전기방사를 이용하여 지름이 제어된 공액 고분자 나노섬유 제조 및 이에 기반한 태양전지 특성 분석

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2012. 8. 박종래.태양전지는 빛을 흡수하여, 전력을 생산하는 기기로, 전하를 수집하는 전극과 생성하는 광활성층으로 이루어져 있다. 광활성층이 유기 물질로 된 경우, 유기 태양전지라 하며, 일반적으로 전자 주개 물질과 전자 받개 물질을 잘 섞어, 벌크 이종접합 구조의 광활성층을 사용한다. 벌크 이종접합 구조는, 이중층 구조에 비해 전자 주개 물질과 받개 물질 간의 계면을 크게 증가시킬 수 있고, 이에 따라 엑시톤의 분리가 더 효과적으로 일어날 수 있다. 하지만, 전자 주개 물질과 받개 물질이 서로 뒤섞여 광활성층을 형성하기 때문에, 중간중간 독립된 상을 만들게 된다. 이러한 상에서는, 분리된 전하가 전극으로 이동할 수 없고, 재결합하여 에너지를 방출하게 된다. 따라서, 전하 수송을 원활히 하기 위해, 광활성층에 하나로 이어진 전하 이동 통로가 형성되어야 한다. 이와 관련하여, 1-D 구조 공액 고분자는, 지름 대비 길이 비율이 크기 때문에, 전하 이동 통로를 형성하기에 적합하다. 전기방사는 대부분의 고분자를 이용하여 1-D 구조의 나노섬유를 만들 수 있는, 간편한 방법이다. 본 연구에서는, 전기방사를 통해 가장 대표적인 전자 주개 물질인 P3HT 를, 얇은 지름의 나노섬유로 제조하고, 이를 유기 태양전지 광활성층으로서 적용가능성을 확인해 보고자 한다. 더 얇은 지름으로 조절하기 위해, 전기방사용액에 보조 고분자인 PEO 와 극성 용매인 DMF, acetic acid 를 적정량 첨가하였다. PEO 첨가로 전기방사용액의 점성을, 극성 용매 첨가로 전기전도도를 적정 수준으로 증가시켰다. 개선된 점성과 전기전도도로 인해, 뭉침 현상 없이 얇은 나노섬유를 제조하였다. 부도체인, PEO 를 제거한 이후, 80 nm의 얇은 지름을 갖는 P3HT 나노섬유를 형성하였다. 특히, 새로운 전자 주개 물질 중 하나인, PCDTBT 나노섬유의 지름은 30 nm 로 조절되었다. PL quenching 현상을 통하여 제조된 P3HT 나노섬유에서 엑시톤 분리가 효과적으로 일어나고 있음을 확인하였고, 이를 광활성층으로 적용하여 1 %의 효율을 갖는 태양 전지 셀을 만들 수 있었다. 추후, 최적화 공정을 통하여 셀 효율을 상승시킬 수 있을 것이라 기대된다.Organic photovoltaic (OPV) device is an energy conversion device which converts light into electricity. To improve the efficiency of the OPV, bulk heterojunction (BHJ) structured active layer is commonly used to increase the interfacial area between donor and acceptor, which cannot normally be accomplished in the bilayer structure. The extension of the interfacial area between donor and acceptor is expected to improve the exciton dissociationthereby increasing the efficiency. However, randomly orientated phases, which appear in the BHJ structured active layer, can result in unconnected islands and therefore reduce the charge transport efficiency. To improve the charge transport efficiency, continuous pathway should be fabricated in an active layer of BHJ OPV. For this purpose, electrospinning is utilized as a facile method for the fabrication of 1-D conjugated polymer nanofibers. For nanofibers with thinner diameter of nanofibers, a proper amount of PEO as an auxiliary polymer, along with DMF and acetic acid as polar solvents were added to the electrospinning dope solution. The addition of an auxiliary polymer increased the viscosity of the electrospinning dope solution and the addition of polar solvent increased the charge density of the electrospinning dope solution. Enhanced viscosity and enhanced charge density resulted in the fabrication of beadless, thin nanofibers. After PEO, which is an insulator, was removed, thin P3HT nanofibers with a diameter of 80 nm was fabricated. In addition, the fabrication of PCDTBT nanofibers with a diameter of approximately 30 nm was accomplished by a similar method. The exciton dissociation of the fabricated P3HT nanofibers was confirmed by photoluminescene quenching, which implies that the fiber can be utilized as an efficient OPV cell material. The power conversion efficiency of electrospun P3HT nanofiber-based OPV cells was c.a. 1 % and would be expected to be increased after the proper optimization processes.Contents 1. Introduction 1 1.1 Organic photovoltaic cells 1 1.1.1 General introduction of OPVs 1 1.1.2 Operating principle and efficiency of OPVs 4 1.1.3 Structure of active layer 8 1.2 1-D conjugated polymer 14 1.2.1 Merit of 1-D conjugated polymer 14 1.2.2 Fabrication of 1-D conjugated polymer 14 1.2.2.1 Merits and demerits of fabrication methods…...…..14 1.2.2.2 Electrospinning………………….…………………17 1.3 State of the art of electrospun 1-D conjugated polymer…20 1.3.1 Conventional electrospun P3HT fibers 20 1.3.2 Difficulty of electrospun P3HT fiber with small diameter 20 1.4 Objective of present work 25 2. Experimental 28 2.1 Chemicals and materials 28 2.2 Electrospinning of conjugated polymer nanofiber 28 2.3 Fabrication of electrospun nanofiber-based OPVs 30 2.4 Characterization 31 3. Result and discussion 33 3.1 Effects of additives in electrospinning dope solution 33 3.1.1 Effects of auxiliary polymer (PEO) 33 3.1.2 Effects of polar solvents 40 3.2 Fabrication of conjugated polymer nanofibers with a small diameter………………………………………………………...45 3.2.1 Electrospun conjugated polymer nanofibers……………...45 3.2.2 Removal of auxiliary polymer (PEO) 47 3.3 Characterization of optical properties and photoluminescene performance of electrospun P3HT nanofiber 52 3.3.1 Optical properties of electrospun P3HT nanofiber 52 3.3.2 PL performance of electrospun P3HT nanofiber 56 3.4 Performance of electrospun P3HT nanofiber-based OPVs 59 4. Conclusions 63 5. Reference. 65 초 록 68Maste

