• Journal of Plant Biology
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• 제25권2호
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• pp.65-72
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• 1982

The oxygen consumption of fresh and aged slices of potato tuber was 40.6 and 168.0 ,$0_2$ $\mu$l/g fr $wt{\cdot}h$, respectively. After initial burst of oxygen consumption within 2 minutes(i.e., 40% for fresh and 12% for aged slices) in the treatmentof $50{\mu}M$ alantolactone, gradual decrease of respiration rate was observed during 3 hours of incubation. In case of the aged slices the initial burst of oxygen consumption was not observed by salicylhydroxamic acid (SHAM) or KCN. The combined effect of SHAM and alantolactone showed increase of 12%, while SHAM and KCN combination showed 60% decrease. In addition, the lipophilicity of cell membrane of onion inner epidermis was increased by lantolactone treatment. The results suggest that the primary effect of alantolactone on the cellular respiration may be associated with an alteration of lipophilic phase of cell membrane and a consequent increase of electron flow throuh the cytochrome system.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.867-872
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• 2011

For the prolonged delivery and sustained release rates of low molecular weight drugs, poly(lactic-co-glycolic acid) (PLGA) microparticles containing the drug SKL-2020 have been investigated. On increasing polyvinyl alcohol (PVA) concentration (from 0.2% to 5%), the size of microparticles decreased (from $48.02{\mu}m$ to $10.63{\mu}m$) and more uniform size distribution was noticeable due to the powerful emulsifying ability of PVA. A higher drug loading (from 5% to 20%) caused a larger concentration gradient between 2 phases at the polymer precipitation step; this resulted in decreased encapsulation efficiency (from 34.19% to 25.67%) and a greater initial burst (from 61.71% to 70.05%). SKL-2020-loaded PLGA microparticles prepared with different fabrication conditions exhibited unique release patterns of SKL-2020. High PVA concentration and high drug loading led to an initial burst effect by rapid drug diffusion through the polymer matrix. Since PLGA microparticles enabled the slow release of SKL-2020 over 1 week in vitro and in vivo, more convenient and comfortable treatment could be facilitated with less frequent administration. It is feasible to design a release profile by mixing microparticles that were prepared with different fabrication conditions. By this method, the initial burst could be repressed properly and drug release rate could decrease.

• 폴리머
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• 제29권3호
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• pp.260-265
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• 2005

약물의 서방화에 있어서 독성이 특히 강하거나 유효 치료영역이 좁은 약물일수록 초기 버스트는 매우 중요하다. 이러한 약물의 전달을 위한 단일층으로 이루어진 나노미립구의 이용은 표면에 존재하는 약물 때문에 초기 버스트가 커서 서방화에 적절치 못하다. 따라서 본 연구에서는 생분해성 고분자인 덱스트란과 락타이드-글리콜라이드 공중합체(PLCA)를 이용한 이중층 나노미립구를 제조하여 서방성 방출 거동을 보이는 약물 전달체 제조에 대한 연구를 수행 하였다. 덱스트란과 PLCA의 나노미립구는 W/O/W법을 이용하여 이중 에멀젼 과정을 통해 제조하였고 계면활성제로는 폴리(비닐 알코올)(PVA)을 사용하였다. 덱스트란의 생체외 방출 거동을 확인하기 위해 동결 건조된 시료를 직경 $3{\times}1mm$ 몰드를 이용하여 웨이퍼를 제조하여 증류수에서 7일간 방출 거동을 확인하였다. 이중층 나노미립구는 각각의 단일고분자로 이루어진 나노미립구에 비해 다른 방출거동을 보였다. 특히 유화제인 PVA농도가 $0.2\%$인 것이 0차 방출에 가까운 결과를 보였다. 본 실험을 통해 대조군인 물리적인 혼합 모델, 덱스트란 또는 PLGA로만 이루어진 웨이퍼 및 단일층 미립구에 비해 이중층 나노미립구의 내부물질인 덱스트란의 방출 거동이 서방형을 보임을 확인할 수 있었으며 PVA의 함량에 따라 방출 거동을 조절할 수 있었다.

