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- Gu, Y. W., et al.
(författare)
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Structural evolution in Ti-Si alloy synthesized by mechanical alloying
- 2004
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 352:1-4, s. 299-304
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical alloying of Ti-Si powder mixture was performed by high-energy ball milling at ambient temperature (25 °C). The structural and compositional evolutions during the mechanical alloying process were investigated by X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. Results showed, that the crystallite size of Ti and Si decreased with increasing milling time and the steady-state crystallite size was between 5 and 15nm. The mechanically alloyed Ti-Si powder was predominantly nanocrystalline with traces of the remnant amorphous phase. It was found that a significant increase in solid solubility of Si in Ti was achieved by mechanical alloying. Interdiffusion between the two elements occurred during milling and the dissolution of Si in Ti was obtained after 60 h milling, forming Ti(Si) solid solution. The lattice parameter ratio c/a and the unit cell volume of h.c.p. Ti(Si) were found to decrease with increasing milling time, indicating that the shrinkage of Ti lattice was caused by diffusion of Si atoms into Ti. © 2004 Elsevier B.V. All rights reserved.
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| 4. |
- Gu, YC, et al.
(författare)
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Laminin isoform-specific promotion of adhesion and migration of human bone marrow progenitor cells
- 2003
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 101:3, s. 877-885
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Tidskriftsartikel (refereegranskat)abstract
- Laminins are alphabetagamma heterotrimeric extracellular proteins that regulate cellular functions by adhesion to integrin and nonintegrin receptors. Laminins containing alpha4 and alpha5 chains are expressed in bone marrow, but their interactions with hematopoietic progenitors are unknown. We studied human bone marrow cell adhesion to laminin-10/11 (alpha5beta1gamma1/alpha5beta2gamma1), laminin-8 (alpha4beta1gamma1), laminin-1 (alpha1beta1gamma1), and fibronectin. About 35% to 40% of CD34(+) and CD34(+)CD38(-) stem and progenitor cells adhered to laminin-10/11, and 45% to 50% adhered to fibronectin, whereas they adhered less to laminin-8 and laminin-1. Adhesion of CD34(+)CD38(-) cells to laminin-10/11 was maximal without integrin activation, whereas adhesion to other proteins was dependent on protein kinase C activation by 12-tetradecanoyl phorbol-13-acetate (TPA). Fluorescence-activated cell-sorting (FACS) analysis showed expression of integrin alpha6 chain on most CD34(+) and CD34(+)CD38(-) cells. Integrin alpha6 and beta1 chains were involved in binding of both cell fractions to laminin-10/11 and laminin-8. Laminin-10/11 was highly adhesive to lineage-committed myelomonocytic and erythroid progenitor cells and most lymphoid and myeloid cell lines studied, whereas laminin-8 was less adhesive. In functional assays, both laminin-8 and laminin-10/11 facilitated stromal-derived factor-1alpha (SDF-1alpha)-stimulated transmigration of CD34(+) cells, by an integrin alpha6 receptor-mediated mechanism. In conclusion, we demonstrate laminin isoform-specific adhesive interactions with human bone marrow stem, progenitor, and more differentiated cells. The cell-adhesive laminins affected migration of hematopoietic progenitors, suggesting a physiologic role for laminins during hematopoiesis. (C) 2003 by The American Society of Hematology.
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| 5. |
- Ji, W, et al.
(författare)
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3-D computational modeling of SiC epitaxial growth in a hot wall reactor
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 220:4, s. 560-571
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional computational model for chemical vapor deposition (CVD) of silicon carbide (SiC) in a hot wall reactor is developed, where the susceptor is tapered with a rectangular cross-section. The present work focuses on the advection-diffusion-reaction process in the susceptor. The precursors are propane and silane, and the carrier gas is hydrogen with mass fraction higher than 98%. Computed growth rates under different system pressures and precursor concentrations are compared with the experimental data measured on samples grown in the Linkoping CVD reactor. The gas composition distribution and the growth rate profile are shown. Dependence of the growth rate on precursor concentrations is investigated.
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| 11. |
- Lofgren, PM, et al.
