• Biotechnology and Bioprocess Engineering:BBE
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• 제6권5호
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• pp.326-331
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• 2001

With the aim of developing of pH-sensitive controlled drug release system, a poly(Llysine) (PLL) based cationic semi-interpenetrating polymer network (semi-IPN) has been synthesized. This cationic hydrogel was designed to swell at lower pH and de-swell at higher pH and therefore be applicable for achieving regulated drug release at a specific pH range. In addition to the pH sensitivity, this hydrogel was anticipated to interact with an ionic drug, providing another means to regulate the release rate of ionic drugs. This semi-IPN hydrogel was prepared using a free-radical polymerization method and by crosslinking of the polyethylene glycol (PEG)-methacrylate polymer through the PLL network. The two polymers were penetrated with each other via interpolymer complexation to yield the semi-IPN structures. The PLL hydrogel thus prepared showed dynamic swelling/de-swelling behavior in response to pH change, and such a behavior was influenced by both the concentrations of PLL and PEG-methacrylate. Drug release from this semi-IPN hydrogel was also investigated using a model protein drug, streptokinase. Streptokinase release was found to be dependent on its ionic interaction with the PLL backbones as well as on the swelling of the semi-IPN hydrogel. These results suggest that a PLL semi-IPN hydrogel could potentially be used as a drug delivery platform to modulate drug release by pH-sensitivity and ionic interaction.

• Archives of Pharmacal Research
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• 제16권2호
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• pp.129-133
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• 1993

Temperature sensitive liposomes(TSL) containing adriamycin (ADM) and cytarabine (Ara-C) were prepared. ADM and Ara-C were selected as model compounds of amphiphilic and hydrophilic drug, respectively. Encapsulation efficiency of ADM entrapped into TSL was about twice greater than that of Ara-C. It might be due to different polarity of the drug, Lipid compositions of TSL had no effect on the encapsulation efficiency of drugs. Thermal behavior of TSL using a differential scanning calorimetry (DSC) was also investigated. Phase transition of TSL using a differential scanning calorimetry (DSC) was also investigated. Phase transition temperature $(T_c)$ of TSL was dependent on the lipid compositions of TSL ADM broadened thermogram of TSL but Ara-C did not. However, $T_c$ of TSL was not changed by any drug. Release rate of drugs was highly dependent on temperature. The release profile of ADM was similar to that of Ara-C. The maximum release rate of drugs from TSL was occurred at the near $T_c$ and observed at $39-41^\circ{C}$ for DPPC (Dipalmitoylphosphatidylcholine) only, $52-54^\circ{C}$ for DPPC and DSPC (1:1), respectively. Effect of human serum alburmin (HAA) on the release rate of ADM was investigated. HSA had no significant effect on the release of ADM below $T_c$. However, ADM release from TSL was increased at the near and above $T_c$. The HSA-induced leakage of drug may result from the interaction of liposomal constituents with HSA structure at the near TEX>$4^\circ{C}$. From the fact that the release profiles of ADM from freshly prepared TSL and stored TSL for 1 week at TEX>$4^\circ{C}$ was not changed, the TSL was considered to be stable for at least 1 week at TEX>$4^\circ{C}$. Based on these findings, TSL may be useful to deliver drugs to preheated target sites due to its thermal behaviors.

• 방사성폐기물학회지
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• 제5권1호
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• pp.53-64
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• 2007

고연소도 경수로사용후핵연료를 이용하여 voloxidation 및 소결 열처리 공정으로부터 세슘의 시간에 따른 방출 거동을 실험적으로 평가하였다. 사용후핵연료 voloxidation 공정에서는 fragment 형태의 시편을 사용하여 최대 $1,500^{\circ}C$의 산화 및 환원 분위기에 따른 세슘 방출 거동을 상호 비교하였으며, 소결 공정에서는 압분체를 이용하여 4% H2/Ar 환원분위기 에서 열처리 온도 변화에 따른 세슘방출 특성 변화를 분석하였다. 산화 분위기에서 fragment 형태의 사용후핵연료로부터 세슘 방출 온도 구간은 $800{\circ}C{\sim}1,200^{\circ}C$였으며, 환원 분위기에서 압분체로부터 방출 온도 구간은 $1,100{\circ}C{\sim}1,400^{\circ}C$로서, 산화에 의한 사용후핵 연료의 분말화가 세슘 방출 거동에 영향을 미치는 것으로 나타났다. 아울러 사용후핵 연료로부터 세슘 방출 거동에 영향을 미치는 주요 인자는 사용후핵 연료내 세슘 화합물의 화학적 형태뿐만 아니라 결정립 및 핵연료 표면으로의 확산 속도에 지배를 받음을 알 수 있었다.

• Macromolecular Research
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• 제14권5호
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• pp.530-538
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• 2006

There are three important components in tissue engineering: the cells, signaling factors (cytokines and growth factors), and scaffolds. To obtain finely engineered tissue, all three components should perform their individual functions and be fully integrated with each other. For the past few years, we have studied the characteristics of photodimerizable HA (CHA)/alginate (CA) composite materials. CHA/CA complex hydrogels, which were irradiated under UV light and, then treated with calcium ions, were found to have good biocompatibility, mechanical properties and water resistance for implantable tissue scaffolds. In this study, we introduced a cell growth factor (basic fibroblast growth factor; bFGF) into the CHA/CA scaffolds and studied its release behavior. We also introduced tetracycline hydrochloride and flurbiprofen into the same scaffolds as model activation factors and evaluated their release behaviors from the scaffolds. The drug release rate from the materials was influenced by various parameters, such as the degree of crosslinking, the cross linker type, the physico-chemical properties of the drug, and the amount of the drug in the polymer. The results indicated that the negatively charged CHA/CA composite materials showed sustained release behavior and that HA has a particularly strong negative charge, making it attractive toward tetracycline hydrochloride and bFGF, but repulsive toward flurbiprofen.

