• Polymer(Korea)
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• v.35 no.5
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• pp.483-487
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• 2011

For the preparation of effective non-vascular drug eluting stent (DES), pullulan acetate (PA) was investigated as a coating material for polytetrafluorethylene (PTFE)-covered stent. PA was coated on PTFE-covered stent (PTFE-stent) by dip coating technique, and then its surface morphology, drug release behavior and cellular toxicity were tested. Field emission-scanning electron microscopy (FE-SEM) result indicated that its surface was smoother after PA coating without any cracking. The sustained release behavior of paclitaxel from PA-coated PTFE membrane was observed for 80 days. Also, the biological stability of paclitaxel in the membrane was confirmed by annexin V binding assays. Furthermore, the antitumor activity was demonstrated by an in vivo test against CT-26 murine colorectal tumors. From the results, we concluded that PA was expected as a useful coating material to design an effective non-vascular DES.

• Polymer(Korea)
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• v.33 no.3
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• pp.219-223
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• 2009

The nanofibers fabricated by using an electrohydrodynamic process has been used as various applications, such as nano-device, filtering system, protective clothes, wound dressing, and drug delivery system (DDS). Of these applications, the DDS should be needed to minimize side effects of drugs, maximize the properties of medicine, and efficiently deliver the required amount of drugs to the diseased area. In this paper, by using the electro spinning process, which is one of electrohydrodynamic processes, two different types, polycarprolactone and poly(ethylene oxide)/Rhodamine B, of electrospun mats were fabricated layer by layer and the release behavior of Rhodamine B was characterized with time. In addition, to show the feasibility of DDS of this type, we tested release behavior of a peptide of the nanofiber system, a PCL/(Peptide+PEO)/PCL nanofiber mat. The released peptide did not loss biological activities. From these results, we believe that the layered nanofiber mat as a DDS has enough function of a new drug delivery system.

• Proceedings of the Korean Vacuum Society Conference
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• 2009.08a
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• pp.310-310
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• 2009

• 월간산업보건
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• s.42
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• pp.25-28
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• 1991

산업현장에서는 대단히 많은 화학물질이 원료, 기타 용도로 이용되고 있으며, 근로자는 항상 폭로 내지는 중독의 위험을 받고 있다. 따라서 그 관리를 함에 있어서는 산업에서 쓰이는 화학물질의 종류와 양, 사용공정, 근로자의 폭로 상황에서부터 폐기에 이르기까지 모든것을 파악함과 동시에 그 작업환경관리, 작업관리 및 건강관리에 관해서 법규나 실제를 상세하게 알아둘 필요가 있다. 1. 관리는 기본적으로 법규에 의거하여 실시되는데, 여기에는 최소한의 규칙이 있으며, 실제 관리에 있어서는 임기응변의 최대한 노력이 필요하다. 2. 환경관리를 하는데는 기본적으로 허용농도가 이용되며, 국제적으로는 생물학적 한계치가 제창되어 응용되고 있다. 3. 법규 또는 독성에 의거하여 특정 화학물질, 기타 각종 호칭이 쓰이고 있으며 이러한 단어는 어떤내용을 지니고 있기 때문에 충분하게 정립해 둘 필요가 있다. 4. 화학물질에 의한 중독예는 해마다 감소되고 있는데 반하여 때로 대참사를 일으키는 수도 많아서 예전부터 화학물질에 의한 급성중독에서부터 만성장기폭로로 인한 영향에 대해 관심을 모으고 있다. 특히 직업성암에 대한 문제가 대두되고 있다. 5. 사고성 대량방출이나 산소 결핍증에는 구조자나 제3자에 대한 이차성 피해가 발생되기 쉬우므로 이 점에 주의를 요한다. 6. 일반환경으로의 방출로 인해 주민에게 미치는 영향도 주의해야 한다. 7. 근로자는 화학물질의 위험성에 대하여 잘 알지 못하거나 습관적인 취급으로 인해 주의가 산만해지기 때문에 충분한 보건교육이 있어야 한다. 8. 화학물질에 의한 건강장해예방의 기본은 발생억제, 격리, 제거(배기), 체내 침입방지, 장해예방(건강진단, 생활 등)이다.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.205-210
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• 2008

Poly(D,L-lactide-co-glycolide) (PLGA) has been widely used as carriers in controlled release delivery systems due to its biodegradability and relatively good biocompatibility. However, Release pattern of carriers fabricated using PLGA have disadvantage an initial burst within a few days, lag time several days and then sudden release changes. To solve these problems of PLGA, we fabricated PLGA wafer including monomer. Also, drug release behavior restraint sudden burst effect using recrystallization of PLGA. Recrystallized PLGA was characterized the morphological difference by SEM and in vitro release behavior measured by HPLC. The PLGA molecular weight analyzed to recognize monomer influence during degradation process of polymer using GPC. In this study, drug release duration cut short up to three days and was eliminated the lag time based on the bulk erosion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.409-415
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• 2017

