| 11. |
- Huang, Daming, et al.
(författare)
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A Modified Charge-Pumping Method for the Characterization of Interface-Trap Generation in MOSFETs
- 2009
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 56:2, s. 267-274
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Tidskriftsartikel (refereegranskat)abstract
- A novel recovery-free interface-trap measurement method is presented in detail. This method is the modification of the conventional charge pumping (CP) by extending the pulse low level to the stress-bias and minimizing the pulse high-level duty cycle to suppress the recovery effect. The method is applied to study the negative-bias temperature instability in p-MOSFETs. As compared with the conventional CP, a much larger interface-trap generation under stress is observed by the new method. A power law time dependence (similar to t(n)) of interface-trap generation is observed. The index n. is less than that derived from conventional CP and increases with temperature, demonstrating a dispersive process involved in the trap generation dynamics.
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| 12. |
- Liu, Jin-ming, et al.
(författare)
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Mid-term effects of lung volume reduction surgery on pulmonary function in patients with chronic obstructive pulmonary disease
- 2007
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Ingår i: Chinese Medical Journal. - 0366-6999. ; 120:8, s. 658-662
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Tidskriftsartikel (refereegranskat)abstract
- Background Now lung volume reduction surgery (LVRS) has become one of the most effective methods for the management of some cases of severe chronic obstructive pulmonary disease (COPD). We evaluated the mid-term effects of LVRS on pulmonary function in patients with severe COPD. Methods Ten male patients with severe COPD aged 38-70 years underwent LVRS and their pulmonary function was assessed before, 3 months and 3 years after surgery. The spirometric and gas exchange parameters included residual volume, total lung capacity, inspiratory capacity, forced vital capacity, forced expiratory volume in one second, diffusion capacity for CO, and arterial blood gas. A 6-minute walk distance (6MWD) test was performed. Results As to preoperative assessment, most spirometric parameters and 6MWD were significantly improved after 3 months and slightly 3 years after LVRS. Gas exchange parameters were significantly improved 3 months after surgery, but returned to the preoperative levels after 3 years. Conclusions LVRS may significantly improve pulmonary function in patients with severe COPD indicating for LVRS. Mid-term pulmonary function 3 years after surgery can be decreased to the level at 3 months after surgery. Three years after LVRS, lung volume and pulmonary ventilation function can be significantly improved, but the improvement in gas exchange function was not significant.
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| 13. |
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| 14. |
- Wei, Jian-Feng, et al.
(författare)
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Formation of Kv2.1-FAK complex as a mechanism of FAK activation, cell polarization and enhanced motility
- 2008
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Ingår i: Journal of Cellular Physiology. - : Wiley. - 0021-9541 .- 1097-4652. ; 217:2, s. 544-557
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Tidskriftsartikel (refereegranskat)abstract
- Focal adhesion kinase (FAK) plays key roles in cell adhesion and migration. We now report that the delayed rectifier Kv2.1 potassium channel, through its LD-like motif in N-terminus, may interact with FAK and enhance phosphorylation of FAK(397) and FAK(576/577) Overlapping distribution of Kv2.1 and FAK was observed on soma and proximal dendrites of cortical neurons. FAK expression promotes a polarized membrane distribution of the Kv2.1 channel. In Kv2.1-transfected CHO cells, formation of the Kv2.1-FAK complex was stimulated by fibronectin/integrin and inhibited by the K channel blocker tetraethylammonium (TEA). FAK phosphorylation was minimized by shRNA knockdown of the Kv2.1 channel, point mutations of the N-terminus, and TEA, respectively. Cell migration morphology was altered by Kv2.1 knockdown or TEA, hindering cell migration activity. In wound healing tests in vitro and a traumatic injury animal model, Kv2.1 expression and co-localization of Kv2.1 and FAK significantly enhanced directional cell migration and wound closure. It is suggested that the Kv2.1 channel may function as a promoting signal for FAK activation and cell motility.
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| 15. |
- Wei, Kun, et al.
(författare)
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The Intergranular Microstructure of Magnesium Based Die-Cast AE Alloys
- 2009
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Ingår i: Magnesium Technology 2009. - : The Minerals, Metals & Materials Society (TMS). - 9780873397308 ; , s. 261-266
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Konferensbidrag (refereegranskat)abstract
- A systematic investigation on microstructures of magnesium based die-cast Mg-Al-RE alloys (AE alloys) has been performed by XRD, SEM and TEM. The alloys are with content of Al around 4wt% and various content of rare earth (RE). Samples of these alloys are in as-cast condition as well as in aged condition at 200°C and 250°C. The intergranular microstructure of the alloys has been studied in details. Three type binary Al-RE phases were found intergranularly. Al11RE3 is predominant intergranular phase in the as cast alloys. Al3RE particles and small amount of Al2RE phase were found in alloys with high RE content. Thermal stability of the Al-RE phases in AE alloys was suggested to decrease in sequence: Al2RE→ Al11RE3 →Al3RE. The Al/RE ratio of the die cast alloys determined their phase constitutions. Promising AE alloys for creep resistance is suggested to have an Al/RE ratio not higher than 1.8.
