Non-equilibrium temperatures and heat transport in nanosystems with defects, described by a tensorial internal variable

AbstractThe paper deals with the meaning of non-equilibrium temperatures in nanosystems with an internal variable, describing defects inside them, and implications on heat transport. In equilibrium all definitions of temperature lead to the same value, but in nonequilibrium steady states they lead to different values, giving information on different degrees of freedom. We discuss the caloric and entropic non-equilibrium temperatures and the relations among them, in defective nanosystems (crystals with dislocations or porous channels, carbon nanotubes in a solid matrix and so on), crossed by an external energy flux. Here, we present a model for nanocrystals with dislocation defects submitted to an external energy flux. The dislocations may have a strong influence on the effective thermal conductivity, and their own dynamics may be coupled in relevant way to the heat flux dynamics. In the linear case the constitutive relations, the rate equations for the internal variable and the heat flux are worked out and a generalized telegraphic heat equation is derived in the anisotropic and isotropic case, describing the thermal disturbances with finite velocity

Multiscale heat transport with inertia and thermal vortices

In this paper, we present a Hamiltonian and thermodynamic theory of heat transport on various levels of description. Transport of heat is formulated within kinetic theory of polarized phonons, kinetic theory of unpolarized phonons, hydrodynamics of polarized phonons, and hydrodynamics of unpolarized phonons. These various levels of description are linked by Poisson reductions, where no linearizations are made. Consequently, we obtain a new phonon hydrodynamics that contains convective terms dependent on vorticity of the heat flux, which are missing in the standard theories of phonon hydrodynamics. Moreover, the equations are hyperbolic and Galilean invariant, unlike current theories for beyond-Fourier heat transport. The vorticity-dependent terms violate the alignment of the heat flux with the temperature gradient even in the stationary state, which is expressed by a Fourier-Crocco equation. The new terms also cause that temperature plays in heat transport a similar role as pressure in aerodynamics

A geometric model for magnetizable bodies with internal variables

In a geometrical framework for thermo-elasticity of continua with internal variables we consider a model of magnetizable media previously discussed and investigated by Maugin. We assume as state variables the magnetization together with its space gradient, subjected to evolution equations depending on both internal and external magnetic fields. We calculate the entropy function and necessary conditions for its existenc

Thermodynamics of heterogeneous and anisotropic nonlinear ferroelastic crystals

In a previous paper, in a geometrized framework for the description of simple materials with internal variables, the specific example of ferroelastic crystals with anisotropy grain-tensors à la Maruszewski was considered and the relevant structure of the entropy 1-form was derived. In this contribution the linear morphism defined on the fibre bundle of the process and the transformation induced by the process are obtained as new results within the geometrical model. Furthermore, Clausius-Duhem inequality for these media is exploited, and, using a Maugin technique (see also Colemann-Noll procedure), the laws of state, the extra entropy flux and the residual dissipation inequality are worked out. Finally, following Maugin, the heat equation in the first and the second form are derived

Nonlinear heat transport in superlattices with mobile defects

We consider heat conduction in a superlattice with mobile defects, which reduce the thermal conductivity of the material. If the defects may be dragged by the heat flux, and if they are stopped at the interfaces of the superlattice, it is seen that the effective thermal resistance of the layers will depend on the heat flux. Thus, the concentration dependence of the transport coefficients plus the mobility of the defects lead to a strongly nonlinear behavior of heat transport, which may be used in some cases as a basis for thermal transistors

Glycosaminoglycans in the tongue of birds

We examined the literature to verify whether adaptations and modifications in the structure and glandular secretions of birds' tongues are related to habitat and can be ascribed to evolutionary processes. The data are discussed in relation to species taxonomy, following the Sibley and Ahlquist classification [C. G. Sibley and J. E. Alquist, Philogeny and Classification of Birds. A Study in Molecular Evolution (Yale University Press, New Haven, 1990)]. The following conclusions are drawn: gustatory papillae and taste buds are present in varying numbers in most species. The composition of gland secretions is also found to be variable. Proteic secretion is documented in Larus modestus, Sula variegata, Fulica atra only. Acid proteoglycans both with sulfomucins and carboxymucins, and also glycoproteins, are consistently found. Sialic and hyaluronic acids are found in many species. Our overview indicates that the presence or absence of gustatory papillae is related to adaptation processes that these structures undergo in response to environmental factors, and that the absence of front tongue glands can be ascribed to habitat and feeding habits. Referring to the Sibley and Ahlquist classification, proteins are present in the glandular secretion of less evolved species, whereas more evolved species exhibit a gradual decrease in proteins with the exception of hyaluronic acid, which is absent, and a progressive increase in glycoproteins and acid proteoglycans

Legge di evoluzione delle discontinuità e tempo critico in un particolare modello dielettrico non lineare

We obtain the Bernoulli's equation governing the propagation of weak discontinuities in the case of a non linear dielectric. The critical time for the breakdown of the solution is pointed out explicitly in terms of initial data when a particular ferroelectric material is considered