a review of vasculogenesis models

Mechanical and chemical models of vasculogenesis are critically reviewed with an emphasis on their ability to predict experimentally measured quantities. Final remarks suggest a possibility to merge the capabilities of different models into a unified approach

A note on light velocity anisotropy

It is proved that in experiments on or near the Earth, no anisotropy in the one-way velocity of light may be detected. The very accurate experiments which have been performed to detect such an effect are to be considered significant tests of both special relativity and the equivalence principleComment: 8 pages, LaTex, Gen. Relat. Grav. accepte

Modeling sand slides by a mechanics-based degenerate parabolic equation

Avalanching plays a crucial role in granular materials dynamics, in particular in the evolution of the shape of the leeward side of sand dunes. This paper presents a physically-based mathematical model capable of reproducing the kinematic evolution of the surface of sand piles and to obtain eventually the stationary configurations, in the presence of external sources as well. Simulation results with different boundary conditions and geometries are reported in order to show the high flexibility of the model. The model is also validated by means of comparison with the experimental results of different authors

Force traction microscopy: An inverse problem with pointwise observations

Force Traction Microscopy is an inversion method that allows to obtain the stress field applied by a living cell on the environment on the basis of a pointwise knowledge of the displacement produced by the cell itself. This classical biophysical problem, usually addressed in terms of Green functions, can be alternatively tackled using a variational framework and then a finite elements discretization. In such a case, a variation of the error functional under suitable regularization is operated in view of its minimization. This setting naturally suggests the introduction of a new equation, based on the adjoint operator of the elasticity problem. In this paper we illustrate the rigorous theory of the two-dimensional and three dimensional problem, involving in the former case a distributed control and in the latter case a surface control. The pointwise observations require to exploit the theory of elasticity extended to forcing terms that are Borel measure

Coherent Fe-rich nano-scale perovskite oxide phase in epitaxial Sr2FeMoO6 films grown on cubic and scandate substrates

We report the growth of high-quality epitaxial Sr2FeMoO6 (SFMO) thin films on various unconventional oxide substrates, such as TbScO3, DyScO3, and Sr2Al0.3Ga0.7TaO6 (SAGT) as well as on the most commonly used one, SrTiO3 (STO), by pulsed laser deposition. The films were found to contain a foreign nano-scale phase coherently embedded inside the SFMO film matrix. Through energy dispersive X-ray spectroscopy and scanning transmission electron microscopy, we identified the foreign phase to be Sr2−xFe1+yMo1−yO6, an off-stoichiometric derivative of the SFMO compound with Fe rich content (y ≈ 0.6) and a fairly identical crystal structure to SFMO. The films on STO and SAGT exhibited very good magnetic properties with high Curie temperature values. All the samples have fairly good conducting behavior albeit the presence of a foreign phase. Despite the relatively large number of items of the foreign phase, there is no significant deterioration in the properties of the SFMO films. We discuss in detail how magneto-transport properties are affected by the foreign phase. INT

Ferromagnetism and ferroelectricity in epitaxial BiMnO3 ultra-thin films

We studied the ferroelectric and ferromagnetic properties of compressive strained and unstrained BiMnO3 thin films grown by rf-magnetron sputtering. BiMnO3 samples exhibit a two-dimensional cube-on-cube growth mode and a pseudo-cubic structure up to a thickness of 15 nm and of 25 nm when deposited on (001) SrTiO3 and (110) DyScO3, respectively. Above these thicknesses, we observe a switching to a three-dimensional island growth mode and a simultaneous structural change to a (00l) oriented monoclinic unit cell. While ferromagnetism is observed below a T-C approximate to 100K for all samples, signatures of room temperature ferroelectricity were found only in the pseudo-cubic ultra-thin films, indicating a correlation between electronic and structural orders

Multiphase modelling of tumour growth and extracellular matrix interaction: mathematical tools and applications

Resorting to a multiphase modelling framework, tumours are described here as a mixture of tumour and host cells within a porous structure constituted by a remodelling extracellular matrix (ECM), which is wet by a physiological extracellular fluid. The model presented in this article focuses mainly on the description of mechanical interactions of the growing tumour with the host tissue, their influence on tumour growth, and the attachment/detachment mechanisms between cells and ECM. Starting from some recent experimental evidences, we propose to describe the interaction forces involving the extracellular matrix via some concepts coming from viscoplasticity. We then apply the model to the description of the growth of tumour cords and the formation of fibrosis

Percolation, Morphogenesis, and Burgers Dynamics in Blood Vessels Formation

Experiments of in vitro formation of blood vessels show that cells randomly spread on a gel matrix autonomously organize to form a connected vascular network. We propose a simple model which reproduces many features of the biological system. We show that both the model and the real system exhibit a fractal behavior at small scales, due to the process of migration and dynamical aggregation, followed at large scale by a random percolation behavior due to the coalescence of aggregates. The results are in good agreement with the analysis performed on the experimental data.Comment: 4 pages, 11 eps figure