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| 16. |
- Wei, Liu-Ying, et al.
(författare)
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A TEM study of microstructural change in Mg alloys during creep
- 2007
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Ingår i: 8th Multinational Congress on Microscopy.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- M5-10 A TEM Study of Microstructural Change in Mg Alloys during Creep Wei L.-Y. Wei K. and Warren R. Division of Materials Science, School of Technology and Society Malmö University, 205 06 Malmö Sweden liu-ying.wei@ts.mah.se Due to their low densities and a good combination of castability and different properties, magnesium alloys have been attractive materials for automotive industry for weight saving. Die-cast AZ91 is one of the most widely used alloys. It exhibits excellent die castability, good strength properties and a fair ductility but its mechanical properties, especially the creep resistance, decrease on exposure at temperature above 120ºC [1]. Softening and coarsening of the interdendritic phase β-Al12Mg17 in AZ91 can readily occur at elevated temperatures due to its low melting temperature (Tm = 437°C) [2]. Rare earth in magnesium alloys usually brings about alloy strengthening through the formation of thermally stable intergranular phases and the complete suppression of the β-Al12Mg17 phase formation. In the present work tensile creep behavior of the die-cast magnesium alloys AZ91 and AE42 and their microstructural change during plastic deformation in creep have been studied. The objective of the work is to study the active creep mechanisms on the basis of the creep data in combination with the microstructural investigations. The SEM micrographs in Fig. 1 (a-b) illustrate the as-cast microstructures of the two die cast alloys showing a typical dendritic solidification structure with a fine-scale grain size. Segregation of Al adjacent to the dendrite boundaries can be seen clearly in AZ91D. Phases with a bright contrast and surrounded by high Al-segregated eutectic α-Mg are β-Al12Mg17 phase. Segregation of Al seems not obvious in AE42. The dominant interdendritic phase is Al11RE3. Mn-containing phases also formed during solidification in both AZ91 and AE42. The TEM micrographs in Fig. 2 (a-c) illustrate the structural changes during creep in AZ91 and AE42. Fig. 2 (a) shows the formation of denuded zones around the dendrite boundaries and the formation of discontinuous precipitates Al12Mg17. TEM/XEDS revealed that the Al content in the denuded zones decreased after creep test, from the original 5.5% to 2.5% (wt%). Fig. 2 (b-c) illustrates the formation of dislocation sources in the (0001) basal planes under a relatively high stress and the movement of dislocations from the sources towards the dendrite boundaries. The existence of the supersaturated Al-segregated zones adjacent to the dendrite boundaries is the main reason for the recovery of AZ91 at operating temperatures above 100ºC. Under loading plastic deformation occurred by the diffusion of Al atoms along the boundaries from compressive to tensile grain boundaries that caused the formation of the denuded grain boundaries and as a consequence the formation of the discontinuous precipitates Al12Mg17. Dislocation climb process also operated and tended to become a dominant process at stress above 60MPa.The low level of Al in AE42 suppresses the formation of Al supersaturated zones adjacent to the dendrite boundaries that, combining with the formation of the thermally stable interdendritic phase Al11RE3 (Tm~640ºC), provides AE42 a much better creep performance. Diffusion accompanying with the dislocation climb also occurred and became more dominant at a relatively high stress. Figure 1 SEM micrographs of the die cast alloys (a) AZ91D; (b) AE42. Fig. 2 TEM micrographs of the crept samples, (a-b) AZ91 after creep test at 100ºC/100MPa (n=3), (c) AE42 after creep at 175ºC/60MPa (n=2-7). References: 1. I.J. Polmer, 2nd Mg conference, DGM Informationsgesellschaft, Germany (1992), 201 2. M.S. Dargush, G.L. Dunlop, K. Pettersen, in: W. Higgins (Ed.), Trans. of 19th Intern. Die Casting Cong., North American Die Casting Association, Rosemont, IL, 1997, 131–137. Acknowledgements: Norsk Hydro ASA is gratefully acknowledged for providing the test bars
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| 17. |
- Wei, Liu-Ying, et al.
