| 51. |
- Carlberg, Björn, 1983, et al.
(författare)
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Electrospun polyurethane scaffolds for proliferation and neuronal differentiation of human embryonic stem cells.
- 2009
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Ingår i: Biomedical materials (Bristol, England). - : IOP Publishing. - 1748-605X .- 1748-6041. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Adult central nervous system (CNS) tissue has a limited capacity to recover after trauma or disease. Hence, tissue engineering scaffolds intended for CNS repair and rehabilitation have been subject to intense research effort. Electrospun porous scaffolds, mimicking the natural three-dimensional environment of the in vivo extracellular matrix (ECM) and providing physical support, have been identified as promising candidates for CNS tissue engineering. The present study demonstrates in vitro culturing and neuronal differentiation of human embryonic stem cells (hESCs) on electrospun fibrous polyurethane scaffolds. Electrospun scaffolds composed of biocompatible polyurethane resin (Desmopan 9370A, Bayer MaterialScience AG) were prepared with a vertical electrospinning setup. Resulting scaffolds, with a thickness of approximately 150 microm, exhibited high porosity (84%) and a bimodal pore size distribution with peaks at 5-6 and 1 microm. The mean fiber diameter was measured to approximately 360 nm with a standard deviation of 80 nm. The undifferentiated hESC line SA002 (Cellartis AB, Göteborg, Sweden) was seeded and cultured on the produced scaffolds and allowed propagation and then differentiation for up to 47 days. Cultivation of hESC on electrospun fibrous scaffolds proved successful and neuronal differentiation was observed via standard immunocytochemistry. The results indicate that predominantly dopaminergic tyrosine hydroxylase (TH) positive neurons are derived in co-culture with fibrous scaffolds, in comparison to reference cultures under the same differentiation conditions displaying large proportions of GFAP positive cell types. Scanning electron micrographs confirm neurite outgrowth and connection to adjacent cells, as well as cell attachment to individual fibers of the fibrous scaffold. Consequently, electrospun polyurethane scaffolds have been proven feasible as a substrate for hESC propagation and neuronal differentiation. The physical interaction between cells and the fibrous scaffold indicates that these scaffolds provide a three-dimensional physical structure; a potential candidate for neural tissue engineering repair and rehabilitation.
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| 52. |
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| 53. |
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| 54. |
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| 55. |
- Chen, S., et al.
(författare)
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Coffin-Mansson equation of Sn-4.0Ag-0.5Cu solder joint
- 2009
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Ingår i: Soldering and Surface Mount Technology. - : Emerald. - 1758-6836 .- 0954-0911. ; 21:2, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this paper is to fit Coffin-Manson equation of Sn-4.0Ag-0.5Cu lead free solder joint by using results of solders joint reliability test and finite element analysis. Also to present a novel device for solder joint reliability test. Design/methodology/approach: Two-points bending test of Sn-4.0Ag-0.5Cu lead free solder joint was carried out at three deflection levels by using a special bending tester that can control displacement exactly by a cam system. The failure criterion was defined as resistance of solder joint getting 10 percent increase. The X-section was done for all failure samples to observe crack initiation and propagation in solder joint. Finite element analysis was presented with ANSYS for obtaining shear strain range, analyzing distribution of stress and strain and supporting experimental results. Findings: The experimental results indicate that the fatigue life decreased obviously with the displacement increased. By using optical microscope and SEM photographs, two kinds of failure mode were found in solder joint. The majority failure mode took place at the bottom corner of solder joint under the termination of resistor initially, and propagated into the solder matrix. Another failure mode was delamination. It appeared at the interface between the termination of resistor and its ceramic body. The distribution status of stress and strain in solder joint and the calculation results of shear strain range at different deflection levels were obtained from simulation result. The Coffin-Manson equation of Sn-4.0Ag-0.5Cu lead free solder joint was fitted by combining experimental data with result of finite element analysis. Originality/value: This paper presents Coffin-Manson equation of Sn-4.0Ag-0.5Cu solder joint with two-points bending test. An effective and economical device was designed and applied.
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| 56. |
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| 57. |
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| 58. |
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| 59. |
- Ekstrand, Lisa, 1974, et al.
(författare)
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Characterization of thermally conductive epoxy nano-composites
- 2005
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Ingår i: 28th International Spring Seminar on Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 2005; Wiener Neustadt; Austria; 19 May 2005 through 20 May 2005. - 9780780393240 ; , s. 35-39
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Konferensbidrag (refereegranskat)abstract
- This work aims to develop an Anisotropic Conductive Adhesive (ACA) paste with improved thermal conductivity. ACA consists of a polymer based resin and conductive filler particles. We introduce an electrically insulating but thermally conductive phase into the adhesive. Nano and micro scale particles of alumina oxide, silicon carbide and carbon nanotubes are used with and without surface treatment. The thermal measurements are carried out by transient hot wire method. So far, the thermal conductivity of the epoxy has been increased with more than 100%.
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| 60. |
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