The effects of the antioxidant α-tocopherol on cisplatin-induced ototoxicity in HEI-OC1 auditory cells

의과대학/석사Objectives Alpha-tocopherol is a class of methylated phenols, known as fat-soluble antioxidants, and is a different form of vitamin E, which reduces free radicals and acts as an antioxidant. We hypothesized that the antioxidative effect of α-tocopherol could protect against cisplastin-induced cytotoxicity, and thus evaluated its effects on cisplatin-induced ototoxicity in HEI-OC1 auditory cells. Methods HEI-OC1 cells were pretreated with α-tocopherol at a concentration of 10 μM for 24 h, and then exposed to 15 μM cisplatin for 48 h. The cellular viability was measured by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The intracellular reactive oxygen species (ROS) level was measured by using a fluorescent dye, 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Both Annexin V-FITC and propidium iodide (PI) staining were performed to analyze the pattern of apoptosis. The enzymatic activity of caspase-3 was assayed with caspase3/CPP32 fluorometric assay kit. Also, it was assessed by immunoblotting technique of poly-ADP-ribose polymerase (PARP). Results Pretreatment with 10 μM α-tocopherol protected HEI-OC1 auditory cells against cisplatin-induced cytotoxicity. Alpha-tocopherol significantly reduced the cisplatin-induced increase in ROS. Alpha-tocopherol treatment induced a 15% reduction of ROS and 50% decrease in necrosis and late apoptosis as compared to cisplatin treatment. Alpha-tocopherol also decreased the activation of caspase-3 and reduced levels of PARP. Conclusion This study was investigated the protective effects of α-tocopherol on cisplatin-induced ototoxicity in an auditory cell line. Tocopherol significantly reduced a cisplatin-induced increase in ROS, thereby inhibiting cisplatin-induced cytotoxicity.ope

