10 results on '"XIAN-FENG TIAN"'
Search Results
2. Acquisition approach of moment of inertia based on brushless DC torque motor
- Author
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YaoYao Wang, Wei Feng, ShuHeng Chen, Jiang Xian Feng Tian, Lun Kuan Ye, and DaWei Gu
- Subjects
History ,Computer Science Applications ,Education - Abstract
In order to meet the requirements of the small moment of inertia of the brushless DC torque motor, the optimal design of the shafting and the research on the measurement method were carried out on the basis of the structure of the flat motor rotor and the high-precision sensor. In this paper, ProE5.0 software is used to model and simulate the shaft structure of the permanent magnet synchronous motor. After comparing the common measurement methods of the moment of inertia, the single-wire torsional oscillation method is used to test and verify the moment of inertia of typical structural parts. The moment of inertia of the motor rotor is simulated and identified by the speed jammer identification algorithm.The test results show that the identification error of the constructed identification algorithm is less than 5% for the moment of inertia identification. After the brushless DC torque motor is assembled, the method can be used as a verification method for the parameters of the moment of inertia, which has strong practical significance.
- Published
- 2023
3. Therapeutic angiogenesis by transplantation of human embryonic stem cell-derived CD133+ endothelial progenitor cells for cardiac repair
- Author
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Ru San Tan, Wei Seong Toh, Abdul Jalil Rufaihah, Eugene K.W. Sim, Lei Ye, Xian Feng Tian, Husnain Khawaja Haider, Tong Cao, and Boon Chin Heng
- Subjects
Pluripotent Stem Cells ,Vascular Endothelial Growth Factor A ,CD31 ,Embryology ,Cell Survival ,Angiogenesis ,Myocardial Infarction ,Biomedical Engineering ,CD34 ,Neovascularization, Physiologic ,Apoptosis ,Biology ,Adenoviridae ,Cell Line ,Mice ,Antigens, CD ,Transduction, Genetic ,Animals ,Humans ,AC133 Antigen ,Progenitor cell ,Cell Shape ,Embryonic Stem Cells ,Glycoproteins ,Wound Healing ,Myocardium ,Endothelial Cells ,Embryo, Mammalian ,Flow Cytometry ,Molecular biology ,Embryonic stem cell ,Rats ,Cell biology ,Endothelial stem cell ,Gene Expression Regulation ,Heart Function Tests ,Blood Vessels ,Cytokines ,Stem cell ,Peptides ,Stem Cell Transplantation ,Adult stem cell - Abstract
Objective: This study aim to enhance endothelial differentiation of human embryonic stem cells (hESCs) by transduction of an adenovirus (Ad) vector expressing hVEGF165 gene (Ad-hVEGF165 ). Purified hESC-derived CD133+ endothelial progenitors were transplanted into a rat myocardial infarct model to assess their ability to contribute to heart regeneration. Methods: Optimal transduction efficiency with high cell viability was achieved by exposing differentiating hESCs to viral particles at a ratio of 1:500 for 4 h on three consecutive days. Results: Reverse transcription-PCR analysis showed positive upregulation of VEGF, Ang-1, Flt-1, Tie-2, CD34, CD31, CD133 and Flk-1 gene expression in Ad-hVEGF165 -transduced cells. Additionally, flow cytometric analysis of CD133, a cell surface marker, revealed an approximately fivefold increase of CD133 marker expression in Ad-hVEGF165 -transduced cells compared with the nontransduced control. Within a rat myocardial infarct model, transplanted CD133+ endothelial progenitor cells survived and participated, both actively and passively, in the regeneration of the infarcted myocardium, as seen by an approximately threefold increase in mature blood vessel density (13.62 ± 1.56 vs 5.11 ± 1.23; p < 0.01), as well as significantly reduced infarct size (28% ± 8.2% vs 76% ± 5.6%; p < 0.01) in the transplanted group compared with the culture medium-injected control. There was significant improvement in heart function 6 weeks post-transplantation, as confirmed by regional blood-flow analysis (1.72 ± 0.612 ml/min/g vs 0.8 ± 0.256 ml/min/g; p < 0.05), as well as echocardiography assessment of left ventricular ejection fraction (60.855% ± 7.7% vs 38.22 ± 8.6%; p < 0.05) and fractional shortening (38.63% ± 9.3% vs 25.2% ± 7.11%; p < 0.05). Conclusion: hESC-derived CD133+ endothelial progenitor cells can be utilized to regenerate the infarcted heart.
