Mathematical analysis of the Tyson model of the regulation of the cell division cycle

In this paper, we study the mathematical properties of a family of models of Eukaryotic cell cycle, which extend the qualitative model proposed by Tyson [Proc. Natl. Acad. Sci. 88 (1991) 7328–7332]. By means of some recent results in the theory of Lienard's systems, conditions for the uniqueness of the limit cycle and on the global asymptotic stability of the unique equilibrium (idest of the arrest of the cell division) are given.     

Analysis of a two-phase cell division model

In this paper we mainly study an equal mitosis two-phase cell division model. By using the C₀-semigroup theory, we prove that this model is the well-posed in L¹[0, 1] × L¹[0, 1], and exhibits asynchronous exponential growth phenomenon as time goes to infinity. We also give a comparison between this two-phase model with the classical one-phase model. Finally, we briefly study the asymmetric two-phase cell division model, and show that similar results hold for it.     

Moving boundary problem for a one-dimensional crawling nematode sperm cell model

This paper is a continuation of the authors’ investigation of the crawling nematode sperm cell model proposed by Mogilner and Verzi in 2003 (J. Stat. Phys. 110 (2003) 1169). In the earlier papers (J. Math. Biol. 49 (2004) 310 and J. Math. 8 (2004) 399), the first and last authors and Juliet Lee proved the existence of traveling wave solutions for the nematode sperm cell model. In this paper, we prove local existence of solutions to the same model and global existence under certain additional assumption on the initial data. Finally, we also provide numerical evidence that the traveling wave solutions found in (J. Math. Biol., accepted for publication) is globally asymptotically stable.     

Existence of solutions to a model for sparse, one-dimensional fluids

We prove the global existence of solutions to a model for a viscous, compressible, barotropic fluid initially occupying a general open subset of a finite, one-dimensional interval. The fluid equations are applied only on the support of the density, understood in the sense of distributions. This support must be tracked and accommodation must be made for the possibly infinite number of collisions of fluid packets occurring on a possibly dense set of collision times. Our approach avoids certain nonphysical properties of solutions which are constructed as limits of solutions in which artificial mass has been inserted.     

Test of a new bosonization algorithm for a simple one-dimensional model

Different aspects of a new bosonization algorithm are tested by numerical simulations of a simple one-dimensional model. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 113, No. 1, pp. 58–67, October, 1997.     

Measurement model for division as a tool in computing applications

The paper describes the use of a spreadsheet in a mathematics teacher education course. It shows how the tool can serve as a link between seemingly disconnected mathematical concepts. The didactical triad of using a spreadsheet as an agent, consumer, and amplifier of mathematical activities allows for an extended investigation of simple yet intriguing properties of whole numbers. The authors argue that revisiting elementary content in a technological context enables pre-service teachers to appreciate the role that conceptual knowledge can play in the development of a spreadsheet-enabled pedagogy.     

Numerical stabilization from the boundary for solutions of a model one-dimensional of a model one-Dimensional RBMK reactor

The problem of construction of first kind boundary conditions providing an asymptotic change of the trivial solution of a model one-dimensional RBMK reactor to the required stationary state is numerically studied according to specific features of this model. Results of calculations are presented for different admissible modes. The principal feasibility of efficient stabilization of the dynamics of occurring processes by boundary control of fast and slow neutrons is shown as well as its essential slow-down in the control of only fast neutrons.     

On a bi-scale and tri-phasic model for the description of growth in biological tissue using the example of the human liver

The human liver is important for hepatic metabolism regulations which depend on complex and time depending biochemical reactions coupled to the hemodynamic blood perfusion. Growth effects can impair the perfusion and therefore affect the metabolism. Such influences can be observed during the accumulation of fat in the liver tissue. The fat accumulation results from the lipid metabolism which comprises synthesis and degradation of lipids in liver cells. Individual addictions to alcohol and high fat diets are possible causes which result in an excessive synthesis of lipids. The liver sensitively reacts to such changes which could affect the viability of the organ. To observe these coupled influences of perfusion-metabolism-growth effects we use a computational model with a multi-component/tri-phasic/bi-scale approach to simulate the functionality of the human liver with respect to fat deposition. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Asymptotic profile in a one-dimensional steady-state nonisentropic hydrodynamic model for semiconductors

We study the stationary flow for a one-dimensional nonisentropic hydrodynamic model for semiconductor devices. This model consists of the continuous equations for the electron density, the electron current density and electron temperature, coupled the Poisson equation of the electrostatic potential. In a bounded interval supplemented by the proper boundary conditions, we investigate the zero-electron-mass limit, the zero-relaxation-time limit and the Debye-length (quasi-neutral) limit, respectively. We show the strong convergence of the sequence of solutions and give the associated convergence rate.     

Nonlinear dynamics in a complex cubic one-dimensional model for sensory psychophysics

A cubic recursion with complex variable, has different properties in the phase spases of the reals and the imaginaries. The separation of the dynamics of the parts may be interpretable in terms of sensory intensity signal transmission through higher neural networks in man.This work was supported by the Australian Research Grants Scheme, Grant No. A28515714I in 1986, held by Prof. Gregson, to whom requests for offprints should be directed.     