지열히트펌프시스템의 최적 설계를 통한 저온지열자원의 활용성 평가

학위논문 (박사)-- 서울대학교 대학원 : 지구환경과학부, 2015. 2. 이강근.Simulation models for evaluating utilization of low-enthalpy geothermal resources through the optimally designed geothermal heat pump (GHP) system is suggested. Firstly, a numerical model for the simulation of temperature changes in a borehole heat exchanger (BHE) with fluid circulating through U-tubes is developed. The model can calculate the thermal energy transferred from heat pumps to BHEs while considering the nonlinear relationship between temperature of the circulating fluid and the thermal energy. The use of the developed model enables also the design of a GHP system with the view of pursuing efficiency and financial benefit. The developed model is validated by comparing two measurement datasets with their respective simulation results. In addition, it is used to analyze the sensitivities of design parameters that can affect the performance of the closed-loop GHP system. The most sensitive parameters on the system are the thermal conductivity of the ground and the Darcian groundwater velocity considering acceptable distribution range in the realm of nature. Maximum change of the circulating fluid temperature at the BHE outlet is about 4℃ when thermal conductivity of the ground changes from 2 W/mK to 5 W/mK and the Darcian groundwater velocity changes from 10-8 m/s to 10-6 m/s, respectively. The numerical evaluation of a real GHP system with 28 BHEs and 79 heat pumps involves consideration of the base case and modified cases. In all cases, the temperatures of the circulating fluid at the BHE inlet and outlet, heat pump efficiency, and the heating power and electric power of heat pumps are obtained. The most cost-effective system in this case is for there to be 4, 6, and 6 BHEs on the first, second, and third floors, respectively. The next version of the numerical simulator and grid generator is developed to consider multiple BHEs simultaneously. Thus, massively parallel computing procedures into the simulator are introduced to improve distributing memory requirements and computational efficiency for solving large simulation problems with a great number of grid-blocks. The new grid generator is designed to produce a simulation domain with multiple BHEs. The newly developed simulation model can consider thermal interactions among BHEs when the system is in operation and storing thermal energy in the ground after the operation period of the system. These two mechanisms should be considered in the evaluation of long-term performance of the BHE. The developed simulation model is tested for the performance improvement through parallelization. The computational efficiency of the developed simulation model is considerably increased in direct proportion to the number of the processors. The model is then applied to evaluate the performance of the KIGAM GHP system for a 25-year operation. The temperature of the ground in the vicinity of BHEs is gradually increased with time because of the imbalance of the injected/extracted thermal power to/from the ground during the cooling/heating seasons. It causes the decrease of the efficiency of the system during the cooling seasons for the long-term operation. Finally, a versatile simulation model is developed to simulate not only the vertical closed-loop GHP system, but also the standing column well and open-loop GHP systems. A method to generate an unstructured Voronoi grid for its use in simulations of geothermal heat pump systems is presented. A series of codes is developed to create Voronoi cell center points that are placed at specific positions for well- or pipe-shaped Voronoi grids, to generate a three-dimensional grid from generated Voronoi cell vertices, and to visualize the generated grid and simulation results by ParaView. AMESH program is used to calculate the x- and y-coordinates of the Voronoi cell vertices from the Voronoi cell center points. The developed series of codes can generate the desired form of the grid. The generated grid is tested with confidence through simulations of water production/injection from/to the various kinds of the geothermal wells.Abstract i Contents iv List of Tables vii List of Figures viii Chapter 1. Introduction 1 1.1. Backgrounds 1 1.2. Objectives 6 Chapter 2. Simulation modeling of a borehole heat exchanger 10 2.1. Introduction 10 2.2. Method 11 2.2.1. Physical background 11 2.2.2. Simulation model development 12 2.3. Study area 20 2.4. Model setup and validation 25 2.4.1. Model setup 25 2.4.2. Model validation 26 2.5. Sensitivity analysis 31 2.6. BHE design evaluation 33 2.6.1. Criteria and guidelines for the design evaluation 34 2.6.2. Simulation results for the base case 36 2.6.3. Simulation results for the modified cases 40 2.6.4. Cost analysis 44 2.7. Summary and conclusion 46 Chapter 3. Simulation modeling of multiple borehole heat exchangers 48 3.1. Introduction 48 3.2. Method 49 3.3. Speedup test 60 3.4. Evaluation of the long-term performance of the KIGAM GHP system 62 3.4.1. Study area 62 3.4.2. Model setup 64 3.4.3. Guidelines 66 3.4.4. Results and discussion 69 3.5. Summary and conclusion 75 Chapter 4. Voronoi grid for simulation of geothermal heat pump systems 77 4.1. Introduction 77 4.2. Method 83 4.3. Results 89 3.4.1. Examples of generated grids 89 3.4.1. Examples of generated grids 92 4.4. Conclusion 100 Chapter 5. Discussion 102 Chapter 6. Summary and conclusions 105 References 107 Abstract (in Korean) 115Docto

勞使關係와 經營者의 會計情報利用에 관한 硏究

학위논문(석사)--서울대학교 대학원 :경영학과 경영학전공,2000.Maste

The clinical features and prognosis of inflammatory bowel disease in patients with obesity

