| 1. |
- Li, Wen Bin, et al.
(författare)
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Stresses developed in reaction-bonded ceramics
- 1995
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Ingår i: Ceramic materials and components for engines. - : World Scientific Publishing Co Pte Ltd. - 9810219059 ; , s. 465-468
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Konferensbidrag (refereegranskat)abstract
- For a number of reaction-bonded ceramics, the reaction starts from the surface of the particles, forming a shell of products surrounding a reactant core. The reaction is continued by inward growth of the shell by means of diffusion of the reactant elements from the particle surface to the interface between the shell and core and vice versa. Since there exists a volumetric change due to the reaction, the products forming at the shell/core interface will be severely constrained. Strain and stress fields are then built up within the particles. A physical and mathematic model to calculate the strain and stress during and after the reaction bonding process is constructed. The preliminary results of estimation of stresses within the particles and their possible effect on reaction kinetics are presented and briefly discussed
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| 2. |
- Li, Wen Bin, et al.
(författare)
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Stresses developed in reaction-bonded ceramics
- 1999
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 19:3, s. 277-283
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Tidskriftsartikel (refereegranskat)abstract
- A physical model is presented that predicts the stress distribution created in a particle during its reaction with a surrounding reactant to form a uniform layer of reaction product on its surface, when the reaction involves a volume change. The results of the model are applied specifically to the case of silicon reacting with nitrogen to form Si3N4. The model predicts the generation of a high, tensile hydrostatic stress in the Si core as well as high tensile radial stress and compressive tangential stress in the nitride layer. Although the model is restricted to elastic deformation only and therefore predicts unrealistically high stresses in some cases, the results are anyway of relevance in the consideration of possible non-elastic processes such as creep and fracture and also in assessing the possible effect of stress on the reaction equilibrium. It is predicted that the nitride reaction layer would fracture during the nitridation process. A second model is also presented predicting the residual stresses arising during cooling of a partially reacted particle as a result of the difference in thermal expansion of the reactant core and the reaction product layer. In the case of the reaction of silicon to silicon nitride these thermal expansion mismatch stresses are significant but small compared to the stresses due to the chemical reaction.
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| 3. |
- Yuan, XiMing, et al.
(författare)
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The establishment of two cell lines from a mouse uterine cervical carcinoma (U14) and their metastatic phenotype changes
- 1995
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Ingår i: Clinical and Experimental Metastasis. - 0262-0898 .- 1573-7276. ; 13:6, s. 463-73
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the heterogeneity of metastatic potential of murine cervical carcinoma (U14). Two cell lines, P11-90 and L10-90, were established from a pulmonary metastatic substrain (U14AP11) and a lymphatic metastatic substrain (U14AL10), which were selected from U14 in vivo after 11 and 10 passages, respectively. The biologic differences between the two cell lines are as follows. (1) The cells of the P11-90 line grow more rapidly compared with the L10-90 line. From the 40th passage the medium pH was different. (2) The median number of chromosomes in P11-90 and L10-90 was 72 and 64, respectively; the rates of gap aberration were 88% and 78%, respectively. (3) The number of T lymphocytes and T helper lymphocytes in the peripheral blood from hosts with P11-90 were higher than that of hosts transplanted with L10-90, but the number of B lymphocytes in the latter was larger than that in the former. (4) The metastatic potential of each cell line partially decreased compared to the relative tumor substrain, but their organ preference still remained and the transplant locations, axillary or footpad, had a prominent influence on their metastatic behavior. To observe the effects of metastatic target organs on the metastatic phenotypes of tumor cells, as well as to explore a method for the establishment and maintenance of the metastatic organ preference of tumor cells, conditioned medium (CM) from pulmonary or lymphatic node diploid cells was added to the culture medium of P11-90 and L10-90. Two sublines, P + P11-90 and Ln + L10-90, were thus established. Using stereological methods we found that the majority of P + P11-90 cells became larger and their nuclei also increased in size compared with their parental lines, but the majority of Ln + L10-90 cells became smaller in size, though the nuclei were enlarged. The pulmonary metastatic rate and lymphatic metastatic rate of P + P11-90, as well as the lymphatic metastatic rate of Ln + L10-90, were restored dramatically. The results suggest that by taking advantage of the interaction between tumor cells and the CM of host cells the metastatic potential of tumor cell lines can be maintained in vitro. Our work may offer an experimental model for the manipulation of metastasis of cell lines coming from the same parent strain but with different metastatic potentials.(ABSTRACT TRUNCATED AT 400 WORDS)
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