Ricerc@Sapienza

In this paper, we review classical and recent results on the Lagrangian description of dissipative systems. After hav-
ing recalled Rayleigh extension of Lagrangian formalism to equations of motion with dissipative forces, we describe
Helmholtz conditions, which represent necessary and sufficient conditions for the existence of a Lagrangian function for
a system of differential equations. These conditions are presented in different formalisms, some of them published in the

Different cell lineages growing in microgravity undergo a spontaneous
transition leading to the emergence of two distinct phenotypes. By returning
these populations in a normal gravitational field, the two phenotypes
collapse, recovering their original configuration. In this review, we hypothesize
that, once the gravitational constraint is removed, the system freely
explores its phenotypic space, while, when in a gravitational field, cells are
“constrained” to adopt only one favored configuration. We suggest that the