- Published
- 2010
4. Directing endothelial differentiation of human embryonic stem cells via transduction with an adenoviral vector expressing the VEGF165 gene
- Author
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Xian Feng Tian, Wei Seong Toh, Lei Ye, Abdul Jalil Rufaihah, Kathy Lu, Tong Cao, Boon Chin Heng, Eugene K.W. Sim, and Husnain Khawaja Haider
- Subjects
Vascular Endothelial Growth Factor A ,Angiogenesis ,Cellular differentiation ,Genetic Vectors ,Fluorescent Antibody Technique ,Apoptosis ,Embryoid body ,Biology ,Adenoviridae ,Viral vector ,chemistry.chemical_compound ,Transduction (genetics) ,Antigens, CD ,Transduction, Genetic ,Drug Discovery ,Genetics ,Humans ,AC133 Antigen ,Progenitor cell ,Molecular Biology ,Cells, Cultured ,Embryonic Stem Cells ,Genetics (clinical) ,Cell Proliferation ,Glycoproteins ,Reverse Transcriptase Polymerase Chain Reaction ,Endothelial Cells ,Cell Differentiation ,Vascular Endothelial Growth Factor Receptor-2 ,Embryonic stem cell ,Molecular biology ,Vascular endothelial growth factor ,Phenotype ,Gene Expression Regulation ,chemistry ,embryonic structures ,Molecular Medicine ,Peptides - Abstract
Endothelial progenitors derived from human embryonic stem cells (hESCs) hold much promise in clinical therapy. Conventionally, lineage-specific differentiation of hESCs is achieved through supplementation of various cytokines and chemical factors within the culture milieu. Nevertheless, this is a highly inefficient approach that is often limited by poor replicability. An alternative is through genetic modulation with recombinant DNA. Hence, this study investigated whether transduction of hESCs with an adenoviral vector expressing the human VEGF165 gene (Ad-hVEGF165) can enhance endothelial-lineage differentiation. The hESCs were induced to form embryoid bodies (EBs) by culturing them within low-attachment plates for 7 days, and were subsequently trypsinized into single cells, prior to transduction with Ad-hVEGF165. Optimal transduction efficiency with high cell viability was achieved by 4-h exposure of the differentiating hESCs to viral particles at a ratio of 1 : 500 for three consecutive days. ELISA results showed that Ad-hVEGF165-transduced cells secreted human vascular endothelial growth factor (hVEGF) for more than 30 days post-transduction, peaking on day 8, and the conditioned medium from the transduced cells stimulated extensive proliferation of HUVEC. Real-time PCR analysis showed positive upregulation of VEGF, Ang-1, Flt-1, Tie-2, CD34, CD31, CD133 and Flk-1 gene expression in Ad-hVEGF165-transduced cells. Additionally, flow cytometric analysis of CD133 cell surface marker revealed an approximately 5-fold increase in CD133 marker expression in Ad-hVEGF165-transduced cells compared to the non-transduced control. Hence, this study demonstrated that transduction of differentiating hESCs with Ad-hVEGF165 facilitated expression of the VEGF transgene, which in turn significantly enhanced endothelial differentiation of hESCs. Copyright © 2007 John Wiley & Sons, Ltd.
