78 research outputs found
CUHK electronic theses & dissertations collection
No full textKwok, Chun Kit.Thesis Ph.D. Chinese University of Hong Kong 2015.Includes bibliographical references (leaves 215-238).Abstracts also in Chinese.Title from PDF title page (viewed on 29, September, 2016)
Hemodynamic regulation of metalloendopeptidases EC3.4; 24.15 and EC3.4; 24.16: expression and function in the vascular endothelium
Get PDFHemodynamic forces, namely shear stress and cyclic strain, have been well characterised as modulators of vascular endothelial function, and have been assigned an important role in the maintainence of vascular tone, haemostasis, and regulation of vascular growth and health. They exert their influence in part by effecting changes in the production and release of vasoactive compounds by the endothelium, and by effecting changes in the levels and activity of various enzymes. Thimet oligopeptidase (EC3.4.24.15, EP24.15) and neurolysin (EC3.4.24.16, EP24.15) are closely related zinc metalloendopeptidases that have been shown to be expressed and active in the vascular endothelium. Their substrates include the vasoactive peptides bradykinin and angiotensin I, which have been identified as important regulators of both blood pressure and angiogenic processes. Other related peptidases, namely endothelin converting enzyme (ECE) and angiotensin converting enzyme (ACE), have been shown to be regulated by hemodynamic forces in the vascular endothelium. As such EP24.15 and EP24.16 are likely candidates for regulation by hemodynamic forces.
In this regard we have investigated the effect of cyclic strain on the expression and activty of EP24.15 and EP24.16 in cultured bovine aortic endothelial cells (BAECs). We have shown that exposure to cyclic strain significantly increases the mRNA expression as well as both the cellular and secreted activity of both enzymes. We have demonstrated that up-regulation of both enzymes is dependent on Gi-protein mediated signalling, although with varying Gia/G(3y subunit specificity for either enzyme. Using immunocytochemistry, we have also demonstrated a strain-dependent increase in EP24.15 protein expression within the nucleus and cytoplasm in parallel with an increase in membrane associated EP 24.15
The effects of strain on the ability of BAECs in culture to cleave both Ang I, and BK in an EC24.15/EC24.16 specific manner was also studied. We observed that exposure to cyclic strain induces a significant increase in the EP24.15 specific hydrolysis of both exogenously added BK and Ang I.
The potential of the observed effects of cyclic strain on EP24.15 to effect changes in endothelial cell function were also examined. Use of the dual EP24.15/EP24.16 inhibitor, cFP-AAF-pAB, and the EP24.15 specific antisense, FLIP, was seen to significantly attenuate cyclic strain-induced endothelial cell tubule formation and migration. We also found that the effects of FLIP transfection on cyclic strain-induced endothelial cell tubule formation could be largely reversed by addition of exogenous Ang-(l-7). Taken together these results suggest that strain-induced endothelial cell angiogenesis and migration putatively involves EP24.15 cleavage of vasoactive peptide substrates
Development of an artificial neural network topology for generating the motion of robotic manipulator
Get PDFMotion planning is an important issue in robot industry. Without an appropriate motion planning, a robot may be colliding with obstacles or passing through undesirable points. In order to control the motion of a robot manipulator, a person has to possess the knowledge of kinematics, dynamics, and trajectory planning.
However, there are two main problems in using conventional methods. Firstly, the equations are hard to be derived and the calculations are complex. Secondly, the characteristics of different trajectories are different and there is no mathematical solution for unknown trajectory. Hence, the first objective in this research is to simplify the complex calculations in terms of solving kinematics and trajectory
planning issues simultaneously. Another objective of this research was to help in computing the motion of a manipulator even though the characteristic of the
trajectory is unknown. In order to achieve these research goals, artificial neural network (ANN) was proposed as a solution.
In the early stage, a virtual manipulator was developed and subjected to different primitive trajectories. In order to examine the ability of ANN in tracking the motion of a robot manipulator, a primitive ANN would be used to track the moving path of the virtual robot manipulator’s end effector in the virtual environment. This ANN was developed based on the fundamental of back-propagation neural network
(BPNN) topology. The topology of ANN would be modified for reducing the errors and deviations. Eventually, the developed ANN would be validated through a real time 5 catalyst robot. Besides, obstacle avoidance planning would be integrated into the developed ANN. Virtual obstacles would be allocated within the robot’s workspace randomly and the performances of developed ANN would be observed
through simulation experiments.
