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Mechanism of Albumin Release from Alginate and Chitosan Beads Fabricated in Dual Layers
남윤식,배민수,김성원,노인섭,서준교,이강봉,권일근 한국고분자학회 2011 Macromolecular Research Vol.19 No.5
Biocompatible polysaccharides, such as alginate and chitosan are widely used as drug carriers. Microspheres based on the electrostatic interaction between these two polymers have been attractive as a means to deliver protein drugs because the use of organic solvents can be avoided during their preparation. On the other hand, the mechanisms for drug release, such as disintegration of microspheres, are not completely understood. This paper examined the phenomena of disintegration of the core-shell type microspheres consisting of alginate and chitosan. The microspheres formed by either chitosan-coated alginate or alginate-coated chitosan were generated using a labmade instrument consisting of a syringe pump connected to a glass nozzle. Using fluorophore-labeled polysaccharides,the disintegration of each polymer layer from the microspheres was monitored as a function of time. The alginate-coated chitosan microspheres demonstrated enhanced stability with increasing concentration of the chitosan core. The presence of an alginate shell itself also increased the stability of the microsphere compared to the microspheres without an alginate coating. The chitosan concentration, however, did not have any effect on the stability of the chitosan-coated alginate microspheres. The microspheres synthesized with alginate in the core demonstrated concentration-dependent stability. In these microsphere experiments, the microsphere stability was found to be related directly to the protein release kinetics. In the alginate/chitosan-based microspheres, the disintegration property is the primary factor modulating the encapsulated drug release, which suggests the easiest simple method for time-dependent protein drug delivery.
직접 수치 모사법을 이용한 섬유 강화 복합재료의 열팽창계수 예측
남윤식(Youn-Sic Nam),오민환(Min Hwan Oh),김광식(Kwang Sik Kim),조진연(Jin Yeon Cho) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.9
본 논문에서는 직접 수치 모사 기법을 이용해 섬유 강화 복합재료의 열팽창계수를 예측하였다. 직접 수치 모사 기법을 통해 구한 열팽창계수 예측치와 실험치의 비교를 통해 본 논문에서 제안한 직접 수치 모사 기법을 이용하면 인위적인 가정을 최소화하면서 기존의 방법과 유사하게 복합재료 열팽창계수를 예측할 수 있음을 확인하였다. 또한 섬유 체적비 변화에 따른 열팽창계수의 변화를 예측하고 그 경향성을 고찰하였다. In this paper, thermal expansion coefficients of fiber-reinforced composite materials are predicted by direct numerical simulation. From comparing the predicted results with experimental results, it is confirmed that direct numerical simulation gives similar results to the previously proposed methods while minimizing artificial assumptions. Additionally trend of variation in thermal expansion coefficients is investigated according to the fiber volume fraction.
김현철,남윤식,김병철,김기일,김기성,Kim, Hyun Chul,Nam, Yun Sik,Kim, Byoung Chul,Kim, Ki Il,Kim, Ki Sung 한국자동차안전학회 2017 자동차안전학회지 Vol.9 No.1
Small Overlap test decided on IIHS (Insurance Institute for Highway Safety) evaluates a robustness of the car body and a passenger injury protection. A current vehicle is satisfied with a robustness of the car body for Small Overlap test but not meet the requirements of passenger injuries because it is difficult to inquire into the actual state of injury mechanism for Small Overlap test. The study shows the new injury mechanism which represents the relation between a structure of the vehicle placed with the lift foot and the low extremity injury.
NMR methods for structural analysis of RNA: a Review
김낙균,남윤식,이강봉 한국자기공명학회 2014 Journal of the Korean Magnetic Resonance Society Vol.18 No.1
In last three decades, RNA molecules have been revealed to play the central roles in many cellular processes. Structural understanding of RNA molecules is essential to interpret their functions, and many biophysical techniques have been adopted for this purpose. NMR spectroscopy is a powerful tool to study structures and dynamics of RNA molecules, and it has been further applied to study tertiary interactions between RNA molecules, RNA-protein, and RNA-small molecules. This short article accounts for the general methods for NMR sample preparations, and also partially covers the resonance assignments of structured RNA molecules.