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Staged Growth of Optimized Arterial Model Trees (2000)

Karch, Rudolf ; Neumann, Friederike ; Neumann, Martin ; [et al.]

Springer

Annals of biomedical engineering 28 (2000), S. 495-511

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ISSN: 1573-9686

Keywords: Heart ; Epicardial and endocardial differences ; Vascular growth model ; Mathematical model ; Computer simulation ; Constrained constructive optimization

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: Abstract There is a marked difference in the structure of the arterial tree between epi- and endocardial layers of the human heart. To model these structural variations, we developed an extension to the computational method of constrained constructive optimization (CCO). Within the framework of CCO, a model tree is represented as a dichotomously branching network of straight cylindrical tubes, with flow conditions governed by Poiseuille's law. The tree is grown by successively adding new terminal segments from randomly selected points within the perfusion volume while optimizing the geometric location and topological site of each new connection with respect to minimum intravascular volume. The proposed method of “staged growth” guides the generation of new terminal sites by means of an additional time-dependent boundary condition, thereby inducing a sequence of domains of vascular growth within the given perfusion volume. Model trees generated in this way are very similar to reality in their visual appearance and predict diameter ratios of parent and daughter segments, the distribution of symmetry, the transmural distribution of flow, the volume of large arteries, as well as the ratio of small arterial volume in subendocardial and subepicardial layers in good agreement with experimental data. From this study we conclude that the method of CCO combined with staged growth reproduces many characteristics of the different arterial branching patterns in the subendocardium and the subepicardium, which could not be obtained by applying the principle of minimum volume alone. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8719Hh, 4760+i

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1114/1.290

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Zur Rekombinationsenthalpie von Radikalen - Thermochemie der Ringöffnung von Cyclophanen (1996)

Roth, Wolfgang R. ; Hopf, Henning ; de Meijere, Armin ; [et al.]

Weinheim : Wiley-Blackwell

Liebigs Annalen 1996 (1996), S. 2141-2154

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ISSN: 0947-3440

Keywords: Diradicals ; Gasphase kinetics ; Trapping, NO and O2 ; Supercritical fluid reactions ; Reaction forcefield ; Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Radical Recombination Enthalpy. - Thermochemistry of the Ringopening of CyclophanesBy thermolysis of the cyclophanes 1, 5, 8, 11, 14, 18, and 21 in the presence of NO or O2 the enthalpy profiles for the ring opening were determined from the temperature, NO, or O2 dependance of the trapping rates of the intermediate diradicals. The experimental enthalpy wells, which varied between 3 and 12 kcal · mol-1, can be simulated well with a reaction forcefield making use of the EVBH method of Malrieu et al. This result gives confidence that also meaningful recombination barriers of radicals can be obtained by this method.

Additional Material: 18 Ill.