Equilibrium regime

The current frontiers for the subject of non-equilibrium thennodynamics are rich and active. Two areas dommate interest non-linear effects and molecular bioenergetics. The linearization step used in the near equilibrium regime is inappropriate far from equilibrium. Progress with a microscopic kinetic theory [38] for non-linear fluctuation phenomena has been made. Carefiil experiments [39] confinn this theory. Non-equilibrium long range correlations play an important role in some of the light scattering effects in fluids in far from equilibrium states [38, 39]. [Pg.713]

Saveant and co-workers have shown that the kinetics for C—C cleavage of radical cations of NADH model compounds fall into this pre-equilibrium regime. Similarly, the slope of log(A obs) vs. AG°ab for a number of C—C containing ion radicals also is about -1/(2.303/ 7 ). The first clear demonstration of the transition from activation to counterdiffusion control was found in a study of the fragmentation of anion radicals of a-aryloxyacetophenones (ArC(0)CH20Ar ). This study used a combination... [Pg.111]

We now wish to envision the de-equilibration to times t when the condition (13.18) is not yet satisfied and values of Et vary from cell to cell (i.e., from point to point in space) in a smooth fashion to be described. In this near-equilibrium regime, Et can be properly... [Pg.431]

Vol. 18 Transport Mediated by Electrified Interfaces Studies in the linear, non-linear and far from equilibrium regimes. [Pg.327]

Mazzella, N., J.-F. Dubemet, and F. Delmas. 2007. Determination of kinetic and equilibrium regimes in the operation of polar organic chemical integrative samplers application to the passive sampling of the polar herbicides in aquatic environments. J. Chromatogr. A 1154 42-51. [Pg.65]

Spectroscopic methods are very useful for determining molecular properties. Time-resolved spectroscopic methods are useful for monitoring the evolution of the molecular properties in real time. Moreover, time-resolved spectroscopic techniques have the best time resolution available among all kinds of time-resolved experimental techniques. Thus, very often time-resolved spectroscopic methods reveal the dynamics of a molecular system in the non-equilibrium regime. In this section, the density matrix method is applied to calculate the spectroscopic properties of molecular systems. These include the linear and non-linear optical processes, in equilibrium or non-equilibrium cases. The approach is based on the susceptibility theory. [Pg.147]

Thermally Activated Systems. The equilibrium (high pressure) kinetic isotope effect in thermal activation systems is the one conventionally measured and the theoretical basis for this limiting case has been well formulated.3 In the low-pressure non-equilibrium regime, very large inverse statistical-weight secondary isotope effects can occur. 20 b These effects are dependent on the ambient temperature and the thermal energy distribution function the latter is considered in Sec. III-E, and discussion of these effects is postponed until Sec. III-E,4. [Pg.35]

In an out-of-equilibrium environment, no well-defined thermodynamical temperature does exist. Since, in an out-of-equilibrium regime, even if stationary, the FDTs are not satisfied, one can try to rewrite them in a modified way, and thus to extend linear response theory, with the help of a (frequency-dependent) effective temperature. [Pg.312]

Within the framework of the theory of dissipative structures, thermodynamic buffering represents a new bioenergetics regulatory principle for the maintenance of a nonequilibrium conditions. Due to the ATP production in oxidative phosphorylation, the phosphate potential is shifted far from equilibrium. Since hydrolysis of ATP drives many processes in the cell, the shift inXp to far from equilibrium results in a shift of all the other potentials into the far from equilibrium regime. [Pg.590]

Conductivity data for n-type and p-type samples above the equilibration temperature are shown in Fig. 7.4 and similar data are in Fig. 5.2. The conductivity is activated with a prefactor of 100-200 cm for both doping types and the activation energy is 0.3-0.4 eV in n-type material and 0.4-0.6 eV in p-type. In the thermal equilibrium regime, the Fermi energy is pinned by the defect and dopant states and consequently the statistical shift is small, as is discussed in Section 6.2.2. Yp may be calculated from a numerical... [Pg.230]

The effect of the statistical shift can be calculated from Eq. (7.18) and the density of states distribution, just as for the equilibrium state except that the density of electrons is now constant. The resulting values of Yp are in the range 3k-6k, so that the correction to the prefactor of exp(Yp/ ) from the statistical shift is a factor of 10-100. The calculated conductivity is shown in Fig. 7.5 and a good fit to the data is found with a conductivity prefactor of 100 cm and the same transport energy as was obtained from the analysis of the equilibrium regime. The modeling of the conductivity therefore shows that the only difference... [Pg.233]

Polymerization in the equilibrium regime does provide the control of the molecular weight and a narrow molecular weight distribution. The integration of the kinetic equations for the moments of the distribution (see section IV) leads to equations for the number-average degree of polymerization (An) and the polydispersity index PDI = A4 /A4 = Aw/An. [Pg.286]

Figure 4. Evolution of the total number-average degree of polymerization An and the polydispersity index with conversion during a polymerization in the equilibrium regime for kp = 5000IVP1 s 1, k = 108 IVP1 s 1, k = 0.0045 s-, k = 2.2T07 IVP1 s 1, [M]0 = 10 M, and [I]0 = 0.1 M as obtained by numerical integrations and eqs 24 and 25 (circles).

In the transition region between the initial and the equilibrium regime, the details of the time evolutions are complicated.17 However, for the equilibrium regime where apt] = 1, the integration of eq 44 leads to eqs 18.17 These solutions are obeyed until rj approaches 1 and p approaches 1/a, and this happens at the approximate time t= [I]0/3 A Wt. For nitroxide-based systems with a large equilibrium constant, K = 10 8 M (Table 1), a rather small initiator concentration, [I]0 = 10 2 M and kt = 108 M 1 s 1, the equilibrium, and that is also the persistent radical effect, lasts for about 90 h, and it is entered at rather short times of at most seconds.17... [Pg.298]

Polymerizations are studied typically in time ranges between 100 s and 30 h, that is, in the equilibrium regime. Therefore, for polymerizing systems, one can use eq 20, insert it into the rate equation of the monomer consumption (21), integrate, and obtain eq 22. The further derivation of the control involves the calculation of the moments mk of the chain length distribution and of their time dependencies. [Pg.298]

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...