배경: 비만의 유병률은 전 세계적으로 증가하고 있으며 염증성장질환의 유병률 또한 증가하고 있다. 염증성장질환은 일반적으로 영양실조 및 악액질과 관련이 있지만 비만과의 관련성은 여전히 논란의 여지가 있다. 따라서 우리는 비만 환자에서 염증성장질환의 특성과 예후를 평가하고자 하였다. 연구방법: 서울아산병원에서 진료를 보고 추적한 IBD 환자 코호트 기록을 후향적으로 검토했다. 체질량 지수가 30 이상인 IBD 환자와 BMI가 30미만인 IBD 대조군의 임상양상과 예후를 비교하였다. 결과: 1989년 6월부터 2016년 12월까지 서울아산병원 IBD 코호트에 등록된 6803명의 IBD 환자[크론병 3171명 및 궤양성 대장염 3632명] 중 진단 시 BMI가 30 이상인 크론병 환자 16명과 UC 환자 27명을 선별하였다. 그들의 임상적 특징과 경과를 1:4로 짝지어진 64명의 크론병 환자와 108명의 궤양성 대장염 환자와 비교하였다. BMI 30 이상과 30 이하의 크론병 환자들에서 스테로이드(HR 0.633; 95% CI 0.289–1.388, P=0.254), 면역조절제(HR 0.831; 95% confidence interval [CI] 2.226–3.374, P=0.517), 항-TNF 제제(HR 1.539; 95% CI 0.136–1.022, P=0.351) 사용 및 장절제술(HR 1.858; 95% CI 0.674–5.119, P=0.231)의 위험률에는 유의한 차이가 없었다. UC 환자에서도 BMI 30 이상과 30이하 군 간의 스테로이드(HR 0.613; 95% CI 0.317–1.185, P=0.145), 면역조절제(HR 0.492; 95% CI 0.205–1.177, P=0.111), 항-TNF 제제(HR 0.385; 95% CI 0.125–1.180, P=0.095)의 사용 및 장 절제술(HR 0.262; 95% CI,0.052–1.319, P=0.104)의 위험률에는 유의한 차이가 없었다. 결론: 비만한 염증성장질환 환자의 임상양상 및 예후는 체질량 지수 30 이하의 염증성장질환 환자와 비교하여 유의한 차이가 나지 않았다.Maste

A study on the effects of chewing patterns to occlusal wear 저작형태가 교합면 마모에 미치는 영향에 관한 연구

Thesis (master`s)--서울대학교 대학원 :치의학과 치과보철학전공,1996.Maste

Administrator System of Enterprise Bankruptcy Law of the Peoples Republic of China

중국은 을 제정하여 2007. 6. 1.부터 시행하면서 비로소 파산절차에 관리인제도를 도입하였다. 본 논문은 중국의 기업파산절차에서 관리인의 任免에 직접 관련된 절차적인 부분, 관리인에 대한 감독과 관리인의 책임을 주로 살 폈다. 법원은 미리 편제된 관리인명부에서 파산신청수리결정과 동시에 주로 사회중개 기구를 관리인으로 지정한다. 사회중개기구는 주로 변호사사무소, 회계사사무소와 파산청산사무소를 가리킨다. 청산조와 개인(변호사나 회계사)도 관리인을 맡을 수 있는데 청산조는 행정부서와 기구의 인원으로 구성된다. 관리인명부는 법원의 평가 심사위원회가 심사 확정한다. 법원의 관리인선임은 무작위, 경쟁, 추천의 세 가지 방식 에 의한다. 피지정자가 부적격 혹은 직책수행에 부적당하다고 인정하는 경우 법원은 직권이나 채권자회의의 신청에 따라 교체할 수 있다. 관리인보수는 파산재산의 규모에 따라 일정한 비율로 계산한다. 청산조 중 관련 정부부서에서 파견된 자는 보수를 따로 받지 않는다. 관리인에 대한 감독은 법원을 위주로 하여 채권자회의와 채권자위원회의 등에 의하여 이루어진다. 관리인이 근면의무와 충실의무에 위반하는 경우에는 손해 배상책임과 과태료를 부담하는 외에 형사책임을 부담할 수도 있다. 중국 기업파산법의 관리인은 기본적으로는 국제적으로 통용되는 방식에 따라 선임 되고, 업무를 수행하지만 청산조나 파산청산사무소 등의 특색이 있으며, 법원의 실무 관행이 아직은 충분히 확립되지 않았다. 한국 기업의 중국진출과 경영과정에서 최근에 불거진 비정상철수의 원인 중 주요한 것으로 중국 기업파산제도에 대한 이해부족을 들 수 있는데 파산절차에서 관건적인 역할을 수행하는 관리인에 대한 본 연구는 이 러한 문제를 해결하는데 일정한 기여를 할 것이다.이 논문은 2008년 정부(교육과학기술부)의 재원으로 한국학술진흥재단의 지원을 받아 수행된 연구임(KRF-2008-332-B00546)

