였다. 또한 증기폭발에서 냉각수 포기 기공율의 영향을 계산, 검토하였으며, 금속의 발열반응의 영향을 분석할 수 있는 열역학적 모델을 제시하였다.

• Applied Biological Chemistry
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• 제25권4호
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• pp.248-251
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• 1982

3가지 단백질과 CBG250과의 반응에 의해서 생성되는 복합체(複合體)의 분광학적(分光學的) 성질(性質)과 결합당량(結合當量)을 측정(測定)하였다. CBG250은 사용한 몇 가지 용매(溶媒)에 따라 최대흡광파장(最大吸光波長)$({\lambda}_m)$이 이동(移動)하였으며, ethanol용액 중 $({\lambda}_m=610nm)$에서 흡광계수(吸光係數)는 82.4, 몰 흡광계수(吸光係數)는 $70.4{\times}10^3$이었다. CBG250은 ethanol―인산(燐酸)―수용액(水溶液)에서 갈색$({\lambda}_m=465nm)$을 가지나 일단 단백질과 결합하면 청색(靑色)$({\lambda}_m=590nm)$으로 변환되었으며, 파장(波長) 590nm에서의 흡광도(吸光度)와 단백질 함량(含量) 사이에는 제한된 범위에서 비례관계를 나타냈다. 반응조건에서 단백질과 CBG250은 신속하게 복합체(複合體)를 형성하였다. 단백질의 CBG250에 대한 결합당량(結合當量)은 단백질의 종류(種類)와 함량(含量)에 따라 현저하게 변하였다. BSA, Cytochrome C, ${\gamma}-globulin$의 그것은 각각 110, 103, $88{\mu}g\;$CBG250/100{\mu}g$ protein이었다.

• 전기학회논문지
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• 제65권4호
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• pp.628-634
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• 2016

This paper demonstrates a microfluidic electrochemical sensor for detecting endocrine disruptor such as estradiol at a very low concentration by using preconcentration technique. In addition, self-assembled monolayer(SAM) was also employed on the working electrode of the electrochemical sensor in order to increase the estradiol capture efficiency of the sensor. SAM treatment on the working electrode enhanced the specific binding between the surface of the working electrode and the estradiol antibody. The estradiol antibody was applied on the working electrode at different concentrations(10, 20, 50, 100, 200 pg/ml) for observing the concentration dependency. The measured electrochemical redox current changed with the amount of the bound estradiol on the Au working electrode surface and the sensor can detect all the target material when the immobilized antibody amount is more than the estradiol amount in the water. The elecrochemical estradiol sensor without SAM treatment showed a low current of 7.79 nA, while the sensor treated with SAM resulted in 339 nA at 200 pg/ml, which is more than 40 fold higher output current. When combining the preconcentration technique and the SAM-treated electrode, the measured current became more than 100 fold higher than that of the sensor without neither SAM treatment nor preconcentration technique. The combination of these two techniques can would enable the proposed microfluidic electrochemical sensor to detect a very low concentration endocrine disruptor.

• BMB Reports
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• 제35권4호
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• pp.389-394
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• 2002

$[Ru(bpy)_2(dppz)]^2+$ (bpy=2,2'-bipyfidine, dppz=dipyrido[3,2-a:2',3'-c]phenazine) (RuBD), a long-lifetime metal-ligand complex, displays favorable photophysical properties. These include long lifetime, polarized emission, but no significant fluorescence from the complex that is not bound to DNA. To show the usefulness of this luminophore (RuBD) for probing the bending and torsional dynamics of nucleic acids, its intensity and anisotropy decays when intercalated into supercoiled and relaxed pTZ18U plasmids were examined using frequency-domain fluorometry with a blue light-emitting diode (LED) as the modulated light source. The mean lifetimes for the supercoiled plasmids (< $\tau$ >=148 ns) were somewhat shorter than those for the relaxed plasmids (< $\tau$ >=160 ns). This suggests that the relaxed plasmids were shielded more efficiently from water. The anisotropy decay data also showed somewhat shorter slow rotational correlation times for supercoiled plasmids (288 ns) than for the relaxed plasmids (355 ns). The presence of two rotational correlation times suggests that RuBD reveals both the bending and torsional motions of the plasmids. These results indicate that RuBD can be useful for studying both the bending and torsional dynamics of mucleic acids.

