The course re-elaborates some theoretical aspects of the mechanics of growth and structural reorganization (remodeling) of biological tissues by proposing an interpretation suggested by Analytical Mechanics and Variational Principles. For this purpose, the contents of the course will be framed in the context of Field Theories, and studied by following a Continuum Mechanics approach, which will be suitably generalized to include chemo-mechanical phenomena. Since growth and remodeling are the results of phenomena of various nature, their investigation necessitates transversal competencies. This leads to an interdisciplinary environment that, although being very fruitful from the scientific point of view, requires to reconcile well-acknowledged physical principles, such as Balance Laws, with phenomenological laws that are introduced ad hoc and that, in spite of being compatible with experimental data, may sometimes lack of a clear theoretical justification. The main goal of the course is to provide the Participants with the methodological instruments necessary for a systematic formulation of the models of growth and remodeling, thereby proposing a theoretical interpretation also of the phenomenological laws. In particular, for a given tissue and for a given problem, the course proposes: (1) To define the problem’s kinematics by extending the concept of Lagrangian parameter to the descriptors of the internal structure of the tissue; (2) To identify and classify the constraints to which the tissue is subjected, in order to interpret possible phenomenological laws that relate the variations of the kinematic parameters with the other physical quantities characterizing the tissue itself; (3) To define the generalized forces acting on the tissue and, if possible, to characterize them constitutively; (4) To determine the dynamic equations of the systems under study. Once the constraints are given, and the dynamic equations are determined, the course aims at supplying criteria that, through the employment of appropriate invariance (or covariance) principles, establish the admissibility of the relationships connecting the variables of a model. Finally, it will be discussed how the structural transformations induced in a tissue by growth and remodeling influence the material symmetries of the tissue itself and, for this purpose, the proposed topics will be discussed in light of Noether’s Theorem.

Basic notions (of the Bachelor and/or Master of Science level) of Mathematical Analysis, Linear Algebra, Geometry, and Rational Mechanics. It is preferable, but it is not strictly required, to have basic knowledge of Functional Analysis, Differential Geometry and Continuum Mechanics.

1. Brief review on Continuum Mechanics (5 hours) 1.1. Definition of the principal tensor quantities employed in Continuum Mechanics. 1.2. Bilby-Kröner-Lee decomposition. 2. Brief review on Analytical Mechanics (5 hours) 2.1. Kinematics, Definition and classification of kinematic constraints. 2.2. Generalised forces. Determination of the dynamic equations for a constrained system. Lagrange’s multipliers. 3. Mechanics of growth and remodelling (10 hours) 3.1. Dynamic equations for a tissue subjected to growth and remodelling. 3.2. Invariance principles for the admissibility of evolution laws. 3.3. Material symmetries and Noether’s Theorem.

On site

Oral presentation

P.D.2-2 - April