• Asian-Australasian Journal of Animal Sciences
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• 제30권4호
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• pp.449-454
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• 2017

Recently, increasing attention has been paid to the welfare of farm animals, which have been evaluated using behavioral and physiological measures. However, so far, the measures have almost always been used to estimate poor welfare. In this review, firstly we focus on how oxytocin (OT) relates to positive social behavior, pleasure, and stress tolerance, and second on which management factors stimulate OT release. OT induces maternal and affiliative behaviors and has an anti-stress effect. Further, OT is produced during enjoyable events, and has positive feedback on its own release as well. Therefore, to some extent, the relationship of OT to positive normal behavior was mutually beneficial-heightened OT concentration owing to comfortable rearing conditions induces positive social behavior, which in turn may increase OT concentration. Hence, studies on animal welfare should pay more attention to increasing comfort and the stress tolerance, rather than only focusing on when stress occurs in farm animals.

• Journal of Pharmaceutical Investigation
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• 제26권2호
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• pp.125-135
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• 1996

Solid lipid nanoparticles(SLN) are particulate systems for parenteral drug administration and suitable for controlled release. SLN were prepared by homogenization process. Dispersion at increased temperature (molten lipid) was performed to yield SLN loaded with lipophilic drugs. Tetracaine base, lidocaine base, prednisolone, methyltestosterone and ethinylestradiol were used as model drugs to access the loading capacity and to study the release behavior. To investigate production parameters(lipids, surfactant concentration, homogenizing rpm) in the formation of SLN, particle size was performed by laser diffraction analysis. The mean particle size of SLN with stearic acid or trilaurin was below 1 micron. By decreasing the particle size and increasing the surfactant concentration, the release rate was increased especially in the case of highly lipophilic drug loaded SLN. Methyltestosterone or ethinylestradiol loaded SLN showed a distinctly prolonged release over a few days.

• Archives of Pharmacal Research
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• 제29권10호
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• pp.921-927
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• 2006

Prolonged release micro particles of clarithromycin (CL) were prepared using Eudragit RL 100 and RS 100 by spray-drying and casting-drying techniques. For the characterization of those microparticles, preparation yield, particle size distribution, X-ray diffraction, thermal behavior, active agent content and in vitro dissolution from the microparticles were performed. HPLC was used for the assay of clarithromycin and the assay method was validated. All the formulations obtained showed prolonged release when compared to pure clarithromycin. Microparticles prepared by spray-drying method had a slower release compared to those of casting drying method. Spray-drying method seems to be a more suitable method to prepare microparticles for prolongation in release.

• 한국ITS학회 논문지
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• 제16권1호
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• pp.38-49
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• 2017

일반적으로 철도운영기관에서는 수익성 극대화를 위해 티켓팅 해제시간을 적용하여 티켓을 판매하고 있다. 본 연구에서는 이같은 해제시간이 KTX 예매행태에 어떻게 영향을 미치는지를 분석하였다. 예매행태는 예매시간을 의미하며 예매시각과 출발시각의 차이로 계산하였다. 분석자료는 KTX 경부선 매표자료이며, 요일별 차이를 보기위해 평일(목요일)과 토요일, 일요일의 자료를 이용하였다. 예매시간에 미치는 요인으로 해제시각이외에 요일, 운행거리, 운행방향 등을 고려하였다. 분석결과, 대부분 출발 3시간 전에 티켓을 예매하는 것으로 나타났으며, 주말 상행노선 이용객의 경우 대부분이 출발 하루 전에 예매를 하는 것으로 나타났다. 또한 해제시간 전에는 상행노선, 장거리 구간, 일요일인 경우에 예매시간이 길게 나타났으며, 반면에 해제시간 이후에는 일요일인 경우와 장거리 구간인 경우에 예매시간이 짧게 나타났다.

• Fisheries and Aquatic Sciences
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• 제9권2호
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• pp.91-96
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• 2006

The movement range and diurnal behavior of 17 wild black rockfish (Sebastes schlegeli) were monitored within the marine ranching area of Tongyeong from 27 July to 7 November, 2005 using acoustic telemetry. Coded transmitters were surgically implanted into the abdomen of fish. Two of ten fish released in summer moved about 2 km away from the capture point for 1 day. The others stayed within a 500-m radius of the release point for 1 week after release. The seven fish released in autumn stayed within 500 m of the release point. Most fish were more active and had a greater range of horizontal diurnal movement at night than during the day. Additionally, the range of horizontal diurnal variation was greater in summer than in autumn. While fish released in summer were more vertically active at night than during the day, those released in autumn preferred to move vertically during the day.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 추계학술논문발표회 논문집
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• pp.3-6
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• 2008

Heat release characteristics of live fire load are an important parameter for performance oriented fire safety design of a building. While investigations have been carried out on the fire load and its burning behavior in office, residential and commercial buildings and so on, little effort has been paid for the rational treatment of fire load in bookstore. In this report, burning behavior of typical combustible objects in bookstore are studied by measuring heat release rates of bookshelf with book.