• 생명과학회지
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• 제5권2호
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• pp.25-25
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• 1995

The antitumor activities of the cell bound polysaccharide(CBP), water soluble polysaccharide(WSP) and sulfated polysaccharide(SP) of Zoogloea sp. were observe. The results obtained were as follows : 1) The CBP, WSP, and SP showed cytotoxic effect on the Meth A cells in vitro, however, the effect of CBP and WSP was more ten-fold greater than that pf SP. 2) When CBP, WSP, and SP was inoculated into the peritoneal cavity of the Meth A cells transplanted mice, the average survival days tended to prolonged slightly as compared with the control. 3) When Meth A cells were transplanted subcutaneously into the back side of mice, and then CBP, WSP, and Sp was inoculated into the peritoneal cavity of mice, the tumor growth inhibition ratio was 46.9% for WSP, 40.4% for CBP, and 16.2% for SP. 4) The phagocytic activity of peritoneal macrophages elicited with CBP, WSP, and SP was significantly increased than that of control. 5) The production of nitric oxide in the peritoneal macrophages stimulated with CBP, WSP, SP, and LPS aloneo was not increased than that of control. The production of nitric oxide in the peritoneal macrophages stimulated with IFN-r and CBP, IFN-r and WSP and IFN-r and SP was significantly increased than that of control, but in the case of stimulated with IFN-r and WSP was increased 50% for CBP and SP. These results suggest that the CBP, WSP and SP of Zoogloea sp. showed direct cytotoxic effect and tumor growth inhibition on Meth A cells in vitro and in vivo, and induced nitric oxide production of activated macrophages.

• Biomaterials and Biomechanics in Bioengineering
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• 제1권2호
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• pp.95-104
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• 2014

The objective of this study was to evaluate the cytotoxicity of poly (lactic acid) (PLA) nanoparticles. We used a water-soluble, amphiphilic phospholipid polymer, poly (2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (PMB30W), as a stabilizer for the PLA nanoparticles. The PLA nanoparticles and PMB30W-modified PLA (PLA/PMB30W) nanoparticles were prepared by evaporating tetrahydrofuran (THF) from its aqueous solution. Precipitation of the polymers from the aqueous solution produced PLA and PLA/PMB30W nanoparticles with a size distribution of $0.4-0.5{\mu}m$. The partial coverage of PMB30W on the surface of the PLA/PMB30W nanoparticles was confirmed by X-ray photoelectron spectroscopy (XPS) and dynamic light-scattering (DLS). A high-content automated screening assay (240 random fields per group) revealed that the PLA nanoparticles induced apoptosis in a mouse macrophage-like cell line (apoptotic population: 73.9% in 0.8 mg PLA/mL), while the PLA/PMB30W nanoparticles remained relatively non-hazardous in vitro (apoptotic population: 13.8% in 0.8 mg PLA/mL). The reduction of the apoptotic population was attributed to the phosphorylcholine groups in the PMB30W bound to the surface of the nanoparticle. In conclusion, precipitation of PLA in THF aqueous solution enabled the preparation of PLA nanoparticles with similar shapes and size distribution but different surface characteristics. PMB30W was an effective stabilizer and surface modifier, which reduced the cytotoxicity of PLA nanoparticles by enabling their avoidance of the mononuclear phagocyte system.

• 한국대기환경학회지
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• 제28권1호
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• pp.39-51
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• 2012

Aerosol slurry samples were collected in 60-min interval using Korean Semi-continuous Elements in Aerosol Sampler (KSEAS) between May 19 and June 6, 2010 at an urban site of Gwangju. The $PM_{2.5}$ samples were collected with a flow rate of 16.7 L/min and particles are grown by condensation of water vapor in a condenser maintained at ${\sim}5^{\circ}C$ after saturation by direct injection of steam. The resulting droplets are collected in a liquid slurry with a airdroplet separator. Concentrations of 16 elements (Al, Fe, Mn, Ca, K, Cu, Zn, Pb, Cd, Cr, Ti, V, Ni, Co, As, Se) in the collected slurry samples were determined off-line by ICP-MS. KSEAS sample analysis encompassed the sampling periods for which 24-hr average elemental species concentrations were calculated for comparison with those derived from 24-hr integrated filter samples. Relationship between elemental species measured by two methods indicated high correlation coefficients (r), mostly greater than r of 0.80. However, we note that concentrations of Al, K, Ca, Mn, and Fe, which are often associated with crustal elemental particles, in the KSEAS samples, were substantially lower (1.4~11 times) than those found in the typical filter-based samples. This discrepancy is probably due to difficulties in transferring insoluble dust particles to the collection vials in the KSEAS. Temporal profiles of elemental concentrations indicate that some transient events in their concentrations are observed over the sampling periods. For the elemental species studied, atmospheric concentrations during the transient events increased by factors of 4 in Mn~80 in Zn, compared to their background levels. Principle component analyses were applied to the hourly KSEAS data sets to identify sources affecting the concentrations of the metal constituents observed. In this study, we conclude that hourly measurements for particle-bound elemental constituents were extremely useful for revealing the short-term variability in their concentrations and developing insights into their sources.

