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RISS 인기검색어
- 검색키워드
- 저자 : 김관우 (검색결과 56 건)
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활성산소종 및 저산소 조건하에서 능동적 약물방출위한 페로센 나노입자개발
A slightly acidic and hypoxic environment is found in common solid cancers. Nanoparticles containing ferrocene and azobenzene groups can control drug release by the concentration of reactive oxygen species (ROS) and oxygen. In this study, ferrocenylmethyl methacrylate (FMMA) - Methacrylic acid (MA) - [Methacrylic acid – 4,4’-Azodianiline – Azobenzene-4,4′-dicarboxylic acid – Doxorubicin (MA-DOX)] random copolymer, i.e., ferrocene and azobenzene polymers containing groups were synthesized through radical polymerization. And, ferrocene-doxorubicin-containing nanooparticles (FDNPs), which are highly reactive to tumor microenvironments, were prepared using the synthesized polymer. The spherical FDNPs synthesized had a diameter of about 120-150 nm and an average surface charge of -33.6 mV. FDNPs reacted sensitively to H₂O₂ and Na₂S₂O₄ used as ROS and hypoxia models respectively, and it was confirmed that they were completely degraded after 24 hours. In addition, the drug release controlled by the tumor microenvironment suggests that the prepared FDNPs have great potential as drug carriers to effectively treat various cancers.
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Purpose: Intracerebral hemorrhage (ICH) is one of the devastating types of stroke and has a high risk of morbidity and mortality. Human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) have potential to help the brain damage recovered following ICH. The purpose of this study is to identify beneficial effects of the transplantation of hUCB-MSCs in the ICH rat model and investigate whether hUCB-MSCs may have the ani-inflammatory properties by neurotrophic factors or cytokines for ICH brain. Material & Method: hUCB-MSCs were transplanted in collagenase induced ICH rat model. At 2, 9, 16, 30 days after ICH, rotarod test and limb placement test were performed to measure behavioral outcomes. ICH rats were sacrificed to evaluate volume of lesion using H&E staining. Neurogenesis, angiogenesis, anti-apoptosis in the brain tissue of the rats was examined by immunofluorescence staining at 4 weeks after transplantation. Anti-inflammatory factors [TNF-, COX-2, microglia and neutrophil were analyzed by immunofluorescence staining, RT-PCR and Western blot at 3 days after transplantation. Results: hUCB-MSCs transplantation after ICH was associated with the effect of neurological benefits and reducing volume of lesion. hUBC-MSCs treated group revealed high level of neurogenesis, angiogenesis and anti-apoptosis at 4 weeks after transplantation. The expression of inflammatory factors were decreased in rats of hUCB-MSCs treated group compared with rats of control group. Conclusion: Our study suggests that hUCB-MSCs may improve neurological outcome and modulate inflammation-associated immune cells and cytokines in ICH-induced inflammatory responses.
