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Vasculogenesis and angiogenesis are two different mechanisms for blood
vessel formation. Angiogenesis occurs when new vessels sprout from
pre-existing vasculature in response to external chemical stimuli.
Vasculogenesis occurs via the reorganization of randomly distributed
cells into a blood vessel network. Experimental models
of vasculogenesis have suggested that the cells exert traction forces
onto the extracellular matrix and that these forces may play
an important role in the network forming...
Si presenta un metodo di soluzione di una classe di problemi di diffusione nonlineare che hanno origine dalla teoria delle popolazioni con struttura di età.
A conceptual minimal model demonstrating spatially heterogeneous wave regimes
interpreted as pursuit-evasion in predator-prey system is constructed and investigated. The
model is based on the earlier proposed hypothesis that taxis accelerations of prey and
predators are proportional to the density gradient of another population playing a role
of taxis stimulus. Considering acceleration rather than immediate velocity allows
obtaining realistic solutions even while ignoring variations of total...
A quite general model of the nonlinear interaction of two impulse systems describing some types of cardiac arrhythmias is developed. Taking into account a refractory time the phase locking phenomena are investigated. Effects of the tongue splitting and their interweaving in the parametric space are found. The results obtained allow us to predict the behavior of excitable systems with two pacemakers depending on the type and intensity of their interaction and the initial phase.
A simple model of biological evolution of community food webs is introduced. This model
is based on the niche model, which is known to generate model food webs that are very
similar to empirical food webs. The networks evolve by speciation and extinction.
Co-extinctions due to the loss of all prey species are found to play a major role in
determining the longterm shape of the food webs. The central aim is to design the model
such that the characteristic...
This paper deals with modeling the passive
behavior of skeletal muscle tissue including
certain microvibrations at the cell level. Our
approach combines a continuum mechanics model
with large deformation and incompressibility at
the macroscale with chains of coupled
nonlinear oscillators.
The model verifies that an externally applied
vibration at the appropriate frequency is able to synchronize
microvibrations in skeletal muscle cells.
From the numerical analysis point of view,
one faces...
About twenty five years ago the first discrete mathematical model of the immune system
was proposed. It was very simple and stylized. Later, many other computational models have
been proposed each one adding a certain level of sophistication and detail to the
description of the system. One of these, the Celada-Seiden model published back in 1992,
was already mature at its birth, setting apart from the topic-specific nature of the other
models. This...
In this paper, a modified van der Pol equation is considered as a description of the heart action. This model has a number of interesting properties allowing reconstruction of phenomena observed in physiological experiments as well as in Holter electrocardiographic recordings. Our aim is to study periodic solutions of the modified van der Pol equation and take into consideration the influence of feedback and delay which occur in the normal heart action mode as well as in pathological modes. Usage...
This paper considers a Volterra's population system of fractional order and describes a bi-parametric homotopy analysis method for solving this system. The homotopy method offers a possibility to increase the convergence region of the series solution. Two examples are presented to illustrate the convergence and accuracy of the method to the solution. Further, we define the averaged residual error to show that the obtained results have reasonable accuracy.
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