12,545 research outputs found
Cheng Zhe Jin
No full text학위논문(박사)----아주대학교 일반대학원 :의학과,2007. 8In recent years, cartilage tissue engineering for reconstruction or repair of a cartilage injury has been emerged as alterative solutions based on the application of selected chondrocytes and scaffold. The purpose of present study is to evaluate the feasibility of novel cell-derived extracellular matrix (ECM) scaffold on cartilage tissue engineering in vitro and in vivo as nude mouse and rabbit model.
Chapter I: A porous cell-derived ECM scaffold was prepared with a freeze-drying protocol using porcine chondrocytes. The ECM scaffold had highly uniform porous microstructure by scanning electron microscope (SEM). It showed an average pore diameter of 504±108um, a porosity of 90±10.4%, a surface area of 905±204 m2/g and a tensile strength of 0.34±0.09 MPa, respectively. In vitro study, Then, rabbit chondrocytes were seeded dynamically on the ECM scaffold and cultured for 2 days, 1, 2 and 4 weeks in vitro for analysis. The neocartilage-like tissue was observed after 1 week of culture, and the volume and compressive strength were significantly increased with culture time. The DNA, glycosaminoglycan (GAG) and collagen contents also increased gradually with time. Histological staining for GAG (Safranin O staining) and type II collagen (immunohistochemistry) showed sustained accumulation of the ECM molecules along with time, which gradually and uniformly filled the porous space in the ECM scaffold.
Chapter II: In vivo study as nude mouse, cell-seeded ECM scaffold was cultured for 2 days in vitro, and then implanted into the nude mouse subcutaneously. They were retrieved at 1, 2, and 3 weeks post-implantation. Under macroscopic analysis, the cartilage-like tissue formation matured by time and developed a smooth, white surface. And, the size of the neocartilage tissue increased slightly by the 3rd week and remained more stable. Total GAG content and the GAG/DNA ratio increased significantly by time in the chemical analysis. The histology exhibited a sustained accumulation of newly synthesized sulfated proteoglycans. Immunohistochemistry, Western blot, and RT-PCR clearly identified type II collagen at all time points. Compressive strength of in vivo neocartilage increased from 0.45±0.06MPa at 1 week to 1.18±0.17MPa at 3 weeks.
Chapter III: In vivo study as rabbit model, the knee defects were implanted with in vitro cultured tissue engineering cartilage using ECM scaffold and allogenic rabbit chondrocytes as 2days, 2, and 4 weeks (experimental group 2, 3, and 4), respectively. The left knee defects were not implanted as control (group 1). The maturity of cultured implants was evaluated by histological, chemical and mechanical assay in chapter I. The repair examination was evaluated with macroscope and histological assay at 1 and 3 months post-surgery. After 1 month, fibro/hyalinecartilge was found on histological examination in the group 1, 2 and hyalinecartilage was found in group 3, 4. However, a mature matrix and a columnar organization of chondrocytes can be observed with Saflanin-O staining in group 4 at 3 months. Moreover, the subchondral bone was well remodeled and the more type II collagen was expressed at that time in the group 4. Thus ICRS histological score were significantly increased in the group 4 at that time.
In conclusion, this study demonstrated that the novel cell-derived ECM scaffold could provide a promising environment for generating a high quality cartilage in vitro and in vivo as nude mouse. Moreover, the engineered cartilage using the cell-derived ECM scaffold and allogenic chondrocytes could regenerate the cartilage defects particularly when cultured mature cartilage provided better results.ABSTRACT i
TABLE OF CONTENTS iv
LIST OF FIGURES vi
LIST OF TABLES viii
I.INTRODUCTION 1
II.MATERIALS AND METHODS 10
III.RESULTS 21
IV.DISCUSSION 42
V.CONCLUSION 54
REFERENCES 55
국문요약 67Maste
這樣學動畫! 從原理,製程到產業,一次完整了解動畫這一行 [Zhe yang xue dong hua! : cong yuan li . zhi cheng dao chan ye, yi ci wan zheng liao jie dong hua zhe yi xing]
No full text這樣學動畫! 從原理,製程到產業,一次完整了解動畫這一行 [Zhe yang xue dong hua! : cong yuan li . zhi cheng dao chan ye, yi ci wan zheng liao jie dong hua zhe yi xing
Zhongguo neng cheng wei shi jie gong chang ma?
No full textBen shu shou ru lun wen 41 pian, nei rong wei rao " zhong guo neng fou cheng wei shi jie gong chang " zhe ge zhu ti. bian zhe ren wei : mu qian zhong guo hai bu shi " shi jie gong chang " huo " shi jie zhi zao ye ji di " ; zhong guo zhi shi zai lao dong li mi ji xing chan ye yi ji lao dong mi ji xing yu ji shu mi ji xing xiang jie he de zu zhuang jia gong ye ling yu, ke yi shuo yi cheng wei shi jie de gong chan
這樣學動畫! 從原理,製程到產業,一次完整了解動畫這一行 [Zhe yang xue dong hua! : cong yuan li . zhi cheng dao chan ye, yi ci wan zheng liao jie dong hua zhe yi xing]
No full text這樣學動畫! 從原理,製程到產業,一次完整了解動畫這一行 [Zhe yang xue dong hua! : cong yuan li . zhi cheng dao chan ye, yi ci wan zheng liao jie dong hua zhe yi xing
AUGUSTO TEIXEIRA GARCIA AND COMPARATIVE LAW: A HAPPY MARRIAGE?
