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Park, K.,Bae, K.H. North-Holland Pub. Co 2014 Nuclear engineering and design Vol.278 No.-
Concentration on a hydrogen explosion mitigation strategy increased after the accident in Fukushima. A passive autocatalytic recombiner (PAR) is considered as the most realistic mitigation technology during a severe accident where electric power is lost. Hydrogen distribution and concentration might be accurately predicted because PAR must be installed in a place having a proper amount of hydrogen in order to produce positive performance. In this paper, hydrogen distributions and concentrations were predicted and analyzed during hydrogen release from different direction failure places, and then PAR installation was examined. The result shows that the hydrogen concentrations are randomly changed in the containment overall, and the behavior of hydrogen in the case of upper part failure is completely different from the case of a side part failure. It is expected that PAR works well in the area among small compartments located at the lower part of the containment building; however, the performance of PAR installed on another area is inferior.
A potent reporter applicable to the monitoring of caspase-3-dependent proteolytic cleavage
Park, K.,Kang, H.J.,Ahn, J.,Yi, S.Y.,Han, S.H.,Park, H.J.,Chung, S.J.,Chung, B.H.,Kim, M. Elsevier Science Publishers 2008 Journal of biotechnology Vol.138 No.1
In this study, we developed a chimeric caspase-3 substrate (GST:DEVD:EGFP) comprised of glutathione-S transferase (GST) and enhanced green fluorescent protein (EGFP) with a specialized linker peptide harboring the caspase-3 cleavage sequence, DEVD. Using this reporter, we assessed the proteolytic cleavage of the artificial caspase-3 substrate for caspase-3. The common feature of this approach is that the presence of the DEVD sequence between GST and EGFP allows for caspase-3-dependent cleavage after the Asp (D) residue, resulting in the elimination of EGFP from the GST:DEVD:EGFP reporter. To the best of our knowledge, this study reports the first application employing a chimeric protein substrate, with the similar accuracy level compared to the conventional methods such as fluorometric assays. As a result, using this GST:DEVD:EGFP reporter, caspase-3 activation based on proteolytic properties could be monitored via a variety of bioanalytical techniques such as immunoblot analysis, glutathione-agarose bead assay, and on-chip visualization, providing both technical and economical advantages over the extensively utilized fluorogenic peptide assay. Our results convincingly showed that this versatile reporter (GST:DEVD:EGFP) constitutes a useful system for the monitoring of caspase-3 activation, potentially enabling the monitoring of the proteolytic activities of different intra-cellular proteases via the substitution of the cleavage sequence within the same schematic construct.
Park, K.,Park, J.,Lee, S.,Cho, H.j.,Kang, M. Pergamon Press ; Elsevier [distribution] 2012 Atmospheric environment Vol.62 No.-
Size-resolved chemical constituents (organics, sulfate, nitrate, ammonium, and chloride) of nonrefractory submicrometer particles were measured in real time using a quadruple aerosol mass spectrometer (QAMS) at an urban area of Gwangju, Korea in the fall (8/30/2011-9/19/2011) and winter (12/19/2011-12/30/2011). Organics were found to be the most dominant chemical species (~50%) in the total aerosol mass loading. The average mass concentrations of organics were 4.7 +/- 1.8 μg m<SUP>-3</SUP> and 6.3 +/- 1.8 μg m<SUP>-3</SUP> in the fall and winter, respectively. The organics increased in the morning and evening times, and decreased in the afternoon in both the fall and winter, with a more pronounced diurnal pattern observed in the winter. The ratio of m/z 44 to organics and sulfate increased significantly in the afternoon, which is contrary to the behavior of the total organics, suggesting that intense photochemical activity led to the production of oxidized organics and sulfate in the afternoon. The average sulfate concentration was 1.8 μg m<SUP>-3</SUP>, which was the lowest reported in East Asian countries due to there being few SO<SUB>2</SUB> emission sources around the sampling site. The most significant difference in concentrations between the fall and winter was found for nitrate; the concentration was ~4 times higher than in the fall (2.45 μg m<SUP>-3</SUP> versus 0.62 μg m<SUP>-3</SUP>). It was also observed that sulfate, nitrate, and chloride were fully neutralized by the ammonium in the winter, whereas these anions were not fully neutralized in the fall. Size distribution data showed that sulfate had only one D<SUB>va</SUB> peak at 600 +/- 100 nm, regardless of season, and that organics had one peak (600 +/- 100 nm) in the fall and a bimodal distribution (200 +/- 100 nm and 600 +/- 100 nm) in the winter. The absence of the first mode (i.e., D<SUB>va</SUB> ~200 nm) in organics in fall and the higher ratios of m/z 44 to organics in fall (0.10 +/- 0.02) than winter (0.07 +/- 0.01) suggest that oxidized organic species would be more dominant than hydrocarbon-like organics. Air-mass dependent concentrations of species showed that the northwest air mass (i.e., long-range transported from industrial areas in China) and southeast air mass (i.e., transported from industrial area in Korea) were mainly responsible for the high loadings of organics and sulfate.
Park, K.,Paulino, G.H. Pergamon Press ; Elsevier Science Ltd 2012 Engineering fracture mechanics Vol.93 No.-
A potential-based cohesive zone model, so called the PPR model, is implemented in a commercial software, e.g. ABAQUS, as a user-defined element (UEL) subroutine. The intrinsic cohesive zone modeling approach is employed because it can be formulated within the standard finite element framework. The implementation procedure for a two-dimensional linear cohesive element and the algorithm for the PPR potential-based model are presented in-detail. The source code of the UEL subroutine is provided in Appendix for educational purposes. Three computational examples are investigated to verify the PPR model and its implementation. The computational results of the model agree well with the analytical solutions.