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  • HMWK  (1)
  • Polymer and Materials Science  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 22 (1994), S. 184-193 
    ISSN: 1573-9686
    Keywords: Mathematical model ; Factor XII ; Kallikrein ; HMWK ; Cascade ; Mass transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This work analyzes, for the first time, the combined role of blood flow, protein transport and the reaction network of the contact phase up to the “common pathway” of the blood coagulation cascade. The model is comprised of a set of 20 dominant reactions with 11 components. Systems of ODEs reducible to 4 coupled equations describe rigorously the dynamic behavior, while systems of algebraic equations, reducible to a single polynomial equation, model the steady state concentrations of the coagulants. The analysis showed that there is never more than onestable steady state. This is in contrast to the analysis of common pathway that gives rise to multiple concentration states. It also revealed a general robustness of the system to changes in procoagulant concentrations, inhibition rates and most activation rate constants. The system is largely impervious to the level of activated Factor XII, given that a trace (non-zero) level is present. In contrast, the system displays a dual response to flow and surface activity: A change in either of these factors alone can promote, have no effect on, or (in the case of flow) impede the progress of coagulation, depending on the value of the other factor. Their effects must therefore be examined in unison. These results may help resolve contradictory findings attributed to one or the other factor alone.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 1315-1326 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The present article builds on elementary fluid dynamics and previous analyses by the author to delineate approximate boundaries of mural thrombus height HP, maximum shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma _{{\rm Max}} $\end{document}, and flow pulsatility beyond which thrombi are subject to either very high or very low probabilities of embolization. A thrombus height of ∼0.1 mm emerges as a critical dividing line: Below it, the maximum embolizing shear stress τs is independent of thrombus height and varies only linearly with shear rate. Above it, τs quickly approaches a strong quadratic dependence on both thrombus height and shear rate: \documentclass{article}\pagestyle{empty}\begin{document}$ \tau _{\rm s} \sim (H_{\rm p} \dot \gamma)^2 $\end{document}, significantly increasing the likelihood of an embolizing event. By contrast, convective-diffusive removal of blood components during the initial stages of thrombus formation varies only weakly with \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma ^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} $\end{document} in all but the smallest vessels. These maximum embolizing stresses are due principally to fluid drag. Acceleration (pulsatile) forces only begin to make their presence felt at \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma} $\end{document} 〈 500 s-1 and reach parity with fluid drag at \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma} $\end{document} ∼ 10 s-1, i.e., at a level where the presence of pulsatility is questionable. The results are used to provide maps of domains with high and low probabilities of an embolytic event and of vessel patency. The maps reveal that relatively modest changes in shear rate and/or vessel lumen can cause shifts from high to low likelihood of vessel patency, opening up possible ways of controlling blockage by manipulation of these variables.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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