This study examines the effect of pay dispersion on labor productivity by focusing on the inflow of newcomers into the tournament and the outflow of stayers from the tournament. According to tournament theory, the expansion of pay dispersion within the organization contributes to enhanced organizational performance by attracting high performers externally and by removing low performers internally within the organization. However, previous studies regarding tournament theory have overlooked the participant aspects. Therefore, this study explores how external hiring and involuntary turnover influence the effect of pay dispersion on labor productivity. This paper hypothesizes that pay dispersion will have a positive effect on labor productivity. Moreover, this paper predicts that the inflow of new competitors will strengthen the positive effects of pay dispersion on labor productivity, whereas the outflow of incumbents will weaken this relationship. Empirical results showed that pay dispersion increased labor productivity and the inflow of newcomers strengthened this positive relationship. However, contrary to our prediction, the outflow of incumbents weakened the positive effect between pay dispersion and labor productivity. These theoretical arguments and empirical findings highlight the proper conditions should be equipped to practically achieve the positive effect of pay dispersion on labor productivity.

• Polymer(Korea)
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• v.31 no.3
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• pp.201-205
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• 2007

Biodegradable polymers such as polylactide, polyglycolide and poly (lactide- co-glycolide) (PLGA) have been extensively investigated because of easily controlled drug release rate, completely degradable materials without the toxic by-product, and good biocompatibility. But, according to the bulk erosion property of PLGA in vitro test, it had the disadvantage that first-order release reduced releasing amount slowly after excessive initial burst. In this study we used PLGA powder obtained through recrystallization to revise bulk erosion property of PLGA. The PLGA used in this study was prepared by vacuum drying method and to estimate release profiles of BCNU loaded PLGA wafer. We also evaluated the release profile of drug with the water soluble additive. It was found that the drug loaded PLGA recrystallized by vacuum drying method exhibited the initial burst and the constant rate of drug release compared to that prepared by a conventional method.

• Polymer(Korea)
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• v.27 no.1
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• pp.9-16
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• 2003

Ipriflavone (IP) stimulates proliferation and differentiation of osteoblast and also enhances calcitonin secretion in the presence of estrogen. Poly(lactide-co-glycolide) (PLCA) due to its controllable biodegradability and relatively good biocompatibility is one of the most significant candidates for the study of drug controlled release system. In this study, IP-loaded PLGA microspheres (MSs) was prepared by using conventional O/W solvent evaporation method. The size of MSs was in the range of 5~200 $mu extrm{m}$. The morphology of MSs was characterized by SEM. And, in vitro release amounts of IP were analyzed by HPLC. The highest encapsulation efficiency were obtained by using gelatin and polyvinyl alcohol (PVA) as emulsifiers. The morphology, size distribution, and in vitro release pattern of MSs were changed by several preparation parameters such as molecular weights (8, 20, 33 and 90 kg/mol), polymer concentrations (2.5, 5, 10 and 20%), emulsifier types (PVA, gelatin and Tween 80), initial drug loading amount (5, 10, 20 and 30%) and stirring speed (250, 500 and 1000 rpm). The release of IP in vitro was more prolonged over 30 days, with close to zero-order pattern by controlling the preparation parameters. The physicochemical properties of IP-loaded PLGA MSs were investigated by XRD and DSC.

• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.39-44
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• 2000

We reinvestigate UV line emissions of 44i Boo, W UMa, AW UMa and VW Cep, which are indicaters of chromospheric activity of these stars. C I, C II, C IV, Si IV lines show significant variation in orbital phase. Among those lines, the Line of C IV showed the strongest line flux. while other Si IV and N V lines showed relative low line intensities. 44i Boo emitted the strongest flux than other stars. UV light curves of target stars shoed UV maximum at phase around 0.2 an 0.8 Such UV emissions are generally believed to be observed at the active regions and contacting parts of the two stars due to the clear visibility at the phase 0.2 and 0.8. Total emissivity of four transitions lines lead to conclude that the activity of this region is 40 times larger than the quiet sun. It is obvious that the activity decrease according to increase period. We obtained also Mg II light curve of AW UMA and VW Cep. These stars showed more clearly phase-dependent light curves. We estimated effective temperature of two star, AW UMa and VW Cep, using by Mg II flux.

• Polymer Science and Technology
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• v.24 no.5
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• pp.481-487
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• 2013