- Published
- 2007
5. The early dementia prevention programme in Singapore
- Author
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Shu-Qiao Yao, Xian-Feng Tian, Rathi Mahendran, Ee Heok Kua, Lei Feng, and Da-Xing Wu
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Gerontology ,Psychiatry and Mental health ,business.industry ,Early dementia ,Optometry ,Medicine ,business ,Biological Psychiatry - Published
- 2015
6. Conversion of Sox17 into a pluripotency reprogramming factor by reengineering its association with Oct4 on DNA
- Author
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Xian Feng Tian, Andrew P. Hutchins, Calista Keow Leng Ng, Irene Aksoy, Prasanna R. Kolatkar, Paaventhan Palasingam, Paul Robson, Jiaxuan Chen, Ralf Jauch, and Lawrence W. Stanton
- Subjects
Models, Molecular ,animal structures ,Cellular differentiation ,Amino Acid Motifs ,Induced Pluripotent Stem Cells ,Molecular Sequence Data ,Biology ,Protein Engineering ,DNA-binding protein ,SOX Transcription Factors ,Mice ,SOX2 ,HMGB Proteins ,SOXF Transcription Factors ,Animals ,Computer Simulation ,Amino Acid Sequence ,Induced pluripotent stem cell ,Transcription factor ,Embryonic Stem Cells ,Genetics ,Base Sequence ,SOXB1 Transcription Factors ,fungi ,Endoderm ,Cell Differentiation ,Cell Biology ,DNA ,Embryonic stem cell ,Cell biology ,DNA-Binding Proteins ,embryonic structures ,Mutagenesis, Site-Directed ,Molecular Medicine ,Protein Multimerization ,Reprogramming ,Octamer Transcription Factor-3 ,Sequence Alignment ,Developmental Biology ,Protein Binding - Abstract
Very few proteins are capable to induce pluripotent stem (iPS) cells and their biochemical uniqueness remains unexplained. For example, Sox2 cooperates with other transcription factors to generate iPS cells, but Sox17, despite binding to similar DNA sequences, cannot. Here, we show that Sox2 and Sox17 exhibit inverse heterodimerization preferences with Oct4 on the canonical versus a newly identified compressed sox/oct motif. We can swap the cooperativity profiles of Sox2 and Sox17 by exchanging single amino acids at the Oct4 interaction interface resulting in Sox2KE and Sox17EK proteins. The reengineered Sox17EK now promotes reprogramming of somatic cells to iPS, whereas Sox2KE has lost this potential. Consistently, when Sox2KE is overexpressed in embryonic stem cells it forces endoderm differentiation similar to wild-type Sox17. Together, we demonstrate that strategic point mutations that facilitate Sox/Oct4 dimer formation on variant DNA motifs lead to a dramatic swap of the bioactivities of Sox2 and Sox17.
- Published
- 2011
7. Histological evaluation of osteogenesis of 3D-printed poly-lactic-co-glycolic acid (PLGA) scaffolds in a rabbit model
- Author
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Victor Fan, Zigang Ge, Jin-Fei Yeo, Tong Cao, Boon Chin Heng, and Xian-Feng Tian
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Male ,Scaffold ,Materials science ,Histology ,Time Factors ,Biocompatibility ,Biomedical Engineering ,Bioengineering ,Biocompatible Materials ,Bone tissue ,Iliac crest ,Bone and Bones ,Biomaterials ,chemistry.chemical_compound ,Polylactic Acid-Polyglycolic Acid Copolymer ,Osteogenesis ,Periosteum ,medicine ,Animals ,Lactic Acid ,Bone regeneration ,Tissue Scaffolds ,Magnetic Resonance Imaging ,PLGA ,medicine.anatomical_structure ,chemistry ,Bone Substitutes ,Rabbits ,Tomography, X-Ray Computed ,Cancellous bone ,Polyglycolic Acid ,Biomedical engineering - Abstract
Utilizing a suitable combination of lactide and glycolide in a copolymer would optimize the degradation rate of a scaffold upon implantation in situ. Moreover, 3D printing technology enables customizing the shape of the scaffold to biometric data from CT and MRI scans. A previous in vitro study has shown that novel 3D-printed poly-lactic-co-glycolic acid (PLGA) scaffolds had good biocompatibility and mechanical properties comparable with human cancellous bone, while they could support proliferation and osteogenic differentiation of osteoblasts. Based on the previous study, this study evaluated PLGA scaffolds for bone regeneration within a rabbit model. The scaffolds were implanted at two sites on the same animal, within the periosteum and within bi-cortical bone defects on the iliac crest. Subsequently, the efficacy of bone regeneration within the implanted scaffolds was evaluated at 4, 12 and 24 weeks post-surgery through histological analysis. In both the intra-periosteum and iliac bone defect models, the implanted scaffolds facilitated new bone tissue formation and maturation over the time course of 24 weeks, even though there was initially observed to be little tissue ingrowth within the scaffolds at 4 weeks post-surgery. Hence, the 3D-printed porous PLGA scaffolds investigated in this study displayed good biocompatibility and are osteoconductive in both the intra-periosteum and iliac bone defect models.