(författare)
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Creep behaviour and microstructure of magnesium die cast alloys AZ91 and AE42
- 2007
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Ingår i: Materials Science Forum. - : Trans Tech Publications. ; 546-549, s. 73-76
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Tidskriftsartikel (refereegranskat)abstract
- Tensile creep behaviour of the die-cast magnesium alloys AZ91 and AE42 has been studied at temperatures between 85oC and 200oC and at stresses in the range from 30 to 100 MPa. Microstructural investigations, mainly by TEM, have been performed on the selected crept samples to characterise the microstructural change during the plastic deformation, which reveals several phenomena related to the creep process including formation of dislocation sources, denuded zones around grain boundaries and microvoids, and changes in the nature of intermetallic phases. The active creep mechanisms have been discussed on the basis of the creep data in combination with the microstructural change during creep.
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| 18. |
- Adnan, Safdar, et al.
(författare)
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Microstructures of electron beam melted (EBM) biomaterial Ti-6Al-4V
- 2009
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Ingår i: Mechanics of Biological and Biomedical Materials;1132-Z09-06. - : The Materials Research Society (MRS).
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Konferensbidrag (refereegranskat)abstract
- Ti-6Al-4V alloy is an attractive biomaterial. The current work evaluates the microstructures of the solid and net-shape Ti-6Al-4V alloy produced by Electron Beam Melting (EBM) system using SEM/EDX and optical microscope. The microstructures are influenced by the cooling rate, processing parameters of the EBM system and re-heating of the existing layer during the melting of subsequent layers. Layer structure and columnar grains have been observed, with growing direction parallel to the built direction. The interior of these grains consists of alternating α / β phases. The β phase in the colonies resembles rod shape embedded in the α platelet. Along the grain boundaries more or less continuous α layers were observed. In comparison to solid samples uneven surfaces and pores were seen in the net shape structure. Microhardness evaluation of the EBM produced alloys was also carried out and compared with conventionally produced alloys.
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| 19. |
- Bailey, C., et al.
(författare)
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Coffin-Manson constant determination for a Sn-8Zn-3Bi Lead-Free Solder Joint
- 2006
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Ingår i: Soldering and Surface Mount Technology. - : Emerald. - 1758-6836 .- 0954-0911. ; 18:2, s. 4-11
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Tidskriftsartikel (refereegranskat)abstract
- Purpose To determine the Coffin-Manson (CM) equation constants for fatigue life estimation of Sn-8Zn-3Bi solder joints, since Sn-8Zn-3Bi solder has a melting temperature of around 199°C which is close to that of the conventional Sn-Pb solder which has previously been used in the electronics assembly industry. Design/methodology/approach Three dimensional finite element (FE) simulation analysis was used for comparison with the experimentally measured data and to determine the CM constants. Low cycle fatigue tests and FE simulations were carried out for these lead-free solder joints, and eutectic Sn-37Pb solder was used as a reference. Findings The CM equation for Sn-8Zn-3Bi solder joints was fitted to the lifetimes measured and the shear strains simulated. The constants were determined to be 0.0294 for C, the proportional constant, and for the fatigue exponent, β, −2.833. Originality/value The CM equation can now be used to predict the reliability of Sn-8Zn-3Bi solder joints in electronics assembly and the knowledge base for the properties of the Sn-Zn solder system has been increased.
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| 20. |
- Birney, Ewan, et al.
(författare)
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Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 799-816
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Tidskriftsartikel (refereegranskat)abstract
- We report the generation and analysis of functional data from multiple, diverse experiments performed on a targeted 1% of the human genome as part of the pilot phase of the ENCODE Project. These data have been further integrated and augmented by a number of evolutionary and computational analyses. Together, our results advance the collective knowledge about human genome function in several major areas. First, our studies provide convincing evidence that the genome is pervasively transcribed, such that the majority of its bases can be found in primary transcripts, including non-protein-coding transcripts, and those that extensively overlap one another. Second, systematic examination of transcriptional regulation has yielded new understanding about transcription start sites, including their relationship to specific regulatory sequences and features of chromatin accessibility and histone modification. Third, a more sophisticated view of chromatin structure has emerged, including its inter-relationship with DNA replication and transcriptional regulation. Finally, integration of these new sources of information, in particular with respect to mammalian evolution based on inter- and intra-species sequence comparisons, has yielded new mechanistic and evolutionary insights concerning the functional landscape of the human genome. Together, these studies are defining a path for pursuit of a more comprehensive characterization of human genome function.
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