Search results for "Reversible"
showing 10 items of 140 documents
Extended thermodynamics of polymers and superfluids
2008
Abstract Polymer solutions and turbulent superfluids have in common the presence of a complex tangle of lines – macromolecules in the former, quantized vortex lines in the latter – which contribute to the internal friction and viscous pressure of the system and make them typical non-Newtonian fluids. Here we briefly review some recent studies on such tangles and their consequences on the dynamics and thermodynamics of the whole system, using the framework of extended irreversible thermodynamics. For polymer solutions, we deal with the coupling of diffusion and viscous pressure and its effects on the stability of the solution and shear-induced phase separation; for superfluids, we focus our …
A Continuum Theory of Superfluid Turbulence based on Extended Thermodynamics
2009
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 f…
Towards a nonequilibrium thermodynamic description of incoherent nonlinear optics
2007
pa href="http://oe.osa.org/virtual_issue.cfm?vid=36"Focus Serial: Frontiers of Nonlinear Optics/a/pThis concise review is aimed at providing an introduction to the kinetic theory of partially coherent optical waves propagating in nonlinear media. The subject of incoherent nonlinear optics received a renewed interest since the first experimental demonstration of incoherent solitons in slowly responding photorefractive crystals. Several theories have been successfully developed to provide a detailed description of the novel dynamical features inherent to partially coherent nonlinear optical waves. However, such theories leave unanswered the following important question: Which is the long term…
Extended irreversible thermodynamics of liquid helium II
1993
In this work a macroscopic monofluid theory of liquid helium II, which is based on the extended irreversible thermodynamics, is formulated both in the presence and in the absence of dissipative phenomena. The work is a generalization of previous papers, where the extended thermodynamics of an ideal monoatomic fluid was applied to liquid helium II. It is shown that the behavior of helium II can be described by means of an extended thermodynamic theory where four fields, namely density, temperature, velocity, and heat flux are involved as independent fields. In the presence of dissipative phenomena, constitutive relations for the trace and the deviator of the nonequilibrium stress tensor are …
A monofluid flow mathematical model of liquid helium II based on extended non-equilibrium thermodynamics
1994
The present work is a generalization of a previous analysis which aims at a single-fluid description of the macroscopic behaviour of helium II. A single-fluid model of helium II, with a wider range of temperatures and pressures than the one previously described, is formulated here using the extended thermodynamics of a non-ideal fluid in the absence of dissipation. The model here formulated includes, according to experimental data, the propagation of the two sounds typical of superfluid helium, a relationship between the stress deviator and the square of heat flux and an explanation of the fountain effect.
Relative importance of second-order terms in relativistic dissipative fluid dynamics
2014
[Introduction] In Denicol et al. [Phys. Rev. D 85 , 114047 (2012)], the equations of motion of relativistic dissipative fluid dynamics were derived from the relativistic Boltzmann equation. These equations contain a multitude of terms of second order in the Knudsen number, in the inverse Reynolds number, or their product. Terms of second order in the Knudsen number give rise to nonhyperbolic (and thus acausal) behavior and must be neglected in (numerical) solutions of relativistic dissipative fluid dynamics. The coefficients of the terms which are of the order of the product of Knudsen and inverse Reynolds numbers have been explicitly computed in the above reference, in the limit of a massl…
Diffusion of single molecular and macromolecular probes during the free radical bulk polymerization of MMA : towards a better understanding of the Tr…
2016
Free radical bulk polymerizations exhibit complex kinetics due to the viscosity increase during the polymerization process. Especially the termination rate constant can be strongly influenced by the mobility of polymer chains in the polymerization mixture. As a consequence an autoacceleration period, the so-called Trommsdorff effect, can be observed often. In order to investigate this behaviour on a nanoscopic scale, we directly visualized the mobility of molecules and macromolecules in polymerizing MMA solutions using a combination of highly sensitive fluorescence correlation spectroscopy and widefield fluorescence microscopy. For this purpose, rather monodisperse PMMA chains were synthesi…
Bioreducible Poly-l-Lysine-Poly[HPMA] Block Copolymers Obtained by RAFT-Polymerization as Efficient Polyplex-Transfection Reagents
2015
Polylysine-b-p[HPMA] block copolymers containing a redox-responsive disulfide bond between both blocks are synthesized by RAFT polymerization of pentafluorphenyl-methacrylate with a macro-CTA from Nϵ-benzyloxycarbonyl (Cbz) protected polylysine (synthesized by NCA polymerization). This polylysine-b-p[PFMA] precursor block copolymer is converted to polylysine(Cbz)-b-p[HPMA] by postpolymerization modification with 2-hydroxypropylamine. After removal of the Cbz protecting group, cationic polylysine-b-p[HPMA] copolymers with a biosplittable disulfide moiety became available, which can be used as polymeric transfection vectors. These disulfide linked polylysine-S-S-b-p[HPMA] block copolymers sho…
New hyaluronic acid based brush copolymers synthesized by atom transfer radical polymerization.
2013
Abstract In this work, an efficient method for the synthesis of hyaluronic acid based brush copolymers using atom transfer radical polymerization (ATRP) has been reported. At first, two different hyaluronic acid (HA) based macroinitiators have been prepared and then they have been used for the polymerization via ATRP of hydrophilic or hydrophobic molecules carrying vinyl portions. In particular, by linking 2-bromo-2-methylpropionic acid (BMP) to the primary hydroxyl groups of tetrabutyl ammonium salt of HA (HA–TBA) or to amino groups of the ethylenediamino derivative of HA–TBA (HA–TBA–EDA), two macroinitiators (HA–TBA–BMP and HA–TBA–EDA–BMP) have been obtained. Then they have been used for …