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지구화학적 반응을 고려한 역학적 계면활성제-CO2 폼 공법 모델링
To enhance the oil recovery, hybrid surfactant-CO2 foam flood introduces synergetic effects including improved mobility, wettability, permeability reduction. A comprehensive description of the destruction/regeneration of foam is of importance for the accurate estimation of oil recovery. Coupled with geochemical reaction model, the mechanistic model of the surfactant-CO2 foam has been developed to describe the destruction/regeneration reactions of the foam. Because the CO2 has solubility into brine, geochemical reactions, incorporated with the dissolved CO2, influence the destruction/regeneration of foam. The model has been examined to simulate surfactant-CO2 foam floods with and without geochemical reactions in multi-layered reservoir. Compared with continuous CO2 injection, the synergetic effects of hybrid foam flood processes are manifested for foam floods with and without geochemical reactions. When geochemical reactions are not considered, the hybrid foam flood increases oil recovery by 19.9% over CO2 injection. The in-situ destruction/regeneration of foam are affected by geochemical reactions, especially mineral dissolution. The mineral dissolution increases the concentration of dissolved CO2 in brine by 7%, as a result leads to influencing the destruction/regeneration of surfactant-CO2 foam contributing to the synergetic effects. Consequently, foam flood with geochemical reactions produces less oil recovery by 5.3% in comparison to that without geochemical reactions. Therefore, an assessment of geochemical reactions is of importance for an accurate prediction of the surfactant-CO2 foam flood. 계면활성제-이산화탄소 폼 공법은 유동도 비 개선, 습윤도 변화, 투과도 감소의 시너지 효과를 통해 오일 회수율을 높일 수 있다. 오일 회수율을 정확하게 예측하려면 폼의 생성/분해 반응을 포괄적으로 묘사하는 것이 중요하다. 본 연구에서는 지구화학 반응과 연계한 역학적 계면활성제-이산화탄소 폼 모델을 개발하여 생성/분해 반응을 표현하였다. 수용성 이산화탄소는 지구화학 반응을 통하여 폼의 생성과 분해 반응에 영향을 미친다. 다층 저류층에서 지구화학 반응 포함 및 비포함 모델을 이용하여 폼 공법을 시뮬레이션하였다. 이산화탄소 연속주입 공법과 비교하면 복합 폼 공법에 의한 시너지 효과가 두 모델 모두에서 나타났다. 지구화학 반응을 고려하지 않았을 때 이산화탄소 주입 공법에 비해 계면활성제-이산화탄소 폼 공법의 오일 회수율이 19.9% 증가하였다. 저류층 내 폼 분해/생성 반응은 방해석 용해 반응의 영향을 크게 받는다. 방해석 용해로 인하여 염수 내 용존 이산화탄소 농도가 7% 증가함에 따라 폼의 생성/분해 반응 속도에 영향을 준다. 결과적으로 지구화학 반응을 고려한 폼 모델의 오일 회수율은 비고려 모델에 비해 5.3% 낮게 나타났다. 계면활성제-이산화탄소 폼 공법을 정확하게 예측하기 위하여 지구화학 반응을 반영하는 것이 중요함을 확인하였다.
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본 논문은 군용 공중폭발탄에 사용하는 고주파 발진기의 수신감도 안정화에 관한 것으로 고도의 정확도와 안정된 동작성능이 발휘되도록 동작시의 에러 확률을 최소화 하여, 그 성능을 극대화시키기 위한 방법의 하나로 시뮬레이션과 매우 유사한 형태인 통계적 모델링 방법을 제안하고, 그것을 증명하였다. 제안된 방법은 실제 사용 환경 하에서도 항상 일정하고 안정된 출력성능이 발휘되도록 회로를 구성하고 있는 각 부품들 중 회로에 가장 큰 영향을 미치는 핵심인자를 선정하여 각각의 상호관계를 고려한 최적 해를 구하고, 구하여진 최적 해를 이용하여 출력의 안정화를 꾀할 수 있는 조합조건을 만드는 것으로 실험 모델은 실제 사용 중인 제품을 대상으로 하였으며, 사전 실험 계획법인 DOE(Design of Experiment)에 기초하였고, 그 결과로부터 도출된 데이터와 그것의 통계적인 해석을 통하여 새로운 형태의 방정식을 구하였다. 그리고 그를 바탕으로 각각의 전자 부품을 조합하여 항상 일정한 출력을 구현 할 수 있도록 모델링 하고, 그 결과에 기초하여 제작한 제품의 실험결과를 모델링 데이터와 비교하고, 그 유용성 및 정확도, 정밀도를 입증하였다.