• 한국통신학회논문지
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• 제31권6A호
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• pp.627-633
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• 2006

MBC(meteor burst communications)는 그 전송로의 많은 장점에도 불구하고 도통율이 수%이하로 낮다는 큰 결점이 있다. 이를 위해 큰 경제적 부담 없이 전송 채널의 도통율을 향상시키는 방법으로서 간단한 구조의 DS(Direct Sequence)시스템을 제안하였다. 제안된 DS 간이 수신방식은 동기신호의 포착이나 유지에 소요되는 시스템을 생략할 수가 있어서 MBC가 가지는 경제성을 만족시킬 수 있으나, 잡음의 영향을 크게 받아 도통율이 떨어지는 단점이 있다. 이를 위해 제안된 DS 시스템에 Transversal Filter회로를 적용하여 SNR을 6dB이상 향상시켰다. 이 방법으로 개선되는 효과는 수신신호가 약한 환경에서 보다 더 큰 것으로 나타나는데 시뮬레이션에 의하면 SNR이 약 6dB 개선되었을 때 평균 버스트 길이가 100ms인 것은 70%로 개선되어 170ms로 되고, 50ms환경에서는 130%개선되어 115ms가 되어 수신신호가 약한 환경에서 도통율이 크게 개선됨을 확인할 수 있었다.

• Journal of Korean Neurosurgical Society
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• 제51권4호
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• pp.203-207
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• 2012

Objective: The purpose of this prospective study was to evaluate the efficacy and safety of screw fixation without bone fusion for unstable thoracolumbar and lumbar burst fracture. Methods: Nine patients younger than 40 years underwent screw fixation without bone fusion, following postural reduction using a soft roll at the involved vertebra, in cases of burst fracture. Their motor power was intact in spite of severe canal compromise. The surgical procedure included postural reduction for 3 days and screw fixations at one level above, one level below and at the fractured level itself. The patients underwent removal of implants 12 months after the initial operation, due to possibility of implant failure. Imaging and clinical findings, including canal encroachment, vertebral height, clinical outcome, and complications were analyzed. Results: Prior to surgery, the mean pain score (visual analogue scale) was 8.2, which decreased to 2.2 at 12 months after screw fixation. None of the patients complained of worsening of pain during 6 months after implant removal. All patients were graded as having excellent or good outcomes at 6 months after implant removal. The proportion of canal compromise at the fractured level improved from 55% to 35% at 12 months after surgery. The mean preoperative vertebral height loss was 45.3%, which improved to 20.6% at 6 months after implant removal. There were no neurological deficits related to neural injury. The improved vertebral height and canal compromise were maintained at 6 months after implant removal. Conclusion: Short segment pedicle screw fixation, including fractured level itself, without bone fusion following postural reduction can be an effective and safe operative technique in the management of selected young patients suffering from unstable burst fracture.

• 한국통신학회논문지
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• 제18권7호
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• pp.980-988
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• 1993

본 논문에서는 멀티미디어 트래픽올 갖는 B-ISBN의 스위치/멀티플렉서 등에서 중요한 파라메타로 결정되는 버퍼 크기에 대한 트래픽의 성능을 분석하였다. 멀티미디어 트래픽은 포아송 분포 트래픽, 그리고 기하분포와 지수 분포의 ON 시간 주기 (버스트 분포)를 갖는 버 스트 트래픽이 혼합되는 트래픽으로 모델링 하였다. 멀티미디어 트래픽으로 모델링한 트래픽에 대해서 성능을 분석하고 양질의 서비스를 제공할 수 있는 셀손실률에 대한 버퍼의 크기를 제시 하였다. 시뮬레이션은 PC SIMSCRIPT II.5를 이용하였고 시뮬레이션 프로그램은 PREAMBLE, MAIN, INITIAL, ARRIVAL., DEPARTURE및 STOP·SIM의 모듈로 구성하였다. 특히 혼합된 트래픽의 시뮬레이션에서는 ARRIVAL모듈을 I, II로 나누고 셀을 각각의 모듈에서 독립적으로 발생시켜 시뮬레이션을 수행하였다. 시뮬레이션 모델링은 이벤트 스케줄링 (Event Scheduling) 방식을 적용하여 시행하였다.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.282-282
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• 1996