Global solution for a one-dimensional model problem in thermally radiative magnetohydrodynamics

The dynamics of gaseous stars is often described by magnetic fields coupled to self-gravitation and radiation effects. In this paper we consider an initial-boundary value problem for nonlinear planar magnetohydrodynamics (MHD) in the case that the effect of self-gravitation as well as the influence of radiation on the dynamics at high temperature regimes are taken into account. Based on the fundamental local existence results and global-in-time a priori estimates, we establish the global existence of a unique classical solution with large initial data to the initial-boundary value problem under quite general assumptions on the heat conductivity.     

A numerical study on the estimation of the stable size distribution for a cell population balance model

The presence of a steady‐state distribution is an important issue in the modelization of cell populations. In this paper, we analyse, from a numerical point of view, the approach to the stable size distribution for a size‐structured balance model with an asymmetric division rate. To this end, we introduce a second‐order numerical method on the basis of the integration along the characteristic curves over the natural grid. We validate the interest of the scheme by means of a detailed analysis of convergence.     

Mechanisms for oscillations in a biological competition model

A four-dimensional dynamical system that models perceptual bistability in the brain is analyzed. Two variables represent the activity of two competing neural populations and they evolve in fast time; other two variables are slow and they are associated with an intrinsic negative feedback to each population. The external stimulus strength I is the bifurcation parameter. We construct the normal form and prove that oscillations occur in the system through supercritical Hopf bifurcations: as I decreases from large to moderate values a limit cycle is born; then it disappears for lower values of I. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Derivation of the hydrodynamical equation for one-dimensional Ginzburg-Landau model

Summary The hydrodynamical behavior of one-dimensional scalar Ginzburg-Landau model with conservation law is investigated. The dynamics of the system is given by solving a stochastic partial differential equation. Under appropriate space-time scaling, a deterministic limit is obtained and the limit is described by a certain nonlinear diffusion equation.Dedicated to Professor Takeyuki Hida on his 60th birthday     

Cohesive zone model for a transverse breathing crack in a rotor

The breathing mechanism of a transversely cracked rotor and its influence on a rotor system that appears due to the shaft weight is studied. This breathing mechanism is based on experimental and simulation result for the crack shape reported in the literature. If the crack depth is small, the crack closure line is a straight line while for larger crack depths the crack closure becomes more curved. For both cases, a method is proposed for the evaluation of the stiffness losses in the cross section that contains the crack. This method is based on a cohesive zone model (CZM) instead of linear elastic fracture mechanics (LEFM) approach, because LEFM is valid only for the fully open crack and cannot be extended to other intermediate situations. As the crack is closed, the stress intensity factor (SIF) will not appear at the boundary between the closed cracked areas and the open cracked areas. The CZM is developed for mode-I plane strain conditions and accounts explicitly for triaxiality of the stress state by using constitutive relations. The proposed model gives more realistic results than models based on LEFM for the stiffness losses of the crack rotor system for a wide range of the crack depth. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some limit analysis in a one-dimensional stationary quantum hydrodynamic model for semiconductors

In this paper, we study the steady-state hydrodynamic equations for isothermal states including the quantum Bohn potential. The one-dimensional equations for the electron current density and the particle density are coupled self-consistently to the Poisson equation for the electric potential. The quantum correction can be interpreted as a dispersive regularization of the classical hydrodynamic equations. In a bounded interval supplemented by the proper boundary conditions, we investigate the zero-electron-mass limit, the zero-relaxation-time limit, the Debye-length (quasi-neutral) limit, and some combined limits, respectively. For each limit, we show the strong convergence of the sequence of solutions and give the associated convergence rate.     

Mathematical justification of a one-dimensional model for general elastic shallow arches

We present a bending model for a shallow arch, namely the type of curved rod where the curvature is of the order of the diameter of the cross section. The model is deduced in a rigorous mathematical way from classical tridimensional linear elasticity theory via asymptotic techniques, by taking the limit on a suitable re-scaled formulation of that problem as the diameter of the cross section tends to zero. This model is valid for general cases of applied forces and material, and it allows us to calculate displacements, axial stresses, bending moments and shear forces. The equations present a more general form than in the classical Bernoulli–Navier bending theory for straight slender rods, so that flexures and extensions are proved to be coupled in the most general case. © 1998 by B. G. Teubner Stuttgart–John Wiley & Sons Ltd.     

Correlators of densities in the one-dimensional hubbard model

The one-dimensional Hubbard model with infinitely strong repulsion between electrons is considered. Explicit expressions for the two-point correlators of local densities (dependent on time, temperature, the chemical potential, and the external field) are obtained. Bibliography: 12 titles. Dedicated to O. A. Ladyzhenskaya on the occasion of her jubilee Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 249, 1997, pp. 7–19. Translated by A. G. Izergin and A. G. Pronko.