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열원 모델링 기법 개발에 의한 레이저 응용 가공 공정해석
Laser-applied machining is dependent on absorbed energy density into workpiece. Generally, the absorptivity of laser beam is dependent on wave length of laser, materials, surface roughness, etc. Various shapes and energy densities for beam irradiation can be used to laser-applied machining. In this thesis, efficient method of heat source modeling was developed and designed by using one or two fundamental experimental trials. And then, various laser-applied machinings were simulated by using commercial FEM code MARC. Designed model of heat source of laser beam has been applied to thermal boundary conditions for FEA. The designed model is defined by surficial or volumetric heat flux in MARC. Moreover, it was considered that route of moving heat source was linear or helical type. Analysis model was a plate or a cylinder. A fine mesh has been used for areas in contact with the laser beam since they experienced a complicated thermal sequence of momentary heating and cooling. Properties of the material were dependent on temperature. The volumetric heat flux has been applied to thermal analysis for pulsed laser welding and defined with shape factors and energy densities. The shape factors and the energy density were determined by comparing fusion zones of analytical and experimental results for two beam powers. A proportional expression of the shape factors and energy density was developed for various beam powers and was used to model the heat source. The surficial heat flux has been applied to thermal analysisses for cutting, surface hardening and LAM(Laser Assisted Machining). It was mathematically defined with shape factors and energy density. The shape factors could be determined by using a burn pattern or a profile for irradiation of laser beam. And then, the value of energy density was determined with comparisons of analytical and experimental results for one condition of beam power. FE analysisses of various laser machining were conducted using commercial FE software. The simulated results were confirmed by experimental trials with the same condition. The following conclusions may be drawn. 1. The efficient method of heat source modeling was developed and needs one or two fundamental experimental trials. Various laser-applied machining should be rapidly simulated. Therefore, the developed method of heat source modeling will be a very useful to set thermal boundary condition of FEA 2. For various laser-applied machining, the simulated results were in good agreement with experimental results. These analytic studies will be useful to predict machining zone, to analyze mechanism of thermal machining, etc. in the field. 3. Laser breaking of glass was simulated to optimize breaking condition. Various shapes of heat sources were applied to the analysis and the distance between heating and cooling source were varied for each simulation. The shapes of heat sources were circle, single and double ellipse and the distance was varied from 0 to 30 mm. As a result, double elliptical shape of heat source was the most suitable among them in laser breaking of glass. And it should be useful to determine optimal condition of laser breaking for glass. 4. In the pulsed laser welding simulation, a heat source model for selecting the pulse laser beam conditions was successfully designed using a comparison of the FE simulation results and experimental data. A proportional expression of the shape factors and the maximum energy density was developed by comparing simulated results with experimental trials and used to model the heat source for various beam powers. The simulated results agreed closely with experimental data obtained under the same conditions. 5. Prediction of the fusion zone and temperature distribution with the designed heat source at various beam powers and welding velocities was verified experimentally. This means that the approach proposed in this thesis is effective at determining suitable laser beam conditions for various variables in pulsed laser welding. 6. Laser surface hardening for rod-shaped workpiece was successfully simulated. Route of moving heat source is helical type. Hardened zone was predicted at various laser, shape of irradiation, working distance, measuring point, etc. The simulated results agreed closely with experimental data obtained under the same conditions. The analytic approach in this thesis is effective at determining suitable conditions for laser heat treatment and it is useful to save time and cost in the heat treatment industry. 7. In these studies of LAM for cast iron and ceramic, simulations and experiments with various contents were carried out for determining suitable conditions of pre-heating and laser-assisted turning process. Temperature distribution of cutting zone could be predicted by simulation. In the LAM for pressureless sintered Si3N4 ceramic, the suitable temperature of cutting zone will be between 1000 and 1400 ℃.
