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nr. 477 - 2011 - Institut for Natur, Systemer og Modeller (NSM)

nr. 477 - 2011 - Institut for Natur, Systemer og Modeller (NSM)

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vi Contents<br />

Significance of the Apoptotic Wave . . . . . . . . . . . . . . . . . . . . . 33<br />

Michaelis-Menten versus a Hill function . . . . . . . . . . . . . . . . . . 34<br />

Implication of secretion of cytokines upon Ba phagocytosis . . . . . . . 35<br />

Activation by phagocytosis of necrotic β-cells . . . . . . . . . . . . . . . 36<br />

5.8 Discussion of Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 37<br />

Reversible or irreversible activation? . . . . . . . . . . . . . . . . . . . . 38<br />

The DuCa model with turnover of Ma . . . . . . . . . . . . . . . . . . . 41<br />

6 The Intermediated Model 45<br />

Model observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47<br />

6.1 Fixed Points of the IM Model . . . . . . . . . . . . . . . . . . . . . . . . 48<br />

Stability of the fixed points . . . . . . . . . . . . . . . . . . . . . . . . . 50<br />

Downfall of the IM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53<br />

Phase plane analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54<br />

A brief note on linearizing . . . . . . . . . . . . . . . . . . . . . . . . . . 59<br />

6.2 The IM Including Crowding-Terms . . . . . . . . . . . . . . . . . . . . . 60<br />

6.3 Recapitulation of The Analysis of the IM . . . . . . . . . . . . . . . . . 63<br />

7 A Brief Introduction to Bifurcation Analysis and Numerical Methods 65<br />

7.1 Generic Bifurcations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65<br />

7.2 The Hopf bifurcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66<br />

7.3 Biol<strong>og</strong>ical Relevance of Bifurcation Analysis . . . . . . . . . . . . . . . . 69<br />

7.4 Choice of Bifurcation Parameters . . . . . . . . . . . . . . . . . . . . . . 69<br />

7.5 Locating the Fixed Points . . . . . . . . . . . . . . . . . . . . . . . . . . 70<br />

Evaluation of stability of the fixed points and detection of bifurcations . 71<br />

8 Bifurcation Diagrams and Analysis 73<br />

8.1 Codimension One Bifurcations . . . . . . . . . . . . . . . . . . . . . . . 73<br />

8.2 Using f1 as the bifurcation parameter . . . . . . . . . . . . . . . . . . . 74<br />

Basic features of the NOD bifurcation diagram . . . . . . . . . . . . . . 74<br />

Eigenvalues, manifolds and behavior of the fixed points on the NODf1-USB 75<br />

Eigenvalues, manifolds and behavior of the fixed points on the NODf1-LUB 79<br />

Combining the analysis of the NODf1-USB and LUB . . . . . . . . . . .<br />

Hidden features in figure 8.1 . . . . . . . . . . . . . . . . . . . . . . . . .<br />

81<br />

84<br />

The Balb/c bifurcation diagram . . . . . . . . . . . . . . . . . . . . . . . 87<br />

8.3 Using f2 as the bifurcation parameter . . . . . . . . . . . . . . . . . . . 88<br />

8.4 Reducing the DuCa-model . . . . . . . . . . . . . . . . . . . . . . . . . . 93<br />

9 Discussion of the Bifurcation Analysis 97<br />

9.1 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101<br />

10 Conclusion 1 103<br />

11 Expanding and Modifying the DuCa model 105<br />

11.1 Including a Compartment of Healthy β-cells . . . . . . . . . . . . . . . . 105<br />

Model criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105<br />

11.2 First approximation to a governing equation – Model A . . . . . . . . . 106<br />

11.3 Modifying the governing equation – Model B . . . . . . . . . . . . . . . 110

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