MULTILAYER ADSORPTION ON FRACTAL SURFACES: EFFECT OF THE ADSORBATE-ADSORBATE INTERACTIONS ON THE SORPTIONAL EQUILIBRIUM

ABSTRACT

An analytical isotherm equation that can be applied to water vapor-biopolymer systems, was developed. The model describes the multilayer adsorption on fractal surfaces with energetic interactions adsorbate-adsorbate (measure in terms of free energy) different from that of bulk water. Assuming explicit mathematical functionalities for the variation of the free energy with the number of adsorbed layers, it is possible to evaluate the effect of the adsorbate-adsorbate interactions on the adsorption capacity of solids of high degree of surface irregularity. For those surfaces with relatively low degree of irregularity (D values slightly larger than 2) it results that the free energy variation with the layer number in the multilayer region affects considerably the sorption capacity of the adsorbent, even for water activities lower than those corresponding to the monolayer moisture content. This effect becomes less marked as the fractal dimension increases (D approaching to 3), being relevant for water activities much larger than those corresponding to the monolayer value, only. The isotherm was tested, using published experimental equilibrium data of various biopolymers.     

Ownership Structures in Network Industries when the Rationality of Regulators is Bounded

This paper analyses the implication for allocative efficiencyof diffrent ownership structures of vertically related industriesin a simple game-theoretic setting. The upstream sector is monoplizedand regulated, while the downstream sector is imperfectly competitive.Regulation is imperfect in that the regulatory authority suffersfrom bounded rationality, and is not able to enforce optimalregulation. We consider both bomogenous and differentiated compositegoods. It generally turns out that when the regulator's enforcementcapabilities are limited, preventing the upstream monoplistfrom entering the downstream industry is socially undesirableunless the independent downstream rival enjoys a substantialproduction cost advantage. This holds true in spiteof the downstreamindustry is socially undesirable, unless the independent downstreamrival enjoys a substantial production cost advantage. This holdstrue in spite of the incentiveof the vertically integrated monopolistto manipulate accounts in order to raise the costs of the downstreamrival. Such reasoning especially applies when composite goodsare close substitures for one another.     

Stability of Permanent Magnet Bearings under Parametric Excitations

Permanent magnet pairs offer negligible friction and no wear, but also static instability. Stability may be recovered if a suitable periodic axial motion is imposed on the levitated element of the pair.     

On efficiency of both single fuel cells and stacks II

The model developed in the first part of this work is used to predict the cell potentials and the irreversible Gibbs free energy of a stack of 15 cells. The model starts from a phenomenological equation of a polarization curve with the extent of reaction as the independent variable. Two extreme kinds of flow of reagents, defined as Chain and Separate Flows respectively, are considered. The cell potentials are obtained by a combination of the potential of the two extreme cases of flow. The stack cell potentials and the efficiencies, estimated by the model, reproduce the general characteristics obtained by the experiments.     

Factors influencing the service-like thermomechanical fatigue test cycle endurance of 1% CrMoV rotor steel

Service‐like thermomechanical fatigue tests have been performed in order to characterize the endurance of 1% CrMoV rotor steel under such transient thermal conditions. The key features of these tests are low strain rates (≤10^?5 s^?1) and longer hold periods. In all testpieces, ratcheting with progressive section reduction is observed in the central portion of the gauge length accompanied by local amplification of the strain range. The finite‐element‐based analysis of this phenomenon allows the measured endurances to be rationalized with those determined from isothermal tests. Post‐test inspection has revealed the development of two concurrent damaging mechanisms in the testpieces: (i) fatigue at the surface and (ii) creep in the interior. Different methods of damage calculation for creep–fatigue interaction are applied and compared in their predictive capabilities.     

Application of the parametric bootstrap method to determine statistical errors in quantitative X-ray microanalysis of thin films

We applied the parametric bootstrap to the X‐ray microanalysis of Si‐Ge binary alloys, in order to assess the dependence of the Ge concentrations and the local film thickness, obtained by using previously described Monte Carlo methods, on the precision of the measured intensities. We show how it is possible by this method to determine the statistical errors associated with the quantitative analysis performed in sample regions of different composition and thickness, but by conducting only one measurement. We recommend the use of the bootstrap for a broad range of applications for quantitative microanalysis to estimate the precision of the final results and to compare the performances of different methods to each other. Finally, we exploited a test based on bootstrap confidence intervals to ascertain if, for given X‐ray intensities, different values of the estimated composition in two points of the sample are indicative of an actual lack of homogeneity.     

Nonenzymatic Browning In Liquid Model Systems of High Water Activity: Kinetics of Color Changes Due to Reaction Between Glucose and Glycine Peptides

The rate of browning of solutions (water activity adjusted to 0.90 by adding sodium chloride) of glucose-glycine peptides (diglycine and triglycine) was well described by a “mixed-order” kinetic model having two rate coefficients, k_o and k_l. Activation energies for these parameters were calculated and compared with values for the same reaction of glucose with the amino acid (glycine). At pH below 6 the rate of browning of peptide solutions was higher than that of the amino acid (glycine) at the same molar concentration; at higher pH the reverse was observed.