- Published
- 2009
8. Conversion of Sox17 into a Pluripotency Reprogramming Factor by Reengineering Its Association with Oct4 on DNA.
- Author
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JAUCH, RALF, AKSOY, IRENE, HUTCHINS, ANDREW PAUL, KEOW LENG NG, CALISTA, XIAN FENG TIAN, JIAXUAN CHEN, PALASINGAM, PAAVENTHAN, ROBSON, PAUL, STANTON, LAWRENCE W., and KOLATKAR, PRASANNA R.
- Subjects
PROTEINS ,EMBRYONIC stem cells ,TRANSCRIPTION factors ,AMINO acids ,BIOMOLECULES ,DNA - Abstract
Very few proteins are capable to induce pluripotent stem (iPS) cells and their biochemical uniqueness remains unexplained. For example, Sox2 cooperates with other transcription factors to generate iPS cells, but Sox17, despite binding to similar DNA sequences, cannot. Here, we show that Sox2 and Sox17 exhibit inverse heterodimerization preferences with Oct4 on the canonical versus a newly identified compressed sox/oct motif. We can swap the cooperativity profiles of Sox2 and Sox17 by exchanging single amino acids at the Oct4 interaction interface resulting in Sox2KE and Sox17EK proteins. The reengineered Sox17EK now promotes reprogramming of somatic cells to iPS, whereas Sox2KE has lost this potential. Consistently, when Sox2KE is overexpressed in embryonic stem cells it forces endoderm differentiation similar to wild-type Sox17. Together, we demonstrate that strategic point mutations that facilitate Sox/Oct4 dimer formation on variant DNA motifs lead to a dramatic swap of the bioactivities of Sox2 and Sox17. STEM CELLS 2011;29:940-951 [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
9. Proliferation and Differentiation of Human Osteoblasts within 3D printed Poly-Lactic-co-Glycolic Acid Scaffolds.
- Author
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ZIGANG GE, LISHAN WANG, BOON CHIN HENG, XIAN-FENG TIAN, KAI LU, TAI WENG FAN, VICTOR, JIN FEI YEO, TONG CAO, and TAN, EUNICE
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BONE cells ,CELL proliferation ,CELL differentiation ,CELL culture ,ALKALINE phosphatase ,BONE growth - Abstract
Bone repair and regeneration can be enhanced through implantation of biocompatible and biodegradable scaffolds, which serve primarily as osteoconductive moieties. In this study, the mechanical properties and microenviroment of 3D printed poly-lactic-co-glycolic acid (PLGA) scaffolds are examined. Additionally, the proliferation and differentiation of human fetal osteoblasts are evaluated after 3 weeks of in vitro culture on the scaffolds. The results showed that the PLGA scaffolds examined had mechanical properties similar to that of trabecular bone, but was still much weaker compared to cortical bone. In addition to general porosity, the PLGA scaffolds also had micropores within macropore walls. Cultured human osteoblasts could proliferate upon seeding on the PLGA scaffolds. Alkaline phosphatase activity and osteonectin expression of the osteoblasts cultured on the PLGA scaffolds remained stable over three weeks, whilst expression of collagen type I and osteopontin decreased. The alkaline phosphatase activity of osteoblasts cultured on PLGA scaffolds is comparable with that from two commercially-available scaffolds -- OPLA and collagen scaffolds (Becton-Dickinson (BD) Inc., Franklin Lakes, NJ, USA). Hence, the results suggested that the PLGA scaffolds examined are conducive for promoting osteogenesis. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
10. Discussion of the process for wool blended yarn with high percentage tussah.
- Author
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Mm-na PENG, Jie LU, and Xian-feng TIAN
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BLENDED yarn ,SPINNING (Textiles) ,DYES & dyeing ,QUALITY control ,TEXTILE industry - Abstract
The paper discused on the processing technology of the worsted wool yarn of high percentage of tussah. According to the property of dye and spun for tussah, we optimized and improved the technology from dyeing, re-washing process, combing to spinning. During the tussah production process many experiments were done on the key process technology and the quality control. The practice showed that the colorability was the best at 90 °C to keep temperature time, it may reduce static generation in the combing process by re-washing twice and adding oil-water agent twice, quality of yarn was the best under the condition of ensuring the relative humidity of the former spinning workshop and the storage time of the wool top from the first needle carding process, and at same time some main parts such as the roller should be treated especially. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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