(författare)
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3-d thermal and flow modeling of hot wall epitaxial chemical vapor deposition reactors, heated by induction
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 338-3, s. 153-156
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Tidskriftsartikel (refereegranskat)abstract
- A three dimensional computational model for temperature and flow predictions in hot wall chemical vapor deposition (CVD) reactors, heated by induction, is presented. It includes heating by a Radio Frequency (RF) coil, flow and heat transfer. Thermal radiation is modeled by a modified Monte Carlo method. Model predictions are compared to full scale experiments at Linkoping CVD reactor for epitaxial growth of silicon carbide (SIC). Both streamwise and spanwise temperature gradients are well predicted, with the temperature maximum location shifted slightly upstream compared to the measured. Additionally, the model succeeds in predicting a recirculation zone just downstream of the susceptor. It is demonstrated how thermal gradients can be greatly reduced by simple geometrical changes.
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| 12. |
- Lofgren, P.M., et al.
(författare)
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Modeling of silicon carbide epitaxial growth in hot-wall chemical vapor deposition processes
- 2000
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 147:1, s. 164-175
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Tidskriftsartikel (refereegranskat)abstract
- A complete two-dimensional axisymmetric model for chemical vapor deposition (CVD) is presented, incorporating reduction heating by a radio frequency coil, flow, heat transfer (radiation included), and gas and surface chemistry, applied to epitaxial growth of silicon carbide (SiC) with H2 as the carrier gas and C3H8 and SiH4 as precursors. Temperatures range from 1873 to 1923 K. Predictions are compared to full-scale experiments carried out in the Linkoping hot-wall CVD reactor for epitaxial growth. Temperature predictions have previously shown to agree well with experiments, consequently, this paper focuses on the reaction mechanism model. Three different reaction mechanisms are compared to experiments where mechanisms contain 35 gas, seven surface, and two bulk species including gas and surface reactions. The predicted growth rate agrees well with experiments for 300 mbar but is slightly low for 50 mbar and somewhat high for 550 mbar. By including a recent mechanism for decomposition of SiH4, morphological conditions can be predicted comparing partial pressures of Si and C2H2 to experimental data from the literature. The predicted growth rate is not influenced by this additional model. It is demonstrated that when a model for hydrogen etching of the susceptor graphite is included, correct growth limitation is predicted.
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| 13. |
- Scherer, SW, et al.
(författare)
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Human chromosome 7: DNA sequence and biology
- 2003
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 300:5620, s. 767-772
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Tidskriftsartikel (refereegranskat)abstract
- DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.
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| 16. |
- Weng, J., et al.
(författare)
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Functional consequences of mutations in the MODY4 gene (IPF1) and coexistence with MODY3 mutations
- 2001
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 44:2, s. 249-258
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis. The aim of this study was to examine the putative role of mutations in the insulin promoter 1 (IPF1) gene in early-onset diabetes. Methods. We carried out mutation screening of the IPF1 gene in 115 Scandinavian families with at least two members with onset of diabetes younger than 40 years. The allele frequencies were also tested in 183 unrelated patients with late-onset Type II (noninsulin-dependent) diabetes mellitus and in 92 nondiabetic control subjects. Results. Two novel IPF1 variants (G212R and P239Q) and one previously reported (D76N) IPF1 variant were identified in the 115 families (3.5%). The D76N variant was found in one MODY3 family (S315fsinsA of HNF1 alpha) and also in two families with late-onset Type II diabetes. The P239Q variant was identified in two families with early-onset diabetes including one with MODY3 (R272C of HNF1 alpha) and in three families with late-onset Type II diabetes. Despite the fact that the variants did not segregate completely with diabetes, the non-diabetic carriers of the IPF1 variants had increased blood glucose concentrations (p < 0.05) and reduced insulin:glucose ratios (p < 0.05) during an oral glucose tolerance test compared with non-diabetic family members without these variants. In addition, when the G212R and P239Q variants were expressed in cells without IPF1 i.e.. Nes2y cells, both variants showed about a 50% reduction in their ability to activate insulin gene transcription compared to wild-type IPF1, as measured by reporter gene assay. Conclusion/interpretation. Although mutations in the IPF-1 gene are rare in early- (3.5%) and late-onset (2.7%) Type II diabetes, they are functionally important and occur also in families with other MODY mutations.
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