No full textThe Article explores the studies made by Augusto Teixeira Garcia in a comparative perspective, to consider the contribution of comparative law in its scholarly works
Ru jia si xiang yu xian dai shi jie
No full textBen shu suo shou ru de lun wen shi zhong yang yan jiu yuan zhong guo wen zhe yan jiu suo tui dong de " dang dai ru xue zhu ti yan jiu ji hua " di yi qi zhi bu fen cheng guo. bao gua " fo xue, xi xue yu dang dai xin ru jia -- hong guan de zhe xue kao cha " deng lun we
Jia zhi jiao yu de zhe xue tan suo
No full text伍美蓮.呈交日期: 2003年1月.論文(哲學博士)-香港中文大学, 2002.參考文獻 (p. 227-241).中英文摘要.Cheng jiao ri qi: 2003 nian 1 yue.Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Mode of access: World Wide Web.Wu Meilian.Zhong Ying wen zhai yao.Lun wen (zhe xue bo shi)--Xianggang Zhong wen da xue, 2002.Can kao wen xian (p. 227-241)
Coupled MPS-modal superposition method for 2D nonlinear fluid-structure interaction problems with free surface
No full textIn this paper, a coupled MPS-modal superposition method is developed for 2D nonlinear fluid-structure interaction problems. In this method, the rigid-body and relatively small elastic deformation are coupled together, which considers the mutual effect between them. The elastic deformation of the structure is represented by a mode superposition formulation, which is more efficient compared with FEM, regardless of the size of the structure. For 2D cases, if the first three modes are chosen to represent the flexible deformation of the structure, it only results in a 6×6 matrix equation to be solved. For the fluid motion, the modified Moving Particle Semi-implicit (MPS) method, which significantly reduces the fluctuation of pressure calculation of the original MPS method, is used.Two nonlinear problems, i.e. breaking-water-dam impacting a floating beam and flexible wedge slamming into the water are simulated to demonstrate the performance of the developed method. The numerical simulations show that this coupling model is capable of providing stable results that are generally in good agreement with the available experimental data. For the highly nonlinear case with very large rigid motions, the mutual effect between elastic deformation and rigid motions could accumulate to a relatively remarkable level shown by the curves of trajectories or acceleration history of the body mass centre. This also indicates the importance of mutual effect to analyse highly nonlinear FSI problems with large rigid-body motions and relatively small flexible deformation.KeywordsMoving particle semi-implicit (MPS) method; Fluid structure interaction (FSI); Modal superposition; Free surface flow; Floating beam; Flexible wedge droppin
Modified MPS method for the 2D Fluid structure interaction problem with free surface
No full textAs a Lagrangian mesh-free method, the Moving Particle Semi-implicit (MPS) method is very suitable for simulating violent flows, such as breaking waves on free surface. However, despite its wide range of applicability, the original MPS algorithm suffers from some inherent difficulties in obtaining an accurate fluid pressure in both spatial and time domain. Different modifications to improve the method have been proposed in the literature. In this paper, we propose the following modifications to improve the accuracy of pressure calculations and the stability of the method: i) A mixed source term in the pressure Poisson equation with no artificial term in the formulation, ii) New solid and free surface boundary handling methods, iii) Particle position shifting and collision handling, and iv) A new version of “cell-link” neighbour particle searching strategy, which reduces about 6.5/9 (?72%) of the searching area compared with traditional “cell-linked” algorithm.The proposed modifications are verified and validated by some model free-surface flow problems, such as a two-dimensional dam break (with rigid and flexible structures on the impacting end - FSI model), liquid sloshing and ship cross section dropping problems. The numerical results obtained are found to be in good agreement with the available numerical or experimental results. With the proposed modifications, the stability and accuracy of the pressure field are improved in spatial and time domains
Tribological assessment of oil condition sensors for marine launching equipment.
No full textProblems in hydraulic systems associated with hydraulic fluids are an important area of research. Time has proven that contamination control in hydraulic and lubricating systems are fundamental to reliability and performance.
Contamination control is needed to guarantee the quality of the oil and machine reliability. Among the several condition monitoring techniques, oil and wear analysis are the most effective for contamination control in hydraulic equipment. An emerging maintenance philosophy is oil condition based maintenance, in which the active monitoring of oil parameters determines the machine health and the variable service intervals. This new maintenance
philosophy requires sensor technology able to provide real time indicators of the status of the system.Nowadays, oil condition monitoring sensors are not a mature technology and their performance has not been widely assessed under controlled experimental conditions. This research explains the physical fundamentals of commercially available sensors and it discusses and evaluates their effectiveness under
controlled experimental conditions.Tribology tests were performed for sliding contacts as they are the most
predominant type of contacts within hydraulic systems. Results reveal that several characteristics of the sensors must be improved for a more meaningful output and for an earlier detection of abnormal trends which are typical
indicators of the onset of faults.Finally, of all the future trends of oil condition monitoring sensors, the
novel methodology to calculate the particle size distribution from ferrous debris density measurements is the most useful and important contribution to knowledge of this research. The proposed method when compared to current
technology would bring a new type of particle counter that could break the technological size limitation of particle counters based on magnetometry (the most extended type in industrial and military machinery), leading to earlier
fault detection. Improvements of this methodology would allow further development of low cost particle counters in the micrometer and submicrometer range which can be widely applied in many industrial processes and scientific
disciplines
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