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| 2. |
- Grubin, C. E., et al.
(författare)
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A novel radioligand binding assay to determine diagnostic accuracy of isoform-specific glutamic acid decarboxylase antibodies in childhood IDDM
- 1994
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Ingår i: Diabetologia. - 0012-186X. ; 37:4, s. 344-350
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Tidskriftsartikel (refereegranskat)abstract
- Insulin-dependent diabetes mellitus (IDDM) is associated with autoreactivity against GAD but the diagnostic sensitivity (positivity in disease) and specificity (negativity in health) of isoform-specific GAD antibodies have yet to be defined in assay systems suitable for screening large number of samples. One set of IDDM patient (n=10) and control (n=50) standard sera were used to develop quantitative antibody assays with in vitro synthesized recombinant 35S-methionine-labelled GAD65 and GAD67, respectively, and protein A-Sepharose to separate free from antibody-bound ligand. Binding levels were not normally distributed (p<0.0001) and therefore, the diagnostic accuracy of GAD antibodies was analysed by the ROC plots in population-based, consecutively-diagnosed, recent onset, 0-14 year-old patients (n=105), and matched, healthy control subjects (n=157). The ROC plots showed that the diagnostic sensitivity of GAD65 antibodies was 77% and the specificity 92% compared with 8% and 98%, respectively for GAD67 antibodies. In the IDDM sera, GAD65 and GAD67 antibodies were concordant in 7% (6 of 81) and GAD65 antibodies and ICA in 89% (72 of 81) without a correlation between the autoantibody levels. Autoantibodies to recombinant human islet GAD65 are specific and sensitive markers for childhood IDDM in this immunoassay with in vitro synthesized 35S-methioninelabelled recombinant GAD.
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| 3. |
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| 4. |
- Li, W.-B, et al.
(författare)
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Influence of particle shape on zener drag
- 1990
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Ingår i: Acta Metallurgica et Materialia. - 0956-7151. ; 38:6, s. 1045-1052
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Tidskriftsartikel (refereegranskat)abstract
- Practically all papers concerned with grain refinement based on pinning by particle dispersions have considered spherical particles. This paper avoids this restriction and develops Zener pinning equations for ellipsoidal particles of any shape, orientation and degree of coherency. Theoretical predictions are verified using soap bubble model experiments. It is found that within well defined conditions of particle orientation, disk or needle-shaped particles may offer greater pinning resistance, or Zener drag to migrating boundaries than spherical ones. However, the pinning resistance of non-spherical particles is sensitive to particle orientation. Their use in alloys is best utilised in systems based on mono-orientation dispersions
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| 5. |
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| 6. |
- Li, W.B., et al.
(författare)
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Mechanisms of indentation creep
- 1991
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Ingår i: Acta Metallurgica et Materialia. - 0956-7151. ; 39:12, s. 3099-3110
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Tidskriftsartikel (refereegranskat)abstract
- A physically-based theoretical model is developed for describing the phenomenon of indentation creep over the whole temperature range, from 300 K to melting. In agreement with experimental data collected, the model predicts that most materials, including ceramics, exhibit indentation creep at temperatures down to 300 K. It is established that the principal mechanism causing indentation creep is dislocation glide plasticity. The dominance of this mechanism over the whole temperature range is due to the very high stresses involved in indentation creep. If, however, the grain size is small (typically less than 0.3-0.4 μm) indentation creep may be dominated by grain boundary (Coble) diffusive creep instead. The implications of these results in terms of the design, forming and application of the so-called "hard materials" is discussed.
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| 7. |
- Li, W.B., et al.
(författare)
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Model for nano-indentation creep
- 1993
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Ingår i: Acta Metallurgica et Materialia. - 0956-7151. ; 41:10, s. 3065-3069
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Tidskriftsartikel (refereegranskat)abstract
- A new model is developed to describe that stage of nano-intentation creep prior to `pop-in', i.e. when the indentation load induces purely elastic stresses within the sample. Expressions for the stress fields due to a conical indenter are derived and the resulting chemical potential and diffusion fluxes established. The considerations lead to a creep rate equation which is found to fit well with existing experimental data on tungsten. The model is hence used to predict nano-indentation creep rates at various temperatures. It is found, for example, that at a temperature as low as 100 °C, the indentation creep rate of tungsten can be considerable
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| 8. |
- Ringer, S.P., et al.
(författare)
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On the rotation of precipitate particles
- 1992
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Ingår i: Acta Metallurgica et Materialia. - 0956-7151. ; 40:2, s. 275-283
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Tidskriftsartikel (refereegranskat)abstract
- An energetically unfavourable situation can develop when coherent particles are bypassed by migrating grain boundaries. This is due to the precipitates being exposed to incoherent interfaces in the new matrix. In this work, the rotation of precipitate particles to low energy, coherent orientations in the new matrix is shown to be one of several possible responses to this situation. A physical and kinetic model for the rotation is put forward and the results of calculations of rotation rate presented. It is shown that particle rotation is controlled by interfacial diffusion and depends upon alloy composition, time, temperature and particle size and shape. The possibility of particle rotation occurring during particle/boundary contact is also discussed. This is shown to depend upon the nature of the boundary type. Generally, boundaries moving under large driving pressures with high velocities (e.g. phase transformation interfaces), are less likely to allow rotation during particle/boundary contact than less mobile boundaries such as those in grain growth and recrystallization. Experimental results, from SAD and TEM of a Ti stabilized austenitic stainless steel containing a dispersion of coherent TiC precipitates is also presented and supports the particle rotation model
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| 9. |
- Tan, Z., et al.
(författare)
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On analysis and measurement of residual stresses in the bending of sheet metals
- 1994
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Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 36:5, s. 483-491
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Tidskriftsartikel (refereegranskat)abstract
- A new method for evaluating distribution of residual stresses in bent sheet metals is presented. Due to the non-uniform distribution of strain and stress across thickness, springback on unloading induces residual stress in a bent specimen. The authors have formulated the problem and shown that the springback and residual stresses can be expressed as a function of geometric parameters and material properties of sheet metals, e.g. bending curvature, thickness, Young's modulus, work-hardening index, etc. The layer-removing method was used to determine the residual stresses in the study. By simulating the layer-removing process, analytical measurement of the residual stress was made. The analytical results were compared with the experimental data measured, and a good agreement was found.
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| 10. |
- Vishnu, P. Ravi, et al.
(författare)
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Heat flow model for pulsed welding
- 1991
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Ingår i: Materials Science and Technology. - : Informa UK Limited. - 0267-0836 .- 1743-2847. ; 7:7, s. 649-659
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Tidskriftsartikel (refereegranskat)abstract
- An analytical model of the heat flow during pulsed welding is constructed by first developing a solution for the temperature distribution due to an instantaneous, stationary, Gaussian heat source. This solution is first extended to treat the case of a moving heat source for a single pulse and then extended to treat the case of pulsed welding by summing the temperature changes due to a series of pulses. Test gas tungsten arc welds in mild steel are used to confirm the validity of the model.
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