Volume 34, Issue 3

Complex and multi-scale processes regulate the mechanical and chemical interactions between cells and matrices. These dynamic interactions play an essential role in the mediation and regulation of a series of physiological processes including cell adhesion, migration, proliferation, apoptosis, and bi-directional signal transduction. The majority of these interactions are regulated by transmembrane heterodimeric integrin receptors. While the structure and function of integrin receptors have been studied in some detail, the fundamental thermodynamic processes mediating integrin receptors are the major mediators in cell–membrane interactions. To fully understand the equilibrium and non-equilibrium processes involving receptors, ligands, and solvents, a quantitative description of receptor mediated cell–matrix interactions is critical. This review presents recent progress in the area of the quantification of the interactions at the cell–matrix interface in both equilibrium and non-equilibrium conditions in a variety of physiological scenarios.

Starting from the mesoscopic description of the state equations for the vapor and liquid pure phases of a single chemical species, we propose a phase-field model ruling the liquid–vapor phase transition. Two different phases are separated by a thin layer, rather than a sharp interface, where the phase field changes abruptly from 0 to 1. All thermodynamic quantities are allowed to vary inside the transition layer, including the mass density. The approach is based on an extra entropy flux which is proved to be non-vanishing inside the transition layer only. Unlike classical phase-field models, the kinetic equation for the phase variable is obtained as a consequence of thermodynamic restrictions and it depends only on the rescaled free enthalpy. The system turns out to be thermodynamically consistent and accounts for both temperature and pressure variations during the evaporation process. Few commonly accepted assumptions allow us to obtain the explicit expression of the Gibbs free enthalpy and the Clausius–Clapeyron formula. As a consequence, the customary form of the vapor pressure curve is recovered.

We use the methodology of the extended irreversible thermodynamics (EIT) to get physical insight into the viscoelastic parameters appearing in models based on spring and dashpots. Application is made to the Burgers model to represent the properties of a viscoelastic solid. Dynamic response of the model is also analyzed.

The Onsager heat of transport Q * for ammonia at the surface of water was measured at ammonia partial pressures from 12 to 875 Torr and found to be independent of pressure over that range, with an average value of –7.7 ± 2.8 kJ mol –1 (95% confidence limits). Plots of Δ P versus Δ T initially showed a change of slope, or “knee”, at Δ T ~ 0.5 °C. After the stainless-steel Onsager cell had been conditioned by exposure to several hundred Torr of ammonia, plots of Δ P versus Δ T were linear up to Δ T ~ 6 °C. The conditioning is reversible, and is attributed to the effect of chemisorbed ammonia on thermal accommodation coefficients at the metal surface. The results are discussed in relation to the free-energy barrier to evaporation at the surface of a liquid, and in relation to field measurements of the rates of air–sea exchange of greenhouse gases.

A thermodynamical model of inhomogeneous superfluid turbulence previously formulated is extended in this paper to nonlinear regimes. The theory chooses as fundamental fields the density, the velocity, the energy density, and two extra variables, in order to include the specific properties of the fluid in consideration: the averaged vortex line length per unit volume and a renormalized expression of the heat flux. The relations which constrain the constitutive quantities are deduced from the second principle of thermodynamics using the Liu method of Lagrange multipliers. Using a Legendre transformation, it is shown that the constitutive theory is determined by the choice of only two scalar functions of the intrinsic Lagrange multipliers. The complete non-equilibrium expressions of the mass chemical potential, of the chemical potential of vortices, and of the entropy flux are determined: these relations are exact, because no approximation is used for their determination, and maintain their validity also for processes far from equilibrium.