The purpose of this study was to prepare the nifedipine dry elixir (NDE) and coated nifedipine dry elixir (CNDE) containing nifedipine ethanol solution for improving the dissolution rate and bioavailability of nifedipine. NDE containing nifedipine and ethanol in wall materials of dextrin was prepared using a spray-dryer and then NDE was coated with eudragit acrylic resin to make CNDE. Shape and size of the NDE and CNDE were monitored by scanning electron micrograph and laser particle size analyzer In vitro dissolution tests were performed in simulated gastric and intestinal fluid. Bioavailability of NDE and CNDE were compared with drug powder suspension and commercial soft capsule after oral administration of the preparations to rats. NDE and CNDE are spherical in shape. Cross-sectional view of dry elixirs indicates the large inter cavity containing ethanolic drug solution in shell. Geometric mean diameter of NDE and CNDE is about 6.64 and 8.70 $\mu\textrm{m}$, respectively. Drug dissolution rate within first 5 min from NDE increased dramatically irrespective of dissolution medium. However, CNDE showed a particularly retarded dissolution rate in pH 1.2 simulated gastric fluid compared with NDE. The bioavailability of nifedipine in the NDE was increased dramatically compared with drug powder suspension. CNDE reduced initial burst-out plasma peak compared with NDE. CNDE as a sustained release delivery system could reduce the initial burst-out plasma peak due to controlling the release rate of nifedipine from NDE and maintain the effective plasma level over a longer period within therapeutic window with enhanced bioavailability of nifedipine.

• Journal of Pharmaceutical Investigation
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• 제41권6호
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• pp.323-329
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• 2011

In order to develop new protein carrier replacing poly(DL-lactic acid-co-glycolic acid) (PLGA) microspheres, succinylated pullulan acetate (SPA) was investigated to fabricate a long term protein delivery carrier. SPA microspheres loaded with lysozyme (Lys) as a model protein drug were prepared by a water/oil/water (W/O/W) double emulsion method. An acidity test of SPA copolymers after hydrolysis was performed to estimate the change of protein stability during releasing proteins from the microspheres. There was no pH change of SPA copolymers, but pH of PLGA polymers after hydrolysis was significantly decreased to around pH 2, indicating that the long-term stability of proteins released from SPA microspheres can be guaranteed. Loading efficiency of proteins into SPA microspheres was three times higher than those into conventional PLGA microspheres, indication of inducing stronger charge interaction between proteins and succinyl groups in SPA microspheres. Although initial burst behaviors were monitored in Lys-loaded SPA microspheres due to relatively strong hydrophilic succinyl segments in SPA microspheres, initial burst issues would be circumvented if the ratio of charge density of succinyl moieties and hydrophobic acetate groups is harmonically controlled. Therefore, in this study, a new attempt of protein delivery system was made and functional SPA was successfully confirmed as a new protein carrier.

• Archives of Pharmacal Research
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• 제8권3호
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• pp.159-168
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• 1985

In attempt to develop a drug delivery system using serum albumin microspheres, bovine serum albumin microspheres containing antitumor agent, cytarabine, were prepared. The shape, surface characteristics, size distribution, behavior of in vitro distribution, drug release behaior, and degradation of albumin microspheres in animal liver tissue homogenate and proteolytic enzyme were investigated. The shape of albumin microspheres was spherical and the surface was smooth and compact. The size distribution of the albumin microspheres was affected by dispersion forces during emulsification and albumin concentration. Distribution of albumin mirospheres after intravenous administration in rabbit was achieved immediately. In vitro, albumin microsphere matrix was so hard that it retained most of cytarabine except initial burst during the first 10 minutes, and the level of drug release during the initial burst was affected by heating temperature, drug/albumin concentration ratio and size distribution. After drug release test, the morphology of albumin micropheres was not changed. Albumin microsphere matrix was degraded by the rabbit liver tissue homogenate and proteolytic enzyme. The degree of degradation was affected by heating temperature.

• 한국항행학회논문지
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• 제13권3호
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• pp.337-343
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• 2009

본 논문에서는 D8PSK 변조 방식을 이용하는 VDL Mode-2 수신기에 적용 가능한 버스트 모드 심벌 타이밍 복원기를 제안하고 성능 분석과 연동실험을 실시하였다. IIR 루프필터를 사용하여 심볼 타이밍 에러를 최소화 하는 방식은 수렴 속도가 늦기 때문에 버스트 모드에 적용하기 곤란하다. 즉 빠른 수렴 특성이 중요시 된다. 본 논문에서 제안한 방식은 프리앰블을 이용하여 초기 동기가 이루어진 후 최대 심벌 전력을 갖는 방향으로 한 샘플 빠르게 또는 한 샘플 느리게 샘플 클럭을 이동하여 최적의 심벌을 취하는 방식이다. 제안된 방식을 적용한 수신기와 호주 ADS사 송신 장비와 연동 시험한 결과 100 ppm 이상에서도 잘 동작함을 확인하였다.