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나재식 ( Jae Sik Na ) 한국키틴키토산학회 2009 한국키틴키토산학회지 Vol.14 No.3
Chitosan에 초음파 분해는 초기반응에서 효율이 가장 높고, 반응시간에 따라 감속되어 진행되며, 2시간의 실험조건하에서 약 35~40%의 분해효율을 나타내었다. 다분산도에는 큰 영향이 없는 것으로 관찰되어 초음파 분해에 대한 일정한 pattern이 있을 것으로 추정되었다. 반응효율 및 반응속도에서 반응온도는 중요한 변수로서, 50℃의 고온보다는 10℃의 저온에서 반응효율이 높고, 30℃의 실온 영역에서 분해효율이 10% 증가된 가장 높은 효율을 나타내었다. Cavitation energy변화에 따른 cavitation의 형성과 용액내 고분자 사슬의 유동성이 변수로 고려되며, 이러한 변수들의 최적조건이 고효율의 초음파 분해반응을 만드는 것으로 판단되었다. Chitosans of different molecular weight are usually prepared by various hydrolysis methods such as acid hydrolysis, oxidative degradation method, enzyme hydrolysis method, a microbial method, mechanical energy methods. Ultrasonic degradation of the mechanical methods has been proved to be a highly effective method for degrading macromolecules because it reduces their molecular weight simply by splitting the most susceptible chemical bond of the chain. The purpose of this study was to examine the effect of temperature on variation of physicochemical properties of ultrasonicated chitosan in acetic solution, inferred by reduction in solution viscosity, molecular weight and polydispersity. The ultrasonic conditions were studied in parameters of temperature and reaction time with ultrasonic power at 200W. Ultrasonic degradation has been characterized by colloid titration method, ubbelohde viscometer, and gel permeation chromatography. Results show that the intrinsic viscosity and the molecular weight of chitosan in acetic acid solution were decreased by ultrasonic reaction, and chitosan was more easily degraded in lower temperature than in higher temperature. The ultrasonic degradation rate of chitoan can be accelerated at room temperature.
류마트스 : 22세 남자에서 시상경색으로 나타난 신경정신루푸스 1예
나지선 ( Ji Sun Na ),정재식 ( Jae Sik Jung ),백종훈 ( Jong Hyun Bak ),기영재 ( Young Jae Ki ),김윤성 ( Yun Sung Kim ),김현숙 ( Hyun Sook Kim ) 대한내과학회 2012 대한내과학회지 Vol.82 No.6
전신홍반루푸스는 상대적으로 가임기 여성에서 흔하게 나타나지만 본 증례는 젊은 성인남자에서 전정신경 안진을 동반한 시상경색으로 나타난 신경정신루프스를 고용량 스테로이드와 싸이클로포스파마이드 충격요법을 사용하여 성공적으로 치료한 사례로 이에 고찰과 함께 보고하는 바이다. Systemic lupus erythematosus (SLE) is an autoimmune disease that can manifest systemically in many organs. It is most common in women of child-bearing age. Neuropsychiatric SLE is characterized by central nervous system (CNS) symptoms. CNS manifestations of SLE have been discovered in all parts of the brain, although thalamic infarcts associated with SLE are rare, especially in males. Here, we report a thalamic infarction in a 22-year-old male SLE patient.