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복잡계 네트워크 구조 위에서 전파되는 정보의 동역학적 특성에 관한 연구
I study social contagion models on various social networks with asymmetric interaction. In order to investigate the diversity of information, I map the information values of the height of the interface. From the numerical simulations, I find that the width does not satisfy the well-known Family-Viscek finite-size scaling ansatz on searching low dimensional lattices. The dynamic exponent should be modified for the studied model. On 1-d lattices, I find that the width diverges in the thermodynamic limit. This means that there are many pieces of information that compete with each other on 1-d lattices due to the limited path to spread the information. However, On 2-d lattices, I show that two different phases are depending on the value of the control parameters. From the numerical simulation, I find that the width decreases in the thermodynamic limit. When both the information creation rate, , and feedback parameter, , are relatively large. On the other hand, When and are small, I find that the width goes to in the thermodynamic limit. Therefore, On 2-d lattices, The investigated model undergoes a transition from rough phase to flat phase depending on the values of and . I also study the information diversity on both the random networks and scale-free networks. On random networks, the Cayley state value of the width does not depend on and . This corresponds to the smooth phase in the kinetic roughening phenomena. However, I find that the width diverges in the thermodynamic limit on the scale-free networks. This means that the model is in a rough phase. These results indicate that the studied model undergoes a transition between rough phase and smooth phase depending on the underlying topology.
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Calcineurin inhibitor 와 Mycophenolate mofetil의 병용요법이 간이식 이후 후기거부반응을 줄일수 있는가
INTRODUCTION: With advances in immunosuppression, graft and patient survival rates have significantly increased, but acute cellular rejection still remains an important problem following liver transplantation. Compared to early acute rejection, late-onset acute rejection occurs in a smaller percentage of recipients, and with important sequelae. Some risk factors for late acute rejection have been identified. Yet, the cause of late-onset acute rejection (LAR) has not been fully investigated. The efficacy of Mycohonolic acid (MMF) administered in combination with Calcineurin inhibitor (CNI) for reduction of LAR has been demonstrated. AIM: To investigate the incidence and risk factors of LAR and impact of combination therapy of CNI with MMF for LAR. METHODS: Liver transplantation (LT) of 402 cases was performed in our center from January of 2006 to August of 2007. Adult LT recipient (n=309) were enrolled in this study. Biopsy-proven acute rejection that occurred more than 6months after LT was defined as late-onset acute rejection. Our immunosupprssion regimens were classified CNI single or CNI with MMF group used continuous for at least 6months after LT. Steroid was early tapered within 3months. We analyzed LAR including factors affecting its occurrence, immunosuppression group (CNI or CNI+MMF) and outcome. The median follow up period was 34.8months (range 25-46). RESULTS: LAR was observed in 17 cases (5.5%) and one recipient of 17 cases diagnosed chronic rejection. She expired due to fetal pneumonia p.o 15months. The incidence of LAR in CNI single (N=126) or CNI with MMF group (n=166) were 8.6%(n=12), 2.9%(n=5), respectively(p=0.015). Multivariate Cox-regression confirmed CNI single versus CNI with MMF therapy to be associated with a decreased risk of LAR (relative risk, 0.33, p=0.04). CONCLUSION: Incidence of LAR in CNI with MMF group was significantly lower than CNI single group. Consequently, Continuous use of CNI with MMF may offer a better immunosuppression regimen to decrease rate of LAR.
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모바일 환경에서의 개인문서 정리를 위한 폴더 템플릿 프로바이더
최근 모바일 디바이스와 웨어러블 디바이스의 보편화로 인하여 개인이 유지 및 관리해야 하는 문서의 수가 점차 많아 지고 있다. 이렇게 관리해야 하는 문서의 수는 점차 많아지고 있지만, 이를 효과적으로 관리할 수 있는 체계에 대한 연구는 그리 많지 않다. 이러한 이유로 컴퓨터 사용에 익숙하지 못한 사용자들은 개인문서를 유지 관리하는 것에 어려움을 겪고 있다. 따라서 본 논문에서는 컴퓨터 사용에 익숙하지 못한 사용자를 대상으로 개인문서의 체계적인 정리를 위한 폴더 템플릿을 제시하고, 또한 이를 이용하여 사용자에게 실질적으로 도움이 될 수 있는 Topic기반 문서접근 방법을 제시한다.
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