빌리루빈이 신장 근위세뇨관 세포주에서 Hypoxia-induced factor 1α (HIF-1α) 의 발현에 미치는 영향

학위논문 (박사)-- 서울대학교 대학원 : 의학과 면역학전공, 2015. 8. 진호준.Introduction: Renal dysfunction has a common process of tubular cell death and tubulointerstitial inflammation followed by fibrosis, whereas initiation of such dysfunction is likely to have multi-hit characteristics. Renal tubulointerstitial hypoxia causes fibrogenesis and also stimulates infiltration and maturation of immune cells to generate inflammation. Hypoxia-inducible factor (HIF) is influenced by the level of reactive oxygen species (ROS) and plays an integral role in the body's response to hypoxia. Bilirubin has been reported to be an effective antioxidant, and has the beneficial effects on renal diseases. However, the exact mechanisms controlling HIF expression under hypoxia are not resolved. The aim of this study is to elucidate the effect of bilirubin on HIF-1 expression under hypoxia and the possible mechanism of HIF-1 regulation by bilirubin in human proximal tubular cells in vitro. Methods: The human proximal tubular kidney (HK2) cells treated with actinomycin D were cultured for 15 h in 5% oxygen with or without bilirubin. HIF-1α messenger RNA (mRNA) and protein expression were measured in the cells cultured with 0.1 mg/dL bilirubin and compared to the control cells. Next, in order to elucidate the molecular mechanism of bilirubin on HIF system, the changes of ROS and HIF system were measured after treating the cell with the inhibitors of PI3K/mTOR, PI3K/AKT, and ERK 1/2 pathways which affect the transcription and translation of HIF-1α expression. Then, HIF-1α expression and phosphorylation of P70S6 kinase were measured after treating the cell with 10μM exogenous hydrogen peroxide (H2O2) to investigate the effect of NADPH oxydase system which is another major source of ROS generation in mitochondria possibly contributing to HIF system. Finally, NOX4 gene, which is also known to affect the expression of HIF system, was blocked by small interfering RNA (siRNA) and then HIF-1α mRNA expression was evaluated. Results: The messenger RNA (mRNA) expression of HIF-1α that was suppressed by actinomycin D was increased by 1.69 ± 0.05 folds in the cells cultured with 0.1 mg/dL bilirubin, compared to the control cells. The inhibitor (miltefosin) of PI3K/AKT pathway attenuated HIF-1α expression increased by bilirubin whereas the inhibitors of PI3K/mTOR and ERK 1/2 pathways did not. HIF-1α expression was decreased by 10μM exogenous H2O2scavenger of ROS with or without bilirubin in the HK2 cells increased HIF-1α concentration more than that in the cells without bilirubin. Exogenous H2O2 decreased the phosphorylation of P70S6 kinase, which was completely reversed by bilirubin treatment. Knockdown of NOX4 gene by small interfering RNA (siRNA) increased HIF-1α mRNA expression. Conclusions: Bilirubin enhanced HIF-1α mRNA transcription as well as the upregulation of HIF-1α protein translation through 1) inhibition of oxidaive stress, at least partly by downregulating subunits of NADPH oxidase and 2) activation of PI3K/AKT pathway in HK2 cells cultured under hypoxia. These findings suggest that bilirubin could be a cytoprotective molecule with antioxidative properties in renal tubular injury. * This work is published in J Korean Med Sci. Sep 201429(Suppl 2): S146?S154.Content Introduction………………………………………………………………………1 Methods……………………………………………………………………………6 Cell culture……………………………………………………………………6 Detection of ROS generation ………………………………………………7 Western blotting………………………………………………………………7 RNA extraction and reverse transcription-polymerase chain reaction (RT-PCR)………………………………………………………………………8 Statistical analysis…………………………………………………………9 Results…………………………………………………………………………10 The effect of bilirubin on HIF-1α protein expression………………10 The effect of bilirubin on HIF-1α mRNA transcription…………………12 The mechanism of increased HIF-1α translation by bilirubin: Inhibitors of PI3/AKT/mTOR pathway ………………………………………15 Endogenous and exogenous H2O2 …………………………………………… 18 NADPH oxidase ……………………………………………………………………… 21 NADPH oxidase subunits ………………………………………………………… 24 The effect of bilirubin on apoptotic signals……………………………27 Discussion …………………………………………………………………27 Reference…………………………………………………………………32 국문초록……………………………………………………………………40Docto