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Koo, Jaseung,Koga, Tadanori,Li, Bingquan,Satija, Sushil K.,Rafailovich, Miriam H. American Chemical Society 2016 Macromolecules Vol.49 No.9
<P>We investigated the effect of density fluctuation of supercritical carbon dioxide (scCO(2)) on anomalous swelling of multilayer polymer thin films On the ridge in the pressure temperature phase diagram of CO2. In order to measure the swelling ratio along the film depth, we alternatively deposited hydrogenated poly(methyl Methacrylate) (PMMA) and deuterated polystyrene (dPS) thin films and performed the neutron reflectivity measurements as a function of CO2 pressure at 36 degrees C. The results showed that, in contrast to previous studies, CO2 was to penetrate deeply:throughout the, multilayer thin film where the magnitude of swelling along the density fluctuation ridge of CO2 was independent of film thickness. Block copolymer thin films of dPS-b-PMMA with a parallel lamellar orientation also showed similar swelling behavior in scCO(2). However, it is well-known that single-layer polymer thin films exhibit anomalous swelling behavior only the film surface. This difference is probably due to the fact that the multilayer thin films have the CO2-philic PMMA layer sandwiched between dPS layers, which can function, as a CO2 reservoir, thereby transferring the CO2 molecules from the PMMA layers to the adjacent dPS layers. Furthermore, we found that the interaction between polymers and substrates was not significant in scCO(2) from diffusion dynamics results using neutron reflectivity, thereby facilitating anomalous dilation of polymers near the substrates without a pinning effect.</P>
Control of Anti-Thrombogenic Properties: Surface-Induced Self-Assembly of Fibrinogen Fibers
Koo, Jaseung,Galanakis, Dennis,Liu, Ying,Ramek, Alexander,Fields, Adam,Ba, Xiaolan,Simon, Marcia,Rafailovich, Miriam H. American Chemical Society 2012 Biomacromolecules Vol.13 No.5
<P>Wound healing is a complex process initiated by the formation of fibrin fibers and endothelialization. Normally, this process is triggered in a wound by thrombin cleavage of fibrinopeptides on fibrinogen molecules, which allows them to self spontaneously-assemble into large fibers that provide the support structure of the clot and promote healing. We have found that the fibrous structures can also form without thrombin on most polymer or metal surfaces, including those commonly used for stents. We show that the relatively hydrophobic E and D regions of the fibrinogen molecule are adsorbed on these surfaces, exposing the αC domains, which in turn results in the formation of large fiber structures that promote endothelial cell adhesion. We show that the entire process can be suppressed when stents or other substrates are coated with polymers that are functionalized to bind the αC domains, leading to the development of potentially nonthrombogenic implant materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bomaf6/2012/bomaf6.2012.13.issue-5/bm2015976/production/images/medium/bm-2011-015976_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bm2015976'>ACS Electronic Supporting Info</A></P>
A Study on Solidification of Uranium Contaminated Soil Waste Based on Glass-ceramization
Jaewoong Hwang,Jaseung Koo,Keunyoung Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
The decommissioning of nuclear-related facilities at the end of their design life generates various types of radioactive waste. Therefore, the research on appropriate disposal methods according to the form of radioactive waste is needed. This study is about the solidification of uranium contaminated soils that may occur on the site of nuclear facilities. A large amount of radioactively contaminated soil waste was generated during the decommissioning of the uranium conversion plant in KAERI, and research on the proper disposal of this waste has been actively conducted. Numerous minerals in the soil can become glass-ceramic through the phase change of minerals during the sintering process. This method is effective in reducing the volume of waste and the glassceramic waste form has excellent mechanical strength and leaching resistance. In this study, the optimum temperature and time conditions were established for the production of glass-ceramic sintered body of soil. The compressive strength and leachability of the sintered body made by applying the optimal conditions to simulated waste was confirmed. The basic physicochemical properties of simulated soil waste were identified by measuring the pH, moisture content, density, and organic matter content. The elemental compositions in the soil was confirmed by XRF. Soils were classified by particle size, and each sample was compressed with a pressure of 150 MPa or more to prepare a green body. Based on the TG-DSC analysis, an appropriate heating temperature was set (>1,000°C), and the green body was maintained in a muffle furnace for 2~6 hours. The optimal sintering conditions were selected by measuring the compressive strength and volume reduction efficiency of the sintered body for each condition. The difference between the green body and sintered body was observed by XRD and SEM. In the experiments for evaluation of additives, the selected chemical substances were mixed with the soil sample in a rotator. Based on the results of TG-DSC, sintered body was made at 850°C, and the compressive strength and volume reduction were compared. Based on the results, the most effective additive was determined, and the appropriate ratio of the additive was found by adjusting the range of 1~5 wt%. This study was confirmed that the sintered soil waste showed sufficient stability to meet the disposal criteria and effective volume reduction for final disposal.
Effect of Additives for the Stabilization of Radioactive Soil Waste by Glass Composite Materials
Jaewoong Hwang,Keunyoung Lee,Jaseung Koo 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1
As the design life of nuclear power plants are coming to the end, starting with Kori unit 1, nuclear power related organizations have been actively conducted research on the treatment of nuclear power plant decommissioning waste. In this study, among various types of radioactive waste, stabilization and volume reduction experiments were conducted on radioactive contaminated soil waste. Korea has no experience in decommissioning nuclear power plants, but a large amount of radioactively contaminated soil waste was generated during the decommissioning of the KAERI research reactor (TRIGA Mark- II) and the uranium conversion facility. This case shows the possibility of generating radioactive soil waste from nuclear power plants and nuclear-related facilities sites. Soil waste should be solidified, because its fluidity and dispersibility wastes specified in the notification of the Korea Nuclear Safety and Security Commission. In addition, the solidified waste forms should have sufficient mechanical strength and water resistance. Numerous minerals in the soil are components that can make glass and ceramics, for this reason, glass-ceramic sintered body can be made by appropriate heat and pressure. The sintering conditions of soil were optimized, in order to make better economical and more stable sintered body, some additives (such as additives for glass were mixed) with the soil and sintering experiments were conducted. Uncontaminated natural soil was collected and used for the experiment after air drying. Moisture content, pH, bulk density, and organic content were measured to understand the basic properties of soil, and physicochemical properties of the soil were identified by XRD, XRF, TG, and SEM-EDS analysis. In order to understand the distribution by particle size of the soil, it was divided into Sand (0.05–2 mm) and Fines (< 0.05 mm). The green body was manufactured in the form of a cylinder with a diameter of 13mm and a height of about 10mm. Appropriate pressure (> 150 MPa) was applied to the soil to make a green body, and appropriate heat (> 800°C) was applied to the sintered body to make a sintered body. The sintering was conducted in a muffle furnace in air conditions. The volume reduction and compressive strength of the sintered body for each condition were evaluated.