폴리에틸렌 왁스와 무수 말레인산의 그라프팅 중합 반응에서 용매가 미치는 영향
유시원,최중소,나재식,Yu, Si-Won,Choi, Joong-So,Na, Jae-Sik 한국자원리싸이클링학회 2014 資源 리싸이클링 Vol.23 No.1
본 연구에서는 고밀도 폴리에틸렌 제조공정에서 부산물로 생성되는 폴리에틸렌 왁스를 대상으로 무수말레인산을 그라프트 반응 시킬 때, 반응 용매가 가지는 성질의 영향에 대해서 조사하였다. 측정결과, 자일렌이 톨루엔보다 우수한 모노머 용해성, 팽윤성, 혼화성을 가지며, 그라프트 반응을 더욱 촉진함을 알 수 있었고, 반응 용매의 함량에 따라서는 0 ~ 200% v/w영역에서 200% v/w 조건이 최대의 그라프트 율을 보이고, 그이상의 용매가 사용될 경우에는 그라프트 율이 다시 감소하다가 일정해짐을 확인하였다. 가교도 함량 값은 용매 존재 하에 거의 생성되지 않았으며, 용매가 용매분자로 사슬이동반응 시켜 가교반응을 방지하는 것으로 판단되었다. $140^{\circ}C$에서 측정된 용융 점도 값은 폴리에틸렌 왁스에 무수말레인산이 그라프트 된 후에 증가하는 경향을 보임을 알 수 있었다. In this study, we have investigated the influence of the nature of solvent on the grafting reaction of maleic anhydride onto polyethylene wax obtained as a by-product in a high density polyethylene plant. The results show that the grafting ratio in xylene as a solvent was higher than toluene. This is because xylene has excellent monomer solubility, swelling property and miscibility. It has been also observed that grafting degree shows an initial jump in percentage of grafting with increasing amount of solvent, from 0% v/w to 200% v/w giving maximum grafting in 200% v/w and then slightly decreases on further increase in the amount of solvent and becomes almost constant. It can be also seen that gel content was not formed under the use of solvent. It means that solvent prevented cross-linking reaction due to chain transfer reactions to solvent molecules. Studies of melt viscosity at $140^{\circ}C$ showed that viscosity increased after grafting of maleic anhydride onto polyethylene wax.
이용윤 ( Yong Yoon Lee ),나재식 ( Jae Sik Na ) 한국키틴키토산학회 2014 한국키틴키토산학회지 Vol.19 No.4
A chitosan hybridized acrylic emulsion was prepared by emulsion polymerization using chitosan and acrylic monomers such as methyl methacrylate (MMA), 2-ethyl hexylacrylate (2-EHA), acrylic acid (AA). With increasing amounts of chitosan in the emulsion, the efficiency of the emulsion reaction has produced similar results, and the particle size and viscosity in emulsion increased with increasing chitosan content. It was shown that chitosan existed both in polymer particles and in water phases, and was strongly related to the particle size and its distribution. It is assumed that chitosan has a important role on the properties of chitosan acrylic composite film by the emulsion polymerization.
제니핀에 의해 가교된 다공성 젤라틴/키토산 지지체의 조직공학적 특성 분석
배민수 ( Min Su Bae ),김성은 ( Sung Eun Kim ),나재식 ( Jae Sik Na ),권일근 ( Il Keun Kwon ) 한국조직공학과 재생의학회 2010 조직공학과 재생의학 Vol.7 No.2
Blended natural polymers composed of β-chitosan (Cs) and gelatin (G) with various composition ratios were produced as candidate materials for biomedical application. Novel cross-linked porous scaffold compared of gelatin/chitosan 7:3 5:5 3:7 and different amounts of genipin concentration (0.001, 0.01 and 0.03 mg/ml). Genipin was used to crosslinking agent of gelatin/β-chitosan blends, promoting the formation of primary amine and tertiary amine between chitosan and gelatin, or by itself. The effects of composition and crosslinking on the physical-chemical properties of GCs composite scaffolds were evaluated by ATR-FTIR analysis, water uptake, degradation and in vitro cell viability test. The SEM analysis showed that the pore size of gelatin/chitosan porous scaffolds were increased with increasing blend ratio of chitosan. The ATR-FTIR showed that the amount of amine group of gelatin/ chitosan was decreased with increasing genipin concentration. As the genipin concentration in the scaffold decreased resulting in an enhanced water uptake ability. In this study, NIH3T3 cells were seeded gelatin/β-chitosan porous scaffolds for the cell cytotoxicity, cell proliferation. The porous scaffolds did not affect cell growth because of low cytotoxicity. The porous cross-linked scaffold with the improved characterization and cell viability may be suitable as a biocompatable scaffold for tissue engineering.