The results indicated that ANN possessed ability in tracking the motion of a robot manipulator in terms of solving kinematics and trajectory planning issues
simultaneously and it was able to compute the motion of a manipulator even though the characteristic of the trajectory was unknown. Obstacle avoidance planning was
integrated into the architecture of developed ANN for better performances and the results were satisfactory. With this developed method, a person is able to compute a
safe path for a robot manipulator to avoid obstacles (objects which enclosed in a sphere)
Practical Research on Project-Based Learning (PBL) in Film and Television Production in Xiamen Vocational Education
Get PDFThe film and television industry plays a crucial role in the development of the global cultural sector. In recent years, vocational education in the field of film and television has experienced rapid growth in China. However, the current talent training model for this profession fails to meet the demands of the fast-paced industry development and lacks effective support for its advancement. Project-based learning is a student-centered teaching approach that employs authentic projects as the primary medium for learning. This study presents an empirical investigation conducted in a vocational college in Xiamen, where project-based learning was incorporated into the film and television production courses to assess its effectiveness. The findings of this research demonstrate that the implementation of project-based learning in the context of film and television production is viable. In comparison to traditional didactic instruction, project-based learning significantly enhances students\u27 motivation to learn, practical skills, critical thinking abilities, and teamwork abilities. Consequently, it holds significant value in cultivating applied talents
Tire oil from waste tire scraps using novel catalysts of manufacturing sand (M Sand) and TiO<sub>2</sub>: Production and FTIR analysis
No full textIsolation and characterisation of mouse amniotic fluid stem cells: study of their origin, regenerative potential and reprogramming into pluripotent cells
Get PDFIntroduction: Stem cells are defined by their ability to proliferate for a long period of time, a property known as ‘self-renewal’, and to give rise to differentiated cells. Stem cells can be distinguished into totipotent, pluripotent, multipotent, oligopotent and unipotent. They can also be classified into embryonic, adult and fetal stem cells. Embryonic stem (ES) cells are obtained from inner cell mass (ICM) of blastocyst and are puripotent. Primordial germ cells (PGC) in the embryo give rise to gametes but they are not pluripotent, albeit they express Oct4, Nanog and Sox2. They can be reprogrammed in vitro, becoming pluripotent embryonic germ (EG) cells. Amniotic fluid stem (AFS) cells are fetal stem cells that can be isolated from the amniotic fluid (AF) by the expression of the marker c-kit, both in human and mouse, but their origin is unknown. Human AFS are multipotent in vitro, while both human and mouse AFS have hematopoitic potential, in vitro and in vivo. Recently it has been demonstrated that human AFS from first and second thrimester can be reprogrammend into pluripotent cells in vitro, after supplementation with Valproic Acid (VPA). Cells from the AF have also been used to obtain induced pluripotent stem (iPS) cells. For all these reasons AFS cells seems to be a promising sources of cells for regenerative medicine. Spinal muscular atrophy (SMA) is an autosomal recessive disease, caused by an homozygous deletion or mutation of the motor neuron 1 (SMN1) gene. Bone marrow (BM) transplantation in a murine model of SMA attenuates the myopathic phenotype without a full recovery and without long-term therapeutic effects.
Aims of the thesis: Characterisation of fresh mouse AFS cells, evaluation of their myogenic potential into a model of SMA (HSA-Cre, SmnF7/F7 mouse) investigation of their putative PGC origin and induction to pluripotency through a non-viral method (PiggyBac, PB).
Materials and Methods: Mouse AFS cells were obtained by amniocentesis and selected as c-kit+ cells with magnetic beads. Freshly isolated-AFS cells were analized for the expression of different markers (CD90, CD45, CD44, CD34, CD31, Flk1, Sca1, CD105) by flow citometry and the expression of Oct4, Sox2, c-Myc, Klf4 and Sca-1 by qRT-PCR at different embryonic stages. Hematopoitic potential was evaluated in vitro, while the teratoma assay was performed in Rag2-/-γc-/- mice. For the reprogramming into EG cells cells were seeded into a feeder layer of mitotically inactivated STO or Sl4-m220, in a PGC medium supplemented with LIF and basic fibroblast growth factor (bFGF) and in N2B27 2iLIF medium. For the treatment of HSA-Cre, SmnF7/F7 mice, GFP+ cells were injected via the tail vain and sacrificed one month after transplantation. Tibialis Anteriour (TA) muscles were stained with hematoxylin and eosin, Masson’s trichrome and analized by immunofluorescence for positivity for GFP/dystrophin. The experiments for the origin of AFS have been conducted using two mouse models: Oct4-GFP and TNAP-Cre. For the induction to pluripotency cells were obtanied from Oct4-GFP positive embryos, and transfected with the PB-TET transposon plasmid containing four genes (Oct-4, Sox-2, c-Myc and Klf4) under the transcriptional control of the tetO2 tetracycline/doxycycline inducible promoter. The expression of pluripotency gene was induced with doxycycline. iPS cells obtained were tested for the expression of Nanog, SSEA-1 and for positivity to alkaline phosphatase.