• 미생물학회지
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• 제38권4호
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• pp.287-292
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• 2002

봄철 cyanobarteria가 우점하는 천호지에서 fluorescent in situ hybridization (FISH) 방법을 이용하여 세균군집구조를 조사하였다. 조사기간동안 총세균수는 0.6～$1.3{\times}10^7 \cells{\cdot}ml^-1$ 의 범위로 매우 높게 나타났다. 또, 총세균수에 대한 eubacterial group이 차지하는 비율의 경우 29.8～45.8%로 작은 분포를 차지하였다. 세균군집구조를 분석한 결과, $\alpha$-group은 1.4～l2.5%, $\beta$-group은 0.9～4.9%, $\gamma$-group은 0.6～8.3%, $\circledcirc$Cytophaga-Flavobacteruim group은 1.0～8.3%를 나타내어 본 연구에서 조사된 각 group이 차지하는 비율은 낮고 상대적으로 unknown eubacteria의 비율이 높았다. 이러한 군집구조는 일반적으로 다른 담수호에서 나타나는 세균의 군집구조와는 다른 군집구조 이며 특히, aggregates에 부착한 세균 군집구조와 비슷한 양상이었다. 또, cyanobacteria의 조성 이 Anabaena속에서 Microcystis속으로 천이가 일어난 시기에 Cytophaga-Flavobacteruim group이 크게 증가하는 것으로 나타나 세균군집의 크기는 식물플랑크톤의 영향을 받는 것으로 확인되었다.

• Composites Research
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• 제28권2호
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• pp.70-74
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• 2015

본 논문에서는 탄소나노튜브(CNT)와 마이크로 글래스 버블(GB)을 포함한 폴리아마이드 6(PA6) 복합재의 열전 특성을 다뤘다. 복합재에 포함된 GB은 복합재 내에서 큰 공간을 차지하게 되는데, 이때 CNT는 GB가 없는 공간으로 밀려나면서 고밀도로 격리된(segregated) 네트워크를 형성한다. CNT의 분산을 위해, 소니케이션(Sonicatoin)으로 CNT를 분산시킨 PA6, 포름산 용액을 증류수를 이용하여 응고시킨 후 압축성형하여 복합재 판을 제조하였다. 복합재 판의 열전성능을 평가하기 위해서 열전도도, 전기전도도, 제벡계수(Seebeck coefficient) 등을 측정하였고, 최고 0.016의 성능지수를 얻었다.

• Tribology and Lubricants
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• 제33권5호
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• pp.228-233
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• 2017

Chemical Mechanical Polishing of chemically stable sapphire substrates is dominantly affected by the mechanical processing of abrasives, in terms of the material removal rate. In this study, we investigated the effect of electrostatic force between the abrasives and substrate, on the polishing. If potassium chloride (KCl) is added to slurry, water molecules are decomposed into $H^+$ and $OH^-$ ions, and the amount of ions in the slurry changes. The zeta potential of the abrasives decreases with an increase in the amount of $H^+$ ions in the stern layer; consequently, the electrostatic force between the abrasives and substrate decreases. The change in zeta potential of abrasives in the slurry is affected by the slurry pH. In acidic zones, the amount of ions bound to the abrasives increases if the amount of $H^+$ ions is increased by adding KCl. However, in basic zones, there is no change in the corresponding amount. In acidic zones, zeta potential decreases as molar concentration of potassium increases; however, it does not change significantly in basic zones. The removal rate tends to decrease with increase in molar amount of potassium in acidic zones, where zeta potential changes significantly. However, in basic zones, the removal rate does not change with zeta potential. The tendencies of zeta potential and that of the frictional force generated during polishing show strong correlation. Through experiments, it is confirmed that the contact probability of abrasives changes according to the electrostatic force generated between the abrasives and substrate, and variation in removal rate.