Results: Mouse AFS number chaged during the course of gestation. These cells expressed hematopoietic markers (CD45, CD34, Sca1), mesenchymal markers (CD90, CD105) together with Flk1, CD31 and CD44. On the basis of c-kit expression two populations were defined: c-kithigh and c-kitlow which showed differential expression of the aforementioned markers. c-kitlow are the more abundant, but during the course of gestation they decreases in numbers while the number of c-kithigh cells increases. Both populations had hematopoietic potential vitro. Gene expression analysis showed that mouse AFS cells expressed at low levels Oct4 and Sox2 and high levels c-Myc and Klf4, and their expression changed during the course of gestation. Single cell PCR showed that at E13.5 there 5% of cells co-expressed Oct4, Sox2 and Klf4. Mouse AFS cells didn't form teratoma. In the cell therapy experiments HSA-Cre, SmnF7/F7 control mice died at the age of 10 months, while mice treated with GFP+ AFS or bone marrow (BM) cells had a survival rates increased by 75% and 50% respectively. HSA-Cre, SmnF7/F7 mice treated with AFS cells recovered more than 75% of force compared to the untreated animals. One month after transplantation, muscles from AFS-treated mice displayed very low number of regenerating myofibers (<1%) and normal dystrophin expression; moreover, 37.86% (± 9.48%) of the fibers were GFP+. 15 months after transplantation BM-treated mice displayed a high number of central nucleated fibers and consistent infiltration of interstitial tissue and no GFP+ myofibers, while AFS-treated mice had a mild-phenotype, close to wild-type mice, and 58.00% (± 2.43%) of the myofibers were GFP+. Similar results were obtained with HSA-Cre, SmnF7/F7 treated with mouse AFS cells expanded in culture.
To evaluate if mouse AFS cells were PGC cells, they were cultivated following the protocol established to obtain pluripotent EG cells from PGC cells. Two different culture protocols were used, but no EG cells were obtained. AFS cells isolated from Oct4-GFP fetuses at different embryonic stages showed no presence of Oct4+ cells. The TNAP-Cre line resulted to be unspecific. iPS clones obtained transfecting mouse AFS cells were doxycycline indipendent, they expressed Oct4, they were positive for Nanog and SSEA1, and for the alkaline phosphatase.
Discussion: Mouse AFS cells are an heterogenous population, and their phenotype changed during the course of gestation. They expressed mesenchymal, hematopietic and endothelial markers. The two populations (c-kithigh and c-kitlow) should be tested in vivo to asses their differentiative potential. Gene expression analysis at population and single cells level confirmed the heterogeinity of mouse AFS cells. AFS showed a myogenic potential, even after long-term transplantion, suggesting an interesting therapeutic potential of these cells. AFS could contribute to the formation of new myofibers by fusing with existing ones or after integration within the stem cell niche of the muscle. The study of their origin suggested that mouse AFS cells aren't PGC. However it is important to remind that the Oct4-GFP mouse is not a lineage-tracking model; therefore more experiments are needed to confirm these results and to find the origin of these cells. iPS cells are a promising research tool to obtain a model of several diseases or as a source of cells for therapeutic approaches. Here it has been shown that the PB system is a suitable method for the reprogramming of mouse AFS cells. These are only preliminary results and more experiments will be necessary to complete the characterisation of these cells
Open the box : video drama
No full textThis report is a companion and comprehensive guide to our short feature film, Open The Box.Bachelor of Communication Studie
A Highly Computationally Efficient Explicit-Iterative Hybrid Algorithm for Colebrook-White Equation
No full textIdentification and Prioritization of Risk Factors in an Electrical Generator Based on the Hybrid FMEA Framework
No full textThe oil and gas industry is looking for ways to accurately identify and prioritize the failure modes (FMs) of the equipment. Failure mode and effect analysis (FMEA) is the most important tool used in the maintenance approach for the prevention of malfunctioning of the equipment. Current developments in the FMEA technique are mainly focused on addressing the drawbacks of the conventional risk priority number calculations, but the group effects and interrelationships of FMs on other measurements are neglected. In the present study, a hybrid distribution risk assessment framework was proposed to fill these gaps based on the combination of modified linguistic FMEA (LFMEA), Analytic Network Process (ANP), and Decision Making Trial and Evaluation Laboratory (DEMATEL) techniques. The hybrid framework of FMEA was conducted in a hazardous environment at a power generation unit in an oil and gas plant located in Yemen. The results show that mechanical and gas leakage FM in electrical generators posed a greater risk, which critically affects other FMs within the plant. It was observed that the suggested framework produced a precise ranking of FMs, with a clear relationship among FMs. Also, the comparisons of the proposed framework with previous studies demonstrated the multidisciplinary applications of the present framework
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